阅读说明：本技术 通信系统及通信系统的通信方法 (Communication system and communication method of communication system ) 是由 野上英克 片冈新 川上健太 本嶋弘明 于 2020-02-06 设计创作，主要内容包括：本发明提供一种通信系统,其能够在不导致系统的复杂化的情况下,对读写器设定优先级来与无线标签进行通信。各读写器若在与射频识别标签(4)通信之前检测到其他读写器的电波,则进行使通信开始待机规定的待机时间的处理。栅极用读写器(2)的待机时间的平均值设定为短于架管理用读写器(3)的待机时间的平均值。(The invention provides a communication system which can set priority to a reader/writer to communicate with a wireless tag without complicating the system. When each reader/writer detects a radio wave from another reader/writer before communicating with the radio frequency identification tag (4), the reader/writer performs a process of waiting for a predetermined waiting time for starting communication. The average value of the standby time of the gate reader/writer (2) is set to be shorter than the average value of the standby time of the shelf management reader/writer (3).)

1. A communication system including a plurality of readers/writers for performing at least either one of reading and writing of data to a plurality of radio frequency identification tags,

each reader-writer comprises a detection part and a standby part,

the detection unit detects an electric wave generated when another reader/writer communicates with the rfid tag,

the standby unit performs at least one of the following processes:

a process of starting communication with the rfid tag of the communication object and waiting for a predetermined waiting time when the radio wave of another reader/writer is detected before communication with the rfid tag of the communication object; and

processing for waiting for a predetermined standby time after the communication processing with the rfid tag of the communication object is completed;

in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

2. The communication system of claim 1,

the standby unit of the first reader/writer sets a standby time to 0.

3. The communication system of claim 1,

the standby section of the first reader/writer randomly determines a standby time from a range of T3 or more and T4 or less at each standby time.

4. The communication system according to any of claims 1 to 3,

the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time.

5. The communication system of claim 3,

the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and the value of T4 is smaller than the value of T5.

6. The communication system of claim 3,

the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and T4 is equal to T5.

7. The communication system of claim 3,

the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and the value of T4 is larger than the value of T5.

8. The communication system according to any of claims 1 to 7,

the first reader/writer is fixed in its own disposition position and communicates with a radio frequency identification tag passing through a communication area,

the second reader communicates with the rfid tag, which is not moved, by moving itself.

9. A communication method of a communication system including a plurality of readers/writers for performing at least one of reading and writing of data to a plurality of radio frequency identification tags,

each reader/writer includes a detection step and a standby step,

the detecting step detects an electric wave emitted when the other reader/writer communicates with the radio frequency identification tag,

the standby step is to perform at least any one of the following processes:

a process of starting communication with the rfid tag of the communication object and waiting for a predetermined waiting time when the radio wave of another reader/writer is detected before communication with the rfid tag of the communication object; and

processing for waiting for a predetermined standby time after the communication processing with the rfid tag of the communication object is completed;

in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

Technical Field

The present invention relates to a communication system that prevents mutual interference between readers/writers (R/W) that transmit and receive information to and from a wireless tag.

Background

Conventionally, the use of wireless tags has been widespread for the purpose of identifying articles and the like. As an example of a means for preventing interference due to simultaneous activation of a plurality of readers/writers, a reader/writer for transmitting and receiving information with a wireless tag has a Listen Before Talk (LBT) function. However, when only the LBT function is used, the right to perform communication is equally given to the reader/writer, and thus it is not possible to cope with a demand for increasing the priority of a specific reader/writer.

In contrast, patent document 1 discloses the following technique: the management server controls the start/end of carrier sense by an interrogator (corresponding to a reader/writer) and the transmission/stop of a radio signal. In addition, the following methods are disclosed: the worker gives priority to each interrogator in advance, and when the management server gives the right to perform wireless communication, the management server gives the right to perform wireless communication first to the interrogator having high priority.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2007-317174

Disclosure of Invention

Problems to be solved by the invention

However, in the conventional technique as described above, since the priority of the reader/writer is controlled by the management server which is a higher-level system, the system becomes complicated, and there is a problem that the cost is increased or the management is complicated. In addition, since the communication right of the reader/writer is mediated by the management server, a waiting time is generated by the processing and communication accompanying the mediation. Therefore, for example, there are the following problems: when real-time performance is required such as passing a wireless tag through a gate, the wireless tag may not be able to sufficiently cope with the situation.

An object of one embodiment of the present invention is to provide a communication system capable of setting priority to a reader/writer to communicate with a wireless tag without complicating the system.

Means for solving the problems

In order to solve the above problem, a communication system according to an embodiment of the present invention includes a plurality of readers/writers for performing at least one of reading and writing data from and into a plurality of Radio Frequency Identification (RFID) tags, and the communication system has a structure in which: each reader/writer includes a detection section that detects an electric wave emitted when another reader/writer communicates with the RFID tag, and a standby section that performs at least any one of the following processes: a process of starting communication with the RFID tag of the communication object and waiting for a predetermined waiting time when the radio wave of another reader/writer is detected before communication with the RFID tag of the communication object; and a process of waiting for a predetermined waiting time after the communication process with the RFID tag of the communication target is completed; in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

In addition, a communication method of a communication system according to an embodiment of the present invention is a communication method of a communication system including a plurality of readers/writers for performing at least either one of reading and writing data from and to a plurality of RFID tags, wherein each reader/writer includes a detection step of detecting a radio wave generated when another reader/writer communicates with an RFID tag and a standby step of performing at least either one of the following processes: a process of starting communication with the RFID tag of the communication object and waiting for a predetermined waiting time when the radio wave of another reader/writer is detected before communication with the RFID tag of the communication object; and a process of waiting for a predetermined waiting time after the communication process with the RFID tag of the communication target is completed; in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to an embodiment of the present invention, the reader/writer can be set with priority to communicate with the wireless tag without causing complication of the system.

Drawings

Fig. 1 is a block diagram showing a configuration of a communication system 100 according to the present embodiment.

Fig. 2 is a flowchart showing a flow of communication processing with the RFID tag 4 in the Reader/Writer (R/W) 2 for gate and the R/W3 for shelf management.

Fig. 3 is a timing chart showing an example of a communication sequence when the gate R/W2 and the rack management R/W3 receive a communication instruction at the same timing and detect an electric wave from another reader/writer at this point in time when the standby time is set to be constant.

Fig. 4 is a sequence diagram showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set in a fixed manner.

Fig. 5 is a timing chart showing another example of a communication sequence when no radio wave is transmitted from another reader/writer when the standby time is set in a fixed manner.

Fig. 6 is a timing chart showing an example of a communication sequence when the gate R/W2 and the rack management R/W3 receive a communication instruction at the same timing and detect an electric wave from another reader/writer at this point in time when the standby time is set so that the standby time of the gate R/W2 is set to 0.

Fig. 7 is a timing chart showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set so that the standby time of the gate R/W2 is set to 0.

Fig. 8 is a timing chart showing another example of a communication sequence when no radio wave is transmitted from another reader/writer when the standby time is set to a fixed state.

Fig. 9 is a timing chart showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set in a random manner.

Fig. 10 is a diagram showing an example of setting of the standby time due to a change in the setting of the standby time by the random method.

Fig. 11 is a flowchart showing a flow of communication processing with the RFID tag 4 in the gate R/W2 and the rack management R/W3 when the post-communication standby processing is performed.

Fig. 12 is a sequence diagram showing an example of a communication sequence when no radio wave is transmitted from another reader/writer in the case of performing the post-communication standby process.

Detailed Description

Hereinafter, an embodiment (hereinafter, also referred to as "the present embodiment") according to one aspect of the present invention will be described with reference to the drawings. All aspects of the present embodiment described below are merely exemplary of the present invention. Of course, various modifications and changes can be made without departing from the scope of the present invention.

Application example § 1

(Structure of communication System)

First, an example of a case where the present invention is applicable will be described with reference to fig. 1. Fig. 1 is a block diagram showing a configuration of a communication system 100 according to the present embodiment. As shown in fig. 1, the communication system 100 includes a gate R/W (first reader/writer) 2 and a shelf management R/W (second reader/writer) 3 that perform at least one of reading and writing of data to the plurality of RFID tags 4.

The gate R/W2 includes: a detection unit 27 that detects radio waves emitted when another reader/writer communicates with the RFID tag 4; and a standby unit 26 that, when detecting an electric wave from another reader/writer before communicating with the RFID tag 4 of the communication target, starts standby for a predetermined standby time in communication with the RFID tag 4.

Similarly, the rack management R/W3 includes: a detection unit 37 that detects radio waves emitted when another reader/writer communicates with the RFID tag 4; and a standby unit 36 configured to start standby for a predetermined standby time when the radio wave of another reader/writer is detected before the communication with the RFID tag 4 of the communication target.

Here, the average value of the standby time of the gate R/W2 is set to be shorter than the average value of the standby time of the rack management R/W3. Thus, communication can be performed in a state where the priority of the gate R/W2 is higher than that of the rack management R/W3.

The communication system 100 includes three or more readers/writers to be set with priorities, and the length of the standby time can be set to be shorter as the priorities of the readers/writers are higher.

Construction example 2

The configuration of the communication system 100 will be described in more detail below. As shown in fig. 1, the communication system 100 includes: a gate R/W2, a rack management R/W3, a Programmable Logic Controller (PLC) 1 as a host system that collectively manages the plurality of readers/writers, and Radio Frequency Identification (RFID) tags 4 on the carrier vehicle 5 and the rack 6 that transmit and receive data to and from the readers/writers. The PLC1 is communicatively connected to the gate R/W2 and the rack management R/W3 via a communication network. Although not shown, the communication system 100 may include a reader/writer in addition to the gate R/W2 and the rack management R/W3.

When the transport vehicle 5 passes through the gate, the gate R/W2 communicates with the RFID tag 4 attached to the product mounted on the transport vehicle 5. That is, the arrangement position of the gate R/W2 itself is fixed, and communication is performed with the RFID tag 4 passing through the communication area. This allows the products loaded on the transport vehicle 5 to be identified, which have passed through the gate.

The gate R/W2 includes an upper communication unit 21, a Radio Frequency (RF) communication unit 22, and an antenna 23. The upper communication unit 21 controls communication with the PLC1, transmits an instruction from the PLC1 to the RF communication unit 22, and transmits an output from the RF communication unit 22 to the PLC 1. The RF communication unit 22 performs communication control of radio waves transmitted and received by the antenna 23. Here, since it is assumed that the RFID tag 4 to be communicated with the gate R/W2 is moving, the wireless communication in the gate R/W2 requires real-time performance.

The standby unit 26 included in the RF communication unit 22 holds standby time information indicating a standby time. The standby time information can be changed according to an instruction from the outside. For example, the standby time information may be rewritten in accordance with an instruction from the PLC1, or may be rewritten in accordance with a Personal Computer (PC) or the like directly connected to the gate R/W2 via a Universal Serial Bus (USB) or the like. The gate R/W2 may include an input unit for receiving an input from a user, and the standby time information may be rewritten by the input unit (button, switch, touch panel, or the like).

The rack management R/W3 communicates with the RFID tag 4 attached to the product mounted on the rack 6. That is, the rack management R/W3 moves by itself by being carried by the user, and thereby communicates with the RFID tag 4 that does not move. This makes it possible to identify which product is placed on the rack 6.

The rack management R/W3 includes an upper communication unit 31, an RF communication unit 32, an antenna 33, and a trigger switch 34. The upper communication unit 31, the RF communication unit 32, and the antenna 33 have the same functions as those of the upper communication unit 21, the RF communication unit 22, and the antenna 23. The trigger switch 34 receives an operation by the user, and transmits an instruction to start communication with the ID tag 4 to the RF communication unit 32 at a timing of the user operation. Further, an instruction to start communication with the ID tag 4 may be received from the PLC 1.

Here, since the RFID tag 4 to be communicated with the rack management R/W3 is stationary, the wireless communication in the rack management R/W3 is not required to be real-time as compared with the gate R/W2.

In fig. 1, two RFID tags 4 are shown on the carrier vehicle 5 and the rack 6, respectively, but the present invention is not limited to this, and may be one or more RFID tags.

(flow of communication processing)

Fig. 2 is a flowchart showing a flow of communication processing with the RFID tag 4 in the gate R/W2 and the rack management R/W3. Since the basic communication processing flows of the gate R/W2 and the rack management R/W3 are the same, the gate R/W2 will be described here as an example.

First, in step 1 (hereinafter, referred to as S1), when the host communication unit 21 receives a signal indicating a reading instruction from the PLC1, it transmits the instruction to the RF communication unit 22. In the case of the rack management R/W3, the trigger switch 34 may transmit an operation input by the user as a read instruction to the RF communication unit 22.

Next, in S2, the detection section 27 in the RF communication section 22 confirms whether or not radio waves from other reader/writers are detected by the antenna 23 by the Listen Before Talk (LBT) function. If YES in S2, that is, if the detection unit 27 detects an electric wave from another reader/writer, the standby unit 26 in the RF communication unit 22 performs a process of causing RF communication to stand by for a predetermined standby time (S3). When the standby processing is completed, the processing returns to the processing from S2.

On the other hand, if NO in S2 (NO), that is, if NO radio wave from another reader/writer is detected, the RF communication section 22 starts RF communication and performs communication processing with the RFID tag 4 (S4).

Note that although the case where the read instruction is received in S2 has been described above, the same processing is performed when the write instruction is received.

(Change in setting of Standby time)

Next, a change in the setting of the standby time will be described. The standby time setting methods for the gate R/W2 and the rack management R/W3 are roughly classified into a fixed method and a random method.

The fixed system is a system in which the standby time is set to a fixed value in each reader/writer. The standby time of the gate R/W2, which is a reader/writer with a high priority, is set to T1 (fixed value), and the standby time of the rack management R/W3, which is a reader/writer with a low priority, is set to T2 (fixed value), and is set to T1 < T2.

The random method is a method in which each time standby processing occurs in each reader/writer, the standby time is set to a random value including a predetermined range. The standby time of the gate R/W2, which is a reader/writer with a high priority, is set to a random value in the range of T3 to T4, and the standby time of the rack management R/W3, which is a reader/writer with a low priority, is set to a random value in the range of T5 to T6. The average of the random values in the range of T3 to T4 is set to be shorter than the average of the random values in the range of T5 to T6. Further, T3 may be 0. In addition, either one of the gate R/W2 and the rack management R/W3 may be fixed, and the other may be random.

(specific example of communication sequence based on fixed mode)

A specific example of a communication sequence with the RFID tag 4 in the gate R/W2 and the rack management R/W3 when the standby time is set in a fixed manner will be described below. Fig. 3 is a timing chart showing an example of a communication sequence when the gate R/W2 and the rack management R/W3 receive a communication instruction at the same timing and detect an electric wave from another reader/writer at this point in time when the standby time is set to be constant.

The gate R/W2 and the rack management R/W3 perform LBT when the communication instruction is received. In the LBT, a radio wave from another reader/writer is detected, and therefore, a standby process is performed. In the gate R/W2, the standby process is performed during the period T1, and then LBT is performed again. At this point, since no radio wave from another reader/writer is detected, the communication process is performed after the LBT is completed.

On the other hand, in the rack management R/W3, LBT is performed at the time of reception of the communication instruction. In the LBT, a radio wave from another reader/writer is detected, and therefore, a standby process is performed. In the rack management R/W3, the standby process is performed for a period of T2 longer than T1, and then LBT is performed again. At this point, since the communication process is performed in the gate R/W2, the LBT detects the radio wave from the gate R/W2. Therefore, the standby process is subsequently performed during a period T2. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, it is understood that the communication process of the gate R/W2 is preferentially performed by setting the standby time of the gate R/W2 to be shorter than the standby time of the rack management R/W3.

Fig. 4 is a sequence diagram showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set in a fixed manner.

In this example, first, the gate R/W2 starts LBT first. In the LBT, since no radio wave from another reader/writer is detected, the gate R/W2 starts a communication process. On the other hand, the rack management R/W3 starts LBT with a slight delay from the gate R/W2, and detects the radio wave from the gate R/W2 in the middle of LBT. Therefore, in the rack management R/W3, the standby processing is performed during the period T2.

Then, in the R/W2 for gate, after the first communication process is completed, LBT is performed to perform the second communication process. Since no electric wave from another reader/writer is detected in the LBT, the gate R/W2 starts the second communication process. On the other hand, the rack management R/W3 performs LBT again after the standby processing is finished, and detects radio waves from the gate R/W2 again in the middle of LBT. Therefore, the rack management R/W3 performs the standby process again during the period T2. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, it is understood that the communication process of the gate R/W2 is preferentially performed also in the example shown in fig. 4.

Fig. 5 is a timing chart showing another example of a communication sequence when no radio wave is transmitted from another reader/writer when the standby time is set in a fixed manner.

In this example, first, the rack management R/W3 starts LBT. In the LBT, since no radio wave from another reader/writer is detected, the rack management R/W3 starts the communication process. On the other hand, the gate R/W2 starts LBT with a slight delay from the rack management R/W3, and detects the radio wave from the rack management R/W3 in the middle of LBT. Therefore, in the gate R/W2, the standby process is performed during the period T1.

Then, in the gate R/W2, LBT is performed again after the standby processing, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

On the other hand, in the rack management R/W3, after the first communication process is completed, LBT is performed to perform the second communication process. In the middle of the LBT, the rack management R/W3 detects the radio wave from the gate R/W2. Therefore, in the rack management R/W3, the standby processing is performed during the period T2. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, in the example shown in fig. 5, even in a situation where the rack management R/W3 starts LBT first and performs communication processing, the gate R/W2 acquires the communication right thereafter and performs communication processing. The reason for this is that: the probability of acquiring the communication right is increased by setting the standby time of the gate R/W2 to be shorter than the standby time of the rack management R/W3. That is, it is understood that the communication process of the gate R/W2 is preferentially performed also in the example shown in fig. 5.

Fig. 6 is a timing chart showing an example of a communication sequence when the gate R/W2 and the rack management R/W3 receive a communication instruction at the same timing and detect an electric wave from another reader/writer at this point in time when the standby time is set so that the standby time of the gate R/W2 is set to 0.

In this example, the standby time of the gate R/W2 is set to 0. The gate R/W2 and the rack management R/W3 perform LBT when the communication instruction is received. In the LBT, since electric waves from other reader/writers are detected, LBT is continuously performed with the standby time of 0. At the time of the third LBT, since no radio wave from another reader/writer is detected, the communication process is performed after the LBT is completed.

On the other hand, in the rack management R/W3, LBT is performed at the time of reception of the communication instruction. In the LBT, a radio wave from another reader/writer is detected, and therefore, a standby process is performed. In the rack management R/W3, the stand-by process is performed during the period of T2, and then LBT is performed again. At this point, since the communication process is performed in the gate R/W2, the LBT detects the radio wave from the gate R/W2. Therefore, the standby process is subsequently performed during a period T2. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, even when the standby time of the gate R/W2 is set to 0, the communication process of the gate R/W2 is preferentially performed.

Fig. 7 is a timing chart showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set so that the standby time of the gate R/W2 is set to 0.

In this example, first, the rack management R/W3 starts LBT. Since no radio wave from another reader/writer is detected in the LBT, the rack management R/W3 starts a communication process. On the other hand, the gate R/W2 starts LBT with a slight delay from the rack management R/W3, and detects the radio wave from the rack management R/W3 in the middle of LBT. Therefore, in the gate R/W2, LBT is continuously performed with the standby time of 0 while the communication process is performed by the rack management R/W3.

When the communication process in the rack management R/W3 is completed, the LBT of the gate R/W2 does not detect the radio wave from another reader/writer, and therefore the communication process is performed after the LBT is completed.

On the other hand, in the rack management R/W3, after the first communication process is completed, LBT is performed to perform the second communication process. In the middle of the LBT, the rack management R/W3 detects the radio wave from the gate R/W2. Therefore, in the rack management R/W3, the standby processing is performed during the period T2. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, it is understood that the communication process of the gate R/W2 is preferentially performed also in the example shown in fig. 7.

When the standby time of the gate R/W2 is set to 0, the communication sequence is the same as that of fig. 4 when the gate R/W2 first starts LBT as in fig. 4.

Here, a problem that occurs when the communication cycle TA of the gate R/W2 matches the standby time of the rack management R/W3 will be described. Fig. 8 is a timing chart showing another example of a communication sequence when no radio wave is transmitted from another reader/writer when the standby time is set to a fixed state.

In the example, as described above, the communication cycle TA of the gate R/W2 coincides with the standby time of the rack management R/W3. In this case, the rack management R/W3 cannot always obtain the communication right according to the LBT start timing of the rack management R/W3. That is, as shown in fig. 6, when the shelf management R/W3 performs LBT during the communication process of the gate R/W2, the radio wave from the gate R/W2 is detected to perform the standby process during the T2. Here, since the standby time T2 coincides with the communication cycle TA, the LBT after the standby process in the rack management R/W3 overlaps with the timing of the next communication process in the gate R/W2 every time. In addition, the above phenomenon may occur when there is a reader/writer having a fixed communication cycle regardless of the priority level, and the standby time of the other reader/writers coincides with the refresh cycle.

That is, when the standby time is set in a fixed manner, there is a problem that the above-described phenomenon occurs depending on the situation. As a method for solving the above problem, an example of setting the standby time in a random manner will be described below.

(specific example of communication sequence based on random System)

A specific example of the communication sequence with the RFID tag 4 in the gate R/W2 and the rack management R/W3 when the standby time is set at random will be described below. Fig. 9 is a timing chart showing an example of a communication sequence when no radio wave is emitted from another reader/writer when the standby time is set in a random manner.

In this example, when the rack management R/W3 performs LBT during the communication process of the gate R/W2, the stand-by process is performed by detecting radio waves from the gate R/W2. The time between T5 and T6 is set at random as the time of the standby process.

Then, the gate R/W2 performs a second communication process after the communication period TA. At the timing of the communication process, the rack management R/W3 performs LBT after the standby process, and performs the standby process again by detecting the radio wave of the gate R/W2. The time between T5 and T6 is set at random as the time of the standby process. After the standby process, the shelf management performs LBT using R/W3. At this timing, the gate R/W2 does not perform the communication process, and therefore the rack management R/W3 performs the communication process after LBT. On the other hand, the gate R/W2 performs LBT after the next communication period TA, and performs standby processing by radio waves of the gantry management R/W3. The time between T3 and T4 is set at random as the time of the standby process.

As described above, when the standby time is set randomly, the standby time of the rack management R/W3 does not continuously coincide with the communication cycle of the gate R/W2, and therefore, the communication right may be given to the rack management R/W3. That is, according to the random scheme, when there is a reader/writer having a fixed communication cycle, the risk of giving a communication right to a specific reader/writer can be eliminated.

(Change of setting of Standby time in random System)

Here, the range setting of the random values of the standby time of the gate R/W2 and the rack management R/W3 will be described. As described above, the standby time of the gate R/W2 is set to a random value in the range of T3 to T4, and the standby time of the rack management R/W3 is set to a random value in the range of T5 to T6. In this case, there are three kinds of variations as the range setting method of the random values of both. The random pattern 1 is a pattern in which T4, which is the upper limit of the range of the random value of the standby time of the gate R/W2, is smaller than T5, which is the lower limit of the range of the random value of the standby time of the rack management R/W3 (T4 < T5). The random pattern 2 is a pattern in which T4 is equal to T5(T4 — T5). Random pattern 3 is a pattern in which T4 is greater than T5(T4 > T5).

In the case of the random mode 1, the standby time of the gate R/W2 is shorter than that of the rack management R/W3, and therefore the priority of the gate R/W2 can be reliably increased. In the case of the random mode 2, the standby time of the gate R/W2 and the standby time of the rack management R/W3 may be equal to each other according to the situation. That is, when the standby time is equal, the priority of the gate R/W2 is equal to that of the rack management R/W3. In the case of the random mode 3, the standby time of the gate R/W2 may be longer than that of the rack management R/W3 according to circumstances. That is, when the standby time of the gate R/W2 is longer than the standby time of the rack management R/W3, the priority of the gate R/W2 is lower than the priority of the rack management R/W3. However, as described above, the average of the random values in the range of T3 to T4 is set to be shorter than the average of the random values in the range of T5 to T6, and therefore, in any of random mode 1 to random mode 3, the priority of the gate R/W2 is higher than that of the rack management R/W3.

Fig. 10 is a diagram showing an example of setting of the standby time due to a change in the setting of the standby time by the random method. Fig. 10 (a) shows an example in which the standby time of the gate R/W2 is shorter than that of the rack management R/W3 in the case of the random access method 1. Fig. 10 (b) shows an example in which the standby time of the gate R/W2 is equal to the standby time of the rack management R/W3 in the case of the random mode 2. Fig. 10 (c) shows an example in which the standby time of the gate R/W2 is longer than that of the rack management R/W3 in the case of the random mode 3.

(example of performing a Standby Process after communication Process)

Next, an example in which the standby process is performed after the communication process is performed will be described. Fig. 11 is a flowchart showing a flow of communication processing with the RFID tag 4 in the gate R/W2 and the rack management R/W3 when the post-communication standby processing is performed. Since the basic communication processing flows of the gate R/W2 and the rack management R/W3 are the same, the gate R/W2 will be described as an example.

The processing of S11 to S14 is the same as the processing of S1 to S4 in the description relating to the flowchart shown in fig. 2, and therefore the description thereof is omitted. When the communication process in S14 is completed, the standby unit 26 in the RF communication unit 22 performs the post-communication standby process in S15. The start of the standby process after the communication process may be the end time of the communication period secured in the communication process, or may be the end time of the communication process required before the end time of the communication period.

Fig. 12 is a sequence diagram showing an example of a communication sequence when no radio wave is transmitted from another reader/writer in the case of performing the post-communication standby process.

In this example, first, the rack management R/W3 starts LBT. Since no radio wave from another reader/writer is detected in the LBT, the rack management R/W3 starts a communication process. The rack management R/W3 performs standby processing after the communication processing is completed. On the other hand, the gate R/W2 starts LBT with a slight delay from the rack management R/W3, and detects the radio wave from the rack management R/W3 in the middle of LBT. Therefore, the gate R/W2 performs standby processing.

Then, in the gate R/W2, LBT is performed again after the standby processing, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

On the other hand, in the rack management R/W3, after the first communication process is completed and the standby process is completed, LBT is performed to perform the second communication process. In the middle of the LBT, the rack management R/W3 detects the radio wave from the gate R/W2. Therefore, the rack management R/W3 performs standby processing. Then, LBT is performed again, and at this point, since no radio wave from another reader/writer is detected, communication processing is performed after LBT is completed.

As described above, the communication process is followed by the standby process, and thus there is a possibility that the other reader/writer obtains the communication right during the standby process. Therefore, the possibility that a specific reader/writer continuously secures the communication right can be reduced.

The standby time of the standby process after the communication process may be set to be shorter as the priority of the reader/writer is higher. Specifically, the average value of the standby time of the standby process after the communication process in the gate R/W2 may be set to be shorter than the average value of the standby time of the standby process after the communication process in the rack management R/W3. In this case, the possibility that the gate R/W2 acquires the communication right can be further increased. In addition, the standby time of the standby process after the communication process may be set to a fixed value or may be set to a random value, as in the standby time after the LBT.

The time for the standby process after LBT may be set equal for each reader/writer, and the time for the standby process after communication process may be set to be shorter as the priority of the reader/writer is higher. This also increases the possibility that the reader/writer with a high priority will obtain the communication right.

[ software-based implementation example ]

The control blocks (particularly, the upper communication unit 21, the RF communication unit 22, the upper communication unit 31, and the RF communication unit 32) of the gate R/W2 and the rack management R/W3 may be implemented by a logic circuit (hardware) formed in an integrated circuit (ic) chip or the like, or may be implemented by software.

In the latter case, the gate R/W2 and the rack management R/W3 include computers that execute instructions of programs as software for realizing the respective functions. The computer includes, for example, one or more processors, and includes a computer-readable recording medium storing the program. In the computer, the processor reads the program from the recording medium and executes the program, thereby achieving the object of the present invention. As the processor, for example, a Central Processing Unit (CPU) can be used. As the recording medium, a tape, a disk, a card, a semiconductor Memory, a programmable logic circuit, or the like can be used in addition to a "non-transitory tangible medium", such as a Read Only Memory (ROM), or the like. In addition, a Random Access Memory (RAM) or the like for expanding the program may be included. The program may be supplied to the computer via an arbitrary transmission medium (a communication network, a broadcast wave, or the like) through which the program can be transmitted. In addition, an embodiment of the present invention can be realized in the form of a data signal embedded in a carrier wave, the data signal embodying the program by electronic transmission.

(conclusion)

As described above, the communication system according to an embodiment of the present invention includes a plurality of readers/writers for performing at least one of reading and writing data from and to a plurality of RFID tags, and is configured as follows: each reader/writer includes a detection unit that detects an electric wave emitted when another reader/writer communicates with the RFID tag, and a standby unit that performs at least any one of the following processes: a process of starting a standby for a predetermined standby time in communication with the RFID tag of the communication target when the radio wave of the other reader/writer is detected before the communication with the RFID tag of the communication target; and a process of waiting for a predetermined waiting time after the communication process with the RFID tag of the communication target is completed; in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

In addition, a communication method of a communication system according to an embodiment of the present invention is a communication method of a communication system including a plurality of readers/writers for performing at least one of reading and writing data from and to a plurality of RFID tags, wherein each reader/writer includes a detection step of detecting radio waves emitted when another reader/writer communicates with an RFID tag and a standby step of performing at least one of the following processes: a process of starting a standby for a predetermined standby time in communication with the RFID tag of the communication target when the radio wave of the other reader/writer is detected before the communication with the RFID tag of the communication target; and a process of waiting for a predetermined waiting time after the communication process with the RFID tag of the communication target is completed; in the plurality of readers/writers, the average value of the standby time of the first reader/writer is set shorter than the average value of the standby time of the second reader/writer.

According to the structure or method, the average value of the standby time of the first reader/writer is set to be shorter than the average value of the standby time of the second reader/writer, and therefore the possibility that the first reader/writer acquires the communication right can be increased. Therefore, the priority of communication can be set higher for the first reader/writer than for the second reader/writer.

Since the priority can be set by setting the standby time of each reader/writer, control by a host system is not necessary, and the priority can be set without complicating the system.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby unit of the first reader/writer sets a standby time to 0.

According to the above configuration, the communication process can be started quickly with the highest priority of the first reader/writer and without standby time.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby section of the first reader/writer randomly determines a standby time from a range of T3 or more and T4 or less at each standby time.

According to the above configuration, for example, when a specific reader/writer performs communication in a predetermined communication cycle, the first reader/writer can be prevented from completely losing the opportunity to acquire the communication right because the communication cycle is equal to the standby time.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time.

According to the above configuration, for example, when a specific reader/writer performs communication in a predetermined communication cycle, the second reader/writer can be prevented from completely losing the opportunity to acquire the communication right due to the communication cycle and the standby time being equal to each other.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and the value of T4 is smaller than the value of T5.

According to the above configuration, the standby time of the first reader/writer is surely shorter than that of the second reader/writer, and therefore the priority of the first reader/writer can be surely increased.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and T4 is equal to T5.

According to the above configuration, the standby time of the first reader/writer and the standby time of the second reader/writer may be equal to each other depending on the situation, and in this case, the priorities of the first reader/writer and the second reader/writer may be equal to each other.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the standby section of the second reader/writer randomly determines a standby time from a range of T5 or more and T6 or less at each standby time, and the value of T4 is larger than the value of T5.

According to the above configuration, depending on the situation, the standby time of the first reader/writer may be longer than the standby time of the second reader/writer, and in this case, the priority of the first reader/writer may be lower than the priority of the second reader/writer. That is, the priority of the first reader/writer can be set weak.

In the communication system according to an embodiment of the present invention, the configuration may be such that: the first reader/writer is fixed in its own disposition position and communicates with the RFID tag passing through the communication area, and the second reader/writer communicates with the RFID tag not moving by moving itself.

In the structure, the first reader/writer needs to communicate with the mobile RFID tag for a limited time. On the other hand, the second reader/writer may communicate with RFID tags that are not moving, and there is no time limit. Therefore, in such a system, since the priority can be set to be appropriately high for the first reader/writer, the communication right can be given in a preferable state.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Description of the symbols

1：PLC

2: R/W for grid (first reader-writer)

3: R/W for rack management (second reader/writer)

4: RFID tag

5: conveying vehicle

21. 31: upper communication unit

22. 32: RF communication unit

23. 33: antenna with a shield

26. 36: standby machine part

27. 37: detection part

34: trigger switch

100: communication system