Cache-Aided Interference Alignment In Wireless Networks With Delayed CSIT

With the development of wireless communication technology and the diversification of communication services,users have higher and higher requirements on transmission rate.In order to meet the higher transmission rate,intensive network deployment is now carried out.However,due to the scarcity of spectrum resources,the wireless network communication needs to rely on spectrum reuse,which leads to interference.Therefore,effective interference management technology is very important.Interference Alignment(IA),as a useful interference management technology,can effectively eliminate interference and improve the performance of the system.However,the traditional interference alignment technology needs perfect the channel state information at the transmitters(CSIT),which is difficult to achieve in reality,therefore,interference alignment with delay CSIT has been widely studied.In addition,cache at users can be used to eliminate interference in wireless communication networks.Therefore,in this paper,for the single-input single-output(SISO)X network,a cache-aided interference alignment scheme with delay CSIT is proposed.In this paper,an SISO X network is considered,which contains a library,two transmitters and K users.The transmitters are connected to the library and the transmitters are connected to the users through the wireless links.Each transmitter can deliver desired symbols for any users.The transmitters and the users are equipped with cache.When the system is idle,the transmitters and the users can cache the files in the library.However,each transmitter and each user have the limit of the cache capacity and cannot cache all the files in the library.For this system,a cache-aided interference alignment scheme with delayed CSIT is proposed in this paper.The scheme consists of two phases,namely the Prefetching Phase and Delivery Phase.In the Prefetching Phase,we carefully choose the context in transmitter cache and user cache,so as to relieve the traffic pressure in the peak period.In the Delivery Phase,each user has specific requirements.According to the contents at users,transmitters only need to deliver the uncached part.In this paper,different transmission schemes are proposed for different system configurations,so that the base station can utilize the delayed CSIT to construct high order symbols for transmission.Meanwhile,this paper presents the calculation method of Degrees of Freedom(DOF).In addition,under a special system configuration,this paper provide a lemmma to characterize the Do F of the system.Finally,this paper analyzes the performance of this scheme through simulation.The results show that the proposed scheme can achieve up to 79% Do F gain against the IA scheme with delayed CSIT but without cache,while up to 29% Do F gain against the cache-aided time divide multiple access(TDMA)scheme.Note that in the proposed scheme,the generation of order-2 symbols does not need CSIT,while in the existing scheme of interference alignment with delayed CSIT,the generation of order-2 symbols requires CSIT.Therefore,when only order-2 symbols are sent,and no higher order symbols are generated,the scheme in this paper will reduce to a blind transmission scheme.Therefore,for the specific system configuration where only order-2 symbols are delivered,the scheme will be reduced to blind transmission scheme.