Full-Duplex Amplify-and-Forward Relay Selection in Cooperative Cognitive Radio Networks

This paper investigates relay selection policies in a full-duplex (FD) based underlay cooperative cognitive radio network. We consider a scenario consisting of multiple pairs of primary users (PUs) with access to the spectrum, and multiple pairs of secondary users (SUs) with no dedicated spectrum access. Each pair (PU or SU) comprises of a unique set of transmitter and receiver. The secondary transmitter (ST) supports the FD transmission with the simultaneous transmission of the information to its own receiver and reception of the designated PU signal for relaying. Firstly, we formulate an optimization problem to maximize the PU rate by optimizing the transmission power at the relay (i.e., ST), while keeping the SU rate fixed. Secondly, we propose two low-complexity relay selection schemes based on the sum rate maximization, namely, centralized successive and distributed prioritized matching schemes. Numerical results show that the proposed schemes perform close to exhaustive selection schemes.