Research On Energy Efficiency Of Heterogeneous Cellular Networks Based On Stochastic Geometry

The explosive growth of mobile services makes the traditional cellular network structure difficult to meet the impact of data volume and users' requirements for communication quality.Heterogeneous cellular networks(Het Nets)have been identified as the network architecture of the fifth generation cellular mobile communication.Due to the uncertainty of the location of small base stations,the network topology and link characteristics will change accordingly.The traditional network analysis model is not suitable for Het Nets,so it is necessary to study the spatial distribution model of base stations.With the rapid increase of mobile traffic,it is of great practical significance to study and optimize the energy efficiency(EE)of Het Nets in order to save energy and reduce emissions,reduce the energy consumption of cellular networks and realize green communication.The main work and contributions of this thesis are as follows:(1)The performance of multi-antenna relay-assisted cellular network downlink is studied,in which the macro base stations(MBSs)and relay stations(RSs)are deployed in Euclidean plane according to independent homogeneous Poisson point process(PPP).The coverage probability and average achievable rate of the MBS to user equipment(UE),the MBS to RS and the RS to UE are derived by using stochastic geometry.According to the proposed power consumption model,the EE expression of the system is derived.At the same time,the performance of the system when the MBS adopts the random sleep strategy is analyzed.The downlink performance of the relay-assisted cellular network is analyzed through simulation and compared with the performance of the single-antenna relay cellular network.The simulation results confirm the theoretical analysis results,and show that the coverage probability and EE of the downlink of MBS with multi-antenna are better than that of single antenna network.(2)The EE of multi-antenna Het Nets with relay sleep strategy is studied.This thesis proposes a relay sleep strategy,which dynamically changes the relay mode according to whether the number of users of relay service exceeds the given threshold.A geometric model was built to derive the coverage probability and mean achievable rate from the MBSs to UE,the MBS to RS and the RS to UE links.According to the power consumption per unit area and the average achievable rate per unit area,the EE of the system is derived.The performance of multi-antenna cellular network with relay sleep strategy is analyzed by simulation.It is determined that the system can get higher EE by setting appropriate threshold and the MBS transmission power.In addition,the spectrum efficiency and EE of the system when the MBS adopt multi-antenna are better than that of a single antenna network.(3)The EE of two-tier Het Nets based on non-Poisson point process is studied.The deployment of MBSs is modeled by ?-Ginibre point process(?-GPP).Firstly,the approximate signal-to-interference ratio(SIR)analysis method based on PPP is used to obtain the SIR distribution of the two-tier heterogeneous networks,that is,the SIR distribution of the non-Poisson network can be obtained by scaling the given threshold of the SIR distribution in the Poisson network model according to the gain factor.Then the expressions of coverage probability,average achievable rate and EE of each link in Het Nets are derived.Finally,an effective EE optimization algorithm is proposed to find the optimal transmit power of pico base station(PBS)to maximize the EE.(4)The EE analysis and performance optimization of multi-antenna Het Nets are studied.Considering the fact that the distribution of MBSs is exclusive,the deployment of MBSs is modeled by the Matérn hard-core point process(MHCPP).Firstly,the gain method based on the mean interference-to-signal ratio(MISR)is used to approximate the SIR distribution of MHCPP.Secondly,the expressions of coverage probability,average achievable rate and EE of multi-antenna Het Nets are derived.Then,an optimization algorithm is proposed to improve the EE of multi-antenna Het Nets by controlling the transmit power of PBSs.Finally,the performance of the system is simulated and analyzed by SISO,SDMA and SUBF.The results show that the multi-antenna transmission has better system performance than the single antenna transmission,and the EE of the system can be effectively improved by selecting the appropriate transmit power.In addition,two-tier MHCPP-PPP Het Nets have higher EE than two-tier PPP-PPP Het Nets.