Assume that there is a cell going on between two parties over a voice channel. When the mobile unit moves out of coverage area of a particular cell site, the reception becomes weak. Then the present cell site will request a hand off.
The system will switch the call to a new cell site without interrupting the call or changing the user. This procedure is called as hand off.
The user can continue talking without even noticing that the hand off procedure has taken place. The advantage of this is to increase in the effectiveness of the mobile system.
There are different types of hand off:
- Hard: A hard hand off is if a mobile station transmits between two base stations having different frequency assignments.
- Soft: A soft hand off is if the mobile station starts communication with a new base station without stopping the communication with the older base station.
- Delayed: In many situations, instead of one level, a two level handoff procedure is used, in order to provide a high opportunity for successful handoff. A handoff can be delayed for 5 seconds if no available cell could take the call.
- Forced: A forced hand off is defined as the hand off which would normally occur but is prevented from happening or a handoff that should not occur but is forced to happen.
- Queued: In the queued hand off procedure, the MTSO arranges the handoff requests in a queue instead of rejecting them, if the new cell sites are busy.