S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems Spring 2005 Shreekanth Mandayam ECE Department Rowan University Lecture 11b April 20, 2005

S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityPlan Digital Bandpass Communications M-ary PSK and M-ary QAM Different ways of looking at a digitally modulated signal Data Processing & Data Communications Communications Networks Packet Switched Networks OSI 7-Layer Protocol Architecture TCP-IP Protocol Architecture Broadcast Transmitters and Receivers AM Broadcast Transmitter Class-C Amp Collector Modulator TRF Receiver Superheterodyne Receiver

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

S. Mandayam/ ECOMMS/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/ ECOMMS/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/ ECOMMS/ECE Dept./Rowan University M-ary Phase Shift Keying (M-ary PSK) I Q Octophase I-Q Constellation

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

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Different ways of looking at a digitally modulated signal

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Time & Frequency Domain View Reproduced from:

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Frequency & Power View Reproduced from:

S. Mandayam/ ECOMMS/ECE Dept./Rowan University I-Q Constellation Diagram Reproduced from: Matlab Demo: qpsk.m

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Eye Diagram Reproduced from: Matlab: >>eyediagram

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

S. Mandayam/ ECOMMS/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 Recall

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

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

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

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

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

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

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 octets

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 octets

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

S. Mandayam/ ECOMMS/ECE Dept./Rowan University AM Broadcast Transmitter Temp. Stabilized Crystal Oscillator Buffer Amplifier Class-C Modulated Power Amp. Stage Class-C Modulated Power Amp. Stage Impedance Matching Network Audio Amplifier Modulator Driver Amplifier Demodulator Audio Input  + -

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Amplifier Classification icic tt  icic tt icic tt icic tt Class A Class B Class AB Class C

S. Mandayam/ ECOMMS/ECE Dept./Rowan University BJT Collector Modulator Circuit Output Characteristics

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Circuit Operation BJT Collector Modulator

S. Mandayam/ ECOMMS/ECE Dept./Rowan University AM Receiver Purpose Demodulate received signal Requirements Carrier frequency tuning Filtering Amplification

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuning Circuits Series Tuned Circuit + - V r C L I

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Series Tuned Circuit function [f,A]=resonance(f0,Q) %ECOMMS Spring 00 Class Demo %S. Mandayam, ECE Dept., Rowan University %To illustrate series resonance and Q-factor close all; %defining frequency axis f=f0-f0/2:0.1:f0+f0/2; %calculating relative response y=(f/f0)-(f0./f); A=20*log10(1./(1+(y*Q).^2).^0.5); plot(f-f0,A);grid on; xlabel('Shift from resonant frequency in Hz'); ylabel('Relative Response in dB'); title('Series Tuning Circuit');

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuning Circuits Parallel Tuned Circuit + - V r C L I Active Tuned Circuits?

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuned Radio Frequency (TRF) Receiver Active Tuning Circuit Detector Circuit Local Oscillator Bandpass Filter Baseband Audio Amp

S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityHeterodyning Heterodyning (Upconversion/ Downconversion) Subsequent Processing (common) All Incoming Frequencies Fixed Intermediate Frequency

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Superheterodyne Receiver RF Amplifier H 1 (f) Mixer Local Oscillator IF Amplifier H 2 (f) Detector Audio Amp Common tuning f RF or f c f LO f IF fmfm fmfm Downconversion f IF = |f RF - f LO | Upconversion f IF = f RF + f LO

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