S. Mandayam/ECE Dept./Rowan University Digital Communications / Fall 2002 Shreekanth Mandayam ECE Department Rowan University Lecture 1 September 9, 2002

S. Mandayam/ECE Dept./Rowan University Plan 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 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 SIP protocols.com

S. Mandayam/ECE Dept./Rowan University Wireless Comm Evolution/Revolution: UMTS (3G)

S. Mandayam/ECE Dept./Rowan University Evolution TECHNOLOGYFEATURES 1-G Late 1970’s, early 1980’s AMPS Advanced Mobile Phone Service -Analog voice service - No data service 2-G 1990’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-G 2000 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…. Joseph M. Nowack,

S. Mandayam/ECE Dept./Rowan University 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?

S. Mandayam/ECE Dept./Rowan University Digital Communications Please read these!!!! Digital Modulation in Communications Systems: An Introduction, Hewlett-Packard Application Note Mirrored at: E.pdf Source Basics, Agilent Technologies Teachers Tools Slide Presentation Mirrored at: scrbas.ppt

S. Mandayam/ECE Dept./Rowan University Digital Communication Paradigms Multiplexer Message 2 Message 3 Message S S Demultiplexer Message 2 Message 3 Message 1 Packetizing Message 2 Message 3 Message 1 1H H 2 3 H H 2 1H 3 H H 2 1H 3 H Message 2 Message 3 Message 1 Depacket -izing Circuit Switching Packet Switching Sync bits Header bits

S. Mandayam/ECE Dept./Rowan University Course Logistics

S. Mandayam/ECE Dept./Rowan University ECOMMS ng.rowan.edu/~ shreek/spring02 /ecomms/

S. Mandayam/ECE Dept./Rowan University What is a communications system? Communications Systems: Systems designed to transmit and receive information Info Source Info Source Info Sink Info Sink Comm System

S. Mandayam/ECE Dept./Rowan University Block Diagram Receiver Rx received message to sink Transmitter Tx s(t) transmitted signal Channel r(t) received signal m(t) message from source Info Source Info Source Info Sink Info Sink

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

S. Mandayam/ECE Dept./Rowan University Digital Modulation Carrier signal: A c cos (2  f c t +  ) Modulation: m(t) Modulated signal:A c (t) cos (2  f c (t) t +  (t)) Vary Vary Vary amplitude frequency phase Variations are discrete!!!!!  m(t); discrete

S. Mandayam/ECE Dept./Rowan University Principle ……… 1 0 Analog message Digital code Digital message Sinusoidal carrier modulate AM FM PM AM & PM 1 0

S. Mandayam/ECE Dept./Rowan University Signal Vector Representation Phase Magnitude S 0 degrees I Q I-Q Plane s(t) = A c (t) cos (2  f c t +  (t)) fixed!!!

S. Mandayam/ECE Dept./Rowan University Signal Changes: Representation in the IQ Plane S1S1 S2S2 I Q Magnitude Change S1S1 S2S2 I Q Phase Change S1S1 S2S2 I Q Magnitude & Phase Change Frequency Change ??? I-Q Diagrams or Constellations

S. Mandayam/ECE Dept./Rowan University Quadrature Phase Shift Keying (QPSK) I Q 11 IQ Diagram s(t) = A c cos(2  f c t +  (t)) t  (t)     

S. Mandayam/ECE Dept./Rowan University M-ary Quadrature Amplitude Modulation (M-ary-QAM) I Q 16 QAM I-Q Constellation

S. Mandayam/ECE Dept./Rowan University Laboratory Software Matlab & Simulink DSP Toolbox DSP Blockset Communications Toolbox Communications Blockset

S. Mandayam/ECE Dept./Rowan University Summary