A new SDM transmit scheme using HARQ with MRC

In this paper, we propose a new space division multiplexing (SDM) packet transmit scheme using hybrid automatic repeat request (HARQ) and maximum ratio combining (MRC). In the proposed SDM system, a receiver makes replicas of retransmitted packets using the stored erroneous packets. By subtracting each of these replicas from the received signal, cochannel interference (CCI) is reduced. As a result, the receiver can employ MRC before decoding the packets. Thus, the proposed system has larger diversity gain than SDM/HARQ systems with only space-filtering. Simulation results show the throughput performance of the proposed system is larger than that of the conventional SDM/HARQ system. Furthermore, we have evaluated the orthogonal frequency division multiplexing (OFDM) system using the proposed scheme. The results also confirm the proposed scheme is effective for improving the throughput performance of SDM-OFDM systems using HARQ.