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.htmlhttp://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 http://telecom.tbi.net/

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 log 2 M 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 SNR db 10 log 10 (Signal Power / Noise Power) C = B log 2 ( 1 + SNR)

18. LAB Volt Unit 1