Scheduling Model for Cognitive Radio

The priority queue model divides CR (cognitive radio) system users into primary user and secondary user. The primary user has preemptive priority over secondary user, while the same priority level users are FIFO served. This paper models the CR system based on scheduling technology. The secondary users are further divided into different priority levels. A hybrid priority dynamic policy, which indicates primary user's preemptive priority and secondary user's nonpreemptive priority, is developed to reduce spectrum switch overhead during spectrum leasing process. Theoretical analyzing shows that hybrid priority reduces the spectrum switch overhead and the hybrid priority improvement is a non-negative mono-increasing function of priority level. Based on the proposed policy, CR scheduling model is built and CR scheduling rule is provided and proved. Experimental comparison between CR scheduling and priority queue shows that CR scheduling gets a smaller weighted staying time sum than priority queue and the improvement increases as system becomes more congested.