Voice quality control in packet switched wireless networks
Date
2013-07-19
Authors
Nageshar, Nikesh
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Abstract
Wireless systems have engaged the evolutionary migration from traditional circuit switch
technology to packet based technology. Presently all next generation wireless networks have
been specified with a packet based Radio Access Networks (RAN), which implies that all the
flaws of traditional packet based networks now also apply to voice. These flaws result in
decreased speech quality derived from increased latency, jitter and packet loss. This thesis
provides the basis for a solution that will facilitate voice quality control in a packet switched
wireless network based on the integrated approach of providing Quality of Service (QoS) control
across the Admission Control (AC) component, Bearer or Service Flow component and
mapping across these components to the appropriate Quality of Service (QoS) metrics at the
transport network.
The original contribution of knowledge to the field of electrical and information engineering is
the proposal of a Quality of Service (QoS) framework and control mechanisms that result in the
transmission of quality voice over a packet switched wireless network autonomous to voice
specific signalling or media protocols. These proposals include: Heuristic Analysis in the
Admission Control (AC) component; the addition of a voice service class Admission Control
(AC) model; selection of a voice specific Bearer or Service Flow and the mapping thereof to a
voice specific Quality of Service (QoS) queue or Service Flow at the transport or backhaul
network. All these solutions are presented with the goal of ensuring the preservation of quality
voice over a packet switched wireless network as governed by network quality metrics such as
latency, jitter and packet loss.
This research delivers a comprehensive analysis of 4th Generation (4G) networks such as,
Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE),
as specified by the standards bodies yet with focused orientation to the Quality of Service (QoS)
framework provided by each of the standards. Specific investigations are targeted towards the
Admission Control (AC) and Scheduling of physical resources over the air interface by the Media
Access Control (MAC) and Radio Link Control (RLC) layer. Current research and industry led
initiatives in the provisioning of quality voice, such as Circuit Switch Fallback (CSFB) and IP
Multimedia Subsystem (IMS) are presented and include the associated advantages and
disadvantages.
The results and recommendations of this research consist of a multi-faceted solution,
commencing with the addition of Heuristic Analysis with Deep Packet Inspection (DPI) being
proposed at the eNodeB or WiMAX Base Station (BS) level. An Admission Control (AC)
scheme tailored for voice utilising Heuristic Analysis as an input is created, thereafter an
identified QoS Class Identifier (QCI) Bearer or Service Flow and transportation Quality of
Service (QoS) Identifier for voice is triggered by the User Equipment (UE) application or Bearer
initiation procedures. The LTE Bearers and WiMAX Service Flows are tested with the intention
of recommending an LTE Bearer and WiMAX Service Flow that will ensure compliance to the
minimum required network quality metrics. Finally the testing of the invoking mechanisms is
presented mapping the Quality of Service (QoS) metrics across each of the network components
thereby completing the solution.