Wilson, Ashton (2008) QoS oriented framework for link selection in heterogeneous wireless environments. (PhD thesis), Kingston University, .
Abstract
Wireless is now common for access to multimedia services, with many different devices and choice of access technology. Access methods have become varied and with more types of services, which requires more consideration for coordinating existing protocols and quality of service (QoS). Increasingly, new wireless access technologies co-exist on the same devices, for example, smartphones already have third-generation cellular and WiFi. Devices with multiple links are described under the umbrella term ‘heterogeneous environments’. A trend towards heterogeneous wireless environments and varied types of media services requires that QoS and user satisfaction are prominent in next-generation networks. The problems in next-generation heterogeneous wireless environments include many levels of complexity; from link coexistence to user-centric policies and contexts. This thesis explores the issue of QoS in interface selection for devices with more than one wireless access link. A solution that provides link selection for QoS policy is investigated using analytical and simulation techniques. Different wireless networks have capabilities and limitations, determined by radio technology and network conditions. The research focused on an approach to improve QoS by leveraging the differences in wireless networks. However, it is complicated by issues such as: different protocols, physical device co-existence, mobility, and application QoS requirements. Following a review of artificial intelligence (AI) techniques, finite-state machines (FSMs) and fuzzy decision-making (FDM) are proposed as a solution approach. An agent-based prototype is used to combine FSMs and FDM for automating link selection, determined by user and QoS policy. Prototype evaluation was performed using sensitivity analysis for FDM, and discrete-event simulation for generating QoS metrics in wireless environments. The results are comparisons of FDM prototypes using different parameters; different agent prototypes were run with different QoS conditions for comparing points of handover between UMTS and WLAN networks for one service type. The research has shown an agent model can reduce the complexity for a user in wireless interface selection, while including QoS metrics and user preferences into the decision process. Core decision-making techniques in the design are relevant for emerging standardisation frameworks such as 802.21, and the next-generation of wireless networks to support heterogeneous access.
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