Power efficient multicast for multiple description media in wireless mesh networks

In this paper, we study multicasting media traffic that uses multiple description coding (MDC) in a wireless mesh network (WMN), where an access point (AP) transmits multiple descriptions to the mobile stations (MSs) through relay stations (RSs). The MSs have different quality of service (QoS) requirements in terms of number of required descriptions, and each RS can forward at most one description. All RSs forwarding the same descriptions form a multicast tree. Our objective is to minimize total transmission power of the RSs, subject to satisfying the QoS requirements of the MSs. We study two problems, building node-disjoint multicast trees and allocating transmission power. The former is to decide which RSs should forward the same description, and the latter is to determine an adequate transmission power level for each RS. An optimization problem is first formulated, and two heuristic schemes are then proposed. The first scheme is a greedy method that iteratively adds new paths to individual multicast trees and assigns transmission power to RSs, and the second one is a simplified version of the first. Numerical results demonstrate that both schemes achieve much lower power consumption compared to a spanning-tree-based scheme that builds the multicast trees one after another, and the power consumption of the first scheme is much lower than the second one at a price of higher complexity.