Research On Spectrum Handoff For Delay-sensitive Service Over Cognitive Radio Networks

Nowadays delay service has been an important type of traffic over cognitive radio network(CRN). As the key technology in CRN, spectrum handoff technology directly determines the performance of transmission services. Different with traditional communication networks, the Primary Users(PUs) have a priority to use channels. However, the Secondary Users(SUs) only could access idle channel in an opportunistic manner. The unique property of CRN leads to the system unstable, the spectrum handoff technology is born to solve this problem. By designing the channel allocation rules, spectrum handoff realize the coordinated scheduling between users. The research on spectrum handoff for multimedia traffic over CRN is so rare that require in-depth research on spectrum handoff in multimedia.Delay service is featured with high delay requirements. In the past, data-oriented traffic adopte ”Best Effort” model, but this traffic model increasingly unable to meet the requirements of delay services. Based on the traditional spectrum handoff technology, we poposed a spectrum handoff strategy for delay service transmission scenario according to the characteristics of delay services. In chapter II, breifly introduce the concepts of spectrum handoff technology, after reading a mount of relevant literature, then summarized the spectrum handoff schemes and a detailed analysis of the pros and cons of different spectrum handoff strategies, in addition introduced the applications scenarios. In chapter III, we take into account the bandwidth requirement of delay services and studied the role of buffer queue mechanism to improve channel utilization, lower blocking probability and force termination probability. Taking into account the characteristics of delay-sensitive of delay services, delay services in the chapter IV will be divided into different priorities,focusing on the influence of priority policy to handoff delay.Finally, taking into account the different QoS needs of different types of delay service, in Chapter V, delay services are divided into four-class of priorities. And based on the research foundation of the previous two chapters, we presented a spectrum handoff scheme which is integreted buffer queue mechanisim and multi-priorities strategy. In this chapter, delay services are divided into two types, real-time services and non-real-time services, and real-time services have a higher priority than non-real-time services; secondary users are divided into handoff users and new arrived users and handoff users have a higher priority than new arrived users. If the system is not available for the channel,the secondary users can enter into the finite-size buffer queue waiting for service. On the one hand, finite buffer queue reduced the force termination probability and incread system throughput, on the other hand to ensure the fairness among users. In addition,the introduction of a central base station is responsible for users to synchronize information to avoid collisions between users. This thesis established a preemptive resume priority M/M/c/c + k Markov model was used to analyze the spectrum handoff algorithm performance, including call blocking probability, throughput, average completion time of transmission of real-time traffics. And using MATLAB to simulation, theoretical analysis and simulation results show that the proposed algorithm can satisfy the QoS requirements of different types of businesses.