KR20080112444A - Anti-collision method for radio frequency identification readers and radio frequency identification reader - Google Patents

Abstract

A method for preventing collision between RFID readers in a multiple reader-tag system and an RFID reader are provided to reduce poser consumption of the reader and solve a problem about collision between readers without the hardware change of a tag. Information is switched by periodically receiving and transmitting announcement signal between readers within communication distance. A first reader which it preferentially reads tags is determined. The first reader reads the tag. A second reader is determined in order for the first reader to read the tags based on the announcement signal.

Description

Anti-collision between wireless readers and wireless readers {ANTI-COLLISION METHOD FOR RADIO FREQUENCY IDENTIFICATION READERS AND RADIO FREQUENCY IDENTIFICATION READER}

1 is a table for explaining a conventional session for preventing collision between multiple reader-tag.

2 is a flowchart illustrating a process of adding to a neighbor leader list when receiving self notification signals between readers according to an exemplary embodiment of the present invention.

3 is a flowchart illustrating a process of deleting from the list of neighboring readers when the self notification signal between the readers is not received for a predetermined time according to an embodiment of the present invention.

4 is a flowchart for preventing collision between readers when only readers are in a standby mode according to an embodiment of the present invention.

5 is a flowchart for preventing a collision when two or more readers are in a read mode according to an embodiment of the present invention.

6 is a block diagram showing the configuration of a reader according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

6000: RFID Reader

610: antenna 620: RF signal processing unit

630: control unit 640: memory

650: Self notification signal generator 660: Ordering signal generator

The present invention relates to RFID, and more particularly, to an anti-collision method between RFID readers and a RFID reader for the same in a multiple reader-tag system.

Recently, Radio Frequency Identification (RFID) has emerged as a part of providing a ubiquitous network environment. RFID collects unique data stored in the IC chip of a tag attached to an object by using a radio wave in a non-contact manner through an antenna and a reader. Short-range wireless communication technology that processes information in real time by reading and recognizing objects.

RFID system is classified into mutual induction method and electromagnetic wave method according to mutual communication method between reader and tag, and is classified into active type and passive type according to whether tag operates with its own power. Moreover, according to the frequency used, it is classified into a long wave, a medium wave, a short wave, an ultra-short wave, and an ultra-short wave type. In accordance with the above classification, various kinds of standards are enacted or in preparation for enactment.

Meanwhile, the UHF (Ultra-High Frequency) (860-960 MHz) band is expected to be widely used in the logistics and distribution fields. Version 2 (hereinafter referred to as EPC Gen2) of the UHF band established by EPC global, which has been adopted as the international RFID standard, is a method that allows multiple readers to simultaneously access tags without collision. To provide.

1 is a table for explaining a conventional session for preventing collision between multiple reader-tag.

The tag has four sessions, and one session has one flag (see ISO-IEC 18000-6 Type C). The flag may be set to one of A and B. This flag is used by one reader to access a tag only once. Before the reader reads the tag, it first uses a SELECT command to initialize the flag of the tag in the accessible range. For example, if the reader is set to read a tag whose session 1 flag is set to A, the reader sends a SELECT command to set the session 1 flag of the tag within the access range to A.

The reader uses the commands QUERY, QUERY_ADJUST, QUERY_REP, etc. to specify one tag among the tags to communicate with the reader. The flag of session 1 is set to B so that the specified tag is not accessible to the reader again. Since the reader is to read only the tag of flag A of session 1, it must be initialized by sending a SELECT command to access this tag again. In this way, a reader accesses the tags once.

Multiple readers use multiple sessions to access a tag once. Tags running in one session ignore the commands in the other session. That is, when the first reader and the second leader want to access one tag, the first reader uses session 1 and the second reader uses session 3. For example, when moving a ship's load from a port to a warehouse using a truck, the ship's leader uses Session 1 so that the tags attached to the loads can be read without collision by the ship's leader, the truck's leader, and the warehouse leader. The truck leader uses session 2, and the warehouse leader uses session 3.

However, when using the above scheme, when multiple readers using the same session attempt to access the tags, they malfunction. If there are readers nearby that read the same flag in the same session, tags that other readers have read once cannot read only some of the tags. On the other hand, if you have a dense reader that reads different flags in the same session, the tag will be read indefinitely. Until now, RFID has been applied only to limited places such as warehouses and most fixed readers have been able to prevent collisions between multiple reader-tags even with a system having four sessions. With the spread of RFID readers, four sessions will not prevent collisions between readers.

In order to prevent such a malfunction, there is a method of reading all tags repeatedly and randomly without using a session, and determining whether a duplicate access is performed by storing a predetermined number of information of the tag that has been read. However, this method is not suitable for mobile RFID readers with limited power, because the power is continuously used and consumes a lot of power. Therefore, there is a need for a reader that can prevent collision between multiple reader-tags in the existing EPC global Gen2 environment.

In order to solve the above problems, an object of the present invention is to provide a collision avoidance method between RFID readers in a multiple RFID reader environment.

Another object of the present invention is to provide an RFID reader applicable to a collision avoidance method between RFID readers in the multi-RFID reader environment.

Furthermore, an object of the present invention is to provide an RFID system using an RFID reader that can prevent collision between RFID readers in the multiple RFID reader environment.

In order to achieve the above object, an anti-collision method between radio frequency identification (RFID) readers according to an embodiment of the present invention exchanges information by periodically transmitting and receiving self notification signals between readers within a communication range. do. Determine a first reader of the readers to read the tags preferentially, and the first reader reads the tags. After the first reader has read all of the tags, the first reader determines a second reader to read the tags next based on the self notification signal.

In the collision avoidance method between the RFID readers, the first reader may transmit an ordering signal to the second reader.

In the collision avoidance method between the RFID readers, a dedicated frequency channel may be designated to transmit and receive the self notification signal and the ordered signal between readers.

The self notification signal may include ID, session information, and information on an operation mode of each of the readers.

In the collision avoidance method between the RFID readers, the first reader periodically searches for the existence of the tags, sets an operation mode to a waiting mode when the tags do not exist, and when the tags exist. The operation mode may be set to a reading mode. The first reader may read the tags by switching to a standby mode when there is no response from the tags.

In the collision avoidance method between the RFID readers, each of the readers adds another reader that has sent a self notification signal to the neighbor reader list, and deletes another reader from the neighbor reader list that has not sent the self notification signal for a predetermined time. The self notification signal may be transmitted and received to exchange information.

In the collision avoidance method between the RFID readers, when there is only one reader within the communication range, the one reader may be determined as the first reader.

In the collision avoidance method between the RFID readers, when there are only readers in the standby mode within the communication range, the reader having the largest ID among the readers in the neighbor reader list may be determined as the first reader. In addition, one of the leaders in the neighbor leader list of the first leader may be randomly selected to determine the second leader.

In the collision avoidance method between the RFID readers, when there are two or more readers in the read mode within the communication range, the reader having the smallest ID in the neighbor reader list among the readers in the two or more read modes is selected as the first reader. It can be decided by the leader. In addition, the remaining readers other than the first leader among the readers of the two or more read modes are switched to the standby mode, and among the leaders in the neighbor leader list of the first leader, one of the readers has been preferentially switched to the standby mode. May be selected at random to determine the second leader.

In order to achieve the above object, an RFID reader according to an embodiment of the present invention is dedicated to transmit and receive signals with an external reader and tags, an antenna for transmitting and receiving radio frequency (RF), an operation mode, and an external reader. A control unit for designating a frequency channel, a high frequency signal processor for demodulating and transmitting the high frequency signal received from the outside to the control unit, or modulating and transmitting the high frequency signal received from the control unit to the antenna, ID of the reader, session information, operation A memory including information about a mode and a list of neighbor readers, a self notification signal generator for generating a self notification signal transmitted and received with external readers through the dedicated frequency channel, and a next reader through the dedicated frequency channel And an ordering signal generator for generating an ordering signal.

In order to achieve the above object, an RFID system according to an embodiment of the present invention includes one or more RFID tags and one or more RFID readers including a transmitter and a receiver. Each of the at least one RFID reader may include an antenna for transmitting and receiving a radio frequency (RF) signal with an external reader and tags, an operation mode, and a controller for designating a dedicated frequency channel for transmitting and receiving a signal with external readers. A high frequency signal processor for demodulating and transmitting the received high frequency signal to the controller, or modulating the high frequency signal received from the controller and transmitting the received high frequency signal to the antenna, ID of the reader, session information, information on an operation mode, and a list of neighboring readers. A self-signaling signal generator for generating a self-signaling signal transmitted and received with external readers through the dedicated frequency channel, and an ordered signal for generating an ordered signal for designating and transmitting a next reader through the dedicated frequency channel. It includes a generation unit.

Therefore, the collision avoidance method between the readers according to the present invention can solve the collision problem between the readers only by upgrading the readers without changing the hardware of the tags, and reduce the power consumption of the readers.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms may be used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between. Other expressions describing the relationship between components, such as "between" and "immediately between," or "neighboring to," and "directly neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It should be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. .

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention.

For convenience, Radio Frequency Identification (RFID) readers are referred to as readers.

In order to prevent conflicts between leaders, information exchange between leaders is needed to understand each other's status. Therefore, the present invention uses a self-report signal to transmit its information to other readers and to receive information from other readers. Each leader periodically transmits a self notification signal including its ID, session information, and information about the mode of operation to the leaders within range of the communication. The communication distance is a signal transmission / reception distance between readers and may be designed to be twice the signal transmission / reception distance between the reader and the tag.

On the other hand, each leader receives the self-report signal of the other readers to determine the status of the readers within the communication range. Each leader stores and manages the information of identified neighboring leaders in their neighbor leader list.

Each reader has a dedicated frequency channel for transmitting and receiving signals between the readers. The dedicated frequency channel divides the frequencies used by the readers for each band and designates one of them. The designated dedicated frequency channel is used as a dedicated channel for signals transmitted and received only between readers.

2 is a flowchart illustrating a process of adding to a neighbor leader list when receiving self notification signals between readers according to an exemplary embodiment of the present invention.

When each reader receives the self-signal signal of the other reader for the first time, based on the information contained in the received self-signal signal, the readers of the other readers may identify the ID of the counterpart reader, the reception time and operation mode of the self-signal signal. Save it to the list.

Referring to FIG. 2, when receiving a self notification signal of another reader (S210), it is checked whether an ID of the corresponding reader that has transmitted the self notification signal is included in its neighbor reader list (S230). If it is included in the list of nearby readers, the received time of the self notification signal of the corresponding reader is corrected and stored (S240). If it is not included in the peripheral reader list, the ID of the reader, mode information, and a reception time of the self notification signal are stored in the peripheral reader list (S250).

3 is a flowchart illustrating a process of deleting from the list of neighboring readers when the self notification signal between the readers is not received for a predetermined time according to an embodiment of the present invention.

In the process of FIG. 2, when each reader receives the self notification signals of other readers, the respective readers are stored in their neighbor leader list, and when the readers do not receive the self notification signals again for a predetermined time (for example, T time). Delete from the leader list.

Referring to FIG. 3, the reader checks whether the T time has elapsed since the last reception of the self notification signal of the corresponding reader in the process of checking the neighbor leader list (S310). If the T time has not passed, the next leader is checked in the neighbor leader list (S320). If the T time elapses, after deleting information such as an ID of the corresponding leader from the neighbor leader list (S330), the next reader is checked (S320).

As shown in FIG. 2 and FIG. 3, each leader adds or deletes and manages the neighbor leader list based on the self-information signal of the counterpart leaders.

When multiple readers are present, two or more readers should be prevented from reading the same tag to avoid collisions of the readers. Hereinafter, a method of identifying a mode of neighboring readers based on the self notification signal and operating without collisions between the readers in some cases will be described.

If there are no other readers around, the reader searches for nearby tags at predetermined time intervals. If no tag is present, the reader remains in waiting mode. When a tag is detected, the reader switches to a reading mode and communicates with the detected tag. In addition, the self-information signal of the self-information signal is switched to the read mode to transmit the communication distance between the readers. The readers receiving the self notification signal of the reader that has been switched to the read mode remain in the standby mode until receiving the ordering signal from the reader.

When there is a reader in a read mode and a reader in a standby mode, when receiving a self notification signal for the first time, IDs, mode information, and reception times of the self notification signals are stored in the neighbor reader list. The reader in the standby mode maintains the standby mode until receiving the ordering signal from the reader in the read mode.

The reader in the read mode reads all surrounding tags. After reading all the surrounding tags, if there is no response from the read tags for a certain time, the reader enters a standby mode and transmits a self-report signal to the communicable distance switched to the standby mode. Meanwhile, in order to determine a reader to read the tags, one reader is randomly selected from a neighbor reader list, and an ordering signal is transmitted. Upon receiving the ordering signal, the reader enters a read mode, searches for neighboring tags, and starts reading the found tags. On the other hand, the self notification signal that has been switched to the read mode is transmitted to the readers within the possible distance.

4 is a flowchart for preventing collision between readers when only readers are in a standby mode according to an embodiment of the present invention.

When there are only readers in the standby mode, when receiving the self-signal signal of the other leader for the first time, the ID, mode information, and reception time of the self-signal signal are stored in the neighboring reader list.

When the reader does not detect the self-recognition signal of the reader in the read mode for a predetermined time, the reader checks the neighbor reader list and the reader having the largest ID is switched to the read mode to search the surrounding tags and read the searched tags. To start. At this time, the readers remain in the standby mode until receiving the ordering signal from the reader switched to the read mode except the leader having the largest ID.

When the reader has read all the tags and there is no response from the read tags for a certain time, the reader switches to the standby mode and transmits a self-report signal to the communicable distance, which has been switched to its standby mode in the vicinity. Meanwhile, in order to determine a reader to read the tags, one reader is randomly selected from a neighbor reader list, and an ordering signal is transmitted. The reader receiving the ordering signal switches the operation mode to the read mode, searches for neighboring tags, and starts reading the found tags. Meanwhile, the self notification signal, which has been switched to the read mode, is transmitted to the readers within the communication range.

Referring to FIG. 4, when there are two or more readers in the standby mode, the reader receiving the read start signal received from the outside starts communication with the tags (S410). However, if the read start signal is not received and the self notification signal of the reader in the read mode is not received for a predetermined time (S430), the neighbor reader list is checked to determine whether its ID is the largest (S450). The reader having the largest ID is switched to the read mode, searches for neighboring tags, and starts reading the found tags (S470). The other readers except the leader having the largest ID maintain the standby mode (S480).

When the reader has read all the tags and there is no response from the read tags for a certain period of time, the reader enters the standby mode and transmits a self notification signal with the information switched to the standby mode to the readers in the communication range. do. Also, to determine the reader to read the tags next, one reader is randomly selected from the neighbor reader list, and an ordering signal is sent to the selected reader. Upon receiving the ordering signal, the reader enters the read mode to start reading the tags and transmits the self notification signal converted to the read mode to the readers in the communication range.

5 is a flowchart for preventing a collision when two or more readers are in a read mode according to an embodiment of the present invention.

When there are two or more readers in the read mode, when receiving the self-signal signal of the opponent leader for the first time, the ID, mode information, and reception time of the self-signal signal are stored in the neighboring reader list. When other readers in the read mode are detected as a result of receiving the self notification signal, the reader having the smallest ID of the reader is checked in the read mode, and the neighbor tags are searched and the read tags are read. At this time, the readers other than the reader with the smallest ID are switched to the standby mode and remain in the standby mode until the ordering signal is received.

When the reader has read all the tags and there is no response from the read tags for a certain period of time, the reader enters a standby mode and transmits a self notification signal that has been switched to the standby mode to the communicable distance. Meanwhile, in order to determine a reader to read the tags, one reader is first selected from among the readers switched from the read mode to the standby mode from the neighbor reader list to transmit an ordering signal.

Referring to FIG. 5, the reader in the read mode receives a self notification signal of another reader to check whether there is another reader in the read mode (S510). If there is no other reader in the read mode, the tags are read by maintaining the read mode (S570). However, if there is another reader in the read mode, check whether its ID is the smallest (S530). The readers other than the reader with the smallest ID are switched to the standby mode (S580). The reader with the smallest ID thereof stores other readers that have been switched to the standby mode in their peripheral leader list (S550). In addition, the neighboring tags are searched by maintaining the read mode and the read tags are started (S570).

When the reader who has read all the tags has no response from the read tags for a certain period of time, the reader enters the standby mode, and then selects the reader to read the tags. At this time, unlike other cases, the readers in the read mode are preferentially selected.

In the step in which the leader having the smallest ID has been switched to the standby mode, the readers may be stored in their neighbor leader list, for example, in the Temp assigned to the neighbor leader list (S550). A reader reading all the tags may randomly select one of the readers stored in Temp and transmit the ordering signal.

6 is a block diagram showing the configuration of a reader according to an embodiment of the present invention.

Referring to FIG. 6, the reader 6000 includes an antenna 610, an RF signal processor 620, a controller 630, a memory 640, a self notification signal generator 650, and an ordered signal generator 660. ) May be included.

The antenna 610 transmits or receives a radio frequency (RF) with a tag or a reader external to the reader 6000.

When the RF signal is received from the antenna 610, the RF signal processor 620 demodulates the received RF signal and outputs the demodulated signal to the controller 630, or modulates the RF signal when the RF signal is received from the controller 630. To the antenna 610. As the modulation and demodulation method of tag, phase shift key (PSK), frequency shift key (Frequency Shift Keying, FSK), amplitude shift method (Amplitude Shift Key, ASK), etc. are used. The protocol design is different.

The controller 630 determines an operation mode of the reader 6000. That is, the operation mode of the reader 6000 may be switched to the standby mode or the read mode based on the read start command received from the outside, the order designation signal, and the neighbor leader list. According to an embodiment of the present invention, the controller 630 may designate one of the frequency channels used by the reader as a dedicated frequency channel between the readers so that it can be used only for signal transmission and reception between the readers.

The memory 640 may store an ID of the reader 6000, session information, information on an operation mode, and the like. According to an embodiment of the present invention, the neighbor leader list 641 may be included. The reader 6000 adds information of other external readers that have transmitted the self-report signal to the neighbor leader list 641, and displays information of the external readers who have not transmitted the self-report signal for a predetermined time. At 641, the neighbor leader list is managed.

The self notification signal generator 650 generates a self notification signal for the reader 6000 to transmit its information to readers within a communication range. The self notification signal includes an ID of the reader 6000, session information, information on an operation mode, and the like. When the operation mode is switched by the controller 630, a new self-designated signal is generated by reflecting the changed information. The generated self-report signal is transmitted to the readers in the communication distance through the dedicated frequency channel between the readers.

The ordering signal generator 660 generates an ordering signal. The ordering signal is a command signal for the reader 6000 in the read mode to read the tags after reading all the surrounding tags. The next reader to read the tag is selected based on the peripheral reader list 641 of the reader 6000.

As described above, the collision avoidance method between the reader and the readers using the reader according to an embodiment of the present invention allows only one reader to read the tags at a time, thereby preventing collision between the readers and reducing power consumption of the reader.

As described above, the collision avoidance method between the RFID readers using the self-notification signal according to an embodiment of the present invention can solve the collision problem between the readers only by upgrading the reader without changing the hardware of the tag, and reduce the power consumption of the reader. Can be reduced.

In addition, the RFID reader according to an embodiment of the present invention can solve the collision problem between the readers, and can reduce the power consumption of the reader.

Furthermore, the RFID system including the reader according to an embodiment of the present invention can solve the collision problem between the readers and reduce the power consumption of the reader.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (14)

Periodically exchanging information by transmitting and receiving self notification signals between readers within a communication range; Determining a first reader of the readers to read the tags preferentially; Reading, by the first reader, the tags; And And determining, by the first reader, a second reader to read the tags next on the basis of the self notification signal. The method of claim 1, And the first reader transmitting an ordering signal to the second reader. The method of claim 2, And specifying a dedicated frequency channel for transmitting and receiving the self notification signal and the ordering signal between readers. The method of claim 1, wherein the self notification signal is And the ID, session information, and operation mode information of each of the readers. The method of claim 1, wherein the first reader reads the tags. Periodically searching for the presence of the tags; Setting an operating mode to a waiting mode when the tags are not present and setting the operating mode to a reading mode when the tags are present; And And switching to a standby mode when there is no response from the tags. The method of claim 1, wherein exchanging information by transmitting and receiving the self notification signal, respectively. Adding another reader to the list of nearby leaders, each of the readers having sent a self notification signal; And And removing other readers from the peripheral reader list, each reader having not sent a self notification signal for a predetermined time. 7. The method of claim 6, wherein determining the first leader is If there is only one reader within the communication distance, determining the one reader as the first reader. 7. The method of claim 6, wherein determining the first leader is If there are only readers in the standby mode within the communication range, determining the reader having the largest ID among the readers in the neighbor reader list as the first reader. 9. The method of claim 8, wherein determining the second leader is And randomly selecting one of the readers of the neighbor reader list of the first reader to determine the second reader. 7. The method of claim 6, wherein determining the first leader is If there are two or more readers in the read mode within the communication range, determining a reader having the smallest ID in the neighbor leader list among the readers in the two or more read modes as the first leader. Anti-collision method between RFID readers. The method of claim 10, wherein determining the first leader is The method of preventing collision between RFID readers, wherein the remaining readers other than the first reader of the two or more read mode readers are switched to a standby mode. 12. The method of claim 11, wherein determining the second leader is And randomly selecting one of the readers in the standby mode among the readers in the neighbor reader list of the first reader and determining the second reader as the second reader. Way. An antenna for transmitting and receiving a radio frequency (RF) signal with external readers and tags; A high frequency signal processor for demodulating the high frequency signal received from the outside and outputting the demodulated signal to the control unit and modulating the high frequency signal received from the control unit and outputting the modulated high frequency signal to the antenna; A self notification signal generator configured to generate a self notification signal and transmit the self notification signal to the external readers; A memory for storing a list of peripheral readers created based on the self notification signal received from the external readers; An ordering signal generation unit configured to generate an ordering signal for designating and transmitting a reader to read tags among the external readers; And And a controller configured to determine an operation mode based on the list of peripheral readers and an ordering signal received from the external readers. One or more RFID tags including a transmitter and a receiver; And Include one or more RFID readers, Each RFID reader, An antenna for transmitting and receiving a radio frequency (RF) signal with external readers and tags; A high frequency signal processor for demodulating the high frequency signal received from the outside and outputting the demodulated signal to the control unit and modulating the high frequency signal received from the control unit and outputting the modulated high frequency signal to the antenna; A self notification signal generator configured to generate a self notification signal and transmit the self notification signal to the external readers; A memory for storing a list of peripheral readers created based on the self notification signal received from the external readers; An ordering signal generator configured to generate an ordering signal for designating and transmitting a reader to read tags among the external readers; And And a controller configured to determine an operation mode based on the neighbor leader list and the ordered signal received from the external readers.

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