Radio transmitting system, radio base station apparatus, and communication channel selecting method

The present invention relates to a radio transmission system using a communication channel that may interfere with radar waves, a radio base station device, and a communication channel selection method, and particularly in a passenger accommodation area of a transportation means such as a passenger aircraft or a train. The present invention relates to a wireless transmission system, a wireless base station apparatus, and a communication channel selection method suitable for providing a video / audio information distribution service such as.

Services that deliver entertainment content such as music and movies to each seat in the transportation of passenger aircraft and trains are widespread. Conventionally, these services were transmitted by a wired cable laid in the passenger accommodation area in the transportation system, but from the viewpoint of weight reduction of the system and flexibility for changing the seat layout, it is considered to replace it with a wireless transmission method. There is.

As a wireless transmission method suitable for such applications, there is a wireless LAN system such as IEEE802.11a / b / g / n. Wireless LAN systems are already widely used in enterprises and general households, and have a proven track record as systems that can realize high-speed data communication of several tens of Mbps or more in a relatively stable manner. In particular, since IEEE 802.11a / n uses radio waves in the 5 GHz band, there is little interference with other systems, and the physical layer transmission speed is high at 50 Mbps or higher for IEEE 802.11a and 300 Mbps or higher for IEEE 802.11n. Data communication can be performed stably. Moreover, since it is widely used as described above, the device price is relatively low.

However, this 5GHz band is partly shared with the frequency for weather radar (hereinafter referred to simply as "radar"), and in areas where radar is operated, wireless LAN radio waves may not adversely affect the radar, or It is necessary to select the communication channel so that the wireless LAN will not be disturbed by radar waves.

For this reason, the wireless LAN device has a built-in DFS (Dynamic Frequency Selection) function that dynamically changes the communication channel. When the wireless LAN device detects a radar wave, it avoids the communication candidate channel of that frequency and communicates. You are asked to select a channel. In addition, radar wave detection is performed not only when the wireless LAN is activated, but also during operation, and if a radar wave is detected during operation, it operates so as to immediately change the communication channel.

FIG. 6 is a diagram showing a frequency map showing the wireless communication channels of IEEE802.11a in Japan. As shown in Fig. 6, eight communication candidate channels with a center frequency of 5.18 GHz to 5.32 GHz are prepared every 20 MHz in the 200 MHz band of 5.15 to 5.35 GHz. Of these, 5.25 to 5.35 GHz is used for radar, so the four communication candidate channels of 5.26 to 5.32 GHz may interfere with radar waves. The wireless LAN device can detect this interference by DFS, reselect a communication candidate channel that has no problem, and continue communication.

However, when the information to be communicated is real-time data that requires simultaneity (real-time performance) such as video and audio during streaming, data transmission is temporarily interrupted when the communication channel is changed by DFS. Therefore, there has been a problem that the reproduced video / audio is temporarily interrupted or transient noise is generated.

Therefore, conventionally, in areas where radar is operated, a method has been proposed in which communication is performed while avoiding the use of communication candidate channels in the frequency band shared with the radar (see, for example, Patent Document 1). Once the geographical location where the wireless LAN device is installed is determined, it is possible to know in advance whether or not radar is operating in the vicinity of that area, so if applicable, do not select a communication candidate channel in the radar shared frequency band. It is operating in.

If all radar operation information in Japan is stored in the storage means in the wireless LAN device in advance, the possibility of interference can be determined in advance by inputting the geolocation information where the wireless LAN device is installed. are doing. As a result, when operating the wireless LAN in an area where interference with the radar can be predicted in advance, only communication candidate channels outside the radar frequency band are used, so that real-time data can be stably transmitted.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2007-53726</text></patcit>

<p> As described above, in the method of Patent Document 1, the possibility of interference with the radar is estimated in advance based on the radar operation information and the installation position information of the wireless LAN device, and the communication candidate channel existing within the shared frequency with the radar is selected. By prohibiting the above, it becomes possible to transmit video and audio information that requires simultaneity without interruption. However, the method of Patent Document 1 has the following two problems.</p><p> First, the information transmitted wirelessly is not limited to video and audio information that requires simultaneity. Even if the video / audio information is not a streaming type but a download type, if the downloaded information can be stably played back and viewed from a hard disk or the like, the temporary interruption at the time of downloading does not become a big problem. Rather, it is desirable that the average transmission speed is high so that the download can be performed in a short time. It goes without saying that there is no problem with temporary interruption of transmission of control information, e-mail, still images, Web screens, etc. that are not video and audio information, and high average transmission speed is important. In this way, it is important to transmit non-real-time data that does not require simultaneity as fast as possible.</p><p> If the use of communication candidate channels within the radar frequency band is restricted in advance as in the method of Patent Document 1, only the remaining communication candidate channels will be used simultaneously by a plurality of wireless LAN devices. The average transmission speed per unit drops significantly. This problem arises not only when a plurality of wireless access points are used in the system, but also when there are wireless access points of other systems in the vicinity of the system.</p><p> Video content data such as movies in the in-flight entertainment system of a passenger aircraft may be downloaded in advance from a wireless base station device to a wireless terminal device while parked at an airport on the ground. In an airport environment, there is a high probability that radar is being operated, so as mentioned above, it is assumed that only some of the communication candidate channels will have to be downloaded at low speed. In addition, when frequency hopping technology is used for meteorological satellites, etc., it is obligatory to implement DFS because one satellite uses multiple channels of wireless LAN by dynamically changing the frequency. Many of the available channels may not be available. In the case of IEEE802.11a shown in FIG. 6, the communication channel is selected and used only from the four communication candidate channels out of the eight communication candidate channels.</p><p> Second, in transportation such as passenger aircraft, the position changes from moment to moment. Therefore, inputting geolocation information, which is not a problem in a fixed stationary wireless LAN device as assumed in Patent Document 1, is a complicated and difficult operation. It is virtually impossible for a user to input his / her own position information that changes from moment to moment, and a system that automatically updates the position information using, for example, GPS is required. As a result, the scale and price of the system will increase. In addition, since aircraft change routes complicatedly due to the influence of weather conditions, etc., even if the position of the aircraft can be grasped by GPS, it is not possible to grasp the influence of radar and register it in the database at all points on the earth. It is virtually impossible.</p><p> In addition, as a result of updating the location information in this way, the communication channel that was available until just before can no longer be used suddenly due to interference with the radar in the new area of the destination, without interrupting the video and audio information. The original purpose of transmission cannot be achieved.</p><p> The present invention has been made to solve such a problem, and can stably transmit real-time data such as video and audio information that requires simultaneousness even in an environment where interference with a radar exists, and at the same time. It is an object of the present invention to provide a wireless transmission system, a wireless base station apparatus, and a communication channel selection method capable of maintaining high speed for transmission of non-real-time data that does not require sex.</p>

<p> In order to achieve the above object, the wireless transmission system of the present invention includes a first communication candidate channel included in a predetermined radio frequency band and shifts to another channel when the radio wave of the channel is detected, and a predetermined radio frequency. A wireless transmission system that transmits data between a wireless base station device and a wireless terminal device via a communication path having a second communication candidate channel that is not included in the band, and the data is real-time data or non-real-time data. Based on the determination result of the data determination means for determining whether the data is data, the radio wave detection means for detecting the radio wave of the first communication candidate channel, and the determination result of the data determination means, the first communication candidate channel or the second communication candidate channel It is characterized by being provided with a communication channel selection means for selecting a communication channel for transmitting data from the inside.</p><p> As a result, an appropriate communication channel can be selected from the communication candidate channels depending on whether the data to be transmitted is real-time data or non-real-time data. Therefore, the communication path can be used efficiently. Furthermore, it is not necessary to have a database of radars that can be detected at each location where the device is installed. In addition, even in a moving body such as an aircraft, it is not necessary for the user to input the position information that changes from moment to moment, or to acquire it from GPS etc. and perform complicated arithmetic processing, so it is small and inexpensive. You can build a system.</p><p> Further, in the wireless transmission system of the present invention, when the data determination means determines that the data is real-time data, the communication channel selection means may select a communication channel from the second communication candidate channels.</p><p> This makes it possible to stably wirelessly transmit real-time data such as video / audio information during streaming, which requires simultaneity, without interruption.</p><p> Further, in the wireless transmission system of the present invention, when the data determination means determines that the data is non-real-time data, the communication channel selection means is the first communication candidate channel or the first communication candidate channel based on the detection result of the radio wave detection means. A communication channel may be selected from the second communication candidate channel.</p><p> As a result, in wireless transmission of non-real-time data such as control information that does not require simultaneity and video / audio information at the time of download, transmission is performed while maintaining a high average transmission speed without reducing the number of communication candidate channels. Can be done.</p><p> Further, in the wireless transmission system of the present invention, the communication channel selection means may preferentially select a communication channel from the first communication candidate channels.</p><p> As a result, the communication candidate channel assigned to the real-time data is not used for the transmission of the non-real-time data, so that more stable real-time data transmission can be performed.</p><p> Further, in the wireless transmission system of the present invention, the predetermined radio frequency band may be a radar radio frequency band.</p><p> This enables stable wireless transmission of real-time data without interruption even in an environment affected by radar waves.</p><p> Further, in the wireless transmission system of the present invention, the wireless base station device and the wireless terminal device may be installed in the passenger accommodation area of the transportation facility.</p><p> As a result, real-time data can be transmitted wirelessly without interruption even when a transportation vehicle such as a passenger aircraft passes through a place affected by radar waves during operation. Therefore, it is possible to provide passengers with high-quality video / audio content in the passenger aircraft entertainment service.</p><p> The radio base station apparatus of the present invention includes a first communication candidate channel that is included in a predetermined radio frequency band and shifts to another channel when a radio wave of the channel is detected, and a second communication candidate channel that is not included in the predetermined radio frequency band. A wireless base station device that transmits data to a wireless terminal device via a communication path having a communication candidate channel of the above, and a radio wave detection means for detecting the radio wave of the first communication candidate channel, and whether the data is real-time data. It is characterized by including a communication channel selection means for selecting a communication channel for transmitting data from the first communication candidate channel or the second communication candidate channel according to the non-real-time data.</p><p> Further, in the wireless base station apparatus of the present invention, when the data is real-time data, the communication channel selection means may select a communication channel from the second communication candidate channel.</p><p> Further, in the radio base station apparatus of the present invention, when the data is non-real-time data, the communication channel selection means is the first communication candidate channel or the second communication candidate channel based on the detection result of the radio wave detection means. You may select a communication channel from among.</p><p> Further, in the radio base station apparatus of the present invention, the communication channel selection means may preferentially select a communication channel from the first communication candidate channels.</p><p> Further, in the radio base station apparatus of the present invention, the predetermined radio frequency band may be a radar radio frequency band.</p><p> Further, the radio base station device of the present invention may be installed in a passenger accommodation area of a transportation facility.</p><p> The communication channel selection method of the present invention includes a first communication candidate channel that is included in a predetermined radio frequency band and shifts to another channel when a radio wave of the channel is detected, and a second communication candidate channel that is not included in the predetermined radio frequency band. This is a communication channel selection method for transmitting data between a wireless base station device and a wireless terminal device via a communication path having the same communication candidate channel, and determines whether the data is real-time data or non-real-time data. A data determination step to be performed, and a communication channel selection step for selecting a communication channel for transmitting data from the first communication candidate channel or the second communication candidate channel based on the determination result in the data determination step are provided. It is characterized by that.</p><p> Further, in the communication channel selection method of the present invention, when the data is determined to be real-time data in the data determination step, the communication channel selection step may select a communication channel from the second communication candidate channels. ..</p><p> Further, in the communication channel selection method of the present invention, when the data is determined to be non-real-time data in the data determination step, the communication channel selection step is performed from the first communication candidate channel or the second communication candidate channel. You may select a communication channel.</p><p> Further, in the communication channel selection method of the present invention, the communication channel selection step may preferentially select a communication channel from the first communication candidate channels.</p>

<p> According to the present invention, real-time data such as video and audio information that requires simultaneous transmission can be stably transmitted even in an environment where interference with a radar exists, and high speed is obtained for non-real-time data that does not require simultaneousness. It is possible to provide a wireless transmission system, a wireless base station apparatus, and a communication channel selection method capable of transmitting while maintaining the characteristics.</p>

According to the present invention, when transmitting data from a wireless base station device to a wireless terminal device, real-time data such as video and audio information that requires simultaneity does not interfere with radar. Communication candidate channels (without DFS function) Select a communication channel from (communication candidate channels), and non-real-time data that does not require simultaneity may interfere with the radar. Radar from all communication candidate channels including communication channels (communication channels with DFS function). Select a communication candidate channel that does not interfere with. As a result, real-time data can be stably transmitted without interruption during transmission, and non-real-time data can be transmitted while maintaining high speed.

Hereinafter, the wireless transmission system according to the embodiment of the present invention will be described with reference to the drawings.

(First Embodiment) First, the wireless transmission system according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a block diagram showing a basic configuration of a video / audio information distribution system to which the wireless transmission system according to the present embodiment is applied. Content to be distributed, such as video content and music content, is stored in the content server 101. The stored content is wirelessly transmitted to the wireless terminal devices 104 and 105 and the wireless terminal device 106 via the wireless base station device 103. Although the number of wireless terminal devices is set to three for convenience of explanation, there is no particular limitation on the number of wireless terminal devices, and the number may be set according to the form and scale of the system to be used.

In large transportation such as large passenger aircraft, it may be difficult to cover the entire area of the cabin with one wireless base station device, so a system consisting of wireless base station device 103 and wireless terminal devices 104 to 106. May be installed more than once.

Further, the wireless base station device 103 is connected to an external network 102 such as the Internet as needed. As a result, the wireless terminal devices 104 to 106 can connect to a website to acquire information and send / receive e-mail.

It is also conceivable to install a plurality of wireless base station devices 103 and use them separately for real-time data and non-real-time data.

FIG. 2 is a block diagram showing a configuration of a part related to communication channel selection of the wireless base station apparatus 103 used in the wireless transmission system according to the present embodiment.

The transmission data to be transmitted to the wireless terminal devices 104 to 106 is first stored in a predetermined frame format by the frame processing unit 201, digitally carrier-modulated by the modulation unit 202, and further converted to an appropriate transmission frequency by the transmission unit 203. After being amplified, it is transmitted as an RF signal in the air. OFDM, BPSK, QPSK, 16QAM, etc. are used as digital carrier modulation in wireless LAN.

On the other hand, the data is determined whether the transmitted data is real-time data that requires simultaneity such as video / audio information during streaming, or non-real-time data that does not require simultaneity such as control information or video / audio information during download. The determination is made by the unit 206, and the determination result is input to the communication channel selection unit 205 as the synchronism identification information. For example, the content server 101 may add simultaneity identification information for each content and transmit the data. Alternatively, a method of transmitting the simultaneity identification information in advance for each content by a command may be used. The addition of the simultaneity identification information can be manually written by the user in advance according to the content and usage method of each content. Alternatively, the content server or the like can automatically add the content according to the attribute of the content (for example, the extension of the file). Further, the radar wave detection unit 204 detects whether or not there is an operating radar in the vicinity of the radio base station device 103, and the detection result is input to the communication channel selection unit 205.

The communication channel selection unit (communication channel selection means) 205 transmits the simultaneity identification information which is the judgment result from the data judgment unit (data judgment means) 206 and the radar wave detection result of the radar wave detection unit (radio wave detection means) 204. The communication channel with the wireless terminal devices 104 to 106 is selected from the first and second communication candidate channels. Here, the first communication candidate channel is a communication candidate channel included in the radio frequency band used for radar, and when a radar wave is detected, it shifts to another channel by the DFS function, and is a second communication candidate. A channel is a communication candidate channel that is not included in the radio frequency band used for radar.

First, when the simultaneity identification information indicates "simultaneity unnecessary", all communication candidate channels are selected. In the case of FIG. 6, all 8 channels are candidates. Under that condition, if there is a communication candidate channel that interferes with the radar wave based on the radar wave detection result, that channel is avoided and the communication channel is selected.

Next, when the simultaneity identification information indicates "simultaneity required", the communication channel selection unit 205 selects a communication candidate channel (second communication candidate channel) outside the radar frequency band as a communication channel selection candidate. To. In the case of Fig. 6, one of the four communication candidate channels of 5.18 to 5.24 GHz will be selected. In this case, even if the radar wave detection unit 204 does not detect the radar wave, the communication candidate channel (first communication candidate channel) in the radar frequency band is not selected. When a communication candidate channel within the radar frequency band is used, the DFS function communicates when the radar operation is started during transmission of video and audio information, or when a new radar is detected due to the movement of an aircraft or the like. This is because it is necessary to change the channel, and the transmission of video and audio information is interrupted.

In the above description, the data determination unit 206 is provided in the wireless base station device 103, but the data determination unit 206 includes a content server 101 installed outside the wireless base station device 103, a control device that controls the entire system, and the like. It may be provided (not shown). In this case, the communication channel selection unit 205 receives the simultaneity identification information directly from the outside.

As a specific example, when the data determination unit 206 is provided in the content server 101, the content server 101 can identify whether the data to be transmitted is real-time or non-real-time, so that the communication channel selection unit 205 Information is transmitted to the communication channel selection unit 205 inside the radio base station apparatus 103 via the communication path. Not limited to this example, various modifications are possible.

Further, since the communication channel selection unit 205 is generally mounted on the CPU inside or outside the wireless chip, the CPU should input the radar wave detection unit 204 and the simultaneity identification information and transmit the transmission unit 203. It is configured to select a channel. Such various mounting methods are possible.

FIG. 3 is a flowchart showing an operating procedure of the wireless transmission system according to the present embodiment. In FIG. 3, the communication channel selection unit 205 reads the simultaneity identification information of the transmission data in step S101, and determines in step S102 whether or not the transmission data requires simultaneity. If it is determined in step S102 that the information requires simultaneity (when "YES"), it is actually used from the communication candidate channels (second communication candidate channel) outside the radar frequency band in step S103. Select the communication channel to use.

On the other hand, if it is determined in step S102 that the information does not require simultaneity (in the case of "NO"), the process proceeds to step S104, and the radar wave detection result is read from the radar wave detection unit 204. After that, in step S105, the communication channel selection unit 205 actually uses the communication channel among all the wireless communication channels, excluding the communication candidate channel having radar wave interference detected in step S104. Select.

When the communication channel is selected by the above operation and the transmission data is transmitted, the next transmission data is waited in step S106. If the simultaneity identification information is transmitted to the radio base station apparatus 103 by a command in advance, the processes of steps S101 and S102 may be executed at least once. That is, if the information requires simultaneity, the process of step S103 is executed, and if the information does not require simultaneity, the processes of steps S104 and S105 are repeated. At this time, the process of step S106 is skipped.

Further, since the DFS function (not shown in FIG. 3) by the radar wave detection unit 204 is normally always in operation, the communication channel selected in step S105 is a communication candidate channel within the radar frequency band (No. 3). In the case of 1 communication candidate channel), if interference with the radar wave is detected by the DFS function, it moves to another communication candidate channel within the radar frequency band, or communication outside the radar frequency band. It is possible to move to a candidate channel.

In the present embodiment, all channels are selected for non-real-time information. However, for example, when the amount of non-real-time information is small, a channel affected by DFS may be selected in advance. ..

(Second embodiment) Next, the wireless transmission system according to the second embodiment of the present invention will be described with reference to the flowchart showing the operation procedure of FIG. In the flowchart of FIG. 4, the same operation steps as those of the flowchart of FIG. 3 are designated by the same reference numerals. In FIG. 4, when the simultaneity identification information of the transmitted data needs to be simultaneous (when YES in step S102), the communication channel is set according to steps S101 to S103 as in the case of FIG. Select from the communication candidate channels (second communication candidate channel) outside the radar frequency band. On the other hand, when the simultaneity identification information does not require simultaneity (when NO in step S102), the communication channel selection unit 205 reads the radar wave detection result from the radar wave detection unit 204 in step S104, and then the communication channel selection unit 205 reads the radar wave detection result from the radar wave detection unit 204. In step S107, it is detected whether there is a communication candidate channel available in the radar frequency band.

As shown in Fig. 6, in the case of the 5 GHz band, the radar frequency band includes four communication candidate channels (first communication candidate channel), and one of them has an interference relationship with the radar wave. But the remaining three are available. If it is determined in step S107 that there is a communication candidate channel available (if "YES"), the process proceeds to step S108, and the communication channel is selected from the communication candidate channels within the radar frequency band without radar wave interference. Do.

If it is determined in step S107 that all communication candidate channels in the radar frequency band interfere with the radar wave, that is, there are no available communication candidate channels (in the case of "NO"), the process proceeds to step S109. To do. In step S109, the communication channel selection unit 205 selects a communication channel from a communication candidate channel (second communication candidate channel) outside the radar frequency band.

As a result, when the transmission data does not need to be simultaneous, the communication channel selection unit 205 first gives priority to the selection of the communication candidate channel (first communication candidate channel) in the radar frequency band, so that the transmission data can be transmitted at the same time. It is possible to preserve the communication candidate channel (second communication candidate channel) outside the radar frequency band used in the case of video / audio information that requires sex.

Even if the communication candidate channel in the radar frequency band is selected as the communication channel in step S108, if the radar wave detection unit 204 detects a radar wave that interferes with the communication channel from the middle, DFS Depending on the function, the communication channel selects a communication channel from other communication candidate channels in the radar frequency band. At this time, the wireless transmission is interrupted, but in the present embodiment, the transmission data that requires simultaneity is not sent to the communication channel that may be interrupted, so that the interruption or noise in the reproduction of the video / audio information is caused. It never happens.

When the simultaneity identification information is transmitted to the radio base station apparatus 103 by a command in advance, the processing is the same as that of the first embodiment, and the differences are that steps S107, S108, and step S109 are added. That is the point.

FIG. 5 shows a configuration example in which the wireless transmission system according to the embodiment of the present invention is installed and used in a transportation means such as a passenger aircraft. Screen display units 311 to 313 and audio reproduction headsets 321 to 323 are attached to passenger seats 301 to 303. That is, each passenger views the video / audio information by the screen display units 311 to 313 and the audio reproduction headsets 321 to 323. A wireless access point 330 is installed on the side wall or ceiling of the passenger accommodation area and is connected to the content server 101 and other wireless access points by a wired cable 331.

At this time, the wireless access point 330 is a wireless base station device 103 itself or a wireless transmission / reception unit mainly composed of the wireless base station device 103, and communicates with a plurality of wireless terminal devices 104 to 106.

The screen display units 311 to 313 are thin display devices using, for example, a liquid crystal display, and are attached to the back surface of the backrest of each passenger seat 301 to 303. In addition, wireless terminal devices 104 to 106 are built in the screen display units 311 to 313, respectively, and receive and display various contents transmitted from the wireless access point 330.

The audio reproduction headsets 321 to 323 are used as stereo headphones for the audio information among the video / audio information received by the wireless terminal devices 104 to 106.

Large passenger aircraft, train cars, etc. have a large number of seats of several hundred or more, so it is common to prepare multiple sets as shown in Fig. 5 to cover all seats.

In the above description, the wireless terminal devices 104 to 106 are built in the screen display units 311 to 313, but they are built in their own housing and the video signal is transmitted from the housing to each screen display unit 311 to. The audio information may be output to 313 to each audio reproduction headset 321 to 323.

As described above, according to the wireless transmission system according to the embodiment of the present invention, real-time data such as video and audio information that requires simultaneity does not interfere with radar as a communication candidate channel (without DFS function). Select a communication channel from (communication candidate channels), and non-real-time data that does not require simultaneity may interfere with the radar. Radar from all communication candidate channels including communication channels (communication channels with DFS function). Select a communication candidate channel that does not interfere with. As a result, real-time data such as video / audio information during streaming can be stably transmitted without interruption during transmission, and non-real-time data such as video / audio information during download can be transmitted while maintaining high speed. Can be done.

In addition, it is not necessary to have a database of radars that can be detected for each place where the device is installed. Since ground exploration satellites and meteorological satellites move by themselves and change the transmission direction in time toward the earth, the database becomes large and complicated by the conventional method. Therefore, it is a great advantage for the system to be able to omit the work of creating this database. In addition, it is not necessary for the user to input his / her own position information, which changes from moment to moment in a moving body such as an aircraft, or to acquire it from GPS or the like and perform complicated arithmetic processing. This makes it possible to build a small-scale, low-cost system.

Furthermore, by preferentially assigning a communication channel having a DFS function to a non-real-time data communication channel, the communication candidate channel assigned to the real-time data is not used for non-real-time data transmission, so that more stable real-time data transmission is performed. Can be done.

In the above embodiment, the video / audio information from the content server 101 and the information such as the WEB screen and e-mail from the external network 102 are transmitted from the same wireless base station apparatus 103 (wireless access point 330) in a time-divided manner. Although it has been explained that transmission is performed to 104 to 106, different radio base station devices may be used depending on the type of information.

Further, in the above embodiment, the case where the channel (frequency) to be used is changed due to the influence of the radar is taken as an example, but it is clear that the effect peculiar to the present invention is obtained even when the channel is changed by other than the radar. Yes, and therefore are not excluded from the scope of the invention.

Further, in the above embodiment, an example of determining the frequency to be used for each individual radio base station device 103 has been described, but when a plurality of radio base station devices are installed, each radio base station as a whole system The frequency used by the device may be determined. As a specific example, radar detection information is aggregated in the content server 101, the content server 101 determines the frequency used by each wireless base station device 103 as a whole system, and each wireless base station device 103 is given a command or the like. You may send an instruction or the like.

Further, in the above embodiment, an aircraft is taken as an example, but the radar is not limited to this, and the detected radar changes with time even at a stationary position, so that the radar is not limited to a moving object such as an aircraft. In all cases that may be detected, the invention is valid and therefore does not exclude it from the scope of the invention.

INDUSTRIAL APPLICABILITY The present invention is useful for a wireless transmission system, a wireless base station apparatus, and a communication channel selection method for wirelessly transmitting video and audio information that are required to be simultaneous in a passenger transportation system such as a passenger aircraft.

<figref num="1">A block diagram showing a basic configuration of a wireless transmission system according to the first embodiment of the present invention.</figref><figref num="2">A block diagram showing a configuration of a part related to communication channel selection of the radio base station apparatus according to the first embodiment of the present invention.</figref><figref num="3">A flowchart showing an operating procedure of a wireless transmission system according to the first embodiment of the present invention.</figref><figref num="4">A flowchart showing an operating procedure of a wireless transmission system according to a second embodiment of the present invention.</figref><figref num="5">The figure which shows the configuration example in the case where the wireless transmission system in embodiment of this invention is installed and used in a transportation system.</figref><figref num="6">The figure which showed the frequency map which shows the wireless communication channel of IEEE802.11a in Japan</figref>

Code description

101 Content Server 102 External network 103 Radio base station equipment 104 ~ 106 Wireless terminal device 201 Frame processing unit 202 Modulator 203 transmitter 204 Radar wave detector (radio wave detection means) 205 Communication channel selection unit (communication channel selection means) 206 Data judgment unit (data judgment means) 301 ~ 303 Passenger seats 311 ~ 313 Screen display unit 321 ~ 323 Audio playback headset 330 wireless access point 331 Wired cable