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Lecture 1

Lecture 1. Professor: Dr. Miguel Alonso Jr. Outline. Intro to the History of Data Communications A Basic Communication System Elements of Microwave and Satellite Communication Data Communications Terminology Shannon’s Law. Intro to the History of Data Communications.

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Lecture 1

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  1. Lecture 1 Professor: Dr. Miguel Alonso Jr.

  2. Outline • Intro to the History of Data Communications • A Basic Communication System • Elements of Microwave and Satellite Communication • Data Communications Terminology • Shannon’s Law

  3. Intro to the History of Data Communications • Source: http://www.k12.hi.us/~telecom/datahistory.html • 26 million phone lines • 7.5 million cellular phone users • 5 thousand AM radio broadcast stations • 5 thousand FM radio stations • 1 thousand television broadcast stations • 9 thousand cable television systems • 530 million radios • 193 million television sets • 24 ocean cables • scores of satellite facilities!

  4. One of the earliest forms of digital communications was smoke signals • Words were encoded into data represented by puffs of smoke • The first electrical communication system was the telegraph, 1844

  5. The first telephone was then patented in 1876 • Long distance call today are transmitted digitally! • The first analog radio was demonstrated in 1895 • Television subsequently dominated communication in the 1950s

  6. Since the Invention of the transistor, digital communication has exploded and will continue to develop! • Cell Phones • The Internet • HD Television and Satellite Television (DirecTV, etc.) • mp3’s • Exercise: Read this article on the history of communications and comment on three facts that you did not know… • http://www.k12.hi.us/~telecom/datahistory.html • http://telecom.tbi.net/ Great Resource for info on telecom

  7. A Basic Communication System • Typical Digital Communication System

  8. Tasks of a communication system • Exchange data between two parties • Source-> Transmitter -> Transmission System _> Receiver -> Destination • Efficient Transmission System Utilization • Interfacing • Signal Generation • Synchronization • Error Detection and Correction • Addressing, Routing, Recovery, Message Format, Security and Finally network management

  9. Elements of Microwave and Satellite Communication • Satellite Communication system uses satellites to relay radio transmissions between two points on earth • Active (Provides boost) • Passive (Reflective)

  10. Components of a satellite communication system • Transmitter (Power requirements) • Antennas • Power Generation (Efficiency, Solar Panels, Lack of Sun)

  11. Data Communications Terminology • Information: the communication or reception of knowledge or intelligence • Analog Signal: Continuous and vary in amplitude, frequency, or phase • Digital signal: Discrete and discontinuous and only have two voltage levels

  12. Bit: a binary digit, 0 or 1, used to store information • Baud: number of distinct symbols changes made to the transmission medium per second • Bit rate and Baud are not equal! • Example: Transmission of 3000 bps in a 3bit symbol transmission system is said to operate at 1000 Baud

  13. Nyquist and Shannon’s Law • Channel capacity: Maximum rate at which data can be communicated • Data rate (bps) • Bandwidth (constrained by transmitter and medium) • Noise • Error Rate • Goal of a good communication system is to achieve the highest data rate possible given the limitations of BW, Noise, and Error Rate

  14. Nyquist Bandwidth • First, consider a noise free channel • In this environment, the limitation on data rate is simply the bandwidth of the signal • If the rate of signal transmission is 2B, then a signal with frequencies no greater than B is sufficient to carry the signal • Similarly, given a bandwidth B, the highest signal rate that can be carried is 2B

  15. Example: transmitting binary signals over a voice channel • BW = 3100Hz • C=2B = 6200 bps • If more levels are used however, • C=2B log2M • Where M is the number of distinct levels • M = 8, C = 18600

  16. Example: Compute the Channel Capacity for: • BW = 44kHz, M = 2 • BW = 22.5kHz, M = 4 • BW = 100MHz, M = 8

  17. Shannon’s Law • The presence of noise complicates matters • Claude Shannon developed a formula that allows for the computation of the maximum theoretical channel capacity given the bandwidth of the channel and the signal to noise ratio • SNRdb10 log10 (Signal Power / Noise Power) • C = B log2 ( 1 + SNR)

  18. LAB Volt Unit 1

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