A sorted parallel detector for coded MIMO systems

Computing the log likelihood ratios (LLR's) of the transmitted bits in a multiple-input multiple-output (MIMO) system is an NP hard problem. Many suboptimal soft MIMO detectors have been proposed to reduce the detection complexity. The state-of-the art tries to combine the search for the maximum a posteriori (MAP) estimate and the counter-hypotheses in a single tree pass. However, not all possible counter-hypotheses are tested and have to be selected to reduce complexity. In this paper, the sorted parallel detector (SPD) is developed that is based on the parallel smart candidate adding (PSCA). SPD has a better bit error rate (BER) performance than the PSCA and exhibits a lower average number of visited tree nodes. Moreover, SPD has a fixed complexity and is suitable for hardware implementation.