【作者】 刘侠；

【导师】 蒋铃鸽；

【作者基本信息】 上海交通大学 ， 通信与信息系统， 2010， 博士

【摘要】 移动通信技术是当代通信领域发展最迅速、更新最活跃的研究热点之一。随着无线通信技术的飞速发展以及全IP技术的广泛应用,下一代移动通信网络必将成为基于全IP技术的异构融合系统,能够支持不同无线技术的平滑接入和移动终端的无缝漫游。为了在无线异构网络中实现移动终端的自由移动,并且保持通信的连续性,必须采用行之有效的移动性管理技术。切换算法和移动性管理机制是实现有效移动性管理的关键技术,需要指出的是,异构网络间的切换定义为垂直切换。因此如何设计基于下一代无线网络的合理、高效的垂直切换算法和移动性管理机制,成为一个有重大研究意义的应用课题,也是无线资源管理技术中最具挑战性的问题之一。本论文考虑不同接入技术的网络特性和移动用户的业务特征,针对无线异构网络中垂直切换算法和移动性管理机制二个关键问题展开系统深入的研究,提出一系列算法和机制,并通过建立理论分析模型和性能仿真实验证明提出的方案能够有效改进系统的切换性能。本文提出的三种垂直切换算法是依据对网络资源需求的不同角度而进行优化的方法,基于接收信号强度(RSS)的改进算法是一种从用户角度出发的快速切换方法,未考虑网络条件的动态调整机制;联合无线资源管理技术的改进算法是从运营商的角度出发的优化异构网络带宽利用、区分业务优先级的切换判决方法,需要的信息交互和系统开销大;基于模糊逻辑的改进算法是采用智能信号处理技术的切换判决方法,利用信号预测技术、结合预判决方法或动态调整权值来提高切换的准确性,在网络条件利用和处理开销方面是前两者的折中。本文的两种移动性管理机制是基于不同协议层提出的,基于网络层的改进机制是为了提高移动MIPv6协议的切换性能,以满足异构网络移动管理的要求;而基于分离层的移动性管理机制是为了弥补现有分离层协议的不足,是对分离层协议的功能扩展。本文的具体研究内容如下:(1)通过分析现有无线接入网络可以采用的异构融合方式,确定合理的网络拓扑,构建基于UMTS和WLAN的松耦合异构网络。接着,以获知每个异构小区的可得到带宽、主机的移动模型为前提,提出了一种利用接收信号强度及其累积量,同时结合带宽和位置信息作为判决准则的垂直切换算法,对该算法的切换概率和丢包率进行理论分析,并通过仿真实验表明与传统的RSS算法相比,本文提出的改进算法对平均切换次数、切换阻塞率方面具有显著改善。(2)提出一种区分业务类型的联合不同无线资源管理技术的垂直切换算法(RRM-VHO)。根据三种不同业务类型的优先级,使资源分配有利于对网络性能要求高、适应性较差的话音业务。采用联合准入控制、带宽借用和补偿、以及负载均衡控制的联合管理方法执行切换控制。建立基于各个控制方法的可扩展模块化仿真平台,针对呼叫阻塞率、掉话率和传输质量进行分析和比较,表明RRM-VHO算法能够提供较高的切换性能,适合无线异构网络的多业务通信。(3)考虑到模糊逻辑方法能够适应无线网络的动态条件和垂直切换的复杂性,本文首先提出了一种基于差分预测的模糊逻辑垂直切换算法(DP-VHO),采用差分预测方法获得的RSS预测值来触发切换,缩短切换的发现时间;利用预判决处理模块,对输入信号进行筛选以减少处理的采样点;同时简化模糊逻辑控制器,利用RSS和可用带宽的模糊隶属度进行固定权值的联合判决,实现移动用户对不同网络的最佳接入。进一步考虑到快衰落环境下的信号预测精度,以及准确反映网络参量的异构特性问题,提出一种基于灰度预测的模糊逻辑垂直切换算法(GPA-VHO),(4)针对进行不同接入网络之间的切换都依靠MIPv6,未能解决大范围移动过程中信令开销大、更新时间长和丢包严重的问题,本文提出了一种基于全局移动的IDMP切换管理机制(IDMP-MM)。利用IDMP的两层结构特性,将一个无线蜂窝网域中的WLAN小区聚合为一个子网,构成具有异构网络特性的分层网络结构。增强代理服务器的缓存机制和包格式转换功能,并采用快速切换机制和预先注册方法改进切换更新机制。建立性能分析模型,通过仿真证明IDMP-MM机制可以有效改进切换性能,实现同构和异构网络的全局切换管理。利用灰度预测算法来提高RSS的预测准确性;扩展模糊逻辑控制模块的输入参量为RSS、网络带宽和网络费用,并且采用实时动态调整的权值进行切换判决;仿真结果表明,GPA-VHO算法能够提高切换准确性,并且不受主机移动速度的影响。(5)由于异构网络环境中会出现主机的家乡代理失效、主机的多宿特性以及多宿环境中主机会改变家乡地址的问题,本文提出进行主机身份标识和位置标识分离协议的研究。首先分析和比较了现有主机身份标识和位置标识分离协议各自的优缺点,并提出一种基于终端侧分离协议的通用型快速切换管理机制,实现分离协议在移动环境中的无缝切换,能够支持单方主机移动和双方主机同时移动的场景。接着给出基于Shim6协议的快速切换应用实例,详细描述快速切换流程,以及相应信令格式的修改,并通过性能分析验证,提出的快速切换管理机制可以有效地减少数据丢包,降低了切换延时,明显改善现有分离协议的移动性管理能力。最后,对全文进行总结,同时给出下一步的研究方向。更多还原

【Abstract】 Mobile communication technologies have become one of the most challenging and promising issues in modern communications. With the fast development of wireless communication technologies and the wide deployment of all-IP technique, the next-generation wireless mobile network must be integrated with various radio access technologies to support seamless roaming of mobile hosts. In order to guarantee mobile hosts roaming among different subnets freely meanwhile maintaining on-going sessions, it is vital to use effective mobility management methods. How to conceive rational and optimized vertical handoff algorithms and mobility management schemes has become significant in Radio Resource Management (RRM) for the next-generation mobile communication system.All-IP wireless heterogeneous integrating system is composed of cellular mobile networks, wireless local area network, satellite communications and broadcast communications. In view of various types of access networks and traffics such as voice, data, and multimedia, this dissertation focuses on mobility management in all-IP wireless heterogeneous networks, covers vertical handoff algorithms and mobility management schemes. Several novel algorithms and schemes have been proposed and verified to be effective by both analyses and simulations, which can be described as follows.Firstly, this dissertation proposes an efficient handoff algorithm for wireless heterogeneous networks constructed by the loosing couple architecture between wireless local area network (WLAN) and universal mobile telecommunications system (UMTS). This vertical handoff algorithm takes the received signal strength and its accumulation as handoff trigger criterion to adapt with the network conditions and deduce theoretic analysis of mean handoff number and dropping probability. The results of simulations indicate that the proposed algorithm has better performance than the conventional algorithm based on the absolute received signal strength (RSS).Secondly, this dissertation studies vertical handoffs combined with RRM technologies to improve system performance. The proposed vertical handoff algorithm introduces access control, bandwidth borrowing and compensation, and load balance control to allocate radio resource based on different traffic types. The results of simulations indicate that the proposed algorithm is able to reduce the dropping probability under the same block probability, and guarantee the best quality of service for voice in the three traffic types.To minimum unnecessary handoff number, this dissertation proposes an improved vertical handoff algorithm considers some network parameters including velocity, current RSS, predicted RSS and available bandwidth unity of candidate networks. The forward differential prediction algorithm is used to get the predictive RSS, which can trigger a handoff in advance. And the pre-decision method is applied before the handoff decision module, which can filter the unnecessary data and provide accurate handoff trigger. Fuzzy logic principle based evaluation and decision algorithm is applied to the overlay network of UMTS and WLAN, which can save the mobile host memory to store the rule bases and saves the time to defuzzy within the rule bases. Furthermore, the intelligent vertical handoff algorithm with the aid of grey theory and dynamic weights adaptation is proposed. The Grey Prediction Algorithm (GPA) predicts the predictive received signal strength accurately. The decision rule based on fuzzy logic theory takes received signal strength, available bandwidth, and monetary cost of candidate networks as input metrics. And the weight of each metrics is adjusted along with the networks changing to trace the network condition. Simulation results demonstrate that the proposed algorithm provides high performance in heterogeneous as well as homogeneous network environment.Fourthly, this dissertation presents an improved IDMP-based macro-mobility management (IDMP-MM) mechanism for heterogeneous wireless networks. The proposed mechanism adopts Layer-2 fast handoff trigger, the edge-cells controller for improving intra-domain mobility, and the pre-registration method with the aid of address-table mapping between mobility agents to enhance inter-domain mobility. It describes the procedures of intradomain and interdomain handoff in IDMP-MM solution, and gives the performance analyses of IDMP-MM. The simulation results show that the IDMP-MM mechanism can provide efficient mobility management to reduce the binding update signaling cost, the number of buffering in-flight packets, and execute fast handoff for ongoing calls.In the end, this dissertation focuses on mobility management schemes for the protocols of identifier and locator separation. The generic mobility management scheme for protocols of terminal-based identifier and locator separation is proposed. By combining with Fast Mobile IPv6, the proposed scheme provides fast and simultaneous-moving handoff management without packets loss. And it gives the fast handoff procedure of the proposed scheme and several modified signal formats. This scheme is applicable to support Shim6 mobility, which is demonstrated the benefits on handoff latency and handoff signaling cost.Finally, the conclusion is presented as well as future research trends.更多还原