Telecommunications demystified copy

Telecommunications Demystified A Streamlined Course in Digital Communications (and some Analog) for EE Students and Practicing Engineers by Carl Nassar Eagle Rock, Virginia www.LLH-Publishing.com www.elsolucionario.net Librar y of Congress Cataloging-in-Publication Data Nassar, Carl, 1968­ Telecommunications demystified / by Carl Nassar p c.m (Demystifying technology series) Includes bibliographical references and index ISBN 1-878707-55-8 (alk paper) Telecommunication I Title II Series TK5101 N257 2000 621.382 dc21 00-062902 Copyright © 2001 by LLH Technology Publishing All rights reser ved No part of this book may be reproduced, in any form or means whatsoever, without written permission from the publisher While ever y precaution has been taken in the preparation of this book, the publisher and author assume no responsibility for errors or omissions Neither is any liability assumed for damages resulting from the use of the information contained herein Printed in the United States of America 10 Cover design: Jim Johnson Developmental editing: Carol Lewis Production: Kelly Johnson Visit us on the web: www.LLH-Publishing.com For revisions and updates, check www.telecommunicationsdemystified.com www.elsolucionario.net www.elsolucionario.net Introducing Telecommunications Communication Systems Definition The Parts of a Communication System An Example of a Communication System The Transmitter The Channel The Receiver 2 3 Telecommunication Systems Definition Four Examples and an Erratic History Lesson Analog and Digital Communication Systems Some Introductory Definitions Definitions And Digital Became the Favorite Making It Digital Congrats and Conclusion Problems 10 11 Telecommunication Networks Telecommunication Network Basics Connecting People with Telephones Connecting More People, Farther Apart Multiplexing�An Alternative to a Lot of Wire First There Was FDM Along Came TDM 14 16 16 18 POTS: Plain Old Telephone System 19 Local Calls Long Distance Calls Connecting the Call The Signals Sent from Switching Center to Switching Center Class to Class Other Signals between Switching Centers 19 20 20 21 22 24 Communication Channels 24 Transmission Lines (Wires) Terrestrial Microwave Satellite Connections Fiber-optic Links 24 26 28 29 Data Communication Networks Mobile Communications Local Area Networks (LANs) Conclusion Problems 31 33 35 37 38 A Review of Some Important Math, Stats, and Systems Random Variables Definitions The Distribution Function: One Way to Describe x The Density Function: A Second Way to Describe x The Mean and the Variance Example 3.1 Multiple Random Variables 3 40 41 43 44 Random Processes 45 www.elsolucionario.net A Definition Expressing Yourself, or a Complete Statistical Description Expressing Some of Yourself, or a Partial Description And in Telecommunications � Example 3.2 45 47 47 48 48 Signals and Systems: A Quick Peek 50 A Few Signals Another Way to Represent a Signal: The Fourier Transform Example 3.3 Bandwidth A Linear Time Invariant (LTI) System Some Special Linear Time Invariant (LTI) Systems 50 51 52 53 55 56 Onward Problems 58 x Source Coding and Decoding: Sampling Ideal Sampling The Sampling The Information in the Samples Getting Back All the Information from the Samples Some Commonly Used Words Example 4.1 Zero-order Hold Sampling The Information in the Samples Example 4.2 Natural Sampling The Information in the Samples 4 62 64 65 66 67 67 68 69 70 Quantization 71 Meet the Quantizer Example 4.3 Who wants it? Quantizer Terms Types of Quantizers Example 4.4 The Good Quantizer What Is a Good Quantizer? Measures of Performance A �Classic� Creating the Good Quantizer Example 4.5 The Quantizer and the Telephone The Idea 71 73 73 74 75 76 77 77 77 78 81 86 88 88 Source Coding: Pulse Code Modulator (PCM) 92 Introducing the PCM PCM Talk The �Good� PCM Source Decoder: PCM Decoder 92 93 94 95 Predictive Coding 96 The Idea Behind Predictive Coding Why? The Predicted Value and the Predictive Decoder The Delta Modulator (DM) How the DM creates an The Block Diagram of the DM The Sampler and the Quantizer in the DM 97 97 98 99 99 100 100 www.elsolucionario.net The Signals in the DM Example 4.6 Overload and Granular Noise Differential PCM (DPCM) The Predicted Value Example 4.7 The Block Diagram 104 105 107 107 109 109 Congrats and Conclusion Problems 110 111 Getting It from Here to There: 5.1 An Introduction Modulators 5.1 116 Baseband Modulators NRZ Modulators RZ Modulators Phase-encoded Modulators Which Modulator to Use? Example 5.1 Bandpass Modulators ASK PSK FSK QAM Example 5.2 Choosing a Modulation Method 116 117 118 120 122 124 124 125 127 129 130 131 131 Just-in- Time Math, or How to Make a Modulator Signal Look Funny 133 The Idea Example 5.3 Representing Modulated Signals BPSK PSK ASK QAM 134 136 138 139 140 143 145 Bring it Home, Baby, or Demodulators 146 What Demodulators Do The Channel and Its Noise Building a Demodulator, Part I�the Receiver Front End What it does An orthonormal basis for r(t) Representing r(t) as a vector using the orthonormal basis Building the Receiver Front End Example 5.4 The Rest of the Demodulator, Part II�The Decision Makers What It Does How It Works How to Build It The Correlator Receiver Example 5.5 The Matched Filter Receiver�Version The Matched Filter Receiver �Version 146 147 148 148 148 149 151 152 152 152 153 156 156 157 158 159 How Good Is It Anyway (Performance Measures) 161 A Performance Measure Evaluation of for Simple Cases The BPSK Modulator Remembered 161 162 162 162 www.elsolucionario.net The BPSK Demodulator: A Summary Evaluating the P( Some Well-known P( s 162 163 166 166 What We Just Did Problems 166 167 Channel Coding and Decoding: Simple Block Coding 172 The Single Parity Check Bit Coder Example 6.1 Some Terminology Rectangular Codes Channel Coders for Rectangular Codes Channel Decoders for Rectangular Codes Example 6.2 172 174 175 175 175 176 176 Linear block codes 177 Introduction Example 6.3 Understanding Why Systematic Linear Block Codes Example 6.4 The Decoding Example 6.5 Example 6.6 177 178 179 181 181 182 184 186 Performance of the Block Coders 188 Performances of Single Parity Check Bit Coders/Decoders The Performance of Rectangular Codes The Performance of Linear Block Codes Example 6.7 188 189 189 190 Benefits and Costs of Block Coders Conclusion Problems 192 193 194 Channel Coding and Decoding: Convolutional Coders Our Example Making Sure We� ve Got It Polynomial Representation The Trellis Diagram Example 7.1 199 200 201 202 Channel Decoding 203 Using a Trellis Diagram Example 7.2 The Viterbi Algorithm Example 7.3 204 206 206 212 Performance of the Convolutional Coder Catastrophic Codes Building Your Own Problems 213 214 216 217 Trellis-Coded Modulation (TCM) The Idea Improving on the Idea 222 225 www.elsolucionario.net Example 8.1 229 The Receiver End of Things 230 The Input The TCM Decoder Front End The Rest of the TCM Decoder Example 8.2 Searching for the Best Path 231 233 234 236 237 Problems 242 Channel Filtering and Equalizers i Modulators and Pulse Shaping i Example 9.1 248 The Channel That Thought It Was a Filter 249 Example 9.2 250 Receivers: A First Try 251 The Proposed Receiver Making the Receiver a Good One The Proposed Receiver: Problems and Usefulness Example 9.3 251 254 256 257 Optimal Receiver Front End Optimal Rest-of-the-Receiver 258 262 The Input A Problem with the Input, and a Solution The Final Part of the Optimal Receiver Example 9.4 An Issue with Using the Whitening Filter and MLSE 262 264 265 270 271 Linear Equalizers 271 Zero Forcing Linear Equalizer MMSE (Minimum Mean Squared Error) Equalizer Example 9.5 272 273 273 Other Equalizers: the FSE and the DFE Conclusion Problems 274 275 276 10 Estimation and Synchronization 10 Introduction Estimation: Part 10 280 Our Goal What We Need to Get an Estimate of a Given r Estimating a Given r, the First Way Estimating a Given r, the Second Way Estimating a Given r, the Third Way Example 10.1 280 281 281 282 283 283 Evaluating Channel Phase: A Practical Example 285 Our Example and Its Theoretically Computed Estimate The Practical Estimator: the PLL Updates to the Practical Estimator in MPSK 285 290 292 Conclusion Problems 295 296 11 Multiple Access Schemes 11 What It Is The Underlying Ideas 11 300 Example 11.1 302 www.elsolucionario.net TDMA 303 Example 11.2 305 FDMA CDMA 305 306 Introduction DS-CDMA FH-CDMA MC-CDMA 306 310 312 313 CIMA Conclusion Problems 315 318 319 12 Analog Communications 12.1 Modulation�An Overview Amplitude Modulation (AM) 12.1 322 AM Modulators�in Time Example 12.1 AM Modulation�in Frequency Demodulation of AM Signals�Noise-Free Case An Alternative to AM�DSB-SC Example 12.2 323 325 326 328 330 333 Frequency Modulation (FM) 334 The Modulator in FM Example 12.3 The Demodulator in FM 335 338 339 The Superheterodyne Receiver Summary Problems 339 341 342 Annotated References and Bibliography Index 175 www.elsolucionario.net ... www.LLH-Publishing.com For revisions and updates, check www.telecommunicationsdemystified.com www.elsolucionario.net www.elsolucionario.net Introducing Telecommunications Communication Systems ... www.elsolucionario.net www.elsolucionario.net Chapter Introducing Telecommunications I can still recall sitting in my first class on telecommunications as an undergrad—the teacher going off into... Complete Statistical Description Expressing Some of Yourself, or a Partial Description And in Telecommunications � Example 3.2 45 47 47 48 48 Signals and Systems: A Quick