Research On Interference Alignment With Limited Feedback

With the rapid expansion of wireless communication systems,the wireless spectrum resources become much scarcer.Multiple-Input Multiple-Output(MIMO)wireless technology can greatly improve the spectral efficiency and transmission rate without additional costs of the system bandwidth.However,with the increasing number of users and transmit antennas,the interference problems become a key issue in the capacity of wireless communication system.Interference alignment(IA)is a promising approach that can effectively reduce the interference and improve the system capacity.For IA approaches,the channel state information must be available at each transmitter.However,the channel state information needs to be obtained from the feedback channel in practical situations.The accuracy of the channel state information has a sufficient effect on performance of interference alignment scheme.To solve the problem of interference leakage caused by limited feedback of channel state information,a novel method for interference alignment based on dynamic feedback is proposed.Then on this basis,an improved method of interference alignment based on dynamic feedback and power allocation is proposed.Firstly,the basic theories of IA and limited feedback have been studied.Degree of freedom and precoding methods are introduced.Then,several typical IA algorithms are analyzed.Then,we analyze the performance of IA with heterogeneous path loss in K-user MIMO interference channels.The relationship between system sum rate and the allocation for channel state feedback bits is analyzed theoretically,and the formula of sum rate of the system considering dynamic feedback is derived.Based on the above analysis,the model of optimizing allocation for feedback bits is set to improve the throughput of system.Then,the feedback bit scheme is obtained by the Lagrange multiplier method.Simulation results show that the proposed method can effectively reduce the interference leakage and improve the system rate.Finally,we analyze the performance of IA in multiple data streams with limited feedback.The relationship between system sum rate and the allocation for channel state feedback bits and transmitting power is analyzed theoretically,and the formula of sum rate of the system considering dynamic feedback and power allocation is derived.To maximizing the sum rate of the interference system,a novel method for interference alignment based on dynamic feedback and power allocation is proposed.Simulation results show that the proposed method can further reduce interference leakage and improve the system sum rate.