1. Digital Communications 0909.402.03/0909.504.01 Fall 2002
Lecture 2 September 16, 2002
Shreekanth Mandayam
ECE Department
Rowan University

2. Plan ECOMMS Review QUIZ Baseband Data Transmission Digital Signaling
Orthogonal representation
Vector Representation
Binary and Multilevel Signals
Baud Rate, Bit Rate and Bandwidth

3. Digital Communications Transceiver
Anti-
aliasing
Filter
Data
Encryption
Encoder
Error
Control
Encoder
Source
Encoder
Channel/
Line
Encoder
Sampling
Quantization
MUX
Modulator
ADC
Analog i/p
CODEC
MODEM
Multiple access channel
Analog o/p
Data
Encryption
Decoder
Error
Control
Decoder
Audio
Amp
Reconstruction/
DAC
Source
Decoder
Equalization /
Decision
Circuits
DEMUX
Demod-ulator

4. Vector Representation of a 3-bit Binary Signal
s(t) T
T0=3T t 5V
Digital signal
p(t) T t 5V
Bit shape pulse
p1(t) t 5V
p2(t)
p3(t)
0 T 2T 3T
Orthogonal set j1 s j2 j3
Signal vector

5. Multilevel Signaling Binary l-bit Source DAC Binary signal
D symbols/second
= R bits/second
L=2l Multilevel Signal
D symbols/second = R/l
R bits/second
Binary
Source
l-bit
DAC

6. Summary