RED BOX RULES ARE FOR PROOF STAGE ONLY. DELETE BEFORE FINAL PRINTING.

Cover design by Sandra Heath

www.wiley.com/go/benvenuto2

Principles of Communications

Networks and Systems

Principles of Com

munications N

etworks

and Systems

Editors | Nevio Benvenuto and Michele Zorzi

Principles of Communications Networks

and SystemsEditors | Nevio Benvenuto and Michele Zorzi, Both of University of Padova, Italy

EditorsBenvenuto and Zorzi

Addressing the fundamental technologies and theories associated with designing complex communications systems and networks, Principles of Communications Networks and Systems provides models and analytical methods for evaluating their performance. Including both the physical layer (digital transmission and modulation) and networking topics, the quality of service concepts belonging to the different layers of the protocol stack are interrelated to form a comprehensive picture.

The book is designed to present the material in an accessible but rigorous manner. It jointly addresses networking and transmission aspects following a unifi ed approach and using a bottom up style of presentation, starting from requirements on transmission links all the way up to the corresponding quality of service at network and application layers. The focus is on presenting the material in an integrated and systematic fashion so that students will have a clear view of all the principal aspects and how they interconnect with each other.

• A comprehensive introduction to communications systems and networks, addressing both network and transmission topics

• Structured for effective learning, with basic principles and technologies being introduced before more advanced ones are explained

• Features examples of existing systems and recent standards as well as advanced digital modulation techniques such as CDMA and OFDM

• Contains tools to help the reader in the design and performance analysis of modern communications systems

• Provides problems at the end of each chapter, with answers on an accompanying website

PRINCIPLES OFCOMMUNICATIONSNETWORKS AND SYSTEMS

PRINCIPLES OFCOMMUNICATIONSNETWORKS AND SYSTEMS

Editors

Nevio Benvenuto and Michele ZorziUniversity of Padova, Italy

This edition first published 2011© 2011 John Wiley & Sons Ltd.

Registered officeJohn Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,West Sussex, PO19 8SQ, United Kingdom

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse thecopyright material in this book please see our website at www.wiley.com.

The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs andPatents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by anymeans, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and PatentsAct 1988, without the prior permission of the publisher.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronicbooks.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product namesused in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is notassociated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritativeinformation in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in renderingprofessional services. If professional advice or other expert assistance is required, the services of a competent professional shouldbe sought.

Library of Congress Cataloging-in-Publication DataBenvenuto, Nevio.

Principles of communications networks and systems / Editors N. Benvenuto, M. Zorzi.p. cm.

Includes bibliographical references and index.ISBN 978-0-470-74431-4 (cloth)

1. Telecommunication systems. I. Zorzi, Michele. II. Title.TK5101.B394 2011621.382–dc23 2011014178

A catalogue record for this book is available from the British Library.

Print ISBN: 9780470744314ePDF ISBN: 9781119978596oBook ISBN: 9781119978589ePub ISBN: 9781119979821mobi ISBN: 9781119979838

Set in 10/12 pt Times Roman by Thomson Digital, Noida, India

Contents

Preface xiii

List of Acronyms xvii

List of Symbols xxi

1 Introduction to Telecommunication Services, Networks and Signaling 1

1.1 Telecommunication Services 11.1.1 Definition 11.1.2 Taxonomies According to Different Criteria 21.1.3 Taxonomies of Information Sources 4

1.2 Telecommunication Networks 51.2.1 Introduction 51.2.2 Access Network and Core Network 9

1.3 Circuit-Switched and Packet-Switched Communication Modes 111.4 Introduction to the ISO/OSI Model 13

1.4.1 The Layered Model 131.4.2 The ISO/OSI Model 16

1.5 Signaling 181.5.1 Introduction 191.5.2 Channel-Associated and Common-Channel Signaling 191.5.3 SS7 20

vi CONTENTS

1.5.4 PDH Networks 221.5.5 SDH Networks 24References 25

2 Deterministic and Random Signals 27

2.1 Time and Frequency Domain Representation 272.1.1 Continuous Time Signals 272.1.2 Frequency Domain Representation for Periodic Signals 342.1.3 Discrete Time Signals 36

2.2 Energy and Power 392.2.1 Energy and Energy Spectral Density 392.2.2 Instantaneous and Average Power 42

2.3 Systems and Transformations 462.3.1 Properties of a System 462.3.2 Filters 472.3.3 Sampling 502.3.4 Interpolation 51

2.4 Bandwidth 542.4.1 Classification of Signals and Systems 562.4.2 Uncertainty Principle 582.4.3 Practical Definitions of Band 582.4.4 Heaviside Conditions 602.4.5 Sampling Theorem 612.4.6 Nyquist Criterion 64

2.5 The Space of Signals 662.5.1 Linear Space 662.5.2 Signals as Elements in a Linear Space 702.5.3 Gram–Schmidt Orthonormalization in Signal Spaces 712.5.4 Vector Representation of Signals 762.5.5 Orthogonal Projections onto a Signal Space 79

2.6 Random Variables and Vectors 812.6.1 Statistical Description of Random Variables 822.6.2 Expectation and Statistical Power 842.6.3 Random Vectors 882.6.4 Second Order Description of Random Vectors and Gaussian Vectors 942.6.5 Complex-Valued Random Variables 97

2.7 Random Processes 992.7.1 Definition and Properties 992.7.2 Point and Poisson Processes 1012.7.3 Stationary and Ergodic Random Processes 1082.7.4 Second Order Description of a WSS Process 1102.7.5 Joint Second-Order Description of Two Random Processes 1152.7.6 Second-Order Description of a Cyclostationary Process 117

CONTENTS vii

2.8 Systems with Random Inputs and Outputs 1182.8.1 Filtering of a WSS Random Process 1192.8.2 Filtering of a Cyclostationary Random Process 1222.8.3 Sampling and Interpolation of Stationary Random Processes 123Appendix: The Complementary Normalized Gaussian Distribution Function 126Problems 130References 136

3 Sources of Digital Information 137

3.1 Digital Representation of Waveforms 1373.1.1 Analog-to-Digital Converter (ADC) 1383.1.2 Digital-to-Analog Converter (DAC) 1403.1.3 Quantizer 1423.1.4 Uniform Quantizers 1433.1.5 Quantization Error 1453.1.6 Quantizer SNR 1483.1.7 Nonuniform Quantizers 1503.1.8 Companding Techniques and SNR 152

3.2 Examples of Application 1583.3 Information and Entropy 162

3.3.1 A Measure for Information 1623.3.2 Entropy 1643.3.3 Efficiency and Redundancy 1713.3.4 Information Rate of a Message 172

3.4 Source Coding 1733.4.1 The Purpose of Source Coding 1733.4.2 Entropy Coding 1743.4.3 Shannon Theorem on Source Coding 1773.4.4 Optimal Source Coding 1803.4.5 Arithmetic Coding 183Problems 188References 196

4 Characterization of Transmission Media and Devices 197

4.1 Two-Terminal Devices 1984.1.1 Electrical Representation of a Signal Source 1984.1.2 Electrical Power 1984.1.3 Measurement of Electrical Power 2004.1.4 Load Matching and Available Power 2014.1.5 Thermal Noise 2034.1.6 Other Sources of Noise 2054.1.7 Noise Temperature 205

viii CONTENTS

4.2 Two-Port Networks 2064.2.1 Reference Model 2064.2.2 Network Power Gain and Matched Network 2074.2.3 Power Gain in Terms of Electrical Parameters 2084.2.4 Noise Temperature 2094.2.5 Noise Figure 2114.2.6 Cascade of Two-Port Networks 213

4.3 Transmission System Model 2164.3.1 Electrical Model 2164.3.2 AWGN Model 2174.3.3 Signal-to-noise Ratio 2174.3.4 Narrowband Channel Model and Link Budget 220

4.4 Transmission Media 2234.4.1 Transmission Lines and Cables 2234.4.2 Power-Line Communications 2294.4.3 Optical Fiber 2344.4.4 Radio Links 2374.4.5 Underwater Acoustic Propagation 242Problems 250References 256

5 Digital Modulation Systems 259

5.1 Introduction 2595.2 Digital Modulation Theory for an AWGN Channel 260

5.2.1 Transmission of a Single Pulse 2605.2.2 Optimum Detection 2625.2.3 Statistical Characterization of Random Vectors 2635.2.4 Optimum Decision Regions 2655.2.5 Maximum A Posteriori Criterion 2695.2.6 Maximum Likelihood Criterion 2705.2.7 Minimum Distance Criterion 2705.2.8 Implementation of Minimum Distance Receivers 2735.2.9 The Theorem of Irrelevance 276

5.3 Binary Modulation 2775.3.1 Error Probability 2775.3.2 Antipodal and Orthogonal Signals 2825.3.3 Single Filter Receivers 285

5.4 M-ary Modulation 2885.4.1 Bounds on the Error Probability 2885.4.2 Orthogonal and Biorthogonal Modulations 292

5.5 The Digital Modulation System 2965.5.1 System Overview 2965.5.2 Front-end Receiver Implementation 301

CONTENTS ix

5.5.3 The Binary Channel 3025.5.4 The Inner Numerical Channel 3035.5.5 Realistic Receiver Structure 306

5.6 Examples of Digital Modulations 3075.6.1 Pulse Amplitude Modulation (PAM) 3075.6.2 Quadrature Amplitude Modulation (QAM) 3135.6.3 Phase Shift Keying (PSK) 3235.6.4 Frequency Shift Keying (FSK) 3295.6.5 Code Division Modulation 333

5.7 Comparison of Digital Modulation Systems 3365.7.1 Reference Bandwidth and Link Budget 3365.7.2 Comparison in Terms of Performance, Bandwidth and

Spectral Efficiency 3385.8 Advanced Digital Modulation Techniques 339

5.8.1 Orthogonal Frequency Division Multiplexing 3395.8.2 Spread Spectrum Techniques 342

5.9 Digital Transmission of Analog Signals 3445.9.1 Transmission through a Binary Channel 3455.9.2 Evaluation of the Overall SNR 3465.9.3 Digital versus Analog Transmission 3485.9.4 Digital Transmission over Long Distances: Analog versus

Regenerative Repeaters 352Problems 355References 370

6 Channel Coding and Capacity 373

6.1 Principles of Channel Coding 3736.1.1 The Purpose of Channel Coding 3736.1.2 Binary Block Codes 3756.1.3 Decoding Criteria. Minimum Distance Decoding 376

6.2 Linear Block Codes 3836.2.1 Construction of Linear Codes 3836.2.2 Decoding of Linear Codes 3866.2.3 Cyclic Codes 3906.2.4 Specific Classes of Linear Block Codes 3926.2.5 Performance of Linear Codes 395

6.3 Convolutional Codes 3976.3.1 Construction and Properties 3976.3.2 Decoding of Convolutional Codes and the Viterbi Algorithm 401

6.4 Channel Capacity 4056.4.1 Capacity of a Numerical Channel 4056.4.2 Capacity of the AWGN Channel 411

x CONTENTS

6.5 Codes that Approach Capacity 4206.5.1 Soft Decoding 4206.5.2 Concatenated Codes 4226.5.3 Low Density Parity Check Codes 423Problems 424References 429

7 Markov Chains Theory 431

7.1 Introduction 4327.2 Discrete-Time Markov Chains 432

7.2.1 Definition of Discrete-Time MC 4327.2.2 Transition Probabilities of Discrete-Time MC 4357.2.3 Sojourn Times of Discrete-Time MC 4377.2.4 Chapman–Kolmogorov Equations for Discrete-Time MC 4397.2.5 Transition Diagram of Discrete-Time MC 4407.2.6 State Probability of Discrete-Time MC 4417.2.7 Classification of Discrete-Time Markov Chains 4447.2.8 Asymptotic Behavior of Discrete-Time MC 455

7.3 Continuous-Time Markov Chains 4677.3.1 Definition of Continuous-Time MC 4687.3.2 Transition Probabilities of Continuous-Time MC 4687.3.3 Sojourn Times of Continuous-Time MC 4697.3.4 Chapman–Kolmogorov Equations for Continuous-Time MC 4747.3.5 The Infinitesimal Generator Matrix Q 4747.3.6 Forward and Backward Equations for Continuous-Time MC 4767.3.7 Embedded Markov Chain 4787.3.8 Flow Diagram of Continuous-Time MC 4827.3.9 State Probability of Continuous-Time MC 4827.3.10 Classification of Continuous-Time MC 4877.3.11 Asymptotic Behavior of Continuous-Time MC 488

7.4 Birth-Death Processes 4927.4.1 Definition of BDP 4927.4.2 Time-Dependent Behavior of BDP 4947.4.3 Asymptotic Behavior of BDP 500Problems 507References 516

8 Queueing Theory 517

8.1 Objective of Queueing Theory 5188.2 Specifications of a Queueing System 518

8.2.1 The Arrival Process 5218.2.2 The Service Process 523

CONTENTS xi

8.2.3 The Queueing Structure 5248.2.4 The Service Discipline 5258.2.5 Kendall Notation 526

8.3 Performance Characterization of a QS 5278.3.1 Occupancy Measures 5288.3.2 Time Measures 5298.3.3 Traffic Measures 531

8.4 Little’s Law 5348.5 Markovian Queueing Models 537

8.5.1 The M/M/1 Queueing System 5428.5.2 The M/M/m Queueing System 5548.5.3 The M/M/1/K Queueing System 5658.5.4 The M/M/m/m Queueing System 5738.5.5 The M/M/m/K Queueing System 577

8.6 The M/G/1 Queueing System 5818.7 The M/D/1 Queueing System 589

Problems 590References 596

9 Data Link Layer 597

9.1 Introduction 5989.2 Medium Access Control 599

9.2.1 Deterministic Access: TDMA and FDMA 6049.2.2 Time-Division Multiple Access 6049.2.3 Frequency-Division Multiple Access 6069.2.4 Comparison between TDMA and FDMA 6079.2.5 Demand-Based Access: Polling and Token Ring 6099.2.6 Random Access Protocols: ALOHA and Slotted ALOHA 6249.2.7 Carrier Sense Multiple Access 6339.2.8 Performance Comparison of Channel Access Schemes 659

9.3 Automatic Retransmission Request 6629.3.1 Stop-and-Wait ARQ 6669.3.2 Go Back N ARQ 6689.3.3 Selective Repeat ARQ 6719.3.4 Performance Comparison of ARQ Schemes 6759.3.5 Optimal PDU Size for ARQ 677

9.4 Examples of LAN Standards 6799.4.1 Ethernet 6799.4.2 Wireless Local Area Networks 6829.4.3 IEEE 802.11 6849.4.4 Bluetooth 691Problems 697References 703

xii CONTENTS

10 Network Layers 707

10.1 Introduction 70810.1.1 Switching and Connecting 70810.1.2 Networks and Network Topology 710

10.2 Routing 71410.2.1 Routing Objectives 71510.2.2 Routing Algorithms 72210.2.3 Technical Aspects of Routing Implementation 73210.2.4 Routing Strategies 73810.2.5 Routing Protocols 744

10.3 The Internet and IP 74710.3.1 The Internet Protocol 74810.3.2 IP Addressing System 75010.3.3 Control Protocols 756

10.4 The Transport Layer 75910.4.1 User Datagram Protocol 76210.4.2 Transmission Control Protocol 763

10.5 The Application Layer 76910.5.1 Domain Name Server 76910.5.2 Email Exchange and the World Wide Web 772References 774

Index 777

Preface

This book addresses the fundamentals of communications systems and networks, providingmodels and analytical methods for evaluating their performance. It is divided into ten chapters,which are the result of a joint effort by the authors and contributors. The authors and thecontributors have a long history of collaboration, both in research and in teaching, whichmakes this book very consistent in both approach and in the notation used.

The uniqueness of this textbook lies in the fact that it addresses topics ranging from thephysical layer (digital transmission and modulation) to the networking layers (MAC, routing,and transport). Moreover, quality of service concepts belonging to the different layers of theprotocol stack are covered, and the relationships between the metrics at different layers arediscussed. This should help the student in the analysis and design of modern communicationssystems, which are better understood at a system level.

A suitable selection of chapters from this book provides the necessary teaching mate-rial for a one-semester undergraduate course on the basics of telecommunications, but someadvanced material can be also used in graduate classes as complementary reading. The bookis also a useful comprehensive reference for telecommunications professionals. Each chapterprovides a number of problems to test the reader’s understanding of the material. The numer-ical solutions for these exercises are provided in the companion website, www.wiley.com/go/benvenuto2.

The content of each chapter is briefly summarized below.

Chapter 1 Overview of modern communications services, along with the presentation ofthe OSI/ISO model.

xiv PREFACE

Chapter 2 Analyzes both deterministic signals and random processes. The chapter revisesthe basics of signal theory and introduces both continuous and discrete time signals, and theirFourier transform with its properties. The concepts of energy, power and bandwidth are alsoreviewed, together with the vector representation of signals by linear space methodologies.Lastly, this chapter introduces the basics of random variables and random processes, theircommon statistical description, and how statistical parameters are modified by linear systems.

Chapter 3 Describes how information produced by a source, either analog or digital, can beeffectively encoded into a digital message for efficient transmission. We will first introduce thereference scheme for analog-to-digital conversion, and focus on quantization, the operationof approximating an analog value with a finite digit representation. We will also present thefundamentals of information theory with the notion of information carried by a digital message.Lastly we introduce the principles of source coding, state the fundamental performance boundsand discuss some coding techniques.

Chapter 4 Models a transmission medium. Firstly, a description of the two-port network isgiven. A model of noise sources is then provided and its description in terms of parameterssuch as the noise temperature and the noise figure is presented. A characterization, especially interms of power attenuation, of transmission lines, power lines, optical fibers, radio propagationand underwater propagation concludes this chapter.

Chapter 5 Deals with digital modulations. The general theory is first presented, relying onconcepts of linear spaces and hypothesis testing. Performance is measured by the bit error prob-ability, which again can be expressed in terms of system parameters. Then, the most importantmodulations are presented as examples of the general concept. These include pulse amplitudemodulation, phase shift keying, quadrature amplitude modulation, frequency shift keying andothers. A comparison between the different modulation schemes is carefully drawn. Then,more advanced modulation techniques are briefly presented, namely orthogonal frequencydivision multiplexing and spread spectrum. Finally, the performance of the digital approach iscompared against analog transmission, explaining why digital transmission is so widely used.

Chapter 6 Investigates how an information message can be robustly encoded into the signalfor reliable transmission over a noisy channel. We describe the principles of channel codingtechniques, where robustness is obtained at the price of reduced information rate and complexityof the decoding process. Then, based upon the fundamentals of information theory introducedin Chapter 3, we aim to establish upper bounds on the amount of information that can beeffectively carried through a noisy channel, by introducing the concept of channel capacity.We conclude by describing briefly how recently devised coding schemes allow such upperbounds to be approached closely while maintaining moderate complexity.

Chapter 7 Introduces some basic statistical methods that are widely used in the performanceanalysis of telecommunication networks. The topics covered are the elementary theory ofdiscrete-time and continuous-time Markov chains and birth-death processes. This theory willbe applied in Chapters 8 and 9, where we analyze simple queueing systems, and the performanceof channel access and retransmission protocols.

PREFACE xv

Chapter 8 Presents some basic principles of queueing theory. It starts with the definitionof a queueing system in terms of arrival, departure, service processes, queueing processesand service discipline. We then define some basic performance metrics for queueing systems,which are classified as occupancy measures (number of customers in the different parts ofthe system), time measures (system and queueing times) and traffic measures (average rate atwhich customer arrive and leave the system). We discuss the concept of system stability, bothfor blocking and nonblocking queueing systems and we illustrate Little’s law, a simple butfundamental result of queueing theory. The chapter concludes with a performance analysis offundamental queueing models, featuring Markovian as well as non-Markovian statistics forthe service process. Examples of the application of the developed theory to practical problems,including some unrelated to telecommunications, are provided throughout the chapter.

Chapter 9 Presents and analyzes link-layer algorithms, especially focusing on aspects relatedto channel access and retransmission of lost or corrupted data packets over point-to-pointlinks – a technique often referred to as Automatic Retransmission reQuest (ARQ). Channelaccess protocols are subdivided into the following classes: deterministic access, demand-basedaccess, random access and carrier sense multiple access. Mathematical models are given foreach class of protocols, thus obtaining the related performance in terms of throughput anddelay. The different channel access schemes are then compared as a function of the trafficload of the system. Next, the chapter presents three standard ARQ schemes, namely, stop andwait, go back N and selective repeat ARQ, which are characterized analytically in terms oftheir throughput performance. The chapter ends with the presentation of some relevant LANstandards: Ethernet, IEEE 802.11 and Bluetooth, with emphasis on their link-layer techniques.

Chapter 10 Describes all the layers above the data link layer dealing with the interconnectionof distinct devices so as to form a communication network. The chapter begins by reviewing auseful mathematical tool for network analysis, namely graph theory. Routing methodologies,i.e., how to find efficient paths in the network, are identified and discussed within this frame-work. Subsequently, we review how the network layer is implemented in the Internet detailingthe Internet Protocol (IP), as well as related issues, including Address Resolution Protocol(ARP) and Network Address Translation (NAT). The chapter describes the implementation ofTransport Control Protocol (TCP) and the User Datagram Protocol (UDP)) and application(Domain Name Server (DNS)) layers for the Internet. Some examples of application proto-cols, that is, HyperText Transport Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP)are given.

List of Acronyms

1P-CSMA one persistent CSMA1P-CSMA/CD one persistent CSMA/CDpP-CSMA p persistent CSMAACK acknowledgmentACL asynchronous connection-lessADPCM adaptive differential pulse-coded modulationADSL asymmetric digital subscriber loopAM amplitude modulationAMR adaptive multirateARCNET attached resource computer networkARQ automatic repeat requestARR adaptive round robina.s. almost surelyATM asynchronous transfer modeAWGN additive white Gaussian noiseBDP birth-death processBER bit error rateBMAP bit mapBPF bandpass filterBPSK binary phase shift keyingBSC binary symmetric channelBSS basic service set

xviii LIST OF ACRONYMS

CA collision avoidanceCBR constant bit rateCD collision detectionCDF cumulative distribution functionCDM code division modulationCDMA code division multiple accessCTS clear to sendDSLAM digital subscriber line access multiplexerETSI european telecommunications standards instituteCRC cyclic redundancy checkCSMA carrier sense multiple accessCSMA/CA CSMA with collision avoidanceCSMA/CD CSMA with collision detectionDBPSK differential binary phase shift keyingDC direct currentDCF distributed coordination functionDIFS distributed inter frame spaceDNS domain name serverDPSK differential phase shift keyingDQPSK differential quadrature phase shift keyingDSB double side bandDSSS direct sequence spread spectrumDVB digital video broadcastingERR exhaustive round robinESS extended service setFCC federal communication commissionFDDI fiber distributed data interfaceFDM frequency division multiplexingFDMA frequency division multiple accessFEC forward error correctionFH frequency hoppingFHS frequency hopping synchronization packetFHSS frequency hopping spread spectrumFM frequency modulationFSK frequency shift keyingFtf Fourier transformGBN-ARQ go back N ARQgcd greatest common dividerGD gap detectionGPS global positioning systemGSM global system for mobile communicationsHPF highpass filterHTML hypertext markup languageHTTP hypertext transfer protocolIANA Internet-assigned numbers authorityIBMAP inverse bit map

LIST OF ACRONYMS xix

IBSS independent basic service setISDN integrated services digital networkIEEE Institute for Electrical and Electronic Engineersiid independent and identically distributedIP Internet protocolISI intersymbol interferenceISM industrial scientific and medicalJPEG Joint Photographic Experts GroupLAN local area networklcm least common multiplierLDPC low density parity checkLLC logical link controlLPF lowpass filterLRR limited round robinLTI linear time invariantMAC medium access controlMAP maximum a posterioriMC Markov chainMIMO multiple-input multiple-outputML maximum likelihoodMSDU medium access control service data unitm.s. mean squareNAK negative acknowledgmentNAT network address translationNAV network allocation vectorNBF narrowband filterNP-CSMA nonpersistent CSMANP-CSMA/CD nonpersistent CSMA/CDNTF notch filterOFDM orthogonal frequency division multiplexingOFDMA orthogonal frequency division multiple accessPAM pulse amplitude modulationPBX private branch exchangePCF point coordination functionPCI protocol control informationPCM pulse code modulationPDA personal digital assistantPDF probability density functionPDH plesiochronous digital hierarchyPDU packet data unitPOTS plain old telephone servicePM phase modulationPMD probability mass distributionPRR pure round robinP/S parallel-to-serialPSD power spectral density

xx LIST OF ACRONYMS

PSK phase shift keyingPSTN public switched telephone networkQAM quadrature amplitude modulationQM quadrature modulationQoS quality of serviceQPSK quaternary phase shift keyingQS queueing systemrp random processRTP real-time protocolRTS request to sendRTT round trip timerv random variablerve random vectorSAP service access pointSCO synchronous connection orientedSDH synchronous digital hierarchySDM spatial division multiplexingSDU service data unitSIFS short interframe spaceSMTP simple mail transfer protocolSNR signal-to-noise ratioSONET synchronous optical networkingS/P serial-to-parallelSSB single side bandSR-ARQ selective repeat ARQSW-ARQ stop-and-wait ARQTCP transmission control protocolTDD time division duplexTDMA time division multiple accessUDP user datagram protocolUMTS universal mobile telecommunications systemUTP unshielded twisted pairUWB ultra-wide bandVBR variable bit rateVCS virtual carrier sensingVSB vestigial side bandWGN white Gaussian noiseWi-Fi wireless fidelityWLAN wireless local area networkWSS wide sense stationaryWWW World Wide Web

List of Symbols

∠z and arg(z) phase of the complex number z

〈x, y〉 inner product between x and y

(x ∗ y)(t) convolution between x and y

A alphabeta(f ) power attenuationargmaxx f (x) value of x which maximizes f (x)argminx f (x) value of x which minimizes f (x)Bmin minimum bandwidth for a given modulationB bandwidth of a signal (measure of B)B band of a signalχ {A} indicator function of the event A

dmin minimum distancedH(x, y) Hamming distance between x and y

D(ρ; n) probability function for determining optimum decision regionsδ(t) Dirac delta function (impulse)δm Kronecker delta functionE [x] expectation of the rv x

Eb average energy per bitEs average signal energyEx energy of the signal x(t)Exy cross energy of the signals x(t) and y(t)Ex(f ) energy spectral density of the signal x(t)η throughput

xxii LIST OF SYMBOLS

Fs sampling frequencyF Fourier transform operatorF noise figure of a two-port network� reference signal-to-noise ratioφi(t) ith signal of an orthonormal basisf0 carrier frequencyG offered trafficGCh(f ) transmission-channel frequency responsegCh(t) transmission-channel impulse responseg(f ) power gainhTx(t) filter/waveform at transmissionHn hypothesis in signal detectionH(x) entropy of the rv x

H(x1, . . .) joint entropy of the rvs x1, . . .

H(x|y) conditional entropy of the rv x given the rv y

� imaginary part of a complex quantityI signal space dimensionI(x, y) mutual information between the rvs x and y

kxy covariance of the rvs x and y

kx covariance matrix of the rve x

λ average customers arrival rate� SNR�M SNR between statistical powers�P SNR between electrical powers�q signal-to-quantization noise ratioM alphabet cardinalityMx average power of the signal x(t)Mx statistical power of the rv x or the rp x(t)Mxy cross power of the signals x(t) and y(t)Mxy cross power of the rps x(t) and y(t)m number of servers in a queueing systemmx mean (expectation) of the rv x or the rp x(t)mx mean vector, expectation of the rve xN02 power spectral density of white noise at the receiver input

ν spectral efficiency sample space of a probability spacePbit bit error probabilityP [A] probability of the event A

P [A|C] conditional probability of the event A, given the event C

P [C] probability of correct decisionP [E] probability of errorPe probability of errorPx(f ) PSD of the rp x(t)Pxy(f ) cross PSD of the rps x(t) and y(t)P average power (electrical)p(f ) average power density (electrical)

LIST OF SYMBOLS xxiii

Px(a) CDF of the rv x

px(a) PDF, or PMD, of the rv x

px|y(a|b) conditional PDF, or PMD, of the rv x given y

px(a) PDF, or PMD, of the rve x

px(a; t) first order PDF, or PMD, of the rp x(t)P(n) transition matrix of a discrete-time Markov chain in n stepsP transition matrix of a discrete-time Markov chain in one stepPi,j(n) transition probability of a discrete-time Markov chain from state i to state j in

n stepsPi,j transition probability of a discrete-time Markov chain from state i to state j in

one stepP(t) transition matrix of a continuous-time Markov chain in a time interval of length

t

Pi,j(t) transition probability of a continuous-time Markov chain from state i to statej in the time interval of length t

Pblk call-blocking probabilitypx (row) vector of the asymptotic PMD of x(t) as t → ∞π asymptotic state probability vector of a MCπj asymptotic probability of state j ∈ S of a MCQ (a) normalized Gaussian complementary distribution functionQ infinitesimal generator matrix of a continuous-time Markov chain real part of a complex quantityRn decision region associated to the transmitted waveform sn(t)Rb bit raterxy cross correlation of the rvs x and y

rx(τ) autocorrelation of the rp x(t)rxy(τ) cross correlation of the rps x(t) and y(t)rx correlation matrix of the rve x

ρ correlation coefficientS useful trafficsn(t) transmitted waveform associated to the symbol a0 = n

sn vector representation of waveform sn(t)sTx(t) transmitted signalsRc(t) received signal (useful component)σ2

x variance of the rv x or the rp x(t)Ts sampling periodT temperature, in KT0 standard temperature of 290 KTeff effective noise temperature of a systemw(t) noise, typically Gaussianw vector representation of noise w(t)wRc(t) noise at the receiver inputX(f ) Fourier transform of the signal x(t)x∗ complex conjugate of x

xT transpose of x

xH conjugate transpose (Hermitian) of x

Chapter 1

Introduction to Telecommunication Services,Networks and SignalingLorenzo Vangelista

The goal of telecommunication architectures is to provide people (and machines) with telecommu-nication services. In this chapter we give the basic definition of telecommunication services and weprovide an introduction to telecommunication networks and signaling as well as to the well-knownISO/OSI model.

1.1 Telecommunication Services

1.1.1 Definition

The definition of telecommunication service is quite broad; basically, it can be considered asthe transfer of information. In a telecommunication service at least three actors are usuallyinvolved:

1. one or more sources;

2. a carrier;

3. one or more receivers.

Principles of Communications Networks and Systems, First Edition. Edited by Nevio Benvenuto and Michele Zorzi.© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd.

2 INTRODUCTION TO TELECOMMUNICATION SERVICES, NETWORKS AND SIGNALING

The source(s) and the receiver(s) are not necessarily human beings; they can also be computers,for example. Usually, they are also called “customers” or “users”, when we do not need todistinguish between the two roles. The carrier is normally a company owning equipment andresources, for example, frequencies, in the case of radio services. The equipment (hardwareand software) that allows the information exchange is called telecommunication network, andthis can be classified as a “local area network” when serving a specific small geographic areaor a “wide area network” when serving a large geographic area. As an example the networkserving an university campus is a local area network, while a large Internet provider networkis a wide-area network.

Telecommunication networks can be categorized in many different ways. The most commonclassification refers to the services the networks carry. We have then:

• telephony networks carrying voice related services;

• data networks.

Using another criterion, still based on services, we have:

• networks dedicated to one specific service, such as the plain old telephone service (POTS);

• integrated services networks designed to carry different services at the same time, forexample, the integrated services digital network (ISDN).

1.1.2 Taxonomies According to Different Criteria

In this section we classify telecommunication services according to different criteria, includingsymmetry, configuration and initialization. We would like to remark that the roles of source andreceiver in a communication are not exclusive, that is, each party involved in the communicationclearly can act as

1. a source only;

2. receiver only;

3. both source and receiver, at different time intervals;

4. both source and receiver, at the same time (think of ordinary phone calls).

Regarding the symmetry characteristic of telecommunication services, we can distinguishbetween

• unidirectional services, for example, television broadcasting;

• bidirectional asymmetric services, for example, Web browsing,1 where there is a bidi-rectional exchange of information between the user and the Web server but the amount of

1 Here we refer to the so-called Web 1.0; with Web 2.0, user-generated content plays a major role.

TELECOMMUNICATION SERVICES 3

information flowing from the server to the user is by far larger than that flowing from theuser to the Web server;

• Bidirectional symmetric, for example, the usual telephone conversation.

If we turn our attention to the configuration of services we can make the followingdistinction:

• point-to-point services, where only two users are involved in the telecommunicationservice, which in turn can be either unidirectional or bidirectional;

• multipoint services, involving multiple users, some acting as sources and some as re-ceivers, possibly changing their roles dynamically;

• broadcast services, where a single source of information transmits to many receivers.

Telecommunications services can also be categorized based on their initialization; there arebasically three categories

• Call-based services: any user needs to have an identifier to activate its service and thiscan be established at any time. A classical example is a telephone call or conference call.

• Reservation-based services: similar to call-based services, except that the service made tothe carrier must be scheduled. This is often the case for conference call services nowadaysor for bulk-data transfers, usually scheduled overnight.

• Permanent-mode services: service is negotiated by a contract between the carrier andthe parties involved (two or more) and it is always running from the contract signatureon. Examples include data connection between two data centers of a large companyor, for a wireless operator without fixed infrastructure, a connection between two ofits switches.

From the above examples, we would like to remark that in modern telecommunication net-works there must be a mechanism to establish a service as easily as possible; this fundamentalmechanism is actually hidden from users. Also, it is a network on its own, with users (usuallythe real end users) and specific protocols2 called signaling protocols, which will be discussedin detail in section 1.5.

Finally, we consider the classification of telecommunication services according to theircommunication mode. Here we have interactive services and broadcast services. As far as theinteractive services are concerned we can distinguish between:

• conversational services, usually bidirectional, where there must be very little delay indelivering the information; consider, for example, a telephone call and how annoying adelay could be – it sometimes happens for internet-based calls or for calls using satellitecommunication links;

2 We have not introduced the notion of protocol yet. We can think of a protocol as a set of procedures and rules toexchange data or to let two entities agree on certain actions to be performed.

4 INTRODUCTION TO TELECOMMUNICATION SERVICES, NETWORKS AND SIGNALING

• messaging services, where there are no strict real time constraints but still the deliverytime matters. An example is instant messaging, which is very popular nowadays;

• information retrieval services, where the interactivity and real time constraints can bemild, as is the case for a database search.

As far as broadcast services are concerned, considering them from the communication modepoint of view, we may distinguish between services

• Without session control where a user has no control on what is delivered.

• With session control where a user can have some control on how the information is pre-sented to her. An example could be the delivery of the same movie on a broadcast channelusing different subchannels starting at different times, so that the user can somehow con-trol the start of the movie at her convenience.

1.1.3 Taxonomies of Information Sources

In this section we classify information sources according to their time-varying characteristicsand there are two types of sources:

• constant bit rate (CBR): the bit rate3 emitted by the source is constant over time;

• variable bit rate (VBR): the bit rate may vary over time.

◦Example 1.1 A The digital encoding of speech according to the ITU G.711 standard (also knownas pulse-code modulation or PCM encoding) produces 64 000 bit/s. This values is constant over timeregardless of whether the source user actually speaks or not. We can conclude that a voice signal encodedaccording to the ITU G.711 standard is a constant bit rate source.

Example 1.1 B adaptive multirate (AMR) is a voice-encoding standard employed mainly in cellularnetworks like universal mobile telecommunications system universal mobile telecommunications system(UMTS) and it is designed to exploit both the speaker’s periods of silence and to adapt to the differentconditions of the transmission channels over which the bits are transmitted. If the speaker is silent aspecial sequence of bits is sent and then nothing is emitted until the speaker starts speaking again. On thereceiving side when this sequence is received, noise is randomly reproduced, as a comfort feature, just tokeep the receiver aware that the link is not broken. The AMR is basically made of eight source encoderswith bit rates of 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15, and 4.75 kbit/s. Indeed, even if the link betweenthe transmitter and the receiver is fed at a constant bit rate, when the transmission channel deteriorates atsome point in time, AMR is informed and selects a lower bit rate. Hence, more redundancy bits can beused (resorting to channel coding techniques) for protecting the voice encoded bits from channel errors.We can conclude that a voice signal encoded according to the AMR standard is a variable-rate source.

◦

3 The term “bit rate” has not been defined yet; the reader should rely on an intuitive meaning as the number of binarydigits or bits per second (bit/s) sent over the channel.