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Dimensioning Links for IP Telephony
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
2001 (English)In: In Proceedings of the 2nd IP-Telephony Workshop, pages 14-24, New York, USA, April 2001., 2001, 14-24 p.Conference paper, Published paper (Refereed)
Abstract [en]

Packet loss is an important parameter for dimensioning networklinks or traffic classes carrying IP telephony traffic. We present amodel based on the Markov modulated Poisson process (MMPP) whichcalculates packet loss probabilities for a set of superpositioned voice inputsources and link properties. We do not introduce another new model tothe community, rather try and verify one of the existing models via extensivesimulation and a real world implementation. A plethora of excellentresearch on queuing theory is still in the domain of ATM researchers,hence we attempt to highlight their validity to the IP (Telephony) community.Packet level simulations show reasonable correspondence with the predictionsof the model. Our main contribution is the verification of theMMPP model with measurements in a laboratory environment. The lossrates predicted by the model are in general close to the measured lossrates and the loss rates obtained by simulation. The general conclusionis that the MMPP-based model is a tool well suited for dimensioninglinks carrying packetised voice in a system with limited buffer space.

Place, publisher, year, edition, pages
2001. 14-24 p.
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-14293OAI: oai:DiVA.org:kth-14293DiVA: diva2:332072
Note
QC 20100802Available from: 2010-08-02 Created: 2010-08-02 Last updated: 2010-08-02Bibliographically approved
In thesis
1. Quality aspects of internet telephony
Open this publication in new window or tab >>Quality aspects of internet telephony
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Internet telephony has had a tremendous impact on how people communicate.Many now maintain contact using some form of Internet telephony.Therefore the motivation for this work has been to address the quality aspectsof real-world Internet telephony for both fixed and wireless telecommunication.The focus has been on the quality aspects of voice communication,since poor quality leads often to user dissatisfaction. The scope of the workhas been broad in order to address the main factors within IP-based voicecommunication.

The first four chapters of this dissertation constitute the backgroundmaterial. The first chapter outlines where Internet telephony is deployedtoday. It also motivates the topics and techniques used in this research.The second chapter provides the background on Internet telephony includingsignalling, speech coding and voice Internetworking. The third chapterfocuses solely on quality measures for packetised voice systems and finallythe fourth chapter is devoted to the history of voice research.

The appendix of this dissertation constitutes the research contributions.It includes an examination of the access network, focusing on how calls are multiplexed in wired and wireless systems. Subsequently in the wireless case, we consider how to handover calls from 802.11 networks to the cellularinfrastructure. We then consider the Internet backbone where most of ourwork is devoted to measurements specifically for Internet telephony. The applications of these measurements have been estimating telephony arrival processes, measuring call quality, and quantifying the trend in Internet telephony quality over several years. We also consider the end systems, since they are responsible for reconstructing a voice stream given loss and delay constraints. Finally we estimate voice quality using the ITU proposal PESQ and the packet loss process.

The main contribution of this work is a systematic examination of Internet telephony. We describe several methods to enable adaptable solutions for maintaining consistent voice quality. We have also found that relatively small technical changes can lead to substantial user quality improvements.A second contribution of this work is a suite of software tools designed to a certain voice quality in IP networks. Some of these tools are in use within commercial systems today.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 89 p.
Series
Trita-EE, ISSN 1653-5146 ; 2009:025
Series
SICS Dissertaion Series, ISSN 1101-1335 ; 51
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-10572 (URN)978-91-7415-313-2 (ISBN)
Public defence
2009-06-05, sal D2, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20100802Available from: 2009-05-27 Created: 2009-05-27 Last updated: 2013-09-09Bibliographically approved

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