【作者】 赵爽；

【导师】 汪清； 黄建尧；

【作者基本信息】 天津大学 ， 电子与通信工程， 2018， 硕士

【摘要】 随着移动互联网和物联网的飞速发展,当前移动通信数据流量面临指数增长。第五代移动通信网络已提上日程,超密集小区部署和软件定义网络是两个关键驱动力,同时为移动性管理问题带来了新的挑战。本文旨在解决密集网络中越区切换时发生的频繁切换、乒乓效应、信令开销以及候选基站选择的问题。具体研究了在软件定义网络(software defined network,SDN)体系架构下LTE回程网络中和超密集网络中的移动性管理问题。针对回程网络的移动性管理问题,本文提出了一种SDN用户协作的移动性管理方法。设计了用户终端在密集蜂窝中越区切换时信令交互的流程。另外,采用动态的本地转发链方案,为正在进行的会话转发数据包,减少密集网络中用户移动产生的信令开销。基于这种方案,正在进行通信的数据包可以由源基站到目标基站进行转发,而不用切换整个传输路径(整个传输路径是指从网关到目标基站)。理论分析研究和仿真结果表明,与传统的路径切换策略相比,这种机制可以显著地降低信令开销但会增加一些转发成本。对数据传输的性能分析表明,引入额外的转发成本是可以接受的,甚至在短转发链或大回程网络延迟的情况下可以忽略不计。对于超密集网络中的移动性管理问题,本文提出了一种环境感知的多目标移动性管理方法。提出了改进的非随机学习模型,收集小型基站的动态环境竞争分数来决策切换基站的序列。并引入了切换损耗这一概念,严格控制切换的发生,使切换频率降低,解决了超密集网络中的频繁切换问题,最后用用户满意度参数和切换次数评价基站选择方案的优劣。仿真证明了所提出的算法在没有延迟和丢包的理想情况下以及存在反馈延迟或丢包的情况下均有效。更多还原

【Abstract】 With the rapid development of mobile Internet and Internet of Things,the current mobile communication data traffic is facing exponential growth.The fifth generation mobile communication network has been put on the agenda,ultra-dense network deployment and Software Defined Network(SDN)are two key driven forces,while the mobility management issues usher in new challenges.This paper aims to solve the frequent handover,ping-pong effect and signaling overhead and the selection of candidate base stations in dense network.The problem of mobility management in LTE backhaul under SDN architecture and ultra-dense network is studied in detail.Aiming at the problem of mobility management in the backhaul network,this paper proposes a method of UE assisted mobility management based on SDN.The process of signaling interaction is designed for the handover of UE in dense cells.In addition,the dynamic local forwarding chain scheme is used to forward the data packets for the ongoing session and reduce the signaling overhead caused by UE’s mobility in dense network.Based on this scheme,the packets can be forwarded from the source base station to the target base station without switching the entire transmission path(from the gateway to the target base station).Theoretical analysis and simulation results show that compared with the traditional path switching strategy,this mechanism can significantly reduce the signaling overhead but will increase some forwarding costs.The performance analysis of the data transmission shows that the introduction of additional forwarding costs is acceptable,even negligible in the case of short forwarding chains or large backhaul hops.For the mobility management problem in ultra-dense network,this paper proposes a multi-objective context-aware mobility management approach.An improved non-stochastic learning model is proposed to collect the dynamic Contextual Competition Scores of small base stations to determine the sequence of switching base stations.And the concept of handover overhead is introduced to strictly control the occurrence of handover,FHO problem in the ultra-dense network is solved.Finally,the performance of the base station selection scheme is evaluated by user satisfaction ratio parameter and the number of handover times.The simulation shows the validity of the proposed algorithm in the case of ideal network with delay or packet loss and non-ideal network with delay or packet loss.更多还原