Multicast Scheduling in Cellular Data Networks

Applications that benefit from multicast are now being deployed over 3G wireless data networks. Multicast scheduling in this context is challenging: there is no endpoint feedback mechanism, and the default schemes transmit data at a fixed rate assuming there is always a user at the edge of the cell. This conservative approach significantly limits throughput for users close to the base station. We propose a set of multicast scheduling algorithms at the air interface in the downlink direction to improve data throughput in cellular data networks that use TDM. Our algorithms take into account (1) the data rate request (DRC) feedback (from the unicast channel) and (2) the average throughput from users inside the cell, and use this information to select an appropriate data rate for each group. We prove that our algorithms maintain proportional fairness among groups, and among all users served by the base station. We evaluate our algorithms via extensive packet-level simulations.