Adaptive Puncturing and Rate Selection in Single-Codeword Turbo-Coded OFDMA

This paper proposes using adaptive puncturing for rate-adaptive OFDMA systems utilizing turbo codes. The scheme is based on adaptively puncturing a single code word (SCW) and hence adaptively changing the rate within the codeword. We compare the SCW against the multiple code-words (MCWs) scheme where different rates are obtained by separate encoding, puncturing, and interleaving on a per-tile basis. Noticeable gains are obtained over the MCW scheme due to the use of larger turbo block sizes and hence larger interleavers. The SCW has around 1 dB gain in goodput compared to MCWs, with much improved BER performance. We also propose a novel rate selection scheme for the SCW which we call recursive mutual information effective SNR mapping (R-MIESM) and compare it against the conventional MIESM scheme. The R-MIESM provides further goodput performance gains for the SCW compared to the MIESM method.