This paper investigates the achievable sum rates of MIMO SC-FDMA systems with different receivers in frequency selective fading channels. It considers zero forcing (ZF), linear MMSE, and proposed per subcarrier maximum likelihood (PSML) receivers. Closed form expressions for the upper and lower bounds of achievable sum rates are derived for ZF, MMSE, and PSML receivers. These expressions characterize the behavior of the receivers for various channel lengths and subcarrier numbers. The PSML receiver can obtain the optimal sum rate with reduced complexity in flat fading channels compared to the optimal receiver. The upper and lower bounds can accurately approximate achievable sum rates for ZF or MMSE receivers under certain conditions.

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Achievable Sum Rates of MIMO SC-FDMA Systems with Different
Receivers
Abstract:
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.