JP2000013295A - Radio communication system and synchronization multi- carrier multi-beam transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system that utilizes effectively frequencies without the need for much precision for position control of a flying body and to provide a synchronization multi-carrier and multi-beam transmitter that uses a multi-beam antenna array. SOLUTION: In the radio communication system where an airship is resident in the stratosphere, deviation in the directivity characteristic is corrected for a beam position error due to a position shift of the airship by selectively using k-sets of parabolic antennas with directivity closest to a cell going to be sent among parabolic antennas 180-18k+1 and 200-20k+1 or by feeding simultaneously pluralities of the parabolic antennas. An information rate is decreased by sending a multi-carrier signal from multi-carrier transmitters 11-1k so as to reduce a timing error in time division transmission reception and selection of the antennas is made for a guard interval period to reserve stable transmission channels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system and a synchronous multi-carrier multi-beam transmitter, and more particularly to a radio communication system and a synchronous multi-carrier multi-beam transmitter used for a radio relay system in which an airship stays in the stratosphere. .

[0002]

2. Description of the Related Art Transmission of information having a relatively large amount of information such as a digital video signal requires a wide frequency band according to the amount of information. Therefore, transmission is generally performed using a high-frequency carrier. It is. Highly public TV
In broadcasting and the like, the VHF band and the UHF band are used, but in the field of subscriber-based wireless communication having strong personal use characteristics, high frequency bands such as submillimeter waves and millimeter waves are used.

[0003] Conventionally, in the transmission of digital information,
The Internet, which runs communication-type multimedia, is used to transmit digital information by connecting a modem to an ISDN (Integrated Services Digital Network) or analog telephone line. However, the data rate of the Internet is on the order of several tens of kilobits per second, and at most, only information on the order of still images can be transmitted. For transmission of information called multimedia, it is desirable to be able to transmit a moving image of 1 to 6 megabits per second, and it is desired to construct an infrastructure for that.

An optical cable is laid to each home and CATV
If optical fiber networking (fiber-to-the-form (FTTH)), which provides various other communication services, functions, a bit rate enough to transmit moving images can be obtained, but construction of optical cable terminals The cost is extremely high, estimated at 30 trillion yen. This means 300 Japanese households
Assuming that there are 10,000 households, this is a calculation that costs 1 million yen per household. At present, implementing fiber-to-the-form (FTTH) is quite difficult.

There is xDSL as a communication means for securing a transmission rate of several Mbps per second by means other than the optical cable. This method uses a twisted pair telephone line that is wired to the home.In Japan, however, the characteristics of the telephone line vary greatly, making it difficult for the home to reliably compensate for the required transmission rate. In fact, it is difficult to introduce and operate them in practice.

Attention has been paid in this regard to flying objects such as airships and balloons staying in the stratosphere (altitudes of about 10 km to 50 km) where the weather conditions are relatively stable. This is a wireless communication system that performs wireless communication by considering it as such (Yoshihiro Hase et al., "Proposal of high-speed wireless access network using stratospheric wireless platform", IEICE Technical Report, SST97-54, RCS97-93 (1997-09)).

In this wireless communication system, the construction cost of the optical cable is expensive near the residential area of the individual, but since the signal arrives at the window facing the flying object such as an airship, a device for receiving the radio wave from the airship is installed. However, a relatively large amount of information can be introduced into the home. Further, in this wireless communication system, since the flying object such as an airship is hovering at an altitude of about 20 km, the altitude is lower than that of the geostationary satellite, and the transmission power from the terrestrial transmitting terminal is smaller than that of the geostationary satellite. And a short delay time, it is possible to construct a nationwide multimedia network by deploying a large number of wireless platforms.

Conventionally, in a system in which a flying object staying in the stratosphere is regarded as a relay station and performs radio communication, a reference frequency of a radio platform (air station) received from a reference earth station with high frequency stability is high. There is also known a system capable of transmitting a signal having a frequency stability satisfying a requirement of an applied communication system to each user ground station such as a mobile station by reproducing the signal from the signal (Japanese Patent Laid-Open No. 5-25995).
No. 2).

[0009]

However, among the above-mentioned systems for performing wireless communication by regarding a flying object staying in the stratosphere as a relay station, the former one is intended to construct a high-speed wireless ATM network. The stratospheric wireless platform projects about 64 multi-beams, and the coverage (cell) of one beam is set to a cell (about 5 km square) of the same size as the terrestrial cellular system.

[0010] Further, among the above-mentioned systems for performing wireless communication by regarding a flying object staying in the stratosphere as a relay station, the latter system depends on the frequency of a radio signal transmitted from each stratospheric wireless platform (air station). In order to solve the problem that the radio signal interference occurs at a specific position determined by the arrangement condition of each aerial station, the radio signal frequency is made different for each aerial station, so that there is a problem that the frequency utilization efficiency is poor.

At present, the transmission rate of information signals in the Internet communication generally used is 3
0 to 64 kbps. Therefore, information that can be transmitted is naturally limited. Therefore, it is preferable that a communication network capable of transmitting a video of the current TV broadcast quality be prepared, so that a high-quality Internet system is constructed. Therefore, if a communication network capable of using a transmission rate of 6 Mbps per subscriber is to be realized by using a flying object that stays in the stratosphere, the following problem occurs.

That is, the frequency currently considered and internationally assigned to flying vehicles such as airships staying in the stratosphere is 800 even when the 47 GHz band is used.
MHz. If QPSK is used as the modulation method, the obtained transmission rate cannot exceed 1.6 Gbps, and only 200 or more subscribers can be serviced.

Therefore, it is conceivable to provide services to more subscribers by repeatedly using frequencies by area division. As one example, a seven-cell system using seven frequencies is known. However, if the area of the cell is made as small as possible, the number of frequency repetitions can be increased, and the service can be provided to more subscribers. From that aspect, it is preferable that the beam width of the beam antenna mounted on the flying object be as small as possible, and the beam antenna be divided into many cells for use.

On the other hand, in a system in which a flying object staying in the stratosphere is regarded as a relay station and performs wireless communication, a westerly wind is blowing in the stratosphere, so that the flying object moves against the westerly wind and moves with respect to the earth. The technology of position control for controlling and operating the vehicle so that it can be stopped still with high accuracy has been researched and developed.

However, in order to accurately stop the flying object with respect to the earth, a large amount of energy is required for controlling the position of the flying object, but the amount of energy that the flying object can obtain from the solar cell is naturally limited. Therefore, there is naturally a limit to the position control of the flying object.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a radio communication system capable of effectively utilizing a frequency without requiring a great degree of accuracy for position control with respect to a flying object, and a synchronous multi-carrier multi-beam transmitting apparatus using a multi-beam antenna array.

It is another object of the present invention to provide a radio communication system and a synchronous multi-carrier multi-beam transmission device capable of constructing a high-quality multimedia communication network with a higher transmission rate.

[0018]

In order to achieve the above object, a system according to the present invention is provided in a wireless communication system for wirelessly transmitting a digital information signal to the ground in a high frequency band from a flying object such as an airship staying in the stratosphere. An area composed of a plurality of cells, which is a terrestrial reception area for receiving signals of different frequencies, is arranged so that cells in adjacent areas are repeatedly used so as to receive signals of different frequencies. Is converted into multi-carrier signals of different frequencies in a high frequency band by a number corresponding to a plurality of cells in the area, and when the plurality of multi-carrier signals are set as one set, the number of areas to be transmitted is set. Generates multiple multi-carrier signals and projects the beam individually to all cells that make up the area to be transmitted. At this time, the directions of the beam antennas equal to or greater than all the cells constituting the area to be transmitted are detected, and a beam antenna having directivity closest to the cell to be transmitted among the beam antennas is selected and used. And transmitting a multicarrier signal to all cells constituting an area to be transmitted from the flying object.

According to the present invention, by selecting and using a beam antenna having directivity closest to the cell to be transmitted among the beam antennas, the beam direction of the antenna is corrected according to the position of the flying object and transmitted. A multicarrier signal can be individually transmitted to all cells constituting the area to be tried.

In addition, the system of the present invention defines a virtual cell having a midpoint at the boundary between adjacent cells, and, in addition to the beam antenna, the number of virtual cells equal to or greater than all cells constituting the area to be transmitted. Prepare a cell beam antenna, and select and use a directional beam antenna or a virtual cell beam antenna closest to the cell to be transmitted, from the beam antenna and the virtual cell beam antenna. A multi-carrier signal is transmitted to all cells constituting an area to be transmitted. In the present invention, one cell or less, or one cell
Even if there is a beam position error with respect to a cell exceeding the cell, the beam direction can be corrected in accordance with the error.

Further, the present invention provides a method of simultaneously supplying the same multicarrier signal to a plurality of beam antennas among the beam antennas instead of selecting and using the beam antennas, and transmitting the signals using a combined beam of the plurality of beam antennas. A multi-carrier signal is transmitted to all cells constituting an area to be used. According to the present invention, even if there is a beam position error with respect to a cell that is equal to or less than one cell or exceeds one cell without using the virtual cell beam antenna, it is possible to correct the beam direction corresponding to the error.

Further, the multi-carrier signal has a guard interval period, and the selection and use of the beam antenna can be switched by using the guard interval period. This is desirable because the occurrence of odor can be reduced.

Further, the transmitting apparatus of the present invention has a configuration capable of realizing the above-described radio system of the present invention. When the cells in the area to be used are repeatedly used so as to receive signals of different frequencies, the number of beams of the beam antenna array mounted on the apparatus is equal to or larger than all cells constituting the area to be transmitted. The first beam antenna array, which is a set of antennas that individually project beams to all cells constituting the area to be transmitted, and a plurality of subscriber data are provided in the area. The number of cells corresponding to a plurality of cells is converted into multi-carrier signals of different frequencies in a high frequency band, and the plurality of multi-carrier signals are converted. And a multi-carrier transmitter that generates a plurality of multi-carrier signals by the number of areas to be transmitted when the number of areas to be transmitted is equal to a set, and a displacement between a cell projection position on the cell by the first beam antenna array and the cell. Based on the antenna direction detecting means to be detected, and based on the detection result of the antenna direction detecting means, select and use the directional antenna closest to the cell to be transmitted among the antennas constituting the first beam antenna array. ,
Antenna switching means for transmitting a multicarrier signal from a multicarrier transmitter.

In communication with a subscriber using a flying object such as an airship (hereinafter, referred to as an airship), if transmission and reception of signals are performed for each beam, the total number of subscribers covered by one beam is calculated. It is necessary to have the capacity to cover the transmission rate of It is not difficult to increase the server's capacity for large transmission capacity because the airship has a server.

As a modulation system, a multicarrier is used, so that the communication speed can be kept low, transmission and reception can be switched by time division, and the signal speed on the terminal side is not faster than necessary. Can be set without too much burden on the user. In multi-carrier communication, a multi-level QAM level can be set for each carrier.

[0026]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a synchronous multi-carrier multi-beam transmitting apparatus according to the present invention, and FIG. 2 is an explanatory view of radio wave directivity in an embodiment of the present invention. As shown in FIG. 2, the wireless communication system according to the present embodiment has an airship 1 in the stratosphere at an altitude of about 20 km, as in the above-described stratospheric wireless platform.
1 in the air, and a large-capacity communication device A
It is equipped with a TM (asynchronous transfer mode) switch, a server connected to a large-capacity ATM network, and a synchronous multicarrier transmitting apparatus according to the present invention, and performs wireless communication with a ground station.

This wireless communication system is intended to realize, by a wireless system, an advanced multimedia society which is to be realized by an optical cable. Since free space is used as a transmission line, transmission distortion is small and a geostationary satellite is used. Since the airship 11 stays in the low altitude compared to the conventional system, the delay time is small, and the cost for realizing the airship 11 is lower than that of FTTH or the like. Has the features as they are.

Further, in this embodiment, in addition to the above-mentioned features, effective use of frequency is also realized by the following method. Here, the used frequency is a submillimeter wave band or a millimeter wave band, and a frequency band of about 800 MHz is secured. The transmission bandwidth required by multimedia is 6 Mbp per subscriber required by the main level of MPEG-2.
want to secure more than s. If the transmission frequency is 47GH
In the case of using the z band, a parabolic antenna having a diameter of 10 cm realizes a half-value angle of 5 degrees as directivity. For this reason, when this parabolic antenna is used, as shown in FIG. 2, communication can be performed under the airship 11 in an area 12 having a diameter of 1.7 km, and the elevation angle with respect to the airship 11 is 45 degrees (distance is 28 km). The service area 13 whose angle is 5 degrees has an elliptical shape with a short axis of 2.5 km and a long axis of 3.5 km.

That is, even if the frequency used for communication is common, a service can be provided to subscribers existing in a plurality of different areas. That is, in the present embodiment, as described later, a plurality of antennas having different directivities are mounted on the airship 11, and communication is performed by dividing the communication regionally, thereby achieving effective use of frequency.

FIG. 3 shows an arrangement of a beam pattern of a transmission wave projected on the ground by a parabolic antenna array mounted on the airship 11. Each beam shown here provides services to different subscribers, but adjacent beams need to communicate at different frequencies to prevent mutual interference. That is, it is necessary to set a plurality of frequencies so that the same frequency is not used in adjacent areas. For example, in FIG. 3, different frequencies are used in an area 15 painted black at the center and six areas adjacent thereto.

Further, in this embodiment, an area composed of a plurality of cells, which is a terrestrial reception area for receiving signals of different frequencies, is repeated so that cells of adjacent areas also receive signals of different frequencies. To use. That is, FIG. 4 shows an arrangement of frequency repetition of 7 waves and 7 cells repetition in one embodiment of the present invention.
In FIG. 4, one hexagon is one cell, and a number indicates a cell number. The same frequency is used for cells with the same cell number,
Radio communication is performed for cells with different cell numbers using different frequencies. Assuming that adjacent cells use different frequencies, cell numbers 1 to 7 surrounded by a thick solid line
The area consisting of the seven cells is repeatedly used so that cells in adjacent areas also receive signals of different frequencies.

That is, the example of FIG. 4 shows that seven types of frequencies are required. This indicates that, in a subscriber system in which different information is transmitted in each cell, the frequency is required to a greater or lesser degree. Such a cell arrangement itself is conventionally known in the field of mobile communication, but in this embodiment, a multicarrier signal from a parabolic antenna is individually transmitted to each cell. One area in FIG. 3 corresponds to one cell in FIG. In FIG. 4, a repeating unit composed of seven cells is called an area.

A case is considered in which a multimedia signal including a video of a current broadcast grade is transmitted in the cell having the above configuration. When transmitting a signal on the order of the main level of MPEG-2, a minimum transmission rate of 6 Mbps is required as described above. If an information signal modulated by QPSK is to be transmitted at 6 Mbps, the frequency band required for transmission is 5M if error correction data is included.
Hz is required.

MPE for each beam (for each cell)
When trying to provide G-2 main level services per subscriber, the frequency required here is 35 (= 5 ×
7) MHz, 7 when trying to secure this in both directions
0 MHz is required. If only a frequency band of 700 MHz can be secured, the number of terminals is limited to 20 per area even if only one-way service is considered.

In order to cope with this situation, communication is performed using a cell as small as possible. However, along with that, the beam width of radio waves used for transmission and reception has also become narrower,
When the airship shakes, the beam deviates from the cell, the attenuation of the transmission path increases, and it is not preferable that the airship receives interference from signals for neighboring cells transmitted at the same frequency. The following measures have been taken.

Next, a modulation / demodulation system used in the radio communication system according to the present embodiment will be described. In the case of providing services to individual subscriber systems using multi-beams, signals between seven adjacent areas (beams) need to be transmitted in a separable state. Methods for separation include time division, frequency division, and code division. In the case of time division and code division, it is necessary to set the operation time of the demodulation circuit faster than that of frequency division, and this is not a very good method when trying to handle a 6 Mbps video signal. Therefore,
A method for implementing these functions by frequency division is adopted.

In the frequency division, the modulation signal is composed of multi-carriers, and a symbol period is provided for the same period in order to maintain orthogonality between the multi-carriers. That is, in generating a multicarrier signal in which a large number of carriers to be frequency division multiplexed are dispersed and modulated by one information signal, a symbol period in which a digital data sequence indicating information signal content to be a modulated signal is arranged is defined by each multipath. The same is assumed for the carrier signal.

There are the following two methods for frequency division. The first frequency division method is a method of dividing the entire transmittable frequency band into seven divided frequency bands indicated by 21 to 27 as shown in FIG. Here, seven divisions are taken as an example, but the number of divisions is determined according to the system to which the system is applied, and it is needless to say that the number of divisions is not limited to this.

According to the second frequency division method, as shown in FIG. 6A, a plurality of carriers are arranged at a predetermined frequency interval (for example, 100 kHz interval) in the entire transmittable frequency band. As shown in FIG. 6 (b), transmission of a plurality of carriers (every plural
In the example of (b), nine lines are used, and they are dispersed and modulated with digital data and multiplexed and transmitted. In the second frequency division method, the total number of carriers transmitted in all frequency bands is, for example, p × q (where p ≦ q) in which all used frequency bands are arranged at predetermined frequency intervals.
q) Of the q carriers, a total of p sets of carrier groups different from each other consisting of q carriers are obtained, so that each set of carrier groups is multiplexed as one multicarrier signal. In other words, when the number of repetition frequencies is r and the transmission cell number is s, s, r + s, 2r +
s,. . . , Nr + s is assigned to the cell of transmission cell number s.

Compared to the first frequency division method shown in FIG. 5, the second frequency division multiplexing method shown in FIG. 6 transmits over a wide frequency band, and thus is slightly advantageous for frequency selective fading. is there. In other words, in the first frequency division method shown in FIG. 5, the predetermined carrier frequency is canceled by the influence of the multipath in the opposite phase, and when there is a sharp level drop, the level of the carrier adjacent in frequency is also greatly attenuated. Likely to be. If some of the carriers to be decoded are damaged, the lost data can be recovered by the error correction method. However, if many carriers are damaged at the same time, the error correction method Restoration is difficult. In this sense, the second frequency division method according to FIG. 6 has the effect of frequency interleaving and is advantageous for frequency selective multipath fading.

The wireless transmission of the subscriber system in which the area is limited has been described above. However, in the embodiment of the present invention,
In addition to this, using a beam antenna with a sharp directional pattern, the direction of the beam changes with the shaking of the airship,
At that time, the beam antenna is switched so that the beam direction is always directed to the cell targeted for communication.

Next, an embodiment of the synchronous multi-carrier multi-beam transmitting apparatus according to the present invention will be described with reference to the block diagram of FIG. This embodiment is mounted on an airship 11 staying in the stratosphere, and has a total of k multicarrier transmitters ₁₁ to 1 _k and an antenna direction detector 8.
Antenna switching control circuit 9, antenna switching device 10
And _k with sharp directivity individually connected to the multicarrier transmitters 1 ₁ to 1 _k via the antenna switch 10.
+2 first parabolic antenna 18 ₀ ~ 18 _{k + 1,} multicarrier transmitter via the antenna switching equipment 10 ₁ 1 -
It is composed of a total of k + 2 second parabolic antennas 20 _{0 to} 20 _{k + 1} which are individually connected to 1 _k and have sharp directivity.

The parabolic antennas 18 ₀ to 18 _{k + 1} constitute a first beam antenna array, and the parabolic antennas 20 _{0 to} 20 _{k + 1} constitute a second beam antenna array. Although the first and second beam antenna arrays are arranged one-dimensionally in FIG. 1 for simplicity of explanation, it goes without saying that they are actually arranged two-dimensionally.

The multicarrier transmitter ₁ 1 to 1 _k are each identical configuration, the interface circuit 2 ₁ to 2 _k, multi-frequency oscillator 3 ₁ to 3 _k, the control circuit 4 ₁ to 4 _k, adders 51 _to
5 _k , DA converters 6 _{1 to} 6 _k , and frequency converters 7 _{1 to} 7 _k (in FIG. 1, the multi-carrier transmitter 1 is shown).
Only _one configuration is shown as a representative. ). These multi-carrier transmitter 1 ₁ to 1 _k are normally different subscriber data is inputted to each other, the same information may be inputted. These subscriber data are data transmitted from the ground station, but data stored in a rewritable storage medium or the like can also be used.

In this embodiment, the directions of the parabolic antennas 18 ₀ to 18 _{k + 1} and the parabolic antennas 20 _{0 to} 20 _{k + 1} are detected by the antenna direction detector 8, and the detection signals are transmitted to the antenna switching control circuit. 9. The antenna switching control circuit 9 controls the antenna switching unit 1 according to the input detection signal.
Controls 0, selects the output end of the multi-carrier transmitter ₁ 1 to 1 _k k number of parabolic antennas 18 ₀ ~ 18 _{k + 1,} or k-number of the parabolic antenna 20 ₀ to 20 _{k + 1} Connect.

The antenna direction detector 8 includes a reference signal receiving beam antenna having sharp directivity for receiving a reference signal from a reference signal transmitting station provided on the ground, and an antenna surrounding the reference signal transmitting station. After obtaining the received signals from a plurality of beam antennas for the surrounding area with sharp directivity, and receiving signals from these beam antennas, comparing their signal levels and calculating the antenna direction according to the comparison result And outputs a detection signal.

For example, in FIG. 3, when a reference signal transmitting station is installed in an area 15 on the ground indicated by a black circle,
The direction of the reference signal receiving beam antenna of the antenna direction detector 8 is set so that the signal from the reference signal transmitting station in the area 15 can be received at the maximum level, and the other beam antennas of the antenna direction detector 8 are Six beam antennas whose directivity directions are separately set in six areas surrounding the area 15, and their directivity directions are separately set in twelve areas on the outer periphery of the six areas. And 12 beam antennas. In this case, when the position of the airship 11 is at the normal position, the reference signal can be received at the maximum level from the reference signal receiving beam antenna, and the reception level of the reference signal is weak from the other peripheral beam antennas, and the reception signal is low. The level is below a predetermined threshold.

Next, the operation of this embodiment will be described. In Figure 1, subscriber data of the first channel is inputted to the interface circuit 2 ₁ of a multi-carrier transmitter 1 ₁ serially, where it the amount of data that can be transmitted is taken for each symbol period m bits × after being converted into parallel signals of n columns, signal m bits to each oscillator of the multi-frequency oscillator 3 in ₁ made of an oscillator which is arranged on at least n parallel are input as the control signal.

The control circuit 4 _1, or causing any oscillation output of the multi-frequency oscillator 3 ₁ is controlled in response to the signal content to be input. For example, when a multicarrier signal to be transmitted is a signal modulated by 16QAM, the control circuit 4 ₁ based on the 4-bit input subscriber data, 16 multi-frequency oscillator 3 in ₁ (m = 1, (n = 16) is determined. Thus, from the multi-frequency oscillator 3 ₁ is taken out as an equivalent modulator output signal in 16QAM signal.

[0050] Thus, for multi-frequency oscillator 3 number of carriers to be transmitted from the ₁ (where n book), a type of information of the oscillation signal needed by the state of the multi-level In addition, a modulated wave modulated by an m-bit input signal using a predetermined modulation method is dispersed and output by n modulated carriers. The same symbol period of each carrier is modulated with the same data, and the frequency interval of each carrier is set to be an integral multiple of the symbol synchronization frequency.

Multi-frequency oscillator 3₁N pieces taken from
Is modulated by an adder 5₁Frequency division multiplexing
Into one multiplex signal (multi-carrier signal)
Later, the DA converter 6₁Digital-to-analog conversion
And converted to an analog signal. ₁Supply to
The frequency is converted to a millimeter wave band and the antenna switch 10
Is input to

[0052] Similarly, other multi-carrier transmitter 1 ₂ to 1 _k, converts the subscriber data for individual subscribers, each separately multicarrier signal, antenna switching and further frequency-converted into the millimeter wave band Input to the container 10. The k multi-carrier signal in total output from the multi-carrier transmitter 1 ₁ to 1 _k are the same millimeter wave band but different frequency bands, and the second frequency-division multiplexing method shown in FIG. 6, respectively From a plurality of channels.

When the position of the airship on which the synchronous multi-carrier multi-beam transmitter shown in FIG. 1 is mounted is detected by the antenna direction detector 8 as being at a proper position, the antenna direction detector 8 Based on the output detection signal, the antenna switching control circuit 9 controls the antenna switching device 10 so as to supply the output multicarrier signals of the multicarrier transmitters ₁₁ to 1 _k to the parabolic antennas 18 ₁ to 18 _k , respectively.

Thus, the parabolic antennas 18 ₁ to 18 ₁
Each of the multicarrier signals is wirelessly transmitted from 8 _k ,
Project k different narrow beam patterns on the ground,
The subscriber system data is transmitted in the form of a multicarrier signal to the k cells where the beam pattern is located. Here, when k is set to “7”, subscriber data can be transmitted in the form of a multicarrier signal to one repetition area including seven cells shown in FIG.

Here, an error occurs in the position of the airship for some reason such as a westerly wind, and the antenna direction detector 8 detects that the directivity of the mounted antenna has shifted by one cell with respect to each cell. If found,
On the basis of the output detection signal of the antenna orientation detector 8, parabolic antenna switching control circuit 9, each output multicarrier signal of a multicarrier transmitter 1 ₁ to 1 _k to correct the position error according to a position error direction Antenna _180-
The antenna switching unit 10 is controlled so as to supply the antenna switch 18 _k-1 or the parabolic antennas 18 ₂ to 18 _{k + 1} respectively.

[0056] Thus, even if an error occurs in the position of the airship, a multicarrier signal transmitted parabolic antenna 18 ₀ ~18 _k-1, or from parabolic antenna 18 ₂ ~18 k + _1, the airship the normal position , A narrow beam pattern is projected on the same predetermined k cells, and the subscriber data can be transmitted to the k cells in the form of a multicarrier signal.

Here, the radiation of radio waves to the predetermined k cells is transmitted to the predetermined k cells of the parabolic antennas 18 ₀ to 18 _{k + 2} constituting the first beam antenna array. The case where transmission is performed using an antenna having close directivity has been described. However, it is convenient when the amount of displacement is one cell, but when the displacement is less than one cell or exceeds one cell, the cell is shifted. An error of half the size occurs. Therefore, in order to obtain a closer beam, in this embodiment defines a second cell placement across multiple cells, the second parabolic antenna 20 ₀ having directivity corresponding thereto
The beam direction is corrected by using also the second beam antenna array composed of ２０20 _{k + 2} .

FIG. 7 is an explanatory diagram showing a virtual cell arrangement of the second beam antenna array. That is,
The second cell arrangement defines the cells in such a positional relationship as to span three cells in the first cell arrangement. In FIG.
Each cell of numbers 1 to 7 is a cell arrangement for the first beam antenna array, while a thick line 18 indicates the position of the first cell (virtual cell) of the second beam antenna array. This second
The position of the first cell (virtual cell) 18 of the beam antenna array is defined on each of the first, third, and seventh cells of the first beam antenna array, and is placed over an area equal to each cell. Have been. Thus, the cell arrangement of the second beam antenna array is defined as a new cell spanning between the three cells of the first beam antenna array.

When radio waves are emitted from the antenna giving the closest directivity while switching the parabolic antenna mounted on the airship, if only the first beam antenna array cell arrangement is used, the position is shifted by half a cell. Sometimes. In order to obtain a good DU ratio even for a subscriber located near the boundary of a cell with respect to a radio wave emitted from two adjacent distant cells where radio waves are emitted at the same frequency, a fine antenna is used. It is important to be able to adjust the directivity.

The cell arrangement for the second beam antenna array is defined as described above, and the beam antenna array having the closest directional characteristic among the first and second beam antenna arrays is specified and used for communication. Then, the interference signal transmitted from the adjacent antenna separated by two cells and transmitted at the same frequency can be reduced, and a wireless communication network that effectively uses the frequency can be constructed.

The antenna direction detector 8 detects that the reference signal reception levels from the reference signal reception beam antenna and the two neighboring cell beam antennas having the maximum directivity for the two adjacent cells are substantially the same. If
Detects that there is a deviation of the half cell fraction described above, the antenna switching control circuit 9, each output multicarrier signal of a multicarrier transmitter 1 ₁ to 1 _k to correct the position error according to a position error direction parabolic antenna 20 _1-2
0 _k, or a parabolic antenna 20 ₀ ~20 _k-1, or controls the antenna switching unit 10 so that each is supplied to the parabolic antenna 20 ₂ ~20 _{k + 1.}

When the position error of the beam antenna array is small, by arranging two or more reference signal transmitting stations, the position error and the angle error can be corrected, and the position of the beam antenna array can be adjusted. In this way, even when the displacement of the airship is less than one cell or more than one cell, the parabolic antennas 20 _{0 to} 20 _{k + 1}
, The error of half the cell size can be corrected, and a sharper beam can be projected onto the desired k cells to transmit a multicarrier signal. As a result, the number of frequency repetitions can be increased (the area of the repetition area can be reduced), and effective use of frequencies can be realized.

FIG. 1 shows an example in which one beam antenna is switched and used one by one with respect to the transmitting apparatus. However, if more beam antennas are used, even if the positional deviation of the antenna becomes large, two cell antennas are used. It is obvious that a larger positional shift can be corrected by connecting to a beam antenna at a position separated by a plurality of cells for three cells.

Here, in the present invention, the speed of the modulation signal is reduced by using a multicarrier. Although it is a short time, a multicarrier signal is provided with a guard interval period to reduce the influence of the multipath even for a multipath used for transmission and reception in a building street. That is, it is well known that a multicarrier signal (OFDM signal) performs data transmission in units of transmission symbols, and each transmission symbol includes an effective symbol period and a guard interval period for reducing the influence of multipath. .

The parabolic antennas 18 ₀ to 18 _{k + 1} , 20 _{0 to} 20 _{k + 1} by the antenna switching device 10 performed under the control of the antenna switching control circuit 9 when the position of the airship deviates.
Is selected during the guard interval of the multi-carrier signal to be transmitted, so that an error component is not mixed into the transmission signal even for a discontinuous signal generated at the time of antenna switching.

As described above, in this embodiment, all the subscribers to receive the service in the frequency band permitted to be used by the airship can transmit and receive various digital information different from each other. Laying optical cables costs about 1 million yen per household, but the communication system using airships allows the entire Japan to be networked with a multimedia communication network due to the equipment burden of about one digit below that cost. .

It should be noted that the present invention is not limited to the above-described embodiment, and various other modifications can be considered. For example, an output signal operating at 47 GHz
It is difficult to switch the antenna to be connected while reducing the loss. Therefore, there is a method of arranging a large number of transmission units in which a millimeter wave transmitter and a beam antenna are integrated, and switching the input signal.

Also, the description has been given of the second beam antenna array in which the cells correspond to the positions complementary to the first beam antenna array. However, this characteristic is based on the plurality of parabolic elements constituting the first beam antenna array. By transmitting simultaneously from the antenna, the characteristics may be realized in a pseudo manner. For example, for the virtual cell 25 shown in FIG. 7, by transmitting simultaneously from three parabolic antennas toward the first, third, and seventh cells, a beam directed to the intersection of these three cells is transmitted. Can fire a signal. Similarly, a beam directed to an intermediate position between the two cells can be achieved by providing the transmit power to two parabolic antennas. However, since the half-width of a beam formed by combining a large number of antennas becomes small, it is necessary to operate while considering the influence.

As another application, there is a method of always supplying power simultaneously to a plurality of beam antennas, reducing the beam width, and increasing the number of frequency repetitions. Furthermore, switching antennas in the millimeter wave band can be technically difficult, and can also provide the same effect as switching the input of a transmitter operating at a relatively low frequency, and the transmission frequency band, and switching the antenna. .

In the above embodiment, the number of parabolic antennas is nine for simplicity. However, as shown in FIG. 4, when there are 49 (= 7 × 7) cells in total, A data multi-carrier transmitter and a parabolic antenna each require 49 or more, and the beam antenna array is composed of more than 49 parabolic antennas. In practice, more than 100 multi-carrier communication devices and corresponding multi-beam arrays are used.

Since the reference signal transmitting station needs to detect not only the displacement of the airship but also the rotation of the airship, it is necessary to install two stations separated by a predetermined distance. It is desirable to set the reference signal transmitting stations at three positions so as to be located at the vertices. In this case, the number of sets of the beam antenna array in the antenna direction detector 8 is, of course, a number corresponding to the number of reference signal transmitting stations.

[0072]

As described above, according to the present invention,
Large-capacity communication equipment and large-capacity ATM for flying objects such as airships
Equipped with a server connected to the network, subscriber data is converted to a multicarrier signal by a multicarrier transmitter, supplied to multiple antennas, and individually transmitted to multiple cells by the narrowed beam, When a beam antenna mounted on a flying object such as an airship shifts, the beam is corrected by switching the antenna or supplying the same multi-carrier signal to multiple beam antennas at the same time to obtain the correct beam position. Control, it is possible to use a sharper beam, increase the number of frequency repetitions, and achieve effective use of the frequency, thus enabling efficient operation of the frequency band and higher A multimedia communication network including a high-quality video signal at a transmission rate can be constructed.

Further, according to the present invention, since a multicarrier is used as a modulation method of a transmission signal, a communication speed can be kept low, transmission and reception can be switched by time division, and a signal on a terminal side can be transmitted. Since the speed is not faster than necessary,
The level of information can be set depending on whether the communicating party is a mobile station or a fixed station because the level of multi-level QAM can be set for each carrier without increasing the load on the hardware. Transmission can be performed.

Further, according to the present invention, the guard interval period can reduce the interference from the delayed signal, and can reduce the occurrence of data errors due to the discontinuity of the signal generated when the beam antenna is switched. A multimedia communication network can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a synchronous multicarrier multibeam transmitting apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of an embodiment of a wireless communication system according to the present invention.

FIG. 3 is a diagram showing an example of a beam pattern projected on the ground.

FIG. 4 is a cell layout diagram using seven frequencies repeatedly for seven cells.

FIG. 5 is an explanatory diagram of a method of dividing a frequency for each frequency band.

FIG. 6 is a diagram illustrating a method of dividing a frequency by using frequencies at predetermined frequency intervals.

FIG. 7 is a diagram for explaining cells located in the middle of a seven-frequency repetition seven-cell arrangement.

[Explanation of symbols]

Reference Signs List 1 ₁ to 1 _k multi-carrier transmitter 2 ₁ interface circuit 3 ₁ multi-frequency oscillator 4 ₁ control circuit 5 ₁ adder 6 ₁ DA converter 7 ₁ frequency converter 8 antenna direction detector (antenna direction detecting means) 9 antenna switching control circuit (the antenna switching means) 10 antenna switching equipment (antenna switching means) 11 airship 18 ₀ ~ 18 _{k + 1} parabolic antenna (first beam antenna array) 20 ₀ to 20 _{k + 1} parabolic antenna (second beam Antenna array)

Claims (7)

[Claims] 1. A wireless communication system for wirelessly transmitting a digital information signal to the ground in a high frequency band from a flying object such as an airship staying in the stratosphere, comprising: a plurality of cells which are reception areas on the ground for receiving signals of mutually different frequencies. The area consisting of, and the cells of the adjacent areas are arranged to be repeatedly used so as to receive signals of different frequencies, a plurality of subscriber data,
The number corresponding to the plurality of cells in the area, converted into multi-carrier signals of different frequencies in the high frequency band, the number of areas to be transmitted when the plurality of multi-carrier signals as a set When generating a plurality of multi-carrier signals by the number of sets and individually projecting and transmitting beams to all cells constituting the area to be transmitted, transmitting all the cells constituting the area to be transmitted Detect the directions of the above number of beam antennas, select and use a directional beam antenna closest to the cell to be transmitted among the beam antennas, and select the area to be transmitted from the flying object from the flying object. A wireless communication system, wherein the multicarrier signal is transmitted to all constituent cells. 2. A virtual cell having a midpoint at a boundary between cells adjacent to each other is defined, and in addition to the beam antenna,
Prepare the virtual cell beam antennas in a number equal to or greater than all the cells constituting the area to be transmitted, and direct the beam antenna and the virtual cell beam antenna to the position closest to the cell to be transmitted. 2. The multicarrier signal is transmitted from the flying object to all cells constituting the area to be transmitted from the flying object by selectively using a beam antenna having a characteristic or the beam antenna for the virtual cell. A wireless communication system as described. 3. In place of the selective use of the beam antennas, the same multi-carrier signal is simultaneously supplied to a plurality of beam antennas among the beam antennas, and the transmission is performed by a combined beam of the plurality of beam antennas. The wireless communication system according to claim 1, wherein the multicarrier signal is transmitted to all cells constituting an area where the wireless communication is performed. 4. The wireless communication system according to claim 1, wherein the multicarrier signal has a guard interval period, and the selection and use of the beam antenna are switched using the guard interval period. 5. A plurality of reference signal transmitting stations for transmitting a reference signal to the flying object are installed on the ground at predetermined intervals of two or more cells, and have directivity to the plurality of reference signal transmitting stations. By comparing each received signal level of a reference signal beam antenna and a peripheral beam antenna having directivity to cells around the plurality of reference signal transmitting stations, the position of the multicarrier signal transmitting beam antenna with respect to the ground is compared. An error is calculated, and based on the obtained position error, the multicarrier signal transmitting beam antenna is selectively used to transmit the multicarrier signal from the flying object to all cells constituting the area to be transmitted. 3. The wireless communication system according to claim 1, wherein: 6. A synchronous multi-carrier transmission device mounted on a flying object such as an airship staying in the stratosphere and wirelessly transmitting a plurality of synchronized multi-carrier signals in a high frequency band to the ground, comprising: An area consisting of a plurality of cells, which is a terrestrial reception area for receiving a signal, is arranged so as to be used repeatedly so that the cells of adjacent areas also receive signals of different frequencies. A first beam antenna array, which is a set of antennas each of which is provided with a number equal to or greater than all the cells constituting the area and which individually projects a beam to all the cells constituting the area to be transmitted, Of the subscriber system data in a number corresponding to a plurality of cells in the area, and multi-carriers of different frequencies in the high frequency band. A multi-carrier transmitter that converts the plurality of multi-carrier signals into signals and generates the plurality of multi-carrier signals as many as the number of the areas to be transmitted when the plurality of multi-carrier signals are grouped; the first beam antenna An antenna direction detecting means for detecting a displacement between a beam projection position of the cell with respect to the cell and the cell by the array; and transmitting the antenna among the antennas constituting the first beam antenna array based on a detection result of the antenna direction detecting means. Antenna switching means for selecting and using an antenna having directivity at a position closest to a cell to be transmitted and transmitting a multicarrier signal from the multicarrier transmitter. . 7. When defining a virtual cell having a midpoint at a boundary between adjacent cells, all cells constituting the area to be transmitted project beams individually to the virtual cell. The apparatus further includes a second beam antenna array including the above-described number of virtual cell antennas, and the antenna switching means includes an antenna forming the first beam antenna array and a virtual beam forming the second beam antenna array. 7. The synchronization according to claim 6, wherein a multi-carrier signal from the multi-carrier transmitter is transmitted by selecting and using a directional antenna closest to a cell to be transmitted among cell antennas. Multi-carrier multi-beam transmitter.