Digital Communications

Contents

How to Use and Preface
How to use the combined book and CD
Preface

Chapter 1: Background material
1.1 Time/frequency representation of digital signals
Fourier series
Fourier series (cont.)
The frequency domain
Spectrum of a periodic pulse train
Spectrum of a data pulse
Spectrum of a baseband binary data stream
Factors affecting signal bandwidth
Factors affecting signal bandwidth (cont.)
The Fourier transform
1.2 Trigonometric relationships
The basic mixing process
The basic mixing process (cont.2)
The basic mixing process (cont.3)
Complex mixing processes
The vector modulator
1.3 Communications networks and signalling protocols
What is a network?
A typical network configuration
Network hierarchy
Transmission standards
Integrated Services Digital Network (ISDN)
What is a protocol?
The seven-layer OSI model
Network types: circuit and packet switched network operation
Network management
Network link layer
Synchronous/asynchronous communications
Synchronous transmission
Asynchronous transmission
ASCII character format
Advantages and disadvantages of synchronous data communications
1.4 Definition of terms
Characteristics of message type
Analogue
Digital
Elements of a communications link
Transmitter
Transmission channel
Receiver
Sources of link degradation
Distortion
Interference
Noise
Transmission protocols
Simplex
Half duplex
Full duplex
Unipolar vs bipolar waveforms

Chapter 2: Data transmission fundamentals
2.1 Factors affecting system design
Technological limitations: Hardware and software availability
Technological limitations: Power consumption and Component size
Government regulations and standards
Commercial realities
2.2 Data transmission fundamentals
How quickly can information flow?
Methods of communication
Binary signalling
Multi-level signalling
Multi-level symbol operation
The bandwidth and noise trade-off
Information transfer rate
Symbol rate (baud rate)
Bandwidth efficiency
2.3 Multi-level signalling (M-ary signalling)
The relationship between bits and symbols
Example: 8-ary signalling
Advantages and disadvantages of M-art signalling
2.4 Calculation of channel capacity
Limitation due to finite bandwidth
Limitation due to finite bandwidth (cont.)
Minimum transmission bandwidth
Channel capacity restriction due to noise - the Shannon-Hartley theorem
Channel capacity restriction due to noise - the Shannon-Hartley theorem (cont.)
Power and bandwidth efficiency
Graphical representation

Chapter 3: Baseband data transmission
3.1 Introduction

3.2 Intersymbol interference (ISI)
The problem of intersymbol interference
Pulse shaping for zero ISI: Nyquist channel filtering
Pulse shaping for zero ISI: Nyquist channel filtering (cont.)
Achieving a Nyquist channel response
Nyquist filtering - example: cellular radio application
3.3 Eye diagrams
Generation of eye diagrams
Diagnosis using the eye diagram
Example of complex eye diagram
3.4 Raised cosine filtering
Raised cosine filter family
Impulse response of raised cosine filter
Eye diagrams for raised cosine filtered data
The root raised cosine filter
Implementation of digital Nyquist filters
Care with eye diagrams
Symbol timing recovery
Symbol timing circuits
Symbol timing circuits (cont.)
Summary: choice of a
3.5 Matched filtering
Recovery of symbols from noise
Recovery of symbols from noise (cont.)
The concept of an optimum (matched) filter
Designing a matched filter with ISI in mind
Bit error rate (BER) performance for baseband data systems
BER performance for matched filter detection
BER performance for matched filter detection (cont.)
Unipolar vs bipolar symbols
BER performance for M-ary signalling
Bit error rate vs symbol error rate
Gray coding
3.6 Partial response signalling
Duo-binary signalling
Duo-binary signalling (cont.)
Modified duo-binary signalling
Chapter 4: Sources and examples of channel degradation

4.1 Introduction

4.2 Gain, phase and group delay distortion
Gain distortion - filters
Gain distortion - amplifiers
Gain distortion - the channel
Phase distortion - filters
Group delay - filters
Phase distortion - amplifiers
Phase distortion - the channel
Frequency errors
Local oscillator error
Doppler shift
4.3 Interference and noise
Sources of interference
Dealing with interference
Sources of noise
Thermal noise
Shot, flicker and atmospheric noise
Characteristics of noise
4.4 The telephone channel
AC-coupled channels
NRZ vs Manchester encoding
Bandwidth efficiency of encoded data
Data encoding and the telephone channel
4.5 The wireless channel
Unguided propagation
Multipath distortion
Multipath fading
Frequency flat vs frequency selective fading
Multipath fading - the time domain problem
Coping with multipath fading
Reference sounding
Parallel transmission
Spectral spreading
Channel equalizers
Directional antenna
Predicting multipath distortion
How propagation changes with operating frequency

Chapter 5: Bandpass digital modulation

5.1 Introduction

5.2 Amplitude shift keying (ASK)
What is ASK?
Symmetry in ASK
Spectral occupancy of ASK: ASK data spectrum
Generation of ASK modulated signals
Bandwidth limited ASK
Bandpass filtering method
Baseband filtering method
Non-coherent detection
Coherent detection
Coherent detection vs non-coherent detection
Coherent detection vs non-coherent detection
Carrier recovery for ASK
Matched filtering for ASK
Symbol timing recovery
BER performance of ASK
Constellation diagrams
5.3 Frequency shift keying (FSK)
FSK waveforms
FSK generation
The vector modulator
Spectrum of FSK
Spectrum of CPFSK
Filtered FSK
Non-coherent FSK detection
Non-coherent PLL-based FSK detection
Coherent FSK detection
BER performance for FSK
Advantages and disadvantages of FSK
5.4 Phase shift keying (PSK)
Principle of PSK
Spectral occupancy for PSK
PSK generation
The effect of filtering on the PSK waveform
Detection of PSK
Carrier recovery of coherent PSK
Carrier recovery of coherent PSK
The Costas loop
Phase ambiguity in PSK carrier recovery
Differential data encoding
Differential data decoding
Differential PSK (DPSK)
Symbol timing recovery for PSK
Constellation diagram for PSK
BER performance for PSK
5.5 Comparison of binary modulation schemes
Relative BER performance
Equal average symbol energy
Equal peak symbol energy

Chapter 6: Multi-level digital modulation

6.1 Introduction

6.2 M-ary amplitude shift keying (M-ary ASK)
Implementation of M-ary ASK
Performance of M-ary ASK
6.3 M-ary frequency shift keying (M-ary FSK)
M-ary FSK application
Orthogonal signalling
Properties of orthogonal symbols
Orthogonal FSK detection
BER performance for M-ary orthogonal FSK
6.4 M-ary phase shift keying (M-ary PSK)
Quadrature phase shift keying (QPSK)
Implementation of QPSK - modulator
Implementation of QPSK - demodulator
Bit error performance of QPSK
Symbol error performance of QPSK
Differential QPSK (DQPSK)
BER performance of DQPSK
p/4 QPSK
Offset QPSK (OQPSK)
Spectrum of M-ary PSK
Performance of M-ary PSK
6.5 Combined amplitude and phase keying
Introduction
QAM generation
QAM detection
M-ary QAM vs M-ary PSK
BER performance for QAM
M-ary Amplitude and Phase Keying (M-ary APK)
Gray coding
6.6 Relative performance of multi-level bandpass modulation formats
Symbol error curves for M-ary formats
The Shannon limit - how close can we get?
Table of CCITT telephone modem characteristics

Chapter 7: Coding theory and practice

7.1 Source coding
Introduction
Waveform coding - A./D converters
Nyquist sampling
Nyquist sampling theorem - aliasing
Dynamic range
Quantization noise
Companding
Voice coding
Voice coding (cont.)
Intelligent source coding
7.2 Channel coding
Introduction
Types of ARQ operation
Parity
Parity (cont.)
Types of FEC coding
7.3 Block coding
Basics of block coding
Block coding analogy
Coding efficiency
Hamming codes - an example of a block code
Hamming distance
BER performance for a (7,4) Hamming code
Higher order Hamming codes
Implementation complexity
7.4 Advanced block coding
Block code families
Interleaving
Implementation
Reed-Solomon (RS) codes
7.5 Convolutional coding
Introduction
Soft decision coding
Trellis diagrams
Soft vs hard decision decoding
7.6 Combined coding and modulation
Introduction
Trellis coded modulation (TCM)
Practical issues with TCM
TCM and the Shannon limit
Source, channel and modulation coding - complete

Chapter 8: Multi-user digital modulation techniques

8.1 Introduction

8.2 Frequency division multiple access (FDMA)
Basic system operation
Wireless FDMA operation
Power control in wireless FDMA systems
Advantages of FDMA
Disadvantages of FDMA
Wavelength division multiplexing
8.3 Time division multiple access (TDMA)
Basic system operation
TDMA in a wireless environment
Example of a TDMA system
Example of a TDMA system (cont.)
Advantages of TDMA operation
Disadvantages of TDMA operation
8.4 Code division multiple access (CDMA)
CDMA systems
Frequency hopped CDMA (FH-CDMA)
Example of frequency hopped CDMA
Direct sequence CDMA
Direct sequence CDMA (cont.)
Example of direct sequence CDMA
Example of direct sequence CDMA (cont.)
Advantages of CDMA
Disadvantages of CDMA
8.5 Combined multiple access systems
Examples of FDMA/TDMA combinations
Examples of FDMA/CDMA and FDMA/FDMA combinations

Glossary

References

Index

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