Research On Capture-aware And Blocking Anti-collision Algorithms For RFID Tag Identification

In many radio frequency identification(RFID)applications,to get the real-time numbers and types of tags or the read rate of 100%,the reader identifies the tags in its scope repeatedly.In these cases,the tag in the reader's scope is a staying tag or an arriving tag.The reader already stores the IDs of all staying tags,so it can just verify the existence of these tags to rapidly identify them.As a result,the reader can spend the main time in recognizing arriving tags,which is called blocking technology.Besed on the blocking technology,both the collisions caused by staying tags and collisions between staying tags and arriving tags are prevented.The identification efficiency of the reader is improved greatly.In the real RFID system,when several tags reply data to the reader simultaneously,among these tags,if a tag's signal strength is much larger than the other tags',the reader can still receive the tag's data correctly,which is called capture effect.Many studies have proven that the capture effect may often happen.The reader will not recognize all the tags in its range when the capture effect happens.Therefore,we need to proposed effective tag anti-collision algorithms to cope with the capture effect.This paper mainly researches on the capture-aware and blocking anti-collision algorithms for RFID tag identification.The research contents and results are as follows:(1)The capture-aware and blocking Binary Tree(BT)algorithms.As the capture effect may not happen in some cases,we propose an anti-collision algorithm with short reply for RFID tag identification(ACSR),which is a blocking method.In ACSR,each staying tag emits a short reply to indicate its continued existence.Therefore,the data amount transmitted by staying tags is reduced significantly.Simulation and analysis results show that ACSR greatly outperforms the existing methods.To cope with the capture effect and recognize staying tags rapidly,we present a capture-aware and blocking binary tree protocol for RFID tag identification(CBBT).Simulation and analysis results show that,CBBT outperforms the existing algorithm significantly in terms of identification delay,the number of collision slots and the data amount transmitted by tags.(2)The capture-aware and blocking Query Tree(QT)algorithms.In the non-capture environment,we propose a slot allocated blocking anti-collision algorithm(SABA).In SABA,the reader assigns a unique slot to each tag in its range by using a slot allocation mechanism.Based on the allocated slot,each staying tag only replies a short data to the reader in the identification process.The simulation and analysis results show that the performance of SABA is superior to the existing algorithms significantly.In the capture environment,we present a capture-aware blocking anti-collision algorithm for RFID tag identification(CABA).In CABA,the number of bits transmitted by staying tags is reduced greatly and arriving tags can be identified completely.The simulation results show that CABA outperforms the existing methods significantly.(3)The capture-aware and collecting bit tracking algorithms.In the bit tracking technology,the reader can get the precise locations of all colliding bits,which can be used to realize the tag collecting operation.In the non-capture environment,we present a collected blocking collision tree algorithm with bit tracking for RFID tag identification(CBCT).Two key mechanisms are adopted in CBCT which are collecting and refreshing.By using the collecting mechanism,the reader can identify many tags in a slot.The refreshing mechanism is used by the reader to keep the continuity of all the staying tags.Simulation and analysis results show that the proposed algorithm is superior to the algorithms with bit tracking technology.In the capture environment,we present a collecting collision tree protocol for RFID tag identification with capture effect(CCT).When the capture effect happens,a CCT reader can recognize all the tags in its range.If the CCT reader identifies the tags in its range repeatedly,it can identify many staying tags in a slot by using a collecting mechanism.As a result,the reader's efficiency is improved greatly.(4)Tag-grouping methods.When the reader identifies arriving tags,an appropriate grouping method can be used to improve the efficiency of an anti-collision algorithm.In the existing tag-grouping methods,an assumption is connotative,which is that a collision slot,success slot and idle slot of the RFID system have the same time duration.However,the length of an idle slot is obviously shorter than a success slot or a collision slot in most cases.When the time durations of three types of slots(success,collision and idle)are different,we study the groping methods in BT,QT and bit tracking algorithms and propose general tag-grouping methods.Besides,we also research the tag-dispersing methods in the main standards of ISO/IEC 18000-6C and GJB 7377.1-2011.The reader's efficiency is improved by adoping the tag-dispersing methods proposed in this paper.