The Study Of Anti-collision Radio Frequency Identification Technology For Large Volume Of Tags

RFID(Radio frequency identification)is a non-contact information collection technology,which can automatically identify and read the object data through radio frequency signal.RFID is not only regarded as one of the most promising IT(Information technology)at twenty-first century,but also one of the four core technology supporting Internet of Things(IoT).RFID enables fast non-line-of-sight,mobile,multi-object recognition,position and tracking.It has been widely using in intelligent management and monitoring of people,object and asset in various fields penetrating into our daily lives because of its long identification distance,fast speed,and the tag's large memory capacity and reusability,etc.In various RFID application systems,a reader usually need to quickly and accurately identify a large number of tags within its radiation zone.Since the reader communicates with the tags via a shared wireless channel,the information collision occurs when multiple tags respond to the reader simultaneously.Such phenomenon is termed as multi-tag collision.The multi-tag collision gives rise to reduced identification efficiency,increased omission ratio and identification latency,which eventually limits the RFID applications.With the enhancement of tag's identification sensitivity,the increase of reader's identification range,the extension of identification zone,and the increase of the number of tags,the multi-tag collision problem of a modern RFID system become more prominent.To tackle such collision problem,the reader needs to implement an anti-collision algorithm to coordinate the communication between the reader and tags.Restricted by the low-cost and power consumption,the anti-collision efficiency of a RFID system depends mainly on the effectiveness,reliability and stability of the built-in anti-collision algorithm of the RFID reader.The mainstream anti-collision algorithm suffers from low throughput,high complexity and poor stability.Therefore,the research on new mechanism,technique and method of an anti-collision algorithm with efficiency,stability and reliability for large volume of tags has important scientific significance and widespread application value.In this dissertation,focusing on the low throughput,high complexity,and poor stability of the existing anti-collision algorithm of RFID system,we firstly study the dual prefix matching,sub-frame observation,frame breaking and idle slots elimination mechanisms,and then propose a series of anti-collision solutions together with the corresponding algorithms.Simulation and experimental results show that the proposed solutions have the characteristics of high throughput,good stability,low computation complexity,and strong feasibility.The main research contributions of the dissertation can be summarized as follows:1.Based on the research of m-ary query and idle slots elimination,a consecutive collision bit mapping algorithm(CCMA)with custom query command and collision bit mapping is proposed to cope with the low throughput and long identification cycle existing in QT algorithms.The CCMA algorithm can remove the idle queries introduced by m-ary search.Theoretical analysis and numerical results indicate that the proposed CCMA algorithm outperforms the classic QT algorithms and achieves the throughput at 0.46.On the basis of CCMA,a dual-prefix probe scheme(DPPS)is designed.Unlike the conventional multi-bit collision arbitration mechanism,the DPPS can make use of a collided slot to identify the tag and completely remove the idle slots introduced by m-ary search,which significantly improves the identification performance.Both theoretical analysis and simulation results demonstrate that the DPPS algorithm can significantly improve the throughput,which effectively reduce the identification time.2.Based on the research of sub-frame observation and frame breaking,a sub-frame based dynamic framed slotted Aloha(SUBF-DFSA)algorithm is presented to tackle the high computation complexity and low time efficiency existing in the conventional DFSA algorithm.The SUBF-DFSA algorithm makes effective use of the idle and collision statistics during a sub-frame to estimate the tag backlog,determine the optimal frame size for the next identification round,so that it can dramatically improve the identification efficiency for large volume of tags.It has been implemented into the conventional RFID reader meeting ISO/IEC 18000-6C standard because of the low computation overhead.Aiming at the low throughput of the conventional DFSA algorithm,a new algorithm based on the frame breaking policy,named detected based DFSA(ds-DFSA),is proposed.The ds-DFSA algorithm can optimize the frame size,reduce the impact of irrational frame size,and hence improve the identification efficiency and stability.Simulation results show that the average throughput of the ds-DFSA algorithm is 0.41 by assigning the individual frame for each collided slot while the maximum throughput of the conventional DFSA algorithm is 0.368.Although the ds-DFSA algorithm currently cannot be directly applied to existing UHF RFID reader,its implementation complexity is low,i.e.,adjusting the state machine structure at the tag side and designing the custom commands at the reader side.3.Based on the research on binary splitting and idle slots elimination,an idle slots elimination based binary splitting(ISE-BS)algorithm is proposed to deal with the deficiency of TS algorithm with high identification latency and low identification efficiency.The ISE-BS algorithm can remove the idle slots of the conventional TS algorithm,save the coordination time during identification process,and hence improve the identification efficiency.Moreover,since part of collisions can be informed by 1 bit Q signal,the unnecessary data exchange between reader and tags can be eliminated,which can help reducing the reader's energy consumption.Based on the ISE-BS algorithm,two novel adaptive tree slotted Aloha(ATSA)algorithms are presented.In ATSA algorithms,the reader assigns a proper frame size for tags,and a tag randomly selects a time slot from a frame to respond to the reader.If collision occurs,the collided tags will be resolved by the enhanced ISE-BS algorithm.Performance evaluation shows that the proposed ATSA algorithms achieve the throughput of 0.46,outperforming the existing algorithms.Similarly,the implementation of ISE-BS and ATSA algorithms also requires the custom commands at the reader side and extra state flag indicator at the tag side.In summary,according to the application demands of reliable identification for the large-volume tags,the multi-tag collision mechanism has been in-depth researched.The six anti-collision algorithms are proposed to improve the identification performance of the RFID system.Theoretical analysis and numerical results verify that the proposed algorithm has the advantages of high throughput,good stability,low complexity and strong feasibility.These improvements will significantly promote the widespread use of the RFID technology and the development of IoT and the industry.