Performance issues for VOIP in access networks

Abstract

The is a general consensus that the Quality of Service (QoS) of Voice over Internet Protocol (VOIP) is of growing importance for research and study. In this dissertation we investigate the performance of VOIP and the impact of resource limitations in the performance of Access Networks. The impact of VOIP performance in access networks is particularly important in regions where Internet resources are limited and the cost of improving these resources is prohibitive. It is clear that perceived VOIP performance, as measured by mean opinion score in experiments where subjects are asked to rate communication quality, is determined by end to end delay on the communication path, delay variation, packet loss, echo, the coding algorithm in use and noise. These performance indicators can be measured and the contribution in the access network can be estimated. The relation between MOS and technical measurement is less well understood. We investigate the contribution of the access network to the overall performance of VOIP services and the ways in which access networks can be designed to improve VOIP performance. Issues of interest include the choice of coding rate, dynamic variation of coding rate, packet length, methods of controlling echo, and the use of Active Queue Management (AQM) in Access Network routers. Methods for analyzing the impact of the access network on VOIP performance will be surveyed and reviewed. Also, we consider some approaches for improving performance of VOIP by doing some experiment using NS2 simulation software with a view to gaining a better understanding of the design of access networks.