Robust multi-branch space-time beamforming for OFDM system with interference

Space-time receive beamforming is a promising technique to suppress co-channel multiuser interference for orthogonal frequency division multiplexing (OFDM) systems. However, the performance of existing receive beamforming methods is highly sensitive to the memory length of time-domain equalizer. In this paper, we propose a new robust solution of space-time receive beamforming to combat co-channel multiuser interference for OFDM systems. The proposed method performs subspace analysis for the received space-time snapshots from both the training block and few data blocks, and constrains the space-time beamforming vectors to lie in the corresponding signal subspace. A few beamforming vectors are then carefully designed to suppress interference as well as provide the potential multi-branch diversity gain. The numerical results are provided to corroborate the proposed studies. We show that the proposed method not only can outperform the exiting competitors but also has the advantage of being quite insensitive to the memory length of time-domain equalizer.