In telecommunication, the term handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another. In satellite communications it is the process of transferring satellite control responsibility from one earth station to another without loss or interruption of service.
The actual process of transferring the call is referred to as a handover. In telecommunication there are two reasons why a handover might be conducted. If the user has moved out of range from one base station and can get a better connection from a stronger transmitter or if one base station is full the connection can be transferred to another nearby base station.
The most basic form of handover is that used in most 1G and 2G systems where a phonecall in progress is redirected from one cell transmitter and receiver and frequency pair to another cell transmitter and receiver using a different frequency pair without interrupting the call. If the terminal can only be connected to one base station and therefore needs to drop the connection for a brief period of time before being connected to the other, stronger transmitter, this is referred to as a hard handover.
In 3G (and 2.5G) systems the user can be connected to several base stations simultaneously, combining the data from all transmitters in range into one signal using a RAKE receiver. The set of base stations the terminal is currently connected to is referred to as the active set. A soft handover happens when there are several base stations in the active set and the terminal drops one of these to add a new one. In W-CDMA there is a special case called softer handover where several connections in the active set point to the same base station. The softer handover happens when one of these connections is dropped for another from the same base station.
There are also inter system handovers where a connection is transferred from one access technology to another, e.g. a call being transferred from GSM to W-CDMA.
Handoff is the procedure by which a user's radio link is transferred between radio ports in the network without an interruption of the user connection.
The handoff procedure is performed to ensure the integrity of a radio connection and to minimize interference to the users in the coverage area of neighboring cells [4, 8].
After the handoff is completed, the initial radio port migrates the user connection to an optimal route in the network provided that the portable stays within the coverage area of the new radio port for an extended period of time.
In cellular telecommunications, the term handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another.
In telecommunications there are two reasons why a handoff (handover) might be conducted: if the phone has moved out of range from one cell site (base station) and can get a better radio link from a stronger transmitter, or if one base station is full the connection can be transferred to another nearby base station.
The most basic form of handoff is that used in GSM and analog cellular networks, where a phonecall in progress is redirected from one cell site and its transmit/receive frequency pair to another base station (or sector within the same cell) using a different frequency pair without interrupting the call.
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