An apparatus, system and techniques for determining a location of an RFID tag among a population of tags are disclosed. The system includes an RFID reader with at least one antenna port and a population of RFID tags. The population of tags can be homogenous or heterogeneous. The RFID reader varies its transmit power through one or more antenna ports resulting in a grouping of the RFID tags into clusters. In one embodiment, the reader utilizes multiple antennas to further define RFID tag clusters among the population. Each read tag is then uniquely associated with a defined cluster. Tag agents also can be provided among the population of tags facilitating definition of the clusters.