Multiuser detection of overloaded systems employing HARQ

We propose two schemes to perform multiuser detection (MUD) for multiuser multiple-input multiple-output (MIMO) systems under overload. Typically linear MUD algorithms fail to perform under overload and maximum likelihood detection is often prohibitively complex. In this paper, we use hybrid automatic repeat request (HARQ) retransmissions to transform an overloaded system into a critically or underloaded system based on the concept of virtual receive antennas. Hence, low complexity linear MUD algorithms can be used and achieve diversity gains. Simulation results clearly highlight the advantages obtained by the proposed schemes.