Research On Spectrum Handoff Technology Based On Cognitive Radio

The development of wireless communication technology causes very heavilyincreasing demand for spectrum resources. However, the utilization of the existingspectrum allocation method in a fixed way is very low. In order to solve such situation,the idea of cognitive radio has been proposed. The cognitive users can occupy spectrumresources in an opportunistic way, which is not used by authorized users. Throughspectrum sharing, the problem of spectrum resources scarce is well resolved meanwhiledo not change established allocation of spectrum resources.Characteristics of dynamically available of cognitive radio spectrum resourcesmake frequent changes in the use of spectrum resources. Thus, spectrum switch is a keytechnology in the cognitive radio spectrum. Its core study aims to solve two problems:1.ensure cognitive user communications continuity2.minimize the interference to primaryusers. We study exist switch technology in detail from this two aspects and comparereactive handoff and proactive handoff method. This paper we focus proactive handoffmethod and propose an improving proactive handoff algorithm. We simulate andcompare each of different strategies meanwhile considering exist shortcoming ofsimulation and scene of multiple users.Firstly, we research the basic theory of cognitive radio and analyze the situation ofcognitive radio spectrum handoff, handoff execution process and key technology. Basedon existing research we propose an improved proactive handoff algorithm. Underdifferent situation our improved algorithm have better performance in reduce collisioncompared with original algorithm, we also analysis the factor which can affecting thealgorithm performance, the analysis is verified by the simulation.And then we do ansimulation in different strategy,compared with pure reactive handoff and reactivehandoff based on channel estimation，proactive handoff shows better performance,which verify the effectiveness of the proactive handoff. Finally, based on the proactivehandoff algorithm we use queuing theory analyze the handoff process in multi-userscenarios. We analysis the handoff process in different strategies which include randomaccess strategy and user priority strategy.In the two strategies we compare the performance of reactive handoff and proactive handoff. The simulation shows that inboth strategies our proactive handoff can decrease the conflicts and reduce theinterference.