An Efficient Protocol For Continuous Scanning In RFID Systems

Radio frequency pattern recognition(RFID)technology is widely used in many areas such as warehouse management,logistics management and so on.Continuous scanning is an important application of RFID technology.The reader cannot collect all tags'IDs in one location when the distribution range of RFID tags is large.The continuous scanning protocols enable the reader to collect the IDs of all tags in different locations efficiently.The existing continuous scanning protocols have a high probabili ty of misjudgment.A data structure ONV is designed in order to reduce the probability of misjudgment.Several Bloom Filter arrays are compressed into an order number vector ONV,which greatly reduces the amount of data to be transmitted.A method of inactivating known tags by ONV vector is proposed.This method is called ONV method in this paper.The back-end server first generates an ONV vector and then sends ONV vector to tags through the reader.The tag uses the ONV vector to determine if it is a known tag.If the tag determines that it is a known tag,it will be inactivated.The ONV method can inactivate known tags efficiently with low overhead of communication and low probability of misjudgment.Based on the ONV method,we propose an ONV-based Continuous Scanning protocol(OCS)in this paper.The OCS first calculates a ratio and then selects the less time consuming method from the two ID collection methods according to the ratio.If the ratio is less than or equal to 1,the OCS directly collects IDs of all active tags using the existing CA method.If the ratio is greater than 1,the OCS inactivates known tags with ONV method and then collects IDs of unknown tags with the existing CA method.In order to evaluate the performance of OCS,we take the time cost and misjudgment rate as the evaluation indexes and compare OCS with the existing continuous scanning protocols in this paper.The experimental results show that OCS has low time cost and low misjudgment rate.The OCS protocol proposed in this paper has good performance.