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
S. Mandayam/ECE Dept./Rowan University
PlanPlan• Introduction Digital Communications
• Evolution• Rationale
• Course Logistics
• Review of ECOMMS• Signals• Systems• Digital Communications Transceiver (CODEC/MODEM)• Principles
• Introduction to Lab
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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/
S. Mandayam/ECE Dept./Rowan University
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?
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
Course LogisticsCourse Logistics
http://engineering.rowan.edu/~shreek/fall02/digcomm/
S. Mandayam/ECE Dept./Rowan University
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/
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
Signal Vector RepresentationSignal Vector Representation
PhaseM
agnit
ude
S
0 degreesI
Q
I-QPlane
s(t) = Ac(t) cos (2fct +(t))
fixed!!!fixed!!!
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
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
S. Mandayam/ECE Dept./Rowan University
M-ary Quadrature Amplitude ModulationM-ary Quadrature Amplitude Modulation(M-ary-QAM)(M-ary-QAM)
I
Q
16 QAMI-Q
Constellation
S. Mandayam/ECE Dept./Rowan University
Laboratory SoftwareLaboratory Software
• Matlab & Simulink
• DSP Toolbox
• DSP Blockset
• Communications Toolbox
• Communications Blockset
S. Mandayam/ECE Dept./Rowan University
SummarySummary