关键词: 物联网, 超高频射频识别, 防冲突, 功率控制, 退避算法

Abstract: The system of Internet of Things (IoT) based on ultra high frequency Radio-Frequency-IDentification (RFID) usually needs multiple readers to work simultaneously in the same area. Multi-reader collision takes place under this multi-reader environment, which will affect the system performance. Based on backscatter modulation, Signal to Interference Ratio (SIR) was selected as the measurement of communication quality, and the reader anti-collision algorithm based on power control and backoff algorithm was proposed in this paper. Readers dynamically adjust their transmission power according to SIR, to ensure the detection range and to reduce redundancy of their coverage area for anti-collision. Considering that some target SIR may not be achieved yet when the transmit power is adjusted to maximum, a new backoff algorithm was proposed. In backoff process, the reader reduced its power actively, and kept it for some time which is mapped into the proportion of target SIR iteration. The simulation results show the reader can adjust the power with fast convergence, and improve the real-time and reliability of RFID system. The backoff algorithm ensures the fairness of channel occupation. More importantly, it can reduce the power consumption, which is important for mobile readers. The reader anti-collision algorithm can effectively reduce redundancy of their coverage area and thereby minimize the reader collision, but also can ensure the detection range and thereby enhance read rate.

Key words: Internet of Things (IoT), Ultra-High-Frequency Radio-Frequency-IDentification (UHF RFID), anti-collision, power control, backoff algorithm