Reduced-state cyclic Viterbi receiver for localized SC-FDMA uplink system

For the single-carrier localized frequency-division-multiple-access (SC-LFDMA) uplink system, it is shown that the equivalent channel can be modeled as a cyclic ISI (CISI) channel. Under such a channel, we derive the optimum cyclic Viterbi (CV) receiver, which outperforms those suboptimal frequency-domain equalizers. In order to apply CV to SC-LFDMA system in practice, we then consider a reduced-state CV by using decision feedback (DF) with local tentative decisions. However, the CV-DF receiver will suffers from error propagation when the CISI channel is non-minimum phase. Therefore, an all-pass prefilter (APPF) is further designed in cepstrum-domain to tame the channel phase response, resulting in a CV-APPF-DF receiver which provides a good tradeoff between error performance and complexity. Computer simulation results are included to demonstrate the excellent performance of the full-state CV receiver, and the near optimum performance of the CV-APPF-DF receiver.