A method includes transmitting, by a radio frequency identification (RFID) reader, a series of RF signals to RFID tags in a time sequence. A first RF signal includes a first message for responding when received signal strength corresponds to a first power level and a second RF signal includes a second message for responding when the received signal strength of the RF signal corresponds to a second power level. The method further includes receiving, by the RFID reader, a first set of responses from a first set of RFID tags that received the first and second RF signals at a received signal strength corresponding to the first power level. The method further includes receiving, by the RFID reader, a second set of responses from a second set of RFID tags that received the first and second RF signals at a received signal strength corresponding to the second power level.