This paper analyzes the performance of cyclic prefixed single-carrier transmission under multiuser interference (MUI). For multi-user receivers using single carrier frequency domain adaptive antenna array, we derive the signal to interference plus noise ratio by analyzing the time domain estimated signal after the transformation from frequency domain to time domain. By assuming the MUI follows the Gaussian distribution, we can derive the analytical expression for the bit error rate (BER) performance. The analytical result is verified by the numerical results generated by Monte Carlo method. It is concluded from the analytical results that if the number of receive antennas goes to infinity as assumed in massive multiple input multiple output (MIMO) system, the BER performance will be determined by two ratios: signal to noise ratio as well as the N to U ratio, where N is the number of receive antennas and U is the number of users.