Noncausal filters in multipath channel shaping

The use of the Viterbi algorithm in its simplified versions for detection of a data sequence is more effective in the case of minimum phase channels. A method is proposed for equalization of nonminimum phase channels. It employs noncausal allpass filters operating in reversed time. A minimum phase channel is obtained without enhancing the noise level. The method can be modified to obtain a desired impulse response with few nonzero samples with only minor variations in noise level providing significant complexity reduction in the Viterbi algorithm. Several simulation results are presented to illustrate the capability of the proposed method