The Origins of Spread-Spectrum Communications
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Transmission Media Transmission Media Are Actually Located Below the Physical Layer and Are Directly Controlled by the Physical Layer
SYBScIT /Sem III / Computer networks UNIT II • MULTIPLEXING Multiplexing is the set of technique that allow the simultaneous transmission of multiple signals across a single data link.In a multiplexed system, n lines share the bandwidth of one link. The lines on the left direct their transmission streams to a multiplexer (MUX), which combines them into a single stream (many-to-one). At the receiving end, that stream is fed into a demultiplexer (DEMUX), which separates the stream back into its component transmissions (one- to-many) and directs them to their corresponding lines. In the figure, the word link refers to the physical path. The word channel refers to the portion of a link that carries a transmission between a given pair of lines. One link can have many (n) channels. There are three basic multiplexing techniques: frequency-division multiplexing, wavelength- division multiplexing, and time-division multiplexing. • Frequency-Division Multiplexing(FDM) Frequency-division multiplexing (FDM) is an analog technique that can be applied when the bandwidth of a link (in hertz) is greater than the combined bandwidths of the signals to be transmitted. In FDM, signals generated by each sending device modulate different carrier frequencies. These modulated signals are then combined into a single composite signal that can be transported by the link. Carrier frequencies are separated by sufficient bandwidth to accommodate the modulated signal. These bandwidth ranges are the channels through which the various signals travel chapter SYBScIT /Sem III / Computer networks Channels can be separated by strips of unused bandwidth—guard bands—to prevent signals from overlapping. FDM is an analog multiplexing technique that combines analog signals. -
Spread Spectrum and Wi-Fi Basics Syed Masud Mahmud, Ph.D
Spread Spectrum and Wi-Fi Basics Syed Masud Mahmud, Ph.D. Electrical and Computer Engineering Dept. Wayne State University Detroit MI 48202 Spread Spectrum and Wi-Fi Basics by Syed M. Mahmud 1 Spread Spectrum Spread Spectrum techniques are used to deliberately spread the frequency domain of a signal from its narrow band domain. These techniques are used for a variety of reasons such as: establishment of secure communications, increasing resistance to natural interference and jamming Spread Spectrum and Wi-Fi Basics by Syed M. Mahmud 2 Spread Spectrum Techniques Frequency Hopping Spread Spectrum (FHSS) Direct -Sequence Spread Spectrum (DSSS) Orthogonal Frequency-Division Multiplexing (OFDM) Spread Spectrum and Wi-Fi Basics by Syed M. Mahmud 3 The FHSS Technology FHSS is a method of transmitting signals by rapidly switching channels, using a pseudorandom sequence known to both the transmitter and receiver. FHSS offers three main advantages over a fixed- frequency transmission: Resistant to narrowband interference. Difficult to intercept. An eavesdropper would only be able to intercept the transmission if they knew the pseudorandom sequence. Can share a frequency band with many types of conventional transmissions with minimal interference. Spread Spectrum and Wi-Fi Basics by Syed M. Mahmud 4 The FHSS Technology If the hop sequence of two transmitters are different and never transmit the same frequency at the same time, then there will be no interference among them. A hopping code determines the frequencies the radio will transmit and in which order. A set of hopping codes that never use the same frequencies at the same time are considered orthogonal . -
Advanced Imaging Technology
MICROELECTRONICS LABORATORY SPOTLIGHT ON Advanced Imaging Technology KEY FEATURES • World’s lowest readout noise, Digital focal plane array. highest quantum efficiency CCD imagers MIT Lincoln Laboratory has long been a leader • Geiger-mode (GM) APDs with in advanced imaging for defense and scientific single-photon sensitivity and applications. Our imaging capabilities are broadly noiseless digital readout classified into three categories: charge-coupled • DFPAs containing a complete devices (CCDs), avalanche photodiodes (APDs), analog-to-digital converter in every pixel, enabling image and digital focal plane array (DFPA) technology. processing on the focal plane Technology in Support of National Security www.ll.mit.edu SPOTLIGHT ON Advanced Imaging Technology Charge-Coupled Devices Our CCDs are used in ground, air, and spaced-based applications of interest to the government and scientific research community. These CCDs span a range of wavelengths including visible, near infrared, ultraviolet, and soft X-ray. Among imagers employing our CCDs are the two 1.4-billion- pixel Panoramic Survey Telescope and Rapid Response System’s (Pan-STARRS) focal plane arrays, the largest focal planes fabricated to date, and the Space Surveillance Telescope’s curved focal planes that provide a uniform and wide field of view. Optical micrograph of back-illuminated CCD wafer. Geiger-Mode Avalanche Photodiodes For passive imaging, the noiseless readout of our GM-APDs enables photon counting, providing both the requisite sensitivity for low-light applications and photon count rates for high-speed imaging. APDs are also employed in active ladar systems to time-stamp photon arrival times, enabling 3D imaging in compact airborne systems. We also fabricate APD arrays on compound semiconductor materials, expanding these capabilities further into the infrared. -
Digital Communication Systems 2.2 Optimal Source Coding
Digital Communication Systems EES 452 Asst. Prof. Dr. Prapun Suksompong [email protected] 2. Source Coding 2.2 Optimal Source Coding: Huffman Coding: Origin, Recipe, MATLAB Implementation 1 Examples of Prefix Codes Nonsingular Fixed-Length Code Shannon–Fano code Huffman Code 2 Prof. Robert Fano (1917-2016) Shannon Award (1976 ) Shannon–Fano Code Proposed in Shannon’s “A Mathematical Theory of Communication” in 1948 The method was attributed to Fano, who later published it as a technical report. Fano, R.M. (1949). “The transmission of information”. Technical Report No. 65. Cambridge (Mass.), USA: Research Laboratory of Electronics at MIT. Should not be confused with Shannon coding, the coding method used to prove Shannon's noiseless coding theorem, or with Shannon–Fano–Elias coding (also known as Elias coding), the precursor to arithmetic coding. 3 Claude E. Shannon Award Claude E. Shannon (1972) Elwyn R. Berlekamp (1993) Sergio Verdu (2007) David S. Slepian (1974) Aaron D. Wyner (1994) Robert M. Gray (2008) Robert M. Fano (1976) G. David Forney, Jr. (1995) Jorma Rissanen (2009) Peter Elias (1977) Imre Csiszár (1996) Te Sun Han (2010) Mark S. Pinsker (1978) Jacob Ziv (1997) Shlomo Shamai (Shitz) (2011) Jacob Wolfowitz (1979) Neil J. A. Sloane (1998) Abbas El Gamal (2012) W. Wesley Peterson (1981) Tadao Kasami (1999) Katalin Marton (2013) Irving S. Reed (1982) Thomas Kailath (2000) János Körner (2014) Robert G. Gallager (1983) Jack KeilWolf (2001) Arthur Robert Calderbank (2015) Solomon W. Golomb (1985) Toby Berger (2002) Alexander S. Holevo (2016) William L. Root (1986) Lloyd R. Welch (2003) David Tse (2017) James L. -
Novel Index Modulation Techniques: a Survey
IEEE COMMUNICATIONS SURVEYS & TUTORIALS, VOL. 21, NO. 1, FIRST QUARTER 2019 315 Novel Index Modulation Techniques: A Survey Tianqi Mao , Student Member, IEEE,QiWang , Member, IEEE, Zhaocheng Wang , Senior Member, IEEE, and Sheng Chen , Fellow, IEEE Abstract—In fifth generation wireless networks, the escalating BICM-ID Bit-Interleaved Coded Modulation with teletraffic and energy consumption has necessitated the devel- Iterative Decoding opment of green communication techniques in order to further BLAST Bell Labs Layered Space-Time enhance both the system’s spectral efficiency and energy effi- ciency. In the past few years, the novel index modulation (IM) BMST Block Markov superposition has emerged as a promising technology that is widely employed transmission in wireless communications. In this paper, we present a survey BPSK Binary Phase Shift Keying on IM in order to provide the readers with a better understand- CD Channel Domain ing of its principles, advantages, and potential applications. We CD-IM Channel-Domain IM start with a comprehensive literature review, where the concept of IM is introduced, and various existing IM schemes are classi- CIR Channel Impulse Response fied according to their signal domains, including the frequency CP Cyclic Prefix domain, spatial domain, time domain and channel domain. Then CPEP Conditioned PEP the principles of different IM-aided systems are detailed, where CSI Channel State Information the transceiver design is illustrated, followed by descriptions of CSIT CSI at the Transmitter typical systems and corresponding performance evaluation. A range of challenges and open issues on IM are discussed before D/A Digital-to-Analog Converter we conclude this survey. -
Classmate Biographies
CLASSMATE BIOGRAPHIES 38 David Jeffrey Abeshouse Course: VIII Tell us about your recollections of your student years at MIT: I lived in Student House, which is essentially on the B.U. campus. If I recall correctly, it was a mile walk to MIT. That walk, in all kinds of weather, is one of my strongest, if not favorable, memories of my years there. Unless something unusual happened, I made the round trip just once a day. Student House is near Kenmore Square and Fenway Park. The gates to Fenway would open in the sixth inning then, and there were mostly afternoon games, so we would go up to the park occasionally to see, for free, the last three innings. We saw Ted Williams regularly. Student House was also next to the Charles, and it was fun to go down near the river in pleasant weather. I struggled to survive academically, but I did it. I don't remember the name of the professor who lectured our freshman chemistry course, but he spoke in a monotone, and I fell asleep practically every time. I finally went to a different lecture section. I have a poor sense of direction and was regularly lost around the campus and often rushing to get to class. Once in my sophomore year I was rushing and rounded a corner and almost flattened Norbert Wiener. He had a large abdomen, and, from my point of view, the collision was soft. The work on my senior paper was done in building 20. That was a fine place to spend a lot of time. -
Analysis of FHSS-CDMA with QAM-64 Over AWGN and Fading Channels Prashanth G S1
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 08 | Aug -2017 www.irjet.net p-ISSN: 2395-0072 Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels Prashanth G S1 Assistant Professor, Dept. of ECE, JNNCE, Shivamogga, Karnataka, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – CDMA is a type of channel access method in huge amount of power which result in implementation of which users using the same channel will use the same extra hardware to normalize the power requirement. [2] frequency band and also can access the channel at the same Frequency-hopping spread spectrum (FHSS) is a time. Using CDMA, more users can be allocated in the channel method of transmitting radio signals by rapidly compared to TDMA and FDMA. CDMA can be achieved using switching a carrier among many frequency channels Direct sequence spread spectrum(DSSS) and Frequency using a pseudo random sequence known to both transmitter hopping spread spectrum(FHSS). FHSS-CDMA consumes less and receiver. FHSS-CDMA consumes less power compared to power compared to DSSS-CDMA. High data rate modulation DSSS-CDMA. High data rate modulation schemes are used schemes are used along with FHSS-CDMA to deliver high along with FHSS-CDMA to deliver high quality multimedia quality multimedia content. High data rate modulation content. QAM-64 modulation technique as good bandwidth techniques have good bandwidth efficiency in FHSS-CDMA. In efficiency with wideband FHSS-CDMA. Author in [4], wireless communication, QAM is one of the most commonly discusses about broadband wireless access techniques. used modulation technique. Due to noise and interference, For 4G systems data rates up to 100 Mbps will be high data rate modulation techniques are prone to errors. -
MIT Lincoln Laboratory Division and Group Descriptions
MIT Lincoln Laboratory Division and Group Descriptions October 2012 AIR AND MISSILE DEFENSE TECHNOLOGY DIVISION 3 The Air and Missile Defense Technology Division’s role is to work with government, industry, and laboratories to develop an integrated air and missile defense system. The division’s main focus is investigating system concepts, developing technology, building prototypes, and conducting measurements to support the development of radar and optical sensors, interceptors, and networks for air and missile defense systems. A strong emphasis is placed on partnerships and the transfer of technology to industry. Group 31—Systems and Architectures The Systems and Architectures Group examines near- and long-term technology opportunities for charting the future development of U.S. air and missile defenses. As the country proceeds with the deployment of new missile defense systems, Lincoln Laboratory and this group are working on the next generation of architectures and technologies. The group investigates advanced radar concepts, new infrared sensors, missile designs, space-based platforms, and future distributed command-and-control software to help identify opportunities to develop, test, and deploy these technologies. The group also devotes considerable effort to investigating the impact of various countermeasures on U.S. air and missile defense systems, particularly with respect to various types of electronic warfare. Staff members in the group have a wide variety of backgrounds, including physics, electrical engineering, mathematics, and astrodynamics. Group 33—Advanced Sensor Systems and Test Beds The Advanced Sensor Systems and Test Beds Group supports the Department of Defense by designing and developing modern sensor systems and components to support airborne air defense radars as well as the ballistic missile defense system. -
4 Classical Error Correcting Codes
“Machines should work. People should think.” Richard Hamming. 4 Classical Error Correcting Codes Coding theory is an application of information theory critical for reliable communication and fault-tolerant information storage and processing; indeed, Shannon channel coding theorem tells us that we can transmit information on a noisy channel with an arbitrarily low probability of error. A code is designed based on a well-defined set of specifications and protects the information only for the type and number of errors prescribed in its design. Agoodcode: (i) Adds a minimum amount of redundancy to the original message. (ii) Efficient encoding and decoding schemes for the code exist; this means that information is easily mapped to and extracted from a codeword. Reliable communication and fault-tolerant computing are intimately related to each other; the concept of a communication channel, an abstraction for a physical system used to transmit information from one place to another and/or from one time to another is at the core of communication, as well as, information storage and processing. It should however be clear 355 Basic Concepts Linear Codes Polynomial Codes Basic Concepts Linear Codes Other Codes Figure 96: The organization of Chapter 4 at a glance. that the existence of error-correcting codes does not guarantee that logic operations can be implemented using noisy gates and circuits. The strategies to build reliable computing systems using unreliable components are based on John von Neumann’s studies of error detection and error correction techniques for information storage and processing. This chapter covers topics from the theory of classical error detection and error correction and introduces concepts useful for understanding quantum error correction, the subject of Chapter 5. -
F. Circuit Switching
CSE 3461: Introduction to Computer Networking and Internet Technologies Circuit Switching Presentation F Study: 10.1, 10.2, 8 .1, 8.2 (without SONET/SDH), 8.4 10-02-2012 A Closer Look At Network Structure: • network edge: applications and hosts • network core: —routers —network of networks • access networks, physical media: communication links d. xuan 2 1 The Network Core • mesh of interconnected routers • the fundamental question: how is data transferred through net? —circuit switching: dedicated circuit per call: telephone net —packet-switching: data sent thru net in discrete “chunks” d. xuan 3 Network Layer Functions • transport packet from sending to receiving hosts application transport • network layer protocols in network data link network physical every host, router network data link network data link physical data link three important functions: physical physical network data link • path determination: route physical network data link taken by packets from source physical to dest. Routing algorithms network network data link • switching: move packets from data link physical physical router’s input to appropriate network data link application router output physical transport network data link • call setup: some network physical architectures require router call setup along path before data flows d. xuan 4 2 Network Core: Circuit Switching End-end resources reserved for “call” • link bandwidth, switch capacity • dedicated resources: no sharing • circuit-like (guaranteed) performance • call setup required d. xuan 5 Circuit Switching • Dedicated communication path between two stations • Three phases — Establish (set up connection) — Data Transfer — Disconnect • Must have switching capacity and channel capacity to establish connection • Must have intelligence to work out routing • Inefficient — Channel capacity dedicated for duration of connection — If no data, capacity wasted • Set up (connection) takes time • Once connected, transfer is transparent • Developed for voice traffic (phone) g. -
2-Page-Tree-Saving Format
M P Corp. SS&C Conf. .O. Box 8236 Box .O. onterey, CA 93943 CA onterey, FORTY-SIXTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS November 4–7, 2012 Asilomar Hotel and Conference Grounds Technical Co-sponsor FORTY-SIXTH Welcome from the General Chairman ASILOMAR CONFERENCE ON Prof. Miloš Doroslovački SIGNALS, SYstEMS & COMPUTERS The George Washington University Welcome to this unique conference. Many of us come here from year to year to be exposed to new ideas and to do brainstorming Organized in cooperation with about them in an informal and relaxed way, surrounded by magnificent nature. To cite John Steinbeck, Nobel Prize laureate in literature and local to this part of California: “Ideas are like ATK SPACE SYstEMS rabbits. You get a couple and learn how to handle them, and pretty Monterey, California soon you have a dozen.” I am sure that the conference will be stimulating for your future professional endeavors. and Technical Co-sponsor The biggest credit for the intellectual value of the conference goes to the Technical Program Chair Erik G. Larsson and his team, made of Technical Area Chairs and Session Chairs, as well as to IEEE SIGNAL PROCESSING SOCIETY all of you who contributed with papers. Erik and his team prepared an excellent program of 435 papers, including 171 invited, and a tutorial session. For their outstanding work in shaping the technical program, I would like to thank Erik and the Technical Area Chairs: Henk Wymeersch, Gerald Matz, Vincent Poor, Erchin Serpedin, Marius Pesavento, Arye Nehorai, Joseph Cavallaro, Ghassan CONFERENCE COMMITTEE AlRegib and Phil Schniter. -
2016 Annual Report (Pdf)
MIT LINCOLN LABORATORY LINCOLN MIT Follow MIT Lincoln Laboratory online. Facebook: MIT Lincoln Laboratory LinkedIn: http://www.linkedin.com/company/ mit-lincoln-laboratory Twitter: @MITLL YouTube: MIT Lincoln Laboratory Instagram: https://www.instagram.com/ lincoln_laboratory/ 2016 Annual2016 Report MIT Lincoln Laboratory 2016 ANNUAL REPORT www.ll.mit.edu Communications and Community Outreach Office: 781.981.4204 Approved for public release: distribution unlimited. This material is based upon work supported under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Air Force. TECHNOLOGY IN SUPPORT OF NATIONAL SECURITY © 2016 Massachusetts Institute of Technology TECHNOLOGY IN SUPPORT OF NATIONAL SECURITY Massachusetts Institute of Technology Lincoln Space Surveillance Complex, Westford, Massachusetts MIT Lincoln Laboratory Reagan Test Site, Kwajalein Atoll, Marshall Islands MIT LINCOLN LABORATORY 2016 Table of Contents MISSION 2 Leadership Technology in Support 3 Organizational Changes of National Security 4 Letter from the Director 5 Vision, Values, and Strategic Directions MIT Lincoln Laboratory employs some of the nation’s best technical talent to support system and 7 Technology Innovation technology development for national security needs. 8 Swarm of Miniature Aircraft Autonomously Maintains Flight Formation Principal core competencies are sensors, infor- 10 Technology Investments mation extraction (signal processing and embedded 16 Achieving a Near-Ideal Laser Beam computing), communications, integrated sensing, and 18 Localizing Ground-Penetrating Radar decision support. Nearly all of the Lincoln Laboratory 20 Discovering the Vast Asteroid Population efforts are housed at its campus on Hanscom Air 22 Technology Transfer Force Base in Massachusetts.