JP3731379B2 - Transmitting apparatus and receiving apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a cable television (CATV) transmission line or the like to transmit a BS digital broadcast in which a transport stream having a frame configuration and transmission multiplexing control information indicating a modulation scheme in the frame and a transport stream configuration are transmitted. The present invention relates to a method and a transmission / reception apparatus that perform stable transmission / reception.
[0002]
[Prior art]
Regarding digital transmission of CATV, the Television Society Technical Report (vol. 19, No. 42) published on September 21, 1995, pages 19 to 24, “Telecommunication Technology Council Provisional System Digital Cable Television Broadcasting” It is shown in "Transmission experiment". According to this report, a data stream of a format called a transport stream in which digital data such as an image compressed by a digital image compression technique called MPPEG 2 (MPEG2) is multiplexed is used for signal processing such as Reed-Solomon error correction. Modulated by a digital modulation technique called 64QAM (64-value quadrature amplitude modulation) and transmitted to a CATV transmission line with a transmission capacity of about 30 Mbps.
[0003]
Also, as a digital channel TV multi-channel digital video distribution method, there is a satellite digital television broadcast. The broadcast is described in the article “70” on page 149 of the Nikkei Electronics September 2, 1996 issue. As described in “Japan's first digital satellite broadcasting that realizes multiple channels in the vicinity”, a single transformer in which multiple digitally compressed (MPEG2) programs and data are packet-multiplexed and scrambled for correction encoding. The port stream is transmitted by QPSK digital modulation. The satellite digital broadcasting has a problem that the C / N deterioration due to rain attenuation or the like occurs rapidly with respect to the analog system, thereby causing a service interruption.
[0004]
In conventional digital CATV, after demodulating the digital video distributed by QPSK modulation, it is remodulated to 64QAM or other digital modulation and transmitted to the CATV transmission line. However, satellite digital video distribution is blocked by rain attenuation etc. Even if the service stopped, no particular consideration was given.
[0005]
[Problems to be solved by the invention]
In the newly planned BS digital broadcast, not only a plurality of conventional digital television broadcasts but also a high-definition television broadcast is transmitted to one channel of a conventional BS analog broadcast transmission channel. The transmission of BS digital broadcasting is described in “BS Digital Broadcasting System and Equipment” on pages 24 to 31 of the Journal of the Video Media Society (vol. 52 No. 11 1998) in November 1998. BS digital broadcasting has a transmission capacity of about 60 Mbps, and a plurality of modulation schemes can be used in one repeater. A transport stream such as video, audio, and data has a frame structure, and a transmission multiplex control signal (TMCC signal) is used for transmission of control information of the modulation method and transport stream structure in the frame. TMCC, from the Ministry of Posts and Telecommunications Order No. 57, uses the synchronization signal portion of the transport stream and transmits it separately for each frame (= 48 slots, 1 slot = 204 bytes) before the main signal, and 1 superframe (= 8 Frame). The structure is shown in the Ministry of Posts and Telecommunications Notification No. 260, the transmission mode / slot information is used for selecting the digital demodulation means, and the relative TS / slot information and the relative TS / TSID correspondence are of the desired transport stream ID (TSID). Used for selective output. In addition, there are transmission / reception control information such as a change instruction number and emergency information, and an extended information area.
[0006]
In BS digital broadcasting, in order to reduce service interruption due to rain, layered transmission is possible by using a feature that enables transmission by combining a plurality of modulation schemes. The operation guidelines for layered transmission are described in “Chapter 3 Operation Guideline for Layered Modulation Service System” on pages 81 to 85 of the Radio Industry Association Standard (ARIB STD-B20 Version 1.0) of November 6, 1998. In the MPEG transport stream, a hierarchical transmission descriptor indicating the hierarchical relationship of programs is introduced. For example, trellis 8-phase PSK (TC8PSK) is transmitted as normal television broadcasting (higher layer), and QPSK and BPSK that can be received even at low C / N are transmitted as minimum information (lower layer) that can understand the contents of the same program. It is shown that the operation of the higher and lower layers by the layer transmission descriptor is performed on the basis of a signal that detects a decrease in C / N and an increase in error rate.
[0007]
However, in the above-described conventional digital CATV technology, transmission and reception of hierarchical transmission planned in BS digital broadcasting are not considered.
[0008]
The present invention relates to a method and a transmission / reception apparatus for performing stable transmission / reception of BS digital broadcasting using a CATV transmission line or the like.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, for example, a receiving unit that receives digital data in a transport stream format composed of a plurality of layers, a measuring unit that measures information about an error in the digital data received by the receiving unit, Multiplexing means for multiplexing the digital data received by the receiving means, transmission multiplexing control information of the transport stream, and information about the error, and information multiplexed by the multiplexing means is a 64-value QAM And a modulation means for digital modulation and an output means for outputting a plurality of modulated waves including the output of the modulation means.
[0012]
As described above, it is possible to perform stable transmission / reception of hierarchical transmission planned for BS digital broadcasting using a CATV transmission line or the like.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a block diagram showing a transmitting apparatus and a receiving apparatus according to an embodiment of the present invention. In FIG. 1, 100 is a digital demodulation circuit, 101 is a transmission line decoding circuit, 102 is a TS separation circuit, 103 and 109 are TS synthesis circuits, 104 and 110 are 6 4 QAM modulation circuits, 105 is a frequency multiplexing circuit, and 106 is a TMCC. Decoding circuit 107, error rate measurement circuit 108, TMCC reconstruction circuit 200, BS digital broadcast modulation signal 201, CATV transmission path 202, TMCC information signal 203, transport stream format data 204 Video signal, 205, audio signal, 300, CATV transmission device, 301, receiving side terminal device, 400, 401, retransmission modulation unit, 500, frequency demultiplexing circuit, 501, 64QAM demodulation circuit, 502, error correction circuit, 503 Is a TMCC / TS separation circuit, 504 is a hierarchical switching determination circuit, and 505 is a TS Packet separating circuit, 506 is an MPEG video decoder circuit, audio decoder circuit 507, 508 is a receiving terminal TV receiver. In this embodiment, only main functional units are shown, and peripheral circuit blocks such as a control microcomputer are omitted.
[0015]
The modulated signal 200 of the hierarchical BS digital broadcast received by the outdoor unit (not shown) is input to the retransmission units 400 and 401 in the CATV transmission apparatus via the cable, and the channel of the channel determined by the digital demodulation circuit 100 is input. Digital demodulation is performed, error correction and energy diffusion are performed by the transmission path decoding circuit 101, and the transport stream demultiplexing circuit 102 converts BS digital broadcasting of about 60 Mbps into 2 to 2 so as to correspond to about 30 Mbps of CATV transmission capacity. Is divided into three (in this embodiment, divided into two), and each is input to the transport stream synthesis circuit 109. After superimposing the transmission multiplex control signal TMCC on the synchronous part, multi-level modulation is performed by the 6 4 QAM modulation circuits 104 and 105. The The output of the retransmission modulation unit 400, including the output from the other retransmission unit 401, is input to the frequency multiplexing circuit 105 and frequency multiplexed, and then output to the CATV transmission line 201.
[0016]
In the receiving side terminal device, the signal of the CATV transmission line 201 is input to the frequency demultiplexing circuit 500 to select a desired channel, the channel selection output is demodulated by a 64QAM demodulation circuit, and the error correction circuit 502 performs error correction. After that, the TMCC / TS separation circuit 503 separates the transport stream format data from the TMCC, and the separated transport stream is input to the TS packet separation circuit 505 to separate the video and audio packets. The video packet data is decoded by the MPEG video decoder 506 to obtain the video signal 204, and the audio packet is decoded by the MPEG audio decoder 507 to obtain the video signal 204 and the audio signal 205, which are input to the television receiver 508.
[0017]
In order to cope with the hierarchical BS digital broadcasting service, the transmission facility 300 includes an error rate measurement circuit 107 and a hierarchical switching determination circuit 504 on the receiving terminal side. The error rate measurement circuit 107 estimates the error rate of the received BS digital broadcast signal by comparing the input and output of, for example, a Viterbi decoding circuit (not shown, included in the transmission path decoding circuit 101), and determines in advance. When the error rate exceeds the flag, the TMCC reconfiguration circuit 108 sets a flag indicating that the error rate of the transmission path is large in the transmission multiplexing control information. FIG. 2 is a reference diagram for explaining the configuration of transmission multiplexing control information. Reference numeral 600 denotes a transmission multiplex control signal, and reference numeral 601 denotes extended information in the transmission multiplex control signal. The transmission multiplexing control information has 384 bits in total, but the last 62 bits of extended information 601 are not defined. For example, a part of the extended area 601 is used as the error rate deterioration flag. The transmission multiplexing control information in which the error rate degradation flag is set in the TMCC reconfiguration circuit 108 is superimposed on the transport stream format data of the main signal by the TS synthesis circuits 103 and 109 and transmitted to the CATV transmission path. The receiving terminal 301 separates the TMCC information from the data in the transport stream format that has been error-corrected by the TMCC / TS separation circuit 503, and determines whether or not there is an error rate deterioration flag by the layer switching determination circuit 504. If set, the TS packet separation 505 selects the low-layer data and outputs it to each decoder. FIG. 3 is a reference diagram of slot assignment in hierarchical BS digital broadcasting. Reference numeral 602 denotes an example of a high-layer TC8PSK modulation slot, reference numeral 603 denotes a BPSK-modulated low-layer TV service slot, and reference numeral 604 denotes a dummy slot set by a low-layer modulation scheme. Normally, the packet separation circuit 505 selects a slot of the TC8PSK 602, but when detecting an error rate increase flag, the packet separation circuit 505 selects a lower layer, in this example, a BPSK modulation slot. In this example, the error rate measurement circuit 107 has been described for detecting the deterioration of the transmission line. However, as will be described later, C / N deterioration may be used instead of the error rate measurement.
[0018]
FIG. 4 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention. In the figure, the same numbers as in the other figures indicate the same functional blocks, 111 is a C / N measurement circuit, 112 is a hierarchical switching signal generation circuit, 113 is a downlink signal modulation circuit, 509 is a downlink signal demodulation circuit, 510 Is a hierarchy switching signal decoding circuit. In this example, the C / N measurement circuit 111 is used to detect the deterioration of the transmission path. When the C / N is deteriorated from the set C / N, a signal is generated by the layer switching signal generation circuit 112, and downlink signal modulation (for example, FSK) is performed. Flag information is superimposed on (modulation) and transmitted to the CATV transmission line 201. In the receiving terminal 301, the downlink signal is separated by the frequency demultiplexing 500, the downlink signal demodulating circuit 509 demodulates the downlink signal, and the hierarchy switching signal decoding circuit 510 decodes the hierarchy switching signal from the demodulated output. If the layer switching flag is detected, the generation of the flag is transmitted from the layer switching decoding circuit 510 to the TS packet separation 505, and the low layer slot is selected.
[0019]
FIG. 5 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention. In the figure, the same reference numerals as those in the other figures indicate the same functional blocks. In the present embodiment, the output of the TS separation circuit 102 outputs only the TC8PSK modulation slot 602 of FIG. 3, and the low-level BPSK modulation slot 601 outputs, for example, as a dummy slot. Now, when the result of the C / N measurement circuit 111 deteriorates from a set C / N value, a signal is generated from the hierarchical switching circuit 112, and the output of the TS separation circuit 102 is conversely the area of the TC8PSK modulation slot 602 is a dummy slot. BPSK modulation slot 601 is output, 68QAM modulated, and sent to CATV transmission line 201. The receiving terminal 301 has a feature that does not require a circuit for selecting hierarchization.
[0020]
FIG. 6 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention. In the figure, the same numbers as in the other figures indicate the same functional blocks, and 512 is an error measurement circuit in TS packet separation. In this embodiment, the CATV transmitting apparatus 300 side does not switch the hierarchized signal due to the error rate or C / N deterioration, and the error measuring circuit 512 is provided in the TS packet separation 505 of the receiving side terminal 301. That is, when the layered BS digital broadcast signal deteriorates C / N due to rain attenuation or the like and the error rate increases, an error occurs in the processing of the TS packet separation 505, the MPEG video decoder 506, or the audio decoder 507. In this embodiment, when these errors are measured and the errors exceed a set value, the slot selection in the TS packet separation is changed from the TC8PSK slot 602 in FIG. 3 to the BPSK modulation slot 601 for processing. It is.
[0021]
The low-layer modulation examples described so far have been described using BPSK modulation. However, the present invention is not limited to this, and it is obvious that the effect can be obtained even when QPSK modulation is used.
[0022]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the transmission / reception apparatus which can perform stable transmission / reception of BS digital broadcasting using a CATV transmission line etc. can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a transmission apparatus and a reception apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of transmission multiplexing control information.
FIG. 3 is an example of slot assignment in hierarchical BS digital broadcasting.
FIG. 4 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention.
FIG. 5 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention.
FIG. 6 is a block diagram showing a transmitting apparatus and a receiving apparatus according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Digital demodulation circuit, 101 ... Transmission path decoding circuit, 102 ... TS separation circuit, 103, 109 ... TS synthesis circuit, 104, 110 ... 68QAM modulation circuit, 105 ... Frequency multiplexing circuit, 106 ... TMCC decoding circuit, 107 ... Error Rate measurement circuit 108... TMCC reconfiguration circuit 111... C / N measurement circuit 112. Hierarchical switching signal generation circuit 113. Downlink signal modulation circuit 300 300 CATV transmission device 301. , 401 ... Retransmission modulation unit, 500 ... Frequency demultiplexing circuit, 501 ... 64QAM demodulation circuit, 502 ... Error correction circuit, 503 ... TMCC / TS separation circuit, 504 ... Hierarchical switching determination circuit, 505 ... TS packet separation circuit, 506... MPEG video decoder circuit, 507. Audio decoder circuit, 508. End side of the TV receiver, 509 ... downlink signal demodulation circuit, 510 ... layered switching signal decoding circuit, 512 ... error measuring circuit.

Claims (6)

Receiving means for receiving digital data in a transport stream format composed of a plurality of layers;
Measuring means for measuring information relating to errors in the digital data received by the receiving means;
Multiplexing means for multiplexing the digital data received by the receiving means, transmission multiplexing control information of the transport stream, and information on the error;
Modulation means for digitally modulating the information multiplexed by the multiplexing means with 64-value QAM;
An output device comprising: output means for outputting a plurality of modulated waves including the output of the modulation means. A transmission device that receives a digital broadcast signal and retransmits the digital broadcast signal to a cable television transmission line,
Means for measuring the C / N or error rate of the received digital broadcast signal ;
And multiplexing means for multiplexing the transmission multiplex control information of the transport stream format of the digital data and the transport stream comprising a plurality of layers,
First modulation means for digitally modulating with 64-value QAM multiplexed by the multiplexing means;
Second modulation means for digitally modulating information based on the result of C / N or error rate measured by the measurement means by FSK;
A transmission apparatus comprising: frequency multiplexing output means for frequency multiplexing and outputting a plurality of modulated waves including the output of the first modulation means and the output of the second modulation means. Selecting means for inputting transport data of a plurality of hierarchies and inputting the transport stream digital data and the transport stream;
Multiplexing means for multiplexing the transport stream selected by the selection means, other transport streams, transmission multiplexing control information, and data related to errors in digital data in the transport stream format composed of the plurality of layers ;
Modulating means for digitally modulating the signal multiplexed by the multiplexing means with 64-value QAM, and frequency multiplex output means for frequency-multiplexing a plurality of modulated waves including the output of the modulating means and outputting them to a CATV transmission line. A transmission apparatus comprising: In claims 1 to 3,
Satellite digital broadcast receiving means for receiving satellite digital broadcast signals;
Means for demodulating the satellite digital broadcast signal received by the digital broadcast receiving means;
A transmission apparatus comprising: a receiving unit comprising transport stream format digital data composed of a plurality of hierarchies and decoding means for decoding the transmission multiplexing control information. Receiving means for receiving a modulated wave signal digitally modulated by 64-value QAM transmitted from a device that receives a digital broadcast signal in a transport stream format composed of a plurality of layers, and the modulated wave signal transmitted from the device Contains information about errors in the digital broadcast signal,
Demodulating means for demodulating the modulated wave signal digitally modulated with 64-value QAM received by the receiving means ;
Receiving apparatus, comprising: a selective decoding unit that selects and decodes a layer of a transport stream using information on an error of the digital broadcast signal included in the modulated wave signal demodulated by the demodulating unit . Receiving means for receiving a modulated wave signal digitally modulated by 64-value QAM or FSK, transmitted from a device that receives a digital broadcast signal in a transport stream format composed of a plurality of layers;
The modulated wave signal received by the receiving means includes video information, audio information, transmission multiplex control information, and information related to errors in the digital broadcast signal,
First demodulating means for demodulating a digital modulated wave signal by 64-value QAM received by the receiving means ;
Second demodulation means for demodulating the digital modulated wave signal by FSK received by the receiving means ;
The transmission multiplex control information and video and audio information contained in the modulated wave signal is demodulated by the first demodulating means,
Information regarding the error of the digital broadcast included in the modulated wave signal is demodulated by the second demodulating means ,
Selective decoding means for selecting and decoding one layer transport stream in the layered transport stream format using the demodulated transmission multiplexing control information and the error-related information. A receiving device.

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