1. Presentation on
Handover
By-
Ankita Khadatkar
Pooja Jaiswal
Puja Thosar
Nikita Borikar

2. THE TERM HANDOVER
The process of transferring an ongoing call
or data session from one channel to another
in a cellular network
The core network performs handovers at
various levels of the system architecture
It is a key component in cellular network
mobility management as it requires a
specific latency on server interruption time.

3. Basic reasons why a handover might be
conducted:
 If the mobile device moves out of the range of one
cell and a different base station can provide it with a
stronger signal
 If all channels of one base station are busy then a
nearby base station can provide service
to the device

4. Handover process
Important one in any cellular network
Must be completed efficiently and without
inconvenience to the user
Different networks use different types of handover
techniques

6. Two main types of handover
Hard handover
- GSM systems
Soft handover
- CDMA systems

8. Hard Handover
Existing radio link must be dropped for a small
period of time
Then taken over by another base station
A call in progress redirected not only from a base
station to another base station but also from its
current transmit–receive frequency pair to another
frequency pair
An ongoing call can not exchange data or voice
for this duration

9. Call drop in hard handover
Break in call transmission
Handover takes place in a few ms (at best in 60 ms)
Interruption is hardly discernible by the user
Handover to another cell is required when the signal
strength is low and error rate is high. GSM systems
perform hard handovers

10. Soft Handover
A soft handover is one in which the channel in the
source cell is retained and used for a while in parallel
with the channel in the target cell
 In this case the connection to the target is
established before the connection to the source is
broken, hence this handover is called make-before-
break

11. Soft handovers may involve using connections to
more than two cells: connections to three, four or more
cells can be maintained by one phone at the same time
 When a call is in a state of soft handover, the signal
of the best of all used channels can be used for the call
at a given moment or all the signals can be combined
to produce a clearer copy of the signal
Softer handovers are possible when the cells involved
in the handovers have a single cell site.

12. Inter and Intra System Handover

13. Inter System Handoff
If during ongoing call mobile unit moves from one
cellular system to a different cellular system which is
controlled by different MTSO, a handoff procedure
which is used to avoid dropping of call is referred as
Inter System Handoff.

14. An MTSO engages in this handoff system. When a
mobile signal becomes weak in a given cell and
MTSO can not find other cell within its system to
which it can transfer the call then it uses Inter
system handoff.
Before implementation of Inter System Handoff
MTSO compatibility must be checked
In Inter System Handoff local call may become
long distance call.

15. Intra System Handover
If during ongoing call mobile unit moves from one
cellular system to adjacent cellular system which is
controlled by same MTSO, a handoff procedure
which is used to avoid dropping of call is referred as
Intra System Handoff.

16.  An MTSO engages in this handoff system
 In Intra System Handoff local calls always remain
local call only since after handoff also the call is
handled by same MTSO
 When a mobile signal becomes weak in a given
cell and MTSO finds other cell within its system to
which it can transfer the call then it uses Intra system
handoff.

17. Advantages
Overcome fading through micro diversity
Reduce Node Power which in turn decreases
interference and increases capacity
Increases battery life

18. Disadvantages
Using several radio links requires more channelize
at ion codes
High handover signalling resulting in slower
handover initiation

19. Summary
Handover when the mobile device moves out of
the range of one cell (base station) and a different
base station can provide it with a stronger signal or
when present cell traffic high
Hard handover in GSM
Call drop for hard handover
Soft handover in CDMA

20. References :
Wikipedia, The Free Encyclopedia, [Online]:
http://en.wikipedia.org
MobileCompChap03L11GSMHandover
handoverinnetworks-13071790379332-phpapp01-
110604041918-phpapp01
trial_lecture on handover