2 the Wireless Channel
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Vision-Based Mobile Free-Space Optical Communications Kyle Cavorley, Wayne Chang, Jonathan Giordano, Taichi Hirao Advisor: Prof
Vision-Based Mobile Free-Space Optical Communications Kyle Cavorley, Wayne Chang, Jonathan Giordano, Taichi Hirao Advisor: Prof. Daut Abstract Methodology The implementation of a free-space optical (FSO) communication system capable of interfacing with moving receivers such as unmanned ground or aerial vehicles. Two way communication Inexpensive laser diodes are used to transmit data at rates of up to 1 Mbps. A computer vision and tracking system controls a pan-tilt platform for target Transmit side Receive side acquisition and tracking. Complex package components, suchs as a laser driver and photo receiver, are avoided when possible to study the design of low-level system components. A two way communication system is made possible utilizing a reflective optical chopper (ROC) at the receiver end. Motivations and Objectives Motivations: -High power efficiency with high throughput Fig. 2: Photodiode Amplifier and Comparator Circuit. Fig. 4: Laser Diode Driver Circuit. -Increased security Objectives: -Construct optical communication link capable of 1 Mbps at thirty feet range -Form and maintain two way optical communication channel -Build computer vision tracking system and platform Fig. 6: Boston Micromachines Reflective Optical Chopper (ROC); used in two-way communication Fig. 3: Output Response of photodiode Fig. 5: Schmitt Trigger Circuit. Only one end of the communication link amplifier/comparator. requires a visual tracking/laser targeting system. Results ❑ 2 Mhz signal successfully transmitted 14 feet using 5 mW 670 nm laser. ❑ AD8030 Op-amp used to amplify photodiode response signal from a range [60 mV, 1 V] to 5V before entering comparator that generates a TTL output. Fig. 1: Vision Based FSO Communication Block Diagram. -
Unit 7: Choosing Communication Channels
UNIT 7: CHOOSING COMMUNICATION CHANNELS Unit 7 highlights the importance of selecting an appropriate channel mix for a communication response and describes five categories of communication channels: mass media, mid media, print media, social and digital media and interpersonal communication (IPC). For each of these channels, advantages and disadvantages have been listed, as well as situations in which different channels may be used. Although this Unit has attempted to differentiate the channels and their uses for simplicity, there is recognition that channels frequently overlap and may be effective for achieving similar objectives. This is why the match between channel, audience and communication objective is important. This unit provides some tools to help assess available and functioning channels during an emergency, as well as those that are more appropriate for reaching specific audience segments. Once you have completed this unit, you will have the following tools to support the development of your SBCC response: • Worksheet 7.1: Assessing Available Communication Channels • Worksheet 7.2: Matching Communication Channels to Primary and Influencing Audiences What Is a Communication Channel? A communication channel is a medium or method used to deliver a message to the intended audience. A variety of communication channels exist, and examples include: • Mass media such as television, radio (including community radio) and newspapers • Mid media activities, also known as traditional or folk media such as participatory theater, public talks, announcements through megaphones and community-based surveillance • Print media, such as posters, flyers and leaflets • Social and digital media such as mobile phones, applications and social media • IPC, such as door-to-door visits, phone lines and discussion groups Different channels are appropriate for different audiences, and the choice of channel will depend on the audience being targeted, the messages being delivered and the context of the emergency. -
Modeling and Simulation of an Asynchronous Digital Subscriber Line Transceiver Data Transmission Subsystem
Modeling and Simulation of an Asynchronous Digital Subscriber Line Transceiver Data Transmission Subsystem Elmustafa Erwa ABSTRACT Recently, there has been an increase in demand for digital services provided over the public telephone line network. Asymmetric digital subscriber line (ADSL) transmit high bit rate data in the forward direction to the subscriber, and lower bit rate data in the reverse direction to the central office, both on a single copper telephone loop. I implemented a Synchronous Dataflow (SDF) model for an ADSL transceiver’s data transmission subsystem in LabVIEW. My implementation enables designers to simulate and optimize different ADSL transceiver designs. The overall implementation is compliant with the European Telecommunications Standards Institute’s ADSL specification. 1. INTRODUCTION With the emergence of the Internet as the cornerstone of communications in this age, the demand for high speed Internet access has only been increasing. Asymmetric digital subscriber lines (ADSL) is one of the technologies that provide high-speed Internet access in residences and offices [1]. It facilitates the use of normal telephone services, Integrated Services Digital Network (ISDN), and high-speed data transmission simultaneously. Hence, bandwidth-demanding technologies, such as video-conferencing and video-on-demand, are enabled over ordinary telephone lines. ADSL standards use discrete multi-tone (DMT) modulation [2]. DMT divides the effectively bandlimited communication channel into a larger number of orthogonal narrowband subchannels. This allows for maximizing the transmitted bit rate and adapting to changing line conditions. Designing ADSL systems is inherently complex. However, advances in the digital signal processor (DSP) technology allowed programmable DSP based solutions to replace application-specific integrated circuit based implementations. -
3 Characterization of Communication Signals and Systems
63 3 Characterization of Communication Signals and Systems 3.1 Representation of Bandpass Signals and Systems Narrowband communication signals are often transmitted using some type of carrier modulation. The resulting transmit signal s(t) has passband character, i.e., the bandwidth B of its spectrum S(f) = s(t) is much smaller F{ } than the carrier frequency fc. S(f) B f f f − c c We are interested in a representation for s(t) that is independent of the carrier frequency fc. This will lead us to the so–called equiv- alent (complex) baseband representation of signals and systems. Schober: Signal Detection and Estimation 64 3.1.1 Equivalent Complex Baseband Representation of Band- pass Signals Given: Real–valued bandpass signal s(t) with spectrum S(f) = s(t) F{ } Analytic Signal s+(t) In our quest to find the equivalent baseband representation of s(t), we first suppress all negative frequencies in S(f), since S(f) = S( f) is valid. − The spectrum S+(f) of the resulting so–called analytic signal s+(t) is defined as S (f) = s (t) =2 u(f)S(f), + F{ + } where u(f) is the unit step function 0, f < 0 u(f) = 1/2, f =0 . 1, f > 0 u(f) 1 1/2 f Schober: Signal Detection and Estimation 65 The analytic signal can be expressed as 1 s+(t) = − S+(f) F 1{ } = − 2 u(f)S(f) F 1{ } 1 = − 2 u(f) − S(f) F { } ∗ F { } 1 The inverse Fourier transform of − 2 u(f) is given by F { } 1 j − 2 u(f) = δ(t) + . -
Rayleigh Fading Multi-Antenna Channels
EURASIP Journal on Applied Signal Processing 2002:3, 316–329 c 2002 Hindawi Publishing Corporation Rayleigh Fading Multi-Antenna Channels Alex Grant Institute for Telecommunications Research, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia Email: [email protected] Received 29 May 2001 Information theoretic properties of flat fading channels with multiple antennas are investigated. Perfect channel knowledge at the receiver is assumed. Expressions for maximum information rates and outage probabilities are derived. The advantages of transmitter channel knowledge are determined and a critical threshold is found beyond which such channel knowledge gains very little. Asymptotic expressions for the error exponent are found. For the case of transmit diversity closed form expressions for the error exponent and cutoff rate are given. The use of orthogonal modulating signals is shown to be asymptotically optimal in terms of information rate. Keywords and phrases: space-time channels, transmit diversity, information theory, error exponents. 1. INTRODUCTION receivers such as the decorrelator and MMSE filter [10]; (b) mitigation of fading effects by averaging over the spatial Wireless access to data networks such as the Internet is ex- properties of the fading process. This is a dual of interleav- pected to be an area of rapid growth for mobile communi- ing techniques which average over the temporal properties cations. High user densities will require very high speed low of the fading process; (c) increased link margins by simply delay links in order to support emerging Internet applica- collecting more of the transmitted energy at the receiver. tions such as voice and video. -
Fading Channels: Capacity, BER and Diversity
Fading Channels: Capacity, BER and Diversity Master Universitario en Ingenier´ıade Telecomunicaci´on I. Santamar´ıa Universidad de Cantabria Introduction Capacity BER Diversity Conclusions Contents Introduction Capacity BER Diversity Conclusions Fading Channels: Capacity, BER and Diversity 0/48 Introduction Capacity BER Diversity Conclusions Introduction I We have seen that the randomness of signal attenuation (fading) is the main challenge of wireless communication systems I In this lecture, we will discuss how fading affects 1. The capacity of the channel 2. The Bit Error Rate (BER) I We will also study how this channel randomness can be used or exploited to improve performance diversity ! Fading Channels: Capacity, BER and Diversity 1/48 Introduction Capacity BER Diversity Conclusions General communication system model sˆ[n] bˆ[n] b[n] s[n] Channel Channel Source Modulator Channel ⊕ Demod. Encoder Decoder Noise I The channel encoder (FEC, convolutional, turbo, LDPC ...) adds redundancy to protect the source against errors introduced by the channel I The capacity depends on the fading model of the channel (constant channel, ergodic/block fading), as well as on the channel state information (CSI) available at the Tx/Rx Let us start reviewing the Additive White Gaussian Noise (AWGN) channel: no fading Fading Channels: Capacity, BER and Diversity 2/48 Introduction Capacity BER Diversity Conclusions AWGN Channel I Let us consider a discrete-time AWGN channel y[n] = hs[n] + r[n] where r[n] is the additive white Gaussian noise, s[n] is the -
Designing Asymmetric Digital Subscriber Line with Discrete Multitone Modulator
ISSN (Online) 2321-2004 IJIREEICE ISSN (Print) 2321-5526 International Journal of Innovative Research in Electrical, Electronics, Instrumentation and Control Engineering Vol. 7, Issue 11, November 2019 Designing Asymmetric Digital Subscriber Line with Discrete Multitone Modulator Attiq Ul Rehman1, Maninder Singh2 M. Tech., Student, ECE Department, Haryana Engineering College, Jagadhri, Haryana, India1 Assistant Professor, ECE Department, Haryana Engineering College, Jagadhri, Haryana, India2 Abstract: The objective of Digital Subscriber Line (DSL) is to propagate signal from the transmitter to the receiver over telephone lines. In communication industry Asymmetric Digital Subscriber Line (ADSL) is widely used because it can handle both phone services and internet access services at same time. As the communication industry develops, its main concern is to maximize the user handling capacity of communication systems. For this purpose, ADSL uses Discrete Multitone (DMT) modulator with QAM bank. But as the number of users increases the system complexity and interference also increases. The communication channel is not free from the effects of channel impairments such as noise, interference and fading. These channel impairments caused signal distortion and Signal to Ratio (SNR) degradation. One method that can be implemented to overcome this problem is by introducing channel coding. Channel encoding is applied by adding redundant bits to the transmitted data. The redundant bits increase raw data used in the link and therefore, increase the bandwidth requirement. So, if noise or fading occurred in the channel, some data may still be recovered at the receiver. While at the receiver, channel decoding is used to detect or correct errors that are introduced to the channel. -
The Wireless Communication Channel Objectives
9/9/2008 The Wireless Communication Channel muse Objectives • Understand fundamentals associated with free‐space propagation. • Define key sources of propagation effects both at the large‐ and small‐scales • Understand the key differences between a channel for a mobile communications application and one for a wireless sensor network muse 1 9/9/2008 Objectives (cont.) • Define basic diversity schemes to mitigate small‐scale effec ts • Synthesize these concepts to develop a link budget for a wireless sensor application which includes appropriate margins for large‐ and small‐scale pppgropagation effects muse Outline • Free‐space propagation • Large‐scale effects and models • Small‐scale effects and models • Mobile communication channels vs. wireless sensor network channels • Diversity schemes • Link budgets • Example Application: WSSW 2 9/9/2008 Free‐space propagation • Scenario Free-space propagation: 1 of 4 Relevant Equations • Friis Equation • EIRP Free-space propagation: 2 of 4 3 9/9/2008 Alternative Representations • PFD • Friis Equation in dBm Free-space propagation: 3 of 4 Issues • How useful is the free‐space scenario for most wilireless syst?tems? Free-space propagation: 4 of 4 4 9/9/2008 Outline • Free‐space propagation • Large‐scale effects and models • Small‐scale effects and models • Mobile communication channels vs. wireless sensor network channels • Diversity schemes • Link budgets • Example Application: WSSW Large‐scale effects • Reflection • Diffraction • Scattering Large-scale effects: 1 of 7 5 9/9/2008 Modeling Impact of Reflection • Plane‐Earth model Fig. Rappaport Large-scale effects: 2 of 7 Modeling Impact of Diffraction • Knife‐edge model Fig. Rappaport Large-scale effects: 3 of 7 6 9/9/2008 Modeling Impact of Scattering • Radar cross‐section model Large-scale effects: 4 of 7 Modeling Overall Impact • Log‐normal model • Log‐normal shadowing model Large-scale effects: 5 of 7 7 9/9/2008 Log‐log plot Large-scale effects: 6 of 7 Issues • How useful are large‐scale models when WSN lin ks are 10‐100m at bt?best? Fig. -
Telecommunication Through Broadband Services of Bsnl: a Bird’S Eye View
International Journal of Technical Research and Applications e-ISSN: 2320-8163, www.ijtra.com Volume 1, Issue 2 (may-june 2013), PP. 37-41 TELECOMMUNICATION THROUGH BROADBAND SERVICES OF BSNL: A BIRD’S EYE VIEW Dr Shilpi Verma Assistant Professor Deptt. of Library & information Science (School for Information Science & Technology) Babasaheb Bhimrao Ambedkar University (A Central University) Vidya Vihar, Rai-bareli Road Lucknow-226025 (UP) Abstract: In the cut throat competition every country telecommunication technologies are playing very vital want to be information equipped, the role. The consumers or users are demanding for faster and telecommunication is helping a lot in achieving the reliable bandwidth for purpose of e-commerce, same. Integrated communication is emerged as a boom videoconferencing, information retrieval and such other in communication world. The growth of data, applications. Broadband seems as a answer to these communication market and the networking questions. Broadband provides means of accessing technology trend has amplified the importance of technologies to bridge the customer & the service telecommunication in the field of information provider throughout the world. It basically provides high communication. Telecommunication has become one speed internet access, whereas the dial up connections of the very important part that is very essential to the was having their limitations and low speed. These socio-economic well being of any nation. The paper broadband services allow the user to send or receive video deals with concept of Broad band services of BSNL, or audio digital content and having real time features also. technology options for broadband services. Bharat It is able to provide interactive services. -
The Future of Passive Multiplexing & Multiplexing Beyond
The Future of Passive Multiplexing & Multiplexing Beyond 10G From 1G to 10G was easy But Beyond 10G? 1G CWDM/DWDM 10G CWDM/DWDM 25G 40G Dark Fiber Passive Multiplexer 100G ? 400G Ingredients for Multiplexing 1) Dark Fiber 2) Multiplexers 3) Light : Transceivers Ingredients for Multiplexing 1) Dark Fiber 2 Multiplexer 3 Light + Transceiver Dark Fiber Attenuation → 0 km → → 40 km → → 80 km → Dispersion → 0 km → → 40 km → → 80 km → Dark Fiber Dispersion @1G DWDM max 200km → 0 km → → 40 km → → 80 km → @10G DWDM max 80km → 0 km → → 40 km → → 80 km → @25G DWDM max 15km → 0 km → → 40 km → → 80 km → Dark Fiber Attenuation → 80 km → 1310nm Window 1550nm/DWDM Dispersion → 80 km → Ingredients for Multiplexing 1 Dark FiBer 2) Multiplexers 3 Light + Transceiver Passive Mux Multiplexers 2 types • Cascaded TFF • AWG 95% of all Communication -Larger Multiplexers such as 40Ch/96Ch Multiplexers TFF: Thin film filter • Metal or glass tuBes 2cm*4mm • 3 fiBers: com / color / reflect • Each tuBe has 0.3dB loss • 95% of Muxes & OADM Multiplexers ABS casing Multiplexers AWG: arrayed wave grading -Larger muxes such as 40Ch/96Ch -Lower loss -Insertion loss 40ch = 3.0dB DWDM33 Transmission Window AWG Gaussian Fit Attenuation DWDM33 Low attenuation Small passband Reference passBand DWDM33 Isolation Flat Top Higher attenuation Wide passband DWDM light ALL TFF is Flat top Transmission Wave Types Flat Top: OK DWDM 10G Coherent 100G Gaussian Fit not OK DWDM PAM4 Ingredients for Multiplexing 1 Dark FiBer 2 Multiplexer 3) Light: Transceivers ITU Grids LWDM DWDM CWDM Attenuation -
Performance Evaluation of Power-Line Communication Systems for LIN-Bus Based Data Transmission
electronics Article Performance Evaluation of Power-Line Communication Systems for LIN-Bus Based Data Transmission Martin Brandl * and Karlheinz Kellner Department of Integrated Sensor Systems, Danube University, 3500 Krems, Austria; [email protected] * Correspondence: [email protected]; Tel.: +43-2732-893-2790 Abstract: Powerline communication (PLC) is a versatile method that uses existing infrastructure such as power cables for data transmission. This makes PLC an alternative and cost-effective technology for the transmission of sensor and actuator data by making dual use of the power line and avoiding the need for other communication solutions; such as wireless radio frequency communication. A PLC modem using DSSS (direct sequence spread spectrum) for reliable LIN-bus based data transmission has been developed for automotive applications. Due to the almost complete system implementation in a low power microcontroller; the component cost could be radically reduced which is a necessary requirement for automotive applications. For performance evaluation the DSSS modem was compared to two commercial PLC systems. The DSSS and one of the commercial PLC systems were designed as a direct conversion receiver; the other commercial module uses a superheterodyne architecture. The performance of the systems was tested under the influence of narrowband interference and additive Gaussian noise added to the transmission channel. It was found that the performance of the DSSS modem against singleton interference is better than that of commercial PLC transceivers by at least the processing gain. The performance of the DSSS modem was at least 6 dB better than the other modules tested under the influence of the additive white Gaussian noise on the transmission channel at data rates of 19.2 kB/s. -
Passband Data Transmission I Introduction in Digital Passband
Passband Data Transmission I References Phase-shift keying Chapter 4.1-4.3, S. Haykin, Communication Systems, Wiley. J.1 Introduction In baseband pulse transmission, a data stream represented in the form of a discrete pulse-amplitude modulated (PAM) signal is transmitted over a low- pass channel. In digital passband transmission, the incoming data stream is modulated onto a carrier with fixed frequency and then transmitted over a band-pass channel. J.2 1 Passband digital transmission allows more efficient use of the allocated RF bandwidth, and flexibility in accommodating different baseband signal formats. Example Mobile Telephone Systems GSM: GMSK modulation is used (a variation of FSK) IS-54: π/4-DQPSK modulation is used (a variation of PSK) J.3 The modulation process making the transmission possible involves switching (keying) the amplitude, frequency, or phase of a sinusoidal carrier in accordance with the incoming data. There are three basic signaling schemes: Amplitude-shift keying (ASK) Frequency-shift keying (FSK) Phase-shift keying (PSK) J.4 2 ASK PSK FSK J.5 Unlike ASK signals, both PSK and FSK signals have a constant envelope. PSK and FSK are preferred to ASK signals for passband data transmission over nonlinear channel (amplitude nonlinearities) such as micorwave link and satellite channels. J.6 3 Classification of digital modulation techniques Coherent and Noncoherent Digital modulation techniques are classified into coherent and noncoherent techniques, depending on whether the receiver is equipped with a phase- recovery circuit or not. The phase-recovery circuit ensures that the local oscillator in the receiver is synchronized to the incoming carrier wave (in both frequency and phase).