JPH1056630A - Bidirectional catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a broadcasting group spread over a plurality of transmission lines by allocating multi-address broadcasting to a TDM frame previously designated for each of the plurality of transmission lines. SOLUTION: A broadcasting device 1 decodes a select signal, determines a route to a plurality of subscribers based on the table of a broadcasting block number and a broadcasting object group number and lets an exchange 7 set the multicast path of audio data to be multi-address broadcasted to plural outgoing TDM frames. Besides, the broadcasting device 1 transmits multicast data having the group number of the broadcasting destination, block number, multi-address channel number and broadcasting class information through the multicast path set by the exchange 7 to a TDMA device 13. At the device 13, the transmitted signals are converted and transmitted through bidirectional CATV transmission lines 19a and 19b to subscriber devices 20a and 20b of all the subscribers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bidirectional CATV.
The present invention relates to a (Cable Television) system, and more particularly, to a function of communicating between subscriber terminals and a function of broadcasting a broadcast group including all subscriber terminals or arbitrary subscriber terminals.

[0002]

2. Description of the Related Art When a two-way CATV system that satisfies a communication function between subscribers is constructed, a CAT is used by a subscriber.
The connection to the V station is made using TDMA (Time Division).
n Multiple Access) or FDMA
(Frequency Division Multi
ple Access) is used. But C
The total number of allowable communication channels on the ATV transmission line is limited. For this reason, it has been difficult to sufficiently allocate the number of channels for speech and broadcast.

Therefore, as a method of increasing the number of broadcast channels in a pseudo manner, a CATV transmission line is divided into divided regions, and a multicast channel for broadcasting is allocated to a CATV transmission line for each region, thereby simultaneously broadcasting. There is a method of increasing the number of channels by spatial division. That is, in the FDMA system, a broadcast call from a subscriber included in a branched CATV transmission line area is restricted within the same CATV transmission line, and a frequency is set so that a broadcast can be received. Conversion has increased the total number of broadcast channels in the entire CATV system.

[0004]

However, the above C
In the ATV system, when a call between subscribers and a broadcast from a CATV station are simultaneously performed, the total number of channels allowed by the CATV system is divided and used, so that the number of channels used by both is limited. Also, if there is a set of broadcast calls over a branched CATV transmission line area, the subscribers who receive the call are limited to the subscribers in the corresponding CATV transmission line area. There is a drawback that it is necessary to configure The present invention has been made under such a background,
A two-way CATV system that can make the most effective use of channels for calls and broadcasts on a CATV system, and does not need to limit the CATV transmission path of a broadcast calling subscriber and a broadcast receiving subscriber. The purpose is to provide.

[0005]

According to the first aspect of the present invention,
A CATV station, a plurality of subscriber terminals, and a plurality of transmission paths for connecting the CATV station and the plurality of subscriber terminals, respectively, wherein a plurality of transmission paths are transmitted from the plurality of subscriber terminals to the CATV station. In a two-way CATV system using one data and second data transmitted from the CATV station to the plurality of subscriber terminals, a plurality of predetermined plurality of subscriber terminals among the plurality of subscriber terminals are provided. Storage means for storing a table indicating a correspondence between a broadcast group and a plurality of broadcast blocks comprising the plurality of broadcast groups, and a table indicating a broadcast destination included in the first data. Selecting means for selecting the predetermined block including the predetermined plurality of broadcast groups of the broadcast destination as a transmission destination of the second data.

According to a second aspect of the present invention, in the two-way CATV system according to the first aspect, the information indicating the broadcast destination is the broadcast group and a number indicating the broadcast group. 1. Bidirectional CA described in 1.
TV system. According to a third aspect of the present invention, in the two-way CATV system according to the first aspect, the first data as a request from any subscriber terminal included in the broadcast group includes a call request and a broadcast request. Is characterized by having information for determining According to a fourth aspect of the present invention, in the two-way CATV system according to the first or third aspect, there is provided a broadcasting means for broadcasting the broadcast, and the broadcast request is received from any of the subscriber terminals. If
The broadcast means analyzes the first data in the table, and selects the broadcast, the broadcast group number, the broadcast block number, the broadcast type, and the broadcast channel number from which the broadcast is transmitted. Output to According to a fifth aspect of the present invention, in the two-way CATV apparatus according to the first or third aspect, the broadcast block selected by the selecting means is a downlink of the plurality of transmission paths and a carrier of the second data. It is characterized in that it is allocated in advance for each frequency carrier. According to a sixth aspect of the present invention, in the two-way CATV device according to the first or fifth aspect, the plurality of transmission paths or the plurality of the transmission groups are transmitted to a plurality of the broadcast groups included in the broadcast block corresponding to the broadcast. A downlink TDM frame as the second data is transmitted for each of a plurality of transmission line frequencies.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a bidirectional CATV system according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a bidirectional CATV system according to an embodiment of the present invention, which can simultaneously perform a call and a broadcast. This bidirectional CATV system includes a broadcasting device 1, a switching device 7, and a TDMA device 13.

The broadcasting device 1 is a device for broadcasting image and audio data. In the broadcast device 1, the broadcast sound source unit 2 is a device for transmitting a broadcast from a station. The interface control unit 3 has a broadcast group and a broadcast block target table, selects a broadcast channel corresponding to a broadcast request from a subscriber, and transmits broadcast audio data received from the subscriber who has requested the selected channel. It is a device for broadcasting.

The trunk 4 is a device for transmitting a broadcast from a CATV station and a subscriber to the exchange 7. Trunk 5
Is a device for decoding a selection signal consisting of a broadcast group number requested by a subscriber and transferring the broadcast group number data to the interface control unit 3. The broadcast control information transmitting unit 6 is a device for transmitting broadcast control information including a broadcast block number, a broadcast group number, a broadcast channel number, and the like to the exchange 7.

The exchange 7 is a device for switching a data transmission path between a telephone call and a broadcast communication. The trunk 8 in the exchange 7 is a device that receives broadcast audio data from a broadcast device for each broadcast channel. Trunk 9
Is a device that transmits to the broadcasting device 1 a selection signal including voice data from a subscriber and a broadcasting group number.

The broadcast control information receiving unit 10 is a device for receiving broadcast control information from the broadcast control information transmitting unit 6 inside the broadcasting device 1. The switch 11 is a device for exchanging signal paths from the broadcasting device 1 and the TDMA device 13 and performing fixed multipath connection of signals from the trunk 8 to the digital interface 12. The digital interface 12 is a device for interfacing data between the exchange 1 and the TDMA device 13.

The TDMA device 13 is provided between the exchange 7 and the head-end device 17 and performs conversion and inverse conversion for multiple access of speech, broadcast data and broadcast control information. The digital interface unit 14 in the TDMA device 13 is a device for performing a call between the exchange 7 and the TDMA unit 15 and an input / output operation of broadcast data and broadcast control information.

The TDMA section 15 is a device for multiplexing a signal from the digital interface section 14 and transmitting the multiplexed signal to the modulation / demodulation section 16, decoding a signal from the modulation / demodulation section 16 and transmitting the decoded signal to the digital interface section 14. The modulation / demodulation unit 16 is a device for modulating and converting the signal from the TDMA unit 15 to transmit the signal to the head end device 17, demodulating the signal from the head end device 17, and transmitting the demodulated signal to the TDMA unit 15.

The head end device 17 is a TDMA device 1
3 and two-way CATV transmission lines 19a and 19b, and is composed of mixing and distributing units 18a and 18b. Mixing and distributing section 18 in head end device 17
a and 18b are TDM / T signals from the TDMA device 13.
This is an apparatus for performing mixed distribution of a DMA frame, a TV (Television) signal, and the like.

A plurality of subscriber units 20a are connected to the bidirectional CATV transmission line 19a.
A telephone 21a is connected to 0a. The subscriber device 20a is a device having a speaker for broadcasting and having an exchange terminating function for receiving audio data broadcasting from a CATV station and for talking. The standard telephone set 21a is a device for performing a broadcast operation from the subscriber side and for performing a normal telephone call.

A plurality of subscriber units 20b are connected to the bidirectional CATV transmission line 19b.
0b is connected to a standard telephone set 21b. The subscriber device 20b is a device having an exchange terminating function for receiving audio data broadcasts from a CATV station and for talking. The standard telephone 21b is a device for performing a broadcast operation from the subscriber side and for performing a normal telephone call.

Next, an example of a TDM / TDMA frame used in the bidirectional CATV system will be described with reference to FIG. Downlink TDM sent from CATV station to subscriber
The frame 22 includes a frame synchronization signal 23 for timing the multiplexed frame, and a demand assignment control time slot 24 for performing TDMA operation control.
And a broadcast time slot 25 for transmitting broadcast voice data, and a call time slot 26 used for transmitting general call voice data.

The upstream TDMA frame 27 sent from the subscriber to the CATV station includes a delimiter 28 indicating a signal delimiter and an access time slot for performing a demand access requesting allocation of a burst for transmitting information by calling. 29 and a call time slot 30 for calling and broadcasting from a subscriber.

Next, the operation of the above embodiment will be described with reference to FIGS. FIG. 3 is a sequence diagram showing a procedure at the time of broadcasting transmission from a subscriber. The TDMA device 13 constantly broadcasts the free time slot information 31 to the subscriber devices 20a and 20b of each subscriber via the bidirectional CATV transmission lines 19a and 19b. For example, when a subscriber makes a call, the subscriber may call the standard telephone 21a.
, The subscriber device 20a transmits a time slot allocation request 32 to the TDMA device 13 via the bidirectional CATV transmission line 19a.

The TDMA device 13 transmits a response signal 33 to the subscriber device 20a in response to the time slot allocation request 32 from the subscriber device 20a, and simultaneously transmits the off-hook information 34 of the subscriber device 20a to the exchange 7. The exchange 7 converts the dial tone 36 with the TDMA device 13 to notify that the time slot allocation information 35 and the allocated time slot have been allocated according to the off-hook information 34 and the allocated time slot has been completed, and that a free time slot has been secured. The data is transmitted to the subscriber device 20a via the bidirectional CATV transmission line 19a.

After the subscriber confirms the dial tone 36 with the subscriber unit and inputs a specific number for transmitting a broadcast from the standard telephone 21a, a selection signal 37 is transmitted from the subscriber unit 20a to the bidirectional CATV transmission line. The data is transmitted to the TDMA device 13 via the communication line 19a. TDMA device 13
Decrypts the selection signal 37 and transmits it to the exchange 7. The exchange 7 decodes the decoded selection signal 37, and
The transmission path 38 is set.

After the selection signal 37 is processed, the selection signal 39 including the broadcast target group number is sent to the subscriber unit 20a.
Is transmitted to the TDMA device 13 via the bidirectional CATV transmission line 19a. The TDMA device 13 outputs a selection signal 39
And transmits it to the exchange 7. The exchange 7 transmits the selection signal 39 to the broadcasting device 1 via the set transmission path 38.

The broadcast apparatus 1 decodes the selection signal 39 and determines a route to one or a plurality of subscribers based on a table of broadcast block numbers and broadcast target group numbers.
The broadcasting device 1 is configured to transmit a single or a plurality of downlink TDMs (Time Divs), which are routes for transmitting broadcast audio data.
The switch 7 sets the multicast path 40 in an “Ission Multiplex” frame. This route is
These are downlink TDM carriers that are space-divided and frequency-divided for each bidirectional CATV transmission path. That is,
The route of the multicast path 40 can be freely set.

The broadcast apparatus 1 transmits multicast data having a broadcast destination group number, a broadcast destination block number, a broadcast channel number and broadcast type information to the exchange 7.
Is transmitted to the TDMA device 13 through the multicast path 40 set in the step (1). The transmitted signal is transmitted to the TDMA device 1
3 and the subscriber units 20a and 20 of all subscribers.
b via the bidirectional CATV transmission lines 19a and 19b. That is, the TDMA device 13 transmits the multicast path data of voice and data and the broadcast control information to the broadcast target group, for example, the bidirectional CATV transmission path 1.
Broadcast 41 to 9a.

Next, the operation in the case of a general call will be described. The TDMA device 13 constantly transmits the free time slot information 31 to the subscriber devices 20a and 20b. For example, when the subscriber picks up the standard telephone set 21a and places it in the off-hook state, the time slot allocation request 32 is transmitted from the subscriber apparatus 20a to the TDMA apparatus 13 via the bidirectional CATV transmission line 19a, and the call is permitted. Become.

The TDMA device 13 sends off-hook information 3
4 is transmitted to the exchange 7, the exchange 7 and the subscriber unit 20
A communication path is set between a. After the communication path is set, the subscriber receives a selection signal 37 from the subscriber device 20a.
To the TDMA device 1 via the bidirectional CATV transmission line 19a.
Upon transmission to 3, the TDMA device 13 decodes the selection signal 37 and transmits it to the exchange 7. Then, the exchange 7 decodes the selection signal 37 and sets a communication path with a communication destination corresponding to the request of the subscriber, for example, the subscriber device 20b. After setting the communication path, the subscriber device 20b of the communication destination responds,
The subscriber can talk on the standard telephone 21a and the standard telephone 21b.

Next, the operation of the interactive CATV system in response to a broadcast request from a subscriber will be described. The subscriber requesting the broadcast transmission can be transmitted to the subscriber device 20 in the same manner as a general call.
a transmits a time slot allocation request 32 to the TDMA device 13 via the bidirectional CATV transmission line 19a.
The TDMA device 13 transmits the time slot allocation request 32
And the off-hook information 34 is transmitted to the exchange 7.
The exchange 7 receives the off-hook information 34 and sets up a communication path between itself and the subscriber device 20a using an up-only channel.

The subscriber device 20a transmits the selection signal 37 to the TDMA device 13 via the bidirectional CATV transmission line 19a. The TDMA device 13 decodes the selection signal 37 and transmits it to the exchange 7. The exchange 7 decodes the selection signal 37 and establishes a path 38 which is a transmission path between itself and the broadcasting device 1 instead of the subscriber devices 20a and 20b. After outputting the selection signal 37, the subscriber unit 20a transmits the selection signal 39 to the T via the bidirectional CATV transmission line 19a.
The data is transmitted to the DMA device 13.

The selection signal 39 is information on a broadcast destination group number. Broadcasting apparatus 1 receives selection signal 39 and sets multicast path 40 for exchange 7 based on a preset table indicating the relationship between the broadcast block number and the broadcast group number. In setting the multicast path 40, which is the broadcast destination, all broadcast channels or a single broadcast channel are alternatively selected.

At the same time, the broadcast apparatus 1 sends the multicast path data including the broadcast channel number, the broadcast destination block number and the broadcast destination group number to the exchange 7 from the broadcast control information transmitting section 6 to the broadcast control information receiving section 10 of the exchange 7. Transmit to The exchange 7 always holds a transmission path for connecting the multicast path 40 to a plurality of TDM frames in a fixed multipath manner based on the received multicast path data.
That is, one broadcast transmission path is allocated in advance for each broadcast block.

Broadcast voice and data signals from the subscriber are transmitted from the exchange 7 via the TDMA device 13 to, for example, the bidirectional CATV transmission lines 19a and 19b. The subscriber units 20a and 20b, when the broadcast group number to which they belong is present in the broadcast control information in the demand assignment control time slot 24 shown in FIG. The broadcast time slot 25 including the broadcast is received.

Next, with reference to FIG. 7, a description will be given of the relationship between the broadcast block number and the broadcast group number when performing broadcast on the bidirectional CATV transmission lines 19a and 19b. In FIG. 7, the broadcast block is divided into two sections, a block 46 and a block 45. Block 46 is a bidirectional CA
This is a set of subscribers spanning both the TV transmission lines 19a and 19b. Block 45 is a set of only the subscribers connected to the bidirectional CATV transmission line 19a.

For example, in the table showing the relationship between the broadcast block numbers and the broadcast group numbers in the broadcast device 1 shown in FIG.
0, group 61 and simultaneous data are set. Block 45 includes a group 62 and a group 6
3 and simultaneous data are set. Group 60
Is composed of a subscriber 50, a subscriber 51, and a subscriber 52.

The group 62 is composed of subscribers 53 and 54. Group 63 is made up of subscribers 55. The group 61 includes a subscriber 56, a subscriber 57, and a subscriber 58. A subscriber 59 is connected to the bidirectional CATV transmission line 19b.

For example, if subscriber 50 has a two-way CATV
The system requests broadcast to the group 60, and the subscriber 53 calls a broadcast to the group 62. The subscriber 55 requests a broadcast to the group 63, and the subscriber 59 requests a broadcast to the group 61. The downstream TDM frame 47 and the downstream TDM frame 48 shown in FIG. 9 are transmitted from the TDMA units 16a and 16b to the bidirectional CATV transmission line 19a. Downlink TDM frame 49 is transmitted to bidirectional CATV transmission line 19b.
It is transmitted from the DMA unit 16c.

Downward TD on bidirectional CATV transmission line 19a
Broadcast channel 71 of M frame 47 and bidirectional CATV
The broadcast channel 75 of the downlink TDM frame 49 on the transmission path 19b is the subscriber 50 of the group 60, the subscriber 51
And the contents are the same because the broadcast is sent to the subscriber 52. The broadcast channel 76 of the downlink TDM frame 49 is
Subscriber 56, subscriber 57 and subscriber 5 of group 61
8 is a broadcast.

The broadcast channel 73 of the downstream TDM frame 48 is a broadcast for the subscribers 53 and 54 of the group 62. Downlink TDM frame 48
Is a broadcast channel for the subscribers 55 of the group 63.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes may be made without departing from the spirit of the present invention. Even if present, it is included in the present invention. In FIG. 1, the broadcast control information is transmitted from the broadcast control information transmitting section 6 in the exchange 1 to the broadcast control information receiving section 10 in the exchange 7.
The broadcast control information transmitting unit 6 in the exchange 1 may transmit the broadcast control information to the broadcast control information receiving unit 42 in the TDMA device 13 as shown in FIG.

In this case, the TDMA device 13 can insert the broadcast control information received by the broadcast control information receiving section 42 into a downlink TDM frame. And TDMA
From the device 13 to the bidirectional CATV transmission line 19a or 19b
It is possible to use not the demand assignment control time slot 24 in FIG. 2 but the broadcast control time slot 43 having the group number of the broadcast destination dedicated to the broadcast shown in FIG.

In the first and second embodiments, the broadcast is performed based on a request from a subscriber. However, as shown in FIG. 6, a standard telephone 44 is connected to the exchange 7 as shown in FIG. Broadcasting from the exchange 7 using the standard telephone 44 becomes possible.

[0041]

As described above, according to the first aspect of the present invention, a CATV station, a plurality of subscriber terminals, and a plurality of transmissions respectively connecting the CATV station and the plurality of subscriber terminals. And first data transmitted from the plurality of subscriber terminals to the CATV station, and the CATV station.
In a two-way CATV system using second data transmitted from a station to the plurality of subscriber terminals, a plurality of broadcast groups each including a predetermined plurality of subscriber terminals in the plurality of subscriber terminals, and the plurality of broadcast groups. Storage means for storing a table indicating a correspondence with a plurality of broadcast blocks composed of a plurality of broadcast groups; and information indicating a broadcast destination included in the first data, the predetermined broadcast destination being determined from the table. And selecting means for selecting the predetermined block including a plurality of broadcast groups as a transmission destination of the second data, so that the broadcast channel is not shared with the communication channel in the entire bidirectional CATV system. Since a broadcast is assigned to a TDM frame specified in advance for each of a plurality of transmission paths to which a broadcast group is connected,
Broadcasting can be performed without increasing the call loss rate of a call, and there is an effect that a broadcast group extending over a plurality of transmission paths can be set.

According to the second aspect of the present invention, in the two-way CATV system according to the first aspect, since the information indicating the broadcast destination is the broadcast group and a number indicating the broadcast group, the broadcast is performed. The effect is that a plurality of broadcast groups including the broadcast destination subscriber can be easily searched from the broadcast destination block. According to the invention described in claim 3,
2. The interactive CATV system according to claim 1, wherein the first data as a call from any subscriber terminal included in the broadcast group has information for distinguishing between a call request and a broadcast request. By setting a broadcast channel corresponding to each broadcast block in advance, it is possible to set a route of a broadcast group for broadcast according to a broadcast request from a subscriber. . According to the fourth aspect, the bidirectional CA according to the first or third aspect is provided.
The TV system further comprises a broadcasting unit for broadcasting the broadcast, and when the broadcast request is received from the arbitrary subscriber terminal, the broadcast unit analyzes the first data in the table, In order to output the broadcast, the broadcast group number, the broadcast block number, the broadcast type, and the broadcast channel number for sending the broadcast to the selection unit, the switching unit serving as the selection unit switches to the corresponding broadcast group. There is an effect that information can be simultaneously inserted into a plurality of TDMAs, which are the routes of. According to the fifth aspect of the present invention, the bidirectional CATV according to the first or third aspect is provided.
In the apparatus, since the broadcast block selected by the selection means is assigned in advance for each of the plurality of transmission paths in the downlink direction and the frequency carrier of the carrier of the second data, a plurality of downlink blocks corresponding to each broadcast group are assigned.
By including the broadcast data indicating the number corresponding to the broadcast group in the DM frame, there is an effect that the broadcast can be performed for all the predetermined broadcast groups. According to the invention described in claim 6, the bidirectional CAT according to claim 1 or 5 is provided.
In the V apparatus, transmitting the downlink TDM frame as the second data for each of the plurality of transmission paths or the plurality of frequencies in the transmission paths to the plurality of broadcast groups included in the broadcast block corresponding to the broadcast. Therefore, there is an effect that a broadcast group can be set without limiting the transmission path to which the subscriber who has requested the broadcast is connected and the transmission path to which the subscriber receiving the broadcast is connected.

[0043]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a bidirectional CATV system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a downlink TDM frame and an uplink TDMA frame used in the bidirectional CATV system according to the embodiment of the present invention shown in FIG.

FIG. 3 is a sequence diagram showing an operation of the bidirectional CATV system according to the embodiment of the present invention shown in FIG. 1;

FIG. 4 shows a bidirectional CAT according to a second embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a V system.

FIG. 5 is a configuration diagram of a downlink TDM frame used in the bidirectional CATV system according to the second embodiment of the present invention shown in FIG.

FIG. 6 shows a bidirectional CAT according to a third embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a V system.

FIG. 7 is a configuration diagram of a broadcast block and a broadcast group of the interactive CATV system according to the first embodiment of the present invention shown in FIG. 1;

8 is a table showing a relationship between a broadcast block and a broadcast group in the interactive CATV system of FIG. 7;

FIG. 9 is a diagram showing a downlink TDM frame used in FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Broadcasting apparatus 2 Broadcast sound source part 3 Interface control part 4, 5, 8, 9 Trunk 6 Broadcast control information transmitting part 7 Exchanger 10, 42 Broadcast control information receiving part 11 Switch 12, 14 Digital interface part 13 TDMA device 15 TDMA Unit 16 modem unit 17 head end unit 18 mixing / distributing unit 19, 19a, 19b bidirectional CATV transmission line 20, 20a, 20b subscriber unit 21, 21a, 21b, 44 standard telephone 22, 47, 48, 49 downlink TDM frame 23 Frame synchronization signal 24 Demand assignment control time slot 25 Synchronization time slot 26 Communication time slot 27 Uplink TDMA frame 28 Delimiter 29 Access time slot 30 Communication time slot 31 Free time slot information 32 Time slot allocation Request 33 response signal 34 off-hook information 35 time slot allocation information 36 dial tone 37, 39 selection signal 38 communication path 40 multicast path 41 broadcast 43 synchronization control time slot 45, 46 broadcast block 50, 51, 52, 53, 54, 55 Subscribers 56, 57, 58, 59 Subscribers 60, 61, 62, 63 Broadcast groups 71, 72, 73, 74, 75, 76 Broadcast channels

Claims (6)

[Claims] 1. A communication system comprising: a CATV station; a plurality of subscriber terminals; and a plurality of transmission paths for connecting the CATV station and the plurality of subscriber terminals, respectively, from the plurality of subscriber terminals to the CATV station. Data transmitted to the CAT and the CAT
In a two-way CATV system using second data transmitted from a V station to the plurality of subscriber terminals, a plurality of broadcast groups each including a predetermined plurality of subscriber terminals in the plurality of subscriber terminals, Storage means for storing a table indicating correspondence with a plurality of broadcast blocks formed by the plurality of broadcast groups; and information indicating a broadcast destination included in the first data. Selecting means for selecting the predetermined block including the predetermined plurality of broadcast groups as a destination of the second data, a bidirectional CATV system. 2. The interactive CATV system according to claim 1, wherein the information indicating the broadcast destination is the broadcast group and a number indicating the broadcast group. 3. The method according to claim 2, wherein the first data as a call from any of the subscriber terminals included in the broadcast group has information for distinguishing between a call request and a broadcast request. 2. The bidirectional CATV system according to 1. 4. A broadcasting means for broadcasting the broadcast, wherein when the broadcast request is received from any of the subscriber terminals, the broadcast means analyzes the first data in the table. , The broadcast, the number of the broadcast group,
4. The bidirectional CATV system according to claim 1, wherein a number of the broadcast block, a broadcast type, and a broadcast channel number for transmitting the broadcast are output to the selection unit. 5. The broadcast block selected by the selection means is assigned in advance for each of the plurality of transmission paths in the down direction and a frequency carrier of a carrier wave of the second data. Item 3. The bidirectional CATV system according to Item 3. 6. A downlink TDM frame as the second data for each of the plurality of transmission paths or the plurality of frequencies in the transmission paths to a plurality of broadcast groups included in the broadcast block corresponding to the broadcast. The bidirectional CATV system according to claim 1 or 5, wherein the transmission is performed.