Multipath Unicast and Multicast Video Communication over Wireless Ad Hoc Networks
Technical Report Identifier: EECS-2006-186
December 18, 2006
Abstract: With the increase in the bandwidth of wireless channels and in the computational power of mobile devices, video applications are expected to become available on wireless ad hoc networks in a near future. However there are many challenges for supporting video communication over wireless ad hoc networks, e.g. the mobility of wireless nodes, random packet loss due to channel error or collision and small bandwidth, which make video communication over wireless ad hoc networks a challenging proposition.
In this dissertation, we introduce new path diversity schemes in order to provide robustness for both unicast and multicast video communication applications over wireless ad hoc networks. We first propose a general architecture for multipath video streaming over wireless ad hoc networks in order to increase the robustness of video applications. This architecture includes a video encoder with error control, a traffic allocator, which decides how to distribute video packets into multiple paths, a multipath unicast/multicast routing protocol, and a rate control scheme.
For the unicast case, we propose multipath streaming with two node-disjoint paths, which have minimum concurrent Packet Drop Probability (PDP) among all path pairs. This approach minimizes the probability of concurrent loss of all the descriptions, thus optimizing the worst case Multiple Description Coding (MDC) video quality over all times. We model the effects of interference between different wireless links, and estimate the concurrent PDP of two node-disjoint paths. We show that the above optimization is an NP-hard problem. Then we propose a heuristic PDP aware multipath routing protocol based on our path selection model, whose performance is shown to be close to that of the "optimal routing", and significantly better than that of the node-disjoint multipath routing and the shortest-widest routing, through extensive NS simulations and actual experiments.
For the multicast case, we propose multiple tree video multicast with MDC to provide robustness for video multicast applications. Specifically, we first propose a simple distributed protocol, Serial Multiple Disjoint Tree Multicast Routing (Serial MDTMR). This scheme results in reasonable tree connectivity while maintaining disjointness of two trees. In order to reduce the routing overhead and construction delay of Serial MDTMR, we further propose Parallel Multiple Nearly-disjoint Trees Multicast Routing (Parallel MNTMR), which constructs two nearly disjoint trees simultaneously in a distributed way. Simulation shows that video quality of multiple tree multicast video communication is significantly higher than that of single tree multicast video communication, with similar routing overhead and forwarding efficiency.