TABLE OF CONTENTS This chapter covers the critical topic of forward error correction (FEC), briefly introduced in Chapter 4. Along with modulation, FEC drives, in large measure, the performance of the satellite link, the effective channel throughput, and the service availability that one is able to obtain over the satellite link. This chapter only presents a basic introduction to this topic, and focuses pragmatically only on commercial satellite applications.
The FEC is the key subsystem required to achieve high performance in satellite links given the typical presence of high levels of noise and interference. It is a system of error control for data transmission where the receiving device has the capability to detect and correct, in a simplex mode (one-way communications channel), any character or code block that contains fewer than a predetermined number of symbols in error; it is accomplished by adding bits to each transmitted character or code block using a predetermined algorithm [ANS200001]. In other words, FEC codes can detect and correct a limited number of errors without retransmitting the data stream. FEC refers to the ability to overcome both erasures (losses) and bit-level corruption. There are two basic types of FEC codes:
Block codes. In these algorithms, the encoder processes a block of message symbols and then outputs a block of code word symbols. Reed Solomon (RS) codes belong to the family of block codes. They first appeared in the literature in 1960. The input to an FEC encoder is a certain number k of equal-length...
