Digital Communication Systems

CHAPTER

10

Error-Control Coding

10.1  Introduction

In the previous three chapters we studied the important issue of data transmission over communication channels under three different channel-impairment scenarios:

• In Chapter 7 the focus of attention was on the kind of channels where AWGN is the main source of channel impairment. An example of this first scenario is a satellite-communication channel.
• In Chapter 8 the focus of attention was intersymbol interference as the main source of channel impairment. An example of this second scenario is the telephone channel.
• Then, in Chapter 9 we focused on multipath as a source of channel impairment. An example for this third scenario is the wireless channel.

Although, indeed, these three scenarios are naturally quite different from each other, they do share a common practical shortcoming: reliability. This is where the need for error-control coding, the topic of this chapter, assumes paramount importance.

Given these physical realities, the task facing the designer of a digital communication system is that of providing a cost-effective facility for transmitting information from one end of the system at a rate and level of reliability and quality that are acceptable to a user at the other end.

From a communication theoretic perspective, the key system parameters available for achieving these practical requirements are limited to two:

• transmitted signal power, and
• channel bandwidth.

These two parameters, together with the power spectral ...