July 8, 2003
(Mr MELVIN, Mr MURPHY)
Title: Internet Telephony: Performance gains through use of Synchronized Time
Abstract:
Synchronized clocks constitute a basic building block of the traditional PSTN. We
propose that by incorporating synchronized time into networks that provide Internet Telephony
services, significant gains in voice playout quality can be achieved through use of delay-aware
applications. Conventional delay-unaware adaptive playout strategies result in some degree of late
packet loss that in many cases is unnecessary, given the actual mouth-to-ear (M2E) delays. We
extensively test our delay-aware playout strategy over real and simulated networks and quantify gains
through use of the ITU-T E-model. We also examine the extent to which clock skew issues can effect
both conventional adaptive playout and delay-aware playout strategies and show how a high-level
solution developed by the authors can be integrated into the playout strategy.