Filter-and-forward relay beamforming in cognitive two-way relay networks

In this paper, a novel approach to filter-and-forward relay beamforming in an underlay based cognitive two-way relay network with frequency selective channels is proposed. In our scheme, two secondary transceivers communicate which other through multiple relays simultaneously with the primary network transmission over same spectrum. Such a network suffers from both inter-symbol interference (ISI) and bidirectional interference between networks. Our proposed approach mitigates these two types of interference by minimizing the peak interference power from the secondary network to the primary network subject to the quality of service (QoS) requirements for both secondary transceivers. Simulation results show that the proposed technique improves system performance considerably in frequency selective environments in comparison to the traditional amplify-and-forward strategy.