The Research Of Proactive Spectrum Handoff Approach In Cognitive Radio Networks

Spectrum resources become more valuable due to the growing demands of mobile communication and wireless broadband access business. Fixed frequency assignment gradually shows its inherent drawbacks, especially for the spectrums in some certain frenquencies that lack of resources. This situation triggers communication industry to seek a better solution to deal with this issue. Cognitive radio technology has been proposed to solve the contradiction between spectrum shortage and growing demand. Cognitive radio technology improves spectrum utilization by enabling secondary users to access unutilized spectrum of primary user in an oppotunistic manner. However, spectrum mobility causes disruptions to both primary and secondary users'communication and leads to high switching overhead.In this thesis, we focus on spectrum handoff issues. We propse a novel proactive spectrum handoff approach based on time estimation (TPSH). This can reduce the communication disruptions to primary users and increase the channel utilization efficiency.In section 3, we propose a proactive spectrum handoff model. Based on the analysis of existing spectrum management methods, we describe the details of the design of our model. In section 4, we propose our proactive spectrum hadoff approach. Secondary users utilize past channel histories to maintain a list of estimation results of channel remaining idle periods and make predictions on future spectrum availability, and then schedule the channel usage in advance. We propose a smart target channel selection and switching algorithm to improve the above approach. Simulation results show that our approach can significantly reduce the communication disruption to primary users by up to 32%, and improve the overall channel efficiency by about 7%-18%.