Chapter 1 Channel Codes and Modulation

Abstract

This chapter reviews fundamental results of coding and modulation theory that are essential to a full understanding of spread-spectrum systems. Channel codes, which are also called error-correction or error-control codes, are vital in fully exploiting the potential capabilities of spread-spectrum communication systems. Although direct-sequence systems greatly suppress interference, practical systems require channel codes to deal with the residual interference and channel impairments such as fading. Frequency-hopping systems are designed to avoid interference, but the possibility of hopping into an unfavorable spectral region usually requires a channel code to maintain adequate performance. In this chapter, coding and modulation theory are used to derive the required receiver computations and the error probabilities of the decoded information bits. The emphasis is on the types of codes and modulation that have proved most useful in spread-spectrum systems.