Feedback Decoding of Convolutional Codes

Publisher Summary In recent years, convolutional coding-decoding techniques have become increasingly popular in digital communication systems where there is a requirement to provide error correction and to improve communication efficiency. This chapter focuses on the feedback decoding of the convolutional codes. Convolutional encoding with feedback decoding is capable of providing error correction performance superior to that of block codes for the same level of equipment complexity. Convolutional encoding-decoding is more desirable than competing block encoding-decoding techniques in most of these applications because, for a given error correction capability or improvement in communication efficiency, the systems based on convolutional codes are less complex and hence less costly. This has been shown theoretically and in practical equipment designs and implementations. In general, feedback decoder implementations have the added attraction that they can be made effective on burst error channels. Interleaving of data in the encoder and deinterleaving in the decoder can be performed in a straightforward manner, effectively breaking up error bursts and making the channel appear memory less to the decoder. Feedback decoders are simple to implement. Feedback decoding is especially attractive on burst error channels as very effective interleaving, to break up long bursts, can be implemented simply with no increase in code synchronization requirement.