KR102199126B1 - RFID Reader, and Method for controlling Time Division Multiplexing for avoding Communicational Conflict between RFID Readers - Google Patents

Abstract

Disclosed are an RFID reader, and method for controlling time division multiplexing for avoiding communicational conflict between first and second readers performing RFID communication for RFID tags. When an activation signal allowing communication activation for the RFID tag is inputted from the second reader to the first reader, the first reader is switched to an active mode. When an activation signal from the first reader is inputted to the second reader and the second reader satisfies an additional condition, the second reader switches the communication mode from an inactive mode to the active mode. The additional condition refers to whether or not the communication mode of the first reader has ever been in an active mode. A collision phenomenon in which two RFID readers access one RFID tag at the same time is prevented. In addition, a deadlock, of continuously maintaining the inactive mode because both readers cannot find a condition to be switched into the active mode in the inactive mode, is prevented from occurring.

Description

[RFID Reader, and Method for controlling Time Division Multiplexing for avoding Communicational Conflict between RFID Readers}

The present invention relates to a time division communication control method for avoiding communication collisions between RFID readers in a state capable of simultaneously communicating with respect to one RFID tag, and to an RFID reader used therein.

When a plurality of RFID readers for RF communication are operated in an environment in close proximity to each other, RF interference occurs. As a method to avoid this, time division multiplexing (TDM) and frequency division multiplexing (FDM) can be used.

As a method to prevent RF interference, several readers are set as a group, but one leader for each group is designated as the master leader, and the remaining leaders are designated as slave leaders, and a frequency hopping notification signal is transmitted to hop to different frequencies between groups. Is used. This is a method of separating the reader into groups and preventing interference through frequency hopping for each group. The master reader generates a frequency hopping notification signal and transmits it to the slave reader to control communication. However, in the case of such a frequency division multiple access-based method, in the case of a tag that operates entirely dependent on the RF energy of the reader like a passive RFID system, the tag cannot respond normally if the frequency channel receives other radio waves at the same time. It is difficult to avoid collision.

As another method for preventing RF interference, a separate device generating a synchronization signal between readers or a method of configuring a separate network so that transmission/reception between readers can be centrally controlled is used. This is a TDM method, and the reader must be connected to a separate network device, and through a separate control program, communication is controlled in order after a predetermined time has elapsed according to the communication time set for each reader. However, this method has a problem that a separate network configuration and a separate control program are required.

As another method, to minimize the interference between the RFID reader and the RFID reader, the RFID reader and the RFID reader use a control module that controls the participation of the new RFID reader or the departure of the existing RFID reader by performing sync connection and circulation. A method of minimizing periodic interference is used. However, this method has a problem in that a separate control module is required as a method of managing the participation and departure of the leader while performing sync connection and circulation between the readers through a separate control module.

-Korean Patent Application No. 2007-0049895: Real-time time division communication control method of an RFID reader in a congested environment. -Korean Patent Application No. 2008-0068358: Control method of multiple RFID readers. -Korean Patent Application No. 2009-0131959: A system for minimizing interference between RFID readers and a method for minimizing interference

It is an object of the present invention to provide a method of implementing time division multiple access by exchanging information that can confirm whether another reader occupies media through a handshaking mechanism between a plurality of RFID readers. It is aimed at.

Another object of the present invention is to provide a method for preventing a deadlock state in which all of a plurality of RFID readers are in an inactive mode and access to an RFID tag is impossible.

In order to achieve the above object, the present invention provides a time-division communication control method for avoiding communication collisions between a first reader and a second reader performing RFID communication with respect to an RFID tag, a) from the second reader to the first reader. When an activation signal allowing communication activation for the RFID tag is input, switching a communication mode of the first reader from an inactive mode in which communication is not performed with respect to the RFID tag to an active mode in which communication is performed; And b) when the activation signal is input from the first reader to the second reader and the second reader satisfies a predetermined additional condition, the communication mode of the second reader is changed from the inactive mode to the active mode. A method of controlling a time division communication for avoiding a communication collision between a first reader and a second reader, comprising: switching.

Here, the additional condition may be whether the communication mode of the first reader has been the active mode.

In addition, the additional condition may be whether the activation signal is input after a deactivation signal disallowing communication activation for the RFID tag is input to the second reader.

The second reader may include a plurality of readers.

According to another aspect of the present invention, a communication interface for performing communication with respect to an RFID tag; A receiver configured to receive an activation signal for allowing communication activation for the RFID tag and a deactivation signal for disallowing communication activation from an external reader; A transmitter for transmitting the activation signal and the deactivation signal to the other reader; And controlling the communication interface such that a communication mode for the RFID tag is switched from an inactive mode in which communication is not performed to an active mode in which communication is performed, as the activation signal is received by the receiver from the other reader, and the RFID tag The communication interface is controlled so that the communication mode is switched from the active mode to the inactive mode as the communication sequence is completed or a predetermined time required for the completion of the communication sequence elapses, and the activation signal is sent to the other leader. An RFID master reader comprising: a control unit for controlling the transmission unit to be transmitted.

The control unit controls the transmission unit to transmit the deactivation signal to the other reader while the communication interface is in an active mode.

The other reader may include a plurality of readers. In this case, when the activation signal is received from all of the plurality of readers, the controller controls the communication interface so that the communication mode is switched to the active mode.

According to another aspect of the present invention, a communication interface for performing communication with respect to an RFID tag; A receiver configured to receive an activation signal for allowing communication activation for the RFID tag and a deactivation signal for disallowing communication activation from an external reader; A transmitter for transmitting the activation signal and the deactivation signal to the other reader; And the communication interface so that the communication mode for the RFID tag is changed from an inactive mode in which communication is not performed to an active mode in which communication is performed, as the activation signal is received by the receiver from the other reader and a predetermined additional condition is satisfied. Control, and control the communication interface so that the communication mode is switched from the active mode to the inactive mode as the communication sequence for the RFID tag is completed or a predetermined time required for completion of the communication sequence elapses, and An RFID slave reader comprising: a control unit for controlling the transmitting unit so that an activation signal is transmitted to the other reader.

Here, the additional condition may be whether the communication mode of the other reader has been the active mode.

In addition, the additional condition may be whether the activation signal is input after the deactivation signal is input from the other reader.

The control unit controls the transmission unit to transmit the deactivation signal to the other reader while the communication interface is in an active mode.

The other reader may include a plurality of readers. In this case, when the activation signal is received from all of the plurality of readers, the controller controls the communication interface so that the communication mode is switched to the active mode.

According to the present invention, a collision phenomenon in which two RFID readers simultaneously access one RFID tag is prevented.

In addition, according to the present invention, the occurrence of a deadlock state in which the inactive mode state is continuously maintained is prevented because both readers cannot find a condition to be switched from the inactive mode to the active mode.

1 is a diagram showing the configuration of an RFID reader according to the present invention.
2 is a diagram showing a process performed by each RFID reader of FIG. 1;
3 is a timing diagram of a process performed by each RFID reader of FIG. 1;
4 is a timing diagram for explaining a deadlock state occurring between each RFID reader in the process of FIGS. 2 and 3;
5 is a diagram illustrating a process of detecting whether a master reader has changed from an inactive mode to an active mode in an inactive mode of a slave reader.
6 is a diagram illustrating a process in which a slave reader is changed to an active mode when a mode change is detected in FIG. 5.
7 is a diagram showing an integration process of a master/slave leader.

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

First, before describing the characteristic configuration of the present invention, a basic configuration and operation of an RFID reader to which the present invention is applied will be described.

In general, the RFID reader operates by repeating the RF ON section and the RF OFF section. Here, the RF ON section means the section in which the communication mode of the RFID reader is an active mode that performs communication for the RFID tag, and the RF OFF section is the inactive mode where the communication mode of the RFID reader does not communicate with the RFID tag. Means a section.

The RFID reader reads or writes information of the RFID tag while transmitting and receiving data by accessing the RFID tag in the RF ON section. The time required for the RF ON section is generally variable and has a value between 2 and 20 ms depending on the presence or absence of an RFID tag and the normal termination of access to the RFID tag. The RF ON period may not be set variably, but may be fixedly set at a predetermined time. In addition, the RFID reader does not perform data transmission/reception operation for the RFID tag in the RF OFF period. The RF OFF section is generally set to a fixed value and is usually set to a value of 3ms or more.

When a plurality of RFID readers operating as described above exist in an adjacent area, and thus overlapping of the RF signal areas occurs, RF collision may occur. Hereinafter, the configuration of the present invention for preventing this will be described.

1 is a diagram showing the configuration of an RFID reader according to the present invention. In the following embodiment, the state in which two RFID readers 10 and 20 are provided is illustrated, but the present invention can be applied even when three or more readers are provided.

The first reader 10 includes a transmitting unit 12, a receiving unit 14, a storage unit 15, a communication interface 16, and a control unit 18.

The transmission unit 12 functions to transmit an activation signal and an inactivation signal to an external other reader, that is, the second reader 20, and the receiving unit 14 is an activation signal transmitted from an external other reader, that is, the second reader 20. And receiving a deactivation signal. Here, the activation signal is a signal that allows activation of communication for the RFID tag 30, and the deactivation signal is a signal that disallows activation of communication for the RFID tag 30.

The storage unit 15 stores a set value that is set by distinguishing whether the first reader 10 is a master reader or a slave reader. As will be described in detail later in the description of the characteristic configuration of the present invention, in the present invention, each reader is divided into a master reader and a slave reader to differentiate their operation. Accordingly, the first reader 10 needs a configuration to store a set value for whether it is a master reader or a slave reader, and the storage unit 15 functions to store such set values. As an example, if "1" is stored in the storage unit 15, it is a master reader, and if "0" is stored, it is a slave reader. For convenience of explanation, in the present invention, "1" is stored in the storage unit 15 of the first reader 10 so that the first reader 10 is set as the master reader.

The communication interface 16 functions to communicate with the RFID tag 30. That is, when the RFID tag 30 is located adjacent to the first reader 10 within a communicable distance, the first reader 10 communicates with the RFID tag 30 through the communication interface 16 to provide a required communication sequence. Perform. This communication sequence may be, for example, a process of charging a subway fare to an RFID tag including a function of paying a subway fare.

The control unit 18 functions to control the transmission unit 12 and the communication interface 16. Specifically, when an activation signal is received by the receiving unit 14 from another reader, that is, the second reader 20, the control unit 18 performs communication in the communication mode of the first reader 10 with respect to the RFID tag 30. The communication interface 16 is controlled to switch from an inactive mode that does not do so to an active mode that performs communication. In addition, the control unit 18 controls the transmission unit 12 to transmit a deactivation signal to the second reader 20 while the communication interface 16 is in the active mode.

Further, when the first reader 10 completes the communication sequence for the RFID tag or a predetermined time required for the completion of the communication sequence elapses, the controller 18 controls the first reader 10 for the RFID tag 30 The communication interface 16 is controlled so that the communication mode is switched from the active mode to the inactive mode, and the transmission unit 12 is controlled so that an activation signal is transmitted to the second reader 20. If the RF ON period is variably set, the controller 18 will switch the communication mode to the inactive mode when the communication sequence is completed. On the contrary, if the RF ON section is fixedly set, the controller 18 will switch to the inactive mode when a preset time elapses. For efficient operation of the process, it is desirable to variably set the RF ON section.

Like the first reader 10, the second reader 20 includes a transmitting unit 22, a receiving unit 24, a storage unit 25, a communication interface 26, and a control unit 28. The function is the same as each configuration of the first reader 10. The signal from the transmitter 12 of the first reader 10 is received by the receiver 24 of the second reader 20, and the signal from the transmitter 22 of the second reader 20 is transmitted from the first reader 10. It is received by the receiver 14. As described above, when the first reader 10 is set as a master leader, the second leader 20 is set as a slave leader. Accordingly, in the storage unit 25 of the second reader 20, “0”, which is the set value of the slave reader, is stored.

2 is a diagram illustrating a process performed by each RFID reader of FIG. 1, and FIG. 3 is a diagram illustrating a timing diagram of a process performed by each RFID reader of FIG. 1.

The first reader 10 and the second reader 20 have the same configuration and operate symmetrically. Accordingly, although the process shown in FIG. 2 is shown centering on the first reader 10, an operation symmetrical thereto is performed by the second reader 20 in the same manner. Hereinafter, the process of the present invention will be described centering on the first reader 10. In FIG. 3, RX1 and RX2 are signals received from the receiving unit 14 of the first reader 10 and the receiving unit 24 of the second reader 20, respectively, and the high state is an activation signal and the low state is an inactive signal. Indicates what is being input. In addition, TX1 and TX2 are signals output from the transmitting unit 12 of the first reader 10 and the transmitting unit 22 of the second reader 20, respectively, and the high state is the activation signal and the low state is the deactivation signal. Show. TX1 is the same as RX2 and TX2 is the same as RX1.

The first reader 10 continuously checks whether an activation signal is input from the second reader 20 in the RF OFF state (interval t1 in FIG. 3), which is an inactive mode. (S10) From the second reader 20 When an activation signal is input (at the end of period t1), first, the first reader 10 transmits an inactivation signal to the second reader 20 through the transmission unit 12 (S20). ) Receives the deactivation signal through the receiving unit 24, and the control unit 28 of the second reader 20 controls the communication interface 28 to switch to an inactive mode, the RF OFF state. Accordingly, the second reader 20 is in a state that does not communicate with the RFID tag 30 (interval t2). Then, the controller 18 of the first reader 10 controls the communication interface 18. Thus, the active mode is converted to the RF ON state (S30) (section t2). Accordingly, the first reader 10 is in a state in which communication with the RFID tag 30 is performed. In the present embodiment, it is illustrated that step S30 is performed after step S20 is performed, but step S20 and step S30 may be performed at the same time, or step S30 may be performed before step S20. Preferably, step S30 is performed after step S20 so that the first reader 10 is activated after the second reader 20 is first deactivated, so that the two readers 10 and 20 access the RFID tag 30 at the same time. Do not occur

In the active mode, the first reader 10 performs a communication sequence reading information from the RFID tag 30 (S40). Accordingly, an operation such as, for example, charging a subway fare for the RFID tag 30 is performed. do. After completing the communication sequence (if the RF ON interval is set to a variable time interval), or after a predetermined time required for the completion of the communication sequence (if the RF ON interval is set to a fixed time interval), the first The reader 10 switches the communication mode from the active mode to the inactive mode, the RF OFF state. (S50) (interval t3) Then, the first reader 10 transmits an activation signal through the transmitter 12 ( S60), accordingly, the second reader 20 is switched to the active mode. (S60) (Section t3) In this embodiment, it is illustrated that step S60 is performed after step S50, but steps S50 and S60 are performed simultaneously. Alternatively, step S60 may be performed prior to step S50. Preferably, step S60 is performed after step S50 so that the first reader 10 is deactivated and then the second reader 20 is activated, so that the two readers 10 and 20 access the RFID tag 30 at the same time. Do not occur

Since the RF OFF section (t3 section) in the deactivated state of the first reader 10 is set as a fixed time section, the control unit 18 of the first reader 10 checks whether a preset time has elapsed, It returns to the state of step S10. (S70) After that, steps S10 to S30 are performed again, so that the first reader 10 is in the RF ON state, which is an active mode (section t4).

As this process is performed, only one of the first reader 10 and the second reader 20 has an active state, and thus the RFID tag 30 communicates with the two readers 10 and 20 at the same time. The collision state is avoided.

Meanwhile, in the present embodiment, a collision avoidance method between two readers 10 and 20 is illustrated, but the present invention can be applied even between three or more readers. That is, when looking at the first reader 10 as the center, when the second reader 20 includes a plurality of readers, the first reader 10 receives activation signals from all of the plurality of readers in step S10. Steps S20 to S70 are performed only when. In this way, all readers included in the second reader perform the same. That is, each reader switches itself to the active mode when all other readers other than itself transmit an activation signal, that is, when all other readers are switched to the inactive mode. Accordingly, a collision state is prevented even between a plurality of readers.

A communication deadlock may occur between the readers 10 and 20 having the above configuration. Here, the deadlock state means a state in which the inactive mode state is continuously maintained because both of the readers 10 and 20 cannot find a condition to switch to the active mode from the state in which they are both inactive mode. In the deadlock state, no readers 10 and 20 can access the RFID tag 30.

4 is a timing diagram illustrating a deadlock state occurring between each RFID reader in the process of FIGS. 2 and 3. In the diagram of FIG. 4, the period of t1 to t3 is the same as the diagram of FIG. 2, and the state in which the operation is stopped as shown in FIG. 2 by falling into a deadlock state in the time period corresponding to the period t4 of FIG. It is shown as a section.

In section t5 of FIG. 4, the second reader 20 is in the RF OFF state as in section t4 of FIG. 2, and accordingly, TX2 transmits an activation signal. By the way, when the thread sampling RX1 (= TX2) in the receiving unit 12 of the first reader 10 enters the pending state by the scheduling of the OS, the receiving unit 12 of the first reader 10 receives RX1 (= TX2). ) Is an activation signal, but it is not recognized. Accordingly, the first reader 10 fails to change the communication mode to the active mode and maintains the inactive mode (RF OFF), and the transmitter 14 of the first reader 10 transmits an activation signal. Becomes. In a normal state, the state of section t4 of FIG. 2 is the same as that of section t2, but in section t5 of this situation, the communication mode of the first reader 10 and TX1 are in the opposite state to that of FIG. 2, and the two readers 10, 20) Everyone goes into inactive mode.

However, in this situation, since activation signals are input to both the first and second readers 10 and 20 to RX1 and RX2, both of the readers 10 and 20 are switched to the RF ON state, which is an active mode. In this case, since both the readers 10 and 20 communicate with the RFID tag 30, an error occurs. Therefore, in order to prevent this, it is preferable that the two readers 10 and 20 are configured to determine an additional condition rather than simply determine whether an activation signal is input from the counterpart reader 20 or 10. Here, the additional condition is whether or not the other reader is in the RF ON state while one of the readers is in the RF OFF state. In this way, if both the readers 10 and 20 perform the additional condition, a situation in which the two readers 10 and 20 are activated at the same time can be prevented. However, in this case, as described above, when both readers (10, 20) are in RF OFF state in section t5, as a result, both readers (10, 20) are both RF OFF state and the other party also RF ON Since it is a state, the state of the period t5 is maintained, and both of the readers 10 and 20 are locked into an inactive mode.

Hereinafter, a characteristic configuration of the present invention for preventing such a deadlock will be described.

In the present invention, the first reader 10 is set as a master reader and the second reader 20 is set as a slave reader. At this time, the deadlock is prevented by changing the conditions for changing to the active mode for the master reader and the slave reader. do.

Specifically, it is proposed to weaken the condition for changing to the active mode for the master reader, and strengthen the condition for changing to the active mode for the slave reader compared to the master reader. Hereinafter, a condition commonly required for the master reader and the slave reader is referred to as a first condition, and an additional condition additionally required for the slave reader is referred to as a second condition.

The first condition is whether or not an activation signal is input from the counterpart reader. The first condition is a condition that is commonly applied to both the master leader and the slave leader, and each of the master leader and slave leader determines whether or not they are satisfied.

In section t5 of FIG. 4, if the first reader 10 is changed to the active mode as long as the activation signal is input from the second reader 20, the first reader 10 can be switched to the RF ON state. . Accordingly, since the state of the first reader 10 becomes the same as the period t4 of FIG. 2, it is possible to escape from the deadlock state.

The second condition is whether the communication mode of the counterpart reader has been an active mode in the past, which is to determine whether the counterpart reader has ever communicated with the RFID tag in the past. The second condition may be determined by whether the slave reader has ever changed the signal received from the master reader from the deactivation signal to the activation signal. That is, the slave reader is changed to the active mode when the first condition is satisfied and the second condition is satisfied as described above. Hereinafter, a specific method for the slave reader to determine whether the second condition is satisfied will be described.

5 is a diagram illustrating a process of detecting whether a master reader has changed from an inactive mode to an active mode in an inactive mode of a slave reader. 5 is a process performed by the second reader 20 in the RF OFF state. The following process is performed by the control unit 28 of the second reader 20.

The second reader 20 has three variables (sync_value, prev_value, and H_in_low2high). The sync_value is a variable in which a signal RX2 input to the receiver 24 of the second reader 20, that is, a value of the TX1 signal output from the first reader 10 is stored. prev_value is a variable that stores the previous state value of sync_value. That is, sync_value stores the value of RX2, and prev_value stores the value of the state before the change when sync_value is changed. H_in_low2high is a variable that stores a value for checking whether the communication mode of the second reader 20 has changed from an inactive mode (RF OFF) to an active mode (RF ON). Meanwhile, in FIG. 5 (and FIGS. 6 and 7), “H_in” is a symbol indicating the value of RX2 (=TX1) received by the receiver 24 of the second reader 20.

First, an initial value (INIT VALUE) and an unconfirmed value (FALSE) are stored in each variable of prev_value and H_in_low2high as the initial state. (S110) Here, prev_value is a variable that stores the previous state value of sync_value, so the initial value ( INIT VALUE) is set so that sync_value has a value that is neither an activation signal nor an inactivation signal. For example, if the activation signal is "1" and the deactivation signal is "0", INIV VALUE is set to a value other than "0" and "1". Since H_in_low2high is a variable that stores the final confirmation result, it is initially set to have a FALSE value indicating unconfirmed.

When the initial value setting is completed, the second reader 20 reads the received RX2 signal and stores it in sync_value (S120).

Then, the second reader 20 determines whether the sync_value is Low and the prev_value is High (S130). This condition determines whether the signal RX2 received from the first reader 10 has changed from high to low. As a condition for determining, as a result, it is a condition for determining whether the first reader 10, which is the master reader, has been changed from an inactive mode (RF OFF) to an active mode (RF ON).

If the condition is not satisfied in step S130, the second reader 20 stores the current sync_value value as a prev_value value (S150), and then reads the RX2 signal and stores it in the sync_value (S120). If the condition is satisfied in step S130, the value of the H_in_low2high variable is set to TRUE (S140), and the current sync_value value is stored as the value of prev_value (S150).

By performing this process, if the first reader 10 is switched from the inactive mode (RF OFF) to the active mode (RF ON) is detected by the second reader 20, and the detection progress is stored in the H_in_low2high variable. do.

6 is a diagram illustrating a process in which a slave reader is changed to an active mode when a mode change is detected in FIG. 5.

The second reader 20 checks whether the sync_value is high, that is, whether the received RX2 (=TX1) value is high (that is, whether the first reader 10 is in an RF OFF state in an inactive mode). S210) This is a process of checking whether the second reader 20 satisfies the first condition. When this condition is satisfied, the second reader 20 checks whether the value of the H_in_low2high variable is TRUE (S220). This is a process of checking whether the second reader 20 satisfies the second condition. If this condition is also satisfied, the second reader 20 changes the H_in_low2high variable back to FALSE (S230) and changes the communication mode of the second reader 20 to an active mode (RF ON) (S240). Through the process, the second reader 20 is changed to the active mode when both the first condition and the second condition are satisfied. Meanwhile, step S230 is performed in order to normally perform the process of FIG. 5 after the second reader 20 enters the inactive mode again in the future.

7 is a diagram showing an integration process of a master/slave leader.

Each of the readers 10 and 20 functions as a master or slave according to a value set in the storage units 15 and 25 as described above. In the RF OFF state of the readers 10 and 20, each control unit 18, 28 first determines whether it is a master leader or a slave leader by inquiring the storage units 15 and 25 (S310).

Then, when the control unit determines that the master reader is the master reader, it determines whether the sync_value is high, that is, whether an activation signal is input from the slave reader, which is the counterpart leader (S312), and when the activation signal is input, its state is set to the active mode (RF ON). ) To change (S330)

If the control unit determines that it is a slave leader, the process of FIG. 6 is performed (steps S322, S324, S326, and S330 of FIG. 7 are the same as steps S210, S220, S230, and S240 of FIG. 6, respectively). , The process of FIG. 5 is performed from the moment the slave reader enters the inactive mode (RF OFF), and is completed before the process of FIG. 6 is performed.

Through this process, the first reader 10, which is the master leader, is switched to the active mode under more relaxed conditions than the slave reader, that is, when an activation signal is input from the slave reader. In addition, the second reader 20, which is a slave leader, is changed to an active mode under an enhanced condition compared to the master reader. Therefore, when the two readers 10 and 20 are in the same state as the period t4 in FIG. 4 for some reason, only the first reader 10 is turned into the RF ON state and the second reader 20 maintains the RF OFF state. As a result, it is converted to a normal state like the t2 section. Accordingly, a deadlock is prevented and an error state in which both the readers 10 and 20 are activated is also prevented.

Meanwhile, in the above embodiment, the relationship between one master reader and one slave reader has been described, but the present invention may be applied even when there are a plurality of slave readers. In this case, the processes of FIGS. 5 and 6 are performed at different time intervals for each slave. For example, when there are 4 slave readers, the first reader 10 divides the RF OFF state into 4 sub time periods, and each slave occupies any one of the 4 time periods, so that the process of FIGS. 5 and 6 Can be done. Accordingly, it is prevented that any one of the plurality of slaves is changed to the active mode and the entire readers fall into deadlock.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is only exemplary, and those of ordinary skill in the art will understand that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the attached registration claims.

Claims (12)

As a time division communication control method for avoiding communication collisions between a first reader and a second reader performing RFID communication on an RFID tag,
a) When an activation signal allowing communication activation for the RFID tag is input from the second reader to the first reader, the communication mode of the first reader is changed from an inactive mode in which communication is not performed with the RFID tag. Switching to an active mode for performing communication; And
b) when the activation signal is input from the first reader to the second reader and the second reader satisfies a predetermined additional condition, the communication mode of the second reader is switched from the inactive mode to the active mode The step of doing;
Time division communication control method for avoiding a communication collision between the first reader and the second reader comprising a.
The method of claim 1,
The additional condition is a time division communication control method for avoiding a communication collision between a first reader and a second reader, characterized in that whether the communication mode of the first reader has ever been the active mode.
The method of claim 1,
The additional condition is whether or not the activation signal is input after a deactivation signal for disallowing communication activation for the RFID tag is input to the second reader, and communication collision avoidance between the first reader and the second reader, characterized in that Time division communication control method for
The method of claim 1,
The second reader is a time division communication control method comprising a plurality of readers.
A communication interface for performing communication with respect to the RFID tag;
A receiver configured to receive an activation signal allowing communication activation for the RFID tag and a deactivation signal disallowing communication activation from an external reader;
A transmitter for transmitting the activation signal and the deactivation signal to the other reader; And
As the activation signal is received by the receiver from the other reader, the communication interface is controlled so that the communication mode for the RFID tag is switched from an inactive mode in which communication is not performed to an active mode in which communication is performed, and the RFID tag Controls the communication interface so that the communication mode is switched from the active mode to the inactive mode as the communication sequence is completed or a predetermined time required for the completion of the communication sequence elapses, and the activation signal is transmitted to the other reader. A control unit for controlling the transmission unit to be possible;
RFID master reader comprising a.
The method of claim 5,
And the control unit controls the transmission unit to transmit the deactivation signal to the other reader while the communication interface is in an active mode.
The method according to claim 5 or 6,
The other reader is configured to include a plurality of readers,
And the control unit controls the communication interface to switch the communication mode to the active mode when the activation signal is received from all of the plurality of readers.
A communication interface for performing communication with respect to the RFID tag;
A receiver configured to receive an activation signal allowing communication activation for the RFID tag and a deactivation signal disallowing communication activation from an external reader;
A transmitter for transmitting the activation signal and the deactivation signal to the other reader; And
The communication interface is configured such that the communication mode for the RFID tag is switched from an inactive mode in which communication is not performed to an active mode in which communication is performed as the activation signal is received by the receiver from the other reader and a predetermined additional condition is satisfied. Control, and control the communication interface such that the communication mode is switched from the active mode to the inactive mode as the communication sequence for the RFID tag is completed or a predetermined time required for the completion of the communication sequence elapses, and the activation A control unit for controlling the transmission unit to transmit a signal to the other reader;
RFID slave reader comprising a.
The method of claim 8,
The additional condition is whether or not the communication mode of the other reader has been the active mode.
The method of claim 8,
The additional condition is whether the activation signal is input after the deactivation signal is input from the other reader.
The method of claim 8,
And the control unit controls the transmission unit to transmit the deactivation signal to the other reader while the communication interface is in an active mode.
The method according to any one of claims 8 to 11,
The other reader is configured to include a plurality of readers,
Wherein the controller controls the communication interface so that the communication mode is switched to the active mode when the activation signal is received from all of the plurality of readers.

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