TABLE OF CONTENTS In this first chapter we introduce the basic components of a communication system. The system diagram is shown in Figure 1.1.
We have emphasized the major elements of the system as the transmitter, channel, and receiver. Each of these elements has several subcomponents. We shall work our way through this diagram starting with the information source, and ending with the recovered information. The ideas and issues pertinent to each sub-block will be described.
The task of the transmitter is to take an information source and after several steps of processing, produce a signal at some carrier frequency over the air.
Since we are dealing with digital communications, information will, regardless of the source, eventually be converted into bits. However, the origins of the information may be either digital or analog.
Types of sources that might be considered digital include a text message (e.g., Stop), a numeric value (e.g., 78 F), or a tuning command to some object (e.g., a missile). As an example, the Global Positioning Satellite (GPS) system has a 50-bps data message that provides the user with system time information and the ephemeris data of the transmitting satellite.
The most common types of analog sources are voice and pictures. These sources are sampled, according to the rules of Chapter 1, and the results are converted to a bit pattern.
In many cases, the data is not independent from one sample...
