Research On Heterogeneous Network Interference Management Technology Based On Space-time Interference Alignment

As one of the key technologies for the fifth-generation mobile communication technology to achieve high speed and large capacity,the ultra-dense heterogeneous networking based on large-scale multiple input and multiple output can improve spectrum efficiency,energy efficiency and system capacity.Although ultra-dense heterogeneous networks have great research value,as the types and numbers of nodes in heterogeneous networks increase,the types of interference introduced are diversified,especially the cofrequency caused by co-frequency multiplexing between different nodes.Interference will seriously affect the communication performance in the network.Eliminating different types of interference in ultra-dense heterogeneous networks is the key to improving service quality.The research content and main contributions of this paper are as follows:1)For two-tier heterogeneous networks,a joint space-time interference alignment(JSTIA)scheme using current and outdated channel state information at the transmitter(CSIT)is proposed.First,the space-time interference alignment in the homogeneous network is extended to the multiple-input single-output(MISO)hybrid channel of the two-tier heterogeneous network,and the relationship between the achievable degree of freedom and the CSI feedback delay is studied.The results show that increasing the number of antennas at the transmitter can increase the degree of freedom of the system.Then,the space-time interference alignment is extended to the multiple-input multipleoutput(MIMO)hybrid channel of the two-tier heterogeneous network.The influence of the antenna ratio of the transmitter and the receiver on the degree of freedom of the system is studied,and the influence of the number of antennas at the receiver on the feedback delay is explored.Theoretical and simulation analysis show that the JSTIA scheme can eliminate the interference signal in the two-tier heterogeneous network in a shorter time slot,and obtain a higher degree of freedom.2)Aiming at the loss of freedom that may be caused by the antenna ratio of the transmitter and the receiver in the MIMO hybrid channel of the two-tier heterogeneous network,a multiphase interference regeneration scheme is proposed.Studies have shown that the multiphase interference regeneration scheme can further reduce the loss of freedom and increase the degree of freedom of the system.In order to break through the JSTIA scheme's limitation on the number of picocells,the space-time interference alignment scheme of the MISO hybrid channel of the two-tier heterogeneous network under arbitrary picocell configuration is studied,a heterogeneous multi-node extended interference alignment scheme is proposed.This scheme eliminates the interference signal generated by the increase in the number of micro cells.Furthermore,a multiphase JSTIA scheme is proposed for the MIMO hybrid channel of two-tier heterogeneous network under arbitrary pico cell configuration.By designing the precoding matrix at the transmitter and constructing a retrospective decoding structure,this solution can make up for the loss of system freedom and increase the reachable rate of the system.