V.S.B .Engineering College, Karur Department of Electronics and Communication Engineering

EC6801 - WIRELESS COMMUNICATION

2 MARKS QUESTIONS WITH ANSWERS UNIT I WIRELESS CHANNELS 1. What are the propagation mechanisms of EM waves? The four propagation mechanisms of EM waves are

i Free space propagation ii Reflection iii Diffraction iv Scattering

2. What is the significance of propagation model? The major significance of propagation models are:

i. Propagation model predicts the parameter of receiver. ii. It predicts the average received signal strength at a given distance from the transmitter.

3. What do you mean by small scale fading? Rapid fluctuations of the amplitude, phase as multipath delays of a radio signal over a short period of time is called small scale fading.

4. What are the factors influencing small scale fading? The factors which influence small scale fading are: Multipath propagation, Speed of the mobile, Speed of surrounding objects and Transmission bandwidth of the signal.

5. When does large scale propagation occur? Large scale propagation occurs due to general terrain and the density and height of buildings and vegetation, large scale propagation occurs.

6. Differentiate the slow fading and fast fading.(April/May 2018)

Slow Fading Fast Fading Slow variations in the signal strength. Rapid variations in the signal strength. Mobile station (MS) moves slowly. Local objects reflect the signal causes fast fading. It occurs when the large reflectors and It occurs when the user terminal (MS) diffracting objects along the transmission moves for short distances. paths are distant from the terminal. Eg. Rayleigh fading, Rician fading and Doppler shift

7. Define Doppler shift. If the receiver is moving towards the source, then the zero crossings of the signal appear faster and the received frequency is higher. The opposite effect occurs if the receiver is moving away from the source. The resulting chance in frequency is

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known as the Doppler shift (fD). FD = fr – f0 = -f0V/C Where f0 -> transmission frequency fr -> received frequency

8. Differentiate time selective and frequency selective channel. The gain and the signal strength of the received signal are time varying means then the channel is described as time selective channel. The frequency response of the time selective channel is constant so that frequency flat channel. The channel is time invariant but the impulse response of the channel show a frequency-dependent response so called frequency selective channel.

9. Define coherence time and coherence bandwidth.(Nov/Dec 2015)(April/May 2017) Coherence time is the maximum duration for which the channel can be assumed to be approximately constant. It is the time separation of the two time domain samples. Coherence bandwidth is the frequency separation of the two frequency domain samples.

10. What do you mean by WSSUS channels? In multipath channels, the gain and phase shift at one delay are uncorrelated with another delay is known as uncorrelated scattering of WSSUS.

11. What is free space propagation model? The free space propagation model is used to predict received signal strength, when unobstructed line-of-sight path between transmitter & receiver. Friis free space equation is given by,

The factor (λ/4πd)2 is also known as the free space loss factor.

12. Define EIRP. EIRP (Equivalent Isotropically Radiated Power) of a transmitting system in a given direction is defined as the transmitter power that would be needed, with an isotropic radiator, to produce the same power density in the given direction. EIRP=PtGt Where Pt-transmitted power in W, where Gt-transmitting antenna gain

13. Explain path loss. The path loss is defined as the difference (in dB) between the effective transmitted power and the received power. Path loss may or may not include the effect of the antenna gains.

14. What is intrinsic impedance and Brewster angle? Intrinsic impedance is defined by the ratio of electric to magnetic field for a uniform plane wave in the particular medium. Brewster angle is the angle at which no reflection occurs in the origin. Brewster angle is denoted

by θB as shown below,

15. Define radar cross section. Radar Cross Section of a scattering object is defined as the ratio of the power density of the signal scattered in the direction of the receiver to the power density of the radio wave incident upon the scattering object & has units of squares meters.

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16. What is scattering? When a radio wave impinges on a rough surface, the reflected energy is spread out in all directions due to scattering.

17. Name some of the outdoor propagation models? Some of the commonly used outdoor propagation models are i. Longely-Rice model ii. Durkin‟s model iii. Okumura model.

18. Define indoor propagation models. The indoor propagation models are used to characterizing radio propagation inside the buildings. The distances covered are much smaller, and the variability of the environment is much greater for smaller range of Transmitter and receiver separation distances. Features such as lay-out of the building, the construction materials, and the building type strongly influence the propagation within the building.

19. Mention some indoor propagation models? Some of the indoor propagation models are: i. Long –distance path loss model ii. Ericson multiple break point model iii. Attenuation factor model.

20. What are merits and demerits of Okumara‟s model? Merits: Accuracy in parameter prediction. Suitable for modern land mobile radio system. Urban, suburban areas are analyzed. Demerits: Rural areas are not analyzed. Analytical explanation is not enough.

21. List the advantages and disadvantages of Hata model? Advantages: Suitable for large cell mobile system. Cell radius on the order of 1km is taken for analysis. Disadvantages: Not suitable for PCS model. This model does not have any path specific correction. 22. What is the necessity of link budget? The necessities of link budget are: i. A link budget is the clearest and most intuitive way of computing the required Transmitter power. It tabulates all equations that connect the Transmitter power to the received SNR ii. It is reliable for communications. iii. It is used to ensure the sufficient receiver power is available. iv. To meet the SNR requirement link budget is calculated. 23. Write the effects of fading. 1. Rapid changes in signal strength over a small travel distance or time interval. 2. Random frequency modulation due to varying Doppler shifts on different multipath signals 3. Time dispersion caused by multipath propagation delays.

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24. Define coherence bandwidth. (April/May 2016) The coherence bandwidth is related to the specific multipath structure of the channel. The coherence bandwidth is a measure of the maximum frequency difference for which signals are still strongly correlated in amplitude. This bandwidth is inversely proportional to the rms value of time delay spread.

25. What is coherence time?(Nov/Dec 2018) It is defined as the required time interval to obtain an envelope correlation of 0.9 or less.

26. Define Doppler shift. The shift in received signal frequency due to motion is called the Doppler shift.

27. What is Doppler spread? It is defined as the range of frequencies over which the received Doppler spectrum is essentially non-zero.

28. What are the effects of multipath propagation? Slow fading and fast fading

29. What is flat fading?(Nov/Dec 2017) If the mobile radio channel has a constant gain and linear phase response over a bandwidth which is greater than the bandwidth of the transmitted signal, then the received signal will undergo flat fading.

30. Write the conditions for flat fading. BW of signal<>Delay spread, T >>ơλ

31. What is frequency selective fading?(Nov/Dec 2016) If the channel possesses a constant gain and linear phase response over a bandwidth that is, smaller than the bandwidth of transmitted signal, then the channel creates frequency selective fading on the received signal.

32. Write the conditions for frequency selective fading. BW of signal>BW of channel Bs>Bc Symbol period< Delay spread Ts<ơλ

33. Define fast fading channel. The channel impulse response changes rapidly within the symbol duration. This type of channel is called fast fading channel.

34. Define slow fading channel. The channel impulse response changes at a rate much slower than the transmitted baseband signal. This type of channel is called slow fading channel.

35. What is meant by link budget? A link budget is the clearest and the most intuitive way of computing the required transmit power.

36. What is the need of path loss models in link budget design? The path loss models are used to estimate the received signal level as the function of distance it becomes possible to predict the SNR for a mobile communication system.

37. What is ISI? Intersymbol interference (ISI) is a form of distortion of a signal in which one symbol interferes with subsequent symbols.

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38. What is meant by small scale fading? (April/May 2013) The rapid fluctuations of the amplitudes, phases; or multipath delays of a radio signal over a short period of time or travel distance is known as small scale fading.

39. What is meant by large scale fading? (April/May 2013) The rapid fluctuations of the amplitudes, phases, or multipath delays of a radio signal over a long period of time or travel distance is known as large scale fading.

40. What are the factors influencing small scale fading? Speed of surrounding objects, Multipath propagation, Speed of the mobile, Transmission bandwidth of the signal.

41. What is free space propagation model? It is a model which is used to predict received signal strength, when unobstructed line of sight path.

42. What is meant by frequency dispersion? The received signal has a larger bandwidth than that of the transmitted signal, due to the different Doppler shifts introduced by the components of the multipath between transmitter and receiver.

43. What are Fresnel zones? The concentric circles on the transparent plane located between a transmitter and receiver represent the loci of the origins of secondary wavelets which propagate to the receiver such that the total path length increases by λ/2 for successive circles. These circles are called Fresnel zones.

44. Explain knife-edge diffraction model. Knife edge is the simplest of diffraction models, and the diffraction loss can be readily estimated using the classical Fresnel solution for the field behind the knife edge.

45. Find the far field distance for an antenna with maximum dimension of 2m and operating Frequency 1GHz?(Dec 2015)

Df = 2D2/λ= 2 * 2 * 2/0.3 = 26.7 m

45. Define Snell‟s law. (May 2013) Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the reciprocal of the ratio of the indices of refraction:

46. Calculate the Brewster Angle for a wave impinging on ground having a permittivity of εr = 5. (May 2016)

= 0.409Brewster Angle = sin -1 (0.409) = 24.14 47.What is frequency flat and frequency selective fading? Selective fading or frequency selective fading is a radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by two different paths, and at least one of the paths is changing (lengthening or shortening). Frequency flat :A type of small scale fading where all frequency signal components experience the same magnitude of fading; corresponds to the case where the signal bandwidth is smaller than the channel coherence bandwidth 48.What is the major advantage of wireless communication?(April/May 2017) Increased efficiency Access and availability. Flexibility. Cost savings. Wireless Communication, Prepared by P.Poornima AP/ECE Page 5

New opportunities. Security. Installation problems. Coverage

PART B:

1. Discuss in brief about the Free-space model. (April/ May 2018) 2. What are the factors influencing small scale fading? (Nov/Dec 2016) 3. Explain the effects of multipath time delay spread and fading effects due to Doppler spread. (Nov/Dec 2016) 4. What do you mean by path loss model? Explain in detail about log distance path loss model. (Nov/Dec 2017) 5. Explain i) Fading and ii) Multipath propagation. 6. Derive the path loss considering a two ray model for the propagation mechanism wireless channel. Is considering just two rays alone sufficient? Why? (April/ May 2017) 7. Write short notes on i) time-selective channels ii) frequency-selective channels(Nov/Dec 2018) 8. Differentiate narrowband and wideband channels. 9. Explain the advantages and disadvantages of two ray ground reflection model in the analysis of path loss. (Nov/Dec 2015) 10. What is link budget? Explain with an example how it can be computed for noise limited system. 11. Write short notes on WSSUS channels. 12. Derive the impulse response model of a multipath channel and also obtain the relationship between bandwidth and received power. (Nov/Dec 2015) 13. Explain coherence time and coherence bandwidth with expressions. 14. Explain in detail about the parameters of mobile multipath channels. (April/ May 2016) (April/ May 2017) (May/June 2016) 15. Explain briefly on outdoor propagation model. (Nov/Dec 2014) 16. Describe in detail Two Ray Rayleigh Fading Model. (Nov/Dec 2014) 17. Explain the time invariant two path model of a wireless propagation channel. (Nov/Dec 2016) 18. In free space propagation describe how the signals are affected by reflection, diffraction and scattering. (April/ May 2016) 19. Describe small scale fading and derive the expressions for parameters of mobile multipath channels.(Nov/Dec 2018)

PART C:

1. Explain Okumura-Hata empirical and Nakagamimodel in detail. 2. (i) Explain on path loss estimation techniques using path loss models. (ii)Describe on Ricean Distribution. 3. In free space propagation describe how the signals are affected by reflection, diffraction and scattering. (May/June 2016) 4. Consider a transmitter which radiates a sinusoidal carrier frequency of 1850MHz. Forvehicle moving 60 mph, compute the received carrier frequency if the mobile is moving directly toward the transmitter. 5. Determine the proper spatial sampling interval required to make small scale propagation measurements which assume that consecutive samples are highly correlated in time. How many samples will be required over 10m travel distance if fc = 1900MHz and v=50m/s. how long would it take to make these measurements, assuming they could be made in real time from a moving vehicle. What is the Doppler spread BD for the channel. 6. Analyze and compare the error performance in fading channels with and without diversity reception techniques. (Nov/Dec 2017) 7. Determine the error probability for different fading channels with diversity reception.

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UNIT II CELLULAR ARCHITECTURE 1. What is meant by frequency reuse?(April/May 2018)(Nov/Dec 2017) If an area is served by a single Base Station, then the available spectrum can be divided into N frequency channels that can serve N users simultaneously. If more than N users are to be served, multiple BSs are required, and frequency channels have to be reused in different locations. Since spectrum is limited, the same spectrum has to be used for different wireless connections in different locations. This method of reusing the frequency is called as frequency reuse.

2. What are the trends in cellular radio systems? The trends in personal cellular radio systems are: i. PCS – Personal Communication Services ii. PCN – Personal Communication Networks

3. What do you mean by forward and reverse channel? Forward channel is a radio channel used for transmission of information from base station to mobile. Reverse channel is a radio channel used for transmission from mobile to base station.

4. What is the function of control channel? What are the types? The function of control channel is to transmit call setup, call request, call initiation and Control. There are two types of control channels, i. Forward control channel ii. Reverse control channel

5. What is channel assignment? What are the types? For efficient utilization of radio spectrum a frequency reuse scheme with increasing capacity and minimizing interference is required. For this channel assignment is used. The types of channel assignment are: i. Fixed channel assignment ii. Dynamic channel assignment.

6. What is fixed channel assignment? If the channels in each cell are allocated to the users within the cell, it will be called as fixed channel assignment. If all channels are occupied, the call will be blocked.

7. What is dynamic channel assignment? If the voice channels are not allocated permanently in a cell, it will be called as dynamic channel assignment. In this assignment, channels are dynamically allocated to users by the MSC.

8. Define MS, BS and MSC. MS – Mobile station. A station in the cellular radio service intended for use. BS – Base Station. A fixed station in a mobile radio system used for radio communication with MS. MSC – Mobile Switching Centre. Mobile switching centre coordinates the routing of calls in large service area. It connects the base station and mobiles to PSTN. It is also called as MTSO (Mobile telephone switching office. 9. Write the types of hand off. Types of handoff are: i. Hard hand off – Mobile monitors BS and new cell is allocated to a call with strong signal. ii. Soft hand off – MS with 2 or more calls at the same time and find which is the strongest signal BS, the MSC automatically transfers the call to that BS.

10. Define hand off and mode of hand off.(May/June 2016) A handoff refers to the process of transferring an active call or data session from one cell in a Wireless Communication, Prepared by P.Poornima AP/ECE Page 7

cellular network to another or from one channel in a cell to another. A well- implemented handoff is important for delivering uninterrupted service to a caller or data session user. Modes of hand off are: i. MCHO – Mobile Controlled Hand off ii. NCHO – Network Controlled Hand off iii. MAHO – Mobile Assisted Hand off

11. Define Cell, Cluster. For a large geographic coverage area, a high powered transmitter therefore has to be used. But a high power radio transmitter causes harm to environment. Mobile communication thus calls for replacing the high power transmitters by low power transmitters by dividing the coverage area into small segments, called cells. Each cell uses a certain number of the available channels and a group of adjacent cells together use all the available channels. Such a group is called a cluster.

12. What do you mean by foot print and dwell time? The region over which the signal strength lies above this threshold value x dB is known as the coverage area of a BS and it must be a circular region, considering the BS to be isotropic radiator. Such a circle, which gives this actual radio coverage, is called the foot print of a cell. The time over which a call may be maintained within a cell without hand off is called the dwell time.

13. What are the major types of cellular interference? The major types of cellular interferences are as follows i. CCI – Co-channel interference is the interference between signals from co-channel cells. ii. ACI – Adjacent channel interference resulting from signals which are adjacent in frequency to the desired signal.

14. What are the techniques used to expand the capacity of cellular system? Cell splitting, Sectoring, Coverage Zone approaches are the techniques used to expand the capacity of cellular system. Cell splitting – Cell-splitting is a technique which has the capability to add new smaller cells in specific areas of the system. i.e. divide large cell size into small size. Sectoring – use of directional antennas to reduce Co-channel interference. Coverage Zone approaches – large central BS is replaced by several low power transmitters on the edge of the cell.

15. What is frequency reuse ratio? If the cell size and the power transmitted at the base stations are same then co-channel interference will become independent of the transmitted power and will depend on radius of the cell (R) and the distance between the interfering co-channel cells (D). If D/R ratio is increased, then the effective distance between the co-channel cells will increase and interference will decrease. The parameter Q is called the frequency reuse ratio and is related to the cluster size. For hexagonal geometry

Q=D/R = From the above equation, small of `Q' means small value of cluster size `N' and increase in cellular capacity.

16. Define FDMA, TDMA and CDMA.(April/May 2018) FDMA - the total bandwidth is divided into non-overlapping frequency sub bands. TDMA – divides the radio spectrum into time slots and in each slot only one user is allowed to either transmit or receive. CDMA – many users share the same frequency same tome with different coding.

17. Define Grade of service.(Nov/Dec 2016) Grade of service is defined as the measure of the ability of a user to access a trunked system

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during the busiest hour.

18. What is blocked call clear system (BCC)? In a system, a user is blocked without access by a system when no channels are available in the system. The call blocked by the system is cleared and the user should try again .This is called BCC system.

19. What is blocked call delay system? If a channel is not available immediately, the call request may be delayed until a channel becomes available. This is called as blocked call delay system.

20. Define cell splitting. Cell splitting is the process of subdividing congested cells into smaller cells each with its own base stations and a corresponding reduction in antenna height and transmitter power. It increases the capacity of cellular system. 21. What is sectoring? Sectoring is a technique for decreasing co-channel interference and thus increasing the system performance by using directional antennas.

22. What are the features of TDMA? Features of TDMA are: i. TDMA shares a single carrier frequency with several users, where each user makes use of non overlapping time slots. ii. Data transmission occurs in bursts. iii. Handoff process is much simpler iv. Duplexers are not required, since transmission and reception occurs at different time slots.

23. What are the features of FDMA? Features of FDMA are: i. FDMA channel carries only one phone circuit at a time ii. The bandwidth of FDMA channels is relatively narrow as each channel supports only one circuit per carrier.

24. What are the different types of multiple access schemes? (Dec 2013) (May 2016). FDMA-Frequency division multiple access-different frequencies are assigned to different users TDMA-Time division multiple access-different time slots are assigned to different users. CDMA- Code division multiple access-each user is assigned a different code.

25. What are the disadvantages of FDMA? 1. Sensitivity to fading 2. Sensitivity to random frequency modulation 3. Inter modulation 26. What are the advantages of FDMA? The transmitter and receiver require much less digital signal processing, Synchronization is simple.

27. Define SAMA. Spread Aloha Multiple Access is a combination of CDMA and TDMA. The CDMA better suits for connection oriented services only and not for connection less burst data traffic because it requires to program both sender and receiver to access different users with different codes.

28. Define CDMA.(April/May 2018) Code Division Multiple Access systems use codes with certain characteristics to separate different users. To enable access to the shared medium without interference. The users use the same frequency and time to transmit data. The main problem is to find good codes and to separate this signal from noise. The good code can be found the following 2 characteristics 1.Orthogonal. 2. Autocorrelation.

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29. What is SDMA? Space Division Multiple Access (SDMA) is used for allocating separated spaces to users in wireless networks. The basis for the SDMA algorithm is formed by cells and sectorized antennas which constitute the infrastructure implementing space division multiplexing (SDM).

30. What is FDD? In FDMA, the base station and the mobile station establish a duplex channel. The two directions, mobile station to base station and vice versa are separated using different frequencies. This Scheme is called Frequency Division Duplex (FDD)

31. What limits the number of user in TDM and FDM compared to CDM? The code space is huge compared to the frequency space and time space. Because of the limited time space and frequency space, the number of user in TDM and FDM are limited.

32. How does near and far effect influence CDMA? What are counter measurements? The near and far effect is a server problem of wireless networks using CDM. All signals should arrive at the receiver with more or less the same strength. Precise power control is needed to receive all senders with the same strength at a receiver.

33. Define FCA and DCA. Allocating a fixed frequencies for a channel is called as Fixed channel Allocation (FCA). In Dynamic Channel Allocation (DCA) scheme frequencies can only be borrowed, but it is also possible to freely allocate frequencies to cells. With dynamic assignment of frequencies to cells, the danger of the interference with cells with same frequency exists. Thus the borrowed frequencies in the surroundings cells can be blocked.

34. What is guard space? Guard spaces are needed to avoid frequency band overlapping is also called channel interference.

35. When handoff occurs? Hand-off occurs when a received signal from its serving cell becomes weak and another cell site can provide a stronger signal to the mobile subscriber. If the new cell-site has some free voice channels then its assigns one of them to the handed-off call.

36. Differentiate soft and hard handoff. (May 2016). Hard handoff mode is characterized by a mobile having a radio link with only AP at any time. Thus, the old connection is terminated before a new connection is activated. This mode of operation is referred to as break before make. In Soft handoff, the mobile can simultaneously communicate with more than one AP during the handoff. This new connection is made before breaking the old connection, and is referred to as make before break.

37. What is the function of Medium Access Control Layer? The functions of Medium Access Control Layer are responsible for stablishes, maintains, and releases channels for higher layers by activating and deactivating physical channels.

38. What are the 2 sub layers in DLC? Logical Link Control (LLC), Media Access Control (MAC)

39. Define traffic multi frame and control multi frame? The periodic pattern of 26 slots occurs in all TDMA frames with a TCH. The combination of these frames is called traffic multi frame TDMA frames containing data for the other logical channels are combined o a control multi frame.

40. What is the function of Medium Access Control Layer? Wireless Communication, Prepared by P.Poornima AP/ECE Page 10

The functions of Medium Access Control Layer which are responsible for establishes, maintains, and releases channels for higher layers by activating and deactivating physical channels.

41. What is orthogonality? Orthogonality means if we have “n” users and n-bit sequences, then a set of vectors in n-space are orthogonal if any point in n-space may be expressed as only linear combination of these vectors. CDMA is a communication technique that allows multiple users to communicate over one frequency. This is achieved through the use of spreading codes, whereby a single data bit is spread over a longer sequence of transmitted bits. These codes known as chip sequence, must be carefully chosen so that data may be correctly despread at the receiver. Such codes are known as orthogonal codes.

42. Define Set-up time. The time required to allocate a trunked radio channel to a requesting user.

43. What is a blocked call? Call which cannot be completed at time of request, due to congestion. Also referred to as lost call.

44. Define Holding-time. Average duration of a typical call. Denoted by „H‟ (in seconds).

45. State advantages of CDMA over FDMA? (Nov/Dec2014)(Nov/Dec2016) CDMA technology has bandwidth thirteen times efficient than FDMA and forty times efficient than analog systems. CDMA also have better security and higher data and voice transmission quality because of the spread spectrum technology it uses, which has increased resistance to multipath distortion. CDMA has greater coverage area when compared to FDMA. The main advantage of the CDMA is that, in the single detection method it is more flexible than FDMA or joint detection. CDMA is said to have higher capacity than FDMA.

46.Define co-channel reuse ratio? (Nov/Dec2015) Co-channel reuse ratio Q is given as Q = D/R, D – is the distance between centers of cells, R – radius of the hexagonal cell

47. Define Grade of Service? (Nov/Dec2015) Grade of Service in Wireless communication can be defined as ability of the user to connect on a call when the cell is being used by multiple users. It can be given by the ratio of number of blocked calls to the number of offered calls. 48.Write down the features of cellular concept?(Nov/Dec 2018) The cellular concept was a major breakthrough in solving the problem of spectral congestion and user capacity. It offered very high capacity in a limited spectrum allocation without any major technological changes. The cellular concept is a system-level idea which calls for replacing a single, high power transmitter (large cell) with many low power transmitters (small cells), each providing coverage to only a small portion of the service area.

PART B:

1. Compare and Contrast the TDMA, FDMA and CDMA techniques. (May 2016) (June 2013). 2. Summarize the features of various multiple access techniques used in wireless mobile communication. State the advantages and disadvantages of each technique. (May/June 2016) 3. Explain the Channel Assignment and handoff Strategies in detail. (April/May 2018) (April/May 2017) 4. Explain in detail how to improve coverage and channel capacity in cellular system. (May/June 2016) 5. Describe the Operations of Cellular systems and Explain it steps with a neat sketch(June 2013) 6. Explain in detail about multiple accesses with collision avoidance scheme. Also explain the advantages of the same. (Nov/Dec 2013)

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7. Derive the expressions for cellular CDMA schemes for both noise limited and interference limited scenarios. (April/May 2017) 8. Explain about co-channel interference and adjacent channel interference. Describe the technique to avoid interference. (Nov/Dec 2016) 9. Explain the concept of cell planning with relevant diagrams and expressions. 10. Identify the channel capacity of TDMA in a cell system. (Nov/Dec 2017) 11. Explain the principle of cellular networks and various types of Handoff techniques. (Nov/Dec 2013) (Nov/Dec 2014) 12. Write a short notes on i) trunking ii) grade of service. (Nov/Dec 2017) 13. Illustrate Cellular Frequency Reuse with a neat sketch. 14. Discuss the technical challenges faced by the wireless communication. (May/June 2014) 15. How is hand-off in a cellular system implemented. Explain the different types of hands- offs(Nov/Dec 2018) 16. How can capacity of a cellular communication system be improved? Explain any two capacity expansion techniques.(Nov/Dec 2018) 17. Discuss the impact of interference in a cellular system and system capacity.(Nov/Dec 2018) PART C:

1. A spectrum of 33MHZ is allocated to a wireless FDD cellular system which uses two 25KHZ simplex channels to provide full duplex voice and control channels, compute the number of channels available per cell if a system uses ( a)four-cell reuse (b)seven-cell reuse ,and (c)12-cell reuse. If 1MHZ of the allocated spectrum is dedicated to control channels, determine an equitable distribution of control channels and voice channels in each cell for each of three systems. 2. If a signal to interference ratio of 15db is required for satisfactory forward channel performance of the cellular system, what is the frequency reuse factor and cluster size that should be used for maximum capacity if the pathloss exponent is (a) n=4 (b) n=3? Assume that there are six co-channel cells in the first tier and all of them are at the same distance from the mobile. Use suitable approximations. 3. Consider global system for mobile which is a TDMA/FDD system that uses 25MHz for the forward link, which is broken into radio channels of 200MHz. If 8 speech signals are supported on a single radio channel and if no guard band is assumed, find the number of simultaneous users that can be accommodated in GSM. 4. If GSM uses a frame structure where each frame consists of 8 time slots, and each time slot contains 156.25 bits, and data is transmitted at 270.833 Kbps, in the channel, find (1) the time duration of a bit (2) the time duration of a slot (3) the time duration of a frame and (4) how long must a user occupying a single time slot wait between two successive transmissions. 5. Explain the various methods that increase the channel capacity and coverage. (April/May 2016)

UNIT III DIGITAL SIGNALLING FOR FADING CHANNELS

1. List the advantages of digital modulation techniques. The advantages of digital modulation techniques are: i. Immunity to channel noise and external interference. ii. Flexibility operation of the system. iii. Security of information. iv. Reliable since digital circuits are used. v. Multiplexing of various sources of information into a common format is possible. vi. Error detection and correction is easy.

2. Define power efficiency and bandwidth efficiency. Power efficiency describes the ability of a modulation technique to preserve the fidelity of the digital message at low power levels. ɳp = Eb/N0 = Bit energy / Noise power spectral density Ability of a modulation scheme to accommodate data within a limited bandwidth is called bandwidth efficiency. ɳB = R/B = Data rate / Bandwidth in bps/Hz

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3. What is QPSK? The Quadrature Phase Shift Keying (QPSK) is a 4-ary PSK signal. The phase of the carrier in the QPSK takes 1 of 4 equally spaced shifts. Two successive bits in the data sequence are grouped together. 1 symbol = 2 bits This reduces bit rate and bandwidth of the channel. Coherent QPSK = 2 x coherent BPSK system The phase of the carrier takes on one of four equally spaced values such as π/4, 3π/4, 5π/4 and 7π/4.

4. Define offset QPSK and π/4 differential QPSK. In offset QPSK the amplitude of data pulses are kept constant. The time alignment of the even and odd bit streams are offset by one bit period in offset QPSK. In π/4 QPSK, signaling points of the modulated signal are selected from two QPSK constellations which are shifted by π/4 with respect to each other. It is differentially encoded and detected so called π/4 differential QPSK.

5. What is meant by MSK? A continuous phase FSK signal with a deviation ratio of one half is referred to as MSK. It is a spectrally efficient modulation scheme.

6. List the salient features of MSK scheme. Salient features of MSK are: i. It has constant envelope, smoother waveforms than QPSK. ii. Relatively narrow bandwidth. iii. Coherent detection suitable for satellite communications. iv. Side lobes are zero outside the frequency band, so it has resistance to co- channel interference.

7. Why GMSK is preferred for multiuser, cellular communication?(Nov/Dec 2018) It is a simple binary modulation scheme. Premodulation is done by Gaussian pulse shaping filter, so side lobe levels are much reduced. GMSK has excellent power efficiency and spectral efficiency than FSK. For the above reasons GMSK is preferred for multiuser, cellular communication.

8. How can we improve the performance of digital modulation under fading channels? By the using of diversity technique, error control coding and equalization techniques performance of the digital modulation under fading channels are improved.

9. Write the advantages of MSK over QPSK.(April/May 2017) Advantages of MSK over QPSK: i. In QPSK the phase changes by 90degree or 180 degree .This creates abrupt amplitude variations in the waveform, Therefore bandwidth requirement of QPSK is more filters of other methods overcome these problems , but they have other side effects. ii. MSK overcomes those problems. In MSK the output waveform is continuous in phase hence there are no abrupt changes in amplitude.

10. Define M-ary transmission system? In digital modulations instead of transmitting one bit at a time, two or more bits are transmitted simultaneously. This is called M-ary transmission.

11. What is quadrature modulation? Sometimes two or more quadrature carriers are used for modulation. It is called quadrature modulation.

12. What is QAM?

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At high bit rates a combination of ASK and PSK is employed in order to minimize the errors in the received data. This method is known as “Quadrature Amplitude Modulation”.

13. Define QPSK QPSK is defined as the multilevel modulation scheme in which four phase shifts are used for representing four different symbols.

14. What is linear modulation? In linear modulation technique the amplitude of the transmitted signal varies linearly with the modulating digital signal. In general, linear modulation does not have a constant envelope.

15. Define non linear modulation. In the non linear modulation the amplitude of the carrier is constant, regardless of the variation in the modulating signals. Non-linear modulations may have either linear or constant envelopes depending on whether or not the baseband waveform is pulse shaped.

16. What is the need of Gaussian filter? Need for Gaussian Filter: i. Gaussian filter is used before the modulator to reduce the transmitted bandwidth of the signal. ii. It uses less bandwidth than conventional FSK.

17. Mention some merits of MSK. Merits of MSK: i. Constant envelope ii. Spectral efficiency iii. Good BER performance iv. Self-synchronizing capability v. MSK is a spectrally efficient modulation scheme and is particularly attractive for use in mobile radio communication systems.

18. Give some examples of linear modulation. Examples of linear modulation: i. Pulse shaped QPSK ii. OQPSK

19. What are the techniques used to improve the received signal quality? Techniques such as, following are used to improve the received signal quality.  Equalization  Diversity  Channel coding

20. What is the need of equalization?(Nov/Dec 2017) Equalization can be used to compensate the Inter Symbol Interference created by multipath within time dispersion channel.

21. What is diversity?(Nov/Dec 2013) Diversity is used to compensate the fading channel impairments and is usually implemented by using two or more receiving antennas. Diversity improves transmission performance by making use of more than one independently faded version of the transmitted signal.

22. Define spatial diversity.(Nov/Dec 2017) The most common diversity technique is spatial diversity, whereby multiple antennas are

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strategically spaced and connected to a common receiving system. While one antenna sees a signal null, one of the other antenna may sees a signal peak, and the receiver is able to select the antenna with the best signals at any time.

23. Define STCM.(Nov/Dec 2017) Channel coding can also be combined with diversity a technique called Space- Time Coded Modulation. The space-time coding is a bandwidth and power efficient method for wireless communication.

24. Define adaptive equalization?(May/June 2016) To combine Inter Symbol Interference, the equalizer coefficients should change according to the channel status so as to break channel variations. Such an equalizer is called an adaptive equalizer since it adapts to the channel variations.

25. Define training mode in an adaptive equalizer? First, a known fixed length training sequence is sent by the transmitter then the receivers equalizers may adapt to a proper setting of minimum bit error detection where the training sequence is a pseudo random binary signal or a fixed and prescribed bit pattern.

26. What is tracking mode in an adaptive equalizer? Immediately following this training sequence the user data is sent and the adaptive equalizer at the receiver utilizes a recursive algorithm to evaluate the channel and estimate filter coefficients to compensate for the distortion created by multipath in the channel.

27. Write a short note on linear equalizers and non linear equalizers?(Nov/Dec 2016) Linear equalizers: If the output d(t) is not used in the feedback path to adapt the equalizer. This type of equalizers is called linear equalizer. Nonlinear equalizers: If the output d(t) is fed back to change the subsequent outputs of the equalizers is called non linear equalizers.

28. Why non linear equalizers are preferred? The linear equalizers are very effective in equalizing channels where ISI is not severe. The severity of the ISI is directly related to the spectral characteristics. In this case that there are spectral noise in the transfer function of the effective channel, the additive noise at the receiver input will be dramatically enhanced by the linear equalizer. To overcome this problem non linear equalizers are used.

29. What are the nonlinear equalization methods used? Commonly used non linear equalization methods are: i. Decision feedback equalization ii. Maximum likelihood symbol detection iii. Maximum likelihood sequence estimation

30. What are the factors used in adaptive algorithms? Rate of convergence Mis adjustments Computational complexity

31. Define diversity concept. If one radio path undergoes a deep fade, another independent path may have a strong signal. By having more than one path to select from, both the instantaneous and average SNRs at the receiver may be improved often by as much as 20dB to 30dB. The principle of diversity is to ensure that the same information reaches the receiver on statistically independent channels.

33. Define modulation. It is defined as the process by which some parameters of a high frequency s g al termed as carrier,

Wireless Communication, Prepared by P.Poornima AP/ECE Page 15 is varied in accordance with the signal to be transmitted.

34. What is demodulation? It is the process of recovering the original modulating signal from a modulated signal.

35. Write the advantages of digital over analog modulation. Greater noise immunity, Robustness to channel impairments, Easier multiplexing of various forms of information, Greater security.

36. What is meant by Amplitude shift keying? If amplitude of the carrier is varied depending on the incoming digital signal, then it is called Amplitude shift keying.

37. What is meant by Frequency shift keying? If the frequency of the sinusoidal carrier frequency is varied depending on the incoming digital signal, then it is called Frequency shift keying.

38. What is meant by Phase shift keying? If phase of the carrier is varied depending on the input digital signal, then it is called phase shift keying.

39. Define M-ary transmission system, In digital modulation instead of transmitting one bit at a time, two or more bits are transmitted simultaneously. This is called M-ary transmission.

40. What is Quadrature modulation? Sometimes two or more Quadrature carriers are used for modulation. It is called Quadrature modulation.

41. Explain the following terms a) Baud rate b) Bit rate Baud rate: Speed at which symbols are transmitted in a digital communication system, i.e. no of symbols/second. Bit rate: Speed at which data bits is transmitted in a digital communication system, i.e. no of bits/sec.

42. What is QAM? At high bit rates, a combination of ASK and PSK is employed in order to minimize the errors in the received data. This method is known as Quadrature amplitude modulation.

43. What is meant by QPSK? QPSK is a multi-level modulation in which four phase shifts are used for representing four different symbols.

44. What is linear modulation? In linear modulation technique, the amplitude of the transmitted (carrier) signal varies linearly with the modulating digital signal. In general, linear modulation does not have a constant envelope.

45. Write the merits of linear modulation. Bandwidth efficient, Very attractive for use in wireless communication systems, Accommodate more and more users within a limited spectrum.

46. What is nonlinear modulation? In nonlinear modulation, the amplitude of the carrier is constant regardless of the variation in the modulating signal.

47. Mention the merits and demerits of nonlinear modulation.

Merits:

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a. Lower efficient class c amplifiers can be used without introducing degradation in the spectrum occupancy of the transmitted signal. b. Low out of band radiation of the order of -60dB to -70dB can be achieved. c. Limiter-discriminator detection can be used, which simplifies receiver design and provides high immunity against random FM noise and signal fluctuations due to Rayleigh fading.

Demerits: a. Constant envelope modulations occupy a larger bandwidth than linear modulation scheme b. In situations where bandwidth efficiency is more important than power efficiency, constant Envelope modulation is not well suited.

48. What is the advantage of MSK over QPSK? In QPSK the phase changes by 90 or 180 degrees. This creates abrupt amplitude variations in the waveform. Therefore bandwidth requirement of QPSK is more. MSK overcomes this problem. In MSK, the output waveform is continuous in phase hence there are no abrupt changes in amplitude.

49. Why MSK is called as fast FSK? (May 2016). MSK is called fast FSK, as the frequency spacing used is only half as much as that used in conventional non- coherent FSK.

50. Mention some merits of MSK. Constant envelope, Spectral efficiency, Good BER performance, Self-synchronizing capability

51. Why MSK cannot be directly used in multi user communications? 1. The main lobe of MSK is wide. This makes MSK unsuitable for the applications where extremely narrow bandwidths and sharp cut-offs are required. 2. Slow decay of MSK power spectral density curve creates adjacent channel interference. Hence MSK cannot be used for multiuser communications.

52. What is the need of Gaussian filter? (Dec 13) Gaussian filters used before the modulator to reduce the transmitted bandwidth of the signal. It uses less bandwidth than conventional FSK.

53. Define M-ary FSK. In M-ary system, M=2N different symbols are used and N no of bits per symbol. Every symbol uses separate frequency for transmission.

54. Mention any two criteria for choosing a modulation technique for a specific wireless application? (May/June 2013) The spectral efficiency of the modulation format should be as high as possible. This can best be achieved by a higher order modulation format. This allows the transmission of many data bits with each symbol. Adjacent channel interference must be small. This entails that the power spectrum of the signal should show a strong roll-off outside the desired band. Furthermore, the signal must be filtered before transmission.

55. Define cyclic prefix.(April/May 2018)(Nov/Dec 2016) In OFDM, delay dispersion leads to a loss of orthogonality between the subcarriers and thus leads to Inter Carrier Interference (ICI). These negative effects can be eliminated by a special type of guard interval called the cyclic prefix.

56. Define Windowing.(May 2016). Windowing is a technique proposed to help reduce sensitivity to frequency offsets in an OFDM system. This process involves cyclically extending the time domain signal with each symbol by „v‟ samples. The resulting signal is then shaped with a window function.

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57. Define PAPR.(Nov/Dec 2018)(Nov/Dec 2017) The peak to average power ratio PAPR is an important attribute of a communication system. A low PAPR allows the transmit power amplifier to operate efficiently, where as a high PAPR forces the transmit power amplifier to have a large back off in order to ensure linear amplification of the signal. 58.What is the advantage of OFDM?(April/May2017) Immunity to selective fading Resilience to interference Spectrum efficiency Resilient to ISI Resilient to narrow-band effects Simpler channel equalisation

PART B

1. Explain QPSK transmitter and receiver with signal space diagram and give an expression for spectral efficiency. (Nov/Dec 2013)( Nov/Dec 2014) 2. Explain π/4 Differential QPSK & OQPSK transmitter and receiver with signal space diagram and give an expression for spectral efficiency. (May/June 2013) (April/May 2016). 3. Derive the bit error rate for binary phase shift keying modulation for frequency flat fading channels. (April/May 2018) 4. Explain BFSK transmitter and receiver with signal space diagram and give an expression for spectral efficiency.( Nov/Dec 2014) 5. Explain MSK transmitter and receiver with signal space diagram and give an expression for spectral efficiency. (June 2013), (Nov/Dec 2015) 6. What is offset QPSK? What is the advantage? Describe the offset-QPSK scheme. 7. Discuss about the performance of digital modulation in fading channels. (Nov/Dec 2013) 8. Explain the Nyquist criterion for ISI cancellation. (Nov/Dec 2013) 9. Importance of MSK in wireless communication system(Nov/Dec 2018) 10. Explain in detail about OFDM modulation technique with necessary diagrams.List out its advantages and disadvantages(Nov/Dec 2018) (April/May 2018) 11. Prove the OFDM system converts the delay spread channel into a set of parallel fading channels, using the concept of cyclic prefix. (April/May 2018) 12. (i) Describe with a block diagram π/4 Quadrature phase shift keying and its advantages. (ii)What is MSK? Explain its power spectral density. (Dec 2014) 13. Describe with neat diagram the modulation technique of QPSK. (Nov/Dec 2017) 14. List the advantages and applications of BFSK. (Nov/Dec 2017) 15. Explain the principle of MSK modulation and derive the expression for power spectral density. (Nov/Dec 2017)

PART C

1. With neat diagrams explain the modulation and demodulation of π/4 DQPSK modulation technique. (April/May 2018) 2. A 880 MHz carrier signal is frequency modulated using a100 kHz sinusoidal modulating waveform. The peak deviation of the FM signal is 500 kHz. If this FM signal is received by a super heterodyne receiver having an IF frequency of 5MHz, determine the IF bandwidth necessary to pass the signal. 3. Demonstrate the generation, deduction and bit error probability of QPSK scheme. 4. Examine the principle of MSK modulation and derive the expression for power spectral density. 5. Explain GMSK transmitter and receiver with signal space diagram and give an expression for spectral efficiency. (Nov/Dec 2015) (April/May 2016)

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UNIT IV MULTIPATH MITIGATION TECHNIQUES

1. What are the techniques used to improve the received signal quality? Equalization, Diversity and Channel coding

2. What are the factors used in adaptive algorithms? Rate of convergence, Misadjustment, Computational complexity and numerical properties.

3. What is the need of equalization? Equalization is used to compensate the inter-symbol interference created by multipath within time dispersion channel.

4. Write the functions of diversity. (Nov/Dec 2013) i. Diversity is used to compensate for fading channel impairments, and is usually implemented by using two or more receiving antennas. ii. Diversity improves transmission performance by making use of more than o e independently faded version of the transmitted signal.

5. Define spatial diversity.(Nov/Dec 2017) The most common diversity technique is called spatial diversity, whereby multiple antennas are strategically spaced and connected to a common receiving system. While one antenna sees a signal null, one of the other antennas may see a signal peak, and the receiver is able to select the antenna with the best signals at any time.

6. What is equalizer? (Nov/Dec 2013) The device which equalizes the dispersive effect of a channel is referred to as an equalizer.

7. What are the operating modes available in an adaptive equalizer? Training and tracking modes.

8. Define adaptive equalizer. (April/May 2016). To combat ISI, the equalizer coefficients should change according to the channel status so as to track the channel variations. Such an equalizer is called an adaptive equalizer since it adapts to the channel variations.

9. What is training mode in an adaptive equalizer? First, a known fixed length training sequence is sent by the transmitter, then the receiver's equalizer may adapt to a proper setting of minimum bit error rate detection, where the training sequence is pseudorandom binary signal or a fixed and prescribed bit pattern.

10. What is tracking mode in an adaptive equalizer? Immediately following the training sequence, the user data is sent, and the adaptive equalizer at the receiver utilizes a recursive algorithm to evaluate the channel and estimate filter coefficients to compensate for the distortion created by multipath in the channel.

11. Write a short note on i) linear equalizers ii) non-linear equalizers(Nov/Dec 2018) If the output is not used in the feedback path to adapt, then this type of equalizer is called linear equalizer. If the output is fed back to change the subsequent outputs of the equalizer, this type of equalizer is called nonlinear equalizers.

12. Write the advantages of lattice equalizer. It is simplest and easily available, Numerical stability, Faster convergence, Unique structure of the lattice filter allows the dynamic assignment of the most effective length of the lattice equalizer and When the channel becomes more time dispersive, the length of the equalizer can be increased by the algorithm without stopping the operation of the equalizer.

13. Why nonlinear equalizers are preferred? Wireless Communication, Prepared by P.Poornima AP/ECE Page 19

The linear equalizers are very effective in equalizing channels where ISI is not severe. The severity of ISI is directly related to the spectral characteristics. In this case there are spectral nulls in the transfer function of the effective channel; the additive noise at the receiver input will be dramatically enhanced by the linear equalizer. To overcome this problem, nonlinear equalizers can be used.

14. What are the nonlinear equalization methods used? Decision feedback equalization (DFE), Maximum likelihood symbol detection and Maximum likelihood sequence estimation (MLSE).

15. Where DFEs are used? DFE is particularly useful for channels with severe amplitude distortions and is widely used in wireless communications.

16. Define rate of convergence. The no of iterations required for the algorithm in response to stationary inputs to converge close enough to the optimum solution.

17. Write the advantages of LMS algorithm. It maximizes the signal to distortion at its output within the constraints of the equalizer filter length, Low computational complexity and Simple program

18. What is the need for diversity schemes? To increase signal to noise ratio, for error free digital transmission, to degrade the bit error probability.

19. Explain Diversity concept. If one radio path undergoes a deep fade, another independent path may have a strong signal. By having more than one path to select from, both the instantaneous and average SNRs at the receiver may be improved.

20. List out the four types of combining methods. Selection combining, switched combining, Equal gain comb i g, Maximum ratio combining.

21. Differentiate between Macrodiversity and Microdiversity. (Dec 2014)

Macrodiversity Microdiversity In antenna (or micro) diversity the signal from antennas mounted at separate locations are In site (or macro) diversity the receiving combined antennas are located at different receiver sites

Signals from within a cell may be received at These antennas are located on the vehicle or at the the different corners of the hexagonal ar a. same base station tower and their spacing is a few The advantage is that not only the multipath wavelengths. The received signal amplitude is fading attenuation is independent at each correlated, depending on the antennas separation d branch but that the shadowing and path relative to the wavelength. losses are also uncorrelated to some extent

22. What are the benefits of Rake Receiver? (April/May 2016). 1. Rake receiver gives the best performance among all the CDMA receivers. 2. Since correlators form the main working system of the receiver. The best version of the received signal is selected and given as output.

23. State the principle of diversity.(June 2013) Diversity: It is the technique used to compensate for fading channel impairments. It is implemented

Wireless Communication, Prepared by P.Poornima AP/ECE Page 20 by using two or more receiving antennas. While Equalization is used to counter the effects of ISI, Diversity is usually employed to reduce the depth and duration of the fades experienced by a receiver in a flat fading channel. These techniques can be employed at both base station and mobile receivers. Spatial Diversity is the most widely used diversity technique.

24. Draw the structure of a linear transversal equalizer (Nov/Dec 2015)

25. How the link performance can be improved? Link performance can be improved by various techniques such as i. Equalization ii. Diversity iii. Channel coding

26. Why diversity and equalization techniques are used? To reduce ISI, Equalization technique is used. Diversity is used to reduce fading effects.

27. What is diversity? Signal is transmitted by more than one antenna via channel. It ensures that the same information reaches the receiver on statistically independent channels. 28. Define Switched Diversity If the signal level falls below the threshold, then the receiver switches to a new antenna which is called as switched diversity.

29. Differentiate selection diversity Combining Diversity.

Selection Diversity Combining Diversity The best signal is selected and processed All signals are combined before while all other signals are discarded. processing and the combined signal is decoded. Simple circuits are used. At individual receiver, phasing circuits are needed. None of the signal is not in acceptable It works well. SNR.

30. Define feedback or scanning diversity. All the signals are scanned in a fixed sequence until one signal is found to be above a predetermined threshold.

31. Define temporal diversity. Wireless propagation channel is time variant, so for sufficient decorrelation, the temporal distance

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between antennas must be atleast the half of maximum Doppler frequency.

32. What is meant by frequency diversity? Correlation is increased by transmitting information on more than one carrier frequency. Frequencies are separated by more than one coherence bandwidth of the channel. So the signals will not experience same fades. 33. What is transmit diversity? Diversity effect is achieved by transmitting signals from several transmit antenna.

34. What is an equalizer? Equalizer is a linear pulse shaping circuit which is used to reduce ISI.

PART B

1. Explain the classification of equalizers. 2. Analyze various diversity techniques used in wireless communication. (Nov/Dec 2017) 3. Briefly explain about linear and non-linear equalizers. (Dec 2013)(May 2016). 4. Discuss about DFE. 5. Explain the principles of RAKE receiver in detail. (April/May 2018) (April/May 2017)(Nov/Dec 2018) 6. Explain about MLSE equalizer.(Dec 2013) 7. Explain in detail various factors to determine the algorithm for adaptive equalizer. Also derive the least Mean Square algorithm for adaptive equalizer. (Nov/Dec 2016) 8. Discuss in detail about the different micro diversity concepts. (May 2016) 9. Explain about theoretical model for polarization diversity. 10. Derive an expression for performance improvement due to maximal ratio combining. (Nov/Dec 2017) 11. Describe in detail about i) Linear equalizers ii) Non linear equalizers (Nov/Dec 2017) 12. Discuss the performance of a RAKE receiver with a neat diagram.(Dec 2013) 13. Explain any two diversity techniques to combat small scale fading(June 2013)(Nov/Dec 2018) 14. With relevant diagrams explain Rake receiver. Also discuss how time diversity is achieved in a CDMA technique in Rake receiver. (Nov/Dec 2016) 15. Describe any two adaptation algorithms for Mean square error Equalizers(June 2013) 16. (i) With a neat block diagram explain the principle of Macrodiversity (ii)Explain the operation of an adaptive equalizer at the receiver side (Dec 2014) 17. (i) Explain with block diagram Maximal ratio combiner (ii) Describe on Polarization and space diversity. (Dec 2014) 18. Derive the mean square error for a generic adaptive equaliser (Dec 2015). 19. What is zero forcing equalizer algorithm. Explain.(Nov/Dec 2018)

PART C

1. Consider uncoded spatial multiplexing over a MIMO channel with MR>=MT. Show that ML, MMSE and ZF receivers perform equally well if the channel is orthogonal. What is the per stream SNR? 2. Describe the role played by equalization and diversity as multipath mitigation techniques. Compare and contrast these two techniques. (April/May 2017) 3. Discuss in detail the capacity of fading and non fading channels. (April/May 2017) 4. With valid statements, analytically prove that the adaptive equalizers exhibit superior performance over the conventional equalizers. (Nov/Dec 2017) 5. Consider the design of the US digital cellular equalizer, where f=900MHz and the mobile velocity v=80Km/hr, determine the maximum Doppler shift, the coherence time of the channel and the maximum number of symbols that could be transmitted without updating the equalizer assuming that the symbol rate is 24.3 k symbols/sec. 6. Assume four branch diversity is used, where each branch receives an independent Rayleigh fading signal. If the average SNR is 20dB, determine the probability that the SNR will drop below 10dB. Compare this with the case of single receiver without diversity.

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7. Describe the role played by equalization and diversity as multipath mitigation techniques. Compare and contrast these two techniques.

UNIT V MULTIPLE ANTENNA TECHNIQUES

1. What is Beamforming? The multiple antennas at the transmitter and receiver can be used to obtain array and diversity gain instead of capacity gain. In this setting the same symbol weighted by a complex scale factor is sent over each transmit antenna, so that the input covariance matrix has u it rank. This scheme is also referred to as MIMO beamforming.

2. What are the advantages of Beamforming? Beamforming provides diversity and array gain via coherent combining of the multiple signal paths.

3. What is multiplexing gain? Multiple antennas are used to improve wireless system performance. One option is to obtain capacity gain by decomposing the MIMO channel into parallel channels and multiplexing different data streams onto these channels. This capacity gain is also referred to as multiplexing gain.

4. Define Transmitter diversity. (April/May 2016). In transmit diversity there are multiple transmit antennas, and the transmit power is divided among these antennas. Transmit diversity is desirable in systems where more space, power and processing capability is available on the transmit side than on the receive side. Transmit diversity design depends on whether or not the complex channel gain is known to the transmitter.

5. What is RAKE receiver? A more complicated receiver can have several branches, with each branch synchronized to a different multipath component .This structure is called a RAKE receiver, and it assumes there is a multipath component at each integer multiple of a chip time.

6. Write the advantages of RAKE receiver. RAKE‟s provide a simple mechanism to obtain diversity benefits. When spread spectrum signalling is chosen for its other benefits such as multiuser or interference rejection capabilities.

7. Explain the concept of Rake receiver. In Multipath environment, if the multiple versions of the signal arrive more than one chip interval apart from each other. The receiver can recover the signal from multiple paths and then combine them with suitable delays. This method achieves better performance than simply recovering dominant signal and treating remaining signals as noise.

8. What are MIMO systems? (May 2016). Systems with multiple antennas at the transmitter and receiver, which are commonly referred to as multiple-input multiple-output (MIMO) systems. The multiple antennas can be used to increase data rates through multiplexing or to improve performance through diversity.

9. Draw the MIMO model.

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Mt transmit antenna and Mr receive antennas.

10. Write the advantages of MIMO systems. i. Multiple-input multiple-output systems can significantly enhance performance of wireless systems through multiplexing or diversity gain. ii. For a given transmit energy per bit, multiplexing gain provides a higher data rate whereas diversity gain provides a lower BER in fading. iii. Support a higher data rate for a given energy per bit, so it transmits the bits more quickly and can then shut down to save energy.

11. Write the disadvantages of MIMO systems. i. MIMO systems entail significantly more circuit energy consumption than their single antenna counterparts, because separate circuitry is required for each antenna signal path. ii. Signal processing associated with MIMO can be highly complex.

12. Mention the applications of MIMO systems. i. MIMO can reliably connect devices in home, such as computer networking devices, cabled video devices, phone lines, music, storage devices etc. ii. The IEEE 802.16e standard and the IEEE 802.11n standard also use MIMO system. iii. MIMO is used in mobile radio telephone standard such as 3GPP and 3GPP2 standard. iv. 3GPP High Speed Packet Access Plus (HSPA+) and Long Term Evolution (LTE) standard use MIMO. 13. How does spatial multiplexing work?(Nov/Dec 2016, 2017) Spatial multiplexing uses MEA‟s (Multiple element antennas) at the transmitter for transmission of data streams. An original high-rate datastream is multiplexed into several parallel streams, each of which is sent from one transmit antenna element. The channel mixes up these datastreams so that each of the receive antenna elements sees a combination of them.

14. State the importance of spatial multiplexing. The basic premise of spatial multiplexing is to send Mt independent symbols per symbol period using the dimensions of space and time. To obtain full diversity order, an encoded bit stream must be transmitted over all Mt transmit antennas. This can be done through serial encoding.

15. What is transmit diversity?(May/June 2016) In transmit diversity more antennas are used on the transmitter side than on the receiver side. Transmit diversity is used to reduce the effect of fading. In transmit diversity the same information is transmitted from two different antennas. Data from the second antenna is encoded differently to differentiate it from the first antenna. This can be done to able the user equipment on the receiver side to identify that the information is coming from the different locations and properly decode it. Space- time coding is used to create redundant signals.

16. What are smart antennas and MIMO systems? A MIMO system consists of several antenna elements, plus adaptive signal processing at both transmitter and receiver, the combination of which exploits the spatial dimension of the mobile radio channel. A smart antenna system is a system that has multiple antenna elements only at one link end.

17. What is array gain?(April/May 2018) Array gain is defined as the average increase in the SNR and depends on the number of transmit and receive antennas. Transmit/Receive array gain needs channel information in the transmitter and receiver respectively. Channel information is typically available in the receiver whereas the channel state information in the transmitter is more difficult to maintain in general.

18. What is diversity gain?(April/May 2018) Wireless Communication, Prepared by P.Poornima AP/ECE Page 24

Diversity is a powerful technique to reduce fading effect in wireless communications. Diversity gain is defined as the reduction in the probability of error due to multiple independent paths produced between the transmitter and receiver. In other words if there are M transmits, N receive antennas, the order of diversity is M.N. There is no diversity gain if the medium is line of sight channel.

19. What is multiplexing gain? Multiplexing gain is defined as the increase in the data rate; since independent data streams are send through independent paths between multiple transmitters and multiple receivers. In other words if there are M (> 1) transmit antennas and N (> 1) receive antennas, the increase in the data rate is min (M, N)-fold

20. What is meant by co-phasing? “Co-phase the signals” means that we need to multiply signals by ejɸi for some constant phase angle ɸi on channel i, so that the (otherwise random) phases of the signals on the different channels line up. If we don‟t co- phase the signals before combining them, we end up with the multipath fading problem signals sometimes add together destructively. Without co-phasing, the branch signals would not add up coherently in the combiner, so the resulting output could still exhibit significant fading due to constructive and destructive addition of the signals in all the branches.

21. Describe threshold combining. Selection combining for systems that transmit continuously may require a dedicated receiver on each branch to continuously monitor branch SNR. A simpler type of combining, called threshold combining, avoids the need for a dedicated receiver on each branch by scanning each of the branches in sequential order and outputting the first signal whose SNR is above a given threshold γT . As in SC, co-phasing is not required because only one branch output is used at a time. Hence this technique can be used with either coherent or differential modulation.

22. Define channel capacity of MIMO system. A very important factor for the profitability of a wireless networks is its capacity. MIMO system provides high capacity by using multiple antennas at both the transmitter and receiver end of the radio link. Multiple antennas are used to improve the capacity over SISO system when operated in multi- path environment. MIMO system capacity is me sured in bits per second per hertz and is bounded by Shannon Hartley capacity. But it has become app rent that MIMO system can exceed the Shannon Hartley limit of SISO depending on the channel properties and the number of antennas.

23. What is Precoding. Pre-coding is generalized to allow multi-layer transmission in MIMO systems. As conventional beamforming considers as linear single layer pre-coding , increasing the signal power at the output of the receiver by emitting the same signal from each of the transmit antennas with suitable weighting. When multiple antennas are used at the receiver, the signal level s ot maximized simultaneously at all of the multiple receive antennas, so in that case pre-coding is used for multi-layer beamforming to increase the throughput performance of a multiple receive antennas. In pre-coding the transmit antennas transmit the multiple streams with independent and suitable weighting per ach ante a such that higher link throughput is obtained at the receiver output.

24. What is Alamouti‟s scheme? Alamouti‟s scheme is designed for a digital communication system with two-antenna. Transmit diversity. The scheme works over two symbol periods and it is assumed that the Channel gain is constant over his time. Over the first symbol period, two different symbolsS1 and S2 (each with energy Es/2) are transmitted simultaneously from antennas 1 and 2, respectively. Over the next symbol period, symbol −S*2 is transmitted from antenna 1 and symbol S*1 is transmitted from antenna 2, each again with symbol energy Es/2.

25. What is Antenna Diversity? (Dec 2015) Antenna Diversity or Space Diversity or Spatial Diversity can be given as the diversity scheme

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followed in wireless communications to overcome multipath fading. More than one antenna are used for transmission and reception, and the main concept behind this method is the signals transmitted by different antennas undergo different fading and there is at least one robust version of the signal being received. This method requires more sophisticated hardware for synchronisation.

26. Write the two types of spread spectrum? Types of spread spectrum are: Direct Sequence Spread Spectrum (DS-SS) Frequency hop spread spectrum (FH-SS)

27. What do you mean by spread spectrum? Spread spectrum multiple access uses signals which have a transmission bandwidth whose magnitude is greater than the minimum required RF bandwidth. A pseudo noise (PN) sequence converts a narrowband signal to a wideband noise like signal before transmission

28. What is PN sequence? Pseudo noise sequence is a coded sequence of 1‟s and 0‟s with autocorrelation properties.

30. When is the PN sequence called as maximal length sequence?(Nov/Dec 2013) m When the pseudo-noise sequence generated by linear feedback shift register has the length (N) of 2 -1 where m is number of stages in shift register is called maximal length sequence. 31. Write the properties which a PN sequence should have. Properties of PN sequence are: i. Balance property ii. Run property iii. Correlation property

32. Define chip duration and chip rate. The duration of every bit in PN sequence is known as chip duration. The number of bits (chips) per second is called chip rate.

33. List the advantages and disadvantages of DS-SS.

Advantages of DS-SS: i. The performance of DS-SS in presence of noise is superior to FH-SS. ii. Good antijamming capability. iii. Low multipath interference. Disadvantages of DS-SS: i. Poor synchronization. ii. Requires large bandwidth. iii. Long acquisition time so that the system is slow.

34. Define jamming and jamming margin. Jamming is a multitone or powerful broad band noise. It is the ratio of the average interference power and the signal power. Jamming margin in dB as the difference between the processing gain in dB and minimum SNR in dB.

35. What is meant by anti-jamming? With the help of spread spectrum method, the transmitted signals are spread over the mid frequency band. Hence these signals appear as noise. Then it becomes difficult for the jammers to attack our signal. This method is called antijamming.

Wireless Communication, Prepared by P.Poornima AP/ECE Page 26

36. List the advantages and disadvantages of FH-SS. Advantages of FH-SS: i. High processing gain than DS-SS. ii. Shorter acquisition time makes the system fast. Disadvantages of FH-SS: i. FH-SS requires large bandwidth. ii. Circuit used for FH-SS is complex. Expensive frequency synthesizers are required.

37. List the types of FH-SS. Types of FH-SS are: i. Slow frequency hopping ii. Fast frequency hopping

38. Compare slow and fast FH-SS.

Slow FH-SS Fast FH-SS More than one symbol is transmitted per One symbol is transmitted with more than hop. one hops. Chip rate is equal to the symbol rate. Chip rate is equal to the hop rate. Same carrier frequency is used to One symbol is transmitted over multiple transmit one or more symbols. carriers in different hops. 39. State the principles of CDMA. Principles of CDMA: i. Many users share the same frequency. ii. Each user is assigned a different spreading code.

40. Compare DS-SS and FH-SS. DS-SS FH-SS PN sequence is multiplied with narrow Data bits are transmitted in different band signal. frequency slots which are changed by PN sequence. Modulation used is BPSK-coherent. Modulation used is M-ary FSK noncoherent. Faster than DS-SS. Fixed chip rate. Variable chip rate. Long acquisition time is required. Short acquisition time. Effect of distance is high. Effect of distance is less.

41. How the capacity can be increased in CDMA? Capacity in CDMA can be increased by i. Quiet periods during speech transmission is shared by many users. ii. Flexible data rate. iii. Soft capacity. iv. Error Correction coding used.

42. Write short notes on OFDM. OFDM splits the information into N parallel streams which are modulated by N distinct carriers and then transmitted. In order to separate the subcarriers by the receiver, they have to be orthogonal.

43. Why cyclic prefix? In delay dispersive channel, inter carrier interference occur. To overcome the effect of inter carrier interference and ISI, cyclic prefix is introduced. It is a cyclically extended guard interval

Wireless Communication, Prepared by P.Poornima AP/ECE Page 27

whereby each symbol sequence is preceded by a periodic extension of the sequence itself.

44. Write the goals of GSM standard. Better and more efficient technical solution for wireless communication. Single standard was to be realized all over Europe enabling roaming across borders.

45. What is W-CDMA? It is a 3G wireless standard for cellular telephony. It provides better efficiency, higher peak rates upto 2 Mbps. Bandwidth of 5 MHz. Supports multimedia applications.

46. What are the services offered by GSM? Services offered by GSM are: i. Telephone services ii. Bearer or Data services iii. Supplementary services 47.What is channel state information?(Nov/Dec 2018) In wireless communications, channel state information (CSI) refers to known channel properties of a communication link. This information describes how a signal propagates from the transmitter to the receiver and represents the combined effect of, for example, scattering, fading, and power decay with distance. The method is called Channel estimation

PART B

1. Briefly explain Multiple-input multiple output systems. 2. Explain Pre-coding and Beam forming.(Nov/Dec 2018) 3. Define Beam forming and briefly explain MIMO diversity gain. (April/May 2016) 4. Discuss transmit diversity with channel known at transmitter. 5. Distinguish between different beamforming techniques. (Nov/Dec 2017) 6. What is meant by MIMO systems? Explain the system model with necessary diagrams. (Nov/Dec 2017)(Nov/Dec 2018) 7. Discuss transmit diversity with channel unknown at transmitter – The Alamouti scheme. 8. Explain receiver diversity in detail.(Nov/Dec 2018) 9. Discuss receiver diversity with selection combining and threshold combining. 10. Explain in detail spatial multiplexing of a MIMO system. (May/June 2016) 11. Explain in detail how inherent delay in multi user system is overcome by beamforming. (May/June 2016) 12. Briefly discuss Maximal-Ratio combining and Equal-Gain combining. 13. Discuss the capacity of time-varying frequency-selective fading channels with respect to time- invariant channels and time-varying channels. 14.Discuss in detail the classification of algorithms for MIMO based system. (Nov/Dec 2016) 15.Explain parallel decomposition of the MIMO channel. 16.Explain the architectures of spatial multiplexing with neat diagram. (April/May 2016). 17.Determine the capacity of frequency selective fading and explain the concept of water filling/ water pouring models. (Nov/Dec 2015). 18.Explain with relevant diagrams the layered space time structure with respect to MIMO systems. (April/May 2016).

PART C

1. Prove that 2X2 MIMO system (without channel state information) at the transmitter provides the diversity gain of 4 and array gain of 2 using Alamouti scheme. (April/May 2018) 2. Discuss in detail the capacity in fading and non fading channels. (April/May 2017)(Nov/Dec 2018) 3. Write a brief outline about the impact of channel in MIMO systems. 4. Compare the capacity of a fading and a non fading channel for information transmitted from a wireless system.

Wireless Communication, Prepared by P.Poornima AP/ECE Page 28

5. What is the function of smart antennas and explain the various purposes of it. 6. Classify precoding schemes based on channel state information at transmitter and receiver sides . 7. Design the capacity for MIMO systems in flat fading channels and compare it with fading and non- fading channels. 8. Describe MIMO systems with emphasis on their requirement in a wireless communication environment. 9. Derive an expression for the capacity of the following systems. (i) SIMO system assuming that the channel is known at receiver. (ii) MISO system assuming that the channel is known at transmitter. (iii)MIMO system assuming that the channel is unknown at transmitter.

Wireless Communication, Prepared by P.Poornima AP/ECE Page 29

V.S.B ENGINEERING COLLEGE,KARUR

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

EC6802 WIRELESS NETWORKS

UNIT - I: WIRELESS LAN

PART – A (2 Marks)

1. What is infrared (IR) transmission?

Infrared light transmission is one of the important technologies used in wireless LAN. It is based on the transmission of infrared light at 900 nm wavelength. 2. What is the principle behind infrared technology? (N/D 2018)

Infrared technology uses diffuse light reflected at walls, furniture etc. Or directed light when line of sight (LOS) exists between sender and receiver. 3. What are the advantages of infrared technology? (N/D 2018)

Shielding is easy and no need for license for infrared technology.

Electrical devices do not interfere with infrared transmission. 4. What are the disadvantages of infrared transmission? (N/D 2018)

Low bandwidth

Cannot penetrate through walls or other obstacles. 5. Define – Spread Spectrum

Spread spectrum involves spreading the bandwidth needed to transmit data. The main advantage of using spread spectrum is the resistance to narrow interference. 6. What are the spread spectrum techniques?

There are two basic methods for spread spectrum transmissions.

Direct Sequence Spread Spectrum (DSSS) Frequency Hopping Spread Spectrum (FHSS) 7. What is the principle behind FHSS? Frequency Hopping Spread Spectrum is evolved in order to avoid jamming. Hence in this method, the transmitter shifts the center frequency of transmitted signal. The shifts in frequency or frequency hops, occur according to a random pattern is known only to the transmitter and receiver. 8. What are the major issues in WLAN? Two Major issues in WLAN are as follows Hidden station problem Exposed station prob

9. List out the applications of WLAN.

Transfer of medical images

Remote access to patient records

Remote monitoring of patients

Remote diagnosis of patients at home or in an ambulance

In telemedicine

Surveillance

Internet supporting database.

10. What is IEEE 802.11? (A/M 2018)

The IEEE 802.11 is the first WLAN standard that has secured the market in large extent. The primary goal of the standard was the specification of a simple and robust that offers time bounded and asynchronous services. 11. Define - Short Inter Frame Space (SIFS)

Short IFS is the shortest IFS used for the high priority frames like acknowledgement frames, CTS frames, poll response etc. 12. Define - Distributed coordination function Inter Frame Space (DIFS)

DCF-IFS is used for transmitting data frames. It is equal to SIFS plus two time slots and is the longest inter frame gap. 13. What are the functions of MAC layer in IEEE 802.11? (A/M 2018) The functions of MAC layer are  Media Access Control  Reliable delivery of data units  Management functions  Authentication encryption 14. What is the need for WATM?

WATM systems had to be designed for transferring voice, classical data, video, multimedia etc.

15. What is HIPERLAN?

The HIPERLAN stands for High PERformance Radio LAN is an initiation of RES-10 group of the ETSI as a PAN European standard for high speed wireless local networks.

16. Give any two requirements of HIPERLAN.  Data rates of 23.529 Mbps,  Support of time bounded services  Multi-hop and Ad-hoc networking

17. What are the three phases in channel access in HIPERLAN-1?

Prioritization phase

Contention phase Transmission phase

18. Give any three differences between HIPERLAN 1 and HIPERLAN 2. (A/M 2018)(A/M 2015)

HIPERLAN 1 HIPERLAN 2

Application Wireless LAN Access to ATM fixed networks

Range 50 m 50 – 100 m

Data rate 23.5 M bits/ sec > 20 M bits / s

19. What is meant by BRAN?

The BRAN (Broadband Radio Access Networks (BRAN) is standardized by the European Telecommunications Standards Institute (ETSI). Primary motivation of BRAN is the deregulation and privatization of the telecommunication sector. BRAN technology is independent from the protocols of the fixed network. BRAN can be used for ATM and TCP/IP networks. 20. List the functional requirements of HIPERLANS. The functional requirements of HIPERLAN are

Data rates of 23.529 Mbps, Asynchronous file transfer at 13.4 Mbps

Support both synchronous and asynchronous traffic

Power saving support, Low mobility of 1.4 m/s Video at 2 Mbps, 100 ns latency and audio at 32 Kbps, 10 ns latency To coverage multihub features, Support of time bound services

21. What is Bluetooth?

Bluetooth is an inexpensive personal area Ad-hoc network operating in unlicensed bands and owned by the user. It is an open specification for short range wireless voice and data communications that was developed for cable replacement in PAN (Personal Area Network).

22. What is the advantage of piconet /scatternet. ?

The advantage of the Piconet / Scatternet scheme is that it allows many devices to share the same physical area and make efficient use of bandwidth. 23. What are the states of Bluetooth? Bluetooth specifies four states, they are

Master-M, Standby- SB Slave- S, Parked- P

24. List the two major states in the operation of Bluetooth. The major states in the operation of Bluetooth are

Standby state Connection state

25. What is Piconet and Scatternet?

Bluetooth specification defines a small cell called as piconet which has upto 8 devices grouped together. Two or more piconets grouped together know as scatternet. 26. What type of modulation used in Bluetooth?

Bluetooth uses Gaussian-shaped Frequency Shift Keying (GFSK) modulation with a nominal modulation index of K = 0.3 27. What is the data rate of Bluetooth?

The maximum data rate is 721Mbps for asymmetric mode.

28. List the logical channels provided by L2CAP.(N/D 2017)

L2CAP provides three types of logical channels. They are:

Connectionless

Connection oriented

Signaling

29. What is the need for WIMAX? (N/D 2018)

The main reason for the development of WIMAX( World Interoperability Microwave Access ) is the demand of high data rates not only the faster downloading but also for the use of new applications like Voip, Video, streaming multimedia conferencing and interactive gaming.

30. What is WIMAX? (N/D 2018)

WIMAX is the air interface for the actual radio interface network, where both fixed and mobile users can have access to the network. Its specification is IEEE 802.16. 31. Write the throughput feature in WIMAX.

WIMAX supports throughput up to 63 Mbps on the downlink and 28 Mbps on the uplink, assuming a 10 MHZ bandwidth channel with TDD frames and with 64 QAM 5/6 as modulation scheme. 32. What are the frequency bands of IEEE 802.16?

The 802.16 standard defines a number of air interfaces that can be divided into,

10-66 GHz licensed band

Below 11 GHz licensed bands Below 11 GHZ unlicensed bands

33. Differentiate shadow fading and fast fading (N/D)-2015 Fast fading Shadow fading High Doppler spread Low Doppler spread Coherence time < symbol period Coherence time >> symbol period Impulse response changes rapidly within the Impulse response changes much slower than symbol duration. the transmitted signal. It occur very low data rates. It occur fast data rates.

34. State the MAC management function (N/D)-2017

 Synchronization: Functions to support finding a wireless LAN, synchronization of internal clocks, generation of beacon signals.  Power Management: Functions to control transmitter activity for power conservation, e.g., periodic sleep, Buffering, without missing frame.  Roaming: Function for joining a network (association), changing access points, scanning for access points.

35. What is the functionality L2CAP? List the different types of logical channels. (N/D)-2017

L2CAP is a data link control protocol on top of the baseband layer offering logical channels between Bluetooth devices with QOS properties.

 Connectionless: These unidirectional channels are typically used for broadcasts from a master to its slave(s).  Connection-oriented: Each channel of this type is bidirectional and supports qos flow specifications for each direction.  Signaling: This third type of logical channel is used to exchanging signaling messages between L2CAP entities. Each channel can be identified by its channel identifier (CID).

36. Define the term ‗Doppler spread‘. (N/D)-2015 The range of frequencies over which the received doppler spectrum is essentially non zero is called Doppler spread.

37. Write the necessity of MAC protocol for communication. (N/D)-2015 In computer networking, a media access control address (MAC address) or Ethernet hardware address(EHA), hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapter or network interface cards(NIC) by the manufacturer for identification. 38. Classification of the MAC protocols. (A/M-2015)  Contention-based protocols without reservation/scheduling  Contention-based protocols with reservation mechanisms  Contention-based protocols with scheduling mechanisms  Protocols that do not fall to any of these categories

39. What is WIMAX? mention its features. (N/D 2018)

WiMAX (Worldwide Interoperability for Microwave Access) is a telecommunications protocol describing fixed and fully mobile Internet access services. The protocol conforms to certain parts of the IEEE 802.16 Standard features:  WiMAX support multipath  WiMAX support multipath  WiMAX offer high speed data rate  WiMAX support reliability of data

40. What is the principle behind infrared technology? What are the advantages and disadvantages of infrared technology? (N/D 2018) The molecules emit infrared radiation as they move, and emit more radiation, including visible light, as they get hotter. This is why a heated metal emits a red or white glow. The function of the Thermopile is to absorb infrared radiation and convert it to heat. Advantages:  These devices very cheap  These devices consume low power, light weight. Disadvantages:  It requires both transmitter and receiver in line of sight.  Used for very short distance applications.

41. What is the difference between the 802.11 and HIPERLAN-2: (A/M-2015)

Parameters HIPERLAN-1 HIPERLAN-2 802.11 WLAN

Application Wireless LAN Access to ATM Wireless networks fixed network

Frequency band 5 GHz 5 GHz 2.4 GHZ

Maximum Data rate 23.5 Mbps 54 Mbps 2 Mbps

Topology Decentralized Cellular, Can be adhoc or infra- adhoc/infrastructure centralized based

42. What are the characteristics of wireless communication? (N/D)-2015  Path loss  Fading  Interference  Doppler shift

43 . What is frequency reuse? (N/D)-2015

The design process of selecting and allocating a channel groups for all of the cellular gases Station within a system is called ―frequency reuse‖ or ―frequency planning‖.

UNIT II : MOBILE NETWORK LAYER

Part – A (2 Marks)

1. What is a Mobile IP?

Mobile IP is a protocol developed to allow internetwork mobility for wireless nodes without them having to change their IP addresses.

2. What are the entities of Mobile IP?

Mobile Node (MN)

Correspondent Node (CN)

Home Network (HN)

Foreign Network (FN)

Foreign Agent (FA)

Home Agent (HA)

3. What are the benefits of Mobile IP?

The major benefit of Mobile IP is that it frees the user from a fixed location. Mobile IP makes invisible the boundaries between attachment points, it is able to track and deliver information to mobile devices without needing to change the device‘s long-term Internet Protocol (IP) address.

4. What is Care-Of Address (COA)?

The Care of Address defines the current location of the MN from an IP point of view. All IP packets sent to the MN are delivered to the COA, not directly to the subnet.

5. What is agent advertisement?

Home Agent (HA) and Foreign Agent (FA) advertise their presence periodically using agent advertisement messages. These advertisement messages can be seen as a beacon broadcast into the subnet. 6. What is the need for registration?

The main purpose of the registration is to inform the HA of the current location for correct forwarding of packets.

7. Define – Encapsulation and Decapsulation

Encapsulation is the mechanism of taking a packet consisting of packet header and data and putting it into the data part of a new packet. The reverse operation, taking a packet out of the data part of another packet, is called Decapsulation. 8. What is triangular routing?

Tunneling in its simplest form has all packets to Home Network and then sent to MN via a tunnel. The inefficient behavior of a non-optimized mobile IP is called triangular routing. 9. What is DHCP?

The Dynamic Host Configuration Protocol (DHCP) is based on the bootstrap protocol (BOOTP), which provides the framework for passing configuration information to hosts on a TCP/IP network. DHCP adds the automatically allocate reusable network addresses and configuration options to internet hosts. 10. What is SIP?

The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for creating, modifying and terminating sessions with one or more participants. It is a IETF (Internet Standard) RFC 3261 protocol.

11. What are the functions of Session Initiation Protocol(SIP)? SIP has following major functions

SIP allows for the establishment of user location SIP provides a mechanism for call management

SIP provides feature negotiation, so that all the parties in the call can agree to the features supported among them.

12. What are the characteristics of MANET?(M/J-12)

The characteristics of MANET are

Dynamic Topologies

Bandwidth Constraints and Variable Capacity Links

Energy Constrained Operations

Limited Physical Security

13. Differentiate an ad hoc network and a cellular network with respect to

a) Bandwidth usage

b) Cost effectiveness (N/D - 12)

PARAMETER CELLULAR NETWORK AD HOC NETWORK

Bandwidth reservation requires Easier to employ bandwidth complex medium access control reservation Bandwidth protocols

Usage Guaranteed bandwidth (designed for Shared radio channel (more suitable voice traffic) for best-effort data traffic)

Self-organization and maintenance Cost Cost of network maintenance is high properties are built into the network. Effectiveness (backup power source, staffing, etc.) Hencethecostofnetwork maintenance is less.

14. What are the challenging issues in ad hoc network maintenance?(M/J 12)

The challenging issues in ad hoc network are

Medium access scheme

Routing

Multicast routing

Transport layer protocol

Pricing Schemes

 Quality of Service Provisioning

Self-Organization

Security

Addressing and Service Discovery

Energy Management

Scalability

Deployment considerations

15. Why are ad hoc networks needed?(M/J - 12)

Ad hoc networking is often needed where an infrastructure network cannot be deployed and managed. The presence of dynamic and adaptive routing protocols enables quick formation of ad hoc networks and is suitable for emergency situations like natural disasters, spontaneous meetings or military conflicts. 16. List out the applications of ad hoc networks. Ad hoc networks are widely used in

Military applications and battlefields Collaborative and distributed computing Emergency search and rescue operations Wireless sensor and mesh networks

17. Give the classifications of routing protocol in MANET.

The classifications of routing protocol in MANET are

a) Proactive protocols: This protocol attempt to evaluate continuously the routes within the network, so that when a packet needs to be forwarded, the router is already known and can be immediately used.

b) Reactive protocols: This protocol invoke a route determination procedure only on demand.

The routing protocols may also be categorized as follows:

Table-driven protocols.

Source-initiated on-demand protocols.

18. List the Source-initiated On-Demand Routing Protocols. The Source-initiated On-Demand Routing Protocols are

Ad-hoc On-Demand Distance Vector Routing (AODV)

Dynamic Source Routing (DSR)

Temporarily Ordered Routing Algorithm (TORA)

Associatively Based Routing (ABR)

Signal Stability Based Routing (SSR)

19. Differentiate proactive and reactive routing protocols. Write examples for each. (M/J- 12)

S.No. Proactive Reactive

1 Route is pre-established Route establishment is on-demand

2 Continuously discover the routes Route discovery by some global search

Updates topology information(table) 3 No information update is done Periodically

longer delay due to latency of route 4 No latency in route discovery discovery

Large capacity is needed to update 5 Large capacity is not needed network information

A lot of routing information may never be May not be appropriate for real-time 6 Used communication

7 Eg: DSDV, WRP Eg: AODV, ABR

20. What is DSDV?

Distance-Vector Routing (DSDV) is a table driven routing scheme for ad-hoc mobile networks. The main contribution of the algorithm was to solve the routing loop problem.

21. List out the advantages and disadvantages of DSDV routing protocols. The advantages and disadvantages of DSDV routing protocols are Advantages

 Less Delay is involved in route setup process.

 DSDV protocol guarantees loop free path.  Incremental updates with sequence number tags make the existing wired network protocols adaptable to ad-hoc wireless networks.Count to infinity problem is reduced in DSDV.  Path Selection: DSDV maintains only the best path instead of maintaining multiple paths to every destination. With this, the amount of space in routing table is reduced.

Disadvantages:

 Updates due to broken links lead to heavy control overhead during mobility.

The control overhead is directly proportional to the number of nodes.

Small network with high mobility or large network with low mobility can choke the available bandwidth.

Wastage of bandwidth due to unnecessary advertising of routing information even if there is no change in the network topology.

Delay in obtaining information about a node could result in stale routing at the nodes.

22. What is a mobile IP? What are the entities of mobile IP? (A/M 2018)

Mobile IP is an internet protocol designed to support host mobility. Its goal is to provide the ability of a host to stay connected to the internet regardless of their location. Mobile IP is able to track a mobile host without needing to change the mobile host‘s long-term IP address.

23. What is mobile assisted handoff? (N/D)-2015

A mobile assisted handoff (MAHO) is a process used in GSM cellular networks where a mobile phone assists/helps the cellular base station to transfer a call to another base station. It is a technique used in mobile telecom to transfer a mobile phone to a new radio channel with stronger signal strength and improved channel quality. Mobile assisted handoff can also be referred to as mobile assisted handover.

24. List the different types of control channels in GSM networks. (N/D)-2015  Broadcast control channel  Common control channel  Dedicated control channel

25. If a total of 33MHZ of bandwidth is allocated to a particular celluar telephone system which uses two 25KHz simplex channel to provide full duplex voice and control channels compute the number of channels available per cell if a system uses four-cell reuse. (A/M-2015) Solution Total bandwidth=33MHzChannel bandwidth=25 kHz×2 simplex channels=50 kHz/duplex Channel Total available channels = 33000/50 = 660 channels.

26. State the issues in designing a MAC protocol for adhoc wireless networks. (A/M-2015) Bandwidth Efficiency „ QoS support „ synchronization„ Hidden and Exposed Terminal Problems „ Error -Prone Share Broadcast Channel Prone Share Broadcast Channel

27. Differentiate infrastructure topology and Ad-hoc topology. (N/D)-2015 parameters Infrastructure mode Ad-hoc mode

In infrastructure mode, the In ad-hoc mode, each node communication occurs only communicates directly with other Definition between the wireless nodes and nodes, so no access point access points (AP) , but not control is needed. directly between wireless nodes Access points acts as,a bridge Nodes in Ad-hoc can External Communication to other wireless/wired network communicate if they are within the same range. Physical needs Physical infrastructure is needed No physical infrastructure is needed. Complexity Designing is simple as most of As no central co-ordination the network functionality lies exists, we need to use within AP and client is just a decentralized MAC protocols simple machine. such as CSMA/CA, with all nodes having same functionality. This shoots up the complexity and cost. When it can‘t be used: It can‘t be used in critical It is not always fully connected situations like disaster relief as two mobile nodes may where no infrastructure is left temporarily be out of range. Applications IEEE 802.11 & HIPERLAN2 are Bluetooth is a typical ad-hoc based on infrastructure mode. network.

28. Differentiate adhoc wireless network and celluar network. (A/M-2015)

Parameters Cellular network Ad Hoc network Centralized, all the traffic goes Distributed, No centralized system Network routing through the Base Station such as Base station needed Switching Type Circuit Switching Packet Switching Number of Hops single hop type Multiple hops Topology Star Mesh

29. What is meant by hidden and exposed problems? (N/D)-2015  In the case of hidden terminal problem, unsuccessful transmissions result from collisions between transmissions originated by a node such as node A which cannot hear the ongoing transmissions to its corresponding node B. The probability of such a collision is proportional to the total number of terminals hidden from node A.  In the case of exposed terminal, unsuccessful transmissions result from nodes such as node A being prevented from transmitting, because their corresponding node is unable to send a CTS. Again such unsuccessful transmissions are proportional to the number of exposed terminals. Both these events lead to degradation of a node‘s throughput.

30. What is the need for self organization in a adhoc networks. (A/M-2015)

The general idea of a self-organization is that a global order arises form local interactions between system components and a higher level of order is called emergent property of the system. Therefore we could say that an ad hoc network can be considered as a self-organizing system and connectivity as an emergent property.

31. Define SIP. Write the functions of SIP. (N/D 2018) Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, modifying and terminating real-time sessions that involve video, voice, messaging and other communications applications and services between two or more endpoints on IP networks . Functions:  Name mapping and redirection  Capabilities negotiation  Participant management  Capabilities management

UNIT – III: MOBILE TRANSPORT LAYER

PART – A (2 Marks)

1. Define Traditional TCP?

The Traditional Control Protocol (TCP) is the most widely used transport protocol in the internet architecture 2. What are the services of TCP?

TCP provides connection-oriented, reliable, byte-stream service that is both flow and congestion control to the upper layer. 3. What are the algorithms used for congestion control in TCP?

The congestion control functionality of TCP is provided by four main algorithms namely Slow start

Congestion avoidance Fast transmit Fast recovery

4. What is slow start mechanism?(A/M-2018)

Slow start is a mechanism used by the sender to control the transmission rate. The sender always calculates a congestion window for a receiver. The start size of the congestion window is one TCP packet.

5. What is Fast Retransmit algorithm in TCP?(A/M-2018)

During TCP congestion control, when three or more duplicate ACKs are received, the sender does not even wait for a retransmission timer to expire before retransmitting the segment. This process is called the Fast Retransmit Algorithm.

6. What is Congestion Avoidance algorithm?(N/D-2018)

In the Congestion Avoidance algorithm a retransmission timer expiring or the reception of duplicate ACKs can implicitly signal the sender that a network congestion situation is going on. The sender immediately sets its transmission window to one half of the current window size, but to at least two segments. If congestion was indicated by a timeout, the congestion window is reset to one segment, which automatically puts the sender into Slow Start mode.

7. What are the techniques for classical improvements?

With the goal of increasing TCPs performance in wireless and mobile environments several scheme were proposed,

Some of them are:

1. Indirect TCP

2. Mobile TCP

3. Snooping TCP

4. Fast Transmit/ Fast Recovery

5. Transmission/ time-out freezing

6. Selective Retransmission

8. Write a short note on I- TCP.(N/D-2018)

Indirect TCP is a split connection solution that utilizes the resources of Mobility Support Routers (MSRs) to transport layer communication between mobile hosts and fixed hosts. It uses the standard TCP for its connection over the wireless hop and like other spit connection protocols, attempts to separate loss recovery over the wireless link from the wired link.

9. What are the advantages and disadvantages of I – TCP?

(N/D2018) (A/M-2017)

Advantages:

I-TCP does not require any changes in the TCP Protocol Transmission errors on the wireless link cannot propagate into the fixed network. Optimizing new mechanisms is quite simple because they only cover one single hop.

Disadvantages:

The loss of the end-to-end semantics of TCP might cause problems if the foreign agent partitioning the connection crashes.

10. What are the advantages and disadvantages of Mobile TCP?(A/M-2017)

Advantages

M-TCP maintains the TCP end-to-end semantics. The Supervisory Host (SH) does not send any ACK itself but forwards the ACKS from the MH. If the MH is detached, it avoids useless transmissions, slow starts or breaking connections by simply shrinking the sender‘s window to zero.

11. What is Snooping TCP?

The main drawback of I-TCP is the segmentation of the single TCP connection into two TCP connections, which losses the original end-to-end TCP semantics. A new enhancement which leaves the TCP intact and is completely transparent, is Snooping TCP. The main function is to buffer data close to the mobile hast to perform fast local retransmission in the case of packet loss.

12.What is time-out freezing?

The MAC layer informs the TCP layer about an upcoming loss of connection or that the current interruption is not caused by congestion. TCP then stops sending and freezes the current state of its congestion window and further timers. When the MAC layer notices the upcoming interruption early enough, both the mobile and correspondent host can be informed.

13. What are the advantages and disadvantages of time out freezing?

Advantages:

 It offers a way to resume TCP connections even after long interruptions of the connections.  It can be used together with encrypted data as it is independent of other TCP mechanisms such as sequence no or acknowledgements.

Disadvantages

 TCP on mobile host has to be changed, mechanism depends on MAC layer.  Need resynchronization after interruption.

14. What is Selective Retransmission?

TCP acknowledgements are collective. They acknowledge in-order receipt of packets Upto certain packets. Even if a single packet is lost, the sender has to retransmit everything starting from the lost packet.To overcome this problem, TCP can indirectly request a selective retransmission of packets. The receiver may acknowledge single packets and also trains of in-sequence packets.

15. What are the applications of TCP?

Some applications of TCP are www-browsing-mail and FT

16. what is the need for I-TCP? (N/D)-2017

I-TCP splits the connection into two parts: a wired/fixed and a wireless/mobile part. I-TCP isolate problems on the wireless link from the fixed networks.

17. Define fast recovery. (N/D)-2017

TCP sends an acknowledgement only after receiving a packet. If a sender receives several

Acknowledgements for the same packet, this is due to a gap in received packets at the receiver.

It indicates that the receiver got all packets up to the gap and is actually receiving packets, but

some are missing. Sender concludes that packet loss is not due to congestion, continue with

current congestion window(do not use slow-start), just retransmit all packets from beginning of

reported gap(go back N).

18. What is I-TCP? List its merits and demerits. (N/D 2018)

I-TCP segments a TCP onto fixed part and wireless part. Standard TCP is used to connect to the AP from fixed computer. No computer over the internet recognises any change to the TCP.

Advantages:

 I-TCP does not require any changes in TCP protocol as used by the different hosts in network.  Because of a strict partition between the two connections, transmission error on the wireless link will not propagate to the wired link.  Therefore, flow will always be in a sequence.  The delay between the FA and Mobile host is small and if optimized properly, precise time- outs can be used to carry out retransmission of lost packets.

Disadvantages:

 The end-to-end connection for which TCP has been designed will fail if the Foreign Agent (FA) crashes.  The foreign agent (FA) must be a trusted entity as the TCP connections end at this point.  In practical terms increased handover may latency may be much more problematic. (During handover from old FA to new FA, some delay will occur.During this period, some extra data will come at old FA. This data also needs to be send!!)

19. Differentiate proactive and reactive routing protocols. Write examples for each. (N/D 2018)

Proactive: A table -driven approach, follows a static route throughout the lifetimeReactive: Dynamically changes the Routing decisions based on the present network conditions.

Examples:  Distance Vector (DV) Protocol  Wireless Routing Protocol (WRP)

20. Define the term slow start mechanism and fast retransmit algorithm in TCP. (A/M 2018)

TCP slow-start algorithm:

Sender calculates/negotiates a congestion window threshold for a receiver.Start with a Congestion window size equal to one segment. Exponential increase of the congestion window up to the congestion threshold, then linear increase.Missing acknowledgement causes the reduction of the congestion threshold to one half of the current congestion window. Congestion window starts again with one segment.

TCP fast retransmit:

TCP sends an acknowledgement only after receiving a packet. If a sender receives several acknowledgements for the same packet, this is due to a gap in received packets at the receiver. It indicates that the receiver got all packets up to the gap and is actually receiving packets,but some are missing. Sender concludes that packet loss is not due to congestion, continue with current congestion window(do not use slow-start), just retransmit all packets from beginning of reported gap(go back N).

21. What is congestion avoidence algorithm? (N/D 2018)

Congestion can occur when data arrives on a big pipe (a fast LAN) and gets sent out a smaller pipe (a slower WAN). Congestion can also occur when multiple input streams arrive at a router whose output capacity is less than the sum of the inputs. Congestion avoidance is a way to deal with lost packets.

22. How does GPRS module differ from GSM module? (A/M-2015)

GSM GPRS GSM is standard bearer of 2G technologies. GPRS is he upgrade over the basic GSM features. It allow the mobile handset to obtain much higher data speed than what standard GSM can offers. In GSM traffic and signaling follow different In GPRS traffic and signaling both follow multi-frame structure. common multi-frame structure. i.e. 52 frame MF i.e. 51 frame MF used for signaling and 26 used for both signaling as well as traffic. frame MF used for traffic.

GSM used circuit switching traffic GPRS used for packet switching traffic. In GSM UE will be in two states ,i.e In GPRS UE will be in three states, IDLE and READY. i.e IDLE, READY and STANDBY.

UNIT IV: WIRELESS WIDE AREA NETWORK

Part – A (2 Marks)

1. What are the applications of 3G?

Applications for a 3G wireless network range from simple voice-only communications to simultaneous video, data, voice and other multimedia applications.

2. Name some of the wireless technology services? Some of the wireless technology services are

General Packet Radio Services (GPRS) Enhanced Data for GSM evolution (EDGE) service Wideband Code Division Multiple access (WCDMA) Universal Mobile telecommunications Services (UMTS) High- Speed Downlink Packet Access (HSDPA)

3. What is UMTS? (A/M-2018)

Universal Mobile telecommunications Services (UMTS) is a new radio access network based on 5 MHz WCDMA and optimized for efficient support of 3G services. UMTS can be used in both new and existing spectra. 4. What are the layers of UMTS? (A/M-2018)

The UMTS terrestrial radio access network (UTRAN) has an access layer and non access layer.

The access layer includes air interface and provides functions related to OSI layer 1, layer 2, and the lower part of layer 3.

The non-access layer deals with communication between user equipment (UE) and core network (CN) and includes OSI layer 3 (upper part) to layer 7.

5. What is radio resource control (RRC)?

The radio resource control (RRC) layer broadcasts system information, handles radio resources such as code allocation, handover, admission control, measurement/control report.

6. What are the duties of Radio network control (RNC)?(N/D-2018) The major duties of RNC are

Intra UTRAN handover

Macro diversity combining/ splitting of Iub data systems. Outer loop power control IU interface user plane setup Serving RNS (SRNS) relocation Radio resource allocation

7. What are the planes of UTRAN? There are three planes

Control plane

User plane Transport network control plane.

8. What are the functions provided by 3G-MSC?

The following functionality is provided by the 3G-MSC:

Mobility management Call management

Supplementary services Short message services (SMS) OAM (operation, administration, and maintenance) agent functionality.

9. What is Transport Network Control Plane (TNCP)?

Transport Network Control Plane (TNCP) carries information for the control of transport network used within UCN.

10. What is 3G-SGSN?

The 3G-SGSN (serving GPRS Support Node) provides the appropriate signaling and data interface that includes connection to an IP-based network toward the 3G-GGSN, SS7 towards the HLR/EIR/AUC and TCP/IP or SS7 toward the UTRAN. 11. What is 3G-GGSN?

The GGSN (Gateway GPRS Support Node) is connected with SGSN via an IP-based network.

It provides interworking with the external PS network.

12. What are the functions provided by 3G-GGSN? (N/D-2018)

Macro-Mobility (maintaining information locations at SGSN level) Gateway between UMTS packet network and external data networks Initiate mobile terminate route Mobile Terminated Packets User data screening/security.

13. What is SMS-GMSC?

THe SMS-GMSC (gateway MSC) is a MSC which can receive a terminated short message

14. What is meant by firewall? (N/D)-2017

This entity is used to protect the service providers‘ backbone data networks from attack from external packet data networks. The security of the backbone data network can be ensured by applying packet filtering mechanisms based on access control lists or any other methods deemed suitable.

15. What is UMTS? What are the layers of UMTS? (A/M 2018)

The UMTS network architecture is partly based on existing 2G network components and some new #G network components. It inherits the basic functional elements from GSM architecture on the core network(CN) side. The CN provides circuit switched(CS) functions as well as packet switched(PS) junctions.

16. List the functions provided by 3G-GGSN? (N/D 2018)

 Gn—These interfaces (―n‖ for network) connect to the mobile portion of the network, such as the Serving GPRS Support Node (SGSN). The SGSNs connect to the mobile stations themselves through the radio network.  Gi—These interfaces (―i‖ for IP) connect to the IP packet portion of the network, such as the Internet or private corporate networks.  Ga-These interfaces (―a‖ for administration) connect to the network management and operations portion of the network, such as the charging servers.

17. Distinguish between flat and frequency selective fading. (A/M-2015)

Flat fading : In this bandwidth of the signal is smaller than the bandwidth of the channel. In the flat fading all the components of the frequency of the signal will have the same magnitude of fading with respect to each other. Selective fading: Here the bandwidth of the signal is larger than the bandwidth of the channel. Different components of the frequency signal will not experience the same fading.

UNIT V: 4G NETWORKS

1. What are the main functions of Cognitive Radio?

The main functions of Cognitive Radio are Spectrum Sensing, Dynamic Spectrum Management and Adaptive Communications.

2. Define Cognitive Radio.(N/D-2017)

The Federal Communications Commission FCC defined Cognitive Radio as ―A radio that can change its transmitter parameters based on interaction with the environment in which it operates.

3. Write a short note on time slot scheduler. The time slot scheduler shares the spectrum efficiently between users by satisfying the QoS requirements. When the channel quality for each radio link can be predicted for a short duration into the future and accessible by the link layer, then ARQ with an adaptive modulation and coding system can be selected for each user to satisfy the Bit Error Rate(BER) requirement and offer throughput.

4. What is meant by MIMO?

MIMO means Multiple Input and Multiple Output that represents multiple individual, parallel data streams that are carried on the air interface.

5. What are the benefits of SmartAntennaTechnology?

The benefits of Smart Antenna Technologyare:

a. Reduction in Co – Channel Interference

b. Range Improvement

c. Increase in Capacity

d. Reduction in Transmitted Power

e. Reduction in Handoff

6. What is meant by receiver diversity?

The Single Input Multiple Output (SIMO) configuration of the radio channel is known as receiver diversity. The input the channel is single transmitter signal that feeds two receiver paths. Depending on multipath fading and the correlation between two receiver gain is achieved in the form of fading resistance.

7. What is cognitive radio? (N/D)-2017 Cognitive radios(CRs) intelligently exploit available side information share the spectrum about,  Channel conditions  Activity  Codebooks and  Messages

8. List some of the applications of 4G system. (N/D)-2017

Applications of 4G will be virtual presence, virtual navigation, tele-medicine, tele-geo-processing applications, and online education. 4G is still in a formative stage. Its commercial application is likely to be in 2010. The ITU-WG 8F has started to consider 4G requirements

9. List the characteristics of 4G network. (A/M 2018)

In the 4 G system network coverage/capacity will change dynamically to accommodate changing user patterns. User will change automatically move from congested routes to allow the network to dynamically self-balance. The 4G technologies will include instantaneous channel condition estimations of several users to distribute transmission load, better access methods than 3G, adaptive antenna, adaptive coding and modulation, adaptive channel/code allocation, and scheduling among sectors and users.

10. Give the advantages of Multicarrier modulation over single carrier schemes. (A/M 2018)

MCM‘s advantages are better performance in the intersymbol-interference environment and avoidance of single-frequency interferers. However, MCM increases the peak-to-average ratio of the signal, and to overcome intersymbol interference a cyclic extension or guard band must be added to the data.

11. What is meant by multi carrier modulation? Mention its merits and demerits? (N/D 2018)

Multi-carrier modulation (MCM) is a method of transmitting data by splitting it into several components, and sending each of these components over separate carrier signals. The individual carriers have narrow bandwidth , but the composite signal can have broad bandwidth.

Advantages:  Makes efficient use of the spectrum by allowing overlap.By dividing the channel into narrowband flat fading subchannels, OFDM is more resistant to frequency selective fading than single carrier systems are.  Eliminates ISI and IFI through use of a cyclic prefix.  Using adequate channel coding and interleaving one can recover symbols lost due to thefrequency selectivity of the channel.  Channel equalization becomes simpler than by using adaptive equalization techniques withsingle carrier systems.

Disadvantages :  The OFDM signal has a noise like amplitude with a very large dynamic range, therefore itrequires RF power amplifiers with a high peak to average power ratio.  It is more sensitive to carrier frequency offset and drift than single carrier systems are dueto leakage of the DFT.

12. Name the functions of radio network control? (N/D 2018) A radio network controller (RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some mobility management functions and encrypts data before it is sent to and from the mobile.

13. What is Smart Antenna?

A Smart Antenna is a multi- element antenna where the signals received at each antenna element are intelligently combined to improve the performance of the wireless system.

14. Define Multi Carrier Modulation (MCM) (N/D-2018)

Multi Carrier Modulation (MCM) is a baseband process that uses parallel equal bandwidth sub channels to transmit information and is normally implemented with Fast Fourier Techniques (FFT) techniques.

15. What are the types of MCM that are likely preferred for 4G?

The two different types of MCM that are likely preferred for 4G are:

a. Multi Carrier Code Division Multiple Access

b. Orthogonal Frequency Division Multiplexing (OFDM) using TDMA

16. What are the advantages of

MCM? (N/D-2018)

The advantages of MCM are

 Better performance in the Inter Symbol Interference environment

 Avoidance of single frequency interference

17. What are the technologies used in 4G?

The technologies used in 4G are

a. Multi Carrier Modulation (MCM)

b. Smart Antenna Techniques

c. OFDM – MIMO Systems

d. Adaptive Modulation and Coding with Time Slot Scheduler and Cognitive Radio

18.List out the applications of 4G technologies.(N/D-2017)

The applications of 4G technologies are a. Virtual Presence

b. Virtual Navigation

c. Tele-Medicine

d. Tele-Geo-Processing applications

e. Gaming

f. Cloud Computing

g. Crisis detection and prevention

h. Education

18. What are the techniques to improve network survivability in different

layers? (N/D-2018)

The techniques to improve network survivability in different layers are

Prevention

Network design and capacity allocation

Traffic Management and restoration

19. What are the challenges of 4G?(N/D-2018)

The main challenges are

a. Multimode user terminals

b. Wireless System Discovery and Selection

c. Terminal Mobility

d. Network Infrastructure and QoS Support

e. Security and Privacy

f. Fault tolerance and Survivability

g. Multiple Operators and Billing Systems

h. Personal Mobility

20. What are the main issues in terminal mobility of

4G?

The two main issues in terminal mobility are

a. Location Management

b. Handoff Management

With location management, the system tracks and locates a mobile terminal fir possible connection

Handoff management maintains ongoing communications when the terminal roams.

22. Define 4G

4G can defined as MAGIC

a. Mobile Multimedia

b. Anytime Anywhere

c. Global Mobility Support

d. Integrated Wireless Solution

e. Customized Personal Services

f. Also known as Mobile Broadband Everywhere

23. What are the goals of 4G?

The ambitious goal of 4G is to allow everyone to access the Internet anytime and everywhere. The provided connection to Internet will allow users to access all types of services including text, databases and multimedia. Unlike 3G, 4G is IP based, that is every user connected to the Internet will have an IP address.

24. .Compare 3G with 4G

Content 3G 4G Packet Switching, Message Switching Technique Packet Switching switching

Peak Download Rate 100 Mbps 1Gbps

Frequency Band 1.8 – 2.5 MHz 2-8 GHz

Access Wideband CDMA Multi-Carrier – CDMA or OFDM

25. what are the features of 4G Wireless

Systems?

(A/M-2017)

The features of 4G Wireless Systems are,

a. Support interactive multimedia, voice, video, wireless internet and other broadband services.

b. High speed, high capacity and low cost per bit.

c. Global mobility, service portability, scalable mobile networks

d. Seamless switching, variety of services based on Quality of Services requirements.

26. Write a short note on security challenges in 4G.(A/M-2017)

The security challenges with IP network is one of the most significant factors that slows down the further adoption of network technologies. An end to end system approach to security is required in next generation wireless networks, including:

a. Platform hardening

b. User/Operator authentication, authorization and auditing

c. Secure protocols, communication and data storage

d. Software and configuration integrity

27. Define path loss. (A/M-2015)

Path loss (or path attenuation) is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. This term is commonly used in wireless communications and signal propagation.

UNIT 1 PART B QUESTIONS 1. How mobility is restricted using WLANs ? What additional elements are needed for roaming between networks, how and where can WLANs support roaming? Mention the capabilities of layer 2 where WLANs reside. 2. What are the basic differences between wireless WANs and WLANs, and what are the common features? Consider mode of operation, administration, frequencies, capabilities of nodes, services, national/international regulations. 3. With a focus on security, what are the problems of WLANs? What level of security can WLANs provide, what is needed additionally and how far do the standards go? 4. Compare IEEE 802.11,Hiper LAN2, and Bluetooth with regard to their ad-hoc capabilities. Where is the focus of these technologies? 5. If Bluetooth is a commercial success, what are remaining reasons for the use of infra red transmission for WLANs? 6. Explain WLAN technologies in detail? 7. Why is the PHY layer in IEEE 802.11 subdivide? What about hiperLAN2 and Bluetooth? 8. Compare the power saving mechanisms in all three LANs introduced in this chapter? 9. What are the negatives effects of the power saving mechanisms, what are the trade off between consumption and transmission QOS? 10. Compare QOS offered in all three LANS in adhoc mode. What are the advantages does an additional infrastructure offer? How is Qos provided in Bluetooth? Can one of the LAN technologies offer hard QOS? 11. How do IEEE 802.11,Hiper LAN2 and Bluetooth, respectively, solve the hidden terminal problem? 12. How are fairness problems regarding channel access solved in IEEE 802.11 , Hiper LAN2 and Bluetooth respectively? How is the waiting time of a packet to transmit reflected? 13. What different solutions do all three networks offer regarding an increased reliability of data transfer? 14. In what situations can collisions occur in all three networks? Distinguish between collisions on PHY and MAC layer. How do the three wirelessnetworks try to solve the collisions or minimize the probability of collisions? 15. Compare the overhead introduced by three medium access schemes and the resulting performance at zero load, light load, high load of the medium. How does the number of collisions increase with the number of stations trying to access the medium, and how do three networks try to solve the problems? 16. What is the overall scalability of the schemes in number of nodes? 17. How is roaming on layer 2 achieved, and how are changes in topology reflected? 18. What are the differences between infrastructure based and ad-hoc based networks regarding roaming? 19. Explain Bluetooth protocol stack? 20. What are advantages and problems of forwarding mechanisms in Bluetooth networks regarding security, power saving and network stability? 21. Name the reasons for the development of WATM. What is one of the ain differences to internet technologies from this point of view? Why did WATM not succeed as stand - alone technology, what parts of WATM succeeded? 22. Explain the frame format in Bluetooth technology? 23. Explain in detail Bluetooth security features and security levels with proper diagrams? 24. Discuss Wimax. What are the main differences between WIFI and Wimax?

UNIT 2 PART B QUESTIONS 1. What are the differences between AODV and the standard distance vector algorithm? Why are extensions needed? 2. How does dynamic source routing handle routing? What is the motivation behind dynamic source routing compared to other routing algorithm from fixed networks? 3. How does the symmetry of wireless links influence the routing algorithms proposed? 4. Why are special protocols for the support of micro mobility on the networks layer needed? 5. What are the benefits of location information for routing in ad-hoc networks, which problems arise? 6. Think of ad-hoc networks with fast moving nodes, What problems arise even for the routing algorithms adapted to ad-hoc networks? What is situation on highways? UNIT 3 PART B QUESTIONS 1. What are the influences of encryption on the proposed schemes? Consider for example IP security that can encrypt the payload, (TCP packet) 2. Name further optimizations of TCP regarding the protocol overhead which are important especially for narrow band connections. Which problems may occur? 3. Can the problems using TCP be solved by replacing TCP with UDP? Where could this be useful and why is it quite often dangerous for network stability? 4. How and why does 1-TCP isolate problems on wireless link? What are the main drawbacks of this solution? 5. Show the interaction of mobile IP with standard TCP. Draw the packet flow from a fixed host to a mobile host via foreign agent. Then a handover takes place. What are the following actions of mobile IP and how does TCP react? 6. Now show the required steps during handover for a solution with a PEP. What are the state and function of foreign agents, home agents, corresponding host, mobile host, PEP and care of address before, during and after handover? What information has to be transferred to which entity to maintain consistency for the TCP connection?

UNIT 4 PART B QUESTIONS 1. What are three channel types that are used in UMTS? Discuss the role of each channel type. 2. Give the detailed radio access network overview. Explain in detail functions of Node B and RNC. Also draw UTRAN logical architecture. 3. Discuss UMTS bearer service layered architecture. 4. Explain the following i) HSDPA ii) UMTS 5. Discuss the responsibilities of RNC in the UMTS network. 6. Explain E-UTRAN with suitable diagram. 7. Explain the UMTS core network architecture with neat diagram.

UNIT 5 PART B QUESTIONS 1. Explain about OFDM-MIMO systems 2. Discuss about Adaptive modulation and coding with time slot schedule. 3. Explain in detail about cognitive radio with neat diagram. 4. Discuss the 4G features and challenges. And list out the applications of 4G. 5. Write short notes on i) smart antenna techniques ii) Multi carrier modulation. 6. Explain OFDM concept in detail and also explain the implementation of transceivers in OFDM system. V.S.B. ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

GE6075 PROFESSIONAL ETHICS IN ENGINEERING

UNIT I HUMAN VALUES SYLLABUS: Morals, values and Ethics – Integrity – Work ethic – Service learning – Civic virtue – Respect for others – Living peacefully – Caring – Sharing – Honesty – Courage – Valuing time – Cooperation – Commitment – Empathy – Self-confidence – Character – Spirituality – Introduction to Yoga and meditation for professional excellence and stress management.

Course Objectives: To create awareness on professional ethics and Human Values 1. What are human values? Values decide the standard of behavior. Some universally accepted values are freedom justice and equality. Other principles of values are love, care, honesty, integrity, self-respect.

2. What are ethical values? Trustworthiness, respect, responsibility, fairness, caring is ethical values

3. Distinguish values from ethics and culture. Values are mainly related to individuals and since they are related to justice, they remain the some for everyo ne. E.g. truth, honesty, empathy, self respect. Values do not change from individual to individual. Ethics is common to a group of individuals; the group may be religious or professional. Ethics is mostly based on some code or law and judgment of any action is based on code of conduct or law. Ethics change from individual to individual Culture commonly refers to conduct of a group. E.g system of worship, marriage. It may differ from society to society, nation to nation or religion to religion.

4. What is integrity? Integrity is the unity of character based on moral values. Consistency in attitudes, emotions and conduct in relations to morally justified actions and values are also the part of integrity of individual. It implies honesty, trustworthiness.

5. Define work ethics By one‟s work one cannot harm others. Any worker cannot escape accountability. Worker has the moral responsibility to see that no other person‟s right, private or freedom is impaired or transgressed.

6. What is service learning? Service learning tells that one has moral responsibility to increase the desirable effects and to decrease the harmful effects. Any service should increase the desirable result.

7. Mention some civic virtues? Good citizen demand civic virtue. It is the principle of not harming the surroundings .it also includes living peacefully, respect for others, protecting the environment and being normally and ethically good.

8. Write short notes on caring and sharing. Caring is the essence of moral life. Caring involves feelings, relationship, contends with other persons and protecting others and causing least damage to others. Sharing means sharing of feelings, ideas IV YR/VIII SEM 1 V.S.B. ENGINEERING COLLEGE, KARUR DEPARTMENT OF ECE

thoughts, resources and profits. Sharing is always mutually beneficial. Sharing morally acceptable feelings, resources and materials is a value.

9. Write notes on honesty. Any human being should imbibe honesty-honesty in acts, honesty in speech and honesty in beliefs. Honesty is the fundamental virtue in human relationship even though in may be difficult to follow some times.

10. What is courage as a value? Courage implies self-respect and governs confrontations with danger and risk. It isnot excessive rashes or cowardice, but it is the middle ground. Taking calculated risks and boldness in facing crises are the hallmarks of courage as a human value. It defines the mental make up of an individual in taking bold decisions even under adverse situations.

11. Define co-operation. Co-operation means extending help to others, for a good cause. Co-operation may be through an idea, a suggestion, an assistance or physical work which extends to others for common benefit.

12. Define empathy. Empathy means putting self in a position of someone else and thinking as the later and reasoning suitable action.

13. Define spirituality. Spirituality raises a man above the materialistic world into a realm where he seeks peace and real happiness.

14. Define Integrity? Integrity is the bridge between responsibility in private and professional life.

15. Define Compromise? In a negative sense it means to undetermined integrity by violating one‟s fundamental moral principles. In a positive sense, however, it means to settle differences bymutual concessions or to reconcile conflicts through adjustments in attitude and conduct.

16. Give the two aspects of Honesty? Truthfulness – meeting responsibilities concerning truth-telling. Trustworthiness –Meeting responsibilities concerning trust.

17. Differentiate Self-respect and Self-esteem? Self-respect: It is a moral concept; refers to the virtue properly valuing oneself. Self-esteem: It is a psychological concept; means having a positive attitude toward Oneself, even if the attitude is excessive or otherwise unwarranted.

18. What are Human values? Explain briefly. Values are the rules by which we make decisions about right and wrong, should and shouldn't, good and bad. “Emotional beliefs in principles regarded as particularly favorable or important for the individual.” Types of Values: (a) Right conduct, (b) Peace (c) Truth, (d) Love, (e) Nonviolence. IV YR/VIII SEM 2 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

19. Factors That Demonstrate a Strong Work Ethic:  Integrity,  Sense of Responsibility, Emphasis on Quality, Discipline, and  Sense of Teamwork.

20. Five Characteristics of a Good Work Ethic: Reliability, Dedication, Productivity, Cooperation, and Character

21. Explain CIVIC VIRTUE. Civic virtues are the moral duties and rights, as a citizen of the village or the country or an integral part of the society and environment. Civic virtues are divided into four categories: 1. Civic Knowledge 2. Self-Restraint 3. Self-Assertion 4. Self-Reliance

22. Explain Respect for others. Respect is a positive feeling of admiration or deference for a person. Respect can be a specific feeling of regard for the actual qualities of the one respected. It can also be conduct in accord with a specific ethic of respect. Treating people with respect makes your world a nicer place to live in, whether it's at home, at school, or out in your community. Don't insult people or make fun of them.

23. Explain Living Peacefully. To live peacefully, one should start install peace within (self). Charity begins at home. Then one can spread peace to family, organization where one works, and then to the world, including the environment. Only who are at peace can spread peace. You cannot gift an article which you do not possess. The essence of oriental philosophy is that one should not fight for peace. It is oxymoron. War or peace can be won only by peace, and not by wars ! One should adopt the following means to live peacefully, in the world

24. Explain Stress Management. Stress management refers to the wide spectrum of techniques and psychotherapies aimed at controlling a person's levels of stress, especially chronic stress, usually for the purpose of improving every day functioning. Stress is a normal psychological and physical reaction to the ever-increasing demands of life. Surveys show that many Americans experience challenges with stress at some point during the year.

25. Define spirituality? (Nov/Dec 15) Spirituality raises a man above the materialistic world into a realm where he seeks peace and real happiness

26. Explain Self- Confidence, Character and Spirituality.(May/June 16) Self- Confidence: Certainty in one‟s own capabilities, values, and goals. These people are usually positive thinking, flexible and willing to change. They respect others so much as they respect themselves. Character: To determine the ideals. Spirituality: Spirituality is a way of living that emphasizes the constant awareness and recognition of the spiritual dimension (mind and its development) of nature and people, with a dynamic balance between the material development and the spiritual development.

IV YR/VIII SEM 3 V.S.B. ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

27. What are the values? (May/June 16) Values denote something‟s degree of importance, with the aim of determining what action of life is best to do or live or to describe the significance of different actions.

28. What are the qualities of a self-confident people? (Nov/Dec 15) 1. Ambitious 2. Self-Love 3. Risk-takers 4. Self-awareness 5. Change agent Part –B (16 marks) 1. Write short notes honesty. (R) (Nov/Dec 2015) 2. What is courage? What are the salient features of courage?(R) (Nov/Dec 2015) 3. What is service learning?(R) 4. Distinguish values from ethics and culture.(U) 5. What do you understand by the term spirituality? Explain in detail.(U)(May/June 16) 6. Spirituality raises a man above the materialistic world into a realm where he seeks peace and real happiness (E) 7. Define the terms Values, Morals & Ethics?(R) 8. Define Human Values? ?(R) 9. Explain the importance of self-confidence in ethics(U)(May/June 2016)

Course Outcome: Students understand the core values that shape the ethical behavior of an engineer and Exposed awareness on professional ethics and human values.

UNIT II ENGINEERING ETHICS

SYLLABUS: Senses of „Engineering Ethics‟ – Variety of moral issues – Types of inquiry – Moral dilemmas – Moral Autonomy – Kohlberg‟s theory – Gilligan‟s theory – Consensus and Controversy – Models of professional roles – Theories about right action – Self-interest – Customs and Religion – Uses of Ethical Theories.

COURSE OBJECTIVES: To create awareness on Engineering Ethics providing basic knowledge about engineering Ethics, Variety of moral issues and Moral dilemmas, Professional Ideals and Virtues.

PART A

1. Define moral Dilemma? (MAY/JUNE 2012) Dilemmas are certain kind of situations in which a difficult choice has to be made. Moral dilemmas can also be called moral problems. Moral Dilemmas have two or more folding„s - moral obligations, duties, rights, goods, or ideals come disagreement with each other. 2. What are the chief characteristics of a profession? (MAY/JUNE 2012) Knowledge Organization Public Good IV YR/VIII SEM 4 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

3. What is the significance of engineering ethics? (MAY/JUNE 2011) An activity and an area of inquiry. Ethical problems, issues and controversy Set of beliefs, attitudes and habits. Morally correct.

4. What is engineering ethics? (MAY/JUNE 2011, MAY/JUNE 2014) Study of the moral issues and decisions confronting individuals and organizations engaged in engineering / profession. Study of related questions about the moral ideals, character, policies and relationships of people and corporations involved in technological activity. Moral standards /values and system of morals.

5. What is meant by normative inquiry? (MAY/JUNE 2011) Engineering ethics involves normative inquiry in order to aim at identifying and justifying the morally desirable norms or standards that ought to guide individuals or groups. Normative questions include what ought to be? and what is good?

6. What do you mean by ethical pluralism?(APRIL/MAY 2010) Ethical pluralism is the view that there may be alternative moral perspectives that are reasonable, but no one of which must be accepted completely by all rational and morally concerned persons.

7. Differentiate Moral and Ethics? (MAY/JUNE 2010) Moral: o Refers only to personal behavior. o Refers to any aspect of human action. o Social conventions about right or wrong conduct.

Ethics:

Involves defining, analyzing, evaluating and resolving moral problems and Developing moral criteria to guide human behavior. Critical reflection on what one does and why one does it. Refers only to professional behavior.

8. State Rawls principles? (NOV/DEC2010) Each person is entitled to the most extensive amount of liberty compatible with an equal amount for others. Differences in social power and economic benefits are justified only when they are likely to benefit everyone, including members of the most disadvantaged groups.

9. Write any three uses of ethical theories. (NOV/DEC2010, MAY/JUNE 2014) Ethical theories are very useful in understanding and resolving moral dilemmas. In estimating the professional obligations and ideals. Determine to what extent, the obligations can be exercised in a given situation.

10. What are the types of Theories about Morality/ Right action? (MAY/JUNE 2009) Virtue ethics – Virtues and vices

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Utilitarianism – Most good for the most people Duty ethics – Duties to respect people Rights ethics – Human rights

11. Explain Ethical Egoism (MAY/JUNE 2009) It deals with self-interest. Each person is the best judge of their own self-interest and is responsible for maximizing their own interest. Egoism preaches selfishness but morality should encourage love, compassion etc.

12. Differentiate Ethical Relativism and Ethical Egoism? (MAY/JUNE2008) Ethical egoism – the view that right action consist in producing one„s own good. Ethical relativism – the view that right action is merely what the law and customs of one„s society require.

13. Explain moral integrity? (MAY/JUNE2008) Moral integrity is the strength of character on the basis of moral concern and moral values. Integrity is the bridge that links the responsibilities between personal life and professional carrier.

14. Explain profession and professionalism? (NOV/DEC 2008) Profession is a job through which someone makes living. Professionalism cover comprehensively all areas of practice of a particular profession. It requires skills and responsibilities involved in engineering profession.

15. Give the importance of Lawrence Kohlberg‟s and Carol Gilligan‟s theory? (NOV/DEC 2008) Kohlberg gives greater emphasis to recognizing rights and abstract universal rules. Gilligan Stresses the importance of maintaining personal relationships based onmutual caring.

16. What is consensus and controversy? Consensus means agreement and controversy means disagreement. Both plays the vital roles while considering moral autonomy.

17. What is the relationship between moral autonomy and authority? Moral' autonomy is exercised on the basis of moral concern for other people and recognition of good moral reasons. Authority provides the frame work inwhich learning can takes place in class room/work place.

18. What are the types of virtues? Self-direction – commitment, self-discipline, courage Public spirited – justice, generosity. Teamwork – cooperation, loyalty, respect for authority, leadership qualities. Proficiency- technical skill, creativity.

19. What are the cardinal virtues/ Chief Virtues? Wisdom - courage -temperament -justice

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20. What are the concepts of pre-conventional & conventional level in Gilligan's theory? Carol Gilligan recast the theory of Kohlberg as follows. Pre conventional level: Desire to derive benefits for oneself. Right conduct is viewed in a selfish manner as solely what is good for oneself. Conventional level: Here the basic motive is willingness to sacrifice one's own interests and a strong desire to hurt other's interests. Mostly women are always willing to give up their personal interests in order to serve the needs of others.

21. Define Ethics. Mention some universally accepted ethical standards. (NOV/DEC 13) "Ethics" as the "discipline dealing with what is good and bad and with moral duty and obligation," "a set of moral principles or value" or "a theory or system of moral values." Ethics assists individuals in deciding when an act is moral or immoral, right or wrong. Ethics can be grounded in natural law, religious tenets, parental and family influence, educational experiences, life experiences, and cultural and societal expectations. Ethical Standard such as Focus on ethics, Corporate culture, Managerial

22. Define moral values with suitable Example. (NOV/DEC 2013),(APR/MAY2015) Moral values are the standards of good and evil, which govern an individual„s behavior and choices. Individual„s morals may derive from society and government, religion, or self-Honesty, respect for others, loyalty, responsibility for personal actions, generosity and kindness are all examples of moral values.

23. What is meant by normative enquiry?(APRIL/MAY 2011) Normative ethics an approach to ethics that works from standards of right or good action. There are three types of normative theories: virtue theories, deontological theories, and teleological theories.

24. Define “Professionalism‟. (APRIL/MAY 2015) Professionalism means behaving in an ethical manner while assuming and fulfilling your rightful responsibilities in every situation every time, without fail. To get a bit more granular, one can say that it means, in part, conducting your affairs in such a way as to engender trust and confidence in every aspect of your work.

25. Define Moral Autonomy (NOV/DEC2014) Moral autonomy, usually traced back to Kant, is the capacity to deliberate and to give oneself the moral law, rather than merely heeding the injunctions of others. Personal autonomy is the capacity to decide for oneself and pursue a course of action in one's life, often regardless of any particular moral content. PART-B 1. What are the stages of moral development according to Gilligan? Discuss (R)(8)(MAY/JUNE 2012, (MAY/JUNE 2014) 2.Apply both Kohlberg„s and Gilligan„s theory in Heinz Dilemma and justify your arguments(8)(MAY/JUNE2011,MAY/JUNE2012, (MAY/JUNE 2014), (APR/MAY2015)(NOV/DEC 2014(Ap)

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3.What are the uses of ethical theories explain? (16) (U)(MAY/JUNE 2012) 4. Explain 1. Professional responsibility (4) 2. Integrity and self-respect. (8) 3. Utilitarianism (4) (MAY/JUNE 2011) (U) 5.Explain Kohlberg„s theory in detail?(12)(U)(MAY/JUNE2011) (APR/MAY2015) 6. What are the scopes of engineering ethics? (R)(16) (MAY/JUNE 2011) 7. What are the different ethical theories available for right action, self-interest, duty Ethics.(U) (16)(MAY/JUNE 2010, (NOV/DEC 2013), (APR/MAY2015) 8. Discuss the different models of professional roles?(16)(U) (MAY/JUNE 10) 9. Highlight the importance of engineering ethics? (16) (R)(MAY/JUNE 11) 10. What are the general types of inquiries involved in engineering inspection? Explain in detail the specific virtues of professional responsibility (U) (MAY/JUNE 2014, (NOV/DEC 2013), (APR/MAY2015) (NOV/DEC 2014) 11. Explain the vital role of consensus and controversy while considering moral autonomy in engineering ethics.(U) (MAY/JUNE 2014) 12. Write short notes on Moral autonomy(R) ( NOV/DEC 2013)

COURSE OUTCOME:

The students will understand the basic perception of profession, professional ethics, various moral issues & uses of ethical theories

UNIT –III ENGINEERING AS SOCIAL EXPERIMENTATION SYLLABUS: Engineering as Experimentation – Engineers as responsible Experimenters – Codes of Ethics – A Balanced Outlook on Law.

COURSE OBJECTIVE: To provide basic familiarity about Engineers as responsible Experimenters, Research Ethics, Codes of Ethics, Industrial Standards

PART A

1. What are the pros and cons of industrial standardization? (MAY/JUNE 2012) Accuracy in measurement, interchange ability, eases of handling. Prevention on of injury, death and loss of income or property. Fair value of price. Competence in carrying out tasks. Sound design, ease of communications. IV YR/VIII SEM 8 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

2. What are the limitations of ethical code? (MAY/JUNE 2011)(NOV/DEC 2014) Codes are restricted to general and vague wording.Codes can„t give a solution or method for solving the internal conf Codes cannot serve as the final moral authority for professional conduct.

3. Define ethical accountability?(MAY/JUNE 2011) The inherent tendency of accepting moral responsibility for the actions of an individual and also the spontaneous willingness to subject himself to the moral scrutiny in an open-minded manner is called e t h i c a l accountability.

4. Name the aerospace ace experts and scientists who were associated with the Launching of challenger? (MAY/JUNE 2010) Allan McDonald of Morton-Thiokol at Cape Kennedy, Arnold Thomson and Roger Bois joly who were the seal experts at Morton-Thiokol and engineering managers, Bob Lund and Joe Kil minster were the experts associated with the launching of challenger space program.

5. Name some of the important code of ethics published by engineering societies. (MAY/JUNE 2010) National society of professional Engineers. Board of Ethical review. NSPE opinion of the Board of ethical review. American Association of Engineering societies(AAES). Institute of Electrical and Electronics Engineers (IEEE).

6. What was the primary reason that caused the failure of space shuttle program “challenger” (NOV/DEC 2010) The consequent rupturing of O-ring that constitute the field joints due to extreme cold weather was the primary reason that resulted in the failure of challenger space shuttle.

7. What are the problems with the law in engineering?(NOV/DEC 2010) a. Minimal compliance b. Many laws are without enforce able sanctions.

8. How engineering could be regarded as preventive technology?(MAY/JUNE 2009) As per the familiar proverb that "prevention is better than cure", the ultimate process of solving the scientific-based problems is not by curing alone, but effectively by the preventive measures. Such type of defensive measures to prevent scientific ills is called preventive technology.

9. What are the general features of morally responsible engineers?(MAY/JUNE 2009) a.Conscientiousness. b.Comprehensiveperspective. c.Autonomy. d.Accountability.

10. What is the specific role of informed consent in engineering experimentation? Informed consent is the vital concept to interact engineers with public society.

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It reflects the respects for the fundamental rights of minority people involved in the experimental procedures. It enables both the public and clients to be aware of the practical risks and benefits of that experimentation.

11. What are the differences between engineering and standard experiments? Engineering experimentation involves human subjects as control groups, unlike in the standard experimentation .The process of obtaining the informed consent from the human-engineering experimentation. Unlike in the scientific experiments, new knowledge is not gained in engineering experiment.

12. Differentiate scientific experiments and engineering projects? Scientific experiments are conducted to gain new knowledge, while ―engineering projects are experiments that are not necessarily designed to produce very much knowledge‖.

13. How Titanic tragedy be brought under engineering as social experimentation? Failure in the far-sighted approach of not providing enough number of lifeboat sand non-availability of proper safe exits handled to the sinking of titanic ship that caused the death toll of 1522 persons on board. These in designing are the reasons for bringing titanic tragedy under engineering as social experimentation

14. Define the term moral autonomy. The moral beliefs and attitudes of an individual with a committed action towards the specific principles and goals is called moral autonomy.

15. What are the uncertainties occur in the model designs? Model used for the design calculations. Exact characteristics of the materials purchased. Constancies of materials used for processing and fabrication. Nature of the pressure, the finished product will encounter.

16. What is meant by engineering as experimentation? (MAY/JUNE2014) (APR/MAY 2015)(NOV/DEC 2014) Experimentation (Preliminary tests or Simulations) plays a vital role in the design of a product or process. In all stages of converting a new engineering concept into a design likes, first rough cut design, usage of different types of materials and processes, detailed design, further stages of work design

17. State the importance of Ethics codes. (MAY/JUNE2014) Engineers shall uphold and advance the integrity, honor, and dignity of the engineering

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profession by: •using their knowledge and skill for the enhancement of the human race; •being honest and impartial and serving with fidelity the public, their employers, and clients. •striving to increase the competence and prestige of the engineering profession. •supporting the professional and technical societies of their discipline

18. What are the senses of engineering ethics?(NOV/DEC 2013) An activity and area of inquiry.

. Ethical problems, issues and controversies. . Ethical problems, issues and controversies. o Particular set of beliefs, attitudes and habits. . Morally correct.

19. Define Engineering Ethics.(NOV/DEC 2013) Study of the moral issues and decisions confronting individuals and organizations Engaged in engineering / profession. Study of related questions about the moral ideals, character, policies and relationships Of people and corporations involved in technological activity. Moral standards / values and system of morals

20. List the advantages of industrial standards.(APR/MAY 2015) o Increased marketability o Reduced operational expenses o Better management control o Increased customer satisfaction o Improved internal communication

PART-B

1. What is meant by professional responsibility and discuss the theories about virtues? (MAY/JUNE2012)(R) 2. Explain a Balanced Outlook on Law (NOV/DEC2010)(U) 3.Discuss the theories pertaining to moral autonomy with specific reference to consensus and controversy?(MAY/JUNE 2011)(U) 4. Where and how do moral problems arise in engineering?(An) (MAY/JUNE2009) 5. Discuss on the different roles played in the code of ethics set by professional societies? (U, MAY/JUNE 2012,MAY/JUNE2011,NOV/DEC 2013)(NOV/DEC2014) 6.Give justification on how the challenger disaster could have been avoided by engineers? (NOV/DEC 2011/MAY/JUNE 2012)(An) 7. How engineering project differ from standard experimentation? (U)(NOV/DEC 2013)

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8. Discuss on the different roles played in the code of ethics set by professional societies? (NOV/DEC 2013)(U) 9. Explain Engineers as responsible Experimenters.(U) (NOV/DEC 2012) 10. Briefly discuss the space shuttle challenger accident. What is the ethical problem involved in this? (MAY/JUNE 2014) (NOV/DEC 2014)(An) 11. Discuss about Research ethics. ?(U) (MAY/JUNE 2014) (NOV/DEC 2014) 12. What is meant by informal consent when bringing an experimental product to the market? (An, MAY/JUNE 2014) 13. How the ethical codes provide discipline among the engineers?(An) (MAY/JUNE2014), (APR/MAY2015) (NOV/DEC 2014) 14. Explain the work ethics in detail. (U) (NOV/DEC 2013) 15. Whom do you think should take public accountability „for unsafe machine? From the Designer to the final promoter, identify the roles and responsibilities towards safety and justify your views through a detailed case study. (E)(APRIL/MAY 2012) 16. Discuss briefly the role of industrial standards.(U) (APRIL/MAY 2015) 17. Discuss the ethical issues involved in challenger case study (U) (APRIL/MAY 2015) 18. Compare and contrast engineering experiments with standard experiments.(An) (NOV/DEC2014)

COURSE OUTCOME: The students will understand various social issues, industrial standards, code of ethics and role of professional ethics in engineering field.

UNIT-IV SAFETY, RESPONSIBILITIES AND RIGHTS

SYLLABUS: Safety and Risk – Assessment of Safety and Risk – Risk Benefit Analysis and Reducing Risk – Respect for Authority – Collective Bargaining – Confidentiality – Conflicts of Interest – Occupational Crime – Professional Rights – Employee Rights – Intellectual Property Rights (IPR) – Discrimination.

COURSE OBJECTIVE: To inculcate knowledge and exposure on Safety and Risk, Risk Benefit Analysis and have an idea about the Collective Bargaining, Confidentiality, Professional, Employee, Intellectual Property Rights PART A 1. What is conflict Interest?( MAY/JUNE 2012) Types of Conflicts of interest Actual conflict of interest Potential conflict of interest Apparent conflict of interest IV YR/VIII SEM 12 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

Interest in other companies Moonlighting Insider information 2. What are the reasons for Risk-Benefit Analysis? (NOV/DEC 2011, NOV/DEC 2013)) i. Risk-benefit analysis is concerned with the advisability of undertaking a project. ii. It helps in deciding which design has greater advantages. iii. It assists the engineers to identify a particular designs cores higher with that of t h e another one. 3. What are the safety measures an engineer must know before assessing a risk of any product?(MAY/JUNE 2009) The factors are: a. Does the engineer have the right data? b. Is he satisfied with the present design? c. How does he test the safety of a product? d. How does he measure and weight he risks with benefits for a product.

4. Explain the two types of Risk?( (MAY/JUNE 2012) i. Personal Risk: An individual, who is given sufficient information, will be in a position to Decide whether to take part in a risky activity or not . They are more ready to take on voluntary risks than in voluntary risks. ii. Public Risks: Risks and benefits to the public are more easily determined than to individuals, as larger number of people is taken in to account .Involuntary risks are found here.

5. Give the reasons for the Three Mile Island disaster? i. In adequate training to the operators. ii. Use of B&W reactors.

6. Define “risk‟.(May/June 2011)(NOV/DEC2014) A risk is the potential that something unwanted and harmful may occur.Risk = Probability X Consequences.

7. What do you mean by voluntary risk? (May/June 2010, May/June 2010) If a person knowingly takes any risk, then he feels it safe. In contrast, if the same risk is forced to him, then he feels it unsafe.

In simple terms the voluntary risks are considered as safe and the involuntary risks are considered as unsafe. 8. What is safe risk and acceptability of risk? (IT Dec 2009,May 2010) Acceptability of risk:

A risk is acceptable when those affected are generally no longer apprehensive about it. Apprehensiveness mainly depends on how the risk is perceived by the people. IV YR/VIII SEM 13 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

Safe Risk:

If a person knowingly takes any risk then he feels it safe. In the same way voluntary risks are considered as safe risk 9. List the methods that can be applied when testing is inappropriate. (May/june 2009 )(NOV/DEC2014) Scenario Analysis Failure modes and effects analysis Fault free analysis Event free analysis 10.What is the use of knowledge of risk acceptance to engineers? Though past experience and historical data give better information about safety of products designing there are still inadequate .The reasons are a. The information is not freely shared among industries b. There also new applications of old technologies that provides available data, which are less useful. c. So, in order to access the risk of a product, the engineers must share their knowledge and information with others in a free manner.

11. What are the positive uncertainties in determining risks? a. Purpose of designing b. Application of the product c. Materials and the skill used for producing the product 12. What is the Risk Transfer? It refers to the legal assignment of the cost of certain potential losses from one party to another. The most common way of affecting such transfer is by insurance.

13. What are the steps involved in design for safety? 1. Define the problem 2.Generate alternate solutions 3. Analyses each solution 4.Test the solution 5. Select the best solution 6 .Implement the chosen solution.

14. State the industrial definition on safety .(MAY/JUNE 2014) A ship in harbor is safe, but that is not what ships are built for‖ – John A. Shedd ‗A thing is safe if its risks are judged to be acceptable„ - William W. Lawrence We buy an ill-designed Iron box in a sale-> Underestimating risk We judge fluoride in water can kill lots of people -> Overestimating risk We hire a taxi, without thinking about its safety -> Not estimating risk

15. What is meant by Disaster? (MAY/JUNE 2014, NOV/DEC 2013))

A DISASTER = A seriously disruptive event + A state of unprepared ness. e.g., Titanic collision with an iceberg, at night: Emergency Fewer lifeboats, inadequate training and warnings of icebergs unheeded ->Disaster

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16. What is informed consent? (MAY/JUNE 2011)(APR/MAY 2015) Informed consent is the process by which the treating health care provider discloses appropriate information to a competent patient so that the patient may make a voluntary choice to accept or refuse treatment. It originates from the legal and ethical right the patient has to direct what happens to her body and from the ethical duty of the physician to involve the patient in her health care.

17. What is the use of risk analysis? (APR/MAY 2015) Risk analysis is the process of defining and analyzing the dangers to individuals, businesses and government agencies posed by potential natural and human-caused adverse events.

18. What is collegiality?( May/June 2011, Nov/June 2009, NOV/DEC 2014),(APR/MAY2015) Collegiality is a kind of connectedness grounded in respect for professional expertise and in a commitment to the goals and values of the profession and collegiality includes a disposition to support and cooperate with one„s colleagues.

19. What are the elements of collegiality? ( May/June 2010, NOV/DEC 2014) Respect Commitment Connectedness Cooperation 20. What do you meant by employee rights and lists its categories? (Nov/Dec 2012) Employee rights are rights, moral or legal, that involve the status of being an employee. They include some professional rights that apply to the employer-employee relationship.

21. What is the Basic Right of Professional Conscience? (MAY/JUNE 2011) The right to do what everyone agrees it is obligatory for the professional engineers to do the basic professional right is an entitlement giving one the moral authority to act without interference from others.

22. What is Institutional Recognition of Rights? (NOV/DEC 2011) One should have moral right, having it respected by others and given Recognition with in the institution is the other. Koning states in 1975, conference on Engineering Ethics- that one item that should be in the code of ethics is that engineers have the right at all times to exercise the dictates of their own conscience.

23. State the specific right. Specific rights can be stated as a particular professional obligation to apply Professional rights according to specific circumstances.

24. What are the two basic rights of professional/conscience First is to proceed piecemeal by reiterating the justification given for the specific professional duties Second, is to justify the right of professional conscience, which involves grounding it more directly in the ethical theories, for organizing moral reflections and approaching practical probles.

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25. What is Duty Ethics? (May/June 2011) Duty ethics rights are not the ultimate moral appeal . Engineers have a right to do something it is only because other have duties or obligations to allow him to do it . No employer has the right to threat engineers with loss of the jobs for refusing to work on project they see as likely to lead to the death or injury of unsuspecting victims.

26. What is Utilitarianism? Utilitarianism will justify the right of professional conscience by referring to the Basic goal of producing the most good for the greatest number of people the public good is certain to observed by allowing professionals to meet their obligations to the public.

27. What is meant by collective Bargaining?(May/June 2014) Collective bargaining is a process of negotiations between employers and a group of employees aimed at reaching agreements to regulate working conditions. The interests of the employees are commonly presented by representatives of a to which the employees belong. The collective agreements reached by these negotiations usually set out wage scales, working hours, training, health and safety, overtime, grievance mechanisms, and rights to participate in workplace or company affairs

28. What is meant by Occupational crime? (May/June 2014) Occupational Crime Occupational crimes are illegal acts made possible through one„s lawful employment. It is the secretive violation of laws regulating work activities. When committed by office workers or professionals, occupational crime is called ‗white collar crime„.

29. List the factors that shape the self confidence in a person. (NOV/DEC 2013),(APR/MAY2015)

Emphasize Strengths Take Risks. Use Self-Talk. Self-Evaluate.

30. Difference between Bribe and Gift. (NOV/DEC 2014)

Gift: Something of value given without the expectation of return Bribe: Something of value given with the hope of a future influence or benefit

PART-B 1. Discuss the notion of safe exit using evacuation plans for communities near power plants or Chemical processing plants? (U) (May/June 2010) (MAY/JUNE 2014) 2. What is r i s k -benefit analysis? Explain the different analytical method used when testing is inappropriate ? (U) (Nov/Dec 2010, May/June2011) (NOV/DEC 2014) 3. State the necessity of risk benefit analysis (R)(MAY/JUNE 2014) 4. Discuss the Bhopal disaster .Explain the responsibility of engineer in the design stage itself before the event of an accident. (U) MAY/JUNE 2014)(APR/MAY 2015) 5. Define the term risk and safety .How will an engineer assess the safety? (An)(NOV/DEC 2014) IV YR/VIII SEM 16 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

6. What are the factors that affect risk acceptability? What is the use of knowledge of risk acceptance to engineers? (U) (NOV/DEC 2013) 7. a) Describe the concept of (16) (R) (Apr/May 2015) 1) Risk benefits analysis. 2) Fault tree analysis. 8. Explain in detail the effect of information on risk assessment with an example (U) (NOV/DEC 2014) 9. Discuss the concept of safety exists in the Chernobyl Case Studies(U)(NOV/DEC 2014) 10. Write short notes on (i) Whistle blowing (ii) Occupational crime (iii) Intellectual property rights (iv) Discrimination (V) Institution Authority (R, APRIL/ MAY 2013,NOV/DEC 2013)( APRIL/ MAY 2015) 11. Name and describe four important responsibilities of engineers as employees.(U)(NOV/DEC 2011) 12. Write a detailed note about the employee rights and professional rights that the engineers are entitled. (APRIL/ MAY 2010), (NOV/DEC 2013) ,(APRIL/ MAY 2015)(R) 13. Discuss about Collegiality and Loyalty(U)(MAY/JUNE 2014) (NOV/DEC 2014) 14.What are the main element of IPR ?Give example of discrimination(MAY/JUNE 2014)(R) 15.Discuss human rights,professional rights and employee rights in an engineer field.(U) MAY/JUNE 2014) 16. Discuss the significance of intellectual property rights.Also explain the legislations covering intellectual property rights in india.(NOV/DEC 2013) (NOV/DEC 2014)(U) 17. Discuss the significance of loyalty and collegiality in team work? (APRIL/ MAY 2015)(U)

COURSE OUTCOME: The students will be aware of responsibilities of an engineer for safety and risk benefit analysis, professional rights and responsibilities of an engineer. , UNIT V GLOBAL ISSUES

SYLLABUS : Multinational Corporations – Business Ethics - Environmental Ethics – Computer Ethics - Role in Technological Development – Weapons Development – Engineers as Managers – Consulting Engineers – Engineers as Expert Witnesses and Advisors – Honesty – Moral Leadership – Sample Code of Conduct.

IV YR/VIII SEM 17 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

COURSE OBJECTIVE: To have an adequate knowledge about MNC„s, Business, Environmental, Computer Ethics, Honesty, Moral Leadership, sample Code of Conduct.

PART A

1. What is embezzlement? (APRIL/ MAY 2011) The process of computing computer crimes such as stealing or cheating clients and conspiracy in the fraudulent uses of computer networks is called embezzlement.

2. What the hired guns? (APRIL/ MAY 2011) Engineers are hired by attorneys to help them to establish the facts in away favorable to their clients. The hired guns violate the standards of honesty and also due care in conducting investigations.

3. What is technology transfer? (APRIL/ MAY 2010) Technology transfer is a process of changing the technology to a new setting and implementing it. Technology includes hardware such as machines and installations as well as techniques such as technical, organizational and managerial skills and procedures.

4. What does moral leadership mean?(APRIL/MAY2010) (NOV/DEC 2014) Whenever the goals of a leader become permissible and also morally valuable, it is known as moral leadership. Moral leadership also means that employing morally acceptable ways to motivate the groups to move towards morally desirable ways. The ways are depending on the situations.

5. State the most important ethical mistake made by the multinational corporation which caused Bhopal gas plant disaster. (NOV/DEC 2010)

o The tanks used to store Methyl Iso-cyanate were overloaded to a tune of 75%. o The emergency plant was also filled with a large amount of chemicals. o The entire refrigeration unit had been shut down as a measure to reduce the cost and this led to increase of temperatures to a higher level. o One of the disappointed workers unscrewed a pressure gauge on a tank and inserted a hosepipe into it, knowing that it would cause damage, but not to this extent. o Scrubber has also been shut down. o Flare tower was also not in an operating condition. o Unfortunately there were no emergency drills or evacuation plants available.

6. Define Conflict resolution. (APRIL/ MAY 2010) Conflict resolution is the result based on some objective standard and corporate usually uses general standards for evaluating the results.

7. What is contextualize? (APRIL/MAY 2010) In accordance to Gilligan women try hard to preserve personal relationship will all people. This context-oriented emphasis on maintaining personal relationship is called as ethics of care in contrast with ethics of rules and rights.

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8. What are ethical pluralism and ethical relativism? (APRIL/MAY 2010) Ethical pluralism: According to this view there may be alternative moral perspectives that are reasonable, but no one of which must be accepted completely by all rational and morally concerned persons. Ethical relativism: Actions are morally right when they are approved by law or custom they are wrong when they violate laws or customers.

9. What should an ethical expert witness, even though hired by a company, expected to do? ( APRIL/MAY 2010) Engineers should not become the hired-guns to their clients, but instead remain as objective as humanly possible in their investigations and the conclusions they reach .they should avoid biases resulting from money ego, and sympathy.

10. What are the international rights listed by Donaldson? (NOV/DEC 2014) Thomas Donaldson in his book ‗The ethics of International Business„ has listed the following as the International rights: The right to freedom of physical movement The right to ownership of property The right to freedom from torture The right to a fair trial The right to nondiscriminatory treatment The right to physical security The right to freedom of speech and association The right to minimal education The right to political participation The right to subsistence.

11. Define appropriate technology? (IT Nov 2008) Appropriate technology refers to the identification, transfer and implementation of the most suitable technology for a new set of conditions.

12. List out four examples for Multinational Corporation. (IT Nov 2010) Large corporations having investment and business in number of countries are known as Multinational or Transnational corporation. Some of them are : Hindustan Lever, Ford, Toyota, Sony, LG, Smith Kline Beecham, ITC, Ponds etc.

13. Define computer ethics?(DEC/NOV2010) Computers contribute to a variety of moral problems. In order to evaluate andact appropriately with such problems, a new field of applied ethics termed as ‗computer ethics„ has been developed. The study of ethical issues that are associated with computer, its peripheral and accesses series and the computing profession is called as computer ethics.

14. What is meant by globalization? Our lives are increasingly dependent upon the goods/services produced over the world and are IV YR/VIII SEM 19 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

influenced by the business from around all the corners of the world. In general world has become a global village and have a global economy. The increasing international flow of capital, technology, trade, and people have had the effects of changing the nature of local organizations governments and people of countries and have led to social changes and developments.

15. What are the three senses of relative values? (DEC/ NOV 2012) Ethical Relativism Descriptive Relativism Moral Relativism

16. What are the normal issues arise in Multinational Corporation?(MAY/JUNE 2014) Ethical dilemmas faced by certain companies may be specific to their industry or company, other types of ethical issues are common to all types of companies. Handling ethical decisions with wisdom is especially important for small businesses, given the potentially devastating effects these companies may face if such issues aren't handled correctly.

17. Differentiate the Eye witness and expert witness in the legal system (MAY/JUNE 2014) An eyewitness is one who testifies what they perceived through his or her senses (e.g. seeing, hearing, smelling, touching). That perception might be either with the unaided human sense or with the aid of an instrument, e.g., microscope or stethoscope, or by other scientific means, e.g.a chemical reagent which changes color in the presence of a particular substance An expert witness is one who allegedly has specialized knowledge relevant to the matter of interest, which knowledge purportedly helps to either make sense of other evidence, including other testimony, documentary evidence or physical evidence (e.g., a fingerprint)

18. What is meant by Moral Leadership (NOV/DEC 2013) Moral Leadership is a very different kind of leadership. Rather than aspiring to being followed, Moral Leaders aim to serve. Instead of showcasing their own skills, Moral Leaders tend to develop the capacities of others.

19. Define the term „honesty‟ and „moral leadership‟ Honesty :A facet of moral character that connotes positive and virtuous attributes such as integrity, truthfulness, and straightforwardness, along with the absence of lying, cheating, or theft „Moral L eadership‟: A process of social influence in which one person enlists the aid and support of others in accomplishing a common task.

20. What do you understand by „business ethics‟? Business ethics (also corporate ethics) is a form of applied ethics or professional ethics that examines ethical principles and moral or ethical problems that arise in a business environment. It applies to all aspects of business conduct and is relevant to the conduct of individuals and entire organizations.

PART B

1. Explain in detail the issues pertaining to environment issues? (R) (APRIL/ MAY 2011) 2. Describe the Bhopal Gas Tragedy and its effects?(R)(APRIL/MAY 11) IV YR/VIII SEM 20 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

3. Is there any relationship among engineering ecology and economics? discuss.(An)(NOV/DEC 2012) 4. Write briefly on(R) (i) Engineer used as expert witness. (ii) Engineers as good managers. (iii)Engineers with social responsibilities.(MAY/JUNE 2013) 5. Discuss the following in detail(MAY/JUNE 2014)(U) Business Ethics Environmental Ethics Computer Ethics Weapons Development(NOV/DEC 2013) 6. What is environment ethics?Why it is important to study. Discuss any environment issues in the ethical point of view to engineers. (NOV/DEC 2013),(APR/MAY 2015) (NOV/DEC 2014)(An) 7. Discuss the following in detail (MAY/JUNE 2014)(U) Engineers as Managers Engineers as advisors Engineers as consultant Moral leadership 8. Discuss the various global issues that have an impact on business.(U)(APR/MAY2015) 9. Discuss the ethical issues related to computer ethics and internet (U)(NOV/DEC2014)

COURSE OUTCOME:

The students will acquire knowledge about various roles of engineers in variety of global issues and able to apply ethical principles to resolve situations that arise in their professional lives

IV YR/VIII SEM 21 V.S.B ENGINEERING COLLEGE,KARUR DEPARTMENT OF ECE

COURSE OUTCOMES

Course Name : PROFESSIONAL ETHICS IN ENGINEERING (GE6075) Year/Semester : IV / VIII Year of Study : 2016 –2017 (R – 2013) On Completion of this course student will be able to

C410.1 Understand the core values that shape the ethical behavior of an engineer and Exposed awareness on professional ethics and human values. C410.2 understand the basic perception of profession, professional ethics, various moral issues & uses of ethical theories C410.3 understand various social issues, industrial standards, code of ethics and role of professional ethics in engineering field C410.4 Aware of responsibilities of an engineer for safety and risk benefit analysis, professional rights and responsibilities of an engineer. acquire knowledge about various roles of engineers in variety of global issues C410.5 and able to apply ethical principles to resolve situations that arise in their professional lives

CO – PO MATRIX: CO PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12

C410.1 - - - - - 1 1 3 1 2 - - C410.2 - - - - - 1 1 3 1 2 - - C410.3 - - - - - 3 2 3 - 1 - - C410.4 - - - - - 3 2 1 - - - - C410.5 - - - - - 3 2 2 - 1 3 - AVG - - - - - 2.2 1.6 2.4 1 1.5 3 - COURSE OUTCOMES AND PROGRAM SPECIFIC OUTCOMES MAPPING CO – PSO MATRIX: CO PSO1 PSO2 PSO3 C410.1 - - 1 C410.2 - - - C410.3 - - - C410.4 - - 1 C410.5 - - 1 AVG - - 1

IV YR/VIII SEM 22

EC 6019 Data Converters Department of ECE V.S.B.Engineering College, Karur Department of Electronics and Communication Engineering SYLLABUS

EC6019 DATA CONVERTERS L T P C 3 0 0 3 OBJECTIVES  To explain the basic operational and design principles of CMOS Analog to Digital and Digital to Analog converter architectures.  To introduce the design calculations for developing the various blocks associated with a typical CMOS AD or DA converter.  To make students decide the dimensions and bias conditions of all the MOS transistors involved in the design.

UNIT I SAMPLE AND HOLD CIRCUITS 9 Sampling switches, Conventional open loop and closed loop sample and hold architecture, Open loop architecture with miller compensation, multiplexed input architectures, recycling architecture switched capacitor architecture.

UNIT II SWITCH CAPACITOR CIRCUITS AND COMPARATORS 9 Switched-capacitor amplifiers, switched capacitor integrator, switched capacitor common mode feedback. Single stage amplifier as comparator, cascaded amplifier stages as comparator, latched comparators.

UNIT III DIGITAL TO ANALOG CONVERSION 9 Performance metrics, Reference multiplication and division, switching and logic functions in AC, Resistor ladder DAC architecture, Current steering DAC architecture.

UNIT IV ANALOG TO DIGITAL CONVERSION 9 Performance metric, flash architecture, Pipelined Architecture, Successive approximation architecture, Time interleaved architecture.

UNIT V PRECISION TECHNIQUES 9 Comparator offset cancellation, Op Amp offset cancellation, Calibration techniques, range overlap and digital correction. TOTAL: 45 PERIODS

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EC 6019 Data Converters Department of ECE OUTCOMES Upon completion of the course, the student should be able to  Explain sample and hold circuits  Design ADC/DAC circuits  Analyze ADC/DAC Architecture and Performance  Discuss calibration techniques

TEXT BOOK 1. Behzad Razavi, “Principles of data conversion System Design”, IEEE press, 1995.

REFERENCES 1. Franco Maloberti, “Data Converters”, Springer, 2007. 2. Rudy Van de Plassche, “CMOS Integrated Analog-to-Digital and Digital-to-Analog Converters”, Kluwer Academic Publishers, Boston, 2003.

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EC 6019 Data Converters Department of ECE

2 MARK QUESTIONS AND ANSWERS

UNIT I SAMPLE AND HOLD CIRCUITS 1 What is Data Converter? Data Converter is a device that converts analog signals to digital data or vice versa. Devices that convert analog signals to digital are referred to as ADC and devices that convert digital signals to analog are called DAC. 2 What do you mean by data conversion? Data conversion is the conversion of data from one format to another. In a computer, data is encoded in a variety of ways. 3 Specify the applications of Data Converter. . Precision Measurement and Sensor Conditioning . Multichannel Data Acquisition Systems . Digital Potentiometers . Digital Audio . Digital Video and Display Electronics . Software Radio and IF Sampling . Direct Digital Synthesis (DDS) . Precision Analog Microcontrollers 4 What are the advantages and disadvantages of sampling switches? Advantages . Increase available network bandwidth . Reduce the workload on individual computers . Increase network performance . Connect directly to workstations Disadvantages . Slow speed (2N clock pulses for N-bit conversion) . Hard to generate precise ramp required for high resolution ADCs

5 Define settling time. Settling time is defined as the time takes for the converter to settle within some specified amount of final value (usually 0.5 LSB). 6 What is a zero order hold? The zero order hold (ZOH) is a mathematical model of the signal reconstruction done by a conventional digital-to-analog converter (DAC). It describes the effect of converting a discrete-time signal to a continuous-time signal by holding each sample value for one sample interval. 7 What is a holding circuit interlock? The holding circuit interlock is an open auxiliary contact on magnetic starters or contactors. It is used in three wire control schemes with momentary inputs. 8 What is a peak detector circuit? A peak detector is a series connection of a diode and a capacitor outputting a DC voltage equal to the peak value of the applied AC signal. 9 What is the purpose of Sample and Hold Circuit? A sample and hold circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified period of time.

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EC 6019 Data Converters Department of ECE 10 Define D/A and A/D converter. An electronic circuit that converts analog signals to digital, or vice-versa. An analog signal is a continuously varying voltage or current. Its digital counterpart is a stream of digital numbers, each representing the amplitude of the analog signal at a moment in time. 11 Specify 3 mechanisms in MOS transistor operation and introduces an error. . Channel Charge Injection . Clock Feedthrough . Thermal noise 12 Define Static Error. Static errors are errors that affect the accuracy of the converter when it is converting static (dc) signals and can be completely described by four terms. These are offset error, gain error, integral nonlinearity and differential nonlinearity. 13 List 4 types of Static Error. . Offset error . Gain error . Integral nonlinearity and . Differential nonlinearity 14 What is sampling speed? Sampling speed is given by the on-resistance of the switch and the value of the sampling capacitor. 15 Define sampling rate. The sampling rate is the rate at which samples can be continuously converted and is typically the inverse of the settling time. 16 What is offset error and how it affects? Offset Error is defined as the difference between the nominal and actual offset points. This error affects all codes by the same amount and can be compensated by a trimming process. If trimming is not possible, this error is referred to as the zero scale error. 17 Define gain error. How do you measure gain point in ADC and DAC circuit? Gain error is defined as the difference between the nominal and actual gain points on the transfer function after the offset error has been corrected to zero. For an ADC, the gain point is the mid-step value when the digital output is full scale, and for a DAC it is the step value when the digital input is full scale. 18 What is differential nonlinearity error? The differential nonlinearity error is defined as the difference between an actual step width (for an ADC) or step height (for a DAC) and the ideal value of 1 LSB. Therefore if the step width or height is exactly 1 LSB, then the differential nonlinearity error is zero. 19 Define integral nonlinearity error or linearity error. The integral nonlinearity error or linearity error is defined as the deviation of the values on the actual transfer function from a straight line. 20 What is Aperture error? Aperture error is caused by the uncertainty in the time at which the sample/hold goes from sample mode to hold mode. This variation is caused by noise on the clock or the input signal. 21 Give 3 sampling techniques. 1. Ideal sampling 2. Zero – order hold and 3. Track and hold

22 Define acquisition time.

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EC 6019 Data Converters Department of ECE Acquisition time is the time after the sampling command required for the SHA output to experience a full scale transition and settle within a specified error band around its final value. 23 What is droop rate? Droop rate is the rate of discharge of the capacitor during the hold mode. 24 Define SNDR. It is the ratio of the signal power to the total noise and harmonic power at the output in the hold mode. 25 How do you determine the acquisition time? Acquisition time is determined by the recovery delay of 퐵1 푎푛푑 퐵2, the on-resistance of 푆1 the value of 퐶퐻 and the maximum allowable error. 26 Define dynamic range. It is the ratio of the maximum allowable input swing and minimum input level that can be sampled with specified accuracy. 27 Write the equation for on-resistance as per square law NMOS device. ퟏ 푹 = 풐풏 푊

휇푛 퐶표푥 퐿 푉퐺푆 − 푉푇퐻 Where 휇푛 = Electron mobility in the channel 퐶표푥 = Gate oxide capacitance per unit area W and L = Effective width and length of the device 푉퐺푆 = Gate source voltage 푉푇퐻 = Threshold voltage 28 Specify the limitations of sampling switches. 1. Acquisition time 2. Aperture jitter 3. Nonlinearity 4. Pedestal error 5. Feedthrough and 6. SNDR 29 Write the 2 types of sampling switches. 1. CMOS and (MOS Switches) 2. Bipolar SHAs. (Diode Switches) 30 List the features of dual loop multiplexed input architecture. 1. Input independent pedestal error 2. Nonlinearity occur (but very small) 3. If the sampling capacitors and switches are same then the pedestal produced at two inputs are same. 31 Specify the drawbacks of dual loop multiplexed input architecture.  Suffers from tradeoff between acquisition speed and droop rate.  Small nonlinear  Slower time response  Limited input range 32 What are the advantages of recycling architecture? 1. Small pedestal error 2. High linearity 3. Relatively high speed

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EC 6019 Data Converters Department of ECE 33 Compare MOS and Diode switches. Sl. Diode Switches MOS Switches No. 1 Low on-resistance High on-resistance On-resistance and charge More attractive for high precision 2 injection depend much less on the open loop applications. input voltage Operate with clock voltage Allowing sharper edges and better 3 swings an order of magnitude definition of sampling points in smaller time. 4 Low jitter Comparatively high 5 Input voltage range is small High More complex and dissipate more 6 Less power

34 Compare open loop and closed loop architecture.

Sl. Open loop architecture Closed loop architecture No. Input and output buffer amps are Closed loop architecture is 1 each configured as voltage configured as either a follower followers. output or an integer output. 2 High speed Speed is less Acquisition and settling time are Acquisition and settling time are 3 short because there is no feedback long comparatively. between the buffer amps. No accuracy because of lack of 4 Comparatively high accuracy feedback

35 Give the advantages and disadvantages of switched capacitor architecture. Advantages 1. Linearity achieved upto 13 bits. 2. Large voltage swing Disadvantages 1. Delay in the acquisition mode 2. Harmonic distortion in the sampled signal

PART – B & C 1 Explain the following sample and hold circuit architectures: (a) Closed Loop (b) Open loop architecture with miller capacitance 2 State and explain Miller effect. 3 Explain the principle of sample and hold circuit with neat diagram. 4 Explain the switched capacitor architecture with a neat diagram. 5 Describe the conventional architecture with pedestal cancellation method. 6 Write technical notes on (i) Recycling Architecture and (ii) Switched Capacitor Architecture

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EC 6019 Data Converters Department of ECE 7 Explain the operation of multiplexed input architecture with neat diagrams. 8 Differentiate Diode switch and MOS switch. 9 Explain in detail about multiplexed input architecture with necessary diagram. 10 Give the features of MOS switches. 11 Elaborate diode switches using modified circuit with clamp diodes and also specifies the advantages. 12 Discuss sampling bridge with bootstrapped clamp voltage with diagram. 13 What are the factors degrading the phase margin and specify the drawbacks. 14 Compare open and closed loop architecture, multiplexed input architectures, recycling architectures and switched capacitor architecture with proper circuit diagram. 15 Compare (i) Open loop (ii) Closed loop (iii) Closed loop with miller capacitance (iv) Closed loop with pedestal cancellation architecture

UNIT II SWITCH CAPACITOR CIRCUITS AND COMPARATORS PART A 1 What is switched capacitor? A switched capacitor is an electronic circuit element used for discrete-time signal processing. It works by moving charges into and out of capacitors when switches are opened and closed. 2 What is an opamp? The operational amplifier is a multiterminal device which is complex internally. An operational amplifier is a direct coupled high gain amplifier usually consisting of one or more differential amplifiers and usually followed by a level translator and an output stage. 3 Mention applications of op-amp. . AC and DC signal amplification . Active filters . Comparators . Oscillators and . Regulators 4 What are the characteristics of ideal op-amp? . Open loop voltage gain (퐴01) = ∞ . Input impedance (푅푖) = ∞ . Output impedance (푅0) = 0 . Bandwidth (BW) = ∞ . Zero offset (푉0) = 0 when 푉1 = 푉2 = 0. 5 What is the usage of op-amp? An operational amplifier is available as a single integrated circuit package. It is a versatile device that can be used to amplify dc as well as ac input signals and was originally designed for computing such mathematical operations. 6 Define linear op-amp circuit. An op-amp circuit which has the output signal with the same shape as that of the input signal is called linear op-amp circuit. The op-amp does not go to saturation during its cycle.

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EC 6019 Data Converters Department of ECE 7 Define nonlinear op-amp circuit. An op-amp circuit which has the output signal with a different shape from the input signal is called non linear op-amp circuit. The op-amp saturates during part of its input cycle. 8 Give the applications of integrator. . Analog computers . Analog to digital computers . Wave shaping circuits . Ramp generators 9 Specify the effects of parasitic capacitor. The effects of parasitic capacitors are . 푪풑ퟏ − 풅풓풊풗풆풏 풃풚 풐풑풂풎풑 . 푪풑ퟐ − 풐풑 − 풂풎풑 풗풊풓풕풖풂풍 품풓풐풖풏풅 . 푪풑ퟑ − 풄풉풂풓품풆풔 풕풐 푽풊풏 풂풏풅 풅풊풔풄풉풂풓품풆 풊풏풕풐 푪ퟏ 10 Define opamp comparator. The Op-amp comparator compares one analogue voltage level with another analogue voltage level, or some preset reference voltage, VREF and produces an output signal based on this voltage comparison 11 Mention the importance of single stage amplifier based on comparators. . Maximum gain-bandwidth product for given technology. . Gain obtained by using complex schemes . Power supply rejection . Overdrive recovery . Power consumption 12 Give some applications of Comparators. . Zero crossing detector . Window detector . Time marker generator . Phase detector 13 Define slew rate. Slew rate is defined as the maximum rate of change of output voltage caused by a step input voltage. An ideal slew rate is infinite which means that op-amp’s output voltage should change instantaneously in response to input step voltage.

14 What causes slew rate? There is a capacitor with-in or outside of an op-amp to prevent oscillation. It is this capacitor which prevents the output voltage from responding immediately to a fast changing input. 15 What is input offset in comparator? Input offset is the voltage that must be applied to the input to get the transition between the low and the high state. 16 Define response time. It is the time interval between the application of a step input and time when the output reaches the respective logic level. 17 What are the drawbacks of switched capacitor integrator? . The input dependent charge injection of S1 introduces nonlinearity in the charge stored on capacitor on C1. . The nonlinear capacitance at node P resulting from the source / drain junctions of S1 and S2 leads to a nonlinear charge-to-voltage conversion when C1 is switched to X.

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EC 6019 Data Converters Department of ECE 18 What are the applications of current sources? Transistor current sources are widely used in analog ICs both as biasing elements and as load devices for amplifier stages. 19 Draw the switched capacitor integrator. Continuous Time Integrator

Discrete Time Integrator

20 Define CMRR of an op-amp. The relative sensitivity of an op-amp to a difference signal as compared to a common mode signal is called the common –mode rejection ratio. It is expressed in decibels. CMRR= Ad/Ac 21 What are the characteristics of a comparator?  Speed of operation  Accuracy and  Compatibility of the output 22 What is voltage comparator? A voltage comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger.

Mention the importance of open loop cascade amplifier offset voltage.  There is no frequency compensation required.  Generate digital output voltage.

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EC 6019 Data Converters Department of ECE 23 Draw latched comparators circuit.

24 Draw architecture of CMOS based latched comparators.

25 Mention the advantages and disadvantage of offset and output cancellation method. Advantages . Complete cancellation . Closed loop stability is not required Disadvantages . Gain per stage must be small . Offset storage C in the signal path could slow the overall performance.

26 What happens when the common terminal of V+ and V-sources is not grounded? If the common point of the two supplies is not grounded, twice the supply voltage will get applied and it may damage the op-amp

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EC 6019 Data Converters Department of ECE 27 What is meant by Clock Bootstrapping?

Ф Ф1 Ф2 … VDD CS In Out Ф M1

Small on-resistance leads to large switches → large parasitic caps and large clock buffers Clock bootstrapping keeps VGS of the switch constant → constant on-resistance and less parasitic of the PMOS.

PART- B & C 1 Explain the principle of cascaded switched capacitor amplifier stages with neat diagrams. 2 Explain the operation of switched capacitor amplifier with a circuit diagrams. 3 Give an account on applications of Switched capacitor integrator. 4 Explain the working of single stage switched capacitor amplifier. 5 Discuss in detail about switched capacitor common mode feedback amplifier. 6 Explain the concept of switched capacitor integrator with neat diagrams. 7 Explain in detail about latched comparators. 8 Briefly explain the working principle of cascaded amplifier stage as comparator. 9 Explain in detail about the architecture which employs a binary search algorithm in a feedback Loop including a 1- bit A/D converter. 10 Compare single stage amplifier as comparator, cascaded amplifier stages as comparator and latched comparators. 11 Discuss precision multiply-by-two circuit and explain their operation in sampling mode and amplification mode. 12 Specify the design issues while designing the comparator circuit and also explain the performance characteristics. 13 Explain about offset cancellation and specify their different types of techniques.

UNIT III DIGITAL TO ANALOG CONVERSION PART A 1 What are the applications of DAC Architectures?  Music players to convert digital data streams into analog audio signals.  Televisions and mobile phones to convert digital video data into analog video signals. 2 Define latency. It is the total delay from the time of digital input changes to the time of analog output has settled within a specified error band around its final value. 3 How to minimize the glitch impulse in DAC Circuits?  Segmented architectures are used to minimize the glitch impulse in DAC circuits. 4 Define glitch energy. Glitch impulse area is the maximum area under any extraneous glitch that appears at the output after the input code changes. This parameter is also called glitch energy.

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EC 6019 Data Converters Department of ECE 5 List the drawbacks of binary weighted resistor technique of D/A conversion. . They require tight device matching to achieve monotonicity. . They exhibit large glitch impulses. . Mismatch of resistor 6 The basic step of a 9 bit DAC is 10.3 mV. If 000000000 represents 0Volts, what is the output for an input of 101101111? The output voltage for input of 101101111 is = 10.3 mV (1×28+0*27+1×26+1×25+0×24+1×23+1×22+1×21+1×20) = 10.3 × 10-3 (256+0+64+32+0+8+4+2+1) = 10.3 × 10-3 (367) = 3.78V 7 What is meant by linearity? The linearity of an ADC/DAC is a measure of its accuracy & tells us how close the converter output is to its ideal transfer characteristics. A good converter exhibits a linearity error of less than ±½LSB. 8 Define Monotonicity. The ability of a DAC's analog output to move only in the direction that the digital input moves (i.e., if the input increases, the output doesn't dip before asserting the correct output.) 9 What are the advantages and disadvantages of R-2R ladder DAC? Advantages: . Easier to build accurately as only two precision metal films are required. . Number of bits can be expanded by adding more sections of same R/2R values. Disadvantage: . In this type of DAC, when there is a change in the input, changes the current flow in the resistor which causes more power dissipation which creates non-linearity in DAC. 10 What are the specifications of D/A converter? The specifications are . Accuracy . Offset voltage . Monotonicity . Resolution and . Settling time 11 Draw the architecture of R-2R Ladder.

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EC 6019 Data Converters Department of ECE 12 What are the advantages of intermeshed ladder over single ladder architectures? . Same resolution . Same equivalent resistance at each tap . Faster recovery . The secondary ladder does not switch their loading on the primary ladder is constant and uniform. 13 Draw the graph to measure the gain error in DAC circuits.

Analog Output .

Digital Input

Ideal Output Positive Offset Errorr Negative Offset Error

14 Why high speed D/A converters are based on current steering architectures? This architecture can drive resistive loads directly, they do not require high speed amplifiers at the output and hence are potentially faster than other types of DACs. 15 What is the function of timing skews in DAC architectures? Timing Skews can be suppressed through the use of on-chip latches to sample and align the incoming digital signals and apply only the sampled values to the current switches. 16 Draw the architecture of Voltage Division and its specification.

17 What is meant by Capacitor mismatching DAC circuits? Mismatching in an array of capacitors arises from both gradients and random variations. 18 What is the use of Clocks circuits in DACs DACs do not need any clocks; the digital input simply ripples through and eventually generates an analog output. In practice, most high-speed DACs use clocks and latches to synchronize (align) the date and also perform the logic in pipelined stages.

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EC 6019 Data Converters Department of ECE 19 Convert binary to thermometer DAC circuits with an example.

20 What is meant by Capacitor mismatching DAC circuits? W L

tox

 퐶 = 푊  퐿  푡표푥 ∆퐶 ∆푊 ∆퐿 ∆푡 = + − 표푥 퐶 푊 퐿 푡표푥 21 Sketch the architecture of Binary weighting using R-2R networks.

PART B & C 1 Explain the concept of a simple DAC with a diagram. 2 Describe the switching and logic functions in DAC. 3 Explain how switching functions are realized in resistor–ladder DAC. 4 Explain the segmented architecture of current steering DAC. 5 Explain in detail the current steering DAC architecture with a neat diagram. 6 Explain the concept of intermeshed ladder architecture in detail. 7 Explain the principle of reference multiplication and division in detail. 8 What is reference multiplication? Explain how it is performed in DAC circuits using a suitable example.

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EC 6019 Data Converters Department of ECE 9 Explain in detail about the binary to thermometer code conversion. 10 Write short notes on (i) voltage division (ii) current division (iii) charge division 11 Specify the drawbacks of uniform current division and binary current division. Explain about segmented array and binary array with necessary diagram. 12 Draw I-V characteristics of MOS and Bipolar and explain in detail.

UNIT IV ANALOG TO DIGITAL CONVERSION Performance metric, flash architecture, Pipelined Architecture, Successive approximation architecture, Time interleaved architecture. 1. Define SNR. Signal to noise ratio is the ratio of the signal power to the total noise and harmonic power at the output, when the input is sinusoid. 2. What is meant by kickback noise? Strobe comparators generate a great deal of noise at their inputs during the transition from latching to tracking. This noise sees different impedances at the input terminal and at the ladder taps, and hence produces a differential error. 3. Define metastability. Metastability occurs when the difference at the input of a comparator is small, making the circuit take a long time to produce a well defined logic output. 4. How the interleaved architectures suffered from sampling circuits? While attaining high conversion rates, interleaved architectures suffer from accuracy due to parameter mismatches in gain, differential and integral nonlinearity, timing and offset give rise to higher noise power in the overall output. 5. What is the function of successive approximation register in ADC? Successive approximation register employs a binary search algorithm in a feedback loop including a 1-bit A/D converter. 6. Define charge redistribution principle. Successive approximation converters are based on the charge redistribution principle. In the sampling mode, the top plate is grounded, while all the bottom plates are grounded and causing the top plate voltage to be equal to the negative of sampled level. 7. How to avoid the long settling time in successive approximation register? The ratio of the largest and smallest capacitors in the array must be decreased. For example, rather than scaling all the capacitors in the array must be decreased. 8. Mention the concept of pipelining. The concept of pipelining used in digital circuits, can also be applied in the analog domain to achieve higher speed where several operations must be performed serially.

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EC 6019 Data Converters Department of ECE 9. What is the function of grey encoding in Flash architecture? Two errors in flash converters namely metastability and sparkles that can be suppressed using grey encoding as an intermediate step between thermometer and binary code. 10. Define clock jitter. SNR is degraded when there is jitter in the sampling clock. This becomes noticeable for high analog-input frequencies. To achieve accurate results, it is critical to provide the ADC with a low-jitter, sampling clock source. 11. Mention the different types of Flash architectures. . Reference Ladder DC and AC Bowing . Non linear input capacitance . Kickback noise . Sparkles in Thermometer code . Metastability 12. Define Sparkles code. Comparator outputs will be a thermometer code, such as 00011111. Errors can

cause an output like 00010111, meaning that there is a spurious zero in the result. This

out-of-sequence 0 is called a sparkle, which is caused by imperfect input settling or

comparator timing mismatch. The magnitude of the error can be quite large.

13. Define Quantization error. The approximation or rounding effect in A/D converters is called quantization and the difference between the original input and the digitized output is called the quantization error.

14. Distinguish between Flash vs Pipelined ADCs. Sl. Flash ADCs Pipelined ADCs No. It employs a parallel structure and works Comparator only needs to be low offset 1 on one to a few bits of successive samples and to resolve its inputs to a digital level concurrently There is no linear settling time and It improves speed at the expense of power 2 requires preamplifiers to drive the and latency comparators. Each pipeline stage is much slower than a 3 Pipeline stage is high comparatively. flash section.

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EC 6019 Data Converters Department of ECE 15. How the dynamic range has specified in SNR? Dynamic range is the ratio of the power of a full scale sinusoidal input to the

power of a sinusoidal input for which SNR=0db.

16. What is the advantage and disadvantages of flash type ADC? . Flash type ADC is the fastest as well as the most expensive. . The disadvantage is the number of comparators needed almost doubles for each added bit . For a n-bit convertor 2(n-1) comparators and 2n resistors are required).

17. Define conversion time. It is defined as the total time required converting an analog signal into its digital output. It depends on the conversion technique used and the propagation delay of circuit components. The conversion time of a successive approximation type ADC is given by

Tc =T(n+1) clock period Where, T- time period n - no. of bits 18. Which is the fastest ADC and why? Simultaneous type A/D converter(flash type A/D converter) is the fastest because A/D conversion is performed simultaneously through a set of comparators .

19. Give the disadvantages of flash type A/D converter. The simultaneous type A/D converter is not suitable for A/D conversion with more than 3 or 4 digital output bits. Then (2n-1) comparators are required for an n-bit A/D converter and the number of comparators required doubles for each added bit.

20. Compare various ADC types with their parameters. Type Speed (relative) Cost (relative) Dual Slope Slow Med Flash Very Fast High Successive Medium Fast Low Approximation Sigma-Delta Slow Low

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EC 6019 Data Converters Department of ECE PART B & C

1. Explain the pipelined architecture of ADC and discuss its merits and demerits. 2. Explain the flash ADC architecture and its features in detail. 3. Explain the successive approximation architecture in detail with a neat diagram. 4. Describe in detail about the principle of interleaved architecture. 5. Explain in detail about how gray coding technique is used in ADC. 6. Compare SAR architecture and interleaved architecture. 7. Write detailed notes on . Kickback noise . Meta stability 8. Briefly explain about range overlap and digital correction. 9. Elaborate interpolation and folding architectures and also note the two observations when combining folding and interpolation. 10. How pipelined architecture used in analog circuits to achieve high speed. 11. Explain charge redistribution principle with the help of successive approximation converters. 12. Discuss about two step architectures and specify the timing issues in the absence of front-end SHA and also compare timing in flash architecture.

UNIT V PRECISION TECHNIQUES

Comparator offset cancellation; Op Amp offset cancellation, Calibration techniques, range overlap and digital correction.

1. Mention the techniques used to cancel the offset.  Laser wafer trimming  Fuse techniques 2. What is the need for offset cancellation techniques? The need for reliable offset cancellation has led to authorizing techniques in CMOS and BiCMOS comparators, wherein the offset is periodically sensed, stored and added to the input in such a way as to cancel itself.

3. List out the various types of offset cancellation techniques.  Input offset storage  Output offset storage  Multistage offset storage  Comparators using offset canceled latches 4. Define calibration technique. A calibration technique is based on measuring and digitizing the residual voltages obtained for a binary capacitor array and storing and combining the results digitally.

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EC 6019 Data Converters Department of ECE 5. Define digital calibration technique. It has been proposed for two steps ADC’s that employ switched capacitor inter stage D/A conversion and subtraction. This method computes the additional charge that must be pumped onto the DAC output to correct the reconstructed analog signal. 6. Define Input Offset Storage (IOS). Input offset storage is defined to measure the input offset of the preamplifier by closing a unity gain feedback loop around it and stores the resulting offset on capacitors in series with the input. 7. What are the drawbacks of Input Offset Storage? Input offset storage contributed by the preamplifier that can be reduced by employing a high gain, degrading the power speed trade–off, charge injection mismatch and attenuation consideration. 8. Define Output Offset Storage (OOS). It refers the output referred offset of the preamplifier by grounding its input and stores the result on capacitors in series with the preamplifier output. 9. Mention the advantages of OOS over IOS?  Potentially lower offset  OOS usually less input capacitance than IOS and  More suitable for parallel ADC architectures. 10. Specify the uses of Op amp Offset cancellation technique. Op-amp offset cancellation technique is used as an auxiliary amplifier that isolates the signal path from offset storage capacitors while cancelling the offset of the main amplifier. 11. Write the primary feature of DAC Calibration technique algorithm. It performs the calibration using only adders, and simple logic gates, with no need for digital multipliers. In a typical design, the digital circuitry amounts to approximately 400 gates and 120 bits of RAM. 12. Mention the concept of Dynamic element matching. The equivalent matching of current sources can be substantially improved using the concept of dynamic element matching this method performs time averaging on nominally equal current sources so as to produce precisely matched currents. 13. What is the advantage of using capacitor error averaging technique? The accuracy of this gain depends on capacitor matching. In order to suppress the effect of capacitor mismatch, capacitor error averaging can be used.

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EC 6019 Data Converters Department of ECE 14. Mention the advantage of half flash architecture method. A powerful technique to relax the speed resolution trade off multistep A/D converters is to provide overlap between the quantization range of successive stages and digitally correct the binary data produced by each stage. 15. What are the methods available in ADC calibration Techniques?  Capacitor Error Averaging  Capacitor Trimming  Digital calibration 16. Define settling time. The settling time of an amplifier is the time elapsed from the application of an ideal instantaneous step input to the time at which the amplifier output has entered and remained within a specified error band, usually symmetrical about the final value. 17. Mention the importance of MDAC, CDAC and SDAC. Main DAC (MDAC),A calibration DAC (CDAC),and Sampling DAC (SDAC) along with control logic and small memory. In the calibration mode, the output corresponding to each code is examined and the error is detected and stored. 18. Mention the importance of Multistage offset storage. The circuit comprises a cascade of capacitive coupled amplifiers followed by a latch.

In the offset cancellation mode the inputs of A1…An and the latch are grounded and the offset of each amplifier is stored on capacitors in series with its output. 19. Define Capacitor error averaging. 1 bit per stage architecture each stage amplifiers the residue by a precise factor of 2. The accuracy of the gain depends on capacitor matching. In order to suppress the effect of capacitor mismatch capacitor error averaging can be used. 20. What is the purpose of using capacitor DACs in DAC circuits? The capacitor DAC achieve both a wide dynamic range and relatively fast settling and are often utilized in multistep A/D converters. These DACs have been especially popular in successive approximation architectures, where they are normally PART B & C

1. Write technical notes on . Calibration techniques. . Comparator offset cancellation 2. Discuss the concept of comparator offset cancellation in detail with neat block diagram. 3. Discuss a technique to cancel offset in comparator as well as in op-amp. 4. Explain any two calibration techniques of DAC.

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EC 6019 Data Converters Department of ECE 5. Explain in detail about the architecture which employs a 10 bit A/D converter using a resistor Ladder DAC. 6. Describe in detail about the two step sub ranging architecture. 7. Explain in detail about residue generation in 10 bit two steps A/D converter. 8. Describe about comparator using offset canceled latches technique. 9. Elaborate OOS and specify their drawbacks. Compare IOS and OOS with necessary diagrams. 10. Discuss in detail about multistage offset storage and how to design multistage offset cancellation circuit using CMOS inverters. 11. Explain the operation of OP AMP offset cancellation circuit using auxiliary amplifier. 12. Compare stating and dynamic testing with examples. 13. Write short notes on i. Stating testing ii. Direct ADC-DAC test iii. Beat frequency and envelope test iv. Code density test v. FFT test vi. Sine fitting test

UNIVERSITY QUESTIONS WITH ANSWERS 1 Why conventional open loop architecture is replaced by open loop architecture with miller capacitance?  Suffers from speed-precision trade off  Same capacitor is used for both acquisition and hold hence limitations occur. 2 Define sampling rate. Sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. 3 Draw the circuit diagram of switched capacitor amplifier.

4 What is latched comparator? Latched comparators employ strong positive feedback for a "regeneration phase" when a clock is high, and have a "reset phase" when the clock is low. 5 What is integral non linearity? It is the maximum deviation of the input/output characteristic from a straight line passed through its end points. 6 Why pipelined architectures are used in analog domain?  Sampling rates from a few Msps up to 100Msps and more  High speed  High resolution and  Low power

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EC 6019 Data Converters Department of ECE 7 How to minimize the glitch impulse in DAC Circuits? To minimize the glitch impulse in DAC Circuits  Connect a large capacitor between the DAC output and ground  Low pass filter combination of RDAC and C reduces the amplitude of the glitch. 9 What is the principal trade-off among different varieties of analog to digital converter architecture?  Speed and  Precision 10 What are the different methods used to enhance the speed precision trade-offs of the data acquisition system? Multiplexed DAQ systems, generally, can achieve high density, high throughput, and good energy efficiency by: 1. Using a high speed precision SAR ADC 2. Using the minimum sampling rate per channel 3. Maximizing the SAR 11 What is measured by output offset storage? The measurement is made at the amplifier output using an accurate digital voltmeter. The offset referred to the input (RTI) is calculated by dividing the output voltage by the noise gain. The small source resistance seen by the inputs results in negligible bias current contribution to the measured offset voltage. April / May 2019 1 Define SNDR It is the ratio of the signal power to the total noise and harmonic power at the output in the hold mode. 2 State the limitations of sampling switches. . Slow speed (2N clock pulses for N-bit conversion) . Hard to generate precise ramp required for high resolution ADCs 3 Draw the architecture of CMOS based latched comparators. Mention its advantages.

4 What is meant by clock bootstrapping? Small on-resistance leads to large switches → large parasitic caps and large clock buffers Clock bootstrapping keeps VGS of the switch constant → constant on-resistance and less parasitic of the PMOS.

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EC 6019 Data Converters Department of ECE Ф Ф1 Ф2 … VDD CS In Out Ф M1

5 Why high speed D/A converters are based on current steering architectures? For the majority of communication circuits, the most commonly used high-speed D/A converter is the current-steering architecture. As the number of bits increases, so does the difference between the size of transistors in the current mirrors, thus increasing the error due to device mismatches. 6 The basic step of a 9bit DAC is 11mV. If 000000000 represents 0 Volts, what is the output for an input of 101101100? The output voltage for input of 101101100 is = 10.3 mV (1×28+0*27+1×26+1×25+0×24+1×23+1×22+0×21+0×20) = 10.3 × 10-3 (256+0+64+32+0+8+4+0+0) = 10.3 × 10-3 (364) = 3.75V 7 How the interleaved architectures are related to sampling circuits?  Efficient architectures for achieving accuracy at high speed.  sampling rate of over 20 GS/s could not be achieved 8 Enumerate the different types of Flash architectures.  Reference ladder DC and AC bowing  Nonlinear input capacitance of a bipolar flash ADC  CMOS flash ADC 9 What is the significance of offset cancellation techniques?  Trimming - Trimming is performed during production to eliminate offset.  Chopping and  Auto-zeroing - Auto-zeroing is a sampling technique in which the offset is measured and then subtracted in subsequent clock phases 10 What is the concept of Dynamic element matching?

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EC 6019 Data Converters Department of ECE April / May 2018 1 Specify the application of data converters. . Precision Measurement and Sensor Conditioning . Multichannel Data Acquisition Systems . Digital Potentiometers . Digital Audio . Digital Video and Display Electronics . Software Radio and IF Sampling . Direct Digital Synthesis (DDS) . Precision Analog Microcontrollers 2 Define sampling rate. The sampling rate is the rate at which samples can be continuously converted and is typically the inverse of the settling time. 3 What is input offset in comparator? Input offset is the voltage that must be applied to the input to get the transition between the low and the high state. 4 What is switched capacitor? A switched capacitor is an electronic circuit element used for discrete-time signal processing. It works by moving charges into and out of capacitors when switches are opened and closed. 5 Define monotonicity. The ability of a DAC's analog output to move only in the direction that the digital input moves (i.e., if the input increases, the output doesn't dip before asserting the correct output.) 6 Draw latched comparator circuit.

7 What is slew rate of a comparator? Slew rate is defined as the maximum rate of change of output voltage caused by a step input voltage. An ideal slew rate is infinite which means that op-amp’s output voltage should change instantaneously in response to input step voltage. 8 What are the types of analog to digital converters?  Flash architecture  Pipelined architecture  Successive approximation architecture  Time interleaved architecture

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EC 6019 Data Converters Department of ECE 9 Define calibration techniques. A calibration technique is based on measuring and digitizing the residual voltages obtained for a binary capacitor array and storing and combining the results digitally. 10 What is the drawback of input offset storage and output offset storage? Drawbacks of Input offset storage  Input offset storage contributed by the preamplifier that can be reduced by employing a high gain  Degrading the power speed trade–off  Charge injection mismatch and  Attenuation consideration. Drawbacks of Output offset storage  It cannot employ high gain  Single stage amplifier with a gain less than 20  Limited input common mode range

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