Research On Spectrum Access Algorithm Based On Game Theory In Cognitive Radio Networks

Due to Cognitive Radio(CR) has the characteristics of secondary usage for free spectrum resources, it can help secondary users(SUs) dynamically using one or more period of idle spectrum resource under the premise of not interfere with primary users(PUs) communication quality, realize the sharing of unoccupied spectrum hole between the user and the primary user, and solve the problems of reusing non-renewable spectrum resource and the problem of low spectrum utilization. Therefore, CR technology is known as one of the most important technology of new generation wireless communications development.Spectrum access technology as one of core technology in cognitive radio provides a feasible solution for SUs reasonably and efficiently using idle spectrum resources in a changeable environment, and waiting for an opportunity to use idle spectrum resources for data information transmission in a certain time, space and frequency. The selection process that SUs in CR system compete with each other to waiting for an opportunity to access to a period of idle spectrum of the PUs system can be seen as a spectrum rental market. In the process, there are the game process among the SUs for leasing idle spectrum, the game process among the PUs for renting idle spectrum and the united game process between PUs and SUs. Therefore, we can use game theory method in microeconomic theory to find the Nash equilibrium point for the game process of leasing idle spectrum, which is the optimal strategy point in the spectrum access.The paper explores in detail the two specific research areas of spectrum access technology, namely MAC protocol and spectrum allocation technology. Firstly, the paper classifies and analyzes the MAC protocols in detail, and according to the different ways of spectrum access, and the paper emphatically expounds the advantages and disadvantages of different MAC protocols. Secondly, the paper classifies and discusses spectrum allocation technology comprehensively. Finally, the paper has analyzes the performance according to different nature classification of the spectrum allocation technology with the classical mathematical model or microeconomic theory model, and provides specific solutions including the following four aspects: the graph coloring model based on graph theory, interference temperature model, auction model and game theory model.In addition, the paper focuses on studying the spectrum access problems in CR using game theory model, gives the general model of spectrum access based on game theory in CR, builds a system model suitable for the spectrum access in CR, and designs two kinds of spectrum access algorithm based on the duopoly game model, namely Cournot game model and Stackelberg game model. The spectrum access problem is formulated as the times users to maximize their effectiveness in game when the lease spectrum, and the primary user in order to maximize their earnings, reasonably determine the sale price of the spectral behavior. The paper specifies the spectrum access problem more visually and intuitively to the game process of SUs who maximizes their own benefits when leasing spectrum and PUs who reasonably determines the behavior of the spectrum sale prices in order to maximize their own profits.Finally, the paper verifies the proposed algorithm by using Matlab7.1 tool. The paper analyzes that SUs reasonably adjust the spectrum bandwidth leased behavior from four aspects: the existence of Nash equilibrium point, the game process and convergence of SUs, the total amount of spectrum rented by SUs and the income of SUs. Simulation results show that the scheme makes full use of idle spectrum resources and at the same time maximizes the utility of SUs and PUs. In addition, under the condition of the same SNR, compared with the Cournot model, Stackelberg game model can pursue more amount of leasing spectrum bandwidth, ultimately make that the total amount of leased spectrum of SUs is greater than the latter, and improves the spectrum utilization rate, but increases the lease spectrum price, leading to the income of the former is lower than the latter.