ece8700 communications system engineering …yiminzhang.com/ece8700/ece8700_2014_1_ch1.pdfece8700...

ECE8700Communications System Engineering

Lecture 1

Yimin D. Zhang, Ph.D.

Department of Electrical & Computer EngineeringVillanova University

Spring 2014Y. D. Zhang ECE-8700 Spring 2014 1

Course Outline

Y. D. Zhang ECE-8700 Spring 2014 2

InstructorDr. Yimin D. ZhangOffice: Tolentine 401APhone: 610-519-4544E-mail: [email protected] HW submission: [email protected]: http://www.yiminzhang.com

Lecture Time Wednesdays 6:15 - 8:45 pm

Office Hours Wednesdays 4:00 - 5:30 pm, or by appointment.

Course Websitehttp://www.yiminzhang.com/ECE8700/

Course Outline


Grading Policy – In-classAttendance - 10%Homework Assignments - 40%Mid-Term Exam - 20%Projects - 30% (15% each)

Homework* Homework is due at the beginning of the class (6:15 pm) on the day it is

due (This also applies to distance learning students).* DL students please submit by e-mail to [email protected] (preferred)

or fax (follow instruction). In-class students can submit in hardcopy (allpages should be stapled together and include the student name), or bye-mail to [email protected].

* No late homework will be accepted, and you are welcome to turn inhomework early. It is important that an honest effort be made towardevery homework problem.

Grading Policy – Distance Learning

Homework Assignments - 50%Mid-Term Exam - 20%Projects - 30% (15% each)

Textbook


Textbook (required)Digital Communication Systems, 1st Editionby Simon Haykin

Wiley, 2013. ISBN : 978-0-471-64735-5

References (not required)Many books are available. The following books were used as textbook in the past.

John Proakis and Masoud Salehi, Digital Communications, 5th EditionMcGraw-Hill, 2007. ISBN 978-0-072-95716-7

Simon Haykin, Communication Systems, 4th Edition Wiley, 2001. ISBN 0-471-17869-1

Introduction

Chapter 1


History and evolution of mobile radio

Invention of Radio• Maxwell: predicted the existence of electromagnetic waves

(1864)• Hertz: confirmed Maxwell's work in lab experiment (1887)• Marconi: commercializing wireless telephony

– Found Wireless Telegraph Company (1897)– Wireless transmission across the Atlantic (1901)

Maxwell (1831–1879) Hertz (1857-1894) Marconi (1874 -1937)


• Major boost during World War II• Boost of non-military applications after World War II• AT&T introduces first mobile telephony system in St. Louis

(1946)• Bell Labs invented the concept of cellular systems (1947)

1970’s: Wireless communication era was born Development of highly reliable, miniature solid state radio frequency hardware

• 1971 AT&T, RCA and Motorola file proposals to use 800 MHz band for cellular systems

• 1983 FCC grants first commercial cellular licenses• 1983 Ameritech launched first commercial cellular system in

Chicago



0G (1971- )Autoradiopuhelin(ARP), or Car Radio Phone, pre-cellphone mobile telephony technology.

1G (1980s-)Analog tech-nology. In US, Advanced Mobile Phone System (AMPS) was used.

2G (1990s-)Digital techno-logy for higherspectral and power efficiency. GSM were most widely adopted. Digital AMPS and CDMA were also popularly used in US.

3G (2000s-)Provide both packet-switched and circuit-switched domains. Support larger numbers of voice and multimedia data.

5G?Hot R&D area but no specification yet in any official document by any telecommunication standardization body.

4G (2010s-)Provides mobile ultra-broadband internet access to other mobile devices like smartphones and mobile PCs.





The early portable units were big, heavy, and expensive.



Mobile PCs and tablets become a class of more capable devices with wireless communication capabilities

Modern cell phones are small, fast, low-cost, and support multimedia communications

Rapid increase of device-to-device (D2D) traffic in recent years.



(from Wikipedia)

Wireless communications standards


4G in the U.S.A. WiMax could soon be overshadowed by a rival technology.

(from IEEE Spectrum 2010, issue 1)

(from CEDMagazine.com)

Clearwire (WiMax)

Verizon (LTE)

4G wireless systems


Broadband services go to wireless

WiMax/LTE provides wireless solutions to last mile broadband connection.


Speed and mobility


What’s next


1 Petabyte (PB) = 1,000,000 Gigabytes (GB)

How to support the rapidly increasing data traffic?

Source: CISCO

Where we stand


How to deliver the required amount of info in the Physical layer?!

Overview of the Course


Course Overview


Probability (Ch. 3)Fourier analysis (Ch. 2)

Stochastic processes (Ch. 4)

Information Theory (Ch. 5)

Conversion into Coded Pulses (Ch. 6)Signaling over AWGN channels (Ch. 7)

Signaling over band-limited channels (Ch. 8)

Signaling over fading channels (Ch. 9)

Error control coding (Ch. 10)

How much information can be transferred

How

to a

chie

ve e

ffici

ent

info

rmat

ion

tran

sfer

Math foundation

Spread spectrum communications (9.13)

Orthogonal Frequency Division Multiplexing (9.12)

20

Communication System Preview

Y. D. Zhang ECE-8700 Spring 2014

Source of Information: Voice Music Picture Video Computer dataIn digital communications, type of information sources becomes less important

Channels:- WiredCable, fiber, DSL, LAN…

- Wirelesscell phone, satellite, wireless LAN…

NoiseAttenuationDistortion

…

21

Ch 6 Conversion into Coded Pulses


Continuous-Wave Modulation

Analog Pulse Modulation

Sampling

Quantization

Digital Pulse Modulation

Coding

… PAM

… PCM

22Y. D. Zhang ECE-8700 Spring 2014

Ch 5 Information Theory

Primary Communication Resources

• Transmit power• Channel bandwidth• Transmission time

Goal of a communication system

The message signal is delivered to the user both efficiently reliably

subject to certain design constraints: allowable transmit power available channel bandwidth affordable cost of building the system

How good is good? How to make a fair comparison between different platforms?

23

Shannon & Information Theory

• In 1948 Claude Shannon published his famous paper A Mathematical Theory of Information, which is considered the starting point of modern Information Theory.

• Shannon made three important contributions.– Quantization of information, the bit– The source coding theorem – The channel coding theorem

Claude Shannon1916 - 2001


Shannon’s Channel Coding Theorem

• For every channel, there is a limit to what informationtransfer rate can be achieved, the so called Channelcapacity C.

• For a channel of bandwidth W, disturbed by additive, whiteGaussian noise (AWGN), having signal-to-noise-ratioSNR, the channel capacity can be calculated

Communication is always possible, even with poor SNR,we just have to go slow enough.

• Two ways to achieve a high data rate.– Small W and high SNR: … conventional, narrowband

radio system.– Large W and low SNR: … CDMA, UWB

2log (1 )C W SNR


25

Shannon’s Channel Coding Theorem

• We know Shannon’s channel capacity

The theorem has two parts.• Direct part: for rate R < C, there exists a coding system with

arbitrarily low error rates.• Converse part: for R > C, the error rates are strictly bounded

away from zero for any system.

Shannon showed “can,” not “how”, which is what to be studied.

• Modulation schemes: efficient and suited for the channel

• Channel coding: to reduce the error probability

2log (1 )C W SNR


Digital Communication Systems


27

Why Digital?


Increased data transmission efficiency Source code for data compression Channel coding to minimize the effects of noise, distortion, and interference

Standardization of signals Irrespective of their type, origin or the services they support

Higher performance Signal quality Encryption for security

Programmability One hardware can perform several tasks Upgradeability and flexibility Nonlinear and time-varying operations

Repeatability Identical performance from unit to unit No drift in performance due to temperature or aging

Accuracy Flexible control of accuracy and dynamic range Immune to noise

Price and reduced time-to-market

28

Ch 6 Conversion of Analog Waveforms into Coded Pulses


Analog Source Digital signals!

Required sampling rate?

Effect of quantization?

More efficient coding schemes?

Fourier analysis

29

Ch 7 Signaling over AWGN Channels


In the presence of noise,

Is it possible to recover the information correctly?

How much info can be transmitted?

How much errors should be expected?

What is the optimum receiver structure?

Noise

AWGN: Additive white Gaussian noise

Probability & Stochastic process

30

Baseband vs. Passband Transmissions


Digital ModulatorBaseband Channel

Digital Demodulator

RF Channel

Up Converter

DownConverter

Baseband or Passband (RF)?

31

Ch 8 Signaling over Band-Limited Channels


Rectangular waveforms occupy too wide spectrum.

Ideal spectrum requires infinite impulse response.

What are realistic and efficient?

Fourier analysis

32

Ch 9 Signaling over Fading Channels


• Path loss

• Shadowing effect• Log-normal

• Multipath fading• Rayleigh• Ricean

RTTx

R GGPdgP )(10 10/2Probability & Stochastic process

33

Spatial Diversity


Probability & Stochastic process

Outage probability can be improved if using multiple receive antennas!

34

Spatial Diversity


Slope = -1Rayleigh fading

Slope = -2Diversity with two branches(Diversity gain = 2)

Energy saving to achieve the same BER

What happens if the receiver only has a single antenna, but the transmitter has many?

35

Spatial Diversity


SISO: single-input single-outputSIMO: single-input multiple-outputMISO: multiple-input single-outputMIMO: multiple-input multiple-output

Linear Algebra would

be helpful!

36

Inter-Symbol Interference


Local scattering

Remote scattering

Inter-Symbol Interference (ISI)

37

Equalization


Frequency

Channel response

Frequency

Equalizer response

Frequency

Combined response

)( fHeq

)( fF

)()( fHfF eq

Audio Graphic Equalizer -adjusting the strength in each frequency

38

OFDM: Orthogonal Frequency Division Multiplexing


Monocarrier Multicarrier

Drawbacks Selective fading Very short pulses ISI is significant Poor spectral efficiency

Advantages Flat fading per subcarrier Long pulses ISI is insignificant

Pulse duration: 1/B Pulse duration: N/B

Signalchannel N subcarriers

B Bf

OFDM is used in all wireless systems 4G and beyond!

39

Spread Spectrum and CDMA


FDMA:FrequencyDivisionMultipleAccess

TDMA:TimeDivisionMultipleAccess

40

Ch 10 Error-Control Coding

• The purpose of channel coding is to – Increase the level of reliability in the presence of noise and

channel distortion – By selectively introducing redundancies in the transmitted data. – Achieve a data rate that is close to the channel capacity.


41

Ch 10 Error-Control Coding


• Information stream: 1 0 1 0 0 1 ( )• If we separate the stream into two parts, and add checksum

bits as1 0 1 00 0 1 11 0 0 1

• If the received signal is 1 1 1 0 wrong row0 0 0 11 0 0 1

^wrong column

• Then the location of the error bit can be identified and corrected.

Ncc ...1

42

Power Efficiency of Binary Channel Codes


Mariner1969

Turbo Code1993

Galileo:BVD1992Galileo:LGA

1996

Pioneer1968-72

Voyager1977

OdenwalderConvolutionalCodes 1976

0 1 2 3 4 5 6 7 8 9 10-1-2

0.5

1.0

Eb/No in dB

Cod

e R

ate

r

UncodedBPSK

IS-951991

Iridium1998

510bP

Spe

ctra

l Effi

cien

cy

arbitrarily lowBER:

LDPC Code2001

Chung, Forney,Richardson, Urbanke

Course Plan – Subject to Change!


Summary

• Important course to understand the digital communications in the digital age!

• Requires certain knowledge of– Basics of modulation– Fourier analysis– Probability– Stochastic process– Complex numbers– Matlab

• Homework – separate sheet (Due 1/22 before class)


ece8700 communications system engineering …yiminzhang.com/ece8700/ece8700_2014_1_ch1.pdfece8700...

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