ECE 457 Communication Systems Selin Aviyente Assistant Professor Electrical & Computer Engineering
Announcements Class Web Page: http://www.egr.msu.edu/~aviyente/ece 457.htm M, W, F 10:20-11:10 a.m. Office Hours: MW 11:30-1:00 pm or by appointment (2210 EB) Textbook: Principles of Communications, Rodger E. Zimmer and William H. Tranter, John Wiley, 5 th Edition, 2002.
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 No labs this week The first lab starts on Wednesday January 15 th.
Course Requirements 2 Midterm Exams (50%) February 21, April 4 Final Exam, April 30 (30%) Weekly HW assignments (20%) Up to 3 students can turn in one writeup Assigned on Fridays due next Friday Will have MATLAB problems No late HWs
Tentative Syllabus Overview of Communication Systems Review of Signal Analysis (ECE 360) Deterministic Modulation (Linear and Angle Modulation) Review of Probability and Random Processes Noise in Modulation Systems Digital Modulation
Communication Systems A communication system conveys information from its source to a destination. Examples: Telephone TV Radio Cell phone PDA Satellite
Elements of a Communication System A communication system is composed of the following elements Source Input Transducer Transmitter Channel Receiver Output Transducer
Elements of a Communication System Input Transducer: Converts the message produced by a source to a form suitable for the communication system. Example: Speech waves Microphone Voltage
Transmitter Couple the message to the channel Operations: Amplification, Modulation Modulation encodes message into amplitude, phase or frequency of carrier signal (AM, PM, FM) Modulation can make transmitted signal robust to channel distortions. Examples: TV station, radio station, web server
Why modulation? Translates a message signal to a new spectral location For free space, necessary to translate to a frequency that can be radiated with antennas. Many message signals, one channel Multiplexing
Channel Physical medium that does the transmission Examples:Air, wires, coaxial cable, radio wave, laser beam, fiber optics Every channel introduces some amount of distortion, noise and interference
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
Output Transducer Converts electrical signal into the form desired by the system Example: Voltage Loudspeakers Sound waves
Fundamental Limitations Bandwidth Noise
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
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.
Frequency Spectrum Example Application AM Radio TV (Channels 2-6) FM Radio TV (Channels 7-13) Cellular mobile radio Frequency Band 0.54-1.6 MHz 54-66 MHz 88-108 MHz 174-216 MHz 806-901 MHz
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)
Brief History of Communications Year 1838 1876 1933 1936 1953 Event Telegraphy (Morse) Telephone (Bell) FM radio TV broadcasting Color TV
History of Communications Year 1962 1972 1985 1990s Event Satellite communication Cellular phone Fax machines GPS, HDTV, handheld computers