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Handover mechanisms in next generation heterogeneous wireless ...

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DYNAMIC NEIGHBOUR TRUST INFORMATION RETRIEVAL FOR GLOBAL ROAMING<br />

The third prerequisite on trust relationship requires that a mobile user’s home network<br />

must have a trust relation with the mobile’s visited network. This is usually available by<br />

enabl<strong>in</strong>g a roam<strong>in</strong>g agreement between the two operators. A mobile user can roam to a<br />

visited network that has a roam<strong>in</strong>g agreement with its home network due to security<br />

considerations. The co-existence and collaboration of a large number of operators<br />

<strong>in</strong>evitably result <strong>in</strong> complicated network trust relationships that are subject to changes <strong>in</strong><br />

the roam<strong>in</strong>g agreements over time. In order to access resources of global operators, a<br />

mobile user would have to deal with new trust-related challenges dur<strong>in</strong>g global roam<strong>in</strong>g.<br />

Research issues related to trust relationship for seamless roam<strong>in</strong>g are be<strong>in</strong>g addressed.<br />

Sh<strong>in</strong> et al. [52] suggested that three k<strong>in</strong>ds of trust relationship are essential for secured<br />

access <strong>in</strong> a roam<strong>in</strong>g scenario: 1) The explicit Trust Relationship (TR) between a mobile<br />

user and its home network that is established through service subscription; 2) The<br />

explicit TR between a visited network and the mobile’s home network, which can be set<br />

up by roam<strong>in</strong>g agreements between the two network operators; 3) The implicit TR<br />

between the mobile user and its visited network, which is transitive and derived from<br />

the two explicit TRs. These relationships are shown <strong>in</strong> the Figure 4.1 below.<br />

Figure 4.1 Trust relationships <strong>in</strong> a multi-operator environment<br />

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