【作者】 陈琳；

【导师】 李明禄；

【作者基本信息】 上海交通大学 ， 计算机应用技术， 2007， 博士

【摘要】 近年来,随着网络技术和无线通信技术的飞速发展,无线Ad Hoc网络逐渐成为人们研究的热点。在Ad Hoc网络从军事领域扩展到商业领域的过程中,其规模和应用范围急剧扩大,网络承担的任务种类愈来愈多,如何成功的对无线Ad Hoc网络进行资源管理和控制,提高网络的性能和服务质量,保证信息的安全和可靠传输,已成为一项亟待解决的任务。为了实现资源的有效管理,本文就异构骨干网结构、联合拓扑控制与路由,以及多速率感知的功率控制等三个重要问题展开了研究。首先本文提出了一种可扩展的多接口多信道异构无线网络结构,并在此基础上设计了灵活的信道分配、功率控制以及路由联合调整机制以进一步提高网络吞吐量,最后对多速率感知状况下的最优发射功率控制问题进行了理论分析。本文的主要贡献和创新点为:(1)提出了一种简单可行的可扩展多接口多信道异构无线网络结构,用于无线Ad Hoc网络的骨干网部分,可改善无线网络的吞吐量和扩展性。无线介质的广播特性造成节点接入竞争和相互干扰,使得信道的容量大大降低。早期多跳网络理论分析和实验结果表明由于受数据报多次转发的影响,网络的吞吐量随着网络规模的扩大而急剧降低,网络可扩展性较差。本文提出的可扩展多接口多信道异构无线网络结构,赋予了超级节点和路由器节点不同的传送能力,借助超级节点的长距离转发来减少跳数,从而提高网络的可扩展性;同时超级节点和路由器节点具有不同的网络接口数和信道分配,多信道的使用大大缓解了强发射功率对周围节点所产生的干扰以及不对称链路引起的隐终端的影响,并进一步提高了网络的吞吐量。(2)提出位于MAC层和网络层之间的联合拓扑控制与路由协议,该协议根据信道状况通过协调多个无线节点的发射功率、信道分配和路由选择来降低节点之间的干扰,以达到提高网络吞吐量的目的。IEEE 802.11提供的正交信道数毕竟有限,每个节点所配备的接口数目更是远远少于可用信道数,再加上信道分配时节点之间信道依赖和连通性保证的影响,网络吞吐量的改进往往不能达到令人满意的程度。本文侧重于同时考虑信道多样性和空间复用性,提出了联合拓扑控制与路由协议。该协议的特点是:基于两跳内链路负载和节点信道信息,根据性能指标ECATM对各种可行的调整候选方案进行量化,找出最优方案,然后相应的调整节点不同接口的发射功率、信道分配以及路由选择以改善当前网络状况。(3)对多速率感知状况下的发射功率控制问题进行分析并建立了理论模型,该模型揭示了空间复用和单条链路物理层数据传输速率之间的折衷关系,能得出最大化网络吞吐量的节点最优发射功率。现有工作着重考虑发射功率和跳数之间的折衷而忽略了多速率对最优发射功率影响,或是基于时分复用的MAC假设,其结论难以应用到真正的Ad Hoc网络。本文使用p-persistent CSMA,采用马尔可夫链从理论上对基于IEEE 802.11 MAC的多速率感知发射功率控制问题进行分析,对单跳数据流、多跳数据流、以及存在并发干扰和隐终端状况下的吞吐量进行了建模,揭示了多速率感知状况下发射功率的最优选择。通过这些模型,可以得出不同发射功率下网络的整体吞吐量,数据发送延迟等信息,最后通过数值计算分析了模型的正确性。更多还原

【Abstract】 With the rapid development of networking and wireless communication technologies,wireless ad hoc network has been a hot research topic. Nowadays, wireless ad hoc net-work has been utilized not only in military but also the commercial area. The dimensionsand the application ranges are rapidly extended. Hence, how to manage the resource rea-sonably, improve the network performance as well as service quality, and ensure the secureand reliable information transmissions has been an important task of the wireless ad hocnetwork. In order to realize the efficient resource management, this dissertation focuses onthe research of heterogeneous backbone architecture, joint topology control and routing, andthe multi-rate aware transmission power control problem. Firstly, a scalable multi-channelmulti-radio wireless backbone architecture is proposed in this dissertation. Based on that,a ?exible joint channel assignment, transmission power control and routing adjustment pro-tocol is designed to further improve the network throughput. Finally, the multi-rate awareoptimal transmission power control problem is analyzed theoretically. Major contributionsand the originalities of this dissertation are as follows:(1) A scalable multi-radio multi-channel heterogeneous wireless ad hoc network archi-tecture is proposed in this dissertation. This architecture can be utilized as the backbone ofwireless ad hoc network and aims to improve the network performance and scalability.Due to the in?uence of contention and interference on the wireless broadcast channel,the network throughput is far from satisfactory. Early simulation experience also suggeststhat the throughput decreases sharply with the increase of hops, therefore the network is notscalable with network size. The proposed scalable multi-radio multi-channel heterogeneousarchitecture offers different transmission capabilities to super nodes and router nodes. By theaid of the long-range transmission of super nodes, the hop count is reduced and consequentlythe scalability is enhanced. Meanwhile, super nodes and router nodes have different num-ber of radios and channel assignment. The utilization of multi-channel multi-radio greatly reduces the interference of super nodes to other nodes and alleviates the in?uence of hiddenterminals caused by asymmetric links.(2) A novel joint topology control and routing protocol is proposed in this dissertation.It resides between MAC and network layer and aims to reduce the interference and conse-quently improve the network throughput by coordinating the transmission power, channelassignment and route selection among multiple nodes in a distributed way.The number of available channels in IEEE 802.11 is limited, and the radios equippedon each node are generally less than channels. Besides, due to the channel dependencyand connectivity requirement among nodes, the co-channel interference can only be reducedto a certain degree. This dissertation focuses on considering both channel diversity andspatial reusability to reduce co-channel interference, and presents a joint topology controland routing protocol. Based on the traffic information measured and exchanged among two-hop neighbor nodes, this protocol quantifies the difference of various adjustment candidatesby the aid of ECATM, then selects feasible adjustment candidate with the smallest ECATMvalue, and finally coordinates affected nodes to adjust the transmission power at each node,the channel selection on each wireless interface, and route selection between nodes.(3) The multi-rate aware optimal transmission power control problem is theoreticallymodeled and analyzed in this dissertation. This model illustrates the tradeoff between spatialreuse and physical layer data rate. The optimal transmission power can be derived based onthis model which maximizes the network throughput.Previous works mainly focus on the tradeoff between transmission power and hop counton path while neglecting the impact of multiple rates, or they are based on the assumption oftime division MAC so that their results can hardly be applied to wireless ad hoc network. Inthis dissertation, the behavior of basic IEEE 802.11 DCF is approximated by the p-persistentCSMA through a Markov chain model. Various factors, such as hidden terminals, multi-hopdata ?ow and concurrent interference are incorporated to shed light on the rate-aware optimaltransmission power choice problem. From these models, the average per-node throughput,the optimal transmission power and expected transmission delay for given scenario can bederived. Finally the correctness of this model is analyzed by numerical results.更多还原