Achievable Sum Rate Comparison of MIMO OFDMA and SC-FDMA Systems with Linear Receivers

This paper compares the achievable sum rates of multiple-input multiple-output (MIMO) single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA) systems with linear receivers in spatially uncorrelated frequency selective Rayleigh fading channels. Zero forcing (ZF) and linear minimum mean-squared error (MMSE) receivers are considered. We derive closed form expressions for lower bounds on the achievable sum rates of SC- FDMA so as to compare them with the achievable sum rates of OFDMA. In addition, the comparison in the asymptotic regimes of high and low signal-to-noise ratios (SNRs) is also presented. It is analytically demonstrated that, for ZF and MMSE receivers, the achievable sum rate of SC-FDMA is approximately equal to that of OFDMA when the number of transmitter and receiver antennas grows with a fixed ratio of less than one, in both high and low SNR regimes. The results apply to scenarios with arbitrary numbers of subcarriers and arbitrary-length channels.