S. Mandayam/ECE Dept./Rowan University Digital Communications 0909.402.03/0909.504.01 Fall 2002 Shreekanth Mandayam ECE Department Rowan University shreek/fall02/digcomm

S. Mandayam/ECE Dept./Rowan University

Digital CommunicationsDigital Communications0909.402.03/0909.504.010909.402.03/0909.504.01

Fall 2002Fall 2002

Shreekanth MandayamECE Department

Rowan University

http://engineering.rowan.edu/~shreek/fall02/digcomm/

Lecture 1Lecture 1September 9, 2002September 9, 2002


PlanPlan• Introduction Digital Communications

• Evolution• Rationale

• Course Logistics

• Review of ECOMMS• Signals• Systems• Digital Communications Transceiver (CODEC/MODEM)• Principles

• Introduction to Lab


Digital CommunicationsDigital Communications

• Some Milestones• Claude Shannon, 1948• X.25 (Telephony)• IEEE 802.3 (Ethernet)• ARPANET, 1969• IEEE 802.5 (FDDI)• ISO-OSI 7-layer Network Reference Model• CDMA• GSM• VOIP

• SIPprotocols.com


Wireless Comm Wireless Comm Evolution/Revolution: UMTS (3G)Evolution/Revolution: UMTS (3G)

http://www.3g-generation.com/http://www.nttdocomo.com/reports/010902_ir_presentation_january.pdf


Evo

luti

on

Evo

luti

on

TECHNOLOGY FEATURES

1-GLate 1970’s, early 1980’s

AMPS Advanced Mobile Phone Service

-Analog voice service

- No data service

2-G1990’s

CDMA Code Division Multiple Access

TDMA Time Division Multiple Access

GSM Global System for Mobile Communications

PDC Personal digital cellular

Digital voice service

- 9.6K to 14.4K bit/sec.

- CDMA, TDMA and PDC offer one-way data transmissions only

- Enhanced calling features like caller ID

- No always-on data connection

3-G2000 and beyond

W-CDMA Wide-band Code Division Multiple Access

CDMA-2000 Based on the Interim Standard-95 CDMA standard

TD-SCDMA Time-division synchronous CDMA

- Superior voice quality

- Up to 2M bit/sec. always-on data

- Broadband data services like video and multimedia

- Enhanced roaming


And there’s more….And there’s more….

3

A View of 4GA View of 4GA View of 4G

• Domain of 4G extends beyond 1G, 2G, and 3G• > 2 Mbps in a wide-area mobile system (> 20 Mbps peak)

• Could coexist with 2G and 3G

• 4G is not necessarily defined by the bit rate, but by a significant advance in system capability beyond what can be achieved with 3G

Data Rate

Coverage Area,

Mobility

Macrocell,High Mobility

Microcell,Limited Mobility

Fixed Access

64kbps 2Mbps 200Mbps

P-MP (LMDS)Milli-wave LAN

2G2G

WLAN

4G4G3G3G

Joseph M. Nowack, http://www.jacksons.net/~tac/


Digital Communications: Digital Communications: RationaleRationale

• Information Theory:• What is the fundamental limit on the compression and

refinement of information generated by the source?

• What is the fundamental limit on the transmission rate of information over a noisy channel?

• How do we approach these limits?


Digital CommunicationsDigital Communications

• Please read these!!!!• Digital Modulation in Communications Systems: An Introduction,

Hewlett-Packard Application Note 1298 http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf Mirrored at:

http://engineering.rowan.edu/~shreek/spring00/ecomms/notes/ 5965-7160E.pdf

• Source Basics, Agilent Technologies Teachers Tools Slide Presentation http://www.educatorscorner.com/tools/lectures/slides/srcbas.html Mirrored at: http://engineering.rowan.edu/~shreek/spring00/ecomms/notes/ scrbas.ppt


Digital Communication ParadigmsDigital Communication Paradigms

Mu

ltip

lexe

rMessage 2

Message 3

Message 1

1 2 3 S 1 2 2 3 S

Dem

ult

iple

xer

Message 2

Message 3

Message 1

Pac

keti

zin

g

Message 2

Message 3

Message 1

1H

H 2

3H

H 2

1H

3H

H 21H

3HMessage 2

Message 3

Message 1Depacket-izing

Depacket-izing

Depacket-izing

Circuit Switching

Packet Switching

Sync bits

Header bits


Course LogisticsCourse Logistics

http://engineering.rowan.edu/~shreek/fall02/digcomm/


Probability

Inform ation

Entropy

Channel Capacity

Discrete

Pow er & Energy S ignals

Continuous Fourier T ransform

Discrete Fourier T ransform

Baseband and Bandpass S ignals

Com plex Envelope

G aussian Noise & SNR

Random VariablesNoise Calculations

Continuous

Signals

AMSw itching M odulator

Envelop Detector

DSB-SCProduct M odulatorCoherent Detector

Costas Loop

SSBW eaver's M ethodPhasing M ethod

Frequency M ethod

Frequency & Phase M odulationNarrow band/W idebandVCO & S lope Detector

PLL

Analog

Source EncodingHuffm an codes

Error-control EncodingHam m ing Codes

Sam plingPAM

QuantizationPCM

Line Encoding

T im e Division M uxT 1 (DS1) Standards

Packet Sw itchingEthernet

ISO 7-Layer Protocol

BasebandCODEC

ASKPSKFSK

BPSK

QPSK

M -ary PSK

QAM

BandpassM ODEM

DigitalDigita l Com m T ransceiver

System s

Electrical Com m unication System s

ECOMMSECOMMS

http://engineering.rowan.edu/~shreek/spring02/ecomms/


What is a communications What is a communications system?system?

• Communications Systems: Systems designed to transmit and receive information

Info Source

Info Source

Info Sink

Info Sink

CommSystem


Block DiagramBlock Diagram

ReceiverRx

receivedmessage

tosink

)(~ tm

TransmitterTx s(t)

transmittedsignal

Channelr(t)

receivedsignal

m(t)message

from source

Info Source

Info Source

Info Sink

Info Sink


Digital Communications TransceiverDigital Communications Transceiver

Anti-aliasingFilter

Sampling QuantizationData

EncryptionEncoder

SourceEncoder

ErrorControlEncoder

Channel/Line

Encoder

Modulator

MU

X

AudioAmp

SourceDecoder

DataEncryption

Decoder

ErrorControlDecoder

Equalization /DecisionCircuits

Demod-ulatorD

EM

UX

Reconstruction/DAC

ADC

CODEC MODEM

Analog o/p

Mu

ltip

le a

cces

s ch

ann

el

Analog i/p


Digital ModulationDigital Modulation

Carrier signal: Ac cos (2fct +)

Modulation: m(t)

Modulated signal: Ac (t) cos (2fc(t) t +(t))

Vary Vary Vary amplitude frequency phase

Variations are discrete!!!!!

m(t); discrete


PrinciplePrinciple

1 0 1 0………1 1

0 0

Analog message

Digitalcode

Digital message

Sinusoidal carrier

modulate

AM

FM

PM

AM &PM

1 0 1 0


Signal Vector RepresentationSignal Vector Representation

PhaseM

agnit

ude

S

0 degreesI

Q

I-QPlane

s(t) = Ac(t) cos (2fct +(t))

fixed!!!fixed!!!


Signal Changes:Signal Changes:Representation in the IQ PlaneRepresentation in the IQ Plane

S1

S2 I

QMagnitudeChange

S1

S2

I

Q

PhaseChange

S1

S2

I

QMagnitude& PhaseChange

FrequencyChange

???

I-Q Diagrams or

Constellations


Quadrature Phase Shift KeyingQuadrature Phase Shift Keying(QPSK)(QPSK)

I

Q

11

IQ Diagrams(t) = Ac cos(2fct + (t))

t

(t)

01

10

00

00

10

01

11


M-ary Quadrature Amplitude ModulationM-ary Quadrature Amplitude Modulation(M-ary-QAM)(M-ary-QAM)

I

Q

16 QAMI-Q

Constellation


Laboratory SoftwareLaboratory Software

• Matlab & Simulink

• DSP Toolbox

• DSP Blockset

• Communications Toolbox

• Communications Blockset


SummarySummary

Documents

S. Mandayam/ECE Dept./Rowan University Digital Communications 0909.402.03/0909.504.01 Fall 2002 Shreekanth Mandayam ECE Department Rowan University shreek/fall02/digcomm