KR100805034B1 - System and method for rfid tags identification using the grouping - Google Patents

Abstract

A system and a method for recognizing RFID(Radio Frequency IDentification) tags by grouping are provided to raise a tag recognition rate and improve tag recognition throughput of an RFID reader by recognizing a plurality of RFID tags placed in coverage of the RFID reader by grouping the tags repeatedly based on a predetermined condition. An RFID reader(200) groups a plurality of RFID tags(100) into a predetermined number of groups, recognizes the RFID tags, and regroups the RFID tags when a plurality of tags is continuously collided for a predetermined slot over a predetermined number or generates a blank response continuously for the predetermined slot. The RFID reader regroups the RFID tags into 2n groups when the RFID tags are continuously collided for the predetermined slot over the predetermined number. The RFID reader regroups the RFID tags into n/2 groups when the RFID tags generate the blank response continuously for the predetermined slot.

Description

System And Method For RFID Tags Identification Using the Grouping}

1 is a view showing the configuration of an RFID tag identification system using grouping according to an embodiment of the present invention.

2 is a signal flowchart of an RFID tag identification system using grouping according to an embodiment of the present invention.

3 is a flowchart illustrating a method of identifying an RFID tag using grouping according to an exemplary embodiment of the present invention.

4 is a view showing the performance of the RFID tag identification method using grouping according to an embodiment of the present invention.

5 is a diagram illustrating a performance comparison between an RFID tag identification method and other methods using grouping according to an embodiment of the present invention.

The present invention relates to an RFID tag identification system and method using grouping. In particular, a plurality of tags located within a radio wave range of a reader are repeatedly grouped under a predetermined condition to estimate the total number of tags, The present invention relates to an RFID tag identification method using grouping for estimating the number of tags of a group based on the number of tags.

RFID (Radio Frequency IDentification) is a type of automatic recognition and data acquisition technology that reads data stored in a tag with a microchip by using radio frequency without connection. It consists of a reader (also called a reader or interrogator) that reads data.

The tag can be mounted on various types of objects so that its position can be moved from time to time, and when the tag is located within the radio range emitted from the reader, the tag receives radio waves emitted from the reader. Such a tag consists of a microchip in which an object's unique identification code (ID) and information related to the object are stored, and an RF antenna part that exchanges information with a reader through a wireless device.

The reader is mounted on a wireless terminal device such as a mobile phone, a personal digital assistant (PDA), a DMB terminal, and a portable multimedia player (PMP), and its position can be changed at any time. Such a reader typically emits radio waves continuously using an antenna, and the radio waves emitted from the reader are transmitted to at least one tag within the radio range. There are two ways in which a reader recognizes a tag. The first is a method in which a reader can recognize only one tag at a time, and may be applied to a case in which articles are sequentially moved, such as a conveyor belt. The second method is to recognize a plurality of tags at the same time in the reader, and can be applied to storing goods and checking out items in a store. However, in the second method, as multiple tags respond at the same time, interference and collisions occur between response signals, and thus the response signals of each tag do not reach the reader.

An anti-collision protocol is essentially used to prevent interference and collision between the plurality of tag response signals. Accordingly, various collision avoidance methods are required to minimize collisions between tag response signals.

Aloha (ALOHA) type, which is a collision avoidance method currently used, has a problem that a lot of collision occurs and a processing speed becomes slow when an arbitration phase and an identification phase are performed in one slot. In addition, when the Aloha type separates the mediation step from the recognition step, there is less collision, but an additional mediation step causes excessive time. In addition, since the Aloha type cannot determine in advance the number of RFID tags existing within the radio range of the RFID reader, the Aloha type performs an arbitration step of assigning an arbitrary slot number. For this reason, when the number of RFID tags is larger than the randomly assigned slot number, excessive time is taken due to the occurrence of collision, and even when the number of tags is smaller than the randomly assigned slot number, excessive time is required due to the blank response. do.

An object of the present invention for solving the above problems is to provide an RFID tag identification system and method using grouping that can increase the tag identification rate.

Another object of the present invention is to provide an RFID tag identification system and method using grouping that can significantly improve the throughput in which a reader recognizes a tag by identifying a plurality of tags using a method of grouping and regrouping. .

In order to achieve the object of the present invention as described above, the RFID tag identification method using the grouping according to an embodiment of the present invention is a slot Aloha-based tag identification method, when Kc, Ke are different natural numbers, the number of readers Dividing a tag of into K K groups; Re-grouping the plurality of tags into Ke groups when the tags belonging to the first group of the Kc groups are continuously collided more than a predetermined number of times or in a continuous blank response state in the process of identifying the tags belonging to the frame having a certain number of slots. Repeating; And identifying a plurality of tags belonging to the regrouped groups for each group.

The identifying for each group may include identifying a number of tags of a first group in the regrouping complete group; Regrouping and optimizing the remaining total tags based on the number of tags in the first group; Identifying a plurality of tags belonging to the optimized regrouping for each group.

The number of slots allocated to the first frame for identifying the number of tags of the group whose tag number is not identified is characterized in that the number of tags is equal to the arithmetic mean value of the number of tags of the identified groups.

When the tag continuously collides with the predetermined slot the predetermined number of times, the Ke is twice the Kc.

When the tag is in the continuous blank response state for the predetermined number of times for the specific slot, Ke is characterized in that 1/2 of the Kc.

RFID tag identification system using grouping according to an embodiment of the present invention comprises a plurality of tags; Grouping the plurality of tags into a predetermined number of groups and recognizing the plurality of tags, and regrouping the plurality of tags when the plurality of tags continuously collide with the predetermined slot more than a predetermined number of times or a continuous blank response occurs. The reader; characterized in that it comprises a.

The reader may regroup the plurality of tags into 2n groups when the plurality of tags continuously collide with the predetermined slot for the predetermined number of times.

The reader may regroup the plurality of tags into n / 2 groups when the plurality of tags become a continuous blank response state for the predetermined number of times for the specific slot.

The above and other objects and features and advantages of the present invention will become more apparent using the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to the description, in the present invention, a frame is a unit for the reader to recognize a tag, and a unit obtained by dividing the frame by a predetermined interval is called a slot. Slots are assigned a sequential number from zero, where a tag with a number corresponding to the number assigned to each slot is identified for providing data to that slot.

The Select signal, the RN16 signal, the Query signal, the Ack signal, and the Data signal described below are examples of defining signals transmitted and received for identification between the reader and the tag of the present invention, and the names defined in the EPC standard are used. It is not limited to the names of the signals of the present invention and the EPC standard. That is, the present invention is not limited to the names of the signals and the flow of the signals, and in recognizing a plurality of tags, all tag identification methods using the method of repeatedly dividing into a proper group into a frame having a slot having a predetermined size. Can be applied.

Meanwhile, the 'select signal' described in the present invention is a signal including a matching bit transmitted from a reader to a tag and an address of the matching bit, and the 'query signal' is a slot allocated to a frame defined by the reader ( This signal indicates the number of slots.

In addition, the 'RN (Random Number) 16' signal is a signal that the tag receiving the Query signal selects a slot and transmits it to the selected slot, and the 'Ack signal' is an RN16 to the corresponding tag when the reader receives the RN16 signal without collision. Is a signal indicating that the reception has been successfully received, the 'Data signal' is a signal containing the information of the object including the tag, the 'QueryRep (QueryRepeat) signal' is a signal indicating the start of the next slot.

Hereinafter, an RFID tag identification system using grouping according to an embodiment of the present invention will be described in detail with reference to FIG. 1.

1 is a block diagram illustrating an RFID tag identification system using grouping according to an embodiment of the present invention.

Referring to FIG. 1, an RFID tag identification system using grouping according to an embodiment of the present invention includes a plurality of tags 100 having IC chips, an object 150 on which each of the tags is mounted, and a plurality of tags 100. It consists of a reader 200 to identify.

The plurality of tags 100 are passive devices that receive radio waves emitted from an IC chip (not shown) and a reader 200 having a memory and a random number generator, and transmit and receive signals to and from the reader 200. RF antenna (not shown). Here, the random number generator generates a random number and 'RN16'. The tag 100 is identified according to any random number generated using the random number generator. For example, if the tag selects a random random number 0, the leader 200 participates in a competition in the slot of the highest priority, that is, slot 0, of the frame held by the reader 200, and sets its own 'RN16' to the leader 200. To send). In the next slot, the tag or tags selected as number 1 participate in the competition and transmit their 'RN16' to the reader 200.

The plurality of tags 100 use radio waves emitted from the reader 200 as an energy source, and unique identification codes of the object 150 mounted with the RN16 signal and the tag on the reader 200, for example, 64-bit electrons. The data signal including the product code (Electronic Product Code EPC) is transmitted.

The reader 200 includes an RF antenna 210 that transmits and receives signals to and from a plurality of tags 100, and a controller 230 that generates a Select signal, a Query signal, an Ack signal, and a QueryRep signal, and is generated by the controller 230. The transmitted signal is transmitted to the tag 100 through the RF antenna 230. In detail, the reader 200 transmits a select signal to the plurality of tags 100 to divide the plurality of tags 100 into n (natural numbers) groups. In addition, when the reader 200 recognizes a tag group having a priority, the reader 200 continuously collides with a predetermined number of times or a continuous blank response occurs in a first frame, that is, a frame in which the reader 100 starts to recognize the priority group. When the plurality of tags 100 are regrouped to a certain number. In addition, when the reader 200 allocates a slot to a frame to recognize the i th tag group, the reader 200 allocates the same slot number as the arithmetic mean value of the number of tags up to the i-1 th tag group.

2 is a signal flowchart of an RFID tag identification system using grouping according to an embodiment of the present invention, and FIG. 3 is a flowchart illustrating a RFID tag identification method using grouping according to an embodiment of the present invention.

Prior to the description, the first number and the first group defined below do not define the number or order of specific groups, and do not define any order. That is, the first number may have any number selected within a natural number range, and the first group may indicate any one group among a plurality of groups. The signal related to tag identification described below uses a signal name defined in the EPC standard, but the present invention is not limited to the signal name according to the EPC standard. That is, the present invention divides a plurality of tags into an arbitrary number of groups, and can further improve tag identification throughput by repartitioning the remaining tags into any other number adaptively according to a condition of tag identification of a specific group. have.

2 to 3, in the RFID tag identification method according to an embodiment of the present invention, the reader 200 first divides a plurality of tags into a tag group having an arbitrary first number (S101). The 200 transmits a select signal to a plurality of tags 100 belonging to any tag group, for example, the first group, among the first number of groups (S102).

In the step S101 and the step S102, the arbitrary first number is an arbitrary number of tag groups for the entire tag, which can be determined within a range of natural numbers, and experimentally, between 4 and 16, in particular 4 tags You can have a group. In detail, the plurality of tags 100 located within the propagation range emitted from the reader 200 receive the Select signal and become a “Ready” state, and compare the matching bits included in the Select signal with information stored in the memory. To determine whether to participate in the competition in the current frame. That is, the matching bits included in the select signal inform the plurality of tags 100 of the bit ranges to compare from which bit of the tag unique IDs stored in the memories of the plurality of tags 100. The plurality of tags 100 are divided into n (natural numbers) groups for each tag having a matched bit to correspond to a matching bit, and a tag group having a priority bit. For example, the first tag group identifies a tag. The first frame to start doing, for example, enters the competition from the first frame. Here, assuming that there is an optimal number of groups according to the grouping of tags 100 through such competition participation, but do not know the total number of tags located within the propagation range of the reader 200, it is assumed that the tags 100 are identified. Since the optimal number of groups is unknown, the tags 100 may not be divided into the optimal number of groups. In the initial stage of randomly grouping the tag 100 in the reader 200, as the number of tag groups increases, the time required to identify each group decreases, thereby increasing the gain through grouping, but correspondingly, the tag 100 This will increase the time it takes to group them. Therefore, when a certain number of groups is arbitrarily determined initially at the time of identifying a plurality of tags 100, the number of groups can be grouped into four groups, for example, the number of groups which is somewhat experimentally calculated.

Next, the reader 200 transmits a query signal to the first tag group (S103).

In step S103, the Query signal includes the number of slots allocated to the first frame. Each tag belonging to the first tag group receives a Query signal, generates a random number using a random number generator, selects a slot corresponding to the random number, and maintains a "Ready" state. For example, if the Q value included in the query signal is 4, the number of slots of the current frame is 2 ^Q, that is, 16, and the tags select slots between 0 and 2 ^Q -1. The tag that selects slot 0 becomes "Reply" state, the tag of the first tag group which selects other slot becomes "Arbitrate", and the tags belonging to the other tag group except the first tag group continue to be "Ready" state. . Here, since the tag uses a random number generator, a number generated from a plurality of tags may select a single slot multiple times, and a situation may occur in which no tag is selected for a specific slot.

Subsequently, as the RN16 signal is sequentially transmitted to the reader 200 from the tag selected from slot 0, the tag 100 participating in the competition to register in the first frame has a predetermined number of consecutive collisions or blank responses. Check whether this occurs (S104).

In step S104, when a plurality of tags transmit an RN16 signal in one slot, a collision occurs in the corresponding slot, and a blank response with no response occurs in a slot in which no tag is selected.

Next, the reader 200 regroups a plurality of tags to have a second number of groups when a continuous collision or a continuous blank response occurs more than a predetermined number of times in step S104 (S105).

In step S105, if the first tag group of the plurality of tags 100 continuously collides with a predetermined number of times in the first frame, the reader 200 repartitions the tags 100 into twice the number of groups, and If more than one consecutive blank response occurs, it is subdivided into half the current number of groups. Here, if the predetermined number is made too small, the number of times the tag is regrouped in response to the collision between the tags is increased, thereby reducing the effect of grouping the tags. Also, if a certain number is made too large, it takes a lot of time to identify the number of tags by reacting insensitive to collisions between the tags. If there is an optimal threshold of regrouping according to the number of tags, that is, a certain number of times but the total number of tags is not known, five times can be selected experimentally. That is, when a plurality of tags 100 are divided into four groups, when five consecutive collisions occur, the plurality of tags are divided into eight groups, and when five consecutive blank responses occur, the four groups are divided into two groups. . For example, when a tag belonging to a first tag group collides five times consecutively in a first frame, it may be assumed that the collision occurs because the number of slots is smaller than the number of tags. Accordingly, the plurality of tags 100 may be re-divided at twice the number of currently divided groups to prevent a large number of tags from competing in one slot. In addition, when a tag belonging to the first tag group generates 5 consecutive blank responses in the first frame, it may be assumed that an empty slot occurs because the number of slots is larger than the number of tags. Accordingly, the plurality of tags 100 may be re-divided into 1/2 times the number of currently divided groups to prevent the occurrence of empty slots. After step S105, the specific group of the regrouped tag, for example, the tags of the first group are branched to step S102 to re-check whether the tag is divided into an appropriate tag group.

In the step S104, when the continuous collision and the blank response do not occur more than a predetermined number of times, the reader 200 identifies the number of tags belonging to the first tag group (S106).

In step S106, the reader 200 transmits an Ack signal to a tag that has successfully transmitted the RN16 signal. The tag that receives the Ack signal changes from the "Reply" state to the "Acknowledged" state, and transmits a data signal to the reader. The tag in the other state does not change from the previous state even when the Ack signal is received. When the reader 200 receives the data signal, the reader 200 transmits a QueryRep signal to a plurality of tags to indicate the start of the next slot. If the reader 200 does not identify all of the number of tags belonging to the first tag group in the first frame, the reader 200 transmits a query signal to the plurality of tags 100 to notify the start of a new first frame. As for the number of slots allocated to the first frame, the "2.39n _c rule" is applied. The "2.39n _c rule" is an algorithm proposed by FS Schoute, which allocates the number of slots collided in the previous frame, that is, the number of slots equal to the value of 2.39 times to n _c to a new frame. For example, if five slots collide with each other in the first frame, the number of slots of the new frame is 5 * 2.399511.95, which is approximately 12. As such, the reader 200 transmits a frame to which the “2.39n _c rule” is applied to the plurality of tags to identify all the number of tags belonging to the first tag group.

Next, the reader 200 regroups all remaining tags into an optimal group by using the number of tags of the first tag group (S107).

In step S107, by identifying all the number of tags of the first tag group, it is possible to know the number of tags of the first tag group, and accordingly, by multiplying the remaining total tag group number by the number of tags of the first tag group, The remaining total number of tags can be roughly estimated. That is, by continuously regrouping all the tags to an arbitrary number in order to set the first tag group, it is possible to know the number of tag groups at a time when no more than a predetermined number of consecutive collisions and blank responses occur in the first tag group. The number of first tag groups may be known by identifying the number of the first tag groups. By using the obtained information, the number of tags roughly included in the remaining groups except the first tag group may be known, and thus the total number of the remaining tags except the first tag group may be known. The total number of tags may be regrouped having an optimal number of groups based on the size of the frame, for example, a frame having 16 slots.

Meanwhile, the optimization of regrouping in step S107 may be omitted since the respective groups may be divided into optimized tag numbers in the process of repeating steps 102 through 105.

Next, the first group among the regrouped tag groups, for example, identifies the number of tags of the second tag group next to the first tag group (S108).

In step S108, the tag number identification of the second tag group is performed in the same manner as the identification of the first tag group. That is, the tag number identification of the second tag group identifies the number of tags through the transmission and reception of a select signal and the transmission and reception of a query signal. In this case, the rule 2.39 may be applied when more than a predetermined number of consecutive collisions and a space response occur.

Next, the number of tags of the third tag group is identified, and at this time, the Query signal transmits a Query signal having a Q value equal to the number of tags of the second tag group (S109).

In operation S109, the reason why the Q value of the Query signal is the same as the number of tags belonging to the second tag group will be described with reference to Equations 1 to 4 below.

m: number of tags, n: number of slots

Equation 1 represents a probability that one tag is allocated to one slot, Equation 2 represents a probability of a slot that successfully receives data of a tag without collision in one frame, and Equation 3 represents It shows the performance of the RFID tag identification method using the grouping according to the embodiment. Referring to Equations 1 to 3, the performance is maximized when the number of slots allocated in one frame is equal to the number of tags, that is, when n = m. However, since it is not possible to know exactly how many tags belong to each tag group, a plurality of tags 100 are divided into n 'groups having the same size by repeating regrouping, and thus the second tag group whose number of tags is identified. The number of tags in the remaining tag groups is estimated based on the number of tags in. In order to more accurately estimate the number of tags belonging to each tag group, the arithmetic mean value of the number of tags belonging to the previously identified tag group may be equal to the number of tags of the tag group to identify the tag number.

If this is formulated, it can be expressed as Equation 4.

In order to identify the number of tags of the i th tag group through Equation 4, the number of slots of the first frame transmitted from the reader is allocated to be equal to the arithmetic mean value of the number of tags from the first tag group to the i-1 th tag group. Able to know.

Therefore, when the third tag group receives the Query signal including the same slot number as the number of tags belonging to the second tag group, the number of tags is identified by performing the Select signal transmission and reception and the Query signal transmission and reception.

라 추정할 수 있다. 따라서, 리더가 제 4 태그 그룹에 전송하는 제 1 프레임의 슬롯 수는

할당된다. 제 4 태그 그룹은 제 3 태그 그룹과 동일하게 Select 신호 송수신, Query 신호 송수신을 수행함으로써 태그 수가 식별된다.In addition, the number of tags belonging to the fourth tag group is an arithmetic mean value of the number of tags m ₁ belonging to the second tag group and the number of tags m ₂ belonging to the third tag group.

Can be estimated. Therefore, the number of slots of the first frame transmitted by the reader to the fourth tag group is

Is assigned. In the fourth tag group, the number of tags is identified by performing Select signal transmission and reception and Query signal transmission and reception in the same manner as the third tag group.

Next, the leader 200 checks whether it is the last group among the entire group (S110), and if it is not the last group, branches to step S109 to identify all the tags 100 belonging to the last group, The number of each tag belonging to the group is all identified (S111).

The RFID tag identification method using grouping according to the embodiment of the present invention as described above can achieve a throughput improvement, as shown in FIG. 4, and the Q-algorithm, which is a conventional Aloha method, as shown in FIG. 5. However, it shows significantly improved performance over the 2.39n _c rule. Although the Q-algorithm or 2.39n _c rule shows performance that is less than the theoretical limit of 1 / e (36.8%) of the Framed Slotted Aloha method, the RFID tag identification method using grouping according to an embodiment of the present invention has a theoretical limit of 36.8. Significantly better performance than%.

As described above, in the RFID tag identification system and method using grouping according to an embodiment of the present invention, after dividing a plurality of tags into at least one group, by regrouping according to a predetermined condition, the tag according to the split gain Throughput of identification rate can be improved.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be possible to various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the scope of the claims You will have to look.

Claims (8)

In the slot Aloha-based tag identification method, If Kc and Ke are different natural numbers, the leader divides a plurality of tags into Kc groups, Re-grouping the plurality of tags into Ke groups when the tags belonging to the first group of the Kc groups are continuously collided more than a predetermined number of times or in a continuous blank response state in the process of identifying the tags belonging to the frame having a certain number of slots. Repeating; And Identifying a plurality of tags belonging to the regrouped groups for each group; RFID tag identification method using grouping. The method of claim 1, The identifying step for each group Identifying the number of tags of a first group in the regrouping complete group; Regrouping and optimizing the remaining total tags based on the number of tags in the first group; Identifying a plurality of tags belonging to the optimized regrouping for each group; and RFID tag identification method using grouping. The method of claim 1, And the number of slots allocated to the first frame for identifying the number of tags of the group for which the number of tags is not identified is equal to the arithmetic mean value of the number of tags of the identified groups. The method of claim 1, And if the tag continuously collides with the predetermined slot a predetermined number of times, Ke is twice as large as Kc. The method of claim 1, And if the tag is in the continuous blank response state for the predetermined number of times with respect to the specific slot, the Ke is 1/2 of the Kc.  Multiple tags;  Grouping the plurality of tags into a predetermined number of groups and recognizing the plurality of tags, and regrouping the plurality of tags when the plurality of tags continuously collide with the predetermined slot more than a predetermined number of times or a continuous blank response occurs. RFID tag identification system using a grouping comprising a. The method of claim 6, And the reader regroups the plurality of tags into 2n groups when the plurality of tags continuously collide with the predetermined slot for the predetermined number of times. The method of claim 6, And the reader regroups the plurality of tags into n / 2 groups when the plurality of tags become a continuous blank response state for the predetermined number of times for the specific slot.

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