An efficient symbol-level combining scheme for MIMO systems with hybrid ARQ

This paper proposes a new combining scheme for multiple-input multiple-output (MIMO) systems with hybrid automatic-repeat-request (HARQ). The proposed combining scheme is proved to have the optimal decoding performance. Furthermore, the proposed combining scheme is shown to have low memory requirement and reduced complexity compared to other optimal combining schemes. Simulation results under IEEE 802.16e setting with UMTS channel models verify that the proposed combining scheme achieves the optimal decoding performance and performs much better than other suboptimal combining schemes.