JP4338323B2 - Digital signal receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital signal receiving apparatus, and more particularly to a digital signal receiving apparatus suitable for receiving terrestrial digital digital television broadcasting (hereinafter also simply referred to as “terrestrial digital broadcasting”).
[0002]
[Prior art]
In recent years, digital television broadcasting, which replaces conventional analog television broadcasting, is being introduced for the purpose of improving image quality, increasing the number of channels, enhancing functionality, and improving quality.
[0003]
In terrestrial digital broadcasting in Japan, it has been decided that orthogonal frequency division multiplexing (OFDM) will be adopted as a transmission method.
[0004]
OFDM is called a multi-carrier scheme, and is characterized in that several thousand carriers are set up in a transmission band, and data is allocated to each carrier for broadcasting. For this reason, even if it is partially damaged, it can be covered with another carrier wave, so that it has the advantage of being strong against ghosts that cause problems with terrestrial waves. For this reason, there are expectations for new applications such as mobile communications.
[0005]
8 and 9 are first and second diagrams for explaining the structure of a data signal used for terrestrial digital broadcasting.
[0006]
Referring to FIG. 8, one OFDM frame period (hereinafter also simply referred to as “one frame period”), which is a basic unit of a data signal used for terrestrial digital broadcasting, is a time of symbols # 0 to # 203. It consists of 204 OFDM symbols (hereinafter also simply referred to as “symbols”) transmitted in series on the axis.
[0007]
Referring to FIG. 9, each symbol is assigned to a different frequency, a data signal DS corresponding to transmission data obtained by encoding a normal audio signal or video signal, a null signal NS corresponding to dummy data, and A pilot signal PS is included.
[0008]
The pilot signal PS includes a data structure of transmission data, information on demodulation, and the like, and has a level larger than that of the data signal DS and the null signal NS. According to the terrestrial digital broadcasting standard, the pilot signal PS is called TMCC (Transmission and Multiplexing Configuration Control) signal, which is necessary for the demodulation operation of the receiving device such as the data configuration and transmission parameters of each OFDM segment. A signal for transmitting demodulation information is included. The encoded demodulation information is transmitted by the TMCC signal. Hereinafter, the demodulation information transmitted by the TMCC signal is also referred to as “TMCC information”.
[0009]
The arrangement position of the TMCC signal in each symbol is determined in advance according to the standard. Therefore, knowing the arrangement position of the TMCC signal in each symbol with reference to the position of the start pulse STP indicating the start position of the data in one symbol generated based on the signal transmitted in synchronization with the data Can do. In each symbol, a predetermined number of TMCC signals that are determined according to a mode and a segment type described later are included.
[0010]
In each symbol, 1-bit data for indicating TMCC information is transmitted. That is, the 13 TMCC signals included in one symbol all transmit the same signal level (“1” or “0”), and the receiving device extracts the TMCC signal for each symbol received. Thus, an operation for obtaining one bit of TMCC information included in the symbol is executed.
[0011]
As described above, each symbol includes a plurality of signals respectively arranged in a predetermined frequency band. As described above, since one frame is formed by these 204 symbols inputted in time series, information of 204 bits can be obtained by receiving one frame regarding TMCC information. .
[0012]
Furthermore, in the data standard according to terrestrial digital broadcasting, the number of carriers to be used can be switched to three modes. Specifically, three types of mode 1, mode 2, and mode 3 are set. In mode 2, the number of carriers twice that of mode 1 is used, and in mode 3, the number of carriers twice that of mode 2 is used. Data transmission is executed.
[0013]
FIG. 10 is a conceptual diagram for explaining the data structure of each symbol corresponding to each mode.
[0014]
Referring to FIG. 10A, mode 1 corresponds to the minimum carrier number mode, and the number of carriers is set to 2k. One OFDM symbol includes one unit section F0. Pilot signal PS and data signal DS including the TMCC signal are included in the unit interval. A null signal NS and a signal corresponding to the guard interval are included outside the unit interval in each OFDM symbol.
[0015]
Referring to FIG. 10B, in mode 2, the number of carriers is set to 4k, and one OFDM symbol includes unit intervals F0 and F1. Therefore, in mode 2, twice as many carriers as in mode 1 are used.
[0016]
Referring to FIG. 10C, mode 3 performs data transmission using a carrier number that is twice that of mode 2. Specifically, one OFDM symbol includes unit intervals F0 to F3.
[0017]
Each of the unit sections F0 to F3 includes the same number of carriers. However, since the frequency band used is the same even if the modes are different, the frequency bandwidth corresponding to each unit section changes according to the mode. That is, the interval (frequency domain) between the carriers changes according to the mode. In addition, since data transmission is executed in synchronization with a clock having a constant frequency independent of the mode, the transmission time per OFDM symbol becomes longer as the mode number increases.
[0018]
Thus, since the number of carriers in one symbol increases as the mode number increases, the number of TMCC signals included in each OFDM symbol increases correspondingly. However, the point that 1-bit TMCC information is transmitted by a plurality of TMCC signals included in one OFDM symbol is the same even if the mode is changed.
[0019]
Therefore, the arrangement pattern of TMCC signals in modes 2 and 3 of terrestrial digital broadcasting is a repetition of the arrangement pattern in mode 1 corresponding to the minimum carrier number mode. That is, in the unit section F1 in mode 2, TMCC signals that transmit the same signal level as the unit section F0 are arranged in the same manner as the unit section F0.
[0020]
Similarly, also in the unit sections F1 to F3 in the mode 3, TMCC signals for transmitting the same signal level as the unit section F0 are repeatedly arranged as in the unit section F0.
[0021]
That is, in mode 2, one bit of TMCC information is decoded and extracted from the TMCC signal transmitted using both unit sections F0 to F1, and in mode 3, TMCC transmitted using unit sections F0 to F3. One bit of TMCC information is decoded and extracted from the signal.
[0022]
In an ideal transmission state, the decoding result of each TMCC signal included in the same OFDM symbol is aligned with either “1” or “0”. Therefore, in each symbol, 1-bit TMCC information corresponding to the symbol can be determined by executing the majority process between the decoding results of the plurality of TMCC signals.
[0023]
[Problems to be solved by the invention]
However, if the transmission path characteristics are disturbed in time due to fading, etc., or if the transmission path characteristics are greatly disturbed in frequency due to the influence of multipath, etc., it corresponds to the section where the transmission path characteristics are disturbed. The TMCC information may not be obtained correctly.
[0024]
In particular, when the transmission path characteristics are disturbed in a relatively wide frequency range, and the signal level of the TMCC signal cannot be correctly transmitted in the frequency range, the result of the majority processing in the symbol is the TMCC information to be transmitted originally. May be different from 1 bit.
[0025]
In such a case, TMCC information, that is, information necessary for the demodulation operation cannot be obtained on the receiving device side, and there is a possibility that terrestrial digital broadcasting cannot be received normally.
[0026]
The present invention has been made to solve such a problem, and an object of the present invention is to insert demodulation information of the transmission data between transmission data represented by terrestrial digital broadcast data. The present invention provides a configuration of a digital signal receiving apparatus that can accurately extract the demodulation information in receiving a digital signal.
[0027]
[Means for Solving the Problems]
According to one aspect of the present invention, there is provided a digital signal receiving apparatus for receiving a digital data sequence including transmission data and a demodulated information signal obtained by encoding demodulated information necessary for demodulating the transmission data. A demodulator for extracting and demodulating a demodulated information signal inserted based on a predetermined pattern in order to transmit unit information constituting demodulated information for each predetermined section, and demodulated data from the demodulator And a demodulating information processing unit for obtaining demodulated information. The same demodulated information signal is repeatedly transmitted in each of N (N: natural number) unit sections forming the same predetermined section. The demodulating information processing section receives a counter section for detecting the boundary between the unit section and the predetermined section, and receives demodulated data from the demodulating section and the detection result of the counter section, and handles each unit information independently for each unit section. The highest reliability is selected from the first decoding processing unit for generating the decoding result and the N decoding results output from the first decoding processing unit corresponding to the same predetermined section And a second decoding processing unit.
[0028]
Preferably, each unit information corresponds to 1-bit data constituting demodulation information, and a predetermined number of demodulation information signals are inserted in each unit section. The first decoding processing unit executes majority processing based on an integrated value of a predetermined number of demodulated data corresponding to the unit section.
[0029]
Preferably, the digital data string is a signal conforming to the standard of terrestrial digital broadcasting, and each predetermined section is determined corresponding to each of the OFDM symbols, and each unit section is in the minimum number of carriers mode. Includes one unit interval, and includes multiple unit intervals in other modes .
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0031]
FIG. 1 is a schematic block diagram showing a main part extracted from the configuration of a digital television receiver 1 shown as a representative example of a digital signal receiver according to the present invention.
[0032]
Referring to FIG. 1, in digital television receiver 1, an RF signal received from an antenna (not shown) is selected by tuners 6a and 6b and provided to demodulation units 100a and 100b, respectively.
[0033]
Demodulated signals from the demodulating units 100 a and 100 b are respectively supplied to transport stream decoders (hereinafter also referred to as “TS decoders”) 8 a and 8 b, and are supplied to the MPEG decoding unit 10 via the changeover switch 9. That is, the TS decoders 8a and 8b extract the baseband signal from the selected channel.
[0034]
The MPEG decoding unit 10 receives the data stream supplied from the changeover switch 9 and converts it into a video signal and an audio signal by using a random access memory (RAM) 15 as a buffer for temporarily storing data.
[0035]
Here, as described above, two systems are provided: a system from the tuner 6a to the TS decoder 8a and a system from the tuner 6b to the TS decoder 8b. By providing such a plurality of systems, it becomes possible to receive independent channels in parallel. For example, when a mode for displaying a 4-channel multi-screen is provided, four systems are provided.
[0036]
In the following description, tuners 6a and 6b are generically referred to simply as tuner 6, demodulation units 100a and 100b are generically referred to as demodulation unit 100, and TS decoders 8a and 8b are generically referred to as TS decoder 8 respectively. .
[0037]
The digital television receiver 1 further receives a signal from the TS decoders 8a and 8b through the data bus BS1 and stores it in the built-in storage device 48 and the data bus BS1 in the built-in storage device 48. An arithmetic processing unit 44 for performing a predetermined process on the accumulated data and outputting it, a ROM 40 for recording a program used for the arithmetic processing of the arithmetic processing unit 44, and an operation for the operation of the arithmetic processing unit 44 A RAM 42 providing a memory area and a high-speed digital interface 46 for inputting / outputting data between the data bus BS1 and the outside are provided. Although not particularly limited, as the internal storage device 48 and the ROM 40, for example, a flash memory capable of electrically writing and reading data can be used.
[0038]
The data after the arithmetic processing unit 44 performs processing on the data stored in the internal storage device 48 in accordance with an instruction given from outside is sent from the on-screen display processing unit 30 to the synthesizer 61. Given.
[0039]
The synthesizer 61 synthesizes the output from the MPEG decoding unit 10 and the output from the on-screen display processing unit 30, and then gives them to the video output terminal 64. The output from the video output terminal 64 is given to the display unit 4 and displayed.
[0040]
Further, the digital broadcast receiving apparatus 1 receives data obtained as a result of processing by the arithmetic processing unit 44 based on data stored in the built-in storage device 48, and generates sound effects and the like for the video output in the display unit Then, the additional sound generator 65 to be given to the synthesizer 60 and the data processed by the arithmetic processing unit 44 based on the data stored in the built-in storage device 48 are received to generate an audio signal and synthesizer 61. PCM decoder 22 is provided.
[0041]
The synthesizer 60 receives the output from the MPEG decoding unit 10 and the outputs from the additional sound generator 65 and the PCM decoder 22, and gives the synthesis result to the audio output terminal 62. The audio signal given to the audio output terminal 62 is output as an audio signal from the audio output unit 2.
[0042]
The digital broadcast receiving apparatus 1 may be configured to include a modem 50 for exchanging data with the outside and an IC card interface 52 for receiving information from the IC card, if necessary.
[0043]
Via the high-speed digital interface 46, for example, an external storage device 80 such as an HDD device for a home server and a remote control (or keyboard or the like) 82 as an external input device are connected to the data bus BS1.
[0044]
The digital broadcast receiving apparatus 1 may have a configuration integrated with a display unit 4 that receives video output and displays it on a display, or an audio output unit 2 such as a speaker that receives audio output signals and outputs audio.
[0045]
FIG. 2 is a block diagram illustrating a configuration of the demodulation unit 100.
Referring to FIG. 2, the demodulating unit 100 performs analog / digital conversion on the signal down-converted by the tuner 6 to convert it into a digital signal, and an A / D corresponding to I-axis data. The Hilbert transform unit 104 that generates the D-axis data by shifting the digital signal from the transform unit 102 by 90 degrees, the delay unit 105, the I-axis data output from the A / D conversion unit 102 and the Hilbert transform unit 104, and A symbol synchronization unit 106 that receives the Q-axis data and performs synchronization adjustment for each symbol.
[0046]
The delay unit 105 delays the digital signal from the A / D conversion unit 102 by a processing time necessary for generating the Q-axis data in the Hilbert conversion unit 104 and transmits the digital signal to the symbol synchronization unit 106 as I-axis data. Thereby, the timing is adjusted between the I-axis data and the Q-axis data input to the symbol synchronization unit 106, and the I-axis data and the Q-axis data generated based on the same digital signal are the same at the same timing. Is transmitted to the symbol synchronization unit 106.
[0047]
In the symbol synchronization unit 106, narrowband AFC (Auto Frequency Control), which is frequency adjustment within the carrier interval, is executed, and clock signal synchronization and the like are performed.
[0048]
The demodulator 100 further receives digital data synchronized for each symbol in the symbol synchronizer 106 and executes a fast Fourier transform (FFT) process for converting the signal from the time domain to the frequency domain. An FFT unit 108 and a wideband AFC unit 110 for adjusting a frequency shift in units of carrier intervals with respect to an output signal from the FFT unit 108 converted into the frequency domain are included.
[0049]
The demodulating unit 100 receives a digital data sequence including I-axis data and Q-axis data that has been converted to the frequency domain and further subjected to synchronization processing, frequency adjustment, and the like, and a TMCC decoding unit 150 for extracting a TMCC signal A detection unit 112 for performing detection such as differential detection or synchronous detection on the digital data string, and frequency deinterleaving and time deinterleaving for canceling time interleaving and frequency interleaving performed on the transmission side, respectively. It further includes a deinterleaving unit 114 that performs interleaving, and an error correction unit 116 for decoding error correction coding performed on the transmission side.
[0050]
The detection processing by the detection unit 112, the deinterleaving processing by the deinterleaving unit 114, and the error correction processing by the error correction unit 116 are performed by the modulation scheme, interleave length, and error coding rate included in the TMCC information obtained by the TMCC decoding unit 150. This is performed based on the demodulation information. The digital data sequence processed by the error correction unit 116 from the detection unit 112 is sent to the TS decoder 8 as transport stream data (TS data).
[0051]
FIG. 3 is a block diagram illustrating the configuration of the TMCC decoding unit 150.
Referring to FIG. 3, TMCC decoding unit 150 receives a digital data sequence (digital data Di, Dq), a mode signal MDS and a start pulse STP from a wideband AFC (Auto Frequency Control) unit, and is included in the data sequence. The TMCC signal is extracted and the synchronization timing is adjusted for each frame.
[0052]
Based on the start pulse STP and the mode signal MDS, the TMCC decoding unit 150 counts the count data CNT1 that counts 1404 periods corresponding to the number of carriers included in one unit section described in FIG. 10 and the number of unit sections. In order to do so, it includes a counting unit 152 that generates CNT2.
[0053]
FIG. 4 is a diagram for explaining the operation of the counter unit 152.
Referring to FIG. 4 (a), count data CNT1 performs a count-up operation from initial value 0 to full count value 1403 corresponding to the number of carriers 1404 in each of unit intervals F0 to F3 shown in FIG. It starts in response to the start pulse STP. When the count value CNT1 reaches the full count value 1403, the counter unit 152 returns the count value CNT1 to the initial value 0.
[0054]
Therefore, for example, in mode 3, the count data CNT1 reaches the full count value four times within one OFDM symbol.
[0055]
The count data CNT2 is incremented by 1 from the initial value 0 every time the count data CNT1 reaches the full count value 1403. The full count value of the count data CNT2 varies depending on the mode. In mode 3, since four unit sections are included, the count value CNT2 is incremented by setting the initial value to “0” and the full count value to “3”.
[0056]
Referring to FIG. 4B, in mode 2, since the unit interval included is two, the count value CNT2 is incremented by setting the initial value to “0” and the full count value to “1”. Executed.
[0057]
Referring to FIG. 4C, in mode 1, the count data CNT2 is 0 for both the initial value and the full count value, and the count data CNT2 is not updated. This is because mode 1 includes one unit section.
[0058]
In this way, each unit interval and each symbol boundary can be detected by the count data CNT1 and CNT2.
[0059]
As already described, in each of unit sections F0 and F1 in mode 2, TMCC signals indicating the same signal level (“0” or “1”) are included based on the same arrangement pattern. . Similarly, in mode 3, TMCC signals indicating the same signal level are included in each of unit intervals F0 to F3 based on the same arrangement pattern.
[0060]
Referring to FIG. 3 again, demodulating section 150 includes a DBPSK demodulating section 154 for extracting a TMCC signal from the digital data string and executing DBPSK demodulation (Differential Binary Phase Shift Keying).
[0061]
By the count operation in the counter unit 152, the position of the TMCC signal in the data string according to the standard can be specified. Therefore, the DBPSK demodulator 154 extracts the TMCC signal in the digital data string based on the count signal CNT1.
[0062]
FIG. 5 is a conceptual diagram illustrating a demodulation method for DBPSK demodulation. DBPSK modulation is discrete phase modulation based on a differential method.
[0063]
Referring to FIG. 5, DBPSK demodulation section 154 compares the phases of TMCC signals at the same position in each symbol between symbols and outputs demodulated data based on the phase comparison result. FIG. 5 shows a comparison of TMCC signals of the nth n symbol (n: integer from 0 to 202) and the next (n + 1) symbol. Note that DBPSK demodulation is also executed for the 203rd symbol during the 0th symbol of the next frame period.
[0064]
As shown in FIG. 5A, when the TMCC signal has the same phase between n symbols and (n + 1) symbols, “0” is obtained as demodulated data. On the contrary, as shown in FIG. 5B, when the phase of the TMCC signal is reversed between n symbols and (n + 1) symbols, “1” is obtained as demodulated data.
[0065]
FIG. 6 is a block diagram illustrating the configuration of the TMCC processing unit 160.
Referring to FIG. 6, TMCC processing unit 160 receives a demodulated data from DBPSK demodulating unit 154 and count data CNT1 and CNT2, and executes a majority processing unit 162 that executes majority processing for each unit section. The majority processing result for each unit section from the processing unit 162 is compared in the same symbol, and the majority processing result comparison unit 164 and the majority processing result comparison unit 164 for selecting the most reliable majority result are selected by the majority processing result comparison unit 164. And a majority processing determination unit 166 for determining the selected majority result.
[0066]
As already described, since a plurality of TMCC signals included in the same symbol are intended to transmit the same signal level, ideally, from the DBPSK demodulator 154 corresponding to one OFDM symbol. All demodulated data is unified to “0” or “1”.
[0067]
Therefore, under an ideal transmission state, the majority decision result TFD corresponding to the integrated value of the demodulated data in each unit section is expressed by the number of predetermined TMCC signals included in one unit section as M (M: natural number). ), It will be either “0” or “M”.
[0068]
The value of M varies depending on the segment type. In particular, the arrangement position of the TMCC signal differs depending on the segment format (differential or synchronous), but the arrangement of the TMCC signal of the synchronous segment is included in the arrangement of the TMCC signal of the differential segment system. Therefore, in applying the present invention, only the arrangement of TMCC signals in accordance with the synchronous segment method needs to be considered. Since M = 13 in the arrangement pattern of the synchronous segment method, the case where M = 13 will be described in the following description.
[0069]
By executing such a majority process, even if there is a partial frequency range in which the TMCC signal cannot be correctly transmitted in each unit section, the majority result TFD is either “0” or “13”. If it is determined whether the 1-bit data transmitted by the TMCC signal in the symbol is “0” or “1”, it can be estimated.
[0070]
Based on the count data CNT2 for counting the number of unit sections in one OFDM symbol, the majority processing section 162 determines the majority processing result TFD based on 13 (M) TMCC signals corresponding to one unit section. Output. That is, the majority processing result TFD is 4-bit data indicating an integer of 0 to 13 (M).
[0071]
The majority processing result comparison unit 164 selects the most reliable result within the same symbol from the majority processing results obtained corresponding to each unit section.
[0072]
That is, in mode 1, the majority processing result comparison unit 164 outputs the majority processing result TFD from the majority processing unit 162 as it is as the selected majority processing result TSD, but in mode 2, the unit sections F0 and F1 The two majority processing results TFD respectively corresponding to are compared, a more reliable one is selected and output as a majority processing result TSD. Similarly, in mode 3, the majority processing result comparison unit 164 executes comparison processing three times, and the most reliable processing result TFD corresponding to each of the four unit sections F0 to F3 is the most reliable. A high majority processing result is selected and output as a majority processing result TSD.
[0073]
Here, the majority processing result TFD is more reliable as it is closer to “0” or “13”. That is, when the majority processing result TFD is in the range of 0 to 6, it indicates that the signal level transmitted by the TMCC signal is “0”. However, the smaller the value of the majority processing result TFD, the more reliable it is. Is considered high.
[0074]
On the other hand, when the majority processing result TFD is in the range of 7 to 13, it indicates that the signal level transmitted by the TMCC signal is “1”. However, the larger the value of the majority processing result TFD, the more reliable it is. It is judged that the nature is high.
[0075]
The majority processing determination unit 166 determines the majority processing result TSD selected by the majority processing result comparison unit 164, and sets the TMCC bit TMB indicating 1-bit data transmitted by the TMCC signal in the symbol to “0” and “1”. Set to one of the following.
[0076]
Specifically, when the majority processing result TSD is in the range of 0 to 6, the TMCC bit TMB is set to “0”. Conversely, when the majority processing result TSD is in the range of 7 to 13, the TMCC bit TMB is set to “1”.
[0077]
Referring to FIG. 3 again, TMCC decoding unit 150 further includes a synchronization word detection unit 156 for receiving a TMCC bit TMB obtained by TMCC processing unit 160 and detecting a synchronization word.
[0078]
The synchronization word detection unit 156 has a register 157 for accumulating 16 bits of the TMCC bits TMB output by the TMCC processing unit 160. The register 157 accumulates the TMCC bit TMB by a FIFO method (First In First Out). That is, when a new TMCC bit TMB is input, the oldest TMCC bit TMB stored in the register 157 is deleted.
[0079]
The synchronization word detection unit 156 detects the frame head position by comparing the 16-bit TMCC bits stored in the register 157 with a predetermined 16-bit synchronization word pattern for each symbol. Specifically, the synchronization word detection unit 156 activates the frame start trigger FTG when the data stored in the register 157 matches the synchronization word pattern. At the same time, frame head detection protection is executed.
[0080]
According to the standard of terrestrial digital broadcasting, a predetermined 16-bit synchronization word pattern is inverted and set for each frame. For example, when the synchronization word pattern in the m-th frame (m: natural number) is “1100101000010001”, the synchronization word pattern in the (m + 1) -th frame is set to “0011010111101110”. Therefore, it is possible to detect the synchronization word pattern by utilizing this property, and execute the detection of the frame head position and the protection of the frame head detection.
[0081]
Since the symbol number can be determined from the detected frame head position in this way, various TMCC information can be obtained by executing differential demodulation and majority processing in the frequency direction within the same symbol. Obtainable.
[0082]
The TMCC information TSB extracted by the TMCC processing unit 160 is sequentially sent to the error correction decoding unit 158.
[0083]
In each frame, error correction coding is performed on the TMCC information TSB included in the 20th to 203rd symbols of the 0th to 203rd symbols. The error correction decoding unit 158 operates based on the frame start trigger FTG, performs error correction decoding applied to the TMCC information TSB corresponding to the 20th and subsequent symbols, and is inserted into the transmission data and transmitted TMCC information is extracted.
[0084]
The timing adjustment unit 170 is generated by the completely decoded TMCC information, the digital data string including the I-axis data Di and the Q-axis data Dq from the wideband AFC unit, the start pulse STP, and the synchronization word detection unit 156. In response to the frame pulse, the timing between these data is adjusted and output to the next block, that is, the detector 112 in FIG.
[0085]
Referring to FIG. 6 again, TMCC processing unit 160 generates a majority processing result TSD (4 bits) selected by majority processing result comparison unit 164 and a TMCC generated by majority processing determination unit 166 based on majority processing result TSD. Either one of the bits TMB is transmitted to the error correction unit 158 as TMCC information TSB.
[0086]
By performing error correction using the majority processing result TSD, the circuit scale for 4 bits is required, while the error correction capability can be improved, and TMCC information can be decoded more accurately. On the other hand, by performing error correction using the TMCC bit TMB, the circuit scale of the error correction unit 158 can be suppressed.
[0087]
In addition, in the standard conforming to terrestrial digital broadcasting, information on the segment format (differential or synchronous) is also included in the TMCC information. Therefore, before decoding the TMCC signal, the segment format of the currently received data is changed. I can't know. However, as already described, since the arrangement of TMCC signals in the synchronous segment is included in the arrangement of TMCC signals in the differential segment system, only the arrangement of TMCC signals according to the synchronous segment system is taken into consideration. May be applied.
[0088]
Referring to FIG. 4 again, in mode 1 where the number of carriers is 2k, TMCC signal extraction is performed using the TMCC signal included in unit interval F0. However, in mode 2 and mode 3 in which the number of carriers is 4k and 8k, one OFDM symbol includes a plurality of unit intervals. Here, it is assumed that in mode 3, the transmission path characteristics are very disturbed in terms of time or frequency.
[0089]
FIG. 7 is a conceptual diagram for explaining the disturbance of the transmission path characteristics.
Referring to FIG. 7, if there is a frequency band in which transmission path characteristics are disturbed in the same symbol, it becomes difficult to extract desired TMCC information in the section. Therefore, if the majority process is executed over one OFDM symbol, the majority process result may be incorrect. As a result, it is conceivable that TMCC information cannot be extracted accurately and the subsequent demodulation operation is hindered.
[0090]
Furthermore, as shown in FIG. 7, the frequency region in which the transmission path characteristics are disturbed may vary with time.
[0091]
Therefore, in the present invention, using the periodicity of the TMCC signal, in mode 2 or mode 3, the majority process is executed independently for each unit section, and the reliability is determined from the majority results in each unit section. Select one with a high value.
[0092]
If such majority processing is executed, TMCC information can be accurately decoded in mode 2 and mode 3 as long as the transmission path characteristics are good in any of a plurality of unit sections. In other words, in a mode including a plurality of unit sections in which TMCC signals are inserted in the same pattern, such as mode 2 or mode 3, even when the transmission path characteristics are extremely disturbed in some unit sections, the TMCC is satisfactorily performed. Information can be decoded.
[0093]
As a result, it is possible to receive a digital signal more accurately in response to disturbances in temporal or frequency transmission path characteristics.
[0094]
Furthermore, since it is sufficient to provide a circuit for executing the majority process on a scale corresponding to one unit section, the hardware circuit scale can be reduced.
[0095]
In the present embodiment, reception of terrestrial digital broadcasting has been described as a representative example, but application of the present invention is not limited to this. That is, the present invention has a configuration in which transmission data and demodulation information necessary for demodulation of transmission data are included in the same data string, and the demodulation information is periodically inserted for each unit section of the data string. It can be widely applied to the reception of digital signals.
[0096]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0097]
【The invention's effect】
A digital signal receiving apparatus according to the present invention generates a decoding result of a demodulated information signal independently for each unit section in a predetermined section of a digital data sequence formed by a plurality of unit sections, and decodes corresponding to the same predetermined section Demodulation information is generated using a highly reliable decoding result among the results. As a result, even when the transmission path characteristics are disturbed corresponding to some unit sections, it is possible to correctly decode the demodulated information and receive the digital signal normally.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a main part extracted from a configuration of a digital broadcast receiving apparatus 1 shown as a representative example of a digital signal receiving apparatus according to the present invention.
FIG. 2 is a block diagram showing a configuration of a demodulator shown in FIG.
FIG. 3 is a block diagram illustrating a configuration of a TMCC decoding unit shown in FIG.
4 is a diagram for explaining the operation of the counter unit shown in FIG. 3; FIG.
FIG. 5 is a conceptual diagram illustrating a demodulation method for DBPSK demodulation.
6 is a block diagram illustrating a configuration of a TMCC processing unit illustrated in FIG. 3. FIG.
FIG. 7 is a conceptual diagram for explaining disturbance of transmission path characteristics.
FIG. 8 is a first diagram for explaining the structure of a data signal used for terrestrial digital broadcasting.
FIG. 9 is a second diagram for explaining the structure of a data signal used for terrestrial digital broadcasting.
FIG. 10 is a conceptual diagram for explaining a data structure of each symbol corresponding to each of a plurality of modes in terrestrial digital broadcasting.
[Explanation of symbols]
100, 100a, 100b Demodulation unit, 150 TMCC decoding unit, 152 counter unit, 154 DBPSK demodulation unit, 156 Sync word detection unit, 158 Error correction unit, 160 TMCC processing unit, 162 Majority processing unit, 164 Majority processing result comparison unit, 166 Majority determination unit, 170 timing adjustment unit, F0 to F3 unit section, STP start pulse, CNT1, CNT2 count data, MDS mode signal.

Claims (3)

Digital signal receiving apparatus for receiving a digital broadcast signal of an orthogonal frequency division multiplex system in which a data sequence in which demodulation information is inserted in a predetermined pattern for each unit section is repeatedly transmitted according to a transmission mode Because
A first counter that sets the number of carriers in the unit interval to a maximum value;
A second counter that sets a maximum count value according to a transmission mode of the received digital broadcast signal;
A demodulator that extracts the demodulated information and outputs demodulated data;
A majority processing unit for performing majority processing of demodulated data from the demodulation unit;
With
The majority processing unit extracts a majority processing result of the majority processing unit in a counting period of the first counter;
A digital signal receiving apparatus, wherein the demodulated data having the highest reliability is selected by comparing a plurality of the majority results extracted in the counting period of the second counter.   The digital signal receiving apparatus according to claim 1, wherein the majority processing unit executes a majority processing based on an integrated value of the demodulation information in a counting period of the first counter. The demodulation information is subjected to error correction coding,
The digital signal receiving apparatus according to claim 2, further comprising an error correction decoding unit that performs error correction decoding based on the demodulated data selected by the majority processing unit.

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