Achievable sum rates of MIMO SC-FDMA systems with different receivers

This paper investigates the achievable sum rates of multiple-input multiple-output (MIMO) single carrier frequency division multiple access (SC-FDMA) systems with different receivers in spatially uncorrelated frequency selective Rayleigh fading channels. Zero forcing (ZF), linear minimum mean-squared error (MMSE) and the proposed per subcarrier maximum likelihood (PSML) receivers are considered. Closed form expressions for the upper and lower bounds on the achievable sum rates of ZF, MMSE and PSML receivers are derived. Through these expressions, we characterize the behavior of the receivers in various scenarios of different channel lengths and subcarrier numbers. It is found that compared with the optimal receiver, the PSML receiver can obtain the optimal sum rate with significantly reduced computational complexity in flat fading channels. In addition, for ZF or MMSE receivers, either the upper or lower bound can be an accurate approximation of the achievable sum rate under certain conditions and can also provide a theoretical reference to practical systems.