Robust multicast scheduling based on relaying, power control, and rate adaptation in wireless networks

In this paper, we present a class of heuristic algorithms for executing an adaptive power, adaptive rate TDMA schedule for multicasting messages from base stations to clients in a cellular system. Messages that are targeted for multicast over an area of operation are distributed across a backbone network to the base stations. Members of the multicast group are scattered across the area cells. The presented basic algorithm strives to achieve a high receive throughput rate. In each time slot within a multicast interval, a specific group of base stations is scheduled to transmit their multicast messages to their associated clients at specified transmit power and rate levels. To enhance the performance robustness of the system, under base station failure events, we extend the basic algorithm by introducing an opportunistic relay aided multicasting operation. Under the extended multicasting protocol, in addition to using base stations to multicast messages to nodes that are located closer to them, mobile stations can be elected to relay multicast messages that they have received directly from their base stations to peripheral nodes in their neighborhood. We show that this extended adaptive power and rate multicasting scheduling algorithm is effective in adapting to a failure of a base station node, limiting the performance degradation that is incurred. For an illustrative scenario, the extended relay aided scheme is noted to yield a throughput rate that is higher than that attained by a scheme that doesn´t employ relay nodes by about 20%, while consuming less energy resources.