Handover mechanisms in next generation heterogeneous wireless ...

TRUST ASSISTED HANDOVER ALGORITHM FOR RELIABLE HANDOVER
m
D � tMD
��
( tAC
� � � hn,
j �tTAH
� tAAA)
(Equation 5.11)
5.5.2 System Model
j
The simulation scenario is designed as such. A MH will be trying to complete a series
of handover in a heterogeneous wireless environment with overlapped radio coverage.
The MH makes efforts to make sure it’s always best connected when network
conditions change. There are a total of 10 POAs in a proposed hotspot. five are UMTS
POAs and the rest are WLAN POAs. The MH retrieves network condition information
of each POA from its periodic advertisement being broadcast. It can associate with one
POA at any time.
The POA may establish a trust relationship with the MH’s home network or have it
disabled by the operator’s roaming policies. All the POAs share a common AAA proxy
network to the MH’s home network. The TAH h n vectors for the UMTS POAs and the
UMTS
WLAN POAs are � �1, 3,
5,
7,
9�
WLAN
h and � h � � �2, 4,
6,
8,
10�
respectively. The POA(s)
1
5
6
having their trust associations to the MH’s home network disabled is(are) randomly
selected. Every POA is assumed to be able to supply 3 handover metrics: available
bandwidth, network latency, and packet loss, the weights of which are quantified by
Analytic Hierarchy Process (AHP) presented in [84]. The time between these metric
values being changed varies according to an exponential probability distribution with
the mean of u. The change in the value of the metrics follows a Markov chain with the
below transition probability matrix. The 4� 4 matrix below shows the transition
probability matrix for a metric with four possible values.
�0.
5
�
�0.
3
� 0
�
�
� 0
0.
5
0.
4
0.
3
0
0
0.
3
0.
4
0.
5
0 �
�
0 �
0.
3�
�
0.
5�
�
The available bandwidth vector of the UMTS POAs is [32, 64, 128, 384, 768, 1024,
2048, 3600] kbps, while the WLAN POAs have [1, 2, 4, 6.5, 8, 11] Mbps. For the
network latency factor, [20, 60, 100, 150, 210] is given to the UMTS POAs and [10, 30,
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