Group coding of RF tags

RFID, radio frequency identification, is an automatic identification technology which identifies individual physical objects according to the unique IDs recorded by the RF tags attached on these objects. On the other hand, real-space objects often form a group. With RFID, we want to not only identify individual objects but also verify the integrity of the group of objects. In existing RFID systems, this “group verification” is done by looking up the list of grouped objects after the individual identification. This method requires some network connectivity to share the list of grouped objects and cannot be applied in the off-line environment. Against this problem, this thesis proposes the “group coding” of RF tags, which can check the integrity of the group in the off-line environment with writing the group related information into the memory of grouped RF tags. In addition, when some RF tags are missing from the group, the group coding can determine the information of RF tags missing from the group, the number of missing RF tags or the unique IDs of missing RF tags. Numerical simulation reveals that the determination of the number of missing RF tags can be done against 10 RF tags out of 20 RF tags within 0.5% error rate with writing 96-bit group related information into each RF tag’s memory. It is also revealed that the determination of the unique IDs can be done against 64 missing RF tags out of 100 within 0.5% error rate with writing 840-bit group related information into each RF tag’s memory. The validity of the theory and the numerical simulation is confirmed by the experimental evaluation using the implementation of the group coding on the commercial UHF-band RFID interrogator.