JP5682510B2 - Communication system and master station, slave station and relay station used for this - Google Patents

Description

The present invention relates to a communication system including a wireless LAN for wirelessly transmitting traffic information used for traffic signal control, and a master station, slave station, and relay station that can be suitably used for this communication system.
More specifically, the present invention relates to a measure for easily grasping the communication state of each communication node constituting the wireless LAN.

Traffic signal control has already been performed to systematically or planarly control the color of signal lights at a plurality of intersections. In this case, necessary traffic information needs to be transmitted almost in real time between the traffic signal controllers or between the controller and the vehicle detector or the central device of the control center.
Conventionally, communication between traffic equipment such as traffic signal controllers and vehicle detectors has been mainly wired communication using a communication line buried underground or installed on a utility pole. In some cases, the communication is performed by a wireless local area network (LAN) for the purpose of eliminating or reducing the construction cost (for example, see Patent Documents 1 and 2).

In the case of a wireless LAN used for information transmission between such traffic facilities (hereinafter also referred to as “traffic wireless LAN”), an ISM (Industry-Science-Medical) whose purpose of use has been designated by the International Telecommunications Union (ITU). ) 2.4 GHz band (2400-2500 MHz) radio waves belonging to the band are used.
For this reason, it is important to take measures such as selection of a frequency for avoiding radio wave interference and installation of a relay station for limiting transmission output mainly in traffic wireless LANs in urban areas.

JP 2006-0667462 A JP 2008-205765 A

In general, a wireless LAN installed outdoors is intended for large-capacity transmission to a distant location, so it is affected by jamming by connecting communication nodes one-to-one with a highly directional antenna. Difficult wireless communication can be realized.
However, in the case of a traffic wireless LAN, a star network of one-to-many connection in which a master station that is an access point to an external network connected to a central device and a plurality of slave stations that are connected to a vehicle detector or the like are simultaneously wirelessly communicated. Therefore, the communication range cannot be narrowed down with the above highly directional antenna.

For this reason, traffic wireless LANs are susceptible to interference from various surrounding electrical devices (such as microwave ovens and medical devices), but in order to maintain the desired communication quality, the effects of interference are currently present. It is necessary to identify the frequency receiving the signal using a spectrum analyzer or the like and change the frequency to another frequency.
However, in order to accurately investigate the influence of jamming radio waves generated between communication nodes in a traffic wireless LAN, the reception quality (for example, received electric field strength) of two communication nodes separated by several tens to several hundreds of meters is almost the same. It is necessary to measure at the same time, and such measurement work is actually very difficult.

The reason why the above measurements are performed almost simultaneously is that if the reception quality of two communication nodes is measured one by one in order, the jamming radio wave between the completion of measurement of one communication node and the completion of measurement of the other communication node. This is because the frequency of the change has changed, and the frequency at which interference is occurring cannot be accurately identified.
In addition, it is important to know the past history information of jamming radio waves that occur only during a specified time period, but it is important to determine the optimal frequency. There is also a situation peculiar to the traffic wireless LAN that even the measurement is difficult.

  In view of the conventional problems, the present invention enables a worker who performs maintenance of a traffic wireless LAN to easily grasp the reception quality of each channel being used in the traffic wireless LAN without requiring manual operation. With the goal.

  (1) The communication system of the present invention is a communication system including a wireless LAN for wirelessly transmitting traffic information used for traffic signal control, and each communication node constituting the wireless LAN has a channel in use. A measurement unit that measures the reception quality of the local station, a communication control unit that stores the measured reception quality of the local station in a communication frame addressed to another station, the measured reception quality of the local station, and received by the local station And an output unit that outputs the reception quality of other stations included in the communication frame in a human-readable manner.

  According to the communication system of the present invention, the measurement unit of each communication node measures the reception quality of the own station of the channel being used, and the communication control unit of each communication node determines the measured reception quality of the own station to the other station. Since it is stored in the addressed communication frame, each communication node can obtain the reception quality of the channel in use in all communication nodes including other stations in almost real time.

  Then, since the output unit of each communication node outputs the measured reception quality of the local station and the reception quality of other stations included in the communication frame received by the local station in a human-readable manner, maintenance of the traffic wireless LAN is performed. Based on the output content of the output unit, the worker can easily grasp the reception quality for each channel being used in the traffic wireless LAN without requiring human intervention. For this reason, the maintenance work of the traffic wireless LAN can be simplified.

(2) In the communication system of the present invention, it is preferable that the output unit can output the reception quality corresponding to the communication node in the topology of the wireless LAN in a human readable manner.
In this case, since it becomes possible to estimate which communication device is present in the field, the reception quality of the specific channel output by the output unit can further simplify the maintenance work of the traffic wireless LAN. it can.

(3) In the communication system of the present invention, for example, assuming a traffic wireless LAN in an infrastructure mode, the reception quality of each communication node in a management frame (for example, a beacon) periodically transmitted by a main station as an access point Can also be transmitted.
However, in this case, since the master station cannot collect the measurement data of the reception quality of the slave station until transmission / reception of the management frame is completed with all the communication nodes in the network, the reception quality is notified to the slave station. May be delayed.

Therefore, the communication control unit, the request frame that is the communication frame that requests the transmission of traffic information data, and the response frame that is the communication frame that stores the traffic information in response to the request frame, the measured of the local station It is preferable to store the reception quality.
In this case, since the communication control unit of each communication node stores the reception quality of the own station in the request frame and the response frame, measurement of the reception quality measured by each communication node as compared to the case where the management frame is used. Data can be collected quickly and reliably by the main station, and notification of reception quality to each communication node can be prevented from being delayed.

(4) In the communication system of the present invention, it is preferable that the output unit can simultaneously output the reception qualities of all channels being used in the communication node.
In this case, since the output unit outputs the reception quality of all channels in use at the same time, the operator can determine at a glance which channel is affected by the jamming signal, and the communication quality deteriorates. It is possible to easily identify the channels that are present.

(5) The main station of the present invention is a main station that is an access point of a wireless LAN for wirelessly transmitting traffic information used for traffic signal control, and is any one of the above (1) to (4) The measurement unit, the communication control unit, and the output unit described in 1. are provided.
Therefore, the main station of the present invention has the same effects as the communication system of the present invention described in any of the above (1) to (4).

(6) The slave station of the present invention is a slave station capable of communicating with an external network through a master station that is an access point of a wireless LAN for wirelessly transmitting traffic information used for traffic signal control. It has the said measurement part described in any one of (4), the said communication control part, and the said output part, It is characterized by the above-mentioned.
Therefore, the slave station of the present invention has the same operational effects as the communication system of the present invention described in any of the above (1) to (4).

(7) The relay station of the present invention is a wireless LAN for transmitting traffic information used for traffic signal control wirelessly between a master station as an access point and a slave station that can communicate with an external network through the master station. A relay station that relays the wireless communication, and includes the measurement unit, the communication control unit, and the output unit described in any one of (1) to (4) above.
Therefore, the relay station of the present invention has the same operational effects as the communication system of the present invention described in any of the above (1) to (4).

  As described above, according to the present invention, a worker who performs maintenance of a traffic wireless LAN can easily grasp the reception quality of each channel being used in the traffic wireless LAN without requiring manual operation. Maintenance work can be simplified.

1 is a perspective view of a communication system according to an embodiment of the present invention. It is explanatory drawing which shows an example of the connection form (topology) of the said communication system. It is a block diagram which shows the internal structure of a communication apparatus. It is a figure which shows the format of a communication frame. It is a sequence diagram which shows the content of the data transmission process which a master station, a slave station, and a relay station cooperate. It is explanatory drawing which shows an example of the display part provided in the communication apparatus. It is a road top view for showing the example of a search of a main station.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a perspective view of a communication system according to an embodiment of the present invention.
As shown in FIG. 1, the communication system of the present embodiment has a communication device 1 installed on a utility pole in the vicinity of an intersection J, and a roadside sensor 4 including an ultrasonic vehicle detector, an optical beacon, and the like. The communication apparatus 2 installed and the communication apparatus 3 installed in the relay point between those communication apparatuses 2 and 3 are provided.

The traffic information to be transmitted by the communication system of the present embodiment includes, for example, a signal control command for instructing a signal lamp color switching timing transmitted by the central device of the traffic control center to the traffic signal controller, and the traffic signal control thereof. There is signal control execution information representing the operation history of the controller, which is reported afterwards by the machine to the central unit.
The pulse signal sent from the ultrasonic vehicle sensor to the central device, and VICS (“VICS” is a registered trademark) information provided to the vehicle by the central device via the optical beacon are also used in the communication system of the present embodiment. Included in the traffic information to be transmitted.

Among the communication devices 1 to 3 shown in FIG. 1, the communication device 1 is a wireless communication device of a traffic signal controller (not shown) provided at the intersection J, and the communication device 2 is a wireless communication of the roadside sensor 4. The communication device 3 is a wireless communication device that relays wireless communication between the communication devices 1 and 2.
The wireless communication between these communication devices 1 to 3 uses the 2.4 GHz band belonging to the ISM band. That is, each of the communication devices 1 to 3 is any one in which usable frequencies (2.4000 to 2.4835 HGz) are divided into 14 channels in accordance with a standard such as IEEE802.11b / g as in the case of a normal wireless LAN device. Wireless communication is performed on this channel.

The wireless LAN (traffic wireless LAN) of the present embodiment that wirelessly transmits the traffic information is operated in an “infrastructure mode” that communicates with an external network via an access point, and the communication device 1 is connected to the access point. It has become.
That is, among a plurality of communication nodes constituting a traffic wireless LAN, the communication device 1 is a “main station” serving as an access point with an external network leading to the central device. It is a “slave station” that can communicate with.

The communication device 3 is a “relay station” that relays wireless communication between the master station and the slave station. For this reason, the communication apparatus 3 as a relay station has a repeater function in a WDS (Wireless Distribution System) mode.
In the following, when different items are described depending on the node type of the communication system, the description will be made using “master station 1”, “slave station 2”, and “relay station 3”, and is common to all node types. When the matter is described, the description is made using “communication devices 1 to 3”.

[Connection form of communication system]
FIG. 2 is a diagram illustrating an example of a connection form (topology) of the communication system.
As shown in FIG. 2, the communication system according to the present embodiment includes a total of seven communication nodes including the main station 1. The communication system has a star-type connection form in which four transmission paths are gathered at the main station 1, and one of the four transmission paths (transmission path of node 1 → node 3 → node 4 → node 5). Suppose that two relay stations 3 are included.

That is, using the node numbers 1 to 7 numbered in FIG. 2, the slave station 2 of the node 2 is arranged at a distance that allows direct wireless communication with the master station 1 of the node 1, and the slave stations of the node 6 and the node 7. 2 is also arranged at a distance that allows direct wireless communication with the main station 1.
On the other hand, since the slave station 2 of the node 5 is far from the master station 1, the master station of the node 1 is passed through the two relay stations 3 of the node 3 and the node 4 in order to suppress the output of radio transmission as much as possible. Wireless communication with the station 1 is made.

  However, the connection form of the communication system of the present invention is not limited to the case illustrated in FIG. 2. For example, all the transmission paths gathered at the main station 1 do not include the relay station 3, and conversely The connection form may include a plurality of transmission paths including the relay station 3.

[Internal configuration of communication device]
FIG. 3 is a block diagram illustrating an internal configuration of the communication devices 1 to 3.
As shown in FIG. 3, all of the communication devices 1 to 3 of the present embodiment have basically the same internal configuration.

The communication devices 1 to 3 include a control unit 10, a storage unit 11, a wireless communication unit 12, and a display unit 13. Although the master station 1 further includes the input unit 14, the slave station 2 and the relay station 3 may not include the input unit 14.
The control unit 10 includes a CPU (Central Processing Unit) capable of information processing. The control unit 10 reads out the computer program stored in the storage unit 11 and executes various processes such as communication control and measurement data sharing process described later.

The storage unit 11 includes an EEPROM (Electrically Erasable and Programmable Read Only Memory), a flash memory, and the like, and temporarily stores control information, traffic information, and the like used by the control unit 10 in addition to a computer program executed by the control unit 10. .
The wireless communication unit 12 includes an antenna for transmitting and receiving radio waves of time division multiplex communication, an RF transmission / reception circuit, a modulation / demodulation circuit, a modulation / spreading / encoding processing circuit, and a channel selection circuit for a use frequency (all of them). Not shown).

The wireless communication unit 12 selects any channel from Ch1 to Ch14 in the wireless LAN frequency band, and performs wireless communication with other stations using the selected channel.
The input unit 14 of the main station 1 is an interface that receives information input by a worker, and is configured by a switch that directly receives an artificial operation, or an input interface that receives an input signal from a notebook PC or the like. For example, “channel information” used in the communication apparatuses 1 to 3 and “positioning information” of the communication node in the traffic wireless LAN can be input to the input unit 14.

When “channel information” and “positioning information” are input to the input unit 14, the control unit 10 of the master station 1 generates a management frame including the information, and uses the generated frame as a slave station 2 belonging to the traffic wireless LAN. And transmitted to the relay station 3.
The control unit 10 of the slave station 2 or the relay station 3 that has received the management frame adjusts the frequency of the channel selection circuit of the wireless communication unit 12 to the channel specified by the master station 1, and each of the control frames described in the management frame The communication node positioning information is stored in the storage unit 11 of the own device.

As described above, in the communication system of the present embodiment, the information input to the input unit 14 of the master station 1 sets and switches the frequencies used by the slave station 2 and the relay station 3, and the communication nodes in the topology of the traffic wireless LAN. Notification of positioning information can be performed.
The “positioning information” includes a “route number” and a “station type number”. Among these, the route number is an identification number assigned to each transmission route connected to the main station 1, and the station type number is an identification number of a node type constituting the traffic wireless LAN.

When a plurality of relay stations 3 are present before reaching the terminal slave station 2 in a certain transmission path (in the case of the node 3 and the node 4 in FIG. 2), it is incremented by one from the order close to the master station 1. The value is set to the route number of each relay station 3.
Accordingly, in the topology shown in FIG. 2, the route numbers of the nodes 1 and 2 are “0”, the route number of the node 3 is “2”, the route number of the node 6 is “5”, and the sequence number of the node 7 is “7”. If the station type number of the master station 1 is defined as “0”, the station type number of the slave station 2 is defined as “1”, and the station type number of the relay station is defined as “2”, each of the nodes 1 to 7 is positioned. The information is as follows:

Node 1 positioning information = (0,0)
Node 2 positioning information = (0, 2)
Positioning information of node 3 = (2, 1)
Positioning information of node 4 = (3, 1)
Positioning information of node 5 = (3, 2)
Positioning information of node 6 = (5, 2)
Node 7 positioning information = (7, 2)

[Data transmission processing between master and slave stations]
The control unit 10 of the main station 1 transmits a control frame (hereinafter referred to as “request frame”) requesting uplink transmission of a communication frame including traffic information (hereinafter referred to as “data frame”) for each predetermined cycle. , And transmitted to each slave station 2 included in the network.
Further, the control unit 10 of the slave station 2 that has received the request frame generates a data frame (hereinafter referred to as “response frame”) in which predetermined traffic information acquired by the local station is stored in response to the request. Uplink transmission to the main station 1 is performed.

Hereinafter, a series of communication control that repeats transmission and reception of request frames and response frames performed between the master station 1 and the plurality of slave stations 2 is referred to as “data transmission processing”.
When receiving the request frame from the upper communication node, the control unit 10 of the relay station 3 relays the request frame as it is to the lower communication node of the same transmission path, and conversely, the response from the lower communication node. When a frame is received, communication control is performed to relay the response frame as it is to a higher-order communication node on the same transmission path.

When there is traffic information to be transmitted to the slave station 2, the control unit 10 of the master station 1 can also include the traffic information in the request frame transmitted from the own station.
In the present embodiment, each communication node included in the traffic wireless LAN uses a channel (any one of Ch1 to Ch14) used in its own station in the request frame and response frame used for the data transmission process. The measurement data of the received electric field strength is stored and the measurement data sharing process is performed. Details of this process will be described later.

[Communication frame format]
FIG. 4 is a diagram showing a format of a communication frame.
As shown in FIG. 4, the communication frame used for the wireless communication of the communication devices 1 to 3 includes a physical header and a MAC frame.
The physical header includes a PLCP (Physical Layer Convergence Protocol / Procedure) preamble and a PLCP header.

The PLCP preamble is a bit string of a synchronization signal added at the beginning of a communication frame in the physical layer, and the PLCP header is a header portion in which information such as a modulation scheme and data is written in the physical layer.
The MAC frame includes a header part, a data part (payload), and an FCS (Frame Check Sequence). Among these, the header part includes a field for designating the type of management frame and control frame in accordance with the IEEE 802.11 protocol, and a field for designating a plurality of types of MAC addresses.

In the data portion of the MAC frame, a field for storing measurement data of the received electric field strength measured by each communication node is assigned for each node number.
When transmitting the request frame, the control unit 10 of the main station 1 stores the measurement data of the received electric field strength measured by the own station in a predetermined field for the own station assigned to the data part of the MAC frame.

On the other hand, when transmitting the response frame, the control unit 10 of the slave station 2 stores the traffic information acquired by the local station in the data portion of the MAC frame, and stores the traffic information in the predetermined field for the local station assigned to the data portion. Stores the measurement data of the received electric field strength measured by the own station.
When relaying the request frame, the control unit 10 of the relay station 3 stores the measurement data of the received electric field strength measured by the local station in a predetermined field for the local station assigned to the data portion of the MAC frame. To do.

[Measurement data sharing process]
FIG. 5 is a sequence diagram showing the contents of data transmission processing performed in cooperation by the master station 1, the slave station 2 and the relay station 3.
The master station 1, the slave station 2 and the relay station 3 of the present embodiment exchange the communication frames shown in FIG. 5 and receive the measurement data of the received electric field strength for each channel used by the nodes 1 to 7, respectively. A sharing process for sharing by 1 to 7 is performed.

In FIG. 5, “C” is a cycle time of data transmission processing that is repeatedly performed, and the master station 1, the slave station 2, and the relay station 3 execute the data transmission processing every one cycle time C. .
Since node numbers 1 to 7 in FIG. 5 correspond to node numbers 1 to 7 in FIG. 2, the sequence of communication frames will be described below using node numbers 1 to 7.

First, the node 1 transmits a request frame R2 to the node 2, and the node 2 transmits a response frame A2 corresponding to the request frame R2 to the node 1. At this time, the node 1 includes the received field strength measurement data measured at its own station in the request frame R2, and the node 2 includes the received field strength measurement data measured at its own station in the response frame A2.
Thereby, the node 1 and the node 2 acquire the measurement data of the reception electric field strength of the other party and store them in the storage unit 11 of their own stations.

Next, the node 1 transmits a request frame R5 for the node 5 to the node 3, the node 3 relays the received request frame R5 to the lower node 4, and the node 4 receives the received request frame R5. Is relayed to the lower node 5. At this time, the node 1 includes the measurement data of the received electric field strength of the local station and the obtained received electric field strength of the node 2 in the request frame R5.
Thereby, the node 3 acquires the measurement data of the received electric field strength of the node 1 and the node 2 in addition to the measurement data of the received electric field strength measured by the own station, and stores it in the storage unit 11 of the own station.

Further, when the node 3 relays the request frame R5 to the node 4, the node 3 includes the measurement data of the received electric field strength measured by the local station in the request frame R5.
Thereby, the node 4 obtains the measurement data of the received electric field strength of the node 1, the node 2 and the node 3 in addition to the measurement data of the received electric field strength measured by the own station, and stores it in the storage unit 11 of the own station. .

Further, when the node 4 relays the request frame R5 to the node 5, the measurement data of the received electric field strength measured by the local station is included in the request frame R5.
Thereby, the node 5 acquires the measurement data of the received electric field strength of the node 1, the node 2, the node 3 and the node 4 in addition to the measurement data of the received electric field strength measured by the local station, and stores the storage unit 11 of the local station. Remember me.

On the other hand, the node 5 transmits a response frame A5 corresponding to the request frame R5 to the node 4, the node 4 relays the received response frame A5 to the upper node 3, and the node 3 receives the received response frame A5. Is relayed to the upper node 1.
At this time, the node 5 includes in the response frame A5 the measurement data of the received electric field strength measured by the local station.

Thereby, the node 4 further acquires the measurement data of the received electric field strength of the node 5 from the response frame A5 received from the node 5, and stores it in the storage unit 11 of its own station.
Further, the node 3 further acquires measurement data of the received electric field strengths of the node 4 and the node 5 from the response frame A5 received from the node 4, and stores it in the storage unit 11 of the own station.

Next, the node 1 transmits a request frame R6 to the node 6, and the node 6 transmits a response frame A6 corresponding to the request frame R6 to the node 1.
At this time, the node 1 includes the already obtained measurement data of the received electric field strength from the node 1 to the node 5 in the request frame R6, and the node 6 includes the received electric field strength measurement data measured by the own station in the response frame A6. .

Thereby, the node 6 acquires the measurement data of the received electric field strength from the node 1 to the node 5 in addition to the measurement data of the received electric field strength measured by the own station, and stores it in the storage unit 11 of the own station.
Further, the node 1 newly acquires the measurement data of the received electric field strength of the node 6 from the response frame A6 from the node 6, and stores it in the storage unit 11 of its own station.

Further, the node 1 transmits a request frame R7 to the node 7, and the node 7 transmits a response frame A7 corresponding to the request frame R7 to the node 1.
At this time, the node 1 includes the obtained measurement data of the received electric field strength from the node 1 to the node 6 in the request frame R7, and the node 7 includes the measurement data of the received electric field strength measured by the own station in the response frame A7.

As a result, the node 7 acquires the measurement data of the received electric field strength from the node 1 to the node 6 in addition to the measurement data of the received electric field strength measured by the own station, and stores it in the storage unit 11 of the own station.
Further, the node 1 newly acquires the measurement data of the received electric field strength of the node 7 from the response frame A7 from the node 7, and stores this in the storage unit 11 of its own station.

As described above, the request frame R2, R5, R6, R7 and the response frames A2, A5, A6, A7 transmitted / received during the current cycle C cause the node 1 to have the received electric field strength of the other nodes 2-7. Get all measured data.
Therefore, the node 1 includes, in the request frames R2, R5, R6, and R7 transmitted in the next cycle C, the measurement data of the received electric field strengths of all the nodes 1 to 7 acquired in the current cycle C.

Thereby, the nodes 2 to 7 other than the main station 1 can acquire the measurement data of the received electric field strength measured at the other station by the request frames R2, R5, R6, and R7 acquired after the next cycle C. it can.
When each of the nodes 1 to 7 including the main station 1 receives a request frame or a response frame after the next cycle C, the received field strength of the past local station and the current local station described in the received frame are recorded. If the difference is equal to or greater than a predetermined value, the received field strength is updated to the current received field strength value, and the updated measurement data is stored in the transmission frame.

[Configuration of display section]
FIG. 6 is an explanatory diagram illustrating an example of the display unit 13 provided in the communication devices 1 to 3.
As shown in FIG. 6, the display unit 13 of the present embodiment includes a connection state display unit 20, a communication state display unit 21, and a changeover switch 22, and these members 20 to 22 are all communication devices 1 to 1. 3 is attached to the control board.

The connection state display unit 20 in FIG. 6 includes an electro-optical display device in which a plurality of light emitting elements (for example, LEDs) are two-dimensionally arranged vertically and horizontally. In the example of FIG. It is a piece.
Further, the column number of the connection status display unit 20 corresponds to the path number, the row number corresponds to the station type number, and the control unit 10 determines the path number and station of the positioning information stored in the storage unit 11. The light emitting element located at the lattice point corresponding to the type number is turned on to display that the nodes 1 to 7 of the positioning information stored in the storage unit 11 are included in the traffic wireless LAN.

For example, assuming that the coordinates of the column number and the row number are (x, y), the coordinates of the light emitting element L1 in FIG. 6 are (0, 0), so that the lighting of the light emitting element L1 represents the presence of the node 1.
Further, since the coordinates of the light emitting element L2 are (0, 2), lighting of the light emitting element L2 indicates the presence of the node 2. Similarly, the lighting of the light emitting elements L3 to L7 indicates that the nodes 3 to 7 are included in the traffic wireless LAN, respectively.

Moreover, the control part 10 of the communication apparatuses 1-3 only lights it about the light emitting element showing the positioning information of another station, but blinks it about the light emitting element showing the positioning information of the own station. It is like that. For example, in the example of FIG. 6, the light emitting element L6 of (5, 2) is lit, so that the local station is a communication device having the route number “5” and the station type number “2” (in FIG. 2). Node 6).
Thus, the connection state display unit 20 of the present embodiment has a function of displaying the positioning information of the local station and other stations in the traffic wireless LAN topology in a human-readable manner.

For this reason, if the connection state display unit 20 incorporated in any of the communication devices 1 to 3 is viewed, it can be understood that the entire topology of the traffic wireless LAN is in the connection form shown in FIG. .
Also, from the positioning information of the flashing light emitting element, which type of communication node is the main station 1, the slave station 2 or the relay station 3 in the communication wireless LAN of the local station, It is also possible to grasp the number of relays from the own station to the main station 1.

On the other hand, the communication status display unit 21 of FIG. 6 is composed of an electric display device in which light emitting elements (for example, LEDs) corresponding to the respective channels (Ch1 to Ch14) are arranged in a horizontal row.
These light emitting elements represent the approximate value of the received electric field intensity by the luminescent color. For example, the correspondence between the luminescent color and the intensity level is set as follows.

Red (R): −20 dbm or more Yellow (Y): −30 to less than −20 dbm Purple (P): −40 to less than −30 dbm Green (G): −50 to less than −40 dbm Light blue (A): −60 to − Less than 50 dbm Blue (B): less than -70 dbm

The control unit 10 of the communication apparatuses 1 to 3 reads the measurement data of the received electric field strength for each channel stored in the storage unit 11, applies the value of the read measurement data to the correspondence relationship, and displays the communication state display unit 21. The light emission color of each light emitting element arranged is determined.
6 includes a pair of rotary switches 22A and 22B having the number of contacts corresponding to the number of columns and the number of rows in the connection state display unit 20 (both are 16 contacts in the illustrated example).

The control unit 10 of the communication devices 1 to 3 specifies the positioning information nodes 1 to 7 corresponding to the contacts of both the switches 22A and 22B, and sets the channels (Ch1 to Ch14) used by the nodes 1 to 7 to be used. The corresponding light emitting element of the communication state display unit 21 is blinked.
For example, when the coordinates (5, 2) are designated by the rotary switches 22A, 22B, the control unit 10 selects a channel (for example, Ch7) in use at the node 6 whose positioning information is (5, 2). Reading is performed, and the light emitting element of the channel Ch7 is blinked.

In this way, by switching the rotary switches 22A and 22B, the light emitting elements of the channels in use by the specific nodes 1 to 7 can be blinked.
For this reason, when the worker switches the rotary switches 22A and 22B, the positioning information of the communication node using the channel (Ch7 in the example of FIG. 6) whose communication state is deteriorated due to the jamming radio wave is specified. can do.

[Search example of main station]
FIG. 7 is a plan view of a road for showing a search example of the main station 1 performed with reference to the electric light display by the connection state display unit 20.
In FIG. 7, the points A to G are assumed to be points where the nodes 1 to 7 of FIG. 2 constituting the traffic wireless LAN are actually installed on the site, and the points A to G and the node 1 Assume that the correspondence relationship of ˜7 is unknown. The hatched portion in FIG. 7 is a building.

Here, the conventional communication apparatus does not have a function of displaying the node type of the communication apparatus installed at the points A to G and the number of relays from the communication apparatus to the main station 1 to the outside. .
Therefore, when a worker who has visited the site searches for the main station 1 in order to perform maintenance work on the traffic wireless LAN, each communication device installed at the points A to G is connected to, for example, a notebook PC or the like. In order to find the main station 1, it was very time-consuming.

On the other hand, in the communication system of this embodiment, since all the communication devices 1 to 3 constituting the traffic wireless LAN have the connection state display unit 20 described above, any communication device 1 to 3 is accessed. Since the worker can grasp whether the own station is the master station 1, the slave station 2 or the relay station 3, and the number of relays from the own station to the master station 1, the work of searching for the master station 1 on site Is greatly reduced.
For example, it is assumed that the worker first accesses the communication device at the point E, and the connection state display unit 20 provided in the communication device determines that the communication device at the point E is the node 3.

In this case, since the node 3 is the relay station 3 that directly communicates with the main station 1 in consideration of the arrangement of the communication devices in the road alignment shown in FIG. It can be inferred that it is station 1.
The reason is that point B is farther than point C when viewed from point E, so it is unnatural as the installation position of the main station 1, and point A, point D, and point G are This is because it is almost impossible to perform direct wireless communication with the point E.

Further, since the connection state display unit 20 is also provided in the communication device at the point C or the point F, the communication device is the main station from the display of the connection state display unit 20 of the communication device at any point C or F. If it turns out that it is 1, it will be understood that the main station 1 of the traffic wireless LAN has been reached.
If the communication device that the worker first accessed locally is accidentally the main station 1, the subsequent search is unnecessary.

[Effect of communication system]
As described above, according to the communication system of the present embodiment, each communication device 1 to 3 configuring the traffic wireless LAN displays information that can specify the number of relays from the own station to the main station 1 in a human-readable manner. Since the connection state display unit 20 that performs the maintenance of the traffic wireless LAN, the worker who went to the site uses the display of the connection state display unit 20 of each of the communication devices 1 to 3 to display the main station 1. It can be easily searched. For this reason, the maintenance work of the traffic wireless LAN can be simplified.

  Further, according to the communication system of the present embodiment, the connection status display unit 20 is not only capable of specifying the number of relays from the own station to the master station 1, but the own station is the master station 1, the slave station 2, or the relay. Since the node type of the station 3 is displayed in a human readable manner, compared to the case where the node type is not displayed, the worker can immediately grasp the fact that he has reached the main station 1, Also in this respect, the maintenance work of the traffic wireless LAN is simplified.

According to the communication system of the present embodiment, each of the communication devices 1 to 3 constituting the traffic wireless LAN can acquire the measurement data of the received electric field strength of the channel being used by all the communication nodes in the network, and the acquired reception Since the communication state display unit 21 that displays the electric field strength in a human-readable manner is provided, an operator who has visited the site to perform maintenance of the traffic wireless LAN can receive electric field strength for each channel according to the display content of the communication state display unit 21. Can be grasped.
For this reason, it is possible to easily grasp the received electric field strength for each channel being used in the traffic wireless LAN without requiring manual operation, and to simplify the maintenance work of the traffic wireless LAN.

Further, according to the communication system of the present embodiment, by operating the changeover switch 22, the received electric field strength corresponding to the positioning on the topology of the communication devices 1 to 3 can be displayed on the communication state display unit 21. Therefore, it is possible to estimate which communication device 1 to 3 the reception quality of each channel is in the field.
For this reason, the maintenance work of the traffic wireless LAN can be simplified as compared with the case where it is unclear which communication device 1 to 3 the displayed received electric field strength is.

Further, according to the communication system of the present embodiment, the control unit 10 of each of the communication apparatuses 1 to 3 receives the request frame R2, R5, R6, R7 and its response frames A2, A5, A6, A7 respectively. Since the measurement data of the electric field strength is stored, the main station 1 can quickly collect the measurement data of the received electric field strength measured by each communication node.
For this reason, it is possible to prevent the notification of the received electric field strength to each communication node from being delayed.

  Further, according to the communication system of the present embodiment, the communication status display unit 21 of each of the communication devices 1 to 3 displays the reception quality of all the channels in use at the same time. There is also an advantage that a worker can determine at a glance whether or not the communication quality is deteriorated and can easily identify a channel whose communication quality is deteriorated.

[Other variations]
The above-described embodiments are illustrative and not restrictive. The scope of the right of the present invention is not the embodiment described above, but includes all modifications within the scope equivalent to the scope of the claims.
For example, in the above-described embodiment, the control unit 10 of the communication devices 1 to 3 measures the received electric field strength. However, the reception error rate (bit error rate) of the communication frame or the like can be expressed as other radio wave reception quality. Measurement data may be adopted.

In the above-described embodiment, the connection status display unit 20 displays the node type of the own station and information that can specify the number of relays from the own station to the main station 1 in a human readable manner. For example, only the number of relays may be directly displayed as a numerical value.
Even in this case, based on the number of relays displayed by the connection status display unit 20, it is possible to roughly estimate how far the main station 1 is from the own station, so that the search for the main station 1 is facilitated.

  Furthermore, in the above-described embodiment, the connection state display unit 20 and the communication state display unit 21 are provided in the communication devices 1 to 3, but the control unit 10 of the communication devices 1 to 3 Data necessary for display may be output to an external device such as a notebook PC having a display function, and display substantially equivalent to the display units 20 and 21 may be performed by the external device.

1 Communication device (main station)
2 Communication device (slave station)
3 Communication equipment (relay station)
10 Control unit (measurement unit, communication control unit)
11 Storage Unit 12 Wireless Communication Unit 13 Display Unit (Output Unit)
14 Input unit 20 Connection state display unit 21 Communication state display unit 22 Changeover switch

Claims (7)

A communication system comprising a wireless LAN for wirelessly transmitting traffic information used for traffic signal control,
Each communication node constituting the wireless LAN is
A measurement unit that measures the reception quality of the local station of the channel in use;
A communication control unit for storing the measured reception quality of the own station in a communication frame addressed to another station;
An output unit that outputs the measured reception quality of the local station and the reception quality of the other station included in the communication frame received by the local station in a human-readable manner;
A communication system comprising:   The communication system according to claim 1, wherein the output unit is capable of outputting the reception quality corresponding to the communication node in the topology of the wireless LAN in a human readable manner.   The communication control unit is configured to measure the reception quality of the local station measured in a request frame that is the communication frame for requesting data transmission of traffic information and a response frame that is the communication frame for storing traffic information in response to the request frame. The communication system according to claim 1 or 2, wherein:   The communication system according to any one of claims 1 to 3, wherein the output unit can simultaneously output the reception quality of all channels being used in the communication node. A wireless LAN access point for transmitting traffic information used for traffic signal control wirelessly,
A main station comprising the measurement unit according to claim 1, the communication control unit, and the output unit. A slave station that can communicate with an external network through a master station that is an access point of a wireless LAN for wirelessly transmitting traffic information used for traffic signal control,
A slave station comprising the measurement unit, the communication control unit, and the output unit according to claim 1. It is a relay station that relays wireless communication between a master station that is an access point of a wireless LAN for wirelessly transmitting traffic information used for traffic signal control and a slave station that can communicate with an external network through the master station. And
A relay station comprising the measurement unit according to claim 1, the communication control unit, and the output unit.

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