1. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems ECE.09.331 Spring 2009 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring09/ecomms/ Lecture 13a April 21, 2009

2. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityPlan Data Processing & Data Communications Communications Networks Packet Switched Networks OSI 7-Layer Protocol Architecture TCP-IP Protocol Architecture Performance of Comm. Systems corrupted by Noise Performance Measures: Digital and Analog Thermal (Johnson) Noise Amplitude: Recall Random Variables: lab1.ppt Power Spectral Density Autocorrelation function Wiener-Khintchine Theorem Bit Error Rates (BERs) for Digital Comm. Sys. General Procedure M-ary PSK and M-ary QAM Output SNR for Analog Comm. Sys. AM, DSB-SC, SSB and FM

3. S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics

4. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communications Transceiver Anti- aliasing Filter 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 Sampling Quantization

5. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communication Paradigms Multiplexer Message 2 Message 3 Message 1 1 2 3 S 1 2 2 3 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 Recall

6. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Communications Networking Router Step 1: Step 2: Step 3: …….. Protocol Sender Medium Step 1: Step 2: Step 3: …….. Protocol Receiver Message

7. S. Mandayam/ ECOMMS/ECE Dept./Rowan University A 3-Layer Protocol Architecture File transfer application Communications service module Network access module File transfer application Communications service module Network access module Computer 1 Computer 2 Comm network Files and file transfer commands Comm related messages

8. S. Mandayam/ ECOMMS/ECE Dept./Rowan University ISO OSI 7-Layer Model Physical Data Link Network Presentation Session Transport Application 76543217654321 Please Do Not Touch Steve’s Pet Alligator

9. S. Mandayam/ ECOMMS/ECE Dept./Rowan University TCP-IP Protocol Architecture Physical Network Access Internet Transport (host-to-host) Application TCP-IP Application Presentation Session Transport Network Data Link Physical OSI Hardware Firmware Software Operating system User space

10. S. Mandayam/ ECOMMS/ECE Dept./Rowan University TCP-IP Operation Example Network access protocol #1 Physical IP TCP Host A App X App Y Network access protocol #2 Physical IP TCP Host B App X App Y Logical connection (TCP) Port or Service access point (SAP) Global network address Network 1 Network 2 IP NAP1NAP2 Router J Subnetwork attachment point address Logical connection

11. S. Mandayam/ ECOMMS/ECE Dept./Rowan University TCP-IP Protocol Packet TCP header IP header Network header User Data Application Byte Stream TCP Segment IP Datagram Network Level Packet

12. S. Mandayam/ ECOMMS/ECE Dept./Rowan University IP Header VersionIHLType of ServiceTotal Length IdentificationFlagsFragment Offset Time to LiveProtocolHeader Checksum Source Address Destination Address Options + Padding 0 4 8 16 19 31 20 octets

13. S. Mandayam/ ECOMMS/ECE Dept./Rowan University TCP Header Source PortDestination Port Sequence Number Acknowledgement Number Data OffsetReserved URGURG ACKACK PSHPSH RSTRST SYNSYN FINFIN Window ChecksumUrgent Pointer Options + Padding 0 4 10 16 31 20 octets

14. S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics

15. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Performance of Communications Systems Corrupted by Noise Digital Bit Error Rate (BER) Analog Output SNR

16. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityNoise A random, unwanted fluctuation in signal amplitude Thermal (Johnson) Noise Amplitude vs. time: Gaussian PDF Model See Lab1 Pre-lab Lecture: lab1.pptlab1.ppt We also want to know how much noise power there is per Hz – why?

17. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityWhy? f |W(f)| Baseband 0 f |W(f)| Bandpass 0 fcfc -f c f |W(f)| Bandpass 0 f IF -f IF 1. Modulation 2. Demodulation 3. Demodulation

18. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Power Spectral Density (PSD) Normalized power of a waveform in the frequency domain Used for measuring signal/noise power loss/transfer in communications system blocks

19. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Autocorrelation Function Measure of similarity of a waveform observed at times  seconds apart how rapidly a random waveform fluctuates with time 0 Rx()Rx()  (time delay) Slowly fluctuating signal rapidly fluctuating signal R w (  ) P w (f) F Wiener-Khintchine Theorem Matlab Demo: autocorr.m

20. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Thermal (Johnson) Noise 00.511.522.53 x 10 12 0 0.5 1 1.5 2 x 10 -21 PSD of thermal noise frequency, Hz PSD, W/Hz Matlab script: psd_noise.m

21. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communications System Modulated Signal s(t) Digital Output Noise w(t) Sample & Hold  + + Noisy Receiver Model Processing Threshold

22. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Symbol Error in M-ary PSK Systems Matlab script: dignoise.m

23. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Symbol Error in M-ary QAM Systems Matlab script: dignoise.m

24. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Analog Communications Systems BPF Modulated Signal s(t) Output (Signal + Noise) Noise n(t) Demodulator  + + Noisy Receiver Model LPF Message Signal m(t) Baseband Output (Signal+ Noise) Noise n(t)  + + Baseband Model

25. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Output SNR in Analog Comm. Systems Matlab script: analognoise.m

26. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversitySummary