【作者】 王胡成；

【导师】 陈山枝；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2018， 博士

【摘要】 随着移动互联网技术和物联网技术的发展,未来移动通信网络中将出现多样化的通信场景和差异化的用户/业务需求,这既对传统的架构单一且缺乏可扩展性的移动通信网络提出挑战,也对未来移动通信网络中的移动性管理技术提出了新的需求。因此,面向新场景和新业务的未来移动通信网络架构及移动性管理技术成为国内外信息技术领域的研究热点。移动性管理是移动通信网络的基本特性,对网络的性能、运行效率和用户体验有着重要的影响,因此针对具体的通信场景提供合适的移动性管理是未来移动通信网络关键技术研究的重点之一。本文首先从移动通信网络面临的挑战入手,提出能够实现软件灵活定义的去中心化网络架构。然后围绕按需移动性管理的思想,进一步提出一种按需移动性管理的实现方法,并基于提出的软件定义去中心化网络架构进行了原型设计。最后,针对超密集网络的通信场景,利用软件定义去中心化网络架构和按需移动性管理的思想,提出支持本地化移动性管理的机制。具体研究包括以下方面:(一)针对现有移动通信网络架构不能服务多样化通信场景以及缺乏灵活性和可扩展性的问题,提出了一种软件可定义去中心化移动网络架构SoftNet(Software defined decentralized mobile network architecture)。该架构通过策略控制功能搜集的场景信息进行网络架构的智能定义,基于网络功能虚拟化NFV(Network Function Virtualization)技术实现网络功能的动态激活和灵活部署,基于SDN(Software Defined Networking)技术进行网关锚点的动态分配和网络资源的统一调度。与LTE(Long Term Evolution)网络的定性对比分析显示所提架构在组网方式、可扩展性、健壮性、网络资源利用效率、数据转发效率等方面具有优势。多种终端移动模型下的实验仿真表明所提的去中心化网络相对于LTE网络在移动性管理方面具有更低的信令开销。此外,通过仿真分析,论文还从接入时延、切换时延和数据传输开销方面对SoftNet进行了性能验证。(二)针对为不同通信场景提供按需移动性管理的问题,提出了一种移动性驱动网络切片MDNS(Mobility Driven Network Slicing)的技术思想及实现MDNS的框架方案。MDNS的核心思想是通过感知终端的移动行为特性和业务特征,确定出网络需支持的移动性支持等级(或移动性管理机制),然后基于移动性支持等级创建相应移动性支持能力的网络切片,最后将不同移动性支持需求的终端定向到相应移动性支持能力的网络切片中,实现按需移动性管理。通过三个典型场景的建模,对MDNS使能的按需移动性管理和LTE系统的通用移动性管理机制进行分析比较,证明了 MDNS具有更低的系统开销。(三)针对传统LTE系统的移动性管理机制在5G超密集网络部署的特定场景中所面临的信令开销大、数据传输效率低等问题,根据按需移动性管理的思想,提出基于去中心化网络架构SoftNet的本地化移动性管理机制,充分考虑了网络部署特点和回传网络拓扑。具体的本地化移动性管理机制分为:集中控制的本地化移动性管理机制,其中小基站不具备控制平面移动性管理功能,终端的移动性事件由本地服务中心集中控制管理;分布控制的本地化移动性管理机制,其中小基站具备控制平面移动性管理功能,终端的移动性事件由小基站进行控制管理。根据对所提的本地化移动性管理机制以及LTE系统的移动性管理机制的数值分析和仿真实验,集中控制的本地化移动性管理机制在平均切换信令开销、平均数据包传输开销、平均切换时延和平均核心网信令负载方面均有优势,而分布控制的本地化移动性管理机制主要在切换时延方面差于LTE系统的机制。更多还原

【Abstract】 With the development of mobile internet and internet of things(IoT),diversified communication scenarios with different user or service requirements will emerge in the future mobile communication network,which would not only raise challenges to the traditional mobile communication networks with "one size fits all" architecture and lack of extensibility,but also put forward new requirement to mobility management in future mobile networks.Therefore,future mobile communication network architecture and mobility management techonologies for new communication scenarios and new services become hot research topics in the field of information technology.Mobility management is a fundamental feature of the mobile communication network,which significantly influence the system performance,network efficiency and user experience.Therefore,mobility management for future specific communication scenarios is becoming a key research point for future mobile communication networks.This paper starts with the challenges that current mobile communication network are facing,and puts forward "a software defined decentralized mobile network architecture(SoftNet)".Then based on the idea of on demand mobility management,proposes a new method to realize it,the prototype of which is designed based on the SoftNet.At last,to accommodate Ultra Dense Network(UDN),two localized mobility management schemes are proposed with the help of the SoftNet and the idea of on demand mobility management.Specific studies include the following aspects:(A)To solve the issues that existing mobile communication network architecture can’t efficiently serve diversified communication scenarios and lack flexibility and scalability,a novel mobile network architecture "SoftNet" is proposed.The SoftNet can intelligently define network architecture based on the information of communication scenarios collected by policy control function;dynamically activate network functions and flexibly deploy them with the help of NFV technology;and dynamically distribute gateway anchor and schedule network resource by using SDN technology.Compared with LTE network,the SoftNet has advantages on networking,extensibility,robustness,and efficiency on network resource utilization and data forwarding.The simulation using multiple mobility models shows that the proposed decentralized network has less signaling cost than LTE network.Moreover,via simulation analysis,the paper conducts the performance verification for the SoftNet from access delay,handover latency and packet delivery cost aspects.(B)In order to provide on demand mobility management to different communication scenario in the future,the idea of "Mobility Driven Network Slicing(MDNS)" is proposed as well as a framework to implement MDNS.The main idea of MDNS is to first determine the levels of mobility support(or mobility management schemes)that a operator’s network needs to support by discovering the mobility behavior characteristics of all mobile terminals and the characteristics of services running on those mobile terminals,then create network slices that can provide the required levels of mobility support,and finally direct the mobile terminals with different requirements on mobility support to the corresponding network slices.With these steps,on demand mobility management can be implemented easily.By establishing analytical models,comparable analyses on general mobility management in LTE system and on demand mobility management enabled by MDNS are performed.The result shows that the advantage of the MDNS in system cost.(C)If traditional mobility management in LTE system was applied to 5G UDN,it would lead to high signaling cost,inefficient data transmission etc.,therefore,with the guidance of on demand mobility management,two localized mobility management schemes based on decentralized network architecture are put forward,which takes the network deployment and the backhaul network topology into account.The specific localized mobility management schemes are localized mobility management with centralized control,where small cell based stations have no control plane mobility management function,thus mobility events are handled by local service center,and localized mobility management with distributed control,where small cell based stations have control plane mobility management function,and can handle mobility events by itself.The numerical analyses and simulations on the proposed localized mobility management schemes and traditional mobility management scheme in the LTE system demonstrate that,the localized mobility management scheme with centralized control has the best performance on average handover signaling cost,average packet delivery cost,average handover latency and average signaling load to the core network,but the localized mobility management scheme with distributed control introduces more handover latency than the scheme in the LTE system.更多还原