Schiff M. Introduction to Communication Systems Simulation

Artech House, 2006. - 224 pp.The genesis for this book was my involvement with the development of the SystemView (now SystemVue) simulation program at Elanix, Inc. Over several years of development, technical support, and seminars, several issues kept recurring. One common question was, How do you simulate (such and such)? The second set of issues was based on modern communication systems, and why particular developers did what they did. This book is an attempt to gather these issues into a single comprehensive source.
Chapter 1 presents a discussion of the basic elements of a communication system. It serves as a reference for subsequent chapters by briefly describing the various components of a communication system and their role in the system.
Chapter 2 develops the theory of linear time invariant (LTI) systems, which is the foundation of communication theory. The basic concepts of the filter impulse response and convolutions are presented. From there we consider the workhorses of LTI systems, namely the Fourier and Laplace transforms. We end with the simple development of the fast Fourier transform (FFT), which has revolutionized signal processing.
Chapter 3 deals with the concept of sampling. As digital processors become faster, more and more of the system processing is performed in this domain. A thorough understanding of the Nyquist sampling theorem and other issues is vital to the successful implementation of these systems.
Chapter 4 provides the fundamentals of filters, as they are the most common element of a communication system. We start with the concept of filter phase and group delay via a simple two-tone input example. From there we separate the discussion into the two common classes of filter finite impulse response (FIR), and infinite impulse response (IIR).
Chapter 5 concentrates on the concept of digital detection. Most modern communication systems use digital formats as opposed to analog (AM, FM). The fundamental results of optimum digital detection are derived along with several equivalent processing architectures.
Chapter 6 is concerned with the various methods of conveying information in a digital format. Physically, the transmitted wave is a sine function. One can convey information only by modulating the amplitude, frequency, phase, or combinations thereof this basic signal. This chapter also provides a discussion of spread spectrum modulation concepts including both frequency hopping and direct sequence.
Chapter 7 is the complement of Chapter 6 in that it describes techniques for demodulating the transmitted signal at the receiver. The basic architecture of in-phase and quadrature processing is detailed. In addition, the methods for recovering frequency, phase, and data timing (synchronization) are considered.
Chapter 8 deals with the important concept of baseband pulse shaping. The radio frequency spectrum is an economic quantity that the United States governxiii ment auctions to service providers. The goal of the provider is to provide as many data channels as possible within this spectrum. This goal is commonly achieved by limiting the signal spectra by using baseband processing such as raised and root raised cosine filters.
Chapter 9 presents the heart of digital communication performance analysis: the bit error rate (BER) calculation. Here we detail methods for simulating BER calculations. Two issues are of concern. The first is how to match the timing of the input data stream with the recovered one. The system under test will have various delays via encoders, filters, and so on, so the output data will be delayed in time with respect to the input. The second issue is how to calibrate the signal-to-noise ratio (SNR) for proper interpretation of the results.
Chapter 10 describes what happens to the signal between the transmitter and receiver. This is called the channel. Fading is the most important channel. The signal can bounce off of various objects and present to the receiver several versions of itself modified in amplitude, frequency, phase, and time of arrival. The effect of this is the well-known fading phenomena. This chapter describes various forms of the fading, as well as methods to mitigate their effects.
Chapter 11 deals with the real world of nonlinear amplifiers. The nature of these nonlinearities are described and modeled. Both standard RF amplifiers and satellite- based traveling wave tube amplifiers are discussed.
Chapter 12 concerns the simulation of communication systems using baseband concepts. Unless there are nonlinear elements in the RF section, one can mathematically eliminate the carrier operations from the simulation. This is important since simulating the carrier requires a very high system sample rate to adequately describe the carrier. By contrast, the information content on the carrier may have a information bandwidth several orders of magnitude smaller. The baseband simulation allows accurate simulation while only sampling at a rate sufficient to represent the information source. This presents orders of magnitude savings in the simulation time.
Chapter 13 concludes the book with a look at the emerging technology of ultra-wideband (UWB) systems. The two competing technologies, direct sequence (DS) and orthogonal frequency division multiplexing (OFDM) are presented. As with any lecture course, an attendant laboratory can be used to emphasize and further enhance the material through direct demonstrations. To this end we have included a disc containing example files using the simulation software SystemVue. The reader is urged to run these files, and vary the various system parameters as permitted. It is hoped that these examples will greatly enhance the readers understanding of the text material.Elements of a Communication System
Linear Time Invariant Systems
Sampling
Filters
Digital Detection
Modulation
Demodulation
Baseband Pulse Shaping
Bit Error Rate Calculations
Channel Models
Nonlinear Amplifiers
Baseband Simulation
Ultra-Wideband Systems
Table of Laplace Transforms
Elements of Probability Theory and Random Variables
Error Correcting Codes
Trivia Question