Hard handoff:

• A handoff which is temporarily broken during cell to cell transfer is known as hard handoff.In hard handoff,the link to prior base station is terminated before or as mobile moves from one cell to another cell.This means that the mobile station is always linked to only one base station at a time.Thus a hard handoff is also known as "Break before Make" connection.
• Hard handovers are intended to be instantaneous in order to minimize the disruption to the call.The handoff may be initiated if the signal strength received from near by base stations is greater than the serving base station.
• The advantage of hard handoff is that the mobile user uses only channel at a given time.Also hard handover are cheaper and simpler because the mobile station does not need to be capable of receiving two or more channels.

• The main disadvantage of hard handoff is that if the handover fails then call may be temporarily disrupted or even terminated sometimes.

   

Soft handoff:

• A soft handover mechanism works by first switching the connection to new base station establishing the connection and then terminating the connection with the serving base station.Thus soft handoff are also called as"Make before Break" connection.Soft handoff thus enables the overlapping of the repeater coverage zone,so that each mobile station is always within the range of atleast one or more base stations.
• Soft handoff is usually used in CDMA syatems in which the connections are relatively permanent and the communication is more stable compared to other cellular technologies.This is because in CDMA technology each base station uses the same frequency channel for each mobile set.Thus there is no frequency change or change in timing as the mobile station passes from one base station to another.So practically there are no dead zones and negligible interruptions.
• The advantage of soft hand off is that the chances of call termination due to handoff failure are very less.Soft handoff is some what complex and technical implementation is expensive compared to hard handoff.
• The only disadvantage of soft handoff is that it uses a number of channels for just a single mobile station.Thus the number of free available channels are reduced which further reduce the capacity of the system.