Synchronous communication device, processing method for the same, and program

Abstract

To make it possible to easily synchronize the time of synchronous communication devices connected to a wireless network.SOLUTION: A synchronous communication device has: first determination means for determining whether the self-synchronizing communication device is a synchronization source or a synchronization destination when there is a request for time synchronization between the self-synchronizing communication device connected to a wireless network and other synchronous communication devices; and second determination means for determining whether the wireless mode of the self-synchronizing communication device is in a master unit mode or a slave unit mode in accordance with the determination of the first determination means.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a synchronous communication device, a processing method of the synchronous communication device, and a program.

Background Art

[0002] In recent years, electronic devices such as digital cameras, printers, mobile phones, and smartphones are equipped with a wireless communication function. With the spread of the wireless function, the use cases of performing time synchronization using a network are increasing not only between wired communication devices but also between wireless communication devices.

[0003] Patent Document 1 discloses a technique for performing switching between synchronous control using a wired network and synchronous control using a wireless network regarding synchronous control between communication devices. In a wireless communication section with a lot of radio wave interference, a method of being able to synchronize even in a place where it is difficult to establish synchronization using wireless by using synchronous control using a wired network is described.

[0004] Patent Document 2 discloses a technique for highly accurately performing time synchronization between a plurality of wireless devices. Specifically, it is realized by using an access point (hereinafter referred to as AP) in wireless communication as a synchronization source terminal for time synchronization, and a STA as a synchronization destination terminal for time synchronization, and wirelessly connecting to the synchronization source terminal.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When attempting to achieve high-precision time synchronization, there are the following issues. Regarding Patent Document 1, it is effective when wired time synchronization can be used in combination with wireless time synchronization. However, it cannot be applied when there is no method for time synchronization between network devices other than wireless.

[0007] In order to perform time synchronization processing between wireless devices, first, it is necessary to construct a wireless network. And in order to achieve high precision in time synchronization processing, among the various packets used for time synchronization, time-sensitive packets, that is, packets with time constraints regarding packet transmission, need to be stably transmitted.

[0008] On the other hand, in a wireless LAN network, an infrastructure network composed of one wireless AP and one or more slave devices (hereinafter referred to as STAs) within the network is common. In this network, the communication timing of various packets of all APs / STAs is controlled by the AP. Therefore, it is desirable for the device serving as the time synchronization source that needs to transmit the previous time-sensitive packets to operate in AP mode.

[0009] In Patent Document 2, a user who executes an application using time synchronization in a wireless environment needs to perform wireless settings and time synchronization source / destination settings in view of the above.

[0010] The objective of the present disclosure is to enable easy time synchronization of a synchronization communication device connected to a wireless network.

Means for Solving the Problem

[0011] The synchronous communication device is a synchronous communication device that, when there is a time synchronization request between its own synchronous communication device connected to a wireless network and another synchronous communication device, has a first determination means for determining whether its own synchronous communication device will be the synchronization source or the synchronization destination, and a second determination means for determining whether the wireless mode of its own synchronous communication device will be the master mode or the slave mode according to the determination of the first determination means.

Advantages of the Invention

[0012] According to the present disclosure, the time synchronization of the synchronous communication device connected to the wireless network can be easily performed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0014] (First Embodiment) The synchronous communication device according to the first embodiment will be described. In this embodiment, an example in which the synchronous communication device is applied to a digital camera will be described, but it does not necessarily have to be a digital camera. For example, the synchronous communication device may be other devices such as a mobile phone, a personal computer (PC), a video camera, a smart watch, a PDA, etc.

[0015] FIG. 1 is a block diagram showing a hardware configuration example of a synchronous communication device 101 according to the first embodiment. The synchronous communication device 101 includes a control unit 102, a storage unit 103, a wireless communication unit 104, a display unit 105, an input unit 107, and an imaging unit 108.

[0016] The control unit 102 is a control unit that controls the entire synchronous communication device 101 by executing a control program stored in the storage unit 103. Each operation described later is realized by the control unit 102 executing the control program stored in the storage unit 103. The control unit 102 is constituted by, for example, a CPU (Central Processing Unit).

[0017] The storage unit 103 stores a control program executed by the control unit 102, imaging data generated by the imaging unit 108, and communication packets used for wireless communication transmission and reception with other devices.

[0018] The wireless communication unit 104 is a wireless communication unit for performing wireless communication such as a wireless LAN compliant with the IEEE802.11 series. In this embodiment, the wireless communication unit 104 will be described as being compatible with IEEE802.11v used for time synchronization processing.

[0019] The display unit 105 is a display unit that performs various displays and has a function of outputting information that can be visually recognized such as an LCD or an LED.

[0020] The antenna 106 is an antenna unit connected to the wireless communication unit 104. The antenna 106 transmits and receives necessary wireless packets for performing wireless communication with other devices.

[0021] The input unit 107 is an input unit for the user to perform various inputs and has an operation function for operating the synchronous communication device 101.

[0022] The imaging unit 108 is an imaging unit for performing imaging. The imaging unit 108 is capable of taking pictures with the shutter timing synchronized with other devices based on the time information synchronized with other devices by the synchronization processing unit 209 in FIG. 2 described later. The above is the description of FIG. 1.

[0023] FIG. 2 is a block diagram showing a functional configuration example of the synchronous communication device 101 in FIG. 1. The synchronous communication device 101 includes a communication parameter control unit 202, a packet reception unit 203, a packet transmission unit 204, a data storage unit 205, a service control unit 206, an STA function control unit 207, an AP function control unit 208, and a synchronization processing unit 209. By executing the program stored in the storage unit 103 by the control unit 102 in FIG. 1, the functional configuration units in FIG. 2 can be realized.

[0024] The communication parameter control unit 202 executes a communication parameter sharing process for sharing communication parameters between terminals. The communication parameter control unit 202 provides communication parameters for an AP (Access Point) to wirelessly connect to a wireless network constructed by the AP to a STA (Station). The AP is an example of a master device, and the STA is an example of a slave device.

[0025] Here, the communication parameters include wireless communication parameters necessary for performing wireless LAN communication such as an SSID (Service Set Identifier) as a network identifier, an encryption method, an encryption key, an authentication method, and an authentication key. In addition, the communication parameters may include a connector defined in Wi-Fi DPP, a MAC address, a PSK, a passphrase, an IP address for performing communication at the IP layer, information necessary for upper-layer services, and the usage of the network. DPP is the Device Provisioning Protocol.

[0026] Assume that the communication parameter sharing process executed by the communication parameter control unit 202 is DPP. However, the communication parameter sharing process executed by the communication parameter control unit 202 may be other processes such as WPS (Wi-Fi Protected Setup) or Wi-Fi Direct. When using DPP, the communication parameters provided by the configurator are encrypted by the secret key dedicated to the configurator. Note that for purposes other than time synchronization (e.g., transfer of imaging data, etc.), it is assumed that a wireless network can be formed using the communication parameter control unit 202.

[0027] The packet receiving unit 203 and the packet transmitting unit 204 control the transmission and reception of all packets including the communication protocols of the upper layers. Also, the packet receiving unit 203 and the packet transmitting unit 204 control the wireless communication unit 104 to transmit and receive packets conforming to the IEEE802.11 standard to and from the opposite terminal.

[0028] The data storage unit 205 controls the writing to and reading from the storage unit 103 of the program itself, communication parameters, authentication information, etc.

[0029] The service control unit 206 is a service control unit in the application layer. Here, the application layer refers to the service providing layer in the upper layers of the 5th layer and above in the OSI reference model. That is, the service control unit 206 executes the transfer of imaging data, etc. using the wireless communication by the wireless communication unit 104.

[0030] The STA function control unit 207 provides a function to operate as an STA in the infrastructure mode defined in the IEEE802.11 standard. The STA function control unit 207 performs authentication, encryption processing, etc. when operating as an STA.

[0031] The AP function control unit 208 provides a function to operate as an AP in the infrastructure mode defined in the IEEE802.11 standard. The AP function control unit 208 forms a wireless network and performs authentication / encryption processing for the STA and management of the STA. Note that the AP function control unit 208 has a function to count the number of STAs connected to the wireless network.

[0032] The synchronization processing unit 209 performs time synchronization processing between the AP and the STA using the wireless network connected by the communication parameter control unit 202.

[0033] In this embodiment, the synchronization communication device 101 will be described as having a function that can operate in each of the synchronization source / synchronization destination modes. Note that the time synchronization sequence and processing flow will be described with reference to FIGS. 8, 9, and 10. The above is the description of FIG. 2.

[0034] Next, a communication system 300 and use cases to which the synchronization communication device 101 can be applied will be described with reference to FIG. 3.

[0035] FIG. 3(A) is a diagram showing a configuration example of the communication system 300 according to this embodiment. The communication system 300 includes digital cameras 301, 302, and 303. The digital cameras 301, 302, and 303 are each an example of the synchronization communication device 101 in FIGS. 1 and 2 and have the configurations in FIGS. 1 and 2.

[0036] The digital cameras 301, 302, and 303 are connected by a wireless network 304 in the infrastructure mode defined in the IEEE802.11 standard. Now, the digital camera 301 constructs the wireless network 304 as an AP. Then, the digital cameras 302 and 303 participate in the wireless network 304 as STAs. Here, the number of digital cameras is set to 3, but it may be 2 or 4 or more.

[0037] FIG. 3(B) is a diagram for explaining the time synchronization function of digital cameras 301, 302, and 303. In FIG. 3(B), the times of digital cameras 302 and 303 are adjusted to the time of digital camera 301. Thereby, even if shooting is performed with each of the plurality of digital cameras 301 to 303 and the captured image data is brought in, grouping / sorting etc. can be performed with time stamps.

[0038] FIG. 3(C) is a diagram for explaining an application using the time synchronization function of digital cameras 301 to 303. FIG. 3(C) shows a system in which digital cameras 302 and 303 also release in accordance with the release timing of digital camera 301. All of the digital cameras 301 to 303 are directed at the subject 305, but the subject does not necessarily have to be the same.

[0039] There are cases where highly accurate synchronization processing is required. For example, assuming a case where a 3D model is generated from images of a plurality of digital cameras 301 to 303, if the subject 305 is a moving object, it is because the 3D model will also be clearer when using images captured with as high a synchronization accuracy as possible. The above are examples of the communication system 300 and use cases to which the synchronization communication device 101 can be applied.

[0040] FIG. 4 is a flowchart showing the processing method of the synchronization communication device 101 according to the present embodiment. The processing in FIG. 4 is realized by the control unit 102 executing a program stored in the storage unit 103. The processing in FIG. 4 is roughly classified into three steps S401 to S403.

[0041] In step S401, the synchronization communication device 101 determines a terminal that participates in a wireless network (hereinafter, synchronization wireless network) composed of a group of terminals that perform synchronization processing. The details will be described later with reference to FIG. 5.

[0042] In step S402, the synchronization communication device 101 determines which terminal among the terminals that have participated in the synchronization wireless network will be the synchronization source. The details will be described later with reference to FIG. 6.

[0043] In step S403, the synchronization communication device 101 reconstructs the synchronization wireless network and performs time synchronization processing according to the determined content. The details will be described later with reference to FIG. 7. The above is the overall operation flow of the synchronization communication device 101.

[0044] FIG. 5 is a flowchart showing the details of the process of step S401 in FIG. 4. First, in step S501, the control unit 102 turns on the power of the synchronization communication device 101.

[0045] Next, in step S502, the control unit 102 activates the wireless communication unit 104 of the synchronization communication device 101. This process may be automatically activated by the control unit 102 or activated by an operation of the input unit 107 from the user. Also, at this point, the wireless mode of the wireless communication unit 104 may be either the AP mode or the STA mode. The AP mode is an example of the master device mode, and the STA mode is an example of the slave device mode.

[0046] Next, in step S503, the control unit 102 performs a wireless connection by the wireless communication unit 104. If it starts up in the AP mode, the control unit 102 performs a process of allowing other synchronization communication devices 101 to join the synchronization wireless network in response to a connection request from another synchronization communication device 101. If it starts up as an STA, the control unit 102 performs a process of participating in a desired synchronization wireless network.

[0047] Next, in step S504, the control unit 102 determines whether a synchronization processing request for its own synchronization communication device 101 has occurred. There are two cases where a synchronization processing request occurs. The first is when a synchronization processing request is made by the input unit 107 from the user operating its own synchronization communication device 101. The second is when a synchronization processing request is received from another synchronization communication device 101 participating in the synchronization wireless network. If the synchronization processing request has not occurred, the process proceeds to step S505. If the synchronization processing request has occurred, the process proceeds to step S506.

[0048] In step S505, the control unit 102 waits until a synchronization process request occurs and returns to step S504.

[0049] In step S506, when the synchronization process request is generated by a user operation, the control unit 102 transmits a synchronization process request to other synchronization communication devices 101 participating in the synchronization wireless network via the wireless communication unit 104.

[0050] In step S507, when the control unit 102 receives a synchronization process request, it controls the display unit 105 to display a screen for the user to confirm the number of connected devices. The screen may display the number of terminals that have participated in the synchronization wireless network so far, information about other synchronization communication devices 101, specifically, the MAC address, the name of other synchronization communication devices 101, the hostname, etc.

[0051] Next, in step S508, the control unit 102 updates the information of other connected synchronization communication devices 101 and controls to update the display of the above screen. The acquisition of the display content will be described in steps S512 and S513 below.

[0052] Next, in step S509, the control unit 102 determines whether it has received an instruction that all the synchronization communication devices 101 for which time synchronization is to be performed are connected. The instruction may be received from the input unit 107 by the user operating its own synchronization communication device 101, or may be received from other synchronization communication devices 101 belonging to the synchronization wireless network. If the instruction has not been received, the process proceeds to step S510. If the instruction has been received, the process of step S401 ends.

[0053] In step S510, the control unit 102 waits until an instruction is received, returns to step S508, and repeats the above process. The control unit 102 performs the process of updating the display of the above screen until an instruction is received.

[0054] In step S511, the control unit 102 determines whether the communication mode of the wireless communication unit 104 is the AP mode. If the communication mode is the AP mode, the process proceeds to step S512. If the communication mode is the STA mode, the process proceeds to step S513.

[0055] In step S512, the control unit 102 checks the number of STA mode synchronization communication devices 101 connected to the synchronization wireless network and proceeds to step S514.

[0056] In step S513, the control unit 102 asks the AP about the number of STA mode synchronization communication devices 101 connected to the synchronization wireless network via the wireless communication unit 104 and receives the number of STA mode synchronization communication devices 101 connected to the synchronization wireless network. Then, the process proceeds to step S514.

[0057] In step S514, the control unit 102 updates the number of STA mode synchronization communication devices 101 connected to the synchronization wireless network and controls to display the number of STA mode synchronization communication devices 101 connected to the synchronization wireless network on the display unit 105. Here, the control unit 102 functions as a display control unit.

[0058] Next, in step S515, the control unit 102 determines whether an instruction that all the synchronization communication devices 101 for which time synchronization is to be performed have been connected has been received. If the instruction has not been received, the process returns to step S511. If the instruction has been received, the process of step S401 ends. The above is the description of FIG. 5.

[0059] FIG. 6 is a flowchart showing the details of the process of step S402 in FIG. 4. First, in step S601, the control unit 102 determines whether its own synchronization communication device 101 has an AP function. If it has an AP function, the process proceeds to step S602. If it does not have an AP function, the process proceeds to step S610.

[0060] In step S602, the control unit 102 determines whether or not an arbitrary requirement is satisfied. The arbitrary requirement may be arbitrarily set according to the nature of the synchronous communication device 101, the application to be used, etc. For example, it may include a function related to time such as whether the synchronous communication device 101 is also connected to another network and receives time distribution from the other network. Further, the arbitrary requirement may be, for example, when the synchronous communication device 101 is operating on battery power, whether the remaining battery level is equal to or more than a predetermined amount, which is not related to the time function. This can prevent a situation where the synchronization source unintentionally runs out of battery and cannot perform the function of the synchronization source. If the arbitrary requirement is satisfied, the process proceeds to step S603. If the arbitrary requirement is not satisfied, the process proceeds to step S610.

[0061] In step S603, the control unit 102 determines that its own synchronous communication device 101 is a synchronous communication device capable of operating as a synchronization source, and transmits, via the wireless communication unit 104, that its own synchronous communication device 101 is a candidate for the synchronization source to other synchronous communication devices 101.

[0062] Next, in step S604, the control unit 102 waits for a certain period until all of the synchronous communication devices 101 in the synchronous wireless network complete the above determination and the transmission of the determination result.

[0063] Next, in step S605, the control unit 102 determines whether or not there is another candidate synchronous communication device 101 that can be a synchronization source in the synchronous wireless network. If there is no candidate synchronous communication device 101 for the synchronization source other than its own synchronous communication device 101, the process proceeds to step S613. If there is also a candidate synchronous communication device 101 for the synchronization source other than its own synchronous communication device 101, the process proceeds to step S606 in order to select which one to operate as the synchronization source.

[0064] In step S606, the control unit 102 checks whether the synchronization communication device 101 of the synchronization source candidate complies with IEEE 1588 or supports BMCA (Best Master Clock Algorism). Although a detailed explanation of BMCA is omitted, BMCA is an algorithm for selecting a synchronization source (sometimes expressed as GM: Grand Master) from a group of devices in the network.

[0065] Next, in step S607, the control unit 102 determines whether all the synchronization communication devices 101 of the synchronization source candidates comply with IEEE 1588 or support BMCA. If all support BMCA, the process proceeds to step SS611. If there is one that does not support BMCA, the process proceeds to step S608.

[0066] In step S608, the control unit 102 determines whether its own synchronization communication device 101 is a system operation terminal in order to select a synchronization source by another method. That is, the control unit 102 determines whether its own synchronization communication device 101 is the synchronization communication device 101 that the user is operating via the GUI. If it is the synchronization communication device 101 that the user is operating via the GUI, it is determined to be a system operation terminal, and since the system operation terminal becomes the synchronization source, the process proceeds to step S613. If it is not the synchronization communication device 101 that the user is operating via the GUI, it is determined not to be a system operation terminal, and the process proceeds to step S609.

[0067] In step S609, it is determined whether there is a system operation terminal in the synchronization communication device 101 of the synchronization source candidate. If there is a system operation terminal, since the system operation terminal becomes the synchronization source, the process proceeds to step S610. If there is no system operation terminal, the process proceeds to step S612.

[0068] In step S610, the control unit 102 determines that its own synchronization communication device 101 immediately becomes the synchronization destination, and the process of step S402 ends.

[0069] In step S611, in order to select one synchronization source, the control unit 102 determines, by means of BMCA, whether each synchronization communication device 101 in the synchronization wireless network becomes the synchronization source or the synchronization destination. The BMCA process is performed by transmitting and receiving a packet called an AnnouncePacket. In BMCA, the synchronization communication device 101 that satisfies the function of the time synchronization source transmits an AnnouncePacket. By comparing the information included in the AnnouncePacket of its own synchronization communication device 101 with that of other synchronization communication devices 101, if the priority of its own synchronization communication device 101 becoming the synchronization source is higher, the transmission of the AnnouncePacket is continued. If it is determined that the priority of another synchronization communication device 101 is higher, the transmission of the AnnouncePacket is stopped. As a result, the synchronization communication device 101 that continues to transmit the AnnouncePacket until the end is determined as the synchronization source. Therefore, by starting to transmit the AnnouncePacket from the synchronization communication device 101 found to be Yes in step S607, the BMCA process starts without problems. After that, the process of step S402 ends.

[0070] In step S612, the control unit 102 compares the MAC addresses of the candidate synchronization communication devices 101 of the synchronization source in the synchronization wireless network, and determines that the synchronization communication device 101 with the smallest MAC address value becomes the synchronization source. Then, the control unit 102 determines that the other synchronization communication devices 101 become the synchronization destinations. Note that as long as one synchronization source can be finally determined, the control unit 102 may determine one synchronization source by a method other than the above method. After that, the process of step S402 ends.

[0071] In step S613, the control unit 102 determines that its own synchronization communication device 101 becomes the synchronization source, and the process of step S402 ends.

[0072] Note that there may be a case where there is not even one synchronization communication device 101 that is a candidate for the synchronization source within the synchronous wireless network (all synchronization communication devices 101 are No in S602). In that case, measures such as arranging a synchronization communication device 101 that satisfies the arbitrary requirements or changing the arbitrary requirements and executing the synchronization request again may be taken. For example, if the remaining battery level is included in the arbitrary requirements, it may be advisable to try again after charging. The above is the explanation of FIG. 6.

[0073] As described above, in FIG. 6, the control unit 102 functions as a determination unit, and when there is a request for time synchronization between its own synchronization communication device 101 connected to the wireless network and other synchronization communication devices 101, it determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination.

[0074] When its own synchronization communication device 101 and other synchronization communication devices 101 are candidates for the synchronization source, the control unit 102 determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination so that there is one synchronization source.

[0075] In step S602, the control unit 102 determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination based on the information of its own synchronization communication device 101. For example, the control unit 102 determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination based on the remaining battery level of its own synchronization communication device 101.

[0076] In step S611, the control unit 102 determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination by BMCA.

[0077] In step S612, the control unit 102 determines whether its own synchronization communication device 101 will be the synchronization source or the synchronization destination based on the MAC addresses of its own synchronization communication device 101 and other synchronization communication devices 101.

[0078] FIG. 7 is a flowchart showing details of the process of step S403 in FIG. 4. First, in step S701, the control unit 102 determines whether its own synchronization communication device 101 has been determined as the synchronization source. If its own synchronization communication device 101 has been determined as the synchronization source, the process proceeds to step S702. If its own synchronization communication device 101 has been determined as the synchronization destination, the process proceeds to step S707.

[0079] In step S702, the control unit 102 determines whether the current wireless mode of the wireless communication unit 104 is the STA mode. If the wireless mode is the STA mode, the process proceeds to step S703. If the wireless mode is the AP mode, the process proceeds to step S704.

[0080] In step S703, the control unit 102 causes the wireless communication unit 104 to disconnect from the network once, restarts the wireless communication unit 104 in the AP mode, and proceeds to step S704.

[0081] In step S704, the control unit 102 starts an operation of performing synchronization processing as the synchronization source. Details of the process of step S704 will be described in detail with reference to FIGS. 8 to 10.

[0082] Next, in step S705, the control unit 102 monitors the synchronization status of other synchronization communication devices 101 that are operating as the synchronization source and performing synchronization processing as the synchronization destination, and determines whether the synchronization of all the synchronization communication devices 101 has been completed. As for the monitoring method, if a synchronization method in which the synchronization source can know the synchronization state of the synchronization destination is used, the state may be monitored as it is. If a method in which the synchronization source cannot know the synchronization state of the synchronization destination is used, it is necessary to separately inquire about the synchronization state of the synchronization destination periodically. If there is a synchronization communication device 101 whose synchronization has not been completed, the process proceeds to step S706. If the synchronization of all the synchronization communication devices 101 has been completed, the process proceeds to step S714.

[0083] In step S706, the control unit 102 waits until the synchronization of all the synchronization communication devices 101 is completed, and returns to step S705.

[0084] In step S707, the control unit 102 determines whether the current wireless mode of the wireless communication unit 104 is the AP mode. If the wireless mode is the AP mode, the process proceeds to step S708. If the wireless mode is the STA mode, the process proceeds to step S709.

[0085] In step S708, the control unit 102 restarts the wireless communication unit 104 as the STA mode (S708). Then, the control unit 102 searches for a synchronization wireless network to which its own synchronization communication device 101 wants to participate by the wireless communication unit 104, and if found, participates in the found synchronization wireless network.

[0086] In step S709, the control unit 102 does not change the wireless mode, but if the AP of the synchronization wireless network is changed, the wireless communication unit 104 disconnects from the synchronization wireless network once and then participates in the synchronization wireless network newly constructed by the new AP.

[0087] Thereafter, in step S710, the control unit 102 starts an operation of performing synchronization processing as a synchronization destination. That is, the control unit 102 starts processing to synchronize with the time notified by the synchronization communication device 101 serving as a synchronization source, and proceeds to step S712. The details of the processing in step S710 will be described in detail with reference to FIGS. 8 to 10.

[0088] In step S712, the control unit 102 operates as a synchronization source and monitors the synchronization states of other synchronization communication devices 101 that are performing synchronization processing as synchronization destinations, and determines whether the synchronization of all the synchronization communication devices 101 has been completed. If there is a synchronization communication device 101 whose synchronization has not been completed, the process returns to step S712. If the synchronization of all the synchronization communication devices 101 has been completed, the process proceeds to step S714.

[0089] In step S711, the control unit 102 makes an inquiry to the synchronization source synchronization communication device 101 through the wireless communication unit 104 about the number of synchronization communication devices 101 that have completed the synchronization process, receives the inquiry result, and proceeds to step S713.

[0090] In step S713, the control unit 102 determines whether the synchronization of all the synchronization communication devices 101 has been completed. If there is a synchronization communication device 101 whose synchronization has not been completed, the process returns to step S711. If the synchronization of all the synchronization communication devices 101 has been completed, the process proceeds to step S714.

[0091] In step S714, the control unit 102 controls to display on the screen of the display unit 105 that the synchronization has been completed, and the process of step S403 ends.

[0092] As described above, in steps S703 and S708, the control unit 102 determines whether the wireless mode of its own synchronization communication device 101 will be the AP mode or the STA mode according to the determination of the synchronization source or synchronization destination in FIG. 6.

[0093] In step S703, when the control unit 102 determines that its own synchronization communication device 101 will be the synchronization source, it determines that the wireless mode of its own synchronization communication device 101 will be the AP mode. Specifically, when the control unit 102 determines that its own synchronization communication device 101 will be the synchronization source and the wireless mode of its own synchronization communication device 101 is the STA mode, it changes the wireless mode of its own synchronization communication device 101 to the AP mode.

[0094] In step S708, when the control unit 102 determines that its own synchronization communication device 101 will be the synchronization destination, it determines that the wireless mode of its own synchronization communication device 101 will be the STA mode. Specifically, when the control unit 102 determines that its own synchronization communication device 101 will be the synchronization destination and the wireless mode of its own synchronization communication device 101 is the AP mode, it changes the wireless mode of its own synchronization communication device 101 to the STA mode.

[0095] Next, an example will be used to describe the sequence of the time synchronization process in this embodiment. In this embodiment, an example using the Timing Measurement Protocol (hereinafter referred to as the TM protocol) defined in 802.11v as the time synchronization protocol will be described with reference to FIG. 8. The procedure of the TM protocol will be described below.

[0096] First, in step S801, the AP transmits an Action frame to the STA at time T1. Here, the AP is the synchronization communication device 101 in AP mode, and the STA is the synchronization communication device 101 in STA mode. The Action frame is defined in the 802.11 series.

[0097] In step S802, when transmitting the above Action frame, the AP stores the transmission time T1.

[0098] In step S803, the STA receives the Action frame in step S801 and stores the reception time T2.

[0099] In step S804, the STA transmits an ACK frame to the AP at time T3.

[0100] In step S805, similar to the AP, when transmitting the above ACK frame, the STA stores the transmission time T3.

[0101] In step S806, the AP receives the ACK frame in step S804 and stores the reception time T4.

[0102] In step S807, the AP transmits an Action frame to the STA. This Action frame contains the time information of T1 and T4.

[0103] In step S808, similar to step S802, when the AP transmits the above Action frame, it stores the time of that transmission, i.e., time T´1.

[0104] In step S809, the STA receives the Action frame and, similar to step S803, stores the reception time T´2.

[0105] In step S810, the STA transmits an ACK to the AP.

[0106] In step S811, similar to step S805, when the STA transmits the above ACK, it stores the transmission time T´3.

[0107] In step S812, the AP receives the ACK frame of step S810 and stores the reception time T´4.

[0108] Although not shown in FIG. 8, when the AP next transmits an Action frame, it includes the times of T´1 and T´4. By periodically repeating such processing, the STA can obtain the times T1 to T4 (or T´1 to T´4). Assuming that the delay time Td between the STA and the AP is symmetric in both directions, it is obtained by Equation (1).

[0109] Td = ((T4 - T1) - (T3 - T2)) / 2 ···(1)

[0110] Also, the time offset To between the STA and the AP is obtained by Equation (2).

[0111] To = T2 - (T1 + Td) ···(2)

[0112] The STA can achieve time synchronization with the AP by adding To to its own system time. Note that the times of T1 to T4 in the TM protocol are 32 bits, and 1 bit is defined as 10 nanoseconds. Therefore, to perform synchronization using the system time (for example, a time representation that counts the number of elapsed seconds since 00:00:00 on January 1, 1970, like POSIX time), there are not enough information bits. Therefore, when sending an Action frame, the system time (for example, 64 bits, and 1 bit is 10 nanoseconds) is added to the Vendor Specific ID area to achieve system time synchronization.

[0113] There are two methods for system time synchronization as follows. First, the first method (hereinafter referred to as Pattern A) is to store not only the 32-bit time but also the system time in S802, S803, S805, and S806, and send the system time (the system time at the time of T1 and the system time at the time of T4) in S807. The STA can achieve system time synchronization by the same method if the times T1 to T4 in formulas (1) and (2) are replaced with their respective system times. Of course, for compliance with the TM protocol, it may be implemented to also send the 32-bit time simultaneously in S807. The system time is obtained not only in S802, S803, S805, and S806 but also after S808.

[0114] The second method (hereinafter referred to as Pattern B) is to store the time T1 and its system time (referred to as Ts1) in S802, and send the times T1, T4, and Ts1 in S807. After the STA obtains the delay time Td and To according to formulas (1) and (2), it calculates a new system time Tnew according to the following formula (3). By applying the system time Tnew obtained by formula (3), the STA can be time synchronized with the AP.

[0115] Tnew = Ts1 + To ···(3)

[0116] The STA corrects the time of its own synchronization communication device 101 so as to synchronize with the time of the AP serving as the synchronization source by applying the system time Tnew.

[0117] Also, in parallel with time synchronization, the STA may adjust its own (STA's) clock frequency to match the clock frequency of the AP. The calculation formula (4) is as follows.

[0118] Fratio=(T´1-T1) / (T´2-T2) ···(4)

[0119] When formula (4) is less than 1, it indicates that the clock frequency of the STA is higher than that of the AP. Therefore, the STA adjusts its clock frequency to be slower. Similarly, when formula (4) is greater than 1, the STA adjusts its clock frequency to be faster.

[0120] Note that the TM protocol usually checks between the synchronization communication devices 101 whether they support the TM protocol before transmitting the Action frame in step S801. In this embodiment, since the implementation is based on the premise that the AP and the STA support the TM protocol, the confirmation process is omitted. However, the sequence in FIG. 8 may be started after performing that procedure.

[0121] Also, the time synchronization protocol is not limited to the TM protocol and may be, for example, the Network Time Protocol (NTP) or the Precision Time Protocol (PTP). Even when using a protocol other than the TM protocol for time synchronization, it is assumed that the STA synchronizes with the time of the AP.

[0122] FIG. 9 is a flowchart showing the operation of the AP in the time synchronization sequence of FIG. 8. First, in step S901, the AP transmits a time synchronization Action frame to the STA and stores the transmission time at that time. Note that the AP stores not only the 32-bit transmission time but also the system time (64 bits).

[0123] Next, in step S902, the AP waits until it receives an ACK from the STA that has received the Action frame. When it receives the ACK, it stores the reception time. When the AP implements the aforementioned pattern A, it also stores the system time at this time.

[0124] Next, in step S903, the AP sends an Action frame including the transmission time of the Action frame and the reception time of the ACK to the STA, and stores the transmission time of the Action frame. Similar to step S901, the AP stores the transmission time at that time (32-bit time and system time).

[0125] Next, in step S904, the AP waits until it receives an ACK from the STA that has received the Action frame. When it receives the ACK, it stores the reception time at the time of reception. When the AP implements the aforementioned pattern A, similar to step S902, it also stores the system time at this time.

[0126] Next, in step S905, the AP determines whether it has received an end request from the STA. If it has not received an end request, the process returns to step S903. If it has received an end request, the process proceeds to step S906.

[0127] Note that the end request in step S905 may be determined by a TM Request Frame (see 802.11v for details) with the trigger field set to "0". Also, the end request may be a network disconnection request from the STA (e.g., Deauthentication frame or Disassociation frame), or it may be determined to be an end request by other frames.

[0128] In step S906, the AP sends an ACK for the end request to the STA, and the processing of the flowchart in FIG. 9 ends.

[0129] Figure 10 is a flowchart showing the operation of the STA in the time synchronization sequence of FIG. 8. First, in step S1001, the STA waits until it receives an Action frame from the AP. When it receives an Action frame, it stores the reception time at the time of reception.

[0130] Next, in step S1002, the STA sends an ACK indicating that it has received the Action frame to the AP and stores the transmission time. When the STA is in pattern A, when storing the transmission time and the reception time, it also stores their respective system times.

[0131] Next, in step S1003, the STA calculates Td and To using the reception time of the Action frame it stored, the transmission time of the ACK, the Action frame transmission time and the ACK reception time in the Action frame received in step S1001. The delay time Td is calculated by equation (1). The time offset To is calculated by equation (2).

[0132] Note that since the first received Action frame does not contain valid transmission time and reception time, correct calculation cannot be performed. Therefore, only at the first time, the STA may be implemented to skip step S1003.

[0133] Next, in step S1004, the STA determines whether or not the end condition of time synchronization is satisfied. If the end condition is not satisfied, the process returns to step S1001. If the end condition is satisfied, the process proceeds to step S1005.

[0134] In step S1005, the STA corrects its own (STA) system time using the delay time Td and the time offset To, and the processing of the flowchart in FIG. 10 ends.

[0135] Examples of termination conditions include, for example, the number of calculations of Td and To, and confirmation of the convergence of the delay time Td by statistical processing of the calculation results. Also, as the value used for correction in step S1005, the average value or statistical value of each calculation result may be used.

[0136] From the above description, the AP and STA can achieve time synchronization. The above is an example of a time synchronization processing method using IEEE802.11v.

[0137] According to this embodiment, in a user who wants to execute a synchronization application that requires time synchronization among a plurality of synchronizing communication devices 101 connected wirelessly, a wireless network capable of realizing high-precision time synchronization can be constructed without special knowledge.

[0138] (Second Embodiment) In the first embodiment, in step S401 of FIG. 4, the synchronizing communication device 101 is in a state where it can communicate with all the synchronizing communication devices 101 that perform all the synchronization processes. When newly changing the network ID (hereinafter, BSSID) when constructing a wireless network for time synchronization in S703 within S403, it is advisable to share the new BSSID and the password for connection before the end of S401. By sharing the BSSID, when reconstructing the wireless network, the BSSID can be made stealthy. This can be expected to have effects such as suppressing the participation of wireless networks of devices that require high traffic that may affect synchronization accuracy.

[0139] In the first embodiment, as an example of time synchronization processing using wireless, an example using IEEE802.11v was described. However, when performing time synchronization, it is not necessarily required to be compatible with IEEE802.11v. What is necessary for time synchronization is for the time synchronization destination to correctly acquire the time of the time synchronization source. Therefore, if there is a method that can appropriately estimate the transmission delay in the wireless section, the value can be applied in advance, and when the time synchronization source notifies the time, it can be handled in consideration of the transmission delay time.

[0140] Also, if the time synchronization source can notify the time while reserving the radio band, the influence of the transmission delay in the radio section can be reduced, and good synchronization accuracy can be obtained without necessarily supporting IEEE802.11v.

[0141] (Other embodiments) The present disclosure can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0142] Note that the above-described embodiments are merely specific examples for implementing the present disclosure, and the technical scope of the present disclosure is not limitedly interpreted by these. That is, the present disclosure can be implemented in various forms without departing from its technical idea or its main features.

[0143] The disclosure of the present embodiment includes the following configurations, methods, and programs. (Configuration 1) A synchronization communication device, when there is a request for time synchronization between its own synchronization communication device connected to a wireless network and another synchronization communication device, a first determination means for determining whether its own synchronization communication device becomes a synchronization source or a synchronization destination; a second determination means for determining whether the wireless mode of its own synchronization communication device becomes a master mode or a slave mode according to the determination of the first determination means A synchronization communication device, characterized by comprising: (Configuration 2) The synchronization communication device according to Configuration 1, further comprising synchronization processing means for performing synchronization processing as a synchronization source when it is determined that its own synchronization communication device becomes a synchronization source, and performing synchronization processing as a synchronization destination when it is determined that its own synchronization communication device becomes a synchronization destination. (Configuration 3) The first determination means is When the own synchronization communication device does not have the master unit mode, it is determined so that the own synchronization communication device becomes the synchronization destination. When the own synchronization communication device has the master unit mode and another synchronization communication device does not have the master unit mode, it is determined so that the own synchronization communication device becomes the synchronization source. When the own synchronization communication device and another synchronization communication device have the master unit mode, it is determined whether the own synchronization communication device becomes the synchronization source or the synchronization destination so that there is one synchronization source, the synchronization communication device according to Configuration 1 or 2. (Configuration 4) When the own synchronization communication device and another synchronization communication device have the master unit mode, the first determination means determines whether the own synchronization communication device becomes the synchronization source or the synchronization destination by BMCA, the synchronization communication device according to Configuration 3. (Configuration 5) The first determination means determines whether the own synchronization communication device becomes the synchronization source or the synchronization destination based on the information of the own synchronization communication device, the synchronization communication device according to any one of Configurations 1 to 4. (Configuration 6) The first determination means determines whether the own synchronization communication device becomes the synchronization source or the synchronization destination based on the remaining battery level of the own synchronization communication device, the synchronization communication device according to any one of Configurations 1 to 5. (Configuration 7) The first determination means determines whether the own synchronization communication device becomes the synchronization source or the synchronization destination based on the MAC addresses of the own synchronization communication device and another synchronization communication device, the synchronization communication device according to any one of Configurations 1 to 6. (Configuration 8) When the second determination means determines so that the own synchronization communication device becomes the synchronization source, it determines so that the wireless mode of the own synchronization communication device becomes the master unit mode, the synchronization communication device according to any one of Configurations 1 to 7. (Configuration 9) The synchronization communication device according to any one of Configurations 1 to 8, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization destination, the second determination means determines that the radio mode of its own synchronization communication device becomes a slave unit mode. (Configuration 10) The synchronization communication device according to any one of Configurations 1 to 9, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization source and the radio mode of its own synchronization communication device is a slave unit mode, the second determination means changes the radio mode of its own synchronization communication device to a master unit mode. (Configuration 11) The synchronization communication device according to any one of Configurations 1 to 10, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization destination and the radio mode of its own synchronization communication device is a master unit mode, the second determination means changes the radio mode of its own synchronization communication device to a slave unit mode. (Configuration 12) The synchronization communication device according to any one of Configurations 1 to 11, further comprising first display control means for controlling to display the number of synchronization communication devices in the slave unit mode connected to the wireless network before the determination by the first determination means. (Configuration 13) The synchronization communication device according to Configuration 2, comprising second display control means for controlling to display that synchronization is completed after the synchronization process by the synchronization processing means. (Configuration 14) The synchronization communication device according to Configuration 2 or 13, wherein when the synchronization processing means determines that its own synchronization communication device becomes a synchronization destination, the synchronization processing means corrects the time of its own synchronization communication device so as to synchronize with the time of the synchronization source synchronization communication device. (Method 1) A processing method of a synchronization communication device, When there is a request for time synchronization between its own synchronization communication device connected to a wireless network and another synchronization communication device, a first determination step of determining whether its own synchronization communication device becomes a synchronization source or a synchronization destination, A second determination step of determining whether the wireless mode of the own synchronization communication device becomes either a master device mode or a slave device mode according to the determination in the first determination step A processing method for a synchronization communication device, characterized by comprising the same. (Program 1) A program for causing a computer to function as the synchronization communication device according to any one of Configurations 1 to 14.

Description of Signs

[0144] 101 Synchronization communication device, 202 Communication parameter control unit, 203 Packet reception unit, 204 Packet transmission unit, 205 Data storage unit, 206 Service control unit, 207 STA function control unit, 208 AP function control unit, 209 Synchronization processing unit

Claims

1. A synchronization communication device, when there is a request for time synchronization between its own synchronization communication device connected to a wireless network and another synchronization communication device, a first determination means for determining whether its own synchronization communication device becomes a synchronization source or a synchronization destination; a second determination means for determining whether the wireless mode of its own synchronization communication device becomes a master mode or a slave mode according to the determination of the first determination means A synchronization communication device characterized by comprising.

2. When it is determined that its own synchronization communication device becomes a synchronization source, synchronization processing is performed as a synchronization source, and when it is determined that its own synchronization communication device becomes a synchronization destination, synchronization processing is performed as a synchronization destination. The synchronization communication device according to claim 1, further comprising synchronization processing means.

3. The first determination means when its own synchronization communication device does not have a master mode, determines that its own synchronization communication device becomes a synchronization destination; when its own synchronization communication device has a master mode and another synchronization communication device does not have a master mode, determines that its own synchronization communication device becomes a synchronization source; When its own synchronization communication device and another synchronization communication device have a master mode, the synchronization communication device according to claim 1, wherein it is determined whether its own synchronization communication device becomes a synchronization source or a synchronization destination so that there is one synchronization source.

4. When its own synchronization communication device and another synchronization communication device have a master mode, the first determination means determines whether its own synchronization communication device becomes a synchronization source or a synchronization destination by BMC A. The synchronization communication device according to claim 3, characterized by the above.

5. The first determination means determines whether its own synchronization communication device becomes a synchronization source or a synchronization destination based on the information of its own synchronization communication device. The synchronization communication device according to claim 1, characterized by the above.

6. The first determination means determines whether its own synchronization communication device becomes a synchronization source or a synchronization destination based on the remaining battery level of its own synchronization communication device. The synchronization communication device according to claim 1, characterized by the above.

7. The first determination means determines whether its own synchronization communication device becomes a synchronization source or a synchronization destination based on the MAC addresses of its own synchronization communication device and another synchronization communication device. The synchronization communication device according to claim 1, characterized by the above.

8. The synchronization communication device according to claim 1, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization source, the second determination means determines that the wireless mode of its own synchronization communication device becomes a master unit mode.

9. The synchronization communication device according to claim 1, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization destination, the second determination means determines that the wireless mode of its own synchronization communication device becomes a slave unit mode.

10. The synchronization communication device according to claim 1, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization source and the wireless mode of its own synchronization communication device is a slave unit mode, the second determination means changes the wireless mode of its own synchronization communication device to a master unit mode.

11. The synchronization communication device according to claim 1, wherein when the second determination means determines that its own synchronization communication device becomes a synchronization destination and the wireless mode of its own synchronization communication device is a master unit mode, the second determination means changes the wireless mode of its own synchronization communication device to a slave unit mode.

12. The synchronization communication device according to claim 1, further comprising first display control means for controlling to display the number of synchronization communication devices in the slave unit mode connected to the wireless network before the determination by the first determination means.

13. The synchronization communication device according to claim 2, comprising second display control means for controlling to display that synchronization is completed after the synchronization process by the synchronization processing means.

14. The synchronization communication device according to claim 2, wherein when the synchronization processing means determines that its own synchronization communication device becomes a synchronization destination, the synchronization processing means corrects the time of its own synchronization communication device to synchronize with the time of the synchronization source synchronization communication device.

15. A processing method of a synchronization communication device, comprising: a first determination step of determining whether its own synchronization communication device connected to a wireless network becomes a synchronization source or a synchronization destination when there is a time synchronization request between its own synchronization communication device and other synchronization communication devices connected to the wireless network; a second determination step of determining whether the wireless mode of its own synchronization communication device becomes a master unit mode or a slave unit mode according to the determination in the first determination step; A processing method of a synchronization communication device, characterized by comprising the above steps.

16. A program for causing a computer to function as the synchronous communication device according to any one of claims 1 to 14.

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