1. Electrical Communications Systems ECE.09.433
Digital Communications: Introduction
Dr. Shreek Mandayam
Electrical & Computer Engineering
Rowan University

2. Plan Digital Communications Introduction
Digital Communications Transceiver (CODEC/MODEM)

3. ECOMMS: Topics

4. Digital Communications
Some Milestones
Claude Shannon, 1948
X.25 (Telephony)
IEEE (Ethernet)
ARPANET, 1969
IEEE (FDDI)
ISO-OSI 7-layer Network Reference Model
CDMA
GSM
VOIP
4-G  5-G
protocols.com

5. Digital Communications: Rationale
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?

6. Principle 1 0 1 0……… Digital message 1 1 0 0 Digital Analog code
………
Digital
code
Analog
message
modulate AM
Sinusoidal carrier FM PM
AM & PM

7. Digital Communication Paradigms
Multiplexer
Message 2
Message 3
Message 1 1 2 3 S
Demultiplexer
Circuit Switching
Sync bits
Packet Switching
Header
bits
Packetizing
Message 2
Message 3
Message 1 1 H 2 3
Depacket-izing

8. 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

9. Summary