Graph Theory Based QoS-guaranteed For Cognitive Radio Networks

Spectrum resource is a kind of important fundamentality resource. Recenlty,the number of wireless devices increase sharply, spectrum resource confront aserious challenge which is large scale demand. However, spectrum is controlledby nation telecommunications management department, in order to manageexpediently, the rule which specific business can only be serviced by specificspectrum is adopted to fullfill the spectrum allocation. Large amont of usersmaybe have sparse spectrum to use, while much idle spectrum in authorizedspectrum is rarely usesd. It constitutes a contradictory phenomenon. In order tosolve this bottleneck, cognitive radio techonolgy is proposed and deeplyresearched.In cognitive radio networks, cognitive users who access the spectrumservice opportunitily have little protect because they are not allowed to interferethe authorized users and they should evade the arrival of authorized users.Therefore, cognitive users have lower QoS guarantee. Aimming at this problem,this paper mainly researching how to guarantee the QoS of cognitive users inspectrum allocation link. And main research contents include：Firstly， aimming at specific problem, this paper puts forward theprecondition of research is QoS classification for cognitive users, i.e. accordingto the needs of the various aspects, divide cognitive usrs into high and low levelsaccordingly. Because joint decision involves many parameters, therefore, fuzzydecision process is usesd to classify the QoS level. This part analyzes thespecific features of this solution methods, and do some foreshadowing forfollow-up work.Secondly，this paper presents the physical background and research target,points out the core of research method. In this big framework, this paper ayalyzesthe channel quality for each cognitive users, meanwhile, according to the channelquality, the trasmission time of users will be estimated roughly. To decide whichchannel is the best suitable for the user, we caculate the arriving probability ofauthorized users of each channels during the transimission slot. In the process ofestimating channel state, this paper adoptes two schemes, and analyses theadvantages and disadvantages of each scheme, meanwhile, pointing out theapplication environment and calculating accurate.Finally, through the previous preparetion, aimming at the process of matching the users and channels. This paper proposes two kinds of mathcingalgorithms based on the graph theory matching. The starting point of these twokinds of algorithms is different, but the objective are both complete the matchingprocess effectively. This paper analyzes the performance of the two methods andgives the simulation results of each algorithm, and compares the simulationresults. Through these graphics simulation, verify the evaluation for eachsolution. At last, in order to guarantee system QoS, this paper briefly describeschannels transfer strategy, through the high and low level users have differenttreatment, further guarantee the QoS of cognitive users. Complete the wholecognitive user communication process.