EE4640 Communication Systems (II)

Instructor: Prof. Jen-Ming Wu (吳仁銘吳仁銘吳仁銘吳仁銘)Inst. of communications Engineering

Dept. of Electrical Engineeringjmwu@ee.nthu.edu.tw

Office: EECS 625

EE4640 Communication Systems (II), Spring, 2012 1

Office: EECS 625

Spring, 2012

http://my.com.nthu.edu.tw/~jmwu/ee4640/ee4640.htm

Syllabus

� Text Book: Communication Systems, Simon Haykin (4th Ed.), J. Wiley.� Coverage

� Chap 5: Signal-Space Analysis

� Chap 6: Passband Digital Transmission

� Chap 7: Spread-Spectrum Modulation

� Chap 8: Multiuser Radio Communications

� Chap 9: Fundamental Limits in Information Theory

EE4640 Communication Systems (II), Spring, 20122

� Chap 9: Fundamental Limits in Information Theory

� Class Time & Place: W3W4F4 @ R209� Class Website: http://my.com.nthu.edu.tw/~jmwu/ee4640/ee4640.htm� Grading:

� Homework 20%� Midterm I 25%� Midterm II 25%� Final 30%

� Lecture: Black Board + Viewgraph when needed. Please prepare to take notes.

Why should we understand communication systems?

� Mobile subscribers top 6 Billion in Dec.2011, increasing 2M/day!

� Mobile devices outnumber PCs 5:1

� In some growth areas close to 10:1

� Major Driver for Semiconductor Industry

� Cell phone sales: 1B (2006); 1.15B (2007)

� WiFi chipsets: 200M (2006), 280M (2007), 370 M (2008)

5B

4B

EE4640 Communication Systems (II), Spring, 2012 3

� 5 Billion people to be connected by 2015

(Source: NSN)

� 7 trillion wireless devices serving 7

billion people in 2017 (Source: WWRF)

� 1000 wireless devices per person.

(Source: Nokia)

93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10

3B

2B

1B

4B

Source: ABI Research, 2010

Sports &

Fitness

•Sensors in sports equipment (heart rate belt)

•Sports monitoring devices (pedometer)

•Embedded sport sensors (altimeter in watch)

Healthcare •Healthcare devices (blood pressure monitor)

•Illness treatment (glucose meter)

Mobile

accessories

•PC accessories (wireless mouse)

•Mobile phone and accessories

•Identification systems (PC ID in key chain)

Wireless Applications exist everywhere

4

•Monitoring (tire pressure monitor)

•Alarms (parking assistant)

•Keyless entry (key in wrist watch)

Healthcare

Home &

Entertainment

Automotive

Personal Gadgets

•Illness treatment (glucose meter)

•Monitoring devices (medication dispenser)

•Remote controls (for e.g. music device)

•Gaming sensors (sensors in wrists and knees, Wi)

•Home sensors and switches (remote lock)

•Remote controls (of MP3 player or cell phone)

•Sub-displays (of mobile phone)

•Out of range services (alert forgotten cell phone)4

The Era of Immersive Wireless has Come

UMTS, WLAN,DAB, GSM, TETRA, ...

Personal Travel Assistant,DAB, PDA, laptop, GSM, UMTS, WLAN, Bluetooth, ...

EE4640 Communication Systems (II), Spring, 2012

Scientific Applications:

How to communicate from Mars to Earth?

The Facts• Distance: 56 millions km (Moon-to-Earth is 0.28 M km, Sun-to-Earth 150M km)• Delay Time: 3 minutes and 7 seconds for a signal emitted by the DSN to reach Mars• Noise source: cosmic rays and thermal noise (from Sun and Rx)• Noise Level: -215 dBW/Hz • Tx RF power: 15W ~ 100W• Rx Signal Power: 2x10-16 W or -157 dBW• SNR : 8 dB• SNR : 8 dB• Carrier Frequency: S-, X- and K-bands at frequencies of 2.2, 8.4 and 32 GHz• Bandwidth: 100 kHz• Bit Rate: 166 kbit/s (with BPSK modulation)

Source: http://www.astrosurf.com/luxorion/qsl-mars-communication3.htm

meets with

Claude ShannonClaude Shannon

Communication Systems and IC Design

8

� Traditional technology scaling continues to drive advances in infrastructure

backbone (e.g. data and compute servers, routers, base stations, …)

� But not so for the “Mobile and Sensory Swarm”… traditional scaling rules to

have minor impact [H. De Man, Keynote Address, ISSCC 2005].

� Exponentially increasing number of (ultra-)small components : from “Moore’s

Law” to “More Than Moore” or “Beyond Moore”

� Driven by heterogeneous integration of innovative technologies. ARM delivers

5 Billion devices in 2010, mostly in cell phone devices.

� Opportunity: system and application considerations

Gordon MooreGordon MooreClaude ShannonClaude Shannon

8

Basic Elements of a Communication System.

EE4640 Communication Systems (II), Spring, 20129

Communication Process

� Transmission of information from one point to another

� Generate a message signal: voice, image, data, video, …

� Describe the message in some form by a set of symbols: electrical, aural, visual

� Encode the symbols into a form for transmission

� Transmit the encoded symbols over a physical medium

� Receive, decode and reproduce the symbols

EE4640 Communication Systems (II), Spring, 201210

� Receive, decode and reproduce the symbols

� Re-create the original message signals

� Three Basic Elements

� Transmitter

� Channel

� Receiver

Source Bandwidth

EE4640 Communication Systems (II), Spring, 2012 11

telecomtelecomtelecomtelecom

data comdata comdata comdata com

RF/microwaveRF/microwaveRF/microwaveRF/microwave

Types of Source Information

� Speech

� 16 bits x 20KHz (sample rate) = 320Kb/sec

� Image

� D1: 720x480x12 bits = 4.1472 Mb/image

EE3650 Communication Systems (II), Fall 200912

� Video display rate = 4.1472 Mb/frame x 30 frames/sec

= 124 Mb/sec

� For smaller size image (352x244) and reduced frame rate,

� MPEG2: ~4Mb/s

� MPEG4/H.264: ~1.5Mb/s

� Source compression helps in transmission bandwidth requirement. But

processing of huge raw data in real time is still needed.

Communication Channels

�Two Basic Types of Communication Channels

� Guided Wireline Propagation

� Telephone (e.g. Home/Office phone line)

�Coaxial cable (e.g. xDSL)

�Optical Fiber

EE4640 Communication Systems (II), Spring, 201113

� Wireless Propagation

�Radio broadcast channel (e.g. AM/FM, DVB)

�Mobile/Radio-Frequency channel (e.g. 802.11x, GSM, 3G)

� Satellite channel (e.g. GPS, Satellite TV)

�Microwave channel (e.g. Military)

� Free Space Optics

Electromagnetic Spectrum for Communication

EE4640 Communication Systems (II), Spring, 201214

Communication Spectrum Utilizations

Communication Resources

�Primary Communication Resources

� Transmitted Power (Signal-to-Noise Ratio, SNR)

� Channel Bandwidth (Bit Rate)

�Types of Communication Channels

� Power Limited

EE4640 Communication Systems (II), Spring, 201216

� Power Limited

�Noise

�Propagation Loss

� Finite Power

� Band Limited

� Freq response of medium

�Multiple users share the medium

Elements of a Digital Communication System

X +

(a) Block diagram of transmitter. (b) Block diagram of channel.

EE4640 Communication Systems (II), Spring, 201117

X

(c) Block diagram of receiver.

Block Diagram of Digital Communication SystemBlock Diagram of Digital Communication SystemBlock Diagram of Digital Communication SystemBlock Diagram of Digital Communication System

ErrorCorrection

coding

DigitalModulation D/A PABPF

cos(2πfct)

SourceData

101

RF FrontendBaseband Tx

1101

18

A/D

AWGN

BPF LNAError

Correctiondecoding

DigitalDemodu-

lation

Baseband Rx RF Frontend

cos(2πfct)

11010101

Modulation Process

� What?

� For the purpose of communication, the transmitter usually modifies the message signal into a form suitable for transmission over the channel. (Modulation)

� The receiver re-creates the original message signal from the degraded signal after propagation through the

EE4640 Communication Systems (II), Spring, 201219

the degraded signal after propagation through the channel. (Demodulation)

� How?

Modulation converts a baseband signal to a passband

counterpart.

0 freq

baseband signal

0 fc freq

passband signal

Reasons for Modulation

� For wired comm system, superior shielding at higher

frequencies

� For wireless comm system, the antenna size should be a

significant fraction of the wavelength to achieve a

reasonable gain

� The comm usually occur in a certain part of the spectrum

EE4640 Communication Systems (II), Spring, 2012 20

� The comm usually occur in a certain part of the spectrum

according to the FCC regulation for multiple channel

access

� Sometimes, modulation allows better signal transmission

or simpler detection at the receiver

Typical Block Diagram of Digital Communication System

EE4640 Communication Systems (II), Spring, 201221

Shannon’s Information Capacity Theorem

� Constraints to deliver reliable communication

� Allowable transmit power

� Available channel bandwidth

� Affordable cost to build the system

� Reliability is expressed in terms of BER (Bit Error Rate)

� Shannon’s Information Capacity Theorem (1948)

EE4640 Communication Systems (II), Spring, 201222

� Shannon’s Information Capacity Theorem (1948)

� Under Additive White Gaussian Noise (AWGN) channel, the

channel capacity is

sec/)1(log2 bitsSNRBC +=� Provide a theoretical upper bound of data rate R, given B

(channel bandwidth) and SNR.

� Efficiency η = R/C, measure of communication system efficiency