Location-based subcarrier allocation scheme for secondary systems in cognitive radios

In cognitive radios, SUs (Secondary Users) coexist with PUs (Primary Users). The SUs detect those bands not used by the PUs through spectrum sensing, and transmit signals only within the limit not to interfere with the PUs. If we merely use the spectrum sensing information only in a cell with multiple PUs and SUs, the number of subcarriers that can be allocated to the SUs may be limited and making efficient transmission difficult. In this paper, we propose a location-based subcarrier allocation scheme that can improve the throughput, while avoiding interference related to SUs' locations. The proposed scheme consists of two steps; location information acquisition and location information utilization. In the first step, a proper localization scheme such as time difference of arrival is used to acquire SUs' locations. In the second step, the location information of the SUs is utilized to adaptively allocate the subcarriers of non-contiguous orthogonal frequency division multiplexing to the SUs. Simulation results show that the proposed scheme could allocate the subcarriers more efficiently than the conventional scheme, enable interference avoidance, and thus increase the throughput.