RFID reader and method for recognizing RFID tags

Patent metadata

Field	Value
Publication number	US-10095892-B2
Application number	US-201715430130-A
Country	US
Kind code	B2
Filing date	Feb 10, 2017
Priority date	Feb 12, 2016
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

An RFID reader includes a transmitter, a receiver, and an evaluator. The receiver receives signals from RFID tags within a given number of slots of a time frame with a given frame size and provides a number of successful slots and a number of collided slots. The evaluator sets a modified frame size based on an estimated number of RFID tags which is determined based on the frame size, the number of successful slots, and the number of collided slots. The invention also refers to a corresponding method.

First claim

The invention claimed is:

1. A Radio Frequency Identification (RFID) reader,
comprising a transmitter configured for transmitting a request signal, a receiver configured for receiving signals from Radio Frequency Identification (RFID) tags and an evaluator,
wherein the receiver is configured to receive the signals from the RFID tags within a given number of slots of a time frame with a given frame size,
wherein the receiver is configured to provide a number of successful slots in which one signal has been received and a number of collided slots in which a detection of one single signal was not possible,
wherein the evaluator is configured to set a modified frame size based on an estimated number of RFID tags,
wherein the evaluator is configured to determine the estimated number of RFID tags based on the given frame size, the number of successful slots, and the number of collided slots,
wherein the receiver is configured to perform a collision recovery by identifying a signal within a slot comprising more than one signal,
wherein the receiver is configured to obtain a collision recovery probability α at which the collision recovery is performed by the receiver,
wherein the receiver is configured to provide, in the provision, the number of successful slots, ss, and the number of collided slots, cs, after performing the collision recovery, and
wherein the evaluator is configured to determine the estimated number of RFID tags based on the given frame size L, the number of successful slots ss, the number of collided slots cs, and the collision recovery probability α by calculating the number of collided slots before the collision recovery, Cb, and the number of successful slots before the collision recovery, Sb, according to S b =ss−α/(1−α)*C, and C b =cs/(1 −α) and determining the estimated number of RFID tags based on the given frame size L, the number of the collided slots C b , and the number of the successful slots S b .

2. The RFID reader of claim 1 ,
wherein said evaluator is configured to determine the estimated number of RFID tags using a closed form solution.

3. The RFID reader of claim 1 ,
wherein n est is the estimated number of RFID tags,
wherein L′ is the modified frame size, and
wherein the evaluator is configured to set the modified frame size L′ via L′ =n est +/−(n est ·5%).

4. A Radio Frequency Identification (RFID) reader,
comprising a transmitter configured for transmitting a request signal, a receiver configured for receiving signals from Radio Frequency Identification (RFID) tags and an evaluator,
wherein the receiver is configured to receive the signals from the RFID tags within a given number of slots of a time frame with a given frame size,
wherein the receiver is configured to provide a number of successful slots in which one signal has been received and a number of collided slots in which a detection of one single signal was not possible,
wherein the evaluator is configured to set a modified frame size based on an estimated number of RFID tags,
wherein the evaluator is configured to determine the estimated number of RFID tags based on the given frame size, the number of successful slots, and the number of collided slots,
wherein n est is the estimated number of RFID tags,
wherein L is the given frame size,
wherein cs is the number of collided slots,
wherein ss is the number of successful slots,
wherein said evaluator is configured to determine the estimated number of RFID tags using the following formula:

n
est

=

(

-

b

4
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a

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S
+

0.5
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4

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2

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2
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P

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L

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with
⁢

:

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a
=

1
/

120
*

⁢

(

L
-
cs

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,

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b
=

1
/

24
*

⁢

(

L
-
cs
-

ss
/
5

)

,

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c
=

1
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6
*

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(

L
-
cs
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ss
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4

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,

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d
=

1
/

Assignees

• Fraunhofer Ges Forschung
• Friedrich Alexander Univ Erlangen Nuemberg
• Univ Friedrich Alexander Er

Inventors

• Elsaid Ibrahim Hazem
• Kenawy Hamed
• Robert joerg
• Heuberger Albert
• Strauss Wolfram

Classifications

• G06K7/10029 Primary

  the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot · CPC title

• G06K7/10128

  the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device · CPC title