Accurate One-Way Delay Estimation: Limitations and Improvements

The one-way delay (OWD) is a crucial parameter in interactive multimedia communications to assess the end users´ perception of quality. Precise OWD measurement is a challenge in asymmetric networks in which endpoints are not coordinated and usually without clock synchronization. A usual method estimates the OWD for two endpoints of a connection as equal to one half of the round-trip time, which is not always accurate in the Internet. Employing a third-party node to increase the number of independent equations helps a least-square-error method to estimate the OWD more accurately. Furthermore, adding a couple of constraints to the variables (i.e., OWDs between three nodes) leads to even more precise results. This paper examines the effect of different types of constraints on the accuracy of the cyclic-path method to improve the OWD estimation. To measure the transmission delay, which has a crucial role in the OWD estimation improvement, a simple accurate method is introduced.