AN ADAPTIVE MAXIMUM-LIKELIHOOD SEQUENCE-ESTIMATOR FOR FAST TIME-VARYING INTERSYMBOL INTERFERENCE CHANNELS

This paper proposes an adaptive maximum-likelihood sequence estimator (MLSE), which is a suboptimum approximation to the adaptive maximum-li kelihood detector and is capable of tracking fast time-varying intersy mbol interference (ISI) channels. The adaptive MLSE consists of a chan nel estimator and an MLSE implemented by the Viterbi algorithm (VA). T he novel feature of the proposed adaptive MLSE is a channel estimation scheme, where the channel estimation is accomplished for each state i n the VA along the surviving path connected to each state. This MLSE m akes it possible to estimate a channel impulse response without an inf luence of a decision delay inherent in the VA, and the performance and complexity of the proposed procedure is controlled by the memory leng th of the VA. The bit error rate performance of the proposed MLSE is c onfirmed by experimental results. It is shown that the proposed MLSE h as a capability of excellent tracking performance in a severe environm ent caused by fast time-varying ISI, for example frequency selective m ultipath fading in digital mobile radio communications.