Mobility Tolerant Adaptive Multicast Protocols for Ad Hoc Networks

移动自组织网络由移动主机组成，通过无线信道进行通信，正越来越多地用于局域网、执法、军事行动和无数其他应用。这些应用程序中的大多数（如果不是全部）都涉及将消息从一个主机（源）发送到指定的主机组，并且网络中可能有大量这样的组，用于不同类型的应用程序。多播涉及到将消息发送到受限制的进程组，并形成了在分布式系统上有效实现基于组的应用程序的基础。在静态网络中有效执行多播的许多协议都是可用的，但目前，为自组织网络设计此类协议的一些关键技术问题仍未得到解决，包括对功率限制和高速数据问题的优雅解决方案，由于主机移动而在过渡期间保证消息无损的有效方法，以及在本地控制任何拓扑变化影响的能力。在移动自组织网络中，网络的拓扑结构随着节点的移动、无线电传播条件的变化以及节点电池电量的耗尽而变化。在网络的不同时间和不同区域，拓扑变化的速率可能是不同的。网络可能经历频繁的网络分区，并且可能需要重新配置分区的子网。提出的研究将采用理论和实验相结合的方法，并将其应用于新兴的分布式应用程序。在本提案中，研究人员结合了网络中基于组的通信和异步分布式计算系统中协议稳定领域的专业知识，提出了一个创新的集成研究项目，用于移动自组织网络的容错多播协议设计。拟议的设计旨在展示各种令人印象深刻的好处，包括：(1)协议将支持混合交通的可变利率突然变化的适应能力快速轻松通过动态链接在交通成本估计量(这取决于信道带宽、服务质量(QoS)的应用程序,电池供电的主机,等等)。(2)协议是稳定在任何拓扑变化由于节点的移动性会触发协议和最优组播树将为新拓扑和快速重建。(3)自稳定协议增加了一些特性，以保证在多播树适应新的拓扑时服务仍然可用（即，在恢复期间系统中存在的多播消息不会丢失）。(4)协议的自稳定特性以可控的方式触发，通过使用有效的故障遏制策略，在高移动性的情况下不会使系统崩溃。(5)针对传统的自稳定算法的对抗性预言模型，基于自组织网络的实际情况，开发一种新的分布式系统自稳定算法的执行模型。研究人员期望，这将导致使用自稳定的概念来解决其他现实生活中的问题，包括从短暂的行为中恢复过来。在具有上述优点的移动自组织网络中执行多播的有效解决方案将依赖于底层数据链路层可以提供的支持以及网络层多播协议如何利用这些设施来智能地控制开销，同时提供理想的QoS。本方案将采用协同的方法设计多播协议，使其与底层网络层兼容。拟定的方案将通过模拟进行广泛评估。此外，将在IEEE 802.11 MAC层之上实现一个原型协议栈，以评估对分布式媒体分发和协作应用的QoS改进。

Mobile ad hoc networks consisting of mobile hosts that communicate via wireless radio channels are being increasingly used for local area networks, law enforcement, military operations and myriad of other applications. Most of these applications, if not all, involves sending messages from one host (source) to a specified group of hosts and there can be a large number of such groups in the network for diverse kinds of applications. Multi-cast involves sending messages to a restricted group of processes and forms the basis for efficient implementation of group based applications on a distributed system. Many protocolsfor efficiently performing multi-cast in static networks are available while at this time, a number of critical technical issues in designing such protocols for ad hoc networks remain unresolved, including elegant solutions to issues of power limitations and high speed data, effective methods of assurance for losslessness of the messages during transition period due to host mobility and the ability to contain the effect of any topology change locally. In mobile ad hoc networks the topology of the network changes with node movements, variations in the radio propagation conditions, and depletion of battery power of the nodes. The rate of topological changes can be different at different times, as well as in different regions of the network. The network can experience frequent network partitioning and may require reconfiguration of the partitioned subnetworks. The proposed research will take a combined theoretical and experimental approach and will apply this to emerging distributed applications. In this proposal the researchers with combined expertise in the fields of group based communications in networks and stabilization of protocols in asynchronous distributed computing systems are proposing an innovative integrated research project in fault-tolerant multi-cast protocol design for mobile ad hoc networks. The proposed design intends to demonstrate a variety of impressive benefits including: (1) The protocol will support mixed traffic of variable rates with the ability to adapt fast with ease to sudden changes in traffic via a dynamic link cost estimator (that depends on channel bandwidth, quality-of-service (QoS) to the applications, battery power of the hosts, etc.) (2) The protocol is self-stabilizing in that any topological change due to mobility of nodes will trigger the protocol and the optimal multicast tree will be for the new topology and quickly reconstructed. (3) The self-stabilizing protocols are augmented with features that guarantees that the service remains available while the multi-cast tree is being adapted to the new topology (i.e., multicast messages present in the system during the recovery period are not lost). (4) The self-stabilization features of the protocol are triggered in a controlled manner so as to not overwhelm the system in presence of high mobility by using efficient fault-containment strategies. (5) The research intends to develop a new execution model for the self-stabilizing algorithms in a distributed system based on the real-life conditions of an ad hoc network as opposed to the traditional adversarial oracle model for such algorithms. The researchers expect that this will lead to the use of the concept of self-stabilization to solving other real life problems involving recovery from a transient behavior. Efficient solutions for performing multi-casting in mobile ad hoc networks with the above benefits will rely on what support underlying data link layer can provide and how the network layer multi-cast protocol can exploit these facilities to intelligently control the overheads while providing desirable QoS. This proposal will take a synergistic approach in designing the multi-cast protocols so as to make them compatible with the underlying networking layers. The developed protocols will be extensivaly evaluated through simulation. Further a prototype protocol stack will be implemented on the top of IEEE 802.11 MAC layer to evaluate the improvement in QoS to distributed media distribution and collaboration applications.