Harvesting Spectrum Access Opportunity With Directional Antennas in Indoor Environments

Dynamic spectrum access through time-sharing or power control has been extensively explored in cognitive radio networks (CRNs). However, when a secondary user (SU) is located within the interference range of a primary user (PU), efficient spectrum sharing in the spatial domain becomes a challenge. To further improve spectrum efficiency, we propose a novel coexistence approach to finding spectrum access opportunity for the SU in complicated environments, such as indoor space. Our approach is to enable concurrent transmissions of the SU and the PU even if they are within the interference range of each other. By utilizing the antenna directivity and multipath effect, strong signal power could be achieved at the SU receiver. By adopting the optimal directional transmitting-receiving pattern at the SU pair, we could strengthen the intended signal while suppressing the interference to/from the PU. As a result, the SU pair could harvest the coexistence opportunity with PUs through non-line-of-sight (NLOS) communications. Moreover, the proposed approach potentially contributes to improved signal-to-interference-plus-noise ratio (SINR) and energy consumption. The experimental result confirms that more access opportunities for SUs can be seized with the proposed approach.