Interference Alignment With Delayed CSIT

In recent years,with the rapid development of wireless communication technologies and the upgrading of smart devices,users' demands for communication services have become increasingly diversified,and the required transmission rates have become higher and higher.In order to improve the service performance of the wireless communication system,MIMO technology has begun to be widely applied in modern wireless communication systems.However,the interference caused by multiple cells and multiple users greatly limits the effectiveness of MIMO technology.Therefore,more advanced interference management technology has become one of the most important challenges in wireless communication.As a very promising interference management technology,interference alignment(IA)technology has received great attention from researchers.However,traditional interference alignment schemes require perfect channel state information at the transmitters(CSIT).This requirement is difficult to be satisfied in practical wireless communication systems.Therefore,the research of interference alignment technology based on the delayed CSIT is more practical.This paper mainly studies the interference alignment technique based on the delay CSIT for multi-cell multi-user MIMO interfering multiple access channel(IMAC)system with arbitrary configuration.First of all,this paper give a specific interference alignment scheme based on the delay CSIT for a special case of system configuration.Through this scheme,we briefly introduce how to use the delayed CSIT to accomplish interference alignment and enable readers to have an intuitive understanding of interference alignment schemes based on the delay CSIT.Then,for comparative analysis of performance of the IA scheme proposed in this paper,an existing interference alignment scheme based on the delay CSIT for a two-cell MIMO IMAC system with partially configuration is briefly introduced,along with the degree of freedom achieved by this scheme.Then the interference alignment technique based on the delay CSIT is studied in detail for multi-cell multi-user MIMO IMAC system with arbitrary configuration.The main idea of this technology is that:Users in each cell send their data symbols to the base station in the first few phases,respectively.The number of transmitted data symbols exceeds the decoding capability of the base station.Then in the last phase,the delayed CSIT and the unrequited received signal vectors of each base station in the previous phases are used to design the user's transmit signal vector,so that the users of the two cells can sent their data symbols simultaneously to their own base station at the same time to provide base station with enough additional equations to solve all of their required data symbols without causing new interference to another base station,thereby accomplishing interference alignment to improve performance.In addition,this paper also show that how to use time slot expansion to save the number of time slots required to send the same number of data symbols or to reduce the complexity of the solution design.In addition,it explains in detail why the redundant signal is added to make sure that the proposed schemes works.Furthermore,how to choose the appropriate transmission scheme under different system configurations and how to set suitable parameters for this scheme are discussed in detail.The total degree of freedom(Do F)that can be achieved by all base stations in each time slot of each scheme is characterized.In addition,this paper also compares the performance of the proposed scheme in this paper with the existing two-cell scheme applicable to partial system configuration from theoretical analysis and simulation comparison.