Unknown Tag Monitoring Method For Large Scale RFID Systems

Since the beginning of the 21st century,the Internet of Things(Io Ts)technology has developed rapidly and is widely used in many fields.For example,the application of the Io Ts in intelligent logistics,intelligent transportation,intelligent buildings,environmental monitoring have made major break throughs,and have greatly affected people's production and lifestyle,which greatly increased the productivity,and made human society more intelligent and efficient.Radio Frequency Identification(RFID)technology is one of the core supporting technologies of Io Ts.The emergence of RFID technology has greatly promoted the development of the Io Ts.However,in the promotion and application of RFID technology,there are still many technical challenges and scientific problems,among which tag monitoring for large-scale RFID system is one of the main problems.This paper mainly studies the unknown tag identification and cardinality estimation in large-scale RFID systems.In RFID systems,the tags without registering in advance are called unknown tags,which usually appear in the scenarios,where the tag-attached objects are moved into or misplaced in the reader's interrogating area.Therefore,research on the identification and cardinality estimation of unknown tags is very important for RFID-based applications.The main contents of this paper are as follows:First,we fully study the existing unknown tag detection and identification protocol and tag cardinality estimation protocol.After fully study the existing protocols,we summary the advantages and disadvantages of the existing protocols.Some of these protocols are probabilistic protocols and cannot detect or identify unknown tags completely.Usually RFID system includes known tags and unknown tags.The existence of known tags can interfere with the identification process of unknown tags.Some protocols improve the identification efficiency of unknown tags by deactivating known tags.Second,for the problem of identifying unknown tags,we first propose a basic efficient unknown tag identification protocol based on sampling Bloom filter called UTI-SBF,which consists of known tag deactivation phase and unknown tag identification phase.The idea behind the UTI-SBF protocol is to deactivate the known tags to counteract their interference on the unknown tag identification.Then we propose an enhanced protocol called EUTI-SBF,which eliminates the non-homogeneous slots based on the UTI-SBF protocol to improve the time efficiency.The parameters of the two protocols are theoretically analyzed to maximize the efficiency.We conduct extensive simulations to evaluate the proposed UTI-SBF and EUTI-SBF protocols and the simulation results illustrate that the UTI-SBF and EUTI-SBF protocols outperform the BUIP protocol.In particular,the EUTI-SBF protocol only consumes about 70% of deactivation time compared with the BUIP protocol in the known tag deactivation phase.Finally,in order to save costs,in some practical applications,it is not necessary to know the ID of all unknown tags accurately,and only need to know the number of unknown tags,so another focus of this paper is the estimation of the number of unknown tags.According to the principle of probability theory and mathematical statistics,we first propose an unknown tag counting protocol with controllable precision,called UTC protocol.The UTC protocol consists of two phases,the first phase is the rough estimation phase of the unknown tag number,and the second phase is the accurate estimation phase of the unknown tag number.On the basis of the UTC protocol,we propose the EUTC enhanced protocol.EUTC protocol uses segmented method to make known tags do not respond to the reader,and the non-empty time slots are eliminated,which greatly improves the time efficiency on the basis of ensuring precision.This paper extensively simulates the proposed UTC and EUTC protocols to evaluate protocol performance.The experimental results show that the precision of the estimated number of unknown tags obtained by UTC and EUTC protocols is much higher than the specified precision.For unknown tag identification and unknown tag number estimation problem,this paper proposes UTI-SBF protocol,EUTI-SBF protocol,UTC protocol and EUTC protocol respectively,and verifies the feasibility,efficiency and precision of the protocol through extensive simulation experiments.Through the above protocol,the unknown tags in the RFID system can be fully monitored.In practical applications,the above protocol can comprehensively monitor unknown tags in RFID systems,greatly improving time efficiency and economic efficiency.