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Multiple Description Video Communications in Wireless Ad Hoc Networks
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As developments in wireless ad hoc networks continue, there is an increasing expectation with regard to supporting content-rich multimedia communications (e.g., video) in such networks, in addition to simple data communications. The recent advances in multiple description (MD) video coding have made it highly suitable for multimedia applications in such networks. In this thesis, we study three important problems regarding multiple description video communications in wireless ad hoc networks. They are multipath routing for MD video, MD video multicast, and joint routing and server selection for MD video in wireless ad hoc networks. In multipath routing for MD video problem, we follow an applicationcentric cross-layer approach and formulate an optimal routing problem that minimizes the application layer video distortion. We show that the optimization problem has a highly complex objective function and an exact analytic solution is not obtainable. However, we find that a metaheuristic approach such as Genetic Algorithms (GAs) is eminently effective in addressing this type of complex cross-layer optimization problems. We provide a detailed solution procedure for the GA-based approach, as well as a tight lower bound for video distortion. We use numerical results to compare this approach to several other approaches and demonstrate its superior performance. In MD video multicast problem, we take the similar application-centric, cross-layer approach as in the multipath routing problem. We propose an MD video multicast scheme where multiple source trees are used. Furthermore, each video description is coded into multiple layers in order to cope with diversity in wireless link bandwidths. Based on this multicast model, we formulate the multicast routing as a combinatorial optimization problem and apply Genetic Algorithm (GA)-based metaheuristic procedure to solove this problem. Performance comparisons with existing approaches show significant gains for a wide range of network operating conditions. In the last problem, we study the important problem of joint routing and server selection for MD video in ad hoc networks. We formulate the task as a combinatorial optimization problem and present tight lower and upper bounds for the achievable distortion. The upper bound also provides a feasible solution to the formulated problem. Our extensive numerical results show that the bounds are very close to each other for all the cases studied, indicating the near-global optimality of the derived upper bounding solution. Moreover, we observe significant gains in video quality achieved by the proposed approach over existing server selection schemes. This justifies the importance of jointly considering routing and server selection for optimal MD video streaming in wireless ad hoc networks.
- Masters Theses