Resource-Allocation Strategy for Multiuser Cognitive Radio Systems: Location-Aware Spectrum Access

This paper considers a new power strategy and channel-allocation optimization for secondary users (SUs) in an orthogonal frequency-division multiplexing (OFDM)-based cognitive radio (CR) network where the coverage area of the secondary network is divided into an overlay region and a hybrid region. SUs in the overlay region can adopt the overlay spectrum access method, whereas SUs in the hybrid region may adopt the underlay or sensing-free spectrum access method. We first present a general resource-allocation framework that optimizes the power and channel allocation to SUs who adopt these different spectrum access methods, depending on their locations. To enable sensing-free spectrum access, we then propose a new algorithm that incorporates an interference violation test to decide the parameters in the general framework. The proposed scheme intelligently utilizes frequency and space opportunities, avoids unnecessary spectrum sensing, and minimizes overall power consumption while maintaining the quality of service (QoS) of a primary system. Simulation results validate the effectiveness of the proposed method in terms of energy efficiency and show that enhanced performance can be obtained by utilizing spatial opportunities.