Energy Efficiency Optimization In Cognitive Radio Networks

With the rapid development of wireless communication technologies,limited spectrum resources can no longer meet the growing demand for data services.Fortunately,secondary users(users without licensed)can use cognitive radio technology to access licensed bands in an opportunistic way,which improves spectrum utilization.In the cognitive wireless network,before the secondary user accesses the licensed channel,in order to avoid a collision with the primary user(licensed users),it is necessary to periodically perform spectrum sensing.If the channel is idle,the secondary user can access the channel transmission.However,the secondary user's spectrum sensing and transmission behavior needs to consume energy.If the energy is not properly allocated and managed,the performance of secondary users and even the entire secondary network will be affected.This article focuses on the following two network scenarios for energy optimization of secondary users:1.In cognitive radio networks where the secondary user's energy is limited,this paper optimizes sensing time from the perspective of sensing accuracy,energy consumption and network throughput.And because of the improvement of sensing accuracy can not only reduces the secondary users' interference with the primary user,but also increases the secondary user's transmission opportunities and improves the energy efficiency of the secondary network.Therefore,this paper further proposes the idea of separating the secondary users' spectrum sensing and data transmission process,and introduces a mechanism for assisting the sensing and sharing of the sensing results among secondary users to rational allocation of spectrum sensing and transmission channels.Under the premise of satisfying the spectrum sensing accuracy,the purpose of improving the network energy efficiency is achieved.2.In a cognitive radio network based on energy harvesting technology,the secondary user adopts a working method of first collecting energy and then data transmission in each cycle.When there are multiple licensed channels are available,taking into account the differences in transmission capabilities of secondary users on different channels and the differences in energy collection capabilities of secondary users.With the goal of optimizing secondary network throughput,this paper proposes a channel allocation algorithm considering the user's transmission quality and energy collection efficiency,after determining the transmission channel of the secondary user,under the constraints of the energy causality,we further optimizes the transmission power and transmission time to balance the impact of the two on network throughput.And for the original non-convex optimization problem,the model is solved by converting it into a series of convex optimization subproblems.