Spectrum decision for cognitive radio networks with various-bandwidth channels

Cognitive radio (CR) systems can enhance the licensed spectrum efficiency by finding and allocating the underutilized channels of the primary users to the secondary users. After scanning a wide range of spectrum. A general CR system needs to utilize all the available channels of various bandwidths. Whenever the active primary users appear, the secondary users shall return the borrowed channels, causing interruption even during a transmission period. The behavior of changing the operating channels is called hopping mode in this paper. In this paper we propose an improved preemptive resume priority (PRP) M/G/1 queueing network model for such a general CR system, aiming to characterize the impacts of hopping-mode behaviors and various bandwidth on the delay performance of the secondary users. We further propose a probability-based various-bandwidth channel selection scheme to reduce the overall system time for the hopping-mode secondary users with multiple interruptions, where the overall system time is defined as the sum of transmission time and waiting time. Our analytical results, validated by simulations, show that the proposed probability-based various-bandwidth channel selection scheme can improve the overall system time by 20% compared to the existing methods.