On the optimal relay design for multi-antenna cognitive two-way AF relay networks

Cognitive relaying is an efficient method for tackling the problem of spectrum scarcity by serving new (secondary) users, while keeping the existing (primary) users satisfied with their service. Moreover, additional gains can be attained from employment of the two-way relaying with multiple-antenna relays within the secondary network. In this paper, we consider an underlay two-way cognitive network and propose an efficient algorithm for computing a (nearly) optimal relay precoder matrix subject to the interference constraint towards the primary network. The efficiency of the proposed solution is highlighted by means of numerical simulations.