Long distance signal transmission system

Abstract

To synchronize radio base stations in simple configuration when performing long-range signal transmission using flooding.SOLUTION: The present invention relates to a system for performing signal transmission using flooding via a communication network constructed by a plurality of radio base stations. A slot number for identifying any one of time-divided time slots is allocated to each of the plurality of radio base stations. Transmission timing is set so as to transmit information including data, which should be transmitted, and a slot number allocated to an own radio base station in such timing that a cycle calculated by a timer of the own radio base station is coincident with a cycle of a time slot corresponding to the slot number allocated to the own radio base station in a case there are the data which should be transmitted. In a case where information is received from any other radio base station, the transmission timing is corrected by correcting a time of the timer of the own radio base station based on a slot number included in the information.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a long-distance signal transmission system that transmits signals using flooding as a signal transfer protocol via a communication network constructed by multiple wireless base stations. [Background technology]

[0002] A broadcasting method called flooding using simultaneous transmission has been proposed for signal transmission in a communication network with multiple wireless base stations. In the flooding method using simultaneous transmission, when one wireless base station transmits data, one or more wireless base stations that receive the data broadcast the same data, thereby realizing simultaneous transmission of wireless signals.

[0003] By repeating this simultaneous transmission multiple times at each of multiple wireless base stations, it becomes possible to transmit data to the entire signal transmission system. The adoption of this communication method has the advantage that it does not require pre-settings for routing regarding communication paths.

[0004] There is also a method of preventing interference between signal transmissions from multiple wireless stations by assigning a time slot to each of multiple wireless base stations, with each wireless base station transmitting signals wirelessly only within the time slot assigned to it.

[0005] In a signal transmission system that uses time slots for communication, it is necessary to achieve synchronization among a plurality of wireless base stations. As a method for achieving synchronization, there is a conventional technique that uses a synchronization packet (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-177616 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the conventional techniques have the following problems. In the conventional technology described in Patent Document 1, the process of generating and transmitting a specific synchronization packet, as well as the process of recovering synchronization when the synchronization packet is received, must be implemented in each wireless base station that communicates using time slots.

[0008] Therefore, the configuration required to achieve synchronization is complex, and the implementation of the necessary functions requires time and effort, which is one of the bottlenecks in the introduction of signal transmission systems using flooding.

[0009] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a long-distance signal transmission system that can achieve synchronization with a simple configuration in each wireless base station when performing long-distance signal transmission using flooding. [Means for solving the problem]

[0010] A long-distance signal transmission system according to the present disclosure is a long-distance signal transmission system that transmits signals through a communication network constructed by a plurality of wireless base stations using flooding as a signal transfer protocol, in which each of the plurality of wireless base stations is assigned a slot number for identifying one of the time-divided time slots, and when there is data to be transmitted, the transmission timing is set so that the wireless base station can transmit information including the data to be transmitted and the slot number assigned to the wireless base station at a timing when the period calculated by the wireless base station's own timer coincides with the period of the time slot corresponding to the slot number assigned to the wireless base station, and when the wireless base station receives information from another wireless base station, By timing , and corrects its own timer based on the slot number included in the information. By synchronizing the time of its own timer with the time of the timer of the other wireless base station that is the source of the information, This is to correct the transmission timing. Effect of the Invention

[0011] According to the present disclosure, it is possible to obtain a long-distance signal transmission system that can achieve synchronization in each wireless base station with a simple configuration when performing long-distance signal transmission using flooding. [Brief description of the drawings]

[0012] [Figure 1] 1 is an overall configuration diagram of a long-distance signal transmission system according to a first embodiment of the present disclosure. [Diagram 2] 1 is an explanatory diagram of a case where signal transmission is performed using flooding according to rules 1 and 2 in a long-distance signal transmission system according to the first embodiment of the present disclosure. FIG. [Diagram 3] FIG. 2 is an explanatory diagram of signal transmission using flooding implemented in a long-distance signal transmission system according to a first embodiment of the present disclosure. [Figure 4] 2 is a functional block diagram of each wireless base station in the long-distance signal transmission system according to the first embodiment of the present disclosure. FIG. [Diagram 5] 4 is a flowchart showing a series of processes of signal transmission using flooding performed in each wireless base station according to the first embodiment of the present disclosure. [Figure 6] FIG. 11 is an overall configuration diagram of a long-distance signal transmission system according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment of the long-distance signal transmission system of the present disclosure will be described below with reference to the drawings. The long-distance signal transmission system of the present disclosure has a technical feature in that each wireless base station has a function of correcting its own timer at the timing when it receives information from another wireless base station. As a result, when performing long-distance signal transmission using flooding, it is possible to obtain an effect of being able to synchronize each wireless base station with a simple configuration.

[0014] Embodiment 1 There is a demand for using wireless modules based on LoRa, one of the representative standards for LPWA (Low Power Wide Area) wireless, to transmit information for detecting anomalies in remote locations (for example, monitoring for fallen bridges deep in the mountains).To achieve this, it is necessary to add wireless mesh network functionality and enable long-distance transmission to cover a wide area.

[0015] The widening of the wireless mesh network can be achieved by strengthening two functions: increasing the number of relay wireless stations and increasing the distance between wireless stations. From this perspective, when transmitting information from a fire detection system or a bridge collapse monitoring system deep in the mountains, one solution is to adopt a long-distance signal transmission system that applies flooding as a signal transfer protocol via a communication network constructed by multiple wireless base stations.

[0016] When adopting such a long-distance signal transmission system using flooding, it is important to develop technology that can achieve synchronization with a simple configuration at each wireless base station in the communication network and to solve the problems of the conventional technology.

[0017] In the following, a detailed description will be given of a specific example of detecting a fallen bridge deep in the mountains using a long-distance signal transmission system that transmits signals using flooding. The long-distance signal transmission system of the present disclosure is applicable to various applications that utilize wireless mesh networks.

[0018] Fig. 1 is an overall configuration diagram of a long-distance signal transmission system according to the first embodiment of the present disclosure. Fig. 1 illustrates an example in which a communication network is constructed by a monitoring center 1 installed in a city hall, three sensor networks 2, 3, and 4, and a city network 5.

[0019] The monitoring center 1 is configured to include one wireless base station 10 and a monitoring PC (Personal Computer) 40. An operator in the monitoring center 1 monitors the monitoring PC 40, thereby enabling centralized monitoring of information within the communication network.

[0020] Each of the sensor networks 2 and 3 is configured to include one wireless base station 10 and two wireless base stations 20 dedicated to transmission.

[0021] The sensor network 4 is configured with one wireless base station 10, five transmission-only wireless base stations 20, and a number of sensors 30 installed on bridges that are the subject of bridge collapse monitoring. The city network 5 is configured with five wireless base stations 10 arranged to form a wireless mesh network.

[0022] 1 is merely an example, and the number, arrangement, and connection relationship of the network, wireless base stations, and sensors can be changed as desired depending on the environment in which the long-distance signal transmission system of the present disclosure is applied. In the following description, the wireless base station 10 that transmits and receives data will be simply referred to as the wireless base station 10, and the wireless base station 20 dedicated to transmission will be simply referred to as the wireless base station 20.

[0023] In a communication network constructed by multiple wireless base stations 10 and multiple wireless base stations 20, signal transmission is performed using flooding as a signal transfer protocol in the multiple wireless base stations 10. Flooding is a protocol that transfers signals according to only the following two simple rules.

[0024] Rule 1: When a wireless base station 10 receives a signal transmitted from another wireless base station 10 or a wireless base station 20, it forwards the received signal to all wireless base stations 10 within its radio wave range. Rule 2: If the wireless base station 10 receives the same signal again at a different timing, it does not perform the second transfer.

[0025] Fig. 2 is an explanatory diagram of a case where signal transmission is performed using flooding in accordance with rule 1 and rule 2 in the long-distance signal transmission system according to the first embodiment of the present disclosure. Fig. 2 illustrates an example where signal transmission is performed using flooding by three wireless base stations 10(1) to 10(3).

[0026] More specifically, FIG. 2 illustrates an example in which the wireless base station 10(1) is a source base station, the wireless base station 10(2) is a relay base station, and the wireless base station 10(3) is a destination base station, and a signal transmitted from the wireless base station 10(1) finally reaches the wireless base station 10(3) through flooding.

[0027] [1] to [4] in Figure 2 represent the steps in which signal transmission is performed using flooding. At each step, the following processing is performed in sequence. Step [1]: The wireless base station 10(1) forwards a signal to all wireless base stations 10 within its radio wave coverage in accordance with rule 1. As a result, a signal is transmitted from the wireless base station 10(1) to the wireless base station 10(2).

[0028] Step [2]: According to rule 1, the wireless base station 10(2) transfers the signal to all wireless base stations 10 within its radio wave range. As a result, the signal is transmitted from the wireless base station 10(2) to the wireless base station 10(1) and the wireless base station 10(3). Therefore, through steps [1] and [2], the signal transmitted from the wireless base station 10(1) reaches the wireless base station 10(3), and the original purpose is achieved.

[0029] Step [3]: The wireless base station 10(1) does not forward the same signal in accordance with rule 2. Meanwhile, the wireless base station 10(3) forwards the signal to all wireless base stations 10 within its radio wave range in accordance with rule 1. If rule 3 is set such that "if the signal is addressed to itself, the received data is accepted but not forwarded," the wireless base station 10(3) can be prevented from forwarding in accordance with rule 3.

[0030] Step [4]: ​​The wireless base station 10(2) does not forward any more signals because it has received the same signal as in step [1] in step [3] according to rule 2. As a result, no further forwarding is performed, and signal forwarding within the network is terminated.

[0031] In the communication network in FIG. 1 as well, by transmitting signals by flooding according to rules 1 and 2 as explained in FIG. 2, the wireless base station 10 in the monitoring center 1 can receive signals transmitted from the wireless base stations 10 in the sensor networks 2 to 4 to the wireless base station 10 in the monitoring center 1 via the local network 5.

[0032] The advantages of signal transmission by flooding include the following: Advantage 1: By following rule 2, the signal will not travel back and forth indefinitely. Advantage 2: Since there is no need to prepare a routing table indicating the forwarding party for each destination, operation of a long-distance signal transmission system using a plurality of wireless base stations 10 becomes easier.

[0033] However, the following points should be noted when transmitting signals by flooding: Point to note 1: Because redundant transmissions are performed, collisions and interference of radio waves are likely to occur, making it necessary to control the timing of radio wave transmissions.

[0034] As a part of the measures to address this point, the system according to Patent Document 1 employs a method of allocating time slots to each of the multiple wireless base stations 10 and achieving synchronization. However, the method disclosed in Patent Document 1 aims at highly accurate synchronization to realize versatile and highly efficient transmission, which is more than is necessary for the problem we need to solve as shown in Fig. 1, and the configuration is complicated, so the effort and cost required to implement the function is unnecessarily high.

[0035] Therefore, in the long-distance signal transmission system according to the present disclosure, a method is realized in which synchronization can be achieved with a simple configuration in each wireless base station 10 when performing long-distance signal transmission using flooding. The specific contents will be described in detail with reference to Figs. 3 to 5.

[0036] Fig. 3 is an explanatory diagram of signal transmission using flooding performed in the long-distance signal transmission system according to the first embodiment of the present disclosure. Fig. 4 is a functional block diagram of each wireless base station 10 in the long-distance signal transmission system according to the first embodiment of the present disclosure. Fig. 5 is a flowchart showing a series of processes of signal transmission using flooding performed in each wireless base station 10 according to the first embodiment of the present disclosure.

[0037] In FIG. 3, for the sake of simplicity, a communication network is constructed using three wireless base stations 10(1) to 10(3) and signal transmission is performed using flooding. In reality, however, a fourth or subsequent wireless base station 10 will also be present, and a wireless mesh network will be constructed.

[0038] In FIG. 3(A), ID1 is assigned to the wireless base station 10(1), ID2 is assigned to the wireless base station 10(2), and ID3 is assigned to the wireless base station 10(3), and a state in which signals are transmitted between them is shown.

[0039] In FIG. 3(A), a signal transmitted from the wireless base station 10(1) to which ID1 is assigned is indicated as SG1, a signal transmitted from the wireless base station 10(2) to which ID2 is assigned is indicated as SG2, and a signal transmitted from the wireless base station 10(3) to which ID3 is assigned is indicated as SG3.

[0040] Here, it is assumed that the radio base station 10(1) having ID1 is assigned the slot number SNo1, the radio base station 10(2) having ID2 is assigned the slot number SNo2, and the radio base station 10(3) having ID3 is assigned the slot number SNo3.

[0041] The ID is a unique identifier for identifying each wireless base station 10 in the long-distance signal transmission system, and is not assigned to any other wireless base station. On the other hand, the SNo is a slot number assigned to each wireless base station to specify a time slot for transmission, and may be assigned to any other wireless base station. However, FIG. 3A illustrates a case in which three types of slot numbers are assigned to each of the three wireless base stations without overlapping.

[0042] 3(B) shows a schematic state in which a time slot of time width ΔT is assigned to each of slot numbers SNo1 to SNo3, one for each period T. That is, each of the wireless base stations 10(1) to 10(3) is assigned a slot number SNo for identifying one of the time-divided time slots, and the timing of data transmission is specified.

[0043] Specifically, when each of the wireless base stations 10(1) to 10(3) has data to transmit, it transmits information including the data to be transmitted and the slot number SNo allocated to it at a timing when the period calculated by its own timer matches the period of the time slot corresponding to the slot number SNo allocated to it.

[0044] Next, a series of processes of signal transmission using flooding performed in each of the wireless base stations 10(1) to 10(3) will be described based on the functional block diagram of Fig. 4 and the flowchart of Fig. 5. Note that each of the wireless base stations 10(1) to 10(3) has the same configuration, and will be described as the wireless base station 10 unless there is a need to distinguish them.

[0045] 4, the radio base station 10 is configured to include a reception signal processing unit 11, a synchronization adjustment unit 12, and a transmission signal processing unit 13. The reception signal processing unit 11 has a function of receiving information transmitted from other radio base stations 10 arranged in the vicinity. The reception signal processing unit 11 receives information transmitted from other radio base stations 10 at the timing of a time slot corresponding to a slot number SNo assigned to the other radio base station 10 that is the transmission source.

[0046] The synchronization adjustment unit 12 has a function of correcting the time of a timer indicating a current position in a time slot period based on the slot number SNo included in the information when the received signal processing unit 11 receives information from another wireless base station 10. As a result, the synchronization adjustment unit 12 corrects the time of its own timer to match the time of the timer of the other wireless base station 10 that is the source of the information, thereby synchronizing the timer of the other wireless base station 10 with its own timer and correcting the transmission timing.

[0047] When the reception signal processing unit 11 receives information from another wireless base station 10, the transmission signal processing unit 13 judges whether or not the forwarding conditions based on the rules 1 and 2 are satisfied. If the forwarding conditions are satisfied, the transmission signal processing unit 13 judges that there is data to be transmitted.

[0048] Furthermore, the transmission signal processing unit 13 will transfer information including the data to be transmitted and the slot number SNo assigned to it at a timing when the time on its timer is within the time slot corresponding to the slot number SNo assigned to it.

[0049] In this forwarding process, the transmission signal processing unit 13 can forward the information using its own timer, the time of which has been adjusted by the synchronization adjustment unit 12, at the timing of receiving information from another radio base station 10. Therefore, the radio base station 10 having the configuration of Fig. 4 can adjust the time of its own timer by receiving information from another radio base station 10, and as a result, can achieve synchronization with other surrounding radio base stations 10.

[0050] The time correction process by the synchronization adjustment unit 12 may always be performed when information is received from another wireless base station 10 by the receiving signal processing unit 11, but it is also possible to set the start conditions for the time correction process, such as performing the time correction process only during a certain period of time, or performing the time correction process only when information is received by a specific slot number SNo.

[0051] Next, a series of processes for signal transmission using flooding performed in each wireless base station 10 according to the first embodiment will be summarized as follows using Fig. 5. First, in step 501, the reception signal processing unit 11 in the wireless base station 10 performs reception processing to receive information transmitted from other surrounding wireless base stations 10.

[0052] Next, in step S502, when the synchronization adjustment unit 12 receives the information transmitted in step 501, it corrects the time of its own timer based on the slot number SNo of the other radio base station 10 and the timing at which the information was received.

[0053] Next, in step S503, the transmission signal processing unit 13 judges whether the forwarding conditions based on rules 1 and 2 are satisfied. That is, the transmission signal processing unit 13 judges that the forwarding conditions are satisfied when rule 1 is satisfied and rule 2 is not satisfied, and judges that the forwarding conditions are not satisfied in other cases. When the transmission signal processing unit 13 judges that the forwarding conditions are not satisfied in step S503, it does not perform the forwarding process and ends the series of processes.

[0054] On the other hand, if the transmission signal processing unit 13 determines in step S503 that the transfer condition is satisfied, the process proceeds to step S504, where it waits for the time slot corresponding to the slot number SNo allocated to itself to come based on its own timer that was time-adjusted in step S502. Then, at the timing when the time slot allocated to itself comes, it executes the transmission process of the signal including the data received in step S501 (i.e., the data to be transmitted) and the slot number SNo allocated to itself.

[0055] In this way, each time a transmission process by flooding is performed, the slot number SNo assigned to the source wireless base station 10 is added. Therefore, the wireless base station 10 that receives information including the slot number SNo can identify which time slot the information was transmitted in, and can easily adjust the timer.

[0056] As described above, according to the first embodiment, in each wireless base station, the synchronization adjustment unit can easily correct the time of its own timer used when performing a transfer process using a time slot. As a result, it is possible to realize a long-distance signal transmission system that can achieve synchronization with a simple configuration in each wireless base station in a wireless network when performing long-distance signal transmission using flooding.

[0057] Embodiment 2 In the second embodiment, a method of allocating a slot number SNo to each wireless base station 10 in consideration of communication efficiency in the long-distance signal transmission system according to the present disclosure will be described.

[0058] Fig. 6 is an overall configuration diagram of a long-distance signal transmission system according to the second embodiment of the present disclosure. The overall configuration shown in Fig. 6 is the same as the overall configuration shown in Fig. 1 in the first embodiment. However, in Fig. 6, the following contents are added to the previous Fig. 1.

[0059] The nine wireless base stations 10 are identified by symbols 10(1) to 10(9). Although not shown in Fig. 6, each of the nine wireless base stations 10(1) to 10(9) is assigned a unique identifier ID1 to ID9, making it possible to identify the base stations by the ID. The figure shows a state in which one of four types of slot numbers Sno1 to SNo4 is assigned to each of the wireless base stations 10(1) to 10(9). The first to third routes are identified as desired communication routes using thick arrows.

[0060] In the second embodiment, a case will be described in which the first route is specified as a desired communication route with the highest priority among a plurality of wireless base stations 10. The first route is depicted as a bold white arrow in Fig. 6, and is set as a desired route for quickly transmitting information from the sensor 30 in the sensor network 4 to the monitoring center 1.

[0061] Specifically, the first route is defined as a route passing through radio base station 10(4) → radio base station 10(6) → radio base station 10(9) → radio base station 10(1). In order to transfer information sequentially and quickly using time slots according to slot numbers SNo on this first route, it is appropriate to assign the order of slot numbers SNo according to the order of radio base stations 10 from the source of information to the destination.

[0062] Therefore, in FIG. 6, it is conceivable to allocate the following slot numbers SNo to the four wireless base stations 10 on the first route in accordance with the transmission order of the information on the first route. Wireless base station 10(4):SNo1 Wireless base station 10(6):SNo2 Wireless base station 10(9):SNo3 Wireless base station 10(1):SNo4

[0063] By allocating the slot numbers SNo in this manner, the wireless base station 10(6) can receive information from the wireless base station 10(4) in the time slot of SNo1, and then can immediately transmit information in the time slot of slot number SNo2 allocated to itself.

[0064] Similarly, wireless base station 10(9) can receive information from wireless base station 10(6) in the time slot of slot number SNo2, and can then immediately transmit information in the time slot of slot number SNo3 assigned to itself.

[0065] Finally, the wireless base station 10(1) can receive the information from the wireless base station 10(9) at the timing of the time slot with slot number SNo3. As a result, the monitoring PC in the monitoring center 1 can quickly obtain the information sent from the wireless base station 10(4), which is the sender, after the time equivalent to three time slots has elapsed.

[0066] In Figure 6, the communication path from the sensor network 4 to the monitoring center 1 is set as the first route with top priority, and then a second route shown as a thick arrow with vertical stripes in Figure 6 and a third route shown as a thick arrow with a checker mark in Figure 6 are further set.

[0067] Here, the second route corresponds to a communication path from the sensor network 2 to the monitoring center 1, and is defined as a route passing through the wireless base station 10(2)→wireless base station 10(7)→wireless base station 10(1).

[0068] Then, it is possible to assign the following slot numbers SNo to the three wireless base stations 10 on the second route. Wireless base station 10(2):SNo2 Wireless base station 10(7):SNo3 Wireless base station 10(1):SNo4 Incidentally, the slot number SNo4 has already been assigned to the wireless base station 10(1) when the first route was set.

[0069] By setting such a second route, the monitoring PC in the monitoring center 1 can quickly obtain the information sent from the source wireless base station 10(2) after the passage of two time slots.

[0070] Similarly, the third route corresponds to a communication path from the sensor network 3 to the monitoring center 1, and is defined as a route passing through wireless base station 10(3)→wireless base station 10(9)→wireless base station 10(1).

[0071] Then, it is possible to assign the following slot numbers SNo to the three wireless base stations 10 on the third route. Wireless base station 10(3):SNo2 Wireless base station 10(9):SNo3 Wireless base station 10(1):SNo4 Incidentally, slot numbers SNo3 and SNo4 have already been assigned to radio base stations 10(9) and 10(1), respectively, when the first route was set.

[0072] By setting up such a third route, the monitoring PC in the monitoring center 1 can quickly obtain the information sent from the source wireless base station 10(3) after the passage of two time slots.

[0073] In addition, when the slot numbers SNo are assigned as in FIG. 6, for example, when information is transmitted simultaneously from the radio base station 10(2) and the radio base station 10(6), both of which are assigned the slot number SNo2, to the radio base station 10(7), the transmission signals may interfere with each other.

[0074] However, the wireless base station 10(2) and the wireless base station 10(6) do not always transmit information at the timing of the time slot assigned to slot number SNo2, and data to be transmitted is not frequent. Even if interference occurs, the interference problem can be solved by receiving information via another route constructed in a mesh or by retransmitting the information.

[0075] As described above, according to the second embodiment, sequential slot numbers SNo are assigned to each of the wireless base stations arranged along a desired communication route among a plurality of wireless base stations so that signal transmission can be performed sequentially by flooding according to the order of the slot numbers SNo. As a result, information can be transferred quickly via the desired route.

[0076] As described above, the slot numbers SNo can be sequentially assigned along a desired communication route, but each wireless base station 10 can also automatically assign slot numbers SNo from an ID that is uniquely assigned to itself. For example, when ID1 to ID9 are assigned to each of the nine wireless base stations 10(1) to 10(9) shown in Fig. 6 and four types of slot numbers Sno1 to SNo4 are used as time slots, it is also possible to automatically assign slot numbers SNo to each wireless base station 10 based on the remainder when the ID number is divided by 4.

[0077] In addition, in the first and second embodiments, the transmission timing of the dedicated transmission radio base station 20 is not particularly explained, so a supplementary explanation will be given. The dedicated transmission radio base station 20 corresponds to a radio base station that does not need to transmit signals using flooding. In addition, the dedicated transmission radio base station 20 may receive, for example, a detection result by the sensor 30 as information to be transmitted at any timing. Therefore, when the dedicated transmission radio base station 20 has information to transmit, it is appropriate for the dedicated transmission radio base station 20 to transmit the information immediately from the viewpoint of rapid transmission.

[0078] Therefore, for the transmission-only radio base station 20, it is conceivable to set the transmission timing so that, when there is data to be transmitted, the data to be transmitted can be transmitted at any timing independent of the time slot. [Explanation of symbols]

[0079] 1 Monitoring center, 2~4 sensor networks, 5 city network, 10 wireless base station, 20 wireless base station for transmission only, 30 sensor, 40 monitoring PC.

Claims

1. A long-distance signal transmission system that transmits signals through a communication network constructed by a plurality of wireless base stations using flooding as a signal transfer protocol, Each of the plurality of radio base stations A slot number for specifying one of the time slots allocated to the device is assigned to the device, and when there is data to be transmitted, a transmission timing is set so that the device can transmit information including the data to be transmitted and the slot number allocated to the device at a timing when a period calculated by the device's own timer coincides with the period of the time slot corresponding to the slot number allocated to the device, At the timing when the information is received from another wireless base station, the time of the timer of the wireless base station is corrected based on the slot number included in the information, and the transmission timing is corrected by synchronizing the time of the timer of the other wireless base station that is the source of the information with the time of the timer of the wireless base station. Long distance signal transmission system.

2. Among the plurality of wireless base stations, each of the wireless base stations arranged along a desired communication route is assigned a sequential slot number along the communication route so that the signal transmission can be sequentially performed using the flooding according to the order of the slot numbers.

2. The long-distance signal transmission system according to claim 1.

3. Among the plurality of wireless base stations, a wireless base station dedicated to transmission that does not need to perform the signal transmission using the flooding has the transmission timing set so that, when there is data to be transmitted, the data to be transmitted can be transmitted at any timing independent of the time slot.

3. A long-distance signal transmission system according to claim 1 or 2.

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