End-to-end available bandwidth estimation and time measurement adjustment for multimedia QoS

Congestion control is an important function in a multimedia application. Since multimedia (e.g., audio and video) packets are mostly transmitted in UDP, which lacks the congestion control mechanism in TCP, a separate congestion control is necessary to avoid excessive packet losses and to be fair with competing TCP flows. As UDP congestion control is rate-based, unlike the window-based one used in TCP, end-to-end available bandwidth estimation can play a critical role in UDP congestion control. This paper proposes a new method to estimate the available bandwidth based on the delay trend detection, which is suitable for a multimedia application. We deduct the relationship between delay trend and available bandwidth and also show the Internet experiment results. Various practical time measurement errors are analyzed and their countermeasures are proposed.