WIRELESS COMMUNICATIONS

WIRELESS COMMUNICATIONS P. Muthu Chidambara Nathan Associate Professor Department of Electronics and Communication Engineering National Institute of Technology Tiruchirappalli, Tamil Nadu New Delhi-110001 2013

WIRELESS COMMUNICATIONS P. Muthu Chidambara Nathan 2008 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN-978-81-203-3514-1 The export rights of this book are vested solely with the publisher. Fifth Printing November, 2013 Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi-110092 and Printed by Mudrak, 30-A, Patparganj, Delhi-110091.

To My Parents and Teachers, Wife and Son, Friends and Students

CONTENTS Preface... xiii Abbreviations... xv 1 WIRELESS COMMUNICATION 1 9 1.1 Introduction... 1 1.2 History of Wireless Communication... 1 1.3 Wireless Services... 2 1.3.1 Broadcast... 2 1.3.2 Paging... 2 1.3.3 Cellular Telephony... 2 1.3.4 Cordless Telephony... 2 1.3.5 Wireless Local Area Networks (WLAN)... 3 1.3.6 Ad Hoc Networks... 3 1.3.7 Personal Area Networks (PAN)... 3 1.3.8 Satellite Cellular Communication... 3 1.4 Requirements in Wireless Communication... 4 1.4.1 Data Rate... 4 1.4.2 Range and Number of Users... 4 1.4.3 Mobility... 4 1.4.4 Energy Consumption... 5 1.5 Introduction to Modern Wireless Communication Systems... 5 1.6 Wireless Communication System Definitions... 8 Exercises... 8 v

vi Contents 2 CELLULAR CONCEPT 10 20 2.1 Introduction... 10 2.2 Frequency Reuse... 11 2.3 Channel Assignment Strategies... 14 2.4 Interference... 14 2.5 Cochannel Interference and System Capacity... 14 2.6 Adjacent Channel Interference... 18 2.7 Handover... 19 Exercises... 20 3 CELLULAR CAPACITY AND IMPROVEMENT TECHNIQUES 21 32 3.1 Introduction... 21 3.2 Capacity of Erlang-B System... 22 3.3 Capacity of Erlang-C System... 23 3.4 Improving Capacity in Cellular Systems... 23 3.4.1 Cell Splitting... 23 3.4.2 Cell Sectoring... 25 3.4.3 Coverage Zone Concept... 27 3.4.4 More Efficient Modulation Formats and Coding... 27 3.4.5 Better Source Coding... 27 3.4.6 Discontinuous Transmission... 28 3.4.7 Multiple Antennas... 28 Exercises... 31 4 WIRELESS PROPAGATION MECHANISMS 33 50 4.1 Introduction... 33 4.2 Free Space Propagation Model... 34 4.3 Reflection... 35 4.3.1 Ground Reflection (2-ray) Model... 35 4.4 Diffraction... 38 4.4.1 Knife-edge Diffraction Model... 38 4.4.2 Multiple Knife-edge Diffraction... 44 4.5 Path Loss Prediction over Hilly Terrain... 45 4.6 Introduction to Fading and Diversity Techniques... 47 4.6.1 Small Scale Fading (Fading)... 47 4.6.2 Diversity Techniques... 47 4.6.3 Space Diversity in the Channel... 48 Exercises... 50 5 WIRELESS CHANNEL AND DIVERSITY 51 62 5.1 Introduction... 51 5.2 Overview of the Wireless Communication Channel... 51 5.2.1 Frequency Selective and Flat Fading Channels... 52 5.2.2 Slow and Fast Fading Channels... 53

Contents vii 5.3 Flat and Slow Fading Channels... 54 5.4 Diversity Systems... 54 5.4.1 Establishing Diversity Branches... 55 5.4.2 Factors Affecting Diversity Performance: Power Imbalance... 56 5.4.3 Factors Affecting Diversity Performance: Envelope Correlation... 57 5.4.4 Diversity Combining Techniques... 60 5.4.5 Diversity Gain... 60 5.4.6 Additional Factors Affecting Diversity Systems... 61 Exercises... 61 6 COMBINING SCHEMES AND THE RAYLEIGH CHANNEL 63 80 6.1 Introduction... 63 6.2 Diversity Combining Schemes... 63 6.2.1 Selection Diversity... 63 6.2.2 Maximal Ratio Combining... 68 6.2.3 Equal Gain Combining... 71 6.3 Analysis of Rayleigh Fading Channels... 73 Exercises... 80 7 JOINT PROBABILITY DENSITY FUNCTION OF TWO CORRELATED AND UNBALANCED RAYLEIGH SIGNALS 81 92 7.1 Introduction... 81 7.2 Separating Two Rayleigh Signals into Gaussian Components... 82 7.2.1 Correlation between the Gaussian Components of Two Rayleigh Signals... 83 7.2.2 Joint Probability Density Function of Four Gaussian Variables... 85 7.3 Transforming a Four Dimensional Gaussian pdf into the Joint Probability Density of Two Rayleigh Signals... 87 7.3.1 Joint Probability Density Function of Two Rayleigh Signals... 87 7.3.2 Relating the Gaussian Correlations to the Rayleigh Envelope Correlation and Branch Power... 90 Exercises... 92 8 TWO-BRANCH SELECTION DIVERSITY IN A RAYLEIGH CHANNEL 93 102 8.1 Introduction... 93

viii Contents 8.2 Distribution of the SNR V... 94 S 8.2.1 Probability Density Function of the SNR V... 94 S 8.2.2 Cumulative Distribution Function of the SNR... 98 8.3 Probability Density Function of the SNR... 100 Exercises... 102 9 TWO-BRANCH MAXIMAL RATIO COMBINING IN A RAYLEIGH CHANNEL 103 113 9.1 Introduction... 103 9.2 Distribution of the SNR... 104 V M 9.2.1 Probability Density Function of the SNR... 104 V M 9.2.2 Cumulative Distribution Function of the SNR... 109 V M 9.3 Probability Density Function of the SNR P... 110 M 9.4 Maximal Ratio Combining Example... 111 9.4.1 Interpretation of Diversity Measurements, and Extraction of Statistics... 111 Exercises... 113 10 INTRODUCTION TO 4G WIRELESS TECHNOLOGIES AND SMART ANTENNAS 114 123 10.1 Introduction... 114 10.2 Evolution to 4G Technologies... 114 10.3 Smart Antennas... 117 10.3.1 Switched Beam Antennas... 117 10.3.2 Adaptive Antennas... 119 10.4 4G Tools and Techniques... 120 10.4.1 Advanced Technologies Physical Layer Enhancement... 121 10.4.2 Can You Expand on this 5th Generation (5G) Wireless Features?... 122 Exercises... 122 11 INTRODUCTION TO MIMO SYSTEMS 124 132 11.1 Introduction... 124 11.2 Model of MIMO System... 124 11.2.1 CSI (Channel State Information)... 125 11.2.2 Use of Retro-directive Antennas... 126 11.2.3 Effects of Mutual Coupling at the Antenna Arrays... 126 P s V S

Contents ix 11.3 MIMO System Channel Capacity... 127 11.3.1 Maximum Capacity, if there is no CSI at the Transmitter... 129 11.3.2 Maximum Capacity when Channel is Known to the Transmitter... 129 Exercises... 132 12 CODE DIVISION MULTIPLE ACCESS 133 144 12.1 Introduction... 133 12.2 Basic Principles of Spread Spectrum... 133 12.3 Direct Sequence Spread Spectrum... 135 12.4 Frequency Hopped Spread Spectrum... 136 12.5 Time Hopped Spread Spectrum... 138 12.6 CDMA System Overview... 138 12.6.1 Principle of CDMA... 139 12.6.2 Pseudo-random Noise (PN) Code Sequences... 140 12.6.3 Properties of Maximal Length Sequences... 141 12.7 DSSS Modulation... 142 12.8 DSSS Demodulation... 142 12.9 Overall Process in CDMA... 143 Exercises... 143 13 ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING 145 153 13.1 Introduction... 145 13.2 Advantages of OFDM Transmission Scheme... 146 13.3 Disadvantages OFDM Transmission Scheme... 147 13.4 Multiple Access Techniques... 147 13.4.1 Frequency Division Multiple Access... 147 13.4.2 Time Division Multiple Access... 148 13.4.3 Code Division Multiple Access... 148 13.5 OFDM System Model... 150 13.5.1 Serial to Parallel Conversion... 150 13.5.2 Modulation of Data... 150 13.5.3 Inverse Fourier Transform... 151 13.5.4 OFDM Versus Single Carrier Transmission... 151 13.6 Applications of OFDM... 152 Exercises... 152 14 MULTICARRIER CODE DIVISION MULTIPLE ACCESS (MC-CDMA) 154 160 14.1 Introduction... 154 14.2 What is Orthogonal Multicarrier-CDMA... 155 14.3 Advantages of MC-CDMA... 155 14.3.1 Compared to Direct Sequence (DS) CDMA... 155 14.3.2 Compared to OFDM... 155

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