Cardinality Estimation for Large-scale RFID Systems. Chen Qian , Hoilun Ngan, and Yunhao Liu Hong Kong University of Science and Technology. RFID: Hot Topic. Both in industry and academic society RFID: independent sessions (three or more papers) in PerCom 2007, 2008 2009?.
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Chen Qian, Hoilun Ngan, and Yunhao Liu
Hong Kong University of Science and Technology
To be expanded…
M. S. Kodialam, T. Nandagopal, “Fast and reliable estimation schemes in RFID systems”, MobiCom 2006
J. Myung, W. Lee, “Adaptive splitting protocols for RFID tag collision arbitration”, MobiHoc 2006
Z. Zhou, et. al., "Slotted Scheduled Tag Access in Multi-Reader RFID Systems", ICNP 2007
Qunfeng Dong, et. al., “Load Balancing in Large-Scale RFID Systems”, Infocom 2007
If multiple tags transmit to reader simultaneously, a collision happens, and reader cannot recognize these tags.
Security and traffic control
Extremely long latency
Not applicable for mobile objects
that works well without pre-knowledge?
1/2(t+1)of the tag responses are in time slot t.
The kth bit in bitmap BM[k] will be zero if k>>log2n, or be one if k<<log2n.
The fringe consists zeros and ones for the k whose value is near log2n.
R is the position of the right most zero
P. Flajolet and G. N. Martin, "Probabilistic Counting Algorithms for Data Base Applications," Journal of Computer and System Science, vol. 31, 1985.
If we make several independent estimations and compute the average result, the standard error will be reduced.
Consider the average value
The variable has the expectation and standard deviation that satisfy
Therefore, the improved estimator is
The number of time slots required
for a frame is independent from the
size of tag set.
A frame with 16 slots is enough to
estimate up to 216 = 65536 tags.
Fixed 32-slot length for LoF estimation.
Just the last time!
Thank you !