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Number of tags (with 8*8 grid)
Number of tags (with 8*8 grid)
Figure 4 Percentage of successfully identified tags with the 8*8 tag grid.
CONCLUSION
In this paper we analysed several factors influencing the multiple object identification with passive
RFID technology. The measured results show that the 100 % identification reliability can be achieved
only with small tag populations. The major factors affecting to the certainty besides the number of
tags are the distance between the reader and the tags and the beam width of the reader antenna that
determines the range. The increase of the time interval used for identification does not have significant
impact to the reliability. Furthermore, the measurements showed that the mutual alignment of tags has
an impact to the reliability. As the distance between tags increases, the tags will interfere less with
each other.
Item specific antennas and tag attachments will become an essential factor when designing fast,
passive RFID with the option of multiple object identification. Specific limitations of multiple object
identification with passive RFID technology lie within object and tags mutual alignments.
Furthermore, as the electromagnetic fields easily reflect from metallic surfaces and attenuate to non-
conducting materials the fabrication material of objects to be identified has a great influence to the
identification accuracy.
ACKNOVLEDGEMENTS
The authors would like to thank the Finnish National Technology Agency and Nokia Foundation for
financing the research done for this paper.
REFERENCES
Auto-ID Labs. 860 MHz - 930 MHz Class I Radio Frequency Identification Tag Radio Frequency &
Logical Communication Interface Specification. Published on 14 Nov. 2001
Lim A., Mok K. A study on the design of large-scale mobile recording and tracking systems. IEEE
Proceedings of the 3 P' Hawaii International Conference on System Sciences, 6 - 9 Jan.1998. Kohala
Coast, HI USA. Vol.7, pages 701-710.
Penttila, K., Sydanheimo L., Kivikoski M. Analysis of Multiple Object Identification with Passive
RFID Proceedings of the 5 th International Conference on Machine Automation, ICMA. 24-26 Nov.
2004. Osaka, Japan, pp. 559-564
Vogt H. Efficient Object Identification with Passive RFID Tags. International Conference on
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Wieselthier J.E., Ephremides A., Michaels L.A. An exact analysis and performance evaluation of
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