Tuesday, October 8, 2019

Handoffs or Handover process in cellular communication

What are Handoffs or Handover

In cellular communication, the coverage is divided into many cells, and the base station was installed to provide coverage to the cells. Users in the coverage area served by the specified base station by providing a specific channel. A question comes in mind that.

What will happen if a user on a call leaves the coverage area and moves to another cell served by another base station?


The quality of established a link between Mobile Station and Base station decreasing continuously.

In such a situation, a technique is used to transfer a call from one cell to another cell served by another base station. So we can define Handover as
The switching of an ongoing call to a different channel or cell (base station) is known as handover or handoff.

Why handoff and what parameters required for successful handoff?

Suppose you are on a call with the boss or client receiving necessary instruction while traveling in a subway, and your call gets disconnected, or you start receiving disturbing noise. Ah damn, no one wants such a network, and you will decide to move another network. Usually, this happens when distances between the mobile station and the base station are not quite enough to receive the threshold signal. That's why handover gains attraction of network engineers. Some primary reason is listed below

  1. If signals between the mobile station and base station go down from threshold value, then handoff is required.
  2. It will allow the mobile station to continue voice calls while moving in a high-speed vehicle.
  3. Less call drop and congestion rate, which increases network performance.

As we learn above about the importance of handover, network engineers need to take care of specific parameters to implement a handoff system. That includes

  1. Availability of Channels.
  2. The base station must have information about the signal strength of the connected mobile station.
  3. Signal Strength of nearby base stations.

Process of Handoff/handover

Handoff or handover has different types, and each individual is somehow different from each other. Handover takes place after verifying specific parameters, and it cannot be done in one or two steps. The below-described method is the general format of handover.
  1. Mobile Station monitors signal strength regularly of the adjacent base station.
  2. Its keep updating connected base station about receive signal strength.
  3. In case of signals drop and reach to a minimum acceptable level, then MS acknowledge base station.
  4. Base station checks channel availability and also inform nearby base station about new incoming Ms.
  5. The old base station sends MS information to a new base station.
  6. When a new base station receives MS detail than the old base station free channel for other users.
  7. Now the mobile station is served by the new base station.
Reference Book:
Theodore S Rappaport "Wireless Communications- Principles And Practice"
Gottapu Sasibhushana Rao "Mobile Cellular Communication"

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