【作者】 董芳；

【导师】 仇佩亮；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2008， 博士

【摘要】 无线传感器网络作为新兴的测控网络技术,是能够自主实现数据的采集、融合和传输应用的智能网络应用系统,由大量具有通信与计算能力的微小传感器节点组成,能够根据环境自主完成指定任务。WSN是一种大规模、无人值守、资源严格受限的全分布系统,采用多跳对等的通信方式,其网络拓扑动态变化,具有自组织、自治、自适应等智能属性。它的应用前景不可估量的同时,也给网络的通信、组网、管理和协同信息处理等带来新的问题。WSN设计的难点在于:在有效传输数据的情况下节省有限的能量资源来获取更长的网络寿命。合作通信(又称合作分集)技术是一种新的空间分集技术。该技术通过用户之间共享天线构成虚拟天线阵列,对比于传统的多天线系统(MIMO),并不要求用户终端配备多根天线,大大降低了用户终端的设计复杂度和成本,但同时又享有多天线系统的好处,通过利用空间分集对抗信道衰落,提高传输的质量。由于无线信道的广播特性,十分利于合作传输,因此将合作通信引入自组织网络成为新的研究热点。但是大多数合作通信的研究集中在物理层,合作引入后对于网络的更高层的影响并没有很好的展开讨论。基于合作通信的合作路由是一个新的研究领域,并且现有的研究表明合作能够大大降低自组织网络的能量消耗,这一点十分适合能量资源有限的WSN。本文的贡献在于研究了合作通信对于WSN物理层以上的影响,并提出了相应的MAC协议和路由协议。主要内容归纳如下:●将路径衰落考虑到各个合作协议如AF、DF、AFF、SDF等的中断概率推导中,得到了在相同中断概率的情况下,合作对通信距离的影响。结果表明,合作使得通信距离有较大的增加,尤其是在中断概率较低的情况下。在此基础上,研究了合作带来的通信距离的改变对网络连接度的影响:如果初始网络是连接的,当冗余节点转入休眠后覆盖区域没有减少的情况下‘通信距离R是感知距离r两倍’是保证合作WSN连接度的充分条件。优化节点分布,提出WSN的合作结构,一种介于平面结构和分层结构之间的网络配置,这种结构能够大大减少监测区域内的节点密度。●在研究合作对于通信距离的影响时,发现中继节点位置对合作性能的影响很大,位置信息包括两个因素:中继节点和目的节点之间的距离;中继节点和目的节点在源节点处的夹角。提出了基于角度信息的随机转发路由协议AnRaF,由于角度信息的熵要远远小于地理位置信息的熵,角度信息的获取和维护更为容易。多跳性能、能量性能和时延性能的研究表明,基于角度信息的路由协议能以一半的活动邻节点数取得和其余协议(如GeRaF)相同的性能。●研究合作引入WSN后对于现有的基于竞争机制的无线信道技术和避免碰撞的机制的影响。在基于角度信息路由协议配套的MAC协议基础上,提出了基于合作WSN的MAC协议。●基于角度信息路由协议基础上,提出了基于合作WSN的路由协议,并研究该协议在WSN初始连通时、初始非连通时、合作结构WSN中的性能。此外,改进了角度信息获取方法,使之能适应合作WSN。本文采用MATLAB作为仿真工具。更多还原

【Abstract】 Cooperative communication is able to effectively combat multi-path fading across multiple protocol layers in wireless networks. In this technique, sets of terminals relay signals for each other to create a virtual antenna array, trading of the costs-in power, bandwidth, and complexity-for the greater benefits gained by exploiting spatial diversity in the channel. By contrast, classical network architectures only employ point-to-point transmission and thus forego these benefits.In wireless sensor networks, one of the main design challenges is to save severely constrained energy resources and obtain long system lifetime. Low cost of sensors enables us to randomly deploy a large number of sensor nodes. Thus, a potential approach to solve lifetime problem arises. Recently, cooperative routing in Wireless Sensor Networks has gained much interest due to its ability to exploit the broadcast nature of the wireless medium in designing power-efficient routing algorithms.In this dissertation, we propose a cooperation-based angle routing protocol and its corresponding MAC scheme, which makes full use of the cooperative communications. The contributions can be categorized as follows.Sensor connectivity plays a critical role in WSN, while traditional node’s communication range R only considers direct transmission, and there is a lack of research on utilizing cooperation to improve R. In this dissertation, cooperative range R_C is utilized in WSN, with R_C and connectivity performance being evaluated by means of analytical techniques, in comparison with direct transmission. With cooperation, ’the communication range is twice of the sensing range’ is the sufficient condition to ensure that complete coverage preservation implies connectivity among active nodes if the original network topology (consisting of all the deployed nodes) is connected. Connectivity intensity is presented as performance metric, and simulation results demonstrate that the effectiveness of cooperation. In this sense, cooperative structure is proposed, which is shown as the configuration between flat and hierarchy structure.A novel random forwarding protocol for distributed wireless sensor networks is reported here, and the protocol features the utilization of azimuth angle of the nodes involved and opportunistic selection of the relaying node via contention among neighbors. First, the protocol with precise angle information is discussed and its multi-hop performance is evaluated by means of both simulation and analysis in terms of average number of hops to the sink node. Simulation results show that it performs well especially in network connectivity. As a complement, node mobility is also introduced to evaluate multi-hop performance in real environments. Then, a simple MAC scheme to ensure that the node with the highest angular advantage will be selected as a relay is proposed, and subsequently energy and latency performances based on it are evaluated. It is showed that our protocol can effectively deliver data with half number of active neighbors required in Geographical Random Forwarding (GeRaF). Finally, a practical method is presented to estimate azimuth angle, combined with which, our forwarding protocol is shown to achieve the performance very close to the case with precise angle information.Cooperation have a great effect on WSN, such as the enlargement of communication range, the nonreciprocal link, etc., which require traditional MAC schemes changing a lot. CSMA/CA, BTMA, RTS-CTS handshake are discussed here and variations of them satisfying cooperative WSN are proposed. Finally, a novel MAC scheme for multi-hop WSN with cooperation is presented, featuring opportunistic selection of the relaying node via contention among neighbors.A cooperative angle routing protocol for multi-hop WSN is presented. It exploits the broadcast nature of the wireless channel to enable on-demand cooperative relaying and has an effect as leapfrogging among multi-hop links. The practical method is modified to acclimatize itself to WSN with cooperation.更多还原