KR100615715B1 - Rfid reader having estimating function number of tags and method for estimating thereof - Google Patents

Abstract

An RFID reader having a tag number estimation function and an estimation method thereof are disclosed. The RFID reader having a tag number estimating function according to the present invention transmits a tag number estimation signal including a predetermined number of bit slots to an external tag, and receives a response signal from the tag and receives a response signal for the tag number estimation signal. A counting unit for counting; And a tag number estimating unit estimating the number of tags based on the count result of the counting unit. As a result, the number of tags to be recognized by the RFID reader can be estimated quickly.

RFID, Aloha, Tag Count Estimation, Bit Slot

Description

RDF reader with tag counting function and its estimation method {RFID reader having estimating function number of tags and method for estimating

1 is a block diagram of a general RFID system,

2 is a block diagram of an RFID reader according to a preferred embodiment of the present invention;

3 is a view for explaining the operation of the counting unit shown in FIG. 2, and

4 is a flowchart illustrating a method of estimating the number of tags of an RFID reader according to the present invention.

Explanation of symbols on the main parts of the drawings

100: RFID reader 200: RFID tag

110: communication unit 120: count unit

130: tag number estimation unit 140: control unit

The present invention relates to an RFID reader having a tag number estimating function and an estimating method thereof, and more particularly, to an RFID reader having a tag number estimating function capable of quickly recognizing a tag in an Aloha technique using a slot of a bit time. It is about his estimation method.

With the development of wireless technology, RFID systems are being used in a variety of ways, from prepaid and postpaid traffic cards to various access cards such as parking lots, laboratories, and places requiring security.

RFID (Radio Frequency IDentification) is a type of automatic identification and data capture (AIDC) technology that uses a radio frequency to read data stored in a tag with a microchip. .

The RFID system basically consists of a reader and a tag. When the reader requests the tag data to be transmitted to the tag, the RFID system operates by transmitting the tag data to the reader in the form of a radio frequency.

There are two forms of how a reader recognizes a tag in an RFID system. First, the reader can recognize only one tag at a time, and second, the reader can recognize many tags at the same time.

In a method of recognizing a plurality of tags at the same time in a reader, collisions between response signals may occur as a plurality of tags respond at the same time, and anti-collision techniques are necessarily used to prevent them. Accordingly, various collision avoidance techniques for minimizing collision and recognizing all tags faster have been studied.

Among the various collision avoidance techniques is Aloha. Aloha methods include Slotted ALOHA, Framed Slotted ALOHA, and Dynamic Framed Slotted ALOHA, all using slots.

(n=0~15)개를 전송한다.In using the Aloha method as an RFID collision avoidance technique, the reader may indicate a predetermined number of slots, for example, to inform the tag an area to select a slot to use when transmitting tag data.

Send (n = 0 ~ 15)

In this case, the number of slots is preferably set equal to the number of tags to be recognized by the reader. However, since the number of slots existing in the reading range cannot be known in advance, the reader sets a predetermined initial slot number. use.

If the number of tags existing in the read area of the reader can be grasped in advance, the reader may assign the most suitable slot number to maximize the recognition rate of the tag, thereby minimizing the recognition time of the tag.

Since the prior art cannot determine the number of tags existing in the read area of the reader in advance, a method of estimating the number of tags after assigning a predetermined initial slot number, for example, 16, is used. Doing.

However, in the conventional technology, when the number of tags existing in the read area of the reader is small (for example, one), slots other than the slot used for recognizing one tag are wasted, and when the number of tags is large (E.g. 64) has a problem that many slots are wasted by collision.

Accordingly, an object of the present invention is to provide an RFID reader and a method for estimating the number of tags existing in a read area of a reader by using slots of bit time in an Aloha technique among collision avoidance techniques.

In order to achieve the above object, an RFID reader having a tag number estimation function according to the present invention transmits a tag number estimation signal including a predetermined number of bit slots to an external tag, and receives a response signal for a tag number estimation signal from the tag. A communication unit to count a response signal; And a tag number estimating unit estimating the number of tags based on the count result of the counting unit.

Preferably, the counting unit is divided into a signal-free slot in which no response signal exists at all, a non-collision slot in which only one response signal exists, and a collision slot in which at least two response signals exist, respectively. Can count.

Preferably, the apparatus may further include a controller for controlling the communication unit to transmit a transmission request signal for tag data including the number of bit slots corresponding to the number of tags estimated by the tag number estimating unit.

Meanwhile, the method of estimating the number of tags of an RFID reader according to the present invention comprises the steps of: transmitting a tag number estimation signal including a predetermined number of bit slots to an external tag, receiving a response signal for a tag number estimation signal from a tag, and receiving Counting one response signal; And estimating the number of tags based on the count result.

Preferably, the step of counting the response signal is divided into a signal-free slot in which no response signal exists at all, a non-collision slot in which only one response signal exists, and a collision slot in which at least two response signals exist, respectively. Can count.

Also preferably, the method may further include transmitting a transmission request signal for tag data including the number of bit slots corresponding to the estimated number of tags.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

1 is a block diagram of a general RFID system.

As is known, a general RFID system includes an RFID reader 100 that recognizes a plurality of RFID tags 200 existing in a read area, and an RFID tag 200 that transmits tag data to the RFID reader 100 through a radio frequency. ).

The RFID reader 100 normally radiates radio waves continuously using an antenna. Radio waves emitted from the RFID reader 100 are transmitted to at least one RFID tag 200 in the read area. In addition, the RFID reader 100 is mounted on a wireless terminal device such as a mobile phone and a personal digital assistant (PDA), and its position may be changed at any time.

According to a preferred embodiment of the present invention, the RFID reader 100 transmits a tag number estimation signal to the RFID tag 200 to receive a response signal with respect to the tag number estimation signal from the RFID tag 200, and the RFID tag 200 The number of tags is estimated using the response signal received from

In the above description of the general RFID reader 100, the RFID reader 100 having a tag number estimating function according to the present invention will be described in more detail with reference to FIG.

The RFID tag 200 may be mounted on various types of objects, and thus its position may be moved from time to time. When the RFID tag 200 is located in a read area emitted from the RFID reader 100, the RFID tag 200 receives radio waves emitted from the RFID reader 100. Receive.

According to a preferred embodiment of the present invention, the RFID tag 200 generates a random slot number based on the number of bit slots included in the tag number estimation signal transmitted from the RFID reader 100, Generates a random bit of 0 "or" 1 ". Here, the slot number is used to determine the time point for responding to the RFID reader 100, the random bit is to determine the type of the response signal.

In addition, the RFID tag 200 stores tag data including various kinds of information about a product (or a tag owner) to which the RFID tag 200 is attached, for example, a product description, personal information, and a tag ID. Accordingly, when the RFID tag 200 receives a transmission request signal for the tag data from the RFID reader 100, the RFID tag 200 extracts the previously stored tag data and provides the RFID tag 100 to the RFID reader 100.

2 is a block diagram of an RFID reader according to a preferred embodiment of the present invention.

Referring to FIG. 2, the RFID reader 100 according to an exemplary embodiment of the present invention includes a communication unit 110, a counting unit 120, a tag number estimating unit 130, and a control unit 140.

The communication unit 110 transmits a tag number estimation signal including a predetermined number of bit slots to the RFID tag 200, and receives a response signal for the tag number estimation signal from the RFID tag 200 that receives the tag number estimation signal. do.

In addition, the communication unit 110 transmits a transmission request signal for the tag data to the RFID tag 200 under the control of a controller to be described later, and responds to the transmission request signal from the RFID tag 200 that receives the transmission request signal. Receive signal and tag data.

The counting unit 120 counts the response signal of the RFID tag 200 received through the communication unit 110. According to the present embodiment, the counting unit 120 is divided into a signalless slot in which no response signal exists at all, a non-collision slot in which only one response signal exists, and a collision slot in which at least two response signals exist. Count each one.

The tag number estimator 130 estimates the number of tags based on the count result of the counter 120, that is, the number of no-signed slots, the number of uncollided slots, and the number of collision slots.

As a method for estimating the number of tags in the tag number estimator 130, in the present embodiment, the number of slots without a signal slot, the number of non-collision slots, and the number of collision slots are calculated by the number of bit slots according to Equation (1). Can be.

Here, N is the number of bit slots, n is the number of tags, and r is the number of tags in one bit slot. Given N and n, the probability that there are r tags in one bit slot represents a binomial distribution like B. The presence of r tags in a particular slot is called the occupancy number of the slot. The expected value of the number of slots having the occupancy r may be represented by α.

Based on Equation 1, the number of signalless slots (r = 0), the number of non-collision slots (r = 1), and the number of collision slots (r≥2) are calculated according to the number of bit slots (N), respectively. It was.

N n 2 4 8 16 crash No conflict No signal crash No conflict No signal crash No conflict No signal crash No conflict No signal One 0 One One 0 One 3 0 One 7 0 One 15 2 0.5 One 0.5 0 1.5 2.25 0.125 1.75 6.125 0.0625 1.875 14.0625 3 One 0.75 0.25 0.625 1.6875 1.6875 0.3438 2.2969 5.3594 0.1797 2.6367 13.1836 4 1.375 0.5 0.125 1.0469 1.6875 1.2656 0.6309 2.6797 4.6895 0.3445 3.2959 12.3596 5 1.625 0.3125 0.0625 0.4688 1.582 0.9492 0.9658 2.9309 4.1033 0.5505 3.8624 11.5871 6 1.7813 0.1875 0.0313 1.8643 1.4238 0.7119 1.3322 3.0775 3.5904 0.7919 4.3452 10.8629 7 1.875 0.1094 0.0156 2.2202 1.2458 0.5339 1.7169 3.1416 3.1416 1.0634 4.7525 10.184 8 1.9297 0.0625 0.0078 2.5317 1.0679 0.4005 2.1096 3.1416 2.7489 1.3605 5.092 9.5475 9 1.9609 0.0352 0.0039 2.7986 0.901 0.3003 2.5023 3.0925 2.4053 1.6787 5.3705 8.9508 10 1.9785 0.0195 0.002 3.0239 0.7508 0.2256 2.8888 3.0066 2.1046 2.0144 5.5942 8.3914 11 1.9883 0.0107 0.001 3.2116 0.6194 0.1689 3.2646 2.8938 1.8415 2.364 5.7691 7.8669 12 1.9937 0.0059 0.0005 3.3665 0.5068 0.1267 3.6264 2.7623 1.6113 2.7246 5.9002 7.3852 13 1.9966 0.0032 0.0002 3.4932 0.4118 0.095 3.9717 2.6184 1.4099 3.0934 5.9924 6.9143 14 1.9982 0.0017 0.0001 3.5961 0.3326 0.0713 4.299 2.4674 1.2337 3.4679 6.05 6.4821 15 1.999 0.0009 0.0001 3.6793 0.2673 0.0535 4.6074 2.3132 1.0795 3.846 6.077 6.077 16 1.9995 0.0005 0 3.7461 0.2138 0.0401 4.8965 2.1589 0.9445 4.2258 6.077 5.6972

The tag number estimator 130 refers to Table 1 and calculates a cost function calculated by applying a number corresponding to collision, non-collision, and no signal corresponding to the initially assigned bit slot to Equation 2. Is calculated and the number of tags corresponding to the minimum value is estimated as the number of tags in the read area of the RFID reader 100.

Table 2 below shows an example of calculating the cost function when the number of initially assigned bit slots is 8 and the numbers corresponding to collision, non-collision, and no signal are 2, 3, and 3, respectively. At this time, since the number of tags corresponding to the minimum value is 8 among the calculated cost functions, the tag number estimator 130 estimates the number of tags in the read area of the RFID reader 100 as 8.

Tag count Cost function 2 6.25 3 4.7187 4 3.3789 5 2.2066 6 1.3357 7 0.5663 8 0.5023 9 1.1895 10 1.7908 11 2.5293 12 3.2528 13 3.9434 14 4.5979 15 5.2147 16 5.7931

The controller 140 controls the overall operation of the RFID reader 100. The communication unit 110, the counting unit 120, and the tag number estimating unit may perform the tag number estimation function of the RFID reader 100. 130 control the signal input and output.

The controller 140 controls the communication unit 110 to transmit a transmission request signal for tag data including the number of bit slots corresponding to the number of tags estimated by the tag number estimator 130.

3 is a view for explaining the operation of the counting unit shown in FIG.

), 미충돌 슬롯(

), 및 충돌 슬롯(

)으로 구분하여 각각 카운트한다.As described with reference to FIG. 2, the counting unit 120 receives a response signal of the RFID tag 200 received through the communication unit 110 from a signalless slot (

), Non-collision slots (

), And collision slots (

Count each by separating).

When the RFID reader 100 transmits a tag number estimation signal including a predetermined number of bit slots SN through the communication unit 110, the received RFID tag 200 receives a random number within the range of the number of bit slots. Generate a random bit of "0" or "1".

In addition, when the bit synchronization signal is transmitted from the RFID reader 100, the RFID tag 200 receives and counts the bit synchronization signal and transmits a response signal when it matches the slot number generated by the RFID tag 200. FIG.

The RFID reader 100 may not know how many RFID tags 200 exist in its read area, but in the present embodiment, seven RFID tags 200 exist in the read area of the RFID reader 100. Assume

Slot numbers and random bits generated in the RFID tags 200 of tags # 1 to # 7 are as follows. The slot number of tag # 1 is "6" and the random bit is "1". The slot number of tag # 2 is "3" and the random bit is "1". The slot number of tag # 3 is "3" and the random bit is "0". The slot number of tag # 4 is "6" and the random bit is "0". The slot number of tag # 5 is "1" and the random bit is "1". The slot number of tag # 6 is "2" and the random bit is "0". The slot number of tag # 7 is "7" and the random bit is "0".

The RFID tag 200 counts the bit sync signal transmitted from the RFID reader 100 and transmits a response signal when the RFID tag 200 matches the slot number thereof. Tag # 1 sends a response signal of "1" to slot 6, and tag # 2 sends a response signal of "1" to slot 3. Tag # 3 sends a response signal of "0" to slot 3, and tag # 4 sends a response signal of "0" to slot 6. Tag # 5 sends a response signal of "1" to slot 1, and tag # 6 sends a response signal of "1" to slot 2. In addition, tag # 7 transmits a response signal of "1" to slot 7.

)이다. 또한, 슬롯 1, 슬롯 2, 및 슬롯 7은 하나의 응답신호만이 존재하는 미충돌 슬롯(

)이다. 또한, 슬롯 3, 및 슬롯 6은 적어도 2개 이상의 응답신호가 존재하는 충돌 슬롯(

)이다.As a result, slot 0, slot 4, and slot 5 have no signal slots in which no response signal exists.

)to be. In addition, slot 1, slot 2, and slot 7 are non-collision slots in which only one response signal exists.

)to be. In addition, slot 3 and slot 6 is a collision slot (the at least two response signals exist)

)to be.

)수는 3이고, 미충돌 슬롯(

)수는 3이며, 충돌 슬롯(

)수는 2이다.The RFID reader 100 receives the response signal through the communication unit 110 and counts by the counting unit 120. In the present embodiment, according to the count result of the counting unit 120, there is no signal slot (

) Is 3, and there are no collision slots (

) And the number of collision slots (

The number is two.

When the response signal of the RFID tag 200 is as illustrated in FIG. 3, the tag number estimator 130 determines that there are seven to eight RFID tags 200 in the read area of the RFID reader 100. can do.

4 is a flowchart illustrating a method of estimating the number of tags of an RFID reader according to the present invention.

The RFID reader 100 transmits a tag number estimation signal including a predetermined number of bit slots through the communication unit 110. As a result, all the RFID tags 200 existing in the read area of the RFID reader 100 receive the tag number estimation signal (S300).

Upon receiving the tag number estimation signal, the RFID tag 200 generates a slot number and a random bit within a range of bit slots, and transmits a response signal corresponding to the random bit to the slot number generated by the RFID tag 200. As a result, the RFID reader 100 receives the response signal of the RFID tag 200 through the communication unit 110 (S310).

When the response signal is received through the communication unit 110, the controller 140 controls the counting unit 120 to count the response signal. The counting unit 120 counts the number of non-signed slots, the number of uncollision bits, and the number of collision bits, respectively, based on the response signal of the RFID tag 200 (S320).

When the counting unit 120 finishes counting the number of no-signal slots, the number of non-collision bits, and the number of collision bits, the tag count estimator 130 counts the number of no-signed slots, number of non-collision bits, and collision bits The number of tags is estimated based on the number (S330).

When the tag number estimator 130 estimates the number of tags, the controller 140 determines an optimal number of bit slots based on the estimated number of tags and generates a transmission request signal for tag data. Thereafter, the transmission request signal is transmitted to the RFID tag 200 by the communication unit 110 (S340).

All RFID tags 200 present in the read area of the RFID reader 100 receive a transmission request signal, and the RFID tag 200 transmits response signals and tag data at its response time. This is received through the communication unit 110 of the RFID reader 100 (S350).

As described above, the RFID reader having a tag number estimating function and the estimation method thereof according to the present invention quickly identify the number of tags to be recognized by the RFID reader before receiving tag data from the RFID tag using slots of bit time. There is an advantage that can be estimated.

While the above has been shown and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications may be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (6)

A communication unit for transmitting a tag number estimation signal including a predetermined number of bit slots to an external tag and receiving a response signal to the tag number estimation signal from the tag; A counting unit for counting the response signal; And And a tag number estimating unit for estimating the number of tags based on the count result of the counting unit. The method of claim 1, The counting unit counts each of the received response signals by dividing them into signal-free slots in which no response signals exist, non-collision slots in which only one response signal exists, and collision slots in which at least two response signals exist. RFID reader having a tag number estimation function, characterized in that. The method of claim 1, And a control unit for controlling the communication unit to transmit a transmission request signal for tag data including the number of bit slots corresponding to the number of tags estimated by the tag number estimating unit. Having RFID reader. Transmitting a tag number estimation signal including a predetermined number of bit slots to an external tag; Receiving a response signal to the tag number estimation signal from the tag; Counting the received response signal; And Estimating the number of tags based on the count result. The method of claim 4, wherein The counting of the response signal may be performed by counting each signal into a non-slot slot in which the response signal does not exist, a non-collision slot in which only one response signal exists, and a collision slot in which at least two response signals exist. Tag number estimation method of the RFID reader, characterized in that. The method of claim 4, wherein And transmitting a transmission request signal for tag data including the number of bit slots corresponding to the estimated number of tags to the tag.

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