Research On Non-Orthogonal Multiple Access Resource Allocation Algorithms In Cognitive Radio Networks

With the rapid development of various mobile devices,the demand of users for data rate is growing rapidly.And current mobile communication systems are facing the scarcity problem for available spectrum resources.Compared with the traditional cognitive radio networks,the application of non-orthogonal multiple access technology in cognitive radio networks can improve spectral efficiency and the number of accessible users,which has become a research hotspot in recent years.Due to the rapid increase in energy consumption,energy efficiency of communication systems needs to be further improved,which is significant to green communication.In this thesis,considering the non-orthogonal multiple access technology in cognitive radio networks,power allocation and channel allocation problems are studied respectively with energy efficiency as optimization objective.To solve the non-orthogonal multiple access power allocation problem in cognitive radio networks,a two-stage power allocation algorithm is proposed.Firstly,a secondary users resource allocation model is formulated to satisfy the minimum quality of service of secondary users,interference power of primary users and fairness among users.Secondly,an auxiliary variable called subchannel power consumption rate is defined.And the closed expressions of upper and lower bounds of subchannel power consumption rate are derived respectively.Finally,using the difference of convex(DC)programming algorithm,an iterative power allocation algorithm is proposed to solve the optimal power coefficients of multiplexed users in sub-channels,and then the Dinkelbach-like algorithm and sub-gradient algorithm are used to solve the optimal power consumption rate of sub-channels.The simulation results show that the performance of the proposed power allocation algorithm is better than that of the traditional power allocation algorithms.In order to further improve network energy efficiency,a joint channel allocation and power allocation algorithms are proposed.Firstly,with the constraints of the interference power of primary users,the minimum throughput of secondary users and the maximum number of multiplexed users of a subchannel,the mixed integer nonlinear fractionalprogramming problem is modeled with energy efficiency as the optimization objective.Then,the original problem is decomposed into two sub-problems: channel allocation subproblem and power allocation subproblem.In order to improve the energy efficiency of the system and advoid reusing users with similar channel state information on the same subchannel,a suboptimal fairness adjustable channel allocation algorithm is proposed.Then successive convex approximation and Dinkelbach algorithm are used to solve the optimal subchannel power.The simulation results show that the proposed algorithm effectively improves the energy efficiency of the system and user fairness.