User selection criteria for multiuser systems with optimal and suboptimal LR based detectors

In this correspondence, we investigate user selection criteria for various multiple input multiple output (MIMO) detectors to exploit the multiuser diversity. Different user selection criteria are derived for various MIMO detectors, including the maximum likelihood (ML) detector and low complexity suboptimal detectors. It is shown that the user selection criterion plays a crucial role in exploiting both multiuser and receive (or spatial) diversity. We also show that the ML and even some low complexity suboptimal detectors (based on the lattice reduction (LR)) can achieve a full multiuser and receive diversity when the user selection criterion is properly chosen.