【作者】 朱晓妍；

【导师】 王育民；

【作者基本信息】 西安电子科技大学 ， 密码学， 2009， 博士

【摘要】 本论文研究了无线自组织网络中存在的几个重要问题,分别是网络容量、网络编码的应用以及无线网络安全。首先,研究了具有部分基础设施的合作无线网络的吞吐量和时延问题。已有研究表明:只有当网络中基站数目m与节点数目n的阶相同时,混合无线网络的吞吐量可以随着网络节点数目的增多线性增长。利用MIMO分布式通信的纯无线自组织网络(wireless ad hoc networks,或WANETs)也可以线性增容。那么有一个问题:如果利用MIMO分布式通信技术,不管放置多少个基站,混合无线网络都可以线性增容吗?我们研究了该问题,并且指出应用已有的资源分配策略,混合无线网络并不是都可以线性增容。特别地,我们指出只有当下列两个条件之一成立时,网络才能线性增容。第一,当m =Θ(1 )且所有的资源都分配以自组织传输模式;第二,当m =Θ( n)且所有的资源都分配以基础设施传输模式。此外,在第一种情况下,时延非常大;在第二种情况下,时延为Θ(1 )。其次,研究了网络编码在无线网络中的应用,并提出一个新颖、实用的网络编码(Network Coding)方案,来处理无线网络中的流间(inter-flow)流量和流内(intra-flow)流量。该方案基于COPE,允许网络中每个节点利用流内网络编码技术,来提高传输的可靠性,从而获得更高的吞吐量。我们从理论上证明了该方法的可行性。提出了多路径传输方案,进一步提高链路传输概率较低的无线网络的吞吐量。指出如何在网络中使用网络编码,并讨论了我们所提方案的优点。最后,研究了无线网络的安全。无线自组织网络具有开放的无线链路、缺少固定基础设施、节点计算能力和通信能力有限等特点,某些已有的针对有线网络或传统无线网络的安全方案无法适用。而且,其应用场合大多又非常敏感,对安全性要求很高,所以研究高效、可行的安全机制至关重要。我们利用基于身份的密码学方法,研究资源匮乏的WANETs中的安全问题,证明了基于身份的密码学方法非常适合应用在资源匮乏的无线网络中;并将其应用在无线传感器网络以及无线mesh网络的认证和共享密钥建立上,提出了一种基于位置的传感器网络安全方案,以及一个灵活简单的无线mesh网络安全接入方案。根据无线信道是有损信道且无线终端节点能力差的特点,我们提出了一个多播认证体制MABS,它不仅能够减少数字签名的验证负担,而且能很好地容忍数据包丢失;其增强方案MABS-E可以有效对抗拒绝服务攻击。更多还原

【Abstract】 This dissertation investigates a few important challenging problems, such as network capacity, the application of network coding and network security, in wireless ad hoc networks (WANETs).First, we study the throughput capacity and delay for wireless ad hoc networks with partial infrastructure. It has been shown that only when the number of base stations m and the number of normal nodes are on the same order, can the throughput capacity be linearly increasing with the number of nodes (the scaling law). Moreover, through the use of newly emerging MIMO distributed transmissions schemes, we can also achieve the scaling law for pure wireless ad hoc networks. One question remains: for mixed wireless ad hoc networks with partial infrastructure, can we use MIMO technologies to make the throughput capacity scale? We investigate this problem and point out that with the current resource allocation strategy commonly used today, we cannot make the throughput capacity scale for hybrid ad hoc networks. We have shown that the hybrid WANETs can scale only when one of the following two conditions holds: (1) when m =Θ(1 ) and all resource is allocated to the ad hoc transmission mode; (2) when m =Θ( n) and all resource is allocated to infrastructure transmission mode. Moreover, the delay is very large for the former while isΘ(1 ) for the latter.Second, we look into the application of network coding in wireless ad hoc networks and propose a novel practical network coding scheme to deal with intra-flow and inter-flow traffics. This scheme is based on the previously known COPE and allows each node to use intra-flow network coding to enhance the transmission reliability in order to increase the throughput capacity. Based on a simplified network topology, we derive some analytical results and theoretically demonstrate the feasibility and effectiveness of our proposed scheme. We also propose a multipath transmission scheme to enhance the reliability between two nodes for WANETs with low transmission reliability, and further increase the throughput capacity. We discuss how to effectively utilize network coding and objectively assess the advantages and disadvantages of our scheme.Finally, we investigate the wireless network security. In WANETs, due to the openness of wireless routing paths, the lack of existing infrastructure, and the limited computational and communication capability, many security schemes for wireline networks or traditional wireless networks may not be effective. Moreover, most WANETs are deployed for sensitive applications with high demand on security, and hence it is vital to search for high efficient and feasible security mechanism. In our final research task, we investigate the security problem for resource-constrained WANETs. We show that ID-based cryptography is perfect fit for addressing the security issues in resource-constrained WANETs, and then apply this technique to wireless sensor networks and wireless mesh networks for authentication and key establishment, and come up with a location-based security scheme for wireless sensor networks and a simple yet effective secure access scheme for wireless mesh networks. By observing that wireless channels are lossy and the receiving ends are typically resource-limited for multicast services, we propose a novel authentication scheme MABS, which not only mitigates the computational burden in the signature verifications, but also is resilient to packet loss. Moreover, its enhanced version MABS-E can also effectively counteract the denial of service attack.更多还原