Modified Schnorr-Euchner Sphere Decoding for Iterative Spatial Multiplexing MIMO Receiver

Recent work has shown that the Sphere Decoder (SD) based on Schnorr-Euchner (SE) strategy offers significant reductions in the computation complexity compared to all previously proposed sphere decoders with a near-maximum likelihood (ML) detection performance. This paper proposed a novel modified SE algorithm for iterative spatial multiplexing multiple-input-multiple-output (MIMO) receiver to estimate the maximum a posteriori (MAP) probability of the received symbol sequence. In addition, two schemes are proposed to further improve the performance and reduce the complexity over iterations, one is to improve the ZF-DFE estimate by using the quadratic approximation of a priori information, the other is to improve the tree search by employing starting point zig-zag technique. Simulation results show that significant performance gain and complexity reduction can be obtained compared to existing SE approach.