JP2001275011A - System and method for transmission and reception and device and method for reception - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reproduction by a receiving device at each home without rewriting information of NIT when a digital ground wave broadcast is retransmitted by a community system after having its frequency varied when necessary. SOLUTION: The signal of the ground wave digital broadcast has only its frequency converted by retransmitting facilities 2 when necessary and is transmitted to receiving facilities 4A, 4B, 4C, etc., at respective homes through a transmission line. Receiving devices 31A, 31B, 31C, etc., of the receiving facilities 4A, 4B, 4C, etc., are provided with a conversion table showing the correspondence relation between the frequency of the NIT and the frequency of the signal transmitted through the transmission line. This conversion table is generated by judging whether or not signals can be received while frequencies are set in order in frequency search mode and making frequency information obtained from the NIT and the set frequencies correspond to each other when the signals can be received. When channels are set, reception frequencies are set according to the conversion table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shared listening facility installed in an apartment house such as an apartment,
(Cable Television) A transmission / reception system, method, and reception apparatus suitable for use in a system in which a digital terrestrial broadcast signal received by a common antenna is distributed to homes using a transmission path, such as a system. And methods.

[0002]

2. Description of the Related Art Digital terrestrial broadcasting is being developed. In digital terrestrial broadcasting, a video signal is, for example, MPEG (Moving Picture Coding Experts Group).
Compressed by two methods, OFDM (Orthogonal Frequency D)
ivision Multiplex) and transmitted. OFD
M uses a plurality of carriers that are orthogonal to each other, and is a modulation method that is resistant to multipath that causes ghost. As the working frequency of digital terrestrial broadcasting, use of a lower frequency of the current UHF broadcasting is being studied in relation to the current analog terrestrial broadcasting.

In receiving such digital terrestrial broadcasting, usually, NIT (Network Information Table) is used.
Is obtained. From the NIT table, frequency information is obtained, the reception frequency is set to a desired frequency, and then a PAT (Program Association Table) is referred to. From the PAT information, the packet identifier (PID) of the channel in the carrier is obtained. Video and audio packets are extracted and the desired channel is received.

[0004]

As described above, in digital terrestrial broadcasting, the reception frequency can be set to the frequency of a desired channel by referring to the NIT. As long as digital terrestrial broadcasting is directly received and reproduced, the reception frequency can be set using the information of the NIT as it is.

[0005] However, in apartment houses such as condominiums, a co-listening system for transmitting a signal received by a co-listening antenna to each home through a cable is used. In such a co-listening system, an empty channel is used. It is conceivable that the channel is changed to a channel having a frequency different from the channel used for broadcasting and retransmitted due to reasons such as transmission capacity and transmission capacity. When the frequency of the channel is changed in this way, the frequency information indicated by the NIT does not match the frequency of the signal actually transmitted via the cable, and the receiving operation cannot be performed. Therefore, it is considered necessary to rewrite the NIT according to the frequency of the changed channel in the retransmission facility of the co-listening system.

However, in order to rewrite the NIT information, when the frequency is converted on the retransmission equipment side of the co-listening system, the received signal is demodulated, the NIT information is rewritten, and the NIT information is re-modulated. It must be converted to frequency and retransmitted. In particular, in digital terrestrial broadcasting,
OFDM is used as a modulation method. The OFDM demodulation and modulation processing involves complicated processing.

[0007] In the case of retransmission, without using OFDM modulation, for example, a 64-level QAM (Quadrature Amplitude Modulatio) used in current digital CATV is used.
n) may be used. However, if the modulation scheme is changed from OFDM to 64-QAM when retransmitting, the processing becomes complicated and a normal digital terrestrial broadcasting receiver cannot be used when receiving the transmitted signal. , A special receiver is needed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a co-listening system for transmitting a digital terrestrial broadcast signal received by a shared antenna without rewriting NIT information when retransmitting after changing the frequency. It is an object of the present invention to provide a transmission / reception system and method, and a reception apparatus and method, which can retransmit via the Internet.

Another object of the present invention is to retransmit a digital terrestrial broadcast signal received by a shared antenna via a transmission line without requiring a dedicated receiver and without significant capital investment. It is an object of the present invention to provide a transmitting and receiving system and method and a receiving apparatus and method.

[0010]

SUMMARY OF THE INVENTION The present invention provides a common antenna for receiving digital broadcasting, a digital broadcast receiving signal received by the common antenna, and changing the frequency of the digital broadcasting receiving signal as necessary. In a digital broadcast transmission / reception system comprising a retransmission facility for retransmitting via a transmission path and a receiving facility for each home for receiving and reproducing a signal transmitted via the transmission path, digital broadcast reception is performed. The signal includes information indicating the frequency of each channel, and the receiving device transmits information indicating the frequency of each channel included in the received signal and the signal transmitted through the transmission path. A conversion table is provided that indicates a correspondence relationship with the frequency of the received signal. When a signal of a desired channel is received by the receiving apparatus, the reception frequency is set with reference to the conversion table. A transmission and reception system was.

According to the present invention, a digital broadcast is received by a shared antenna, a received signal of the digital broadcast received by the shared antenna is input, the frequency of the received signal of the digital broadcast is changed as necessary, and the signal is transmitted via a transmission path. In a digital broadcast transmission / reception method in which a signal transmitted via a transmission path is received and reproduced by receiving equipment at each home, the frequency of each channel is included in the received digital broadcast signal. And a conversion table indicating the correspondence between the information indicating the frequency of each channel included in the received signal and the frequency of the signal transmitted through the transmission path to the receiving apparatus. This is a transmission / reception method in which a reception frequency is set with reference to a conversion table when a signal of a desired channel is received by a receiving device.

According to the present invention, in a receiving apparatus for receiving a digital broadcast signal which is received by a shared antenna, whose frequency is changed as necessary, and which is transmitted via a transmission path, the digital broadcast received signal includes , Which includes information indicating the frequency of each channel, and indicates the correspondence between the information indicating the frequency of each channel included in the received signal and the frequency of the signal transmitted through the transmission path. The receiving device includes a table and sets a receiving frequency with reference to a conversion table when receiving a signal of a desired channel.

The present invention relates to a receiving method for receiving a digital broadcast signal received by a shared antenna, of which the frequency is changed as required, and which is transmitted via a transmission line. , Which includes information indicating the frequency of each channel, and indicates the correspondence between the information indicating the frequency of each channel included in the received signal and the frequency of the signal transmitted through the transmission path. This is a reception method in which a table is created and a reception frequency is set with reference to a conversion table when a signal of a desired channel is received.

The terrestrial digital broadcast signal is converted only in frequency at the retransmission equipment as necessary, and sent to the reception equipment in each home via a transmission line. Each home receiver is provided with a conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted via the transmission path. The receiving frequency is set based on this conversion table.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The present invention relates to a shared listening facility installed in an apartment house such as an apartment,
It is used in a system such as a TV system that distributes a digital terrestrial broadcast signal received by a common antenna to each home using a transmission line.

FIG. 1 shows an example of a receiving system to which the present invention is applied. In FIG. 1, a digital terrestrial broadcast signal is received by an antenna 1. The reception output of the antenna 1 is supplied to the retransmission equipment 2.

The retransmission equipment 2 converts the received signal of each channel of the digital terrestrial broadcast received by the antenna 1 into a CA signal.
In order to perform transmission on each frequency channel for TV, frequency conversion is performed as necessary.

In digital terrestrial broadcasting, a video signal is compressed by, for example, the MPEG2 system, modulated by OFDM, and transmitted. As the working frequency of digital terrestrial broadcasting, use of a lower frequency of the current UHF broadcasting is being studied in relation to the current analog terrestrial broadcasting. As a frequency for CATV, a VHF mid band band (108 MHz to 170 MHz) and a super high band band (222 MHz to 470 MHz) are mainly used.

The retransmission equipment 2 includes tuner circuits 22A,
2B, 22C,... And frequency conversion circuits 23A, 23
B, 23C,... And a mixing circuit 24. When the reception output of the antenna 1 is the tuner circuits 22A, 22B, 22
C,. Each tuner circuit 22A, 22
In B, 22C,..., A reception signal of the frequency of each channel is selected from the reception signals from the antenna 1. The outputs of the tuner circuits 22A, 22B, 22C,... Are supplied to frequency conversion circuits 23A, 23B, 23C,. The frequency conversion circuits 23A, 23B, 23C,.
The frequency of the received signal of each channel of digital terrestrial broadcasting is converted to a frequency as needed. The outputs of the frequency conversion circuits 23A, 23B, 23C,... Are supplied to the mixing circuit 24. In the mixing circuit 24, the frequency conversion circuit 23A,
, 23B, 23C,... Are synthesized.

The transmission path 3 is led out of the mixing circuit 24 of the retransmission equipment 2. The signal frequency-converted by the retransmission equipment 2 is transmitted via the transmission path 3 to the reception equipment 4A, 4A, 4
, B, 4C,.

The receiving facilities 4A, 4B, 4C,.
Are provided with receiving devices 31A, 31B, 31C,... And receivers 32A, 32B, 32C,. The signal transmitted via the transmission line 3 is transmitted to the receiving equipment 4 of each home.
A, 4B, 4C,... Receiving devices 31A, 31B, 31
Decoded by C, ... The receiving devices 31A, 31
Are output from the receivers 32A, 32B, 32
C,. Receivers 32A, 32B, 32
.. Reproduce the screen based on the video signals decoded by the receiving devices 31A, 31B, 31C,.

The receiving devices 31A, 31B, 31
, And the receivers 32A, 32B, 32C,... May be integrated to form a television receiver capable of receiving digital terrestrial broadcasts, or the receivers 31A, 31
, B, 31C,... Are set as the configuration of a set-top box for receiving digital terrestrial broadcasting, and the receivers 32A, 32B, 32C,. , 31B, 31
C,... May be connected.

As described above, in the system to which the present invention is applied, the frequency of the received signal of each channel of the digital terrestrial broadcast received by the antenna 1 is converted into the frequency of each channel for CATV by the retransmission equipment 2. Is done.
Then, this signal is transmitted to the receiving facilities 4A, 4B, 4C,.

The retransmission equipment 2 performs frequency conversion, but does not rewrite the NIT. Therefore, the frequency information of each channel indicated by NIT may not match the actual frequency of each channel transmitted via the transmission path 3.

In ordinary terrestrial digital broadcasting, NIT
From the NIT table, frequency information is obtained, the reception frequency is set to a desired frequency, and then the PAT is referred to. From the PAT information, the video packet and audio of the PID of the channel in the carrier are obtained. The packet is retrieved and the desired channel is received. For this reason, the frequency information of each channel indicated by the NIT does not match the actual frequency transmitted through the transmission path 3 (hereinafter, referred to as the frequency of the transmission channel). For this reason, the frequency of the desired channel cannot be set.

Therefore, according to the present invention, the receiving devices 31A, 31B,... In the receiving facilities 4A, 4B, 4C,.
31C,... Are provided with a frequency conversion table indicating the correspondence between the frequency information indicated by NIT and the frequency of the transmission channel.

This frequency conversion table is stored in the receiving devices 31A, 31B, 31
.. Are set in the frequency search mode.

That is, the receiving devices 31A, 31B, 31
At C,..., At the time of initial setting, a frequency search mode is set to search for a channel on which broadcasting is being performed. When this frequency search mode is set, the NIT is acquired, and NIT is obtained from the relationship between the frequency information indicated by the NIT and the frequency information set at that time.
A frequency conversion table indicating the correspondence between the frequency information of the IT and the frequency of the transmission channel is created. Thus, without rewriting the NIT in the retransmitting facility 2, the receiving devices 31A, 31B, 31C,... In the receiving facilities 4A, 4B, 4C,. It is possible to set the reception frequency.

FIG. 2 shows receiving facilities 4A, 4B, 4
The receiving devices 31A, 31B, 31 in C, ...
C,... Are shown. This receiving device 31
A, 31B, 31C,... Are provided with the frequency conversion tables in which the correspondence between the frequency information indicated by the NIT and the frequency of the transmission channel is written as described above. The rest of the configuration is basically the same as that of an ordinary digital terrestrial broadcast receiver.

In FIG. 2, a signal from an input terminal 50 is supplied to a front end unit 51. The front end unit 51 includes a tuner circuit 52 and an OFDM demodulation circuit 5
3 and an ECC decoder 54.

The signal from the input terminal 50 is supplied to a tuner circuit 52 of the front end section 51, and the tuner circuit 52 selects a signal of a desired frequency from the signals transmitted through the transmission path 3. Is done. The output of the tuner circuit 52 is supplied to an OFDM demodulation circuit 53. O
The FDM demodulation circuit 53 performs an OFDM demodulation process. The output of the OFDM demodulation circuit 53 is the ECC decoder 5
4 is supplied. Read by ECC decoder 54
Error correction processing is performed by the Solomon code.

The output of the ECC decoder 54 is supplied to a descrambler 56. The descrambler 56 is supplied with key data for descrambling stored in the IC card 58 mounted on the IC card slot 57. The descrambler 56 descrambles the MPEG transport stream using the key data of the IC card 58. MPEG descrambled
The transport stream 2 is a demultiplexer 6
Sent to 0.

The demultiplexer 60 is connected to the controller 6
1 is to separate a desired packet from the stream from the descrambler 56 on the basis of the instruction from. In a transmission packet, a packet identifier (P
ID) is described. In the demultiplexer 60,
Based on the PID, video packets and audio packets of a desired program, PSI (Program Specific INfor
mation) is extracted. The video packet of the desired program is sent to the video processing circuit 62, and the audio packet is sent to the audio processing circuit 63. The PSI is sent to the controller 61.

The video processing circuit 62 receives the video signal packet from the demultiplexer 60,
A video signal is formed by performing a decoding process of the system. This video signal is supplied to the adding circuit 64. The on-screen display signal is supplied from the OSD circuit 65 to the addition circuit 64. This on-screen display signal is generated based on a signal from the controller 61. The output of the adding circuit 64 is output from the video output terminal 66.

The audio processing circuit 63 receives the audio packet from the demultiplexer 60, performs an audio decoding process of the MPEG system, and forms an audio signal. The output of the audio processing circuit 63 is output from an audio output terminal 67.

An input for operating the receiving device 31 is performed by an input key 71, and an input from the input key 71 is supplied to the controller 61. Further, an infrared signal from a remote controller (not shown) is received by the light receiving section 73, and this signal is supplied to the controller 61. Further, the output of the controller 61 is supplied to the display unit 72,
Various setting states are displayed on the display unit 72. Further, the controller 61 can be connected to a telephone line by a modem 74.

Further, the controller 61 sends an EEP
ROM (Electrically Erasable and Programmable Rea)
d Only Memory) 75, SRAM (Static Random Acce
ss Memory) 76 and a ROM (Read Only Memory) 77 are provided. The SRAM 76 has NIT (Network Info
rmation Table), and a frequency conversion table showing the correspondence between the frequency information of the transmission channel and the frequency information is created. When setting the reception frequency in the tuner circuit 52, this frequency conversion table is referred to.

As described above, the receiving apparatuses 31A, 31B, 31C,... To which the present invention is applied use the frequency conversion table indicating the correspondence between the frequency information indicated by NIT and the frequency of the transmission channel. . This will be described in detail below.

FIG. 3 is an example of a table of NIT sent by digital terrestrial broadcasting. Important information included in the NIT table includes a terrestrial distribution descriptor and a service list descriptor.

FIG. 4A shows a terrestrial distribution descriptor. The terrestrial distribution descriptor includes a descriptor tag (desc
riptor_tag) and descriptor length (descriptor
_Length), an area code (area_code), a guard interval (guard_interval), and a transmission mode (transmission_mode), and a frequency (frequency) is described. The guard interval (guard_interval) is defined as shown in FIG. 5B. The transmission mode (transmission_mode) is defined as shown in FIG. 5C.

FIG. 4B shows a service list. The service list includes a descriptor tag (descript
or_tag) and descriptor length (descriptor_le
ngth), a service ID (service_id), and a service type (service_type). The service type (service_type) is defined as shown in FIG. 5A.

The important information in the NIT table is the frequency (FIG. 4). The frequency indicates a center frequency of a channel (physical transmission frequency) through which a terrestrial digital broadcast signal is transmitted.

Normally, when receiving a broadcast of a desired channel, first, an NIT table is obtained, and the NIT table is acquired.
The table of T gives the frequency,
The receiving frequency is set to a desired frequency. Then P
The AT packet is referred to. The PAT describes channel information within each frequency and the PMT PID indicating the contents of each channel. From the PAT information, the PID video packet and audio packet of the channel in the carrier are extracted, and the desired channel is received.

As described above, normally, the NIT table is acquired and the reception frequency is set. In this system, however, the frequency conversion circuit 23 of the retransmission equipment 2 in FIG.
In A, 23B, 23C,..., Frequency conversion is performed as necessary, and the frequency of the channel transmitted via the transmission path 3 may not match the frequency information of the NIT. Here, frequency information obtained from the NIT,
A frequency conversion table is created which indicates the correspondence between the frequency of the transmission channel transmitted via the transmission path 3 and the frequency.

This frequency conversion table is created in the frequency search mode as follows.

FIG. 6 is a conceptual diagram showing the generation of the frequency conversion table. As shown in FIG. 6A, VHF, UCH including channels used in terrestrial digital broadcasting in Japan
A frequency table in which all channel information of the HF band is registered is prepared.

When set to the frequency search mode, FIG.
The tuning data is sent from the controller 61 to the tuner circuit 52 from the lower frequency to the higher frequency, for example, based on the frequencies registered in the frequency table shown in FIG.

Then, it is determined whether or not the signal can be received at the set frequency. If the signal can be received, NIT is obtained from the received signal, and the tuner circuit 52 determines the frequency set at that time from the NIT. A frequency conversion table is generated based on the correspondence with the obtained frequency information.

For example, in FIG. 6A, when the frequency of “J3ch” is set to 105 MHz in the tuner circuit 52, as shown in FIG.
It is assumed that frequency information of 3 MHz has been acquired. In this case, as shown in FIG.
If it is MHz, the receiving frequency of 52 of the tuner circuit is set to 105
A frequency conversion table that indicates setting to MHz is created.

In the receiving mode, the receiving devices 31A, 31B,
The method of selecting a desired channel by 31C,... Includes (a) a method of appropriately allocating a reception frequency corresponding to a selection button of a remote controller in the same manner as the current reception of analog terrestrial broadcasting; b) a method of inputting a service ID with a remote controller in the same manner as the method of receiving CS digital broadcasting,
Can be considered.

In the method (a), after the frequency conversion table is generated in the frequency search mode as described above, the channel selection button number of the remote control is set to the reception frequency set in the tuner by the converted frequency information. Supported.

For example, the tuning button "8"
By setting the frequency to 5 MHz and selecting a channel with a channel selection button, a signal of the channel can be received. The program can be displayed by determining the default service ID. The default service ID may be, for example, a method of storing the service ID of the last viewed program, or the service ID of the most recently received channel.
It is conceivable to select a program with a small number.

Other service IDs within the receiving channel
Is received, the frequency conversion table is used to refer to the corresponding NIT table, and the corresponding NIT
Get service descriptor from table. For example, if the reception frequency is 105 MHz, the NIT frequency information of 333 MHz is referred to by the conversion table shown in FIG. 6C. As shown in FIG. 6B, this NIT of 333 MHz
The service descriptor is obtained from the table.

In the method (b), the existing digital CS
Similar to the broadcast receiver, the channel including the input service ID is searched from the NIT table, and the channel frequency including the service ID is obtained from the distribution descriptor. Then, according to the frequency conversion table shown in FIG. 6B,
By converting the frequency indicated by NIT into the frequency of the corresponding transmission channel and transmitting the tuning data based on the converted frequency, the desired program can be received.

FIG. 7 is a flowchart showing the processing in the frequency search mode. When the frequency search mode is set, channel selection data is transmitted from the controller 61 to the tuner circuit 52 in the order of, for example, a lower frequency to a higher frequency based on the frequencies registered in the frequency table (FIG. 6A). The tuner circuit 52 sets a frequency based on the channel selection data (step S
1).

The tuner circuit 52 attempts to determine whether a signal can be received at the set frequency. When the signal can be received by the tuner circuit 52, the front end unit 5
From 1, the F / E lock signal can be obtained. The F / E lock signal is a flag indicating that the demodulation circuit and the error correction circuit have correctly operated and the transport stream has been correctly output. Therefore, whether or not the signal can be received at the set frequency can be determined based on whether or not the F / E lock signal can be obtained from the front end unit 51 (step S2). If the F / E lock signal cannot be received in step S2, the process returns to step S1 and is set to the next frequency based on the frequency table.
It is determined whether the F / E lock signal can be acquired at the set frequency.

If the F / E lock signal has been received in step S2, it is determined whether the NIT can be acquired (step S3). When the F / E lock signal can be received, it means that the transport stream has been output from the front end unit 51, so that the NIT can be obtained. If the NIT cannot be obtained, the transport stream is not correctly output or the transport stream does not include broadcast data. In this case, the process returns to step S1.

When the NIT is obtained in step S3, N
The frequency information of the NIT is acquired with reference to the distribution descriptor in the IT (step S4).

At this time, the reception frequency set in the tuner circuit 52 is associated with the NIT frequency information obtained in step S4, and a frequency conversion table is generated (step S5).

Then, it is determined whether or not all the frequencies have been searched (step S6). If all the frequencies have not been searched, the process returns to step S1, where the next frequency is set and the same processing is performed. Repeated. When the search for the frequencies of all the channels is completed, the frequency search mode ends.

Thus, in the frequency search mode,
A frequency conversion table indicating the correspondence between the frequency indicated by the NIT and the frequency of the transmission channel is created.

FIG. 8 is a flowchart showing the operation in the reception mode. In this example, the service ID is input with the remote control in the same way as the receiving method of CS digital broadcasting,
This is an example of setting a channel.

In FIG. 8, when an input for receiving the service ID of the "M" channel is given, a channel including the service ID is searched from the NIT table (step S11). It is determined whether there is a channel including the service ID (step S1).
2) If there is no channel containing the service ID,
A display indicating that reception is not possible is made (step S13).

At step S12, if there is a channel including the service ID, the frequency indicated by NIT is converted to the frequency of the corresponding transmission channel by referring to the frequency conversion table (step S14). Then, the receiving frequency of the tuner circuit 52 is set based on this frequency (step S15).

Then, a PAT packet is obtained (step S16). The PAT includes channel information in each frequency and a PMT indicating the contents of each channel.
Is described. From the PAT information, the PID corresponding to the channel "M" is recognized (step S17). Then, the video packet and the audio packet of the recognized PID are separated (step S1).
8). As a result, the desired “M” channel is received.

As described above, in the system to which the present invention is applied, the terrestrial digital broadcast signal is transmitted to the retransmission equipment 2.
Then, only the frequency is converted as necessary, and sent to the receiving facilities 4A, 4B, 4C,. Each home receiving device 31A, 31B, 31C, ...
Is provided with a conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted via the transmission path. The receiving frequency is set based on this conversion table. Therefore, the retransmission equipment 2 does not need to perform the NIT change processing, and does not need the OFDM demodulation circuit or modulation circuit. Also, the receiving facilities 4A, 4B, 4
C,... Can be used for ordinary digital terrestrial broadcasting reception except that a conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted via the transmission path is provided. it can.

In this example, OFDM is used as a modulation system for digital terrestrial broadcasting. However, the present invention can be similarly applied to other modulation systems.

[0068]

According to the present invention, a terrestrial digital broadcast signal is converted only in frequency at a retransmission facility as required, and sent to a receiving facility in each home via a transmission line. The home receiver is provided with a conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted via the transmission path. Based on this conversion table,
The receiving frequency is set.

For this reason, in the retransmission equipment, it is not necessary to perform the NIT change processing, and the OFDM demodulation circuit and modulation circuit are unnecessary.

The receiving equipment at each home is provided with a standard digital terrestrial broadcast reception except that a conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted through the transmission line is provided. Can be used and does not require a dedicated receiver.

The conversion table indicating the correspondence between the frequency of the NIT and the frequency of the signal transmitted via the transmission path is as follows:
The conversion table is created in the frequency search mode at the time of initial setting, and can be easily realized by software. Further, once the conversion table is created, it is not necessary to create the conversion table later, so that the receiver is not confused.

When the channel is set, the receiving frequency is automatically set based on this conversion table, so that the receiver can operate in exactly the same manner as when receiving ordinary digital terrestrial broadcasting. A program of a desired channel can be received.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a transmission / reception system to which the present invention is applied.

FIG. 2 is a block diagram of an example of a receiving device in a transmission / reception system to which the present invention has been applied.

FIG. 3 is a schematic diagram used for explaining a NIT table.

FIG. 4 is a schematic diagram used for explaining a NIT table.

FIG. 5 is a schematic diagram used for explaining a NIT table.

FIG. 6 is a schematic diagram used for explaining a frequency conversion table.

FIG. 7 is a flowchart used to describe an operation in a frequency search mode in a receiving apparatus in a transmission / reception system to which the present invention is applied.

FIG. 8 is a flowchart used to describe a receiving operation in a receiving device in a transmitting / receiving system to which the present invention is applied.

[Explanation of symbols]

1 ... antenna, 23A, 23B, 23C ... frequency conversion circuit, 3 ... transmission path 3, 4A, 4B, 4C ...
-Receiving equipment, 31A, 31B, 31C ... receiving device,
53: OFDM demodulation circuit, 76: SRAM

Claims (12)

[Claims] 1. A shared antenna for receiving a digital broadcast, a received signal of the digital broadcast received by the shared antenna, a frequency of the received signal of the digital broadcast changed as necessary, and In a digital broadcast transmitting / receiving system comprising a retransmitting facility for retransmitting and receiving a signal transmitted via the transmission path and a receiving facility at each home for receiving and reproducing the signal, the received signal of the digital broadcast includes And information indicating the frequency of each channel is included in the reception device. The reception device includes information indicating the frequency of each channel included in the reception signal and a signal transmitted through the transmission path. A conversion table is provided which indicates a correspondence relationship with the frequency of the received signal. When a signal of a desired channel is received by the receiving apparatus, a reception frequency is referred to by referring to the conversion table. Transmission and reception system which is adapted to set the number. 2. The frequency of a receivable channel is set in order, and it is determined whether a signal has been received at the set frequency. If the signal can be received, the signal included in the received signal is determined. Extracting information indicating the frequency of each channel, and associating the set frequency with the frequency obtained from the information indicating the frequency of each channel included in the received signal, creating the conversion table 2. The transmission / reception system according to claim 1, wherein: 3. A frequency of a channel to which a program of a desired channel is transmitted is extracted from information indicating a frequency of each channel included in the received signal, and a frequency of the channel included in the received signal is extracted. A frequency obtained from information indicating the frequency of each channel is converted into a frequency of a signal transmitted through the transmission path based on the conversion table, and a reception frequency is set to the converted frequency. Item 2. The transmission / reception system according to Item 1. 4. A digital broadcast is received by a shared antenna, a received signal of the digital broadcast received by the shared antenna is input, a frequency of the received signal of the digital broadcast is changed as necessary, and the signal is transmitted through a transmission path. A digital broadcast transmission / reception method in which a signal transmitted via the transmission path is received and reproduced by receiving equipment at each home. Conversion indicating the correspondence between the information indicating the frequency of each channel included in the reception signal and the frequency of the signal transmitted through the transmission path. A table is provided in the receiving device, and when a signal of a desired channel is received by the receiving device, a transmission frequency is set with reference to the conversion table. Shin method. 5. A frequency of a receivable channel is set in order, and it is determined whether a signal is received at the set frequency. If the signal is received, the signal included in the received signal is determined. Extracting information indicating the frequency of each channel, and associating the set frequency with the frequency obtained from the information indicating the frequency of each channel included in the received signal, creating the conversion table The transmission / reception method according to claim 4, wherein 6. A frequency of a channel to which a program of a desired channel is transmitted is extracted from information indicating a frequency of each channel included in the received signal, and a frequency of the channel included in the received signal is extracted. A frequency obtained from information indicating the frequency of each channel is converted into a frequency of a signal transmitted through the transmission path based on the conversion table, and a reception frequency is set to the converted frequency. Item 5. The transmission / reception method according to Item 4. 7. A receiving apparatus for receiving a digital broadcast signal received by a shared antenna, of which frequency is changed as necessary, and transmitted via a transmission path, wherein: Information indicating the frequency of each channel is included, and the correspondence between the information indicating the frequency of each channel included in the received signal and the frequency of the signal transmitted through the transmission path is described. A receiving device comprising a conversion table shown in the table, and setting a reception frequency by referring to the conversion table when receiving a signal of a desired channel. 8. A frequency of a receivable channel is set in order, and it is determined whether or not a signal can be received at the set frequency. If the signal can be received, the signal included in the received signal is determined. Extracting information indicating the frequency of each channel, and associating the set frequency with the frequency obtained from the information indicating the frequency of each channel included in the received signal, creating the conversion table The receiving device according to claim 7, wherein 9. A frequency of a channel on which a program of a desired channel is transmitted is extracted from information indicating a frequency of each channel included in the received signal, and the frequency of the channel included in the received signal is extracted. A frequency obtained from information indicating the frequency of each channel is converted into a frequency of a signal transmitted through the transmission path based on the conversion table, and a reception frequency is set to the converted frequency. Item 8. The receiving device according to item 7. 10. A receiving method for receiving a digital broadcast signal received by a shared antenna, having a frequency changed as necessary, and transmitted via a transmission path, wherein the digital broadcast received signal includes: Information indicating the frequency of each channel is included, and the correspondence between the information indicating the frequency of each channel included in the received signal and the frequency of the signal transmitted through the transmission path is described. A receiving method in which a conversion table shown in the following table is created, and a reception frequency is set with reference to the conversion table when a signal of a desired channel is received. 11. A frequency of a receivable channel is set in order, and it is determined whether a signal has been received at the set frequency. If the signal has been received, the signal included in the received signal is determined. The information indicating the frequency of each channel is extracted, and the conversion table is created by associating the set frequency with the frequency obtained from the information indicating the frequency of each channel included in the received signal. 11. The receiving method according to claim 10, wherein: 12. A frequency of a channel to which a program of a desired channel is transmitted is extracted from information indicating the frequency of each channel included in the received signal, and the frequency included in the received signal is extracted. A frequency obtained from information indicating the frequency of each channel is converted into a frequency of a signal transmitted through the transmission path based on the conversion table, and a reception frequency is set to the converted frequency. Item 11. The receiving method according to Item 10.