Communication Systems Principles Using MATLAB
Description
Communication Systems Principles Using MATLAB covers a variety of systems principles in telecommunications in an accessible format without the need to master a large body of theory. The text puts the focus on topics such as radio and wireless modulation, reception and transmission, wired networks and fiber optic communications. The book also explores packet networks and TCP/IP as well as digital source and channel coding, and the fundamentals of data encryption.
Since MATLAB® is widely used by telecommunications engineers, it was chosen as the vehicle to demonstrate many of the basic ideas, with code examples presented in every chapter. The text addresses digital communications with coverage of packet-switched networks. Many fundamental concepts such as routing via shortest-path are introduced with simple and concrete examples. The treatment of advanced telecommunications topics extends to OFDM for wireless modulation, and public-key exchange algorithms for data encryption. Throughout the book, the author puts the emphasis on understanding rather than memorization. The text also:
* Includes many useful take-home skills that can be honed while studying each aspect of telecommunications
* Offers a coding and experimentation approach with many real-world examples provided
* Gives information on the underlying theory in order to better understand conceptual developments
* Suggests a valuable learn-by-doing approach to the topic
Written for students of telecommunications engineering, Communication Systems Principles Using MATLAB¯® is the hands-on resource for mastering the basic concepts of telecommunications in a learn-by-doing format.
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Person
JOHN W. LEIS, PHD, is an Associate Professor of Electrical and Computer Engineering at the University of Southern Queensland. He has authored a large number of academic papers, and is author of Digital Signal Processing using MATLAB® for Students and Researchers. Dr. Leis's interests include signal processing for data compression and coding, medical signal processing, and advanced instrumentation using signal processing algorithms. He has collaborated nationally and internationally on various research projects, and is a Senior Member of the Institution of Electrical & Electronic Engineers (IEEE).
Content
Preface xiii
Acknowledgments xv
Introduction xvii
About the CompanionWebsite xxi
1 Signals and Systems 1
1.1 Chapter Objectives 1
1.2 Introduction 1
1.3 Signals and Phase Shift 2
1.4 System Building Blocks 3
1.4.1 Basic Building Blocks 3
1.4.2 Phase Shifting Blocks 4
1.4.3 Linear and Nonlinear Blocks 5
1.4.4 Filtering Blocks 8
1.5 Integration and Differentiation of aWaveform 10
1.6 Generating Signals 16
1.7 Measuring and Transferring Power 19
1.7.1 Root Mean Square 19
1.7.2 The Decibel 23
1.7.3 Maximum Power Transfer 25
1.8 System Noise 29
1.9 Chapter Summary 32
Problems 32
2 Wired,Wireless, and Optical Systems 37
2.1 Chapter Objectives 37
2.2 Introduction 37
2.3 Useful Preliminaries 38
2.3.1 Frequency Components When a SignalWaveform Is Known 38
2.3.2 Frequency SpectrumWhen a Signal Is Measured 42
2.3.3 Measuring the Frequency Spectrum in Practice 44
2.4 Wired Communications 50
2.4.1 Cabling Considerations 50
2.4.2 Pulse Shaping 52
2.4.3 Line Codes and Synchronization 62
2.4.4 Scrambling and Synchronization 66
2.4.5 Pulse Reflection 73
2.4.6 Characteristic Impedance of a Transmission Line 80
2.4.7 Wave Equation for a Transmission Line 83
2.4.8 StandingWaves 84
2.5 Radio andWireless 92
2.5.1 Radio-frequency Spectrum 92
2.5.2 Radio Propagation 92
2.5.3 Line-of-sight Considerations 96
2.5.4 Radio Reflection 97
2.5.5 RadioWave Diffraction 99
2.5.6 RadioWaves with a Moving Sender or Receiver 103
2.5.7 Sending and Capturing a Radio Signal 105
2.5.8 Processing aWireless Signal 119
2.5.9 Intermodulation 128
2.5.10 External Noise 131
2.6 Optical Transmission 132
2.6.1 Principles of Optical Transmission 132
2.6.2 Optical Sources 134
2.6.3 Optical Fiber 139
2.6.4 Optical Fiber Losses 145
2.6.5 Optical Transmission Measurements 147
2.7 Chapter Summary 150
Problems 151
3 Modulation and Demodulation 155
3.1 Chapter Objectives 155
3.2 Introduction 155
3.3 Useful Preliminaries 156
3.3.1 Trigonometry 157
3.3.2 Complex Numbers 159
3.4 The Need for Modulation 162
3.5 Amplitude Modulation 164
3.5.1 Frequency Components 167
3.5.2 Power Analysis 170
3.5.3 AM Demodulation 171
3.5.4 Variations on AM 173
3.6 Frequency and Phase Modulation 180
3.6.1 FM and PM Concepts 181
3.6.2 FM and PM Analysis 183
3.6.3 Generation of FM and PM Signals 185
3.6.4 The Spectrum of Frequency Modulation 186
3.6.5 Why Do the Bessel Coefficients Give the Spectrum of FM? 195
3.6.6 FM Demodulation 200
3.7 Phase Tracking and Synchronization 204
3.8 Demodulation Using IQ Methods 215
3.8.1 Demodulation of AM Using IQ Signals 216
3.8.2 Demodulation of PM Using IQ Signals 219
3.8.3 Demodulation of FM Using IQ Signals 222
3.9 Modulation for Digital Transmission 225
3.9.1 Digital Modulation 226
3.9.2 Recovering Digital Signals 228
3.9.3 Orthogonal Signals 237
3.9.4 Quadrature Amplitude Modulation 239
3.9.5 Frequency Division Multiplexing 242
3.9.6 Orthogonal Frequency Division Multiplexing 244
3.9.7 Implementing OFDM: The FFT 247
3.9.8 Spread Spectrum 254
3.10 Chapter Summary 261
Problems 261
4 Internet Protocols and Packet Delivery Algorithms 269
4.1 Chapter Objectives 269
4.2 Introduction 269
4.3 Useful Preliminaries 270
4.3.1 Packet Switching 270
4.3.2 Binary Operations 272
4.3.3 Data Structures and Dereferencing Data 272
4.4 Packets, Protocol Layers, and the Protocol Stack 277
4.5 Local Area Networks 281
4.5.1 Wired LANs 282
4.5.2 Wireless LANs 284
4.6 Device Packet Delivery: Internet Protocol 286
4.6.1 The Original IPv4 286
4.6.2 Extension to IPv6 286
4.6.3 IP Checksum 290
4.6.4 IP Addressing 294
4.6.5 Subnetworks 296
4.6.6 Network Address Translation 298
4.7 Network Access Configuration 300
4.7.1 Mapping MAC to IP: ARP 301
4.7.2 IP Configuration: DHCP 302
4.7.3 Domain Name System (DNS) 302
4.8 Application Packet Delivery: TCP and UDP 303
4.9 TCP: Reliable Delivery and Network Fairness 309
4.9.1 Connection Establishment and Teardown 311
4.9.2 Congestion Control 311
4.9.3 TCP Timeouts 319
4.10 Packet Routing 321
4.10.1 Routing Example 322
4.10.2 Mechanics of Packet Forwarding 323
4.10.3 Routing Tasks 325
4.10.4 Forwarding Table Using Supernetting 326
4.10.5 Route Path Lookup 330
4.10.6 Routing Tables Based on Neighbor Discovery: Distance Vector 343
4.10.7 Routing Tables Based on Network Topology: Link State 348
4.11 Chapter Summary 359
Problems 359
5 Quantization and Coding 363
5.1 Chapter Objectives 363
5.2 Introduction 363
5.3 Useful Preliminaries 364
5.3.1 Probability Functions 364
5.3.2 Difference Equations and the z Transform 366
5.4 Digital Channel Capacity 369
5.5 Quantization 372
5.5.1 Scalar Quantization 373
5.5.2 Companding 379
5.5.3 Unequal Step Size Quantization 382
5.5.4 Adaptive Scalar Quantization 383
5.5.5 Vector Quantization 385
5.6 Source Coding 389
5.6.1 Lossless Codes 390
5.6.1.1 Entropy and Codewords 390
5.6.1.2 The Huffman Code 392
5.6.1.3 Adapting the Probability Table 404
5.6.2 Block-based Lossless Encoders 405
5.6.2.1 Sliding-Window Lossless Encoders 405
5.6.2.2 Dictionary-based Lossless Encoders 407
5.6.3 Differential PCM 409
5.6.3.1 Sample-by-sample Prediction 410
5.6.3.2 Adaptive Prediction 417
5.7 Image Coding 420
5.7.1 Block Truncation Algorithm 422
5.7.2 Discrete Cosine Transform 425
5.7.3 Quadtree Decomposition 430
5.7.4 Color Representation 431
5.8 Speech and Audio Coding 433
5.8.1 Linear Prediction for Speech Coding 434
5.8.2 Analysis by Synthesis 439
5.8.3 Spectral Response and NoiseWeighting 440
5.8.4 Audio Coding 442
5.9 Chapter Summary 447
Problems 447
6 Data Transmission and Integrity 453
6.1 Chapter Objectives 453
6.2 Introduction 453
6.3 Useful Preliminaries 454
6.3.1 Probability Error Functions 454
6.3.2 Integer Arithmetic 458
6.4 Bit Errors in Digital Systems 461
6.4.1 Basic Concepts 461
6.4.2 Analyzing Bit Errors 463
6.5 Approaches to Block Error Detection 470
6.5.1 Hamming Codes 472
6.5.2 Checksums 478
6.5.3 Cyclic Redundancy Checks 482
6.5.4 Convolutional Coding for Error Correction 489
6.6 Encryption and Security 507
6.6.1 Cipher Algorithms 508
6.6.2 Simple Encipherment Systems 509
6.6.3 Key Exchange 512
6.6.4 Digital Signatures and Hash Functions 519
6.6.5 Public-key Encryption 520
6.6.6 Public-key Authentication 522
6.6.7 Mathematics Underpinning Public-key Encryption 522
6.7 Chapter Summary 526
Problems 526
References 531
Index 541
1
Signals and Systems
1.1 Chapter Objectives
On completion of this chapter, the reader should:
- Be able to apply mathematical principles to waveforms.
- Be conversant with some important terms and definitions used in telecommunications, such as root-mean-square for voltage measurements and decibels for power.
- Understand the relationship between the time- and frequency-domain descriptions of a signal and have a basic understanding of the operation of frequency-selective filters.
- Be able to name several common building blocks for creating more complex systems.
- Understand the reasons why impedances need to be matched, to maximize power transfer.
- Understand the significance of noise in telecommunication system design and be able to calculate the effect of noise on a system.
1.2 Introduction
A signal is essentially just a time-varying quantity. It is often an electrical voltage, but it could be some other quantity, which can be changed or modulated easily, such as radio-frequency power or optical (light) power. It is used to carry information from one end of a communications channel (the sender or transmitter) to the receiving end. Various operations can be performed on a signal, and in designing a telecommunications transmitter or receiver, many basic operations are employed in order to achieve the desired, more complex operation. For example, modulating a voice signal so that it may be transmitted through free space or encoding data bits on a wire all entail some sort ofprocessing of the signal.
A voltage that changes in some known fashion over time is termed awaveform, and that waveform carries information as a function of time. In the following sections, several operations on waveforms are introduced.
1.3 Signals and Phase Shift
In many communication systems, it is necessary to delay a signal by a certain amount. If this delay is relative to the frequency of the signal, it is a constant proportion of the total cycle time of the signal. In that case, it is convenient to write the delay not as time, but as a phase angle relative to 360 or (radians). As with delay, it is useful to be able to advance a signal, so that it occurs earlier with respect to a reference waveform. This may run a little counter to intuition, since after all, it is not possible to know the value of a signal at some point in the future. However, considering that a signal repetitive goes on forever (or at least, for as long as we wish to observe it), then an advance of say one-quarter of a cycle or 90 is equivalent to a delay of .
To see the effect of phase advance and phase delay, consider Figure 1.1, which shows these operations on both sine and cosine signals. The left panels show a sine wave, a delayed signal (moved later in time), and an advanced signal (moved earlier). The corresponding equations are
Starting with a cosine signal, Figure 1.1 shows on the right the original, delayed (or retarded), and advanced signals, respectively, with equations
Figure 1.1 Sine and cosine, phase advance, and phase retard. Each plot shows amplitude versus time .
1.4 System Building Blocks
Telecommunication systems can be understood and analyzed in terms of some basic building blocks. More complicated systems may be "built up" from simpler blocks. Each of the simpler blocks performs a specific function. This section looks initially at some simple system blocks and then at some more complex arrangements.
1.4.1 Basic Building Blocks
There are many types of blocks that can be specified according to need, but some common ones to start with are shown in Figure 1.2. The generic input/output block shows an input and an output , with the input signal waveform being altered in some way on passing through. The alteration of the signal may be simple, such as multiplying the waveform by a constant to give . Alternatively, the operation may be more complex, such as introducing a phase delay. The signal source is used to show the source of a waveform - in this case, a sinusoidal wave of a certain frequency . The addition (or subtraction) block acts on two input signals to produce a single output signal, so that for each time instant . Similarly, a multiplier block produces at its output the product .
Figure 1.2 Basic building blocks: generic input/output, signal source, adder, and multiplier.
These basic blocks are used to encapsulate common functions and may be combined to build up more complicated systems. Figure 1.3 shows two system blocks in cascade. Suppose each block is a simple multiplier - that is, the output is simply the input multiplied by a gain factor. Let the gain of the block be and that of the block be . Then, the overall gain from input to output would be just .
To see how it might be possible to build up a more complicated system from the basic blocks, consider the system shown on the right in Figure 1.3. In this case, the boxes are simply gain multipliers such that and , and so the overall output is .
Figure 1.3 Cascading blocks in series (left) and adding them in parallel (right).
1.4.2 Phase Shifting Blocks
In Section 1.3, the concept of phase shift of a waveform was discussed. It is possible to develop circuits or design algorithms to alter the phase of a waveform, and it is very useful in telecommunication systems to be able to do this. Consequently, the use of a phase-shifting block is very convenient. Most commonly, a phase shift of is required. Of course, radians in the phase angle is equivalent to 90. As illustrated in the block diagrams of Figure 1.4, we use +90 to mean a phase advance of 90 and, similarly, -90 to mean a phase delay of 90.
Figure 1.4 Phase shifting blocks. Note the input and output equations.
1.4.3 Linear and Nonlinear Blocks
Let us examine more closely what happens when a signal is passed through a system. Suppose for the moment that it is just a simple DC voltage. Figure 1.5 shows a transfer characteristic, which maps the input voltage to a corresponding output voltage. Two input values separated by , with corresponding outputs separated by , allow determination of the change in output as a function of the change in input. This is referred to as the gain of the system.
Figure 1.5 The process of mapping an input (horizontal axis) to an output (vertical), when the block has a linear characteristic. The constant or DC offset may be zero, or nonzero as illustrated.
Suppose such a linear transfer characteristic with zero offset (that is, it passes through ) is subjected to a sinusoidal input. The output is a linear function of input , which we denote as a constant . Then,
(1.1)With input , the output will be
(1.2)Thus the change in output is simply in proportion to the input, as expected.
This linear case is somewhat idealistic. Usually, toward the maximum and minimum range of voltages which an electronic system can handle, a characteristic that is not purely linear is found. Typically, the output has a limiting or saturation characteristic - as the input increases, the output does not increase directly in proportion at higher amplitudes. This simple type of nonlinear behavior is illustrated in Figure 1.6. In this case, the relationship between the input and output is not a simple constant of proportionality - though note that if the input is kept within a defined range, the characteristic may well be approximately linear.
Figure 1.6 Example of mapping an input (horizontal axis) to an output (vertical), when the block has a nonlinear characteristic. Other types of nonlinearity are possible, of course.
To fix ideas more concretely, suppose the characteristic may be represented by a quadratic form, with both a linear constant multiplier and a small amount of signal introduced that is proportional to the square of the input, via constant . If the input is again a sinusoidal function, the output may then be written as
(1.3)This is straightforward, but what does the sinusoidal squared term represent? Using the trigonometric identities
(1.4) (1.5)we have by subtracting the first from the second, and then putting ,
(1.6)After application of this relation, and simplification, the output may be written as
(1.7)This can be broken down into a constant or DC term, a term at the input frequency, and a term at twice the input frequency:
(1.8)This is an important conclusion: the introduction of nonlinearity to a system may affect the frequency components present at the output. A linear system always has frequency components at the output of the exact same frequency as the input. A nonlinear system, as we have demonstrated, may produce harmonically related components at other frequencies.
1.4.4 Filtering Blocks
A more complicated building block is the frequency-selective filter, almost always just called a...
