Enhanced soft decoding of multi-carrier systems for delay sensitive applications

Bit interleaving, often used to combat frequency selective fading over multi-carrier channels, can introduce long processing delays, unpractical for a number of real-time applications. When such delays cannot be afforded, the performance gain of soft decoders is more attractive. Unfortunately, even if bit interleaving is not considered, adaptive bit allocation allows only sub-optimal soft decoding. This is a bit-wise processing technique originally proposed for bit interleaved coded modulation. In this paper, an enhanced decoder is proposed. It avoids unnecessary intermediate bit metrics. Instead, it directly and more efficiently computes code metrics, which are what is actually required by the Viterbi decoder.