【作者】 王安保；

【导师】 方建安；

【作者基本信息】 东华大学 ， 控制理论与控制工程， 2011， 博士

【摘要】 无线网络是一种移动通信技术与计算机网络技术相结合的产物,其克服了传统网络的不足,实现了可移动的数据交换,为局域网开辟了一个崭新的技术和应用领域。无线局域网(Wireless Local Area Network,WLAN)正以其高度的灵活性、移动性、低成本和较高的传输能力在无线网络的应用中发挥着越来越重要的作用。无线网络与有线网络不同,不仅存在着误码率高、易干扰和隐藏站点/暴露站点等问题,而且还有共享无线信道和可移动性等特性,因此无线网络在路由算法和MAC协议上与有线网络存在许多差异。此外,网络的规模和分布等特性对无线网络的影响与有线网络也有所不同。基于上述多种因素的考虑,节点定位技术、路由算法和MAC层协议的优劣对无线网络至关重要。本文对无线网络中的节点定位技术、路由算法及MAC协议相关技术进行了分析和研究。在现有协议的基础上,提出了改进无线网络路由算法和MAC协议性能的方法,并在模拟环境下对所提出的算法进行了实现和性能分析,为无线网络中的节点定位技术、路由算法及MAC协议的研究提供了新的思路和方法,一定程度上提高了无线网络路由算法及MAC协议的可靠性和可控性,拓展了无线网络在不同需求场合的应用。具体而言,论文主要研究内容和创新点如下：(1)基于OLSR协议实现Ad Hoc网络中节点的定位针对无线Ad Hoc网络中节点已知自己位置(三维坐标,通过在节点中装备GPS或其它的定位设备获取)的情况下,在OLSR无线网络路由协议的基础上,修改了路由计算算法,在节点的路由表中增加目的节点的位置信息。实现了节点对其周围或整个无线Ad Hoc网络中其它节点分布情况的定位,并对具备定位功能的OLSR路由协议与原协议进行性能上的对比和分析。研究内容给一些无线网络中基于位置信息的应用,如路由算法的优化和数据包传输策略的选择等,提供了条件并带来了便利。(2) Ad Hoc网络中节点定位技术的改进针对目的节点较远时路由控制信息的传输存在延时,并进而会影响节点定位的准确性,对原定位算法进行了分析,给出目的节点定位存在误差的主要原因。提出了一种依据路由表中目的节点的当前位置对其实际位置进行预测的算法。在此基础上,设计并实现了节点位置的预测算法,对节点路由表中的位置信息应用预测算法以使其与目的节点的实际位置尽量相近。对算法进行了模拟与分析,证明了算法能较好地减小因目的节点路由信息传输延时等因素而给定位准确性带来的影响。(3)基于节点定位技术改进OLSR协议的MPR选择算法介绍了OLSR路由协议中的MPR技术,指出协议在使用启发式算法寻找最小MPR时存在一定的缺陷。结合本文研究的节点定位技术,给出了一种基于节点位置的改进算法。该算法通过引入节点位置信息,减小了OLSR协议在MPR选择算法中的盲目性,弥补了其对网络资源利用不充分的缺陷,能够在一定程度上减少网络中路由数据包传输的数量,从而提高网络的传输能力。在网络模拟环境下对改进算法进行了实现,分析了实验结果,表明提出的改进算法是可行和适用的,选择基于位置的启发式策略是恰当和正确的。(4)基于节点定位及蚁群优化技术的启发式路由算法提出了一种新的路由算法,使用节点定位技术提供的定位数据作为启发式信息。同时,利用蚁群优化技术,通过分析每个节点所处位置的不同,并结合其一跳及两跳节点的定位信息,在算法的实现中使蚂蚁采用不同的概率转发路由信息到下一跳节点,取得了减少网络维护路由控制信息总量的目的。算法选择多条路径记录在本地路由表中,提高了算法的鲁棒性,并同时采取修复机制创建新路径以提高数据包传输的成功率。仿真结果表明该算法取得了较好的数据包传输成功率与较低的通信延迟。(5)无线网络中错误模型的分析及应用分析了无线网络中导致分组数据传输错误的原因,指出了分组数据的传输错误会导致传输失败、网络性能下降。对无线网络中的错误模型理论进行了分析和研究,探讨了在无线网络中应用802.11a及802.11b协议时各种传输错误的特征。并在网络模拟环境中对常见的错误模型进行了模拟实验,对实验结果进行了分析。(6)基于802.11e标准的统一信道竞争管理算法分析了现有802.11e协议对无线局域网QoS的支持及存在的不足,并在此基础上设计了以802.11e协议为基础平台的统一信道竞争管理算法。利用现有的二维马尔科夫链模型进一步对DCF原理进行分析,提供了判断当前网络状态测量参数的计算方法。设计并实现了动态调整各优先级队列占用信道概率的算法,从而最大程度地保证各个等级业务的公平性,预防饿死现象的发生,并以此提高带宽的利用率。在仿真实验中从吞吐量、延时和公平性等方面对该算法进行了分析。更多还原

【Abstract】 The wireless network is a combining product which integrated mobile communication technology with computer network technology. It has overcome the insufficiency in the traditional network and realized the movable data exchange. Meanwhile, it has also opened up a new area of technology and application for the local area network. Because of the high flexibility, mobility, low cost and relatively high through-put capacity, the wireless local area network (WLAN) is going to play vital role in the wireless communication network applications.There are some differences between wireless and wired network. Wireless network not only has some flaws such as high error rate, interference and hidden terminal\exposure terminal problem, but also shows the characteristics of sharing medium and mobility and so on. Therefore, the protocol designed for the routing algorithm in wireless network is obviously different from the wired network. In addition, the impact of the network scale and other properties deliver obvious different results to wired network and wireless local area network. Considering the factors described above, it is vital important to improve the performance of the routing algorithm and the MAC protocol in wireless local area network.In this paper, the routing algorithm and the MAC protocol in wireless local area network are analyzed and studied. Several algorithms are proposed for the wireless local area network to improve the network performance based on the existing protocols. The proposed algorithms are implemented in the simulated environment and the performance is analyzed. New approaches and methods are provided for the research of the routing algorithms and MAC layer protocol in wireless LAN. The reliability and controllability for the routing algorithm and MAC layer protocol in WLAN are enhanced, and the applications in different occasions are expanded. The compendious novelty and description of the thesis are given as follows:(1) Realizes the node localization based on the OLSR protocol in the Ad Hoc networkWe propose that the wireless Ad Hoc network node knows its position (three-dimensional coordinates, through the node equipped with a GPS or other positioning devices), based on the OLSR routing protocol in wireless network, the routing computation algorithm is modified, and the target node’s location information is added in the routing table for every node. We try to let the node achieve the positions of its surrounding nodes or the entire wireless Ad Hoc network nodes. Additionally, the OLSR routing protocol which has localization function is analyzed and compared with the original protocol. The content of the research can provide conditions and bring convenience to location-based wireless network applications such as routing algorithm’s optimization, packet transmission strategy and so on.(2) Improving the node localization technology in Ad Hoc networkIf the destination node is far from the source node, the transmission of the routing control information for the destination node has some delay and will then affect the accuracy of the node localization. An algorithm is proposed to predict the actual location of the distination node based on its current position information in routing table. The original algorithm is analyzed, and the primary reason that the node localization has some deficiency is pointed out. The node localization forecast algorithm is designed and realized, and the forecast algorithm is used to improve the accuracy of the node localization as far as possible. The algorithm is simulated and analyzed, and it proved that the proposed algorithm can effectively reduce the impact of positioning accuracy caused by the node transmission delay and other factors.(3) Improving MPR selection algorithm in OLSR protocol based on node localization technologyThe MPR technology in the OLSR routing protocol is described, it is pointed out that there are some limitations when the default heuristic algorithm in this protocol is used to find the minimum MPR. In this paper, an improved algorithm based on node localization is proposed combined with node localization technology. Node localization information is used in this algorithm, the blindness is reduced in the MPR selection algorithm in the OLSR protocol, it can make full use of the network resources, the number of routing packets needed to deliver in the network is reduced to a certain extent, and therefore it can improve the network transmission capacity. The improved algorithm is implemented in network simulation environment, the results are analyzed, it shows that the proposed improved algorithm is feasible and applicable, and the location-based heuristic selection strategy is appropriate and correct. (4) A heuristic routing algorithm based on node localization and ACO technologies for Ad Hoc networksA new routing algorithm is proposed which is based on the ant colony optimization algorithm for mobile Ad Hoc networks (MANETs). It also uses the location information from node localization technology and OLSR routing protocol which has the localization function as heuristic information. By analysis, according to its 1-hop and 2-hop location information of the neighbor nodes, every node in different position should use different probability to let the ant forward the routing information to the next hop, so as to greatly reduce the overhead of the packets used for maintaining the route information. The algorithm selects one or two of the paths recorded in its local routing table for the robustness reason. In order to further promote the robustness of the routing algorithm, a mechanism by creating an alternative path to repair the wrong path is proposed. Simulation results show that our algorithm achieves good packet delivery ratio with low communication delay.(5) Analysis and Utilizing of the Error Models in Wireless NetworkThe reasons which cause data packets transmission error is analyzed in the wireless network, it is highlighted that the data packets transmission error will cause transmission failure and the network performance drops. The common error models used in 802.11 standards are introduced and the correlated theories are analyzed and studied. The characteristics of a variety of transmission errors are discussed when the applications use 802.11a and 802.11b as its protocol. Several common error models are simulated using the simulation software, and the results are analyzed. This chapter has not only provided helps to understand and evaluate the characteristics and performance of wireless network, but also brought great convenience to researchers and scholars.(6) United of channel contention management based on IEEE 802.11e NetworksThe shortcomings in the current 802.11e protocol for WLAN to which support the QoS are analyzed. We proposed a united channel contention algorithm based on the platform of IEEE 802.11e protocol. In order to realize the computational methods that can be used to get the measurement parameters of the network state, the principle of the DCF mechanism is further analyzed using the existing two-dimensional markov chain model. An algorithm is designed and implemented to dynamically adjust the probabilities of using the wireless channel for different priority queues. It can improve the resource sharing among the active queues and the efficient using of the bandwidth, preventing the occurrence of the phenomenon of starvation and optimizing the fairness among the different virtual queues in 802.11e. Finally, the throughput, delay and fairness and other aspects of the algorithm are analyzed in the simulation.更多还原