Research On Algorithm For Interference Alignment Based On Rank Minimization In Cognitive Radio

With the development of communication technology and the constant pursuit of network speed,the limited nature of spectrum resources can not meet the constant pursuit of high rate.Therefore,maximizing the use of spectrum resources becomes an urgent problem to be solved.Multi-user multiple input multiple output(MIMO)can increase the spectrum utilization without increasing the spectrum resources,but it also introduces the interference which may lead to serve the performance degradation.There are many ways to eliminate the interference,but most of the methods only can get /1K spectrum resource when K users share spectrum resource.Recently interference alignment becomes a promising approach to enhance the spectrum utilization,as a result each user can get 2/1 spectrum resources.Simulations demonstrate that the degree of freedom of receiving subspace is important to the performance of the whole system,and the method of the rank-bound interference alignment can improve the degree of freedom of useful signal.Therefore,this work develops the rank-minimization interference alignment algorithm in cognitive radio.The contents of this paper are as follows:1.In this paper,The research status and development prospect of cognitive radio(CR),MIMO,interference alignment are expounded,and the interference problem involved in spectrum sharing is reseached.The relevant principle of interference alignment technology is analyzed in depth..2.According to the interference of the secondary users to the primary user,this paper uses the rank constraint interference alignment method as the constraint condition.On the one hand this method can make the interference signal and the desired signal separation,on the other hand it can reduce the dimension of the interference signal,and enhance the desired signal space.3.According to the mutual interference between secondary users,this paper uses the method of rank constraint interference alignment to minimize the interference of secondary users and improve the dimension of secondary users' expectation signals..4.Due to the non-convexity of the rank,this paper uses convex optimization method to approximate the problem,and the iterative method is used to optimize the precoding matrix of the transmitter and the interference suppression matrix of the receiver.5.Considering the different channel state information,this paper analyzes and compares the ideal channel state and non-ideal channel state respectively.6.In order to verify the feasibility of the rank minimization interference alignment,we simulate the convergence of the rate,reuse gain,interference leakage,iteration number and iteration times respectively,the simulation results show that the method of rank minimization interference alignment is feasible.Compared with the traditional minimized power,the performance of the rank minimization interference alignment is better.