JP4562572B2 - Video transmission device - Google Patents

Description

  The present invention relates to a technique for suppressing the interruption of video distribution as much as possible regardless of the location of a mobile terminal device when wirelessly transferring data between a mobile terminal device collecting video and a fixed station.

  In recent years, as described in “Wireless LAN Information Outlet System” (Non-Patent Document 1), as a disaster countermeasure, the risk of river flooding, landslides, debris flow due to heavy rain, fire and house collapse due to earthquake Therefore, a system has been put into practical use that collects images of dangerous areas where disasters are likely to occur, and monitors them at the relevant office. In such a system, video collected by a mobile terminal device provided with mobility is wirelessly transmitted to an access point via a wireless local area network (LAN), and then a high-speed network constructed using an optical fiber or the like is used. A configuration is adopted in which a wired transmission is performed to the jurisdiction office. At this time, the mobile terminal device is equipped with a GPS (Global Positioning System) that measures the location of the mobile terminal device for convenience of video display in the competent office.

As for the wireless transmission speed, generally, if the transmission speed is high, the throughput is high, but the transmission distance is short. Conversely, when the wireless transmission speed is reduced, the throughput is reduced, but the transmission distance is long. Further, if the transmission speed is high, high-quality video can be transmitted, and if the transmission speed is low, low-quality video can be transmitted.
Kazuyoshi Yamauchi and two others, "Wireless LAN Information Outlet System", FUJITSU, Fujitsu Limited, July 2004, Vol.55, No.4, p.288-292

Now, a user who uses such a mobile terminal device transmits video and information as needed while carrying the mobile terminal device.
You may enter a wireless dead zone due to buildings or exit from the access point communication area. In such a case, communication normally performed between the mobile terminal device and the base station is suddenly interrupted. Alternatively, video data that has been transmitted with high quality cannot be received suddenly. However, since the user of the mobile terminal device does not know whether the current location is a dead zone or a communication area, it is difficult for the user to take any measures before communication is interrupted.

  Therefore, if the wireless transmission speed is lowered, the range in which communication is possible becomes wider, and the mobile terminal device detects the change in the wireless transmission speed, and changes the quality of the video to be transmitted according to the transmission speed. In view of the conventional problems as described above, the present invention monitors the location of the mobile terminal device in the wireless communication area, and the mobile terminal device moves outside the wireless communication area or in the dead zone. In this case, an object of the present invention is to provide a video transmission apparatus that suppresses interruption of video distribution as much as possible by reducing the wireless transmission speed and the video quality in advance.

  For this reason, in the present invention, a mobile terminal device that collects images while measuring a location, a fixed station connected to the mobile terminal device via a wireless network, and a base connected to the fixed station via a wired network In a computer connected to a network system configured with a station, the computer cannot perform wireless communication in a wireless communication area centered on a fixed station and in the wireless communication area using the location of the mobile terminal device as a key. A command for reducing the wireless transmission rate to the fixed station via the base station when it is determined that the mobile terminal device has moved out of the wireless communication area or into the dead zone with reference to the database in which the dead zone is stored. It is characterized by transmitting. In addition, the computer refers to the database using the location of the mobile terminal device as a key, and determines that the mobile terminal device has moved into the wireless communication area excluding the dead zone. And transmitting a command for returning the wireless transmission speed.

  According to the present invention, when the mobile terminal device moves outside the wireless communication area or in the dead zone, the wireless transmission rate between the fixed station and the mobile terminal device decreases regardless of the strength of the actual received electric field strength at the fixed station. Accordingly, the mobile terminal device that has detected the wireless transmission rate accordingly reduces the quality of the video to be transmitted. For this reason, before the data link between the mobile terminal device and the fixed station is interrupted, the wireless transmission speed is reduced and the wireless communication area is expanded, and the video quality that can be distributed even at the reduced wireless transmission speed is increased. Will be changed. Therefore, it is possible to suppress the interruption of video distribution as much as possible regardless of the location of the mobile terminal device.

  On the other hand, when the mobile terminal device moves into the wireless communication area excluding the dead zone, the wireless transmission speed between the fixed station and the mobile terminal device is restored regardless of the strength of the actual received electric field strength at the fixed station. At the same time, the quality of the video distributed from the mobile terminal device is restored. For this reason, when the data link between the mobile terminal device and the fixed station is strong, the video delivered from the mobile terminal device is of high quality, and a clear video can be provided as much as possible.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows the overall configuration of a video transmission system according to the present invention.
The video transmission system is distributed from the mobile terminal device 10 brought into a disaster site, at least one fixed station 20 serving as a wireless LAN access point, the base station 30 installed in a jurisdiction office, and the mobile terminal device 10. And a client 50 for monitoring the recorded video.

  The mobile terminal device 10 encodes an image capturing device 12 such as a CCD (Charge Coupled Device) camera that captures an image and an image captured by the image capturing device 12 into at least a high-quality or low-quality MPEG (Moving Picture Experts Group). A wireless communication device 16 that performs wireless data exchange between the encoder 14 and the fixed station 20 and a GPS 18 that measures the location are configured. Here, the wireless communication device 16 transmits the MPEG encoded by the encoder 14 and the position information (latitude, longitude, and altitude) measured by the GPS 18 to the fixed station 20, while using the encoder 14 according to the detected transmission speed. Change the video quality accordingly.

The fixed station 20 is appropriately arranged in an area where communication is to be performed, and is interconnected with the base station 30 via a high-speed network 60 such as an optical fiber so as to mediate between the mobile terminal apparatus 10 and the base station 30. In addition, the fixed station 20 transmits the received electric field strength indicating the data link strength with the mobile terminal device 10 to the base station 30.
The base station 30 includes a server 32, a map DB (Data Base) 34 in which map data covering the danger zone is stored, a wireless communication distance DB 36, a wireless communication area DB 38, a dead zone DB 40, and temporary work. And a work DB 42 used as an area. The server 32 provides dangerous area images to the client 50 based on the MPEG and the position information transmitted from the fixed station 20, while sending various commands for changing the wireless LAN wireless transmission speed as necessary. 20 is transmitted. Note that the server 32 executes the program loaded in the memory so that the first determination unit, the first control unit, the second determination unit, the second control unit, the update unit, and the video distribution unit are provided. Realize each one.

  In the wireless communication distance DB 36, as shown in FIG. 2, a management number for identifying the fixed station 20 and an azimuth angle θ indicating an angle with respect to the reference direction are defined for each wireless transmission speed in order to define antenna directivity characteristics of each fixed station. (0 ° to 359 °), the latitude and longitude of the fixed station 20, and the wireless communication distance D that can secure a data link with the mobile terminal device 10 are stored. Here, the reference direction of the azimuth angle θ may be, for example, true north.

  In the wireless communication area DB 38, for each wireless transmission speed, a wireless communication area centered on each fixed station, that is, an area where a data link can be secured with the mobile terminal device 10 is shown in FIG. As described above, the management number for identifying the fixed station 20, the azimuth angle θ, the latitude, longitude, and altitude of the fixed station 20, and the latitude, longitude, and altitude of each division point obtained by dividing the wireless communication distance D at predetermined intervals are stored. Is done. Here, for example, the predetermined interval may be a 1 m interval starting from the fixed station 20.

  In the dead zone DB 40, as shown in FIG. 4, a fixed station 20 is defined for each wireless transmission speed in order to define a dead zone in each wireless communication area, that is, a region where a data link with the mobile terminal device 10 is interrupted. And the latitude, longitude, and altitude of each dead point constituting the dead zone are stored. Here, as the elevation of the dead point, the elevation of the map data corresponding to the latitude and longitude of the dead point is used.

Next, processing for constructing the wireless communication distance DB 36, the wireless communication area DB 38, and the dead zone DB 40, which are executed when starting the operation of the video transmission system in the server 32 of the base station 30, will be described.
FIG. 5 shows a flowchart of processing for constructing the wireless communication distance DB 36.
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), for example, the management number for identifying the fixed station 20 via the console (not shown), the latitude of the point where the fixed station 20 is installed, and Enter the longitude respectively.

In step 2, the azimuth angle θ is set to zero.
In step 3, the wireless communication distance D at the azimuth angle θ is calculated. That is, when wireless communication is performed between the mobile terminal device 10 and the fixed station 20, the received electric field strength at the fixed station 20 is required to be a predetermined value or more, and the wireless communication distance is based on free space loss in the air. Can be sought. As is apparent from the radio transmission characteristics shown in FIG. 6, the received electric field strength is: transmission output−transmission feeder loss + transmission antenna gain−transmission antenna angle loss−free space loss−reception antenna angle loss + reception antenna gain−reception supply. Calculated from wire loss. Note that the transmission antenna angle loss and the reception antenna angle loss have different values for each azimuth angle θ in the case of a directional antenna. Therefore, the free space loss is transmission output−transmission feed line loss + transmission antenna gain−transmission antenna angle loss−reception antenna angle loss + reception antenna gain−reception feed line loss−reception field strength. And the radio | wireless communication distance D can be calculated | required from following Formula using free space loss. Here, λ in the following equation represents a radio wavelength [m], and is, for example, 0.125 in the 2.4 GHz band.

In step 4, the azimuth angle θ, the latitude and longitude of the fixed station 20, and the wireless communication distance D are sequentially stored in the wireless communication distance DB 36 in association with the management number of the fixed station 20.
In step 5, the azimuth angle θ is increased by one.
In step 6, it is determined whether or not the azimuth angle θ is 360, that is, whether or not the wireless communication distance D is stored for all azimuth angles of 0 ° to 359 °. If the azimuth angle θ is 360, the process is terminated (Yes), while if the azimuth angle θ is less than 360, the process returns to step 3 (No).

FIG. 7 shows a flowchart of processing for constructing the wireless communication area DB 38.
In step 11, the azimuth angle θ is set to zero.
In step 12, the latitude and longitude of each division point obtained by dividing the wireless communication distance D at a predetermined interval are calculated for the azimuth angle θ with reference to the wireless communication distance DB 36.
In step 13, the latitude and longitude of each division point are sequentially stored in the work DB 42.

In step 14, the azimuth angle θ is increased by one.
In step 15, it is determined whether or not the azimuth angle θ is 360, that is, whether or not the latitude and longitude of each division point are stored for all azimuth angles of 0 ° to 359 °. If the azimuth angle θ is 360, the process proceeds to step 16 (Yes), while if the azimuth angle θ is less than 360, the process returns to step 12 (No).

In step 16, one latitude and longitude of the division point is read from the work DB 42, and the latitude and longitude of the division point are deleted from the work DB 42.
In step 17, the map DB 34 is referred to, and the altitude corresponding to the latitude and longitude of the division point is read out.
In step 18, the longitude and latitude of the division point and the altitude corresponding to them are sequentially stored in the wireless communication area DB 38 in association with the management number of the fixed station 20, the azimuth angle θ, and the longitude, latitude and altitude of the fixed station 20.

In step 19, it is determined whether or not the latitude and longitude of the dividing points are stored in the work DB 42, that is, whether or not the addition of the altitude to all the dividing points has been completed. If the latitude and longitude of the dividing point are not stored, the process ends (Yes), while if the latitude and longitude of the dividing point are stored, the process returns to Step 16 (No).
FIG. 8 shows a flowchart of processing for constructing the dead zone DB 40.

In step 21, referring to the wireless communication area DB 38, as shown in FIG. 9, the latitude, longitude, and altitude of each dead point constituting the dead zone where the altitude overlaps with the Fresnel zone are extracted. The Fresnel zone is a theoretical elliptical region that exists between the transmitting antenna and the receiving antenna, which is indispensable for radio waves to propagate.
In step 22, the latitude, longitude, and altitude of each dead point are sequentially stored in the dead zone DB 40 in association with the management number of the fixed station 20.

  According to such a process, the wireless communication distance DB 36, the wireless communication area DB 38, and the dead zone DB 40 that are indispensable in the operation of the video transmission system are automatically constructed, and therefore, the labor required for preparing to start the operation can be reduced as much as possible. Can do. Therefore, the operation of the video transmission system can be started in a short period of time, and disaster countermeasures can be implemented quickly. Note that the wireless communication area DB 38 and the dead zone DB 40 are appropriately updated from the initial state created by the processing of FIGS. 7 and 8 according to the state of communication actually performed between the mobile terminal device and the fixed station. Is.

Next, a process for dynamically changing the wireless transmission speed and the video quality after starting the operation of the video transmission system will be described.
FIGS. 10 and 11 show a flowchart of parallel processing that is repeatedly executed in the server 32 of the base station 30 every predetermined time or every time data is received from the mobile terminal device. Note that the first determination unit and the first control unit are realized by the processing shown in FIG. 10, while the second determination unit and the second control unit are realized by the processing shown in FIG.

In FIG. 10, in step 31, position information indicating the location of the mobile terminal device 10 is read via the fixed station 20 and the high-speed network 60.
In step 32, the wireless communication area DB 38 and the dead zone DB 40 are referred to, and it is determined whether or not the mobile terminal apparatus 10 has moved outside the wireless communication area or in the dead zone. That is, the point identified by the position information of the mobile terminal device 10 is outside the wireless communication area stored in the wireless communication area DB 38, or the dead zone stored in the dead zone DB 40 even within the wireless communication area. Determine if you are in a zone. If the mobile terminal device 10 has moved outside the wireless communication area or in the dead zone, the process proceeds to step 33 (Yes), while if the wireless terminal device 10 has not moved outside the wireless communication area or in the dead zone, the process ends. (No).

In step 33, a speed reduction command for reducing the wireless transmission speed is generated.
In step 34, a speed reduction command is transmitted to the fixed station 20 via the high-speed network 60.
By the process shown in FIG. 10, the server 32 of the base station 30 can keep the communication low by reducing the transmission speed in advance before the mobile terminal device 10 enters the poor communication situation and the communication is interrupted. become.

In FIG. 11, in step 41, position information indicating the location of the mobile terminal device 10 is read via the fixed station 20 and the high-speed network 60.
In step 42, the wireless communication area DB 38 and the dead zone DB 40 are referred to and it is determined whether or not the mobile terminal device 10 has moved to the wireless communication area or has left the dead zone. That is, based on the point specified by the position information of the mobile terminal device 10, it is determined whether or not the mobile terminal device 10 has moved into the wireless communication area excluding the dead zone. If the mobile terminal device 10 moves into the wireless communication area or exits from the dead zone, the process proceeds to step 43 (Yes), while the wireless terminal device 10 does not move into the wireless communication area or exits from the dead zone. The process is terminated (No).

In step 43, a speed increase command for increasing the wireless transmission speed is generated.
In step 44, a speed increase command is transmitted to the fixed station 20 via the high speed network 60.
With the processing shown in FIG. 11, when the mobile terminal apparatus 10 enters a zone with good communication conditions, the server 32 of the base station 30 increases the transmission speed (returns to the normal transmission speed), and high-quality video. Can be transmitted.
FIG. 12 shows a flowchart of processing executed in the wireless communication device 16 of the mobile terminal device 10 triggered by detection of a change in the transmission rate of communication performed with the fixed station 20.

In step 51, it is determined whether or not the wireless LAN wireless transmission rate has been changed. If the wireless transmission rate has been changed, the process proceeds to step 52 (Yes), while if the wireless transmission rate has not been changed, the process waits (No).
In step 52, a video distribution stop command is generated to change the video quality.
In step 53, a video distribution stop command is output to the encoder 14. As a result, the encoder 14 stops encoding and stops video distribution.
In step 54, branch processing is performed according to the transmission rate. That is, if the transmission rate has decreased, the process proceeds to step 55, while if the transmission rate has increased, the process proceeds to step 57.

In step 55, a low quality video distribution start command is generated in order to start low quality video distribution.
In step 56, a low-definition video distribution start command is output to the encoder 14. As a result, the encoder 14 starts distributing low-quality video according to the wireless transmission speed of the wireless LAN that has decreased.

In step 57, a high-definition video distribution start command is generated to start high-definition video distribution.
In step 58, a high-definition video distribution start command is output to the encoder 14. As a result, the encoder 14 starts distributing high-definition video according to the increased wireless transmission speed of the wireless LAN.

  According to such a series of processes, when the mobile terminal device 10 moves outside the wireless communication area or in the dead zone, the wireless LAN wireless transmission rate is reduced regardless of the strength of the actual received electric field strength in the fixed station 20. At this time, the video delivered from the mobile terminal device 10 is changed to a low-quality video as the wireless transmission speed decreases. For this reason, before the data ring between the mobile terminal device 10 and the fixed station 20 is interrupted, the wireless transmission speed is reduced and the wireless communication area is expanded, and the video quality can be distributed even at the reduced wireless transmission speed. And can be switched dynamically. Therefore, at the jurisdiction office where the base station 30 is installed, video distribution in a dangerous area where a disaster may occur is not interrupted, and disaster countermeasures can be effectively performed.

  On the other hand, when the mobile terminal device 10 moves into the wireless communication area or leaves the dead zone, the wireless LAN wireless transmission speed is increased regardless of the strength of the actual received electric field strength at the fixed station 20. At this time, the video delivered from the mobile terminal device 10 is changed to a high-quality video as the wireless transmission speed increases. For this reason, when the data link between the mobile terminal device 10 and the fixed station 20 is strong, the video delivered from the mobile terminal device 10 is a high-definition video, so the jurisdiction where the base station 30 is installed In the office, the danger can be judged through a clear and detailed video of the dangerous area.

  By the way, since the wireless communication area and the dead zone are generated by calculation from the map data stored in the map DB 34, the wireless communication area and the wireless communication area are actually points that can be wirelessly communicated even outside the wireless communication area. However, there may be places where wireless communication is not possible. For this reason, it is desirable to update the wireless communication area and the dead zone as appropriate according to the actual wireless communication status after the operation of the video transmission system is started. Therefore, the server 32 of the base station 30 updates the wireless communication area and the dead zone as appropriate by repeating the process shown in FIG. 13 every predetermined time. The updating unit is realized by the processing shown in FIG.

In step 61, the position information indicating the location of the mobile terminal device 10 and the received electric field strength at the fixed station 20 are read via the fixed station 20 and the high-speed network 60, respectively.
In step 62, the wireless communication area DB 38 and the dead zone DB 40 are referred to and it is determined whether or not the mobile terminal device 10 is outside the dead zone or in the dead zone. If the mobile terminal device 10 is outside the wireless communication area or in the dead zone, the process proceeds to step 63 (Yes). If the mobile terminal device 10 is not outside the wireless communication area or in the dead zone, the process proceeds to step 67 (No). ).

In step 63, it is determined whether or not the received electric field strength at the fixed station 20 is strong, that is, whether or not the received electric field strength is greater than a predetermined value. If the received electric field strength is strong, the process proceeds to step 64 (Yes), while if the received electric field strength is not strong, the process is terminated (No).
In step 64, it is determined whether or not the mobile terminal device 10 is in a dead zone. If the mobile terminal device 10 is in the dead zone, the process proceeds to step 65 (Yes), and the corresponding data corresponding to the location information of the mobile terminal device 10 is deleted from the dead zone DB 40. On the other hand, if the mobile terminal device 10 is not in the dead zone, the process proceeds to step 66 (No), and corresponding data corresponding to the location information of the mobile terminal device 10 is added to the wireless communication area DB 38.

In step 67, it is determined whether or not the received electric field strength at the fixed station 20 is weak, that is, whether or not the received electric field strength is a predetermined value or less. If the received electric field strength is weak, the process proceeds to step 68 (Yes), and the corresponding data corresponding to the position information of the mobile terminal apparatus 10 is added to the dead zone DB 40. On the other hand, if the received electric field strength is not weak, the process is terminated (No).
According to such processing, when the mobile terminal device 10 is outside the wireless communication area or in the dead zone, if the received electric field strength at the fixed station 20 is strong, it is determined that the mobile terminal device 10 is in a communication state capable of delivering high-definition video. can do. For this reason, depending on the location of the mobile terminal device 10, the dead zone stored in the dead zone DB 40 is reduced, or the wireless communication area stored in the wireless communication area DB 38 is expanded, so that the actual situation of the wireless communication state The high-definition video can be distributed as much as possible. On the other hand, when the mobile terminal device 10 is in a wireless communication area excluding the dead zone, if the received electric field strength at the fixed station 20 is weak, it can be determined that the communication state is difficult to distribute high-definition video. For this reason, by expanding the dead zone stored in the dead zone DB 40, it is possible to reflect the actual state of the wireless communication state and prevent the video distribution from being interrupted.

  In the server 32 of the base station 30, a monitoring screen 70 as shown in FIG. 14 is provided to the client 50 via the high-speed network 60 in response to a video distribution request from the client 50. The monitoring screen 70 includes a main screen 72 that occupies most of the screen, a sub-screen 74 that displays a reduced screen, a mobile terminal list 76 for designating the mobile terminal device 10 that performs video distribution, and a display switching button 78. , Including. Note that a video distribution unit is realized by the server 32 that provides the monitoring screen 70.

  In the initial screen provided in response to the video distribution request, the main screen 72 includes map data stored in the map DB 34 and a wireless communication area stored in the wireless communication area DB 38, as shown in FIG. (A range surrounded by a solid line in the main screen 72), a dead zone stored in the dead zone DB 40 (a hatched range in a solid line circle in the main screen 72), and the location of the mobile terminal device 10 An area diagram with superimposed positions is displayed. On the other hand, on the sub screen 74, the video distributed from the mobile terminal device 10 set as default in the mobile terminal list 76 is reduced and displayed.

  When another mobile terminal device 10 is selected from the mobile terminal list 76, a video distributed from the selected mobile terminal device 10 is displayed on the sub-screen 74. When the “video display” button as the display switching button 78 is clicked, the images displayed on the main screen 72 and the sub screen 74 are exchanged as shown in FIG. In this way, if the video is enlarged and displayed on the main screen 72, the situation of the dangerous area can be easily grasped, which can contribute to disaster countermeasures. It should be noted that when returning to the monitoring screen 70 shown in FIG. 5A, an “area display” button as the display switching button 78 may be clicked.

Since the range of the wireless communication area and the dead zone varies depending on the transmission speed of the wireless communication, information corresponding to the communication speed currently being performed between the mobile terminal device and the fixed station is stored in the wireless communication area DB 38 and the dead zone. What is necessary is just to switch and display according to which transmission speed according to an operator's instruction | indication, reading suitably from zone DB40 and displaying.
In this way, it is possible to monitor a dangerous zone where a disaster may occur even in a remote location that is geographically distant from the base station 30. In addition, by presenting an area diagram in which the map data, the wireless communication area, the dead zone, and the location of the mobile terminal device 10 are superimposed and displayed on the monitoring screen 70, it is possible to easily grasp the currently focused area. The operator operating the mobile terminal device 10 can be instructed to change the imaging direction.

  In the above embodiment, the wireless transmission speed and the video quality are switched in two stages. However, the wireless transmission speed and the video quality may be switched discretely or continuously in three or more stages. In this case, the switching may be appropriately performed according to the received electric field strength in the base station 20.

  (Appendix 1) A mobile terminal device that collects video while positioning a location, a fixed station connected to the mobile terminal device via a wireless network, and a base station connected to the fixed station via a wired network And a computer connected to a network system comprising: a database in which a wireless communication area centered on the fixed station and a dead zone where wireless communication is impossible in the wireless communication area are stored; And a first determination unit that refers to a database using the location of the mobile terminal device as a key, and determines whether the mobile terminal device has moved out of a wireless communication area or into a dead zone, and the first determination When it is determined by the means that the mobile terminal device has moved outside the wireless communication area or in the dead zone, the wireless transmission speed is transmitted to the fixed station via the base station. Video transmission apparatus characterized by being configured to include a first control means for transmitting a command to lower the.

  (Additional remark 2) 2nd determination which the said computer refers to a database by using the location of the said mobile terminal device as a key, and determines whether the said mobile terminal device moved into the wireless communication area except a dead zone When the mobile terminal apparatus determines that the mobile terminal apparatus has moved into the wireless communication area excluding the dead zone by the means and the second determination means, the wireless transmission speed is returned to the fixed station via the base station. The video transmission apparatus according to appendix 1, further comprising: a second control unit that transmits a command.

  (Additional remark 3) The said computer was provided with the update means to update the radio | wireless communication area and dead zone respectively stored in the said database based on the location of the said mobile terminal device, and the received electric field strength in the said fixed station The video transmission device according to Supplementary Note 1 or Supplementary Note 2, wherein:

  (Additional remark 4) The said update means corresponds to the location of the said mobile terminal device, when the said mobile terminal device is out of a radio | wireless communication area, and the received electric field strength in the said fixed station is larger than predetermined value. The video transmission system according to appendix 3, wherein data is added to a wireless communication area.

  (Supplementary Note 5) When the mobile terminal device is in a dead zone and the received electric field strength at the fixed station is greater than a predetermined value, the update unit is configured to store data corresponding to the location of the mobile terminal device. The video transmission system according to appendix 3 or appendix 4, wherein the video transmission system is deleted from the dead zone.

  (Supplementary Note 6) When the mobile terminal device is in a wireless communication area excluding a dead zone, and the received electric field strength at the fixed station is equal to or less than a predetermined value, the location of the mobile terminal device The video transmission system according to any one of Supplementary Note 3 to Supplementary Note 5, wherein data corresponding to is added to the dead zone.

  (Supplementary note 7) The video transmission system according to any one of supplementary notes 1 to 6, wherein the computer includes video distribution means for distributing video collected by the mobile terminal device.

  (Supplementary note 8) In addition to the video collected by the mobile terminal device, the video distribution means includes a wireless communication area and a dead zone stored in the database, map data covering these, and the location of the mobile terminal device The video transmission system according to appendix 7, wherein an area diagram in which positions are superimposed is provided.

Overall configuration diagram of video transmission system according to the present invention The concrete structure of radio | wireless communication distance DB is shown, (A) is explanatory drawing of a data structure, (B) is a supplementary explanatory drawing of each item. The specific structure of radio | wireless communication area DB is shown, (A) is explanatory drawing of a data structure, (B) is a supplementary explanatory drawing of each item. The concrete structure of a dead zone DB is shown, (A) is explanatory drawing of a data structure, (B) is a supplementary explanatory drawing of each item. Flowchart of processing for constructing wireless communication distance DB Explanatory diagram showing wireless transfer characteristics Flowchart of processing for constructing wireless communication area DB Flow chart of processing for building dead zone DB Illustration of how to find the dead zone Flow chart of processing executed after starting operation in the base station Flow chart of processing executed after starting operation in the base station Flow chart of processing executed after starting operation in mobile terminal device Flowchart of update processing of wireless communication area and dead zone executed in base station The monitoring screen provided to the client is shown, (A) is an explanatory diagram of an initial screen, (B) is an explanatory diagram of a screen in which video is enlarged and displayed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mobile terminal device 12 Imaging device 14 Encoder 16 Wireless communication device 18 GPS
20 fixed station 30 base station 32 server 34 map DB
38 Wireless communication area DB
40 Dead Zone DB
50 Client 60 High-speed network 70 Monitoring screen 72 Main screen 74 Subscreen

Claims (4)

A mobile terminal device that collects images while measuring a location, a fixed station connected to the mobile terminal device via a wireless network, and a base station connected to the fixed station via a wired network In a computer connected to a network system
The computer
Of the radio communication area centered on the fixed station, and the coordinates including the latitude, longitude, and altitude of the division points obtained by dividing the radio communication area at predetermined intervals, the mobile station apparatus in the fixed station and the radio communication area A database for storing the coordinates where the altitude is superimposed on the Fresnel zone defined between and as a dead zone where wireless communication is impossible,
A first determination unit that refers to a database using a location of the mobile terminal device as a key, and determines whether the mobile terminal device has moved out of a wireless communication area or in a dead zone;
When the first determination means determines that the mobile terminal apparatus has moved out of the wireless communication area or into the dead zone, a command for reducing the wireless transmission rate is transmitted to the fixed station via the base station. 1 control means;
A video transmission apparatus characterized by comprising the above. The computer
A second determination unit that refers to a database using a location of the mobile terminal device as a key and determines whether the mobile terminal device has moved into a wireless communication area excluding a dead zone;
When the second determination means determines that the mobile terminal apparatus has moved into the wireless communication area excluding the dead zone, a command for returning the wireless transmission rate to the fixed station is transmitted via the base station. Second control means to:
The video transmission apparatus according to claim 1, further comprising: The wireless communication area and the dead zone are provided for each wireless transmission speed,
The first determination means determines whether the mobile terminal device has moved out of the wireless communication area or in the dead zone based on the wireless communication area and the dead zone according to the current wireless transmission speed,
The second determination means determines whether the mobile terminal apparatus has moved into a wireless communication area excluding the dead zone based on a wireless communication area and a dead zone corresponding to the wireless transmission speed to be restored. The video transmission apparatus according to claim 2 . The computer includes update means for updating a wireless communication area and a dead zone stored in the database based on a location of the mobile terminal device and a received electric field strength in the fixed station, respectively. The video transmission apparatus according to any one of claims 1 to 3.

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