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1、中国科学技术大学 硕士学位论文 LTE移动负载均衡技术研究 姓名：刘志强 申请学位级别：硕士 专业：通信与信息系统 指导教师：洪佩琳 2011-05 摘 要 I 摘摘 要要 在过去的 20 年间，移动通信在全球范围内得到了迅猛发展，随着数据业务 和应用的重要性与日俱增，用户希望通过移动终端随时随地的交流各种信息，包 括语音、电子邮件、图片、音乐和视频等信息。为了适应业务带宽、传输时延以 及网络覆盖等多方面的需要，第 3 代合作伙伴计划(3rd Generation Partnership Project, 3GPP)启动了长期演进(Long Term Evolution, LTE)项目。 在
2、LTE 中，网络参数数目宏大且复杂性较高，为了减少配置和管理网络的 开销， 3GPP 将自组织网络(Self-Organizing Networks, SON)引入 LTE， 并认为 SON 是降低成本和复杂度的最有效手段。移动负载均衡(Mobility Load Balancing, MLB)是 SON 的重要功能之一， 用于解决 LTE 小区之间的不均衡负载。 目前 MLB 存在许多问题，因此本文对 MLB 展开了深入研究和探讨。论文主要贡献如下： (1) 针对 MLB 与移动鲁棒性优化(Mobility Robustness Optimization, MRO)之 间的冲突问题，提出一种
3、基于限定 MLB 操作的冲突避免机制 MRO 是 SON 中的另一个重要功能，用于解决 LTE 中的切换问题。MLB 与 MRO 都通过调整切换参数的方式进行优化，当两者同时操作时会产生冲突。本 文第 3 章首先分析了 MLB 与 MRO 的冲突原理，然后提出一种基于限定 MLB 操作的冲突避免机制，即通过限定 MLB 的操作来实现与 MRO 之间的冲突。仿 真结果表明， 该机制较好的解决了冲突问题， 并且较为可观的提高了两者的性能。 (2) 分析了 MLB 的操作效率，提出一种基于负载分布的邻居小区选择机制 MLB 操作过程中需要选择一个邻居进行负载均衡。 若选择了不合适的邻居， 则会造成低
4、效率的 MLB 操作。本文第 4 章首先分析了基于小区负载进行邻居小 区选择方案的缺陷，然后提出了一种基于负载分布的邻居小区选择机制，通过结 合邻居小区的负载信息以及边缘负载分布信息来选择最合适的邻居小区。 仿真结 果表明，该机制能够使 MLB 达到更优的性能，实现了高效率的 MLB 操作。 (3) 针对单跳 MLB 不能解决的负载场景，提出一种多跳 MLB 机制 在某些复杂的无线网络环境下，单跳 MLB 无法实现有效的负载均衡。针对 该问题本文第 4 章提出一种多跳 MLB 机制，将单跳 MLB 扩展至两跳，通过邻 居小区来进行 MLB 协作，来实现多个小区之间的负载均衡。仿真结果表明，在
5、某些特定场景下，多跳 MLB 机制下能够较好的实现多个小区之间的负载均衡。 关键词：关键词：长期演进 自组织网络 移动负载均衡 移动鲁棒性优化 冲突避免 邻居选择 多跳负载均衡 Abstract II ABSTRACT In the past 20 years, wireless communication technologies have been developed rapidly. With the increase of the importance of data applications every day, users are willing to communicate wi
6、th others whenever and wherever possible, including voice, email, picture, music, video and so on. In order to satisfy the bandwidth of data application, transmission delay and network coverage, the 3rd Generation Partnership Project (3GPP) has launched the Long Term Evolution (LTE) project. In LTE
7、system, the number and structure of network parameters have become large and complex. To reduce the expenses of operations and maintenances of the network, Self-Organizing Networks (SON) is introduced to LTE, which is considered as the one of the promising area to save operational expenditures. Mobi
8、lity Load Balancing (MLB) is one of the important use cases in SON, which aims to cope with the unequal loads between different cells. There are some problems in MLB, and this paper researches these problems deeply. The main contributions of this paper are: (1) Proposed a novel scheme to resolve the
9、 conflict problem between MLB and Mobility Robustness Optimization (MRO) MRO is another important use case in SON, which is used for coping with the handover problems in LTE. MLB and MRO both choose adjusting handover parameters as optimization actions, the conflict may occur when they are operating
10、 at the same time. In the 3rd chapter, this paper analyzes the reason of the conflict problem at first, and then presents a novel scheme which is based on the restriction on operation of MLB to avoid the conflict. The simulation results demonstrate that the proposed scheme can resolve the conflict p
11、roblem effectively and improve the performances of both functions. (2) Proposed a novel neighbor selection scheme for MLB to achieve the high efficiency In the MLB procedure, the overloaded cell needs to select a neighbor to balance the load. If the overloaded cell selects an unsuitable neighbor, th
12、e operation of MLB will not achieve the high efficiency. In the 4th chapter, after analyzing the drawback of the neighbor selection scheme which is based on the loads of neighbor cells, this paper proposed a novel neighbor selection scheme which combines the loads of neighbor cells and the load dist
13、ribution of the overloaded cell itself. The simulation Abstract III results demonstrate that the operation of MLB can achieve the high efficiency and better performances in the novel scheme. (3) Proposed a multi-hop MLB scheme to resolve the problem which cannot be resolved by the single-hop MLB sch
14、eme In some complex wireless environments, the single-hop MLB scheme cannot deal with the unequal load between different cells. To resolve this problem, the 4th chapter proposed a multi-hop MLB scheme, which expands the single-hop load balancing to multi-hop. In the proposed scheme, the overloaded c
15、ell cooperates with neighbor to distribute the load among multi-cells. The simulation results demonstrate that the multi-hop MLB scheme can distribute the load more equally among multi-cells in some particular environments. Key Words: Long Term Evolution, Self-Organizing Network, Mobility Load Balan
16、cing, Mobility Robustness Optimization, Conflict Avoidance, Neighbor Selection, Multi-hop MLB 中国科学技术大学学位论文原创性声明 本人声明所呈交的学位论文,是本人在导师指导下进行研究工作所取得的成 果。除已特别加以标注和致谢的地方外，论文中不包含任何他人已经发表或撰写 过的研究成果。 与我一同工作的同志对本研究所做的贡献均已在论文中作了明确 的说明。 作者签名：_ 签字日期：_ 中国科学技术大学学位论文授权使用声明 作为申请学位的条件之一， 学位论文著作权拥有者授权中国科学技术大学拥 有学位论文的部分使用权，即：学校有权按有关规定向国家有关部门或机构送交 论文的复印件和电子版，允许论文被查阅和借阅，可以将学位论文编入中国学 位论文全文数据库等有关数据库进
