Reduced-complexity Woven Serial Concatenated TCM for tactical OFDM communications

Orthogonal frequency division multiplexing (OFDM) with adaptive coding and modulation (ACM) gives a communication system that can adapt to varying channel conditions and provide reliable communication at a wider range of signal to noise-ratios (SNRs). We investigate how the number of available transmission rates in the ACM scheme impacts communication performance and feedback requirements. To accommodate for the various rates in the ACM system we use serial concatenated trellis-coded modulation (SCTCM) consisting of a rate-compatible punctured convolutional (RCPC) code or a woven serial concatenated convolutional (WSCC) code, both with a rate-1 inner accumulate code and mapping to a Gray-labeled signal constellation. We show that significant reductions in complexity and corresponding savings in protocol overhead can be obtained without significant performance degradation. It is shown that an equal spacing of available rates over the expected range of SNRs is preferable to an uneven spacing.