1. S. Mandayam/ECE Dept./Rowan University Digital Communications 0909.402.03/0909.504.01 Fall 2002 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall02/digcomm/ Lecture 6 October 14, 2002

2. 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

3. 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

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

5. S. Mandayam/ECE Dept./Rowan University Recall: Multilevel Signaling Binary Source l-bit DAC Binary signal D symbols/second = R bits/second L=2 l Multilevel Signal D symbols/second = R/l R bits/second 0 1 2 3 4 5 6 7 8 4 2 0 -2 -4 TbTb TsTs T0T0 t (ms)

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

7. S. Mandayam/ECE Dept./Rowan University Matched Filter/Correlation Receiver Matched Filter h(t) r 0 (t) = s 0 (t) + n 0 (t) r(t) = s(t) + n(t) X s(t) Integrator t=t 0 r 0 (t) r 0 (t 0 ) s(t) + n(t) T -T T T 2T A A A A2A2 t=t 0 =T s(t) s(-t) h(t)=s(T-t) h(t)*s(t)

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

9. S. Mandayam/ECE Dept./Rowan University Pulse Shaping: Nyquist’s First Method for Zero ISI Transmit Filter H T (f) Channel Characteristics H C (f) Receiver Filter H R (f) v i (t) v 0 (t) H E (f) t 1 0 1 1 t

10. S. Mandayam/ECE Dept./Rowan University Pulse Shaping: The Raised Cosine Response f H e (f) -B -f 0 -f 1 f 1 f 0 B ff ff 1.0 0.5

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

12. S. Mandayam/ECE Dept./Rowan University Summary