Diversity of MMSE Receivers in MIMO Multiple Access Channels

This letter analyzes the performance of MMSE receivers in multiple input multiple output (MIMO) multiple access channel (MAC). The Diversity-Multiplexing Tradeoff (DMT) of the MIMO MAC under MMSE reception easily follows from the single-user DMT, indicating that MMSE receivers are largely suboptimal for MIMO MAC. The main result of this letter is the calculation of the diversity of the MIMO MAC in the fixed-rate regime, i.e., when users transmit at non-zero rates that are not functions of SNR. In this regime, the MIMO MAC MMSE receivers exhibit interesting diversity behaviors whose characterization is completed by the contributions of this letter.