A new turbo coded modulation approach exploiting non-binary field

Abstract

We present a new coded modulation scheme based on the non-binary convolutional codes (CCs) defined over finite field. The outputs of the component codes defined over GF(2q) are directly mapped onto the signal space with 2q-ary constellation points. By choosing the symbols input to each CC from a strict subset of GF(2q), the constellation redundancy is embedded, thereby achieving coding gain. Furthermore, by the parallel concatenation of the two CCs together with iterative decoding, the capacity approaching performance can be achieved. Through the symbol-based extrinsic information transfer (EXIT) chart analysis, an efficient search algorithm for the best tap coefficients of the CCs is developed. The frame error rate (FER) performance comparisons with conventional coded modulation schemes demonstrate the superiority of the proposed approach.