Stochastic Geometry Based Performance Analysis For Mobile Heterogeneous Networks

With the rapid development of new technologies such as mobile Internet,Internet of Things(IoT),and cloud computing,a variety of emerging services such as virtual reality,intelligent transportation,industrial IoT,telemedicine,and smart cities continue to emerge,resulting in explosive growth in mobile data traffic.In order to improve the network carrying capacity,the fifth gen-eration mobile communication(5G)network densely deploys different types of heterogeneous base station nodes in hotspot areas to increase network ca-pacity.On the other hand,by enabling new technologies such as network virtualization and heterogeneous integration of different access networks,the dynamic networking mode and intelligent resource adaptation are realized to meet the personalized and customized service requirements in different appli-cation scenarios.However,the typical applications of 5G such as industrial IoT,autonomous driving,telemedicine,and massive machine type communi-cations(mMTC)have put forward higher performance requirements for the re-liability of mobile networks.The current research on the reliability theory and new technologies of mobile networks is one of the key challenges faced by the beyond 5G(B5G)network research.This dissertation is mainly based on stochastic geometry theory to carry out research on the reliability theory and analysis of mobile heterogeneous networks,and focuses on solving the follow-ing problems:(1)The densification of heterogeneous networks leads to more complicated and strong inter-cell interference,which exacerbates the difficulty in guaranteeing and improving network reliability,and the reliability analysis lacks the basic theoretical support;(2)Heterogeneous multi-layer networking causes more randomized network node distribution,which is significantly dif-ferent from the traditional hexagonal cellular model,and the actual deployment lacks theoretical modeling guidance.This dissertation takes the perspective on the success probability and the new performance metric—meta distribution,and builds a theoretical frame-work model for reliability analysis of mobile heterogeneous networks based on stochastic geometry.On this basic,it conducts in-depth research on relia-bility analysis of mobile heterogeneous networks.In this dissertation,the succ-cess probability characterizing the average reliability of the network is firstly analyzed for the "spatial cooperation" networking scenario,and then the meta distribution analysis is carried out for the first time to reveal the link reliability for the broader "spatial cooperation" networking schemes.Next,this disserta-tion further study the "spatiotemporal cooperation" networking scenario where the cooperation of the spatial and temporal domains are combined with each other,and analyze the meta distribution to characterize the link reliability in this scenario for the first time.Finally,the meta distribution theory analysis framework is extended from single user to multiple user.For the first time,the joint meta distribution of multiple users(or locations)is theoretically derived,and this theory is applied to the theoretical analysis of physical layer security and cooperation scenarios.The main research contributions and innovations of this dissertation are summarized as follows:(1)This dissertation gives the theoretical framework of the stochas-tic geometric based analysis method for mobile heterogeneous networks,and for the "spatial cooperation" networking scenario,the average per-formance analysis of the coordinated multipoint(CoMP)coherent joint transmission(JT)is carried out.First,the basic concepts of the success probability and the meta distribution are formally defined,which construct a theoretical analysis framework.Several effective calculation approaches for the meta distribution such as the Gil-Pelaez approach and the beta approxima-tion are discussed and analyzed.The comparison between the meta distribution and the success probability highlights that the meta distribution can provide more fine-gained information about the individual link reliability.Then,for the downlink of mobile heterogeneous network,a heterogeneous cooperation net-work model and two types of typical user models which include the general user and worst-case user are proposed,and the basic performance metric—success probability is analyzed to characterize the average performance of networks.Based on the stochastic geometry theory,the signal-to-interference ratio(SIR)performance of general users and worst-case users with coherent JT is theo-retically analyzed for the first time.Using two inequalities including Alzer's inequality,the upper bound and approximation of the success probability are given.Finally,numerical results and Monte Carlo simulations verify the accu-racy of the proposed theoretical upper bound,and provide the theoretical guid-ance for the actual network deployment.(2)Aiming at the“spatial cooperation”networking scenario of mo-bile heterogeneous networks,the meta distribution for different network-ing schemes of the base station cooperation is analyzed and derived for the first time.The heterogeneous cooperation network model proposed in(1)is extended to analyze a variety of different downlink CoMP cooperation schemes,including JT and dynamic point selection/blanking(DPS/DPB).Based on the SIR meta distribution,the general scheme JT-DPB combined with JT and DPB has been rigorously analyzed and studied in theory for the first time,as well as the DPS/DPB scheme.The b-th moment of the conditional success probability for the two types of typical users has been derived,and the mean local delay is given in the JT-DPB scheme,where the critical value of the phase transition from finite to infinite is observed from the mean local delay.Using the b-th moment,the Gil-Pelaez approach and beta approximation approach are used to obtain the meta distribution of the above-mentioned different cooperation schemes.The theoretical analysis results show that compared to the success probability,the meta distribution provides more refined link-level reliability information,and can significantly distinguish the performance differences of multiple different cooperation technologies,and reveals the advantages of dif-ferent cooperation schemes and the performance impact of different network parameters.(3)Aiming at the“spatiotemporal cooperation" networking scenario,this dissertation proposes a combined networking scheme of“spatial co-operation”JT-DPB and“temporal cooperation”hybrid automatic repeat request(HARQ),and derives the meta distribution for different types of HARQ techniques in mobile heterogeneous networks to characterize the link reliability performance.For downlink mobile heterogeneous networks,this dissertation mainly focuses on two types of HARQ techniques:Type-?HARQ(independent attempt)and Type-II HARQ(chase combining).Under this spatiotemporal cooperation scheme,the b-th moment of the conditional success probability for two types of users are derived,and the beta approxi-mation approach is used to obtain the meta distribution.For Type-II HARQ,a simplified heterogeneous network model is proposed for the first time,and the tight upper bound of the b-th moment is given.Simulation results verify that the proposed simplified heterogeneous network model has great accuracy,and can be used in the research of a large number of other transmission techniques.Theoretical analysis results show that the balanced combination of spatiotem-poral cooperation can achieve the best user link performance;the larger the size of the cooperation set,the better the approximation of the simplified heteroge-neous network model;Type-? HARQ has a performance equivalent to Type-I HARQ with 3 retransmissions when the number of retransmissions is 2.The analysis provides the theoretical guidance about link reliability for the applica-tion of the spatiotemporal cooperation networking in actual networks.(4)Aiming at multi-user wireless networking scenarios,the meta dis-tribution theory analysis model is expanded from single user to multiple user,and the theoretical analysis framework for the joint meta distribution of multiple users(or locations)is proposed and derived for the first time.Furthermore,this theory is applied to the theoretical analysis of physical layer security,and cooperation scenarios.The generalized definitions of the n order joint meta distribution,the joint conditional success probability,and the simplified n order product meta distribution are given for the first time.Focus-ing on the basic mathematical problems,the 2 order product meta distribution for two users is studied in a one-dimensional and two-dimensional Poisson cel-lular network.The b-th moment of the joint conditional success probability is derived in order to provide the basic analysis method for the product meta distribution.Then,the 2 order joint meta distribution theory is used in two application scenario as the examples,including the physical layer security and cooperative reception.For the physical layer security scenario,a joint perfor-mance analysis model of typical legitimate users and nearby eavesdroppers is constructed to derive the meta distribution of the probability of the opportunis-tic secure spectrum access.For the cooperative reception scenario,a multi-user cooperation reception scheme is proposed,and the meta distribution of its con-ditional cooperation success probability is analyzed.The theoretical analysis results show that,for larger SIR thresholds,the SIR correlation between users cannot be ignored.The joint meta distribution analysis framework can give the accurate performance analysis of wireless networks when multiple links are in-volved,so it is of great significance.As the distance between the eavesdropper and the legitimate user increases,the link reliability of the network will also improve,and it will gradually approach the communication without the secure constraint.