Chapter 2 Introduction to Spread Spectrum

As discussed in Chapter 0, a spread spectrum modulation produces a transmitted spectrum much wider than the minimum bandwidth required. There are many ways to generate spread spectrum signals. We are going to introduce some of the most common spread spectrum techniques such as direct sequence (DS), frequency hop (FH), time hop (TH), and multicarrier (MC). Of course, one can also mix these spread spectrum techniques to form hybrids which have the advantages of different techniques. Spread spectrum originates from military needs and finds most applications in hostile communication environments. We will start by briefly looking at the advantage of spreading the spectrum in the presence of a Gaussian jammer as our motivation to study spread spectrum communications. Toward the end of the chapter, we will also state some common spread spectrum applications. Detailed treatments of some of these applications are left for the coming chapters.