Long-distance signal transmission system

Abstract

To achieve synchronization with a simple configuration in each wireless base station when performing long-distance signal transmission using flooding.SOLUTION: A system for transmitting signals using flooding via a communication network constructed by a plurality of wireless base stations. Each of the plurality of wireless base stations is assigned a slot number for identifying one of time-divided time slots. When there is data to be transmitted, transmission timing is set such that the wireless base station can transmit information including the data to be transmitted and the slot number assigned to it at timing when the period calculated by its own timer matches the period of the time slot corresponding to the slot number assigned to it. The transmission timing is corrected by correcting the time on its own timer at the timing when information corresponding to a specific slot number is received.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 transmitting signals in a communication network with multiple wireless base stations. In this method, when one wireless base station transmits data, one or more wireless base stations that receive the data broadcast the same data, thereby achieving simultaneous transmission of wireless signals.

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

[0004] Another method is to prevent 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 synchronize multiple wireless base stations. As a method for achieving synchronization, there is a conventional technique that uses synchronization packets (see, for example, 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, 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.

[0008] Therefore, the configuration required to achieve synchronization is complex, and the effort and expense required to implement the necessary functions is high. 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 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] 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 the wireless base station at a timing when the period calculated by the wireless base station's own timer matches the period of the time slot corresponding to the slot number assigned to the wireless base station, and when information is received from another wireless base station, the transmission timing is corrected by correcting the time of the wireless base station's own timer based on the slot number included in the information, and the transmission timing is corrected by correcting the time of the wireless base station among the plurality of wireless base stations that is arranged on a desired communication route. Each radio base station is subjected to an allocation process 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 is 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 for the first route is performed first, and then the allocation process for the second route is performed. When the allocation process for 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 for 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. [Effects 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 explanation 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. [Figure 2] 10 is an explanatory diagram illustrating a case where signal transmission is performed using flooding in accordance with rules 1 and 2 in the long-distance signal transmission system according to the first embodiment of the present disclosure. FIG. [Figure 3] FIG. 2 is an explanatory diagram of signal transmission using flooding performed 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 radio base station in the long-distance signal transmission system according to the first embodiment of the present disclosure. FIG. [Figure 5] 4 is a flowchart showing a series of processes of signal transmission using flooding performed in each radio base station according to the first embodiment of the present disclosure. [Figure 6] FIG. 10 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 INVENTION

[0013] The present disclosure relates to a long-distance signal transmission system, and is characterized in that each wireless base station has a function for correcting its own timer when it receives information from another wireless base station. As a result, when long-distance signal transmission is performed using flooding, synchronization can be achieved with a simple configuration in each wireless base station.

[0014] 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 be used 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.

[0015] The expansion of a 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 for fire detection systems or bridge collapse monitoring systems 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 with multiple wireless base stations.

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

[0017] Therefore, in the following explanation, a specific example of detecting a fallen bridge deep in the mountains, etc., using a long-distance signal transmission system that transmits signals using flooding will be described in detail. The long-distance signal transmission system of the present disclosure can be applied to various applications that use 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 from 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 can monitor information within the communication network in a centralized manner by monitoring the monitoring PC 40.

[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 multiple 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, 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, 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 range of radio waves. Rule 2: If the wireless base station 10 receives the same signal again at a different timing, it does not transfer the signal a second time.

[0025] 2 is an explanatory diagram of a case where signal transmission is performed using flooding in accordance with rules 1 and 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 radio base stations 10(1) to 10(3).

[0026] More specifically, FIG. 2 illustrates a case where 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 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 range in accordance with Rule 1. As a result, the signal is transmitted from the wireless base station 10(1) to the wireless base station 10(2).

[0028] Step [2]: The radio base station 10(2) forwards the signal to all radio base stations 10 within its radio wave range in accordance with Rule 1. As a result, the signal is transmitted from the radio base station 10(2) to the radio base station 10(1) and the radio base station 10(3). Therefore, after steps [1] and [2], the signal transmitted from the radio base station 10(1) reaches the radio 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. On the other hand, 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, which states 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]: ​​In accordance with Rule 2, the wireless base station 10(2) receives the same signal as in step [1] in step [3] and therefore does not forward the signal any further. As a result, no further forwarding is performed, and signal forwarding within the network is terminated.

[0031] In the communication network in Figure 1, as explained in Figure 2, by transmitting signals by flooding according to rules 1 and 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 endlessly. 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 a plurality of wireless base stations 10 becomes easier.

[0033] However, the following points should be kept in mind when transmitting signals by flooding. Point to note 1: Redundant transmissions make it easy for radio waves to collide and interfere, making it necessary to control the timing of radio wave transmissions.

[0034] As a measure to address this issue, the system disclosed in Patent Document 1 employs a method of allocating time slots to and synchronizing with each of multiple wireless base stations 10. However, the method disclosed 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 Fig. 1, and as the configuration is complex, 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 that allows synchronization with a simple configuration in each radio base station 10 when performing long-distance signal transmission using flooding. Specific details 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 a long-distance signal transmission system according to embodiment 1 of the present disclosure. Fig. 4 is a functional block diagram of each radio base station 10 in the long-distance signal transmission system according to embodiment 1 of the present disclosure. Fig. 5 is a flowchart showing a series of processes of signal transmission using flooding performed in each radio base station 10 according to embodiment 1 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. However, in reality, 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) assigned ID1 is indicated as SG1, a signal transmitted from the wireless base station 10(2) assigned ID2 is indicated as SG2, and a signal transmitted from the wireless base station 10(3) assigned ID3 is indicated as SG3.

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

[0041] The ID is a unique identifier for identifying each radio base station 10 in the long-distance signal transmission system, and is never assigned to a radio base station in the same way as another radio base station. On the other hand, the SNo is a slot number assigned to each radio base station to specify a time slot for transmission, and may be assigned to a radio base station in the same way as another radio base station. However, Fig. 3(A) illustrates an example in which three types of slot numbers are assigned to each of three radio base stations in such a way that they do not overlap.

[0042] 3(B) schematically shows a state in which a time slot with a 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 radio 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 for 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 a 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 located 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 the slot number SNo assigned to the other radio base station 10 that is the sender of the information.

[0046] The synchronization adjustment unit 12 has a function of correcting the time of a timer indicating the current position in the time slot period based on the slot number SNo included in the information when the received signal processing unit 11 receives information from another radio 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 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.

[0047] When the reception signal processing unit 11 receives information from another wireless base station 10, the transmission signal processing unit 13 determines whether the transfer conditions based on rules 1 and 2 are met. If the transfer conditions are met, the transmission signal processing unit 13 determines 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 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, 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 be synchronized with other surrounding radio base stations 10.

[0050] The time correction process by the synchronization adjustment unit 12 may always be performed when the receiving signal processing unit 11 receives information from another radio base station 10, but it is also possible to set the conditions for starting 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 based on a specific slot number SNo is received.

[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 received signal processing unit 11 in the wireless base station 10 performs a receiving process to receive information transmitted from other wireless base stations 10 in the vicinity.

[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 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, and in other cases, determines that the forwarding conditions are not met. If the transmission signal processing unit 13 determines that the forwarding conditions are not met 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 met, it proceeds to step S504 and waits for the time slot corresponding to the slot number SNo allocated to itself to come based on its own timer, the time of which was adjusted in step S502. Then, when the time slot allocated to itself comes, 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 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, the synchronization adjustment unit in each radio base station can easily adjust the time of its own timer used when performing transfer processing using time slots. As a result, it is possible to realize a long-distance signal transmission system that can achieve synchronization with a simple configuration among radio base stations in a wireless network when performing long-distance signal transmission using flooding.

[0057] 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.

[0058] 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, in Figure 6, the following content has been added to the previous Figure 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 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.

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

[0061] Specifically, the first route is defined as a route passing through the 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 the slot number SNo on this first route, it is appropriate to assign the order of the slot numbers SNo according to the order of the radio base stations 10 from the source of the 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 slot numbers SNo in this manner, the wireless base station 10(6) can receive information from the wireless base station 10(4) at the timing of the time slot SNo1, and then immediately transmit information at the timing of the time slot SNo2 allocated to itself.

[0064] 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 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 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.

[0067] Here, the second route corresponds to the 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 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.

[0069] By setting up 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 two time slots have elapsed.

[0070] 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 the 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 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.

[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 two time slots have elapsed.

[0073] In addition, when slot numbers SNo are assigned as shown in FIG. 6, for example, when information is simultaneously transmitted from both the radio base station 10(2) and the radio base station 10(6), both of which are assigned slot number SNo2, to the radio base station 10(7), there is a risk that the transmitted 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 resolved by receiving or retransmitting information via another route constructed in a mesh.

[0075] As described above, according to the second embodiment, sequential slot numbers SNo are assigned along a desired communication route to each of a plurality of radio base stations arranged 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.

[0076] As described above, the slot numbers SNo can be sequentially allocated along a desired communication route, but it is also possible for each radio base station 10 to automatically allocate slot numbers SNo from an ID uniquely allocated to itself. For example, if ID1 to ID9 are allocated to each of the nine radio 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 allocate slot numbers SNo to each radio base station 10 using the remainder when the ID number is divided by 4.

[0077] Furthermore, in the first and second embodiments, no particular explanation has been given about the transmission timing of the dedicated transmission radio base station 20, so a supplementary explanation will be given 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 result 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 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 sensors, 40 monitoring PCs.

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-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 corresponding to a specific slot number is received based on the slot number included in the information. Long distance signal transmission system.

2. 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, Only when the information is received from another wireless base station during a predetermined time period, the transmission timing is corrected by correcting the time of the timer of the wireless base station based on the slot number included in the information. Long distance signal transmission system.

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 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 for radio base stations other than the same radio base station among the plurality of radio base stations constituting the second route. Long distance signal transmission system.

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