Filter-and-forward distributed beamforming for two-way relay networks with frequency selective channels

In filter-and-forward (FF) based two-phase two-way relay networks, each transmission for data exchange between two transceivers consists of only two phases. In the first phase, both transceivers transmit their data simultaneously to the relays. The received signal of each relay is filtered with a finite impulse response (FIR) filter to compensate for the frequency selectivity of the channels, and then, the output of the filter is forwarded to both transceivers in the second phase. A new approach to distributed cooperative beamforming for such two-way relay networks with frequency selective channels is proposed This approach maximizes the lower signal-to-interference-plus-noise (SINR) of the two transceivers subject to a constraint on the total transmitted power. In the proposed approach, the transmitted powers of the transceivers as well as the coefficients of the relay filters are optimized. Simulation results demonstrate that using an FF relaying strategy can significantly improve the received SINR as compared to the traditional amplify-and-forward relaying approach.