This presentation illustrates different methods and parameters for the handover. In the end, a comparison table is provided.

1. Vertical Handover
Presented By: Wael Ayoub
waaelayoub@gmail.com

2. Introduction
 The Next Generation Wireless Network (NGWNs) allow users to access in
different wireless network and not only limit them to one network.
 The most important issue in heterogeneous environment is to maintain seamless
service continuity under the principle “Always Best Connected” (ABC) [16].
 NGWNs are expected to support the seamless vertical handoff mechanism in
which users can maintain the connections even when they switch from one
network to another with service continuity.
 VHD Algorithms VHDA are useful in the way that help user terminal in
choosing best network to switch on.

3. Handoff management Process in
collaboration with network layers [15]

4. Types of Handoffs [1]
I. Network types involved
I. Vertical handover
II. Horizontal handover
III. Diagonal handover
II. Frequencies Engaged
I. Inter-frequency handover
II. Intra-frequency handover
III. No. of Connections Involved
I. Hard handover
II. Soft handover
III. Softer handover

5. Types of Handoffs
I. Administrative Domain Involved
I. Intra-administrative handover: managed by the same admin.
II. Inter-administrative handover: managed by different admin.
II. Necessity of Handover
I. Obligatory handover: necessary to change
II. Voluntary handover: optional to change
III. User Control Allowance
I. Proactive handover: decided by user
II. Passive handover: not decided by user.

6. Reliable: good quality after handover.
Seamless: smooth and continuous; user does not
experience service degradation or interruption.
Interference: algorithm should avoid high
interference.
Load balancing: balance traffic to eliminate the
needs for borrowing channels from neighboring
cells.
Improve Performance: the number of handovers
should be decreased.
Desirable Handover Features [1]

7. Parameters [3][4][13][15]
• Received Signal Strength (RSS)
• Available Bandwidth
• Power Requirements (if node run on battery)
• Security
• User Preferences
• Speed
• Handoff latency
• Network load Balancing
• Network Throughput
• Monetary service cost
• Number of unnecessary handovers
• Handover failure probability
When a large number of inputs are used, it becomes difficult or impossible to develop
analytical formulations of handover decision processes. Due to this reason, researchers
apply machine learning techniques to formulate the processes.

8. Decision [4]

9. RSS based scheme
RSS is a dynamic criteria for HD.
Disadvantages :
• Optimal results cannot be obtained only
with RSS.
• in hetero. wireless networks RSS cannot
be compared directly, and cannot reflect
the network condition adequately.
• It is very important to provide users with
QoS

10. QoS Based Scheme
Disadvantage :
QoS techniques are mainly for user
satisfaction and non real time applications.
More parameters are involved in the
decision (available bandwidth, user
preferences, SINR).

11. Decision Function Based Scheme
Multiple Criteria
Real-time applications are delay sensitive.
More criteria to gather information from
heterogeneous wireless networks and
additional state-of-the-art techniques need
to be considered, in order to decide the
most suitable network that guarantees user
satisfaction and network efficiency.
Disadvantages :
Most of the solutions make the handover
decisions on the bases of current systems
state only ; consider only current QoS of
the networks and current mobile nodes
conditions. However decisions should also
consider the probabilistic outcome of the
future system states.

12. Multiple Criteria [13]
VHDAs make handoff decisions based on several criteria (such as RSS, network
coverage, network security, and service cost), it is typical Multiple Criteria Decision
Making (MCDM) which is divided from Multiple Attribute Decision Making
(MADM).
MADM Algorithms:
• Simple Additive Weighting (SAW)
• Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)
• Analytic Hierarchy Process (AHP)
• Gray Relational Analysis (GRA)
• Multiplicative Exponent Weighting (MEW)
• s
They are efficient and flexible, and have a medium implementation complexity.

13. Outline Table of VHDA classified as
Multiple Criteria [13]
Name Method Advantages Disadvantage
AHP MADM
Reduce handoff latency and
Computational Overhead
RSS < threshold value is not considered
SAW MADM
Reduce processing delay and
trusted handover
Minimum number of parameters are
considered
MEW MADM
Reduce processing delay and
trusted handover
Minimum number of parameters are
considered
TOPSIS MADM
Excellent performance against
requirement of traffic and user
QoS parameters are Not considered
GRA MADM Reduce procession delay Handoff dropping rate is high
[14]
Context
aware
Fast handoff, less delay,
minimum handoff, simple
Multimedia traffic is not considered

14. Network Intelligence Based Scheme
Computational Intelligence[12][13]
• The access to real-time application in wireless networks is
concerned with the performance of the handover. In order to
improve the performance of handover, it is very important to
make the handover decision wisely and in time .
• Fuzzy logic [5], intelligent IP-based protocols [8][9], and
Artificial neural network [6] are based techniques which have
played a very important role in providing an intelligent aspect
of the decision mechanisms and they are widely used in
decision making process.

15. Network Intelligence Based Scheme
Computational Intelligence

16. NI based VHD Schemes[4]
Category of
Handover
Decision
Scheme
Description of the Scheme Advantages of the Scheme Limitations of the Scheme
ANN based
Schemes
ANN is applied to tackle complex
problems by automatically learning
the network behavior & generalizing
handover in a dynamic situations.
- Successful Handovers
- Better Network Selection
- Lower handover processing
delay
- High Latency
- Slow training & learning
- Supplementary resource
consumption
Fuzzy Logic
based
Schemes
FL is used to carry out network
assisted handover decision by
prioritizing QoS dynamics according
to user preferences
- Reduced handover delay
- Reduced packet loss
- Intelligent network selection
- User satisfaction for QoS
- Increased Complexity
- Higher decision processing
delays
Intelligent
Protocol
based
Schemes
Different mobility protocols are
designed for providing seamlessness
and proper network control handover
mechanisms.
- Reduced packet loss
- Terminal resource
conservation
- Successful handovers
- Security provision
- Comparatively high latency
- Centralized Control
- High signaling overhead

17. Context Based Scheme [10][11]
Defined as an access point (AP) which is
selected not only based on signal quality or
explicit advertisements sent by the AP(s),
but also on the knowledge of the context
information of the MN and the networks, in
order to make better and intelligent
decisions.
Context information [13] is related to the:
• Network
• Terminal
• The service
• User Preference

18. Context Based VHD Schemes
Category of HO
Decision Scheme
Description of the Scheme Advantages of the Scheme Limitations of the Scheme
Mobile Agent Based
Schemes
Mobile Agents are employed for a partially
distributed handover decision solution
where contextual info is gathered and
distributed by agents.
- Intelligent context collection
- Adaptable in different networks
- Proper context storage
- Optimized blocking rate
- Increased communication overhead
- Large no. of agents
- High handover latency
- Deployment issues in the real world
AHP Based Schemes
Predefined objective based handover
decision and network selection are carried
out with the help of scoring mechanisms
and merit functions.
- Optimized handover latency
- Reduced packet loss
- High throughput
- Optimal network selection
- Resource consuming
- Might compromise on QoS if a low
cost network is available
Mobility Prediction
Based Schemes
User’s mobility patterns and historical data
are collected as context for making a
handover decision.
- Reduced ping-pong for low speeds
- Suitable in uncertain network
environments
- Instability for variable speeds
- Longer handover delay
- Higher packet loss
Cooperation Based
Schemes
Completely distributed handover decisions
are made, based on the cooperation of
different network entities.
- Efficient decision making
- Improved QoS
- Fully distributed
- Suitable for real-time streams
- Improved system utilization
- High signaling cost
- Higher packet loss
- Security provision
MIH Based Schemes
Distributed handover decision is made
via certain predefined triggers that
consider user/application contexts.
- Reduced packet loss
- Optimal network selection
- Embedded security
- Reduced latency
- Optimized throughput
- Supplementary signaling
- Context distribution
- Higher resource consumption

19. Comparative Analysis of the VHD Schemes [4]

20. Comparison of various Strategies [15][17]

21. Conclusion
• Almost of the proposed VHDA either lack a comprehensive consideration of
various network parameters, or lack enough details for implementation as the
studies reported these algorithms
• Research in VHDA; in HV difficulty is devising an Algo. which is truly useful
in a wide ranging conditions and user preferences. One possible solution would
be to implement several VHDA and adopt adaptive methods that choose an
algorithm intelligently based on conditions and user preferences.[12]
• Several VHDA prefer MADMA because it considers more no. of parameters in
decision making, and it decomposes problem in hierarchical model to simplify.

22. Reference
[1] P. Tinkhede and P. Ingole, "Survey of handover decision for next generation," International
Conference on Information Communication and Embedded Systems (ICICES2014), Chennai, 2014,
pp. 1-5.
[2] U. Brinkschulte et al., "A microkernel middleware architecture for distributed embedded real-
time systems," Proceedings 20th IEEE Symposium on Reliable Distributed Systems, New Orleans,
LA, 2001, pp. 218-226.
[3] J. Verma and N. Sharma, “Vertical Handoff Decision Model for Next Generation Network Based
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[5] G. Edwards and R. Sankar, “Microcellular handoff using fuzzy techniques,” Wirel. Netw., vol. 4,
no. 5, pp. 401–409, 1998.
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networks,” Wirel. Pers. Commun., vol. 14, no. 3, pp. 235–254, 2000.
[7] J. Kempf, Reasons for Performing Context Transfers between Nodes in an IP Access Network,
RFC 3374, The Internet Society: Network Working Group, September 2002.
[8] C. Perkins, IP Mobility Support for IPv4: RFC3220, Network Working Group, 2002.
[9] C. Perkins, D. Johnson, and J. Arkko, Mobility Support in IPv6: RFC6275, Network Working
Group, 2011.

23. Reference
[10] J.-y. Hong, E.-h. Suh, and S.-J. Kim, “Context-aware systems: A literature review and
classification,” Expert Syst. Appl., vol. 36, no. 4, pp. 8509–8522, 2009.
[11] J. Antoniou, F. C. Pinto, J. Simoes, and A. Pitsillides, “Supporting context-aware multiparty
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[12] X. Yan, Y. Ahmet Sekercioglu and Sathya Narayanan, “A Survey of Vertical Handover Decision
Algorithms in Fourth Generation Heterogeneous Wireless Networks”, Computer Networks,
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Heterogeneous Wireless Networks”, International Journal of Research Studies in Science,
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[16] E. Gustafsson and A. Jonsson, "Always best connected," in IEEE Wireless Communications, vol.
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