VoIP Quality Research Articles

A proposal of VoIP quality assurance method by admission control

AbstractRecently, the use of VoIP, which is a voice communication service based on an IP network, has been spreading rapidly. However, the quality of service of VoIP has not currently reached the quality of service of a conventional circuit‐switched network due to the technical features of an IP network. For IP networks to replace conventional circuit‐switched networks in the future, various types of present‐day problems must be resolved. Therefore, the authors propose a method of performing admission control for VoIP call setup requests to assure voice quality according to management of the number of VoIP sessions based on the assumption that the quality of a fixed capacity is assured according to VoIP priority control in addition to the packet‐level quality provisions of ITU‐T Recommendation Y.1541. They also show experimental results concerning the VoIP quality of service measurement indices required by this proposal, the effectiveness of admission control, and the monitor for the number of VoIP sessions and discuss contributions to standardization for promoting more widespread use of the VoIP quality assurance method. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(2): 12–22, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20331

Assessment of Internet voice transport with TCP

AbstractWe investigate whether the current best‐effort technology of Internet stands up to the high quality standards of real‐time voice communication. More precisely, we assess VoIP quality within the context of transport protocol support and efficiency. Initially, we focus on TCP and UDP supportive role from the perspective of VoIP performance. Applying our metric for real‐time performance, we reach the outcome that UDP is always not the protocol of choice for VoIP, since it occasionally exhibits inadequate performance. Beyond that, we evaluate a solution‐framework based on TCP protocols, which favour real‐time traffic. Based on our measurements, we assess the efficiency of the associated congestion control and congestion avoidance mechanisms in terms of VoIP performance. We also study the effect of packet size on protocol behaviour and VoIP quality. Furthermore, we investigate VoIP traffic friendliness, as well as potential tradeoffs between protocol performance and fairness. Copyright © 2006 John Wiley & Sons, Ltd.

Call admission control for voice over IP

AbstractVoice over Internet protocol (VoIP) is a technology that enables the transmission of voice over an IP network. Recent years have witnessed heavy investment in this area in the commercial world. For VoIP to replace Public Switched Telephone Network (PSTN), it should provide voice quality comparable to circuit‐switched PSTN networks. This paper addresses the mechanisms to guarantee VoIP quality of service (QoS). The focus is given to the call admission control, which blocks voice calls when the required resources are not available to guarantee the QoS for the call. We review call admission control approaches that can be applied to VoIP, and describe the advantages and disadvantages of each approach. In the second part of the paper, we present a measurement‐based admission control scheme that achieves QoS in an efficient and scalable manner. The scheme uses voice traffic load measurements at each router link to compute link‐level blocking policies for new call attempts. Then, these policies are translated into path‐level blocking policies, which are applied to new call set‐up requests. The performance of the scheme is presented for single and multiple‐priority voice calls. Copyright © 2006 John Wiley & Sons, Ltd.

Time synchronization for VoIP quality of service

Various approaches seek to optimize the quality of service of VoIP applications. We propose a system that uses synchronized time to combine the useful characteristics of both fixed and adaptive buffer strategies, thereby improving VoIP quality of service. Using a combination of global positioning system (GPS) technologies and the network time protocol (NTP), hosts can learn the precise end-to-end delay for each packet. This information can benefit both domestic and business Internet telephony users. We outline our proposed system and discuss issues arising from the use of synchronized time.

Quality VoIP — An Engineering Challenge

Initial impressions of VoIP quality have not always been favourable. This paper discusses the issues behind delivering an 'appropriate' quality of service, specifically voice quality, by showing how design choices ultimately affect, and potentially limit, a customer's perception of VoIP quality. The paper continues by introducing new signal processing techniques that are helping to measure and optimise the performance of VoIP solutions.