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.
吴黎明 陈泰伟 项颖. 新颖的物联网RFID传感系统防冲突算法[J]. 计算机应用, 2013, 33(03): 614-617.
WU Liming CHEN Taiwei XIANG Ying. Novel anti-collision algorithm of RFID sensor system for Internet of things. Journal of Computer Applications, 2013, 33(03): 614-617.
WALDROP J, ENGELS D W, SARMA S E. Colorwave: an anticollision algorithm for the reader collision problem[C]// ICC ′03: IEEE International Conference on Communications. Piscataway, NJ: IEEE Press,2003,2:1206-1210.
[3]
BIRARI S M, IYER S. Mitigating the reader collision problem in RFID networks with mobile readers[C]// Proceedings of the 13th IEEE International Conference on Networks. Piscataway, NJ: IEEE Press,2005:463-468.
[4]
HO J, ENGELS D W, SARMA S E. HiQ: a hierarchical q-learning algorithm to solve the reader collision problem[C]// Proceedings of International Symposium on Applications and the Interact Workshops. Piscataway, NJ: IEEE Press, 2006:23-27.
[5]
HWANG K I, KIM K T, EOM D S. DiCA: Distributed tag access with collision avoidance among mobile RFID readers [C]// Proceedings of EUC 2006 Workshops: NCUS, SecUbiq, USN, TRUST, ESO, and MSA. Berlin: Springer, 2006:413-422.
[6]
EPCglobal. EPC radio-frequency identity protocols class-1 generation-2 UHF RFID protocol for communications at 860MHz-960MHz, Version 1.2.0[EB/OL].[2012-07-10].http://www.gs1.org/gsmp/kc/epcglobal/uhfc1g2/uhfc1g2_1_2_0-standard-20080511.pdf.
[7]
European telecommunications standards institute. Final draft ETSI EN 302 208-2 V1.4.1[EB/OL].[2012-07-10].http://www.etsi.org/deliver/etsi_en/302200_302299/30220802/01.04.01_40/en_30220802v010401o.pdf.
LEONG K S, NG M L, COLE P H. The reader collision problem in RFID systems[C]// 2005 IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications. Piscataway, NJ: IEEE Press,2005:658-661.
YU J, LEE W, DU D Z. Reducing reader collision for mobile RFID[J].IEEE Transactions on Consumer Electronics,2011,57(2):574-582.
[17]
CHEN H Y,BAE S,BHADKAMKAR A, et al. Coupling passive sensors to UHF RFID tag[C]// Proceedings of 2012 IEEE Radio and Wireless Symposium. Piscataway, NJ: IEEE Press, 2012:255-258.
2013, Vol. 33 
