Maximum likelihood sequence estimation from the lattice viewpoint

The conventional maximum likelihood sequence estimator using the Viterbi algorithm has a time complexity of O(m^ν+1) operations per symbol and a space complexity of O(δm^ν) storage elements, where m is the size of input alphabet, ν is the length of channel memory and δ is the truncation depth. The author proposes a new sequence estimator for a pulse amplitude modulation system, which has the following desired properties: its expected time complexity grows as δ², as SNR→∞; its space complexity grows as δ; its error performance is effectively optimal for moderate-to-large values of m. Simulation results for an example channel are also presented