Handover mechanisms in next generation heterogeneous wireless ...

DYNAMIC NEIGHBOUR TRUST INFORMATION RETRIEVAL FOR GLOBAL ROAMING
moving in a different trajectory at the same time would contribute to the NTC
exchanges { E FE , EEG,
EGD,
EDH}
as shown in Figure 4.5. In a confined area, as a large
number of mobile users move across network boundaries, each network would have a
great chance of learning the NTC data about its neighbouring networks. In this chapter,
a network’s neighbour NTC pattern is regarded as being established when it has full
knowledge of every neighbouring network’s NTC data. For example, network D needs
two more NTC exchanges { BD , DI } E E to obtain its neighbour NTC pattern.
Figure 4.5 Mobile hosts’ trajectory and the NTC data exchanges
Once a network has established its neighbour NTC pattern, it can provide such trust
information to the attached mobile user to assist its network selection. Instead of relying
on statically cached operator information in mobile terminal, trust information on
demand makes sure that a roaming mobile user can deal with any operator irrespective
of the complexity and versatility of network trust relationship.
4.4 Implementations
The NTC exchange between a network and its adjacent networks relies on the handover
of mobile users between the networks. In a handover, a mobile user’s network selection
is influenced by a variety of factors related to its visited networks, such as placement of
POA, signal strength, and radio propagation. These factors are often beyond the
mobile’s home operator’s control. However, the home operator can still decide when
and where the NTC distribution should occur, since the NTC distribution is always
initiated by the AAA server.
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