Quality of Service Support for Voice over IP in Wireless Access Networks

Olariu, Cristian (2013) Quality of Service Support for Voice over IP in Wireless Access Networks. PhD thesis, Waterford Institute of Technology.

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Voice Over IP (VoIP) is increasingly displacing traditional voice telephony services, but the IP networks that carry the traffic are inherently prone to delays and losses that impact the voice quality. This thesis addresses those quality degradations with particular emphasis on wireless networks. The scenarios considered in the thesis focus on the two most recent wireless access technologies, namely Long Term Evolution (LTE) andWireless Mesh Networks (WMNs). These scenarios have in common the undesired effects of call quality degradation when the increased traffic volume across the network causes congestion. This thesis points out the causes of the congestion and proposes solutions tailored specially for each wireless access technology. The solutions share a common concept, proposed and developed in this thesis, namely the Intermediate Mean Opinion Score (iMOS). The MOS is basically a call quality assessment methodology typically performed at the end-points. The novelty of iMOS resides in the fact that accurate call quality measurements are performed at intermediate points in the network rather than in the end-nodes. The iMOS proposed in this thesis uses the E-Model to estimate the quality of VoIP calls, based on network performance indicators. Measuring the call quality at intermediate points is driven by the operators’ intent to guarantee high levels of VoIP quality of service. The users’ increased need for wireless access generates an unpredicted growth of traffic volume, which is directly reflected in the perceived VoIP call quality. The second part of this thesis addresses this problem and focuses on developing Call Admission Control (CAC) solutions designed to support the quality of service for VoIP while maximizing the amount of traffic allowed to pass through the network. The iMOS concept and iMOS-based CAC solutions are validated through extensive simulations of realistic deployment scenarios of LTE femtocells and WMNs. The results highlight the existence of the call degradation problems and the proposed solutions are shown to have the capability of increasing the call quality and call capacity, and protecting against congestion which causes the undesired call quality degradation.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Wireless access networks
Departments or Groups: *NONE OF THESE*
Divisions: School of Science > Department of Computing, Maths and Physics
Depositing User: Derek Langford
Date Deposited: 18 Nov 2013 16:13
Last Modified: 22 Aug 2016 10:27
URI: https://repository.wit.ie/id/eprint/2752

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