以往，每件商品都需一件一件的朝讀取機掃描。現在，我們為了節省大量的掃描時間，想要在一次掃描時間內辨識出所有的商品，這就是我們所採用的RFID無線射頻技術。
為了達到以上的目的，所要保證的一項重點就是不能有商品的辨識遺漏，滿足了這個條件，接下來的要求是增快辨識速率，以目前捷運悠遊卡為例，讀取一張卡片所需的時間為0.4秒，如果商品移動速度快就可能發生有商品遺漏的情況，因此要降低辨識所需時間。
我們所採用的Protocol是由EPC所以訂製的900MHz Class 0標準，此標準所採取的防止辨識遺漏的方式為binary tree方法。這個方法必須對每一個商品皆須完整讀取其條碼才能做出辨識。
在不影響其標準架構下，我們修改其演算方法，以達到我們所要加快辨識速率的目的，我們將原先的binary tree改進為prefix-tree。首先我們將所需的辨識的條碼註冊於我們所建造的prefix-tree，接著這些條碼需要被辨識時，便在我們所事先建造的prefix-tree做辨識。我們的作法不需完整讀取其條碼即能做出辨識，其效能顯而易見的可比較出。

In the past, it was necessary to scan products one by one to record information about usage or the number of items in stock. Now, to reduce the scanning time, we want to recognize multiple products with only one scan. To this end, we implement a wireless technique called radio frequency identification (RFID), which allows multi-access.
Our objective is twofold. First, we must ensure that the system can recognize every product without loss of information. Second, we need to improve the recognition (scanning) speed. In this thesis, we take Easy Card (issued by Taipei Smart Card Corporation) as an example of RFID, where the reader takes 0.4 seconds to scan a card. Information would lost if the card is moved over the reader in less than 0.4 seconds, so we have to reduce the time required for recognition.
We follow the 900MHz Class 0 Protocol Standard of Electronic Product Code (EPC), which implements a binary tree algorithm for anti-collision to prevent information loss. The system has to read an ID code completely (as a string of binary digits) to ensure recognition.
Without changing whole architecture of the standard protocol, we modify the algorithm, which interacts with the reader and the tag. To speed up the recognition time, we improve the binary tree to prefix-tree. First, the process pre-registers the tags which need to be recognized to build a prefix-tree. Second, when the tags need to be recognized, we operate the prefix-tree for recognition. Our approach does not need to read the whole ID code. It only receives bits of the code that we need, and then the reader can get the IDs of the tags.

[1] “Barcode Standard”, Chinese version, http://www.wuqueqiao.net/club/uploadfile/barcode/barcode_standard.pdf
[2] “Smart Dust: communicating with a cubic-millimeter computer”, Brett Warneke, Matt Last, Brian Liebowitz, Kristofer S.J. Pister, IEEE JNL, JAN 2001
[3] “Smart Dust and RFID Technology Smart Dust and RFID Technology: Solutions for Business and Industry”, John Suh, RFIG SIG Feb23 2005
[4] “U Taiwan: RFID called second IT revolution”, Department of Investment Services, MOEA, April 29, 2005, http://investintaiwan.nat.gov.tw/en/news/200504/2005042902.html
[5] “Smart Identification Frameworks for Ubiquitous Computing Applications”, KAY RÖMER*, THOMAS SCHOCH, FRIEDEMANN MATTERN, THOMAS DUBENDORFER, CH-8092 Zurich, Switzerland, Wireless Networks, Springer 2004
[6] A notification of Wal-Mart to supplier, http://www.1sync.org/documents/Retailers/Wal-Mart/Data%20Sync%20Supplier%20Letter%202006.pdf
[7] “The U.S. Electronic Passport”, http://travel.state.gov/passport/eppt/eppt_2498.html
[8] “United States Department of Defense Suppliers’ Passive RFID Information Guide”, United States Department of Defense, http://www.acq.osd.mil/log/rfid/supplierguide.htm, October 23, 2006
[9] “Sensor Information System for Active Retirees and Assisted Living (SISARL)”, Academia Sinica, National Taiwan University, National Tsing-Hua University and National Chao-Tung University in Taiwan, http://www.sisarl.org/
[10] ” Spreading Pheromones in Everyday Environments through RFID Technology”, Marco Mamei, Franco Zambonelli, DISMI – Università di Modena e Reggio Emilia, Proceedings of the 2nd IEEE Symposium on Swarm 2005
[11] “Reader Protocol Standard, Version 1.1”, EPCglobal, http://www.epcglobalinc.org/standards/, June 21, 2006
[12] “Colorwave: An Anticollision Algorithm for the Reader Collision Problem”, James Waldrop, Daniel W. Engels, Sanjay E. Sarma, MIT Auto-ID Center, Communications, ICC '03. IEEE International Conference
[13] “Draft Protocol Specification for a 900MHz Class 0 Radio Frequency Identification Tag”, MIT Auto-ID Center, 23 Feb 2003, http://www.epcglobalinc.org/standards/specs/
[14] “EPCglobal Tag Data Standards Version 1.3”, EPCglobal, http://www.epcglobalinc.org/standards/, March 8, 2006
[15] “Efficient Memoryless Protocol for Tag Identification”, Ching Law, Kayi Lee, Kai-Yeung Siu, MIT Auto-ID Center, October 2000, http://auto-id.mit.edu/
[16] ” Fast wireless anti-collision algorithm in ubiquitous ID system”, Ho-Seung Choi, Jae-Ryon Cha, Jae-Hyun Kim, Vehicular Technology Conference, 2004. VTC2004-Fall.
[17] “EPC Radio-Frequency Identity Protocols Class 1 Generation 2 UHF RFID Protocol for Communications at 860 MHz – 960 MHz Version 1.0.9”, EPCglobal Inc
[18] “Anti-collision and Transponder Selection Methods for Grouped ‘Vicinity” Cards and RFID tags”, Peter Hawkes, RFID Technology (Ref. No. 1999/123), page 7/1-7/12
[19] “Electronic Privacy Information Center”, EPIC, http://www.epic.org/privacy/rfid/
[20] “Security Analysis of a Cryptographically-Enabled RFID Device”, Stephen C. Bono, Matthew Green, Adam Stubblefield, Aviel D. Rubin, Ari Juels, Michael Szydlo, The Johns Hopkins University, RSA Laboratories, 14th USENIX Security Symposium, 2005
[21] “RFID技術與應用”, Originally published in Japan by Nikkei Business Publication ,Inc., Chinese Traditional Language edition published by Flag Ublishing CO. TD, 2004
[22] ” A Prefix Tree Base Approach for Mining Surprising Patterns Efficiently”, Hsiao-Hung Lin, NTNU ICE, Master Thesis, June 2006
[23] “Poster Abstract: Analysis of RFID anti-collision algorithms using smart antennas”, Jeongkeun Lee, Sajal K. Das, Kyung-ah Kim, Proceedings of the 2nd international conference on Embedded networked sensor systems 2004
[24] “PAT-tree-based keyword extraction for Chinese information retrieval”, Lee-Feng Chien, Institute of Information Science, Academia Sinica, Taipei, Taiwan, ACM SIGIR 1997
[25] “RFID Operation”, http://www.idteck.com/technology/rfid.jsp