Communication system, communication method, and communication program

Abstract

To provide a communication system, a communication method, and a communication program with which it is possible to suppress a communication delay due to the effect of associating master station and slave stations.SOLUTION: In a communication system 10, a tag Tg transmits a search signal for identifying a destination controller 2 for the tag Tg when a prescribed event is detected. When a search signal is received, each controller 2 transmits, to a management server 1, a report including identification information of the controller 2, the identification information of the tag Tg, and the stability of the search signal. The management server 1 corrects, for each controller 2, the stability included in the report received from the controller 2, on the basis of the number of tags Tg associated with the controller 2, determines a destination controller 2 for the tag Tg from among a plurality of controllers 2 on the basis of the stability for each controller 2 after correction, and associates the tag Tg with the determined controller 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a communication system, a communication method, and a communication program.

Background Art

[0002] Conventionally, a communication method (TDMA; Time Division Multiple Access) is known in which one master station (also referred to as a controller, host, etc.) occupies one channel and communicates with a plurality of slave stations (also referred to as slaves) assigned to the master station in a time-division manner in order. For each slave station, a certain period immediately after receiving communication (transmission data) from the master station is assigned as the time during which communication with the host is possible. Each slave station is associated (linked) with one master station and communicates with the master station. Conventionally, a technique for determining one master station from a plurality of master stations and associating the determined master station with a slave station is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, a situation may occur in which slave stations are concentrated and associated with some of a plurality of master stations. For example, in the conventional technology, when a target slave station can communicate with each of a plurality of master stations, the master station with the highest communication stability is selected and the slave station is associated with the master station. In this method, a situation may occur in which the number of slave stations associated with some master stations becomes extremely large or small. And when slave stations are concentrated on some master stations, a problem of communication delay occurs.

[0005] An object of the present disclosure is to provide a communication system, a communication method, and a communication program capable of suppressing communication delay caused by the influence of the association between a parent station and a child station.

Means for Solving the Problems

[0006] A communication system according to an embodiment of the present disclosure is a system including a management server, a plurality of parent stations, and a plurality of child stations. When a target child station detects a predetermined event, the target child station transmits a search signal for identifying the parent station to which the target child station is connected. When each of the plurality of parent stations receives the search signal, the parent station transmits a report including the identification information of the parent station, the identification information of the target child station, and the stability of the search signal to the management server. The management server corrects the stability included in the report received from each parent station for each parent station based on the number of child stations associated with the parent station, and determines a target parent station to which the target child station is connected from among the plurality of parent stations based on the corrected stability for each parent station, and associates the target child station with the determined target parent station.

[0007] A communication method according to an embodiment of the present disclosure is a method in which a management server, a plurality of parent stations, and a plurality of child stations perform wireless communication. In the communication method, one or more processors transmit a search signal for identifying the parent station to which the target child station is connected when the target child station detects a predetermined event, transmit a report including the identification information of the parent station, the identification information of the target child station, and the stability of the search signal to the management server when each of the plurality of parent stations receives the search signal, correct the stability included in the report received from each parent station for each parent station based on the number of child stations associated with the parent station in the management server, determine a target parent station to which the target child station is connected from among the plurality of parent stations based on the corrected stability for each parent station, and associate the target child station with the determined target parent station.

[0008] A communication program according to an embodiment of the present disclosure is a program for a management server, a plurality of parent stations, and a plurality of child stations to perform wireless communication. When a predetermined event is detected in a target child station, the communication program transmits a search signal for identifying the parent station to which the target child station is connected. When each of the plurality of parent stations receives the search signal, it transmits a report including the identification information of the parent station, the identification information of the target child station, and the stability of the search signal to the management server. In the management server, for each parent station, the stability included in the report received from the parent station is corrected based on the number of child stations associated with the parent station. Based on the corrected stability for each parent station, a target parent station to which the target child station is connected is determined from among the plurality of parent stations, and the target child station and the determined target parent station are associated with each other. It is a program for causing one or more processors to execute the above steps.

Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a communication system, a communication method, and a communication program capable of suppressing communication delay caused by the association of parent stations and child stations.

Brief Description of the Drawings

[0010]

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[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following embodiments are an example of embodying the present disclosure and do not have the character of limiting the technical scope of the present disclosure.

[0012] FIG. 1 is a functional block diagram showing a schematic configuration of a communication system 10 according to an embodiment of the present disclosure.

[0013] The communication system 10 includes a management server 1, a controller 2, and a tag Tg. The communication system 10 is introduced, for example, into a work site (such as a factory or a warehouse) where an operator picks a target item from a storage shelf 3 (see FIG. 2) for storing items. The item is not particularly limited and includes items in various fields such as parts, retail products, drugs, books, documents, and sundries. In the present embodiment, as an example of the item, a part used for an assembly operation of a predetermined product (such as a vehicle or an electrical appliance) is taken as an example. That is, the communication system 10 in the present embodiment is introduced into a facility F1 (such as a factory) where an operator picks a target part from a storage shelf 3 for storing parts.

[0014] The management server 1 and the controller 2 are connected to each other via the network N1. The network N1 is a communication network such as the Internet, a LAN, a WAN, or a public telephone line. The controller 2 and the tag Tg are connected by this communication method using radio waves. The tag Tg is installed in each storage shelf 31 (see Fig. 2) of the storage shelf 3. As shown in Fig. 3A, the tag Tg includes a display unit (LCD) for displaying component names and the like, a lamp button B1 that lights up, blinks, and turns off in a plurality of colors, and a communication unit (not shown) that communicates with the controller 2. Further, the lamp button B1 has a button function as a user interface. The tag Tg can display predetermined information on the display unit or turn the lamp button B1 on and off according to an instruction (transmission data) from the controller 2. For example, an operator picks the parts in the storage shelf 31 where the tag Tg with the lit lamp button B1 is installed. The tag Tg notifies the controller 2 that the lamp button B1 has been pressed by this communication method, and the controller 2 notifies the management server 1 of it. If the tag Tg corresponds to the correct part, the management server 1 notifies the tag Tg corresponding to the part to be taken out next to blink the lamp button B1 at a predetermined cycle by this communication method via the controller 2. In Fig. 3A, the state where tag 1 is lit is shown. The management server 1 collectively controls each controller 2 and outputs a transmission instruction of transmission data (such as a lighting instruction for the tag Tg) to a predetermined controller 2 based on the information of the picking target.

[0015] A plurality of storage shelves 3 are arranged in the facility F1. A plurality of controllers 2 are installed dispersedly in the facility F1, and the plurality of controllers 2 communicate with the tags Tg of the plurality of storage shelves 3 arranged in the facility F1. In this way, the communication system 10 constructs a picking system for the facility F1 by controlling a plurality of tags Tg arranged in the facility F1 by a plurality of controllers 2. Specifically, the communication system 10 is a system that manages so that radio communication between the plurality of controllers 2 and the plurality of tags Tg is performed at a predetermined cycle.

[0016] The management server 1 functions as a mediation station that manages and controls the controller 2. The controller 2 functions as a host device, and the tag Tg functions as a slave device. The controller 2 is an example of the master station of the present disclosure, and the tag Tg is an example of the slave station of the present disclosure. Note that one or more of the plurality of controllers 2 may have the functions of the management server 1. That is, the management server 1 may be the controller 2.

[0017] [Management Server 1] As shown in FIG. 1, the management server 1 includes a control unit 11, a storage unit 12, an operation display unit 13, a communication unit 14, and the like. The management server 1 may be an information processing device such as a personal computer. Further, the management server 1 may be configured by a cloud server.

[0018] The communication unit 14 connects the management server 1 to the network N1 by wire or wirelessly, and executes data communication with the controller 2 via the network N1 according to a predetermined communication protocol.

[0019] The operation display unit 13 is a user interface including a display unit such as a liquid crystal display or an organic EL display that displays various information, and an operation unit such as a touch panel, a mouse, or a keyboard that accepts operations.

[0020] The storage unit 12 is a non-volatile storage unit such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory that stores various information. Data such as tag information D1 and related information D2 is stored in the storage unit 12.

[0021] FIG. 4 is a diagram showing an example of tag information D1. Information regarding all tags Tg arranged in the facility F1 is registered in the tag information D1. Specifically, the tag information D1 includes information such as a tag ID, location information, and part name. The tag ID is identification information of the tag Tg. The location information is the location information of the location where the tag Tg is installed, and is information such as the location of the storage shelf 3, the shelf number of the storage shelf 3 (storage shelf 31), and the coordinates on the map of the facility F1. The part name is the name of the part stored in the storage shelf 31 where the tag Tg is installed.

[0022] The tag information D1 is registered, for example, by the administrator of the facility F1. Also, the tag information D1 may be stored in a server different from the management server 1.

[0023] FIG. 5 is a diagram showing an example of related information D2. The related information D2 is information for identifying tags Tg associated with each of the plurality of controllers 2. Specifically, the related information D2 includes information such as a controller ID and a tag ID. The controller ID is identification information of the controller 2, and the tag ID is identification information of the tag Tg. In actuality, since the tag Tg with the most stable communication is associated with each controller 2, the ID of the tag Tg is random and has no regularity.

[0024] As shown in FIG. 6, a plurality of tags Tg are associated with one controller 2. Each controller 2 can communicate with a plurality of tags Tg, and each tag Tg can communicate with one controller 2. For example, controller A can communicate with the tags Tg within communication area AR1, and controller B can communicate with the tags Tg within communication area AR2. In practice, in order to ensure sufficient communication stability, as shown in FIG. 11, one tag Tg often falls within the communication areas AR of a plurality of controllers 2. Each tag Tg is associated with the controller 2 with the most stable communication among those plurality of controllers 2, but this results in an area where the radio waves of the plurality of controllers 2 interfere with each other as shown in FIG. 11. In this embodiment, five controllers 2 (controllers A to E) cover the entire working area of facility F1 and are configured to be able to communicate with all the tags Tg within facility F1. The related information D2 is registered by the processing of the control unit 11 (described later).

[0025] Further, the storage unit 12 may store picking information including the order of taking out parts, etc. The picking information is registered with information such as tag ID, position information, and picking status associated with each part to be picked. The management server 1 registers the information of the picking target in the picking information based on a picking instruction. Note that the management server 1 may obtain the picking instruction from a server that manages the manufacturing process of the product, or may generate the picking information based on the manufacturing process stored in the storage unit 12.

[0026] Also, the storage unit 12 stores control programs such as a communication program for causing the control unit 11 to execute the communication process (refer to FIG. 10) described later. For example, the communication program is non-temporarily recorded on a computer-readable recording medium such as a CD or DVD, and is read by a reading device (not shown) such as a CD drive or DVD drive electrically connected to the management server 1 and stored in the storage unit 12.

[0027] The control unit 11 has a control device such as a CPU. The CPU is a processor that executes various arithmetic processes. Then, the control unit 11 controls the management server 1 by executing various control programs stored in advance in the storage unit 12 with the CPU.

[0028] Specifically, the control unit 11 includes various processing units such as a related processing unit 111, an allocation processing unit 112, and a communication processing unit 113. Note that the control unit 11 functions as the various processing units by executing various processes according to the communication program with the CPU. Also, some or all of the processing units included in the control unit 11 may be configured by electronic circuits. Note that the communication program may be a program for causing a plurality of processors to function as the various processing units.

[0029] The related processing unit 111 executes a process (association process) of associating each of a plurality of tags Tg with any one of the plurality of controllers 2. Note that the "association" of associating the tag Tg with the controller 2 is also referred to as "linking" or "binding".

[0030] For example, as shown in FIG. 5, the association processing unit 111 associates a plurality of tags Tg up to the tag IDs “tg0001 to tg0100” arranged in the communication area AR1 with the controller A having the controller ID “c0001” arranged in the communication area AR1. Further, the association processing unit 111 associates a plurality of tags Tg up to the tag IDs “tg0101 to tg0200” arranged in the communication area AR2 with the controller B having the controller ID “c0002” arranged in the communication area AR2. Further, the association processing unit 111 associates a plurality of tags Tg up to the tag IDs “tg0201 to tg0300” arranged in the communication area AR3 with the controller C having the controller ID “c0003” arranged in the communication area AR3. Further, the association processing unit 111 associates a plurality of tags Tg up to the tag IDs “tg0301 to tg0400” arranged in the communication area AR4 with the controller D having the controller ID “c0004” arranged in the communication area AR4. Further, the association processing unit 111 associates a plurality of tags Tg up to the tag IDs “tg0401 to tg0500” arranged in the communication area AR5 with the controller E having the controller ID “c0005” arranged in the communication area AR5.

[0031] Note that the above association is the result of appropriately assigning numbers after associating with the controller 2 that provides the most stable communication for each tag Tg. The association processing unit 111 registers the information of the controller 2 and the tag Tg associated with each other in the association information D2 (see FIG. 5). A specific example of the above association processing will be described later.

[0032] The allocation processing unit 112 allocates each of the plurality of controllers 2 to each of a plurality of time segments (time slots) obtained by time-division of a predetermined cycle at a predetermined channel. For example, as shown in FIG. 7, when the cycle is "C1", the cycle C1 is divided into a plurality of time segments. Here, the cycle C1 is divided into five time segments t1 to t5. Also, here, it is assumed that a predetermined single channel CH1 is used. To the channel CH1, a number of controllers 2 capable of communicating with a plurality of tags Tg at a predetermined cycle are allocated. For example, the allocation processing unit 112 allocates controller A to the first time segment t1, controller B to the second time segment t2, controller C to the third time segment t3, controller D to the fourth time segment t4, and controller E to the fifth time segment t5.

[0033] The allocation processing unit 112 allocates controllers A to E to the time segments t1 to t5 in order for each cycle C1.

[0034] The communication processing unit 113 causes the controller 2 and the plurality of tags Tg associated with the controller 2 by the related processing unit 111 to communicate within the time segment in each of the plurality of time segments. A specific example of the communication method will be described with reference to FIG. 8.

[0035] In the example shown in FIG. 8, in the channel CH1, the cycle C1 is "200 ms" and the time width of each of the time segments t1 to t5 is "40 ms". The communication processing unit 113 outputs a transmission instruction for transmission data to the controller A in the first time segment t1 of the cycle C1. The transmission data is, for example, a beacon.

[0036] Here, as shown in FIG. 9, the transmission data includes information on a command (command information) for causing the tag Tg to execute a predetermined process and identification information (destination information) for identifying the tag Tg for which the command is to be executed. Specifically, the transmission data includes the destination information for each of a predetermined number of tags Tg and the command information for causing each of the predetermined number of tags Tg to execute a predetermined command. For example, FIG. 9 shows an example of the transmission data transmitted by the controller A. The communication processing unit 113 identifies five tags Tg (see FIG. 4) associated with five parts to be picked among a plurality of tags Tg associated with the controller A (see FIG. 5), and outputs a transmission instruction for the transmission data including the identified five tags 1 to 5 as destinations to the controller A.

[0037] That is, the communication processing unit 113 causes the controller A to transmit the transmission data to a predetermined number of tags Tg among the plurality of tags Tg associated with the controller A. Further, the controller A transmits the transmission data to a predetermined number of tags Tg that can communicate with the controller A within the time division.

[0038] When the controller A acquires the transmission instruction from the management server 1, in the first time division t1 (see FIG. 8), the controller A transmits the transmission data (see FIG. 9) to all the tags Tg (see FIG. 5) associated with the controller A.

[0039] When each tag Tg associated with controller A receives the transmission data, it checks the destination included in the transmission data and executes a predetermined process if a command addressed to itself is included. For example, when tag 1 receives the transmission data including a command addressed to itself to turn on lamp button B1 (see Fig. 3A), it turns on lamp button B1 (see Fig. 3A). Also, when tag 1 executes a command, it transmits a response (acknowledgment) to controller A. Similarly, when each of tags 2 to 5 receives the transmission data, since a command addressed to itself is included, it turns on lamp button B1 (see Fig. 3A) and transmits a response (acknowledgment) to controller A. Controller A receives responses from each of tags 1 to 5 (see Fig. 9). At this time, tags 1 to 5 appropriately transmit at timings where they do not collide with each other according to the position of the command addressed to themselves in the transmission data. In the present embodiment, each tag Tg transmits an acknowledgment response of the same size in the order in which the commands were included, and by leaving a time obtained by adding the time related to each acknowledgment response transmission and a predetermined margin amount, the respective acknowledgment response signals are prevented from colliding.

[0040] Also, in the present embodiment, it is designed such that after all five acknowledgment responses are transmitted within a time division, there remains a tag data reception period R1 (Fig. 9), and the tag Tg whose button function of the lamp has been pressed performs transmission by the CSMA / CA method during the subsequent tag data reception period R1. The tag data reception period R1 shown in Fig. 9 is an uplink period from tag Tg to controller 2 by the CSMA / CA method.

[0041] Note that the acknowledgment response is not limited to button press information, and may be the operation content if other user interfaces are provided. Also, if tag Tg has a sensor function, it may be configured to transmit spontaneously when the measured value satisfies a predetermined condition.

[0042] Controller A transmits the transmission data to Tags 1 to 5 in the first time segment t1 (40 ms) of the period C1 (200 ms). When the execution of the commands of Tags 1 to 5 is completed, the communication processing unit 113 outputs an instruction to transmit the transmission data to Controller B in the next second time segment t2 of the period C1 (200 ms) (see Fig. 8). The transmission data includes the destinations and commands of Tags 6 to 10.

[0043] When each tag Tg associated with Controller B receives the transmission data, it checks the destination included in the transmission data and executes a predetermined process if the command addressed to itself is included. For example, when Tag 6 receives the transmission data including the command to turn on the lamp button B1 (see Fig. 3A) addressed to itself, since the command addressed to itself is included, it turns on the lamp button B1 (see Fig. 3A). Also, when Tag 6 executes the command, it transmits a response (acknowledgment) to Controller B. Similarly, when each of Tags 7 to 10 receives the transmission data, since the command addressed to itself is included, it turns on the lamp button B1 (see Fig. 3A) and transmits a response (acknowledgment) to Controller B. Controller B receives responses from each of Tags 6 to 10.

[0044] Controller B transmits the transmission data to Tags 6 to 10 in the second time segment t2 (40 ms) of the period C1 (200 ms). When the execution of the commands of Tags 6 to 10 is completed, the communication processing unit 113 outputs an instruction to transmit the transmission data to Controller C in the next third time segment t3 of the period C1 (200 ms). The transmission data includes the destinations and commands of Tags 11 to 15 (see Fig. 8).

[0045] When each tag Tg associated with the controller C receives the transmission data, it checks the destination included in the transmission data and executes a predetermined process if a command addressed to itself is included. For example, when tag 11 receives the transmission data including a command addressed to itself to turn on the lamp button B1 (see FIG. 3A), since the command is addressed to itself, it turns on the lamp button B1 (see FIG. 3A). Also, tag 11 transmits a response (acknowledgment) to the controller C when the command is executed. Similarly, each of tags 12 to 15, when receiving the transmission data, turns on the lamp button B1 (see FIG. 3A) because a command addressed to itself is included, and transmits a response (acknowledgment) to the controller C. The controller C receives responses from each of tags 11 to 15 (see FIG. 8).

[0046] When the controller C transmits the transmission data to tags 11 to 15 in the third time segment t3 (40 ms) of the period C1 (200 ms), and when the execution of the commands of tags 11 to 15 is completed, the communication processing unit 113 outputs an instruction to transmit the transmission data to the controller D in the next fourth time segment t4 of the period C1 (200 ms). The transmission data includes destinations and commands for tags 16 to 20.

[0047] When each tag Tg associated with the controller D receives the transmission data, it checks the destination included in the transmission data and executes a predetermined process if a command addressed to itself is included. For example, when tag 16 receives the transmission data including a command addressed to itself to turn on the lamp button B1 (see FIG. 3A), since the command is addressed to itself, it turns on the lamp button B1 (see FIG. 3A). Also, tag 16 transmits a response (acknowledgment) to the controller D when the command is executed. Similarly, each of tags 17 to 20, when receiving the transmission data, turns on the lamp button B1 (see FIG. 3A) because a command addressed to itself is included, and transmits a response (acknowledgment) to the controller D. The controller D receives responses from each of tags 16 to 20 (see FIG. 8).

[0048] At the fourth time period t4 (40 ms) of cycle C1 (200 ms), controller D transmits the said transmission data to tags 16 to 20. When the execution of the commands of tags 16 to 20 is completed, at the next fifth time period t5 of cycle C1 (200 ms), the communication processing unit 113 outputs a transmission instruction of the transmission data to controller E. The said transmission data includes the destinations and commands of tags 21 to 25.

[0049] When each tag Tg associated with controller E receives the said transmission data, it checks the destination included in the said transmission data and executes a predetermined process if a command addressed to itself is included. For example, when tag 21 receives the said transmission data including a command addressed to itself to turn on lamp button B1 (see Fig. 3A), since a command addressed to itself is included, it turns on lamp button B1 (see Fig. 3A). Also, when tag 21 executes a command, it transmits a response (acknowledgment) to controller E. Similarly, when each of tags 22 to 25 receives the said transmission data, since a command addressed to itself is included, it turns on lamp button B1 (see Fig. 3A) and transmits a response (acknowledgment) to controller E. Controller E receives responses from each of tags 21 to 25 (see Fig. 8).

[0050] At the fifth time period t5 (40 ms) of cycle C1 (200 ms), controller E transmits the said transmission data to tags 21 to 25. When the execution of the commands of tags 21 to 25 is completed, at the first time period t1 of the next cycle C1 (200 ms), the communication processing unit 113 outputs a transmission instruction of the transmission data to controller A again. The said transmission data includes the destinations and commands of tags 1 to 5.

[0051] When each tag Tg associated with Controller A receives the transmission data, it checks the destination included in the transmission data and executes a predetermined process if a command addressed to itself is included. For example, when Tag 1 receives the transmission data including a command addressed to itself to turn on Lamp Button B1 (see FIG. 3A), since the command is addressed to itself, it turns on Lamp Button B1 (see FIG. 3A). Also, Tag 1 transmits a response (acknowledgment) to Controller A when the command is executed. Similarly, each of Tags 2 to 5, when receiving the transmission data, turns on Lamp Button B1 (see FIG. 3A) because a command addressed to itself is included, and transmits a response (acknowledgment) to Controller A. Controller A receives responses from each of Tags 1 to 5 (see FIG. 8).

[0052] As described above, in each of a plurality of time segments, the communication processing unit 113 causes Controller 2 and a plurality of tags Tg associated with the Controller 2 to communicate within the time segment. Also, the communication processing unit 113 outputs an instruction to transmit the transmission data to each of the plurality of Controllers 2 in the order of the time segments. Thereby, for example, each of Controllers A to E communicates with the tags Tg controlled by each controller in the order of time segments t1 to t5.

[0053] For example, after Controller A transmits the transmission data to five tags 1 to 5 among the plurality of tags Tg associated with Controller A in the first time segment t1, Controller B transmits the transmission data to five tags 6 to 10 among the plurality of tags Tg associated with Controller B in the second time segment t2 following the first time segment t1.

[0054] Also, after Controller A transmits the transmission data to Tags 1 to 5 in the first time segment t1 and Controller A receives responses from Tags 1 to 5, Controller B transmits the transmission data to Tags 6 to 10 in the second time segment t2.

[0055] Here, the control unit 11 executes a process of synchronizing (time synchronization) the management server 1 and each controller. Also, each controller 2 executes a process of synchronizing (time synchronization) with each corresponding tag Tg. As a result, each controller 2 transmits transmission data to the tag Tg at a predetermined cycle (for example, 200 ms), and each tag Tg receives the transmission data at a predetermined cycle (for example, 200 ms). For example, each tag Tg starts activation in accordance with the reception time of the transmission data and starts receiving the transmission data at the reception time. Also, each tag Tg completes the reception process at the transmission completion time of the transmission data in the controller 2 and performs time synchronization after the completion of the reception process. Each tag Tg sets a timer until the reception time of the next transmission data and waits (power save).

[0056] Note that time synchronization between the controllers 2 may be autonomously performed between the controllers 2 by, for example, the IEEE 1588 Precision Time Protocol. Also, the communication processing unit 113 may notify each controller 2 of the cycle C1 and the time intervals t1 to t5, and control each controller 2 to perform communication at the timings shown in FIG. 7.

[0057] [Communication Processing] Hereinafter, an example of the procedure of the communication process executed in the communication system 10 according to the present embodiment will be described with reference to FIG. 10.

[0058] Note that the present disclosure can be regarded as an invention of a communication method for executing one or more steps included in the communication process, and one or more steps included in the communication process described here may be appropriately omitted. Note that the execution order of each step in the communication process may be different as long as the same operational effects are produced. Furthermore, here, the case where each step in the communication process is executed by the management server 1 and the controller 2 is taken as an example for explanation, but a communication method in which a plurality of processors execute each step in the communication process in a distributed manner is also conceivable as another embodiment.

[0059] Here, the communication method shown in FIGS. 8 and 9 described above will be described by way of example. The control unit 11 of the management server 1 outputs a transmission instruction for transmission data (see FIG. 8) to each of controllers A to E assigned to each of five time segments t1 to t5 (each 40 ms) obtained by time-division of a predetermined cycle (200 ms) using a predetermined channel CH1.

[0060] First, when the first cycle (N = 1) starts (S1), in step S2, the control unit 11 determines whether the first time segment t1 has started. When the first time segment t1 starts (S2: Yes), in step S3, the control unit 11 outputs a transmission instruction for the transmission data to controller A. When controller A acquires the transmission instruction, it transmits the transmission data including a tag Tg (for example, tags 1 to 5) for executing a command to all tags Tg (see FIG. 5) associated with controller A.

[0061] Next, in step S4, the control unit 11 determines whether a response (acknowledgment response) of tag Tg has been received. For example, when tags 1 to 5 receive the transmission data and execute a command (lighting command) and transmit the response to controller A, controller A transmits the received response to the management server 1. As a result, the control unit 11 of the management server 1 receives the response. When the control unit 11 receives the response (S4: Yes), the process proceeds to step S5.

[0062] In step S5, the control unit 11 determines whether the second time segment t2 has started. When the second time segment t2 starts (S5: Yes), in step S6, the control unit 11 outputs a transmission instruction for the transmission data to controller B. When controller B acquires the transmission instruction, it transmits the transmission data including a tag Tg (for example, tags 6 to 10) for executing a command to all tags Tg (see FIG. 5) associated with controller B.

[0063] Next, in step S7, the control unit 11 determines whether it has received a response from tag Tg. For example, when tags 6 to 10 receive the transmission data, execute a command (lighting command), and send a response to controller B, controller B sends the received response to management server 1. As a result, the control unit 11 of management server 1 receives the response. When the control unit 11 receives the response (S7: Yes), the process proceeds to step S8.

[0064] In step S8, the control unit 11 determines whether the third time period t3 has started. When the third time period t3 starts (S8: Yes), in step S9, the control unit 11 outputs a transmission instruction for the transmission data to controller C. When controller C acquires the transmission instruction, it transmits the transmission data including tag Tg (for example, tags 11 to 15) for which a command is to be executed to all tag Tg associated with controller C (see FIG. 5).

[0065] Next, in step S10, the control unit 11 determines whether it has received a response from tag Tg. For example, when tags 11 to 15 receive the transmission data, execute a command (lighting command), and send a response to controller C, controller C sends the received response to management server 1. As a result, the control unit 11 of management server 1 receives the response. When the control unit 11 receives the response (S10: Yes), the process proceeds to step S11.

[0066] In step S11, the control unit 11 determines whether the fourth time period t4 has started. When the fourth time period t4 starts (S11: Yes), in step S12, the control unit 11 outputs a transmission instruction for the transmission data to controller D. When controller D acquires the transmission instruction, it transmits the transmission data including tag Tg (for example, tags 16 to 20) for which a command is to be executed to all tag Tg associated with controller D (see FIG. 5).

[0067] Next, in step S13, the control unit 11 determines whether it has received a response from the tag Tg. For example, when tags 16 to 20 receive the transmission data, execute a command (lighting command), and transmit a response to the controller D, the controller D transmits the received response to the management server 1. Thereby, the control unit 11 of the management server 1 receives the response. When the control unit 11 receives the response (S13: Yes), the process proceeds to step S14.

[0068] In step S14, the control unit 11 determines whether the fifth time segment t5 has started. When the fifth time segment t5 starts (S14: Yes), in step S15, the control unit 11 outputs a transmission instruction for the transmission data to the controller E. When the controller E acquires the transmission instruction, the controller E transmits the transmission data including the tag Tg (for example, tags 21 to 25) for which a command is to be executed to all the tags Tg (see FIG. 5) associated with the controller E.

[0069] Next, in step S16, the control unit 11 determines whether it has received a response from the tag Tg. For example, when tags 21 to 25 receive the transmission data, execute a command (lighting command), and transmit a response to the controller E, the controller E transmits the received response to the management server 1. Thereby, the control unit 11 of the management server 1 receives the response. When the control unit 11 receives the response (S16: Yes), the process returns to step S1.

[0070] When returning to step S1, the second cycle (N = 2) starts. In step S2, the control unit 11 determines whether the first time segment t1 has started. When the first time segment t1 starts (S2: Yes), in step S3, the control unit 11 outputs a transmission instruction for the transmission data to the controller A. When the controller A acquires the transmission instruction, the controller A transmits the transmission data including the tag Tg (for example, tags 1 to 5) for executing the command to all the tags Tg (see FIG. 5) associated with the controller A. Thereafter, the above-described processing is the same. In this way, the communication system 10 executes the communication process.

[0071] As described above, the communication system 10 according to the present embodiment is a communication system in which a plurality of controllers 2 (parent stations) and a plurality of tags Tg (child stations) perform wireless communication at a predetermined cycle. Further, the communication system 10 associates each of the plurality of tags Tg with any one of the plurality of controllers 2. Further, the communication system 10 assigns each of the plurality of controllers 2 to each of a plurality of time segments (time slots) obtained by time-division of the predetermined cycle in a predetermined channel. Further, in each of the plurality of time segments, the communication system 10 causes the controller 2 and the plurality of tags Tg associated with the controller 2 to communicate within the time segment.

[0072] In the above configuration, each controller 2 uses radio waves only during the time segment (40 ms) of the cycle (for example, 200 ms). Further, by allocating (adjusting) so that the radio wave usage times between the controllers 2 do not overlap, one channel (CH1) can be shared by up to five controllers 2. Thereby, even in a state where the communication areas AR of each other overlap as shown in FIG. 11, it becomes possible to install a large number of controllers 2. For example, if the number of frequency channels is 20, it becomes possible to install 100 controllers 2, which is five times the number of channels, even in an area where radio waves interfere with each other.

[0073] In addition, depending on the factory layout and the type of each line, there may be a case where it is desired to allocate while being aware of the maximum number of channels that can be shared by each controller 2. In such a case, as shown in FIG. 12, a display screen (UI) may be provided that can map the numbers of each controller (here, "1" to "64" as an example) to a table with axes of time slots (slot numbers) and channels (frequency channels) set vertically and horizontally for setting. That is, the control unit 11 may visually display each of the predetermined channels and the predetermined time intervals assigned to each of the plurality of controllers 2 (parent stations) so as to be distinguishable.

[0074] Further, the transmission data includes destination information of a plurality of tags Tg. According to the above configuration, using one channel, in each cycle, in each time interval assigned to a plurality of controllers 2, each controller 2 can communicate with a plurality of tags Tg. Therefore, a large number of tags Tg can be installed over a wide range. Also, in the communication system 10, the communication volume can be increased. Thus, it is possible to install a large number of tags Tg while ensuring high-speed responsiveness of communication between the controller 2 and the tag Tg.

[0075] In the communication system 10 according to the present embodiment, a plurality of controllers 2 (parent stations) synchronize with each other in time and communicate within the time interval assigned by the allocation processing unit 112. Also, the plurality of controllers 2 may be connected to each other by wired communication.

[0076] Further, when data to be transmitted is generated in the tag Tg (slave station), the communication processing unit 113 causes the controller 2 to which the tag Tg is associated to transmit the data within the time interval assigned to the controller 2.

[0077] Also, the data to be transmitted in the tag Tg is data observed by the tag Tg. Further, the data observed by the tag Tg is data corresponding to the operation content of the user interface of the tag Tg.

[0078] The present disclosure is not limited to the above-described embodiments and may be the following embodiments. For example, the communication system 10 may include a plurality of channels. In this case, the allocation processing unit 112 allocates each of the plurality of controllers 2 to each of the plurality of time divisions for each channel. Thereby, for example, five controllers A to E share channel CH1, five controllers F to J share channel CH2, five controllers K to O share channel CH3, five controllers P to T share channel CH4, and five controllers U to Y share channel CH5. Each controller 2 communicates with a plurality of tags Tg in each of the plurality of time divisions obtained by time-dividing a predetermined period as in the above-described embodiment. According to this configuration, since the number of installed controllers 2 can be increased according to the number of available channels, it becomes possible to install more tags Tg.

[0079] In the above-described embodiment, an example in which a cycle of 200 ms is divided into five 40-ms slots is shown, but this is just an example. The cycle, the number of divisions, and the slot time may be appropriately set in consideration of the time responsiveness, power consumption, number of slave stations, number of available frequency channels, communication speed, etc. required for each application.

[0080] In the above-described embodiment, the management server 1 (arbitration station) controls a plurality of controllers 2. However, as another embodiment, a specific controller 2 among the plurality of controllers 2 may also have the functions of the management server 1. In this case, the specific controller 2 functions as a master controller, and the other controllers 2 function as slave controllers. The master controller executes an allocation process of allocating each of the plurality of slave controllers to each of the plurality of time segments in a predetermined channel, and a communication process of causing the slave controller and the plurality of tags Tg to communicate in each of the plurality of time segments. The master controller transmits the transmission data to each slave controller in the order of the time segments. Note that the controller 2 functioning as the master controller may be appropriately changed according to the communication status in the entire communication system 10 and the like.

[0081] [Association process] Hereinafter, a specific example of the association process will be described.

[0082] For example, among the plurality of tags Tg, the tag Tg1 (an example of the target slave station of the present disclosure) transmits a search signal including the identification information (tag ID) of the tag Tg1 in order to identify the controller 2 (an example of the target master station of the present disclosure) to which the tag Tg1 is connected. When each of the plurality of controllers 2 receives the search signal transmitted from the tag Tg1, it transmits an analysis report including its own identification information (controller ID), the identification information (tag ID) of the tag Tg1, and signal information regarding the search signal (for example, the reception intensity of the search signal) to the management server 1. The management server 1 determines the controller 2 (for example, controller A) corresponding to the tag Tg1 from among the plurality of controllers 2 based on the plurality of analysis reports received from the plurality of controllers 2, and associates the tag Tg1 and the controller A with each other. The communication system 10 executes the above process for each tag Tg to associate each tag Tg with any one controller 2.

[0083] FIG. 13 shows a specific example of the association process of the target tag Tg (target tag Tg) associated with any one of the controllers 2. Here, it is assumed that a cycle of 200 ms is divided into 16 slots of 12.5 ms. That is, it is assumed that one frequency channel can be shared by a maximum of 16 controllers.

[0084] FIG. 14 shows an example of the procedure for the association process among the management server 1, the plurality of controllers 2, and the target tag Tg. Note that in FIG. 13, step numbers (s1, s5, s6, s9, s10) corresponding to the processing steps in FIG. 14 are added. For example, when a new tag Tg (target tag Tg) is placed, the association process is executed.

[0085] In FIG. 13, for example, controller A transmits transmission data (commands) to a predetermined number (maximum 5) of tags Tg among the plurality of tags Tg already associated with controller A in the operation channel (Operation channel) where a slot of "12.5 ms" is set. Controller A switches the "187.5 ms" excluding "12.5 ms" out of "200 ms" to the search channel. Controller A becomes capable of receiving (in a reception standby state) the search signal transmitted from the target tag Tg in the search channel. Controller B and other controllers also have the same configuration as controller A.

[0086] In the above-mentioned association process, first, the target tag Tg transmits a search signal (step s1 in FIG. 14). Specifically, the target tag Tg transmits a search signal when it receives a predetermined user operation. For example, when the user presses the bottom button E1 of the target tag Tg (see FIG. 3B), the target tag Tg receives the user's pressing operation and transmits a search signal. The target tag Tg transmits the search signal on the search channel. Also, the target tag Tg transmits the search signal multiple times at time intervals (for example, an interval of "15 ms") longer than the slot time (here, "12.5 ms") in the time-division communication assigned to each controller 2. Here, the target tag Tg transmits the search signal four times at an interval of "15 ms" on the search channel. In this way, the controller 2 performs time-division communication with the tag Tg, and the tag Tg transmits the search signal multiple times at a time interval longer than the slot time in the time-division communication. By making the transmission interval of the search signal longer than the slot time, all the controllers 2 can receive the search signal at least multiple times.

[0087] Each of the plurality of controllers 2 receives the search signal transmitted from the target tag Tg in the reception standby state of the search channel. For example, among all the controllers 2 installed in the facility F1, a plurality of controllers 2 installed at locations where the signal from the target tag Tg reaches receive the search signal.

[0088] When each of the plurality of controllers 2 receives the search signal, it transmits an analysis report including the identification information of the controller 2 (controller ID), the identification information of the tag Tg (tag ID), and the signal information regarding the search signal (e.g., reception intensity) to the management server 1 (step s2 in FIG. 14). Further, the analysis report includes the time when the search signal was received and the number of the search signal (information indicating which one it is among the four transmissions when the number of transmissions is four). Based on this, the management server 1 can obtain the reception start time when the tag Tg starts receiving on the announce channel. Since it is desirable that the target tag Tg be associated with a controller 2 with sufficiently stable communication, the controller 2 may be configured not to transmit an analysis report corresponding to the search signal with a reception intensity below a predetermined value.

[0089] When the management server 1 receives the analysis report from each controller 2, it determines the controller 2 to be associated with the target tag Tg (step s3 in FIG. 14). Specifically, the association processing unit 111 of the management server 1 determines the controller 2 to be associated with the target tag Tg based on the stability (communication stability) of the search signal. For example, the association processing unit 111 tabulates the analysis reports corresponding to the target tag Tg and, when it has received, for example, three or more of all the search signals from the first to the last (here, the fourth), determines the controller 2 with the most stable search signal. The association processing unit 111 calculates the stability of the search signal based on the average value of the signal intensities of the search signal. Further, the association processing unit 111 may calculate the stability of the search signal based on the average value of the signal intensities of the search signal, the minimum intensity, the variance of the signal intensities, etc.

[0090] Further, the association processing unit 111 calculates the stability of the search signal based on the number (total number) of tags Tg already associated (linked) with each controller 2. Specifically, the association processing unit 111 corrects the average value of the signal strength of the search signal in each controller 2 with a correction value corresponding to the total number of tags Tg associated with each controller 2, and calculates the corrected average value as the stability of the search signal. For example, for each of the plurality of controllers 2 capable of communicating with the target tag Tg, the association processing unit 111 calculates the average value of the signal strength of the search signals transmitted from the plurality of tags Tg associated with the controller 2, and calculates a correction value based on the following formula (1). Correction value = 10 - (total number of tags Tg associated with the target controller 2 / 10) ··· (1)

[0091] Here, the maximum value of the signal strength received by the controller 2 from the tag Tg is set to "100", and the minimum value is set to "0". The correction coefficient "10" in the above formula (1) is an example and is set according to the maximum value of the signal strength.

[0092] The association processing unit 111 calculates, for each of the plurality of controllers 2 capable of communicating with the target tag Tg, the value obtained by summing the average value and the correction value as the stability of the search signal. In this way, the association processing unit 111 calculates the stability corresponding to the number of tags Tg associated with each controller 2 for each controller 2 capable of communicating with the target tag Tg. Then, the association processing unit 111 determines the controller 2 with the largest calculated stability (stability after correction) among the plurality of controllers 2 capable of communicating with the target tag Tg.

[0093] As another embodiment, the association processing unit 111 may determine a specific controller 2 with a stability of the search signal equal to or higher than a threshold value as an association candidate, and calculate the stability for the determined controller 2 of the association candidate. For example, for each of a plurality of controllers 2 that are association candidates and can communicate with the target tag Tg, the association processing unit 111 calculates an average value of signal strengths of search signals transmitted from a plurality of tags Tg associated with the controller 2, and calculates a correction value based on the following formula (2). Correction value = 20 - ((total number of tags Tg associated with the target controller 2 / total number of tags Tg associated with the controller 2 of the association candidate) × 20) ··· (2)

[0094] Note that the correction coefficient "20" in the above formula (2) is an example and is set according to the maximum value of the signal strength (here, "100").

[0095] The association processing unit 111 calculates the stability (communication stability) of the search signal for each controller 2 that can communicate with the target tag Tg by any of the above correction methods (correction by the above formula (1) or correction by the above formula (2)), and determines one controller 2 corresponding to the target tag Tg.

[0096] When the association processing unit 111 determines the controller 2, it transmits an association schedule (Bind schedule) for associating the target tag Tg to the controller 2 (step s4 in FIG. 14). Here, the association processing unit 111 determines the controller B as the controller 2 for associating the target tag Tg, and transmits the association schedule to the controller B. The association schedule includes at least the address of the controller B and the reception start time (the time 1 second after the time when the last search signal was transmitted) at which the target tag Tg starts reception on the announce channel. Note that it is preferable to perform the transmission process of the association schedule within a predetermined time immediately after the slot time, because the possibility of colliding with the search signals transmitted at 15 ms intervals is reduced.

[0097] When the controller B that has received the association plan from the management server 1 reaches the reception start time included in the association plan, it transmits an association instruction (Bind instruction) addressed to the target tag Tg on the announcement channel (step s5 in FIG. 14). The association instruction includes at least the address of the target tag and the address of the controller B to be associated, and when there are multiple operation channels, it includes information on the operation channel assigned to the controller B.

[0098] At the reception start time, the target tag Tg receives the association instruction on the announcement channel. When the target tag Tg receives the association instruction addressed to its own address, it switches to the specified operation channel and periodically receives the beacon (which may include a command for a lighting instruction) output by the controller B. When the target tag Tg receives a command addressed to itself after switching to the operation channel, it executes the command and returns an acknowledgement signal to the controller B (step s6 in FIG. 14).

[0099] When the controller B receives the acknowledgement signal from the target tag Tg, it transmits an acknowledgement notice to the management server 1 (step s7 in FIG. 14). When the management server 1 receives the acknowledgement notice from the controller B, it returns a completion instruction to the controller B (step s8 in FIG. 14). When the controller B receives the completion instruction from the management server 1, it transmits a completion display instruction to the target tag Tg (step s9 in FIG. 14).

[0100] When the target tag Tg receives the completion display instruction from the controller B, it returns an acknowledgement signal to the controller B (step s10 in FIG. 14) and performs a completion display (step s11 in FIG. 14). For example, the target tag Tg lights up the lamp button B1 (see FIG. 3A).

[0101] Finally, the management server 1 registers the association information between the target tag Tg and the controller B in the association information D2 (see FIG. 5) (step s12 in FIG. 14). Note that the registration to the management server 1 may be performed at the time when the management server 1 receives the confirmation notification described above (step s7 in FIG. 14).

[0102] The communication system 10 executes the above-described processing for each tag Tg to associate one controller 2 with each tag Tg. In this way, the management server 1 notifies at least the identifier or communication channel of the controller B to the target tag Tg, and the target tag Tg communicates with the controller B based on at least the identifier or communication channel of the controller B. Also, in the communication system 10, the channel through which the target tag Tg transmits the search signal is different from the channel through which the target tag Tg communicates with the controller B after being associated with the controller B.

[0103] [Association processing flow] Hereinafter, an example of the procedure of the association processing executed in the communication system 10 according to the present embodiment will be described with reference to FIGS. 15 to 17. FIG. 15 shows an example of the procedure of the association processing executed in the target tag Tg, FIG. 16 shows an example of the procedure of the association processing executed in the controller 2, and FIG. 17 shows an example of the procedure of the association processing executed in the management server 1.

[0104] [Association processing in the target tag Tg] The newly added target tag Tg is initially in a substantially idle state, and in step S21 shown in FIG. 15, it is determined whether the bottom button E1 has been pressed. When the bottom button E1 of the target tag Tg is pressed (S21: Yes), it enters the operating state and the process proceeds to step S22. The target tag Tg waits in the idle state until the bottom button E1 is pressed (S21: No).

[0105] In step S22, the target tag Tg switches to the search channel. In the subsequent step S23, the target tag Tg transmits the search signal a plurality of times at a predetermined interval (step s1 in FIG. 14). For example, the target tag Tg transmits the search signal four times at an interval of "15 ms" on the search channel. The target tag Tg waits until a predetermined time (1 second) elapses after transmitting the last (fourth) search signal (S24).

[0106] Next, in step S25, the target tag Tg switches from the search channel to the announcement channel. Next, in step S26, the target tag Tg attempts to receive the association instruction from the controller 2 (controller B determined by the management server 1) for 500 ms. When the target tag Tg receives the association instruction (S26: Yes) (step s5 in FIG. 14), the process proceeds to step S27. On the other hand, when the target tag Tg does not receive the association instruction within the above 500 ms (S26: No), the process proceeds to step S21.

[0107] In step S27, the target tag Tg switches from the announcement channel to the operation channel specified by the association instruction, and receives the beacon from the controller B while synchronizing based on the address of the controller B obtained from the association instruction.

[0108] Next, in step S28, the target tag Tg determines whether it has received a command addressed to itself from the controller B. When the target tag Tg receives a command addressed to itself from the controller B (S29: Yes), the process proceeds to step S30. On the other hand, when the target tag Tg does not receive a command addressed to itself from the controller B (S29: No), the process proceeds to step S21.

[0109] Next, in step S30, the target tag Tg transmits the confirmation signal to controller B (step s6 in FIG. 14). Thereafter, when the target tag Tg receives the completion display instruction from controller B, it returns the confirmation signal to controller B and lights up the lamp button B1 (see FIG. 3A) (S30) (steps s9, s10 in FIG. 14).

[0110] [Association Processing in Controller 2] In step S31 shown in FIG. 16, controller 2 (here, taking controller B as an example) sets it to the operation channel assigned to itself. Next, in step S32, controller B executes the operation process instructed by management server 1. For example, controller B transmits transmission data (command) to a predetermined number of tags Tg among the plurality of tags Tg that have already been associated.

[0111] Next, when the predetermined operation time (slot time “12.5 ms”) ends (S33: Yes), controller B transfers the process to step S34.

[0112] In step S34, controller B determines whether or not the reception start time at which the target tag Tg starts reception on the announcement channel (the time 1 second after the time when the target tag Tg transmitted the last search signal) has arrived. When the reception start time arrives (S34: Yes), controller B switches from the operation channel to the announcement channel (S35) and transmits the association instruction to the target tag Tg (S36) (step s5 in FIG. 14). When the reception start time has not arrived (S34: No), controller B transfers the process to step S37.

[0113] In step S37, the controller B switches from the announcement channel to the search channel. Next, in step S38, the controller B determines whether it has received the search signal from the target tag Tg. When the controller B receives the search signal (S38: Yes), it transfers the process to step S39. When the controller B does not receive the search signal (S38: No), it transfers the process to step S40.

[0114] In step S39, the controller B transmits the analysis report to the management server 1 (step s2 in FIG. 14). For example, the controller B transmits four copies of the analysis report to the management server 1.

[0115] Next, in step S40, the controller B determines whether the operation start time has arrived. When the operation start time arrives (S40: Yes), it returns to step S31 and switches to the operation channel. The controller B repeats the processes of steps S38 and S39 until the operation start time arrives (S40: No). Each controller 2 repeatedly executes the above-described process.

[0116] [Association process in management server 1] In step S41 shown in FIG. 17, the management server 1 determines whether it has received the analysis reports from a plurality of controllers 2. For example, the management server 1 receives a plurality (three to four search signals' worth) of the analysis reports from the controller B.

[0117] When the management server 1 receives a plurality of the analysis reports from a plurality of controllers 2 (S41: Yes), it aggregates the plurality of the analysis reports (S42), and determines the controller 2 to be associated with the target tag Tg (S43 to S47) (step s3 in FIG. 14).

[0118] For example, for each controller 2, the management server 1 calculates the average value of the signal strengths of the plurality of search signals (S45), and calculates a correction value for the average value (S46). Specifically, the management server 1 calculates the correction value according to the above-described formula (1).

[0119] In step S46, the management server 1 calculates, as the stability (communication stability) of the search signal corresponding to the controller 2, the value obtained by adding the average value corresponding to the controller 2 and the correction value. The management server 1 calculates, as the stability of the search signal, for each of the plurality of controllers 2 capable of communicating with the target tag Tg. When the management server 1 calculates the stability for each of the plurality of controllers 2 capable of communicating with the target tag Tg (S43: Yes), the process proceeds to step S47.

[0120] In step S47, the management server 1 determines one controller 2. For example, the management server 1 determines the controller 2 (here, controller B) having the largest calculated stability among the plurality of controllers 2 capable of communicating with the target tag Tg.

[0121] Next, in step S48, the management server 1 transmits a binding plan for associating the target tag Tg to the determined controller 2 (here, controller B) (step s4 in FIG. 14).

[0122] Upon receiving the binding plan, the controller B transmits a binding instruction to the target tag Tg to perform the association with the target tag Tg. This process corresponds to the communication process of step S36 in FIG. 16.

[0123] When the confirmation of the association between the target tag Tg and the controller B is completed, the management server 1 registers the association information between the target tag Tg and the controller B in the association information D2 (see FIG. 5) (S49) (step s12 in FIG. 14). The management server 1 repeatedly executes the above-described process each time it receives the analysis report from the controller 2.

[0124] As another embodiment, when the management server 1 calculates the correction value according to the above-described formula (2), the management server 1 executes the process shown in FIG. 18. In the process shown in FIG. 18, steps S51 and S52 are added to the process shown in FIG. 17.

[0125] In step S51, the management server 1 determines a specific controller 2 whose stability (communication stability) of the search signal is equal to or higher than a threshold value as an association candidate (connection destination candidate). For example, the management server 1 determines, as an association candidate, a controller 2 for which the average value of the signal strengths of the search signals corresponding to each controller 2 is equal to or higher than the threshold value.

[0126] In step S52, the management server 1 determines whether there is an associated candidate controller 2. When there is an associated candidate controller 2 (S52: Yes), the management server 1 shifts the process to step S43 and executes the processes of steps S43 to S46 described above for each associated candidate controller 2. On the other hand, when there is no associated candidate controller 2 (S52: No), the management server 1 shifts the process to step S47.

[0127] In step S47, the management server 1 determines one controller 2. When there is an associated candidate controller 2 (S52: Yes), the management server 1 determines the controller 2 having the highest stability among the associated candidate controllers 2. On the other hand, when there is no associated candidate controller 2 (S52: No), the management server 1 determines the controller 2 having the highest average value of the signal strengths of the search signals corresponding to each controller 2 among the controllers 2 whose average value of the signal strengths is less than the threshold value.

[0128] The management server 1 may adopt the process shown in FIG. 17 or the process shown in FIG. 18. Further, the management server 1 may be configured to be able to switch between the process shown in FIG. 17 and the process shown in FIG. 18.

[0129] [Relocation of Tag Tg] In the above-described embodiment, when a new tag Tg is added (arranged), a configuration is shown for determining the controller 2 to which the tag Tg is connected. As another embodiment, the management server 1 may be configured to re-associate (re-link) a tag Tg (already associated tag Tg) that is already associated with any one of the controllers 2.

[0130] Hereinafter, an example of re-executing the association process for the target tag Tg will be described. For example, in the arrangement shown in FIG. 19A, it is assumed that 50 tags Tg are associated with controller A and 50 tags Tg are associated with controller B. Also, a part of communication area AR1 and communication area AR2 overlaps, and 50 tags Tg are arranged in the overlapping communication area, and 25 of them are associated with controller A and the other 25 are associated with controller B.

[0131] Here, when a new controller C is added and a part of the communication area AR3 of the controller C overlaps with a part of each of the communication areas AR1 and AR2, the management server 1 executes the association process again. For example, when the total number of tags Tg associated with the target controller 2 is equal to or more than a predetermined number and the ratio of the total number of tags Tg to the total number of the controllers 2 is equal to or more than a predetermined ratio, the association process for the tags Tg associated with the target controller 2 is sequentially re-done. Note that the association processing unit 111 sequentially re-does the association process for a plurality of tags Tg associated with the target controller 2, and when the above conditions are no longer satisfied (when the total number of tags Tg associated with the target controller 2 becomes less than the predetermined number, or when the ratio of the total number of tags Tg to the total number of the controllers 2 becomes less than the predetermined ratio), the re-association process for other tags Tg may be omitted.

[0132] In the example shown in FIG. 19A, when the total number of tags Tg associated with controller A (50 units) is equal to or greater than a predetermined number and the ratio (= 100 units ÷ 3) is equal to or greater than a predetermined ratio, the association processing unit 111 re-executes the association process for each tag Tg associated with controller A. Similarly, when the total number of tags Tg associated with controller B (50 units) is equal to or greater than a predetermined number and the ratio (= 100 units ÷ 3) is equal to or greater than a predetermined ratio, the association processing unit 111 re-executes the association process for each tag Tg associated with controller B. The association processing unit 111 re-determines controller 2 for each tag Tg using the correction method of the above-described formula (1) or formula (2). When the associated controller 2 is changed, the association processing unit 111 updates the association information D2 (see FIG. 5). For example, when the association processing unit 111 determines the connection destination to be controller C by re-doing the association process for the tags Tg associated with controller A and the tags Tg associated with controller B, the connection destination of the tag Tg is updated to controller C.

[0133] According to the above configuration, by adding controller C, as shown in FIG. 19B for example, the number of tags Tg associated with controller A changes from 50 units to 35 units, the number of tags Tg associated with controller B changes from 50 units to 35 units, and the number of tags Tg associated with controller C becomes 30 units. As a result, the number of tags Tg associated with each controller is smoothed.

[0134] FIG. 20A shows another example of re-executing the association process. For example, in the arrangement shown in FIG. 20A, assume that 50 tags Tg are associated with controller A and 50 tags Tg are associated with controller B. Also, assume that a part of communication area AR1 and communication area AR2 overlaps, and 50 tags Tg are arranged in the overlapping communication area, 25 of which are associated with controller A and the other 25 are associated with controller B.

[0135] Here, when Controller B temporarily stops wave transmission (halts radio wave transmission), each of the 50 tags Tg associated with Controller B transmits a search signal, and the association processing unit 111 searches for connection destinations for the 50 tags Tg. Then, the association processing unit 111 associates 25 of the 50 tags Tg included in the communication area AR1 with Controller A. As a result, as shown in FIG. 20B, 75 tags Tg are associated with Controller A.

[0136] When Controller B resumes radio wave transmission after returning from the wave stop state, if the total number of tags Tg associated with Controller A (75) is equal to or greater than a predetermined number and the ratio (= 100 units ÷ 2) is equal to or greater than a predetermined ratio, the association processing unit 111 re-executes the association process for each tag Tg associated with Controller A. The association processing unit 111 re-determines Controller 2 for each tag Tg using the correction method of the above-described formula (1) or formula (2). When the associated Controller 2 is changed, the association information D2 (see FIG. 5) is updated. For example, when the association processing unit 111 determines the connection destination to be Controller B by re-doing the association process for the tags Tg associated with Controller A, the connection destination of the tag Tg is updated to Controller B.

[0137] According to the above configuration, when Controller B returns after the wave stop, as shown in FIG. 20C for example, the number of tags Tg associated with Controller A changes from 75 to 60, and the number of tags Tg associated with Controller B changes from 0 to 40. As a result, the number of tags Tg associated with each controller is smoothed.

[0138] In addition, in the configuration shown in FIGS. 20A to 20C, the association processing unit 111 may preferentially select the tag Tg that is the re - execution target of the association process as the tag Tg that was associated with the controller B before the wave stop. For example, when the controller B returns, the association processing unit 111 preferentially selects the tag Tg that was associated with the controller B before the wave stop and is arranged in the communication area AR1 and the communication area AR2, and re - executes the association process.

[0139] FIG. 21A shows another example of executing the re - association process. For example, in the arrangement shown in FIG. 21A, assume that 50 tags Tg are associated with the controller A and 50 tags Tg are associated with the controller B. Also, a part of the communication area AR1 and the communication area AR2 overlaps, and 50 tags Tg are arranged in the overlapping communication area. Among them, 25 tags Tg are associated with the controller A and the other 25 tags Tg are associated with the controller B.

[0140] Here, when 25 tags Tg associated with the controller B are removed, as shown in FIG. 21B, the number of tags Tg associated with the controller B decreases from 50 to 25, and a bias occurs in the number of tags Tg associated with the controller A.

[0141] In this case, when the total number of tags Tg associated with controller A (50 units) is equal to or greater than a predetermined number and the ratio (= 100 units ÷ 2) is equal to or greater than a predetermined ratio, the related processing unit 111 will execute the association process again for each tag Tg associated with controller A. The related processing unit 111 re - determines controller 2 for each tag Tg using the correction method of formula (1) or formula (2) described above. When the associated controller 2 is changed, the related information D2 (see Figure 5) is updated. For example, when the related processing unit 111 determines that the connection destination is controller B for the tag Tg associated with controller A by re - performing the association process, the connection destination of the tag Tg is updated to controller B.

[0142] According to the above configuration, for example, as shown in Figure 21C, the number of tags Tg associated with controller A changes from 50 units to 40 units, and the number of tags Tg associated with controller B changes from 25 units to 35 units. As a result, the number of tags Tg associated with each controller is smoothed.

[0143] As described above, the management server 1 re - performs the association process for the tags Tg that have already been associated with any of the controllers 2.

[0144] Here, if the association process is re - performed frequently, problems such as increased power consumption for transmitting search signals from the tag Tg and shortened battery life of the tag Tg, and the inability to issue commands to the tag Tg (such as the lighting command of the tag Tg) during the association process, resulting in a decrease in the efficiency of operations (such as picking operations), will occur.

[0145] Therefore, in order to solve the above problems, the management server 1 may further have the following configurations (the first configuration example to the third configuration example).

[0146] As a first configuration example, when the association processing unit 111 executes the association processing for the target tag Tg, it stores all the controllers 2 with a stability equal to or higher than the threshold as stably connectable controllers 2. Then, for each of the plurality of controllers 2 to which the target tag Tg can be connected, the association processing unit 111 calculates the total number of associated tags Tg, and when the difference in the total number for each controller 2 is equal to or more than a predetermined number, it executes the association processing for the target tag Tg. When a new controller 2 is added, or when a controller 2 resumes operation after being stopped, the association processing unit 111 executes the association processing for the target tag Tg regardless of the above condition (when the difference in the total number is equal to or more than a predetermined number).

[0147] As a second configuration example, when a predetermined time (for example, 10 days) has elapsed since the previous execution of the association processing for the target tag Tg, the association processing unit 111 executes the association processing for the target tag Tg. When a new controller 2 is added, or when a controller 2 resumes operation after being stopped, the association processing unit 111 executes the association processing for the target tag Tg regardless of the above condition (when a predetermined time has elapsed). Also, when a communication delay occurs, the association processing unit 111 executes the association processing for the target tag Tg regardless of the above condition (when a predetermined time has elapsed).

[0148] As a third configuration example, the association processing unit 111 does not execute the association processing for the target tag Tg during a time period when there are many commands for the tag Tg (such as a lighting command for the tag Tg), and executes the association processing for the target tag Tg during a time period when there are few commands for the tag Tg.

[0149] The association processing unit 111 may be provided with any one of the first to third configuration examples, or may be provided with two or more of them.

[0150] FIG. 22 shows an example of the procedure for the association processing when the management server 1 is provided with the first to third configuration examples.

[0151] In step S61, the management server 1 determines whether the total number of commands for the tag Tg (such as the lighting command for the tag Tg) is equal to or greater than a predetermined number. If the total number of commands for the tag Tg is less than the predetermined number (S61: No), the management server 1 transfers the process to step S62. If the total number of commands for the tag Tg is equal to or greater than the predetermined number (S61: Yes), the management server 1 ends the process and does not execute the re - association process. Step S61 is the process corresponding to the third configuration example.

[0152] In step S62, the management server 1 determines whether the target controller 2 exists. Specifically, the management server 1 determines whether the controller 2 that is the target of the subsequent determination process remains. If the management server 1 determines that the controller 2 remains (S62: Yes), it transfers the process to step S63. If the management server 1 determines that the controller 2 does not remain (S62: No), it ends the process. The management server 1 executes the following process for each controller 2.

[0153] In step S63, the management server 1 determines whether the controller 2 has been newly added or whether the transmission has resumed after the controller 2 has been stopped. If the controller 2 has been newly added or if the transmission has resumed after the controller 2 has been stopped (S63: Yes), the management server 1 transfers the process to step S65. On the other hand, if the controller 2 has not been newly added and the transmission of the controller 2 has not resumed (S63: No), the management server 1 transfers the process to step S64.

[0154] In step S64, the management server 1 determines whether or not a predetermined time (for example, 10 days) has elapsed since the re - execution of the previous association process. If the management server 1 determines that the predetermined time has elapsed since the re - execution of the previous association process (S64: Yes), it moves the process to step S65. On the other hand, if the management server 1 determines that the predetermined time has not elapsed since the re - execution of the previous association process (S64: No), it returns the process to step S62. Steps S63 and S64 are processes corresponding to the second configuration example.

[0155] In step S65, the management server 1 determines whether or not the total number of tags Tg associated with the controller 2 is equal to or greater than a predetermined number. If the total number of tags Tg associated with the controller 2 is equal to or greater than the predetermined number (S65: Yes), the management server 1 moves the process to step S66. On the other hand, if the total number of tags Tg associated with the controller 2 is less than the predetermined number (S65: No), the management server 1 returns the process to step S62.

[0156] In step S66, the management server 1 determines whether or not the ratio of the total number of tags Tg to the total number of all controllers 2 is equal to or greater than a predetermined ratio. If the ratio of the total number of tags Tg to the total number of all controllers 2 is equal to or greater than the predetermined ratio (S66: Yes), the management server 1 moves the process to step S67. On the other hand, if the ratio of the total number of tags Tg to the total number of all controllers 2 is less than the predetermined ratio (S66: No), the management server 1 returns the process to step S62.

[0157] In step S67, the management server 1 determines whether there is a target tag Tg connected to the controller 2. Specifically, the management server 1 determines whether there is a tag Tg remaining as the target of the subsequent determination process. When the management server 1 determines that the target tag Tg remains (S67: Yes), it causes the process to proceed to step S68. When the management server 1 determines that the target tag Tg does not remain (S67: No), it returns the process to step S62. The management server 1 executes the following process for each tag Tg connected to the controller 2.

[0158] In step S68, the management server 1 executes the same process as in step S63. When a new controller 2 is added, or when transmission is resumed after the controller 2 has been stopped (S68: Yes), the management server 1 causes the process to proceed to step S69. On the other hand, when a new controller 2 has not been added and the transmission of the controller 2 has not been resumed (S68: No), the management server 1 causes the process to proceed to step S71.

[0159] In step S69, the management server 1 compares the number of connections of the tag Tg for each controller 2. Specifically, the management server 1 calculates and compares the total number of associated tags Tg for each of the plurality of controllers 2 to which the tag Tg can be connected.

[0160] In step S70, the management server 1 determines whether the ratio of the maximum number of connections to the minimum number of connections is equal to or less than a predetermined ratio. If the ratio of the maximum number of connections to the minimum number of connections is equal to or less than the predetermined ratio (S70: Yes), the management server 1 returns the process to step S62. On the other hand, if the ratio of the maximum number of connections to the minimum number of connections exceeds the predetermined ratio (S70: No), the management server 1 proceeds with the process to step S71. Note that the management server 1 may also proceed with the process to step S71 when the difference in the total number for each controller 2 is equal to or greater than a predetermined number, and may proceed with the process to step S62 when the difference is less than the predetermined number. Steps S68 to S70 are processes corresponding to the second configuration example.

[0161] In step S71, the management server 1 executes re - execution of the association process. The management server 1 executes the processes of steps S67 to 70 for each target tag Tg connected to the controller 2.

[0162] As described above, when the management server 1 satisfies a predetermined condition corresponding to the first configuration example to the third configuration example, the management server 1 executes re - execution of the association process. Thereby, it is possible to avoid frequent execution of re - execution of the association process. For this reason, problems such as a shortened battery life of the tag Tg and a decrease in the efficiency of the picking operation can be solved.

[0163] [Other Embodiments] As another embodiment of the present disclosure, the tag Tg may transmit the search signal when receiving a predetermined signal. For example, the tag Tg transmits the search signal when receiving a search signal transmission instruction from the management server 1.

[0164] Also, the tag Tg may transmit the search signal when a predetermined time has elapsed. For example, the tag Tg transmits the search signal when a preset time has elapsed. Thereby, the tag Tg can periodically execute the association process and associate with the optimal controller 2.

[0165] Also, the tag Tg may transmit the search signal when the communication becomes unstable. For example, the tag Tg transmits the search signal when the reception status of the above beacon deteriorates, that is, when the received signal level drops below a predetermined state, or when the failure of beacon reception meets a predetermined condition. Thereby, even when the situation changes due to movement of the location or the like, the tag Tg can be associated with the optimal controller 2, and a situation where the operation becomes impossible can be avoided.

[0166] Also, when transmitting the search signal, the tag Tg may perform carrier sense and transmit when it is idle, and retry when it is not idle. Thereby, it becomes possible to efficiently associate a plurality of tags Tg in the same period.

[0167] Furthermore, it is still more preferable to perform random backoff by generating a random number during the above retry.

[0168] In this way, the tag Tg transmits the search signal when it receives a user operation, when it receives a predetermined signal, when the stability of the signal from the controller 2 associated with the tag Tg reaches a predetermined state, or when a predetermined time has elapsed.

[0169] As described above, the communication system of the present disclosure may be configured by the entire communication system 10 (see FIG. 1) including the management server 1, the controller 2, and the tag Tg, or may be configured by the management server 1 and the controller 2, or may be configured by the management server 1 alone or the controller 2 alone.

[0170] Also, the channel (frequency channel) of the present disclosure is applicable to communication methods such as frequency hopping method and direct spread method.

[0171] In addition, in the present disclosure, the channel (operation channel) used to transmit commands to the tag Tg (slave station) by the beacon for control is different from the channel (search channel) for transmitting search signals. By separating the used channels in this way, the influence on normal operation can be avoided.

[0172] Furthermore, in the present disclosure, there is also a channel (announcement channel) for transmitting a signal instructing an association for associating the tag Tg and the controller 2 with each other, and the announcement channel is different from the operation channel and the search channel. By separating the used channels in this way, the influence on normal operation can be avoided.

[0173] In addition, in the present disclosure, when the communication between the first slave station and the first master station associated therewith becomes unstable, the tag Tg transmits the search signal to perform association again. As a result, it becomes possible to re-associate with a better controller 2 in response to environmental changes such as movement of the installation location.

[0174] As described above, the communication system 10 is a system including a management server 1, a plurality of controllers 2 (parent stations), and a plurality of tags Tg (child stations). In the communication system 10, when a target tag Tg detects a predetermined event, the target tag Tg transmits a search signal for identifying the controller 2 to which the target tag Tg is connected. When each of the plurality of controllers 2 receives the search signal, the controller 2 transmits a report including the identification information of the controller 2, the identification information of the target tag Tg, and the stability of the search signal to the management server 1. The management server 1 corrects the stability included in the report received from each controller 2 for each controller 2 based on the number of tags Tg associated with the controller 2, and determines the target controller 2 to which the target tag Tg is connected from among the plurality of controllers 2 based on the corrected stability for each controller 2, and associates the target tag Tg with the determined target controller 2. For example, the management server 1 determines the controller 2 having the largest corrected stability among the plurality of controllers 2 as the controller 2 to which the target tag Tg is connected.

[0175] Note that the predetermined event is any one of a predetermined user operation (for example, an operation in which a user presses the bottom button E1 (see FIG. 3B) of the target tag Tg), reception of a predetermined signal, and elapse of a set time.

[0176] According to the above configuration, many tags Tg are not concentrated and connected to some of the controllers 2, and the tags Tg are evenly distributed and connected to each controller 2. Therefore, it is possible to suppress communication delay caused by the influence of the association (linking) between the controller 2 and the tag Tg.

[0177] In addition, when the total number of tags Tg associated with the first controller 2 among the plurality of controllers 2 is equal to or greater than a predetermined number, and the ratio of the total number of tags Tg to the total number of all controllers 2 is equal to or greater than a predetermined ratio, the management server 1 re-performs the process (association process) of determining the destination controller 2 for the tags Tg associated with the first controller 2. For example, when the difference between the total number of tags Tg associated with the first controller 2 and the total number of tags Tg associated with the second controller 2 is equal to or greater than a predetermined number, the management server 1 re-performs the association process. Thereby, problems such as the problem that the battery life of the tag Tg becomes short and the problem that the efficiency of the picking operation decreases can be solved.

[0178] [Appendix of Disclosure] Hereinafter, the outline of the disclosure extracted from the embodiments will be appended. Note that each configuration and each processing function described in the following appendix can be arbitrarily combined by selection.

[0179] <Appendix 1> A communication system including a management server, a plurality of parent stations, and a plurality of child stations, When the target child station detects a predetermined event, the target child station transmits a search signal for identifying the destination parent station of the target child station, When each of the plurality of parent stations receives the search signal, the parent station transmits a report including the identification information of the parent station, the identification information of the target child station, and the stability of the search signal to the management server, The management server corrects the stability included in the report received from each parent station for each parent station based on the number of child stations associated with the parent station, and determines the target parent station of the destination of the target child station from among the plurality of parent stations based on the corrected stability for each parent station, and associates the target child station with the determined target parent station. Communication system.

[0180] <Appendix 2> The management server determines the target parent station as the parent station among the plurality of parent stations with the greatest corrected stability. The communication system according to Supplementary Note 1.

[0181] <Supplementary Note 3> When the number of slave stations associated with a first parent station among the plurality of parent stations is equal to or greater than a predetermined number and the ratio of the total number of slave stations to the total number of parent stations is equal to or greater than a predetermined ratio, the management server re-performs the process of determining the target parent station for the connection destination for the slave stations associated with the first parent station. The communication system according to Supplementary Note 1 or 2.

[0182] <Supplementary Note 4> When the difference between the total number of slave stations associated with the first parent station and the total number of slave stations associated with a second parent station included in the plurality of parent stations is equal to or greater than a predetermined number, the management server re-performs the process of determining the target parent station for the connection destination. The communication system according to Supplementary Note 3.

[0183] <Supplementary Note 5> The management server notifies at least the identifier or channel of the target parent station to the target slave station. The target slave station communicates with the target parent station based on at least the identifier or channel of the target parent station. The communication system according to any one of Supplementary Notes 1 to 4.

[0184] <Supplementary Note 6> The channel on which the target slave station transmits the search signal is different from the channel on which the target slave station communicates with the target parent station after being associated with the target parent station. The communication system according to any one of Supplementary Notes 1 to 5.

[0185] <Supplementary Note 7> The predetermined event is any one of a predetermined user operation, reception of a predetermined signal, and elapse of a set time. The communication system according to any one of Supplementary Notes 1 to 6.

[0186] <Appendix 8> The master station performs time-division communication with the slave station, The target slave station transmits the search signal a plurality of times at time intervals longer than the slot time in the time-division communication, The communication system according to any one of Appendices 1 to 7.

[0187] <Appendix 9> The stability of the search signal is calculated based on either the value of the signal strength of the search signal or the average value of the signal strength, The communication system according to any one of Appendices 1 to 8.

[0188] <Appendix 10> The management server is any one of the plurality of master stations, The communication system according to any one of Appendices 1 to 9.

Explanation of Reference Numerals

[0189] 1: Management server 2: Controller 10: Communication system 11: Control unit 12: Storage unit 111: Related processing unit 112: Allocation processing unit 113: Communication processing unit AR: Communication area D1: Tag information D2: Related information Tg: Tag

Claims

1. A communication system including a management server, a plurality of parent stations, and a plurality of child stations, wherein when a target child station detects a predetermined event, the target child station transmits a search signal for identifying the parent station to which the target child station is connected, each of the plurality of parent stations, when receiving the search signal, transmits a report including the identification information of the parent station, the identification information of the target child station, and the stability of the search signal to the management server, the management server corrects, for each parent station, the stability included in the report received from the parent station based on the number of child stations associated with the parent station, determines a target parent station to which the target child station is connected from among the plurality of parent stations based on the corrected stability for each parent station, and associates the target child station with the determined target parent station, A communication system.

2. The management server determines the parent station with the highest corrected stability among the plurality of parent stations as the target parent station, The communication system according to claim 1.

3. When the number of child stations associated with a first parent station among the plurality of parent stations is equal to or greater than a predetermined number and the ratio of the total number of child stations to the total number of parent stations is equal to or greater than a predetermined ratio, the management server re-performs the process of determining the target parent station to which the child stations associated with the first parent station are connected, The communication system according to claim 1.

4. When the difference between the total number of child stations associated with a first parent station and the total number of child stations associated with a second parent station included in the plurality of parent stations is equal to or greater than a predetermined number, the management server re-performs the process of determining the target parent station to which the child stations are connected, The communication system according to claim 3.

5. The management server notifies the target child station of at least the identifier or channel of the target parent station, The target child station communicates with the target parent station based on at least the identifier or channel of the target parent station, The communication system according to claim 1.

6. The channel through which the target child station transmits the search signal is different from the channel through which the target child station communicates with the target parent station after being associated with the target parent station, The communication system according to claim 1.

7. The predetermined event is any one of a predetermined user operation, reception of a predetermined signal, and elapse of a set time, The communication system according to claim 1.

8. The parent station performs time-division communication with the child station, The target slave station transmits the search signal a plurality of times at time intervals longer than the slot time in the time-division communication. The communication system according to claim 1.

9. The stability of the search signal is calculated based on either the value of the signal strength of the search signal or the average value of the signal strength. The communication system according to any one of claims 1 to 8.

10. The management server is any one of the plurality of master stations. The communication system according to claim 1.

11. A communication method in which a management server, a plurality of master stations, and a plurality of slave stations perform wireless communication, comprising: at a target slave station, when a predetermined event is detected, transmitting a search signal for identifying the master station to which the target slave station is connected; at each of the plurality of master stations, when the search signal is received, transmitting a report including the identification information of the master station, the identification information of the target slave station, and the stability of the search signal to the management server; at the management server, for each master station, correcting the stability included in the report received from the master station based on the number of slave stations associated with the master station, and determining a target master station to which the target slave station is connected from among the plurality of master stations based on the corrected stability for each master station, and associating the target slave station with the determined target master station; A communication method executed by one or more processors.

12. A communication program in which a management server, a plurality of master stations, and a plurality of slave stations perform wireless communication, comprising: at a target slave station, when a predetermined event is detected, transmitting a search signal for identifying the master station to which the target slave station is connected; at each of the plurality of master stations, when the search signal is received, transmitting a report including the identification information of the master station, the identification information of the target slave station, and the stability of the search signal to the management server; at the management server, for each master station, correcting the stability included in the report received from the master station based on the number of slave stations associated with the master station, and determining a target master station to which the target slave station is connected from among the plurality of master stations based on the corrected stability for each master station, and associating the target slave station with the determined target master station; A communication program for causing one or more processors to execute.

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