KR100662050B1 - Anti-collision method for rfid readers - Google Patents

Abstract

An anti-collision method in an RFID(Radio Frequency IDentification) system is provided to shorten the time necessary for an RFID reader to identify a plurality of RFID tags by reducing the number of times of the transmission of unnecessary commands and the amount of data to be transmitted at the standard protocol of ISO 18000-6 type B. An RFID reader selects a set of RFID tags in its own read zone, changes states of the tags from a 'READY state' to an 'ID state'. The RFID reader generates random numbers of '0' and '1' using a FAIL command, used when a collision is detected, a SUCCESS command, used when there is no collision, and a FAIL_RNG command, used when there is no response from tags, and finds out one among the selected RFID tags. When a tag is selected as the count value of the tag is '0', the RFID reader shifts state of the RFID tag from the ID state to a DATA_EXCHANG state.

Description

Anti-collision method in radio wave identification device {Anti-Collision Method for RFID readers}

1 is a block diagram showing a tag identification process in the ISO 18000-6 type B protocol

FIG. 2 is a random number table generated by tags in FIG.

3 is a counter value table of tags in FIG.

4 is a tag state diagram in the ISO 18000-6 type B protocol

5 is a state diagram of the tag in the collision avoidance method according to the present invention.

6A and 6B are diagrams illustrating a GROUP_SELECT command and response in an ISO 18000-6 type B protocol.

7A and 7B are diagrams illustrating a FAIL command and response in an ISO 18000-6 type B protocol

8A and 8B are diagrams showing the SUCCESS command and response in the ISO 18000-6 type B protocol

9A and 9B are diagrams illustrating the DATA_READ command and response in FIG. 4.

10A and 10B are diagrams illustrating the READ_ACK command and response in FIG.

11A and 11B are diagrams illustrating a FAIL_RNG command and response in a collision avoidance method according to the present invention.

12 is a diagram illustrating a tag identification process using instructions in the ISO 18000-6 type B protocol

13 is a block diagram showing a tag identification process using a command in a collision avoidance method according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Radio Frequency Identification (RFID) system. Specifically, a plurality of tags existing within a read zone of a reader (RF reader) by reducing unnecessary command transmission and amount of transmitted data are provided. The present invention relates to a collision avoidance method in a radio wave identification device capable of accepting data of RFID tags without damage.

Currently, RFID (Radio Frequency Identification) technology is a technology for identifying an electronic tag attached to an object by using an RF signal, and is emerging as a core technology in realizing a ubiquitous environment.

In particular, 900MHz RFID technology is attracting attention as a new technology that can replace bar codes in the distribution and logistics fields.In order for RFID technology to be applied to the distribution and logistics field, many tags must be quickly and accurately Should be discernible.

In RFID systems, readers identify each tag as they communicate over a wireless channel. First, the reader sends a signal and the tags in the reader's recognition area respond to the signal sent by the reader.

If several tags exist in the reader's recognition area, these tags will respond to the reader's signal at the same time, causing collisions. This problem is called 'tag collision'.

In addition, a problem that occurs when two or more readers using the same frequency band attempt to recognize a tag at the same time is called a 'Reader collision'.

Hereinafter, an RFID technology of the related art will be described with reference to the accompanying drawings.

1 is a diagram illustrating a tag identification process in the ISO 18000-6 type B protocol. 2 is a random number table generated by each tag in FIG. 1, and FIG. 3 is a counter value table of each tag in FIG. 1.

An RFID system is a system that processes information by identifying a tag of a thin flat form attached to an object in a non-contact manner through a radio signal. The RFID system consists of an RF reader that reads and decodes, an RF tag with unique information, and operating software and a network. The RF tag consists of a semiconductor transponder chip and an antenna. do.

In RFID systems, readers identify each tag as they communicate over a wireless channel. The reader first signals, and the tags in the reader's recognition area respond to the signal sent by the reader.

If there are multiple tags in the reader's recognition area, these tags will respond to the reader's signal at the same time, resulting in a collision, which will ultimately prevent the reader from obtaining accurate information.

The method of resolving such a collision problem is a core technology of an RFID system that tries to recognize a large number of tags quickly. This is called an anti-collision algorithm.

Current RFID air interface protocols are indispensable for this collision avoidance algorithm.

Representative protocols of the 860MHz to 960MHz RFID air interface include 18000-6 type A and type B established by the International Organization for Standardization (ISO / IEC), and Class 0, Class 1, and Class 1 of EPC Global, which are becoming the de-facto standard. Generation 2 etc. Each of these uses a different anti-collision algorithm.

ISO 18000-6typeB, one of the standard protocols in the 860MHz to 960MHz band, randomly generates "0" and "1" in the tag that caused the collision and divides the tag into two sets to identify the tag.

To do this, the ISO 18000-6 typeB tag has an 8-bit counter and a circuit that randomly generates "0" and "1".

An example of the collision avoidance process according to ISO 18000-6 typeB is shown in FIG. 1.

Fig. 1 shows a case of identifying a tag when three tags exist in the recognition area of the reader.

The tag identification process of FIG. 1 will now be described. Initially, there are three tags 102, 106, and 107 in node S 101, causing a collision, and the three tags 102, 106, and 107 that caused the collision are random number '0' ( 108) or '1' 109.

Here, the generated random number is shown in FIG. As a result of generating the random number at node S 101 (201), Tag C 102 is recognized, and Tag A 106 and Tag B 107 cause a collision at node S1 (103).

Tag A 106 and Tag B 107, which caused a collision at node S1 103, generate a random number again, but generate a '1' 111 likewise, causing a collision at node S11 105 again.

Tag A 106, Tag B 107, which caused the collision, generates a random number again at node S11 105, where Tag B 107 is '0' 112 and Tag A 106 is '1'. The identification process is generated by generating 113 and each tag is recognized.

The reader-to-tag communication method using the ISO 18000-6 typeB protocol is half-duplex, and the tag responds when the reader sends a command.

Steps 1, 2, and 3 of the reader and the tag performing the tag identification process using the instructions of the ISO 18000-6 typeB protocol using the 18000-6 typeB tag state diagram of FIG. 4 and the instructions of FIGS. Divided into as follows.

The first step is to select tags at the reader using the Group_select command (Figure 6A).

Inside the tag, the tag count makes the value count to '0' as the state in the 'Ready state' 402 and the tags selected by the Group_select command (FIG. 6A) are changed to the 'ID state' 403.

The second step is a response from the tag to the reader. Among the tags having 'ID state' 403, the tag having the counter value '0' has a response having its ID (FIG. 6B) to the reader. send.

The third step is performed as follows according to the number of tags to respond.

First, when one or more tags respond, tag identification is performed as follows.

The reader detects the collision and sends a FAIL command (FIG. 7A) to the tag.

And when the tag with 'ID state' (403) receives the FAIL command (Fig. 7a),

Inside the tag, a tag with a counter value of "0", that is, a tag that responds to the previous step, generates a random number "0" or "1". And a tag whose counter value is not '0', that is, a tag that does not respond to the previous step, increases the counter value by '1'.

After this execution process, the tag having the counter value '0' from the tag to the reader, that is, the tag that generated '0' from 1, sends a response with its ID (FIG. 7B) to the reader.

Second, if there is no tag response, tag identification is performed as follows.

The reader sends a SUCCESS command (FIG. 8A) to the tag. Inside the tag, the tag is in 'ID state' 403 and receives the SUCCESS command (FIG. 8A) and decreases its counter value (COUNT) by '1'. After decrement, the tag with counter value COUNT '0' sends a response with its ID (Figure 8B) to the reader.

Third, when one tag responds and recognizes without error, the tag is identified as follows.

The reader sends the tag ID responding to the DATA_READ command (Fig. 9A).

If the tags are in the 'ID state' 403 and receive the DATA_READ command (FIG. 9A), the tags are compared with the received ID and their IDs, and then matched with the 'ID state' 403 to the 'DATA_EXCHANGE state' 404. After the change, the DATA_READ response (Figure 9b) is sent to the reader.

The reader receiving the DATA_READ response (FIG. 9B) sends a SUCCESS command (FIG. 8A) again. Inside the tag, the tag is in 'ID state' 403 and receives the SUCCESS command (FIG. 8A), and decreases its counter value (COUNT) by '1'.

After decrementing, the tag with the counter value COUNT '0' sends a response with its ID (Figure 8b) to the reader.

However, the tag identification and collision prevention method of the prior art RFID technology has the following problems.

Referring to the collision avoidance process of ISO 18000-6 type B in FIG. 4, a tag is called to read tags of a 'read state' 402 as an 'ID state' 403.

One of the tags of the 'ID state' 403 is selected by generating a random number ('0' or '1'). If the selected tag is correctly recognized, the recognized tag is moved from the 'ID state' 403 to the 'DATA_EXCHANGE stae' 404 and the recognized tag is separated from a plurality of tags that are not yet recognized.

This process is performed by moving the 'state' from the 'ID state' 403 to the 'DATA_EXCHANGE state' 404 with the tag recognized using the 'DATA_READ command' (FIG. 9A).

However, this method using the 'DATA_READ command' (FIG. 9A) does not need to read another 64-bit data even though the reader recognizes the ID information of the tag and no longer needs the data.

In addition, the ISO 18000-6 typeB anti-collision algorithm randomly generates' 0 'and' 1 'and divides the tags in the reader recognition area into two groups, and the generated random numbers are all' 0 'or all' If it is 1 ', a problem arises in that a random number must be generated again.

This problem is a structural problem of the ISO 18000-6 typeB collision avoidance algorithm and cannot be eliminated. A more serious problem is that if all the generated random numbers have a '1', then all of the reader's commands and tags have to be responded on the instructions of the 18000-6 typeB protocol more than if all the '0's occur.

If random number '0' is generated in all the collided tags, the same collision occurs again, so the reader sends 'FAIL command' (FIG. 7a) to cause the collided tags to generate random numbers again.

However, if all tags generate a '1', the tag does not respond to the 'FAIL command' (FIG. 7A) sent by the reader, so the reader sends a 'SUCCESS command' (FIG. 8A) to reset the value of the tag counter to '1'. Decrease.

This is the same as when the tag had first crashed after the tag's COUNTER value was decremented, so the tag's response would crash again, so the reader would send a 'FAIL command' (Figure 7a) to force the tag to randomly Should be generated.

This process causes a lot of time delay in the collision avoidance process of tags.

As described above, in the collision avoidance process of recognizing multiple tags in the ISO 18000-6 typeB standard protocol, one of the standard protocols of the RFID air interface, '1' is generated both when one tag is recognized and when collision is prevented. In this case unnecessary waste of time exists.

The present invention is to solve the problem of the collision prevention method of the prior art RFID technology, and reduces the amount of unnecessary command transmission and transmission data in a radio frequency identification (RFID) system reader (RF Reader) It is an object of the present invention to provide a collision avoidance method in an apparatus for identifying a radio wave which can receive data of a plurality of tags (RFID tags) existing in a read zone of a network without damage.

In the anti-collision method of the radio wave identification apparatus according to the present invention for achieving the above object, in the collision avoidance method for recognizing a plurality of tags, by selecting a tag set in the reader's recognition area to determine the state First step of changing from 'READY state' to 'ID state'; FAIL command used for collision detection, SUCCESS command used in case of no collision, used in case of no response from tag Generating a random number of '0' and '1' using the FAIL_RNG command to find one tag among the selected tags; only one tag is in a state in which the counter value is '0' And when selected, a third step of moving the state of the tag from the ID state to the DATA_EXCHANG state.

Here, the FAIL_RNG command is used when the two or more tags respond with a FAIL command from the reader and the reader sends a FAIL command and the reader sends a FAIL_RNG command if there is no response from the tag. It is used to generate 0 'or' 1 '.

The tag moved to the DATA_EXCHANG state is separated from other tags not yet recognized, so that unnecessary data reading process does not occur.

In order to move the state of the tag from the ID state to the DATA_EXCHANG state, the READ_ACK command is used, and the tag with the counter value of '0' that receives the READ_ACK command responds after changing the state from the ID state to the DATA_EXCHANGE state (READ_ACK response). ) Is sent to the reader.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments.

Preferred embodiments of the collision avoidance method in the apparatus for identifying radio waves according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a tag state diagram in a collision avoidance method according to the present invention.

6A, 6B, 7A, 7B, 8A, 8B, 9A, and 9B illustrate a command configuration in an ISO 18000-6 type B protocol, and FIGS. 10A and 10B illustrate a READ_ACK command and response in FIG. 5. It is also.

11A and 11B are diagrams illustrating a FAIL_RNG command and response in the collision avoidance method according to the present invention, and FIG. 12 is a diagram illustrating a tag identification process using commands in the ISO 18000-6 type B protocol.

13 is a block diagram illustrating a tag identification process using a command in a collision avoidance method according to the present invention.

The standardization of RFID systems in various frequency bands from commercially available low frequency below 150KHz to 5GHz and above microwave is in charge of developing, operating and managing standards from IECJTC1 / SC31 / WG4 under ISO.

SG3, one of the five subgroups of WG4, is responsible for the standardization of air interfaces for RFID frequency bands. The present invention is one of the standard protocols established in SG3, Part 6: Parameters for Air Interface Communications at 860MHz to It relates to the improvement of the collision avoidance performance of type B (ISO 18000-6 typeB) at 960 MHz.

According to the present invention, when there are a plurality of RFID tags in a read zone of a reader in a radio frequency identification system, a collision avoidance method is a technique required for a reader to accept data of multiple tags without damage. Anti Collision) method is provided.

To this end, the amount of unnecessary data transmission is reduced, and the number of transmissions of reader commands and tag responses is reduced in executing an anti-collision algorithm.

The present invention selects a tag set in the reader's recognition area to change the state of the tag from 'READY state' to 'ID state' in order to prevent collisions to recognize multiple tags in the ISO 18000-6 typeB protocol. The second step of generating a random number of '0' and '1' by using the FAIL_RNG command together with two commands of the FAIL command and the SUCCESS command in the first step and the tags selected in the first step; And a third step of using the tag state from the ID state to the DATA_EXCHANG state by using the READ_ACK command when only one tag is selected by the reader because the counter value is '0' in the second step. The second and third steps are repeated until all the tag sets selected in the first step are recognized.

The syntax structure of the FAIL command includes Preamble, Delimiter, Command (00 hex 8bit), and CRC-16 according to ISO / IEC 18000-6, as shown in FIG. 7A.

The syntax of the SUCCESS command includes Preamble, Delimiter, Command (00 hex 8bit), and CRC-16 according to ISO / IEC 18000-6, as shown in FIG. 8A.

The syntax structure of the FAIL_RNG command includes Preamble, Delimiter, Command (00 hex 8bit), and CRC-16 according to ISO / IEC 18000-6, as shown in FIG. 11A.

In case of using the FAIL_RNG command, when two or more tags respond, the reader sends a FAIL command, the reader sends a FAIL command, and if there is no response from the tag, the reader sends the FAIL_RNG command and the tags with the counter value '1' are random numbers. Produces '0' or '1'

In using the READ_ACK command, the tag having the counter value '0' receiving the READ_ACK command sent by the reader changes the state from the ID state to the DATA_EXCHANGE state and sends a response consisting of Preamble + ACK + CRC-16 in FIG. 10B.

Specifically, the first step is to select tags in the reader using the Group_select command (FIG. 6A).

Inside the tag, the tag count makes the value count to '0' as the state in the 'Ready state' 502 and the tags selected by the Group_select command (FIG. 6A) are changed to 'ID state' 503.

The syntax structure of the Group_select command includes Preamble, Delimiter, Command, Address, Mask, WORD_DATA, and CRC-16, as shown in FIG. 6A.

The second step is a response from the tag to the reader. Among the tags having the ID state 503, the tag having the counter value '0' has a response having its ID 609 (FIG. 6B). Send it to the reader.

And the third step is done as follows.

In case of recognizing one tag in RFID system, only ID information of most tags is needed. Therefore, reading unnecessary information of 64-bit using 'DATA_READ command' (Fig. 9A) each time slows down the recognition of multiple tags. Cause.

To improve this, the present invention recognizes only the ID of the tag and receives a short acknowledgment (FIG. 10b) each time the tag is recognized. Read the additional information if necessary after ID recognition.

To this end, as shown in FIG. 5, a 'READ_ACK command' (FIG. 10A), which is a short command for moving the 'state' of the tag from the 'ID_state' 503 to the 'DATA_EXCHANGE state' 504, is used.

The READ_ACK command includes Preamble, Delimiter, Command (00 hex 8bit), ID (any 64 bit identifier), and CRC-16 according to ISO / IEC 18000-6, as shown in FIG. 10A.

Looking at the case of generating all '1' when the collision occurs, after tagC 102 is recognized in Figure 1, tag A (107), tag B 106 from S1 node 103 to S11 node 105 It can be seen in the process. In this case, the detailed process of the command of the reader and the tag is shown in FIG. 12.

In the present invention, when all tags causing a collision generate a random number '1', a multi tag recognition speed is improved by removing an unnecessary process of reducing a tag counter value (COUNT) to '0' by sending a 'SUCCESS command'.

To do this, if all the tags that caused the collision generate a '1', instead of lowering the counter value to '0', a tag generates a random number of '0' or '1' and stores the value in the tag counter. After detecting the collision, the reader sends a 'FAIL command' (FIG. 7a) and determines that the tag causing the collision generates the mode '1'.

When the reader detects this, it sends a suggested new command ('FAIL_RNG command' (Figure 11a)) instead of sending a 'SUCCESS command' (Figure 8a).

The role of the 'FAIL_RNG command' is to have tags with a counter value of '1' generate a random number of '0' or '1' and store the value in the tag counter.

The process of using the 'FAIL_RNG command' is shown in FIG. 13, and it can be seen that the response times of the reader command and the tag are reduced as compared with FIG. 12.

As such, the collision avoidance process of recognizing multiple tags in the ISO 18000-6 typeB standard protocol, one of the standard protocols of the RFID air interface, generates '1' when both tags are recognized and collision is prevented. In order to solve the unnecessary waste of time, the present invention implements a new collision prevention method of ISO 18000-6 type B with the addition of the READ_ACK command and the FAIL_RNG command in an RFID system using the standard protocol of ISO 18000-6 type B. Allows quick recognition of multiple tags.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

The collision avoidance method in the radio wave identification apparatus according to the present invention described above has the following effects.

The present invention implements a method for reducing the number of unnecessary command transmissions and the amount of data transmitted in the standard protocol of ISO 18000-6 typeB, which is one of the standard protocols of the RFID air interface currently used in the 860MHz to 960MHz band, so that the reader can The time taken to recognize can be shortened.

In addition, since the present invention is to add a new command to the reader and tag, it is applied to the reader and tag using the current typeB protocol to improve the tag recognition speed.

It is highly applicable by changing the instruction program of the reader and tag without changing the structure of the reader and tag of the current RFID system.

Claims (8)

In the collision avoidance method for recognizing a plurality of tags, Selecting a tag set in a recognition area of the reader to change a state of the tag from a 'READY state' to an 'ID state'; FAIL command used in collision detection, SUCCESS command used in case of no collision, and FAIL_RNG command used in case of no response from tag are used. Generating a random number to find one tag among the selected tags; And a third step of moving the state of the tag from the ID state to the DATA_EXCHANG state when only one tag is selected by the reader because the counter value is '0'. Way. 2. The method of claim 1, wherein the second and third steps are repeatedly performed until all the tag sets in the recognition area of the reader are recognized. The method of claim 1, wherein the FAIL_RNG command, A method of preventing collisions in a radio frequency identification device, characterized in that a reader sends a FAIL command to a tag when two or more tags respond and a reader sends a FAIL_RNG command to the tag after there is no response from the tag. 4. The method of claim 3, wherein the tags having a counter value of '1' generate a random number '0' or '1' by a FAIL_RNG command. The method of claim 1, wherein the tag moved to the DATA_EXCHANG state is separated from other tags not yet recognized, so that an unnecessary data reading process does not occur. The method of claim 1, wherein a READ_ACK command is used to move the state of the tag from the ID state to the DATA_EXCHANG state. 7. The collision according to claim 6, wherein the tag having the READ_ACK command having a counter value of '0' sends a READ_ACK response to the reader after changing the state from the ID state to the DATA_EXCHANGE state. Prevention method. The method of claim 1, wherein the instructions used are in accordance with the ISO 180000-6 type B RFID air interface standard protocol.

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