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Handover mechanisms in next generation heterogeneous wireless ...

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Chapter 5<br />

TRUST ASSISTED HANDOVER ALGORITHM FOR<br />

5.1 Introduction<br />

RELIABLE HANDOVER<br />

Homogeneous <strong>wireless</strong> networks generally employ a centralised handover approach [31,<br />

81, 82], e.g. Network-Controlled <strong>Handover</strong> (NCHO), <strong>in</strong> which network-end<br />

components make handover decisions. However, <strong>in</strong> Next Generation (NG)<br />

Heterogeneous Wireless Networks, it is widely envisioned that the decentralised<br />

Mobile-Controlled <strong>Handover</strong> (MCHO) would be a better choice [31, 81].<br />

In recent years, there have seen a number of papers [82-85] <strong>in</strong>vestigat<strong>in</strong>g how handover<br />

decisions should be made <strong>in</strong> <strong>heterogeneous</strong> <strong>wireless</strong> networks. It is commonly proposed<br />

[83-85] that multiple handover metrics, such as Received Signal Strength (RSS) [86],<br />

service type, and bandwidth, shall be considered <strong>in</strong> the handover decision process so as<br />

to be “always best connected” [34]. The notion of “always best connected” means that<br />

a mobile user is always connected through the best available device and access<br />

technology at all times [34]. At present, handover decision processes tend to adopt a<br />

cost-based approach, which employs multiple handover metrics for the sake of Quality<br />

of Service (QoS). The current approaches have been specifically designed to address the<br />

heterogeneity challenges of handover [13] aris<strong>in</strong>g from the <strong>in</strong>terwork<strong>in</strong>g of multitechnology<br />

networks. However, <strong>in</strong> NG Wireless Networks, disparate network doma<strong>in</strong>s<br />

may belong to multiple network operators, and rely on their roam<strong>in</strong>g agreements to<br />

collaborate between each other [87]. Roam<strong>in</strong>g agreements are subject to changes with<br />

time, and this can subsequently affect trust relationships between the <strong>in</strong>terconnected<br />

networks.<br />

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