NFRA-AIC: A RFID Reader Anti-Collision Protocol With Adaptive Interrogation Capacity

In radio frequency identification (RFID) applications, multiple readers are deployed in the work area to improve their coverage. Such adjacent readers may be faced with reader collision due to their mutual interrogation interference. In this case, the performance of the RFID system will be degraded greatly. Therefore, some researchers proposed a number of the RFID reader anti-collision protocols, such as NFRA and its variants. Based on the technical framework of NFRA, this paper proposes an RFID reader anti-collision protocol with adaptive interrogation capacity (NFRA-AIC). The main contribution is that the interrogation time of a reader is determined by the number of tags within its interrogation region. Among NFRA-AIC, by adding sub-rounds and reserving a period of time between the AC signal and the first OC signal, readers that complete interrogating tags can release the communication resources allocated to them. Therefore, other adjacent readers can have a chance to use these released communication resources to interrogate tags. It is worth pointing out that those readers interrogating tags will not be interrupted by an AC signal. To evaluate the protocol performance, the proposed NFRA-AIC is compared with several protocols, i.e., DCS, PDCS, Colorwave, NFRA, NFRA-C, FRCA1, FRCA2, and BACP, in 12 scenarios. The simulation results show that the proposed NFRA-AIC protocol outperforms the other conventional protocols. Especially, the NFRA-AIC harvests the highest efficiency improvement of more than 110% under both the random and mobile deployment patterns compared to the latest protocol BACP.