Multiuser Detection for Asynchronous Broadband Single-Carrier Transmission Systems

The multiuser multiple-input-multiple-output (MU-MIMO) technique is an attractive candidate in improving spectrum efficiency. However, in the uplink, the difference in the transmit timing among the signals from multiple mobile terminals (MTs) becomes significant. If the arrival timing difference among MTs exceeds the cyclic prefix (CP) length, it is difficult to separate the signal of each MT, and the transmission quality is severely degraded due to the effect of interblock interference (IBI). In this paper, we propose a novel multiuser detection (MUD) technique that can separate the signals, regardless of the arrival timing differences between the MTs. The proposed MUD technique is performed in the frequency domain by overlapping the fast Fourier transform (FFT) blocks, and the technique can suppress the effect of the IBI while retaining a low complexity level. The achievable bit error rate (BER) performance is evaluated by computer simulation in a frequency-selective fading channel, and the results confirm the effectiveness of the proposed technique.