Handover mechanisms in next generation heterogeneous wireless ...

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TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER when the RSS P new of the new point of attachment is larger than the P old by a hysteresis margin H. Pth � P � H (Equation 5.2) Pnew old Pold Pnew Figure 5.1 RSS-based handover decision algorithm Therefore, in the scenario of Figure 5.1, the handover occurs at time t1 if a single RSS metric is used. The handover triggering time is delayed to time t2 when a RSS hysteresis margin is added. Other handover metrics can be used as well for more complex scenarios, such as Microcell/Macrocell overlay [1]. In packet-oriented wireless networks, handover decision has to deal with more things. A variety of services being carried on IP packets may have different requirements related to QoS. The quality of the wireless channel in a handover is no longer the only concern. A number of handover metrics such as bandwidth, service type, monetary cost and so forth would have to be considered in handover decision making for wireless data services. The cost-based Multicriteria Handover Algorithms (MHOA) such as Dynamic Vertical Handover Algorithm [83] and Policy-Enabled Handover Algorithm [88] were proposed to handle multiple handover decision metrics that are required for optimising data services in heterogeneous wireless networks. The basic idea behind the MHOA is easy - 84 -
TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER to understand. The mobile user uses multiple handover metrics as input, and makes decision based on the comparison of the costs of a set of candidate networks using a cost function model. The weight for each metric is determined based on the contribution of that metric to network selection. Basically, the MHOA can be generalised as follows: �m � � C n � w i � N i where ( � w i � 1 ) (Equation 5.3) i where C n means the cost of the nth candidate network. i m and w i represent the ith handover metric and its weight in all handover decision metrics. The parameter i m is normalised to �mi� N using a normalisation function, which ensures the sum of different metrics is of the same magnitude or order. Wang et al. first presented the concept of policy-enabled handover in [88], in which three handover metrics: network bandwidth ( n B ), power consumption ( n P ) and monetary cost ( n C ) were considered in handover decision making for the overlapped heterogeneous networks. These parameters are normalised using logarithm so that all of the parameters can be included in the same cost function f n , which is the normalised cost. Mobile user can change the handover policies by adjusting the weight of each parameter in the cost function. However, Wang’s policy-enabled cost function had three metrics, which are limited and insufficient for a comprehensive evaluation of candidate networks. In the Dynamic Vertical Handover Algorithm with Network Elimination [83], McNair et al. developed a two-dimensional handover cost function that took into account new handover metrics including service type, network conditions, system performance, user preference and so on. In one dimension, the function uses the different types of services requested by the user. In another dimension, it represents the cost to the network according to specific handover parameters [83]. The general form of the cost function is represented as: n �� ws, i � ps i (Equation 5.4) n f � , s i - 85 -
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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
Page 45 and 46: SECURITY FOR HANDOVER ACROSS HETERO
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
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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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