Recursive QR packet combining for uplink single-carrier multi-user MIMO HARQ using near ML detection

Abstract

Abstract-QR decomposition based near maximum likelihood (ML) block detection significantly improves the transmission performance of uplink single-carrier (SC) multi-user multipleinput multiple-output (MU-MIMO). Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high quality packet data transmission. The achievable diversity gain of HARQ depends on the packet combining strategy. In uplink MU-MIMO HARQ, received signal may consist of new packets and retransmitted packets as retransmission for each user acts independently. In this paper, a recursive QR packet combining scheme suitable for uplink SC MU-MIMO HARQ is proposed, which takes into account the number of retransmissions for each user in the detection order. The proposed scheme helps reduce the computational complexity and storage requirement significantly. Moreover, it improves the packet error rate (PER) performance significantly over the conventional bit-level log likelihood ratio (LLR) packet combining, as shown by our computer simulation results.

Single-Carrier Multi-User MIMO Downlink with Time-Domain Tomlinson-Harashima Precoding

“…BS, in order to suppress inter-user interference (IUI). MU-MIMO downlink with precoding may exhibit worse bit error rate (BER) performance than that of MU-MIMO uplink employing a maximum likelihood detection technique [7], [8]. According to [9], nonlinear precoding schemes achieve better BER performance than linear precoding schemes.…”