Offset: this parameter is for serving cell should be better than neighbour cells before going to send measurement report, ensure that serving cell power should be good than neighbours.
Hysteresis: this is for Neighboring cell should be better than serving. Before going to send measurement report, ensure that Neighbouring power should be high/good than serving.
Timetotrigger (TTT): this parameter is used for to avoid pingpong handover when measuring the power levels.
Three parameters used for handover optimization to avoid pingpong Handovers and used for Handover A3 event.