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McGraw hill telecommunications demystified
LICENSE INFORMATION This is a single-user version of this eBook. It may not be copied or distributed. Unauthorized reproduction or distribution of this eBook may result in severe civil and criminal penalties. 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 Copyright © 2001 by LLH Technology Publishing All rights reserved. No part of this book may be reproduced, in any form or means whatsoever, without written permission of the pub- lisher. While every 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 information contained herein. Printed in the United States of America. ISBN 1-878707-77-9 (eBook) LLH Technology Publishing and HighText Publications are trademarks of Lewis Lewis & Helms LLC, 3578 Old Rail Road, Eagle Rock, VA, 24085 iii Contents Foreword xv What’s on the CD-ROM? xvii CHAPTER 1 Introducing Telecommunications 1 1.1 Communication Systems 1 1.1.1 Definition 1 1.1.2 The Parts of a Communication System 2 1.1.3 An Example of a Communication System 2 1.2 Telecommunication Systems 3 1.2.1 Definition 3 1.2.2 Four Examples and an Erratic History Lesson 4 1.3 Analog and Digital Communication Systems 6 1.3.1 Some Introductory Definitions 6 1.3.2 Definitions 7 1.3.3 And Digital Became the Favorite 8 1.3.4 Making It Digital 9 1.4 Congrats and Conclusions 10 CHAPTER 2 Telecommunication Networks 13 2.1 Telecommunication Network Basics 13 2.1.1 Connecting People with Telephones 13 2.1.2 Connecting More People, Farther Apart 14 2.1.3 Multiplexing—An Alternative to a Lot of Wire 16 Click the page number to go to that page. iv Telecommunications Demystified 2.2 POTS: Plain Old Telephone System 19 2.2.1 Local Calls 19 2.2.2 Long Distance Calls 20 2.2.3 The Signals Sent from Switching Center to Switching Center 21 2.3 Communication Channels 24 2.3.1 Transmission Lines (Wires) 24 2.3.2 Terrestrial Microwave 26 2.3.3 Satellite Connections 28 2.3.4 Fiber-optic Links 29 2.4 Data Communication Networks 31 2.5 Mobile Communications 33 2.6 Local Area Networks (LANs) 35 2.7 Conclusion 37 CHAPTER 3 A Review of Some Important Math, Stats, and Systems 39 3.1 Random Variables 39 3.1.1 Definitions 39 3.1.2 The Distribution Function: One Way to Describe x 39 3.1.3 The Density Function: A Second Way to Describe x 40 3.1.4 The Mean and the Variance 41 3.1.5 Multiple Random Variables 44 3.2 Random Processes 45 3.2.1 A Definition 45 3.2.2 Expressing Yourself, or a Complete Statistical Description 47 3.2.3 Expressing Some of Yourself, or a Partial Description 47 3.2.4 And in Telecommunications … 48 3.3 Signals and Systems: A Quick Peek 50 3.3.1 A Few Signals 50 3.3.2 Another Way to Represent a Signal: The Fourier Transform 51 3.3.3 Bandwidth 53 3.3.4 A Linear Time Invariant (LTI) System 55 3.3.5 Some Special Linear Time Invariant (LTI) Systems 56 3.4 Onward 58 v Telecommunications Demystified CHAPTER 4 Source Coding and Decoding: Making it Digital 61 4.1 Sampling 61 4.1.1 Ideal Sampling 61 4.1.2 Zero-order Hold Sampling 67 4.1.3 Natural Sampling 69 4.2 Quantization 71 4.2.1 Meet the Quantizer 71 4.2.2 The Good Quantizer 77 4.2.3 The Quantizer and the Telephone 88 4.3 Source Coding: Pulse Code Modulator (PCM) 92 4.3.1 Introducing the PCM 92 4.3.2 PCM Talk 93 4.3.3 The “Good” PCM 94 4.3.4 Source Decoder: PCM Decoder 95 4.4 Predictive Coding 96 4.4.1 The Idea Behind Predictive Coding 97 4.4.2 Why? 97 4.4.3 The Predicted Value and the Predictive Decoder 98 4.4.4 The Delta Modulator (DM) 99 4.4.5 The Signals in the DM 101 4.4.6 Overload and Granular Noise 105 4.4.7 Differential PCM (DPCM) 107 4.5 Congrats and Conclusion 110 CHAPTER 5 Getting It from Here to There: Modulators and Demodulators 115 5.1 An Introduction 115 5.2 Modulators 116 5.2.1 Baseband Modulators 116 5.2.2 Bandpass Modulators 124 5.3 Just-in-Time Math, or How to Make a Modulator Signal Look Funny 133 5.3.1 The Idea 134 5.3.2 Representing Modulated Signals 138 vi 5.4 Bring it Home, Baby, or Demodulators 146 5.4.1 What Demodulators Do 146 5.4.2 The Channel and Its Noise 147 5.4.3 Building a Demodulator, Part I—the Receiver Front End 148 5.4.4 The Rest of the Demodulator, Part II—The Decision Makers 152 5.4.5 How to Build It 156 5.5 How Good Is It Anyway (Performance Measures) 161 5.5.1 A Performance Measure 161 5.5.2 Evaluation of P() ε for Simple Cases 162 5.5.3 Some well-known P() ε ’s 166 5.6 What We Just Did 166 CHAPTER 6 Channel Coding and Decoding: Part 1–Block Coding and Decoding 171 6.1 Simple Block Coding 172 6.1.1 The Single Parity Check Bit Coder 172 6.1.2 Some Terminology 175 6.1.3 Rectangular Codes 175 6.2 Linear block codes 177 6.2.1 Introduction 177 6.2.2 Understanding Why 179 6.2.3 Systematic Linear Block Codes 181 6.2.4 The Decoding 182 6.3 Performance of the Block Coders 188 6.3.1 Performances of Single Parity Check Bit Coders/Decoders 188 6.3.2 The Performance of Rectangular Codes 189 6.3.3 The Performance of Linear Block Codes 189 6.4 Benefits and Costs of Block Coders 192 6.5 Conclusion 193 vii CHAPTER 7 Channel Coding and Decoding: Part 2–Convolutional Coding and Decoding 197 7.1 Convolutional Coders 197 7.1.1 Our Example 197 7.1.2 Making Sure We’ve Got It 199 7.1.3 Polynomial Representation 200 7.1.4 The Trellis Diagram 201 7.2 Channel Decoding 203 7.2.1 Using a Trellis Diagram 204 7.2.2 The Viterbi Algorithm 206 7.3 Performance of the Convolutional Coder 213 7.4 Catastrophic Codes 214 7.5 Building Your Own 216 CHAPTER 8 Trellis-Coded Modulation (TCM) The Wisdom of Modulator and Coder Togetherness 221 8.1 The Idea 222 8.2 Improving on the Idea 225 8.3 The Receiver End of Things 230 8.3.1 The Input 231 8.3.2 The TCM Decoder Front End 233 8.3.3 The Rest of the TCM Decoder 234 8.3.4 Searching for the Best Path 237 CHAPTER 9 Channel Filtering and Equalizers 245 9.1 Modulators and Pulse Shaping 245 9.2 The Channel That Thought It Was a Filter 249 9.3 Receivers: A First Try 251 9.3.1 The Proposed Receiver 251 9.3.2 Making the Receiver a Good One 254 9.3.3 The Proposed Receiver: Problems and Usefulness 256 9.4 Optimal Receiver Front End 258 viii 9.5 Optimal Rest-of-the-Receiver 262 9.5.1 The Input 262 9.5.2 A Problem with the Input, and a Solution 264 9.5.3 The Final Part of the Optimal Receiver 265 9.5.4 An Issue with Using the Whitening Filter and MLSE 271 9.6 Linear Equalizers 271 9.6.1 Zero Forcing Linear Equalizer 272 9.6.2 MMSE (Minimum Mean Squared Error) Equalizer 273 9.7 Other Equalizers: the FSE and the DFE 274 9.8 Conclusion 275 CHAPTER 10 Estimation and Synchronization 279 10.1 Introduction 279 10.2 Estimation 280 10.2.1 Our Goal 280 10.2.2 What We Need to Get an Estimate of a Given r 281 10.2.3 Estimating a Given r, the First Way 281 10.2.4 Estimating a Given r, the Second Way 282 10.2.5 Estimating a Given r, the Third Way 283 10.3 Evaluating Channel Phase: A Practical Example 285 10.3.1 Our Example and Its Theoretically Computed Estimate 285 10.3.2 The Practical Estimator: the PLL 290 10.3.3 Updates to the Practical Estimator in MPSK 292 10.4 Conclusion 294 CHAPTER 11 Multiple Access Schemes: Teaching Telecommunications Systems to Share 299 11.1 What It Is 299 11.2 The Underlying Ideas 300 11.3 TDMA 303 11.4 FDMA 305 11.5 CDMA 306 11.5.1 Introduction 306 11.5.2 DS-CDMA 310 ix 11.5.3 FH-CDMA 312 11.5.4 MC-CDMA 313 11.6 CIMA 315 11.7 Conclusion 318 CHAPTER 12 Analog Communications 321 12.1 Modulation—An Overview 321 12.2 Amplitude Modulation (AM) 322 12.2.1 AM Modulators—in Time 323 12.2.2 AM Modulation—in Frequency 326 12.2.3 Demodulation of AM Signals—Noise-Free Case 328 12.2.4 An Alternative to AM—DSB-SC 330 12.3 Frequency Modulation (FM) 334 12.3.1 The Modulator in FM 335 12.3.2 The Demodulator in FM 339 12.4 The Superheterodyne Receiver 339 12.5 Summary 341 Annotated References and Bibliography 345 Index 349 [...]... tutorials For MATLAB product information, please contact: The MathWorks, Inc 3 Apple Hill Drive Natick, MA, 01760-2098 USA Tel: 508-647-7000 Fax: 508-647-7101 E-mail: info@mathworks.com Web: www.mathworks.com xix [This is a blank page.] Chapter 1 Introducing Telecommunications I can still recall sitting in my first class on telecommunications as an undergrad—the teacher going off into a world of technical... book, because of the increased importance of telecommunications to our economic and social well-being, we need to encourage students and practicing engineers to enter and maintain their skills in the field Making the requisite technical knowledge accessible is an important step in that direction In short, this book is an important and timely contribution to the telecommunications engineering field Dale... Nassar, Ph.D., is an engineering professor at Colorado State University, teaching telecommunications in his trademark entertaining style He is also the director of the RAWCom (Research in Advanced Wireless Communications) Laboratory, where he and his graduate students carry out research to advance the art and science of wireless telecommunications In addition, he is the founder of the Miracle Center, an... presentation style carried over into his writing I was not disappointed As you will soon see as you browse through these pages, Professor Nassar does have an uncanny ability to demystify the complexities of telecommunications systems engineering He does so by first providing for an intuitive understanding of the subject at hand and then, building on that sound foundation, delving into the associated mathematical... recall sitting in my first class on telecommunications as an undergrad—the teacher going off into a world of technical detail and I in my chair wondering, “What is this stuff called communications and telecommunications? ” So, first, some simple definitions and examples—the big picture 1.1 Communication Systems 1.1.1 Definition A communication system is, simply, any system in which information is transmitted... We’ll consider the example of Gretchen talking to Carl about where to go for lunch, as shown in Figure 1.3 Channel (the air) Figure 1.3 Gretchen talking to Carl at lunch Windpipe Vocal cords Introducing Telecommunications x 3 The Transmitter The transmitter, in this case, is made up of parts of Gretchen, namely her vocal cords, windpipe, and mouth When Gretchen wants to talk, her brain tells her vocal... Chapter One 1.2.2 Four Examples and an Erratic History Lesson Here are four examples of telecommunication systems, ordered chronologically to create what we’ll optimistically call “a brief history of telecommunications. ” Smoking Up In the B.C.’s, smoke signals were sent out using fire and some smoke signal equipment (such as a blanket) The smoke, carried upward by the air, was seen by people far (but... I need you.” Alex had just spilled battery acid down his pants and, as you can imagine, was in quite urgent need of his assistant’s help Figure 1.4 shows an illustration of two people, who Introducing Telecommunications x 5 we’ll call Carl and Monica, using the telephone What follows is a wordy description of how the telephone works Refer to Figure 1.4 to help you with the terms The transmitter consists... clarify, an example is shown in Figure 1.5(c) x(t) x(t) x(t) 1 t (a) T 2T 3T 4T (b) t 0 T 2T 3T 4T (c) Figure 1.5 (a) An analog signal; (b) a discrete time signal; and (c) a digital signal t Introducing Telecommunications x 7 1.3.2 Definitions An analog communication system is a communication system where the information signal sent from point A to point B can only be described as an analog signal An... Figure 1.7 (a) Transmitted analog signal; (b) Received analog signal Noise s(t) s(t) 1 1 0 +5v +5v 0 0 t -5v t -5v (a) (b) Figure 1.8 (a) Transmitted digital signal; (b) Received digital signal Introducing Telecommunications x 9 Here’s the key idea In the digital communication system, even after noise is added, a 1 (sent as +5 V) still looks like a 1 (+5 V), and a 0 (–5 V) still looks like a 0 (–5 V) So, . reproduction or distribution of this eBook may result in severe civil and criminal penalties. Telecommunications Demystified A Streamlined Course in Digital Communications (and some Analog) for EE Students. Multiplexing—An Alternative to a Lot of Wire 16 Click the page number to go to that page. iv Telecommunications Demystified 2.2 POTS: Plain Old Telephone System 19 2.2.1 Local Calls 19 2.2.2 Long Distance. (LTI) System 55 3.3.5 Some Special Linear Time Invariant (LTI) Systems 56 3.4 Onward 58 v Telecommunications Demystified CHAPTER 4 Source Coding and Decoding: Making it Digital 61 4.1 Sampling 61 4.1.1