A comparison of bit and symbol interleaving in MMSE turbo-equalization

The purpose of this paper is to compare bit and symbol interleaving in turbo-equalization (TE) schemes. Considering a single binary encoder and memoryless mapper, the corresponding transmission schemes are respectively bit-interleaved coded modulation (BICM) and trellis-coded modulation (TCM) over a static frequency selective channel. Appropriate turbo processing at the receiver is ensured in both cases. For the sake of tractability, efficient low-complexity MMSE-based implementations are proposed. The asymptotic performance of the resulting bit- and symbol-interleaved TE schemes is then linked with that of the underlying coded modulation schemes. As an extension to [X. Li, J. Ritcey, 1999], this enables to show that bit-interleaved TE with carefully chosen constellation mapping and proper implementation can outperform its symbol-interleaved counterpart.