Research On Inter-cell Interference Suppression Technology Based On Message Passing Algorithm

Deploying dense base stations with higher frequency reuse factor in communication network can make full use of the scarce spectrum resources and significantly improve the system capacity per unit area.However,under the condition of deploying dense base stations,it is inevitably to bring more serious inter-cell interference(ICI),which seriously affects the communication quality of cell-edge users.Therefore,it is urgent to find efficient ICI suppression schemes in future communication network.The generation of base station cooperation technology provides a new idea for suppressing ICI,which can suppress the influence of interference to a large extent by multi-cell cooperation.Centralized cooperation has a quite high requirement of the backhaul capacity,so the distributed cooperation is more widely used at a relatively low overhead.Considering that the message passing algorithm based on factor graph has good characteristics in signal estimation and distributed computing,this paper applies the message passing algorithm based on factor graph to multi-cell base station cooperative system to suppress ICI,achieving good system performance.The main contents of this thesis are as follows:First,this paper studies the generating mechanism of ICI and the ICI suppression technique under base station cooperation,describes the message passing algorithm based on factor graph model,and gives the message calculation formula under the update rules of belief propagation(BP)and variational message passing(VMP).Then,for the uplink system in which the base stations have multi-antenna,the thesis studies the receiver cooperation distributed iterative interference suppression algorithm under multi-cell communication environment.Firstly,the basic theory of iterative receiver technology and its potential advantage are studied,which laid the foundation for the design of cooperative iterative receiver;then the factor graph corresponding to the described system is given;finally,the formula of the message passing between the nodes in the factor graph is deduced,by exchanging information between cooperation receivers,a distributed iterative interference suppression algorithm with receiver cooperation for uplink system is designed.Finally,for the downlink base station cooperative system,a distributed regularized zero forcing pre-coding based on generalized approximate message passing algorithm is designed and implemented.At first,part of pre-coding algorithms in multi-user system are studied,among them the regularized zero forcing pre-coding has a compromise between the complexity and performance,thus it is used in centralized cooperative system to realize the joint pre-coding to suppress ICI.However,the centralized cooperation pre-coding is quite difficult to be realized because of the high complexity and limited backhaul capacity.Therefore,this paper proposes a distributed regularized zero forcing pre-coding algorithm based on generalized approximate message passing algorithm.