A wireless ad hoc network is a self-organized and dynamically reconfigurable wireless network without central administration and wired infrastructure. Nodes in a wireless ad hoc network can instantly establish a communication structure while each node moves in an arbitrary manner. A wireless ad hoc network is useful for mobile nodes working in a group to accomplish certain tasks. On the other hand, multicast is a very useful and efficient means of supporting group-oriented applications. Multicast is an essential technology for many applications such as video distribution and group video conferencing, data dissemination, disaster relief and battlefield.ududVideo multicasting over wireless ad hoc networks is bandwidth-efficient compared to multiple unicast sessions. However, video multicasting poses great challenges over wireless ad hoc networks. Video packets are both delay and loss sensitive. In addition, due to nodes mobility, the topology of wireless ad hoc networks is frequently changed. As a result, the established links are continuously broken, causing quality loss and interruption in the received video signal. Other challenges include limited battery life of wireless nodes and lower wireless network capacity compared to wired networks.ududVideo multicast over wireless ad hoc networks has been an active area in recent years. The main objective of these studies is to improve the quality of the received video by exploiting the error resilience properties of Multiple Description Coding (MDC) along with multiple paths. In other words, MD video is encoded and transmitted over two different paths to each destination node. If only one path is broken, packets corresponding to the other description on the other path can still arrive at the destination node on time.ududLayered Coding (LC) and Multiple Description Coding (MDC) have been proposed as video source coding techniques that are robust against inevitable transmission errors. In contrast to MDC, LC encodes a media source into two or more sub-streams, known as layers, one base layer and several enhancement layers. The base layer can be decoded to provide a basic quality of the received video while the enhancement layers are mainly used to refine the quality of the video that is reconstructed from the base layer. If the base layer is corrupted, the enhancement layers become useless, even if they are received correctly. Therefore, the base layer is critically important and is usually highly protected. For MDC, however, these sub-streams are of equal importance in the sense that each sub-stream, also called a description, can be decoded independently to produce a signal of basic quality. When more descriptions are received, the decoder can gradually increase the quality.ududOne main problem of video multicasting for heterogeneous destinations is the assignment of video descriptions and the construction of multicast tree. However, the assignment of MD video and the construction of multicast tree can greatly affect the user satisfaction (i.e., affect the quality of the received video). In this thesis, we introduce novel approaches to improve the user satisfaction for a set of heterogeneous multicast destinations. The main idea of our approaches is to employ the independent-description property of MDC along with multiple multicast trees. However, many questions are raised: How multiple multicast trees should be constructed? And how MD video should be assigned? Is it better to construct multiple multicast trees first and then assign the video descriptions? Or is it better to assign the video descriptions first and we then construct multiple multicast trees? Should we perform that in a distributed manner or in a centralized one?ududTo answer these questions, we propose different algorithms to construct multiple multicast trees and to assign MD video. The proposed algorithms are: Serial MDC, Distributed MDC, and Centralized MDC. Serial MDC constructs multiple paths, to each destination, and assigns a different video description to each of them. After that, it constructs multiple multicast trees. Distributed MDC assigns MD video and constructs multiple multicast trees in parallel and in distributed fashion. In Centralized MDC, the assignment of MD video and the construction of multiple multicast trees are performed in a centralized manner. However, Centralized MDC first constructs multiple multicast trees and then assigns different video description to each multicast tree. We evaluate and compare our proposed algorithms Under different network conditions. For example, Network size, and multicast group size. Simulation results demonstrate that, indeed, the way of multicast trees construction and the assignment of MD video can greatly affect the user satisfaction. In addition, simulation results show that MDC can achieve higher user satisfaction compared to LC with a small cost in terms of number of pure forwarders nodes, bandwidth utilization, and aggregate tree delay.ududFurthermore, we use our proposed algorithms to develop different multicast protocols for video multicast over wireless ad hoc networks. Specifically, we propose four protocols, namely, Centralized MDMTR (Multiple Disjoint Multicast Trees Routing), Sequential MDMTR, Distributed MDMTR, and Neighbor-aware MDMTR protocols. These protocols take many issues into consideration, rejoining and joining a multicast group, multicast trees maintenance, and mobility of nodes, for example. We evaluate the performance of our proposed protocols and compare them under different network conditions. For example, multicast group size, and mobility of nodes. Simulation results demonstrate that our protocols perform well compared to other protocols in the literature.
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机译：无线自组织网络是无需组织管理和有线基础结构的自组织且可动态重新配置的无线网络。无线自组织网络中的节点可以在每个节点以任意方式移动时立即建立通信结构。无线自组织网络对于成组工作的移动节点完成某些任务很有用。另一方面，多播是支持面向组的应用程序的非常有用和有效的手段。对于许多应用，例如视频分发和组视频会议，数据分发，救灾和战场，多播是一项必不可少的技术。 ud ud与多个单播会话相比，无线自组织网络上的视频多播具有带宽效率。然而，视频多播在无线自组织网络上提出了巨大的挑战。视频数据包对延迟和丢失均敏感。此外，由于节点的移动性，无线自组织网络的拓扑结构经常更改。结果，已建立的链路不断断开，从而导致质量损失和接收视频信号的中断。与有线网络相比，其他挑战包括无线节点的电池寿命有限和无线网络容量较低。 ud ud通过无线自组织网络进行视频多播是近年来的活跃领域。这些研究的主要目的是通过利用多描述编码（MDC）的错误恢复特性以及多路径来提高接收视频的质量。换句话说，MD视频经过编码并通过两条不同的路径传输到每个目标节点。如果只有一条路径断开，则与另一条路径上的另一条描述相对应的数据包仍可以按时到达目标节点。 ud ud分层编码（LC）和多描述编码（MDC）已被提议作为视频源编码技术可以避免不可避免的传输错误。与MDC相比，LC将媒体源编码为两个或多个子流，称为子层，一个基本层和几个增强层。基本层可以被解码以提供所接收视频的基本质量，而增强层主要用于细化从基本层重构的视频的质量。如果基础层损坏，即使正确接收增强层，它们也将变得无用。因此，基础层至关重要，通常受到高度保护。但是，对于MDC，这些子流具有同等重要的意义，因为每个子流（也称为描述）可以独立解码以产生基本质量的信号。当接收到更多描述时，解码器可以逐渐提高质量。 ud ud用于异构目的地的视频多播的一个主要问题是视频描述的分配和多播树的构造。然而，MD视频的分配和多播树的构造会极大地影响用户满意度（即，影响所接收视频的质量）。在本文中，我们介绍了新颖的方法来提高一组异构多播目标的用户满意度。我们方法的主要思想是将MDC的独立描述属性与多个多播树一起使用。但是，提出了许多问题：应如何构造多个多播树？ MD视频应如何分配？首先构造多个多播树然后分配视频描述更好吗？还是先分配视频描述然后再构造多个多播树更好？为了应对这些问题，我们提出了不同的算法来构造多个组播树并分配MD视频。提出的算法是：串行MDC，分布式MDC和集中式MDC。串行MDC构造到每个目的地的多个路径，并为每个路径分配不同的视频描述。之后，它会构造多个多播树。分布式MDC分配MD视频，并以分布式方式并行构造多个多播树。在集中式MDC中，以集中方式执行MD视频的分配和多个多播树的构造。但是，集中式MDC首先构造多个多播树，然后为每个多播树分配不同的视频描述。我们评估并比较了我们在不同网络条件下提出的算法。例如，网络大小和多播组大小。仿真结果表明，组播树的构建方式和MD视频的分配确实可以极大地影响用户满意度。此外，仿真结果表明，与纯LC相比，MDC可以以更高的用户满意度，而在纯转发器节点数，带宽利用率方面却成本较低 ud ud此外，我们使用提出的算法为无线ad hoc网络上的视频多播开发不同的多播协议。具体来说，我们提出了四种协议，即集中式MDMTR（多个不相交多播树路由），顺序MDMTR，分布式MDMTR和可感知邻居的MDMTR协议。这些协议考虑了许多问题，例如重新加入和加入多播组，多播树维护以及节点的移动性。我们评估我们提出的协议的性能，并在不同的网络条件下进行比较。例如，多播组的大小和节点的移动性。仿真结果表明，与文献中的其他协议相比，我们的协议性能良好。
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