Performance Analysis of Anti-collision Algorithm for Tag Identification Time Improvement

Transcription

1 , pp Performance Analysis of Anti-collision Algorithm for Tag Identification Time Improvement Chang-Su Kim 1, Bong-Im Jang 1 and Hoe-Kyung Jung 1* 1 PaiChai University, Doma2-Dong, SeoGu, Daejeon, Korea { ddoja, jjang, hkjung }@pcu.ac.kr Abstract Recently, the use of RFID(Radio Frequency Identification) for object identification is used more often, but the tag collision problem by the use of a radio frequency still exists. Therefore, in this paper, we analyzed tag identification time to minimize tag collisions and improve tag identification time by applying various tag anti-collision algorithms in the suggested method. As a result, we drew a conclusion about the number of optimum readers used in the RFID system environment. Significantly, we expect that the suggested method will be used more efficiently in the simultaneous multi-tags identification RFID system environment. Keywords: RFID, Tag Identification, Anti-collision algorithm, Hash Function 1. Introduction The technology which acquires and manages information by using sensors attached to objects is essential to realize ubiquitous environment [1]. Although, the object identification method using bar code or smart card still exists, the use of RFID recently increases as the alternative for power efficiency and data transmission convenience [2]. RFID, an object recognition system using radio frequency, has the advantage of identifying multiple objects simultaneously without physical contact to the objects [3]. On the other hand, in an RFID system, the problem of tag recognition collision occurs during data transmission because multiple tags respond at the same time when a reader sends a query. To solve this problem, various anti-collision methods [4, 5] were studied, but it is diccicult to apply them to a passive tag-based system due to complicated process procedures. Therefore, this study suggests an effective and efficient method to minimize tag collisions by using multi-reader and to reduce the tag identification time by applying various anticollision methods. The rest of this study was organized as follows, Chapter 2 investigates the existing anticollision methods, and Chapter 3 suggests an efficient tag authentication method based on a multi-reader method. In Chapter 4, the results of performance evaluation of the suggested method were illustrated, and finally Chapter 5 concludes the study and suggests further study plans. 2. Related Work This chapter examines the various tag anti-collision algorithm. * Corresponding Author ISSN: IJSEIA Copyright c 2014 SERSC

2 2.1. Binary Search Algorithm The binary search algorithm is as follows. when multi-numbered tags send data at the same time, the number of tags is decreased, depending on the site where collision occurs, thus all the tags must be identified [6]. For instance, 6 tags are located in the area of a tag reader as shown in Figure 1, the reader calls a tag which satisfies the range of , and if the Nth bit of the tag ID that responded to the call is 1, it marks as 1, and 0 as 0, and if both the 1 and 0 exist, it marks as x, meaning collision. After identifying the collision spot, it calls the tag, covering the range of which designated 0 to the highest bit where the collision occurred, and the rest collision spots was designated to 1. All tags are identified by repeating this process, and when the number of all tags is N, the notation to calculate the average number of iteration, R (N) is shown in the following formula (1) [7]. Figure 1. Execution Process of Binary Search Algorithm (1) 2.2. Dynamic Binary Search Algorithm In binary search algorithm, the amount of data which is sent for tag identification increases as the length of the ID increases because tags send ID bits to all the readers. Thus, both the tag identification time and tag energy consumption increase. To solve this problem, the method of the dynamic binary search algorithm was suggested. Figure 2. Execution Process of Dynamic Binary Search Algorithm The dynamic binary search algorithm is the same as the binary search algorithm in basic method. However, it is different in that readers send Valid Bit which shows collision occurrence except for call command. The dynamic binary search algorithm has the same number of tag identification repetition as the binary search algorithm, but has more efficiency by reducing the amount of data. The execution process of dynamic binary search algorithm is shown in Figure 2 [2]. 2 Copyright c 2014 SERSC

3 2.3. Adaptive Group Separation (AGS) Algorithm The AGS algorithm is a method by which an appropriate prefix size is determined by the number of tags; and tag groups becomes subdivided. Thus, the number of tag calling signals decreases [2]. For instance, if six tag IDs are arranged in the order of 00010, 00101, 01001, 10110, and 11001, the execution process is shown as on Figure 3. After determining a prefix size, a reader subdivides tag groups, calls each group and inspects tags. If collision occurs, it adds 0 and 1 to the highest bit that was faced with collision in order to produce a new query, and calls a tag again. Figure 3. Execution Process of AGS Algorithm If N numbers of tags are used in this AGS algorithm, the formula in order to obtain an average repeat count for searching tags (R (N)) is shown as on the formula (2). (2) 3. Proposed System In this chapter, the configuration of the multiple-reader environment system is suggested for improving the tag identification time. The suggested method is that each reader is devised to read only a designated tag when readers identify objects in the RFID system. This prevents the collision of each tag signal and reduces the tag identification time Tag Recognition Process by using Multi-Reader This paper suggests a tag recognition method which uses multiple readers so as to solve a problem of tag collision occurring in a single reader configuration method. Copyright c 2014 SERSC 3

4 Each reader in the multi-reader configuration system that is suggested by this study initially contains tag IDs previously before recognizing them. Therefore, the reader sends a query to a tag within its recognition range, and when a responding tag appears, the reader stops corresponding to tags which are not in its tag list. Through this identification process, tag collision was minimized, and the process time for tag recognition became shorter Tag Recognition Process by using Identification Bits The tag ID used in the RFID system is an original code system in order to identify each tag. The proposed system suggests the tag ID searching method. In this method tag IDs are divided into a regular code system by using recognition bit based on the uniqueness of this tag ID. In short, the tag ID search time becomes shorter by using the way in which the ID within the relevant range according to the recognition bit is verified instead of general-used total tag ID inspection. The flow chart of the suggested system is shown in the Figure 4. Figure 4. The Flow Chart of the Suggested System 3.3. Tag Authentication Process of the Suggested System Terms and notation which are used to express the process procedure in the whole authentication process of the suggested system are defined in Table 1. Table 1. Definitions of Terms Terms Definitions H( ) Hash Function XOR(exclusive or) ID Tag ID R r Random number produced by a Reader R d Random number produced by a Database Concatenation CP H(ID random number) IdB Identification bits of Tag ID 4 Copyright c 2014 SERSC

5 In this study, the whole authentication process of the suggested system is explained in Figure 5. First, a reader sends Rr to the tag and DB. Second, the tag which receives the query transmits the result value and XOR calculation value of the IdB to the reader after processing self ID and random number of the readers using Concatenation Hash function. Third, the reader sends CP1 to DB after checking the tag using IdB. Fourth, DB sends the self generated random number Rd and CP1 calculation result to the reader after authentication process of tag ID. Finally, a reader sends D and Rd to tag and the tag verifies correspondence between the CP1 from the reader and CP1 self generated. Figure 5. Authentication Process of Proposed Method 4. Performance Evaluation In this chapter, we compare and analyze the whole time of authentication process between the tag recognition method in a single reader configuration and the suggested tag recognition method based on the multi-reader system in order to analyze the performance of the suggested system. There is no collision between readers. Moreover, the time for tag authentication process is calculated and analyzed by applying the binary search and the AGS algorithm. The parameters for analyzing performances of the suggested system are shown in Table 2. Symbol N r N t T rt T rd T db T IB T rt_sum T rd_sum T db_sum T sum Table 2. System Parameter Explanation Number of Reader Number of Tag Communication Time between Reader and Tag (7ms) Communication Time between Reader and Database (3ms) Execution Processing Time in Database (24ms) IB Searching Time (2ms) Total time for communication between Reader and whole tag Total time for whole communication between Reader and Database Whole execution Processing Time in Database Total time for Tag Authentication Copyright c 2014 SERSC 5

6 4.1. Performance Evaluation applying Binary Search Algorithm The first test compares the change of tag recognition time according to the number of reader for the performance evaluation of the suggested system by applying the binary search algorithm. First, the formula to calculate T rt _ sum, the total time between the reader and the tag which reflects the number of tag collisions is shown as (3). (3) Second, the formula to produce T rd _ sum, the total time between the reader and the database which includes IdB searching time is displayed by (4). Third, the formula to calculate T db _ sum, the process time in the database is shown by (5). In order to get T sum, the whole spent time for recognizing tags, formulas (3), (4) and (5) are added in total. With regards to performance analysis, the number of tags of 10~100 and readers of 1~5 were combined, and experimented, but as for single-reader configuration, IdB searching time, T IB is exceptionally calculated. Figure 6 shows the comparing result of tag recognition time between a single reader and double readers. (4) (5) Figure 6. Tag Authentication Time using Binary Search Algorithm(1) Figure 7 shows the result of time difference as the number of tags increases. 6 Copyright c 2014 SERSC

7 Figure 7. Tag Authentication Time using Binary Search Algorithm(2) In the result, Figure 6 and 7 showed that if the number of tags is 50, the improvement rate of process time between the number of readers, 1 and 2, became 46%, but the improvement rate of process time between the number of readers, 2 and 3, became 18%. In addition, if number of tags are 100, the improvement rate of process time between the number of readers, 3 and 4, became 10%, displaying that if the number of readers becomes over 4, the decrease effect of process time is not significant. The result shows that it is more efficient to use 3 or less readers in binary search algorithm environment Performance Evaluation applying AGS Algorithm The second test reflected the number of tag collisions by applying the AGS algorithm. The formula to calculate T rt_sum, the total time between the reader and the tag which reflected the number of tag collisions is shown as (6). The formula to get the value of T rd_sum and T db_sum is the same with the first test. Figure 8 shows the comparing result of tag recognition time between a single reader and double readers. (6) Figure 8. Tag Authentication Time using AGS Algorithm(1) Copyright c 2014 SERSC 7

8 Figure 9 shows the comparing result of tag recognition time as the number of tags increases. Figure 9. Tag Authentication Time using AGS Algorithm(2) In the result of experiments, when the number of readers is increased to 2 as shown in Figure 6, the improvement rate of process time increased to over 40%, but in case of over 3 readers, no significant difference was found in the improvement rate of process time. This result suggests that the use of 2 readers can produce the best efficiency in the system that is applied with the AGS algorithm. 5. Conclusion This study suggested a tag authentication method based on multi-reader and anti-collision algorithm in order to utilize an efficient RFID system. RFID system has tag collision problem in multi-tags recognition environment because it uses radio frequency in sending data between reader and tag. Therefore this study suggests the application of a multi-reader configuration method to minimize tag collision and to reduce the tag recognition time. As a result of the performance analysis, the multi-reader configuration system, compared to single reader configuration system, shows improvement in the process time by 40%. In addition, when applied with a binary search algorithm, the most suitable number of the readers was three or less, and the number of readers was two or less when applied with AGS algorithm. This suggested method is expected to be applied in various fields such as logistics and distributions in which multiple objects should be recognized simultaneously. In future researches, the study for multiple-reader configuration method taking collision among readers into consideration is necessary. References [1] H.-T. Ceong, H.-J. Kim and J.-S. Park, Discovery of and Recovery from Failure in a Costal Marine USN Service, Journal of information and communication convergence engineering, vol. 10, no. 1, (2012), pp [2] H.-S. Lee, S.-H. Lee, S.-K. Kim and S.-I. Bang, Adaptive Group Separation Anti-Collision Algorithm for Efficient RFID System, Journal of the institute of electronics engineers of Korea, vol. 46, no. 5, (2009), pp Copyright c 2014 SERSC

9 [3] S. I. Ahamed, F. Rahman, E. Hoque, F. Kawsar and T. Nakajima, Secure and Efficient Tag Searching in RFID Systems using Serverless Search Protocol, IJSIA, vol. 2, no. 4, (2008), pp [4] C. Wen-Tzu, Performance Comparision of Binary Search Tree and Framed ALOHA Algorithms for RFID Anti-Collision, IEICE transactions on communications, vol. 91, no. 4, (2008), pp [5] W.-Y. Yeo and G.-H. Hwang, Efficient anti-collision algorithm using variable length ID in RFID systems, ICICE Electronics Express, vol. 7, no. 23, (2010), pp [6] L.-F. Jiang, G.-Z. Lu and Y.-W. Xin, Research on anti-collision algorithm in radio frequency identification system, Computer Engineering and Applications, vol. 15, (2007), pp [7] K. Finkenzeller, RFID Handbook, Second Edition, John Wiley&Sons, (2003). Authors Chang Su Kim, he received the B.S., M.S., and Ph.D. degrees from the Department of Computer Engineering of Paichai University, Korea, in 1996, 1998, and 2002, respectively. From 2005 to 2012, he worked for the Department of Internet at Chungwoon University as a professor. Since 2013, he has worked in the Department of Computer Engineering at Paichai University, where he now works as a professor. His current research interests include multimedia document architecture modeling, web 2.0, and the semantic web Bong-Im Jang, she received the M.S. And Ph.D. degree from the Department of Multimedia Engineering form Hannam University, Korea, in 2003 and 2012, respectively. Since 2012, she has worked in the Industry-Academic Cooperation Foundation at the Pai Chai University. Her current research interests include USN, Sensor Web, Multimedia and Web Service. Hoe Kyung Jung, he received the B.S degree in 1987 and Ph. D. degree in 1993 from the Department of Computer Engineering of Kwangwoon University, Korea. From 1994 to 2005, he worked for ETRI as a researcher. Since 1997, he has worked in the Department of Computer Engineering at Paichai University, where he now works as a professor. His current research interests include multimedia document architecture modeling, information processing, information retrieval, and databases. Copyright c 2014 SERSC 9

10 10 Copyright c 2014 SERSC