A combined soft-decision deinterleaver/decoder for the IS95 reverse link

The reverse link encoding steps of the IS95 cellular code-division multiple-access (CDMA) standard consist of convolutional encoding, block interleaving, and orthogonal Walsh function encoding. Deinterleaving individual symbol metrics obtained from the Walsh function matched filters followed by conventional Viterbi decoding produces suboptimal results, as unwanted intersymbol Walsh function correlation is introduced. We propose a combined deinterleaver/decoder with improved performance over existing decoders with little added overhead and no extra decoding delay. Applied to the IS95 reverse link, the proposed decoder has about 1.0-dB gain over soft-decision decoding with interleaved symbol metrics at a bit error rate (BER) of 10^-3