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Journal of Information Science and Engineering, Vol. 25 No. 6, pp. 1671-1690 (November 2009)

Reordering for Indexing in an RFID Tag Database*

SUNGWOO AHN AND BONGHEE HONG
Department of Computer Engineering
Pusan National University
Busan, 609-735 Korea

The trajectories of RFID tags can be modeled as a set of time-parameterized line segments defined by two tag events, namely entering and leaving a specific location. Each tag interval (TI) is specified in a three-dimensional domain, with axes: Tag IDentifier (TID), Location IDentifier (LID), and time (TIME). The query performance for tracing tags depends on the distribution of the TIs in the data space. We investigate a more efficient representation of TIs, which orders the set of values in the three-dimensional domain. Our analysis shows that the ordering of LIDs makes a greater contribution to the efficiency of query processing than TID or TIME. To execute queries efficiently, an optimal ordering of LIDs is important. To solve this problem, we propose a new LID proximity function for reordering an arbitrary LID ordering. We also propose a reordering scheme for LIDs to determine an optimal sequence of LIDs in the domain. Our experiments show that the proposed reordering scheme considerably improves the performance of queries for tracing tag locations, compared with previous methods for assigning LIDs.

Keywords: RFID system, tag, middleware, query for tracing tags, location identifier, proximity, ordering

Full Text () Retrieve PDF document (200911_02.pdf)

Received April 11, 2008; revised June 30 & August 27, 2008; accepted October 31, 2008.
Communicated by Chih-Ping Chu.
* This work was supported by the grant of the Korean Ministry of Education, Science and Technology (The Regional Core Research Program/Institute of Logistics Information Technology).