Interference Suppression for Multiuser Downlink Transmission in Frequency-Selective Fading Channels

This paper presents an interference suppression scheme for multiuser downlink transmission in severe frequency-selective fading environments. Frequency-domain transmit beamforming and pre-equalization based on single-carrier frequency-domain equalization (SC-FDE) technique are employed to cancel co-channel interference (CCI) and to suppress intersymbol interference (ISI) with relatively low complexity. The proposed scheme effectively suppresses the ISI with a zero-forcing constraint on the CCI, and provides a viable solution to an otherwise analytically complex, if not unsolvable, problem. This paper also shows that, in frequency-selective fading channels, a multiuser system with K users and M_t base transceiver station antennas can offer lower bit error rate than a single-user system with M_t - K + 1 BTS antennas, if the proposed frequency-domain multiuser beamforming is employed.