Mumbai university > Comp > SEM 8 > Mobile Communication

Marks: 5M

Year: Revised 2012

Soft Hand off

In soft handoff, a mobile station is temporarily connected to more than one base station simultaneously. Mobile unit may start our assigned to single cell. If the unit enters a region in which transmission for two base stations are comparable (within some threshold of each other),the mobile unit entersthe soft handoff state in which it is connected to the two base stations. The mobile unit remains in this state until one has station clearly predominates at which time it is assigned exclusively to thatcall. Thus soft hand off is a make before break procedure. It reduces the probability of a dropped call during hand off. It makes the hand off virtually undetectable by user.

Hard Hand off

Hard hand off is implemented in AMPS/ETACS and GSM systems.Hard hand off is a break before make arraignment i.e. link to one base station is broken before establishing link with another base station. Hard hand off involves change in frequency of the mobile when mobile moves from one cell to another cell.