JP2005167737A - Catv terminal equipment and catv system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission path for CATV where the signal containing terrestrial digital broadcasts which corresponds to a different modulation system for transmitting terrestrial digital broadcasts is transmitted. <P>SOLUTION: The CATV terminal equipment receives the signal transmitted on the CATV transmission path. The CATV terminal equipment comprises a front end corresponding to a trans-modulation system and the front end corresponding to a path-through system. Whether the front end corresponding to the trans-modulation system or a tuner corresponding to the pass-through system is prioritized, in a default state, can be set in advance. A reception operation is performed by a prioritized transmission system which is pre-set. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a CATV terminal apparatus mainly used for CATV, and more particularly to a CATV terminal apparatus that can cope with different transmission systems for terrestrial digital broadcasting transmitted to CATV. Also, a CATV system using this CATV terminal device.

Conventional CATV terminal devices, such as set-top boxes, not only can receive analog broadcasts, but also realize interactive services via the CATV network and the Internet along with digitalization of broadcasts, and receive digital broadcasts. It is configured to be possible. (For example, see Patent Document 1)

JP 2003-219312 A

However, according to a set top box which is a conventional CATV terminal device, digital broadcasting is configured to receive an OFDM (Orthogonal Frequency Division Multiplexing) modulation system which is a modulation system of terrestrial digital broadcast waves. However, when trying to receive digital terrestrial broadcasts via the CATV network, there are cases where such a configuration cannot be used. That is, there are two main methods for transmitting terrestrial digital broadcast waves to the CATV transmission line. One is to receive the OFDM terrestrial digital broadcast wave at the center station and transmit it to the CATV transmission line with the modulation method as it is. The system (pass-through system) and, secondly, a system that receives an OFDM terrestrial digital broadcast wave at the center station, converts it to the same 64QAM system as the BS digital broadcast retransmission, and transmits it to the CATV transmission line (transformer) There is a modulation system), and which transmission system is adopted differs depending on the CATV provider. Therefore, in order to support CATV, it is necessary to prepare a set top box corresponding to each of the above modulation systems.
In other words, since at least two types of set-top boxes are required in order to support CATV, the production process is complicated and the problem of productivity such as parts management due to the increase in the number of parts occurs. As a result, there was a problem that the cost of the set top box was increased.
Therefore, in this application, it was made to solve these problems.
An object of the present invention is to provide a CATV terminal device that can be transmitted via a CATV transmission path and can handle different transmission methods.
Another object of the present invention relates to a CATV terminal device in which a transmission method for preferential reception operation in a default state can be set in advance.
Another object is to provide a CATV terminal apparatus that supports a plurality of transmission methods for transmitting terrestrial digital broadcasting to CATV in CATV transmitting terrestrial digital broadcasting waves.
Another object of the present invention is to provide a CATV terminal apparatus that can determine the modulation system of terrestrial digital broadcasting transmitted to a CATV transmission path and can automatically switch and receive the signal according to the modulation system.
Another object of the present invention is to provide a CATV terminal device which can set an initial state so as to receive a predetermined modulation method so as to be compatible with the modulation method of digital terrestrial broadcasting transmitted to a CATV transmission line. .
Another object is that the reception operation in the initial state can be set in advance by manual operation or remote operation so as to correspond to the specified modulation method so that it can correspond to the modulation method of terrestrial digital broadcasting transmitted on the CATV transmission line. It is to provide a CATV terminal device.
Another object is to provide a CATV system that provides services between a center station and a plurality of CATV terminal devices that can support different transmission systems via a CATV transmission path.

In order to solve the above problems, the invention of claim 1 is directed to a front end for selecting and demodulating a predetermined channel from a signal transmitted from a center station via a CATV transmission line, and data output from the front end. In a CATV terminal device comprising a data signal decoder unit that decodes a signal and outputs a baseband signal, the CATV terminal device has at least two front panels so as to be able to handle signals of different modulation schemes transmitted from the center station. An end, a switching unit that inputs a data signal output from the front end, selectively switches a signal path, and outputs, and a control that switches a signal path of the switching unit based on a signal received by the front end And a transmission frequency band transmitted from the center station by the front end. From the information obtained by this scanning, the control unit automatically determines the modulation method of the signal transmitted in the transmission frequency band, and also determines the signal transmitted based on the determination result. The signal path is controlled so that the data signal from the front end corresponding to the modulation method is output from the switching unit.

According to the second aspect of the present invention, the front end receiving operation in the initial state of the CATV terminal apparatus can be set in advance so that it is possible to set in advance which front end is prioritized, and reception is performed with priority by the front end set in advance. Configured to perform an action.

The invention according to claim 3 is configured such that the setting of the front end for preferential reception operation is set by either manual setting or setting from an external control device.

According to a fourth aspect of the present invention, the CATV terminal device includes at least a front end corresponding to a trans-modulation method and a front end corresponding to a pass-through method. .

According to a fifth aspect of the present invention, a service is provided by connecting a plurality of CATV terminal apparatuses according to the first to fourth aspects through a center station and a CATV transmission line.

As described above in detail, according to the first aspect of the present invention, the front end for selecting and demodulating a predetermined channel from the signal transmitted from the center station via the CATV transmission line, and the output from the front end In a CATV terminal device comprising a data signal decoder unit for decoding a data signal and outputting a baseband signal, the CATV terminal device has at least two signals so as to be compatible with signals of different modulation schemes sent from the center station. A front end, a switching unit that inputs a data signal output from the front end, selectively switches a signal path, and outputs the signal, and switches a signal path of the switching unit based on a signal received by the front end A transmission frequency band transmitted from the center station by the front end. From the information obtained by this scanning, the control unit automatically determines the modulation method of the signal transmitted in the transmission frequency band, and also determines the signal transmitted based on the determination result. Since the signal path is controlled so that the data signal from the front end corresponding to the modulation method is output from the switching unit, even if the transmission method of the terrestrial digital broadcasting is different for each CATV provider as described above. It is possible to cope with any transmission method by preparing only one CATV terminal device, and the production cost can be reduced.

According to the invention of claim 2, the front end receiving operation in the initial state of the CATV terminal device can be set in advance so that it can be set in advance, and the front end set in advance is prioritized. For example, if the transmission system of the terrestrial digital broadcasting in the CATV facility to which the CATV terminal device is attached is known in advance, it is previously set at the time of shipment so as to correspond to this transmission system. By setting the default, the CATV terminal device does not need to perform extra scanning, and can display images and the like on the television receiver within a short time. A terminal device can be provided.

According to the third aspect of the present invention, since the setting of the front end for preferential reception operation is set by either manual setting or setting from an external control device, for example, this CATV terminal If the transmission system of terrestrial digital broadcasting in the CATV facility to which the apparatus is installed is known, the default setting can be manually set in advance at the time of shipment so as to correspond to this transmission system. Furthermore, if this setting is set from the outside by a personal computer or the like, a CATV terminal device with high production efficiency in the production line can be provided. In addition, since the default state can be set by a plurality of methods, the default setting can be set anywhere according to conditions such as the installation location and the situation after shipment, and the CATV terminal is excellent in versatility and convenience. An apparatus can be provided.

According to the invention of claim 4, the CATV terminal device is configured to include at least a front end corresponding to the trans-modulation method and a front end corresponding to the pass-through method. A CATV terminal apparatus capable of supporting any transmission system, whether a terrestrial digital signal is transmitted by a QAM-modulated transmodulation system or an OFDM-modulated pass-through system. Can do. .

  According to the fifth aspect of the present invention, since the service is provided by connecting a plurality of CATV terminal apparatuses according to the first to fourth aspects through the center station and the CATV transmission line, the operator can A CATV system can be easily provided that can support either the modulation method or the pass-through method for providing the terrestrial digital broadcasting service from the center station.

Hereinafter, an example of an embodiment embodying the present invention will be described in detail with reference to the drawings.
FIG. 1 shows the configuration of a CATV terminal apparatus according to the present invention. FIG. 2 shows another embodiment of the CATV terminal apparatus according to the present invention. FIG. 3 is a flowchart showing an operation state of the reception process of the CATV terminal apparatus according to the present invention. FIG. 4 shows an example of a CATV system using the CATV terminal device of the present application.

The CATV terminal apparatus shown in the present application is capable of providing a two-way service via a CATV transmission line. FIG. 1 shows an example of a set top box as a representative example of a CATV terminal apparatus. Unless otherwise specified, explanation will be made using a set-top box. FIG. 1 specifically shows a part related to the present invention, and generally added functions are not described.
In FIG. 1, a digital signal including at least a terrestrial digital broadcast signal is input from an input terminal Tin via a CATV transmission line. The input digital signal is supplied by the distributor 2 to a QAM modulation type tuner / demodulation unit (hereinafter also referred to as a front end) indicated by 3 and an OFDM modulation type tuner / demodulation unit (hereinafter also referred to as a front end) indicated by 4. ) Etc.

3 receives a digital signal that has been subjected to QAM modulation (Quadrature Amplitude Modulation: hereinafter referred to as QAM modulation) from among the digital signals transmitted to the CATV transmission line, and receives a predetermined signal from the received signal. It is a front end corresponding to a QAM modulation system configured to select and demodulate a signal and output a TS (Transport Stream) signal (hereinafter referred to as a TS signal).
The TS signal generated in the front end 3 of this QAM modulation method is output to the switching unit 7.

4 receives an OFDM modulated (Orthogonal Frequency Division Multiplexing: hereinafter referred to as OFDM modulation) digital signal from the signals transmitted through the CATV transmission path, and receives the received signal from the received signal. It is a front end corresponding to an OFDM modulation system configured to select and demodulate a predetermined signal and output a TS signal.
The TS signal generated in the front end 4 of this OFDM modulation scheme is output to the switching unit 7.

The switching unit 7 is a switching unit for switching the path of the TS signal output from the front end 4 corresponding to the OFDM modulation scheme or the front end 3 corresponding to the QAM modulation scheme. Done in
The TS signal output from the switching unit 7 is input to a CA (Conditional Access) descrambler 5.
The CA descrambler 5 receives a video signal and a video signal by inserting a CA module 5a such as an IC card in the case of receiving a pay broadcast or a copyright-protected signal among the signals transmitted to the CATV transmission line. The audio signal is descrambled so that it can be received.
The TS signal descrambled by the CA descrambler 5 is decoded by the MPEG-2 decoder unit shown in 10 and output from the video output terminal Vout, the audio output terminal Aout, and the like.

Reference numeral 15 denotes a control unit which modulates a terrestrial digital signal transmitted to a CATV transmission line from signals output from the front end 3 for the QAM modulation scheme or the front end 4 for the OFDM modulation scheme. Is a control unit for determining whether is QAM modulation or OFDM modulation. Further, the switching unit 7 is controlled to switch the path for accepting the TS signal input to the CA descrambler 5 from the front end of QAM modulation or from the front end of OFDM modulation according to the result of this determination. In addition, the control unit 15 controls whether a pay broadcast or a copyright-protected broadcast among the signals input to the CA descrambler 5 is received via a CA module 5a such as an IC card.

Further, the control unit 15 can also control the order in which the front end 3 for the QAM modulation system or the front end 4 for the OFDM modulation system operates.
As an example, in the default state when the power of the set top box is turned on, the reception end scans the reception band without deciding the particularly preferred front end, and the signal from the front end that receives the signal of the predetermined modulation method, The TS signal path input to the CA descrambler may be automatically switched via the switching unit 7.

Further, in the default state when the power of the set top box is turned on, control may be performed by the control unit 15 so that a particularly preferred front end can be set in advance. That is, in the default state, priority setting is performed so that the front end 3 for the QAM modulation system scans first, or priority setting is set in advance so that the front end 4 for OFDM modulation scans first. Based on the scanning result (for example, when terrestrial digital broadcasting by the QAM modulation method is not detected), the next modulation method (in this case, by the front end 4 for the OFDM modulation method) is scanned. It is a method to control.

In addition, it may be configured such that the priority front end can be set anytime and anywhere. That is, for example, it may be possible to control whether the priority front end is set to the QAM modulation method or the OFDM modulation method by key input indicated by T1 in FIG. 1, or may be set by a remote controller. Further, the control unit 15 may be configured to control whether the front end to be prioritized by the personal computer provided outside via the Ethernet (R) connector indicated by T2 is the QAM modulation method or the OFDM modulation method. .

Reference numeral 6 denotes a memory, which is obtained by decoding or scanning PSI (Program Specific Information) / SI (Service Information Information) included in the TS signal obtained by selecting and demodulating the signal transmitted from the center station by the front end described above. This is a memory for storing the frequency table information after the operation.
Reference numeral 20 denotes a power supply unit which can be turned on, put on standby, or turned off by a switch (not shown) in the embodiment of the present application. The control unit 15 is configured to determine the state of this switch.
Note that a cable modem may be provided in the set-top box so that interactive service is performed via the CATV network or the Internet.

FIG. 4 shows a CATV system using this set top box. In this figure, signals from satellites and signals such as terrestrial digital broadcasts are received by antennas 50 and 51 and input to a plurality of tuners 53 and 54 via distributors 52 and 54, respectively. The tuner output is modulated by a modulator 58 into a signal suitable for a CATV transmission line, and then sent to a CATV transmission line 70 via a mixer 59.
A set top box (STB) management device 60, a cable modem management device 61, a mail server 62, and the like are connected to a plurality of CMTSs 65 via switching (SW) hubs. The CMTS 65 is connected to the center station 100 via mixers 66 and 59. To the set top box 1 via the CATV transmission line 70. 80 is a personal computer and 81 is a television receiver.

Here, the front end switching will be described in detail. When digital terrestrial broadcasting is to be transmitted via a CATV network, there are two main transmission methods. One is the reception of an OFDM terrestrial digital broadcast wave at a center station, and CATV is transmitted as it is with a modulation scheme. The transmission method (pass-through method) on the transmission path and secondly, the terrestrial digital broadcasting wave of the OFDM method is received by the center station, converted into the same 64QAM modulation method as the retransmission of BS digital broadcasting, etc. and transmitted by CATV There are transmission methods (transmodulation methods) on the road, and which transmission method is adopted depends on the CATV operator.

The trans-modulation method is easy to adopt because the modulation method is the same for an operator who uses CATV to transmit a signal such as BS digital broadcast by the 64QAM modulation method as described above. In the case of CATV, when transmitting terrestrial digital broadcasting via a CATV transmission line, it is possible to receive only the OFDM modulation method (that is, pass-through method), for example, a QAM-modulated terrestrial digital broadcast signal is transmitted. However, it is necessary to prevent reception of QAM modulation of terrestrial digital broadcasting.
Therefore, the set top box of the present application includes a front end 3 compatible with the QAM modulation method and a front end 4 compatible with the OFDM modulation method, and the front end 3 for the QAM modulation method or the front end for the OFDM modulation method. The terrestrial digital signal transmitted to the CATV transmission line among the signals output from 4 is configured to be compatible with either the QAM modulation method or the OFDM modulation method. .

It should be noted that, as a way of dealing with the front end, it may be switched by automatically determining the modulation method. In this case, it can be installed regardless of the modulation method employed by the CATV facility where this set-top box is set.
Further, as a different method in the way of handling the front end, a front end that is preferentially operated in a default state may be set in advance. In this case, the front end that operates preferentially is set in advance so as to correspond to the digital terrestrial broadcasting transmission method adopted by the facility where the set top box of the present application is set. The advantage is that the time until the time can be shortened.
Further, the front end that operates preferentially may be changed by manual operation (for example, setting by a remote controller, setting by key input from the panel, etc.) or external control (for example, a personal computer). This configuration makes it possible to set defaults anytime and anywhere according to conditions such as installation location and post-shipment conditions, and can provide a set-top box that excels in versatility and convenience. .
FIG. 2 shows a configuration example of a set-top box when the front end and the distributor are housed in one housing.

The front end switching process will be described based on the flowchart shown in FIG. This flowchart is for when the default priority setting is preset.
In step 100, it is determined whether the front end 3 for the QAM modulation system is set with priority or the front end 4 for the OFDM modulation system is set with priority. If priority is set for the front end 3 of the QAM modulation system, the CATV transmission band is scanned first with the front end 3 (S101).
Next, in S102, it is determined whether or not a terrestrial digital broadcast is received (for example, the presence or absence of a network ID included in a transmission signal of the terrestrial digital broadcast is detected), and the terrestrial digital broadcast is transmitted by the QAM modulation method. If, for example, the network ID of terrestrial digital broadcasting is demodulated, the front end 3 of the QAM modulation system is set for reception in S103, and the CA descrambler is switched by switching the switching unit 7. 5 is switched to the route from the front end 3.
If it is determined in S102 that the terrestrial digital broadcast is not transmitted by the QAM modulation method (for example, if the network ID included in the transmission signal of the terrestrial digital broadcast is not demodulated), then in S104, the OFDM is transmitted. The reception band is scanned by the front end 4 of the modulation method. If it is determined in S105 that an OFDM-modulated terrestrial digital broadcast is being transmitted, the input path of the CA descrambler 5 is set by setting the OFDM-modulated front-end 4 for reception and switching the switching unit 7 in S106. Is switched to the route from the front end 4.

Next, in S100, if the OFDM modulation front end 4 is preferentially set, the process proceeds to S104, and the reception band is scanned by the OFDM modulation front end 4. If it is determined in S105 that an OFDM-modulated terrestrial digital broadcast is being transmitted, the input path of the CA descrambler 5 is set by setting the OFDM-modulated front-end 4 for reception and switching the switching unit 7 in S106. Is switched to the route from the front end 4.
If it is determined in S105 that the OFDM modulation terrestrial digital broadcast is not transmitted, it is determined that the terrestrial digital broadcast is not transmitted, and the process is terminated.

In this way, the front end that is preferentially operated in the default state is configured in advance so that it corresponds to the terrestrial digital broadcast transmission method adopted by the CATV facility where the set top box of the present application is set. Thus, since the front end operates preferentially, there is a merit that the time from when the power is turned on until it is received can be shortened.
The present invention is not limited to the above-described embodiment, and a front end corresponding to the modulation method being transmitted may be automatically selected. The default may be changed at any time and anywhere according to the conditions. Further, in the embodiment of the present application, an example in which two front ends are provided is shown. However, two front ends and a distributor may be accommodated in one housing, which departs from the gist of the present invention. It is also possible to implement by appropriately changing the configuration of each part within the range not to be.

The structure of the set top box which concerns on this invention is shown. The structure of the other Example of the set top box which concerns on this invention is shown. The flowchart which shows the operation state of the set top box which concerns on this invention is shown. The Example of the CATV system using the set top box 4 which concerns on this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Set top box, 2 ... Distributor, 3 ... Tuner / demodulation part (front end) of QAM modulation system, 4 ... Tuner / demodulation part (front end) of OFDM modulation system, 5 ... CA descrambler, 5a ... CA Modular, 6 ... Memory, 7 ... Switching unit, 10 ... MPEG-2 decoder unit, 15 ... Control unit, 18 ... Display unit, 19 ... Ethernet (R) interface, 20 ... Power supply unit, 50, 51 ... Receiving antenna, 52, 54 ... distributor, 53, 56 ... tuner, 58 ... modulator, 59, 66 ... mixer, 60 ... set top box, 61 ... cable modem management device, 62 ... mail server, etc. 63 ... switching hub, 64 ... Router, 65 ... CMTS, 70 ... CATV transmission path, 80 ... Personal computer, 81 ... TV receiver

Claims (5)

A front end for selecting and demodulating a predetermined channel from a signal transmitted from the center station via the CATV transmission path;
In a CATV terminal device comprising a data signal decoder unit for decoding a data signal output from the front end and outputting a baseband signal,
The CATV terminal device includes at least two front ends so that signals of different modulation schemes transmitted from the center station can be handled.
A switching unit for inputting the data signal output from the front end and selectively switching the signal path for output;
A control unit that switches a signal path of the switching unit based on a signal received by the front end, and
The front end scans the transmission frequency band transmitted from the center station, and from the information obtained by the scan, the control unit automatically determines the modulation method of the signal transmitted in the transmission frequency band. A CATV terminal device configured to control a signal path so that a data signal from a front end corresponding to a modulation method of a signal transmitted based on the determination result is output from a switching unit.
The front-end reception operation in the initial state of the CATV terminal device can be set in advance, which front-end is prioritized, and the reception operation is preferentially performed by a preset front-end. The CATV terminal apparatus according to claim 1, wherein:
3. The CATV terminal device according to claim 2, wherein the setting of the front end for performing the receiving operation with priority is set by manual setting or setting from an external control device.
The CATV terminal apparatus according to any one of claims 1 to 3, wherein the CATV terminal apparatus includes at least a front end corresponding to a trans-modulation method and a front end corresponding to a pass-through method.
  A CATV system characterized in that a service is performed by connecting a plurality of CATV terminal apparatuses according to claims 1 to 4 through a center station and a CATV transmission line.

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