Performance Analysis Of Collaborative Relay Transmission Based On Cluster In Underlay Cognitive Networks

With the rapid development of wireless communication technology,the explosive growth of the number of wireless users leads to the increasing demand for spectrum resources.How to effectively improve the utilization of spectrum is very critical.Cognitive radio is considered as an effective solution to the scarcity of spectrum,and has attracted wide attention.In the underlay mode of cognitive radio,the primary and secondary networks can use the channel together,however the transmitting power of secondary users is strictly limited,so the transmission range is limited and the communication quality is poor.Therefore,scholars have introduced the relay cooperative transmission into cognitive radio.However,previous forwarding strategies can't dynamically adjust forwarding strategies according to actual needs,and many studies don't consider the energy consumption caused by adopting forwarding strategies.And the established system model usually ignores the influence of the primary network on the secondary network.Firstly,a system model with mutual interference is established,and the best relay forwarding strategy with potential relay is proposed under this model.The signal to interference plus noise ratio of the primary and secondary networks are analyzed in detail,and the end-to-end SINR distribution function of the strategy is derived by the convolution formula.The explicit expressions of outage probability and bit error rate are derived.The proposed forwarding strategy is simulated numerically,and it's performance is compared with the traditional best relay and direct communication.Secondly,in order to reduce the energy consumption and prolong the life of the secondary network,a clustering algorithm based on residual energy is proposed.Through two cluster structure determination cycle,all relay nodes are divided into cluster heads or cluster members.Cluster head is responsible for acquiring channel state information and determining the number of forwarding relays,which saves the energy of other relays.And this paper gives the specific operation process and pseudocode of the algorithm.Then,an adaptive relay and forwarding strategy with cluster structure is proposed.By setting the performance requirement threshold?_th and interference thresholdI_th,the number of forwarding relaying can be determined adaptively.The distribution function of SINR of primary network and secondary network is deduced,and the outage probability,bit error rate and throughput of secondary network are calculated.The performance of the primary network is studied when it is disturbed.Finally,the adaptive relay cooperative transmission strategy based on cluster structure is numerically simulated by MATLAB,and compared with best relay and direct communication.The factors affecting the performance of primary and secondary networks are revealed.