Multi-source Cooperative Adaptation for QoE-aware Video Multicast Rate-control

Abstract-We consider a wide-area video conferencing application where the video sources adapt their send rates according to the available bandwidth in the network paths. We advocate a QoE-aware cooperative rate control of the sources to relieve the congestion, instead of running multiple (independent) instances of a singlesource adaptation algorithm in a QoE-oblivious manner and additively superposing their results. Our paper focuses on the architecture of such a QoE-aware video multicast system. Dove-tailed to the core functionality of rate adaptation is the session-layer configuration control mechanisms to deliver video to various end-user devices

Stability of Video Rate Control Algorithms Over Bandwidth-limited Network Paths

Abstract-The paper considers the stability of AIMD-based rate adaptation algorithm for video transmission over a bandwidth-limited network path. We examine the stability aspects from two angles: first, a quick relief from congestion by a faster reduction of send rate, and second, a larger limit-cycle time with a slow rate reduction in the steady-state (and hence lower rate jitter). The stability assessment also considers the loss of feedback signals from the video receiver that indicate the packet loss on data channels. We provide a managementoriented assessment of the convergence properties of video rate control system. This in turn allows an autonomic adjustment of the AIMD parameters and the system controller models for optimal performance

Multi-Hop Probing Asymptotics in Available Bandwidth Estimation: Stochastic Analysis

This paper analyzes the asymptotic behavior of packet-train probing over a multi-hop network path P carrying arbitrarily routed bursty cross-traffic flows. We examine the statistical mean of the packet-train output dispersions and its relationship to the input dispersion. We call this relationship the response curve of path P . We show that the real response curve Z is tightly lower-bounded by its multi-hop fluid counterpart F , obtained when every cross-traffic flow on P is hypothetically replaced with a constant-rate fluid flow of the same average intensity and routing pattern. The real curve Z asymptotically approaches its fluid counterpart F as probing packet size or packet train length increases. Most existing measurement techniques are based upon the single-hop fluid curve S associated with the bottleneck link in P . We note that the curve S coincides with F in a certain large-dispersion input range, but falls below F in the remaining small-dispersion input ranges. As an implication of these findings, we show that bursty crosstraffic in multi-hop paths causes negative bias (asymptotic underestimation) to most existing techniques. This bias can be mitigated by reducing the deviation of Z from S using large packet size or long packet-trains. However, the bias is not completely removable for the techniques that use the portion of S that falls below F

Single-Hop Probing Asymptotics in Available Bandwidth Estimation: Sample-Path Analysis

In this paper, we take the sample-path approach in analyzing the asymptotic behavior of single-hop bandwidth estimation under bursty cross-traffic and show that these results are provably different from those observed under fluid models of prior work. This difference, which we call the probing bias, is one of the previously unknown factors that can cause measurement inaccuracies in available bandwidth estimation. We present an analytical formulation of "packet probing," based on which we derive several major properties of the probing bias. We then experimentally observe the probing bias and investigate its quantitative relationship to several deciding factors such as probing packet size, probing train length, and cross-traffic burstiness. Both our analytical and experimental results show that the probing bias vanishes as the packet-train length or packet size increases. The vanishing rate is decided by the burstiness of cross-traffic