【作者】 郭永洪；

【导师】 詹永照；

【作者基本信息】 江苏大学 ， 计算机应用技术， 2005， 硕士

【摘要】 近年来,随着移动通信技术和计算机网络技术的不断进步,ad hoc网络得到快速发展,其组播路由和拥塞控制技术受到越来越多研究者的关注。本文在比较和分析国内外现有组播路由和拥塞控制算法的基础上,针对ad hoc网络中基于格网结构的组播路由特征,提出拥塞检测、拥塞反馈和速率控制一整套完整的拥塞控制算法,并通过网络仿真软件验证了算法的正确性和有效性。本文的工作主要包括: (1) 分析现有ad hoc网络组播路由协议,给出综合评价,同时采用NS2对典型组播路由协议在各种网络环境下进行了仿真,通过分析仿真结果发现在高负载情况下其性能显著下降,主要原因是它们没有进行有效的拥塞控制。 (2) 研究现有的组播拥塞控制算法,根据不同的分类标准对现有组播拥塞控制算法进行分类讨论,并指出它们的优点和存在的问题。分析了有线网络组播拥塞控制方案不能用于ad hoc网络的原因,对现有ad hoc网络中典型的组播拥塞控制方法进行了比较和评价,指出了它们的不足之处。 (3) 提出了基于格网的ad hoc网络组播拥塞控制方案(GBAMCC)。详细讨论了GBAMCC方案的算法原理,通过分析造成节点拥塞的主要原因,计算出反映节点拥塞程度的数据分组丢弃率,综合考虑下游节点的拥塞程度,向上反馈本节点以下的拥塞情况,并进行发送速率控制,给出了拥塞检测、拥塞反馈和速率控制一套完整的拥塞控制机制,有效地提高了ad hoc组播环境下进行大数据量传输时的服务质量。 (4) 选择格网结构的ODMRP协议作为验证GBAMCC方案的试验平台,采用C++和Otcl语言设计组播拥塞控制算法,通过将该算法加载到ODMRP协议的路由代理中,给出基于ODMRP协议的组播拥塞控制仿真实现,同时设置了相应的网络场景,进行了仿真,并对典型的性能指标进行了分析,结果表明:增加了组播拥塞控制的ODMRP协议的有效性和公平性好于没有拥塞控制的ODMRP协议。更多还原

【Abstract】 Recently, with the development of the technology of the computer network and mobile communication, ad hoc network is developed sharply. The technology of multicast routing and its congestion control for ad hoc networks has received the concerns of more and more researchers. The paper gives a comprehensive survey and analysis of the existing multicast routing and its congestion control technique in ad hoc networks. According to the multicast routing characteristics of ad hoc networks, we present a novel algorithm for the grid-based multicast congestion control in ad hoc networks, which includes congestion detection, congestion feedback and traffic rate adjustment. The validity of algorithm is proved by simulation with NS2. The main aspects of work are described below:(1) The paper analyzes existing multicast protocols in ad hoc networks, and gives a comprehensive evaluation. By simulating some existing typical multicast routing protocols in the different conditions of ad hoc networks with NS2, we find that their performances degrade sharply under the higher load. The poor performances of these protocols stem from their attempts to inject packets into the network without performing any congestion control.(2) After studying the existing algorithms of multicast congestion control, we compare their advantages and shortages according to different criterions. We analyze the reasons that congestion control algorithms of the wired networks are not suitably applied to the ad hoc networks, and point out the deficiency in existing multicast congestion control algorithms of ad hoc networks.(3) A new method, called grid-based multicast congestion control for ad hoc network (GBAMCC), is presented and described in details. The main reasons of congestion are analyzed. By computing dropping packets ratios reflected degrees of congestion in mobile nodes, combining congestion degrees of current node with that of the downstream nodes, feeding them back to its upstream nodes, and adjusting upstream nodes traffic rate, the paper gives a whole multicast congestion control algorithm, which includes congestion detection, congestion feedback and traffic rate adjustment. The qualities of service in the transport of excessive data for ad hoc networks are improved.(4) The ODMRP based on the grid structure is chosen as the experiment platform tocheck the validity of GBAMCC. By employing C++ and Otcl to design algorithm for GBAMCC, and adding it into the routing agent of ODMRP, we give simulations of the algorithm in various scenarios with NS2. The results of the simulations show that ODMRP with congestion control obtains the better efficiency and fairness than that without congestion control.更多还原