JP4939987B2 - Terrestrial digital broadcast apparatus and terrestrial digital broadcast retransmission method - Google Patents

Description

  The present invention relates to a digital terrestrial broadcasting apparatus that can broadcast arbitrary information using an operation mode for mobile terminals in digital terrestrial television broadcasting and digital terrestrial audio broadcasting, for example.

  In the current digital terrestrial television broadcasting, all broadcasting stations in each broadcasting area have started providing a one-segment partial reception layer (so-called one segment), and it has become possible to enjoy digital broadcasting programs on mobile terminals. In recent years, services such as providing local information by 1-segment broadcasting in an area where broadcast radio waves are insensitive have been proposed using this 1-segment broadcasting format. As one of these services, a method of connecting 13 13-segment broadcasts to 13-segment broadcasts has been devised as described in Non-Patent Documents 1 and 2, although this is not permitted in the current digital broadcast system. . However, the above-mentioned document only describes the outline of the service, does not mention a broadcasting apparatus for providing the service specifically, and has not been studied to the extent that the present system can be realized. In particular, since the continuity of SP in the frequency axis direction between connected segments is not ensured, there is a problem that the data at the low frequency end and high frequency end of each segment deteriorate.

An example of segment synchronization processing for connecting a plurality of 1-segment broadcasts is shown in Patent Document 1.
http://www.soumu.go.jp/s-news/2006/pdf/060606_1_073.pdf http://www.soumu.go.jp/s-news/2006/pdf/060606_1_123.pdf JP 2006-109283 A

  As described above, terrestrial digital broadcasting devices that can broadcast arbitrary information using the operation mode of 1-segment broadcasting for mobile terminals in terrestrial digital television broadcasting and terrestrial digital audio broadcasting have been proposed. However, no concrete construction has been made to achieve this. In particular, since the continuity of SPs between connected segments in the frequency axis direction is not ensured, no countermeasure has been proposed for the problem that the data accuracy at the low and high band ends of each segment deteriorates.

  The present invention has been made in consideration of the above circumstances, and when retransmitting a plurality of 1-segment broadcasts of each of multiple channels to have the same band as a normal broadcast, It is an object of the present invention to provide a terrestrial digital broadcast apparatus and a terrestrial digital broadcast retransmission method capable of reducing deterioration in data accuracy at the high end.

  In order to solve the above problem, the digital terrestrial broadcasting apparatus according to the present invention employs an OFDM (Orthogonal Frequency Division Multiplex) scheme, and each OFDM subcarrier has an SP (Scattered Pilot) at a constant period. ) Captures multiple channels of digital terrestrial television / audio broadcasting signals to which data, AC (Auxiliary Carrier) and TMCC (Transmission and Multiplexing Configuration Control) are selectively assigned Then, for each of the broadcast signals of the plurality of channels, SP equalization is performed to extract frequency axis data, and retransmission is performed from symbol points of an OFDM subcarrier for sending data, an OFDM subcarrier for sending AC, and an OFDM subcarrier for sending TMCC. Extract the segment Output means, common synchronization generating means for generating a common synchronization of all channels by taking in a synchronous reproduction result obtained from an input broadcast signal in each of the plurality of channels at the time of extracting the segment, and a plurality of extracted by the extracting means Control means for changing the segment of the channel to the common synchronization generated by the common synchronization generating means so that the timings of the SP subcarriers in the respective segments of the plurality of channels coincide with each other, and the extraction under the control of the control means And a retransmission signal generating means for generating a retransmission signal by connecting segments of a plurality of channels extracted by the means.

  Also, the retransmission method of terrestrial digital broadcasting according to the present invention employs an OFDM (Orthogonal Frequency Division Multiplex) scheme, and each OFDM subcarrier has an SP (Scattered Pilot) symbol at a fixed period. And a plurality of channels of terrestrial digital television / audio broadcast signals to which data, AC (Auxiliary Carrier: auxiliary carrier signal), and TMCC (Transmission and Multiplexing Configuration Control: transmission control signal) are selectively assigned. For each broadcast signal of the channel, SP axis equalization is used to extract frequency axis data, and a segment to be retransmitted from each symbol point of an OFDM subcarrier for sending data, an OFDM subcarrier for sending AC, and an OFDM subcarrier for sending TMCC Extract the segment In the extraction of a plurality of channels, a synchronized reproduction result obtained from an input broadcast signal is taken in each channel to generate a common synchronization for all channels, and the segment of the plurality of channels is changed to the common synchronization to change the segment in each segment of the plurality of channels. The timings of the SP subcarriers are made to coincide with each other, and the re-transmission signal is generated by concatenating the segments of the plurality of channels subjected to the timing control of the SP subcarriers.

  In other words, in the present invention, a terrestrial digital television / audio broadcast signal of a plurality of channels is taken in, and one segment for a mobile unit provided by each broadcast is extracted and connected to obtain the same OFDM broadcast signal as a normal broadcast signal. Resend. At this time, at the time of segment extraction, a synchronized reproduction result is obtained from the input broadcast signal for each of a plurality of channels. Therefore, the synchronous reproduction result of each channel is taken in to generate common synchronization of all channels, and the extracted segments of each of the plurality of channels are changed to the common synchronization so that the timings of the SP subcarriers in each extracted segment coincide with each other. As a result, the continuity of the connected segments in the frequency axis direction of the SP is ensured, and the deterioration of the data accuracy at the low frequency end and high frequency end of each segment is reduced.

  Therefore, according to the present invention, when a plurality of 1-segment broadcasts of a plurality of channels are concatenated and retransmitted with the same band as that of a normal broadcast, the data accuracy of the low frequency end and high frequency end of each segment is deteriorated It is possible to provide a terrestrial digital broadcast apparatus and a terrestrial digital broadcast retransmission method that can reduce the above-described problem.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a digital terrestrial broadcasting apparatus according to the present invention. Here, a case where the broadcast signal is based on a standardized system of ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) will be described.

  In FIG. 1, 11-01 to 11-13 (No. 1 to No. 13) are first to selectively extract predetermined segments by taking in received OFDM signals of terrestrial television and audio broadcasting by the OFDM system, respectively. A thirteenth segment extraction processing unit. Hereinafter, the first segment extraction processing unit 11-01 will be described as a representative.

  In the first segment extraction processing unit 11-01, a terrestrial digital broadcast signal (received OFDM signal) received by a receiving antenna (not shown) is subjected to frequency conversion from a signal on the time axis by FFT processing by an FFT (Fast Fourier Transform) unit 111. Converted to an on-axis signal. This conversion processing is performed based on the clock (CL1) and symbol synchronization (S1) obtained by the synchronous reproduction unit 112.

  The synchronous reproduction unit 112 detects synchronization from the received OFDM signal and the frequency axis signal of the FFT output. For example, symbol synchronization (S1) is detected by guard interval correlation, clock (CL1) is detected by pilot correlation, TMCC (T1) is detected by demodulating OFDM subcarriers transmitting TMCC information, frame synchronization / frame The synchronization phase (F1) is detected from TMCC (T1).

  The SP equalization unit 113 performs waveform equalization by SP after synchronizing the FFT output frequency axis signal with symbol synchronization (S1) and frame synchronization / frame synchronization phase (F1). The determination unit 114 synchronizes the SP equalization output signal with the symbol synchronization (S1) and the frame synchronization / frame synchronization phase (F1), and transmits the OFDM subcarrier for transmitting data, the OFDM subcarrier for transmitting AC, and the TMCC. The symbol point of each OFDM subcarrier to be sent is determined hard.

  The segment extraction unit 115 extracts a necessary segment from the determination output signal of the determination unit 114 and outputs it. The FIFO memory (A) 116 transfers the extracted segment data to the common clock (CL0) generated by the common synchronization generator 21 from the clock (CL1). The FIFO memory (B) 117 transfers symbol synchronization (S1) and frame synchronization / frame synchronization phase (F1) from the clock (CL1) to the common clock (CL0) generated by the common synchronization generator 21. As a result, no. 1-No. 13 clocks are shared.

  The delay control unit (A) 119 calculates the delay time in the symbol from the time difference between the symbol synchronization (S1) of the output of the FIFO memory (B) and the common symbol synchronization (S0) generated by the common synchronization generation unit 21. Thus, the delay amount of the delay unit (A) 118 is controlled. As a result, no. 1-No. 13 symbol synchronizations are shared. Further, the delay control unit (B) 1111 determines the delay time in the frame from the time difference between the frame synchronization (F1) of the output of the FIFO memory (B) and the common frame synchronization (F0) generated by the common synchronization generation unit 21. And the delay amount of the delay unit (B) 1110 is controlled. As a result, no. 1-No. 13 frame synchronizations are shared. Alternatively, the control unit (B) 1111 detects the symbol number from the frame synchronization (F1) output from the FIFO memory (B) and the common frame synchronization (F0) generated by the common synchronization generation unit 21. 1-No. The delay time of 13 SP carrier arrangements is calculated, and the delay amount of the delay unit (B) 1110 is controlled. As a result, SP continuity between adjacent segments can be ensured. At this time, no. 1-No. Although the frame synchronization between 13 does not match, there is no problem when demodulating one segment.

  The TMCC rewriting unit 1112 rewrites, for example, system identification, B layer parameter information, and C layer parameter information in the TMCC information as necessary.

  On the other hand, the common synchronization generation unit 21 inputs the synchronization (clocks (CL1 to CL13), symbols (S1 to S13), frames (F1 to F13)) obtained by the segment extraction processing units 11-01 to 11-13. Generate a common sync. That is, in common frame synchronization (F0), the most delayed frame synchronization among received frame synchronizations (F1 to F13) is defined as common frame synchronization, and common symbol synchronization (S0) is the same as the common frame synchronization (F0). The symbol synchronization of No. is the common symbol synchronization, and the common clock (CL0) outputs the No clock of the frame synchronization as the common clock.

  The TMCC analysis unit 22 inputs the synchronization signals (CL1 to CL13, S1 to S13, F1 to F13), 1-No. 13 Each TMCC information is read and the number of segments after segment connection is calculated. If it is less than 13 segments, the segment signal generator 23 generates a dummy segment based on the common synchronization so as to be 13 segments and sends it to the segment connector 12. The CP generator 24 generates a CP to be added to the high frequency end after segment connection based on the common synchronization.

  The segment connecting part 12 is No. 1-No. 13 segments are arranged by arranging TMCC rewrite outputs of 13 receiving units 11-01 to 11-13, segment signal output generated by the segment signal generating unit 23, and CP output generated by the CP generating unit 24 on the frequency axis. Are connected. The IFFT unit 13 performs inverse Fourier transform on the frequency axis signal after the segment connection to obtain a time signal. The guard interval adding unit 14 adds a guard interval to the output of the IFFT unit 13. As a result, a retransmission signal in which 13 segments are connected is generated.

  That is, in the terrestrial digital broadcasting apparatus having the above-described configuration, the first to thirteenth segment extraction processing units 11-01 to 11-13 individually take in the terrestrial television / audio broadcasting by the OFDM system and extract the respective predetermined segments. . At this time, each segment extraction processing unit 11-01 to 11-13 extracts a predetermined segment based on clock synchronization, symbol synchronization, and frame synchronization / frame synchronization phase obtained by synchronous reproduction.

  Here, in terrestrial digital broadcasting by ISDB-T, as shown in FIG. 3, it is specified that SPs are arranged at regular intervals in the carrier direction and symbol direction of a broadcast signal. However, since the synchronization processing is individually performed between the segments obtained by the processing units 11-01 to 11-13, the SP timings do not match each other. For this reason, when these extracted segments are connected, the data accuracy at the low-frequency end and high-frequency end deteriorates.

  Therefore, the clock synchronization, symbol synchronization, frame synchronization / frame synchronization phase obtained at the time of segment extraction in each processing unit 11-01 to 11-13 is sent to the common synchronization generation unit 21 to generate common synchronization, and each segment is generated. The extracted segments are sent back to the extraction processing units 11-01 to 11-13, and the extracted segments are switched to common synchronization. As a result, the individual extracted segments are synchronized with the common synchronization, so that the SP timings coincide with each other.

  Therefore, the terrestrial digital broadcasting device having the above-described configuration can reduce deterioration in data accuracy at the low end and high end of each segment.

  Further, in the apparatus according to the above embodiment, a CP (Continual Pilot) is generated based on common synchronization and added to the high end of the OFDM spectrum at the time of segment connection. As a result, the CP is also multiplexed with the broadcast signal in a synchronized state, and the equalization accuracy on the receiving side can be improved.

  In addition, in the apparatus according to the above embodiment, if TMCC information cannot be obtained by any of the processing units 11-01 to 11-13, the segments constituting the retransmission signal are less than 13 segments, so that the shortage is not achieved. Minute dummy segments are generated based on the common synchronization and are connected to the extracted segments. As a result, it is possible to transmit in 13 segments as in a normal broadcast signal, and it is possible to reduce deterioration in reception processing due to an insufficient number of connected segments.

  In the above embodiment, the symbol points of the OFDM subcarrier that transmits data, the OFDM subcarrier that transmits AC, and the OFDM subcarrier that transmits TMCC are extracted by hard decision in each of the processing units 11-01 to 11-13. Therefore, it is possible to maintain the position accuracy of the symbol point of the retransmit signal satisfactorily.

  Further, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing an embodiment of a digital terrestrial broadcasting apparatus according to the present invention. The block diagram which shows the specific structure of the segment extraction process part of the terrestrial digital broadcasting apparatus shown in FIG. The figure which shows arrangement | positioning of SP decided by ISDB-T standardization.

Explanation of symbols

  11-01 to 11-13 (No. 1 to No. 13) ... 1st to 13th segment extraction processing unit, 111 ... FFT (Fast Fourier Transform) unit, 112 ... Synchronous reproduction unit, 113 ... SP equalization unit 114 ... determination unit, 115 ... segment extraction unit, 116 ... FIFO memory (A), 117 ... FIFO memory (B), 118 ... delay unit (A), 119 ... delay control unit (A), 1110 ... delay unit ( B), 1111 ... delay control unit (B), 1112 ... TMCC rewrite unit, 12 ... segment connection unit, 13 ... IFFT unit, 14 ... guard interval addition unit, 21 ... common synchronization generation unit, 22 ... TMCC analysis unit, 23 ... segment signal generator, 24 ... CP generator.

Claims (7)

An OFDM (Orthogonal Frequency Division Multiplex) scheme is adopted, and each OFDM subcarrier has SP (Scattered Pilot) symbols arranged at a fixed period, and data, AC (Auxiliary Carrier: auxiliary carrier signal) ), TMCC (Transmission and Multiplexing Configuration Control: transmission control signal) is selectively assigned to a plurality of channels of digital terrestrial television / audio broadcast signals, and a synchronization signal is reproduced for each of the plurality of channels of broadcast signals. Based on the synchronized signal, SP equalization is performed to extract frequency axis data, and a segment to be retransmitted is extracted from each symbol point of the OFDM subcarrier for sending data, the OFDM subcarrier for sending AC, and the OFDM subcarrier for sending TMCC Extraction means to
Common synchronization generating means for acquiring a synchronization signal obtained from an input broadcast signal in each of the plurality of channels at the time of extracting the segment and generating a common synchronization signal for all channels;
A control means for changing the segment of the plurality of channels extracted by the extraction means to the common synchronization signal generated by the common synchronization generation means so that the timings of the SP subcarriers in the segments of the plurality of channels coincide with each other;
A terrestrial digital broadcasting apparatus comprising: a retransmission signal generation unit configured to connect a plurality of channel segments extracted by the extraction unit under the control of the control unit to generate a retransmission signal. The common synchronization generation means takes in a clock synchronization signal of each segment of the plurality of channels and generates a common clock synchronization signal ,
2. The digital terrestrial broadcasting apparatus according to claim 1, wherein the control means changes the segment of the plurality of channels onto the common clock synchronization signal with respect to the extraction means. The common synchronization generation means takes in a frame synchronization signal and a frame synchronization phase signal obtained by demodulating the TMCC of each segment of the plurality of channels in the extraction means, and generates a common frame synchronization signal and a frame synchronization phase signal. ,
2. The digital terrestrial broadcasting apparatus according to claim 1, wherein the control unit changes the segment of the plurality of channels onto the common frame synchronization signal and frame synchronization phase signal with respect to the extraction unit. CP generation means for generating CP (Continual Pilot) based on the common synchronization signal generated by the common synchronization generation means,
2. The digital terrestrial broadcasting apparatus according to claim 1, wherein the retransmission signal generating means adds a CP (Continual Pilot) to the high end of the OFDM spectrum of the retransmission signal. The broadcast signal is a signal defined by a standardized system of ISDB-T (Integrated Services Digital Broadcasting for Terrestrial).
A shortage segment generating means for generating a shortage of dummy segments when the number of segments constituting the retransmission signal is less than 13;
2. The digital terrestrial broadcasting apparatus according to claim 1, wherein the retransmission signal generating means adds and connects the dummy segments when the segments constituting the retransmission signal are less than 13 segments.   2. The digital terrestrial broadcasting apparatus according to claim 1, wherein the extraction means extracts each symbol point of an OFDM subcarrier for sending the data, an OFDM subcarrier for sending AC, and an OFDM subcarrier for sending TMCC by hard decision. . An OFDM (Orthogonal Frequency Division Multiplex) scheme is adopted, and each OFDM subcarrier has SP (Scattered Pilot) symbols arranged at a fixed period, and data, AC (Auxiliary Carrier: auxiliary carrier signal) ), TMCC (Transmission and Multiplexing Configuration Control: transmission control signal) is selectively assigned to terrestrial digital TV / audio broadcasting signals of multiple channels,
The synchronization signal is reproduced for each of the broadcast signals of the plurality of channels, the frequency axis data is extracted by SP equalization based on the reproduced synchronization signal, the OFDM subcarrier for sending data, the OFDM subcarrier for sending AC, and the TMCC are sent Extract a segment to be retransmitted from each OFDM subcarrier symbol point,
At the time of extracting the segment, a synchronization signal obtained from the input broadcast signal in each of a plurality of channels is taken to generate a common synchronization signal for all channels,
Changing the segments of the plurality of channels onto the common synchronization signal so that the timings of the SP subcarriers in the segments of the plurality of channels coincide with each other;
A retransmission method for digital terrestrial broadcasting, wherein a retransmission signal is generated by concatenating the segments of the plurality of channels subjected to timing control of the SP subcarrier.

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