Handover mechanisms in next generation heterogeneous wireless ...

DYNAMIC NEIGHBOUR TRUST INFORMATION RETRIEVAL FOR GLOBAL ROAMING
network’s NTC data to its neighbouring network is initiated by the HAAA after a
mobile user hands over from one network to another. Figure 4.4 illustrates an example
of the NTC data retrieval and distribution process. The MH attaches to the oPOA, and
gets the NTC data between the oPOA and the HAAA retrieved in Step 1. The HAAA
retained the cached NTC data with the oPOA for future use. Then, the MH moves into
the radio coverage of the nPOA, and triggers the handover (Step 2). During the
handover, the authentication messages are exchanged between the MH and the HAAA
via the nPOA. Thus, the HAAA retrieves the NTC data with the nPOA (Step 3). With
the NTC data for both the oPOA and the nPOA, the HAAA initiates the distribution of
the NTC data to the corresponding party (Step 4 and 5). More specifically, the NTC data
for the oPOA would get distributed to the nPOA while the NTC data for the nPOA
would be released to the oPOA. As a result, following each successful handover, an
exchange of the NTC data can be done between arbitrary pair of adjacent networks.
Figure 4.4 The proposed neighbour NTC exchange process
As a MH moves across several networks, a number of the NTC data exchanges would
be performed. In Figure 4.5, the cell is used to abstract a network that is adjacent to six
neighbouring networks. The trajectory of the MH1 would sequentially have the NTC
exchanges { E AB,
EBC,
ECD,
EDE}
to be done. In addition, another mobile user, MH2
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