In-Network Congestion Control for Multirate Multicast

We present a novel control scheme that dynamically optimizes multirate multicast. By computing the differential backlog at every node, our scheme adaptively allocates transmission rates per session/user pair in order to maximize throughput. An important feature of the proposed scheme is that it does not require source cooperation or centralized calculations. This methodology leads to efficient and distributed algorithms that scale gracefully and can be embraced by low-cost wireless devices. Additionally, it is shown that maximization of sum utility is possible by the addition of a virtual queue at each destination node of the multicast groups. The virtual queue captures the desire of the individual user and helps in making the correct resource allocation to optimize total utility. Under the operation of the proposed schemes backlog sizes are deterministically bounded, which provides delay guarantees on delivered packets. To illustrate its practicality, we present a prototype implementation in the NITOS wireless testbed. The experimental results verify that the proposed schemes achieve maximum performance while maintaining low complexity.

I. Introduction

The increasing demand for multimedia applications, such as real-time conferencing, multiview video and video streaming, pushes data networks to their operational limits and motivates efficient resource allocation schemes. Multicast is a candidate method for delivering multimedia streams to multiple users across a network. To optimize individual user experience, it is desired to employ multi-rate multicast transmissions and use layered multimedia coding schemes to adapt users' perceived quality to allowable data rates, see [2], [3]. Since different receivers may require different data rates, we study the problem of per-receiver Network Utility Maximization (NUM) in multi-rate multicast, where each receiver is assigned a potentially different utility function.