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Flexible full-duplex cognitive radio networks by antenna reconfiguration

Full-duplex radio has been recently proposed to enhance spectrum utilization of secondary networks by a "listen-and-talk" (LAT) protocol. It allows one antenna of the secondary user (SU) to sense the spectrum band, while the other antenna simultaneously to perform data transmission. Due to wireless channel characteristics, in this paper, we introduce antenna mode selection to the LAT protocol to achieve additional spatial diversity. Specifically, each SU adaptively selects one antenna for sensing while the other for transmission, according to their channel information. Two selection schemes are given: the optimal antenna mode selection maximizes the secondary throughput performance by comparing the exact secondary throughput of all antenna modes, and a suboptimal method selects the antenna with higher sensing signal to noise ratio (SNR) to transmitting SNR ratio for sensing, named ratio antenna mode selection (R-AMS). Simulation results indicate the throughput improvement caused by additional spatial diversity with antenna mode selection and the effectiveness of R-AMS.