Sub-optimum MLSE detector with a folded state-transition trellis preselection stage

The maximum-likelihood sequence estimation (MLSE) multiuser detector has very good performance but at the expense of the exponentially increasing number of states with the number of users. A scheme that exploits the feature of power-equality in the downlink to reduce the number of states involved has been previously proposed by the authors. In the paper, the folded-trellis detector is combined with MLSE, The main idea here is to use the folded trellis which has a linear complexity to preselect a subset of the bit-combinations and then apply MLSE to this much smaller set.