【作者】 李斌；

【导师】 石文孝；

【作者基本信息】 吉林大学 ， 通信与信息系统， 2011， 硕士

【摘要】 未来的无线通信网络将是一个异构型的体系结构,各种无线接入网通过全IP技术接入到基于全IP化的公共核心网。异构无线网络负载均衡是实现异构无线网络中资源有效共享的重要方法,是异构无线网络的关键技术之一。它可以提高异构网络对无线资源的利用率,降低系统传输时延,扩大系统容量,为用户提供更好的服务。基于IP流分流的负载均衡是一种新兴技术,与传统的硬负载均衡方法相比,它能够更充分地利用异构无线网络资源,并根据各网络承载能力不同的特点为业务传输带来增益。本文将网格技术引入到异构无线网络中,提出一种分层半集中式网络结构(HSCA),给出了HSCA结构各功能实体间传递信令的流程,并推导了HSCA的综合可靠度和信令开销数学表达式。仿真结果表明,HSCA结构具有较高的可靠性和较低的信令开销。HSCA较好地解决了基于集中式网络结构的负载均衡可靠性较低和基于分布式负载均衡资源开销较大的问题。针对传统的硬负载均衡方法不能最大限度地利用异构无线网络资源,以及现有的基于IP流分流的负载均衡方法普遍性较低的问题,提出一种基于带宽分配的IP流分流负载均衡算法(BALBD)。将带宽作为各无线网络为用户提供服务的资源,为每个用户计算最佳分流比率,当用户请求接入或需要切换时,系统根据最佳分流比率将用户业务分成子流,并将各子流接入或切换到相应网络中。与现有的基于IP流分流的负载均衡算法相比,BALBD算法更具普遍性。仿真结果表明,BALBD算法能够很好地均衡异构无线网络负载,并且具有较低的接入和切换阻塞率以及较高的系统吞吐率。考虑到用户的移动性和无线环境的时变性,提出一种动态IP流分流负载均衡算法(DLBD)。研究所有无线接入系统都采用OFDM技术的情况,将由时域上的一个时隙和频域上的一个子信道组成的二维资源单元作为系统资源分配的最小模型,提供了计算最佳分流比率的一般方法。在用户请求接入网络到用户退出网络的整个过程中,系统实时地计算用户的最佳分流比率,并根据最佳分流比率动态地调整用户接入到每一个系统的IP流子流的速率。DLBD算法解决了BALBD算法计算用户最佳分流比率的局限性,以及不能动态地调整子流速率的问题。仿真结果表明,DLBD算法的负载均衡能力比传统的硬负载均衡算法(MLB)提高了45.1%,业务阻塞率和掉话率比MLB算法降低了31.6%,并且具有较低的丢包率和较高的系统吞吐率。本文的工作和成果为基于IP流分流的异构无线网络负载均衡技术提供了参考,并在一定程度上填补了国内在该领域的空白。更多还原

【Abstract】 Radio systems are moving toward forming heterogeneous wireless networks: collaborations of multiple radio access networks, which access to the all-IP based common core networks through the all-IP technology. As one of the key technologies in the convergence of heterogeneous wireless networks, load balancing is a significant method to achieve the resource sharing over heterogeneous wireless networks, and it can improve resource utilization, reduce transport delay, enlarge system capacity, as well as provide better services for users. Load balancing based on dividing IP flow is a new technology, it can use the resource of heterogeneous wireless networks more efficiently than the traditional hard load balancing, it can also bring gains for traffic transport using the feature that different network can bears different load.Bringing grid into heterogeneous wireless networks, we propose a hierarchical semi-centralized architecture (HSCA). For HSCA, the signaling flow among function entities is given, and the arithmetic expression of integrated reliability and signaling overhead are derived. Simulation results indicate that HSCA can improve the system reliability and reduce the signaling overhead effectively. The proposed network architecture has properly solved the problem of low reliability in centralized load balancing and high overhead in distributed load balancing.The traditional hard load balancing can not realize the maximum utilization of resources over heterogeneous wireless networks, and the existing load balancing methods based or dividing IP flow are less universal. To solve the above problems, we present a bandwidth allocation based load balancing algorithm by dividing IP flow (BALBD). BALBD takes bandwidth as the resource used by wireless networks to serve subscribers, and calculates the optimal flow-dividing ratio for subscribers. When there is a new call or handove: requirement, BALBD divides subscriber’s traffic into sub flows according to the optima flow-dividing ratio, and accesses the sub flows to the corresponding networks. Comparec with the existing load balancing methods based on dividing IP flow, BALBD is mon universal. Simulation results show that BALBD can balance the load among heterogeneou: wireless networks effectively, and it can reduce the blocking rate, as well as improve the system throughput.Considering the mobility of subscribers and the time-varying of wireless environment, dynamic load balancing algorithm by dividing IP flow (DLBD) is proposed. We assume tha all of the wireless access networks adopt OFDM technology, and take the two-dimensioi resource unit as the basic resource allocation unit, which is composed of a time slot in tim domain and a sub-channel in frequency domain. DLBD provides a general method fo calculating the optimal flow-dividing ratio. In the whole process from a subscriber require to access to system to he ends the call, DLBD calculates the optimal flow-dividing ratio fo him in real time, and adjusts the rate of sub flows dynamically according to the optima flow-dividing ratio. Although BALBD has good performance, it has some disadvantages:it computing method for optimal flow-dividing ratio is limited into two wireless networks, and it can not adjust the rate of sub flows dynamically. Fortunately, DLBD solves these problems. Simulation results indicate that the load balancing ability of DLBD is 45.1% higher than that of the traditional hard load balancing methods (MLB), while the blocking and call drop rate of DLBD is 31.6% lower than that of MLB. In addition, DLBD can reduce the packet loss rate and increase the system throughput.The work and results of this paper provide a reference for the research of load balancing based on dividing IP flow, and to some extent, fill the domestic blank in the field of load balancing based on dividing IP flow.更多还原