Combined coding for error control and increased robustness to system nonlinearities in OFDM

Abstract

A combined coding scheme for error control and reduced peak to mean envelope power ratio (PMEPR) in OFDM is presented. The proposed scheme and an algorithm for finding the optimum code set for achieving minimum PMEPR is described in detail. The process is illustrated by means of an example, and it is shown that a 4 dB improvement is possible for an (8,4) linear block code. The method is extended to consider larger code sets of lower rate which are expanded through the use of polyphase sequences that are found by means of a natural algorithm. Preliminary results indicate that the PMEPR can be further improved by use of such sequences. Finally, the BER performance of the combined coding method in a typical nonlinear channel is presented.