CoMP-based Energy-spectrum-efficiency Optimization In Heterogeneous Cellular Networks

Due to the same-frequency deployment of multiple base stations,there will be both intra-tier interference and cross-tier interference in the heterogeneous cellular network,which seriously affects the performance of the communication network.Therefore,effective interference management methods have become a research hotspot.The traditional interference management schemes regard interference as a disadvantage,and achieve the purpose of eliminating or suppressing interference through coordination and planning of resources.Although these schemes can reduce interference to a certain extent,they also reduce the utilization efficiency of resources.Coordinated multi-point transmission(CoMP)is an effective interference management mechanism that can convert interference into a signal desired by users,thereby improving network performance.Under the traditional macro base station scenario,the increase of the number of users and the large-scale deployment of low-power nodes will further densify and randomize the network.While the joint processing and transmission mode of CoMP reduces the interference,extra overhead is generated.In view of the characteristics of densification and randomized deployment in the future cellular network,this paper proposes two CoMP-based energy-spectrum-efficiency(ESE)optimization schemes,which can not only effectively improve the ESE of the heterogeneous network,but also provide efficient scheme for network deployment and signal transmission exploiting the closed solution obtained.In addition,in order to reduce the overhead of CoMP,this paper also proposes a base station recombination algorithm based on the weight of the macro base station,which further improves the performance of the heterogeneous network under the single-tier CoMP scheme.This thesis mainly focuses on the following aspects:1.Aiming at the two-tier cellular network composed of macro-cells and pico-cells,an ESE optimization scheme based on the single-tier CoMP is proposed.First,the macro tier and the pico tier are deployed in a different frequency band to eliminate cross-tier interference,and then a cooperation threshold is introduced to characterize the degree of cooperation between pico base stations in the network and determine the user's cooperation mode selection,and finally a closed solution of the network energy spectrum with respect to thecooperation threshold,the base station density,the mobile traffic strength,and the average user rate is obtained by modeling the power consumption of user.The simulation results verify the accuracy of the ESE closed-form solution and characterize the influence of different network parameters on the system ESE,which enables us to quickly design the best solution for the randomly deployed heterogeneous cellular network based on single-tier CoMP.2.To reduce the interference,the single-tier CoMP requires multiple base stations to jointly process signals,leading to extra overhead.In order to reduce the power consumption of large-scale CoMP in the network,a base station recombination algorithm that improves the ESE of the single-tier CoMP is proposed.According to the traffic topology in the network,the macro base station is reselected for the pico base station to access,aiming to convert the CoMP services between the macro base stations into CoMP services in the macro base station,and reduce the power consumption of the cooperative processing signals between the macro base stations.The simulation results show that the proposed algorithm can effectively reduce the overhead of CoMP and further improve the ESE of the system.3.In order to further improve the reuse rate of spectrum resources,an ESE optimization scheme based on cross-tier CoMP is proposed.The same frequency networking is adopted for the macro tier and the pico tier,two cooperation thresholds are introduced to represent the degree of cooperation between macro base station and pico base satation in the network and determine the user's mode selection,and finally a closed solution of the network ESE with respect to the cooperation threshold,the base station density,the mobile traffic strength,and the average user rate is derived.The simulation results verify the accuracy of the closed solution.Compared with not using CoMP scheme,it can greatly improve the ESE of the network.The closed-form solution enables us to quickly design an optimal solution for a randomly deployed heterogeneous cellular network based on cross-tier CoMP.