ECE 457 Communication Systems

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ECE 457Communication Systems

• Selin Aviyente
• Assistant Professor
• ECE

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Announcements

• Class Web Page
• http//www.egr.msu.edu/aviyente/ECE
  457-05.htm
• Lectures M, W, F 1020-1110 a.m. 221 Natural
  Resources Building
• Office Hours M 1130- 100 pm, Th 930-1100 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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Tentative Syllabus

• Overview of Communication Systems
• Review of Signal Analysis (ECE 366/360)
• 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

Source
Output
Input
Channel
Receiver
Transmitter
Transducer
Transducer
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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 waves?Microphone?Voltage

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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 optics
• 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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Fundamental Limitations

• 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