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Page 1
ECE 457Communication Systems
Selin AviyenteAssistant Professor
ECE
Page 2
Announcements• Class Web Page: http://www.egr.msu.edu/~aviyente/ECE
457-05.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 e-mail appointment (2210 EB)
• Textbook: Principles of Communications, Rodger E. Zimmer and William H. Tranter, John Wiley, 5th Edition, 2002.
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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.
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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)
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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 e-mail me before class.
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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.
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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)
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Communication Systems• A communication system conveys
information from its source to a destination.
• Examples: – Telephone– TV– Radio– Cell phone– PDA– Satellite
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Communication Systems• A communication system is composed
of the following:
InputTransducer Transmitter Channel Receiver
Output
Transducer
Source
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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 wavesMicrophoneVoltage
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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
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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
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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
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Output Transducer• Converts electrical signal into the form
desired by the system• Examples: Loudspeakers, PC
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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.
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Fundamental Limitations• Therefore, there are two factors that
determine the capacity of a channel:– Bandwidth– Noise
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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
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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.
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Frequency Spectrum Example
Application Frequency
Band
AM Radio 0.54-1.6 MHz
TV (Channels 2-6)
54-88 MHz
FM Radio 88-108 MHz
TV (Channels 7-13)
174-216 MHz
Cellular mobile radio
806-901 MHz
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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)
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History of Communications Year Event
1838 Telegraphy (Morse)
1876 Telephone (Bell)
1902 Radio transmission (Marconi)
1933 FM radio
1936 TV broadcasting
1953 Color TV
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History of Communications
Year Event
1962 Satellite communication
1972 Cellular phone
1985 Fax machines
1990s GPS, HDTV, handheld computers
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