Channel-Aligned Multiuser Two-Way Relaying Scheme With Finite Feedforward

We consider a multiuser two-way amplify-and-forward relay channel with finite feedforward (FF) of the beamforming weights. The relay decides the beamforming weights of the users based on the full channel knowledge and feeds the beamforming information to the users through the band-limited FF channels. Assuming random vector quantization (RVQ), the performance analysis of the finite-FF system is presented. Similar to the multiuser broadcast channel, the average sum rate saturates at a high SNR with a fixed-size codebook. The scaling rate of the codebook size necessary to overcome the saturation and to follow up the multiplexing gain is presented. Supporting simulation results are presented.