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

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

ECOMMS: Topics

Digital 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 4-G  5-G protocols.com

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?

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

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

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

Summary