Research On Unlicensed Spectrum With Stochastic Geometry In Heterogeneous Cellular Network

With the advent of the Fifth Generation(5G),various emerging technologies and services continue to appear and develop,leading to explosive growth in the types and quantity of communication equipment.Therefore,heterogeneous cellular network(HCN)architecture and unlicensed spectrum technical solutions have received great attention.Although heterogeneous cellular network can use wireless resources more efficiently to improve performance indicators such as throughput and coverage probability of cellular networks,the increase in structural complexity and the randomness of base station location distribution make accurate and efficient modeling a key issue.Making full use of unlicensed spectrum can improve the quality of service for cellular users,but user conflicts in unlicensed spectrum and the impact on the performance of heterogeneous cellular networks are the crucial issues.This thesis applies the mathematical tool stochastic geometry theory to model and analyze heterogeneous cellular networks using unlicensed spectrum technology based on the Poisson point process,study system throughput and coverage performance,derive performance expressions,and based on theoretical analysis and simulation results.Analyze the impact of the application of unlicensed spectrum technology on cellular networks.The main research results of this paper are summarized as follows:Based on the stochastic geometry theory,this thesis researches the performance of a single-layer cellular network in unlicensed spectrum systems,derive its system throughput expression and analyze the performance.Aiming at the random distribution of cellular networks,the Poisson point process is applied to model the location distribution of cellular users,WiFi(Wireless Fidelity)access points,and WiFi users.The unlicensed spectrum sharing scheme for cellular users and WiFi users adopts Listen Before Talk(LBT)which is modeled as a Hard Core Point Process(HCPP).Therefore,the probability of two types of users accessing the unlicensed spectrum applies Medium Access Probability(MAP)to express.On this basis,the throughput expressions of cellular users and WiFi users in unlicensed spectrum systems are derived separately.The simulation results show that the theoretical analysis is consistent with the simulation results,and the use of unlicensed spectrum resources can improve the throughput of the cellular system without significantly affecting WiFi users.The coverage probability performance index of a three-layer heterogeneous cellular network when using unlicensed spectrum technology is further studied.Based on stochastic geometry theory,a three-layer cellular network using unlicensed spectrum technology is modeled.We derive the expression of user coverage probability and analyze the performance of the heterogeneous cellular networks.analysis.The Poisson point process is applied to model the location distribution of macro base stations,micro base stations,cellular users,and WiFi users in the heterogeneous cellular network,and the range of macro cells is divided into random polygons using Voronoi Diagram.The unlicensed spectrum sharing scheme also uses LBT.Under this model,the coverage probability expressions of heterogeneous cellular networks under the two conditions of using and not using unlicensed spectrum are derived.The simulation results show that the simulation results are consistent with the theoretical analysis,and the quantitative results of the influence of different parameters on the network coverage performance are obtained,which has reference value for the deployment of cellular networks under unlicensed spectrum technology.In summary,the results show that higher system throughput and better coverage performance need to consider a more appropriate cellular network configuration,including the density of cellular users and WiFi users,the SINR threshold,the density of small cell users and WiFi users,and the ratio of macro base stations to small base stations.These research results will have certain theoretical guiding significance for the future development of unlicensed spectrum resources in heterogeneous cellular networks.