JP3805935B2 - Satellite communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a satellite communication system that uses a broadcast satellite or a communication satellite to transmit transmission information toward a service area on the ground, and in particular, a re-transmission device is installed to cover a dead zone of radio waves from the satellite. The present invention relates to a system and its retransmission device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, various communication systems have been developed with increasing communication needs and communication technology, and among them, there are satellite communication systems using broadcast satellites and communication satellites. The advantage of the satellite communication system is that it is possible to provide information broadcasting services to a wide service area without having to build a large infrastructure on the ground.
[0003]
By the way, one of the problems that this type of system has is countermeasures against insensitive areas such as Sanin, buildings, and tunnels where direct waves from satellites cannot be received. On the other hand, conventionally, as shown in Japanese Patent Application No. 9-178659, for example, a re-transmission device is installed in a place with a good view from the satellite, such as a rooftop of a building or a steel tower. A so-called gap filler technique has been proposed in which a re-transmission device receives the signal and re-transmits it to the dead band. By adopting this gap filler technology, it is possible to construct a system with a high area coverage rate by eliminating the radio wave insensitive zone.
[0004]
[Problems to be solved by the invention]
However, the re-transmission device for gap filler that has been proposed in the past is used only for relay transmission of radio waves from satellites despite having transmission / reception facilities. It is.
[0005]
The present invention has been made by paying attention to the above circumstances, and the object of the present invention is to effectively use a re-transmission device provided to cover a radio-insensitive area, thereby reducing the cost without newly installing a transmission / reception facility. The object is to provide a satellite communication system and a retransmission apparatus for realizing a service with high added value.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a satellite communication system according to the present invention is a satellite communication 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. Re-transmission apparatus that installs a re-transmission apparatus, receives a signal arriving from the satellite, and re-transmits the received signal toward a partial area in the service area including a radio-insensitive area. In addition to the means, information addition means for adding additional information to the transmission information in the received signal is newly provided, and a transmission signal modulated by the additional information is added to the signal arriving from the satellite and transmitted to the partial area. It is comprised as follows.
[0007]
The retransmitting apparatus according to the present invention receives additional information in addition to 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 the service area. Information adding means for adding to the transmission information in the signal is newly provided, and the additional information is added to the transmission information modulated by the received signal from the satellite and transmitted to the partial area. .
[0008]
Therefore, according to these inventions, it becomes possible to add the additional information to the transmission information and transmit it using the re-transmission device installed to cover the radio wave insensitive area. For this reason, in addition to global broadcasting services to wide areas using satellites, it is possible to broadcast local information specific to each area for each partial area, thereby providing a broadcasting service with high added value. Become. In addition, since it is not necessary to provide a new transmission facility for broadcasting additional information, there is an advantage that a local broadcast service can be realized at low cost.
[0009]
As the configuration of the retransmission apparatus, the following two are conceivable.
One is to demodulate the received signal, reproduce the transmission information once, multiplex additional information on the reproduced transmission information, modulate the transmission signal with the multiplexed transmission information, and transmit it.
According to this configuration, transmission information arriving from the satellite is reproduced once and then retransmitted, so that high-quality broadcast information with good S / N can be transmitted to the partial area.
[0010]
If a code division multiplexing method is used as a multiplexing method of the transmission information and the additional information, a slot for transmitting additional information is prepared in advance on the downlink from the satellite to the terminal as in the case of the time division multiplexing method. Therefore, it is possible to multiplex transmission of additional information relatively easily.
[0011]
The other one is to generate an additional information transmission signal modulated by the additional information, synthesize the additional information transmission signal in synchronism with the received signal, and transmit the resultant signal.
[0012]
According to this configuration, a means for reproducing transmission information received from a satellite is not required, and the configuration of the retransmission apparatus can be simplified and reduced in size.
[0013]
When a code division multiplexing system is used as a multiplexing system, a signal transmitted from a transmission station is assigned to one of a plurality of channels for pilot signal transmission of a fixed pattern and another channel for transmission information transmission, Assume that all channels are multiplexed by code spread modulation. Thus, when the retransmitting device receives the transmission signal from the transmitting station via the satellite, it demodulates the pilot signal transmission channel from the received signal, extracts the pilot signal, and correlates with the fixed pattern. It is possible to detect the synchronization timing, multiplex the code spread modulation signal of the additional information with the received signal and retransmit it based on this synchronization timing, and it is not necessary to demodulate all the channels, thus simplifying the configuration it can.
[0014]
Also, by using the code division multiplexing method as a multiplexing method, the receiving terminal in the service area can receive the signal from the satellite and the signal from the retransmitting device by RAKE combining, and the receiving sensitivity can be improved. Can be improved.
[0015]
In addition, if the retransmission apparatus detects the received signal synchronously, drops it to the baseband, corrects the frequency error, and retransmits it, the frequency tolerance of the receiving terminal is reduced even if the frequency accuracy of the retransmitted signal is reduced. Can be in range.
[0016]
Also, an identification code is assigned to each retransmitting device in advance, and at the transmitting station, the remote monitoring control information with the identification code of each target retransmitting device is multiplexed and transmitted in the transmission signal, and sent to the service area. In the plurality of retransmission apparatuses provided, remote monitoring control information with the identification code of the own apparatus is acquired from the received signal, the corresponding control operation is performed, and the control result is included in the additional information and transmitted. By doing so, it is possible to remotely control each retransmission apparatus without providing a new communication line.
[0017]
Furthermore, if a remote monitoring device is provided that receives retransmission broadcast signals from a plurality of retransmission devices, extracts remote monitoring control results in the additional information, and collectively transmits them to the retransmission device management station, each retransmission device is provided. Remote monitoring can be realized together with remote control of the transmission device.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
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.
This satellite communication system includes a terrestrial broadcasting station BC1, a geostationary satellite SAT1, and a satellite tracking control station BS that monitors and controls the operation state of the geostationary satellite SAT1.
[0020]
The terrestrial broadcasting station BC1 transmits the broadcast program information for a plurality of channels created and edited by each broadcasting company to the geostationary satellite SAT1 via the Ku band (14 GHz) uplink transmission path with two waves. One wave is obtained by multiplexing the broadcast program information of the plurality of channels by the CDM method, and the other one wave is obtained by multiplexing the same broadcast program information by the TDM method.
[0021]
The geostationary satellite SAT1 includes a Ku-band receiving antenna, a Ku-band transmitting antenna, and an S-band (for example, 2.5 GHz) transmitting antenna. Then, the CDM broadcast signal and the TDM broadcast signal sent from the terrestrial broadcast station BC1 via the Ku band (14 GHz) uplink transmission path are received by the Ku band receiving antenna.
[0022]
The geostationary satellite SAT1 converts the frequency of the CDM broadcast signal out of the received two-wave broadcast signal into an S-band (2.5 GHz) broadcast signal by the first repeater, and converts the S-band CDM broadcast signal to the above-mentioned value. Transmission is performed from the S-band transmission antenna to the service area via the S-band (2.5 GHz) downlink transmission path. Of the received two-wave broadcast signals, 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 converted into the Ku-band signal. The data is transmitted from the band transmission antenna to the service area via the Ku band (12 GHz) downlink transmission path.
[0023]
On the other hand, in the service area, for example, a broadcast receiving device (not shown) fixedly installed in an office or home, or an in-vehicle or portable mobile broadcast receiving device MS is used. These broadcast receiving apparatuses MS receive and reproduce CDM broadcast signals broadcast from the geostationary satellite SAT1 via the S-band (2.5 GHz) downlink transmission path. When transmitting a video signal, MPEG4 (moving picture experts group 4) is used as a video encoding method.
[0024]
By the way, in the system according to 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, a re-transmission device is arranged at a key point in the service area. The re-transmission device includes a low-power type first re-transmission device GFa that individually covers a radio-insensitive area due to the shade of a building, and a high-power type that collectively covers a relatively wide area including a plurality of radio-insensitive areas. The second re-transmission device GFb.
[0025]
The first retransmission apparatus GFa is installed, for example, on the rooftop of a building near a radio wave insensitive area. Then, the CDM broadcast signal that has arrived from the geostationary satellite SAT1 via the S-band (2.5 GHz) downlink transmission path is received, and the received CDM broadcast signal is held at the same frequency and retransmitted toward the radio wave insensitive area. To do.
[0026]
FIG. 2 is a circuit block diagram showing the configuration. That is, the CDM broadcast signal arriving from the geostationary satellite SAT1 is received by the S-band receiving antenna 11. The received CDM broadcast signal is sequentially input to the S-band amplifier 13 and the band-pass filter 14 via the distributor 12, and the amplifier 13 and the band-pass filter 14 respectively amplify and remove unnecessary wave components. After that, it is input to the synthesizer 15.
[0027]
By the way, in this first retransmitting device GFa, local broadcast content information (local material) LI1 related to the radio wave insensitive area covered by the own device GFa is added to the CDM broadcast signal received from the stationary satellite SAT1. Has a function to transmit.
[0028]
That is, the received CDM broadcast signal is branched by the distributor 12 and input to the pilot demodulator 17, which detects the CDM synchronization timing. Then, the local material LI1 for one channel input by the material input unit (not shown) is CDM-modulated by the CDM modulation unit 18 in synchronization with the CDM synchronization timing, further amplified by the amplification unit 19, and input to the combiner 15. Is done. In the synthesizer 15, the CDM modulation signal of the local material LI 1 is synthesized with the received CDM broadcast signal input via the band pass filter 14. The synthesized CDM broadcast signal is transmitted from the S-band transmitting antenna 16 toward the radio wave insensitive area.
[0029]
On the other hand, the high-power type second retransmission apparatus GFb is provided in a broadcast tower installed in the center of a city, for example, the roof of a city hall or a ward office. The TDM broadcast signal received from the geostationary satellite SAT1 via the Ku band (12 GHz) downstream transmission path is received and demodulated to reproduce the broadcast program information of each channel, and CDM modulation is performed using the broadcast program information of each reproduced channel. The generated S-band (2.5 GHz) broadcast signal is generated and retransmitted toward a wide retransmission area including a plurality of radio wave insensitive areas.
[0030]
FIG. 3 is a circuit block diagram showing the configuration. That is, a Ku-band TDM broadcast signal arriving from the geostationary satellite SAT 1 is received by the Ku-band receiving antenna 21. 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 converted into parallel data for each channel by a serial / parallel (S / P) converter 24 and then input to the CDM baseband processing unit 25. Here, a case where broadcast program information for up to 35 channels (CH1 to CH35) is received is illustrated.
[0031]
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. The broadcast program information for each channel output from each CDM baseband processing unit 25 is input to the CDM modulator 26.
[0032]
By the way, each broadcast received from the geostationary satellite SAT1 includes local broadcast content information (local material) LI2 to be broadcast to the wide retransmission area covered by the own apparatus GFa. A function for multiplexing and transmitting the program information is provided.
[0033]
That is, the local material LI2 input by a local material input unit (not shown) is input to the baseband processing unit 31. The baseband processing unit 31 generates local information transmission timing based on the synchronization timing output from the TDM demodulator 23 and performs A / D conversion on the input local material LI2. The local material LI2 output from the baseband processing unit 31 is input to the CDM baseband processing unit 32, where baseband processing for CDM modulation such as coding for band compression and error correction coding 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 local channel is transmitted by one channel is illustrated.
[0034]
The CDM modulator 26 modulates the broadcast program information of each channel output from each of the CDM baseband processing units 25 and 32 and the transmission information of the local material with different spreading codes, and then synthesizes and synthesizes them. A CDM broadcast signal is generated. The CDM broadcast signal is subjected to spread spectrum modulation by the spread modulator 26, amplified by a transmission power amplifier 28, and further band-limited to an S band frequency (2.5 GHz) by a band pass filter 29, and then S band. Transmission is performed from the transmission antenna 30 toward the retransmission area. A monitoring control unit 33 controls transmission power according to an instruction from a remote monitoring center (not shown) and performs fault monitoring.
[0035]
Next, the operation of the system configured as described above will be described.
The Ku band (14 GHz) CDM broadcast signal and the TDM broadcast signal transmitted from the terrestrial broadcasting station BC1 are respectively converted into an S band (2.5 GHz) CDM broadcast signal and Ku by the first and second repeaters of the geostationary satellite SAT1. After frequency conversion into a band (12 GHz) TDM broadcast signal, it is broadcast toward the service area via two downstream transmission paths of S band (2.5 GHz) and Ku band (12 GHz), respectively.
[0036]
On the other hand, in the service area, the broadcast receiving apparatus MS that exists in a place where it can directly receive the CDM broadcast signal from the geostationary satellite SAT1 directly receives the S band (2.5 GHz) CDM broadcast signal transmitted from the geostationary satellite SAT1. A wave is received, and broadcast program information of a desired channel is reproduced from broadcast program information of a plurality of channels included in the received CDM broadcast signal. When the broadcast program information consists of video and audio, the video is displayed on the display and the audio is output from the speaker. When the broadcast program information is composed only of sound, this sound is output from the speaker.
[0037]
On the other hand, a CDM broadcast signal is transmitted from the first low-power-type re-transmission device GFa to the broadcast receiving device MS existing in the radio wave insensitive area where the direct wave from the geostationary satellite SAT1 cannot be received. That is, the CDM broadcast signal sent from the geostationary satellite SAT1 via the S-band downlink transmission path is also received by the first retransmission apparatus GFa, and the first retransmission apparatus GFa amplifies the received CDM broadcast signal. Re-send to a radio-insensitive area. For this reason, the broadcast receiving apparatus MS can receive or listen to the broadcast program information of a desired channel by receiving the CDM broadcast signal even when the broadcast receiving apparatus MS exists in a radio wave insensitive area such as behind a building.
[0038]
By the way, in the first retransmitting device GFa, for example, the local broadcast material LI1 provided from a store or the like existing in a radio wave insensitive area is converted into a CDM signal in synchronization with the CDM broadcast signal coming from the geostationary satellite SAT1, and accordingly. After that, it is synthesized with the CDM broadcast signal from the geostationary satellite SAT1 and transmitted to the radio wave insensitive area. Accordingly, the broadcast receiving apparatus MS can receive, view or listen to local broadcast information unique to the area in a state where the broadcast receiving apparatus MS exists in the radio wave insensitive area.
[0039]
Note that, when the broadcast receiving apparatus MS receives local broadcast information, it is usually possible by the user selecting the channel. However, the presence or absence of the received radio wave is monitored by cheating the channel for regular or regular local broadcast, and when the received radio wave is detected, the local broadcast channel is received and the received information is displayed or output as audio. You may make it do. Further, in this case, in order not to prevent viewing or listening to the broadcast program information of the channel selected by the user, the local broadcast information is displayed as text information in a part of the display screen of the display or displayed locally. Audio guidance, music, sound, etc., indicating that broadcast information has been received or the content of the received local broadcast information may be superimposed or interrupted on the audio signal of the broadcast program information and output from the speaker.
[0040]
FIG. 4 shows an example of the broadcast form of the local broadcast material LI1 by the first retransmitting device GFa. In the radio insensitive areas Ea1, Ea2, Ea3, and Ea4, fast food restaurants, gas stations, family restaurants, It is designed to broadcast convenience store advertisements and sales information. If it does in this way, each store can be used as what is called an electric wave signboard which displays existence of a store to vehicles or a pedestrian who is moving. For broadcasters, it is possible to receive the installation location of the first re-transmission device GFa from the store, or to request the store for device maintenance and power supply, and the advantage of facilitating system expansion There is.
[0041]
Note that the installation location of the first re-transmission device GFa is not limited to the radio wave insensitive area, and if there is a store or the like that desires transmission of local information, it may be installed in the peripheral area of this store or the like.
[0042]
On the other hand, the system according to this embodiment includes a high-power type second retransmission apparatus GFb, which performs retransmission of broadcast signals and transmission of local broadcast material LI2 from the second retransmission apparatus GFb. Yes.
[0043]
That is, the TDM broadcast signal that has arrived from the geostationary satellite SAT1 via the Ku band (12 GHz) downlink transmission path is received by the second retransmission apparatus GFb. In the second retransmission apparatus GFb, the received TDM broadcast signal is demodulated and once reproduced into broadcast program information for each channel, and then multiplexed by CDM modulation to generate an S-band CDM broadcast signal. 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.
[0044]
Therefore, in this retransmission area, the broadcast receiving apparatus MS receives the CDM broadcast signal retransmitted from the second retransmission apparatus GFb even when it exists in a radio wave insensitive area such as behind a building, and the desired channel. It is possible to view or listen to the broadcast program.
[0045]
Note that, in the broadcast receiving apparatus MS existing in an area other than the radio wave insensitive area in the retransmission area, both the CDM signal from the geostationary satellite SAT1 and the CDM broadcast signal retransmitted from the second retransmission apparatus GFb are both present. Therefore, if there is a time difference between the transmission timings of both signals, the broadcast receiving apparatus may temporarily lose synchronization. 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 signal reception timing is shifted and resynchronization is achieved. By the time it is temporarily disconnected.
[0046]
However, the broadcast station BC1 gives a delay in advance to the transmission timing of the direct wave transmission signal in consideration of the delay time due to the demodulation and remodulation processing in the second retransmission apparatus GFb. For this reason, in the broadcast receiving apparatus MS, the reception timings of the CDM signal directly received from the geostationary satellite SAT1 and the CDM broadcast signal retransmitted from the second retransmitting apparatus GFb coincide with each other. Occurrence of reception interruption due to loss of synchronization is prevented or only a short time is required. The direct wave delay process can also be performed in the repeater of the geostationary satellite SAT1.
[0047]
By the way, in the second retransmitting device GFb, for example, the local broadcast material LI2 provided from the municipal office is CDM-synchronized and multiplexed on the broadcast program information of each channel that has arrived from the geostationary satellite SAT1 and has been reproduced once. The signal is transmitted to the retransmission area as a signal. For this reason, the broadcast receiving apparatus MS existing in the re-transmission area views or listens to the local broadcast material LI2 provided from the municipal office together with the broadcast program information from the terrestrial broadcast station BC1 that has arrived via the geostationary satellite SAT1. can do.
[0048]
FIG. 5 shows an example of a broadcast form of the local broadcast material LI2 by the second retransmitting device GFb. From the second rebroadcasting device GFb installed on the roof of the ward office to the retransmitting area Eb having a radius of 3 km. , Public information and disaster prevention information of the ward are transmitted as local broadcast materials. In this way, municipalities can broadcast public information, disaster prevention information, etc. to the residents without providing transmission facilities. For broadcasters, the second re-transmission device GFb installation location can be provided from the municipal office.
[0049]
Note that the retransmission area of the second rebroadcast apparatus GFb is not limited to a radius of 3 km, and may be set to a value larger than or smaller than that. In short, it may be set according to the size of the area where the municipality or the like wishes to transmit local information. 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.
[0050]
As described above, in the system according to this embodiment, the first re-transmission device GFa installed to cover the radio wave insensitive area in the service area is input to the local broadcast material LI1 unique to the radio wave insensitive area. The local broadcast material LI1 input by the input means is converted into a CDM signal, and the CDM signal is combined with a CDM broadcast signal that has arrived from the geostationary satellite SAT1 and transmitted.
[0051]
Therefore, it is possible to broadcast local broadcast information peculiar to an area such as information indicating the presence of a store or PR information to each radio wave insensitive area without providing a special local broadcast transmitter.
[0052]
In addition to the low power type first retransmission apparatus GFa described above, a high power type second retransmission apparatus GFb is installed, and this high power type second retransmission apparatus GFb is used. For example, local broadcast material LI2 for a relatively wide area such as publicity of municipalities and disaster prevention information is broadcast.
[0053]
Therefore, for example, when a large number of radio wave insensitive areas due to a building street are scattered in a relatively small area such as an urban area, these radio wave insensitive areas can be covered together by one retransmitting device GFb. It becomes possible. In addition, municipalities can perform administrative broadcasts such as publicity and disaster prevention information without providing their own broadcast transmission facilities.
[0054]
In the system of the present embodiment, broadcast information of the same content is transmitted from the geostationary satellite SAT1 using two types of frequencies, S band and Ku band, and the high power type second retransmission apparatus GFb transmits Ku band. A TDM broadcast signal is received, converted into an S-band CDM broadcast signal, and retransmitted. For this reason, in the second retransmission apparatus GFb, the reception frequency and the transmission frequency are different, and as a result, it is possible to prevent the occurrence of an oscillation phenomenon due to a sneak in the transmission wave.
[0055]
Further, by transmitting the broadcast signal for the second retransmission apparatus GFb by the TDM method, the use band of the Ku band is reduced from about 2/3 to about ½ compared to the case of using the CDM method. Can be narrowed.
[0056]
The present invention is not limited to the above embodiment. For example, the re-transmission target may be a radio wave insensitive zone such as in a tunnel or an underground shopping street, in addition to a radio wave insensitive region on the ground due to the shade of a mountain or a building. When retransmitting such tunnels and underground shopping streets, broadcast signals from geostationary satellites are received by a receiving antenna installed on the ground, and the received broadcast signals are installed in the tunnel or on the ceiling of an underground shopping mall. Transmit to the tunnel or underground shopping center from the S-band transmitting antenna.
[0057]
In addition, the broadcast signal received at that time is transmitted with local information indicating the state of the tunnel or the underground shopping street. As the transmission method, similar to the above embodiment, the received CDM broadcast signal is combined with the CDM signal modulated with the local information and transmitted, or the received broadcast signal is demodulated to reproduce the broadcast program information once. A method can be used in which local information is CDM multiplexed into the reproduced broadcast program information, and then converted into an S-band high-frequency signal and transmitted.
[0058]
As local information to be transmitted to the tunnel or underground mall, traffic information, congestion information, bargain information, emergency disaster prevention information, and the like 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 that is added to the broadcast signal as local information and transmitted. A case of transmitting from the antenna GFc into the tunnel is shown. If it does in this way, the emergency disaster prevention information in a tunnel can be notified to a passing vehicle using the re-transmission apparatus for tunnel insides.
[0059]
In addition, a channel for broadcasting emergency disaster prevention information is fixed, and the broadcast receiver is configured to constantly monitor this emergency broadcast channel. When the emergency disaster prevention information broadcast is received, the reception channel is forcibly switched to the emergency broadcast channel so that the emergency disaster prevention information is notified to the user.
[0060]
The present invention is not limited to the above embodiments, and various modifications can be made to the system configuration, the circuit configuration of the retransmission apparatus, the type and content of local broadcast information, and the like, without departing from the spirit of the present invention. Can be implemented.
[0061]
Next, a specific configuration when the CDM method is used in the system will be described.
FIG. 7 shows a circuit configuration for generating a CDM broadcast signal to be transmitted to the geostationary satellite SAT1 via the Ku band (14 GHz) uplink transmission path in the terrestrial broadcasting station BC1 shown in FIG. An example in which transmission is performed by multiplexing a channel information channel and one control channel is shown.
[0062]
Here, a control signal of the transmission format shown in FIG. 8 is carried on the control channel. This control channel transmission format is such that a pilot signal of a specific bit pattern (CW: Continuous Wave) and a data (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. Information channels # 1 to #N are used for transmission of N pieces of program information (in MPEG4 object units), and are assigned spreading codes # 1 to #N, respectively.
[0063]
The signals of the control channel # 0 and the information channels # 1 to #N are subjected to preprocessing such as addition of error correction codes and interleaving in the baseband processing units 510 to 51N, respectively, and then modulation units 520 to 52N. The primary modulation is performed by QPSK, and the signals are multiplied by the spread codes # 0 to #N generated by the spread code generators 540 to 54N provided for the respective channels by the multipliers 530 to 53N to be code spread modulated. These code spread modulation signals are multiplexed by an adder 55, thereby generating a CDM broadcast signal. The CDM broadcast signal is up-converted from the KuM (14 GHz) signal by the transmitter 56 and then amplified in power, and transmitted from the transmission antenna 57 toward the geostationary satellite SAT1.
[0064]
As described above, the geostationary satellite SAT1 converts the frequency of the Ku-band (14 GHz) CDM broadcast signal sent from the terrestrial broadcasting station BC1 into the S-band (2.5 GHz) broadcast signal, and the S-band (2.5 GHz). ) To the service area via the downstream transmission path.
[0065]
The first retransmission apparatus GFa provided in each service area is specifically configured as shown in FIG. 9 in order to retransmit the CDM signal in the above transmission format. Here, M is the number of channels of local material multiplexed on the retransmit signal.
[0066]
In FIG. 9, a receiving antenna 61 receives a CDM signal transmitted from a geostationary satellite SAT1 via an S-band (2.5 GHz) downlink transmission path. The received CDM signal is received by a receiving unit 62. Receive detection. This received signal is supplied to the correlation unit 63 and also supplied to the adder 64.
[0067]
The correlator 63 is constituted by a matched filter, for example, and by correlating the spread code # 0 from the spread code # 0 generator 65 with the received signal, the CW signal of the control channel # 0 included in the received signal The synchronization timing is detected. FIG. 10 shows a specific configuration of the correlation unit 63 when the spreading code length is k.
[0068]
In FIG. 10, the CDM signal from the receiving unit 62 is sequentially shifted and inputted to k delay stages 6311 to 631k connected in series, and the outputs of the delay elements 6311 to 631k are code generators 6331 to 632k in multipliers 6321 to 632k. After being multiplied by each bit value of the spreading code # 0 generated at 633k, it is added and output by the adder 634. Here, when the outputs of the delay units 6311 to 631k and the bit values of the spread code # 0 generated by the code generators 6331 to 633k match, the output of the adder 634 becomes the maximum, and the match timing is CW. It becomes the synchronization timing with the signal. This synchronization timing is obtained once in one cycle of CW.
[0069]
The CW synchronization timing signal obtained by the correlation unit 63 is supplied to the timing control unit 66. The timing control unit 66 generates control channel timing information for multiplexing in synchronization with the CDM signal that received the local material from the CW synchronization timing signal, and the control channel timing information obtained here is M pieces of control channel timing information. The data is sent to the delay buffers 68N + 1 to 68N + M.
[0070]
The M channel local materials newly multiplexed by the retransmission apparatus GFa are assigned to the information channels # N + 1 to # N + M, respectively, and before the addition of the error correction code, interleaving or the like by the baseband processing units 67N + 1 to 67N + M for each channel. After the processing, the delay buffers 68N + 1 to 68N + M are appropriately delayed based on the control channel timing information and synchronized with the retransmitted CDM signal (chip synchronization). The modulation unit 69N + 1 to 69N + M performs primary modulation by QPSK, and the multipliers 70N + 1 to 70N + M multiply the spread codes # N + 1 to # N + M generated by the spread code generation units 71N + 1 to 71N + M provided for each channel. Code spread modulation.
[0071]
These code spread modulation signals are multiplexed by the adder 64 together with the CDM signal received and detected by the receiving unit 62, thereby generating a CDM broadcast signal in which local materials are multiplexed. The CDM broadcast signal is amplified in the same frequency band by the transmission unit 72 and then transmitted from the transmission antenna 73 toward the service area.
[0072]
According to the above configuration, since the local material can be synchronized and multiplexed without demodulating the CDM broadcast signal in the retransmitting apparatus, the circuit configuration of CDM demodulation and remodulation is not required, and the circuit scale is reduced. be able to. Further, since the broadcast receiving apparatus MS performs RAKE combining processing peculiar to CDM, even when a signal from the geostationary satellite SAT1 and a signal from the relay retransmission apparatus GFa are received simultaneously, demodulation can be performed correctly.
[0073]
Note that the local material multiplexed by the relay retransmission apparatus GFa may be provided via a wired or wireless transmission path from an external broadcast station or the like, or generated by a server or the like inside the relay retransmission apparatus But you can.
[0074]
In the above-described embodiment, the configuration when applied to the first relay retransmission apparatus GFa has been shown and described. However, the second relay retransmission apparatus GFb also uses the M channel local material in the same manner as described above. If the coded modulated signal is generated and multiplexed in synchronization with the CDM broadcast signal converted from the TDM broadcast signal, the same effect as that of the first relay retransmission apparatus GFa can be obtained.
[0075]
By the way, when the allowable deviation of the frequency received by the broadcast receiving apparatus is small, it is necessary to increase the accuracy of the frequency oscillator of the retransmission apparatus. In addition, remote monitoring and control of the state of the retransmission apparatus is also required. In this case, however, a new communication line needs to be prepared for each retransmission apparatus, which increases the running cost.
[0076]
Therefore, in order to cover the dead zone of the broadcast wave, it is used to install a retransmission device having a transmission facility, and even when the reception frequency tolerance range of the reception device for receiving broadcast contents is narrow, the retransmission device In the following, an embodiment in which a highly accurate oscillator is not required, remote monitoring control of the retransmission apparatus is realized, and the running cost of the system is reduced will be described.
[0077]
FIG. 11 shows the system configuration, in which 81 is a broadcasting station, 82 is a broadcasting satellite, 831 to 83n are retransmission devices, and 84 is a remote monitoring device. 85 is a line for transmitting a signal in which remote control information is multiplexed on broadcast content at a frequency of Ku band (12-14 GHz), and 86 is a signal on which remote monitoring information is multiplexed in 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.
[0078]
As an operation of this system, in a broadcasting station 81 that transmits broadcast content to be distributed to the user, an ID is assigned to each of the retransmitting devices 831 to 83n, remote control information managed by this ID is multiplexed on the broadcast content, and a line 85 To the retransmitting devices 831 to 83n. Each of the retransmitting devices 831 to 83n executes the instructed control only when its ID matches the remote control information. The retransmitting devices 831 to 83n also implement local broadcasting by the above-described method, and multiplex their own monitoring information and transmit them in the local broadcasting content.
[0079]
The signals sent from the retransmitting devices 831 to 83n are collectively received by the remote monitoring device 84 via the line 86, and the remote monitoring information is returned to the broadcasting station 81 via the ground line 87. In this case, the remote monitoring device 84 has to be received by an antenna having a high directivity and a high gain, and a system with an economical running cost that can receive broadcast waves from more retransmission devices at one location. Can be built.
[0080]
In the embodiment of FIG. 11, the broadcasting station 81 has been described as being centrally managed for realizing the above-described remote monitoring control. However, in the case where the whole country is divided into a plurality of service stations and managed, the remote monitoring is performed for each site. It is assumed that the retransmission apparatus to be monitored and controlled is managed. However, the line can be realized by using each line in FIG.
[0081]
FIG. 12 shows a specific configuration of the retransmitting apparatus, in which 91 is a Ku-band receiving antenna, 92 is a low noise frequency converter (LNC), 93 is a power source and a local reference frequency oscillator provided to the LNC 92, 94 is a tuner, 95 is a quadrature demodulator, 96 is an A / D converter, 97 is a control circuit for synchronous detection, 98 is a voltage controlled oscillator (VCTXO) for feedback to the tuner 94, and 99 is a low-pass filter (LPF) 100a and 100b are mixers, 101 is a 90 ° phase division hybrid, 102 is an S-band oscillator, 103 is a two-wave synthesis hybrid, 104 is a power amplifier, 105 is a bandpass filter (BPF), and 106 is Each of the S-band transmitting antennas is shown.
[0082]
As an operation of this configuration, a CDM signal received in the 12 GHz band is received via an antenna 91 and an LNC 92, frequency-converted to a baseband by a tuner 94, and then divided into I / Q by an orthogonal 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.
[0083]
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 the synchronization is established in this control loop, an I / Q baseband signal can be obtained. Therefore, after the noise outside the band is reduced by the LPF 99, the QPSK modulators (100a, 100b, 101 to 103 are again used. To a signal having an S-band transmission frequency, and a retransmission signal is generated. Then, the retransmission signal is amplified to necessary power by the power amplification unit 104 and transmitted from the S-band transmission antenna 106.
[0084]
With this configuration, when the Ku band is simply converted to the S band, for example, when the 12 GHz band is dropped to the 2.5 GHz band, the frequency tolerance range of the receiving terminal is ± 100 Hz, and the local frequency of the LNC 92 is If the frequency is 11.3 GHz, the required frequency accuracy is within about 8E-9. However, the frequency error can be reduced to 4E-8 by eliminating the frequency error once by dropping to the baseband as in this embodiment. It becomes possible. Thus, reducing the frequency accuracy has the effect of reducing costs and facilitating maintenance.
[0085]
Furthermore, since synchronous detection is performed once and peripheral noise is removed by the LPF 99, an effect of improving the D / U (signal power to jamming power) ratio of adjacent waves of the retransmitted signal can be obtained. In addition, since synchronous detection is once performed and dropped to the baseband, it becomes easy to match the re-transmission timing for adding the local broadcast, and many advantages are obtained as secondary effects.
[0086]
As described above, according to the present embodiment, the remote monitoring control of the retransmission device that covers the dead zone of satellite broadcasting is realized using the broadcast wave via the satellite and the local broadcast wave from the retransmission device. For this reason, it is not necessary to install a new communication line for every retransmission apparatus, thereby reducing costs. In addition, once the received signal is synchronously detected by the retransmitting device, the frequency error is eliminated, and the frequency is raised to the required frequency again, thereby reducing the accuracy of the frequency oscillator required inside the retransmitting device. .
[0087]
In the above embodiment, the local information related to the area including the radio wave insensitive area is added by the retransmission apparatus. However, the present invention is not limited to this, and the area including the radio wave insensitive area is used. Of course, arbitrary information may be added in addition to the related information.
[0088]
【The invention's effect】
As described above in detail, according to the present invention, a re-transmission device is installed in the service area, information transmission / addition means is newly provided in the re-transmission device, and the additional information is added to the broadcast information modulated by the broadcast signal. And transmitting to the partial area.
[0089]
Also, in the present invention, CDM is used as a transmission method, a synchronization signal is allocated to one channel, and the retransmission apparatus demodulates only the channel of the synchronization signal from the received CDM signal, and the additional information is code spread modulated by synchronizing. In addition, the configuration is such that the received CDM signal is multiplexed and retransmitted, thereby simplifying the configuration.
[0090]
Furthermore, in this invention, each retransmitting device is managed by ID, remote control information for each retransmitting device is put on a broadcast wave, remote control information of the self ID is received by the retransmitting device, and its control is executed. The monitoring information is transmitted on the local information, and the remote monitoring device receives the monitoring information in the local signal from each retransmission device, and transmits it to the management station collectively for remote monitoring of each retransmission device. The line laying is omitted.
[0091]
Therefore, according to the present invention, a satellite communication system that effectively uses a re-transmission device provided to cover a radio-insensitive area, thereby realizing a low-cost and high-value-added broadcasting service without newly installing a transmission / reception device, and its A retransmission apparatus 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.
2 is a circuit block diagram showing a configuration of a first low-power type retransmission apparatus used in the system shown in FIG. 1;
FIG. 3 is a circuit block diagram showing a configuration of a high power type second retransmission apparatus used in the system shown in FIG. 1;
4 is a diagram showing an example of a partial area covered by the low power retransmission apparatus shown in FIG. 2;
FIG. 5 is a diagram showing an example of a partial area covered by the high power retransmission apparatus shown in FIG. 3;
FIG. 6 is a diagram showing another embodiment of a retransmission apparatus according to the present invention.
7 is a circuit block diagram showing a configuration for generating a CDM broadcast signal in the terrestrial broadcast station BC1 shown in FIG. 1;
8 is a diagram showing an example of a control channel transmission format of the circuit shown in FIG.
9 is a circuit block diagram showing a configuration of a retransmission apparatus that receives a CDM signal generated by the circuit shown in FIG. 7;
10 is a circuit block diagram showing a specific configuration of a correlation unit used in the retransmission apparatus shown in FIG. 9;
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.
12 is a circuit block diagram showing a specific configuration of a retransmission apparatus in the system shown in FIG.
[Explanation of symbols]
BC1 ... Terrestrial broadcasting station
SAT1 Geostationary satellite
MS ... mobile station
GFa: Low power type first retransmission apparatus
GFb ... High power type second retransmission apparatus
LI1, LI2 ... Local material
Ea1-Ea4 ... Radio-sensitive area
Eb: Re-transmission area including multiple radio wave insensitive areas
11 ... S-band receiving antenna
12 ... distributor
13 ... S-band amplifier
14, 29 ... band pass filter
15 ... Synthesizer
16, 30 ... S-band transmitting antenna
17 ... Pilot demodulator
18 ... CDM modulation section
19: Transmission amplifier
21 ... Ku band receiving antenna
22 ... Low noise frequency converter (LNB)
23 ... TDM demodulator
24 ... S / P converter
25, 32 ... CDM baseband processing unit
26 ... CDM modulator
27 ... Spreading modulator
28: Transmission power amplifier
31 ... Baseband processing unit
33. Monitoring control unit
510 to 51N: Baseband processing unit
520 to 52N: Modulation unit
530-53N: Multiplier
540-54N: Spreading code generator
55 ... Adder
56: Transmitter
57 ... Transmitting antenna
61 ... Receiving antenna
62: Receiver
63 ... Correlation part
6311-631k ... delay device
6321 to 632k ... multiplier
6331-633k: Code generator
634 ... Adder
64 ... Adder
65: Spreading code # 0 generator
66 ... Timing control section
67N + 1 to 67N + M ... Baseband processing unit
68N + 1 to 68N + M ... delay buffer
69N + 1 to 69N + M: Modulator
70N + 1 to 70N + M ... multiplier
71N + 1 to 71N + M ... Spreading code generator
72: Transmitter
73 ... Transmitting antenna
81 ... Broadcasting station
82 ... Broadcasting satellite
831-83n ... Retransmission device
84 ... Remote monitoring device
85 ... Ku band transmission line,
86 ... S-band transmission line
87 ... Terrestrial line
91 ... Ku band receiving antenna
92 ... Low noise frequency converter (LNC)
93 ... LNC power source / local frequency generator
94 ... Tuner
95: Quadrature demodulator
96 ... A / D converter
97 ... Control circuit for synchronous detection
98 ... Voltage controlled oscillator (VCTXO)
99 ... Low-pass filter (LPF)
100a, 100b ... mixer
101 ... 90 ° phase division hybrid
102 ... S-band oscillator
103 ... Hybrid for two-wave synthesis
104: Power amplifier
105: Band pass filter (BPF)
106 ... S-band transmitting antenna

Claims (11)

In a satellite communication 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,
In the service area, a plurality of retransmitting devices assigned with identification codes in advance are installed to relay and retransmit signals arriving from the satellite to a partial area including a radio wave insensitive area,
The transmitting station attaches an identification code of a retransmission device to be remotely controlled among the plurality of retransmission devices to remote control information, and multiplexes and transmits the transmission signal in a transmission signal,
The retransmission apparatus includes:
Receiving means for receiving a signal arriving from the satellite;
Information adding means for adding additional information to transmission information in the received signal;
Transmitting means for transmitting the transmission information to which the additional information is added by the information adding means to the partial area as a transmission signal;
Remote control processing means for obtaining remote control information with an identification code assigned in advance from the received signal and performing a corresponding control operation;
A satellite communication system, wherein the processing of the information adding means is controlled from the transmitting station side by the remote control information.   The satellite generates a plurality of transmission signals including transmission information in the signal based on a signal arriving from a transmitting station, and one of the plurality of transmission signals can be received by a receiving terminal. Through the first downlink transmission line, and the other transmission signal via the second downlink transmission line in a frequency band other than the frequency band that can be received by the receiving terminal. The satellite communication system according to claim 1, further comprising a function of transmitting toward the service area.   2. The satellite communication system according to claim 1, wherein the retransmission apparatus amplifies a transmission signal with a transmission power set in accordance with a size of the radio wave insensitive area and transmits the amplified signal toward the area. The satellite generates a plurality of transmission signals including transmission information in the signal based on a signal arriving from a transmitting station, and one of the plurality of transmission signals can be received by a receiving terminal. Through the first downlink transmission line, and the other transmission signals via the second downlink transmission line in a frequency band other than the frequency band that can be received by the receiving terminal. Provided with a function to send to the service area,
And the retransmission apparatus comprises:
A signal arriving from the satellite via the first downlink transmission path is received, the additional information is added to the transmission information in the received signal, the transmission signal is reconfigured, and the transmission signal is A first type of retransmission device for transmitting to a partial area including a region;
A signal arriving from the satellite via the second downlink transmission path is received, the additional information is added to transmission information in the received signal, and the signal is converted into a frequency band that can be received by the receiving terminal and transmitted. 2. The satellite communication system according to claim 1, further comprising: a second type retransmission apparatus configured to reconfigure a signal and transmit the transmission signal toward a partial area including the radio wave insensitive area.   5. The satellite communication system according to claim 4, wherein the second type retransmission apparatus amplifies a transmission signal with a transmission power larger than that of the first type retransmission apparatus.   5. The satellite communication system according to claim 2, wherein a frequency band higher than a frequency band of the first transmission path is used for the second transmission path. The signal transmitted from the transmitting station is one in which one of a plurality of channels is allocated for transmission of a fixed pattern pilot signal, the other channel is allocated for transmission information transmission, and all channels are multiplexed by code spread modulation. Yes,
When the retransmitting device receives a transmission signal from a transmitting station via the satellite, it demodulates a pilot signal transmission channel from the received signal, extracts a pilot signal, and takes a correlation with a fixed pattern to synchronize 2. The satellite communication system according to claim 1, wherein a timing is detected, and a code spread modulation signal of additional information is multiplexed on a received signal based on the synchronization timing and retransmitted.   8. The satellite communication system according to claim 7, wherein the receiving terminal in the service area receives the signal from the satellite and the signal from the retransmission apparatus by RAKE combining.   2. The satellite communication system according to claim 1, wherein the retransmission apparatus performs synchronous detection on the received signal, drops the signal to baseband, corrects the frequency error, and then retransmits the signal. 3. The re-transmission device transmits a remote control result of a control operation based on the remote control information included in the additional information,
2. The monitoring apparatus according to claim 1, further comprising monitoring means for receiving a retransmission signal of the retransmission apparatus, extracting the remote control result from additional information in the received signal, and transmitting the result to the retransmission apparatus management station. Satellite communication system.   2. The satellite communication system according to claim 1, wherein the remote control information is information for controlling the retransmission apparatus to include emergency information in the additional information.

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