JP2012237843A - Electronic display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of suppressing the consumption of a battery which becomes a power source by suppressing the power consumption of an electronic display device.SOLUTION: An electronic display system includes: a plurality of electronic display devices 1 driven by a battery, and respectively installed in moving bodies; and an information distributing device 10 for distributing information indicated by the plurality of the electronic display device 1. The information distributing device 10 sends a beacon B in a predetermined sending period Tp. Each of the electronic display devices 1 detects the presence/absence of the beacon B in a predetermined detection period Te. When transmitting data to a specified electronic display device 1, the information distributing device 10 sends a data previous notice command while including that in the beacon B, and transmits the data after the beacon B including the data previous notice command Cd.

Description

  The present invention relates to an electronic display system that includes a plurality of electronic displays that are driven by a battery and are respectively installed on a moving body, and an information distribution device that distributes information displayed by the plurality of electronic displays.

  Various techniques have been proposed for an electronic display system including an electronic display. For example, Patent Documents 1 and 2 disclose a system (a so-called electronic shelf label system) that displays the selling price of a product on an electronic display arranged near the product in a store such as a supermarket or a convenience store. . Here, the electronic display functions as an electronic shelf label that displays the selling price of the product.

  On the other hand, in recent years, for example, in a factory where a line production method has been introduced, an electronic display is installed on a work object (or its container) that is placed on a belt conveyor or the like and sequentially moves within the factory. There has also been proposed an electronic display system for displaying work contents to be performed on a work object on the electronic display. In this electronic display system, for example, when a work object moves to a new work area, the display on the electronic display installed in the work object is switched to be applied to the work object in the new work area. With the configuration of displaying the work content, the electronic display can function as a work instruction device that transmits the work content to the worker.

  In the electronic display system in which the electronic display functions as a work instruction device as in the above example, it is assumed that the electronic display moves. In such an electronic display system, stationary between each electronic display and an apparatus (information distribution apparatus) that distributes various types of information (for example, screen data to be displayed) to each electronic display. In some cases, the communication is continued. When the electronic display moves, for example, there is a possibility that the electronic display may enter an area where good communication with the information distribution apparatus cannot be performed. If communication is continuously performed, the occurrence of such a situation can be immediately detected.

JP 2008-168057 A JP-A-11-219148

  By the way, the electronic display is often driven by a battery in order to make it portable. Therefore, in the electronic display system, it is necessary to devise measures for suppressing power consumption of the electronic display and suppressing consumption of a battery serving as a power source of the electronic display.

  Moreover, in the electronic display system on which the electronic display is assumed to move as in the above example, when each electronic display continues to communicate with the information distribution device constantly, the electronic display Battery consumption is particularly significant. Therefore, in such an electronic display system, a technique for effectively suppressing the power consumption of the electronic display is particularly strongly demanded.

  The present invention has been made in view of the above points, and in an electronic display system on which the electronic display is supposed to move, a battery serving as a power source while suppressing power consumption of the electronic display It is an object to provide a technology capable of suppressing the consumption of the battery.

  The electronic display system which concerns on a 1st aspect is driven by the battery, distributes the information which a plurality of electronic displays respectively installed in a mobile body, and the plurality of electronic displays to the plurality of electronic displays An electronic display system comprising an information distribution device, wherein the information distribution device transmits a first signal to the plurality of electronic displays at a predetermined transmission cycle, and the plurality of electronic devices. When information to be transmitted to a specific electronic display among the displays is generated, a second signal addressed to the specific electronic display including the information is generated, and the generated second signal is A second signal transmission unit that transmits the first signal following the first signal; and when the second signal is transmitted following the first signal, the first signal preceding the second signal is Scheduled to include advance notice information An information providing unit, wherein each of the plurality of electronic displays detects the presence or absence of reception of the first signal at a predetermined detection period, and the first signal detection unit detects the first signal detection unit. And a second signal receiving unit that performs reception processing of the second signal transmitted subsequent to the first signal when the notice information is included in the first signal.

  An electronic display system according to a second aspect is the electronic display system according to the first aspect, wherein the first signal is composed of a plurality of unit signals that are continuously transmitted at a predetermined period, A notice information adding unit includes the notice information in each of the plurality of unit signals constituting the first signal preceding the second signal, and the first signal detecting unit includes the unit signal of the plurality of unit signals. At least one unit signal is detected.

  The electronic display system which concerns on a 3rd aspect is an electronic display system which concerns on a 2nd aspect, Comprising: The said unit signal is continuously transmitted to each of the said several unit signal of the said several unit signal. When rank information indicating which unit signal is transmitted among them is given, and the second signal receiving unit transmits the second signal following the first signal, The reception timing of the second signal is adjusted based on the rank information given to the unit signal detected by the first signal detection unit.

  The electronic display system which concerns on a 4th aspect is an electronic display system which concerns on a 2nd aspect, Comprising: The said unit signal is continuously transmitted to each of these unit signals of these unit signals. Order information indicating which unit signal is transmitted in the order is given, and the order information given to the unit signal when the first signal detection unit detects the unit signal. Based on the above, the timing for receiving the first signal next is adjusted.

  An electronic display system according to a fifth aspect is the electronic display system according to any one of the first to fourth aspects, wherein the information distribution device includes a plurality of repeaters and the plurality of repeaters. And a server for distributing information to the plurality of electronic displays, wherein the first signal transmission unit is located in the communication area of the repeater via each of the plurality of repeaters. Sending the first signal to a display, among the plurality of electronic displays, setting information common to an electronic display in a specific area, and the repeater having a communication area in the specific area Included in the first signal transmitted through the network.

  An electronic display system according to a sixth aspect is the electronic display system according to any one of the first to fifth aspects, wherein the second signal is packetized, and the second signal receiving unit is Based on the header information of the packet of the second signal, it is determined whether the information included in the data portion of the packet is information addressed to the own device, and if it is determined that the information is not addressed to the own device, The reception process of the packet is interrupted and the data part of the packet is not received.

  An electronic display system according to a seventh aspect is the electronic display system according to the sixth aspect, wherein the second signal receiving unit is configured such that the information included in the data part of the packet of the second signal is addressed to the own device. When the reception process of the packet is interrupted because it is not information, information indicating how many packets the second signal is divided from the header portion of the packet, and the packet is the second signal Information indicating the number of packets among the plurality of packets constituting the information, and information indicating the number of retry transmissions of the packet, and the acquired information Based on this, the next transmission timing of the packet addressed to the own apparatus is predicted, and the packet reception process is resumed at the predicted timing.

  An electronic display system according to an eighth aspect is the electronic display system according to the second aspect, wherein the information distribution apparatus includes a plurality of relays and the plurality of electronic displays via the plurality of relays. Each of the plurality of repeaters is assigned a different frequency domain, and each of the plurality of repeaters is assigned to the first frequency domain assigned to its own device. When the electronic display searches for the receivable first signal among the first signals transmitted from each of the plurality of repeaters, the electronic display A basic search process is performed during the transmission period, in which the process of determining whether or not can be received is performed n times (where n is an integer of 2 or more) with an interval of 1 / n of the transmission period of the first signal. M times (however, Is an integer greater than or equal to 1), the output time of the first signal from each of the plurality of repeaters is the minimum integer greater than or equal to the transmission period of the first signal x and ceil (a) a As a result, a predetermined error absorption time is added to the minimum y value satisfying the relationship of n = ceil (x / y).

  An electronic display system according to a ninth aspect is the electronic display system according to the eighth aspect, wherein the basic search process determines whether or not each of the first signals can be received. This process is performed twice with an interval of 1/2 of the transmission period of one signal.

  An electronic display system according to a tenth aspect is the electronic display system according to the second aspect, wherein the information distribution device includes a plurality of relays and the plurality of electronic displays via the plurality of relays. Each of the plurality of repeaters is assigned a different frequency domain, and each of the plurality of repeaters is assigned to the first frequency domain assigned to its own device. When the electronic display searches for the receivable first signal among the first signals transmitted from each of the plurality of repeaters, the electronic display unit can receive the signal as a result of the search. When it is determined that the first signal is not present, the search is repeatedly performed at intervals, and the interval when the search is repeated becomes longer as time elapses.

  In the electronic display system according to the first aspect, when the second signal for the specific electronic display is transmitted from the information distribution device, the advance information is included in the first signal. According to this configuration, the electronic display can measure the timing for performing the reception process of the second signal based on the advance notice information, and therefore, wasteful power consumption due to waiting for the second signal can be suppressed. That is, the power consumption of each electronic display can be suppressed, and the consumption of the battery serving as the power source can be suppressed.

  In the second aspect, the first signal is composed of a plurality of unit signals that are continuously transmitted in a predetermined cycle, and each electronic indicator is at least one of the plurality of unit signals constituting the first signal. One is detected. According to this configuration, it is possible to suppress the power consumed when each electronic display detects the first signal.

  In a 3rd aspect, when a 2nd signal is transmitted following a 1st signal, an electronic indicator receives a 2nd signal based on the order information provided to the unit signal which the self-apparatus detected. Adjust timing. According to this configuration, the electronic display can accurately specify the timing for performing the reception process of the second signal based on the rank information given to the unit signal, and therefore, it is useless for waiting for the second signal. Power consumption can be further suppressed.

  In a 4th aspect, an electronic indicator adjusts the reception timing of a 1st signal based on the order | rank information provided to the unit signal which the own apparatus detected. For example, if the reception timing of the unit signal is adjusted so as to detect the middle of the first signal (that is, the unit signal transmitted in the middle of the unit signals constituting the first signal), the information distribution apparatus Even if the transmission timing of the first signal from is slightly shifted, the possibility of failing to detect the first signal is reduced. That is, it is possible to reliably follow and detect the first signal that is continuously sent out from the information distribution apparatus at the sending cycle determined.

  According to the fifth aspect, the setting information common to the electronic display in the specific area is included in the first signal and sent to the electronic display in the area. Can be delivered to the display.

  According to the sixth aspect, each electronic indicator determines, based on the header information of the packet of the second signal, whether or not the information included in the data portion of the packet is information addressed to itself. If it is determined that the information is addressed to the device, the data portion of the packet is not received, and the power of the electronic display is not wasted by receiving the data portion of the packet addressed to the other device.

  According to the seventh aspect, when the reception processing of the packet of the second signal is interrupted, each electronic display device next transmits a packet addressed to itself based on the information included in the header portion of the packet. Since the packet reception process is resumed at the predicted timing, it is prevented that the packet addressed to itself is missed.

  According to the eighth aspect, the output time of the first signal from each of the plurality of repeaters is n = ceil (x, where the transmission period of the first signal is x, ceil (a) is the smallest integer greater than or equal to a. / Y) is a value obtained by adding a predetermined error absorption time to the minimum y value satisfying the relationship of / y). According to this configuration, no matter what the relationship between the output timing of the first signal from the repeater and the timing at which the electronic display performs the basic search process, The time for sending the first signal from the repeater can be kept small while ensuring that at least one of the times overlaps with the sending time of the first signal. Therefore, it is possible to ensure a long time for sending the second signal from the repeater to the electronic display while ensuring the certainty of the search in the electronic display.

  According to the ninth aspect, the basic search process is a process in which, for each first signal, a process for determining whether or not it can be received is performed twice at intervals of one half of the transmission period of the first signal. As a result, the power consumed by the electronic display in the basic search process can be kept small.

  According to the tenth aspect, the interval at which the electronic display repeats the search becomes longer as time elapses, so that the power of each electronic display can be prevented from being consumed by the useless search.

It is a figure which shows the structure of an electronic display system. It is a figure which shows the structure of an electronic display. It is a figure which shows typically the mode of the data communication in the operation | movement which links an electronic indicator with an access point. It is a figure for demonstrating a beacon. It is a figure which shows typically the mode of the data communication in a series of operation | movement which concerns on handoff control. It is a figure which shows typically the mode of the data communication in the operation | movement which distributes information to a specific electronic display from an information delivery apparatus. It is a figure which shows typically the mode of the data communication in the operation | movement which distributes information to a specific electronic display from an information delivery apparatus. It is a figure for demonstrating the process which specifies the timing which should perform the reception process of transmission data based on order information. It is a figure for demonstrating the process when an electronic display receives the transmission data addressed to another apparatus. It is a figure for demonstrating the process when an electronic display receives the transmission data addressed to an own apparatus. It is a figure for demonstrating the process which an electronic display restarts reception of transmission data. It is a block diagram showing each function implement | achieved in an electronic display system. It is a figure for demonstrating the process which adjusts the timing which performs the detection process of a beacon to the optimal timing. It is a figure which shows typically the mode of communication in a channel search. It is a figure which shows typically the mode of communication in a channel search. It is a figure which shows typically the mode of communication in a channel search. It is a figure which shows typically the detection timing of the electronic display in a channel search. It is a figure for demonstrating the process which enlarges the space | interval which performs a channel search with time.

<1. Configuration of Electronic Display System 100>
A configuration of an electronic display system 100 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an electronic display system 100. In FIG. 1, an electronic display system 100 is introduced into a manufacturing factory in which a work object 91 (work object) 91 is moved by a belt conveyor 92 and sequentially moves through a plurality of work places in a work area 90. The state of being done is shown.

  The electronic display system 100 includes a plurality of electronic displays 1 and an information distribution device 10 that distributes information to the plurality of electronic displays 1.

  Each of the plurality of electronic displays 1 is installed on a moving body. However, the “moving body” here is not limited to a self-moving body (for example, a transport vehicle) provided with a mechanism for moving itself, but includes other-force moving bodies that move by receiving external force. For example, a person or an object moved by a self-moving body (for example, a work object carried by a person, a work object moved on a transport vehicle or a belt conveyor) is also included in the “moving body”. . In the example shown in FIG. 1, each electronic display 1 is placed on a belt conveyor 92 and sequentially moves through each work place in the work area 90 (or a container that accommodates it). Is installed. Therefore, in this case, each electronic display 1 moves sequentially with each work place in the work area 90 together with the work object 91.

  The information distribution apparatus 10 includes a DMS server 3 and a plurality of access points (AP) 2 connected to the DMS server 3 via a network 4 such as a LAN.

  The DMS server 3 can perform data communication with each of the plurality of access points 2 connected via the network 4. Further, the DMS server 3 is a computer system (core system) such as a server device disposed in a headquarters center that manages and manages a manufacturing factory via a communication line (for example, an external network such as the Internet or a LAN) 6. 5, and data communication can be performed with the backbone system 5.

  The configuration of the DMS server 3 as hardware is the same as that of a general computer. Specifically, the DMS server 3 includes components (CPU for performing various arithmetic processes, ROM for storing a boot program, RAM serving as a work area for arithmetic processes, programs, and various types connected to each other via a bus line or the like. A hard disk for storing data files, a display for performing various displays, an input unit including a keyboard and a mouse, a data communication unit having a data communication function via a LAN, and the like.

  The plurality of access points 2 are radio wave repeaters for wireless PAN, for example, and are arranged on the ceiling of the work area 90 at substantially constant distances. As a result, all the electronic displays 1 in the work area 90 can perform radio communication with any of the access points 2 using a radio wave system (or an infrared system or the like). It is like that. That is, all the electronic displays 1 in the work area 90 can communicate with the DMS server 3 via any one of the access points 2.

  The electronic display system 100 is a system that displays information transmitted from the backbone system 5 to the information distribution apparatus 10 on the electronic display 1 that moves in the work area 90. For example, in the example shown in FIG. 1, while the work object 91 passes through the first work place, the electronic display 1 installed on the work object 91 is performed at the first work place. When the work content to be displayed is displayed and the work object 91 moves from the first work place to the second work place, the display on the electronic display 1 is switched to the work content to be performed at the second work place. By performing system control such as enabling the electronic display 1 provided in the electronic display system 100, the work contents are transmitted to the worker who performs work on the work object 91 in the work area 90. It can function as a support device.

<2. Electronic display 1>
The configuration of the electronic display 1 will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the electronic display 1.

  The electronic display device 1 includes a display 11 disposed on the front surface of a casing formed in a rectangular plate shape, and operation buttons 12 for receiving various operations. Inside the housing are a communication unit 13 that communicates with the access point 2, a control unit 14 that comprehensively controls the operation of the electronic display 1, and a small battery 15 that supplies power to the electronic display 1. And are provided.

  The display 11 is a display device that displays various types of information. Specifically, the display 11 is, for example, a dot matrix type non-volatile display unit, and is composed of, for example, electronic paper. In a non-volatile display unit such as electronic paper, display contents can be held without applying driving power. Since the display 11 is a dot matrix type display unit, it can display characters, symbols, figures, and the like. The display 11 is not necessarily a non-volatile display unit, and may be, for example, a volatile liquid crystal panel.

  The communication unit 13 is a functional unit responsible for radio communication with the access point 2 using a radio wave system (or an infrared system or the like). When the communication unit 13 receives data from the DMS server 3 via the access point 2, the data is input to the control unit 14. On the other hand, the data generated by the control unit 14 is transmitted to the access point 2 through the communication unit 13.

  The control unit 14 includes a CPU, a memory, and the like. This memory stores the device code of the device itself. However, the “device code” is a hardware ID unique to each of the plurality of electronic displays 1 provided in the electronic display system 100. The control unit 14 manages each operation of the electronic display 1 by controlling each element of the electronic display 1.

  The control unit 14 functions as a display control unit that controls display on the display 11. That is, when the communication unit 13 receives “display screen data” to be described later from the DMS server 3, the control unit 14 stores the received display screen data in the memory and then controls the display 11 to store the memory. The display screen data is displayed on the display 11.

<3. Overview of Operation of Electronic Display System 100>
Operations performed in the electronic display system 100 will be described.

<3-1. Linking>
The electronic display system 100 performs an operation of associating (linking) each electronic display 1 with any one of the access points 2 at the time of activation. The operation will be described with reference to FIG. FIG. 3 is a diagram schematically showing the state of data communication in the operation.

  When the electronic display system 100 is activated, first, the DMS server 3 gives an activation instruction to each access point 2 (step S1). Each access point 2 that has received the activation instruction starts sending “beacon B” to the electronic display 1.

  The beacon B is a signal for establishing a link between the access point 2 and the electronic display 1, and the access point 2 has a period (hereinafter referred to as “transmission period Tp”) determined from each access point 2. (Broadcast) to one or more electronic displays 1 in the communication area. Note that the timing at which each of the plurality of access points 2 transmits the beacon B does not have to be synchronized with each other, but the transmission cycle Tp of the beacon B at each access point 2 is set to a common value. For example, the transmission cycle Tp of the beacon B of each access point 2 is all set to “4 (seconds)”.

  As described above, the plurality of access points 2 are arranged on the ceiling or the like of the work area 90 at substantially constant distances. Accordingly, all the electronic displays 1 in the work area 90 receive the beacon B transmitted from at least one access point 2. That is, the information distribution apparatus 10 transmits the beacon B with the transmission cycle Tp to all the electronic displays 1 arranged in the work area 90.

  However, the beacons B transmitted from each of the plurality of access points 2 are signals having different frequencies. For this reason, each electronic display 1 can specify the access point 2 which transmitted the beacon B which the own apparatus received based on the frequency of the said beacon B. The beacon B may include the identification information (for example, the access point number) of the access point 2 that transmitted the beacon B. In the case of the configuration, each electronic display 1 is connected to its own device. The access point 2 that sent the beacon B received by can be specified based on the identification number of the access point 2 included in the beacon B.

  Here, the configuration of the beacon B will be described more specifically with reference to FIG. FIG. 4 is a diagram for explaining the beacon B. The beacon B transmitted from each access point 2 at the transmission cycle Tp is composed of a plurality of unit signals b transmitted continuously at a predetermined cycle (hereinafter “unit signal transmission cycle Tm”).

  Therefore, the beacon B is a signal having a certain time (output time) L defined by a value obtained by multiplying the number of unit signals b transmitted continuously by the unit signal transmission period Tm. As will become clear later, in order to increase the communication efficiency of the information distribution apparatus 10 while suppressing the power consumption of the electronic display 1, the output time L of the beacon B is the minimum that satisfies the following (formula 1). It is preferable that the value be slightly larger (for example, about “0.1 (second)”) than the value of “L”. However, in (Formula 1), “ceil (a)” represents “the smallest integer equal to or greater than a”.

2 = ceil (Tp / L) (Equation 1)
When the transmission cycle Tp is set to “4 (seconds)”, the minimum value of “L” that satisfies (Expression 1) is “2 (seconds)”. Therefore, it is preferable to take a value slightly larger than this, for example, a value larger by “0.1 (seconds)”, and set “2.1 (seconds)” as the value of the output time L. For example, the number of unit signals b constituting the beacon B is “525 (pieces)”, and the unit signal b of “525 (pieces)” is transmitted at a unit signal transmission period Tm of “0.004 (seconds)”. In this case, the output time L of the beacon B is “2.1 (seconds)”.

  For each of the plurality of unit signals b transmitted continuously, the order information i (for example, the number of the unit signal b transmitted out of the plurality of unit signals b is the unit signal b). , Serial number). That is, when one beacon B is composed of, for example, “525 (units)” unit signals b that are continuously transmitted, each unit signal b has, for example, 1 to 525, depending on the transmission order. Is given as the ranking information i.

  Refer to FIG. 3 again. While each of the plurality of access points 2 arranged in the work area 90 transmits the beacon B, the control unit 14 of each electronic display 1 in the work area 90 repeats the channel search to detect the detection intensity. It waits for beacon B to be detected that is equal to or greater than a predetermined threshold (hereinafter referred to as “capture threshold Q1”) (step S2). However, the channel search is a process of detecting a receivable frequency region by sweeping the reception frequency over the entire frequency region of the beacon B assigned to each of the plurality of access points 2 while switching the reception frequency one after another. It is.

  When detecting a beacon B having a detection intensity R equal to or greater than a capture threshold Q1 (specifically, at least one unit signal b (see FIG. 4) among a plurality of unit signals b constituting the beacon B), the control unit 14 Specifies the access point 2 that is transmitting the beacon B based on the detected frequency of the beacon B, for example. Then, the identified access point 2 is authorized as an access point to which the device belongs (affiliated access point). The control unit 14 further notifies the information distribution apparatus 10 that the own apparatus belongs to the access point 2. Specifically, a signal (belonging notification signal) including the device code of the own device and the identification information (AP code) of the access point 2 authorized as the belonging access point of the own device is generated, and this is transmitted to the information distribution device. 10 (step S3). However, the affiliation notification signal needs to be transmitted so as not to overlap the transmission timing of the beacon B from the access point 2, for example, at the timing after the output of the beacon B.

  Here, there are a plurality of electronic displays 1 belonging to each access point 2. Therefore, if a plurality of electronic displays 1 simultaneously transmit various signals including the affiliation notification signal transmitted at the time of channel search, the possibility of signal collision increases. In order to avoid such a situation, the electronic display 1 randomly selects one of the timing slots (time sections) obtained by dividing the communication time during the beacon B off period, and selects the selected timing. It is preferable that the signal is transmitted in the slot. Here, each electronic display 1 can be configured to generate, for example, a pseudo random number and determine a timing slot for transmitting a signal based on the obtained value. More preferably, the timing slot for transmitting the signal is determined based on the value of the pseudo random number and the value of the radio wave intensity of the wireless communication. Since the radio wave intensity of wireless communication is likely to change depending on the environment, position, etc. of the electronic display 1, adding the value of the radio wave intensity to the timing slot selection increases the randomness in the timing slot selection. As described above, when the plurality of electronic display devices 1 are configured to transmit signals such as belonging notification signals in the timing slots selected at random, the timing at which signals are transmitted from the respective electronic display devices 1 is distributed, Signal collision is less likely to occur. As a result, the communication efficiency between each electronic display 1 and the access point 2 is improved.

  The affiliation notification signal transmitted from the electronic display 1 is received by the DMS server 3 via the access point 2 (step S4). When the DMS server 3 receives the affiliation notification signal from the electronic display 1, the DMS server 3 stores the device code included in the affiliation notification signal and the AP code in association with each other. As a result, the electronic display 1 and the access point 2 are associated (linked) in terms of data in a one-to-one relationship.

  After transmitting the affiliation notification signal, the control unit 14 of the electronic display 1 transmits the beacon B transmitted from the access point 2 to which the own apparatus belongs at a predetermined period (hereinafter referred to as “detection period Te”). Continue to detect the presence or absence of reception. Specifically, the presence or absence of at least one unit signal b among the plurality of unit signals b constituting the beacon B is continuously detected (see FIG. 3). In this embodiment, it is assumed that the detection cycle Te coincides with the transmission cycle Tp of the access point 2 (Te = Tp).

  The electronic display 1 repeats the transition from the sleep state to the wake-up state at the same cycle as the detection cycle Te. Specifically, when the control unit 14 of the electronic display 1 performs a detection process for detecting the presence / absence of the unit signal b, the control unit 14 shifts its own device to a sleep state in which power consumption is relatively small. Then, when the detection period Te has elapsed since the detection process of the unit signal b and the timing for performing the detection process of the unit signal b constituting the next beacon B has arrived, the own apparatus is changed from the sleep state to the wake-up state. The transition process is performed to detect the beacon B. That is, the control unit 14 is in a wake-up state only for a time necessary to perform the process of detecting the presence / absence of the unit signal b, and in principle is in a sleep state in other time zones. However, if the detected unit signal b includes a command (such as “data notice command Cd” described later), the control unit 14 determines that it is necessary to perform some processing other than the detection processing of the beacon B. Then, the device is shifted from the sleep state to the wake-up state in accordance with the timing at which the processing is to be performed.

<3-2. Handoff control>
As described above, in the electronic display system 100, each electronic display 1 is linked to one access point 2, and this link information is managed by the DMS server 3. As will be described later, the information distribution device 10 distributes information to a specific electronic display 1 via an access point 2 linked to the electronic display 1. That is, the electronic display device 1 in a state where the link is not completed in the DMS server 3 or in a state where good communication cannot be performed with the linked access point 2 is distributed from the information distribution device 10. Cannot receive the information addressed to its own device (hereinafter, such a state of the electronic display 1 is referred to as a “hand-off state”).

  For example, in the example shown in FIG. 1, the electronic display 1 that moves in the work area 90 together with the work object 91 goes out of the communication area of the access point 2 to which the device is currently linked. Sometimes. Then, the electronic display device 1 is in a handoff state, and cannot receive the information addressed to itself from the DMS server 3. In such a state, the display 11 is not properly updated in the electronic display 1.

  In view of this, the electronic display system 100 is provided with a configuration in which the control unit 14 of each electronic display 1 always checks whether or not the device itself is in the handoff state. That is, as described above, the control unit 14 of each electronic display 1 receives the beacon B transmitted from the access point 2 to which the own device belongs in the detection cycle Te (“Te = Tp” in this embodiment). If the detection intensity R of the beacon B is smaller than a predetermined threshold (hereinafter referred to as “handoff threshold Q2”), the device itself is good with the access point 2 It is determined that communication has become impossible (that is, handoff has occurred). As a result, each electronic display 1 can quickly detect that its own device is in the handoff state (specifically, with a response time equal to or shorter than the detection cycle Te). However, the handoff threshold value Q2 is preferably smaller than the capture threshold value Q1. If set in this way, each electronic display 1 can stably belong to an appropriate access point 2 by providing hysteresis. Note that the mode of determining whether or not the handoff state has been reached is not limited to the above mode. For example, when the detection intensity R is smaller than the handoff threshold Q2 for a predetermined number of consecutive times (for example, three consecutive times). You may employ | adopt the aspect which judges that it was in the handoff state.

  When it is determined that the device itself is in the handoff state, the control unit 14 of the electronic display 1 executes processing (handoff control) for canceling the handoff state. Handoff control will be described with reference to FIG. FIG. 5 schematically shows a state of data communication in a series of operations related to the control.

  As described above, the control unit 14 of each electronic display device 1 transmits the beacon B (specifically, a plurality of unit signals b constituting the beacon B) transmitted from the access point 2 to which the device belongs in the detection cycle Te. When the presence or absence of reception of at least one unit signal b (see FIG. 4)) is continuously detected and the detection intensity R of the beacon B becomes smaller than the handoff threshold value Q2, the own apparatus enters the handoff state. Judge that it became. When determining that the own device is in the handoff state, the control unit 14 immediately starts a channel search (step S11).

  When detecting the beacon B whose detection intensity R is greater than or equal to the capture threshold Q1, the control unit 14 identifies the access point 2 that is transmitting the beacon B based on the detected frequency of the beacon B. Then, the identified access point 2 is authorized as an access point to which the own device newly belongs. Further, the control unit 14 generates an affiliation notification signal for notifying the information distribution apparatus 10 that the own apparatus belongs to the access point 2, and transmits this to the information distribution apparatus 10 (step S12). Note that, as described above, the affiliation notification signal needs to be transmitted so as not to overlap with the transmission timing of the beacon B from the access point 2, for example, at the timing after the output of the beacon B. At this time, as described above, the electronic display 1 randomly selects one of the timing slots (time divisions) obtained by dividing the communication time during the beacon B off period, and uses the selected timing slot. It is preferable that the signal is transmitted.

  The affiliation notification signal transmitted from the electronic display 1 is received by the DMS server 3 via the access point 2 (step S13). When receiving the affiliation notification signal from the electronic display 1, the DMS server 3 stores the device code and the AP code included in the affiliation notification signal in association with each other. If there is another AP code previously associated with the device code, the other AP code is discarded. As a result, the electronic display 1 is re-linked to the new access point 2.

  For example, in the example shown in FIG. 1, the electronic display 1 that moves within the work area 90 together with the work object 91 and goes out of the communication area of the access point 2 to which the device is linked is When entering the communication area of the access point 2, the beacon B transmitted from the other access point 2 is strongly detected. Then, when the detected intensity of the beacon B transmitted from the other access point 2 exceeds the capture threshold Q1, the re-linkage is performed with the other access point 2.

  As described above, in the electronic display system 100, the control unit 14 of each electronic display 1 always checks whether or not its own device is in the handoff state, and the control unit of the electronic display 1 in the handoff state. 14 is caused to execute handoff control to cancel the handoff state. Accordingly, in principle, each electronic indicator 1 is always an appropriate access point 2 (that is, an access point 2 with which the device itself can communicate. In other words, the device itself is located within the communication area. The access point 2) is linked (captured). As a result, the distribution of information from the information distribution apparatus 10 to each electronic display 1 is reliably performed.

<3-3. Distribution of transmission data D>
In the electronic display system 100, various information (for example, information on a screen to be displayed on the electronic display 1 and settings of the electronic display 1 are changed from the information distribution device 10 to the specific electronic display 1. Instruction information and the like) is distributed. A series of operations related to the distribution of the information will be described with reference to FIG. FIG. 6 is a diagram schematically showing a state of data communication in the operation.

  When information to be transmitted to a specific electronic display 1 (hereinafter referred to as “target electronic display 1”) is generated, the DMS server 3 includes the information to be transmitted in its data part, and the target electronic is included in its header part. Data including the device code of the display 1 (hereinafter referred to as “transmission data D”) is generated. For example, when information (display information) to be displayed on a specific electronic display 1 is received from the core system 5 (step S21), the DMS server 3 receives screen data (display screen data) representing the received display information. Generate transmission data D including the generated display screen data in the data portion and including the device code of the target electronic display 1 in the header portion.

  When the transmission data D is generated, the DMS server 3 then identifies the access point 2 to which the target electronic display 1 belongs (that is, the access point 2 linked to the target electronic display 1), and the access point 2 The generated transmission data D is transmitted to (hereinafter referred to as “target access point 2”) (step S22).

  As described above, each of the plurality of access points 2 arranged in the work area 90 continues to transmit the beacon B at the transmission cycle Tp after the electronic display system 100 is activated. Here, the target access point 2 that has received the transmission data D from the DMS server 3 includes the “data notice command Cd” in the next beacon B (the beacon B that is transmitted immediately before the time when the transmission data D is received). To do. More specifically, the data notice command Cd is transmitted to each of the plurality of unit signals b constituting the beacon B. Further, the target access point 2 sends the transmission data D received from the DMS server 3 following the beacon B including the data notice command Cd. Here, the “data notice command Cd” is an identification command for notifying the electronic display 1 that the transmission data D is transmitted following the beacon B, and is a notice for notifying the transmission of the transmission data D. It plays a role as information.

  The beacon B including the data notice command Cd (more specifically, the unit signal b including the data notice command Cd) transmitted from the target access point 2 is transmitted to all the electronic devices having the target access point 2 as an affiliated access point. It is received by the display 1 (that is, all the electronic displays 1 in the communication area of the target access point 2). However, the electronic display device 1 includes the target electronic display device 1.

  As described above, each control unit 14 of the plurality of electronic displays 1 arranged in the work area 90 continues to detect the beacon B transmitted from the affiliated access point 2 in the detection cycle Te. The control unit 14 of the electronic display 1 that detects the beacon B (specifically, at least one unit signal b among the plurality of unit signals b constituting the beacon B) transmitted from the affiliated access point 2 is: If the data notice command Cd is included there, it is determined that the transmission data D is sent following the beacon B. In this case, the control unit 14 changes the own apparatus from the sleep state to the wake-up state in accordance with the timing at which the transmission data D is transmitted so as to perform the reception process of the transmission data D. And the reception process of the said transmission data D is performed (step S23).

  As described above, the beacon B including the data notice command Cd transmitted from the target access point 2 is received by all the electronic displays 1 having the target access point 2 as an affiliated access point, and the target access point 2 The transmission data D sent out from is also received by all the electronic displays 1.

  The control unit 14 of each electronic display 1 that has received the transmission data D, first, the device code included in the header portion of the acquired transmission data D is the device code of the device itself stored in the memory of the device itself. It is determined whether or not they match. If the acquired device code does not match that of the own device, the control unit 14 determines that the transmission data D is a signal addressed to another electronic display 1 and ends the process.

  On the other hand, when the acquired device code matches that of the own device, the control unit 14 of the electronic display 1 (that is, the target electronic display 1) determines that the received transmission data D is a signal addressed to the own device. The updated image data included in the data portion of the transmission data D is temporarily stored in the memory. Then, the updated image data stored in the memory is displayed on the display 11 of the own apparatus. As a result, the display on the display 11 of the target electronic display 1 is updated to a screen displaying the display information transmitted from the core system 5.

  When the control unit 14 of the target electronic display 1 receives the transmission data D addressed to itself, the control unit 14 outputs a signal (ACK signal) including information indicating that the transmission data D has been normally received to the communication unit 13. Let However, as will become clear later, the transmission data D may be divided into a plurality of packets Di. In this case, the control unit 14 outputs an ACK signal to the communication unit 13 every time it receives each packet Di. Let The target access point 2 that has received the ACK signal from the target electronic display 1 transmits to the DMS server 3 a notification that the transmission data D has been normally received by the target electronic display 1 (normal response notification). The DMS server 3 that has received the normal response notification determines that the transmitted transmission data D has been normally received by the target electronic display 1, and ends the transmission processing of the transmission data D.

  On the other hand, when the ACK signal is not received from the target electronic display 1, the target access point 2 notifies the DMS server 3 that the transmission data D is not normally received by the target electronic display 1 (abnormal response notification). Send. The DMS server 3 that has received the abnormal response notification determines that the transmitted transmission data D is not normally received by the target electronic display 1, and repeatedly transmits the transmission data D (recovery communication). By performing recovery communication, the display on the electronic display 1 can be reliably updated, and the reliability of the system can be greatly improved.

  The above is a series of operations performed when information is distributed from the information distribution apparatus 10 to the specific electronic display 1 in the electronic display system 100. In the above description, the information distributed from the information distribution apparatus 10 to the specific electronic display 1 is the screen data to be displayed on the electronic display 1, but the distributed information is It is not limited. For example, the instruction information for changing the setting of the electronic display 1 can be distributed to the specific electronic display 1 by the same process as described above.

  Further, in the above description, one transmission data D is transmitted following the beacon B including the data notice command Cd. However, as shown in FIG. Subsequent to the included beacon B, a plurality of transmission data D may be transmitted continuously. In this case, the plurality of transmission data D may be all addressed to the same electronic display 1 or may be addressed to different electronic displays 1. By transmitting a plurality of transmission data D together, the communication efficiency is improved, and effects such as reduction in power consumption of the electronic display 1 and improvement in responsiveness such as display update can be obtained.

<4. Processing flow of electronic display 1>
<4-1. Reception processing start timing>
As described above, when the control unit 14 of the electronic display 1 detects the unit signal b including the data notice command Cd, it determines that the transmission data D is sent following the beacon B including the unit signal b. To do. Then, the control unit 14 changes its own device from the sleep state to the wake-up state in accordance with the timing at which the transmission data D is transmitted in order to perform reception processing of the transmission data D. Perform reception processing.

  Here, the control unit 14 specifies the timing at which the reception process of the transmission data D is to be started (that is, the timing at which the transmission data D is to be changed) based on the rank information i included in the detected unit signal b. This process will be described with reference to FIG. FIG. 8 is a diagram for explaining the processing.

  For example, if the detected unit signal b is transmitted “y-th” and the total number of unit signals b constituting the beacon B is “x”, the remaining (xy) unit signals b Is transmitted at the unit signal transmission period Tm. Therefore, the time ΔT from when the unit signal b is detected until the transmission of the beacon B ends is given by a value obtained by multiplying (xy) by the unit signal transmission cycle Tm (Equation 2).

ΔT = (xy) × Tm (Expression 2)
Since the transmission data D is transmitted following the beacon B, the timing at which the control unit 14 should start the reception processing of the transmission data D is the time when the time ΔT has elapsed since the unit signal b was detected. Based on the rank information i given to the detected unit signal b, the control unit 14 calculates the time ΔT from the above (Equation 2), and when the time ΔT has elapsed from the time when the unit signal b is detected, The state transits to the up state, and the reception process of the transmission data D is started.

<4-2. Interruption of reception processing>
As described above, each electronic display device 1 starts reception processing of the transmission data D regardless of whether the transmission data D transmitted from the information distribution device 10 is addressed to the own device or another device. To do. When the transmitted transmission data D is transmission data D addressed to another device, the reception process is a useless process. Therefore, it is preferable that the control unit 14 of the electronic display 1 is configured to interrupt the reception process when it is determined that the transmitted transmission data D is transmission data D addressed to another device. The flow of the processing will be described in detail with reference to FIGS. 9 and 10 are diagrams for explaining the processing.

  If the transmission data D transmitted from the information distribution apparatus 10 to the electronic display 1 is large, it is divided into a plurality of packets Di (that is, packetized) and transmitted as shown in FIG. . In this case, each of the plurality of packets Di constituting the transmission data D is transmitted in order at a predetermined cycle.

  Each of a plurality of packets Di constituting one transmission data D includes a data part d and a header part h, and the data part d includes various information (for example, partial information of display screen data). Yes. On the other hand, the header part h includes a device code of the electronic display 1 which is a destination to which the packet Di is transmitted.

  The control unit 14 of each electronic display device 1 that has received the header portion h of the packet Di, first, the device code included in the received header portion h is the device code of the device itself stored in the memory of the device itself. It is determined whether or not they match.

  When the device code included in the header portion h does not match the device code of the own device, the control unit 14 determines that the packet Di is a signal addressed to another device, and as shown in FIG. The reception process is immediately interrupted without receiving the data portion of Di.

  On the other hand, when the device code included in the header portion h matches the device code of the own device, the control unit 14 determines that the packet Di is a signal addressed to the own device, and as shown in FIG. Subsequently, the data part d of the packet Di is received. For example, if the packet Di is the first packet Di of the transmission data D divided into x packets Di, the packet Di and a total of x packets continuously transmitted subsequently to the packet Di All of the packets Di are signals directed to the own device. Therefore, in this case, the control unit 14 receives all of the header part h and the data part d of (x-1) packets Di that are continuously transmitted by the same process. When all the x packets Di constituting the transmission data D are received, all of the information included in one transmission data D (for example, one update image data) is received.

<4-3. Resuming reception processing>
As described above, each electronic display 1 determines whether or not the packet Di is addressed to its own device based on the header portion of the packet Di that constitutes the transmission data D transmitted from the information distribution device 10. If it is determined that the packet is addressed to the device, the reception process is immediately interrupted without receiving the data part d of the packet Di (see FIG. 9).

  By the way, as described above, the information distribution apparatus 10 may transmit a plurality of transmission data D following one beacon B (see FIG. 7). In this case, even if the transmission data D received first is data destined for another device, the transmission data D sent next may be data destined for the own device. Therefore, the control unit 14 of the electronic display 1 resumes the reception process at an appropriate timing if necessary even if the reception process of the transmission data D is once interrupted. This process will be described in detail with reference to FIG. FIG. 11 is a diagram for explaining the processing.

  As described above, the transmission data D transmitted from the information distribution apparatus 10 to the electronic display 1 is divided into a plurality of packets Di and transmitted when the size is large. In the header part h of each packet Di constituting the transmission data D, the transmission data D is divided into a number of packets Di in addition to the device code of the electronic display 1 that is the destination for transmitting the packet Di. Information (packet total number information), and information (packet number information) indicating the number of packets Di among the plurality of packets Di constituting the transmission data D are included.

  As described above, the information distribution apparatus 10 is configured to repeatedly transmit (retry transmission) the transmission data D when the ACK signal from the electronic display 1 cannot be obtained (recovery communication). Specifically, when the packet Di is transmitted, if the ACK signal in response to the packet Di is not obtained from the electronic display 1, the information distribution apparatus 10 (specifically, the access point 2) transmits the packet Di. Is sent again (retry transmission). If the ACK signal is not obtained from the electronic display 1 even if the packet Di is repeatedly transmitted by the number of times determined as “the number of retries”, the information distribution apparatus 10 (specifically, the access point 2) The transmission of the transmission data D is stopped (that is, the transmission of the remaining packet Di of the transmission data D is not performed), and the first packet Di of another transmission data D to be transmitted next is transmitted. However, the number of times that retry transmission should be performed (the number of retries) can be arbitrarily set in the DMS server 3 by a system administrator or the like. As described above, there is a possibility that the same packet Di may be repeatedly transmitted by retry transmission from the information distribution apparatus 10, and information indicating the number of times the packet Di has been transmitted is included in the header portion h of each packet Di. (Transmission count information) is included. That is, the transmission count information is information indicating the number of retry transmissions of the packet Di.

  As described above, the control unit 14 of each electronic display device 1 that has received the header portion h of the packet Di first stores the device code included in the received header portion h in its own memory in advance. It is determined whether or not it matches the device code. If it does not match the device code of its own device, the reception process is immediately interrupted without receiving the data part d of the packet Di.

  When the reception process is interrupted, the control unit 14 further addresses the own device based on various information (packet total number information, packet number information, transmission number information, etc.) included in the header part h of the packet Di. The timing at which the packet Di is transmitted is predicted, and the packet reception process is resumed at the predicted timing. An aspect of measuring the timing for resuming the packet reception process will be described in detail.

  When the reception process is interrupted, the control unit 14 belongs to the same transmission data D as the packet Di when the retry transmission of the packet Di is not performed based on the information included in the header part h of the packet Di. The number of remaining packets Di to be transmitted is specified (the number of remaining packets). Specifically, the number of remaining packets is defined by a numerical value obtained by subtracting packet number information included in the header portion h from the total packet number information included in the header portion h.

  Assuming that the number of remaining packets is “x1”, when retry transmission is not performed, the (x1) number of packets Di to be subsequently transmitted must be packets Di addressed to other devices. In other words, it is impossible to determine whether the packet Di transmitted to the (x1 + 1) -th packet is destined for another device or the own device, and the packet Di addressed to the own device is not the (x1 + 1) th packet Di. The possibility of being sent is not zero. Therefore, the control unit 14 calculates the timing at which the (x1 + 1) -th packet Di is transmitted based on the transmission period of the packet Di, and stores this as the first wakeup timing candidate value.

  On the other hand, when the retry transmission of the packet Di is performed based on the information included in the header portion h of the packet Di, the control unit 14 determines how many times the packet Di is transmitted (remaining retry). Number). Specifically, the remaining number of retries is defined by a numerical value obtained by subtracting the number of times of transmission included in the header portion h from the number of retries that is a predetermined value.

  Assuming that the number of remaining retries is “x2”, when retry transmission is performed, the (x2) number of packets Di subsequently transmitted should be packets Di addressed to other devices. In other words, it is impossible to determine whether the packet Di transmitted to the (x2 + 1) -th packet is destined for another device or the own device, and the packet Di addressed to the own device is not the (x2 + 1) -th packet. The possibility of being sent is not zero. Therefore, the control unit 14 calculates the timing at which the (x2 + 1) -th packet Di is transmitted based on the transmission period of the packet Di, and stores this as a second wake-up timing candidate value.

  The control unit 14 cannot know whether retry transmission of the packet Di is performed. Therefore, the control unit 14 causes the own apparatus to transition from the sleep state to the wake-up state at the earlier timing of the first wake-up timing candidate value and the second wake-up timing candidate value, The reception process of the packet Di is resumed.

  In practice, retry transmission may be successful before the number of retries is reached. However, for example, in the above example, when communication succeeds in the n-th retry transmission, the (x1) packets Di transmitted following the successful retry transmission must be packets Di addressed to other devices. is there. That is, if retry transmission is successful before the number of retries is reached, the timing at which a packet Di that may be destined for the own device is transmitted always comes later than the first wakeup timing candidate value. Therefore, it is not necessary to consider such a case.

  The flow of the above processing will be described with a specific example with reference to FIG. Now, when a packet Di addressed to another device is received, the first packet Di (hereinafter referred to as “packet Di (1”) of the transmission data D obtained by dividing the packet Di from the header portion h of the packet Di. / 4) ") is obtained. Further, it is assumed that the information that the packet Di (1/4) is the packet Di (1/4) related to the first retry transmission is obtained. Furthermore, it is assumed that the number of retries is set to “3”.

  In this case, the number of remaining packets is “x1 = 3 (= 4-1)”. That is, when retry transmission is not performed, the first packet Di transmitted subsequently is the second packet Di (2/4) of the transmission data D, and the second packet Di is The third packet Di (3/4) of the transmission data D, the third packet Di is the fourth packet Di (4/4) of the transmission data D, and another transmission is performed for the fourth packet. It can be predicted that the first packet Di of data D will be transmitted. Therefore, if retry transmission is not performed, the fourth packet Di transmitted subsequently may be the packet Di addressed to the own device, and the control unit 14 transmits the fourth packet Di. The incoming timing is calculated based on the transmission period of the packet Di, and this is stored as the first wake-up timing candidate value T1.

  On the other hand, the remaining number of retries is “x2 = 2 (= 3-1)”. That is, when retry transmission is performed, the first packet Di transmitted subsequently is the second retry transmission of the packet Di (1/4), and the second packet Di is the packet It is the third retry transmission of Di (1/4), and it can be predicted that the first packet Di of another transmission data D is transmitted as the third transmission. Therefore, when retry transmission is performed, there is a possibility that the third packet Di transmitted subsequently is a packet Di addressed to the own device, and the control unit 14 transmits the third packet Di. The incoming timing is calculated based on the transmission period of the packet Di, and this is stored as the second wake-up timing candidate value T2.

  Then, the control unit 14 transmits the earlier timing of the first wakeup timing candidate value T1 and the second wakeup timing candidate value T2, that is, the third packet Di. At timing T2, the own apparatus is changed from the sleep state to the wake-up state, and the header part h of the packet Di transmitted in the third packet is received.

<5. Functional block>
Here, each function realized in the electronic display system 100 is organized with reference to FIG. FIG. 12 is a block diagram showing each function realized in the electronic display system 100.

  As has become clear from the above description, in the electronic display system 100, in the information distribution apparatus 10, the transmission period (transmission period Tp) determined for the plurality of electronic displays 1 arranged in the work area 90. The function as the “beacon transmission unit 201” for transmitting the beacon B is realized. In addition, when information to be transmitted to the specific electronic display 1 is generated in the information distribution apparatus 10, the transmission data D addressed to the specific electronic display 1 including the information is generated and generated. A function as a “data transmission unit 202” for transmitting the transmission data D following the beacon B is realized. Furthermore, in the information distribution apparatus 10, when transmitting the transmission data D following the beacon B, the beacon B preceding the transmission data D (specifically, each of the plurality of unit signals b constituting the beacon B) is transmitted. In addition, a function as a “preliminary information adding unit 203” including information for preliminarily transmitting the transmission data D (data preliminary command Cd) is realized.

  On the other hand, in the control unit 14 of each electronic display 1, the beacon B transmitted from the beacon transmission unit 201 (specifically, at least one unit signal b among a plurality of unit signals b constituting the beacon B). Is implemented as a “beacon detection unit 301” that detects the presence or absence of reception at a predetermined detection cycle (detection cycle Te). In addition, in the control unit 14, when the data notice command Cd is included in the beacon B (specifically, the unit signal b) detected by the beacon detection unit 301, the transmission data D transmitted following the beacon B is transmitted. A function as a “transmission data receiving unit 302” for performing the receiving process is realized.

<6. Effect>
In the electronic display system 100 according to the above embodiment, each electronic display 1 detects the beacon B transmitted from the information distribution device 10 at the transmission cycle Tp at the detection cycle Te, whereby the information distribution device 10 and each of the information display devices 10 Communication with the electronic display 1 is established periodically. Accordingly, each electronic display device 1 can quickly detect this when the device itself is in a handoff state and perform handoff control. As a result, in the electronic display system 100, in principle, each of the plurality of electronic displays 1 is always linked to the access point 2 with which the own device can communicate. Is surely distributed to the electronic display 1.

  Further, in the electronic display system 100 according to the above-described embodiment, when the transmission data D for the specific electronic display 1 is transmitted from the information distribution device 10, the beacon B (more specifically, the beacon B Each of the plurality of unit signals b) includes a data notice command Cd serving as notice information for notifying the transmission of the transmission data D. According to this configuration, the electronic display 1 can measure the timing at which the reception process of the transmission data D is to be performed based on the data notice command Cd, so that wasteful power consumption due to waiting for the transmission data D is suppressed. It is done. That is, the power consumption of each electronic display 1 can be suppressed, and the consumption of the battery 15 serving as the power source can be suppressed. For example, the power consumption can be further reduced if the device is set in the sleep mode until the timing at which reception processing is to be performed.

  Moreover, in the electronic display system 100 according to the above-described embodiment, the beacon B includes a plurality of unit signals b that are continuously transmitted at the unit signal transmission cycle Tm. According to this configuration, each electronic display 1 only needs to detect at least one of the plurality of unit signals b, so that it is not necessary to detect the entire beacon B. That is, the power consumed when each electronic display 1 detects the beacon B can be suppressed. Further, since it is only necessary to detect at least one of the plurality of unit signals b constituting the beacon B instead of the entire beacon B, the time required for the detection process can be suppressed to a short time, and sleep can be performed accordingly. The time in the mode becomes longer. As a result, power consumption is suppressed.

  When the data notice command Cd is included in the beacon B, the data notice command Cd is included in each of the plurality of unit signals b constituting the beacon B. Therefore, the electronic display 1 does not need to detect all of the beacons B when detecting the data notice command Cd, and it is sufficient to detect at least one unit signal b.

  Further, in the electronic display system 100 according to the above embodiment, when the transmission data D is transmitted following the beacon B, the electronic display device 1 determines the order given to the unit signal b detected by the own device. Based on the information i, the reception timing of the transmission data D is adjusted. According to this configuration, the electronic display 1 can accurately identify the timing for performing the reception process of the transmission data D based on the rank information i given to the unit signal b, and therefore waits for the transmission data D. It is possible to further suppress unnecessary power consumption.

  In addition, according to the electronic display system 100 according to the above-described embodiment, each electronic display 1 is based on the header information of the packet Di, and the information included in the data portion of the packet Di is information addressed to its own device. If it is determined that the information is addressed to the other device, the data portion of the packet Di is not received. Therefore, the electronic display unit 1 receives the data portion of the packet addressed to the other device. Wasteful power consumption can be suppressed.

  In addition, according to the electronic display system 100 according to the above-described embodiment, each electronic display 1 predicts the next timing when the packet Di addressed to itself is transmitted based on the header information of the packet Di, Since the packet reception process is resumed at the predicted timing, it is possible to prevent the packet addressed to itself from being missed.

<7. First Modification>
As described above, in the electronic display system 100 according to the above-described embodiment, the control unit 14 of each electronic display 1 has the same detection cycle Te as the transmission cycle of the beacon B, and the beacon B (specifically, the beacon B). The presence or absence of reception of at least one unit signal b (see FIG. 4) of the plurality of unit signals b constituting B is continuously detected, and the detection intensity R of the beacon B becomes smaller than the handoff threshold Q2. If this happens, it is determined that the device itself has entered a handoff state.

  By the way, the electronic display 1 detects at least one unit signal b among a plurality of unit signals b constituting one beacon B by one detection process. Accordingly, for example, if the beacon B is composed of “x” unit signals b, the electronic display 1 transmits the x-th unit signal b after the first unit signal b is transmitted. If the detection process of the beacon B is performed at any timing up to then, one of the unit signals b can be detected. In other words, the timing at which the electronic display 1 performs the detection process of the beacon B is in principle the output time L of the beacon B (the first unit signal b constituting the beacon B is transmitted and the xth Any timing during the period until the unit signal b is transmitted).

  However, the most preferable detection processing timing is in the vicinity of the time when the time (L / 2) has elapsed since the transmission of the beacon B is started. If the detection process of beacon B is performed at such timing, even if the transmission cycle of beacon B from access point 2 is disturbed and the transmission timing of beacon B slightly deviates back and forth, the beacon B on the electronic display 1 side This is because the possibility of failing to detect B is reduced.

  Therefore, the control unit 14 of each electronic display 1 may be configured to adjust the timing for performing the detection process of the beacon B to the optimal timing based on the rank information i given to the detected unit signal b. The processing executed by the control unit 14 in this case will be described with reference to FIG. FIG. 13 is a diagram for explaining the processing.

  As described above, the electronic display 1 has the unit signal b transmitted in the middle of the plurality of unit signals b transmitted continuously (that is, after the transmission of the beacon B is started (L / 2)). It is preferable to detect the unit signal b) transmitted in the vicinity of the time when the time elapses. Hereinafter, the unit signal b transmitted in the middle is referred to as “target unit signal b”.

  When the control unit 14 detects one unit signal b by the detection process of the beacon B, the detected unit signal b is the target unit signal b based on the rank information i given to the detected unit signal b. If it is not the target unit signal b, timing adjustment processing is performed. Here, when the detected unit signal b is the unit signal b whose deviation from the target unit signal b is within a predetermined allowable range, the timing adjustment process may be unnecessary. If it is determined that the timing adjustment process is unnecessary, the control unit 14 detects the unit signal b and, after “Te”, transitions to the wake-up state and performs the detection process of the beacon B as a rule.

  When performing the timing adjustment process, the control unit 14 predicts the next timing of sending the target unit signal b based on the detected rank information i of the unit signal b, and enters the wake-up state in accordance with the timing. It changes and performs the detection process of the beacon B.

  For example, if the detected unit signal b is the “y-th” signal, if the total number of unit signals b constituting the beacon B is “x”, the unit signal b is detected and then The time Te ′ until the target unit signal b is sent is given by “Te ′ = (x / 2−y) × Tm + Tp”. The control unit 14 calculates the time Te ′ based on the rank information i given to the detected unit signal b, and transitions to the wake-up state after the time Te ′ has elapsed since the unit signal b was detected. The beacon B is detected.

  According to the above modification, the electronic display 1 adjusts the reception timing of the beacon B based on the ranking information i given to the unit signal b detected by the device itself. For example, as described above, the reception timing of the unit signal b is adjusted so that the unit signal b transmitted in the middle of the beacon B is detected. By adjusting in this way, even if the transmission timing of the beacon B from the access point 2 slightly deviates back and forth, the possibility of failing to detect the beacon B on the electronic display 1 side is reduced. That is, the electronic display 1 can reliably follow the beacon B that is continuously transmitted from the access point 2 to which the device belongs to at the transmission cycle Tp.

<8. Second Modification>
In the electronic display system 100 according to the above-described embodiment, there may be a difference in communication state in various places in the work area 90 such as a factory where the system is introduced. In such a case, a configuration in which various set values in the electronic display 1 are set to different values depending on the access point 2 to which the electronic display 1 belongs is preferable.

  For example, for the access point 2 with a relatively good communication state, the handoff threshold value Q2 is set to a relatively high value, and for the access point 2 with a relatively poor communication state, the handoff threshold value Q2 is set to a relative value. Keep the value low. According to this configuration, each electronic display 1 can appropriately switch the belonging access point 2. In addition, it is difficult to make a difference in the number of electronic display devices 1 belonging to the access points 2, and a situation in which the load is concentrated on a specific access point 2 can be avoided to smoothly operate the electronic display system 100. it can.

  For example, for the access point 2 with a relatively good communication state, the value of the number of retries described above is set to a relatively small value, and for the access point 2 with a relatively poor communication state, the value of the number of retries is set. Set a relatively large value. According to this configuration, each electronic display 1 can reliably receive transmission data D without unnecessarily increasing the load on the DMS server 3 and the access point 2 and the power consumption of each electronic display 1. Can do.

  Here, as in the above examples, when various setting values in the electronic display 1 are different values depending on the access point 2 to which the electronic display 1 belongs, 2 may be included as a command in beacon B transmitted from 2 (specifically, each of unit signals b constituting beacon B). That is, in the electronic display system 100 according to the above embodiment, the configuration in which the data notice command Cd is included in the beacon B is shown, but the beacon B (specifically, the unit signal b constituting the beacon B Each of them may include a command other than the data notice command Cd, for example, a set value of the electronic display 1 that should be different depending on the access point 2.

  When the beacon B (specifically, each of the unit signals b constituting the beacon B) includes a set value of the electronic display 1 that should be different depending on the access point 2, the electronic display system When the access point 2 to which the device belongs is determined at the time of starting 100 or when the access point 2 to which the device belongs is switched by handoff control, the electronic display device 1 receives the beacon received from the newly assigned access point 2. In response to the command included in B, the setting value of the device itself is switched, whereby the setting value of each electronic display 1 becomes a value corresponding to the access point 2 to which the electronic display 1 belongs. Will be. As described above, the beacon B is transmitted from the access point 2 to all the electronic displays 1 in the specific area (communication area of the access point 2). If common setting information is included in the beacon B and transmitted to the electronic display 1 in the area, the setting information can be efficiently distributed to the electronic display 1.

<9. Third Modification>
As described above, in the electronic display system 100, when each electronic display 1 determines that its own device is in the handoff state, the beacon B ( More specifically, a process (channel search) for detecting a beacon B) whose detection intensity R is greater than or equal to the capture threshold value Q1 is performed. In this process, for example, as described above, is it possible to receive the beacon B by sweeping the reception frequency over the entire frequency range of the beacon B allocated to each of the plurality of access points 2 while switching the reception frequency one after another? This is performed by performing a determination process of whether or not (searching for a receivable frequency region). However, in this determination process, it is determined that the beacon B has been received when the unit signal b having a detection intensity R equal to or greater than the capture threshold Q1 is detected.

  Now, in the channel search, the electronic display 1 performs the “basic search process” m times (where m is an integer equal to or greater than 1) during the transmission period Tp. Here, the “basic search process” refers to a process of determining whether or not each beacon B transmitted from each access point 2 can be received by an interval of 1 / n of the transmission period Tp of the beacon B (hereinafter referred to as “beacon B”). This is called “interval Tf” (where “Tf = Tp / n”)) and n times (where n is a positive integer). Hereinafter, the value “n” indicating the number of times the electronic display device 1 performs the determination process in the basic search process of each beacon B is referred to as “basic number n”.

  As described above, the beacon B having a constant transmission time L is transmitted from the access point 2 during the transmission cycle Tp. In other words, there is a time zone during which no beacon B is transmitted from the access point 2. Here, when the electronic display device 1 performs the determination process in a time zone in which the beacon B is not transmitted, the access point 2 is actually in the communication area of the access point 2. There is a risk of making an erroneous determination that beacon B cannot be received. Therefore, it is necessary to ensure that it overlaps with the transmission time L of the beacon B in at least one of the n determination processes in the basic search process.

  As described above, in the electronic display system 100, the transmission period Tp of the beacon B is set to a common value between the access points 2, and the output time L of the beacon B is also set to a common value. However, the beacon B transmission timing is not synchronized. That is, beacons B are transmitted from each access point 2 at different timings.

  Therefore, no matter what timing the beacon B is transmitted, it is necessary to ensure that it overlaps the transmission time L of the beacon B in at least one of the n determination processes in the basic search process. .

  For this purpose, the output time L of the beacon B needs to be a value satisfying the following (formula 3). However, in (Expression 3), “n” is the value of the basic number n in the basic search process, and “Tp” is the transmission cycle Tp of the beacon B from the access point 2. “Ceil (a)” represents “the smallest integer equal to or greater than a”.

n = ceil (Tp / L) (Equation 3)
On the other hand, since it is necessary for the access point 2 to perform data communication with the electronic display 1 during a time period when the beacon B is not transmitted, the output time L is preferably as small as possible in order to increase communication efficiency. . That is, it is most preferable to employ the minimum value among the L values satisfying the above (Expression 3) as the output time L. Hereinafter, the value of the minimum output time L that can be taken by (Equation 3) is referred to as “minimum output time Lm”.

  By the way, in order to keep the power consumption of the electronic display 1 small, it is necessary to keep the power consumption required for the basic search process small. For this purpose, the value of the basic number n is preferably as small as possible.

  However, when the basic number n is “1”, the value of the minimum output time Lm is “Lm = Tp”, that is, a value equal to the transmission cycle Tp, from (Equation 3). In this case, the beacon B is continuously transmitted, and data communication between the access point 2 and the electronic display 1 cannot be performed. Therefore, the basic number n cannot be set to “1”.

  Therefore, when the basic number n is “2”, the value of the minimum output time Lm is given by “Lm = Tp / 2”, that is, half the value of the transmission cycle Tp from (Equation 3).

  In this case, as shown in FIG. 14, 2, in the basic search process, the output timing of the beacon B from the access point 2 is related to the timing at which the electronic display 1 performs the basic search process. In theory, one of the determination processes always overlaps the transmission time L of the beacon B.

  However, in reality, there are errors and variations in timers for measuring the search interval of the access point 2 or the electronic display 1, and the beacon B is divided into unit signals b, so that the electronic display Since it may be assumed that the unit signal b cannot be received immediately after the 1 starts the reception operation, stable detection may not be ensured in this aspect.

  Therefore, as shown in FIG. 15, it is preferable to obtain a value obtained by adding a predetermined error absorption time Δt to the minimum output time Lm as the appropriate output time Lr (Lr = Lm + Δt). The error absorption time Δt can be set to, for example, about “0.1 (second)”, but is preferably defined based on the timer error of the device. As a result, an error corresponding to the time of “± Δt” is allowed between the access point 2 and the electronic display 1. Therefore, if the output time L of the beacon B is set to the appropriate output time Lr, what is the output timing of the beacon B from the access point 2 with respect to the timing when the electronic display 1 performs the basic search process. Even in such a relationship, at least one of the two determination processes in the basic search process surely overlaps the transmission time L of the beacon B.

  Therefore, if the basic search process is performed m times during the transmission cycle Tp, at least m determination processes are performed in the time zone during which the beacon B is transmitted, and a stable channel search is performed. Secured.

  For example, when the transmission cycle Tp is “4 (seconds)”, the value of the minimum output time Lm is “Lm = Tp / 2 = 2 (seconds)”, and the error time Δt is “0.1 (seconds)”. Then, the appropriate output time Lr is “Lr = Lm + Δt = 2.1 (seconds). Therefore, the output time L of the beacon B is set to“ 2.1 (seconds) ”, and the electronic display 1 However, in the basic search process, the process of determining whether or not the beacon B from each access point 2 can be received during the transmission cycle Tp “4 (seconds)” is expressed as “Tf = Tp / 2 = 2.0 ( (Second) ”is performed twice with an interval of“ second) ”, the output timing of the beacon B from the access point 2 is related to the timing at which the electronic display 1 performs the basic search process. , At least one of the two determination processes in the basic search process Times will surely overlap the transmission time L of the beacon B. Here, if the basic search process is performed, for example, twice during the transmission cycle Tp, at least two determination processes are performed in the time zone during which the beacon B is transmitted, as shown in FIG. As a result, a stable channel search is secured. For example, if the timing at which the basic search process is performed is shifted by “ΔTf = Tf / 2”, the timing at which the electronic display 1 performs the determination process can be made periodic. When this aspect is applied in the above example, the process of determining whether or not the beacon B from each access point 2 can be received during the transmission cycle Tp “4 (seconds)” is expressed as “Tf / 2 = Tp / 4 = 1.0 (seconds) "is performed four times with an interval.

  In the above example, the basic number n is “2”, but the value of the basic number n may be 2 or more. For example, when the basic number n is “3”, the appropriate output time Lr is the value of the minimum output time Lm given by (Equation 3) (“Lm = Tp / 3”, that is, 3 minutes of the transmission cycle Tp). This is a value obtained by adding a predetermined error absorption time Δt to 1). In this case, regardless of the relationship between the output timing of the beacon B from the access point 2 and the timing at which the electronic display 1 performs the basic search process, of the three determination processes in the basic search process In theory, one time always overlaps the transmission time L of the beacon B. Increasing the basic number n increases the power consumption of the electronic display 1 for the basic search process, but the output time L at each access point 2 can be kept small (that is, electronic The advantage that a long time for data communication with the display 1 can be ensured) is obtained.

  However, as described above, in the channel search, for each beacon B assigned to each of the plurality of access points 2 (that is, signals having different frequency domains from each other), whether or not the beacon B can be received is determined. Need to do. Therefore, each electronic display 1 performs channel search for each frequency region while shifting the timing, as schematically shown in FIG.

<10. Fourth Modification>
As described above, in the electronic display system 100, each electronic display device 1 performs a channel search when the device itself is in the handoff state, and performs a single channel search (specifically, for example, the basic search described above). When it is determined that the reception of the beacon B whose detection intensity R is greater than or equal to the capture threshold Q1 cannot be detected as a result of the process being performed m times (where m is an integer equal to or greater than 1) during the transmission cycle Tp. It is preferable to repeat the channel search once again at intervals. That is, it is preferable that the channel search is continuously repeated until reception of a beacon B having a detection intensity R equal to or greater than the capture threshold Q1 can be detected.

Here, as shown in FIG. 18, it is more preferable that the interval for repeating the channel search is increased with time. For example, for each frequency region, the first channel search CS (1), the second channel search CS (2), and the interval ΔT (1) is set to “2 (seconds)”. The interval ΔT (2) with the third channel search CS (3) is set to “4 (seconds)”, and the interval ΔT (3 between the third channel search CS (3) and the fourth channel search CS (4) is set. ) Is “8 (seconds)”, and the interval ΔT (n) between the nth channel search CS (n) and the (n + 1) th channel search CS (n + 1) is “2 ⁿ (seconds)”. It is good.

  When the interval for repeating the channel search is increased with time, if the interval for performing the channel search exceeds a value determined as the maximum value, it is preferable that the channel search interval be constant thereafter. For example, in the above example, when the channel search interval is “1024 (seconds)”, the channel search interval can be kept at “1024 (seconds)” thereafter.

  According to this configuration, it is possible to suppress the power of the electronic display 1 from being consumed by a useless channel search. For example, when the electronic display 1 has been moved to a place (for example, in a warehouse) that is out of the communication area of any access point 2, the electronic display 1 frequently (for example, at intervals of 2 (seconds)). If the channel search continues to be performed, the power of the electronic display 1 is wasted. However, according to the above configuration, the frequency of the channel search decreases with time, and the consumed power also decreases. In such a case, it is possible to prevent the battery 15 of the electronic display 1 from being wasted.

<11. Other variations>
The electronic display system 100 according to the above-described embodiment functions as a work support system that is introduced into an article manufacturing factory and supports work in each work process using an electronic display in the manufacturing factory. On the display 1, a screen corresponding to the work place 90 where the device is located at that time (for example, a screen for explaining work contents to be performed at the work place) is displayed. The aspect is not limited to this.

  For example, the electronic display system 100 can be introduced into a company or the like to function as a schedule management system that performs schedule management of the company or the like. Conventionally, schedule management of a company or the like is performed, for example, when an administrator manages schedule information of the entire company on a computer, and the managed schedule information is printed out and posted on paper (or alternatively) The information is transmitted to a computer connected to the administrator's computer via a communication line or the like and displayed on the display of the computer), thereby making it known throughout the company. In this case, every time the latest schedule information comes out, it is necessary to print out the schedule information and post the paper. Alternatively, it is necessary that a computer connected to the administrator's computer via a communication line is arranged at any place in the company.

  If the electronic display system 100 is introduced into a company as a schedule management system, schedule information can be easily disseminated throughout the company.

  When the electronic display system 100 is introduced into a company as a schedule management system, the electronic display 1 is arranged at each location in the company (for example, near the entrance of a conference room, each employee's desk, near each department's window, etc.). A screen for displaying a schedule related to the place where the device is located is displayed on each electronic display 1 (for example, in the case of the electronic display 1 arranged near the entrance of the conference room, the reservation status of the conference room is displayed. For example, in the case of the electronic display 1 arranged at the desk of the employee, a screen for displaying the schedule of the employee sitting at the desk (for example, destination, return time, etc.), for example, near the window of each department In the case of the electronic display 1 arranged, a screen for displaying the schedule of the department for the day is displayed.

  According to this configuration, there is no need to print out and display the schedule information, and the schedule information can be displayed throughout the company without providing a communication line network throughout the company. That is, the schedule information can be easily disseminated throughout the company.

  Further, since the display of each electronic display 1 is immediately updated when the schedule information is updated, the employee can always grasp the latest schedule information.

1 Electronic Display 2 Access Point 3 DMS Server 5 Core System 10 Information Distribution Device 100 Electronic Display System

Claims (10)

An electronic display system comprising a plurality of electronic displays driven by a battery and respectively installed on a moving body, and an information distribution device for distributing information displayed by the plurality of electronic displays to the plurality of electronic displays. And
The information distribution device is
A first signal transmission unit for transmitting a first signal for the plurality of electronic displays at a predetermined transmission period;
When information to be transmitted to a specific electronic display among the plurality of electronic displays is generated, a second signal addressed to the specific electronic display including the information is generated, and the generated first A second signal transmitter for transmitting two signals following the first signal;
When transmitting the second signal following the first signal, a notice information giving unit including notice information for notifying the transmission of the second signal in the first signal preceding the second signal;
With
Each of the plurality of electronic indicators is
A first signal detector that detects whether or not the first signal is received at a predetermined detection period;
A second signal receiving unit that performs reception processing of the second signal transmitted subsequent to the first signal when the advance notice information is included in the first signal detected by the first signal detecting unit; ,
An electronic display system comprising: The electronic display system according to claim 1,
The first signal is composed of a plurality of unit signals transmitted continuously at a predetermined period,
The notice information giving unit includes the notice information in each of the plurality of unit signals constituting the first signal preceding the second signal,
The electronic display system in which the first signal detection unit detects at least one unit signal among the plurality of unit signals. The electronic display system according to claim 2,
Each of the plurality of unit signals is provided with rank information indicating which unit signal is the unit signal transmitted among the plurality of unit signals transmitted continuously,
When the second signal is transmitted following the first signal, the second signal receiving unit, based on the rank information given to the unit signal detected by the first signal detection unit, An electronic display system for adjusting the reception timing of the second signal. The electronic display system according to claim 2,
Each of the plurality of unit signals is provided with rank information indicating which unit signal is the unit signal transmitted among the plurality of unit signals transmitted continuously,
When the first signal detection unit detects the unit signal, the electronic display system adjusts the next reception timing of the first signal based on the rank information given to the unit signal. The electronic display system according to any one of claims 1 to 4,
The information distribution device is
Multiple repeaters,
A server for delivering information to the plurality of electronic displays via the plurality of repeaters;
With
The first signal transmission unit includes:
Sending the first signal to each of the one or more electronic displays in the communication area of the repeater via each of the plurality of repeaters,
An electronic display system that includes setting information common to electronic displays in a specific area among the plurality of electronic displays in the first signal transmitted via the repeater having a communication area in the specific area. . An electronic display system according to any one of claims 1 to 5,
The second signal is packetized;
The second signal receiving unit is
If it is determined based on the header information of the packet of the second signal whether the information included in the data portion of the packet is information addressed to the own device, and if it is determined that the information is not addressed to the own device An electronic display system that interrupts reception processing of the packet and does not receive the data portion of the packet. The electronic display system according to claim 6,
The second signal receiving unit is
When it is determined that the information included in the data portion of the packet of the second signal is not information addressed to the own device and the reception processing of the packet is interrupted, how many second signals are received from the header portion of the packet. Information indicating whether the packet is divided into packets, information indicating what number of packets among the plurality of packets constituting the second signal, and the number of retry transmissions of the packet Information indicating whether the packet is received, based on the acquired information, predicting the next timing when the packet addressed to the device is transmitted, and restarting the packet reception process at the predicted timing Electronic display system. The electronic display system according to claim 2,
The information distribution device is
Multiple repeaters,
A server for delivering information to the plurality of electronic displays via the plurality of repeaters;
With
Each of the plurality of repeaters is assigned a different frequency region, and each of the plurality of repeaters transmits the first signal in the frequency region assigned to the own device,
The electronic indicator is
In searching for the receivable first signal among the first signals transmitted from each of the plurality of repeaters,
Basic search for determining whether each first signal can be received or not n times (where n is an integer of 2 or more) with an interval of 1 / n of the transmission period of the first signal. In the case where the processing is performed m times (where m is an integer of 1 or more) during the transmission cycle,
The output time of the first signal from each of the plurality of repeaters is
The transmission period of the first signal is x, ceil (a) is the smallest integer greater than or equal to a,
n = ceil (x / y)
An electronic display system that is a value obtained by adding a predetermined error absorption time to the minimum value of y that satisfies the above relationship. The electronic display system according to claim 8,
The basic search process is
An electronic display system, which is a process of determining whether or not each of the first signals can be received, and performing the process twice with an interval of a half of the transmission period of the first signal. The electronic display system according to claim 2,
The information distribution device is
Multiple repeaters,
A server for delivering information to the plurality of electronic displays via the plurality of repeaters;
With
Each of the plurality of repeaters is assigned a different frequency region, and each of the plurality of repeaters transmits the first signal in the frequency region assigned to the own device,
The electronic indicator is
In searching for the receivable first signal among the first signals transmitted from each of the plurality of repeaters,
As a result of the search, when it is determined that there is no receivable first signal, the search is repeatedly performed at intervals,
An electronic display system in which the interval when the search is repeated becomes longer as time elapses.

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