Diversity-Multiplexing Tradeoff in ISI Channels
The optimal diversity-multiplexing tradeoff curve for the intersymbol interference (ISI) channel is computed and various equalizers are analyzed using this performance metric. Maximum-likelihood signal decoding (MLSD) and decision feedback equalization (DFE) equalizers achieve the optimal tradeoff without coding, but zero forcing (ZF) and minimum mean-square-error (MMSE) equalizers do not. However if each transmission block is ended with a period of silence lasting the coherence time of the channel, both ZF and MMSE equalizers become diversity-multiplexing optimal. This suggests that the bulk of the performance gain obtained by replacing linear decoders with computationally intensive ones such as orthogonal frequency-division multiplexing (OFDM) or Viterbi, can be realized in much simpler fashion-with a small modification to the transmit scheme.
diversity-multiplexing tradeoff intersymbol interference (isi) decision feedback equalization (dfe) minimum mean-square-error (mmse) equalization maximum-likelihood sequence estimation zero-forcing (zf) equalization