Base Stations and Radio Equipment

Abstract

To enhance the accuracy of time synchronization between a base station and a plurality of radio devices.SOLUTION: A base station 10 executes a packet transmission / reception process with synchronization radio devices 14. The packet transmission / reception process includes a synchronization packet transmission process of broadcasting a synchronization packet to each synchronization radio device 14, and a request reception process of receiving an information request packet transmitted from the synchronization radio device 14 that has responded to the synchronization packet. The synchronization packet includes response designation information that designates which of n synchronization radio devices 14-1 to 14-n should respond to the synchronization packet. The request reception process includes a process of obtaining information request reception time indicating the time when the information request packet was received. The base station 10 includes, in the synchronization packet to be transmitted in the next packet transmission / reception process, synchronization packet transmission time, which indicates the time at which the synchronization packet was transmitted in the previous packet transmission / reception process, and the information request reception time obtained in the previous packet transmission / reception process.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a base station and a wireless device, and more particularly to synchronization processing by transmitting and receiving packets. [Background technology]

[0002] Wireless LANs (Local Area Networks) are widely used. Some wireless LANs are equipped with multiple access points that are communicatively connected to a communication network such as the Internet. Information terminals such as personal computers and smartphones communicate with the access points by packet communication using wireless signals, and are communicatively connected to the communication network via the access points.

[0003] Each access point forms a service area in which wireless communication with an information terminal is possible. Each access point also performs time-division communication with the information terminal, realizing multiple communication lines. When the information terminal moves from one service area to another, uninterrupted communication is achieved by handover processing. In this way, in order for each access point to perform time-division communication and for multiple access points to work in cooperation with each other, the packet transmission and reception timing of each access point must be synchronized.

[0004] Therefore, each access point obtains time information for synchronization processing from a signal transmitted from, for example, a Global Positioning System (GPS).In addition, there are also wireless LANs in which each access point obtains time information from the Internet using the Network Time Protocol (NTP).

[0005] The following Patent Document 1 describes a wireless communication system in which packets are transmitted and received between a base station and multiple synchronization wireless devices, thereby synchronizing the local clocks of each synchronization wireless device with the base station clock of the base station. The base station receives reference time information from a GPS satellite, and synchronizes the time generated by the base station clock with the reference time indicated by the reference time information. As a result, the time generated by the local clocks of each synchronization wireless device is synchronized with the reference time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-184145 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the wireless communication system described in Patent Document 1, a base station broadcasts a synchronization packet to multiple synchronization radio devices, and each synchronization radio device transmits an information request packet to the base station in response to the synchronization packet. Since multiple synchronization radio devices transmit information request packets in response to one synchronization packet transmitted from the base station, the time required for each of the multiple synchronization radio devices to perform one synchronization process becomes longer. This reduces the frequency of synchronization processes, and depending on the number of synchronization radio devices, the accuracy of time synchronization may decrease.

[0008] An object of the present invention is to improve the accuracy of time synchronization between a base station and multiple wireless devices. [Means for solving the problem]

[0009] The present invention is characterized in that, in a base station comprising a radio unit which transmits and receives packets between a plurality of radio devices and a control unit which controls the radio unit, the control unit repeatedly executes, together with the radio unit, a transmission and reception process including a synchronization packet transmission process which broadcasts a synchronization packet to each of the radio devices and a request reception process which receives an information request packet transmitted from the radio device in response to the synchronization packet, the synchronization packet transmission process including a process of including, in the synchronization packet, response designation information which designates the radio device which should respond to the synchronization packet, the request reception process including a process of determining an information request reception time which indicates the time at which the information request packet was received, and the control unit includes, in the synchronization packet to be transmitted in the next transmission and reception process, a synchronization packet transmission time which indicates the time at which the synchronization packet was transmitted in the previous transmission and reception process and the information request reception time determined in the previous transmission and reception process.

[0010] The present invention also provides a base station comprising a radio unit for transmitting and receiving packets between a plurality of radio devices and a control unit for controlling the radio unit, wherein the control unit repeatedly executes, together with the radio unit, a transmission / reception process including a synchronization packet transmission process for broadcasting a synchronization packet to each of the radio devices and a request reception process for receiving an information request packet transmitted from the radio devices in response to the synchronization packet, wherein the synchronization packet transmission process includes a process for including, in the synchronization packet, response designation information for designating the radio device that should respond to the synchronization packet, and the request reception process includes a process for determining an information request reception time indicating the time at which the information request packet was received, and the control unit includes, in the synchronization packet to be transmitted in the next transmission / reception process, the information request reception time determined in the previous transmission / reception process and a synchronization packet transmission time indicating the process at which the synchronization packet will be transmitted in the next transmission / reception process.

[0011] Desirably, the control unit, together with the radio unit, performs a process of transmitting and receiving packets between a plurality of pre-registered radio devices, and includes the response designation information for each of the radio devices in sequence in the repeatedly transmitted synchronization packet so that each of the radio devices is designated in sequence.

[0012] Desirably, if the control unit does not receive the information request packet after transmitting the synchronization packet, the control unit includes in the next synchronization packet to be transmitted the response designation information that designates the same wireless device as the previously transmitted synchronization packet, and if the information request packet is not received by the wireless unit even after transmitting the synchronization packet a predetermined number of times, deletes the registration of the wireless device designated by the response designation information.

[0013] Preferably, the control unit executes, together with the wireless unit, a process of transmitting and receiving packets between the wireless devices registered in advance, and the control unit executes the request reception process and then transmits the next synchronization packet. of A registration process is executed together with the wireless unit during the transmission, and the registration process includes a process of receiving registration request information transmitted from an unregistered device and registering the unregistered device that transmitted the registration request information as a new wireless device.

[0014] The present invention also provides a mobile station comprising a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit. The base station and other wireless devices form a communication system. In the wireless device, the control unit The other wireless device and the From the base station Same report Synchronization packet reception process for receiving transmitted synchronization packets 、 repeatedly executing together with the radio unit; In addition to the broadcast address commonly assigned to the other wireless device and the wireless device itself, executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating the device itself as a response device is included in the synchronization packet; In the communication system, either the other wireless device or the wireless device itself is designated as the responding device in order, and each of the previous signals repeatedly transmitted from the base station is Synchronous packet To , ahead The synchronization packet of Base station from send Bethe synchronization packet transmitted by the base station next to the synchronization packet including the response designation information designating the base station as the response device includes an information request reception time indicating the time at which the information request packet was received by the base station, the synchronization packet reception process includes a process for determining the synchronization packet reception time indicating the time at which the synchronization packet was received, and the request transmission process includes a process for determining an information request transmission time indicating the time at which the information request packet was transmitted, and the control unit determines a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time corresponding to the synchronization packet reception process in which the control unit is designated as the response device.

[0015] The present invention also provides a mobile station comprising a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit. The base station and other wireless devices form a communication system. In the wireless device, the control unit The other wireless device and the From the base station Same report Sent Same Synchronous packet reception process to receive the synchronous packet 、 repeatedly executing together with the radio unit; In addition to the broadcast address commonly assigned to the other wireless device and the wireless device itself, executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating itself as a response unit is included in the synchronization packet; In the communication system, one of the other wireless devices and the wireless device itself is designated as the response device in turn;The synchronization packet includes a synchronization packet transmission time indicating the time when the synchronization packet itself was transmitted from the base station, and the synchronization packet transmitted by the base station after the synchronization packet including the response designation information designating the base station as the response device includes an information request reception time indicating the time when the base station received the information request packet, the synchronization packet reception process includes a process of determining the synchronization packet reception time indicating the time when the synchronization packet was received, and the request transmission process includes a process of determining the information request transmission time indicating the time when the information request packet was transmitted, and the control unit determines the propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time corresponding to the synchronization packet reception process in which the control unit is designated as the response device.

[0016] The present invention also provides a wireless device comprising a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit, wherein the control unit repeatedly executes, together with the wireless unit, a synchronization packet reception process for receiving a synchronization packet transmitted from the base station, and executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating the control unit as the response device is included in the synchronization packet, the synchronization packet including the response designation information designating the control unit as the response device includes a synchronization packet transmission time indicating the time when the base station transmitted the synchronization packet prior to the synchronization packet, and the synchronization packet transmitted by the base station following the synchronization packet including the response designation information designating the control unit as the response device includes an information request reception time indicating the time when the base station received the information request packet, the synchronization packet reception process includes a process of determining a synchronization packet reception time indicating a time when the synchronization packet was received, and the request transmission process includes a process of determining an information request transmission time indicating a time when the information request packet was transmitted, and the control unit determines a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the control unit is designated as the response device; The base station transmits and receives packets to and from a plurality of wireless devices registered in advance, the synchronization packet includes a sequence number indicating the number of times the base station transmits the synchronization packet and a number of registered devices indicating the number of the wireless devices registered by the base station, and the control unit designates itself. The above It is determined whether or not its own registration has been deleted based on the sequence number included in the latest one of the synchronization packets that included response designation information, and the sequence number and the number of registered devices included in the last received synchronization packet. The present invention also provides a wireless device including a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit, the control unit repeatedly executes, together with the wireless unit, a synchronization packet reception process for receiving a synchronization packet transmitted from the base station, and executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information for designating the control unit as a response unit is included in the synchronization packet, the synchronization packet includes a synchronization packet transmission time indicating the time when the synchronization packet itself was transmitted from the base station, the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information for designating the control unit as the response unit includes an information request reception time indicating the time when the information request packet was received by the base station, the synchronization packet reception process includes a process for determining the synchronization packet reception time indicating the time when the synchronization packet was received, and the request transmission process executes a process for determining the synchronization packet reception time indicating the time when the synchronization packet was received, and executes a process for determining the synchronization packet reception time indicating the time when the synchronization packet was received, ... the control unit determines a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process in which the base station is designated as the response device; the base station transmits and receives packets with a plurality of wireless devices registered in advance; the synchronization packet includes a sequence number indicating the number of times the base station has transmitted the synchronization packet and a registered device number indicating the number of wireless devices registered by the base station; and the control unit determines whether or not its own registration has been deleted based on the sequence number included in the latest of the synchronization packets that included the response designation information designating the control unit, and the sequence number and the registered device number included in the synchronization packet that was last received.

[0017] Preferably, when the control unit is not registered with the base station, the control unit, together with the radio unit, executes a process of transmitting a registration request packet to the base station when a predetermined registration request waiting time has elapsed since receiving the synchronization packet.

[0018] The present invention also relates to a wireless device including a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit, wherein the control unit repeatedly executes, together with the wireless unit, a synchronization packet reception process for receiving a synchronization packet transmitted from the base station, and executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information for designating the control unit as a response unit is included in the synchronization packet, and the synchronization packet including the response designation information for designating the control unit as the response unit includes a synchronization packet transmission time indicating the time when the base station transmitted the synchronization packet prior to the synchronization packet, and the response designation information for designating the control unit as the response unit includes a synchronization packet transmission time indicating the time when the base station transmitted the synchronization packet prior to the synchronization packet, the synchronization packet transmitted by the base station next to the synchronization packet including information includes an information request reception time indicating a time when the base station received the information request packet, the synchronization packet reception process includes a process of determining a synchronization packet reception time indicating a time when the synchronization packet was received, and the request transmission process includes a process of determining an information request transmission time indicating a time when the information request packet was transmitted, and the control unit determines a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time corresponding to the synchronization packet reception process for which the control unit is designated as the response device,The base station transmits and receives packets to and from a plurality of preregistered wireless devices, and the control unit, when the base station is not registered with the base station, executes, together with the wireless unit, a process of transmitting a registration request packet to the base station when a predetermined registration request waiting time has elapsed since the reception of the synchronization packet. Characterized by . The present invention also provides a wireless device including a wireless unit for transmitting and receiving packets to and from a base station, and a control unit for controlling the wireless unit, the control unit repeatedly executing, together with the wireless unit, a synchronization packet reception process for receiving a synchronization packet transmitted from the base station, When response designation information that designates itself as the response device is included in the synchronization packet, a request transmission process is executed together with the radio unit to transmit an information request packet, the synchronization packet includes a synchronization packet transmission time indicating a time when the synchronization packet itself was transmitted from the base station, the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates itself as the response device includes an information request reception time indicating a time when the information request packet was received by the base station, the synchronization packet reception process includes a process of determining a synchronization packet reception time indicating a time when the synchronization packet was received, and the request transmission process transmits the information request packet. the control unit calculates a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the control unit is designated as the response device; the base station transmits and receives packets with a plurality of wireless devices that are registered in advance; and when the control unit is not registered with the base station, the control unit, together with the wireless unit, executes a process of transmitting a registration request packet to the base station when a predetermined registration request waiting time has elapsed since the synchronization packet was received.

[0019] Preferably, the time at which the wireless device transmits is determined based on the propagation time. Preferably, the control unit synchronizes the time of a local clock provided in the wireless device to the time of a base station clock provided in the base station based on the propagation time and the synchronization packet transmission time and the synchronization packet reception time corresponding to the synchronization packet reception process for which the control unit is designated as the response device. Preferably, the control unit synchronizes the time of a local clock provided in the wireless device to the time of a base station clock provided in the base station based on the propagation time and the synchronization packet transmission time and the synchronization packet reception time corresponding to the synchronization packet reception process for which the control unit is not designated as the response device. Effect of the Invention

[0020] According to the present invention, it is possible to improve the accuracy of time synchronization between a base station and a plurality of wireless devices. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a communication system. [Diagram 2] 13 is a sequence chart of a synchronization process. [Diagram 3] FIG. 2 is a diagram illustrating a configuration of a packet used in the communication system. [Figure 4] 13 is a sequence chart of a registration process. [Diagram 5] FIG. 13 is a diagram illustrating a configuration of a communication system according to an application embodiment. [Figure 6] FIG. 1 is a diagram illustrating a configuration of an ad-hoc communication system. [Figure 7] FIG. 2 is a diagram illustrating an example of hardware of a base station. [Figure 8] FIG. 2 is a diagram illustrating an example of hardware of a synchronization wireless device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a base station 10, access points 12-1 to 12-n, and an information terminal 20.

[0023] Each access point 12-j (j is an integer from 1 to n) is connected to the Internet 18 and constitutes a wireless LAN. The information terminal 20 is, for example, a business computer, a personal computer, a smartphone, or the like.

[0024] Each access point 12-j forms a service area in which wireless communication with the information terminal 20 is possible. The information terminal 20 performs wireless communication with the access point that forms the service area in which the information terminal 20 is located, and is connected to the Internet 18 for communication.

[0025] The base station 10 is equipped with a base station clock for defining operation timing. The base station 10 receives reference time information from a GPS satellite and synchronizes the time generated by the base station clock (base station time) with the reference time indicated by the reference time information.

[0026] The access point 12-j includes a synchronization wireless device 14-j and a wireless LAN node 16-j. The synchronization wireless device 14-j includes a local clock that outputs time to the wireless LAN node 16-j. The base station 10 stores in its own memory the IDs (Identifications) of the synchronization wireless devices 14-1 to 14-n included in the access points 12-1 to 12-n, respectively, and the synchronization wireless devices 14-1 to 14-n are registered in the base station 10 as wireless communication partners. In the following description, the reference number "14" may be used to collectively indicate the synchronization wireless devices 14-1 to 14-n.

[0027] The base station 10 communicates with the synchronization wireless device 14-j registered therein, and executes synchronization processing together with the synchronization wireless device 14-j. By executing synchronization processing, the synchronization wireless device 14-j synchronizes the time generated by its own local clock with the base station time. The local clock provides the wireless LAN node 16-j with the time synchronized with the base station time. The wireless LAN node 16-j operates at a timing according to the time provided by the local clock. This synchronizes the operations of the wireless LAN nodes 16-1 to 16-3.

[0028] 2 shows a sequence chart of the synchronization process executed in the communication system 100. In the synchronization process, the base station 10 repeatedly transmits a synchronization packet at a predetermined transmission period ST to each synchronization radio device 14. The synchronization packet includes response designation information that designates one of the n synchronization radio devices 14-1 to 14-n that should respond to the synchronization packet (response device).

[0029] The synchronization packet repeatedly transmitted by the base station 10 sequentially includes response designation information for each of the synchronization radio devices 14-1 to 14-n so that the synchronization radio devices 14-1 to 14-n are designated as response devices one by one in turn. In this embodiment, the base station 10 includes response designation information that designates the synchronization radio device 14-1 as the response device in the synchronization packet transmitted for the first time. The base station 10 includes response designation information that designates the synchronization radio device 14-2 as the response device in the synchronization packet transmitted for the second time. ...The base station 10 includes response designation information that designates the synchronization radio device 14-j as the response device in the synchronization packet transmitted for the jth time. ...The base station 10 includes response designation information that designates the synchronization radio device 14-n as the response device in the synchronization packet transmitted for the nth time.

[0030] The base station 10 regards the synchronization packet transmitted the (n+1)th time as the synchronization packet to be transmitted again for the first time. That is, the base station 10 includes response designation information that again designates the synchronization radio device 14-1 as the response device in the synchronization packet to be transmitted again for the first time (the remainder when the actual number of times is divided by n). In this way, the response designation information for each of the synchronization radio devices 14-1 to 14-n is included in the repeatedly transmitted synchronization packet in order so that the synchronization radio devices 14-1 to 14-n are designated one by one in order and further cyclically.

[0031] When each synchronization radio device 14-j receives a synchronization packet that designates itself as a response device, it transmits an information request packet to the base station 10. The base station 10 receives the information request packet and includes information obtained in response to the information request packet in the synchronization packet to be transmitted next. The synchronization radio device designated as the response device receives the j+1th synchronization packet transmitted from the base station 10 and executes synchronization processing using the information included in the synchronization packet.

[0032] 3 shows the structure of a packet used in communication system 100. The packet structure shown in this figure is a rough outline, and various information may be added as necessary. The packet has a header section 30 and a payload section 32. The header section 30 includes a destination address, a source address, type information, and a sequence number.

[0033] The destination address is an address indicating the device to which the packet is addressed. The source address is an address indicating the device that transmits the packet. An ID assigned to the base station 10 or the synchronization wireless device 14 may be used for each address. The type information indicates whether the packet is a synchronization packet, an information request packet, or a registration request packet (described later). The sequence number is a number that is incremented by 1 each time a packet is transmitted, and indicates the number of times the packet has been transmitted. The sequence number is counted independently for each case in which the packet is a synchronization packet, an information request packet, and a registration request packet.

[0034] The payload section 32 includes an initial time, an information request reception time, response designation information, the number of registered devices, and an error correction code. The initial time, the information request reception time, and the response designation information are used when the type of this packet is a synchronization packet. The initial time indicates the time when the synchronization packet was transmitted from the base station 10 in the previous synchronization sequence. The information request reception time indicates the time when the information request packet was received by the base station 10 in the previous synchronization sequence. Here, the synchronization sequence refers to a series of processes executed between the base station 10 and each synchronization radio device 14 during one transmission period ST.

[0035] The response designation information includes the ID of the synchronization wireless device 14 designated as the response device. That is, the synchronization wireless device 14 having the ID included in the response designation information is designated as the response device. The number of registered devices indicates the number of synchronization wireless devices 14 registered in the base station 10. The error correction code is a code that allows the base station 10 and the synchronization wireless device 14 to perform error detection and error correction on the code that constitutes the packet.

[0036] Returning to Fig. 2, the synchronization process will be described in detail. The base station 10 transmits a synchronization packet addressed to the synchronization radio devices 14-1 to 14-n at an initial time t0-j (S1-1). The synchronization packet is a packet transmitted to the synchronization radio devices 14-1 to 14-n to define the timing for executing the synchronization process. When transmitting the synchronization packet, the base station 10 includes in the synchronization packet a broadcast address that is commonly assigned to the synchronization radio devices 14-1 to 14-n. Each synchronization radio device 14 receives the synchronization packet and recognizes that the synchronization packet includes a broadcast address, thereby executing processing according to the synchronization packet.

[0037] 2, at time t1-1 after initial time t0-1, the synchronization radio device 14-1 receives a synchronization packet transmitted from the base station 10 in the first synchronization sequence (S1-1). When the synchronization radio device 14-1 recognizes that the received synchronization packet contains response designation information that designates itself as a response device, it transmits an information request packet to the base station 10 at time t2-1 (S2-1). The base station 10 receives the information request packet at time t3-1.

[0038] Similarly, the synchronization radio device 14-2 receives a synchronization packet transmitted from the base station 10 in the second synchronization sequence at time t1-2 after the initial time t0-2 (S1-2). When the synchronization radio device 14-2 recognizes that the received synchronization packet contains response designation information that designates itself as a response device, it transmits an information request packet to the base station 10 at time t2-2 (S2-2). The base station 10 receives the information request packet at time t3-2.

[0039] In this manner, the synchronization radio device 14-j receives the synchronization packet transmitted from the base station 10 in the j-th synchronization sequence at time t1-j, which is after the initial time t0-j, where j is any integer from 1 to n (S1-j). When the synchronization radio device 14-j recognizes that the received synchronization packet contains response designation information that designates itself as a response device, it transmits an information request packet to the base station 10 at time t2-j (S2-j). The base station 10 receives the information request packet at time t3-i.

[0040] In the j-th synchronization sequence, the base station 10 obtains the initial time t0-j (synchronization packet transmission time t0-j) when the synchronization packet is transmitted by its own base station clock, and stores the initial time t0-j. The base station 10 also obtains the information request reception time t3-j when the information request packet is received by its own base station clock, and stores the information request reception time t3-j.

[0041] The base station 10 includes a synchronization packet transmission time t0-j and an information request reception time t3-j in a synchronization packet to be transmitted in the (j+1)th synchronization sequence.

[0042] In the j-th synchronization sequence, the synchronization wireless device 14-j obtains the synchronization packet reception time t1-j at which the synchronization packet was received using its own local clock, and stores the synchronization packet reception time t1-j. Also, the synchronization wireless device 14-j obtains the information request transmission time t2-j at which the information request packet was transmitted using its own local clock, and stores the information request transmission time t2-j.

[0043] Furthermore, in the (j+1)th synchronization sequence, the synchronization radio device 14-j obtains the synchronization packet transmission time t0-j and the information request reception time t3-j from the received synchronization packet.

[0044] In this way, the synchronization wireless device 14-j executes the jth synchronization sequence and the j+1th synchronization sequence to obtain the synchronization packet transmission time t0-j, the synchronization packet reception time t1-j, the information request transmission time t2-j, and the information request reception time t3-j.

[0045] The synchronization radio device 14-j obtains the propagation time Dj between the synchronization radio device 14-j and the base station 10 according to the following (Equation 1). However, in (Equation 1), the sign "-j" is simply written as "j" to make the equation easier to understand. The propagation time Dj is the delay time required to transmit a packet between the base station 10 and the synchronization radio device 14-j.

[0046] (Math 1)Dj=[(t1j-t0j)+(t3j-t2j)] / 2

[0047] Equation 1 is derived as follows. The initial time t0-j and the information request reception time t3-j are times determined by the base station clock provided in the base station 10, and the synchronization packet reception time t1-j and the information request transmission time t2-j are times determined by the local clock provided in the synchronization wireless device 14-j. If it is assumed that the local clock is ahead of the base station clock by an offset time To, the propagation time Ds of the synchronization packet and the propagation time Dd of the information request packet are expressed as Equation 2 and Equation 3, respectively.

[0048] (Math 2)Ds=t1j-t0j-To (Number 3) Dd = t3j - t2j + To

[0049] Since the propagation time Ds and the propagation time Dd are equal to Dj, Equation 1 can be obtained by adding both sides of Equation 2 and Equation 3 and dividing the result by 2.

[0050] The synchronization radio device 14-j calculates the offset time To according to the following (Equation 4).

[0051] (Math 4)To=(t1j-t0j)-Dj

[0052] The synchronization radio device 14-j synchronizes the time of its local clock with the base station time by subtracting the offset time To from the time of its own local clock. The synchronization radio device 14-j outputs the time of its local clock to the wireless LAN node 16-j (FIG. 1).

[0053] The synchronization radio unit 14-j may obtain the offset time To based on the following (Equation 5) instead of (Equation 4) and synchronize the time of its own local clock with the base station time.

[0054] (Math 5)To=[(t1j-t0j)-(t3j-t2j)] / 2

[0055] Equation 5 is an equation obtained by solving Equation 2 and Equation 3 for the offset time To. Equation 5 can also be obtained by substituting Dj in Equation 1 for Dj in Equation 4.

[0056] Among the n synchronization radio devices 14-1 to 14-n, the other synchronization radio devices 14-k (k is any integer from 1 to n excluding j) other than the synchronization radio device 14-j also execute the same process. That is, the synchronization radio device 14-k executes the k-th synchronization sequence and then executes the (k+1)-th synchronization sequence to obtain the synchronization packet transmission time t0-k, the synchronization packet reception time t1-k, the information request transmission time t2-k, and the information request reception time t3-k. The synchronization radio device 14-k obtains the offset time by the same process as the synchronization radio device 14-j, and adjusts the time of its own local clock to the time obtained by subtracting the offset time from the time of its own local clock. The synchronization radio device 14-k outputs the time generated by its own local clock to the wireless LAN node attached to it.

[0057] Note that the synchronization radio device 14-j may update the propagation time Dj according to (Equation 1) every time it executes the j+1th synchronization sequence, and may execute the synchronization process using the propagation time Dj previously calculated and stored in the hth synchronization sequence that is not the j+1th. That is, in the hth synchronization sequence, the synchronization radio device 14-j may use the propagation time Dj calculated and stored when it executed the previous j+1th synchronization sequence to calculate the offset time To according to the following (Equation 6) which has the same meaning as (Equation 4), and execute the synchronization process. Here, the previous j+1th refers to the j+1th synchronization sequence among the synchronization sequences that previously went through the 1st to nth rounds, as opposed to the last synchronization sequence that went through the 1st to nth rounds.

[0058] (Math 6)To=[t1(h-1)-t0(h-1)]-Dj

[0059] The synchronization packet reception time t1(h-1) in (Equation 6) is the time when the synchronization radio device 14-j receives the synchronization packet in the (h-1)th synchronization sequence. The synchronization packet transmission time t0(h-1) is the synchronization packet transmission time included in the synchronization packet received by the synchronization radio device 14-j in the hth synchronization sequence.

[0060] When executing the j+1th synchronization sequence, the synchronization radio device 14-j may obtain a statistical propagation time dj based on a statistical value of N propagation times Dj obtained according to (Equation 1) for N cycles in which the first to nth synchronization sequences have been repeated N times in the past, and the propagation time Dj obtained according to (Equation 1) for the last cycle. Here, the statistical value may be an average value, a median value, or the like, of the N+1 propagation times Dj. In each synchronization sequence, the synchronization radio device 14-j may obtain the offset time To by using the statistical propagation time dj in (Equation 4) or (Equation 6) instead of the propagation time Dj. Here, (Equation 4) is an equation used after the j+1th synchronization sequence has been executed, and (Equation 6) is an equation used after the hth synchronization sequence has been executed.

[0061] Through this process, each wireless LAN node acquires a time synchronized with the base station time. Because the base station time is synchronized with the reference time transmitted from the GPS satellite, the time recognized by each wireless LAN node is synchronized with the reference time. This synchronizes the operation of each of the multiple wireless LAN nodes.

[0062] In the communication system 100 according to this embodiment, a synchronization sequence is repeatedly executed. Each time a synchronization packet is received, each synchronization wireless device 14 synchronizes the time of its own local clock with the base station time. This causes a synchronization process to be executed for each transmission cycle TS, whereby the time recognized by each wireless LAN node is synchronized with the reference time.

[0063] According to the process executed in the communication system 100, the transmission period ST is shorter than when a plurality of synchronization radio devices execute synchronization processing for one synchronization sequence, as described in Patent Document 1. This increases the frequency of synchronization processing for each synchronization radio device 14, and reduces the error between the time indicated by the local clock and the time indicated by the reference clock. Furthermore, according to the process executed in the communication system 100, among the synchronization radio devices 14-1 to 14-n that have received a synchronization packet, only the device designated as a response device by the response designation information included in the synchronization packet transmits an information request packet to the base station 10. This reduces the number of information request packets received by the base station 10 in one synchronization sequence, and simplifies the synchronization sequence. Furthermore, it is not necessary to include a plurality of information request reception times corresponding to a plurality of synchronization radio devices 14 in one synchronization packet, and the amount of information to be included in the synchronization packet is reduced.

[0064] In IEEE1588, a standard for packet communication, a Sync message, a Follow-up message, and a Delay-Response message are defined as packets transmitted from a master (base station) to a slave (synchronization wireless device). A Delay-Request message is also defined as a packet transmitted from a slave to a master. In the communication system 100 according to the present embodiment, only a synchronization packet equivalent to a Sync message and an information request packet equivalent to a Delay-Request message are used repeatedly for synchronization processing. Therefore, only two types of packets are required, and processing is simpler than in the case of complying with IEEE1588, and synchronization processing is performed quickly.

[0065] In the above, an embodiment has been described in which the initial time t0-j for the synchronization packet previously transmitted from the base station 10 is transmitted from the base station 10 to the synchronization radio unit 14-j by the synchronization packet transmitted next. The initial time t0-j may be transmitted from the base station 10 to the synchronization radio unit 14-j by the synchronization packet itself transmitted at the initial time t0-j. In this case, when transmitting the synchronization packet, the base station 10 obtains the initial time t0-j at which the first synchronization packet is transmitted, and includes the initial time t0-j in the first synchronization packet.

[0066] Each synchronization radio device 14-j that receives the first synchronization packet obtains and stores a synchronization packet reception time t1-j, and extracts and stores an initial time t0-j from the first synchronization packet. Then, it transmits an information request packet, and obtains and stores an information request transmission time t2-j. The synchronization radio device 14-j receives a synchronization packet (second synchronization packet) transmitted from the base station 10 in the next synchronization sequence, and extracts and stores an information request reception time t3-j from the second synchronization packet. The synchronization radio device 14-j obtains an offset time To based on the information request reception time t3-j extracted from the second synchronization packet in addition to the previously stored initial time t0-j, synchronization packet reception time t1-j, and information request transmission time t2-j, and adjusts the time of its own local clock to the base station time.

[0067] In the above, an example is shown in which the synchronization wireless device 14-j is designated as the response device in the j-th synchronization sequence. This example is for convenience of explanation, and the synchronization wireless device 14-j does not necessarily have to be designated as the response device in the j-th synchronization sequence. That is, an arbitrary synchronization wireless device 14 may be designated as the response device in the j-th synchronization sequence, and the synchronization wireless devices 14 may be designated as the response device one by one in turn through multiple synchronization sequences.

[0068] In the communication system 100, the synchronization radio devices 14-1 to 14-n are registered with the base station 10, and the base station 10 executes synchronization processing with the synchronization radio devices 14-1 to 14-n and performs wireless communication with the synchronization radio devices 14-1 to 14-n. The following describes a registration processing in which the base station 10 registers a new synchronization radio device 14-(n+1) different from the already registered synchronization radio devices 14-1 to 14-n.

[0069] 4 shows a sequence chart of the registration process executed in the communication system 100. At time τ1, the new synchronization radio device 14-(n+1) receives the synchronization packet transmitted from the base station 10 at time t0-1. When the registration request waiting time TR has elapsed from time τ1, the synchronization radio device 14-(n+1) transmits a registration request packet to the base station 10 (S3). The registration request packet contains the ID of the synchronization radio device 14-(n+1) that sent it.

[0070] The registration request waiting time TR is determined so that the registration request packet is transmitted from the synchronization radio device 14-(n+1) after the already registered synchronization radio device 14-1 transmits an information request packet to the base station 10. Also, the registration request waiting time TR is determined so that the registration request packet is received by the base station 10 before the synchronization sequence corresponding to the synchronization packet received by the synchronization radio device 14-(n+1) is completed.

[0071] When the base station 10 receives the registration request packet at time τ2, it obtains and stores the sender ID from the registration request packet. As a result, the synchronization radio unit 14-(n+1) is registered with the base station 10.

[0072] The base station 10 includes response designation information that designates the newly registered synchronization wireless device 14-(n+1) as a response device in a synchronization packet that is transmitted in a synchronization sequence immediately following the synchronization sequence in which the synchronization wireless device 14-(n+1) was registered.

[0073] 4, the synchronization radio device 14-(n+1) receives a synchronization packet transmitted from the base station 10 in the second synchronization sequence at time t1-2, which is after the initial time t0-2 (S1-2). When the synchronization radio device 14-(n+1) recognizes that the received synchronization packet contains response designation information that designates itself as a response device, it transmits an information request packet to the base station 10 at time t2-2 (S2-2). The base station 10 receives the information request packet at time t3-2.

[0074] The synchronization radio device 14-2 receives the synchronization packet transmitted from the base station 10 in the third synchronization sequence at time t1-3 after the initial time t0-3 (S1-3). When the synchronization radio device 14-3 recognizes that the received synchronization packet contains response designation information that designates itself as a response device, it transmits an information request packet to the base station 10 at time t2-3 (S2-3). The base station 10 receives the information request packet at time t3-3.

[0075] In this way, in the synchronization sequence immediately following the synchronization sequence in which the synchronization radio device 14-(n+1) transmits a registration request packet to the base station 10, the synchronization radio device 14-2 is not designated as the response device, and the synchronization radio device 14-(n+1) is designated as the response device first. Then, in the synchronization sequence that is repeated after the synchronization radio device 14-(n+1) has been designated as the response device, the synchronization radio devices 14-2 and onwards are designated as response devices in order. As a result, synchronization processing for the newly registered synchronization radio device 14-(n+1) is performed with priority over synchronization processing for the other registered synchronization radio devices 14.

[0076] In the above, the process of registering the synchronization wireless device 14-(n+1) with the base station 10 in the first synchronization sequence has been described. The synchronization wireless device 14-(n+1) may be registered with the base station 10 in the jth synchronization sequence. In this case, in the synchronization sequence immediately following the synchronization sequence in which the synchronization wireless device 14-(n+1) is registered with the base station 10, the synchronization wireless device 14-(n+1) is designated as a response device. Furthermore, another synchronization wireless device 14 that would have been designated as a response device if the synchronization wireless device 14-(n+1) had not been registered is designated as a response device after the synchronization wireless device 14-(n+1).

[0077] The registration request waiting time TR may be a value that is randomly determined for each synchronization radio device 14. In this case, the synchronization radio device 14 executes carrier sense. That is, while an information request packet transmitted from another registered synchronization radio device 14 is being transmitted to the base station 10, the synchronization radio device 14-(n+1) stops transmitting a registration request packet. Then, after the information request packet is transmitted to the base station 10, the synchronization radio device 14-(n+1) transmits a registration request packet to the base station 10.

[0078] In the communication system 100, if the base station 10 does not receive an information request packet within the transmission period ST after transmitting a synchronization packet, the base station 10 designates the same synchronization radio device 14 as in the previous synchronization sequence as the response device in the next synchronization sequence. That is, the base station 10 includes, in the synchronization packet, response designation information that designates the same synchronization radio device 14 as in the previous synchronization sequence as the response device in the next synchronization sequence.

[0079] Reasons why the base station 10 does not receive the information request packet include poor communication conditions, the power supply to the synchronization radio device 14 designated as the response device being cut off, or a malfunction of the synchronization radio device 14 designated as the response device.

[0080] In this way, when the base station 10 does not receive an information request packet, it executes a synchronization sequence that designates the same synchronization radio device 14 as a response device up to M times, including the first synchronization sequence in which no information request packet is received, where M is a predetermined integer of 2 or more.

[0081] As a result, even if the communication conditions accidentally become poor, if the communication conditions become good while the synchronization sequence is being executed M times, synchronization processing is executed between the synchronization wireless device 14 designated as the response device and the base station 10.

[0082] When the base station 10 does not receive an information request packet over the (M+1)th synchronization sequence, it deletes from its own memory the ID of the synchronization wireless device 14 that was designated as the response device in the (M+1)th synchronization sequence, and cancels the registration of that synchronization wireless device 14.

[0083] Next, a process in which the synchronization radio device 14 judges whether or not it is registered with the base station 10 will be described. The synchronization radio device 14 repeatedly receives synchronization packets, and when the synchronization packets contain response designation information that designates the synchronization radio device 14 as a response device, it transmits an information request packet to the base station 10. The synchronization radio device 14 acquires a sequence number and the number of registered devices from each of the synchronization packets it receives in sequence. Then, when the number difference obtained by subtracting the sequence number contained in the synchronization packet that last designated the synchronization device 14 as a response device from the sequence number contained in the last received synchronization packet is M times or more the number of the most recently registered devices, it judges that it is not registered with the base station 10. On the other hand, when the number difference is less than M times the number of the most recently registered devices, the synchronization radio device 14 judges that it is registered with the base station 10. When the synchronization radio device 14 judges that it is not registered with the base station 10, it may transmit a registration request packet to the base station 10 the next time it receives a synchronization packet.

[0084] Fig. 5 shows the configuration of a communication system 102 according to an application embodiment. This communication system 102 is obtained by adding a relay station 42 to the communication system 100 shown in Fig. 1. The relay station 42 includes a relay radio device 44 and a relay base station 46. The relay radio device 44 has a similar configuration to the synchronization radio device 14, and executes the same processing as the synchronization radio device 14. The relay base station 46 has a similar configuration to the base station 10, and executes the same processing as the base station 10.

[0085] The relay radio device 44 executes a synchronization process with the base station 10 and synchronizes the time of its local clock with the base station time. The relay radio device 44 provides the time of its local clock to the relay base station 46. The relay base station 46 synchronizes the base station time of its own base station clock with the time provided by the relay radio device 44.

[0086] The relay base station 46 executes a synchronization process with the synchronization wireless device 14-j provided in each access point 12-j (j=1 or 2). In addition to executing the synchronization process, the synchronization wireless device 14-j provides the time of the local clock to the wireless LAN node 16-j attached thereto.

[0087] Through such processing, each wireless LAN node 16-j is synchronized with the base station time of the relay base station 46, and further acquires time synchronized with the base station time of the base station 10. Each wireless LAN node 16-j operates at a timing according to the time provided by the synchronization wireless device 14-j, thereby synchronizing the operations of a plurality of access points. In addition, since the base station time of the base station 10 is synchronized with the reference time transmitted from a GPS satellite, the time recognized by each access point is synchronized with the reference time.

[0088] In this communication system 102, each access point 12-j performs synchronization processing with the relay station 42, and the relay station 42 performs synchronization processing with the base station 10. Therefore, the distance between the base station 10 and each access point 12-j may be greater than that in the communication system 100 shown in FIG.

[0089] The synchronization wireless device and the wireless LAN node may constitute an access point of the wireless LAN, or may constitute an ad-hoc wireless device. The multiple ad-hoc wireless devices transmit packets from a source ad-hoc wireless device to a destination ad-hoc wireless device by multi-hop communication. Multi-hop communication refers to a communication form in which a packet transmitted from a source ad-hoc wireless device is relayed by one or more other ad-hoc wireless devices, and depending on the communication situation, is directly transmitted to the destination ad-hoc wireless device.

[0090] 6 shows the configuration of an ad-hoc communication system 104. The ad-hoc wireless device 48-j (j=1 to n) includes a synchronization wireless device 14-j and a wireless LAN node 16-j. The synchronization wireless device 14-j executes a synchronization process with the base station 10 and generates a time synchronized with a reference time. The synchronization wireless device 14-j provides the time synchronized with the reference time to the wireless LAN node 16-j. The wireless LAN node 16-j operates according to the time provided by the synchronization wireless device 14-j. This synchronizes the operation timings of the wireless LAN nodes 16-1 to 16-3. The wireless LAN nodes 16-1 to 16-n perform multi-hop communication with their operation timings synchronized.

[0091] An information terminal 20-j is connected to the wireless LAN node 16-j. The information terminal 20-j performs packet communication with a destination information terminal by making the wireless LAN node 16-j perform multi-hop communication.

[0092] 7 shows an example of hardware of base station 10. Base station 10 includes a GPS receiver 50, a base station clock 51, a controller 52, a memory 53, and a radio unit 54. The GPS receiver 50 receives reference time information from a GPS satellite and outputs the reference time to the controller 52. The base station clock 51 outputs the base station time to the controller 52. The controller 52 controls the base station clock 51 to set the base station time to the reference time.

[0093] The wireless unit 54 receives the packets and outputs them to the control unit 52. In addition, the wireless unit 54 transmits the packets output from the control unit 52.

[0094] The control unit 52 is configured by a processor that executes arithmetic processing according to a program loaded from the memory 53 or an external device, or a program written in advance. The control unit 52 executes packet transmission and reception processing together with the wireless unit .

[0095] The packet transmission / reception processing includes, for example, (1) a synchronization packet transmission processing for broadcasting a synchronization packet to each synchronization radio device 14 (radio device), and (2) a request reception processing for receiving each information request packet transmitted from each synchronization radio device 14 in response to the synchronization packet.

[0096] The packet transmission process includes a process of broadcasting a synchronization packet to each synchronization radio device 14, and a process of including in the synchronization packet response designation information that designates the synchronization radio device 14 that should respond to the synchronization packet.

[0097] The request reception process includes a process of determining an information request reception time indicating the time when the information request packet was received. The control unit 52 includes, in a synchronization packet to be transmitted in the next packet transmission / reception process, a synchronization packet transmission time indicating the time when the synchronization packet was transmitted in the previous packet transmission / reception process, and the information request reception time determined in the previous packet transmission / reception process for the synchronization radio device 14. Note that the synchronization packet transmission time may be the time when the synchronization packet itself is transmitted, instead of the time when the synchronization packet was transmitted in the previous packet transmission / reception process.

[0098] The control unit 52 may also execute a process of transmitting and receiving packets to and from a preregistered synchronization radio device 14 together with the radio unit 54. The control unit 52 may include response designation information for each synchronization radio device 14 in order in the repeatedly transmitted synchronization packet so that the multiple synchronization radio devices 14 are designated in order.

[0099] If the control unit 52 does not receive an information request packet after transmitting a synchronization packet, the control unit 52 may include, in the next synchronization packet to be transmitted, response designation information that designates the same synchronization radio device 14 as the previously transmitted synchronization packet. In this case, if the control unit 52 transmits a synchronization packet a predetermined number of times (M times) but does not receive an information request packet at the radio unit 54, the control unit 52 may delete the registration of the synchronization radio device 14 designated by the response designation information.

[0100] After executing the request receiving process, the control unit 52 may execute a registration process together with the radio unit 54 before transmitting the next synchronization packet. The registration process may include a process of receiving registration request information transmitted from a synchronization radio device 14 that is not registered in the base station 10 (an unregistered device), and registering the unregistered device that transmitted the registration request information as a new synchronization radio device 14.

[0101] 8 shows an example of hardware of the synchronization wireless device 14. The synchronization wireless device 14 includes a control unit 56, a local clock 57, an interface 58, a memory 59, and a wireless unit 60. The interface 58 is connected to information processing devices such as the above-mentioned wireless LAN nodes and information terminals. The local clock 57 issues a time that specifies the operation timing of the information processing device connected to the interface 58, and outputs it to the control unit 56.

[0102] The wireless unit 60 receives the packets and outputs them to the control unit 56. In addition, the wireless unit 60 transmits the packets output from the control unit 56.

[0103] The control unit 56 is configured by, for example, a processor that executes arithmetic processing according to a program preloaded from the memory 59 or an external device, or a program prewritten in the memory 59. The control unit 56 executes packet reception processing and request transmission processing together with the wireless unit 60.

[0104] The packet reception process includes, for example, a process of receiving a synchronization packet transmitted from the base station 10. The request transmission process includes, for example, a process of transmitting an information request packet when response designation information that designates itself as a response device is included in the synchronization packet.

[0105] A synchronization packet including response designation information that designates the synchronization radio device 14 as the responding device includes a synchronization packet transmission time indicating the time when the base station 10 transmitted the synchronization packet prior to that synchronization packet. Also, a synchronization packet transmitted by the base station 10 following the synchronization packet including response designation information that designates the synchronization radio device 14 as the responding device includes an information request reception time indicating the time when the base station 10 received the information request packet.

[0106] The synchronization packet reception process includes a process for obtaining a synchronization packet reception time indicating the time when the synchronization packet was received. The request transmission process includes a process for obtaining an information request transmission time indicating the time when the information request packet was transmitted. Note that the synchronization packet transmission time may be the time when the synchronization packet itself was transmitted from the base station 10, not the time when the base station 10 transmitted the synchronization packet in the previous packet reception process.

[0107] The control unit 56 calculates the propagation time between the base station 10 and the synchronization radio device 14 based on the initial time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process in which the synchronization radio device 14 of which the control unit 56 is included is designated as the responding device. The synchronization radio device 14 controls the local clock 57 based on the propagation time calculated in this manner, and the synchronization packet transmission time and the transmission packet reception time in the same synchronization sequence, and synchronizes the time generated by the local clock 57 with the base station time.

[0108] The control unit 56 outputs the time generated by the local clock 57 to an information processing device connected to an interface 58 .

[0109] The synchronization packet may include a sequence number indicating the number of times the base station 10 has transmitted the synchronization packet, and a registered device number indicating the number of radios (synchronization radio devices) registered by the base station 10. In this case, the control unit 56 may determine whether its own registration has been deleted based on the sequence number included in the latest synchronization packet that included response designation information designating the synchronization radio device 14 in which the control unit 56 is mounted, and the sequence number and registered device number included in the last received synchronization packet.

[0110] When the control unit 56 is not registered with the base station 10, the control unit 56 may, together with the radio unit 60, execute a process of transmitting a registration request packet to the base station 10 when a predetermined registration request waiting time has elapsed since receiving a synchronization packet. [Explanation of symbols]

[0111] 10 base station, 12-1 to 12-n access points, 14, 14-1 to 14-n synchronization radio devices, 16-1 to 16-n wireless LAN nodes, 18 Internet, 20 information terminal, 22 header section, 32 payload section, 42 relay station, 44 relay radio device, 46 relay base station, 48-1 to 48-n ad hoc radio device, 50 GPS receiver, 51 base station clock, 53, 59 memory, 52, 56 control section, 54, 60 radio section, 57 local clock, 58 interface.

Claims

1. A wireless unit for transmitting and receiving packets between a plurality of wireless devices; A base station including a control unit that controls the radio unit, The control unit is a synchronization packet transmission process for broadcasting a synchronization packet to each of the wireless devices; a request receiving process for receiving an information request packet transmitted from the wireless device in response to the synchronization packet, The synchronous packet transmission process includes: a process of including, in the synchronization packet, response designation information designating the wireless device that is to respond to the synchronization packet; The request receiving process includes: A process of obtaining an information request reception time indicating a time when the information request packet was received, The control unit is A base station characterized in that a synchronization packet transmission time indicating the time when the synchronization packet was transmitted in the previous transmission / reception process and the information request reception time obtained in the previous transmission / reception process are included in the synchronization packet to be transmitted in the next transmission / reception process.

2. A wireless unit for transmitting and receiving packets between a plurality of wireless devices; A base station including a control unit that controls the radio unit, The control unit is a synchronization packet transmission process for broadcasting a synchronization packet to each of the wireless devices; a request receiving process for receiving an information request packet transmitted from the wireless device in response to the synchronization packet, The synchronous packet transmission process includes: a process of including, in the synchronization packet, response designation information designating the wireless device that is to respond to the synchronization packet; The request receiving process includes: A process of obtaining an information request reception time indicating a time when the information request packet was received, The control unit is A base station characterized in that the information request reception time obtained in the previous transmission / reception process and a synchronization packet transmission time indicating the process at which the synchronization packet will be transmitted in the next transmission / reception process are included in the synchronization packet transmitted in the next transmission / reception process.

3. 3. The base station according to claim 1, The control unit is Executing, together with the wireless unit, a process of transmitting and receiving packets between the plurality of wireless devices registered in advance; A base station comprising: a base station including, in the repeatedly transmitted synchronization packet, the response designation information for each of the wireless devices in order so that each of the wireless devices is designated in order.

4. 4. The base station according to claim 3, The control unit is if the information request packet is not received after the synchronization packet is transmitted, the response designation information that designates the same wireless device as the previously transmitted synchronization packet is included in the next synchronization packet to be transmitted, a base station configured to cancel the registration of the wireless device designated by the response designation information if the information request packet is not received by the wireless unit even after transmitting the synchronization packet a predetermined number of times.

5. 3. The base station according to claim 1, The control unit is Executing, together with the wireless unit, a process of transmitting and receiving packets between the plurality of wireless devices registered in advance; The control unit is After executing the request receiving process, execute a registration process together with the wireless unit until the next synchronization packet is transmitted; The registration process includes: A base station comprising a process of receiving registration request information transmitted from an unregistered device, and registering the unregistered device that transmitted the registration request information as a new wireless device.

6. A radio unit for transmitting and receiving packets to and from a base station; a control unit for controlling the radio unit, the radio device constituting a communication system together with the base station and other radio devices, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet broadcast from the base station to the other radio devices and the radio unit itself; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when the synchronization packet contains response designation information that designates the wireless unit as a response device in addition to a broadcast address commonly assigned to the other wireless device and the wireless unit; In the communication system, one of the other wireless devices and the wireless device itself is designated as the response device in turn; each of the synchronization packets repeatedly transmitted from the base station includes a synchronization packet transmission time indicating a time when the previous synchronization packet was transmitted from the base station; the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is A wireless device characterized by calculating a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time corresponding to the synchronization packet reception process for which the wireless device is designated as the response device.

7. A radio unit for transmitting and receiving packets to and from a base station; a control unit for controlling the radio unit, the radio device constituting a communication system together with the base station and other radio devices, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet broadcast from the base station to the other radio devices and the radio unit itself; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when the synchronization packet contains response designation information for designating the wireless unit as a response device in addition to a broadcast address commonly assigned to the other wireless device and the wireless unit; In the communication system, one of the other wireless devices and the wireless device itself is designated as the response device in turn; The synchronization packet includes: a synchronization packet transmission time indicating the time when the synchronization packet itself was transmitted from the base station; the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is A wireless device characterized by calculating a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time corresponding to the synchronization packet reception process for which the wireless device is designated as the response device.

8. A radio unit for transmitting and receiving packets between a base station and the radio communication device; A control unit for controlling the radio unit, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet transmitted from the base station; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating the device itself as a response device is included in the synchronization packet; the synchronization packet including the response designation information designating itself as the response device includes a synchronization packet transmission time indicating a time when the base station transmitted the synchronization packet prior to the synchronization packet, the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is determining a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the wireless device is designated as the response device; The base station transmits and receives packets to and from a plurality of wireless devices that are registered in advance, The synchronization packet includes: a sequence number indicating the number of times the base station has transmitted the synchronization packet, and a number of registered devices indicating the number of the wireless devices registered in the base station, The control unit is the sequence number included in the latest one of the synchronization packets that includes the response designation information that designates the device itself; and A wireless device which determines whether its own registration has been deleted based on the sequence number and the number of registered devices contained in the last received synchronization packet.

9. A radio unit for transmitting and receiving packets between a base station and the radio communication device; A control unit for controlling the radio unit, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet transmitted from the base station; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating itself as a response unit is included in the synchronization packet; The synchronization packet includes: a synchronization packet transmission time indicating the time when the synchronization packet itself was transmitted from the base station; the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is determining a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the wireless device is designated as the response device; The base station transmits and receives packets to and from a plurality of wireless devices that are registered in advance, The synchronization packet is a sequence number indicating the number of times the base station has transmitted the synchronization packet, and a number of registered devices indicating the number of the wireless devices registered in the base station, The control unit is the sequence number included in the latest one of the synchronization packets that includes the response designation information that designates the device itself; and A wireless device which determines whether its own registration has been deleted based on the sequence number and the number of registered devices contained in the last received synchronization packet.

10. 10. The wireless device according to claim 8, The control unit is A wireless device characterized in that, when the wireless device itself is not registered with the base station, when a predetermined registration request waiting time has elapsed since receiving the synchronization packet, the wireless device executes, together with the wireless unit, a process of transmitting a registration request packet to the base station.

11. A radio unit for transmitting and receiving packets to and from a base station; A control unit for controlling the radio unit, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet transmitted from the base station; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating the device itself as a response device is included in the synchronization packet; the synchronization packet including the response designation information designating itself as the response device includes a synchronization packet transmission time indicating a time when the base station transmitted the synchronization packet prior to the synchronization packet, the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is determining a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the wireless device is designated as the response device; The base station transmits and receives packets to and from a plurality of wireless devices that are registered in advance, The control unit is A wireless device characterized in that, when the wireless device itself is not registered with the base station, when a predetermined registration request waiting time has elapsed since receiving the synchronization packet, the wireless device executes, together with the wireless unit, a process of transmitting a registration request packet to the base station.

12. A radio unit for transmitting and receiving packets to and from a base station; A control unit for controlling the radio unit, The control unit is repeatedly executing, together with the radio unit, a synchronization packet receiving process for receiving a synchronization packet transmitted from the base station; executes, together with the wireless unit, a request transmission process for transmitting an information request packet when response designation information designating itself as a response unit is included in the synchronization packet; The synchronization packet is a synchronization packet transmission time indicating the time when the synchronization packet itself was transmitted from the base station; the synchronization packet transmitted by the base station next to the synchronization packet including the response designation information that designates the base station itself as the response device includes an information request reception time indicating a time at which the base station received the information request packet; The synchronous packet receiving process includes: A process of obtaining a synchronization packet reception time indicating a time when the synchronization packet was received, The request transmission process includes: A process of obtaining an information request transmission time indicating a time when the information request packet was transmitted, The control unit is determining a propagation time between the base station and the wireless device based on the synchronization packet transmission time, the synchronization packet reception time, the information request transmission time, and the information request reception time, which correspond to the synchronization packet reception process for which the wireless device is designated as the response device; The base station transmits and receives packets to and from a plurality of wireless devices that are registered in advance, The control unit is A wireless device characterized in that, when the wireless device itself is not registered with the base station, when a predetermined registration request waiting time has elapsed since receiving the synchronization packet, the wireless device executes, together with the wireless unit, a process of transmitting a registration request packet to the base station.

13. 13. The wireless device according to claim 6, A wireless device which determines a time when the wireless device transmits a signal based on the propagation time.

14. A wireless device according to any one of claims 6 to 13, The control unit is A wireless device characterized in that the time of a local clock provided in the wireless device is synchronized to the time of a base station clock provided in the base station based on the propagation time and the synchronization packet transmission time and the synchronization packet reception time corresponding to the synchronization packet reception process for which the wireless device is designated as the response device.

15. A wireless device according to any one of claims 6 to 14, The control unit is A wireless device characterized in that the wireless device synchronizes the time of a local clock provided in the wireless device to the time of a base station clock provided in the base station based on the propagation time and the synchronization packet transmission time and the synchronization packet reception time corresponding to the synchronization packet reception process in which the wireless device is not designated as the response device.

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