Handoff:

When a mobile moves into a different cell while a conversation is in progress, the MSC automatically transfers the call to a new channel belonging to the new base station. This process of transferring call to a new base station is called as Hand off.

Types of Hand off

1. Mobile Assisted Hand off
2. Intersystem Hand off
3. Delayed Handoff (Two level Hand off)
4. Queued Handoff
5. Hard hand off
6. Soft hand off
7. Inter system handoff

Hand off Process:

• Off does not mean a physical change in the assigned channel but rather than a different base station handles the radio communication task.

• Off is a process of automatically transferring the call to a new frequency channel belonging to a new base station, when the cellular mobile phone moves into a different frequency zone so that the conversation can be continued in a new frequency zone without dialing.

In Mobile Assisted Handoff (MAHO) every mobile station measures the received power from surrounding base stations and continually reports the results of these measurements to the serving base station.

• A handoff is initiated, when the power received from the base station of a neighboring cell begins to exceed the power received from the current base station by a certain level or for a certain period of time.

• In MAHO method call handed over between base stations is much faster than first generation analog systems .As handoff measurements are made by each mobile . MSC no longer constantly monitors signal strengths. MAHO is particularly suited for microcellular environments where handoffs are more frequent. During the course of a call, if a mobile moves from one cellular system to a different cellular system controlled by a different MSC, an intersystem handoff becomes necessary.

• An MSC engages in an intersystem handoff when a mobile signal becomes weak in a given cell and the MSC cannot find another cell within its system to which it can transfer the call in progress.