【作者】 杜文峰；

【导师】 贾维嘉；

【作者基本信息】 中南大学 ， 计算机应用技术， 2006， 博士

【摘要】 随着通信技术和网络技术的迅速发展，网络加速了人们信息交流和协同工作的过程，极大地促进了人类社会的发展。同时，随着无线网络技术的发展，人们希望能够在任何时间，任何地点，以任意的方式高速地使用网络资源。现在无线网络已经能够提供许多原来有线网络才能提供的服务。相对于有线网络而言，无线网络的带宽资源是非常有限的。为了保证在无线网络中运行的服务能够取得较好的服务质量，更加有效地利用无线网络的带宽资源成为无线网络研究的一个关键问题。本文针对无线网络中的多种服务类型，对无线网络的带宽分配和接入方式进行分析，深入分析了不同类型的网络带宽资源分配和调度算法在运行过程中对网络性能的影响。同时，本文也针对切换服务对无线网络带宽分配的影响情况进行了分析，对切换服务的路由重建方式进行优化，提高网络的实际运行性能。本文的主要研究工作如下：1、提出了一种分析无线网络带宽分配过程的状态模型。本课题分析了当前存在的部分无线网络带宽分配算法，并根据无线网络带宽分配算法是否使用预留信道，以及如何使用预留信道对当前存在的带宽分配算法进行了分类。通过使用二维马尔可夫模型对这些带宽分配算法的带宽分配过程进行建模，本课题从新建呼叫阻塞率、切换呼叫中断率和无线信道利用率等方面比较了使用不同信道分配算法的无线网络在运行过程中的性能。2、针对WiMAX网络PMP模式按需分配带宽资源，以及多种数据流类型等特点，本课题提出了一种多重队列对WiMAX网络按用户站分配带宽资源的过程进行分析。本课题通过对基站和用户站的带宽分配过程进行分析，详细描述了基站和用户站在不同运行情况下对到达带宽请求的处理过程，详细分析了UGS数据流、rtPS数据流、nrtPS数据流和BE数据流在不同网络带宽情况下被阻塞的概率，为将来在WiMAX网络上进行带宽分配研究奠定理论基础。3、在轮询带宽调度和随机带宽调度两种经典算法的基础上，提出了一种基于邻居集合的带宽资源调度算法来分析和优化WiMAX网络Mesh模式的带宽分配和调度过程。该算法通过使用邻居集合和优先列表，对使用Mesh模式连接的用户站之间的带宽调度过程进行了优化，使无线网络的带宽资源能够在网络局部得到优化调度，以达到优化整个无线网络的带宽调度效率。NS2模拟结果表明，该算法具有更低的延迟和更高的吞吐量，能够更好地利用网络资源。4、本文在当前几种常见的路由重建算法基础上，提出了一种基于七跳回溯机制的服务切换路由重建算法。根据移动终端的移动速度和网络的实际带宽情况动态选择位置更新信息的逆向回溯跳数k。本算法在位置更新信息的回溯过程中，寻找七跳范围内最优的路由重建公共点，使得呼叫节点经过该节点到达移动终端目标用户站的通信路由能够得到优化。同时，本算法要求接收到位置更新信息的中间节点以其到达目标用户站的最优通信路由转发接收到的数据包，降低服务切换过程中的数据包转发代价，使正在进行的网络服务能够在原用户站和目标用户站之间平滑地切换。更多还原

【Abstract】 With the quick development of communication and network technology, theprocess of information exchanging and cooperation have been accelerated. Meanwhile,with the development of wireless network, people want to access the network servicesat any time, at any place and with any method. A lot of services which were providedby the wired network have been supported by the wireless equipments now.Compared to the wired network, the communication bandwidth in the wirelessnetwork is limited. In order to achieve QoS guaranteed wireless services, efficientutilization of bandwidth resources becomes a fundamental issue. This paper hasanalyzed the bandwidth allocating process of wireless network with different servicestypes and compared the performance of different bandwidth allocating schemes. Atthe same time, this paper also gives an eye to the impact brought by handoff process.We have optimized the handoff rerouting process to improve the performance whenthe handoff process tack place. The main work and contributions are presented in thefollowing aspects.1. Compared to the wired network, the communication bandwidth in the wirelessnetwork is limited. In order to achieve the QoS guaranteed wireless services, efficientutilization of bandwidth resources becomes a fundamental issue. A number of channelallocation schemes have been proposed to fully utilize the wireless bandwidth, butmany of them just proposed the channel allocation scheme without presenting aspecific channel allocation model. In this paper, we propose and analyze threedifferent channel allocation schemes for wireless networks. We build three systemmodels based on two-dimensional Markov chain to compute the performance of basestation in terms of the new call blocking probability, the handover droppingprobability, and the channel utilization.2. The IEEE 802.16 MAC, which is connection-oriented, regulates uplinkchannel access using a Demand Assigned Multi Access (DAMA) TDMA system. Inthe WiMAX PMP mode, BS control uplink bandwidth allocation and SS request fortransmission opportunities on the uplink Sub frame. In this paper, we use multi-layersqueue system to describe the different bandwidth allocating state in Base station and Subscriber station. Meanwhile, Markov chain is used to analysis the performance ofdifferent bandwidth allocating schemes. We also provide some performance metrics toevaluate different bandwidth allocating scheme with this model.3. In order to optimize the bandwidth scheduling, a concept of neighborhood forbandwidth allocation and a new bandwidth scheduling scheme are introduced basedon two classical scheduling algorithms: round-robin and random choice. The proposedscheme first optimizes the bandwidth scheduling for a subset of Subscriber Station(SS), and then provides the optimal performance based on bandwidth scheduling forthe whole WiMAX (world interoperability for microwave access) network, especiallyin the Mesh mode with step-wise approach. Extensive simulation results using NS2show that the proposed scheme incurs a short delay and increases system throughputwhile using the network resource efficiently.4. Reconstruct a new route for network services during the handoff process is afundamental issue of wireless communication. This paper proposes a new reroutingalgorithm to achieve a fast handoff based on k-hop backtracking mechanism. Thealgorithm can dynamically decide the backtracking hops according to the velocity ofwireless devices and the current network band-width through iterative strategy.During the backtracking process, our algorithm is able to find out an optimized routefor the handoff network services and require all intermediate nodes which hasreceived the Location Update informa-tion forward all received packets to MobileTerminal with their optimal route to the destination subscriber station. This willgreatly reduce the cost of packet forwarding during the handoff process.更多还原