JP2000224089A - Stratosphere radio repeating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stratosphere radio repeating system which does not degrade the communication quality, even when a frequency reusing technique is used or the moving amount of a platform is large. SOLUTION: Platforms 11, 12, and 13 respectively emit radio beams to beam irradiating areas 101, 102, and 103. Here, the platforms 11, 12 and 13 use a cental area A as a common service area. In addition, the platforms 11, 12, and 13 are positioned sufficiently far from each other, so that the movement of each platform by winds does not affect the other platforms. Even when the platform 11 is moved by a wind, namely, the other platforms 12 and 13 are located at distant positions where they are uncorrelated with the effects of the wind.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stratospheric radio relay system in which a platform having a radio relay function is arranged in the stratosphere and wireless communication is performed via the stratosphere platform.

[0002]

2. Description of the Related Art A stratospheric radio relay system has been developed in which an airship or the like having a radio relay function is arranged about 20 km above the ground and a ground communication station or a communication terminal communicates via the airship or the like. 2. Description of the Related Art As a conventional stratosphere wireless relay system, for example, as disclosed in Japanese Patent No. 25555510, there is a system based on a single platform in which one balloon or airship having a wireless relay function is placed in the stratosphere. The platform refers to a balloon or an airship having a wireless relay function. There is also a method in which a plurality of platforms having mutually different service areas are placed in the stratosphere, and the platforms are connected by optical communication to form a wide-area communication network. The platform provides a communication relay service to mobile terminals on the ground, for example.

[0003]

However, a platform placed in the stratosphere may move horizontally and vertically under the influence of wind. In that case, in order to keep the communication service area in charge constant, it is necessary to perform control to change the directivity direction of the antenna mounted on the platform, that is, the gain pattern.

However, when a multi-beam antenna is used to subdivide the frequency and allocate the subdivided frequency to each service area to obtain more communication capacity in a limited frequency band, the gain pattern must be highly accurate. Is difficult to control. In addition, when the horizontal movement amount of the platform is relatively large with respect to the spread of the service area, it becomes difficult to control the directivity of the antenna with high accuracy. If accurate antenna pointing control and gain pattern control in the platform are not executed, communication quality will be degraded.

Accordingly, an object of the present invention is to provide a stratospheric radio relay system that does not degrade communication quality even when a frequency reuse technique is used or when the amount of movement of a platform is large. .

[0006]

In the stratospheric radio relay system according to the present invention, there is an area where the beam irradiation by a plurality of platforms overlaps, and the platform that irradiates the beam has a correlation with the movement by the wind that is uncorrelated with each other. At a certain position. Therefore, in that area, the platform can have a diversity configuration, and communication quality can be improved.

[0007] Each platform for irradiating an area where beam irradiation overlaps and a communication terminal in the area are:
It may be configured to perform communication by spread spectrum modulation.

[0008] Each platform may be configured to use different spreading codes. In that case, even if the same frequency is used on the platform,
Identification of the spreading code can reduce frequency interference from other platforms.

[0009] Each platform and the communication terminal may be configured such that when the interference noise from another platform exceeds a reference value, the data communication speed is reduced and the error correction coding rate is increased. In that case, communication quality can be further improved.

A communication terminal in an area where beam irradiation overlaps may be configured to select a platform having the smallest elevation angle as a communication partner. In that case, it is possible to minimize the change in the relative positional relationship due to the movement of the platform or the communication terminal.

[0011] The communication terminal includes a variable beam direction antenna, a control unit for detecting a platform having the smallest elevation angle and controlling the antenna to point in the direction, and a camera for capturing an image of the platform. It may be. According to such a configuration, the platform having the smallest elevation angle can be easily captured.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram showing one configuration example of a stratospheric wireless relay system according to the present invention.
FIG. 1 shows a platform 11 with three airships,
12, 13 are shown. Each platform 11,
Reference numerals 12 and 13 denote beam irradiation areas 101 and 10, respectively.
2, 103 are irradiated with a radio beam. Here, the three platforms 11, 12, and 13 use the central area A as a common service area. That is, a communication terminal (not shown) existing in the area A can communicate with any of the platforms 11, 12, and 13.

Further, three platforms 11, 1
2 and 13 are located far enough apart so that the effects of the movement by the wind are uncorrelated with each other. That is, for example, even if the platform 11 is moved by the wind, the platforms 12 and 13 are located at such separated positions that there is no correlation with the influence of the wind moving the platform 11. Since the influence of the wind can be known based on meteorological knowledge and the like, the three platforms 11, 12, and 13 can be arranged so that the influence of the wind is almost uncorrelated.

As shown in Japanese Patent No. 25555510, generally, each platform 11, 1
The mechanisms 2 and 13 are provided with a mechanism for generating a propulsive force for correcting the position against the wind.

Then, each of the platforms 11, 12,
Reference numeral 13 performs wireless communication relay between a ground station and mobile terminals in a service area. In FIG. 1, an area B is a service area in which a communication service is provided only by the platform 13.

FIG. 2 shows each of the platforms 11, 12,.
13 is a block diagram illustrating an example of the configuration of FIG. In the example shown in FIG. 2, each of the platforms 11, 12, and 13 includes an antenna 1, a wireless transceiver 2, a system control unit 3, a GPS receiver 4 including a GPS antenna, a thrust generating mechanism 5, and a beam forming a multi-beam. A forming part 8 is provided.
The system control unit 3 monitors the reception status of the platform, and notifies necessary information to communication terminals and ground stations in the service area using a network management line different from the communication line. In addition, the GPS receiver 4 is a GPS receiver.
It receives data from satellites, detects its own location, and notifies the location information to communication terminals and ground stations within the service area using a network management line.

FIG. 3 is a perspective view showing an example of the communication terminal. The communication terminal shown in FIG. 3 has a keyboard 31 and a display 32, and is provided with a helical antenna 33 for communicating with a platform. At the tip of the rod-shaped helical antenna 33, a camera 34 is installed.

FIG. 4 is a block diagram showing a configuration example of the communication terminal. As shown in FIG. 4, the communication terminal has a beam control unit 41 that variably controls a beam direction by moving a helical antenna 33. Further, it has a transmission / reception splitter 42, a transmission unit 43, a reception unit 44, a control unit 45, a keyboard interface 46, and a display interface 47. The control unit 45 instructs the beam direction to the beam control unit 41 based on the position information from the platform and the image of the platform captured by the camera 34.

Next, the operation will be described. First, the relay service for the area A shown in FIG. 1 will be described. As described above, the three platforms 11, 1
2 and 13 are located far enough apart so that the effects of the movement by the wind are uncorrelated with each other. Each platform 1
1, 12 and 13 have a propulsion generating mechanism 5 against the wind, but when receiving a wind power exceeding the propulsion capacity, the platform moves. as a result,
The service area by the platform moves.

However, each of the platforms 11, 12,
13 are located far enough apart so that the vertical and horizontal movements are uncorrelated, so that even if the service area by one platform moves, the other platform will cover the service area. That is, the area A
Communication terminals within can receive another platform communication service. In other words, when the movements due to the wind are mutually uncorrelated, the service interruption time can be mutually complemented.

For example, a time rate of 99% within a predetermined range
Platforms 11, 12, 13 that can be stopped at
When the communication service for the area A is provided in the above, the service interruption time rate is 1% × 1% × 1% = 0.001%, and the communication service available time rate is 100% −0.001%. = 99.999%.

That is, this embodiment has a kind of diversity configuration in which a plurality of platforms 11, 12, and 13 mutually complement a communication service. Therefore, system reliability can be improved as compared with a system using a single platform or a system in which a plurality of platforms are in charge of different service areas.

When a plurality of platforms 11, 12, and 13 arranged in the stratosphere provide communication services to the same area A, the platforms 11, 12, and 13 use different frequencies as communication lines. In this case, it is not necessary to consider the frequency interference of the platform. However, if different frequencies are assigned, frequency resources are wasted.
Therefore, it is desirable to use a frequency reuse technique.

For example, spread spectrum modulation is used for communication between the communication terminal and the platform, and different spread codes are used for communication with the respective platforms 11, 12, and 13. Each platform 1
The system control unit 3 in 1, 12, 13 notifies the spreading code to be used by a network management line having a frequency different from that of the communication line.

The spreading code notification function by the system control unit 3 is performed by three platforms 1 in charge of the area A.
One of 1, 12, and 13 may have. In this case, the type of the spreading code to be used in the communication with the platforms 11, 12, and 13 is notified from the one platform to the communication terminal.

Therefore, what kind of spreading code should be used by the control unit 45 in the communication terminal shown in FIG. 3 and FIG. 4 when performing communication with a certain platform? Can be recognized. Control unit 4
5 transmits the recognized spreading code to the transmitting unit 43 and the receiving unit 44
Notify. The transmitting unit 43 and the receiving unit 44 perform spread spectrum modulation and demodulation using the notified spreading code.

As described above, each platform 11,
Even when the same frequency is used in the communication with the devices 12 and 13, the spread code can be identified to reduce the frequency interference from other platforms. Therefore, FIG.
Three platforms 11, 12, as shown in
The service area (area A) according to No. 13 can be constructed with increased frequency utilization.

However, a single platform 1
3 compared with the area B where the communication service is provided by
It is undeniable that the line quality in the area A deteriorates. Therefore, in order to prevent the communication quality from deteriorating in the area A, the system control unit 3 in each of the platforms 11, 12, and 13
The following control is also performed.

When the interference received from another platform for communication with a communication terminal in the service area exceeds an allowable value, the system control unit 3 controls the data transmission rate and increases the error correction coding rate. I do.
Note that an error correction code is usually added to data from a communication terminal. Specifically, the system control unit 3 monitors the signal power to noise power ratio in the receiving unit of the transceiver 2, and when the value falls below the reference value, determines that the interference has exceeded the allowable value. The communication terminal may monitor whether the interference exceeds an allowable value. In this case, if the code error rate of the received data exceeds a reference value, it may be determined that the interference exceeds the allowable value.

When the system control unit 3 detects that the interference received from another platform has exceeded the allowable value, the system control unit 3 sends a signal to the communication terminal via the network management line.
The data transmission rate is reduced and the error correction coding rate is increased so that the effective transmission rate is not reduced.

In monitoring the signal power to noise power ratio or the bit error rate, not only the interference noise received from other platforms but also the overall noise including the thermal noise of the own system is monitored. Eventually, the control is performed so that the total noise corresponding to the reference value for monitoring is kept below a certain value. In addition, even when the information transmission speed decreases when such a variable coding rate communication method is adopted, the communication capacity seen from the communication terminal increases according to the number of platforms constituting diversity, so that a single platform Thus, a throughput comparable to the information throughput in the area B can be realized.

That is, the communication terminals existing in the area A are:
For example, after obtaining a high communication service available time rate of 99.999%, it is possible to obtain the same communication quality as the communication terminal in the area B.

FIG. 5 shows the platforms 11, 12, 1
FIG. 4 is an explanatory diagram showing a state of beam irradiation switching control by No. 3; As shown in FIG. 5, for example, the platform 11
Uses a multi-beam and constantly irradiates the beam to areas C1, C2, and C3 with high traffic densities, and intermittently irradiates beams to areas C4, C5, and C6 with low traffic density. In addition, about the size of the traffic,
It is determined in advance based on population density. The system control unit 3 in the platform 11 outputs information for sequentially specifying an irradiation area to the beam forming unit 8 so that the areas C4, C5, and C6 are sequentially irradiated with the beam. The beam forming unit 8 sequentially irradiates the area C4, C5, C6 with a beam according to the information.

Therefore, the communication terminals existing in the areas C4, C5 and C6 receive the communication service in a time division manner. However, the relay device mounted on the platform 11 does not have to perform the relay operation in all of the six areas C1 to C6, but only has to perform the relay operation in four areas. it can. Although the platform 11 has been described above, the other platforms 12 and 13 perform the same beam irradiation control.

Next, the operation of the communication terminal shown in FIGS. 3 and 4 will be described. The communication terminal existing in the area A can communicate with any of the platforms 11, 12, and 13. In this embodiment, the communication terminal receives the position information from each of the platforms 11, 12, and 13, and Communicate with platforms with small elevation angles.

In communication via a communication satellite, the communication terminal
In many cases, the satellite having the largest elevation angle is selected as the communication target. However, unlike the case of a satellite, when communicating with a platform located in the stratosphere, there is a high possibility that an obstacle in the zenith direction, such as a helicopter rotor blade, will cut off the communication line. It is also conceivable to select the closest platform as the communication target. However, in such a case, when the communication terminal is movable, a change in the relative positional relationship with the platform due to the movement of the communication terminal becomes large. Further, there is a problem that a communication load is concentrated on a platform which is easy to see from the communication terminal and is located at a short distance.

Thus, in this embodiment, the communication terminal selects the platform having the smallest elevation angle from the platforms 11, 12, and 13. Specifically, the control unit 45 of the communication terminal controls each platform 11,
The elevation angles of the platforms 11, 12, and 13 are calculated based on the position information from the platforms 12 and 13. Then, it instructs the beam control unit 41 to direct the beam of the helical antenna 33 to the platform having the lowest elevation angle.

A camera 3 is provided at the tip of the helical antenna 33.
4, the camera 34 captures the image when the helical antenna 33 is directed to the corresponding platform. Therefore, even if the platform moves, the control unit 45 can correct the position of the helical antenna 33 so that the image captured by the camera 34 comes to the center of the video. The image from the camera 34 is displayed on the display 31 via the display interface 47. Therefore, the operator can also correct the direction of the helical antenna 33.

Further, the control unit 45 monitors the reception level of the signal for notifying the position information from the platforms 11, 12, and 13, and corrects the position of the helical antenna 33 so that the reception level becomes maximum. It may be.

As described above, in this embodiment, the communication terminal is configured to communicate with the platform having the smallest elevation angle among the platforms 11, 12, and 13 in the visible range or the range where radio waves can reach. The possibility that the communication load is concentrated on a specific platform or the communication line is cut off is reduced. Furthermore, it is possible to minimize a change in the relative positional relationship due to movement of the platform or the communication terminal. Also, as mentioned above,
Since the communication terminal is provided with a mechanism for facilitating the supplement of the platform, the platform having the smallest elevation angle can be easily captured.

[0041]

As described above, according to the present invention, a stratospheric radio relay system is provided in which an area in which beam irradiation by a plurality of platforms overlaps exists, and the beam irradiating platform has a movement by wind force. Since the configuration is arranged at a position where there is no correlation, there is an effect that the reliability of the system can be increased and the communication quality can be improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a configuration example of a stratospheric wireless relay system.

FIG. 2 is a block diagram illustrating a configuration example of each platform.

FIG. 3 is a perspective view illustrating an example of a communication terminal.

FIG. 4 is a block diagram illustrating a configuration example of a communication terminal.

FIG. 5 is an explanatory diagram showing a state of beam irradiation switching control by a platform.

[Explanation of symbols]

 11, 12, 13 Platform 101, 102, 103 Beam irradiation area 33 Helical antenna 34 Camera 45 Control unit

Claims (6)

[Claims] In a stratospheric wireless relay system that performs wireless communication via a platform arranged in the stratosphere, there is an area where beam irradiation by a plurality of platforms overlaps, and the platform that irradiates the beam with the wind is a wind-powered platform. A stratospheric radio relay system, which is arranged at a position where movements are uncorrelated with each other. 2. The stratospheric radio relay system according to claim 1, wherein each platform for irradiating the beam to the area where the beam irradiation overlaps and a communication terminal in the area communicate by spread spectrum modulation. 3. The stratospheric radio relay system according to claim 2, wherein each platform uses a different spreading code. 4. When each platform and the communication terminal receive interference noise from another platform exceeding a reference value,
The stratospheric wireless relay system according to claim 3, wherein the data communication speed is reduced and the error correction coding rate is increased. 5. The stratospheric radio relay system according to claim 1, wherein a communication terminal in an area where beam irradiation overlaps selects a platform having the smallest elevation angle as a communication partner. 6. A communication terminal, comprising: an antenna with a variable beam direction; a control unit that detects a platform with the smallest elevation angle and controls the antenna to point in that direction; and a camera for capturing an image of the platform. The stratospheric radio relay system according to claim 5.