Factor-Graph-Based Soft-Input Soft-Output Detection for Frequency-Selective MIMO Channels

In this letter we consider a MIMO communication system with iterative detection over a frequency-selective MIMO channel. We present a soft-input soft-output MIMO detector based on a cyclic factor graph representation and the sum-product algorithm with two different message schedules (serial and parallel). Computer simulations show that both schedules provide near-optimum performance in terms of bit error rate, while achieving a remarkable reduction in complexity compared to the optimal MAP detector.