双层异构网络中基于有限反馈的空时干扰对齐研究

Research on Space-Time Interference Alignment with Limited Feed-Back in Two-Tier Heterogeneous Networks

本文针对双层异构网络,提出一种利用当前和过期发射端信道状态信息(Channel State Information at the Transmitters,CSIT)的异构空时干扰对齐(Heterogeneous Space-Time Interference Alignment,HSTIA)方案.该方案将空时干扰对齐拓展至双层异构网络MISO(Multiple Input Single Output)混合信道,研究可达自由度关于CSI(Channel State Information)反馈时延的折中域.结果表明,增加发射端天线数能有效提高可达自由度.基于该结论,将空时干扰对齐技术扩展至双层异构网络MIMO(Multiple Input Multiple Output)混合信道,分析MIMO系统发射端与接收端天线数比对系统自由度的影响,并进一步研究系统达到该自由度时CSI反馈时延的取值范围.结果表明,当发射端与接收端天线数比足够多时,系统自由度的稳健性随接收端天线数的增加而加强.通过仿真分析验证,HSTIA方案利用本地当前和过期CSIT执行发射预编码,实现不同时隙的干扰信号相互消除,从而获得自由度增益,以提高系统的可达速率.

In the context of two-tier heterogeneous networks,a heterogeneous space-time interference alignment(HS⁃TIA)scheme using current and outdated channel state information at the transmitters(CSIT)is proposed.First,the spacetime interference alignment technology is extended to the two-tier heterogeneous network MISO(Multiple Input Single Out⁃put)hybrid channel,and the compromised domain of the achievable degree of freedom on the CSI(Channel State Informa⁃tion)feedback delay is studied.The results show that the achievable degree of freedom is affected by the number of anten⁃nas at the transmitters.Then,the space-time interference alignment technology is extended to the two-tier heterogeneous network MIMO(Multiple Input Multiple Output)hybrid channel.The impact of the ratio of the number of antennas at the transmitters and the receivers of the MIMO system on the degree of freedom of the system is analyzed.Further,the range of the CSI feedback delay when the system achieves the degree of freedom is studied.The results show that when the ratio of the number of antennas at the transmitters to the receivers is sufficient,the robustness of the total degree of freedom of the MIMO system increases with the increase of the number of antennas at the receivers.Theoretical and numerical analy⁃ses show that,by precoding with current and outdated CSIT,HSTIA can achieve better sum-DoF by eliminating inter-user interference perfectly,as well as improve the achievable rate of the system.