digital communication

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Contents PREFACE LIST OF ABBREVIATIONS

VI VIII

1.

INTRODUCTION

1

1.1

Introduction History Background

3 3

Digital and Analog Sources and Systems Advantages of Digital Communication Systems

4

1.2 1.3 1.4

5 7

1.7

Tradeoff in Digital Communication System Block Diagram of a Communication System Major Blocks of Digital Communication Systems

2.

PULSE MODULATION

13

2.1

lntrod uction Sampling Process Sampling Theorem [deal (Instantaneous) Sampling Practical Sampling Errors in Sampling l3and-pass Sampling Theorem Pulse Amplitude Modulation Natural Sampling (Gating) PAM Instantaneous Sampling (Flat-Top) PAM PAM Modulators l' AM Demodulators Comparison between PAM Types Time - Division Multiplexing TDM oj' Signals witil Identical Sampling Rates TDM or Signals with Dissimilar Sampling Rates Pulse time modulation (PTM) Pulse Width Modulation Pulse Position Modulation Generation and Demodulation of PTM Comparison ofPTM and PAM signals PROBLEMS

15 16 16

1.5 1.6

2.2 2.2-1 2.2-2 2.2-3 2.2-4 2.2-5

2.3 2.3-1 2.3-2 2.3-3 2.3-4 2.3-5 2.4

2.4-\ 2.4-2

2.5 2.5-1 2.5-2 2.5-3 2.5-4

8 8

17 20 21 27

29 29 31 34

35 36

36 37 38 42 42 43 43 45 45

3.

CONVERSION OF ANALOG SIGNALS TO DIGITAL

79

3.1 3.2 3.2-1 3.2-2

Introduction Pulse Code Modulation Uniform Quantization NOll-Uniform Quantization Information Transfer Rate and Bandwidth of PCM The Output SNR in PCM 11 Carrier System reM Signals Time-Division-Multiplexing DIGIT AL COMMUNICATIONS

51 51

3.2-3 3.2.4

3.2-5 3.2-6

51 58 63 65

68 71

3.2-7 3.3 3.4 3.4-\ 3.4-2 3.4-3 3.4-4 3.5 3.5-1 3.5-2 3.6 3.7 3.8

Multiplexing Hierarchy of TOM Systems Differential PCM Delta Modulation Introduction The Idea of OM Granular (Threshold) and Slope Overload Noises Quantization Noise in OM Adaptive Delta Modulation Discrete ADM Continuous ADM Delta Pulse Code Modulation Delta-Sigma Modulation Comparison Between PCM and OM Systems PROBLEMS

73 75 78 78 78 82 84 88 89 91 92 94 94 97

4.

BINARY LINE CODING

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15

Introduction Power Spectral Density of Digital Signaling Non Return-to-Zero and Return-to-Zero Polar Signaling Unipolar or On-Off Signaling Bipolar Signaling Duo-Binary Signaling Manchester Signaling High - Density Bipolar Signaling Coded Mark Inversion Signaling Bipolar with n-Zeros Substituted Codes Differential Coding of Data M-any or Multilevel Signaling Spectral Efficiency of Line Codes Comparison of Base-band Line Codes PROBLEMS

105 107 107 110 110 113 116 119 122 126 129 131 135 136 138 140 141

5.

PULSE SHAPING AND INTER-SYMBOL INTERFERENCE

145

5.1 5.2 5.2-1 5.2-2 5.2-3 5.2-4 5.3 5.4 5.4-1

Introd uction Nyquist First Criterion for Zero lSI Ideal Pulse Shape for Zero lSI Raised Cosine Filter Notes About Full-Cosine Filter Pulse Transmission Rate with NFC for Zero lSI Nyquist Second Criterion for Zero lSI Partial Response Signaling Duo-binary Signaling Generation of Duo-binary Pulses Detection procedure and Decoder for Duo-binary Signaling Using Differential Coding with Duo-binary Signaling for Zero lSI Modified Duo-Binary Signaling Coding and Detection with Modified Duo-Binary Signaling

147 147 147 148 151 152 154 156 157 158 159 160 164

5.4.1-\ 5.4.1-2 5.4.1-3

5.4-2 5.4.2-\

DIGITAL COMM UNICA nONS

166

II

5.4.2-2

Precoding for Modified Duo-Binary Signaling PROBLEMS

168

170

6.

PERFORMANCE OF BASEBAND DIGITAL COMMUNICATION SYSTEMS IN THE PRESENCE OF NOISE

173

6.1 6.2

Introduction Matched Filter Matched Filter for White Noise Integrate-And-Dump Matched Filter The Correlator Generalized Binary Receiver Block Diagram Probability of Error Maximum Likelihood Detector Probability of Error with 'Gaussian Noise Optimum Detection Error Probability Performance of Binary Base-band Transmission Systems Unipolar Class Signaling with Full-wave Rectifier Antipodal Class Base-band Signaling Unipolar Class Signaling with Two Thresholds Devicc PROBLEMS

175 176 178 179

6.2-1 6.2-2 6.2-3

6.3 6.4 6.5 6.6 6.7 6.8 6.8-1 6.8-2 6.8-3

7.

DIGITAL CARRIER MODULATION SYSTEMS

7.1 7.2

Introduction Amplitude Shift Keying Power Spectral Density and Bandwidth. Cieneration and Pulse Shaping. Amplitudc Shift Keying Detection Multi-Level Amplitude Shift Keying Frequency Shift Keying Power Spectral Density and Bandwidth (ieneration and Pulse Shaping Frequency Shift Keying Detection M-ary Frequency Shill Keying Phase Shift Keying Power Spectral Density and Bandwidth Constellation Diagram. Phase Shift Keying Generation Phase Shift Keying Detection Carrier Recovery for Coherent PSK Differential Phase Shift Keying M-ary Phase Shift Keying Quadrature Phase Shift Kcying n/4- Quadrature Phase Shill Keying OtI 4 -ary Phase Shift Keying Combined Amplitude and Phase Shift Keying QAM Generation and Detection M-ary Amplitude and Phase Keying Data Modems Table Comparison Between Digital Modulation Types Applications Bandwidth Efficiency Error Performance Problems

280 286 291 291 293 30 I 303 303 303 303 312

8.

SOURCE CODING

8.1

Introduction Information Measure Average Information or Entropy Source Coding Theorems Code Length and Code efficiency Source Coding Theorem I Codes classification Source Coding Theorem II Variable length Prefix-Free Encoding Decoding of Prefix-Free Codes Shannon-Fano Coding Huffman Coding Dictionary Codes: Lempel-Ziv Coding Problems

321 323 324 326 331 332 332 334 337 337 338 339 342 347 351

7.6 7.6-1 7.6-2 6.7-3 7.7 7.7-1 7.7-2 7.7-3

8.2 8.3 8.4 8.4-1 8.4-2 8.4-3 8.4-4

8.5 8.S-1 8.S-2 8.S-3

8.6

9. 9.1 9.2 9.3 9.3-1 9.3-2 9.3-3

FUNDAMENTALS OF BLOCK CODES

Introduction Basic Definitions and Concepts Matrix Description of Linear Block Codes Coet1icient Matrix of Linear Block Codes Generator Matrix of Linear Block Codes The Parity-Check Matrix of Linear Block Codes Syndrome-Former Trellis Representation of Binary Linear Block Codes 9.4 9.4-1 The Syndrome and its properties 9.4-2 The Hamming Bound 9.4-3 The Syndrome -Former Trellis Examples of Binary Linear Block Codes 9.5 9.S.1 Repetition Codes 9.S.2 Single-Parity-Check Codes 9.S.3 Single-Error-Correcting Hamming Codes 9.S.4 Reed-Muller Codes 9.5-S Hadamard Codes 9.S-6 Dual Code Decoding of Linear Block Codes 9.6 9.6-1 Standard Array Decoding 9.6-2 Syndrome Decoding 9.6-3 Maximum Likelihood Decoding DIGITAL COMMUNICATIONS

355 357 358 361 3() I 363 367 369 371 373 376 376 377 377 380 383 385 385 385 385 387 3119

391

Problems

10 10.1 10.2 10.2-1 10.3 10.3-1 lOA

10.5 10.6 10.6-1 10.6-2 10.6-3 10.6-4 10.6-5 10.6-6

CYCLIC BLOCK CODES Introduction Polynomial Description of Cyclic Codes Systematic Cyclic Codes Matrix Description of Cyclic Codes Shortened cyclic code Encoding of Cyclic Codes Decoding of Cyclic Codes Examples of Cyclic Cyclic Hamming Codes Maximum Length Shift-Register Codes Golay Codes Bosc-Chaudh uri -Hocg uenghem Codes Reed-Solomon Codes Cyclic Redundancy Check Codes Problems

11

CONVOLUTIONAL CODES

11.1 11.2 11.2-1 11.2-2 11.2-3 11.2-4 11.2-5 11.2-6 11.2-7 11.2-8 11.2-9 11.2-10 11.3 11.4 11.4-1 I 1.4-2 11.4-3 11.4-4 11.5 11.6 11.7 11.8

Introduction Basic Concepts Code Parameters Code Rate Constraint Length Code Generator Polynomial Selection of Code Polynomials Structure of Convolutional Code States of Code Punctured Codes Str'ucturc of a Code for k > J Systematic Convolutional Codes Coding an Incoming Sequence Encoder Design of Convolutional Codes Look Up Table State Diagram Tree Diagram Trellis Diagram Convolutional Codes Decoding Sequential Decoding of Convolutional Codes Maximnm Likeliho[)d and Vitcrbi Decoding Soft Decision Decoding Problems

REFERENCES INDEX

DIGITAL COMMUNICA nONS

395 397 397 400 403 407 408 410 415 415 417 418 419 420 422 425 427 429 429 429 430 430 430 431 431 432 433 434 434 435 438 438 439 440 441 444 445 448 454 457

495 463

v

Preface Digital communications IS a rapidly advancing applications area. The design and manufacturing of hardware and software for digital communication networks are among the fastest growing engineering areas. In order to adapt and contribute effectively to these changes electrical engineers need to acquire a solid foundation and understanding of digital communications. Most of communications have become digital because of advantages of digital communications over analog communication. Digital communication is rugged in the sense that it is more immune to channel noise and distortion. It is inherently more efficient than analog in realizing the exchange of SNR for bandwidth. Also regenerative repeaters along the transmission path can detect a digital signal and retransmit a new noise-free signal. This prevents accumulation of noise along the path. Digital signals can be coded to yield extremely low error rates and high fidelity. Digital hardware implementation is flexible and permits the use of microprocessors, minicomputers, and digital switching and large-scale integrated circuits. It is easier and more efficient to multiplex several digital signals than analog. The book is primarily intended for a technical audience that has been exposed to introductory communication theory, but that is encountering digital communications for the first time. The primary background assumed the reader is familiarity with elementary probability concepts, plus ability in transform calculus and linear system theory. The text should be appropriate for being under graduate-level courses in digital communications. The material within the book has been developed and refined over many years of lecturing on digital communications to fourth year undergraduates. This book has been written for the beginners. It is the result of class notes from an undergraduate-level course that was taught to students in electrical and computer engineering. The level of exposition in this book has been aimed at undergraduate students in their junior or senior years of study. The text in this book is organized according to the simplified block diagram of a digital communication system consisting of a digital transmitter, di~crete noisy channel and a digital receiver. In chapter I is described the pulse modulation including sampling process, pulse amplitude modulation, pulse width modulation, pulse position modulation, and time division multiplexing of pulse type modulated signals. Types of sampling, errors in sampling and different types of pulse amplitude modulation are included. Chapter 2 discusses pulse code modulation in general. Quantization process, types of quantizers and quantization error is discussed in this chapter. Time-division multiplexing of digital signals, Tl-carrier system and mUltiplexing hierarchies is provided in this chapter. Techniques used to reduce the bandwidth of converted to digital analog signal are discussed in chapter 3. \1ost special types of ADC converters such as delta modulation, adaptive delta modulation, delta pulse code modulation, differential pulse code modulation and delta-sigma modulati on are discussed here. Quantization noise, advantages, disadvantages and comparison between different systems are provided. Chapter 4 discusses binary line codes, their power spectral densities, and most their advantages and disadvantages. The following line signaling techniques are considered polar signaling. unipolar, alternate mark inversion, duo-binary, Manchester, high density bipolar, coded mark inversion, bipolar With n-zeros substituted and M-Ievel signaling. Differential coding, spectral efficiency and comparison between line codes are also provided. DIGlT AL COMMUNICATIONS

VI

Chapter 5 discusses the problem of inter-symbol interference, methods of its solution and effect of the solution on the bandwidth and efficiency of digital signals [n chapter 6 are discussed the performance of base band line codes of chapter 4 in the presence of adaptive Gaussian white noise. The concepts of matched filter, integrate and dump detector, probability of error, and maximum [ikelihood detector are provided. Equations for minimum probability of error for different line codes in the presence of adaptive Gaussian white noise and optimum threshold values are found. Chapter 7 is the main part of the book. Special attention is given to modulation techniques used in modern digital communication systems. In this chapter are provided amp[itllde shift keying. frequency shift keying, phase shift keying, and their M-ary versions. Differential phase shift keying, quadrature phase shift keying, 11/4- quadrature phase shift keying, offsCl quadrature phase shift keying, differential quadrature phase Shift Keying, 1114- differential quadrature phase shift keying. minimum shift keying, and Gaussian minimum shift keying are also studied in details. Special attention is given to quadrature amplitude modulation and amplitude phase shift keying as an example of combined modulation techniques. A comparison between different modulation techniques from bandwidth occupancy. bit error probability, symbol error probability and applications is also provided. In chapter R is discussed the problem of source coding. And given the basic definiliull:-. 01' information. source-coding theorems, and coding and decoding variable length prefix-free codes such as: Shannon-Fano and Huffman, and dictionary codes. Fundamentals of block codes are discussed in chapter 9. Chapter 10 discusses cyclic block codes, an important type of block codes usually used ,is an error detecting technique in data communication networks. As mentioned in the previous chapter error control coding is concerned with methods of delivering information from a source to a destination with a minimum of errors. Codes for error control generally fell into two categories, namely block codes and convolutiona[ codes. Chapter [I provides one of the most important techniques of error detection and elTor correction codes. the convolutional codes. Acknowledgements The author would like to express his thanks and acknowledgement to Professor \Ilansur AIAbbadi (University of Science and Technology - Jordan) for his ted1l1ical review of the book. who gave generously of his time and expertise. and his many he[pful and constructive comments and suggestions for improvement ofthe text. The author also wishes to thank Dr. Sabbar Saadoon Sultan (AI-Ism Private UniversityJordan) for his language reviewing of the text and for his many comments and suggestions for improvement of the text language structure. Acknowledgement is to be made to Professor Sadie Hamed (University of Jordan Jordall) and Professor Gahnim AI-hissaui (Dean of Scientific Research at AI-Ism Uiliversity Jordan) for their encouragement and advice

DIGITAL COMMUN[CATIONS

VII

ERMES ETSI

EVM FCS FDD FDMA FEC

FER FFSK FFT FLEX

FM FSK FT

GFSK Globalstar

GMSK GSM HDBn HDTV iDEN

..

1(;'

IIQ Iridium

lSI IS-54 IS-95 IS-136 LAN

LMDS LPC

LPF LZC

MASK MDPSK MLC MT

MFSK MMDS MQAM MPSK M-PSK MSK NADC

NFC NRZ

NSC OFDM OOK

European Radio Message System European Telecommunications Standards Institute Lrror Vector Magnitude Frame check sequence Frequency Division Duplex Frequency Division Multiple Access Forward error correction Frame Error Rate Fast Frequency Shift Keying Fast Fourier Transform 4-level FSK-based paging standard developed by Motorola Frequency Modulation Frequency Shift Keying Fourier Transform Gaussian Frequency Shift Keying Satellite system using 48 low-earth orbiting satellites Gaussian Minimum Shift Keying Global System for Mobile Communication High-density bipolar coding with n-zeros substituted High Definition Television integrated Dispatch Enhanced Network (Motorola designed system for dispatch, cellular, and conference calling) Intermediate Frequency [n phase/Quadrature Motorola voice/data 66-satel[ite system worldwide Inter symbol Interference Interim Standard for US Digital Cellular (NADC) Interim Standard for US Code Division Multiple Access Interim Standard for NADC with Digital Control Channels local area network Local Multi-point Distribution System Linear Predictive Coding Low Pass Filter Lempel-Ziv Coding Multi-level Amplitude Shift Keying Multi-level Ditferential Phase Shift Keying Maximum length shift-register codes Matched Filter Minimum Frequency Shift Keying Multi-channel Multi-point Distribution System M-ary Quadrature Amplitude Modulation Minimum Phase Shift Keying M-ary Phase Shift Keying Minimum Shift Keying North American Digital Cellular system Nyquist First Criterion Non Return-to-Zero Nyquist Second Criterion Onhogonal Frequency Division Multiplexing On-Oft Keying [X DIGITAL COMMUNICATIO:--lS

OOS OQPSK PACS PAM

pes PCM

POC POF PLL PHS PPM PRBS

PSO PSK PTM PWM QAM

QPSK RAM RF RS RZ RMS SCC SDLC

Sl'iR SQRT

TOO TDM TDMA TETRA TFTS VCO VLSI VSB WLL

On-Off Signaling Offset Quadrature Phase Shift Keying Personal Access Communications Service Pulse Amplitude Modulation Personal Communications System Pulse Code Modulation Pacific Digital Cellular System (formerly JDC) Probability Density Function Phase-Locked Loop Personal Handyphone System (formerly PHP) Pulse Position Modulation Pseudo-Random Bit Sequence Power Spectral Density Phase Shift Keying Pulse Time Modulation Pulse Width Modulation Quadrature Amplitude Modulation Quadrature Phase Shift Keying W ire Ie5S data network Radio Frequency Reed-Solomon Return-to-Zero Root Mean Square systematic cyclic code Synchronous Data Link Control Signal to Noise power Ratio Square Root Time Division Duplex Time Division Multiplexing Time Division Multiple Access Trans European Trunked Radio ferrestrial Flight Telephone System Voltage Controlled Oscillator Vl:ry Large Scale Intl:gration Vestigial Side Band Wire\e,s Local Loop

DiGITAL COMMUNICATIONS

x

LIST OF ABBREVIATIONS \I)C AI)M '\( 'I'

AI)PCM A(;WN AM AMI AMPS

'\PK AHQ

ASK B-CDMA BCH BDMS BW

BER

BFSK BnZS BPSK BW CC CDMA CDPD CMI COFDM

CPFSK CRC CT2 DAB

DAC DCS 1800 DCT DECT

DFT DM DMCA DMS DPCM

l!PCM DPSK DQPSK DSP ~-L:-M

DVB-C DVB-S DVB-T EGSM

Analog to Digital Converter Adaptive Delta Modulation Adjacent Channel Power Adaptive Differential Pulse Code Modulation Adaptive Gaussian White Noise Amplitude Modulation Alternate Mark Inversion Advanced Mobile Phone System Amplitude Phase Keying Automatic-repeat request Amplitude Shift Keying Broadband Code Division Multiple Access Bose-Chaudhuri-Hocquenghem Binary Discrete Memoryless Source Bandwidth Bit Error Rate Binary Frequency Shift Keying Bipolar with n-Zeros Substituted Codes Binary Phase Shift Keying Bandwidth Cyclic Codes Code Division Multiple Access Cellular Digital Packet Data Coded Mark Inversion Coded Orthogonal Frequency Division Multiplexing Continuous Phase Frequency Shift Keying Cyclic Redundancy Check Cordless Telephone 2 Digital Audio Broadcast Digital to Analog Converter Digital Communication System 1800 MHz Discrete Cosine Transform Digital Enhanced Cordless Telephone Discrete Fourier Transform Delta Modulation Digital Multi Channel Access, similar to iDEN Discrete Memory\ess Source Differential Pulse Code Modulation Delta Pulse Code Modulation Differential Phase Shift Keying Differential Quadrature Phase Shift Keying Digital Signal Processing Delta Sigma Modulation Digital Video Broadcast Cable Digital Video Broadcast Satellite Digital Video Broadcast Terrestrial Extended Frequency GSM DIGITAL COMMUNICATIONS

VIII