In mobile communication system, handoff is a technique used to:

SOLUTION

Concept of Handoff:

• Handoff is the process of changing the channel (frequency, time slot, spreading code, or combination of them) associated with the current connection while a call is in progress.
• It is often initiated either by crossing a cell boundary or by a deterioration in the quality of the signal in the current channel.
• In the mobile communication system, the handoff is a technique used to ​maintain an acceptable link quality when a mobile station traverses a cell boundary.

Types of Handoff:

Handoffs are broadly classified into two categories—hard and soft handoffs.

Soft Handoff:

• In the soft handoff, at least one of the links is kept when radio links are added and removed to the mobile station; This ensures that during the handoff, no break occurs
• This is generally adopted in co-located sites; It is a “make before break” policy

Hard Handoff:

• A hard handoff is essentially a “break before make” connection. Under the control of the MSC, the BS hands off the MS’s call to another cell and then drops the call
• In a hard handoff, the link to the prior BS is terminated before or as the user is transferred to the new cell’s BS; the MS is linked to no more than one BS at any given time
• Hard handoff is primarily used in FDMA and TDMA, where different frequency ranges are used in adjacent channels in order to minimize channel interference​