Introduction to Handoff handoff in a handoff in 4G – Networks Vertical handoff process Handoff Algorithms Handoff performance REFERENCES: Review of Vertical Handoff Algorithms in 4G – Networks ( paper)

1. Vertical Handoff Algorithms in
4G
Amr Abdel fattah
Yossry Mostafa

2. Vertical Handoff Algorithms in 4G
⚫ Introduction to Handoff
⚫ handoff in 4G – Networks
⚫ Vertical handoff process
⚫ Handoff Algorithms
⚫ Handoff performance

3. Introduction to Handoff
⚫ the process of shifting a user call control from
poor network area to new cell is known as
Handover or Handoff.

4. Handover in 4G – Networks
One of the major challenges in 4 G is to realize
seamless handoff among various
communications systems with small handoff
latency and packet loss.
support real-time high-speed multimedia
applications require small handoff delay and
high data-rate transmission.

5. Mobility management
The aim of mobility management is to track
where the subscribers are
Location management enables the network to
discover the current attachment point of the
mobile node for call delivery.
Handover management enables the network to
keep a user’s connection as the mobile
terminal continues to move and change its
access point to the network

6. Vertical handoff
A Vertical handoff is a handoff between two
network access points, which are using
different connection technologies.
Mobile Node (MN) handovers from IEEE 802.11b
network to a GPRS network

7. Vertical handoff

8. Vertical handoff
Vertical handoff can be divided into two
subclasses
upward handoff means (mobile switches from the
network with a small coverage to a network of
larger coverage)
downward handoff means(mobile switches from
the network with a larger coverage to a
network of smaller coverage)

9. Vertical Handover Process
1- System Discovery Stage:
collect all the information about the available
networks in order to select network for
handover.
2- Decision Making Stage:
the Vertical handover decide whether to continue
the connection with the current network or to
switch to another network.

10. Vertical Handover Process
3 - Handover Execution Stage:
when the decision has made, the connections
are re-routed from the source network to the
target network.

11. Classification of Vertical Handoff
Algorithms
The main challenge while designing a vertical
handover algorithm is minimizing handoff
latency[delay] and packet drop
⚫ RSS based algorithms
⚫ User preference based algorithms
⚫ Velocity based algorithms

12. RSS based algorithms
This group of algorithms uses Received Signal
Strength (RSS) as main parameter for handoff
decision. The RSSs of the different candidate
network are measured periodically and the
network with the strongest signal strength is
selected as target network.

13. User Preference Based
Algorithms
User preference in terms of MN’s power
consumption , associated service cost, offered
security, and the QoS provided by a candidate
network can be considered for handoff
decision.
These algorithms can be used to maximize the
end-user’s satisfaction while using non-real-
time applications

14. Velocity based algorithms
⚫ If the MS in a heterogeneous environment
moves with a relatively high velocity, the
probability of a call drop may be higher due to
excessive delays caused by the handoff
process.
⚫ it is better to use its previous network without
the handover

15. Performance Evaluation of Vertical
Handoff
Handover delay (handoff latency)
duration between the handoff starting and
handoff completion.
delay depends on the complexity of the handover
management process.
If handoff delay is more, packet loss will be more
Number of handovers
Number of handovers must be reduced to avoid
the wastage of network resources

16. Performance Evaluation of Vertical
Handoff
⚫ Handover failure Probability
A handover failure occurs when the handover is
started but fails to connect to the target
network.
⚫ Throughput
The throughput refers to the data rate delivered
to the mobile terminals on the network.
Handover to a network candidate with higher
throughput