Improved Turbo Fixed-Complexity Sphere Detection for MIMO Communications

In this paper we present a detection algorithm that can be used for MIMO systems that employ many transmit antennas. It is well known that the a posteriori Probability (APP) detector is inapplicable for large MIMO systems due to exponential increase in complexity. The classic one-sweep Fixed-complexity Sphere Detection (FSD) allows to reduce the search space by hard-detecting several reliable signal streams, and recovering the remaining streams in an APP detection manner. Inspired by the Overlapped Subspace Detection (OSD) concept, we introduce an iterative detection mechanism, referred to as Turbo Fixed-complexity Sphere Detection (Turbo-FSD), to improve the reliability of all detected streams. Numerical results show that the capacity of MIMO systems with many transmit antennas can be closely approached at modest complexity increase compared to simple linear receivers.