JP2014183496A - Radio display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio display system that is able to efficiently obtain transmitted information while restraining power consumption of a radio display.SOLUTION: A radio display system comprises: an electronic inventory tag server; a plurality of access points (AP) 30 for transmitting information stored in the electronic inventory tag server; and an electronic inventory tag for receiving information transmitted by one AP to display it. Each AP includes: two antennas 31a, 32a; two radio communication units 31, 32; and a timing change unit 34e. One communication unit periodically transmits a first beacon including its own transmission timing information by means of one antenna. The other communication unit receives a second beacon transmitted by an AP other than itself by means of the other antenna. The second beacon includes transmission timing information on the second beacon. The timing change unit changes the transmission timing of the first beacon such that it becomes closer to the transmission timing of the second beacon at the time of establishment of a prescribed condition.

Description

  The present invention relates to a wireless display system, and more particularly to a wireless display system in which a wireless display device receives information from a server via one access point among a plurality of access points.

  Conventionally, wireless display systems are sometimes used in stores such as supermarkets and convenience stores, factories, and the like. For example, in a wireless display system disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-148074), a plurality of wireless indicators (electronic shelf labels) are installed at a store floor or the like, and each wireless indicator is a transceiver ( The product information is received from the server via the access point), and the display content is updated based on the received product information.

  In such a wireless display system, the communication distance of the access point is limited, and communication between the access point and the wireless display device may be hindered by an obstacle or the like. In many cases, a plurality of access points are used as in Japanese Patent No. 148074. Each wireless indicator receives information from one access point (access point to which the wireless indicator belongs) that is transmitting a signal with sufficient strength to the wireless indicator.

  However, the wireless display device cannot always receive information from the same access point. For example, when a wireless display is moved in a building and cannot receive a signal from an access point that has received information until then, it is necessary to receive information from another access point.

  However, when the access point that receives information (to which the wireless display device belongs) can be changed, the wireless display device has the following problems.

  Each access point transmits a signal called a beacon at a unique timing for a predetermined time per time in order to establish a link with the wireless display. The access point periodically transmits beacons at regular transmission intervals. The wireless indicator can immediately react to the information when the information is transmitted from the server by receiving the beacon from the access point that the wireless indicator should receive the information.

  When the wireless indicator always receives a beacon from the same access point, the wireless indicator stores the timing at which the access point transmits a beacon, and if the beacon is received at that timing, the beacon is always received. Can receive. That is, when the wireless display device always receives a beacon from the same access point, the wireless display device can receive a beacon if the beacon reception operation is performed only once per beacon transmission cycle time.

  However, when the wireless display device is configured to be able to change the access point for receiving information, the timing for transmitting the beacon differs for each access point. Therefore, even if the wireless indicator performs a beacon reception operation once at a certain timing with respect to the beacon transmission cycle time, the wireless indicator can receive a beacon from the access point to which it belongs at that time. Is not limited. Therefore, the wireless display device needs to execute a beacon reception operation a plurality of times for the beacon transmission cycle time so that a beacon from any access point can be received. However, since the wireless display is generally driven by a battery, by performing an unnecessary beacon reception operation (except for the beacon transmission timing from the access point to which the wireless display belongs) By performing the receiving operation), power is consumed and the battery replacement frequency may increase.

  An object of the present invention is a wireless display system in which a wireless display receives information from a server via one access point among a plurality of access points, and suppresses power consumption of the wireless display and transmits the information. An object of the present invention is to provide a wireless display system that can efficiently acquire incoming information.

  A wireless display system according to the present invention includes a server, a plurality of access points, and a wireless display. The server stores information. The access point transmits information stored in the server. The wireless display device receives information transmitted from one access point and performs display according to the received information. The wireless display is battery driven. Each of the access points includes first and second antennas used for signal transmission / reception, a beacon transmission unit, a beacon reception unit, and a timing change unit. The beacon transmission unit periodically transmits the first beacon having the first time length using the first antenna. The beacon receiving unit receives a second beacon transmitted from an access point other than itself using the second antenna. The first beacon includes information related to the transmission timing of the first beacon. The second beacon includes information related to the transmission timing of the second beacon. The timing changing unit changes the transmission timing of the first beacon by the beacon transmission unit so as to approach the transmission timing of the second beacon when the predetermined condition is satisfied.

  Here, the access point receives a beacon of an access point other than itself together with information related to the transmission timing of the beacon so that the transmission timing of its own beacon approaches the transmission timing of other beacons when a predetermined condition is satisfied. change. Therefore, in the wireless display system, it is possible to synchronize the transmission timing of the access point beacon. By synchronizing the transmission timing of the beacon of the access point, the wireless display device can receive the beacon when receiving a beacon at a certain timing when receiving a beacon from any access point. . In other words, the wireless display device does not need to perform a beacon reception operation in vain (at the timing when the beacon is not transmitted from the access point), and information transmitted while suppressing the power consumption of the battery of the wireless display device. Can be obtained efficiently.

  In the wireless display system according to the present invention, each access point preferably further includes a grasping unit. The grasping unit desirably grasps the timing difference between the transmission timing of the first beacon and the transmission timing of the second beacon. The predetermined condition preferably includes that the timing difference is equal to or longer than the second time.

  Thereby, the transmission timing of the beacon of the access point can be synchronized in the wireless display system.

  In the wireless display system according to the present invention, it is desirable that a unique number is assigned to each access point. The first beacon preferably includes information regarding its own unique number. The second beacon preferably includes information on the unique number of the access point that transmitted the second beacon. Preferably, the predetermined condition includes that the own unique number has a predetermined magnitude relationship with the unique number of the access point that transmitted the second beacon.

  Here, in the wireless display system, it is easy to synchronize the transmission timings of beacons of a plurality of access points.

  In the wireless display system according to the present invention, each access point is preferably assigned a unique number, and each access point preferably further includes a storage unit capable of storing a reference number. The first beacon preferably includes information regarding its own unique number. Moreover, when the reference number is memorize | stored in the memory | storage part, it is desirable that the information regarding its own reference number is further contained in the 1st beacon. The second beacon preferably includes information on the unique number of the access point that transmitted the second beacon. Furthermore, it is desirable that the second beacon may include information on the reference number of the access point that transmitted the second beacon. When the timing change unit changes the transmission timing of the first beacon so as to approach the transmission timing of the second beacon, the storage unit stores the reference number of the access point that transmitted the second beacon as follows: It is desirable to store the unique number as its own reference number. When the second beacon includes information related to the reference number of the access point that transmitted the second beacon, the storage unit stores the reference number of the access point that transmitted the second beacon as its own reference number. It is desirable to do. When the second beacon does not include information on the reference number of the access point that transmitted the second beacon, the storage unit stores the unique number of the access point that transmitted the second beacon as its own reference number. It is desirable to do. Preferably, the predetermined condition includes that the own unique number has a predetermined magnitude relationship with the unique number or reference number of the access point that transmitted the second beacon.

  Here, in the wireless display system, it is easy to synchronize the transmission timings of beacons of a plurality of access points.

  In the wireless display system according to the present invention, it is preferable that the server transmits a synchronization signal for synchronizing the transmission timings of the first beacons of all the access points to the access points.

  Thereby, it is possible to roughly synchronize the transmission timing of the beacon of the access point. Therefore, the access point can complete the operation of synchronizing the beacon transmission timing in a short time while receiving the beacon of another access point.

  In the wireless display system according to the present invention, it is desirable that the beacon transmission unit of each access point performs transmission using a channel different from the beacon transmission units of other access points.

  Accordingly, signals transmitted from the access point do not interfere with each other, and the reliability of communication between the access point and the wireless display can be improved.

  In the wireless display system according to the present invention, the wireless display device preferably includes a receiving unit, a determining unit, and a reception timing determining unit. The receiving unit preferably receives the first beacon transmitted from the access point. It is desirable that the determination unit determines which access point receives the information transmitted. It is desirable that the reception unit performs the reception operation of the first beacon for all the channels used by the access point at a time interval shorter than the first time when the wireless display device is introduced. It is desirable that the determination unit determines to receive information using a channel on which the reception unit has received the first beacon having the strongest signal strength when the wireless display device is introduced. The reception timing determination unit uses the timing at which the reception unit receives the first beacon and the transmission cycle time during which the first beacon is transmitted from the access point when the wireless display device is introduced. It is desirable to determine the timing and time interval for performing the beacon receiving operation.

  Here, once the receiving unit of the wireless display device receives the beacon from the access point, the receiving operation is not performed at the timing when the beacon is not transmitted thereafter. In other words, once the receiving unit receives a beacon from an access point, there is no need to perform a useless beacon receiving operation thereafter. Therefore, the transmitted beacon can be efficiently acquired while suppressing the power consumption of the battery of the wireless display.

  Further, in the wireless display system according to the present invention, the reception unit determines when receiving information transmitted from which access point after the introduction of the wireless display device. It is desirable to perform the first beacon reception operation for all channels used by the access point using the timing and time interval for performing the first beacon reception operation. It is desirable that the determination unit determines to receive information using the channel on which the reception unit has received the first beacon having the strongest signal strength.

  Here, in the wireless display system, even if the access point at which the wireless display device receives a beacon changes from one access point to another access point for some reason, the wireless display device performs the beacon reception timing. A beacon can be received without changing the time interval. Therefore, the wireless display device does not need to perform a useless reception operation in preparation for a change in the beacon transmission timing from the access point. As a result, the transmitted information can be efficiently acquired while suppressing the power consumption of the battery of the wireless display.

  In the wireless display system according to the present invention, an access point receives a beacon of an access point other than itself along with information on the transmission timing of the beacon, and when a predetermined condition is satisfied, Change to approach the transmission timing. Therefore, in the wireless display system, it is possible to synchronize the transmission timing of the access point beacon. By synchronizing the transmission timing of the beacon of the access point, the wireless display device can receive the beacon when receiving a beacon at a certain timing when receiving a beacon from any access point. . In other words, the wireless display device does not need to perform a beacon reception operation in vain (at the timing when the beacon is not transmitted from the access point), and information transmitted while suppressing the power consumption of the battery of the wireless display device. Can be obtained efficiently.

It is a figure which shows the electronic shelf label system which concerns on one Embodiment of this invention. It is a figure which shows the example of arrangement | positioning of the electronic shelf label with which the electronic shelf label system which concerns on FIG. It is a figure which shows the external appearance of the electronic shelf label with which the electronic shelf label system which concerns on FIG. 1 is provided. In the electronic shelf label system according to FIG. 1, a state where one electronic shelf label is arranged at a position where it can communicate with a plurality of (two in FIG. 4) access points is depicted. It is a block diagram which shows schematic structure of the electronic shelf label server with which the electronic shelf label system which concerns on FIG. 1 is provided. It is a block diagram which shows schematic structure of the access point with which the electronic shelf label system which concerns on FIG. 1 is provided. It is a figure for demonstrating how the radio | wireless communication part of the access point of FIG. 6 is each used at the time of the reception of the signal from an electronic shelf label, and the transmission of the beacon to an electronic shelf label. In FIG. 7A, both wireless communication units receive signals from the electronic shelf label. In FIG.7 (b), one radio | wireless communication part is transmitting the beacon to the electronic shelf label. The other wireless communication unit receives a beacon of another access point. It is a block diagram which shows schematic structure of the electronic shelf label with which the electronic shelf label system which concerns on FIG. 1 is provided. 7 is a diagram for explaining a basic operation of the access point of FIG. 6. A state in which an access point periodically transmits a beacon to an electronic shelf label and a state in which the access point transmits image data to the electronic shelf label when it receives image data from the electronic shelf label server are depicted. . An identifier received by the access point from the electronic shelf label server is included as information in a beacon transmitted immediately after the access point receives image data from the electronic shelf label server. It is a flowchart for demonstrating the basic operation | movement of the electronic shelf label of FIG. It is a flowchart for demonstrating the link operation | movement with an electronic shelf label and an access point performed at the time of the introduction of the electronic shelf label of FIG. It is a flowchart for demonstrating the handoff control of the electronic shelf label of FIG. It is drawing for demonstrating a problem when the transmission timing of the beacon of an access point is not synchronized in an electronic shelf label system. It is a flowchart for demonstrating the synchronous operation | movement of the transmission timing of the beacon of the access point of FIG. It is a flowchart for demonstrating the synchronous operation | movement of the transmission timing of the beacon of the access point of FIG. It is a flowchart for demonstrating the synchronous operation | movement of the transmission timing of the beacon of the access point of FIG. 7 is a diagram for specifically explaining the operation of synchronizing the beacon transmission timing of the access point in FIG. 6. In FIG. 15A, access points with logical numbers 2 to 4 are arranged around an access point with logical number 1. In FIG. 15B, the access points are arranged irregularly rather than in the order of logical numbers. It is a figure for demonstrating communication with the accelerator point and electronic shelf label in the modification F. FIG. Here, when the access point according to the modification F periodically transmits a beacon to the electronic shelf label, and when the access point according to the modification F receives image data from the electronic shelf label server, the image data Is transmitted to the electronic shelf label. In Modification F, the data notice command is included in the beacon transmitted immediately after the access point receives the image data from the electronic shelf label server. It is a figure for demonstrating communication with the accelerator point and electronic shelf label in the modification F. FIG. In FIG. 17A, the beacon B ″ and the data D1 are enlarged and drawn for the image data transmission cycle of FIG. 16 (for the third cycle from the left in FIG. 16). FIG. 17B corresponds to FIG. 17A and depicts the reception of the beacon B ″ and data D1 by the electronic shelf label and the transmission of the ACK signal by the electronic shelf label.

  Hereinafter, an electronic shelf label system 1 as an embodiment of a wireless display system according to the present invention will be described with reference to the drawings.

  The electronic shelf label system 1 according to the present embodiment is merely an example, and the wireless display system according to the present invention is not limited to the content described below. Other modes can be adopted as long as they do not contradict the gist of the invention.

(1) Overall Configuration The electronic shelf label system 1 is used in a store such as a supermarket or a convenience store to display product information (for example, sales price of a product) of displayed products.

  As shown in FIG. 1, the electronic shelf label system 1 mainly includes an electronic shelf label server 10, a plurality of access points 30, 30,..., A plurality of electronic shelf labels 40, 40,. It is composed of The numbers of access points 30 and electronic shelf labels 40 included in the electronic shelf label system 1 are not limited to the numbers shown in FIG.

  In the electronic shelf label system 1, the product information stored in the electronic shelf label server 10 is transmitted via the access point 30 to the electronic shelf label 40 arranged corresponding to the product displayed on the sales floor. A shelf label display unit 41 (see FIG. 3) of the electronic shelf label 40 performs display according to the received product information.

  The electronic shelf label server 10 is a computer that comprehensively controls the electronic shelf label system 1. Product information displayed on the electronic shelf label 40 is stored in the server storage unit 14 (see FIG. 5) of the electronic shelf label server 10. The electronic shelf label server 10 transmits product information to the electronic shelf label 40 via the access point 30. Here, the electronic shelf label server 10 transmits the product information to the electronic shelf label 40 as image data (image data displayed on the shelf label display unit 41 of the electronic shelf label 40). It is not limited to. For example, the electronic shelf label server 10 may transmit product information such as a selling price as numerical data to the electronic shelf label 40.

  The access point 30 is a radio wave transmitter / receiver. The access point 30 exchanges various signals with the electronic shelf label 40 using radio waves. The access points 30 are attached to a ceiling in a store, for example, with a certain interval. The installation location and the installation interval of the access point 30 are determined so that the electronic shelf label 40 installed in the store can communicate with any access point 30. The access point 30 is connected to the electronic shelf label server 10 via a network 2 such as a LAN (Local Area Network).

  The access point 30 receives image data (product information) transmitted from the electronic shelf label server 10 via the network 2, and transmits the received image data to the electronic shelf label 40 by radio waves. Further, the access point 30 receives a signal transmitted from the electronic shelf label 40 and transmits the received signal to the electronic shelf label server 10 via the network 2.

  The electronic shelf label 40 is a portable device, and is a display device arranged corresponding to each of a plurality of products P handled in a store (see FIG. 2). The electronic shelf label 40 receives image data (product information) transmitted from the electronic shelf label server 10 via the access point 30 and displays the image data on the shelf label display unit 41. As a result, the product information of the product P corresponding to the electronic shelf label 40 is displayed on the shelf label display section 41 of the electronic shelf label 40 (see FIG. 3).

  Note that the electronic shelf label 40 cannot always communicate with the same access point 30. For example, when the electronic shelf label 40 is moved in the store together with the product P for displaying the product information when the store is renovated, the access point 30 with which the electronic shelf label 40 communicates changes. Yes. Further, as shown in FIG. 4, the electronic shelf label 40 may be installed within a communicable range of a plurality of (two in FIG. 4) access points 30. In this case, if the electronic shelf label 40 cannot communicate with one access point 30 (for example, AP1 in FIG. 4) that has been communicating with the electronic shelf label 40 for some reason, the electronic shelf label 40 becomes another access point. Communication is performed with 30 (for example, AP2 in FIG. 4).

(2) Detailed Configuration Hereinafter, the electronic shelf label server 10, the access point 30, and the electronic shelf label 40 will be described in detail.

(2-1) Electronic shelf label server The electronic shelf label server 10 is a computer that manages the electronic shelf label system 1 in an integrated manner. The electronic shelf label server 10 transmits product information to the electronic shelf label 40 via the access point 30. The electronic shelf label server 10 is disposed in a store backyard or the like.

  The electronic shelf label server 10 mainly includes a server communication unit 11, a server display unit 12, a server input unit 13, a server storage unit 14, and a server control unit 15 (see FIG. 5).

(2-1-1) Server Communication Unit The server communication unit 11 is a communication interface for enabling communication between the electronic shelf label server 10 and the access point 30. The server communication unit 11 is also configured to be able to communicate with devices outside the electronic shelf label system 1 (for example, a POS system server and store controller installed in the store together with the electronic shelf label system 1). Image data sent from the server communication unit 11 to the access point 30 is transmitted by radio waves to the electronic shelf label 40 by the access point 30.

(2-1-2) Server display unit The server display unit 12 is a liquid crystal display. Various information related to the electronic shelf label system 1 can be displayed on the server display unit 12.

(2-1-3) Server Input Unit The server input unit 13 is a mouse and a keyboard. A user of the electronic shelf label system 1 can input various commands and various information to the electronic shelf label server 10 via the server input unit 13.

(2-1-4) Server storage unit The server storage unit 14 is mainly configured by a ROM, a RAM, and a hard disk. The server storage unit 14 stores various programs executed by the server control unit 15 described later.

  The server storage unit 14 stores product information (for example, a product name, a normal sales price, a special sales price, and a price per unit weight of the product P) displayed on the electronic shelf label 40.

  The electronic shelf label server 10 stores the device ID of the electronic shelf label 40 and the product ID of the product P (the product ID attached to the product P with a barcode or the like) in association (linked). ing. Further, the electronic shelf label server 10 stores the device ID of the electronic shelf label 40 and the logical number of the access point 30 (identification information of the access point 30) in association (linked). The link between the device ID of the electronic shelf label 40 and the logical number of the access point 30 will be described later. When product information of a product P is transmitted to the electronic shelf label 40 via the access point 30, the device ID (product information of the product information) of the electronic shelf label 40 associated with the product P is displayed together with the product information. The device ID of the electronic shelf label 40 of the transmission destination is transmitted as an identifier. The electronic shelf label 40 determines whether the transmitted product information has been transmitted to itself by comparing the transmitted identifier with its own device ID.

(2-1-5) Server Control Unit The server control unit 15 is mainly composed of a CPU. The server control unit 15 performs various controls based on programs and various information stored in the server storage unit 14.

  Further, the server control unit 15 transmits product information to the electronic shelf label 40 via the access point 30 when the electronic shelf label system 1 is activated or when the display change of the electronic shelf label 40 is necessary. When the display change of the electronic shelf label 40 is necessary, for example, when the product information stored in the server storage unit 14 is updated, or during the special sale period of the product P, the price is changed from the normal sale price to the special sale price. It is time to change the price or change the price from the special sale price to the normal sale price at the end of the sale period of the product P.

  Specifically, the server control unit 15 performs the following processing when transmitting the product information to the electronic shelf label 40.

  First, the server control unit 15 refers to the server storage unit 14 and supplies image data (image data of product information) to be transmitted to the electronic shelf label 40 for the product P that requires display change of the electronic shelf label 40. Generate. Further, the server control unit 15 refers to the server storage unit 14 and acquires, as an identifier, the device ID of the electronic shelf label 40 linked to the product P that needs to be changed. Further, the server control unit 15 refers to the server storage unit 14 and acquires the logical number of the access point 30 that is linked to the device ID of the electronic shelf label 40 acquired as the identifier. Next, the server control unit 15 transmits the image data and the acquired identifier (device ID of the electronic shelf label 40 to be transmitted) to the access point 30 that acquired the logical number. The access point 30 that has received the image data and the identifier transmits them to the electronic shelf label 40 by radio waves.

  As will be described later, when the electronic shelf label 40 receives a beacon including its own device ID as an identifier or image data from the access point 30, the electronic shelf label 40 transmits an ACK signal to the access point 30. The access point 30 that has received the ACK signal from the electronic shelf label 40 transmits the ACK signal to the server communication unit 11 of the electronic shelf label server 10 via the network 2. When the server communication unit 11 receives the ACK signal, the server control unit 15 determines that the communication with the electronic shelf label 40 is successful, and ends the image data transmission process. On the other hand, when the access point 30 does not receive the ACK signal from the electronic shelf label 40 for some reason, the server control unit 15 retransmits the distribution data.

  Further, as will be described later, the server control unit 15 generates a synchronization signal for roughly synchronizing the transmission timings of the beacons of all the access points 30 when the transmission timings of the beacons of the access points 30 are synchronized. And transmitted to the access point 30.

(2-2) Access Point The access point 30 is a radio wave transmitter / receiver. As shown in FIG. 6, the access point 30 mainly includes two antennas 31a and 32a, two wireless communication units 31 and 32, an AP communication unit 33, an AP control unit 34, an AP storage unit 35, Have

  The access point 30 uses antenna selection method diversity. That is, the access point 30 has excellent radio wave conditions for the same signal (for example, an ACK signal transmitted from an electronic shelf label 40 described later) received by the two antennas 31a and 32a in order to maintain high communication quality. A signal received by the antenna (antenna 31a or antenna 32a) is used. When transmitting image data (image data transmitted from the electronic shelf label server 10) to the electronic shelf label 40, an antenna (antenna 31a) having an excellent radio wave condition when receiving a signal from the electronic shelf label 40 is used. Or it transmits using the antenna 32a).

  In the electronic shelf label system 1, each access point 30 performs communication using a channel different from the other access points 30. Therefore, signals transmitted from the access point 30 do not interfere with each other.

  Each access point 30 is assigned with a unique logical number as identification information as an initial setting.

(2-2-1) Antenna and Radio Communication Unit Each radio communication unit 31, 32 is connected to one antenna 31a, 32a, respectively. Each of the wireless communication units 31 and 32 communicates with the electronic shelf label 40 using the antennas 31a and 32a connected to the wireless communication units 31 and 32. The wireless communication unit 31 and the wireless communication unit 32 have the same configuration and the same function. The antenna 31a and the antenna 32a have the same function although there are differences in their installation positions.

  The wireless communication units 31 and 32 are controlled by a wireless communication control unit 34a of the AP control unit 34 described later, and receive, for example, an ACK signal wirelessly transmitted from the electronic shelf label 40 using the antennas 31a and 32a. The ACK signal will be described later. Note that, as described above, both of the two wireless communication units 31 and 32 are used for receiving the ACK signal (see FIG. 7A). When the wireless communication units 31 and 32 receive the ACK signal, the antenna selection unit 34b of the AP control unit 34 to be described later indicates which of the two signals received by the two wireless communication units 31 and 32 is superior in radio wave condition. It is determined whether it is a signal (for example, a signal with strong electric field strength), and an antenna (wireless communication unit) that has received a signal with excellent radio wave conditions is selected as an antenna (wireless communication unit) used for signal reception. Of the two ACK signals received using the antennas 31a and 32a, the ACK signal received by the antenna selected by the antenna selection unit 34d is transmitted to the electronic shelf label server 10 as the ACK signal received from the electronic shelf label 40. Is done.

  Further, for example, the wireless communication units 31 and 32 connected to the antennas 31a and 31b selected by the antenna selection unit 34d are controlled by the wireless communication control unit 34a, and the AP communication unit 33 described later is sent from the electronic shelf label server 10. The received image data is transmitted using an antenna connected to the wireless communication unit.

  The radio communication units 31 and 32 are alternately controlled by the radio communication control unit 34a, and transmit signals called beacons using the antennas 31a and 32a connected to the radio communication units 31 and 32 (FIG. 7). (See (b)). That is, if a beacon is transmitted from the wireless communication unit 31 at a certain timing, the wireless communication unit 32 is used when transmitting the next beacon, and the wireless communication unit 31 is used when transmitting the beacon one after another. Repeated. The transmission timing of beacons from the wireless communication units 31 and 32 is determined by a timing changing unit 34e described later. The beacon will be described later.

  The wireless communication units 31 and 32 that are not used for transmitting a beacon to the electronic shelf label 40 receive a beacon transmitted from an access point 30 other than itself (other than the access point 30 to which the wireless communication unit 31 or 32 belongs) ( (Refer FIG.7 (b)). Reception of the beacon of the access point 30 other than itself by the wireless communication units 31 and 32 is performed, for example, at a timing when the other wireless communication units 32 and 31 are transmitting beacons. Further, for example, the wireless communication unit 31 receives the beacon of the access point 30 other than itself after the other wireless communication unit 32 transmits the beacon until the wireless communication unit 31 transmits the beacon. To be implemented. Further, for example, the reception of the beacon of the access point 30 other than itself by the wireless communication unit 32 is performed after the other wireless communication unit 31 transmits the beacon until the next time the wireless communication unit 32 transmits the beacon. To be implemented.

(2-2-2) AP Communication Unit The AP communication unit 33 is a communication interface that enables communication between the access point 30 and the electronic shelf label server 10 connected via the network 2. The AP communication unit 33 receives image data (product information) and an identifier transmitted from the server communication unit 11 of the electronic shelf label server 10. In addition, the AP communication unit 33 uses the ACK signal received by the antennas 31a and 32a selected by the antenna selection unit 34b of the AP control unit 34, which will be described later, among the ACK signals received by the wireless communication units 31 and 32, as the server communication unit. 11 is transmitted.

(2-2-3) AP Control Unit The AP control unit 34 is mainly composed of a CPU. The AP control unit 34 controls each unit of the access point 30 by executing a program stored in the AP storage unit 35 described later.

  The AP control unit 34 mainly includes a wireless communication control unit 34a, an antenna selection unit 34b, a beacon generation unit 34c, a grasping unit 34d, and a timing change unit 34e as functional units.

(2-2-3-1) Radio Communication Control Unit The radio communication control unit 34a controls the radio communication units 31 and 32 to receive a signal (for example, an ACK signal described later) transmitted from the electronic shelf label 40. . Further, the wireless communication control unit 34a alternately controls the wireless communication units 31 and 32 to transmit a beacon generated by a beacon generation unit 34c described later to the electronic shelf label 40. Further, the wireless communication control unit 34a transfers the image data received by the AP communication unit 33 to the electronic shelf label 40 from the wireless communication units 31 and 32 connected to the antennas 31a and 32a selected by the antenna selection unit 34b described later. To send to.

  Note that the wireless communication control unit 34a receives a signal from the electronic shelf label 40 and transmits a signal to the electronic shelf label 40 in a predetermined channel (assigned to the access point 30). Is used.

  The wireless communication control unit 34a controls the wireless communication units 31 and 32 to receive a beacon transmitted from an access point 30 other than itself (other than the access point 30 to which the wireless communication control unit 34a belongs). Since the other access point 30 uses a channel different from that of its own access point 30, the wireless communication control unit 34a sends all channels used in the electronic shelf label system 1 to the wireless communication units 31 and 32. Among them, beacons are received for channels other than those used by the own access point 30.

(2-2-3-2) Antenna Selection Unit The antenna selection unit 34b determines which of the two ACK signals received by the wireless communication unit 31 and the wireless communication unit 32 is an ACK signal with excellent radio wave conditions (for example, which Whether the ACK signal has a strong electric field strength) and selects one of the antennas 31a and 32a connected to the wireless communication units 31 and 32 that have received the ACK signal with excellent radio wave conditions.

  The AP control unit 34 causes the electronic shelf label server 10 to transmit an ACK signal determined by the antenna selection unit 34 b to be excellent in the radio wave condition via the AP communication unit 33.

  In addition, the wireless communication control unit 34a controls the wireless communication units 31 and 32 connected to the antennas 31a and 32a selected by the antenna selection unit 34b to transmit image data to the electronic shelf label 40.

(2-2-3-3) Beacon generator The beacon generator 34c generates a beacon.

  The beacon is a signal transmitted for the purpose of establishing a link between the access point 30 and the electronic shelf label 40. The link establishment between the access point 30 and the electronic shelf label 40 will be described later.

  The beacon is basically a signal having a predetermined time length that is alternately transmitted from the wireless communication units 31 and 32 at a predetermined cycle. The beacon is transmitted, for example, once every 4 seconds for 100 milliseconds (that is, in this embodiment, the beacon transmission cycle time C is 4 seconds and the beacon transmission time T1 is 100 milliseconds. ). However, when the beacon transmission timing is changed by the timing changing unit 34e described later, the beacon transmission interval may not be instantaneously set to a predetermined time (here, 4 seconds).

  Specifically, a beacon is a signal composed of a plurality of packets. Each packet includes at least information on the logical number of the access point 30 that transmits the beacon and the number of the packet since the transmission of the beacon is started. In addition, when a reference number (to be described later) is stored in the AP storage unit 35 of the access point 30 that transmits the packet, the reference number is also included in each packet as information.

  Since each packet constituting the beacon includes information indicating the number of the packet since the transmission of the beacon is started, as described above, the access point 30 accesses other than itself. When the beacon of the point 30 is received, the access point 30 that has received the beacon can grasp the transmission timing of the received beacon. That is, the information indicating the number of the packet since the start of transmission of the beacon is an example of information regarding the beacon transmission timing.

  When the AP communication unit 33 receives the image data and the identifier and the image data is transmitted from the wireless communication units 31 and 32 to the electronic shelf label 40, a beacon packet transmitted immediately before the image data is transmitted. Further, an identifier, that is, the device ID of the electronic shelf label 40 to which the image data is transmitted is included as information. When the received beacon includes the same identifier as its own device ID, the electronic shelf label 40 switches its operation mode from the sleep mode to the wake-up mode, as will be described later. Prepare for reception of transmitted image data.

(2-2-3-4) Grasping Unit The grabbing unit 34d transmits the beacon transmission timing of itself (the access point 30 to which the grabbing unit 34d belongs) and one access other than the self received by the wireless communication units 31 and 32. The timing difference between the point 30 and the beacon transmission timing is grasped. Note that the timing difference is the time from when the self starts transmission of a beacon until one access point 30 other than the self starts transmitting beacons and when one access point 30 other than the self starts transmission of a beacon. It is the shorter time from the time until the self starts to transmit the beacon. Since the beacon transmission cycle time C is 4 seconds here, the timing difference is a time of 2 seconds or less. The timing difference grasped by the grasping unit 34d is transmitted to the timing changing unit 34e.

(2-2-3-5) Timing changing unit The timing changing unit 34e changes the beacon transmission timing of the wireless communication units 31 and 32, and transmits the beacon at the changed timing to the wireless communication control unit 34a. Instruct.

  Immediately after turning on the access point 30, the wireless communication control unit 34 a starts transmitting a beacon at a timing instructed by the electronic shelf label server 10. More specifically, immediately after the access point 30 is turned on, the wireless communication control unit 34a starts transmitting a beacon at a timing according to the synchronization signal transmitted from the electronic shelf label server 10. To do.

  Thereafter, when the predetermined condition is satisfied, the timing changing unit 34e brings the beacon transmission timing of itself (the access point 30 to which the timing changing unit 34e belongs) closer to the beacon transmission timing of one access point 30 other than itself. change. And it instruct | indicates with respect to the radio | wireless communication control part 34a so that a beacon may be transmitted from the radio | wireless communication parts 31 and 32 at the timing after a change. For example, the timing changing unit 34e transmits the transmission timing of the target access point (the access point 30 to which the transmission timing of the own beacon is made closer) so that the timing difference is shortened by 10 milliseconds. Move closer to.

  The predetermined condition is the following condition.

  The first is that the logical number assigned to itself (the access point 30 to which the timing changing unit 34e belongs) and the logical number or reference number included in the beacon of the other access point 30 are in a predetermined magnitude relationship. is there.

  Second, the timing difference between the own beacon transmission timing and the beacon transmission timing of the other access point 30 grasped by the grasping unit 34d is longer than a predetermined threshold time G (for example, 10 milliseconds). It is.

  Details of the predetermined condition will be described later.

(2-2-4) AP storage unit The AP storage unit 35 is mainly configured by a ROM and a RAM. The AP storage unit 35 stores various programs executed by the AP control unit 34.

  The AP storage unit 35 stores the logical number of the access point 30 to which the AP storage unit 35 belongs. Further, when the timing changing unit 34e changes the transmission timing of its own beacon so as to be close to the target access point (the other access point 30 that is the target to which the transmission timing of its own beacon is close), the target access point The logical number or reference number included in the beacon is stored as its own reference number.

(2-3) Electronic shelf label As described above, the electronic shelf label 40 is arranged corresponding to each of the plurality of products P handled in the store, and displays product information regarding the corresponding product P (see FIG. 2). ). For example, on the electronic shelf label 40, the product name, the unit price per weight, and the sales price of the product P are displayed as product information (see FIG. 3).

  As shown in FIG. 8, the electronic shelf label 40 mainly includes a shelf label display unit 41, a shelf label communication unit 42, a shelf label storage unit 43, a shelf label control unit 44, and a battery 45.

  The electronic shelf label 40 has a sleep mode (standby mode) and a wake-up mode (startup mode) as operation modes. The sleep mode is a mode that suppresses the power consumption of the electronic shelf label 40 to the minimum. In the sleep mode, a shelf label control unit 44 described later controls the shelf label display unit 41, the shelf label communication unit 42, and the shelf label storage unit 43 so that power is not supplied from the battery 45. On the other hand, the wake-up mode is a mode for executing various functions of the electronic shelf label 40 (for example, changing the display of the shelf label display unit 41 or communicating with the access point 30 by the shelf label communication unit 42). In the wake-up mode, the power consumption of the electronic shelf label 40 is greater than in the sleep mode. In the wake-up mode, the shelf label control unit 44 controls the shelf label display unit 41, the shelf label communication unit 42, and the shelf label storage unit 43 so that necessary power is supplied from the battery 45.

(2-3-1) Shelf Label Display Unit The shelf label display unit 41 is a screen for displaying product information stored in a later-described shelf label storage unit 43 (see FIG. 3). Electronic paper is used for the shelf label display unit 41. That is, the shelf label display unit 41 is a dot matrix type display composed of a plurality of pixels arranged in a matrix. The shelf label display unit 41 is non-volatile, and can hold display contents even when power is not supplied. The shelf label display unit 41 is not limited to electronic paper, and for example, a liquid crystal display may be used.

(2-3-2) Shelf label communication unit The shelf label communication unit 42 is an example of a receiving unit. As will be described later, when the access point determination unit 44a described later determines the access point 30 to which the shelf label communication unit 42 belongs when the electronic shelf label 40 is introduced or during handoff control, the access to which the shelf label communication unit 42 belongs is determined. Signals are transmitted and received using the channel used by the point 30.

  The shelf label communication unit 42 receives a beacon and image data transmitted from the access point 30. Note that the beacon reception operation by the shelf label communication unit 42 is normally (except when an electronic shelf label 40 described later is introduced) at a timing determined by a reception timing determination unit 44b described later at a beacon transmission cycle time C. Is performed only once. That is, in the present embodiment, the shelf label communication unit 42 performs a beacon receiving operation once every 4 seconds.

  In addition, when the shelf label communication unit 42 receives image data transmitted to itself or a beacon including the same identifier as its own device ID, the shelf label communication unit 42 follows the instruction of the shelf label control unit 44 to the self. A signal (ACK signal) indicating that the transmitted image data or beacon has been received is transmitted to the access point 30.

(2-3-3) Shelf Label Storage Unit The shelf label storage unit 43 is a storage unit configured by a nonvolatile memory such as an EEPROM. However, the present invention is not limited to this, and a volatile memory such as a RAM may be used for the shelf label storage unit 43.

  The shelf label storage unit 43 includes a program for the shelf label control unit 44 to control each unit of the electronic shelf label 40, a device ID that is a unique identifier of the electronic shelf label 40, and an electronic shelf label server 10. The transmitted image data (product information), the logical number of the access point 30 to which it belongs, the channel used by the access point 30 to which it belongs, and the like are stored.

(2-3-4) Shelf label control unit The shelf label control unit 44 is mainly configured by a CPU. As shown in FIG. 8, the shelf label control unit 44 is electrically connected to each part (the shelf label display unit 41, the shelf label communication unit 42, and the shelf label storage unit 43) of the electronic shelf label 40, and the electronic shelf label 40. Control the operation of each part. The control executed by the shelf label control unit 44 will be described later.

  The shelf label control unit 44 includes an access point determination unit 44a as a functional unit mainly used when an electronic shelf label 40 described later is introduced and handoff control is performed. Further, the shelf label control unit 44 includes a reception timing determination unit 44b as a functional unit mainly used when an electronic shelf label 40 described later is introduced.

(2-3-4-1) Access Point Determination Unit The access point determination unit 44a determines the access point 30 to which the electronic shelf label 40 belongs when an electronic shelf label 40 described later is introduced and during handoff control. The specific operation of the access point determination unit 44a will be described later.

(2-3-4-2) Reception Timing Determination Unit The reception timing determination unit 44b determines the timing and time interval at which the shelf label communication unit 42 performs a beacon reception operation when an electronic shelf label 40 described later is introduced. The specific operation of the reception timing determination unit 44b will be described later.

(2-3-5) Battery The battery 45 supplies driving power to the shelf label display unit 41, the shelf label communication unit 42, the shelf label storage unit 43, and the shelf label control unit 44 of the electronic shelf label 40 (FIG. 8). (See dash-dot line). The shelf label display unit 41, the shelf label communication unit 42, and the shelf label storage unit 43 are each provided with a switch (not shown) such as an FET. The shelf label control unit 44 controls power supply to the shelf label display unit 41, the shelf label communication unit 42, and the shelf label storage unit 43 by controlling these switches.

  As described above, when the operation mode of the electronic shelf label 40 is switched from the wake-up mode to the sleep mode, the shelf label control unit 44 turns off the above switch, whereby the shelf label display unit 41 is switched off. Control is performed so that power is not supplied from the battery 45 to the shelf label communication unit 42 and the shelf label storage unit 43.

(3) Basic Operation of Access Point An outline of basic operation of the access point 30 will be described with reference to FIG. Here, only a single operation of the access point 30 will be described, and synchronization of beacon transmission timing with other access points 30 will be described later.

  Each access point 30 alternately uses the two wireless communication units 31 and 32, as shown in FIG. 9, every beacon transmission time T1 (here 100 mm) every transmission cycle time C (here 4 seconds). Seconds) beacon B is transmitted. The beacon B is composed of a plurality of packets as described above. When the transmission timing of the beacon B is not changed by the timing changing unit 34e, the access point 30 continues to transmit the beacon B at the same timing (in the same cycle).

  When the access point 30 receives the image data and the identifier from the electronic shelf label server 10, the beacon generation unit 34c receives it from the electronic shelf label server 10 instead of the normal beacon B (a beacon that does not include the identifier). A beacon B ′ including the identifier as information is generated. Then, the wireless communication control unit 34a causes the beacon B 'to be transmitted from the wireless communication units 31 and 32 to the electronic shelf label 40 using the antennas 31a and 32a selected by the antenna selection unit 34b. When an ACK signal is transmitted from the electronic shelf label 40 that has received this beacon B ', the access point 30 receives the ACK signal using the two antennas 31a and 32a. The antenna selection unit 34b selects one of the antennas 31a and 31b that has received the ACK signal in a good reception state from the two received ACK signals. Then, the wireless communication control unit 34a controls the wireless communication units 31 and 32 connected to the antennas 31a and 32a selected by the antenna selection unit 34b to transmit the image data D to the electronic shelf label 40.

  As shown in FIG. 9, since the beacon B (or B ′) is transmitted every transmission cycle time C, the time that the access point 30 can use for transmitting the image data D per transmission cycle time C is the transmission cycle. This is a data transmission time T2 obtained by subtracting the beacon transmission time T1 from the time C.

(4) Basic operation of electronic shelf label The basic operation of the electronic shelf label 40 during normal times (except when the electronic shelf label 40 described later is introduced and during handoff control) will be described with reference to the flowchart of FIG. To do.

  In general, the electronic shelf label 40 is basically in a sleep mode in many cases. Accordingly, the normal operation of the electronic shelf label 40 will be described with the state where the electronic shelf label 40 is in the sleep mode as an initial state (step S0).

  First, in step S1, the shelf label control unit 44 performs the beacon transmission cycle of the access point 30 after the shelf label communication unit 42 performs the beacon reception operation last time (from the start of the previous beacon reception operation). It is determined whether the time (here 4 seconds) has elapsed.

  If it is determined that the transmission cycle time has elapsed, the process proceeds to step S2, and if it is determined that the beacon transmission cycle time has not elapsed, the process returns to step S1.

  In step S2, the shelf label control unit 44 changes the operation mode of the electronic shelf label 40 from the sleep mode to the wake-up mode. Thereafter, the process proceeds to step S3.

  In step S <b> 3, the shelf label control unit 44 controls the shelf label communication unit 42 to receive a beacon transmitted from the access point 30. Thereafter, the process proceeds to step S4.

  In step S4, the shelf label control unit 44 includes the same identifier as its own device ID (device ID stored in the shelf label storage unit 43) in the beacon packet received by the shelf label communication unit 42. Determine.

  If it is determined that the beacon packet received by the shelf label communication unit 42 includes the same identifier as its own device ID, the process proceeds to step S5.

  On the other hand, if it is determined that the beacon packet received by the shelf label communication unit 42 does not include the same identifier as its own device ID, the process returns to step S0. That is, the operation mode of the electronic shelf label 40 is switched to the sleep mode.

  In step S5, the shelf label control unit 44 controls the shelf label communication unit 42 to cause the access point 30 to transmit a signal (ACK signal) notifying that a beacon addressed to itself has been received. Thereafter, the process proceeds to step S6.

  In step S6, the shelf label control unit 44 controls the shelf label communication unit 42 to receive image data transmitted from the access point 30 following the beacon including its own device ID as an identifier. Thereafter, the process proceeds to step S7.

  In step S7, the shelf label control unit 44 controls the shelf label communication unit 42 to cause the access point 30 to transmit a signal (ACK signal) notifying that the image data addressed to itself has been received. Thereafter, the process proceeds to step S8.

  In step S <b> 8, the shelf label control unit 44 causes the shelf label storage unit 43 to store the image data addressed to itself received by the shelf label communication unit 42. Thereafter, the process proceeds to step S9.

  In step S <b> 9, the shelf label control unit 44 controls the shelf label display unit 41 such that the image information stored in the shelf label storage unit 43 is displayed on the shelf label display unit 41. Thereafter, the process returns to step S0.

(5) Linking and handoff control at the time of introduction of the electronic shelf label The link operation and handoff control at the time of introduction of the electronic shelf label 40 will be described below with reference to FIGS. Here, the description will be made on the assumption that the beacon transmission timing of each access point 30 is synchronized. The synchronization operation of the beacon transmission timing of the access point 30 will be described later.

(5-1) Linking at the time of introduction Hereinafter, the link at the time of introduction of the electronic shelf label 40 will be described. At the time of introduction of the electronic shelf label 40, it is not determined from which access point 30 the signal is received. Linking determines which access point 30 the newly introduced electronic shelf label 40 receives a signal from (which access point 30 the electronic shelf label 40 belongs to), and the electronic shelf label server 10 This is performed to store (link) the device ID of the electronic shelf label 40 and the logical number of the access point 30 in the server storage unit 14 in association with each other.

  In FIG. 11, description will be made on the condition that there are only two access points 30, AP 1 and AP 2, but the same applies even when there are three or more access points 30.

  When the electronic shelf label 40 is introduced, the access point determination unit 44a finds all the access points 30 with which the shelf label communication unit 42 can communicate, and among them, the access that allows the shelf label communication unit 42 to receive the signal with the best radio wave condition. Point 30 is determined. Therefore, the electronic shelf label 40 first needs to cause the shelf label communication unit 42 to receive all beacons of the access point 30 that can communicate.

  However, the electronic shelf label 40 knows the beacon transmission cycle time C and the beacon transmission time T1 when the electronic shelf label 40 is introduced, but at what timing the access point 30 is transmitting the beacon. I don't know. Therefore, the shelf label control unit 44 causes the shelf label communication unit 42 to perform a beacon reception operation for all channels used in the electronic shelf label system 1 at a time interval t1 shorter than the beacon transmission time T1. In FIG. 11, when the electronic shelf label 40 is introduced, reception is performed only four times. However, in this embodiment, the transmission cycle time C is 4 seconds and the beacon transmission time T1 is 100 milliseconds. It may be necessary to receive more than once. The access point determination unit 44a identifies a beacon (for example, AP1 in FIG. 11) that has the best reception state (for example, the strongest electric field strength). The shelf label control unit 44 controls the shelf label communication unit 42 to transmit an affiliation notification to the AP 1 that is transmitting the beacon specified by the access point determination unit 44a. The membership notification is a notification for notifying that the electronic shelf label 40 has determined the access point 30 to which the electronic shelf label 40 belongs. The affiliation notification includes the device ID of the electronic shelf label 40 and the logical number of the access point 30 (AP1) to which the affiliation belongs (the logical number included in the beacon packet transmitted from AP1). The access point 30 transmits the affiliation notification received by one of the antennas 31 a and 32 a to the electronic shelf label server 10. The server control unit 15 of the electronic shelf label server 10 associates the received device ID of the electronic shelf label 40 with the logical number of the access point 30 to which it belongs (AP1 in FIG. 11) and stores it in the server storage unit 14. . When the electronic shelf label server 10 instructs to change the display of the electronic shelf label 40 associated with a certain product P (transmits image data), the access point associated with the device ID of the electronic shelf label 40 Image data is transmitted via 30 (AP1).

  In addition, once the shelf label communication unit 42 receives the beacon B when the electronic shelf label 40 is introduced, the reception timing determination unit 44b determines the timing at which the shelf label communication unit 42 receives the beacon B when the electronic shelf label 40 is introduced. The beacon B transmission cycle time C is used to determine the timing for performing the beacon B reception operation and the time interval t2 for performing the beacon reception operation. Specifically, if the beacon B is received every transmission cycle time C of the beacon B from the timing when the shelf label communication unit 42 receives the beacon B when the electronic shelf label 40 is introduced, the beacon B is received. Can do. Handoff control to be described later (for example, when the electric field strength of a beacon transmitted from the access point 30 to which the user belongs until now becomes a certain threshold value or less, the access point 30 to which the electronic shelf label 40 belongs is determined again. Even when the control is performed, all access points 30 transmit beacons at the same timing, so there is no need to perform a beacon reception operation unnecessarily (a reception operation is performed in a state where no beacon is transmitted). No need).

  Note that the reception timing determination unit 44b receives information on the transmission timing of the beacon B received by the shelf label communication unit 42 when the electronic shelf label 40 is introduced (the packet of the beacon B received by the shelf label communication unit 42 is The beacon B and the reception operation of the beacon B are more easily synchronized by further using the information indicating the number of the packet since the transmission is started (for example, the beacon in the middle of the beacon transmission time T1). B) may be determined to perform the beacon B reception operation.

(5-2) Handoff Control Hereinafter, handoff control of the electronic shelf label 40 will be described. The handoff control is control for determining the access point 30 to which the electronic shelf label 40 belongs again when the reception state of the beacon transmitted from the access point 30 to which it belongs has deteriorated for some reason. The reception state of a beacon transmitted from the access point 30 to which it belongs is deteriorated, for example, when the electric field strength of the beacon transmitted from the access point 30 to which it belongs is below a predetermined threshold.

  Using FIG. 12 as an example, the reception state of a beacon transmitted from the access point to which the user belongs (AP1 in FIG. 12) deteriorates and the affiliation destination is switched to another access point (AP2 in FIG. 12). explain.

  First, as with the introduction of the electronic shelf label 40, the access point determination unit 44a finds all access points 30 with which the shelf label communication unit 42 can communicate, and among them, the shelf label communication unit 42 has the best radio wave condition. An access point 30 that can receive the signal is determined. For this purpose, the electronic shelf label 40 first needs to cause the shelf label communication unit 42 to receive all beacons of the access point 30 that can communicate.

  What is particularly different from the time of introduction is that in handoff control, the reception timing determination unit 44b performs the beacon B reception operation determined at the time of introduction and the time interval t2 during which the beacon reception operation is performed. It is a point which makes the part 42 perform the reception operation | movement of a beacon. Since all access points 30 transmit beacons at the same timing, the shelf label communication unit 42 can efficiently receive beacons transmitted from the communicable access points 30 as shown in FIG. it can. The subsequent operation of the access point determination unit 44a is the same as that at the time of introduction of the electronic shelf label 40, and thus description thereof is omitted here.

(6) Synchronization of Access Point Beacon Transmission Timing Synchronization of access point 30 beacon transmission timing will be described.

  First, a problem in the case where the beacon transmission timing of the access point 30 is not synchronized will be described with reference to FIG. In FIG. 13, the transmission timing of beacon B is different for each access point 30 (AP1 to AP4).

  In such a case, when the electronic shelf label 40 is newly introduced, the electronic shelf label 40 has a time interval shorter than the beacon transmission time T1 of the beacon B in order to link the electronic shelf label 40. In this embodiment, the beacon B is received at an interval shorter than 100 milliseconds. In FIG. 13, reception is performed only four times with respect to the transmission cycle time C. However, in this embodiment, the transmission cycle time C is 4 seconds and the beacon transmission time T1 is 100 milliseconds. The above reception operation is required. Once the access point 30 to which the electronic shelf label 40 belongs (for example, AP1 in FIG. 13) is determined, while the beacon can be received from the access point 30, the beacon B is transmitted every transmission cycle time C. Receive operation. The process up to this point is the same as when the beacon transmission timing of the access point 30 is synchronized.

  However, once the reception state of the beacon transmitted from the access point 30 to which it belongs is deteriorated, the electronic shelf label 40 does not know when the beacon is transmitted by the access point 30 that can receive the beacon. Similarly to the linking at the time of introduction of the electronic shelf label 40, the electronic shelf label 40 needs to perform the reception operation of the beacon B at a time interval shorter than at least the beacon transmission time T1 of the beacon B.

  As described above, the electronic shelf label 40 is driven by the battery 45. And the electronic shelf label 40 is suppressing the power consumption of the battery 45 using sleep mode. However, when the reception operation of the beacon B is set to a short time interval t1 as shown in FIG. 13, it is necessary to switch the operation mode of the electronic shelf label 40 to the wake-up mode, and the life of the battery 45 is shortened. .

  Further, if the beacon transmission time T1 of the beacon B is increased (for example, 2 seconds), the number of times the operation mode of the electronic shelf label 40 is switched to the wake-up mode is reduced, but the electronic shelf label 40 is still used. It is necessary to switch the operation mode to the wake-up mode in vain (although there is no beacon B to be received). Further, if the beacon transmission time T1 is increased, the ratio of the data transmission time T2 to the transmission cycle time C is reduced, and the time available for transmission of image data and the like is shortened. As a result, the time required to transmit the image data becomes longer and the efficiency is poor.

  Therefore, in the present embodiment, the beacon transmission timing of the access point 30 is synchronized as follows. The synchronization of the beacon transmission timing of the access point 30 will be described using the flowcharts of FIGS. 14A to 14C.

  First, in step S <b> 101, the server control unit 15 of the electronic shelf label server 10 transmits a synchronization signal for roughly synchronizing the beacon transmission timing of the access point 30 to the access point 30.

  Note that step S101 may be omitted. However, since the time for synchronizing the transmission timing of the beacon of the access point 30 can be shortened compared to the case where the transmission timing of the access point 30 is completely separated, a synchronization signal is transmitted from the electronic shelf label server 10. It is desirable. Thereafter, the process proceeds to step S102.

  In step S102, when it is determined that it is not necessary to transmit image data to the electronic shelf label 40 at a certain data transmission time T2 (see FIG. 9), the access point 30 transmits a transmission cycle including the data transmission time T2. Using time C, beacon B transmitted from another access point 30 is received. Specifically, when it is determined that it is not necessary to transmit image data to the electronic shelf label 40 at a certain data transmission time T2, the wireless communication control unit 34a of the access point 30 includes the data transmission time T2. By using the transmission cycle time C to control the radio communication units 31 and 32 connected to the antennas 31a and 32 that are not used for transmitting the beacon B, the beacon B transmitted from the other access point 30 is controlled. Receive. For example, the AP communication unit 33 did not receive the transmission of the image data from the electronic shelf label server 10 until immediately before the start of the transmission cycle time C including the certain data transmission time T2 (for example, 50 milliseconds before). In this case, it is determined that it is not necessary to transmit image data to the electronic shelf label 40 at the data transmission time T2. The reception of the beacon B by the wireless communication units 31 and 32 is performed for all channels other than the channel used by the self among the channels used in the electronic shelf label system 1. Thereafter, the process proceeds to step S103.

  In step S103, the grasping unit 34d grasps the timing difference ΔT between the transmission timing of its own beacon B and the transmission timing of other beacons B (all the beacons B received in step S102). In order to grasp the transmission timing of another beacon B, as described above, the information included in each packet of the beacon B is used to indicate the number of the packet since the start of transmission of the beacon. . Thereafter, the process proceeds to step S104.

  In step S104, the timing changing unit 34e acquires the logical number included as information in the beacon B from all the beacons B received in step S102, and grasps the smallest logical number L1min among them. Thereafter, the process proceeds to step S105.

  In step S105, the timing changing unit 34e determines whether there is a beacon B including a reference number among all the beacons B received in step S102. If no beacon B includes the reference number, the process proceeds to step S106. If any beacon B includes the reference number, the process proceeds to step S120.

  In step S106, the timing changing unit 34e calls its own logical number L stored in the AP storage unit 35, and compares the size with the minimum logical number L1min obtained in step S104.

  When the own logical number L is smaller than the minimum logical number L1min (when L <L1min), the timing changing unit 34e proceeds to step S101 without changing the transmission timing of the own beacon B. Return. On the other hand, when the self logical number L is larger than the minimum logical number L1min (when L> L1min), the timing changing unit 34e proceeds to step S107.

  In step S107, the timing changing unit 34e refers to the timing difference ΔT obtained in step S103, the transmission timing of its own beacon B, the transmission timing of beacon B including the minimum logical number L1min as information, It is determined whether or not the timing difference ΔTL is equal to or greater than the threshold time G (10 milliseconds or more in this embodiment). If it is determined that the timing difference ΔTL is shorter than the threshold time G, the timing changing unit 34e returns to step S101 without changing the transmission timing of its own beacon B. On the other hand, if it is determined that the timing difference ΔTL is greater than or equal to the threshold time G, the process proceeds to step S108.

  In step S108, the timing changing unit 34e changes the transmission timing of its own beacon B so that the timing difference ΔTL is shortened by a predetermined time (in this embodiment, 10 milliseconds). Thereafter, the process proceeds to step S109.

  In step S109, the minimum logical number L1min obtained in step S104 is stored as the reference number of the AP storage unit 35. Thereafter, the process returns to step S101.

  In step S120 (when there is a reference number included in beacon B in step S105), all the reference numbers included as information in beacon B are acquired from beacon B received in step S102. Among them, the smallest reference number R1min is grasped. Thereafter, the process proceeds to step S121.

  In step S121, it is determined whether the minimum logical number L1min determined in step S104 is equal to or smaller than the minimum reference number R1min determined in step S120. If it is determined in step S121 that the minimum logical number L1min is equal to or less than the minimum reference number R1min, the process proceeds to step S122. If it is determined in step S121 that the minimum logical number L1min is greater than the minimum reference number R1min, the process proceeds to step S140.

  Since steps S122 to S125 are the same as the contents of steps S106 to S109, the description thereof will be omitted.

  In step S140, the timing changing unit 34e calls its own logical number L stored in the AP storage unit 35, and compares the size with the minimum reference number R1min obtained in step S120.

  When the own logical number L is equal to or smaller than the minimum reference number R1min (when L ≦ R1min), the timing changing unit 34e returns to Step S101 without changing the transmission timing of the own beacon B. On the other hand, when the self logical number L is larger than the minimum reference number R1min (when L> R1min), the timing changing unit 34e proceeds to step S141.

  In step S141, the timing changing unit 34e refers to the timing difference ΔT obtained in step S103, the transmission timing of its own beacon B, the transmission timing of beacon B including the minimum reference number R1min as information, It is determined whether the timing difference ΔTR is equal to or greater than the threshold time G (10 milliseconds or more in the present embodiment). When it is determined that the timing difference ΔTR is shorter than the threshold time G, the timing changing unit 34e returns to Step S101 without changing the transmission timing of its own beacon B. On the other hand, if it is determined that the timing difference ΔTR is greater than or equal to the predetermined threshold G, the process proceeds to step S142.

  In step S142, the timing changing unit 34e changes the transmission timing of its own beacon B so that the timing difference ΔTR is shortened by a predetermined time (in this embodiment, 10 milliseconds). Thereafter, the process proceeds to step S143.

  In step S143, the minimum reference number R1min grasped in step S120 is stored as the reference number of the AP storage unit 35. Thereafter, the process returns to step S101.

  This will be described using a specific example.

  The circle drawn in FIG. 15 represents the reach range of the beacon of the access point 30 having the numbers in the circle (the numbers outside the parentheses when there are two numbers) as the logical numbers. If the circles overlap, it means that the overlapping access points 30 can receive each other's beacons.

  In FIG. 15A, there are access points 30 with logical numbers 2 to 4 around the access point 30 with logical number 1. In this case, since the access points 30 having the logical numbers 2 to 4 can receive the beacon transmitted by the access point 30 having the logical number 1, the access points 30 having the logical numbers 2 to 4 can access the logical number 1. Match the point 30 beacon transmission timing.

  In FIG. 15B, the access point 30 with the logical number 4 matches the transmission timing of the beacon with the access point 30 with the logical number 2, and the access point 30 with the logical number 2 The beacon transmission timing is not matched with the access point 30. However, by using the reference number, the access point 30 with the logical number 4 matches the beacon transmission timing with the access point 30 with the reference number 1 (the access point 30 with the logical number 3). Further, the access point 30 having the logical number 2 matches the transmission timing of the beacon with the access point 30 having the reference number 1 (the access point 30 having the logical number 4). As a result, the beacon transmission timings of the access points 30 having logical numbers 2 to 4 are all brought close to the beacon transmission timing of the access point 30 having the logical number 1 as a result.

  In FIG. 15B, the access point 30 with a logical number of 4 has a reference number of 1 for both adjacent access points 30, so that the beacon transmission timing is the same as that of the access point 30 with a logical number of 2. There is a possibility of matching with the transmission timing, and there is a possibility that synchronization cannot be achieved well. In order to avoid this, it is desirable that the beacon transmitted from the access point 30 includes the logical number of the access point 30 that actually matches the transmission timing of the beacon as information. The access point 30 is desirably controlled so as not to match the transmission timing with the access point 30 that matches the beacon transmission timing with itself.

  For example, in the example of FIG. 15B, the beacon of the access point 30 having the logical number 2 may be transmitted with the number 4 as the logical number of the access point 30 that actually matches the beacon transmission timing. desirable. Since the access point 30 with the logical number 4 has the beacon transmission timing adjusted to itself (to the access point 30 with the logical number 4), the access point 30 with the logical number 2 has the logical number 2. It is desirable not to match the transmission timing of the beacon with the access point 30.

(7) Features (7-1)
The electronic shelf label system 1 according to the present embodiment includes an electronic shelf label server 10, a plurality of access points 30, and an electronic shelf label 40 as a wireless display. The electronic shelf label server 10 stores information. The access point 30 transmits information stored in the server. The electronic shelf label 40 receives information transmitted from one access point 30 and performs display according to the received information. The electronic shelf label 40 is a battery drive type. Each of the access points 30 includes antennas 31a and 32a used for signal transmission / reception, radio communication units 31 and 32 as examples of a beacon transmission unit and a beacon reception unit, and a timing change unit 34e. One of the wireless communication units 31 and 32 periodically transmits a beacon (first beacon) having a beacon transmission time length using the antennas 31a and 32a. The other of the wireless communication units 31 and 32 receives the beacon (second beacon) transmitted from the access point 30 other than itself using the antennas 31a and 32a. The first beacon includes information related to the transmission timing of the first beacon. The second beacon includes information related to the transmission timing of the second beacon. The timing changing unit 34e changes the transmission timing of the first beacon by one of the wireless communication units 31 and 32 so as to approach the transmission timing of the second beacon when a predetermined condition is satisfied.

  Here, the access point 30 receives the beacon of the access point 30 other than itself together with information related to the transmission timing of the beacon, and when the predetermined condition is satisfied, the transmission timing of the own beacon approaches the transmission timing of other beacons. Change as follows. Therefore, the access point 30 can synchronize the beacon transmission timing. By synchronizing the beacon transmission timing of the access point 30, the electronic shelf label 40 can receive a beacon when receiving a beacon at a certain timing when receiving a beacon from any access point 30. Can do. In other words, the electronic shelf label 40 is transmitted unnecessarily (at the timing when the beacon is not transmitted from the access point 30), and is transmitted while suppressing the power consumption of the battery of the electronic shelf label 40. Information can be acquired efficiently.

  Here, since the beacon transmission timings of all the access points 30 are synchronized, if the electronic shelf label 40 grasps the beacon transmission timings of the access points 30, even if the transmission time is short, the electronic shelf The bill 40 can easily receive a beacon. Therefore, the ratio of the beacon transmission time T1 occupied per beacon transmission cycle time C can be reduced, and the data transmission time T2 can be secured long. Therefore, the data transmission efficiency is improved and the throughput is improved.

(7-2)
In the electronic shelf label system 1 according to the present embodiment, each access point 30 further includes a grasping unit 34d. The grasping unit 34d grasps the timing difference between the transmission timing of its own beacon (first beacon) and the transmission timing of the beacon (second beacon) of another access point 30. The predetermined condition includes that the timing difference is greater than or equal to the threshold value G.

  Thereby, in the electronic shelf label system 1, the transmission timing of the beacon of the access point 30 can be synchronized.

(7-3)
In the electronic shelf label system 1 according to the present embodiment, a logical number is assigned to each access point 30 as a unique number. The beacon transmitted by itself (first beacon) includes information regarding its own logical number. The beacon received from the other access point 30 (second beacon) includes information regarding the logical number of the access point 30 that has transmitted the second beacon. The predetermined condition includes that its own logical number is larger than the logical number of the access point 30 that has transmitted the second beacon.

  Here, in the electronic shelf label system 1, it is easy to synchronize the beacon transmission timings of the plurality of access points 30.

(7-4)
In the electronic shelf label system 1 according to this embodiment, each access point 30 is assigned a logical number as a unique number. Each of the access points 30 has an AP storage unit 35 that can store a reference number. The beacon transmitted by itself (first beacon) includes information regarding its own logical number. When a reference number is stored in the AP storage unit 35, the first beacon further includes information regarding its own reference number. The beacon received from the other access point 30 (second beacon) includes information regarding the logical number of the access point 30 that has transmitted the second beacon. Further, the second beacon may include information regarding the reference number of the access point 30 that transmitted the second beacon. When the timing changing unit 34e changes the transmission timing of the first beacon so as to approach the transmission timing of the second beacon, the AP storage unit 35 of the access point 30 that has transmitted the second beacon as follows, It is desirable to store the reference number or logical number as its own reference number. When the second beacon includes information on the reference number of the access point 30 that transmitted the second beacon, the AP storage unit 35 sets the reference number of the access point 30 that transmitted the second beacon to its own Store as a reference number. If the second beacon does not include information on the reference number of the access point 30 that transmitted the second beacon, the AP storage unit 35 sets the logical number of the access point 30 that transmitted the second beacon to its own Store as a reference number. The predetermined condition includes that its own logical number is larger than the logical number or reference number of the access point 30 that has transmitted the second beacon.

  Here, in the electronic shelf label system 1, it is easy to synchronize the beacon transmission timings of the plurality of access points 30.

(7-5)
Furthermore, in the electronic shelf label system 1 according to the present embodiment, the electronic shelf label server 10 transmits a synchronization signal for synchronizing the transmission timings of the beacons of all the access points 30 to the access points.

  Thereby, it is possible to roughly synchronize the beacon transmission timing of the access point 30. Therefore, the access point 30 can complete the operation of synchronizing the beacon transmission timing in a short time while receiving the beacon of the other access point 30.

(7-6)
In the electronic shelf label system 1 according to the present embodiment, the wireless communication units 31 and 32 as beacon transmission units of each access point 30 have different channels from the wireless communication units 31 and 32 of the other access points 30. Use to send.

  Thereby, the signals transmitted from the access point 30 do not interfere with each other, and the reliability of communication between the access point 30 and the electronic shelf label 40 can be improved.

(7-7)
In the electronic shelf label system 1 according to the present embodiment, the electronic shelf label 40 includes a shelf label communication unit 42 as a reception unit, an access point determination unit 44a as a determination unit, and a reception timing determination unit 44b. Have. The shelf label communication unit 42 receives a beacon transmitted from the access point 30. The access point determination unit 44a determines which information is transmitted from which access point 30. When the electronic shelf label 40 is introduced, the shelf label communication unit 42 performs a beacon reception operation for all channels used by the access point 30 at a time interval shorter than the beacon transmission time. When the electronic shelf label 40 is introduced, the access point determination unit 44a determines that the shelf label communication unit 42 receives information using a channel that has received a beacon having the strongest signal strength (electric field strength). The reception timing determination unit 44b uses the timing at which the shelf label communication unit 42 receives the beacon when the electronic shelf label 40 is introduced and the transmission cycle time C at which the beacon is transmitted from the access point 30 to use the shelf label thereafter. The communication unit 42 determines the timing and time interval at which the beacon reception operation is performed.

  Here, once the shelf label communication unit 42 of the electronic shelf label 40 receives the beacon from the access point 30, the receiving operation is not performed at the timing when the beacon is not transmitted thereafter. In other words, once the shelf label communication unit 42 receives a beacon from the access point 30, it is not necessary to perform a useless beacon receiving operation thereafter. Therefore, the transmitted beacon can be acquired while suppressing the power consumption of the battery 45 of the electronic shelf label 40.

(7-8)
In the electronic shelf label system 1 according to the present embodiment, when the shelf label communication unit 42 determines which access point 30 receives information transmitted after the introduction of the electronic shelf label 40. The beacon reception operation is performed for all channels used by the access point 30 using the timing and time interval at which the reception timing determination unit 44b determines the beacon reception operation. The access point determination unit 44a determines to receive information using the channel on which the shelf label communication unit 42 has received the beacon having the strongest signal strength (electric field strength).

  Here, in the electronic shelf label system 1, even if the access point 30 at which the electronic shelf label 40 receives a beacon is changed from one access point 30 to another access point 30 for some reason, the electronic shelf label 40 does not The beacon can be received without changing the timing and time interval of the beacon receiving operation. Therefore, the electronic shelf label 40 does not need to perform a useless reception operation in preparation for the change in the transmission timing of the beacon from the access point 30. As a result, the transmitted information can be efficiently acquired while suppressing the power consumption of the battery 45 of the electronic shelf label 40.

(8) Modification Examples of the present embodiment will be described below. Note that a plurality of modified examples may be combined as long as they do not contradict each other.

(8-1) Modification A
The electronic shelf label system 1 according to the above embodiment is used in a supermarket department or the like, but the wireless display system of the present invention is not limited to this. For example, the wireless display system may be used in a factory as follows.

  The wireless display is attached to a work object that is moved in the factory by a belt conveyor or the like. The wireless display device receives different information (for example, image data relating to processing content to be performed on the work object in the work area) from a different access point for each work area where the work object exists. The wireless display displays the received information.

  In this way, even when the position of the wireless display changes one after another, the transmission timing of the beacon from the access point is synchronized, so the wireless display is the access that the electronic display should accept the beacon. You can find points instantly. Therefore, the wireless display can easily display correct information (information to be displayed).

(8-2) Modification B
In the electronic shelf label system 1 according to the above embodiment, the access point 30 transmits the beacon by alternately using the antennas 31a and 32a, but is not limited thereto.

  For example, the access point 30 may transmit a beacon using the antenna 31a selected by the antenna selection unit 34b. And you may receive the beacon which the access points 30 other than self transmit using the antenna 32a which the antenna selection part 34b has not selected.

(8-3) Modification C
In the electronic shelf label system 1 according to the above-described embodiment, each access point 30 adjusts the beacon transmission timing to match the beacon transmission timing with the access point 30 having a smaller logical number or reference number than its own logical number. However, the present invention is not limited to this. For example, each access point 30 may adjust the beacon transmission timing to match the beacon transmission timing with the access point 30 having a larger logical number or reference number than its own logical number.

(8-4) Modification D
In the electronic shelf label system 1 according to the above embodiment, the timing changing unit 34e changes the beacon transmission timing by 10 milliseconds, but is not limited thereto. For example, the timing changing unit 34e may change the time for changing the beacon transmission timing according to the magnitude of the beacon transmission timing shift. However, if the access point 30 greatly changes the beacon transmission timing at once, the access point 30 or the electronic shelf label 40 receiving the beacon may lose sight of the beacon. It is desirable to be suppressed within a range that does not affect the operation of the other access points 30 and the electronic shelf label 40.

(8-5) Modification E
In the electronic shelf label system 1 according to the above-described embodiment, the reference number is included as information in the beacon, but is not limited thereto. For example, if the access point 30 is adjusted to match the beacon transmission timing with the other access points 30, the access point 30 may transmit the logical number of the access point 30 with the beacon transmission timing matched to the electronic shelf label server 10. Good. Then, the access point 30 may obtain information on which access point 30 each access point 30 is synchronized with via the electronic shelf label server 10.

(8-6) Modification F
In the electronic shelf label system 1 according to the embodiment, when the access point 30 receives the image data and the identifier from the electronic shelf label server 10, the access point 30 transmits a beacon B ′ including the identifier as information to the electronic shelf label 40, Thereafter, the image data D is transmitted, but the present invention is not limited to this.

  For example, when the access point 30 receives image data and an identifier from the electronic shelf label server 10, the access point 30 includes a beacon B ″ that does not include the identifier as information and includes information indicating that image data is transmitted. The electronic shelf label 40 may be transmitted. Further, at this time, the access point 30 may divide the image data into a plurality of packets and transmit it to the electronic shelf label 40. This will be described in detail with reference to FIGS. 16 and 17.

  FIG. 16 shows that the access point 30 periodically transmits a beacon to the electronic shelf label 40 and transmits the image data to the electronic shelf label 40 when the access point 30 receives image data from the electronic shelf label server 10. The state of doing is drawn. Since the cycle in which image data is not transmitted is the same as that in the above embodiment, only the cycle in which image data is transmitted will be described in detail.

  In the present modification, when the access point 30 receives the image data and the identifier, the access point 30 transmits a beacon B ″. The beacon B ″ does not include the information of the identifier (the device ID of the electronic shelf label 40 that is the transmission target of the image data) as in the above embodiment. Instead, after the beacon B ″ is transmitted, Information indicating that image data is transmitted (data notice command) is included. Therefore, in the configuration of this modification, all the electronic shelf labels 40 belonging to the access point 30 receive data transmitted from the access point (data D1 to D3 in FIG. 16).

  In the configuration of this modification, the access point 30 can transmit image data not only to one electronic shelf label 40 but also to a plurality of electronic shelf labels 40 during the data transmission time T2. . Therefore, data transmission efficiency is good. For example, in FIG. 16, data D1 to D3 are transmitted to three electronic shelf labels 40, respectively. Here, the data D1 to D3 include an identifier indicating to which electronic shelf label 40 the data D1 to D3 are transmitted. The electronic shelf label 40 determines whether or not the identifier included in the received data D1 to D3 matches the own device ID stored in the shelf label storage unit 43, so that the data D1 to D3 is self-registered. Whether the data is addressed can be determined.

  FIG. 17A shows an enlarged view of the beacon B ″ and the data D1 for one cycle for transmitting the image data of FIG. 16 (for the third cycle from the left in FIG. 16). As illustrated in FIG. 17A, the beacon B ″ includes a plurality of packets b ″. Each packet b ″ includes the above data notice command and information indicating the number of the packet in the beacon B ″. The data D1 is composed of a plurality of (n) packets d11 to d1n. Each of the packets d11 to d1n includes a header portion in which an identifier (device ID of the electronic shelf label 40 to which image data is transmitted) is included as data, and an image data portion. The image data portions of the packets d11 to d1n include data obtained by dividing one piece of image data transmitted from the electronic shelf label server 10 to the access point 30, respectively. In other words, when the data of the image data parts of the packets d11 to d1n are combined, it becomes one image data that the electronic shelf label server 10 transmits to the access point 30. In the packets d11 to d1n, the header portion is located at the head of the packets d11 to d1n, and the image data portion is located after the header portion.

  FIG. 17B corresponds to FIG. 17A and depicts the reception of the beacon B ″ and data D1 by the electronic shelf label 40 and the transmission of the ACK signal by the electronic shelf label 40. .

  Communication between the accelerator point 30 and the electronic shelf label 40 will be described with reference to FIGS. 16 and 17A and 17B.

  First, when the access point 30 receives image data and identifiers (three sets of image data and identifiers in the example of FIG. 16) from the electronic shelf label server 10, the access point 30 receives the beacon B ″ generated by the beacon generation unit 34c. Then, the data is transmitted to the electronic shelf label 40 using either one of the antennas 31a and 31b. The beacon B ″ is actually composed of a plurality of packets b ″ as shown in FIG. The beacon transmission timing is the same for both the normal beacon B and the beacon B ''.

  Then, the electronic shelf label 40 that receives the beacon at the timing determined by the reception timing determination unit 44b receives one packet b "in the beacon B".

  The shelf label control unit 44 of the electronic shelf label 40 uses the information related to the transmission timing of the beacon B (information indicating what number packet in the beacon B '' is the beacon B ''). The operation mode of the electronic shelf label 40 is switched from the sleep mode to the wake-up mode at the timing at which the transmission of (i.e., the beacon transmission time T1 ends). Then, the shelf label control unit 44 causes the shelf label communication unit 42 to receive the first packet d11 of the data D1 transmitted from the access point 30.

  The access point 30 transmits the packet d11 to the electronic shelf label 40 using the antennas 31a and 32a used for transmitting the beacon B ″.

  The shelf label communication unit 42 first receives the identifier included in the header part of the packet d11. Then, the shelf label control unit 44 compares the identifier received by the shelf label communication unit 42 with its own device ID (stored in the shelf label storage unit 43).

  If they do not match, the electronic shelf label 40 switches the operation mode to the sleep mode and does not receive the data of the image data portion included in the packet d11. The electronic shelf label 40 switches the operation mode to the wake-up mode again when the next packet d12 is transmitted.

  On the other hand, the shelf label control unit 44 receives the data included in the image data portion of the packet d11 when the identifier included in the header portion of the received packet d11 matches the own device ID. Thereafter, the shelf label control unit 44 controls the shelf label communication unit 42 to transmit an ACK signal in order to notify the access point 30 that the packet d11 has been received.

  The access point 30 receives the ACK signal transmitted from the electronic shelf label 40 using both the two antennas 31a and 32a. Then, the antenna selection unit 34b uses the one antenna 31a, 32a, which has received the ACK signal in a good reception state, among the ACK signals received by the two antennas 31a, 32a, to transmit the packet d12. , 32a.

  Thereafter, the access point 30 transmits the packet d12 using the antennas 31a and 32a selected by the antenna selection unit 34b.

  The shelf label communication unit 42 first receives the identifier included in the header part of the packet d12. Then, in the shelf label control unit 44, the shelf label communication unit 42 compares the identifier with its own device ID. If they do not match, the electronic shelf label 40 switches the operation mode to the sleep mode and does not receive the data of the image data portion included in the packet d12. The electronic shelf label 40 switches the operation mode to the wake-up mode when the next packet d13 is transmitted.

  On the other hand, the shelf label control unit 44 receives the data included in the image data portion of the packet d12 when the identifier included in the header portion of the received packet d12 matches the own device ID. Thereafter, the shelf label control unit 44 controls the shelf label communication unit 42 to transmit an ACK signal to notify the access point 30 that the packet d12 has been received.

  The access point 30 receives the ACK signal transmitted from the electronic shelf label 40 using both the two antennas 31a and 32a. Then, the antenna selection unit 34b uses the one antenna 31a, 32a, which has received the ACK signal in a good reception state among the ACK signals received by the two antennas 31a, 32a, to use the antenna 31a for transmission of the packet d13. , 32a.

  Thereafter, the process is the same up to the transmission of the packet d1n, and the description thereof will be omitted. When the transmission of the data D1 is completed, the access point 30 transmits the data D2 and the data D3 in the same manner, and the electronic shelf label 40 transmits the packets d21 to d2m (m is an integer of 2 or more), packets d31 to d3k (m Is an integer greater than or equal to 2).

  The wireless display system according to the present invention is useful as a wireless display system that can easily acquire transmitted information reliably while suppressing power consumption of the wireless display.

1 Electronic shelf label system (wireless display system)
10 Electronic shelf label server (server)
30 access point (radio wave transmitter)
31a, 32a antenna (first antenna, second antenna)
31, 32 Wireless communication unit (beacon transmission unit, beacon reception unit)
34d grasping unit 34e timing changing unit 35 AP storage unit (storage unit)
40 Electronic shelf label (wireless display)
42 Shelf label communication department (receiver)
44a Access point determination unit (determination unit)
44b Reception timing determination unit C Transmission cycle time G Threshold time (second time)
T1 beacon transmission time (first time)

JP 2001-148074 A

Claims (8)

A server for storing information;
A plurality of access points for transmitting the information stored in the server;
A battery-driven wireless indicator that receives the information transmitted from the one access point and performs display according to the received information;
With
Each of the access points has first and second antennas used for signal transmission / reception, a beacon transmission unit, a beacon reception unit, and a timing change unit,
The beacon transmission unit periodically transmits a first beacon having a first time length using the first antenna,
The beacon receiving unit receives a second beacon transmitted from the access point other than the self using the second antenna,
The first beacon includes information related to transmission timing of the first beacon,
The second beacon includes information related to the transmission timing of the second beacon,
The timing changing unit changes the transmission timing of the first beacon by the beacon transmission unit so as to approach the transmission timing of the second beacon when a predetermined condition is satisfied,
Wireless display system. Each of the access points further has a grasping unit,
The grasping unit grasps a timing difference between the transmission timing of the first beacon and the transmission timing of the second beacon;
The predetermined condition includes that the timing difference is a second time or more,
The wireless display system according to claim 1. Each of the access points is assigned a unique number,
The first beacon includes information about the unique number of itself,
The second beacon includes information regarding the unique number of the access point that transmitted the second beacon,
The predetermined condition includes that the unique number of the self is in a predetermined magnitude relationship with the unique number of the access point that has transmitted the second beacon.
The wireless display system according to claim 2. Each of the access points is assigned a unique number,
Each of the access points further includes a storage unit capable of storing a reference number,
The first beacon includes information related to its own unique number, and if the reference number is stored in the storage unit, further includes information related to the reference number of itself.
The second beacon may include information on the unique number of the access point that has transmitted the second beacon, and may further include information on the reference number of the access point that has transmitted the second beacon. ,
The storage unit
When the timing changing unit changes the transmission timing of the first beacon so as to approach the transmission timing of the second beacon,
When the second beacon includes information on the reference number of the access point that transmitted the second beacon, the reference number of the access point that transmitted the second beacon is Remember as a reference number,
If the second beacon does not include information on the reference number of the access point that transmitted the second beacon, the unique number of the access point that transmitted the second beacon is Remember as a reference number,
The predetermined condition includes that the unique number of itself is in a predetermined magnitude relationship with the unique number or the reference number of the access point that has transmitted the second beacon.
The wireless display system according to claim 2. The server transmits a synchronization signal for synchronizing the transmission timings of the first beacons of all the access points to the access points.
The wireless display system according to any one of claims 1 to 4. The beacon transmission unit of each access point performs transmission using a channel different from the beacon transmission unit of the other access points.
The wireless display system according to any one of claims 1 to 5. The wireless indicator includes a receiving unit that receives the first beacon transmitted from the access point, a determining unit that determines which of the access points transmits the information, and a reception timing determining unit And having
The reception unit performs the reception operation of the first beacon for all the channels used by the access point at a time interval shorter than the first time when the wireless indicator is introduced,
The determination unit determines that the information is received using the channel on which the reception unit has received the first beacon having the strongest signal strength at the time of introduction.
The reception timing determination unit uses the timing at which the reception unit receives the first beacon at the time of introduction and the transmission cycle time during which the first beacon is transmitted from the access point, and thereafter the reception unit. Determines the timing and time interval at which the first beacon is received.
The wireless display system according to claim 6. The reception unit performs the reception operation of the first beacon determined by the reception timing determination unit when determining which information to be transmitted from which access point is received after the introduction. Using the timing and the time interval, perform the reception operation of the first beacon for all the channels used by the access point,
The determining unit determines to receive the information using the channel on which the receiving unit has received the first beacon having the strongest signal strength.
The wireless display system according to claim 7.

Images