A monitored area is provided multiple RFID tags placed at defined coordinates/locations throughout the extended area. These RFID tags respond to receipt of a RF signal by transmitting/broadcasting their unique identifier (ID) within the specific area in which the tag is located. A device, whose location...http://www.google.de/patents/US7295132?utm_source=gb-gplus-sharePatent US7295132 - Self-locating devices via highly directional RFID tags in controlled location
