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VERTICAL HANDOVER APPROACHES
BASED ON IEEE 802.21 MIH STANDARDS
For HETEROGENEOUS NETWORKS
Presented by
M.HARIKRISHNAN(EC1106)
Under the Guidance of
Dr.G.SIVARADJE
OBJECTIVE
The design goal of this project is to provide an
efficient vertical handover decision algorithm based
on IEEE 802.21 standard for best quality of service.
Seamlessly transfer to best access link among all
available candidate with no perceivable interruption.
Probability of handover failure, unnecessary
Handover initiation, Ping-Pong effect should be
minimized.
HANDOVER DECISION BASED ON IEEE
802.21 MIH STANDARDS
The decision to initiate handovers in 3G networks has
traditionally based on the received signal strength and
availability of resources in a new cell.
Such traditional handover decisions use RSS as the only
criteria.
In order to enable seamless vertical handovers, IEEE 802.21
aims to improve user experience of MTs by enabling
handovers between heterogeneous technologies while
maintaining session continuity.
CONTINUED
In a heterogeneous network, handover decisions could also
be initiated for other reasons including RSS, network
connection time, security, bandwidth, data rate and user
preferences.
VERTICAL HANDOVER DECISION BASED ON
MIHF(MIES,MICS,MIIS)
CONTINUED
MIH can provide Link up, Link down and Link going down events (MIES)
to monitor the link status continuously.
Handoff is prepared if the link going down, then the MIH user provides
MICS command to the users to switch links.
The ASCONF-Path Failure sends from MN to CN to notify that the IP
address is going to fail.
The client gets the available network information from the information
server through MIIS queries and responses.
Best candidate is selected. MN sends ASCONF-Delete old IP to indicate
CN to delete old IP address and add new IP address
VERTICAL HANDOVER DECISION BASED ON
MIH STANDARD
The above mentioned idea is implemented based on
conditional probability of link down (RSSi-1) and link going
down (RSSi).
For assumption, in a time (i-1) mobile station is in WLAN
coverage, therefore RSS value is greater than the RSS
threshold and in a time i mobile station is not in WLAN
coverage, therefore RSS value is less than the RSS threshold.
The probability of handover from WLAN to cellular network
is predicted by conditional probability
CONTINUED
• Assume
RSSi <RSSthr = x and RSSi-1 >RSSthr =y
P{RSSi <RSSthr ,RSSi-1 >RSSthr }=P(x,y)
Therefore, 2
1 1 x − µx 2 x − µx y − µy y − µy
P x, y = exp − − 2ρ +
2Πσx σy 1−ρ2 2(1 − ρ2 σx σx σy σy
Thus the probability of handover from WLAN to Cellular networks was found and
will reduces the number of handover occurring by taking periodic RSS sample into
account.
MINIMIZATION OF HANDOVER FAILURE
PROBABILITY AND UNNECESSARY HANDOVER
(RSS MEASUREMENT)
In order to maintain seamless user roaming and optimize network resource
usage, it is desirable to minimize handover failures and unnecessary
handovers.
It takes various network parameters in to account, AP power level, RSS
samples, radius of the network, and velocity of mobile terminal etc.
RSS measurement fluctuates because of fading (Fast and shadow fading)
and affects accuracy of time prediction.
To reduce the impact of shadow fading, collect more RSS samples and
average them in a sliding window.
CONTINUED
Log distance path loss model is given by
Yj (i)=Pj -L j (i)-A j (i)
Pj - power transmitted from BSj,
Lj(i) - mean path-loss
Aj(i) - shadowing loss
The Received Signal Strength is estimated by
lop
RSSi =Ptx +Pref -10nlog +ε
d ref
Ptx - transmitted power from AP
n - path loss exponent
- Gaussian distributed random
MEAN RSS VARIATION DUE TO SHADOW FADING
WITH RESPECT TO DISTANCE
40
Beta=3
20 Beta=4
Beta=5
0 Beta=8
-20
RSS Variation (dB)
-40
-60
-80
-100
-120
-140
0 10 20 30 40 50 60 70 80 90 100
Distance (m)
HANDOVER FAILURE PROBABILITY
0.18
Fixed RSS method
0.16 Hysteresis method
MIH method
0.14
Handover failure probability
0.12
0.1
0.08
0.06
0.04
0.02
0
0 50 100 150
Velocity of Mobile Terminal (km/h)
PROBABILITY OF UNNECESSARY HANDOVER
0.25
Fixed RSS method
Hysteresis method
0.2 MIH method
Unnecessary Handover probability
0.15
0.1
0.05
0
0 50 100 150
Velocity of Mobile Terminal (km/h)
CONCLUSION
A IEEE 802.21 Media Independent Handover scheme has
been presented for seamless vertical handover between
heterogeneous networks for best QoS.
Results show that proposed method outperforms the existing
methods which are based on received signal strength and
hysteresis margin.
The probability of unnecessary handover and handover failure
for the proposed method is minimized by considering shadow
fading and velocity of the mobile terminals into account.
REFERENCES
[1] Daniel Corujo, Carlos Guimaraes, Bruno Santos and Rui L. Aguiar,”Using an Open-
Source IEEE 802.21 Implementation for Network-Based Localized Mobility
Management”, IEEE Communication Magazine, pp. 114-123, 2011.
[2] Xiaohuan Yan, Y.Ahmet Sekercioglu, and Sathya Narayanan, “A Survey of
Vertical Handover Decision Algorithms in Fourth Generation Heterogeneous Wireless
Networks”, Computer Networks, Vol. 54, pp. 1848-1863, 2010.
[3] A. H. Zahran, B. Liang, and A. Saleh,”Signal Threshold Adaptation for Vertical
Handoff in Heterogeneous Wireless Networks, Mobile Networks and Applications”, 11(4):
pp. 625–640, August 2006.
[4] S. Mohanty and I. F. Akyildiz,” A Cross-layer (layer2 + 3) Handover Management
Protocol for Next-Generation Wireless Systems”, IEEE Transactions on Mobile
Computing, 5:1347–1360, October 2006.
[5] X. Yan, N. Mani, and Y. A. Sekercioglu, ”A Traveling Distance Prediction Based Method
to Minimize Unnecessary Handovers from Cellular Networks to WLANs”, IEEE
Communications letters, 12(1): pp. 14–16, January 2008.
