Voice quality control in packet switched wireless networks

摘要

Wireless systems have engaged the evolutionary migration from traditional circuit switchudtechnology to packet based technology. Presently all next generation wireless networks haveudbeen specified with a packet based Radio Access Networks (RAN), which implies that all theudflaws of traditional packet based networks now also apply to voice. These flaws result inuddecreased speech quality derived from increased latency, jitter and packet loss. This thesisudprovides the basis for a solution that will facilitate voice quality control in a packet switchedudwireless network based on the integrated approach of providing Quality of Service (QoS) controludacross the Admission Control (AC) component, Bearer or Service Flow component andudmapping across these components to the appropriate Quality of Service (QoS) metrics at theudtransport network.udThe original contribution of knowledge to the field of electrical and information engineering isudthe proposal of a Quality of Service (QoS) framework and control mechanisms that result in theudtransmission of quality voice over a packet switched wireless network autonomous to voiceudspecific signalling or media protocols. These proposals include: Heuristic Analysis in theudAdmission Control (AC) component; the addition of a voice service class Admission Controlud(AC) model; selection of a voice specific Bearer or Service Flow and the mapping thereof to audvoice specific Quality of Service (QoS) queue or Service Flow at the transport or backhauludnetwork. All these solutions are presented with the goal of ensuring the preservation of qualityudvoice over a packet switched wireless network as governed by network quality metrics such asudlatency, jitter and packet loss.udThis research delivers a comprehensive analysis of 4th Generation (4G) networks such as,udWorldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE),udas specified by the standards bodies yet with focused orientation to the Quality of Service (QoS)udframework provided by each of the standards. Specific investigations are targeted towards theudAdmission Control (AC) and Scheduling of physical resources over the air interface by the MediaudAccess Control (MAC) and Radio Link Control (RLC) layer. Current research and industry ledudinitiatives in the provisioning of quality voice, such as Circuit Switch Fallback (CSFB) and IPudMultimedia Subsystem (IMS) are presented and include the associated advantages anduddisadvantages.udThe results and recommendations of this research consist of a multi-faceted solution,udcommencing with the addition of Heuristic Analysis with Deep Packet Inspection (DPI) beingudproposed at the eNodeB or WiMAX Base Station (BS) level. An Admission Control (AC)udscheme tailored for voice utilising Heuristic Analysis as an input is created, thereafter anudidentified QoS Class Identifier (QCI) Bearer or Service Flow and transportation Quality ofudService (QoS) Identifier for voice is triggered by the User Equipment (UE) application or Bearerudinitiation procedures. The LTE Bearers and WiMAX Service Flows are tested with the intentionudof recommending an LTE Bearer and WiMAX Service Flow that will ensure compliance to theudminimum required network quality metrics. Finally the testing of the invoking mechanisms isudpresented mapping the Quality of Service (QoS) metrics across each of the network componentsudthereby completing the solution.