JP7805502B2 - Long-distance signal transmission system - Google Patents

Description

This disclosure relates to a long-distance signal transmission system that transmits signals using flooding as a signal transfer protocol via a communication network constructed with multiple wireless base stations.

When transmitting signals in a communication network with multiple wireless base stations, a broadcasting method called flooding that uses simultaneous transmission has been proposed. In this method, when one wireless base station transmits data, one or more wireless base stations that receive that data broadcast the same data, thereby achieving simultaneous transmission of wireless signals.

By having multiple wireless base stations each repeat this simultaneous transmission multiple times, it becomes possible to transmit data throughout the entire signal transmission system. The advantage of adopting this type of communication method is that it eliminates the need for pre-configured routing for communication paths.

In addition, there is a method of preventing interference between signal transmissions from multiple wireless stations by assigning a time slot to each of multiple wireless base stations, so that each wireless base station can transmit signals wirelessly only within its assigned time slot.

In signal transmission systems that use time slots for communication, synchronization must be achieved between multiple wireless base stations. One conventional technique for achieving synchronization is to use synchronization packets (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2021-177616

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, and the process of recovering synchronization when the synchronization packet is received, must be implemented in each wireless base station that communicates using time slots.

As a result, the configuration required to achieve synchronization is complex, and implementing the necessary functions requires time and effort, resulting in costs. In other words, the complexity of the configuration required to achieve synchronization has been one of the bottlenecks in the introduction of signal transmission systems that use flooding.

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 at each wireless base station when transmitting signals over long distances using flooding.

The long-distance signal transmission system of the present disclosure is a long-distance signal transmission system that transmits signals via a communication network constructed by multiple wireless base stations using flooding as a signal transfer protocol, in which each of the multiple wireless base stations is assigned a slot number to identify one of the time-divided time slots, and when there is data to be transmitted, the transmission timing is set so that it can transmit information including the data to be transmitted and the slot number assigned 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 assigned to it, and when information is received from another wireless base station, it corrects the transmission timing by correcting the time of its own timer at the timing when it receives information with a specific slot number based on the slot number included in the information.
In addition, the long-distance signal transmission system of the present disclosure is a long-distance signal transmission system that transmits signals via a communication network constructed by multiple wireless base stations using flooding as a signal transfer protocol, and each of the multiple wireless base stations is assigned a slot number to identify one of the time-divided time slots, and when there is data to be transmitted, the transmission timing is set so that it can transmit information including the data to be transmitted and the slot number assigned 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 assigned to it, and only when information is received from another wireless base station during a predetermined time period, it corrects the transmission timing by correcting the time of its own timer based on the slot number included in the information.
Furthermore, a long-distance signal transmission system according to the present disclosure is a long-distance signal transmission system that transmits signals via 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 it at a timing when the period calculated by its own timer matches the period of the time slot corresponding to the slot number assigned to it, and when information is received from another wireless base station, the transmission timing is corrected by correcting the time of its own timer based on the slot number included in the information, and among the plurality of wireless base stations, one that is arranged on a desired communication route is selected. An allocation process is performed on each radio base station to allocate sequential slot numbers along the communication route so that signal transmission can be performed sequentially using flooding in the order of the slot numbers. As desired communication routes, there are a first route that should be set with the highest priority and a second route that should be set with the next highest priority after the first route. If some of the multiple radio base stations constituting the first route and some of the multiple radio base stations constituting the second route are the same radio base station, the allocation process on the first route is performed first, and then the allocation process on the second route is performed. When the allocation process on the second route is performed, the allocation results of the slot numbers already allocated to the same radio base station by performing the allocation process on the first route are maintained as they are, and the allocation process is performed on radio base stations other than the same radio base station among the multiple radio base stations constituting the second route.

This disclosure makes it possible to obtain a long-distance signal transmission system that can achieve synchronization with a simple configuration at each wireless base station when transmitting signals over long distances using flooding.

1 is an overall configuration diagram of a long-distance signal transmission system according to a first embodiment of the present disclosure. 1 is an explanatory diagram illustrating a case where signal transmission is performed using flooding according to rule 1 and rule 2 in a long-distance signal transmission system according to embodiment 1 of the present disclosure. 1 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. FIG. 2 is a functional block diagram of each radio base station in the long-distance signal transmission system according to the first embodiment of the present disclosure. 1 is a flowchart showing a series of processes for signal transmission using flooding performed in each radio base station according to the first embodiment of the present disclosure. FIG. 10 is an overall configuration diagram of a long-distance signal transmission system according to a second embodiment of the present disclosure.

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 the ability to correct its own timer when it receives information from another wireless base station. As a result, when long-distance signal transmission is performed using flooding, it is possible to achieve synchronization at each wireless base station with a simple configuration.

Embodiment 1.
There is a demand for wireless modules that comply with LoRa, one of the major standards for LPWA (Low Power Wide Area) wireless, to transmit information for detecting abnormalities in remote locations (for example, monitoring for collapsed bridges deep in the mountains).To achieve this, it is necessary to add wireless mesh network functionality to enable long-distance transmission so that a wide area can be covered.

Wireless mesh networks can be made wider by strengthening two functions: increasing the number of relay radio stations and extending the distance between radio stations. From this perspective, one solution for transmitting information from systems such as fire detection systems and bridge collapse monitoring systems deep in the mountains is to adopt a long-distance signal transmission system that uses flooding as a signal transfer protocol via a communications network constructed from multiple wireless base stations.

When adopting such a long-distance signal transmission system using flooding, it is important to develop technology that allows for synchronization with a simple configuration at each wireless base station within the communications network and to resolve the issues with conventional technology.

The following explanation will provide a detailed example of a long-distance signal transmission system that uses flooding to transmit signals, and will explain in detail the case of detecting a fallen bridge deep in the mountains. The long-distance signal transmission system disclosed herein can be applied to a variety of applications that utilize wireless mesh networks.

Figure 1 is an overall configuration diagram of a long-distance signal transmission system according to the first embodiment of the present disclosure. Figure 1 illustrates an example in which a communications network is constructed from a monitoring center 1 located within a city hall, three sensor networks 2, 3, and 4, and a city network 5.

The monitoring center 1 is composed of one wireless base station 10 and a monitoring PC (Personal Computer) 40. By monitoring the monitoring PC 40 within the monitoring center 1, an operator can centrally monitor information within the communication network.

Each of the sensor networks 2 and 3 is composed of one wireless base station 10 and two transmission-only wireless base stations 20.

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

Note that the overall configuration shown in Figure 1 is merely an example, and the number, placement, and connection relationships 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, a wireless base station 10 that transmits and receives data will be referred to simply as a wireless base station 10, and a wireless base station 20 dedicated to transmission will be referred to simply as a wireless base station 20.

In a communication network constructed with multiple wireless base stations 10 and multiple wireless base stations 20, signal transmission is performed between the multiple wireless base stations 10 using flooding as a signal transfer protocol. Flooding is a protocol that transfers signals using only the following two simple rules:

Rule 1: When a radio base station 10 receives a signal transmitted from another radio base station 10 or a radio base station 20, it forwards the received signal to all radio 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 will not transfer the signal a second time.

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

More specifically, Figure 2 illustrates a case in which wireless base station 10(1) is the source base station, wireless base station 10(2) is the relay base station, and wireless base station 10(3) is the destination base station, and the signal transmitted from wireless base station 10(1) ultimately reaches wireless base station 10(3) through flooding.

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

Step [2]: In accordance with Rule 1, wireless base station 10(2) forwards the signal to all wireless base stations 10 within its radio wave range. As a result, the signal is transmitted from wireless base station 10(2) to wireless base station 10(1) and wireless base station 10(3). Therefore, after steps [1] and [2], the signal transmitted from wireless base station 10(1) reaches wireless base station 10(3), achieving the original purpose.

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

Step [4]: In accordance with Rule 2, wireless base station 10(2) receives the same signal in step [3] as in step [1], and therefore does not perform any further forwarding. As a result, no further forwarding is performed, and signal forwarding within the network is terminated.

In the communications network shown in Figure 1, as explained in Figure 2, signal transmission by flooding according to rules 1 and 2 allows the wireless base station 10 in monitoring center 1 to receive signals transmitted from wireless base stations 10 in sensor networks 2 to 4 to the wireless base station 10 in monitoring center 1 via the local network 5.

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 partner for each destination, operation of a long-distance signal transmission system using multiple wireless base stations 10 becomes easier.

However, the following points should be kept in mind when transmitting signals by flooding.
Point 1: Because redundant transmission is performed, collisions and interference of radio waves are likely to occur, and control of the timing of radio wave transmission is necessary.

As part of a solution to this issue, the system described in Patent Document 1 employs a method of allocating time slots to each of multiple wireless base stations 10 and achieving synchronization. However, a method like that described in Patent Document 1 aims for highly accurate synchronization to achieve general-purpose, highly efficient transmission, which exceeds the requirements for the problem we are trying to solve, as shown in Figure 1, and as the configuration is complex, the effort and cost required to implement this function is unnecessarily high.

The long-distance signal transmission system disclosed herein realizes a method that allows each wireless base station 10 to achieve synchronization with a simple configuration when transmitting long-distance signals using flooding. Specific details are described below using Figures 3 to 5.

Figure 3 is an explanatory diagram of signal transmission using flooding performed in a long-distance signal transmission system according to embodiment 1 of the present disclosure. Figure 4 is a functional block diagram of each wireless base station 10 in the long-distance signal transmission system according to embodiment 1 of the present disclosure. Figure 5 is a flowchart showing a series of processes for signal transmission using flooding performed in each wireless base station 10 according to embodiment 1 of the present disclosure.

For the sake of simplicity, Figure 3 illustrates a case in which a communications network is constructed using three wireless base stations 10(1) to 10(3) and signal transmission is performed using flooding. However, in reality, a fourth or subsequent wireless base station 10 will also be present, and a wireless mesh network will be constructed.

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

In Figure 3(A), the signal transmitted from the radio base station 10(1) assigned ID1 is shown as SG1, the signal transmitted from the radio base station 10(2) assigned ID2 is shown as SG2, and the signal transmitted from the radio base station 10(3) assigned ID3 is shown as SG3.

Here, assume that SNo1 is assigned as the slot number to radio base station 10(1) having ID1, SNo2 is assigned as the slot number to radio base station 10(2) having ID2, and SNo3 is assigned as the slot number to radio base station 10(3) having ID3.

Note that ID is a unique identifier used to identify each radio base station 10 within the long-distance signal transmission system, and will not be assigned in duplicate to other radio base stations. On the other hand, SNo is a slot number assigned to each radio base station to specify the time slot for transmission, and it may be assigned in duplicate to other radio base stations. However, Figure 3 (A) illustrates an example in which three types of slot numbers are assigned to each of three radio base stations so that they do not overlap.

Figure 3(B) shows a schematic diagram in which slot numbers SNo1 to SNo3 are each assigned one time slot of duration ΔT per period T. That is, each wireless base station 10(1) to 10(3) is assigned a slot number SNo that identifies one of the time-divided time slots, and the timing of data transmission is specified.

Specifically, when each radio base station 10(1) to 10(3) has data to transmit, it transmits information including the data to be transmitted and the slot number S No. assigned 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 S No. assigned to it.

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

As shown in Figure 4, the radio base station 10 is composed of a receiving signal processing unit 11, a synchronization adjustment unit 12, and a transmitting signal processing unit 13. The receiving signal processing unit 11 has the function of receiving information transmitted from other radio base stations 10 located in the vicinity. The receiving signal processing unit 11 receives information transmitted from other radio base stations 10 at the timing of the time slot corresponding to the slot number SNo assigned to the other radio base station 10 that is the source of the information.

When information is received from another radio base station 10 by the reception signal processing unit 11, the synchronization adjustment unit 12 has the function of correcting the time on a timer that indicates the current position in the time slot period based on the slot number SNo included in the information. As a result, the synchronization adjustment unit 12 corrects the time on its own timer to match the time on the timer of the other radio base station 10 that is the source of the information, thereby synchronizing its own timer with the timer of the other radio base station 10 and correcting the transmission timing.

When the receiving signal processing unit 11 receives information from another wireless base station 10, the transmitting signal processing unit 13 determines whether the forwarding conditions based on rules 1 and 2 are met. If the forwarding conditions are met, the transmitting signal processing unit 13 determines that there is data to be transmitted.

Furthermore, the transmission signal processing unit 13 will transfer information including the data to be transmitted and the slot number S No assigned to it when the time on its timer is within the time slot corresponding to the slot number S No assigned to it.

In this transfer process, the transmission signal processing unit 13 can transfer information using its own timer, the time of which has been adjusted by the synchronization adjustment unit 12, at the timing when information is received from another radio base station 10. Therefore, a radio base station 10 having the configuration shown in Figure 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.

The time adjustment process by the synchronization adjustment unit 12 may always be performed whenever the received signal processing unit 11 receives information from another wireless base station 10. However, it is also possible to set the conditions for starting the time adjustment process, such as performing the time adjustment process only during a specific time period, or performing the time adjustment process only when information is received from a specific slot number SNo.

Next, using Figure 5, the series of processes for signal transmission using flooding performed by each wireless base station 10 according to the first embodiment can be summarized as follows. 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.

Next, in step S502, if the synchronization adjustment unit 12 receives the information transmitted in step 501, it adjusts the time on 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.

Next, in step S503, the transmission signal processing unit 13 determines whether the forwarding conditions based on rules 1 and 2 are met. That is, if rule 1 is met and rule 2 is not met, the transmission signal processing unit 13 determines that the forwarding conditions are met; otherwise, it determines that the forwarding conditions are not met. If the transmission signal processing unit 13 determines in step S503 that the forwarding conditions are not met, it does not perform the forwarding process and ends the series of processes.

On the other hand, if the transmission signal processing unit 13 determines in step S503 that the forwarding conditions are met, it proceeds to step S504 and waits for the time slot corresponding to the slot number S No assigned to itself to arrive, based on its own timer, the time of which was adjusted in step S502. Then, when the time slot assigned to itself arrives, it executes transmission processing of a signal including the data received in step S501 (i.e., the data to be transmitted) and the slot number S No assigned to itself.

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

As described above, according to embodiment 1, the synchronization adjustment unit in each wireless base station can easily adjust the time of its own timer used when performing transfer processing using time slots. As a result, a long-distance signal transmission system can be realized that can achieve synchronization with a simple configuration at each wireless base station in the wireless network when performing long-distance signal transmission using flooding.

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

Figure 6 is a diagram showing the overall configuration of a long-distance signal transmission system according to the second embodiment of the present disclosure. The overall configuration shown in Figure 6 is the same as the overall configuration shown in Figure 1 in the first embodiment. However, the following content has been added to Figure 6 compared to the previous Figure 1.

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 ID.
The figure shows a state in which one of four 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.

In this second embodiment, we will explain the case where, among multiple wireless base stations 10, the first route is specified as the desired communication route with the highest priority. The first route is depicted as a bold white arrow in Figure 6, and is set as the desired route for quickly transmitting information from sensors 30 within the sensor network 4 to the monitoring center 1.

Specifically, the first route is defined as a route that passes 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 along this first route using time slots according to slot number SNo, it is appropriate to assign the order of slot numbers SNo according to the order of radio base stations 10 from the source of the information to the destination.

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): SNo.2
Radio base station 10 (9): SNo. 3
Wireless base station 10 (1): SNo. 4

By allocating slot numbers SNo in this manner, wireless base station 10 (6) can receive information from wireless base station 10 (4) in the time slot SNo1, and then immediately transmit information in the time slot SNo2 assigned to it.

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

Finally, wireless base station 10(1) receives information from wireless base station 10(9) at the timing of the time slot with slot number SNo3. As a result, the monitoring PC in monitoring center 1 can quickly obtain the information sent from the source wireless base station 10(4) after three time slots have passed.

In Figure 6, the communication path from the sensor network 4 to the monitoring center 1 is set as the first route with the highest 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.

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

Then, it is conceivable to assign the following slot numbers SNo to the three wireless base stations 10 on the second route.
Radio base station 10 (2): SNo.2
Wireless base station 10 (7): SNo.3
Wireless base station 10 (1): SNo. 4
It should be noted that slot number SNo4 has already been assigned to the wireless base station 10(1) when the first route was set.

By setting up this second route, the monitoring PC in the monitoring center 1 can quickly obtain information sent from the source wireless base station 10 (2) after two time slots have elapsed.

Similarly, the third route corresponds to the 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).

Then, it is conceivable to assign the following slot numbers SNo to the three wireless base stations 10 on the third route.
Wireless base station 10 (3): SNo.2
Wireless base station 10 (9): SNo.3
Wireless base station 10 (1): SNo. 4
It should be noted that slot numbers SNo3 and SNo4 have already been assigned to the radio base stations 10(9) and 10(1), respectively, when the first route was set.

By setting up this third route, the monitoring PC in the monitoring center 1 can quickly obtain information sent from the source wireless base station 10 (3) after two time slots have elapsed.

Note that if slot numbers SNo are assigned as shown in Figure 6, for example, when information is simultaneously transmitted from radio base station 10(2) and radio base station 10(6), both of which are assigned slot number SNo2, there is a risk that the transmitted signals from radio base station 10(7) may interfere with each other.

However, wireless base station 10(2) and 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 does not occur frequently. Furthermore, even if interference occurs, the interference problem can be resolved by receiving or resending information via other routes constructed in a mesh pattern.

As described above, according to the second embodiment, sequential slot numbers SNo are assigned along the desired communication route to each of the multiple wireless base stations located along the desired communication route so that signal transmission can be performed sequentially using flooding in the order of the slot numbers SNo. As a result, information can be transferred quickly via the desired route.

As mentioned above, slot numbers SNo can be assigned sequentially along the desired communication route, but each wireless base station 10 can also automatically assign slot numbers SNo based on its own uniquely assigned ID. For example, if ID1 to ID9 are assigned to each of the nine wireless base stations 10(1) to 10(9) shown in Figure 6, and four slot numbers SNo1 to SNo4 are used as time slots, it is 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.

Furthermore, in the first and second embodiments, no specific explanation was given regarding the transmission timing of the dedicated transmission radio base station 20, so a supplementary explanation will be provided below. The dedicated transmission radio base station 20 corresponds to a radio base station that does not need to transmit signals using flooding. Furthermore, the dedicated transmission radio base station 20 may receive, for example, the detection results of the sensor 30 as information to be transmitted at any timing. Therefore, when there is information to be transmitted, it is appropriate for the dedicated transmission radio base station 20 to transmit that information immediately from the perspective of rapid transmission.

For transmission-only radio base stations 20, it is therefore conceivable to set the transmission timing so that when there is data to transmit, the data can be transmitted at any timing independent of the time slot.

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 (3)

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-divided time slots 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 assigned to the device at a timing when the period calculated by the device's own timer coincides with the period of the time slot corresponding to the slot number assigned to the device,
When the information is received from another radio base station, the transmission timing is corrected by correcting the time of the timer of the radio base station at the timing when the information is received with a specific slot number based on the slot number contained in the information. 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-divided time slots 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 assigned to the device at a timing when the period calculated by the device's own timer coincides with the period of the time slot corresponding to the slot number assigned to the device,
A long-distance signal transmission system in which, only when the information is received from another radio base station during a predetermined time period, the transmission timing is corrected by correcting the time of the radio base station's own timer based on the slot number contained in the information. 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-divided time slots 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 assigned to the device at a timing when the period calculated by the device's own timer coincides with the period of the time slot corresponding to the slot number assigned to the device,
When the information is received from another radio base station, the radio base station corrects the transmission timing by correcting the time of its own timer based on the slot number included in the information;
Among the plurality of radio base stations, each radio base station arranged on a desired communication route comprises:
an allocation process is performed to allocate sequential slot numbers along the communication route so that the signal transmission can be performed sequentially using the flooding in accordance with the order of slot numbers;
When the desired communication route includes a first route to be set with the highest priority and a second route to be set with the next highest priority after the first route, and when a part of the plurality of radio base stations constituting the first route and a part of the plurality of radio base stations constituting the second route are the same radio base station,
performing the allocation process on the first route, and then performing the allocation process on the second route;
When performing the allocation process for the second route, the allocation result of the slot number already allocated to the same radio base station by performing the allocation process for the first route is maintained as it is, and the allocation process is performed on radio base stations other than the same radio base station among the multiple radio base stations constituting the second route.