JPH11340890A - Radio communication system and synchronous multicarrier transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use frequencies effectively by mounting communicating equipment with a large capacity and a server on an airship, and individually transmitting subscriber system data from plural antennas to plural cells on ground with narrowed beams, and transmitting broadcast signals to a large number of persons from a single antenna whose directivity is wide. SOLUTION: This synchronous multicarrier transmitter is mounted on an airship, flying in a stratosphere whose altitude is almost 20 km to conduct radio communication with a ground station. Synchronizing multicarrier transmitters 11 -18 are constituted in the same way, and signals to be inputted are made different from each other. The multicarrier transmitters 11 -17 for subscriber's data convert the data for each subscriber's data into multicarrier signals and transmit them via seven individually connected parabola antenna 81 -87 , the directivity of which is sharp to seven cells on ground with millimeter band. The multicarrier transmitter 18 receives data for broadcasting from the ground and projects beams via an antenna 9 for broadcasting whose directivity is broad over a wide range on the ground.

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 multicarrier transmitting apparatus, and more particularly to a radio communication system and a synchronous multicarrier transmitting apparatus 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 irradiates about 64 multi-beams, and the coverage area (cell) of one beam is the same size (about 5 km square) as the terrestrial cellular system, so it is used for broadcasting etc. When used, the coverage is narrow and many frequencies are required.

[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.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a wireless communication system and a synchronous multicarrier transmission device that can effectively use a frequency.

It is another object of the present invention to provide a radio communication system and a synchronous multi-carrier transmission device capable of realizing multipurpose small area broadcasting.

[0013]

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 to be used repeatedly so that cells of adjacent areas also receive signals of different frequencies, and a plurality of cells from the flying object are arranged. The subscriber system data is converted into a multi-carrier signal of a different frequency corresponding to at least a plurality of cells and converted into a multi-carrier signal at a high frequency band, and a plurality of beam antenna arrays in the area corresponding to the total number of cells in a high frequency band. A common transmission signal to be transmitted individually to the cell and transmitted to a large number of people from the projectile is a multi-carrier signal with a different frequency than the multi-carrier signal. And transmitting simultaneously to 2 or more cells through the antenna broad directional characteristic by Chi carrier signal. According to the present invention, a plurality of subscriber-related data can be individually transmitted to scattered cells, and a common transmission signal to be transmitted to a large number of people can be simultaneously transmitted to a plurality of cells.

Further, according to the present invention, a common transmission signal to be transmitted to a large number of persons is broadcast data, and the broadcast data is a modulated signal arranged in an effective symbol period and provided with a guard interval period. A plurality of flying objects that generate modulated broadcast multi-carrier signals of different frequencies from the multi-carrier signals and transmit them through an antenna with broad directional characteristics are arranged, and broadcasts of the same content from multiple flying objects A multi-carrier signal for broadcasting modulated with data for transmission is transmitted at the same frequency. According to the present invention, the buffer from the delay signal can be reduced by the guard interval period, and the broadcast information of the same content can be transmitted from different flying objects at the same frequency.

[0015] To achieve the above object, the transmitting apparatus of the present invention is mounted on a flying object such as an airship staying in the stratosphere, and wirelessly transmits a plurality of synchronized multicarrier signals in a high frequency band to the ground. A multi-synchronous transmitting apparatus, comprising: a beam antenna array that is an aggregate of a plurality of antennas for individually transmitting radio waves to a plurality of cells that are terrestrial reception areas; and a plurality of cells or two or more cells. And a plurality of antennas constituting a beam antenna array for transmitting a radio wave at the same time and having a broader directional characteristic than a plurality of antennas. A plurality of first signals to be converted into signals and supplied to a plurality of antennas for transmission.
Multi-carrier transmitter, converts a common transmission signal to be transmitted to a large number of persons into a second multi-carrier signal having a frequency different from that of the first multi-carrier signal, and supplies the second multi-carrier signal to a single antenna for transmission. A second multi-carrier transmitter for generating modulated signals of synchronized symbol frequencies, and a plurality of carriers having the same symbol position are frequency-divided. It is configured to generate multiplexed first and second multicarrier signals.

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.

The ultimate obstacle is the relationship between the frequency bands that are allowed to be used by the airship and the bit rates that all subscribers with whom the airship must communicate need to transmit. If individual subscribers want to send and receive different digital information, they are subject to restrictions on the total transmission rate handled by the airship. However, when it takes the form of push-type multimedia broadcasting, there is commonality in the information to be handled, so that it is used to reduce the frequency band used and consequently to transmit individual information. The subscriber can transmit the information.

Therefore, in the present invention, the subscriber system data is converted into a first multicarrier signal by a first multicarrier transmitter and supplied to a plurality of antennas, and is individually transmitted to a plurality of cells by a narrowed beam. The common transmission signal to be transmitted to a large number of persons is converted into a second multicarrier signal having a frequency different from that of the first multicarrier signal by a second multicarrier transmitter, A single antenna with a wide directivity is supplied for transmission.

Since a multicarrier is used as a modulation method, 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.

[0020]

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 multicarrier transmission apparatus according to the present invention, and FIG. 2 is an explanatory diagram of radio wave directivity in an embodiment of a wireless communication system according to the present invention. In this embodiment, similarly to the above-described stratospheric wireless platform, as shown in FIG. 2, the airship 11 is suspended in the stratosphere at an altitude of about 20 km, and a large-capacity communication device, an ATM (asynchronous transfer mode) is installed in the airship 11. ) An exchange, a server connected to a large-capacity ATM network, and a synchronous multicarrier transmitting apparatus according to the present invention are mounted, and perform wireless communication with a ground station. This wireless communication system is intended to realize the advanced multimedia society, which is to be realized by optical cables, using a wireless system. Since free space is used as a transmission path, transmission distortion is small, and compared to geostationary satellites. Airship 11
Has the same features as a wireless communication system using a conventional wireless platform, such as having a low delay due to being in a low altitude, and having a lower cost to implement than FTTH. ing.

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 this embodiment, a plurality of antennas having different directivities are mounted on the airship 11, and communication is performed by dividing the airship 11 locally.
It is intended to make 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 mutually 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.

Next, a case where a broadcast push type application is transmitted will be considered. As a matter of course, it is possible to transmit the same information using a communication network having such a cell arrangement. However, when transmitting a signal on the order of the main level of MPEG-2, a transmission rate of at least 6 Mbps is required as described above. If the QPSK-modulated information signal is to be transmitted at 6 Mbps, the frequency band required for transmission needs to be about 5 MHz including error correction data.

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. This value is too small to realize a network against optical cables, and some countermeasures are required.

Therefore, in this embodiment, the push-type service is transmitted in another form, paying attention to the fact that the information to be transmitted is common. In particular,
As described later, the airship is provided with a beam antenna array in which a large number of fine beam antennas are arranged, and a single antenna having a broad directional characteristic for push-type transmission. If the incoming information is for individual subscribers,
Identify by other means whether it is a common transmission signal to be transmitted to many people, and after identification, transmit from the subscriber's transmitter and antenna, or transmit to a wider area than the common transmitter and antenna Take either one.

Next, a modulation / demodulation system used in the radio communication system of 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 frequency division, the configuration of the modulated signal is based on multicarriers, and a symbol period is provided for the same period in order to maintain orthogonality between the multicarriers. 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 of 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.

In 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 is slightly advantageous for fading of frequency selectivity because of transmission over a wide frequency band. 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.

While the above description has been given of the wireless transmission of the subscriber system in which the area is limited, in the embodiment of the present invention,
In addition to this, it also transmits broadcast signals.
The transmission of the broadcast signal will be described. When providing a service by the frequency division method as shown in FIG.
For example, one of the frequency bands is allocated for broadcasting. In the frequency band allocated for broadcasting, the beam width is kept wide, and the airship emits radio waves to all serviceable areas.

When a service is provided by the comb-shaped frequency division method shown in FIG. 6, a predetermined number of carriers (a plurality of carriers of a predetermined channel) are allocated for broadcasting, and the beam width is kept wide. Launch radio waves in all areas where the airship can service. As described above, broadcast-type push-type services can provide services in a smaller frequency band than those using subscriber-based wireless communication. Therefore, when considering multimedia services using airships staying in the stratosphere, push-type services It has many advantages and can be said to be an advantageous service.

Next, an embodiment of the synchronous multicarrier 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 eight multi-carrier transmitters ₁₁ to ₁₈ and directional antennas individually connected to the multi-carrier transmitters ₁₁ to _17. Seven parabolic antennas with sharp sex 8
₁ over 8 _7, multicarrier transmitter 1 ₈ to a connected directivity broad, or omnidirectional broadcasting antenna 9
And Incidentally, parabola antenna 8 _{1-8 7} constitute a parabolic antenna array.

The multicarrier transmitter ₁ 1 to 1 ₈ are each the same configuration, the interface circuit 2 ₁ to 2 _8, multi-frequency oscillator 3 ₁ to 3 _8, the control circuit 41 _{to 8,} the adder 51 _to
5 ₈ , DA converters 6 _{1 to} 6 ₈ , and frequency converters 7 _{1 to} 7 _8, and input signals are different from each other. However, the same information may be input to the multicarrier transmitters ₁₁ to ₁₇ to which the subscriber data is input. Multicarrier transmitter ₁₈ receives broadcast data. These subscriber data and broadcast data are data transmitted from a ground station, but data stored in a rewritable storage medium or the like can also be used.

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, of the 16 oscillators multi-frequency oscillator 3 in ₁ Decide which oscillator to operate. Thus, from the multi-frequency oscillator 3 ₁ is taken out as an equivalent modulator output signal in 16QAM signal.

[0040] 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
The modulated carrier is added to the adder 5₁With frequency division multiplexing
Into one multiplexed signal (multi-carrier signal)
Later, the DA converter 6₁Digital-to-analog conversion
And converted to an analog signal. ₁Supply to
Is converted to a millimeter-wave band, and a parabolic antenna
8₁From the air.

The even other multicarrier transmitter 1 _{2-1 7} Similarly, convert each subscriber system data for the subscriber in each separate multicarrier signals, parabola antenna 8 _2-8 in the millimeter wave band Send from ₇ . Thus, the parabolic antenna 8 _{1-8 7} projects a narrow beam pattern of seven different widths on the ground, can send subscriber data in the form of a multi-carrier signal to the seven cell located in the beam pattern .

On the other hand, the multi the carrier transmitter 1 _8, broadcast data which is common transmission signal to be transmitted to a large number of people enter, multicarrier transmitter 1 ₁ described above here
Is converted into a multi-carrier signal composed of n carriers, and is converted into a signal in the millimeter wave band and wirelessly transmitted from the broadcasting antenna 9 to the ground. Here, the broadcast antenna 9 has a broad directivity, and projects a beam over a wide area on the ground. For example,
When the airship is standing at an altitude of about 20 km, the diameter is 5
A pattern of about 0 km can be projected.

Thus, according to this embodiment, 7
Multimedia signals (subscriber data) can be transmitted to subscribers scattered in two regions, and broadcast data shared over a wide area can be transmitted in the form of multicarrier signals. Can be used.
Specifically, in the cell arrangement as shown in FIG. 4, only one seventh frequency band can be used for one area, but when transmitting to the entire band, the entire band can be used. Because.

As described above, in this embodiment, all the subscribers who are to receive the service in the frequency band permitted to use for 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. .

[0046] Incidentally, in the above embodiment, the parabolic antenna is described as seven for 8 _{1-8 7} simplicity,
As shown in FIG. 4, when there are 49 (= 7 × 7) cells in total, 49 multi-carrier transmitters and 49 parabolic antennas for subscriber data are required, and the parabolic antenna has 49 beams. Although it is composed of an array, only eight frequency bands including a frequency band for broadcasting are required. In practice, more than 100 multicarrier communication devices and corresponding multibeam arrays are used.

When each symbol period of data for modulating each carrier of the multicarrier signal is composed of an effective symbol period in which data is arranged and a guard interval period arranged before the effective symbol period, the time is determined by the guard interval period. Since it is possible to reduce the interference of long co-channel interference waves, SFN (single frequency broadcast) in which the same content is broadcasted from different airships and service areas are continuously secured is also possible. Further, the multicarrier signal can be applied by any of the frequency division methods shown in FIGS.

[0048]

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, the subscriber system data is converted to a first multicarrier signal by a first multicarrier transmitter, supplied to a plurality of antennas, and transmitted to a plurality of cells by the narrowed beam. A common transmission signal to be transmitted individually and sent to a large number of people is converted by a second multicarrier transmitter to a second multicarrier signal having a different frequency from the first multicarrier signal, Since the signal is supplied to a single antenna with a slightly wider directivity and transmitted, effective use of the frequency in the push-type multimedia broadcasting application to the subscriber in the stratospheric wireless platform is aimed at, and efficient operation of the frequency band is eventually achieved. Can be planned.

Further, according to the present invention, since a multicarrier is used as a modulation system 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 changed. 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 buffer from the delay signal can be reduced by the guard interval period, and the broadcast information of the same content can be transmitted from different flying objects at the same frequency. An area can be secured and SFN is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a synchronous multicarrier transmission 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.

[Explanation of symbols]

1 ₁ to 1 ₇ subscriber data for multi-carrier transmitter 1 ₈ multicarrier transmitter for broadcasting data 2 ₁ to 2 ₈ interface circuit 3 ₁ to 3 ₈ multi-frequency number generator 41 _{to 8} control circuits 5 ₁ to 5 ₈ adder 6 _{1 to} 6 ₈ DA converter 7 _{1 to} 7 ₈ frequency converter 8 ₁ to 8 ₇ parabolic antenna 9 directional broad broadcasting antenna 11 airship

Claims (5)

[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 area are arranged to be repeatedly used so as to receive signals of different frequencies, and a plurality of subscriber-related data from the flying object correspond at least to the plurality of cells. The multi-carrier signals of different numbers are transmitted to the plurality of cells in the area via the number of beam antenna arrays corresponding to the total number of cells in the high frequency band, A common transmission signal to be transmitted to a large number of persons from a plurality of multi-carrier signals is a multi-carrier signal having a different frequency from the plurality of multi-carrier signals. Wireless communication system, characterized by simultaneously transmitted to two or more of the cell via the antenna load directional characteristic. 2. A common transmission signal to be transmitted to a large number of persons is broadcast data, and the broadcast data is arranged in an effective symbol period and modulated by a modulation signal provided with a guard interval period. A plurality of flying objects for generating a broadcast multi-carrier signal having a different frequency from the plurality of multi-carrier signals and transmitting the generated multi-carrier signals via the antenna having the broad directional characteristic are arranged, and the plurality of flying objects have the same contents. The wireless communication system according to claim 1, wherein the broadcast multicarrier signal modulated with broadcast data is transmitted at the same frequency. 3. A synchronous multi-carrier transmitter 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: A beam antenna array that is an aggregate of a plurality of antennas that individually transmit radio waves to each of a plurality of cells, and a directional characteristic that simultaneously transmits radio waves to all of the plurality of cells or two or more cells has the plurality of antennas. A single antenna having broader characteristics and a plurality of antennas constituting the beam antenna array, and convert subscriber data into a first multicarrier signal and supply the first multicarrier signal to the plurality of antennas A plurality of first multi-carrier transmitters, and a common transmission signal to be transmitted to a large number of persons, Obtained by converting the second multi-carrier signal frequency and a second multicarrier transmitter to transmit is supplied to said single antenna, said first
And the second multicarrier transmitter generates a modulated signal having a synchronized symbol frequency, and multiplexes the first and second multicarrier signals obtained by frequency division multiplexing a plurality of carriers having the same symbol position. Synchronous multi-carrier transmission devices, each of which generates a signal. 4. When the cell group consisting of one cell which is a terrestrial reception area and all cells adjacent to the cell is defined as one area, and the cell arrangement is repeated in units of the area, the first multi Carrier transmitters and the plurality of antennas are respectively provided by the number of cells included in the area to be received, and among a plurality of the first multicarrier transmitters, among a plurality of cells constituting the one area, The synchronous multicarrier transmission apparatus according to claim 3, wherein the multicarrier transmitter that transmits the first multicarrier signal transmits first multicarrier signals having different frequencies. 5. The first and second multicarrier signals include q × q (where p ≦ q) carriers in which all frequency bands to be used are arranged at predetermined frequency intervals.
5. The synchronous multicarrier transmission apparatus according to claim 3, wherein the signal is a frequency-division multiplexed signal of any one of a total of p sets of carrier groups different from each other.