Handover mechanisms in next generation heterogeneous wireless ...

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TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER where n p s, i represents the cost in the ith parameter to carry out service s on network n, and w s, i represents the weight assigned to using the ith parameter to perform services. The vertical handover algorithm [83] is actually an extension of the policy-enabled handover [88] by considering both network constraints and network selection requirements of services. Song et al. applied the Analytic Hierarchy Process (AHP) matrix in [84] to determine the weight assigned to handover metric in the cost function. The AHP procedure was introduced to structure a complex problem as a decision hierarchy of independent decision elements. The quantitative weights of decision elements are calculated by doing pairwise comparison of their relative importance. The comparison results constitute an AHP matrix, whose eigenvector determines the element’s appropriate distribution to its parent, and can be transformed into the final weights. 5.3 Problem Definition In homogeneous wireless networks, NCHO or Mobile-Assisted Handover (MAHO) mechanisms are the most widely used handover control approaches. They are implemented at the network end for controlling handover operations. As the handover control entity, the network is in a position of ensuring that any selected point of network attachment is accessible in a handover. In homogeneous wireless network, this is often an integral feature supported by network. Network controllers such as Mobile Switching Centre (MSC) in GSM are able to communicate with both serving Base Station (BS) and candidate BS for relevant trust information. Furthermore, the number of network operators involved in network selection is quite limited due to the prohibitive costs of deploying mobile cellular services. Therefore, the security check on the existence of network trust relationship has been fundamentally integrated within the handover decision process initiated by networks. However, in heterogeneous wireless networks, with a reduced cost of ownership, new access technologies such as IEEE 802.11 Wireless Local Area Network (WLAN) can be readily deployed by independent network operators. New access networks are expected to interwork with current mobile cellular networks and may need to be interconnected - 86 -
TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER with each other. As such, mobile terminals need to deal with both the heterogeneities of networking technologies and the multiplicities of network operators. Network selection coupled with trust relationship would become a prominent issue for roaming mobile users. The network selection issue in heterogeneous wireless networks has raised a lot of concerns in the 3GPP specifications [72, 91] for Public Land Mobile Network (PLMN) and WLAN interworking. In 3GPP, it is proposed that network identity lists that are either user controlled or operator controlled can be used for network selection by mobile users. However, the 3GPP solutions provide very limited support to the multiplicity of network operators in NG wireless networks. State-of-the-art handover algorithms such as the MHOA, aims at optimising QoS by mitigating technology heterogeneity caused by the interworking. Unfortunately, they have not taken into account complex network trust relationships between multiple network operators, and thus are ineffective in resolving the multiplicity problem. Handover failure occurs in two possible cases when a mobile user attempts to attach to its selected network in a handover. In the first case (Case A), handover authentication can fail in the absence of roaming agreements between the selected access network and the home network of the roaming user. This can be promptly detected by the AAA functions at visited networks. In contrast, in the second case (Case B), the HAAA may refuses access to the user-selected network, especially if a fine-grained AAA policy is applied for security reasons. In this case, a long AAA delay would be expected because the HAAA is involved in the validation. In both cases, the mobile user would be forced to reselect another network for roaming related access. Obviously, the mobile user would likely have missed the best time for triggering handover. Long interruption in connections would incur as a consequence. Generally, for the mobile-controlled handover, the unawareness of the network trust relationship between a candidate network and the home network can cause unnecessary handover attempts. This inevitably increases signalling overheads and results in a long latency in a handover. Thus, the MHOA may become inefficient and has limited scalability in a multi-technology and multi-operator environment. Current handover approaches take into account the heterogeneities of access technologies of interworking - 87 -
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Handover Mechanisms in Next Generat
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ACKNOWLEDGMENT First of all, I woul
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TABLE OF CONTENTS 4.4.2 Power Save
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LIST OF FIGURES LIST OF FIGURES Fig
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LIST OF FIGURES Figure 7.2 A generi
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ABSTRACT New access technologies su
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Chapter 1 INTRODUCTION New access t
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INTRODUCTION becomes available. Han
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INTRODUCTION The above multipliciti
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INTRODUCTION network trust pattern
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INTRODUCTION 1.3 Related Publicatio
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INTRODUCTION TECHNICAL REPORTS XIII
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HANDOVER MANAGEMENT horizontally. H
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HANDOVER MANAGEMENT The objective o
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HANDOVER MANAGEMENT air interface,
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HANDOVER MANAGEMENT proposed archit
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HANDOVER MANAGEMENT Access point (A
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HANDOVER MANAGEMENT users. Moreover
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HANDOVER MANAGEMENT For IEEE 802.11
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HANDOVER MANAGEMENT The two schemes
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HANDOVER MANAGEMENT When a MH is mo
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3.1 Introduction Chapter 3 HANDOVER
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SECURITY FOR HANDOVER ACROSS HETERO
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Page 69 and 70: DYNAMIC NEIGHBOUR TRUST INFORMATION
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Page 123 and 124: Chapter 6 PROXY BASED AUTHENTICATIO
Page 125 and 126: PROXY BASED AUTHENTICATION LOCALISA
Page 147 and 148: MULTI-INTERFACE MOBILE MODEL FOR ME
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MULTI-INTERFACE MOBILE MODEL FOR ME
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CONCLUSIONS AND FUTURE RESEARCH WOR
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ABBREVIATIONS 3G 3rd Generation Wir
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ABBREVIATIONS LS Location Server MH
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ABBREVIATIONS THOA Trust Assisted H
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REFERENCES [12] C. Politis, T. Oda,
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REFERENCES [37] Wi-Fi Alliance, "Wi
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REFERENCES presented at IEEE Intern
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REFERENCES [90] R. Verdone and A. Z
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REFERENCES [116] K. E. Malki and H.
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