Page 1 ECE 457 Spring 2005 ECE 457 Communication Systems Selin Aviyente Assistant Professor ECE

Page 2 ECE 457 Spring 2005 Announcements Class Web Page: htm Lectures: M, W, F 10:20-11:10 a.m. 221 Natural Resources Building Office Hours: W 11:30- 1:00 pm, Th 9:30- 11:00 am or by appointment (2210 EB) Textbook: Principles of Communications, Rodger E. Zimmer and William H. Tranter, John Wiley, 5th Edition, 2002.

Page 3 ECE 457 Spring 2005 ECE 457 and ECE 458 ECE 458 is designed to complement this course. ECE 458 focuses on providing practical experience. You will learn material in ECE 457 that is not covered in ECE 458 and vice versa. No labs this week. There is no lab manual this year, everything will be online.

Page 4 ECE 457 Spring 2005 Course Requirements 2 Midterm Exams (50%) –February 25, April 8 in class Final Exam, May 3 (30%) Weekly HW assignments (10%) –Will include MATLAB assignments –HWs should be your own work (no copying!) –Assigned on Fridays due next Friday (except during exam weeks) –No late HWs will be accepted. Quizzes (10%) –They will be unannounced. –Based on HW questions (10-15 minutes long)

Page 5 ECE 457 Spring 2005 Policies Cheating in any form will not be tolerated. This includes copying HWs, cheating on exams and quizzes. You are allowed to discuss the HW questions with your friends, and me. However, you have to write up the homework on your own. There is no make-up for missed quizzes. If you have an excuse for not being in class, please me before class.

Page 6 ECE 457 Spring 2005 Honors Option Honor credit option is available Typical projects have either a software/hardware implementation component and an oral presentation. Past projects include: –Building a FM transmitter –MATLAB simulation of digital modulation systems. Please feel free to come and talk to me about your ideas for a possible project.

Page 7 ECE 457 Spring 2005 Tentative Syllabus Overview of Communication Systems Review of Signal Analysis (ECE 366) Deterministic Modulation –Linear (DSB,AM,SSB,VSB) –Angle Modulation (FM, PM) Review of Probability and Random Processes Noise in Modulation Systems Digital Modulation (as time permits)

Page 8 ECE 457 Spring 2005 Communication Systems A communication system conveys information from its source to a destination. Examples: –Telephone –TV –Radio –Cell phone –PDA –Satellite

Page 9 ECE 457 Spring 2005 Communication Systems A communication system is composed of the following: Input Transducer Transmitter ChannelReceiver Output Transducer Source

Page 10 ECE 457 Spring 2005 Input Transducer Source: Analog or digital Example: Speech, music, written text Input Transducer: Converts the message produced by a source to a form suitable for the communication system. Example: Speech waves  Microphone  Voltage

Page 11 ECE 457 Spring 2005 Transmitter Couple the message to the channel Operations: Amplification, Modulation Modulation encodes message into amplitude, phase or frequency of carrier signal (AM, PM, FM) Advantages: –Reduce noise and interference –Multiplexing –Channel Assignment Examples: TV station, radio station, web server

Page 12 ECE 457 Spring 2005 Channel Physical medium that does the transmission Examples: Air, wires, coaxial cable, radio wave, laser beam, fiber optic cable Every channel introduces some amount of distortion, noise and interference

Page 13 ECE 457 Spring 2005 Receiver Extracts message from the received signal Operations: Amplification, Demodulation, Filtering Goal: The receiver output is a scaled, possibly delayed version of the message signal (ideal transmission) Examples: TV set, radio, web client

Page 14 ECE 457 Spring 2005 Output Transducer Converts electrical signal into the form desired by the system Examples: Loudspeakers, PC

Page 15 ECE 457 Spring 2005 Capacity of a Channel The most important question for a communication channel is the maximum rate at which it can transfer information. There is a theoretical maximum rate at which information passes error free over the channel, called the channel capacity C. The famous Hartley-Shannon Law states that the channel capacity C is given by: C=B*log(1+(S/N)) b/s where B is the bandwidth, S/N is the signal-to-noise ratio.

Page 16 ECE 457 Spring 2005 Fundamental Limitations Therefore, there are two factors that determine the capacity of a channel: –Bandwidth –Noise

Page 17 ECE 457 Spring 2005 Frequency Spectrum Most precious resource in communications is “frequency spectrum” The “frequency spectrum” has to be shared by a large number of users and applications: AM Radio, FM Radio, TV, cellular telephony, wireless local-area-networks, satellite, air traffic control

Page 18 ECE 457 Spring 2005 Frequency Spectrum The frequency spectrum has to be managed for a particular physical medium The spectrum for “over-the-air” communications is allocated by international communications organization International Telecommunications Union (ITU) Federal Communications Commission (FCC) designates and licenses frequency bands in the US.

Page 19 ECE 457 Spring 2005 Frequency Spectrum Example ApplicationFrequency Band AM Radio MHz TV (Channels 2- 6) MHz FM Radio MHz TV (Channels 7- 13) MHz Cellular mobile radio MHz

Page 20 ECE 457 Spring 2005 Noise Internal and External Noise Internal Noise: Generated by components within a communication system (thermal noise) External Noise: –Atmospheric noise (electrical discharges) –Man-made noise (ignition noise) –Interference (multiple transmission paths)

Page 21 ECE 457 Spring 2005 History of Communications YearEvent 1838Telegraphy (Morse) 1876Telephone (Bell) 1902Radio transmission (Marconi) 1933FM radio 1936TV broadcasting 1953Color TV

Page 22 ECE 457 Spring 2005 History of Communications YearEvent 1962Satellite communication 1972Cellular phone 1985Fax machines 1990sGPS, HDTV, handheld computers