Study On The Power Control Technology In Cognitive Radio Network

Cognitive Radio (referred to CR) is considered to be the "Next Big Thing" in the future wireless communication field. As the information age coming, the wireless business and its demand grow rapidly which lead to the scarcity of the spectrum resources. How to improve the spectrum utilization, and then further improve the system capacity and the service quality in next-generation wireless communication is an urgent problem. The power control algorithm is a widely-discussed key technology in CR wireless communication, the main goal of which is to avoid interferences upon secondary users so as to ensure communication quality, and to make sure that the rate of the secondary users meets performance requirement to improve the spectrum utilization.Based on the characteristics of cognitive radio technology, we make a deep study on power control algorithm in cognitive radio networks. This thesis tracks the recent direction of studies on power control in cognitive radio networks and summarizing their pros and cons. A detailed instruction is given on design of the power control algorithms under the effects of centralized and distributed network architecture. Considering the above issues, we give a new cooperated allocation algorithm joint bandwidth and power as well as a new non-cooperated power control algorithm based on new pricing function. The performances of the schemes are proved and examined by mathematic analysis and computer simulation. Meanwhile, we study these algorithms on difference path loss, and further lead to their system throughput respectively. Below are our main innovations.Firstly, we proposed a new noncooperation power control algorithm in cognitive radio networks. The effects of the secondary users towards primary users are considered in algorithm model, and a new pricing coefficient model is proposed in this thesis. The existence and uniqueness of the Nash equilibrium solution for the algorithm is proved through a strict game theory. And we compare our algorithm to SINR balance algorithm and Koskie-Gajic algorithm.Secondly, a cooperated allocation algorithm joint power and bandwidth in centralized cognitive radio networks is proposed in this paper, which considered the effects to channel capacity of the cognitive network due to both power and bandwidth. The total channel capacity is the objective function and multiple optimized. By solving the objective function, the optimal allocation of bandwidth and power is achieved. Simulation results show that, compared with the average distribution of the power and bandwidth, the algorithm in this paper can greatly improve the effectiveness and system performance.Thirdly, difference wireless communication channels have difference path loss, based on which channel capacity of secondary users under difference path loss is analyzed, and then lead to the SU’s channel capacity functions under difference path loss.The last part of the thesis is the summary, where the future research direction is pointed out.