An Anti-Collision Algorithm in RFID Systems Based on Interference Cancellation and Tag Set Partitioning

It is well known that anti-collision protocol plays an essential role in overall tag read time in radio frequency identification (RFID) systems due to the obstruction caused by tag-collision. With an aim at speeding up tag identification process, we propose an anti-collision algorithm, spread partial-Q slot count (SPSQ) algorithm, based on a slotted ALOHA code division multiple access (CDMA) technique along with tag set partitioning. A new packet structure is introduced preceded by a description of the mechanism of partition-wise identification process. In fact, according to received power levels tags are partitioned into a certain number of groups. In the partition-wise identification process tags belonging to two subsets are regrouped as a partition with a guarantee of uniformly largest received power-level difference in a tag set so as to be interrogated by the reader simultaneously. The identification process for each partition is then operated sequentially. Indeed, tag set partitioning in conjunction with spread spectrum techniques could enable a simple multi-tag access detection scheme and improve system throughput as well. Simulations demonstrated that SPSC algorithm outperforms some existing anti-collision algorithms in terms of throughput.