JP7052545B2 - Wireless communication system - Google Patents

Description

The present invention relates to a wireless communication system.

It has a master unit and a wireless communication system consisting of a multi-stage slave unit that is hierarchically wirelessly connected to the master unit, and a center device, and has monitoring information acquired by the slave unit (meter reading of a gas meter or water meter). There is a remote monitoring system that notifies the center device via the master unit (value, gas leak alarm, low battery level alarm, etc.) (Patent Document 1).

In this remote monitoring system, the center device and the master unit communicate with each other via a wireless or wired commercial communication line, and "master unit, first-stage slave unit, second-stage slave unit, ..., Nth stage". Wireless communication in a wireless communication system composed of a "slave unit" (N is an integer of 3 or more) is performed using a specific low power radio or the like.

Sensors such as gas meters, water meters, and gas leak detectors are connected to each handset, and the monitoring information generated by these sensors is acquired, and the message containing the monitoring information is sent to the first-stage handset. The second-stage slave unit, ..., The N-stage slave unit reports directly to the master unit via the upper (upper) slave unit, that is, the upper slave unit is notified to the master unit as a relay slave unit. Perform relay communication.

When constructing such a wireless communication system, it is generally practiced to construct a network area of a wireless communication terminal over a wide area by sequentially installing slave units in the vicinity after installing the master unit.

When installing a handset, it is possible to connect to the subordinates of the surrounding terminals by broadcasting a terminal search message (route search message) to the surrounding terminals and receiving a response from the surrounding terminals (master unit, handset). It is a mechanism to know that. At this time, in order to secure a good communication state, a method of preferentially selecting from terminals that respond with a reception electric field strength of a certain value or more set in advance is generally known.

That is, when installing the handset, the handset broadcasts a terminal search message with the terminal ID (terminal identification information) of its own terminal, and responds from surrounding terminals (master unit, handset) within a predetermined time. Check if there is a certain terminal response message (route response message). When there is a response, the terminal with the received electric field strength equal to or higher than a certain threshold is selected as the upper terminal candidate from the terminal ID, the received electric field strength (received electric field strength of the terminal search message) and the number of stages included in the terminal response message. The terminal ID and the number of stages are stored in the storage unit of the own terminal.

At this time, the average value or the lower value of both is adopted based on both the received electric field strength of the terminal search message and the received electric field strength of the handset of the terminal response message, not the received electric field strength of the terminal search message. It is also known to do. That is, the received electric field strength of the terminal search message and / or the received electric field strength of the handset of the terminal response message is adopted. Hereinafter, in the present specification, the term of the concept including both the received electric field strength of the terminal search message and the received electric field strength of the handset of the terminal response message is referred to as a communication electric field strength.

Next, from the communication electric field strength and the number of stages acquired at this time, route numbers such as the first communication route and the second communication route are assigned in order of, for example, the smaller number of stages and the stronger communication electric field strength. Then, the registration request telegram of these communication routes is transmitted to the center device via the upper terminal candidate on the first communication route. The center device receives the message of the registration request, registers the communication route, and returns the registration completion message. When the slave unit receives the registration completion message, the higher-level terminal candidate becomes the higher-level terminal, and the registration of the communication route is completed.

In addition, if the communication electric field strength decreases due to changes in the surrounding communication environment after installation and communication becomes unstable, there is also a mechanism to reconstruct the route by searching for new surrounding terminals and re-registering higher-level terminals. It is used.

Japanese Unexamined Patent Publication No. 2010-87761

As a wireless characteristic, when the distance from the surrounding terminal becomes long, the communication electric field strength becomes low, and it becomes easy to be affected by the surrounding communication environment. On the other hand, if a high communication field strength threshold is set in search of communication stability, the communication distance with surrounding terminals becomes short, and there is a problem that it is difficult to expand the communication area.

In the midst of these issues, when the slave units are installed facing outwards, centering on the master unit, and the wireless communication area is expanded, the installation conditions of each slave unit are uniformly set to a certain level or higher. When was set as the threshold value, it was necessary to select whether to take the communication stability by the threshold value of the high communication electric field strength or to set the threshold value of the low communication electric field strength to expand the area and sacrifice the communication stability. ..

In addition, since the number of stages of the slave unit may change due to route reconstruction, in a system with a limited number of stages, the number of stages of the relay slave unit has decreased, and the slave units under it have exceeded the stage number limit. In some cases, communication relay may not be possible.

The present invention has been made to solve such a problem, and an object thereof is in a wireless communication system including a master unit and a multi-stage slave unit that is hierarchically wirelessly connected to the master unit. It is possible to expand the communication area by connecting the slave units in multiple stages while maintaining the stability of communication around the master unit.

The present invention is a wireless communication system including a master unit, each of which is a terminal, and a plurality of stages of slave units that are hierarchically wirelessly connected to the master unit, and each terminal receives a terminal search message. Each handset has a terminal response message transmission means for transmitting a terminal response message including the number of stages of its own terminal and the received electric field strength of the terminal search message, and each slave unit broadcasts a terminal search message to surrounding terminals. The received electric field strength included in the search message transmitting means, the terminal response message receiving means for receiving the terminal response message from surrounding terminals to the terminal search message, and the terminal response message received by the terminal response message receiving means. And / or a higher-level terminal candidate registration means for registering a terminal whose communication electric field strength is equal to or higher than a predetermined threshold as a higher-level terminal candidate based on the communication electric field strength consisting of the received electric field strength of the terminal response message at its own terminal. It is a wireless communication system having the threshold value higher as the number of stages is smaller.

According to the present invention, in a wireless communication system consisting of a master unit and a plurality of stages of slave units that are hierarchically wirelessly connected to the master unit, the slave units are multistage while maintaining stable communication around the master unit. It is possible to expand the communication area by connecting.

It is a figure which shows the structure of the remote monitoring system which concerns on embodiment of this invention. It is a figure for demonstrating the setting of the communication electric field strength at the time of installing a handset in the wireless communication system which concerns on embodiment of this invention. It is a figure which shows an example of the 1st electric field strength threshold table and the 2nd electric field strength threshold table in the wireless communication system which concerns on embodiment of this invention. It is a figure which shows an example of the state in which a plurality of surrounding terminals are responding to a newly installed terminal. It is a block diagram which shows the schematic structure of the handset in the wireless communication system which concerns on embodiment of this invention. It is a flowchart which shows the 1st installation determination process in a slave unit. It is a flowchart which shows the 2nd installation determination process in a slave unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<Outline configuration of remote monitoring system>
FIG. 1 is a diagram showing a schematic configuration of a remote monitoring system according to an embodiment of the present invention.

This remote monitoring system is used, for example, for automatic meter reading of gas meters and water meters, and is a multi-stage slave unit that is hierarchically wirelessly connected to the center device 1 and the master unit 2 and the master unit. It has a wireless communication system according to an embodiment of the present invention, which comprises first-stage slave units A to G, second-stage slave units H to N, and third-stage slave units O to Q).

Communication between the master unit 2 and the center device 1 is performed via a commercial communication line such as a mobile phone line. Further, communication in the wireless communication system composed of the master unit 2, the first-stage slave units A to G, the second-stage slave units H to N, and the third-stage slave units O to Q is performed using a specific low-power radio or the like. ..

Sensors such as gas meters, water meters, and gas leak detectors are connected to each slave unit, and the monitoring information generated by these sensors is acquired and relayed via the higher slave unit, that is, the higher slave unit. Notify the master unit 2 as a slave unit. In the following description, when each slave unit is not distinguished, it is referred to as slave unit 3. If the master unit and the slave unit are not distinguished, the terminal is used.

In FIG. 1, the number of stages of the slave unit in the wireless communication system is set to 3 stages, but there are also configurations with 4 or more stages. Further, in FIG. 1, the connection between the slave units is one-to-one, that is, each slave unit has one upper terminal, but there is also a configuration in which a plurality of upper terminals are provided.

<Setting of communication electric field strength threshold value according to the number of stages>
FIG. 2 is a diagram for explaining the setting of the communication electric field strength at the time of installing the slave unit in the wireless communication system according to the embodiment of the present invention. In this figure, the thickness of the arrow represents the strength of the communication electric field strength. Further, R1, R2, and R3 are concentric circles whose radii gradually increase with respect to the master unit 2.

When the slave unit 3 is installed, the slave unit 3 broadcasts a terminal search message to surrounding terminals, receives a terminal response message from surrounding terminals, and registers it as a higher-level terminal candidate. At this time, in general, the installation conditions of each slave unit 3 are uniformly set to a threshold value of the communication electric field strength of a certain level or higher. Therefore, the communication stability is the same at the center and the outside of the circle, but if a certain level of communication stability is required, the installation area cannot be expanded. On the other hand, if the installation area is requested to be expanded and the threshold value of the communication electric field strength is lowered, the communication stability is lowered. In particular, when the communication environment around the master unit 2 deteriorates, it will greatly affect the slave units under its control.

Therefore, in the present embodiment, the threshold value of the communication electric field strength is lowered according to the number of stages of the slave unit 3 centering on the master unit 2. As a result, since the slave unit 3 close to the master unit 2 is allowed to be installed with a high communication electric field strength threshold value, the communication distance is shortened, but it is less affected by the surrounding communication environment. However, by setting the communication electric field strength threshold value stepwise from the master unit 2 toward the outside, it becomes more susceptible to the influence of the surrounding communication environment stepwise. However, since the number of higher-level handsets increases toward the outside, it is possible to secure a large number of communication routes and secure communication stability by switching communication routes. This stepwise setting of the electric field strength threshold value is realized by providing the handset 3 with the electric field strength threshold value table described below.

<Electric field strength threshold table>
FIG. 3 is a diagram showing an example of a first electric field strength threshold table and a second electric field strength threshold table in the wireless communication system according to the embodiment of the present invention. Here, FIG. 3A is a first electric field strength threshold table, and FIG. 3B is a second electric field strength threshold table.

The first electric field threshold table 321 describes the correspondence between the number of stages of the upper terminal (the 0th stage of the master unit) and the communication electric field strength threshold. Specifically, the master unit = 9, the first stage = 7, and the second stage = 4. That is, when the surrounding terminal (hereinafter referred to as a response terminal) that responds to the terminal search message is the master unit, if the communication electric field strength is 9 or more in 10 steps, it is registered as a higher terminal candidate. Further, when the response terminal is the first-stage slave unit and the second-stage slave unit, if the communication electric field strength is 7 or more and 4 or more, it is registered as a higher-level terminal candidate.

However, due to the communication environment around the installed terminal, it is assumed that the communication electric field strength preset at the time of installation cannot be obtained. In such a case, if it is possible to communicate with multiple terminals, it is possible to install it without sacrificing communication stability by securing multiple routes by allowing installation even if the communication electric field strength is lower than the preset communication field strength. It is possible to provide stable communication even if a terminal is connected under it. The second electric field threshold table 322 is used in such a case.

As shown in the figure, the second electric field threshold table 322 describes the communication electric field strength threshold for each stage of the upper terminal when the number of response terminals satisfying the threshold condition is 1 to 5.

Specifically, in the case of one unit conformity, the master unit = 9, the first stage = 7, the second stage = 4, which is the same as the first electric field strength threshold table 321. On the other hand, in the case of conforming to two units, the master unit = 8, the first stage = 6, the second stage = 4, and in the case of conforming to three units, the master unit = 7, the first stage = 5, the second stage = If 3 or 4 units are compatible, the master unit = 6, 1st stage = 4, 2nd stage = 3, 5 units, if the master unit = 5, 1st stage = 4, 2nd stage = 3 be. That is, as the number of compatible response terminals increases, an alternative route can be secured, so that the communication electric field strength that serves as a reference for registering as a higher-level terminal candidate can be set lower.

<Registration of higher-level terminal candidates when there are multiple response terminals>
FIG. 4 is a diagram showing an example of a state in which a plurality of surrounding terminals are responding to a newly installed terminal.

In this case, since there is no master unit in the response terminal and there are five first-stage slave units, refer to the first-stage column of the second electric field strength threshold table 322 and refer to the following (i) to (iv). ) Is executed.
(i) Since there are no response terminals with a communication electric field strength of 7 or more, the table conditions are not met.
(ii) Since there is only one response terminal with a communication electric field strength of 6 or more, it does not meet the table conditions.
(iii) Since there are three response terminals having a communication electric field strength of 5 or more, the table conditions are met.
(iv) In order to meet the condition of "1st stage / 3 units compatible / 5 or more", 3 response terminals (slave unit B, slave unit D, slave unit E) are registered as higher-level terminal candidates.

The communication electric field strength is not as high as the condition of "one unit compatible", but since communication stability can be expected by finding three higher-level terminals, installation can be permitted.

If any of the conditions of the second electric field strength threshold table 322 is not met, and if the installation is permitted even if it is lower than the electric field strength threshold, there is a concern that the communication environment may change after the installation and affect the subordinate terminal. , Only allow installation, do not allow subordinate connections (such as not responding to terminal search messages). However, after that, if the communication state is improved and the table conditions are met by the terminal search again, it can be configured to allow the subordinate connection.

<Outline configuration of handset>
FIG. 5 is a block diagram showing a schematic configuration of a slave unit in the wireless communication system according to the embodiment of the present invention.

As shown in the figure, the slave unit 3 has a control unit 31, a storage unit 32 connected to the control unit 31, a wireless transmission / reception unit 33, an external I / F (interface) unit 34, a display unit 35, and an operation input. The part 36 is provided. An antenna 37 is connected to the wireless transmission / reception unit 33.

The control unit 31 is composed of, for example, a microprocessor and its peripheral circuits, and controls the entire slave unit 3 and performs arithmetic processing and the like. Further, the control unit 31 is a means realized by processing the program and data stored in the storage unit 32, such as a communication electric field strength acquisition means 311, a threshold value condition determination means 312, and a higher-level terminal candidate registration means 313. It is equipped with. Details of these means will be described later.

Further, the control unit 31 processes the program and data stored in the storage unit 32 and controls the wireless transmission / reception unit 33 to control the terminal search message transmitting means, the terminal search message receiving means, and the terminal response according to the present invention. Realizes message transmission means, terminal response message reception, etc.

The storage unit 32 includes a non-volatile memory such as a ROM (including a rewritable one) and a volatile memory such as a RAM. The ROM stores a control program necessary for operating the slave unit 3, various setting data, and the like. Further, the RAM stores each program being executed by the control unit 31 and information (terminal ID, wireless channel, communication electric field strength, number of stages of own terminal) necessary for executing the programs. Here, as the setting data stored in the storage unit 32, the first electric field strength threshold table 321 and the second electric field strength threshold table 322 are shown.

The wireless transmission / reception unit 33 performs wireless communication with another slave unit 3 or a master unit 2 by a specific low power radio or the like. An external device such as a gas meter or a water meter is connected to the external I / F unit 34. The display unit 35 is composed of LEDs or the like, and is a user I / F that displays an operating state of the slave unit 3 or the like. The operation input unit 36 includes buttons, switches, and the like, and is a user I / F for inputting predetermined settings for the slave unit 3.

The communication electric field strength acquisition means 311 receives the received electric field strength and / or the terminal response message included in the terminal response message that the surrounding terminals respond to the terminal search message broadcast from the slave unit 3 to the surrounding terminals. The communication electric field strength is acquired from the received electric field strength in the wireless transmission / reception unit 33. The communication electric field strength is the received electric field strength of the terminal search message, the received electric field strength of the terminal response message, the lower of the two, or the average value of both.

The threshold condition determination means 312 includes the number of stages included in the terminal response message, the communication electric field strength acquired by the communication electric field strength acquisition means 311, and the first electric field strength threshold table 321 or the second electric field strength threshold table 322. Refers to to determine whether or not the threshold condition for registering the terminal that sent the terminal response message as a higher-level terminal candidate is satisfied.

The upper terminal candidate registration means 313 registers (stores) the terminal ID and the number of stages of the response terminal determined to meet the threshold condition by the threshold condition determination means 312 in the storage unit 32.

<First installation judgment process>
FIG. 6 is a flowchart showing the first installation determination process in the slave unit. This process is performed with reference to the first electric field strength threshold table 321.

When the slave unit 3 is newly installed, the terminal search message is read from the storage unit 32 in response to pressing a predetermined button of the operation input unit 36, and is broadcast to surrounding terminals by the wireless transmission / reception unit 33 and the antenna 37. (Step S1).

After broadcasting the terminal search message, the slave unit 3 determines whether or not there is a response terminal, that is, whether or not the wireless transmission / reception unit 33 receives the search response message within a predetermined time (step). S2). If there is no response terminal (step S2: No), the first installation determination process is terminated as it is.

If there is a response terminal (step S2: Yes), the communication electric field strength of the response terminal is acquired (step S3, FIG. 5: communication electric field strength acquisition means). Then, the communication electric field strength is compared with the communication electric field strength threshold value of the first electric field strength threshold value table 321 in order from the response terminal having the lowest number of stages, and it is determined whether or not the condition is satisfied (steps S4, S5, FIG. 5 :). Threshold condition determination means).

As a result of the determination, if the condition is satisfied (step S5: Yes), the response terminal is registered (stored) in the storage unit 32 as a higher-level terminal candidate (step S6), and the first installation determination process is terminated. If the conditions are not met (step S5: No), the first installation determination process is terminated as it is.

After that, the slave unit 3 transmits the registration request message of the communication route to the center device 1 and receives the registration completion message from the center device 1, so that the upper terminal candidate becomes the upper terminal and the communication route. Registration is completed. The same applies to the second installation determination process described later.

<Second installation judgment process>
FIG. 7 is a flowchart showing a second installation determination process in the slave unit. In this figure, steps S11 to S13 are the same as steps S1 to S3 in the first determination process (FIG. 6).

Next, a plurality of response terminals are divided according to the number of stages, and the communication electric field strength of the response terminals is compared with the matching number of the second electric field strength threshold table 322 in order from the response terminal having the lowest number of stages, and it is determined whether or not the conditions are met. (Steps S14, S15, FIG. 5: Threshold condition determination means).

As a result of the determination, if the condition is satisfied (step S15: Yes), a plurality of response terminals are registered (stored) in the storage unit 32 as higher-level terminal candidates (step S16), and the second installation determination process is terminated.

If the conditions are not met (step S15: No), a plurality of response terminals are registered (stored) in the storage unit 32 as higher-level terminal candidates, but the connection of subordinate terminals is set not to be permitted (step S17), and the first step is made. The installation determination process of 2 is completed. Here, instead of setting step S17 independently by the slave unit 3, it may be configured to be set according to the reception of the registration completion message from the center device 1.

As described in detail above, according to the wireless communication system according to the embodiment of the present invention, the threshold value of the communication electric field strength is gradually lowered according to the number of stages of the response terminal, so that it is installed around the master unit. Since the slave unit is installed with a high communication electric field strength, communication is stable, and the slave unit installed under the slave unit is connected to the subordinates of a plurality of slave units connected to the master unit by strong communication.
That is, even if the threshold value of the communication electric field strength is gradually lowered to allow the installation of the slave unit, many stable communication routes can be secured, so that stable communication can be secured in the entire area.

<Modified example of the embodiment of the invention>
When communication becomes unstable due to changes in the communication environment after installation and a terminal search is performed again, the communication electric field strength obtained from a terminal with a certain number of stages (for example, the first stage) at the time of installation can be obtained from the terminal with that number of stages. However, there is a risk that the number of stages of the own terminal will decrease.

Therefore, the communication electric field strength threshold in the electric field strength threshold table is gradually lowered according to the increase in the number of terminal searches, and the number of subordinate terminals is reduced by making it easier to grasp the upper terminal having the same number of stages as before. It makes it possible to lead to stable communication.

In the above embodiment, the newly installed handset 3 "registers a higher-level terminal candidate-> sends a communication route registration request message to the center device 1-> receives a communication route registration completion message from the center device 1. → The procedure of "Registration of higher-level terminal (communication route) is completed" is being executed, but the handset 3 does not exchange information with the center device 1 for communication route registration, and the higher-level terminal is selected only by the handset 3. It may be configured to register. In the case of this configuration, “upper terminal candidate = upper terminal” registered in step S6 of FIG. 6 and steps S16 and S17 of FIG.

2 ... Master unit, 3 ... Slave unit, 31 ... Control unit, 32 ... Storage unit, 33 ... Wireless transmission / reception unit, 34 ... External I / F unit, 35 ... Display unit, 36 ... Operation input unit, 37 ... Antenna, 311 ... Communication electric field strength acquisition means, 312 ... Threshold condition determination means, 313 ... Upper terminal candidate registration means, 321 ... First electric field strength threshold table, 322 ... Second electric field strength threshold table.

Claims (2)

A wireless communication system consisting of a master unit, each of which is a terminal, and a multi-stage slave unit that is hierarchically wirelessly connected to the master unit.
Each terminal has a terminal response message transmission means for transmitting a terminal response message including the number of stages of its own terminal and the received electric field strength of the terminal search message when the terminal search message is received.
Each handset has a terminal search message transmitting means that broadcasts a terminal search message to surrounding terminals, a terminal response message receiving means that receives a terminal response message from surrounding terminals to the terminal search message, and the terminal. The communication electric field strength is predetermined based on the received electric field strength included in the terminal response message received by the response message receiving means and / or the communication electric field strength consisting of the received electric field strength of the terminal response message at the own terminal. A wireless communication system comprising a upper terminal candidate registration means for registering a terminal having a threshold value or higher as a higher terminal candidate, and the threshold value is higher as the number of stages is smaller. In the wireless communication system according to claim 1,
A wireless communication system having means for gradually lowering the threshold value according to an increase in the number of broadcasts of a terminal search message .

Images