【作者】 王琦；

【导师】 韩江洪；

【作者基本信息】 合肥工业大学 ， 计算机应用技术， 2010， 博士

【摘要】 无线移动Ad Hoc网是一种特殊的无线移动通信网络,其中每个节点的地位平等,不需要中心控制节点,可以任意移动并具有报文转发能力,网络通信依靠节点之间的相互协作,以多跳方式完成,因而不依赖于任何固定设施。由于无线移动Ad Hoc网具有的诸多优良特性,可以应用于民用和军事领域,例如,抢险救灾、多媒体会议、视频点播及军事战场数字化通讯等。通过使用不同的调制和编码方法,Ad Hoc网的MAC层采用的IEEE802.11无线接入标准在物理层支持多种传输速率。因此,利用自适应速率调整算法,网络节点可以根据信道质量选择不同的传输速率,从而提高网络的通信能力。研究多速率传输问题对Ad Hoc网络的发展具有重大的意义。本文对无线移动Ad Hoc网上的多速率问题进行了深入研究,具体的研究内容包括多速率多播路由时延的最小化、基于多速率传输的调度问题、基于模糊Petri网的多速率路由选择、基于网络编码的无线局域网中继算法。主要研究成果如下:(1)多速率无线移动Ad Hoc网中的多播路由时延的最小化针对物理层提供的多速率传输特性,研究了无线移动Ad Hoc网多播路由时延的最小化问题。其主要思想是依据关键路径高速率优先的原则,上游节点将对数据包的一次低传输速率传输换为先高后低的多次不同速率的传输,从而缩短关键路径时延,使得多播时延达到最小化。首先将该问题模型化为一个最优化问题,然后提出了一个分布式多播路由时延的最小化(Distributed Minimizing Delay Multicast Routing,DMDMR)算法,并且证明了该算法能够取得最优值。大量模拟实验结果表明,与上游节点对数据包只进行一次传输的经典技术相比,DMDMR算法最高可降低21%的多播时延。(2)基于多速率传输的无线移动Ad Hoc网中的调度问题主要研究无线移动Ad Hoc网中的多速率调度问题。首先将它模型化为一个优化问题,然后根据是否考虑节点缓冲区因素提出了两个多速率条件下的调度算法HRFWICB(Highest Rate First without Considering Buffer)和HRFWCB(Highest Rate First with Considering Buffer),它们的基本思想是在保证数据流基本公平性的前提下,优先调度高速率数据流来降低包的传输时间和时延。实验结果证明,同经典的Luo算法及最大势包优先算法(Greatest Potential Packet First,GPPF)相比,HRFWICB和HRFWCB算法能够明显地降低包的传输时间和时延。(3)基于模糊Petri网的无线移动Ad Hoc网多速率路由问题针对多速率环境下的无线移动Ad Hoc网,研究了期望介质访问时间路由问题,其基本思想是根据链路包的丢失率和传输速率来选择从源节点到目的节点期望传输时间最短的路径。首先用模糊Petri网进行建模,接着提出期望介质访问时间路由算法(Expect Media Visiting Time,EMVT)。因此,候选路由尽可能多地包含了高传输速率和低包丢失率的链路,可以充分利用物理层多速率能力来提高网络吞吐量。模拟实验表明,期望介质访问时间路由算法比最小跳数路由算法和仅仅考虑链路传输速率路由算法相比,可以较大地提高了网络吞吐量并降低时延。(4)基于网络编码的无线局域网中继算法网络编码是21世纪信息领域的一项新技术,它既可提高网络吞吐量又可节省能量消耗。目前的研究成果主要是基于单速率传输,但随着无线网络技术和设备的不断更新,无线局域网MAC层协议已经开始支持多速率传输。本文将网络编码同无线局域网中多速率传输性质相结合,提出基于网络编码的中继算法(Relay Algorithm Based on Network Coding,RABNC),并且分析了其相对传统中继算法的时间减少率。通过模拟实验表明,RABNC算法相对传统的中继算法最高可以节省17%的传输时间。更多还原

【Abstract】 A Wireless Ad Hoc Networks is a set of nodes that can communicate with others in a multi-hop fashion without any assistance of fixed infrastructures and every node can move freely and relay data for others. Its main advantage is that it can be rapidly deployed without base station. The Wireless Ad Hoc Networks can be applied where pre-deployment of network infrastructure is difficult or impossible, for example, mobile meeting, disaster areas, and armies on the march.The IEEE 802.11 wireless media access standard in Wireless Ad Hoc Networks supports multiple data rates at the physical layer by employing different modulation and channel coding schemes. Nodes can utilize auto rate adaptation algorithm by automatically adapting the transmission rate to best match the channel conditions, and achieves better network performance. Research on multiple transmission rates is very important for the advancement of Wireless Ad Hoc Networks. This thesis studies four multi-rate issues for Wireless Ad Hoc Networks, including minimizing delay multicast routing in multi-rate Wireless Ad Hoc Networks, scheduling based on multi-rate transmission in Wireless Ad Hoc Networks,multi-rate routing in Wireless Ad Hoc Networks based on fuzzy petri net,relay algorithm based on network coding in wireless local network.The main results of the thesis are as follows:(1) Minimizing Delay Multicast Routing in Multi-rate Wireless Ad Hoc Networks: According to the multi-rate capacity at PHY layer, the optimal multicast delay in Wireless Ad Hoc Networks is studied. The main idea is replacing a lower rate transmission of upstream node with some transmissions from high to low to minimizing the multicast delay according to critical path based on the priority principle of high rate. Firstly, this problem is formulated as an optimization problem. Moreover, a Distributed Minimizing Delay Multicast Routing (DMDMR) algorithm is present and proved to be an optimal algorithm. The simulation results show that DMDMR algorithm can decrease of up to 21% over the multicast delay than the classic technique that the upstream node broadcast a packet only once.(2) Scheduling Based on Multi-rate Transmission in Wireless Ad Hoc Networks: This paper studies the multi-rate scheduling in Wireless Ad Hoc Networks. Firstly, we formulate it as an optimization problem. Moreover, the Highest Rate First without Considering Buffer (HRFWICB) algorithm and the Highest Rate First with Considering Buffer (HRFWCB) algorithm are present. Their main idea is scheduling prior the flow with higher transmission rate to decrease the transmission time and delay subject to that the minimum channel allocation for each flow is guaranteed. Finally the simulations are performed to compare our algorithms with Luo algorithm and Greatest Potential Packet First (GPPF) algorithm. The results show the algorithms can greatly decrease the transmission time and delay.(3) Multi-rate Routing in Wireless Ad Hoc Networks Based on Fuzzy Petri Net: This paper studies the expect media visiting time routing to improve throughput in multi-rate Wireless Ad Hoc Networks. The main idea is to select a path with the minimum except media visiting time based on the packet loss rate and the transmission rate of a link. Firstly, the problem is formulated as an optimization problem. Moreover, the Expect Media Visiting Time (EMVT) routing algorithm is present. As a consequence, the candidate route may contain a lot of high transmission rate and low packet loss ratio links. Simulation results show that EMVT algorithm can increase throughput and decrease delay over the Minimum Hop Amount routing algorithm and the routing algorithm which only considered the transmission rate.(4)Relay algorithm Based on Network Coding in wireless local network: The network coding is a new technology in the field of information in 21st century. It could enhance the network throughput and save the energy consumption. The present achievement is mainly based on the single rate. However, with the development of wireless network and equipment, wireless local network MAC protocols have already supported the multi-rate transmission. This paper proposes a Relay Algorithm Based on Network Coding (RABNC) and analyzes the transmission time gain of the algorithm over the traditional relay algorithm. The simulation results show that our algorithm could achieve the transmission time decrease of up to 17% over the traditional relay algorithm.更多还原