InRFIDsystems,thegroupingproblemistoefficientlygroupalltagsaccordingtoagivenpartitionsuchthattagsinthesamegroupwillhavethesamegroupID.Unlikepreviousresearchontheunicasttransmissionfromareadertoatag,groupingprovidesafundamentalmechanismforefficientmulticasttransmissionsandaggregate