JP5599267B2 - Digital broadcast signal retransmission system - Google Patents

Description

  The present invention relates to a digital broadcast signal retransmission system for transmitting a digital broadcast signal such as terrestrial digital broadcast using a communication network.

  With the full introduction of digital terrestrial broadcasting, digital terrestrial broadcast stations and relay stations have been established in various locations. However, many users have difficulty viewing terrestrial digital broadcasting. For example, a user outside the service area of a digital broadcast signal or a user who does not receive broadcast waves due to a structure such as a building within the service area. There is a need to retransmit a digital broadcast signal as a countermeasure for such a difficult viewing. That is, there is a need to receive a digital broadcast signal at a place where a digital broadcast signal from a broadcast station can be received, and retransmit the received signal to a receiving device located in the difficult viewing area. Then, by transmitting a digital broadcast signal from the receiving device to the television receiver at each home in a place where viewing is difficult, the broadcast program can be viewed at the television receiver at each home. Such retransmission of the digital broadcast signal is similarly performed when the digital broadcast signal is retransmitted to the CATV network.

  As an example of a method for retransmitting a broadcast signal, an example using an analog transmission method is described as a prior art in Patent Document 1. Patent Document 1 discloses a technique for performing transmission using a PCM (Pulse Code Modulation) signal as a digital transmission method. Further, Patent Document 2 discloses a technique using a TS transmission system that performs transmission using a TS (transport stream) signal as a digital transmission system.

JP 2005-167906 A JP 2007-214946 A

  However, when the analog transmission method is used, transmission cannot be performed to a remote device because the transmission distance is short. Further, there is a problem that a laser that performs optical conversion requires high linearity and is expensive compared to digital transmission. There is also a problem that it cannot be sent to a digital transmission network.

  Therefore, a case where a digital transmission method is adopted can be considered. Here, when the PCM transmission method is adopted as the digital transmission method, the use bandwidth of PCM becomes large, and there is a problem that the capacity that can be transmitted is limited. In addition, when the TS method is adopted, there is an advantage that the use band can be reduced as compared with the PCM transmission method, but there is a problem that a digital processing delay occurs before the digital broadcast signal is converted into the TS signal. is there.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a digital broadcast signal retransmission system that uses a small band and does not cause a digital processing delay.

  A digital broadcast signal re-transmission system according to the present invention receives a digital broadcast signal that is a digitally modulated signal through an interleaving process, converts the digital broadcast signal into a transmission path signal, and sends the transmission path signal to the transmission path. And a receiving device that converts the transmission path signal input to the digital broadcasting signal and outputs the digital broadcasting signal. The transmitting device, an orthogonal demodulator that converts the digital broadcast signal into a digital quadrature signal and outputs it, a carrier demodulator that detects the amplitude and phase of a symbol from the digital quadrature signal output from the quadrature demodulator, A demapping unit that converts the amplitude and phase of the symbol output from the carrier demodulation unit into binary data without deinterleaving, and transmission for transmission of binary data output from the demapping unit in the transmission path A transmission path encoding unit for converting into a path signal. The receiving device receives a transmission path code decoding unit that converts the transmission path signal input from the transmission path into binary data, and the binary data output from the transmission path code decoding unit, and performs an interleaving process. A digital modulation unit that converts the digital broadcast signal into the digital broadcast signal without performing the above.

  The present invention transmits a reproduced signal without performing processing that causes a digital processing delay after inputting a digital broadcast signal, thereby reducing the bandwidth during transmission and retransmitting with little digital processing delay. Can be performed.

It is a block diagram which shows the digital broadcast signal retransmission system in 1st Embodiment. It is a block diagram which shows the digital broadcast signal retransmission system in 2nd Embodiment. It is a figure for demonstrating conversion from binary data to packet data.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a digital broadcast signal retransmission system 100 according to the first embodiment. The digital broadcast signal retransmission system 100 includes a transmission device 110 and a reception device 130 connected to the transmission device 110 via a transmission path 120. Transmitting apparatus 110 includes a channel selection unit 111, an orthogonal demodulation unit 112, a carrier demodulation unit 113, a demapping unit 114, a transmission path encoding unit 115, and a transmission path interface unit 116. In addition, receiving apparatus 130 includes a transmission path interface unit 131, a transmission path code decoding unit 132, and a digital modulation unit 133.

  FIG. 1 shows an example in the case of transmitting a digital broadcast signal that is not mainly OFDM (Orthogonal Frequency Division Multiplexing) such as CATV. Hereinafter, processing of each block will be described.

  First, a digital broadcast signal is input to the channel selection unit 111 of the transmission device 110. This digital broadcast signal is a broadcast signal digitally modulated through interleaving processing, and a plurality of channels are frequency-multiplexed. It is assumed that one channel is selected in advance by an external device. In this case, the channel selection unit 111 of the next block is unnecessary, and the digital broadcast signal is directly input to the orthogonal demodulation unit 112.

  The channel selection unit 111 selects one channel from a digital broadcast signal in which a plurality of channels are frequency-multiplexed, and outputs the selected channel to the orthogonal demodulation unit 112.

  The quadrature demodulating unit 112 performs quadrature demodulation on the broadcast signal of one channel, converts it into a digital quadrature signal, and outputs it to the carrier demodulating unit 113. For example, a 64QAM (quadrature amplitude modulation) demodulated signal is output.

  Carrier demodulation section 113 detects the amplitude and phase of the symbol from the digital quadrature signal.

The demapping unit 114 converts the symbol amplitude and phase detected by the carrier demodulation unit 113 into binary data. For example, since one symbol demodulated by 64QAM has a value of ²⁶ , one symbol is converted into binary data of 6-bit information. Note that the binary data to be converted is data that has not been deinterleaved.

  The transmission path encoding unit 115 adds a header such as a frame synchronization signal and a transmission path monitoring signal for transmitting the transmission path to the converted binary data to generate a transmission path code. Examples of the transmission path code include an IP (Internet Protocol) packet and an SDH (Synchronous Digital Hierarchy) frame.

  For example, when the transmission path is an optical fiber, the transmission path interface unit 116 interfaces with the transmission path, for example, by converting a signal from the transmission path encoding unit into an optical signal.

  The transmission path 120 is a transmission medium for transmitting the output of the transmission apparatus 110 to the reception apparatus 130, and examples thereof include a wired transmission medium such as an optical fiber.

  Here, it should be noted that the transmission apparatus 110 does not include a process with a large digital processing delay. That is, usually, a digital broadcast signal is subjected to an interleaving process in order to increase error correction efficiency for burst errors. The interleaving process is a process of rearranging signals so as to change the transmission order of digital signals on the transmission side. On the receiving side, deinterleaving processing for returning the rearranged signals to the original order is performed. In the interleaving process, a processing delay occurs due to the signal order being changed. In normal digital broadcast signal reception processing (that is, processing for reproducing a TS from a digital broadcast signal), for example, in the example of FIG. 1, deinterleaving processing is performed after the carrier demodulation unit 113, and thereafter Processing in the demapping unit 114 is performed.

  Also in the digital broadcast signal of this embodiment, the digital broadcast signal that has undergone the interleaving process is input to the transmission device 110. Then, processing similar to the normal reception operation (channel selection processing, orthogonal demodulation processing, carrier demodulation processing, demapping processing, etc. as shown in FIG. 1) is performed. However, unlike normal reception processing, this embodiment generates a binary data signal obtained by performing demapping without performing deinterleaving processing (through deinterleaving processing) that causes a large digital processing delay. The binary data signal is transmitted to the transmission line 120 as a transmission line code. It should be noted that the generated binary data signal is completely different from the binary data originally generated for receiving the broadcast because the deinterleaving process is not performed. Therefore, this generated binary data signal needs to be “returned” to the digital broadcast signal again by some other processing (specifically, processing by the receiving device 130 described later), and then reproduced. It should be noted that a digital broadcast program cannot be viewed unless a normal digital broadcast reception process (that is, a reception process that has undergone a deinterleaving process) is performed on the received digital broadcast signal. That is, the signal (transmission path code) transmitted from the transmission device 110 must be returned (converted) to a digital broadcast signal by the reception device 130. Such a set of the transmission device 110 and the reception device 130 is a digital broadcast signal reproduction such as the transmission device 110 arranged in an area where digital broadcast signals can be received and the reception device 130 arranged in a difficult viewing area. It can be said that the configuration matches the characteristics of the transmission system.

Next, the configuration of receiving apparatus 130 will be described.
For example, when the transmission line 120 is an optical fiber, the transmission line interface unit 131 performs an interface with the transmission line 120 such as converting an optical signal input from the transmission line into an electric signal. That is, the reverse process of the transmission path interface unit 116 is performed.

  The transmission path code decoding unit 132 generates (decodes) binary data from a transmission path code to which headers such as a frame synchronization signal and a transmission path monitoring signal for transmitting the transmission path 120 are added.

  The digital modulation unit 133 converts the generated binary data into a digital broadcast signal. Specifically, reverse mapping processing, carrier modulation processing, orthogonal modulation processing, and the like of the transmission apparatus 110 are performed. Of course, it should be noted that the interleaving process is not performed in the receiving apparatus 130. As a result of such processing, for example, a 64QAM modulated digital broadcast signal is converted and generated. Then, the generated digital broadcast signal is transmitted to a cable television network through a cable, for example, and is received by a final home television receiver.

  As described above, by using the transmission device 110, it is possible to realize retransmission of a digital broadcast signal with a small band and a small digital processing delay. Further, through a transmission line such as an optical fiber, it is possible to retransmit a digital broadcast signal to a remote receiving apparatus.

(Second Embodiment)
FIG. 2 is a diagram illustrating a digital broadcast signal retransmission system 200 including the transmission device 210 according to the second embodiment. Parts having the same types of processing and functions as those in FIG. 1 are denoted by the same reference numerals. FIG. 2 is a diagram illustrating an application example of OFDM (Orthogonal Frequency Division Multiplexing) such as terrestrial digital broadcast signals to digital broadcast signal transmission.

  The difference from the block shown in the first embodiment is that an FFT (First Fourier Transform) unit 217 is included between the orthogonal demodulation unit 112 and the carrier demodulation unit 113. The FFT unit 213 performs fast Fourier transform (FFT) on the digital quadrature demodulated signal and converts it into a digital quadrature signal for each subcarrier. The subsequent processing is the same as that described in the first embodiment. That is, as in the second embodiment, even in the case of a terrestrial digital broadcast signal, it is possible to realize retransmission of the digital broadcast signal with a small band and no digital processing delay.

(Third embodiment)
In the third embodiment, a mode using a packet will be described as an example of encoding in the transmission path encoding unit 115 in the first or second embodiment. That is, an example in which binary data converted by the demapping unit 114 is accommodated in an IP packet and transmitted.

  The transmission path encoding unit 115 accommodates binary data in an IP packet. Also, the transmission path code decoding unit 132 extracts binary data from the IP packet.

  Processing for converting binary data with an IP packet will be described with reference to FIG. Depending on the symbol period and data amount, it is not always efficient to send data for one symbol in one packet. Therefore, binary data for a period of m symbols (m is an integer) is divided into n packets (n is an integer), accommodated, and transmitted. This makes it possible to retransmit the digital broadcast signal more efficiently. As a specific method, as shown in FIG. 3, head identification information is added to the header of the head packet among n IP packets. The head identification information is information indicating a head portion of a collection of data having an m symbol period. In the case of a terrestrial digital broadcast signal, since one frame is composed of 204 symbols, signal processing is simplified if m is set to a divisor of 204. Timing information is inserted into the packet header or payload in order to regenerate the clock synchronized with the symbol on the receiving device side. The transmission path code decoding unit 132 on the receiving device side refers to the packet header, detects the head identification information, and reproduces the binary data. For the last packet of n packets, the payload part may not form binary data in some cases, but by sharing information about the data length between the transmission device 110 and the reception device 130, The binary data transmitted from the transmission device 110 can be reproduced by the reception device 130.

(Other)
Although various embodiments have been described above, according to the present invention, in addition to the above, further methods, for example, a method in which control information is not sent, are possible. In the case of a terrestrial digital OFDM signal, it is not necessary to transmit SP (Scattered Pilot) or CP (Continual Pilot) as a control signal from the transmitter 110. This is because the insertion positions of the SP and CP are determined by the modulation parameters, so that even if the SP and CP are not transmitted, the reception apparatus 130 can extract the modulation parameters and generate these control signals. It is. Thereby, the transmission capacity sent to the transmission line 120 can be reduced.

  In addition, when the present invention is applied, processing after demapping required in the TS system, that is, processing such as layer division processing, bit deinterleaving processing, Viterbi decoding processing, and energy despreading processing is not required. Therefore, in addition to not causing the digital processing delay as described above, low power consumption can be realized.

110 Transmission device 120 Transmission path 130 Reception device

Claims (3)

Through interleaving type digital broadcasting signal is a digital modulated signal, a transmitting apparatus for transmitting to a transmission path is converted to the transmission line signals, disposed capable of receiving area of the digital broadcast signal from a broadcasting station And a transmission device that transmits to the reception device located in an area where the digital broadcast signal is retransmitted, and a reception device that converts the transmission path signal input via the transmission path into the digital broadcast signal and outputs the digital broadcast signal. A digital broadcast signal retransmission system comprising:
The transmitter is
An orthogonal demodulator that converts the digital broadcast signal into a digital orthogonal signal and outputs the digital orthogonal signal;
A carrier demodulation unit that detects the amplitude and phase of a symbol from the digital orthogonal signal output from the orthogonal demodulation unit;
A demapping unit for converting the amplitude and phase of the symbol output from the carrier demodulation unit into binary data without deinterleaving;
A transmission path encoding section that converts binary data output from the demapping section into a transmission path signal for transmission in the transmission path, and
The receiving device is:
A transmission path code decoding unit that converts the transmission path signal input from the transmission path into binary data;
A digital broadcast signal retransmission system comprising: a digital modulation unit that inputs the binary data output from the transmission path code decoding unit and converts the binary data into the digital broadcast signal without performing an interleaving process. Orthogonal frequency division multiplexing through the interleaving process is a digital modulated signal (OFDM: Orthogonal Frequency Division Multiplexing) A transmitting apparatus for transmitting to a transmission path to convert the input to the transmission path signal of digital broadcast signal scheme, broadcasting A transmission device that is disposed in an area where the digital broadcast signal can be received from a station and is transmitted to a reception device located in an area where the digital broadcast signal is retransmitted; and the transmission path signal input via the transmission path A digital broadcast signal retransmission system comprising a receiving device that converts and outputs a digital broadcast signal,
The transmitter is
An orthogonal demodulator that converts the digital broadcast signal into a digital orthogonal signal and outputs the digital orthogonal signal;
An FFT unit that converts the digital quadrature signal output from the quadrature demodulation unit into a digital quadrature signal for each subcarrier by performing a fast Fourier transform (FFT);
A carrier demodulation unit that detects the amplitude and phase of a symbol from the digital orthogonal signal for each subcarrier output from the FFT unit;
A demapping unit that converts the amplitude and phase of the symbol output from the carrier demodulating unit into binary data without deinterleaving;
A transmission path encoding section that converts binary data output from the demapping section into a transmission path signal for transmission in the transmission path, and
The receiving device is:
A transmission path code decoding unit that converts the transmission path signal input from the transmission path into binary data;
A digital broadcast signal retransmission system comprising: a digital modulation unit that inputs the binary data output from the transmission path code decoding unit and converts the binary data into an OFDM digital broadcast signal without performing an interleaving process. The transmission path encoding unit divides and stores binary data for m (m is an integer) symbol period output from the demapping unit into n (n is an integer) IP (Internet Protocol) packets, Adding head identification information to the header of the head packet among the n IP packets,
3. The digital broadcast signal retransmission according to claim 1, wherein the transmission path code decoding unit includes a clock recovery circuit that recovers a clock synchronized with the symbol period based on the head identification information. system.

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