Wireless Networks Local and Ad Hoc Networks Ivan Marsic Department of Electrical and Computer Engineering and the CAIP Center Rutgers University Contents CHAPTER 1................................................................................................... INTRODUCTION ..............................................................................................................................1 1.1 Summary and Bibliographical Notes................................................................................................... 6 CHAPTER 2 THE RADIO CHANNEL.......................................................................1 2.1 Introduction........................................................................................................................................ 1 2.1.1 Decibels and Signal Strength ............................................................................................................ 4 2.2 Channel Implementation..................................................................................................................... 5 2.2.1 Transmission Rate ........................................................................................................................... 5 2.2.2 Symbols To Signals.......................................................................................................................... 6 2.2.3 Modulation ...................................................................................................................................... 6 2.2.4 Noise and Error Probability ............................................................................................................. 10 2.3 Continuous Noisy Channel Capacity................................................................................................. 14 2.4 Radio Propagation: Multipath and Doppler ....................................................................................... 20 2.4.1 Large-Scale Path Loss ................................................................................................................... 21 2.4.2 Types of Wave Interactions............................................................................................................. 23 2.4.3 Doppler Shift.................................................................................................................................. 25 2.4.4 Multipath or Small-Scale Fading ...................................................................................................... 26 2.5 Equalization, Coding, and Diversity .................................................................................................. 29 2.5.1 Adaptive Equalization ..................................................................................................................... 30 2.5.2 Channel Coding or Forward Error Correction .................................................................................... 30 2.5.3 Diversity Techniques for Fading Channels........................................................................................ 31 2.5.4 Packet Error Rate .......................................................................................................................... 31 2.6 Summary and Bibliographical Notes................................................................................................. 32 Problems....................................................................................................................................................... 33 CHAPTER 3 MULTIACCESS COMMUNICATION ....................................................36 i Ivan Marsic • Rutgers University ii 3.1 Introduction...................................................................................................................................... 36 3.1.1 MAC Protocol Performance Measures.............................................................................................. 39 3.1.2 Propagation Time and Parameter β ................................................................................................. 40 3.1.3 Vulnerable Period .......................................................................................................................... 41 3.2 ALOHA Protocols ............................................................................................................................. 42 3.2.1 Throughput Analysis....................................................................................................................... 43 3.3 Carrier Sensing Protocols................................................................................................................. 48 3.3.1 Throughput Analysis of Nonpersistent CSMA.................................................................................... 51 3.3.2 CSMA/CD ..................................................................................................................................... 54 3.3.3 CSMA/CA...................................................................................................................................... 54 3.4 Other MAC Protocols........................................................................................................................ 56 3.5 Multiple-access Interference............................................................................................................. 56 3.5.1 Physical Layer Interference............................................................................................................. 57 3.5.2 Link Layer Interference: Hidden and Exposed Stations ...................................................................... 58 3.6 Summary and Bibliographical Notes................................................................................................. 61 Problems....................................................................................................................................................... 61 CHAPTER 4 IEEE 802.11 WIRELESS LAN.............................................................68 4.1 Introduction...................................................................................................................................... 68 4.1.1 Architecture and Services ............................................................................................................... 68 4.1.2 Beacons........................................................................................................................................ 72 4.2 Medium Access Control.................................................................................................................... 72 4.2.1 Interframe Spaces.......................................................................................................................... 73 4.2.2 Virtual Carrier Sensing and Network Allocation Vector ....................................................................... 75 4.2.3 ARQ and Atomic Operations ........................................................................................................... 75 4.2.4 Backoff Procedure with the DCF...................................................................................................... 78 4.2.5 Hidden and Exposed Stations ......................................................................................................... 79 4.2.6 Frame Structure............................................................................................................................. 81 4.3 Physical Layer and Rate Adaptation ................................................................................................. 82 4.3.1 Physical Signals............................................................................................................................. 82 4.3.2 Transmission Rate Adaptation......................................................................................................... 83 4.4 Power-saving Mechanisms ............................................................................................................... 85 4.4.1 Effect on Capacity.......................................................................................................................... 87 4.5 Performance Analysis....................................................................................................................... 88 4.5.1 Channel Event Probabilities ............................................................................................................ 89 4.5.2 Throughput and Delay Performance................................................................................................. 92 Chapter 1 • Introduction to Computer Networks iii 4.6 IEEE 802.11 Family of Standards ...................................................................................................... 94 4.7 Summary and Bibliographical Notes................................................................................................. 98 Problems....................................................................................................................................................... 98 CHAPTER 5 AD HOC NETWORKS ....................................................................103 5.1 Introduction.................................................................................................................................... 103 5.2 Routing Algorithms .......................................................................................................................