Study On Joint Spectrum And Power Allocation Based On Graph Theory In Cognitive Radio

With the rapid development of wireless communication technology, the demand of spectrum resources is increasing drastically. However, the current fixed spectrum allocation policy seriously hampers the sustainable development of wireless communication and applications.Cognitive radio technology can proactively detect wireless communication environment to dynamically access to the vacant band which are not used by licensed users. It also can make spectrum resources shared between cognitive users and licensed users, thus it can significantly increase the capacity of the communication system and improve the spectrum efficiency. Resource allocation is the key technology of cognitive radio, which is an important step for realization of cognitive radio. This paper focuses on the joint spectrum resource and power resource allocation algorithm based on graph theory in cognitive radio systems. The main work of this paper is as follows:(1) The research background and significance of the resource allocation are elaborated. Research status at home and abroad is summarized. The fundamental knowledge of the cognitive radio resource allocation and graph theory is introduced.(2) Aiming at the problem that the basic model cannot be applied to implement the joint allocation of spectrum and power and the problem that the basic model has low spectrum utilization. This paper proposes an improved model and a joint allocation algorithm based on the model (referred to as JSPA-IGTM algorithm). The interferences among secondary users are considered and subdivided fully. The interference threshold vector is used to measure the degree of interference. The allocation of spectrum and its corresponding power is implemented based on the degree of interference. The method of particle swarm optimization is used to realize the process of the system joint resource optimization allocation in this algorithm. Simulation results show that JSPA-IGTM algorithm has better performance compared with the existing resource allocation algorithm based on graph theory model and it improves spectrum utilization effectively.(3) Aiming at the problem that PSO (Particle Swarm Optimization) algorithm is easy to fall into local optimum when it is used to realize the joint optimization allocation for spectrum and power based on the improved model. This paper proposes an improved algorithm to achieve optimal allocation of spectrum and power (referred to as JSPA-IPH algorithm). Both advantages of PSO algorithm and harmony search (Harmony Search, HS) algorithm are integrated in this algorithm respectively. That is, JSPA-IPH algorithm not only has the good global optimization ability, but has the fast convergence rate. Simulation results show that the JSPA-IPH algorithm adapts well to the improved model and it improves the performance of system throughput significantly.