S MandayamECE Dept Rowan University Digital Communications 0909

S. Mandayam/ECE Dept. /Rowan University Digital Communications 0909. 402. 03/0909. 504. 01 Fall 2002 Lecture 6 October 14, 2002 Shreekanth Mandayam ECE Department Rowan University http: //engineering. rowan. edu/~shreek/fall 02/digcomm/

S. Mandayam/ECE Dept. /Rowan University Plan • Baseband Data Transmission • Recall: Detection in the presence of AWGN • Receiver Model • Matched Filter Detector • BER for Unipolar and Bipolar Signaling • BER for multilevel signaling • Correlation receiver • Bandlimited Channels and ISI • Pulse Shaping: Raised Cosine Response • Eye Diagrams

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

S. Mandayam/ECE Dept. /Rowan University Recall: Receiver Model m TX s(t) S n(t) r 0(t) LPF t=t 0 r 0(t 0) VT Comparator ~ m

S. Mandayam/ECE Dept. /Rowan University Recall: Multilevel Signaling Binary Source Binary signal D symbols/second = R bits/second l-bit DAC 4 T 0 2 0 L=2 l Multilevel Signal D symbols/second = R/l R bits/second Ts Tb -2 -4 0 1 2 3 4 5 6 t (ms) 7 8

S. Mandayam/ECE Dept. /Rowan University Average Symbol Error demos/BER_multilevel_baseband. m

S. Mandayam/ECE Dept. /Rowan University Matched Filter/Correlation Receiver s(t) Matched Filter h(t) r(t) = s(t) + n(t) A r 0(t) = s 0(t) + n 0(t) T s(-t) A -T s(t) + n(t) X s(t) r 0(t) Integrator t=t 0 A r 0(t 0) h(t)=s(T-t) T A 2 h(t)*s(t) T 2 T t=t 0=T

S. Mandayam/ECE Dept. /Rowan University Bandlimited Channels: Inter-Symbol Interference (ISI) Band-unlimited Channel Input pulse Output pulse H(f) f t t Transmission Channel Band-limited Channel H(f) Input pulse t -B B f Output pulse t

S. Mandayam/ECE Dept. /Rowan University Pulse Shaping: Nyquist’s First Method for Zero ISI HE(f) Transmit Filter HT(f) vi(t) 1 0 1 Channel Characteristics HC(f) Receiver Filter HR(f) v 0(t) 1 t t

S. Mandayam/ECE Dept. /Rowan University Pulse Shaping: The Raised Cosine Response He(f) 1. 0 f. D 0. 5 -B -f 0 -f 1 f 0 B f

S. Mandayam/ECE Dept. /Rowan University Pulse Shaping: The Raised Cosine Response 2 f 0 he(t) t -3/2 f 0 -2/2 f 0 -1/2 f 0 2/2 f 0 3/2 f 0

S. Mandayam/ECE Dept. /Rowan University Summary