Convolutional double accumulate codes with iterative decoding for broadband OFDM wireless communications

Orthogonal frequency division multiplexing (OFDM) is robust to inter-symbol interference and offers delay diversity that avoids large time-domain interleavers which in turn induce long encoding and decoding latency. We consider a high code-rate differentially modulated OFDM system for broadband wireless communications. By treating the differential modulation scheme as a rate-1 recursive convolutional code, turbo decoding can be applied and numerical results show very good performance, compared to that of the traditional coded coherent modulation schemes. With an extra differential code, large coding gains are achieved, without bandwidth expansion, for both the bit error rate (BER) and frame error rate (FER) in the AWGN channel while significant FER gain can be achieved in broadband frequency-selective radio channels with only a few iterations