新颖的物联网RFID传感系统防冲突算法

Novel anti-collision algorithm of RFID sensor system for Internet of things

基于超高频射频识别(RFID)技术构建物联网系统往往需要将多个读写器同时工作于同一区域,这种多读写器环境势必会造成多读写器冲突,严重影响系统的性能。针对常用的反向散射耦合方式,选取信干比作为系统通信质量的度量,提出基于快速功率控制和退避机制的防多读写器冲突算法。读写器依据信干比情况,动态调节自身发射功率,在保证读写器读写距离的同时,减少信号覆盖区域的冗余,实现防冲突。考虑到发射功率调节至最大时,读写器仍可能无法获取目标信干比,引入了退避机制,使读写器主动降低发射功率,其退避时间映射于目标信干比迭代比例。实验结果表明,读写器能够根据功率控制算法,动态调节发射功率并快速收敛,提高了系统的实时性和可靠性。退避算法的设计提高了读写器信道争用的公平性,而且大大降低读写器功耗,这对移动/手持读写器尤为重要。该防冲突算法有效地最小化信号覆盖区域的冗余,实现防多读写器冲突,同时能够保证读写器的目标识别距离,提高了标签识别率。

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 muhi- 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.