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Meixia Tao @ SJTU
Principles of Communications
Prof. Meixia TaoDept. of Electronic EngineeringShanghai Jiao
Tong University
Chapter 1: Overview of Communication Systems
Selected from Chapter 1 of Fundamentals of Communications
Systems, Pearson Prentice Hall 2005, by Proakis & Salehi
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Meixia Tao @ SJTU
Staff
Lecturer: Meixia Tao
o Office: Room 5-301A, SEIEE Buildingo Tel: 3420-7494-8004o
Email: [email protected] Web:
http://iwct.sjtu.edu.cn/personal/mxtao/
TA: TBD
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TextbookLecture Nodes (Very Important!):
http://iwct.sjtu.edu.cn/personal/mxtao/teaching.html
J. G. Proakis, 2005 , 2007
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References
An introduction to analog and digital communications, by Simon
Haykin, 2nd edition, John Wiley & Sons, 2007
, 2008.6
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Meixia Tao @ SJTU
Objective The primary objective of this course is
to introduce the basic techniques used in modern communication
systems, and
to provide fundamental tools and methodologies in analysis and
design of these systems
After this course, the students are expected to Understand the
principles and technique of modulation,
coding and transmission. Analyze the merits and demerits of
current
communication systems and to eventually design improved new
systems
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Meixia Tao @ SJTU
Syllabus (1/2) Ch01:Introduction (1week) Ch02:Signal, random
process, and spectra (2 weeks) Ch03: Analog modulation (2 weeks)
Ch04: Analog to digital conversion (1 week) Ch05: Digital
transmission through baseband channels (2 weeks) Ch06: Signal space
presentation (1 week) Ch07: Optimal receivers (1 week) Ch08:
Digital modulation techniques (2 weeks) Ch09: Information theory
(1week) Ch10: Channel Coding (1 week) Ch11: Synchronization (1
week)
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Meixia Tao @ SJTU
Syllabus (2/2)
Lab 1: Analog modulation Lab 2: Binary digital modulation
techniques Lab 3: BPSK/QPSK-modulated wireless transmission
system
NI LabVIEW+USRP
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Assessment Homework: 15%
5 sets of homework 5-level grading (A+, A, B+, B, C) for each
homework
Labs: 15% 3 Lab reports + on-site demonstration
Mid-term Test: 10% In-class open-book test
Final Exam: 60%
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What is Communication?The systems and processes that are used to
conveyinformation from a source to a destination efficiently
andreliably, especially by means of electricity or radio waves.
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Meixia Tao @ SJTU
Historical Review 1838: telegraph (S. Morse) 1876: telephone (A.
Bell) 1895: radio by Marconi 1901: trans-atlantic
communication
Early 20th century: Most communication systems are analog.
Engineering designs are ad-hoc, tailored for each
specific application
Nobel Prize for Physics (1909)
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Modern Communication Systems
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Fundamental Questions Is there a general methodology for
designing commu-
nication systems?
Is there a limit to how fast one cancommunicate?
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Harry Nyquist (1928)
Continuous-time Discrete-time
Sampling Theorem
"Certain topics in telegraph transmission theory", Trans. AIEE,
vol. 47, pp. 617644, Apr. 1928
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Claude Shannon (1948)
Information Theory
Analog communication
Digital communication
Fundamental limits of source compression rate and channel
transmission rate
"A Mathematical Theory of Communication", Bell System Technical
Journal. 1948
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Basic Elements of Communications
A slight variation from Shannons diagram of a general
communication system
OutputsignalInformation
sourceInput
Transducer Transmitter Channel ReceiverOutput
Transducer
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Communication Channels
Common characteristics
Channel
Attenuation
Distortion Noise
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Wireless Electromagnetic Channels
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Radio Spectrum
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Radio Spectrum
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Meixia Tao @ SJTU
Propagation Free-space propagation model
: transmit power : receive power : transmit antenna gain
: receive antenna gain : wavelength : distance
200 meters
100 meters
Receives 1/4 of the power
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Mathematical Models The additive noise channel
Linear filter channel
+( )s t ( ) ( ) ( )r t s t n t= +
( )n t
+( )s t0
( ) ( ) ( ) ( )
( ) ( ) ( )
r t s t h t n t
h s t d n t
= +
= +( )n t( )h t
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Meixia Tao @ SJTU
Linear time-variant filter channel
Consider a multi-path signal propagation
+( )s t( ) ( ) ( ; ) ( )
( ; ) ( ) ( )
r t s t h t n t
h t s t d n t
= +
= +( )n t( ; )h t
1( ; ) ( ) ( )
L
k kk
h t a t t =
=
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Types of Communications Systems
Analog Communications
Digital Communications 00011011110
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Analog Communication Systems
Source Modulator
Channel
DetectorOutput
Transmitter
Receiver
Noise
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Digital Communication Systems
Source A/D converterSource encoder
Channelencoder Modulator
Channel
DetectorChannel decoderSource decoder
D/A converter
User
Transmitter
Receiver
Absent if source is
digitalNoise
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Meixia Tao @ SJTU
Why Digital Communications? Robustness to channel noise
and external Interference
Security of information during its transmission from source to
destination
Integration of diverse sources information into a common
format
Low cost DSP chipsby very cheap VLSI designs
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Performance Metrics of Communication Systems
Reliability SNR for analog systems Bit error rate for digital
systems
Efficiency Bandwidth efficiency Energy efficiency
Performance Tradeoff
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Bandwidth Efficiency
bits/sec/Hz= data rate Rbandwidth efficiencybandwidth W
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Meixia Tao @ SJTU
=bit energy
energy efficiencynoise power spectral density
= Eb/No
Energy Efficiency
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Principles of
CommunicationsStaffTextbookReferencesObjectiveSyllabus (1/2)
Syllabus (2/2) AssessmentWhat is Communication?Historical
ReviewModern Communication Systems Fundamental QuestionsHarry
Nyquist (1928)Claude Shannon (1948)Basic Elements of Communications
Communication ChannelsWireless Electromagnetic ChannelsRadio
SpectrumRadio Spectrum 20Mathematical Models 22Types of
Communications SystemsAnalog Communication SystemsDigital
Communication SystemsWhy Digital Communications?Performance Metrics
of Communication SystemsBandwidth EfficiencyEnergy Efficiency
