Handover mechanisms in next generation heterogeneous wireless ...

TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER
60, 120, 180] is assigned to the WLAN POAs. Both UMTS and WLAN have the same
�4
�4
�3
�3
�2
values for the packet loss vector �10 , 5 10 , 10 , 5�10
, 10 �
� .
The parameters for the simulation are illustrated in Table 5.2. When the network
conditions and the trust relationships between network domains are changed, various
handover decision scenarios can be composed. The simulation results will be shown in
Sec. 5.6.
Table 5.2 Simulation parameters
Parameter UMTS (ms) WLAN (ms)
Move detection t MD
[0, 360] [0, 210]
Network discovery � 0 0
HOA computing � 0 0
Address configuration t AC 30 30
MH-to-AR RTT � 330 150
TAH signalling tTAH 30
Home AUTH t AAA
80 80
Local AUTH tauth 60 60
As aforementioned, handover delay is the primary performance concern in the
interworking of heterogeneous wireless networks. The simulation has been designed to
focus on the impact of network trust relationship on handover delay, because of the
initiatives of this study as stated in Sec. 5.3. QoS in handover is examined in order to
evaluate how the proposed trust-assisted handover approach may influence upper layer
services.
A new parameter named trust density is defined to determine the accessibility of access
networks. Trust density refers to the fraction of the total trusted POAs that have
established trust association with a roaming mobile user’s home network. If the trust
density in a hotspot has the value of 1, a mobile user would be able to attach to any
discovered POA.
Load balance factor (LBF) is another parameter proposed to evaluate how handover
incurred load may be distributed among all the available POAs. Upon accepting
handover request, a POA needs to open its local resources to the attached mobile user.
This would place a certain amount of burden l � u�
� on its systems. u denotes the
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