ISS-TCA: An Identified Slot Scan-Based Tag Collection Algorithm for Performance Improvement in Active RFID Systems

The standard tag collection algorithm (TCA) in ISO/IEC 18000-7 has difficulty in collecting data from a massive number of active radio frequency identification (RFID) tags in a timely manner, so it should be improved to allow successful application of active RFID systems to a wide variety of industrial fields. We propose a novel TCA, which is an identified slot scan-based TCA (ISS-TCA), to improve the performance of tag collection (TC) in active RFID systems. In the proposed ISS-TCA, an active RFID reader differentiates identified slots from collided and empty slots via an ISS phase, in which active RFID tags send minimal responses. The reader then avoids collided and empty slots in the following TC phase, in which it collects the actual data from the tags. This reduces the cost of collided and empty slots during TC, resulting in improved TC performance. We carried out simulations to evaluate and compare the performances of the standard TCA and the proposed ISS-TCA in TC. The simulation results with up to 500 tags showed that the proposed ISS-TCA reduced the average time required for TC by 33.2% or 27.3% when the reader collected 50 or 100 bytes of additional data from the tags, respectively. We also experimentally evaluated the performance improvement of TC by the proposed ISS-TCA using an active RFID reader and 60 tags that were implemented for this paper. The experimental results confirmed that the proposed ISS-TCA could improve the TC performance in practice, confirming the simulation results, and showed that it could also decrease the average battery consumption of the tags by 39.3%.