Research On Interference Alignment Techniques In Cognitive Networks

With the emergence of more and more new wireless communication services and technologies,the original fixed spectrum resource allocation strategy is difficult to meet the new requirements.Therefore,the proposal of cognitive radio technology has brought great changes to the utilization of spectrum resources.Cognitive users find spectrum holes through spectrum perception,and adjust their parameters to access the main user’s frequency band without affecting the communication quality of the main user,so as to significantly improve the purpose of spectrum utilization.Interference in the cognitive system is a core problem that cannot be ignored.Therefore,this paper focuses on the interference alignment technology in cognitive multiple-input multiple-output networks.This paper aims at a pair of primary users and many-to-second users cognitive multiple-input multiple-output(MIMO)system,through the two precoding design of the sending end of the secondary user,on the basis of eliminating the interference between the primary and secondary users,the interference between the secondary users is reduced,and the system capacity is effectively improved.The first precoding design uses the water injection method to align the interference of the cognitive user to the primary user to the spatial subchannel that the primary user is not using,and the second precoding design uses the maximum signal-to-interference noise ratio algorithm to eliminate interference between secondary users.The simulation results show that the algorithm effectively eliminates the interference to the primary user,and the throughput of the secondary user is significantly improved compared with the traditional cognitive system water injection power allocation method.In addition,for the cognitive multiple-input multiple-output(MIMO)system of multiple pairs of main users and cognitive users,this paper designs the precoding matrix of the sending end of the cognitive user and the interference suppression matrix of the receiving end,which eliminates the interference of the main user to the cognitive user and the interference of the cognitive user to the main user.Then,the least interference leakage algorithm is used inside the cognitive network and the main user network to eliminate interference within the network.Through the analysis of the simulation results,it can be seen that the throughput of the whole system is improved compared with the traditional distributed interference alignment algorithm under the premise of ensuring the priority of the main user.