Dynamic Rate Multicast Scheduling in Third Generation Wireless Data Networks

Multicast is an efficient means of transmitting the same content to multiple receivers while minimizing network resource usage. Applications that benefit from multicast are now being deployed over 3G wireless data networks. Existing multicast schemes transmit data at a fixed rate assuming there is always a user at the edge of the cell. In general, users belonging to the same multicast group can have widely different channel conditions. Thus existing conservative approaches significantly limit throughput for users close to the base station. We propose two proportionally fair multicast scheduling algorithms at the air interface in the downlink (also referred to as the forward link) direction to adapt dynamic channel states in cellular data networks that use TDM: Multicast Proportional Fairness and Inter-Group Proportional Fairness algorithm. Our algorithms take into account the reported data rate request from users and the average throughput of each user inside the cell and use this information to select an appropriate data rate for each group and a group among groups to transmit data. We prove that Multicast Proportional Fairness and Inter-Group Proportional Fairness algorithm are proportional fairness among all users and among groups inside a cell respectively. We then demonstrate and experiment with a set of unified schedulers that can flexibly vary their characteristics from proportional fair to maximum throughput. We evaluate our algorithms via extensive packet-level simulations.