JP2000244383A - Satellite communication system and its retransmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize broadcasting service at a low cost with a high added value without newly providing a transmitter-receiver by effectively utilizing a retransmitter provided for covering a radio blind zone. SOLUTION: First and second retransmitters GFa to be arranged for covering a radio blind zone within a service area are provided with a function for inputting a local broadcasting material LI1 characteristic to the radio blind zone or an area including the area and a function for converting the inputted material LI1 to a CDM signal then synthesizing it with a CDM broadcasting signal incoming from a geostationary satellite SAT1 to transmit or to CDM-multiplex a local broadcast material to broadcast program information of each channel, which incomes from the geostationary satellite to be reproduced, to transmit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication system for transmitting transmission information to a terrestrial service area using a broadcasting satellite or a communication satellite, and more particularly to covering a dead zone of radio waves from a satellite. And a retransmitting device.

[0002]

2. Description of the Related Art In recent years, various communication systems have been developed in response to an increase in communication needs and development of communication technology, and among them, a satellite communication system using a broadcasting satellite or a communication satellite is known. An advantage of the satellite communication system is that an information broadcasting service can be provided to a wide range of service areas without installing a large infrastructure on the ground.

[0003] One of the problems of this type of system is to take measures against electromagnetic wave insensitive areas such as in the shade of a mountain, behind a building, or in a tunnel where direct waves from satellites cannot be received. On the other hand, in the related art, as shown in Japanese Patent Application No. Hei 9-178649, for example, a retransmitting device is installed in a place where visibility from the satellite is good, such as the roof of a building or a steel tower, and radio waves from the satellite are transmitted. A so-called gap filler technique has been proposed in which a signal is received by a retransmission device and retransmitted to a radio wave dead zone.
By adopting this gap filler technology, it is possible to construct a system having a high area coverage rate without a radio wave dead zone.

[0004]

However, the retransmitting device for the gap filler proposed in the prior art simply relays and transmits radio waves from satellites, despite having transmission / reception facilities. It is currently used only for

The present invention has been made in view of the above circumstances, and an object thereof is to effectively use a retransmitting device provided to cover an area where radio waves are insensitive, and thereby to newly establish a transmitting and receiving facility. It is an object of the present invention to provide an inexpensive and high-value-added satellite communication system and a retransmitting device thereof.

[0006]

In order to achieve the above object, a satellite communication system according to the present invention transmits a signal modulated and transmitted by transmission information at a transmitting station to a predetermined terrestrial service area via a satellite. In a satellite communication system, a retransmission device is installed in the service area, the retransmission device receives a signal arriving from the satellite, and receives the received signal, including a radio wave insensitive area in the service area. In addition to the retransmission means for retransmitting to the partial area, an information addition means for adding additional information to the transmission information in the received signal is newly provided, and the transmission signal modulated by the additional information is added to the signal arriving from the satellite. This is configured to be transmitted to the partial area in addition to the above.

The retransmitting apparatus according to the present invention further includes a retransmitting means for receiving a signal arriving from a satellite and retransmitting the received signal toward a partial area including a radio wave insensitive area in a service area. Information addition means for adding information to the transmission information in the received signal is newly provided, and the additional information is added to the transmission information modulated by the reception signal from the satellite and transmitted to the partial area. Things.

Therefore, according to these inventions, it is possible to transmit additional information by adding the additional information to the transmission information using a retransmitting device installed to cover the radio wave insensitive area. For this reason, in addition to a global broadcasting service using a satellite to a wide area, it is possible to broadcast local information and the like peculiar to the area for each partial area, thereby providing a high value-added broadcasting service. Become. In addition, since it is not necessary to provide a new transmission facility for broadcasting the additional information, there is an advantage that a local broadcast service can be realized at low cost.

The following two are conceivable as configurations of the retransmitting device. One is to demodulate a received signal to temporarily reproduce transmission information, multiplex additional information with the reproduced transmission information, modulate a transmission signal with the multiplexed transmission information, and transmit the modulated transmission signal. According to this configuration, since the transmission information arriving from the satellite is reproduced once and then retransmitted, high-quality broadcast information with a good S / N can be transmitted to the partial area.

When a code division multiplexing system is used as a multiplexing system of the transmission information and the additional information, a slot for transmitting the additional information is previously provided on the downlink from the satellite to the terminal as in the case of the time division multiplexing system. Since it is not necessary to prepare, multiplex transmission of additional information can be performed relatively easily.

Another method is to generate an additional information transmission signal modulated by the additional information, synthesize the additional information transmission signal in synchronization with a reception signal, and then transmit the combined signal.

According to this configuration, there is no need for a means for reproducing the transmission information arriving from the satellite, so that the configuration of the retransmitting device can be made simple and compact.

When a code division multiplexing system is used as a multiplexing system, a signal transmitted from a transmitting station is transmitted by using one of a plurality of channels for transmitting a pilot signal having a fixed pattern.
It is assumed that other channels are allocated for transmission information transmission, and all channels are code-spread modulated and multiplexed. Thereby, in the retransmission device, when a transmission signal from the transmission station is received via a satellite, a pilot signal transmission channel is demodulated from the received signal to extract a pilot signal,
Synchronization timing is detected by correlating with a fixed pattern, and based on this synchronization timing, a code spread modulation signal of additional information can be multiplexed with a received signal and retransmitted, eliminating the need to demodulate all channels. Therefore, the configuration can be simplified.

[0014] Further, by using the code division multiplexing method as a multiplexing method, a receiving terminal in a service area can receive a signal from a satellite and a signal from a retransmitting device by RAKE combining. The receiving sensitivity can be improved.

Further, the retransmitting device synchronously detects the received signal, drops the signal to baseband, corrects the frequency error,
If retransmission is performed, even if the frequency accuracy of the retransmission signal is reduced, the frequency can be kept within the allowable frequency range of the receiving terminal.

An identification code is assigned to each of the retransmitting devices in advance, and the transmitting station multiplexes the remote monitoring control information with the identification code of each of the target retransmitting devices into the transmission signal and transmits the multiplexed signal. In the plurality of retransmitting devices provided in the service area, the remote monitoring control information with the identification code of the own device is obtained from the received signal and the corresponding control operation is performed, and the control result is included in the additional information. In this case, it is possible to remotely control each retransmitting device without newly providing a communication line.

Furthermore, a remote monitoring device for receiving retransmission broadcast signals from a plurality of retransmission devices, extracting a remote monitoring control result from the additional information, and transmitting the result to a retransmission device management station at a time may be provided. In addition, it is possible to realize remote monitoring together with remote control of each retransmitting device.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a satellite communication system having a gap filler function according to the present invention. This satellite communication system includes a terrestrial broadcasting station BC1, a geostationary satellite SAT1, and a geostationary satellite SAT1.
And a satellite tracking control station BS for monitoring and controlling the operation state of the satellite.

The terrestrial broadcast station BC1 transmits broadcast program information for a plurality of channels created and edited by each broadcaster to K
Two waves are transmitted to the geostationary satellite SAT1 via the u-band (14 GHz) uplink transmission path. One wave is obtained by multiplexing the broadcast program information of a plurality of channels by the CDM method.
The wave is obtained by multiplexing the same broadcast program information by the TDM method.

The geostationary satellite SAT1 has a receiving antenna for the Ku band, a transmitting antenna for the Ku band, and a transmitting antenna for the S band (for example, 2.5 GHz). Then, a Ku band (14 GHz) is transmitted from the terrestrial broadcasting station BC1.
The CDM broadcast signal and the TDM broadcast signal transmitted via the uplink transmission path of z) are received by the Ku band receiving antenna.

The geostationary satellite SAT1 frequency-converts the CDM broadcast signal of the received two broadcast signals into an S-band (2.5 GHz) broadcast signal using a first repeater, and performs S-band CDM broadcast. The signal is transmitted from the S-band transmission antenna to the service area via the S-band (2.5 GHz) downlink transmission path. In addition, the received 2
Among the broadcast signals of the waves, the TDM broadcast signal is frequency-converted into a Ku-band (12 GHz) broadcast signal by the second repeater, and the converted Ku-band TDM broadcast signal is transmitted from the Ku-band transmission antenna to Ku. Band (12GH
z) to the service area via the downlink transmission path.

On the other hand, in the service area, for example, a broadcast receiving device (not shown) fixedly installed in an office or home, or a vehicle-mounted or portable movable broadcast receiving device M
S is used. These broadcast receiving apparatuses MS receive and reproduce CDM broadcast signals broadcast from the geostationary satellite SAT1 via an S-band (2.5 GHz) downlink transmission path. When transmitting a video signal, MPEG4 (moving picture experts group) is used as a video encoding method.
4) is used.

By the way, in the system of this embodiment,
In order to cover a so-called radio wave insensitive area where radio waves from the geostationary satellite SAT1 in the service area cannot be received,
Retransmission devices are located at key points in the service area. The retransmitting device includes a first retransmitting device GFa of a small power type which individually covers a radio wave insensitive area due to a building shadow or the like, and a large power type which collectively covers a relatively large area including a plurality of radio frequency insensitive areas. Of the second retransmission device GFb.

The first retransmitting device GFa is installed, for example, on the roof of a building close to a radio wave insensitive area. Then, a CDM broadcast signal arriving from the geostationary satellite SAT1 via an S-band (2.5 GHz) downlink transmission path is received, and the received CDM broadcast signal is retransmitted to a radio wave insensitive area while being kept at the same frequency. I do.

FIG. 2 is a circuit block diagram showing the configuration. That is, the CDM arriving from the geostationary satellite SAT1
The broadcast signal is received by the S-band receiving antenna 11.
The received CDM broadcast signal is sequentially input to an S-band amplifier 13 and a band-pass filter 14 via a distributor 12, and the amplifier 13 and the band-pass filter 14
After amplification and unnecessary wave component removal are performed respectively,
It is input to the synthesizer 15.

By the way, in the first retransmitting device GFa, information (local material) LI of local broadcast contents related to the radio wave insensitive area covered by the own device GFa
1 is added to the CDM broadcast signal received from the geostationary satellite SAT1 and transmitted.

That is, the received CDM broadcast signal is
The signal is branched by the distributor 12 and input to the pilot demodulation unit 17, where the CDM synchronization timing is detected. Then, the local material LI1 for one channel input by the material input unit (not shown) is C
The signal is subjected to CDM modulation in synchronization with the CDM synchronization timing in the DM modulator 18, further amplified by the amplifier 19, and input to the synthesizer 15. The synthesizer 15 converts the CDM modulated signal of the local material LI1 into a bandpass filter 1
4 is combined with the received CDM broadcast signal input through the control unit 4. Then, the synthesized CDM broadcast signal is transmitted from the S-band transmission antenna 16 to a radio wave insensitive area.

On the other hand, the second retransmission device G of the high power type
Fb is provided in a broadcast tower installed in the center of a city, for example, on the roof of a city hall or a ward office. Then, the TDM broadcast signal arriving from the geostationary satellite SAT1 via the Ku-band (12 GHz) downlink transmission path is received and demodulated to reproduce the broadcast program information of each channel, and the CDM modulation is performed by the reproduced broadcast program information of each channel. S band (2.5
(GHz) broadcast signal and retransmit it to a wide retransmission area including a plurality of radio wave insensitive areas.

FIG. 3 is a circuit block diagram showing the configuration. That is, the Ku band TDM broadcast signal arriving from the geostationary satellite SAT1 is transmitted to the Ku band receiving antenna 21.
Received at. The received TDM broadcast signal is down-converted to an intermediate frequency or a baseband frequency by a low-noise frequency converter (LNB) 22 and then demodulated by a TDM demodulator (TDM-DEM) 23. Broadcast program information is reproduced. The broadcast program information of each channel is serial / parallel (S / P)
After being converted into parallel data for each channel by the converter 24, the data is input to the CDM baseband processing unit 25. Here, a maximum of 35 channels (CH1 to C
H35) is shown as an example.

Each CDM baseband processing unit 25 performs baseband processing for CDM modulation such as error correction coding and interleaving on the broadcast program information for each channel. Then, the broadcast program information for each channel output from each CDM baseband processing unit 25 is input to the CDM modulator 26.

By the way, the second retransmitting device GFb receives from the geostationary satellite SAT1 local broadcast content information (local material) LI2 to be broadcast for a wide retransmission area covered by its own device GFa. A function is provided for multiplexing and transmitting the broadcast program information.

That is, the local material LI2 input by the local material input means (not shown) is input to the baseband processing unit 31. This baseband processing unit 3
In step 1, the transmission timing of local information is generated based on the synchronization timing output from the TDM demodulator 23, and A / D conversion is performed on the input local material LI2. The local material LI2 output from the baseband processing unit 31 is input to a CDM baseband processing unit 32, where baseband processing for CDM modulation such as encoding for band compression and error correction encoding is performed. Done. Then, the transmission information of the local material after the baseband processing is input to the CDM modulator 26. Here, the case where the local material is transmitted on one channel is illustrated.

The CDM modulator 26 modulates the broadcast program information of each channel and the transmission information of the local material output from each of the CDM baseband processing units 25 and 32 with different spreading codes, and then synthesizes them. A multiplexed CDM broadcast signal is generated. This CDM broadcast signal is spread-spectrum-modulated by a spread modulator 26, amplified to a large power by a transmission power amplifier 28, and further subjected to an S-band frequency (2.5 GHz) by a band-pass filter 29.
After being band-limited, the signal is transmitted from the S-band transmission antenna 30 to the retransmission area. Reference numeral 33 denotes a monitoring control unit, which controls transmission power according to an instruction from a remote monitoring center (not shown), monitors a failure, and the like.

Next, the operation of the system configured as described above will be described. Ku transmitted from terrestrial broadcasting station BC1
The band (14 GHz) CDM broadcast signal and the TDM broadcast signal are respectively transmitted to the S band (2.5 GHz) CDM broadcast signal and the K band by the first and second repeaters of the geostationary satellite SAT1.
After being frequency-converted to a u-band (12 GHz) TDM broadcast signal, the S-band (2.5 GHz) and K
It is broadcast to the service area via two downstream transmission paths of u band (12 GHz).

On the other hand, in the service area, the broadcast receiving apparatus MS located at a place where the CDM broadcast signal from the geostationary satellite SAT1 can be directly received is provided by the geostationary satellite SAT1.
And receives the direct wave of the S-band (2.5 GHz) CDM broadcast signal transmitted from the PC and reproduces the broadcast program information of a desired channel from the broadcast program information of a plurality of channels included in the received CDM broadcast signal. . When the broadcast program information includes video and audio, the video is displayed on the display and the audio is output from the speaker. If the broadcast program information is composed of only audio, the audio is output from the speaker.

On the other hand, a CDM broadcast signal is transmitted from the low power type first retransmitting device GFa to the broadcast receiving device MS existing in the radio wave blind area where the direct wave from the geostationary satellite SAT1 cannot be received. . That is, the geostationary satellite SAT
The CDM broadcast signal transmitted via the downlink transmission path of S-band from No. 1 is also received by the first retransmitting device GFa, and the first retransmitting device GFa amplifies the received CDM broadcast signal, and amplifies the received CDM broadcast signal. Resubmit to. For this reason, the broadcast receiving apparatus MS can receive a CDM broadcast signal and view or listen to broadcast program information of a desired channel even when the broadcast receiver MS is present in a radio wave insensitive area such as behind a building.

By the way, in the first retransmission device GFa,
For example, a local broadcast material LI1 provided from a store or the like located in a radio wave insensitive area is converted into a CDM signal in synchronization with a CDM broadcast signal coming from the geostationary satellite SAT1, and then converted into a CDM broadcast signal from the geostationary satellite SAT1. The signals are combined and transmitted to a radio wave insensitive area. Therefore, the broadcast receiving apparatus MS can receive, view, or listen to local broadcast information specific to a radio wave insensitive area in a state where the broadcast receiving apparatus MS exists in the radio wave insensitive area.

When the broadcast receiving apparatus MS receives local broadcast information, it is usually possible for the user to select the channel. However, the presence or absence of the received radio wave is monitored by cheating the channel for the local broadcast periodically or constantly, and when the received radio wave is detected, the channel for the local broadcast is received and the received information is displayed or sound output. You may make it. Furthermore, in this case, in order not to hinder viewing or listening to the broadcast program information of the channel selected by the user, the local broadcast information is displayed as text information on a part of the display screen of the display as a telop, or It is preferable that voice guidance, music, sound, or the like indicating that the broadcast information has been received or the content of the received local broadcast information be superimposed or interrupted on the audio signal of the broadcast program information and output from the speaker.

FIG. 4 shows an example of the broadcast form of the local broadcast material LI1 by the first retransmitting device GFa.
Advertisements and business guidance for fast food stores, gas stations, family restaurants, and convenience stores that are close to each other in the radio wave insensitive areas Ea1, Ea2, Ea3, and Ea4 are broadcast. In this way, each store can be used as a so-called radio wave signboard that indicates the presence of the store to moving vehicles or pedestrians. Also, the broadcaster can receive the provision of the installation location of the first retransmission device GFa from the store, or request the store for maintenance and power supply of the device, thereby facilitating the expansion of the system. There is.

The location of the first retransmitting device GFa is not limited to the radio wave insensitive area. If there is a store or the like where transmission of local information is desired, the first retransmitting device GFa is installed in a peripheral area of the store or the like. Is also good.

On the other hand, the system according to this embodiment
A high power type second retransmission device GFb,
The retransmission of the broadcast signal and the transmission of the local broadcast material LI2 are performed from the second retransmission device GFb.

That is, the TDM arriving from the geostationary satellite SAT1 via the Ku-band (12 GHz) downlink transmission path.
The broadcast signal is received by the second retransmitting device GFb. Second
In the retransmitting device GFb, the received TDM broadcast signal is demodulated and temporarily reproduced as broadcast program information for each channel, and then multiplexed by CDM modulation to obtain an S-band C signal.
A DM broadcast signal is generated, and the CDM broadcast signal is transmitted from the S-band transmission antenna 30 to a relatively wide retransmission area including a plurality of radio wave insensitive areas.

Therefore, in this retransmission area, the broadcast receiving apparatus MS receives the CDM broadcast signal retransmitted from the second retransmitting apparatus GFb, even when the broadcast receiving apparatus MS is present in a radio wave insensitive area such as behind a building. It is possible to view or listen to a broadcast program of a desired channel.

Note that, in the broadcast receiving apparatus MS existing in an area other than the radio wave blind area in the retransmission area, the CDM signal from the geostationary satellite SAT1 and the second retransmitting apparatus GFb
And the CDM broadcast signal retransmitted from the receiver, the synchronization may be temporarily lost in the broadcast receiving device if there is a time difference between the transmission timings of the two signals. That is, when the broadcast receiving apparatus MS that has received the direct wave from the satellite receives the signal retransmitted from the second retransmitting apparatus GFb, the reception timing of the signal is shifted and resynchronization is performed. Reception is temporarily stopped by then.

However, the broadcasting station BC1 gives a delay in advance to the transmission timing of the transmission signal for the direct wave in consideration of the delay time due to the demodulation and remodulation processing in the second retransmitting device GFb. For this reason, in the broadcast receiving apparatus MS, the CDM signal directly arriving from the geostationary satellite SAT1 and the second
The reception timing with the CDM broadcast signal retransmitted from the retransmitting device GFb will be coincident, and as a result, the occurrence of reception loss due to temporary loss of synchronization will be prevented, or even if it occurs, it will occur in a very short time. I'm done. Note that the direct wave delay processing can also be performed in the repeater of the geostationary satellite SAT1.

By the way, in the second retransmission device GFb,
For example, a local broadcast material LI provided by the municipal office
2 is multiplexed with the broadcast program information of each channel, which has arrived from the geostationary satellite SAT1 and has been reproduced once, by CDM, and is transmitted as an S-band broadcast signal to the retransmission area. Therefore, the broadcast receiving apparatus MS existing in the retransmission area
Now, terrestrial broadcasting station B arriving via geostationary satellite SAT1
Along with the broadcast program information from C1, it is possible to view or listen to the local broadcast material LI2 provided from the municipal office.

FIG. 5 shows an example of a broadcast form of the local broadcast material LI2 by the second retransmitting device GFb.
The public information of the ward, disaster prevention information, and the like are transmitted as local broadcast materials from the second rebroadcasting device GFb installed on the roof of the ward office to a retransmission area Eb having a radius of 3 km. In this way, municipalities can broadcast public information, disaster prevention information, and the like to inhabitants of a ward without providing transmission facilities on their own. In addition, the broadcaster can receive the installation location of the second retransmission device GFb from the municipal office.

[0049] The retransmission area of the second rebroadcasting apparatus GFb is not limited to a radius of 3 km, but may be set to a value larger than or smaller than 3 km. In short, the setting may be made according to the size of the area where the municipalities or the like desire to transmit the local information. Further, the retransmission area does not need to be circular, and can be formed in any shape by changing the directivity of the transmission radio wave depending on the direction.

As described above, in the system according to this embodiment, the first retransmitting device GFa installed to cover the radio wave insensitive area in the service area is provided with the local broadcast material LI1 unique to the radio wave insensitive area. Input means, and the local broadcast material L input by the input means
I1 is converted into a CDM signal, and a function of combining the CDM signal with a CDM broadcast signal arriving from the geostationary satellite SAT1 and transmitting the signal is provided.

Therefore, it is possible to broadcast local broadcast information peculiar to each region, such as information indicating the presence of a store or PR information, to each radio wave blind region without providing a special local broadcast transmission device. .

In addition to the low power type first retransmitting device GFa, a high power type second retransmitting device GFb is installed, and the high power type second retransmitting device GFb is used. By doing so, for example, local broadcasting materials LI2 for a relatively wide area, such as public information of municipalities and disaster prevention information, etc.
To broadcast.

Therefore, for example, when a large number of radio wave blind areas due to building streets are scattered in a relatively small area such as an urban area, these radio wave blind areas are collectively covered by one retransmitting device GFb. It is possible to do. In addition, municipalities can carry out public broadcasts such as public information and disaster prevention information without providing their own broadcast transmission facilities.

In the system of the present embodiment, the broadcast information of the same content is transmitted from the geostationary satellite SAT1 using two kinds of frequencies of the S band and the Ku band, and the second retransmitting device GFb of the high power type transmits the same broadcast information. A Ku band TDM broadcast signal is received, converted to an S band CDM broadcast signal, and retransmitted. For this reason, the reception frequency and the transmission frequency are different in the second retransmitting device GFb, and as a result, it is possible to prevent the occurrence of the oscillation phenomenon due to the wraparound of the transmission wave.

Further, by transmitting the broadcast signal for the second retransmitting device GFb by the TDM system, the used band of the Ku band can be reduced from 2/3 to 1 / compared to the case where the CDM system is used. It can be as narrow as two.

The present invention is not limited to the above embodiment. For example, the target of retransmission may be a radio wave insensitive zone such as a tunnel or an underground shopping mall, in addition to a radio wave insensitive area on the ground due to a mountain shade or a building shadow. When such a tunnel or underground shopping mall is to be retransmitted, a broadcast signal from a geostationary satellite is received by a receiving antenna installed on the ground, and the received broadcast signal is installed in the tunnel or on the ceiling of the underground shopping mall. From the transmitted S-band transmission antenna to the inside of the tunnel or the underground shopping mall.

The broadcast signal received at that time is transmitted with local information indicating the state of the inside of the tunnel or the underground mall added. As the transmission method, similar to the above embodiment,
A method of combining and transmitting a received CDM broadcast signal with a CDM signal modulated with local information, or demodulating a received broadcast signal to reproduce broadcast program information once, and multiplexing the reproduced broadcast program information with CDM local information. After that, a method of converting into an S-band high frequency signal and transmitting the signal can be used.

The local information transmitted to the inside of the tunnel or the underground mall includes traffic information, congestion information, bargain information,
Emergency disaster prevention information can be considered. FIG. 6 shows an example of transmitting emergency disaster prevention information. In this example, when a fire in a tunnel occurs, message information for notifying the occurrence is added to the broadcast signal as local information and transmitted. The case where the signal is transmitted from the antenna GFc into the tunnel is shown. In this way, the emergency rescue information in the tunnel can be notified to the passing vehicle using the retransmission device for the inside of the tunnel.

A channel for broadcasting emergency disaster prevention information is fixed, and the broadcast receiving device is configured to constantly monitor the emergency broadcast channel. Then, when the broadcast of the emergency disaster prevention information is received, the receiving channel is forcibly switched to the emergency broadcast channel so that the user is notified of the emergency disaster prevention information.

The present invention is not limited to the above embodiments, and the system configuration, the circuit configuration of the retransmission device, the type and contents of local broadcast information, etc., do not depart from the gist of the present invention. Various modifications can be made.

Next, a specific configuration when the CDM method is used in the above system will be described. FIG. 7 shows FIG.
In the terrestrial broadcasting station BC1 shown in FIG.
(GHz), which shows a circuit configuration for generating a CDM broadcast signal to be transmitted to the geostationary satellite SAT1 via an uplink transmission line. Here, an N-channel information channel and a one-channel control channel are multiplexed and transmitted. An example of the case is shown.

Here, a control signal of the transmission format shown in FIG. 8 is put on the control channel. This control channel transmission format has a specific bit pattern (CW:
A continuous wave) pilot signal and a data signal for transmitting various parameter information are repeatedly generated at a constant period (250 μs).
Spreading code # 0 is assigned to this control channel. The information channels # 1 to #N are used for transmitting N pieces of program information (MPEG4 object units), and are assigned spreading codes # 1 to #N, respectively.

The control channel # 0 and the information channel #
The signals # 1 to #N are respectively assigned to the baseband processing units 510 to 510.
After performing pre-processing such as addition of an error correction code and interleaving at 51N, QPSK at modulation sections 520 to 52N.
Is performed, and multipliers 530 to 53N
A spreading code generator 540 provided for each channel at
And multiplied by the spreading codes # 0 to #N generated by .about.54N to perform code spreading modulation. These code spread modulated signals are multiplexed by the adder 55, thereby generating a CDM broadcast signal. The CDM broadcast signal is transmitted to
After the DM signal is up-converted into a Ku band (14 GHz) signal, the DM signal is power-amplified and transmitted.
It is transmitted to the geostationary satellite SAT1.

In the geostationary satellite SAT1, as described above, the Ku band (14 GHz) transmitted from the terrestrial broadcasting station BC1 is used.
z) The frequency of the CDM broadcast signal is converted into an S-band (2.5 GHz) broadcast signal, and the signal is transmitted to a service area via an S-band (2.5 GHz) downlink transmission path.

The first retransmitting device GFa provided in each service area is specifically configured as shown in FIG. 9 for retransmitting the CDM signal in the transmission format. Here, it is assumed that the number of channels of the local material multiplexed on the retransmission signal is M.

In FIG. 9, a receiving antenna 61 receives a CDM signal transmitted from the geostationary satellite SAT1 via the S-band (2.5 GHz) downlink transmission line. The received CDM signal is received by the receiving antenna 61. The received signal is detected by the unit 62. This received signal is supplied to the correlator 63 and also to the adder 64.

The correlation section 63 is formed of, for example, a matched filter, and correlates the spread code # 0 from the spread code # 0 generating section 65 with the received signal, thereby forming the control channel # 0 included in the received signal. It detects the synchronization timing with the CW signal. FIG. 10 shows a specific configuration of the correlation section 63 in the case of the spread code length k.

In FIG. 10, the CDM from the receiving unit 62
The signals are sequentially shifted and input to delay units 6311 to 631 k connected in k stages in series, and outputs of the delay units 6311 to 631 k are output to multipliers 6321 to 632 k by a code generator 633.
After being multiplied by each bit value of the spreading code # 0 generated by 1 to 633k, the result is added and output by the adder 634.
Here, when the output of each of the delay units 6311 to 631k and each bit value of the spread code # 0 generated by the code generators 6331 to 633k match, the output of the adder 634 becomes maximum, and the matching timing is CW. This is the synchronization timing with the signal. This synchronization timing is obtained once in one cycle of CW.

The CW synchronization timing signal obtained by the correlation section 63 is supplied to the timing control section 66. The timing control unit 66 generates control channel timing information for multiplexing the local material in synchronization with the received CDM signal from the CW synchronization timing signal.
The control channel timing information obtained here is sent to M delay buffers 68N + 1 to 68N + M.

The local material of the M channel newly multiplexed by the retransmission device GFa is the information channel #N
+1 to # N + M, and the baseband processing units 67N + 1 to 67N + M perform preprocessing such as addition of an error correction code and interleaving for each channel, and then delay buffers 68N + 1 to 68N + M based on the control channel timing information. The synchronization with the retransmitted CDM signal (chip synchronization) is obtained after being appropriately delayed. And the modulation unit 6
Primary modulation by QPSK is performed by 9N + 1 to 69N + M, and spreading code generators 71N + 1 to 71N + M provided for each channel by multipliers 70N + 1 to 70N + M.
Are multiplied by the spreading codes # N + 1 to # N + M generated in the above, and code spread modulated.

These spread-spectrum modulated signals are multiplexed by the adder 64 together with the CDM signal received and detected by the receiver 62, thereby generating a CDM broadcast signal in which local materials are multiplexed. This CDM broadcast signal is power-amplified in the same frequency band by the transmission unit 72 and then transmitted by the transmission antenna 73.
It is transmitted to the service area.

According to the above configuration, in the retransmission device,
Since local materials can be synchronized and multiplexed without demodulating a CDM broadcast signal, a circuit configuration for CDM demodulation and re-modulation is not required, and the circuit scale can be reduced. In the broadcast receiving apparatus MS, the RAK specific to CDM is used.
Since the E combining process is performed, demodulation can be performed correctly even when a signal from the geostationary satellite SAT1 and a signal from the relay retransmission device GFa are received at the same time.

The local material multiplexed by the relay retransmission device GFa may be provided from an external broadcasting station via a wired or wireless transmission path, or may be provided by a server or the like inside the relay retransmission device. It may be generated.

Further, in the above embodiment, the configuration when applied to the first relay retransmission device GFa has been described. However, the second relay retransmission device Generates a coded modulation signal of a local material, and multiplexes the signal in synchronization with a CDM broadcast signal converted from a TDM broadcast signal.
The same effect as a can be obtained.

When the tolerance of the frequency received by the broadcast receiving apparatus is small, it is necessary to improve the accuracy of the frequency oscillator of the retransmitting apparatus. It is also desired to remotely monitor and control the state of the retransmitting device. In this case, however, it is necessary to prepare a new communication line for each retransmitting device, which increases the running cost.

Therefore, in order to cover the dead zone of the broadcast wave, the use of a retransmitting device having a transmitting facility is utilized, and even if the receiving frequency allowable range of the receiving device for receiving the broadcast content is narrow, An embodiment in which the retransmitting device does not require a highly accurate oscillator and also realizes remote monitoring control of the retransmitting device to reduce the running cost of the system will be described below.

FIG. 11 shows the system configuration.
81 is a broadcasting station, 82 is a broadcasting satellite, 831 to 83n are retransmission devices, and 84 is a remote monitoring device. Reference numeral 85 denotes a line for transmitting a signal in which remote control information is multiplexed to broadcast contents at a frequency of Ku band (12 to 14 GHz), and reference numeral 86 denotes a signal to which remote monitoring information is multiplexed to local broadcast at a frequency of S band (2.5 GHz). A transmission line 87 indicates a ground line (wired or wireless) for returning the remote monitoring information to the broadcasting station 81.

The operation of this system is as follows. A broadcast station 81 for transmitting broadcast contents to be distributed to a user
An ID is assigned to each of the retransmitting devices 831 to 83n.
The remote control information managed by D is multiplexed on the broadcast content and transmitted to each of the retransmitting devices 831 to 83n via the line 85. Each retransmitting device 831 to 83n executes the specified control only when its own ID matches the remote control information. The retransmitting devices 831 to 83n also realize local broadcasting by the above-described method, and multiplex their own monitoring information in the local broadcasting content and transmit the multiplexed monitoring information.

The signals sent from each of the retransmitting devices 831 to 83n are collected together through a line 86,
And returns the remote monitoring information to the broadcasting station 81 via the ground line 87. In this case, the remote monitoring device 84 needs to receive the signal with an antenna having a high directivity and a high gain, and a system having a running cost that is more economical so that broadcast waves from more retransmitting devices can be received in one place. Can be built.

Note that, in implementing the above remote monitoring control, in the embodiment of FIG. 11, it has been described that the broadcasting station 81 performs centralized management. However, when the whole country is divided into a plurality of service stations and managed, a site A retransmitting device that performs remote monitoring and control is managed every time. However, the line can be realized by using each line in FIG.

FIG. 12 shows a specific configuration of the above-mentioned retransmitting apparatus. 91 is a Ku band receiving antenna, 92 is a low noise frequency converter (LNC), 93 is a power supply provided to the LNC 92 and a local oscillator reference. Frequency oscillator, 94 is a tuner,
95 is a quadrature demodulator, 96 is an A / D converter, 97 is a synchronous detection control circuit, 98 is a voltage controlled oscillator (VCTXO) for feedback to the tuner 94, 99 is a low-pass filter (LPF), 100a, 100b is a mixer, 10
1 is a 90 ° phase-division hybrid, 102 is an S-band oscillator, 103 is a two-wave combining hybrid, 104
Is a power amplifier, 105 is a band-pass filter (BP)
F) and 106 indicate S-band transmission antennas, respectively.

The operation of this configuration is as follows. A CDM signal received in the 12 GHz band is received via the antenna 91 and the LNC 92, frequency-converted to baseband by the tuner 94, and then divided into I / Q by the quadrature demodulator 95. . The signal is converted into a digital signal by the A / D converter 96 and output to the synchronous detection control circuit 97.

The synchronous detection control circuit 97 outputs a signal for performing synchronous detection feedback to the VCTXO 98, thereby eliminating the frequency error of the received signal. If synchronization is achieved in this control loop, an I / Q baseband signal can be obtained.
After reducing the out-of-band noise with the LPF 99, the QPSK modulator (100a, 100b, 101-103)
), The signal is converted into an S-band transmission frequency signal, and a retransmission signal is generated. Then, the retransmission signal is amplified to the required power by power amplification section 104 and transmitted from S-band transmission antenna 106.

With such a configuration, the Ku band is simply converted to the S band.
In the case where the frequency is dropped to the 5 GHz band, if the allowable frequency range of the receiving terminal is ± 100 Hz and the local frequency of the LNC 92 is 11.3 GHz, the required frequency accuracy is 8
It is within about E-9, but by once dropping to the baseband to eliminate the frequency error as in this embodiment, 4E-
It is possible to reduce the precision to 8. Reducing the frequency accuracy in this way has the effect of reducing costs and facilitating maintenance.

Further, since the LPF 99 removes the surrounding noise by performing the synchronous detection once, the effect of improving the D / U (signal power to interference power) ratio of the adjacent wave of the retransmitted signal can be obtained. In addition, since the synchronous detection is performed once and dropped to the baseband, it is easy to adjust the retransmission timing for adding the local broadcast, and many advantages can be obtained as secondary effects.

As described above, according to the present embodiment,
In order to realize remote monitoring control of the retransmitting device covering the dead zone of satellite broadcasting by using the broadcast wave via the satellite and the local broadcast wave from the retransmitting device, a new There is no need to install a communication line, thereby reducing costs. Also, the frequency error is eliminated by synchronously detecting the received signal once in the retransmitting device, and the frequency is increased again to the required frequency, so that the accuracy of the frequency oscillator required in the retransmitting device can be reduced. .

In the above embodiment, the local information related to the area including the radio wave insensitive area is added by the retransmitting device. However, the present invention is not limited to this. It goes without saying that not only information relating to the included area but also arbitrary information may be added.

[0088]

As described above in detail, according to the present invention, a retransmitting device is installed in a service area, and an information transmission adding means is newly provided in the retransmitting device, and additional information is modulated by the broadcast signal. It is configured to transmit to the partial area in addition to the broadcast information.

Also, according to the present invention, CD is used as the transmission method.
M, a synchronizing signal is assigned to one channel, and the retransmitting device demodulates only the channel of the synchronizing signal from the received CDM signal, code-modulates the additional information by synchronizing,
It is configured to be multiplexed with the received CDM signal and retransmitted, thereby realizing the simplification of the configuration.

Further, according to the present invention, each retransmitting device
D, the remote control information for each retransmitting device is put on the broadcast wave, the remote control information of the self ID is received by the retransmitting device, the control is executed, and the monitoring information is put on the local information and transmitted. The remote monitoring device receives the monitoring information in the local signal from each retransmitting device and collectively transmits the monitoring information to the management station, so that the line laying for the remote monitoring for each retransmitting device is omitted.

Therefore, according to the present invention, a satellite communication system which realizes an inexpensive and high value-added broadcasting service without newly installing a transmitting / receiving device by effectively utilizing a retransmitting device provided for covering a radio wave insensitive area. A system and its retransmitting device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a satellite communication system having a gap filler function according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a first low-power type retransmission device used in the system shown in FIG. 1;

FIG. 3 is a circuit block diagram showing a configuration of a high power type second retransmitting device used in the system shown in FIG. 1;

FIG. 4 is a diagram showing an example of a partial area covered by the low power retransmission device shown in FIG. 2;

FIG. 5 is a diagram showing an example of a partial area covered by the high-power retransmission device shown in FIG. 3;

FIG. 6 is a diagram showing another embodiment of the retransmission device according to the present invention.

FIG. 7 shows a terrestrial broadcasting station BC1 shown in FIG.
FIG. 2 is a circuit block diagram showing a configuration for generating a DM broadcast signal.

FIG. 8 is a diagram illustrating an example of a control channel transmission format of the circuit illustrated in FIG. 7;

FIG. 9 is a circuit block diagram showing a configuration of a retransmitting device that receives a CDM signal generated by the circuit shown in FIG. 7;

FIG. 10 is a circuit block diagram showing a specific configuration of a correlation unit used in the retransmission device shown in FIG.

FIG. 11 is a schematic configuration diagram showing another embodiment of a satellite communication system having a gap filler function according to the present invention.

FIG. 12 is a circuit block diagram showing a specific configuration of a retransmission device of the system shown in FIG. 11;

[Explanation of symbols]

 BC1 terrestrial broadcasting station SAT1 geostationary satellite MS mobile station GFa low power type first retransmitting device GFb high power type second retransmitting device LI1, LI2 local material Ea1 to Ea4 radio wave insensitive area Eb: Retransmission area including a plurality of radio wave insensitive areas 11: S-band reception antenna 12: distributor 13: S-band amplifier 14, 29: band-pass filter 15: combiner 16, 30, S-band transmission antenna 17: pilot demodulation Unit 18 CDM modulation unit 19 Transmission amplification unit 21 Ku band reception antenna 22 Low noise frequency converter (LNB) 23 TDM demodulator 24 S / P converter 25, 32 CDM baseband processing unit 26 CDM modulator 27 ... spread modulator 28 ... transmission power amplifier 31 ... baseband processing unit 33 ... monitoring control unit 510 to 51 ... Baseband processing sections 520-52N ... Modulation sections 530-53N ... Multipliers 540-54N ... Spreading code generation sections 55 ... Adders 56 ... Transmission sections 57 ... Transmission antennas 61 ... Reception antennas 62 ... Reception sections 63 ... Correlation sections 6311 ６３631k delay unit 6321 to 632k multiplier multiplier 6331 to 633k code generator 634 adder 64 adder 65 spreading code # 0 generation unit 66 timing control unit 67N + 1 to 67N + M baseband processing unit 68N + 1 to 68N + M ... Delay buffers 69N + 1 to 69N + M ... Modulators 70N + 1 to 70N + M ... Multipliers 71N + 1 to 71N + M ... Spread code generators 72 ... Transmitters 73 ... Transmission antennas 81 ... Broadcasting stations 82 ... Broadcasting satellites 831 to 83n ... Retransmitters 84 ... Remote monitoring device 85 ... Ku band transmission line, 86 ... S band transmission line 87 ... Ground line 91 ... Ku band receiving antenna 92 ... Low noise frequency conversion unit (LNC) 93 ... LNC power / local reference frequency oscillator 94 ... Tuner 95 ... Quadrature demodulator 96 ... A / D conversion 97: Synchronous detection control circuit 98: Voltage-controlled oscillator (VCTXO) 99: Low-pass filter (LPF) 100a, 100b: Mixer 101: 90 ° phase division hybrid 102: S-band oscillator 103: 2-wave synthesis Hybrid 104: Power amplification unit 105: Band-pass filter (BPF) 106: S-band transmission antenna

Claims (15)

[Claims] 1. A satellite communication system for transmitting a signal modulated and transmitted by transmission information at a transmitting station to a predetermined terrestrial service area via a satellite, wherein a signal arriving from the satellite is insensitive to the service area. A retransmitting device for relaying and retransmitting to a partial area including a region is installed, the retransmitting device receives a signal arriving from the satellite, and information for adding additional information to transmission information in the received signal. A satellite communication system comprising: an adding unit; and a transmitting unit that transmits the transmission information, to which the additional information has been added by the information adding unit, as a transmission signal toward the partial area. 2. A partial area including a radio wave insensitive area which is used in a system for transmitting a signal modulated and transmitted by transmission information at a transmitting station to a predetermined service area on the ground via a satellite. Receiving means for receiving a signal arriving from the satellite; information adding means for adding additional information to transmission information in the received signal; and additional information added by the information adding means. A retransmitting device for a satellite communication system, comprising: transmitting means for transmitting the transmitted information as a transmission signal toward the partial area. 3. The information adding unit demodulates a signal from a satellite received by the receiving unit to reproduce transmission information once, multiplexes the additional information on the reproduced transmission information, and 3. The retransmission apparatus for a satellite communication system according to claim 2, wherein a transmission signal is modulated by transmission information in which additional information is multiplexed by said information adding means and transmitted. 4. The information adding means generates an additional information transmission signal modulated by the additional information, and synthesizes the additional information transmission signal in synchronization with a signal arriving from the satellite. 3. The retransmitting device for a satellite communication system according to claim 2, wherein the transmitting unit transmits the signal synthesized by the information adding unit. 5. The retransmission apparatus for a satellite communication system according to claim 3, wherein a code division multiplexing method is used as a multiplexing method of the transmission information and the additional information. 6. The satellite generates a plurality of transmission signals including transmission information in the signal based on a signal arriving from a transmission station, and receives one of the plurality of transmission signals by a receiving terminal. Via a first downlink transmission line of a receivable frequency band,
A function of transmitting the signal to the service area and transmitting the other transmission signal to the service area via a second downlink transmission path in a frequency band other than the frequency band receivable by the receiving terminal. The satellite communication system according to claim 1, wherein: 7. The retransmission apparatus according to claim 1, wherein the retransmitting device amplifies a transmission signal with transmission power set according to a size of the radio wave insensitive area and transmits the amplified signal to the area.
A satellite communication system as described. 8. The satellite generates a plurality of transmission signals including transmission information in the signal based on a signal arriving from a transmission station, and a receiving terminal transmits one of the plurality of transmission signals to a receiving terminal. Via a first downlink transmission line of a receivable frequency band,
A function of transmitting the signal to the service area and transmitting the other transmission signal to the service area via a second downlink transmission path in a frequency band other than the frequency band receivable by the receiving terminal. And the retransmitting device receives a signal arriving from the satellite via the first downlink transmission path, adds the additional information to transmission information in the received signal, and reconfigures a transmission signal. Transmitting the transmission signal to a partial area including the radio wave insensitive area.
Receiving a signal arriving from the satellite via the second downlink transmission path, adding the additional information to transmission information in the received signal, and enabling the receiving terminal to receive the signal. A second type of retransmitting device for converting the transmission signal to a specific frequency band, reconstructing the transmission signal, and transmitting the transmission signal toward a partial area including the radio wave insensitive area. A satellite communication system as described. 9. The satellite according to claim 8, wherein said second type of retransmitting device amplifies and transmits a transmission signal with a transmission power larger than that of said first type of retransmitting device. Communications system. 10. The satellite communication system according to claim 6, wherein a frequency band higher than a frequency band of the first transmission line is used for the second transmission line. 11. A signal transmitted from the transmitting station is obtained by allocating one of a plurality of channels for transmitting a pilot signal of a fixed pattern and the other channel for transmitting transmission information, and performing code spread modulation on all channels. When receiving a transmission signal from a transmitting station via the satellite, the retransmission device demodulates a pilot signal transmission channel from the received signal to extract a pilot signal, and obtains a fixed pattern. 2. A satellite communication system according to claim 1, wherein a synchronization timing is detected by taking a correlation with the received signal, and a code spread modulation signal of additional information is multiplexed with a received signal and retransmitted based on the synchronization timing. 12. The receiving terminal in the service area,
The signal from the satellite and the signal from the retransmitter are RA
The satellite communication system according to claim 11, wherein the satellite communication system receives the KE-combined data. 13. The satellite communication system according to claim 1, wherein the retransmitting device synchronously detects the received signal, drops the signal to a baseband, corrects a frequency error, and retransmits the signal. 14. When a plurality of retransmitting devices are provided in the service area, an identification code is assigned to each of the retransmitting devices in advance, and the transmitting station is a remote monitoring control target of the plurality of retransmitting devices. Attaching the identification code of the retransmitting device to the remote monitoring control information to be multiplexed in the transmission signal and transmitting it, the plurality of retransmission devices are each provided with the identification code of its own device from the received signal. 2. The satellite communication system according to claim 1, wherein the monitoring control information is acquired, a corresponding control operation is performed, and the control result is included in the additional information and transmitted. 15. A remote monitoring device for receiving a retransmission signal of each of the plurality of retransmission devices, extracting a remote monitoring control result in the additional information, and transmitting the result to a retransmission device management station at a time. The satellite communication system according to claim 14, wherein: