A Low Latency Scheme for Bulk RFID Tag Reading

Passive RFID tags transmit their ID information to a tag reader upon energization by the reader. These transmitted signals, or IDs, may collide if multiple tags transmit their ID simultaneously, requiring repeated energizations by the reader to read all tag IDs successfully. The number of energizations increases with the number of ID bits in the tag and the number of tags to be read. An increase in energizations results in a greater incurred latency to read the tags, and additionally, more transmissions. This is undesirable in an industry environment especially, and with this comes higher expended energy by the reading system, leading to higher system costs. In this paper, a new proposed scheme is evaluated, the shortcut bisected countdown scheme (SBCS), in terms of the number of energizations by a reader. Three different techniques are progressively combined into three schemes in order to cut down on the number of energizations. The final scheme, SBCS, which is a combination of the three techniques, stabilizes on the number of energizations irrespective of the tag ID length and the number of tags to be read, resulting in a distinct advantage for bulk reading. The three schemes are memoryless meaning that the tags are unable to remember if they were read or not; hence the performance of each of the schemes is compared with the Query Tree protocol since it is also memoryless.