Asynchronous bidirectional relay-assisted communications

In this paper, an asynchronous bidirectional relay network is considered. We assume that the signal path going through each relay has a propagation delay which is different from those of the other relaying paths. Such an assumption leads to inter-symbol-interference (ISI) at the two transceivers. As such, orthogonal frequency division multiplexing (OFDM) is deployed at the two transceivers to tackle ISI, while the relays, for the sake of simplicity, use amplify-and-forward relaying technique. Using a max-min fair design approach, an SNR balancing technique is presented to jointly obtain the beamformer weights and transceivers' subcarrier power loading under a total transmit power budget. Simulation results are presented to show the performance of this approach.