Soft handover is when the UE, while handing over, can have traffic channels with both(or multiple) cells(or sectors) at the same time. If the sectors belong to the same cell, it is known as Softer handoff. It is a make before break. It is only possible if the frequency bands are same in both the Base stations and the UE doesnt have to retune itself, which is the case in CDMA. Which is why it is not supported in LTE as it uses FDMA.