| 20090185505 | MEDIA ACCESS CONTROL (MAC) FOR AN ACTIVE RFID SYSTEM - A system of radio frequency communication between Readers and Tags, the system comprising at least one tag Reader and a plurality of Tags, each tag is given a unique tag ID, deployed in a region in which at least some of the Tags are in radio communication with the tag Reader and a Media Access Control protocol such that the tag Reader is configured to send and receive radio communication to and from at least some of the plurality of Tags. The plurality of Tags are configured to send and receive radio communication to and from the tag Reader and the Media Access Control protocol is configured to control the radio communication between the tag Reader and the plurality of Tags The Media Access Control protocol includes a multi-dimensional addressing scheme allowing Readers to efficiently address tag communities ranging from small to very large in unicast, multicast and broadcast modes. The multi-dimensional addressing scheme enables division of the plurality of Tags into a number of groups for different stages of Media Access Control protocol processing, based on different portions of the tag ID. A hash function is used to transform the tag ID into a pseudo random ID, so as to achieve better spreading of tag population and lower statistical dependency between dimensions. The MAC has an inherent flexibility in the sense that it allows readers to communicate with different versions of tags and also to optimize communication parameters to reader's capabilities, without pre-configuration of the tags. Furthermore, the MAC supports means to achieve very high access reliability, such as relay between tags, and the ability to work with tags that alternate between active and sleep mode) including means for power savings. All of these novel features, coupled with some prior art concepts like collision resolution algorithms, result in a scalable MAC protocol for an active RFID system employing multiple access. | 07-23-2009 |
