On the performance of spectrum sharing two-way relay networks with distributed beamforming

In this paper, we consider distributed beamforming for two-way spectrum-sharing system in an effort to enhance the performance of the secondary system and improve the bandwidth efficiency. In particular, we consider a cognitive radio network where a set of amplify-and-forward (AF) relays are employed to help a pair of secondary transceivers in the presence of multiple primary receivers. This set of the available relays participate in the beamforming process, where the beamformer weights are obtained via a convex optimization method. We analyze the performance of the proposed methods where closed-form expressions for the end-to-end outage and average error probabilities are derived for independent and identically distributed (i.i.d.) Rayleigh fading channels. Numerical results demonstrate the vitality of beamforming in enhancing the secondary system performance in addition to mitigating the interference to the primary users.