Research On Power Allocation In Cognitive Tow-path Relay Network

Cognitive radio is an effective way to improve the spectrum utilization and solve the shortage of spectrum resources.The relay collaboration technology can obtain high transmission rate with low transmission power through multi-hop signal forwarding,and two path relay model is an effective measure to achieve continuous transmission of signals to further improve the transmission rate.Therefore,the combination of cognitive radio and dual path relay collaboration technology to form a dual path relay cognitive network can further improve the utilization of the spectrum,it is an effective way to realize broadband green communication in the future.In a dual path relay cognitive network,the transmission power of each node is limited,and the user signal transmission power and the relay forwarding signal power interfere with the authorized user at the same time.Therefore,the power distribution between the user and the relay,the relay and the relay is not only related to the system capacity of the cognitive relay network itself,but also directly determines the signal interference to the authorized user.In this paper,we study the power allocation problem of dual path relay cognitive network,mainly to complete the following work:(1)Aiming at the Decode-And-Forward(DF)dual-path relay cognitive network,the signal transmission process is deduced theoretically,and an optimal power allocation algorithm is proposed with the minimization of the probability of interruption.Firstly,the performance of the network is analyzed,and the approximate expression of the probability is deduced.Then,using the KKT condition to discuss the optimal power solution under different Lagrangian factors,the power optimal solution of the source node and the relay node are obtained under the given maximum allowable interference power of the main user and the maximum transmit power of the cognitive node.The algorithm optimizes the allocation of the power of the cognitive source node and the relay node under the condition that the communication quality of the authorized user is ensured and the transmission power of the cognitive node is limited.(2)Aiming at the dual-path relay cognitive network of Amplify-And-Forward(AF),the signal transmission process is deduced theoretically,and the throughput of the cognitive receiver is taken as the optimization target,an optimal power allocationalgorithm is proposed.Firstly,the performance of the network is analyzed,and the approximate expression of the system throughput is deduced.Then,the optimal power solution under different Lagrangian factors is discussed by KKT condition.The optimal power of the source node and the relay node is obtained under the condition of the maximum allowable interference power and the maximum transmit power of the cognitive node.The algorithm optimizes the allocation of the power of the cognitive source node and the relay node under the condition that the communication quality of the authorized user is ensured and the transmission power of the cognitive node is limited.Finally,the numerical simulation and performance evaluation of the proposed algorithm are carried out,and the correctness and validity of the scheme are verified by the simulation results.