The study of interference-free multicast using non-orthogonal channels for multi-radio and multi-channel wireless mesh networks

Considering a video/audio server deployed on the gateway node of a wireless mesh network, a large amount of clients distributed on various mesh routers may wish to receive multimedia streams from the server simultaneously. A multicast tree would be a suitable mechanism to deliver subscribed streams to all the destinations. For multi-radio and multi-channel wireless networks, however, it is better to allocate interference-free channels to the multicast tree to improve the quality of multimedia streams transmitted. Instead of only orthogonal channels considered for the multicast tree in the previous works, all the available channels are used for multicast in this study. As a result, the number of links successfully allocated channels should be much more than the method that only orthogonal channels are considered. In addition, the number of stream subscribers are increased. Hence, the goal of this study is to find an interference-free multicast tree that can lead to the maximal number of serviced subscribers. This problem is referred as the MR² problem. To solve the problem, we present two heuristic algorithms that can efficiently construct multicast trees, which are then processed by a load-based DFS channel assignment procedure to allocate interference-free channels to the links. A set of experiments is also designed to do performance and delay comparisons for the multicast trees generated by the approximation algorithms proposed in this study.