JP2013055369A - Multicarrier modulation signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicarrier modulation signal receiver which can maximally extract effects of error correction without including errors in a detection value of interference signal quantity.SOLUTION: A signal is received by an antenna part and processing performed in a conventional receiver such as orthogonal detection processing, FET processing, equalization processing, de-interleave processing, demapping processing, decoding processing, energy inverse spread processing, and Reed-Solomon decoding processing, are performed. A signal to be input to a demapping processing part (symbol point after equalization) is stored separately, while encoding processing is performed to data rows of Reed-Solomon decoding result in the same procedure as that of modulation processing in a transmitter, again. At that time, energy spread processing, convolutional encoding processing and mapping processing for multi-value modulation QAM signal such as QPSK, 16QAM, and 64QAM, are performed.

Description

  The present invention relates to a technique for detecting an interference signal superimposed on a received signal and removing the influence when receiving a multi-carrier modulated signal.

  In recent years, terrestrial digital broadcasting has been started in various countries around the world, and replacement with conventional analog television broadcasting is being promoted. In the European terrestrial digital broadcasting standard (DVB-T) and the Japanese terrestrial digital broadcasting standard (ISDB-T), an OFDM (Orthogonal Frequency Division Multiplexing) system is adopted, and a large number of carriers are used. A signal having a high transmission capacity can be transmitted.

  In the OFDM system, a mechanism to prevent interference from preceding and following symbols called guard intervals makes it less susceptible to interference from reflected waves, or converts the transmission signal to a digital code and performs error correction code processing. As a result, the noise resistance of the received signal is improved. In particular, the ISDB-T standard introduces a data rearrangement called interleaving, a mechanism called hierarchical transmission that transmits a plurality of broadcasts with different noise immunity, and is selectively viewed on the viewer side. Even when it drops, it is possible to view stable broadcasts. The above error correction code processing is an example, and various other signal processing techniques are incorporated, and by performing appropriate processing in the receiving device, it is normal even if there is a decrease in received signal level or radio wave interference. It is possible to keep the reception state.

  Here, the configuration of a multicarrier modulation signal receiving apparatus for receiving ISDB-T broadcast, which is a Japanese terrestrial digital broadcast standard, will be described with reference to FIG. The multicarrier modulation signal receiving apparatus includes an antenna unit 601, a tuner unit 602, an A / D conversion processing unit 603, an orthogonal detection processing unit 611, an FFT processing unit 612, an equalization processing unit 613, and a deinterleave process. Unit 621, demapping processing unit 622, bit deinterleaving processing unit 631, decoding processing unit 632, energy despreading processing unit 634, RS (Reed-Solomon) decoding processing unit 635, and TS (transport stream) ) A reproduction processing unit 671, a TS decoding processing unit 672, and an MPEG (Moving Picture Experts Group) decoding processing unit 673.

  The tuner unit 602 selects a signal in a predetermined frequency band from the signal received by the antenna unit 601 and outputs the signal to the A / D conversion processing unit 603. The A / D conversion processing unit 603 samples the OFDM signal output from the tuner unit 602, converts it to a digital signal, and outputs the digital signal to the quadrature detection processing unit 611.

  The quadrature detection processing unit 611 multiplies the OFDM signal obtained from the A / D conversion processing unit by a sine wave signal having the same frequency as that of the reference carrier wave, converts the signal to a baseband OFDM signal, and outputs the baseband OFDM signal to the FFT processing unit 612. .

  The FFT processing unit 612 extracts a signal sequence of an effective symbol period from the baseband OFDM signal output from the quadrature detection processing unit 611. Then, a discrete Fourier transform is performed on the extracted signal sequence to generate a complex signal. The FFT processing unit 612 outputs the complex signal obtained by the discrete Fourier transform to the equalization processing unit 613.

  The equalization processing unit 613 receives a complex signal from the FFT processing unit 621. Complex signals obtained from the FFT processing unit exist as many as the number of FFT points, and each of them is OFDM symbol data. For example, according to an operation standard called mode 3 of the ISDB-T broadcasting standard, the number of FFT points is 8192, and 8192 complex signals to be output are obtained. Of these, 5617 are signals to be processed and are called OFDM symbols. The OFDM symbol data includes an SP (Scattered Pilot) signal every 12 symbols in the carrier direction. In addition, the SP signals are arranged shifted by 3 symbols in the time direction. Therefore, the equalization processing unit 613 detects and extracts SP signals that are discretely arranged from the OFDM symbol.

  Next, since the SP signal is a known signal, the transmission path characteristic between the transmission and reception of the SP carrier position can be estimated by dividing the extracted SP signal by the known complex signal value. By performing interpolation processing based on the estimated value of the transmission path characteristics at the SP signal positions discretely arranged in the OFDM signal, the transmission path characteristics of the OFDM carrier between the SP signals can also be estimated. Then, by dividing each OFDM symbol by the calculated transmission path characteristic, information on the OFDM symbol point that compensates for the influence of the transmission path can be obtained. The equalization processing unit 613 estimates OFDM symbol point information (hereinafter referred to as “received OFDM symbol point”) compensated for the influence of the transmission channel, and estimation results of transmission channel characteristics corresponding to the “received OFDM symbol point”. Are output to the deinterleave processing unit 621.

  The deinterleave processing unit 621 sequentially receives the “received OFDM symbol point” and the data string of the estimation result of the transmission path characteristics from the equalization processing unit 613. Then, the received data string is rearranged. The rearrangement rule is defined in the ISDB-T standard, and a process of returning signals rearranged randomly in the time direction and the frequency direction in the interleaving process on the transmission side to the original order is performed. Then, the rearranged “mapped OFDM symbol points” and the data string of the estimation result of the transmission path characteristics are output to the demapping processing unit 622.

  The demapping processing unit 622 obtains the “received OFDM symbol points” rearranged from the deinterleaving processing unit 621 and the data string of the estimation result of the channel characteristics. The OFDM symbol is mapped on the complex plane according to the carrier modulation scheme on the signal transmission side. For example, if the carrier modulation method is 64QAM, the signal is converted into one of 64 mapping points according to the obtained bit data.

  Therefore, the demapping processing unit 622 regards the mapping point closest to the “received OFDM symbol point” as the transmission signal point, and generates bit data. Further, the distance information between the “received OFDM symbol point” and the mapping point closest to the “received OFDM symbol point” (hereinafter, the received symbol point distance information), and the “received” received from the deinterleave processing unit 621 separately. Reliability information is generated based on the information on the size of the transmission path characteristic of the carrier including the “OFDM symbol point”.

  At this time, the distance information between the reception points is accumulated for a certain period in OFDM symbol units, and the noise amount for each carrier included in the carrier including the OFDM symbol is calculated separately, and then the noise amount for each carrier and the transmission path characteristics are calculated. Reliability information may be generated from the estimation result and the distance information of the received symbol points. The process of calculating the reliability information as described above and using it in the subsequent decoding processing unit is called “soft decision”. Then, the bit data generated from the mapping point closest to the “received OFDM symbol point” and the reliability information are output to the bit deinterleave processing unit 631.

  The bit deinterleave processing unit 631 rearranges the bit data and reliability information obtained from the demapping processing unit 622 into the original order in accordance with the ISDB-T standard, and then outputs them to the decoding processing unit 632. To do.

  The decoding processing unit 632 obtains bit data and reliability information from the bit deinterleave processing unit 631 and performs decoding processing by weighting the received bit data according to the reliability information. Currently, a decoding process called Viterbi decoding is widely used, but a process according to another decoding algorithm may be used. The data string of the decoding result is output to the decoding processing unit 632 and the byte deinterleaving processing unit 633.

  The byte deinterleave processing unit 633 receives the error-corrected data sequence obtained from the decoding processing unit 632, rearranges the data sequence to the original order in accordance with the ISDB-T standard, and transmits the data to the energy despreading processing unit 634. Output a column.

  The energy despreading processing unit 634 performs processing for restoring the energy spreading processing performed on the signal transmission side in accordance with the ISDB-T standard in accordance with the ISDB-T standard for the data sequence obtained from the byte deinterleaving processing unit 633, and after conversion. The data string is output to the RS decoding processing unit 635.

  The RS decoding processing unit 635 receives the data sequence obtained from the energy spreading processing unit 634, performs Reed-Solomon decoding processing using the assigned outer code, and sends the data after Reed-Solomon decoding to the TS reproduction processing unit 671. Output a column.

  The TS reproduction processing unit 671 obtains a Reed-Solomon decoded data sequence from the RS decoding processing unit 635. The Reed-Solomon decoded data sequence obtained from the RS decoding processing unit 635 is a transport stream packet. In the TS reproduction processing unit 671, since the number of packets of the transport stream obtained from the RS decoding processing unit 635 differs depending on the transmission parameter, an appropriate number of null packets are complemented, and the constant transport stream is not dependent on the transmission parameter. Adjust so that the number of packets is output. The TS reproduction processing unit 671 outputs the transport stream packet after complementing the null packet to the TS decoding processing unit 672.

  The TS decode processing unit 672 obtains the packet of the transport stream output from the TS reproduction processing unit 671, and based on the information included in the transport stream, the video packet, the audio packet, and the PCR (Program Clock Reference) packet Are output to the MPEG decoding processing unit 673.

  The MPEG decoding processing unit 673 includes a video decoder and an audio decoder. The video decoder extracts video packets from the transport stream packets obtained from the TS decoding processing unit 672, decodes the data, and generates image data. The audio decoder extracts an audio packet from the transport stream obtained from the TS decode processing unit 672, decodes the data, and generates audio data.

  Then, the MPEG decoding processing unit 673 adjusts the output timing of the image data and audio data based on the time information included in the PCR packet, and then outputs the image data and audio data to a display device or the like.

  As described above, with the configuration shown in FIG. 9, various processes are performed after receiving an ISDB-T broadcast wave, and as a result, viewing and recording of images and sounds are possible.

  However, in digital broadcasting, when the received signal level falls below a certain level, or when the amount of radio interference exceeds a certain level, the reception state deteriorates rapidly, and images and sounds are partially lost, and video and Audio interruption occurs. The factors that cause deterioration in the reception quality of terrestrial digital broadcasting include delayed waves that are reflected from the signal itself to buildings and mountains, analog TV broadcast waves that are received in the same frequency band, and signals that are at a high level outside the band. Intermodulation distortion caused by distortion due to noise, noise signals such as unwanted radiation generated in the receiver or other devices, etc. can be considered, and if the interference signal level is higher than a certain level with respect to the signal to be received, the reception quality The impact on will appear.

  In this specification, analog TV broadcast waves superimposed on frequency bands used in digital broadcasting, intermodulation distortion, noise signals due to unnecessary radiation such as harmonics of clock signals, etc. An interference signal having a biased characteristic is called a frequency selective interference signal, and a technique for improving resistance to the frequency selective interference signal will be described.

  Conventionally, a technique for detecting and removing the influence of a frequency selective interference signal superimposed on a signal when receiving and demodulating a signal subjected to multi-carrier modulation such as OFDM modulation has been disclosed. For example, in Patent Document 1, in the process of demodulating an OFDM signal, the distance between the demodulation signal point of each of a plurality of carriers and the representative reception symbol point is measured for each carrier and integrated in the time direction to determine the magnitude of the dispersion of the demodulation signal. And detecting the C / N for each carrier by comparing the magnitude of dispersion for each carrier, and detecting the carrier having a poor C / N as having received a frequency selective interference, and the interference detection. An OFDM receiver is disclosed that performs stepwise weighting on a demodulated signal based on C / N information detected by the means and performs error correction processing by a method called soft decision. The value of the distance between the demodulated signal point and the representative reception symbol point is also called MER (Modulation Error Ratio), and uses the MER value calculated for each carrier in the soft decision processing.

  Further, in Patent Document 2, when a transmission path characteristic between transmission and reception is estimated and compensated using a pilot signal regularly arranged in an OFDM signal, a frequency selective interference signal is detected. Is detected, the pilot signal that exists in the vicinity of the disturbed carrier is not used for estimating the channel characteristics, and the pilot signal that has detected the disturbing signal from the pilot signal that is not affected by the disturbing signal is not used. An OFDM receiver used for signal processing by estimating peripheral transmission path characteristics is disclosed.

Japanese Patent No. 2945570 Japanese Patent No. 3363806

  In Patent Document 1, a frequency selective interference signal is detected from an integral value of distances between demodulated signal points and representative reception symbol points of a plurality of carriers. Specifically, a hard decision process is performed in which the equalized symbol is regarded as being received at the closest representative symbol point, and the distance between the equalized symbol point and the adjacent representative symbol point in the time direction for each carrier. The integral is used as an indicator of the amount of interference signal. However, if the OFDM carrier is subjected to multi-level QAM modulation such as 64QAM, the interference signal amount is larger than the inter-symbol distance of the 64QAM signal, or the interference error overlaps with the pilot carrier, resulting in an estimation error of the transmission path characteristics. Largely, as a result of dividing the received signal by the transmission path characteristics including an error, the symbol point after equalization may be far away from the transmission symbol point. At this time, if the distance between the equalized symbol point and the closest symbol point is calculated, the original transmission signal point exists further away, and there is a problem that the amount of interference signal is estimated to be small.

  Further, the error correction capability is improved by using the calculated interference signal amount as reliability information in the error correction code processing unit, but as described above, the distance between the symbol point after equalization and the closest symbol point is increased. If the integrated value is an interference signal amount, the detection value of the interference signal amount may include an error, and thus the error correction effect in the error correction processing unit cannot be maximized.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a multicarrier modulation signal receiving apparatus that can maximize the effect of error correction.

  In order to solve the above-described conventional problem, a multicarrier modulation signal receiving apparatus according to the present invention includes a tuner unit that selects a multicarrier signal of a predetermined frequency band from a signal received by an antenna unit, and an input from the tuner unit. The multi-carrier signal is sampled and converted to a digital signal, and the multi-carrier signal is demodulated from the signal input from the A / D conversion processor, and the received symbol point is transmitted for each carrier. A demodulator that generates a data sequence of path characteristic estimation results, a deinterleave processor that rearranges the received symbol points input from the demodulator and the data sequence of transmission path characteristics estimation results, and inputs from the deinterleave processor The rearranged received symbol points and transmission path characteristic estimation results, and the received symbol points obtained from the inter-symbol distance calculation / accumulation processing unit are mapped. A first demapping processing unit that generates reliability information using distance information with the information of the singing point, and error correction processing based on the reliability information of the bit data input from the first demapping processing unit The first error correction unit for restoring the transmission signal sequence and the data obtained by restoring the transmission signal sequence input from the first error correction unit are encoded, and in parallel with the encoding process, Determining whether or not the processed signal was generated from a signal that could not be error-corrected. An encoding unit that generates a signal indicating an error-correctable range, and carrier-modulated data input from the encoding unit. A mapping processing unit that generates mapping point information and a signal indicating an error-correctable range mapped according to the method, a received symbol point input from the deinterleaving processing unit, and a mapping The inter-code distance calculation / accumulation processing unit that calculates the distance between the received symbol point and the mapping point information by aligning the timing of the mapping point information input from the processing unit and the mapping point error presence / absence information, and the deinterleave processing unit Receiving symbol points input from the mapping point information input from the mapping processor, mapping point error presence / absence information, and received symbol points input from the intersymbol distance calculation / accumulation processing unit A second demapping processing unit that performs demapping processing from the distance information between the mapping point information and the estimation result of transmission path characteristics input from the deinterleaving processing unit, and a bit input from the second demapping processing unit A second error correction unit that performs error correction processing based on the data and the reliability information and generates an original signal sequence. And features. Receives the signal, and performs orthogonal detection processing, FFT processing, equalization processing, deinterleaving processing, demapping processing, decoding processing, energy despreading processing, Reed-Solomon decoding processing, and processing performed in a normal receiving device . Furthermore, while separately holding the signal (symbol point after equalization) input to the demapping processing unit, the data sequence of the Reed-Solomon decoding result is again processed in the same procedure as the modulation processing in the transmission device. The encoding process is performed again. At this time, energy diffusion processing, convolutional code processing, and mapping processing of multilevel modulation QAM signals such as QPSK, 16QAM, and 64QAM are performed.

  As described above, conventionally, the interference signal amount for each carrier and the index value of the signal quality of the received signal are calculated from the distance between the equalized symbol point and the mapping point closest to the equalized symbol point. However, it is possible to improve the demodulation performance of the signal on which the interference signal is superimposed by calculating and using the interference signal amount from the distance between the correct reception point and the equalized symbol point after calculating the correct reception point. . In particular, by feeding back to the first demapping processing section information on the interference signal amount calculated from the distance between the correct reception point generated from the error-corrected signal and the symbol point after equalization, The error correction capability of the error correction unit can be improved.

  Further, by repeating the error correction process and the encoding process a plurality of times, more correct reception point information can be generated, while the processing circuit may be shared.

  According to the multicarrier modulation signal receiving apparatus of the present invention, it is possible to provide a multicarrier modulation signal receiving apparatus that can bring out the effect of error correction to the maximum.

The block diagram which shows the structure of the multicarrier modulation signal receiver in Example 1 of this invention. The block diagram which shows the structure of the multicarrier modulation signal receiver in Example 1 of this invention. 1 is a configuration diagram of a convolutional encoder of a multicarrier modulation signal receiving apparatus according to Embodiment 1 of the present invention. 1 is a configuration diagram of an error information calculation processing unit of a multicarrier modulation signal receiving apparatus according to Embodiment 1 of the present invention. Supplementary explanatory diagram of processing of the mapping processing unit of the multicarrier modulation signal receiving apparatus in Embodiment 1 of the present invention The figure which shows the relationship between noise amount and MER (Modulation Error Ratio: modulation error ratio). The figure for demonstrating the correction method of the Euclidean distance calculated in the intersymbol distance calculation and accumulation process part 152 of Example 1 of this invention. The block diagram which shows the structure of the other multicarrier modulation signal receiver in Example 1 of this invention. The block diagram which shows the structure of the other multicarrier modulation signal receiver in Example 1 of this invention. The block diagram which shows the structure of the conventional multicarrier modulation signal receiver

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

  The description of the first embodiment will be made according to the ISDB-T system which is a Japanese terrestrial digital broadcasting standard. Although there is a difference from other systems such as the DVB-T system, which does not necessarily include processing called interleave processing or hierarchical transmission, the description is omitted because it does not significantly affect the concept of the present invention. To do. Further, since the ISDB-T system is a known standard, only a minimum description will be given here.

  FIGS. 1A and 1B are block diagrams illustrating the configuration of the multicarrier modulation signal receiving apparatus according to the first embodiment. FIG. 1B shows the configuration of FIG. 1A subdivided into finer processing units. As shown in FIGS. 1A and 1B, the multicarrier modulation signal receiving apparatus according to the first embodiment includes an antenna unit 101, a tuner unit 102, an A / D conversion processing unit 103, and a demodulation unit 110. (Orthogonal detection processing unit 111, FFT processing unit 112, equalization processing unit 113), deinterleave processing unit 121, first demapping processing unit 122, and first error correction unit 130 (first Bit deinterleaving processing unit 131, first decoding processing unit 132, first byte deinterleaving processing unit 133, first energy despreading processing unit 134, and first RS (Reed-Solomon) Solomon) decoding processing unit 135), encoding unit 140 (first RS code processing unit 141, error information addition processing unit 142, energy spread processing unit 143, byte interleaving) A processing unit 144, a convolutional code processing unit 145, an error information calculation processing unit 146, a bit interleaving processing unit 147), a mapping processing unit 151, an inter-code distance calculation / accumulation processing unit 152, and a second demapping Processing unit 153, second error correction unit 160 (second bit deinterleaving processing unit 161, second decoding processing unit 162, second byte deinterleaving processing unit 163, and second energy despreading) A processing unit 164, a second RS decoding processing unit 165), a TS (Transport Stream) reproduction processing unit 171, a TS decoding processing unit 172, an MPEG (Moving Picture Experts Group) decoding processing unit 173, It consists of

  Next, the configuration of the multicarrier modulation signal receiving apparatus according to the first embodiment shown in FIGS. 1A and 1B will be described. Compared with FIG. 9, FIG. 1A is the same as the configuration of the antenna unit 101 to the deinterleave processing unit 121, the antenna unit 601 to the deinterleave processing unit 621, and the TS playback processing unit 171 performs MPEG decoding. The configuration of the processing unit 173 and the TS reproduction processing unit 671 to the MPEG decoding processing unit 673 are the same. Then, different processing blocks are added between the deinterleave processing unit 621 and the TS reproduction processing unit 671 in FIG. 9, and the output signal of the added intersymbol distance calculation / accumulation processing unit 152 is the first demapping processing unit. The configuration is input to 122. That is, the signal is input to the second demapping processing unit 153 after passing through the encoding unit 140 and the mapping processing unit 151 for performing the encoding process on the output of the first error correction unit 130 again, After the second error correction unit 160 performs the decoding process again on the output signal of the demapping processing unit 153, the transport stream signal is output from the TS reproduction processing unit 171 and the inter-code distance calculation / accumulation processing unit 152 is output. Are output to the first demapping processing unit 122. Hereinafter, the operation of each block will be described in order with reference to FIG.

  The tuner unit 102 selects a signal in a predetermined frequency band from the signal received by the antenna unit 101, and outputs it to the A / D conversion processing unit 103. The A / D conversion processing unit 103 samples the OFDM signal output from the tuner unit 102, converts the signal into a digital signal, and outputs the digital signal to the demodulation unit 110.

  The demodulator 110 demodulates a multicarrier signal from the OFDM signal obtained from the A / D conversion processor, and generates data in units of carriers. Hereinafter, the operation of the demodulation unit 110 will be described in detail.

  The quadrature detection processing unit 111 multiplies the OFDM signal obtained from the A / D conversion processing unit 103 by a sine wave signal having the same frequency as the reference carrier wave, converts the signal into a baseband OFDM signal, and outputs the signal to the FFT processing unit 112. To do.

  The FFT processing unit 112 extracts a signal sequence of an effective symbol period from the baseband OFDM signal output from the quadrature detection processing unit 111. Then, a discrete Fourier transform is performed on the extracted signal sequence to generate a complex signal. The FFT processing unit 112 outputs a complex signal obtained by the discrete Fourier transform to the equalization processing unit 113.

  The equalization processing unit 113 receives a complex signal from the FFT processing unit 112. Complex signals obtained from the FFT processing unit exist as many as the number of FFT points, and each of them is OFDM symbol data. For example, according to an operation standard called mode 3 of the ISDB-T broadcasting standard, the number of FFT points is 8192, and 8192 complex signals to be output are obtained. Of these, 5617 are signals to be processed and are called OFDM symbols. The OFDM symbol data includes an SP (Scattered Pilot) signal every 12 symbols in the carrier direction. In addition, the SP signals are arranged shifted by 3 symbols in the time direction. Therefore, the equalization processing unit 113 detects and extracts SP signals that are discretely arranged from the OFDM symbol.

  Next, since the SP signal is a known signal, the transmission path characteristic between the transmission and reception of the SP carrier position can be estimated by dividing the extracted SP signal by the known complex signal value. By performing interpolation processing based on the estimated value of the transmission path characteristics at the SP signal positions discretely arranged in the OFDM signal, the transmission path characteristics of the OFDM carrier between the SP signals can also be estimated. Then, by dividing each OFDM symbol by the calculated transmission path characteristic, information on the OFDM symbol point that compensates for the influence of the transmission path can be obtained. The equalization processing unit 113 calculates OFDM symbol point information (hereinafter referred to as “received OFDM symbol point”) compensated for the effect of the transmission channel, and the estimation result of transmission channel characteristics corresponding to each “received OFDM symbol point”. Are output to the deinterleave processing unit 121.

  Similarly to the deinterleave processing unit 621 in FIG. 9, the deinterleave processing unit 121 receives an OFDM symbol and a data sequence of a transmission path characteristic estimation result, and rearranges the data sequence. Then, the rearranged OFDM symbols and the data string of the estimation results of the transmission path characteristics are output to the first demapping processing unit 122. Further, the rearranged OFDM symbol data sequence to the inter-code distance calculation / accumulation processing unit 152 is output to the second demapping processing unit 153, and the rearranged OFDM symbol data sequence and the transmission path characteristic estimation result data sequence are output. To do.

  Similarly to the demapping processing unit 622 in FIG. 9, the first demapping processing unit 122 converts the “received OFDM symbol points” rearranged from the deinterleaving processing unit 121 and the data string of the estimation result of the transmission path characteristics. Obtained and regarded the mapping point closest to the “received OFDM symbol point” as a transmission signal point, and generates bit data. Also, distance information between the “received OFDM symbol point” and the mapping point closest to the “received OFDM symbol point” (hereinafter, “distance information of the received symbol point”), and transmission obtained from the deinterleave processing unit 121 separately. The reliability information is generated by combining the information of the “data string of the estimation result of the path characteristics” and the “interference information in units of carriers” obtained from the inter-code distance calculation / accumulation processing unit 152 in the subsequent stage. A method for generating reliability information will be described separately after the description of the operation of the inter-code distance calculation / accumulation processing unit 152.

  Then, the generated bit data and reliability information are output to the first bit deinterleave processing unit 131.

  The first bit deinterleave processing unit 131 rearranges the bit data obtained from the first demapping processing unit 122 and the reliability information in the same manner as the bit deinterleave processing unit 631 in FIG. The data is output to the decryption processing unit 132.

  Similarly to the decoding processing unit 632 in FIG. 9, the first decoding processing unit 132 obtains bit data and reliability information from the first bit deinterleaving processing unit 131, and receives the received bit data according to the reliability information. The data is weighted and decoded, and the data string of the decoding result is output to the first byte deinterleave processing unit 133.

  Similarly to the byte deinterleave processing unit 633 in FIG. 9, the first byte deinterleave processing unit 133 rearranges the decoding result data sequence obtained from the first decoding processing unit 132 into the original order. The data string is output to the first energy despreading processing unit 134.

  Similarly to the energy despreading processing unit 634 in FIG. 9, the first energy despreading processing unit 134 is the energy applied on the signal transmission side to the data sequence obtained from the first byte deinterleaving processing unit 133. A process of returning the spreading process is performed, and the converted data string is output to the first RS decoding processing unit 135.

  Processing blocks from the first RS decoding processing unit 135 to the second RS decoding processing unit 165 described below are processing blocks newly added to FIG. 9 or processing blocks having different connection destinations of output signals.

  The first RS decoding processing unit 135 receives the data sequence obtained from the first energy spreading processing unit 134, performs the Reed-Solomon decoding process, and then performs the Reed-Solomon decoded transport sequence packet data sequence. Is output to the encoding unit 140 (RS code processing unit 141) and indicates whether or not error correction has been performed for each transport stream packet to the encoding unit 140 (error information addition processing unit 142). Information and a signal for determining the first byte of the transport stream packet are output. Note that an error flag attached to a transport stream packet can be used as information on whether or not an error has been corrected in units of transport stream packets.

  The encoding unit 140 performs the same encoding process as the encoding process performed in the transmission apparatus on the data of the transport stream packet obtained from the first RS decoding processing unit 135. In parallel with the encoding process, a signal for determining whether the encoded signal is generated from a signal containing an error is generated.

  The RS code processing unit 141 performs Reed-Solomon code processing for each transport stream on the transport stream packet data obtained from the first RS decoding processing unit 135. In the Japanese terrestrial digital broadcasting system, processing called a shortened Reed-Solomon code (204, 188) is performed, and an outer code for enabling correction of random errors from 204 bytes to 8 bytes is given. The RS code processing unit 141 outputs data obtained by adding an outer code to the transport stream data to the energy spreading processing unit 143.

  The error information addition processing unit 142 obtains the data stream of the transport stream packet subjected to Reed-Solomon code decoding from the first RS decoding processing unit. Then, based on the information on the error correction result of the packet given to the packet in the transport stream data, the error correction availability information and the synchronization byte part at the head of the packet are discriminated. Is generated and output to the byte interleave processing unit 144.

  Alternatively, the error information addition processing unit 142 obtains the data stream of the transport stream that is output from the first RS decoding processing unit 135 to the RS code processing unit 141, and the RS code processing unit 141 and an energy spreading process to be described later If the processing delay time in the unit 143 is known, only information on whether or not error correction is possible in units of packets is generated, and the output timing of a signal indicating whether or not error correction is possible is output from the energy diffusion processing unit 143 described later. It is good also as a structure aligned with a data sequence. At this time, it is necessary to generate a signal indicating whether or not error correction is possible in consideration of the parity part signal added by the RS code processing unit 141.

  The energy spread processing unit 143 obtains a data string obtained by adding an outer code to the data of the transport stream from the RS code processing unit 141. The transport stream signal excluding the synchronization byte is subjected to energy spreading processing using a pseudo-random code sequence, and a data string is output to the byte interleave processing unit 144.

  The byte interleave processing unit 144 receives the data string from the energy diffusion processing unit 143, “error correction availability information” from the error information addition processing unit 142 (the data obtained from the energy diffusion processing unit 143 is the first RS decoding processing unit In 135, information indicating whether or not error correction has been performed is obtained. At this time, it is assumed that the “error correction propriety information” is aligned with the data sequence obtained from the energy diffusion processing unit 143.

  The byte interleave processing unit 144 then converts the data sequence obtained from the energy diffusion processing unit 143 and the “error correction availability information” obtained from the error information addition processing unit 142 into byte units in the order defined by the ISDB-T standard. Then, the rearranged data string is output to the convolutional code processing unit 145, and the rearranged “error correction availability information” is output to the error information calculation processing unit 146. By the way, in the ISDB-T standard, when the carrier modulation method differs depending on the layer, it is necessary to match the delay time for each layer. Therefore, in the configuration of FIG. 1, the byte interleave processing unit 144 performs the delay correction processing at the same time. Shall be done.

  The convolutional code processing unit 145 performs convolutional code processing on the data sequence obtained from the byte interleave processing unit 144, and outputs the data sequence after the code processing to the bit interleave processing unit 147. When the transmission signal is composed of a plurality of hierarchies and the error correction coding rate is different for each hierarchy, the encoding process is performed for each hierarchy.

  The error information calculation processing unit 146 obtains, from the byte interleaving processing unit 144, “error correction enable / disable information” data that has undergone byte interleaving rearrangement processing. The data processing unit of the error information calculation processing unit 146 is a bit unit. And the data which show the range which the data containing an error influence in the calculation in the convolutional code process part 145 are produced | generated. Data indicating whether or not there is a possibility that the data output from the convolutional code processing unit 145 has an error for the bit interleaving processing unit 147 (hereinafter referred to as a “signal indicating an error-correctable range”). Is output.

  The processing procedure of the error information calculation processing unit 146 will be described with reference to FIGS. FIG. 2 is a configuration example of an encoding circuit for generating a convolutional code in the convolutional code processing unit 145. One code generator polynomial G1 = (1,1,1,1,0,0,1), the other code generator polynomial G2 = (1,0,1,1,0,1,1), An encoding circuit with a constraint length k = 7 and an encoding rate of 1/2 is shown. Data input from the input side is input to the delay circuit, the output of each delay element is subjected to an exclusive OR operation according to a generator polynomial, and two data of X output and Y output are output.

  On the other hand, FIG. 3 shows an arithmetic processing circuit performed by the error information arithmetic processing unit 146. The arithmetic processing circuit of FIG. 3 is different from the encoding circuit of FIG. 2 in that the exclusive OR calculator for generating the X output and the Y output is a logical OR calculator. The error information calculation processing unit 146 in FIG. 3 sets “0” if the “error correction enable / disable information” obtained from the byte interleave processing unit 144 is data that has been error-corrected by the first RS decoding processing unit 135. If “1” is input if the data could not be error corrected, it is determined whether or not the generated code in the convolutional code processing unit 145 is generated from data that may have an error as an output signal. Output data.

  The error division calculation processing unit 146 selects and outputs the X output and Y output of the encoder according to the convolutional coding rate, but the selection procedure of the X output and Y output is the same as that of the convolutional code processing unit 145. The procedure is as follows.

  The bit interleave processing unit 147 obtains the data string subjected to the convolutional code processing from the convolutional code processing unit 145 and obtains a “signal indicating an error-correctable range” from the error information calculation processing unit 146. The data string obtained from the convolutional code processing unit 145 and the “signal indicating the error-correctable range” obtained from the error information calculation processing unit 146 are taken into consideration in accordance with the ISDB-T standard in consideration of not shifting in the time direction. The rearrangement process of the bits of the two data strings is performed, and the rearranged data string and the error correction availability information are output to the mapping processing unit 151.

  The mapping processing unit 151 obtains a data string after bit interleaving and a “signal indicating an error-correctable range” after bit interleaving from the bit interleaving processing unit 147. Then, the data sequence after bit interleaving is divided into OFDM carrier units based on the “signal indicating an error-correctable range”, and mapping is performed according to a carrier modulation scheme such as QPSK, 16QAM, or 64QAM specified for each carrier. Using the case where the carrier modulation scheme is 16QAM as an example, the processing of the mapping processing unit 151 will be described with reference to FIG.

  FIG. 4 shows the relationship between the input data pattern to the mapping processing unit 151 and mapping points when the modulation method is 16QAM, and shows how the real number I and the imaginary number Q are assigned to 4-bit data. It is a thing. In FIG. 4, complex signal points are assigned so that the inter-code distance between adjacent codes is 2, for example, the input data is (b0, b1, b2, b3) = (0, 0, 0, 0). If so, a complex signal of (I, Q) = (+ 3, + 3) is assigned as a mapping point. The mapping processing unit 151 converts the data sequence after bit interleaving obtained from the bit interleaving processing unit 147 into a complex signal (hereinafter referred to as “mapping point information”) representing a mapping point determined from the carrier modulation scheme. At the same time, the inter-code distance calculation / accumulation processing unit 152 and the “signal indicating error correctable range” (hereinafter referred to as “mapping point error presence / absence information”) after bit interleaving corresponding to the mapping point calculation source data The data is output to the second demapping processing unit 153.

  The intersymbol distance calculation / accumulation processing unit 152 obtains, from the mapping processing unit 151, a data string of “mapping point information” and “mapping point error presence / absence information” mapped according to the carrier modulation scheme. Further, the deinterleave processing unit 121 obtains an OFDM symbol data string (hereinafter referred to as “received OFDM symbol point information”). First, the timings of “received OFDM symbol point information”, “mapping point information”, and “mapping point error presence / absence information” are aligned. Since the processing delay amount from the first demapping processing unit 122 to the mapping processing unit 151 or the data is processed in units of OFDM symbols, for example, the beginning of the OFDM symbol is determined, and “mapping point information” and “ The acquisition timing difference from “received OFDM symbol point information” may be counted and adjusted, or a signal indicating the OFDM symbol head may be generated and transmitted in each processing block.

  Next, the inter-code distance calculation / accumulation processing unit 152 calculates a distance between “received OFDM symbol point information” and “mapping point information”. The distance is calculated according to the Euclidean distance calculation procedure. However, “mapping point error presence / absence information” needs to be considered when calculating the distance. If the “mapping point error presence / absence information” corresponding to the “mapping point information” has no error, the “mapping point information” complex signal and the “received OFDM symbol point information” complex signal Euclidean distance between is calculated.

  If the error is biased to one of the real part or imaginary part of the data used to generate the "mapping point information" in the "mapping point error presence / absence information", the following procedure is used. The calculated value is calculated as the distance between “received OFDM symbol point information” and “mapping point information”. For example, if there is a possibility that only the imaginary part of the “mapping point information” has an error, the imaginary part of the “mapping point information” is changed to the symbol point closest to the imaginary part of the “received OFDM symbol point”. Replace with the imaginary part of. The real part of “mapping point information” is not replaced.

  Then, the Euclidean distance between the complex signals of “mapping point information” and “received OFDM symbol point information” with the imaginary part replaced is calculated.

Similarly, when there is a possibility that only the real part of the “mapping point information” has an error, the real part of the “mapping point information” is changed to the symbol point closest to the real part of the “received OFDM symbol point”. Replace with real part. The imaginary part of the “mapping point information” is not replaced.
If there is a possibility that both the real part and the imaginary part of the data used for generating the “mapping point information” may contain errors, the real part and the imaginary part of the “mapping point information” are respectively “received OFDM symbols”. The Euclidean distance between the complex signal of “mapping point information” and “received OFDM symbol point information” with the real part and the imaginary part replaced is calculated. . Note that the MER (Modulation Error Ratio) is calculated by accumulating the Euclidean distance values calculated when there is a possibility that both the real part and the imaginary part of the data used for generating the “mapping point information” include an error. ) And generally called value.

  As described above, if there is a possibility that one of the real part or imaginary part of the data used for generating the “mapping point information” or both the real part and the imaginary part contain an error, “ The Euclidean distance between the “symbol point closest to the symbol point” and the “received OFDM symbol point” is calculated. In the first embodiment, the calculated Euclidean distance value is corrected. The correction procedure will be described with reference to FIGS.

  FIG. 5 illustrates the relationship between the MER value obtained by integrating the Euclidean distance between the “symbol point closest to the“ received OFDM symbol point ”and the“ received OFDM symbol point ”and the amount of noise added to the signal. Is. The horizontal axis represents the amount of noise, and the vertical axis represents the magnitude of the MER value. The solid line in the figure indicates the MER value, and the dotted line indicates the amount of noise added to the signal. As shown in FIG. 5, when the amount of noise is smaller than the value “A”, the MER value and the amount of noise substantially match. On the other hand, when the value of the noise amount increases, the difference between the MER value and the noise amount occurs, and the MER value becomes smaller than the noise amount. This is because the added noise amount is larger than the inter-code distance of the QAM signal, while the Euclidean distance is calculated from the distance to the nearest code point, and as a result, the MER value is calculated to be small.

  6 shows the error rate of the output signal (transport stream packet) of the first RS decoding processing unit 135 of FIG. 1 with respect to the noise amount, and the Euclidean distance calculated by the inter-code distance calculation / accumulation processing unit 152 for the noise amount. The cumulative value of is simultaneously shown. As shown in FIG. 6, when the amount of noise added to the signal increases and falls below a certain amount of noise, the output signal of the first RS decoding processing unit 135 includes an error (the amount of noise is “B”). When the noise amount further increases, the first RS decoding processing unit 135 cannot perform error correction, and all output signals include errors (noise amount is “C”). The MER value is calculated to be smaller than the actually added noise amount when the noise amount is larger than “A”. At this time, the cumulative value of the Euclidean distance value calculated by the inter-code distance calculation / accumulation processing unit 152 is added to the signal when the noise amount is from “A” to “B”. The MER value that represents the amount of noise and whose amount is “C” is output. From the noise amount “B” to the noise amount “C”, according to the error rate of the first RS decoding processing unit 135, the MER value, “information of received OFDM symbol point”, and “information of mapping point” A value obtained by combining the accumulated values of the Euclidean distance values calculated from the distance is output.

  As a result, when the amount of noise added to the signal is larger than “B”, the calculated value does not accurately represent the amount of noise added to the signal, and in some cases, the magnitude relationship may be reversed. . For this reason, in the inter-code distance calculation / accumulation processing unit 152, when the data used for generating the “mapping point information” includes an error, the “symbol point closest to the“ received OFDM symbol point ”and the“ reception point ”are received. A value obtained by correcting the “Euclidean distance from the“ OFDM symbol point ”is corrected. As shown in FIG. 5, the correction method of “Euclidean distance between“ symbol point closest to “received OFDM symbol point” ”and“ received OFDM symbol point ”is the MER value and the amount of noise added to the signal. When the relationship is smaller than the noise amount “A”, the relationship becomes a non-linear relationship. Therefore, in a region where the noise amount is larger than the noise amount “A”, correction for correcting the calculation result of the MER value to a value indicating the actually added noise amount A table is prepared, and the calculation value is corrected according to the correction table for each Euclidean distance calculation result. As a result, in the first RS decoding processing unit 135, the meanings of the calculation results when error correction is possible and when error correction is not possible can be made substantially equal.

  By the way, the Euclidean distance calculated according to the “mapping point error presence / absence information” as described above is calculated in units of OFDM carriers. Then, integration is performed a certain number of times in the symbol direction. For example, the number of integrations may be the same as the longest time of time interleaving performed by the deinterleave processing unit 121. The longest time interleaving time does not indicate the maximum value of the parameters that can be set among the parameters of the time interleaving length specified in the broadcast standard. For example, in the Mode 3 broadcast signal, the interleaving length parameter I = 2 If there is, it indicates the frame length of one OFDM frame (for 204 OFDM symbols). That is, in the case of Mode 3 and interleave length I = 2, the number of integrations of the Euclidean distance is 204. For example, a larger number of integrations such as 256 may be set.

  Then, distance information between “received OFDM symbol point information” and “mapping point information” integrated in symbol units is output to the second demapping processing unit. In the ISDB-T standard, frequency rearrangement processing called “intra-segment carrier rotation” is performed within a segment during frequency interleaving processing on the transmission side. The data is rearranged to the same frequency position. On the other hand, if the data location differs depending on the symbol number in other broadcasting systems, etc., consider the data rearrangement process according to the symbol number when performing the integration process for the Euclidean distance in the symbol direction a certain number of times. Then, it is necessary to integrate the Euclidean distance between the complex signals of “mapping point information” and “received OFDM symbol point information” calculated for signals at the same frequency position.

  Further, the inter-code distance calculation / accumulation processing unit 152 can calculate distance information between “information on received OFDM symbol points” and “information on mapping points” through further detailed processing. Here, the correction procedure of “mapping point information” used for calculating the distance information will be described with reference to FIG. 4 again.

  FIG. 4 shows a mapping rule when the carrier modulation scheme is 16QAM. In the 16QAM modulation system, “mapping point information” is calculated from 4-bit data, and if “mapping point error presence / absence information” indicates “no error”, the mapping point is uniquely determined according to FIG. The “mapping point information” is a value obtained from the mapping processing unit 151.

  Next, when it is determined from the “mapping point error presence / absence information” that 1-bit data is “possibly containing an error”, first, the bit containing the error is (b0, b2) or (b1, b3). To determine whether it is included. As shown in FIG. 4, in the 16QAM modulation system, the real part of the mapping point is uniquely determined from (b0, b2) and the imaginary part is uniquely determined from (b1, b3). On the other hand, since a code point cannot be determined from a pair of bits including an error, a temporary value is assigned. For example, if there is a possibility of error in b0 that is the source of calculation of the real part value and b2 is correct information, the real number of “information of received OFDM symbol point” out of two code points obtained from b2 The real part of the code point closest to the part is defined as new “mapping point information”. The same applies to the case where b2 may be erroneous and b0 is correct.

  If it is determined from the “mapping point error presence / absence information” that the 2-bit data is “possibly containing an error”, one error bit exists for each of the pairs (b0, b2) and (b1, b3). It is conceivable that a 2-bit error is biased to one of the pair (b0, b2) or (b1, b3). Among these, in the former case, the real part and imaginary part of the mapping point are calculated in the same procedure as in the case where only one bit of the above four bits contains an error.

  On the other hand, when 2-bit errors are concentrated on (b0, b2), the real part of the symbol point closest to the real part of “information on received OFDM symbol points” is set as the value of the real part of the mapping point. When errors concentrate on (b1, b3), the real part of the symbol point closest to the imaginary part of “information on received OFDM symbol points” is set as the value of the real part of the mapping point.

  From the “Mapping point error presence / absence information”, if there is a possibility that 3 bits out of 4 bits of data or all 4 bits of data may contain errors, the values of the real part and imaginary part are determined by the above procedure "Mapping point information".

Through the above processing, the inter-code distance calculation / accumulation processing unit 152 calculates the Euclidean distance between the corrected “mapping point information” and “received OFDM symbol point information” in units of OFDM carriers, Integrate a certain number of times in the direction. Then, distance information between “received OFDM symbol point information” and “mapping point information” integrated in symbol units is output to the first demapping processing unit 122 and the second demapping processing unit 153. . (Hereinafter, distance information between “received OFDM symbol point information” and “mapping point information” integrated in symbol units calculated by the inter-code distance calculation / accumulation processing unit 152 is referred to as “carrier unit interference information”. To do)
In the above description, the carrier modulation method is described as the 16QAM modulation method. However, when the carrier modulation method is a modulation method including multi-value information, such as 64QAM, the combination of data error occurrences is different. The same calculation method is adopted by replacing the point closest to “information of received OFDM symbol point” with new “mapping point information” among mapping points calculated from bits without error. be able to. Also, the new “mapping point information” is output to the second demapping processing unit 153 at the subsequent stage, and is output from the mapping processing unit 151 to the second demapping processing unit 153. The reliability information may be calculated instead of “”.

  By the way, the “interference information in units of carriers” calculated by the inter-code distance calculation / accumulation processing unit 152 is calculated from signals obtained as a result of rearranging the data arrangement order in the frequency and time directions by the deinterleave processing unit 121. Value. When calculating the “interference information for each carrier” in the inter-code distance calculation / accumulation processing unit 152, a memory or the like for integrating and holding the Euclidean distances of transmission / reception signal points is required. When the values are stored, the values of the Euclidean distances of the transmission / reception signal points may be rearranged according to the frequency interleaving processing procedure at the time of signal transmission and stored in the memory.

  Then, the “carrier-based interference information” can be rearranged in order from the low-frequency OFDM carrier. For example, when a frequency selective interference signal is superimposed around a specific OFDM carrier of the received signal, A large value is biased toward a certain range of “jamming information per carrier”. In this way, it is possible to determine whether or not the received signal is affected by the frequency selective interference signal from the distribution state in the frequency direction of the “carrier-based interference information”. In addition, the position of the OFDM carrier that is affected by the frequency selective interference signal can be identified more accurately. It is also possible to interpolate or blunt the result of “interference information per carrier” or “subject interference information per carrier” when the number of integrations when calculating “interference information per carrier” is small. .

  In addition, it is conceivable that information on the frequency at which the interference signal exists is obtained from the carrier position where the frequency selective interference signal is generated, and is separately notified to the previous processing unit. For example, it is conceivable to calculate a frequency range to be cut off by a filter when a notch filter process for removing an interference signal is performed on a signal upstream of the FFT processing unit. In addition, as described above, in the case where the arrangement of data is changed at the time of calculating “carrier-based interference information”, the first demapping processing unit 122 and the second demapping processing unit 153 perform “carrier-based interference information”. When the “jamming information” is used, it is necessary to rearrange the “jamming information per carrier” again so that the data and the “jamming information per carrier” are generated from signals at the same carrier position.

  Here, the method of generating reliability information in the first demapping processing unit 122 will be described again. The first demapping processing unit 122 generates information for performing error correction processing called soft decision in the first decoding processing unit 132 in the subsequent stage. First, a “received OFDM symbol point” and a “data string of estimation results of transmission path characteristics” after deinterleaving are obtained from the deinterleave processing unit 121. Then, the mapping point closest to the “received OFDM symbol point” is regarded as the transmission signal point, and the data of the complex signal point of the closest mapping point is calculated. Then, the complex signal is converted into a bit string in accordance with the complex signal point and information bit allocation rule as shown in FIG. 4, and the bit data string is output to the first bit deinterleave processing unit 131.

  In addition, the first demapping processing unit 122 performs “distance information of received symbol points”, “data string of transmission path characteristic estimation results” obtained from the deinterleaving processing unit 121, and inter-code distance calculation / accumulation. The reliability information is generated by combining the “interference information in units of carriers” obtained from the processing unit 152. The reliability information generated by the first demapping processing unit 122 is also called likelihood, and is a value indicating 1-likeness and 0-likeness of data in bit units. For example, a positive value is given as the reliability value when there is a high possibility that a certain bit is 1, and a negative value is given when there is a high possibility that it is 0. If a bit has the same probability of 1 and 0, 0 is given. Also, the higher the reliability, the larger the absolute value. Thereby, in an error correction process by a Viterbi decoder or the like, a decoding process is performed on a code string transmitted based on the zeroness and the oneness of the input bit string.

  By the way, as the cause of error in the received signal of the OFDM signal, if the fluctuation of the transmission path characteristics between transmission and reception and the amount of thermal noise inside the tuner with respect to the received signal level are considered to be main, the reliability value is as follows: Can be calculated.

  First, the influence of the transmission path characteristics between the former transmission and reception is divided in two: transmission path estimation error due to transmission path fluctuation (fading) and signal attenuation between transmission and reception (including multipath attenuation for a specific carrier) and It can be divided into two. Considering the case where the receiving antenna is fixed, the reliability value of the demodulated signal can be calculated from the estimated value of signal attenuation per OFDM carrier between transmission and reception. For each OFDM symbol, the size (for example, a square value) of the estimated value H (ω) of the transmission path characteristic used for the division of the received signal by the equalization processing unit 113 is calculated. Obtained as a “data string” makes it possible to obtain an estimated value of signal attenuation in units of OFDM carriers.

  As for transmission path estimation errors due to transmission path fluctuations, assuming mobile reception such as cars, the effects of transmission path estimation errors due to transmission path fluctuations cannot be ignored, but the transmission path characteristics estimated from pilot signals The estimation error can be reduced by devising the interpolation processing method, and the transmission path estimation error can be further reduced by using a technique for estimating / removing the amount of inter-carrier interference called ICI (Inter Carrier Interference).

  Assuming that the latter thermal noise amount inside the tuner is white noise and follows Gaussian characteristics, the noise amount can be estimated from the C / N amount of the entire OFDM signal band. This can be replaced by a value obtained by integrating the “reception symbol point distance information” in the carrier direction.

  In other words, the reliability value for each bit data is proportional to the size of the transmission path characteristics for each OFDM carrier, considering fluctuations in transmission path characteristics between transmission and reception and the influence of the amount of thermal noise inside the tuner on the received signal level. The reliability value may be given so as to be inversely proportional to the noise amount of the entire signal (proportional to the C / N amount).

  Further, considering the case where a reception error occurs due to the frequency selective interference signal other than the thermal noise inside the tuner, the reliability value calculated as described above is further calculated by the inter-code distance calculation / accumulation processing unit 152. What is necessary is just to correct | amend according to the "jamming information per carrier" calculated per OFDM carrier. If the “carrier-based interference information” is large, the reliability value is corrected to be low or the reliability value is set to “0”. The procedure for correcting the reliability value is in accordance with the correction method conventionally performed by the MER value. However, the “interference information for each carrier” is “mapping point information” generated again from the code corrected by the error correction process. In the case of the Euclidean distance with “information of received OFDM symbol points”, the value directly indicates the magnitude of the interference added to the carrier, and therefore the reliability value is corrected by a more accurate interference signal amount. Is possible.

  However, not all data affected by the interference signal can be error-corrected, and the Euclidean distance between the "mapping point information" and the "received OFDM symbol point information" is accumulated in the time direction for a fixed number of carriers. This value is used as “carrier-based interference information”. The first demapping processing unit 122 determines that “the symbol point closest to the received OFDM symbol point” until “interference information in units of carriers” is calculated by the inter-code distance calculation / accumulation processing unit 152. The reliability value may be corrected using the MER value obtained by integrating the Euclidean distance from the “received OFDM symbol point”. In addition, a carrier that always indicates that the “mapping point error presence / absence information” is an error or that “carrier-based interference information” is prominently large indicates that the carrier has a reliability value of “0”. The data contained in may not be trusted at all.

  Similar to the first demapping processing unit 122, the second demapping processing unit 153 obtains “data of received OFDM symbol points” and a data string of the estimation result of the transmission path characteristics from the deinterleaving processing unit 121, The mapping processing unit 151 integrates “mapping point information” and “mapping point error presence / absence information” from the intersymbol distance calculation / accumulation processing unit 152 into “symbol unit received information” and “received OFDM symbol point information”. Get distance information from "Mapping point information". The second demapping processing unit 153 performs demapping processing in the same manner as the first demapping processing unit 122. However, since the data after the error correction process is once processed, the processing method is switched between the case where the data may contain an error and the case where there is no possibility of the error.

  Based on the "Mapping Point Error Presence Information", determine whether the data from which the "Mapping Point Information" is calculated may have an error, and if there is no error, use the mapping point information as Obtains the “mapping point information” obtained from the mapping processing unit 151 and the “information on received OFDM symbol points” obtained from the deinterleaving processing unit 121, and after aligning the respective processing timings, Information ”is selected as the code point, and the value of the estimation result of the transmission path characteristic is given a large value. The large value is, for example, “1” when the magnitude of the transmission path characteristic when there is no amplitude fluctuation in the transmission path and gives “1”.

  On the other hand, if there is a possibility that the data from which the “mapping point information” is calculated may have errors, the “received OFDM symbol point information” is used to calculate the reliability information. The size of the estimation result of the transmission path characteristics obtained from the deinterleave processing unit 121 (the magnitude of the estimation result of the transmission path characteristics H (ω) calculated for each carrier). At this time, the “mapping point information” newly generated by the intersymbol distance calculation / accumulation processing unit 152 is used as the information of the reception symbol points used for the calculation of the reliability information, and then the size of the transmission path characteristics The information may be a value obtained from the deinterleave processing unit 121.

  Then, the second demapping processing unit 153 determines whether or not the data from which the “mapping point information” is calculated has an error, and if there is no error, the second demapping process The unit 153 uses the distance information between “information on received OFDM symbol points” and “information on mapping points” integrated in symbol units by the inter-code distance calculation / accumulation processing unit 152 to transmit the received symbol points and the transmissions. The value of reliability information calculated from the magnitude of the road characteristic is further corrected.

  Then, the second demapping processing unit 153 outputs the generated bit data and reliability information to the second error correction unit 160 (second bit deinterleaving processing unit 161).

  Further, as described above, the second demapping processing unit 153 obtains “interference information per carrier” from the inter-code distance calculation / accumulation processing unit 152. By averaging the “jamming information for each carrier” in the carrier direction, it can be used separately as an indicator of the amount of jamming signals included in the received signal. If the C / N of the received OFDM signal fluctuates so that the signal level changes in a short time, the second demapping processing unit uses the average value of the interference information for each carrier as the noise amount of the received signal. The reliability information output from 153 to the second error correction unit 160 (second bit deinterleave processing unit 161) may be further corrected. It can also be used as a signal quality value of a signal received by the multicarrier modulation signal receiving apparatus separately.

  Further, the following device can be devised as the signal quality value of the received signal. Since the “information on received OFDM symbol points” obtained by the inter-code distance calculation / accumulation processing unit 152 is a value that has passed through the deinterleaving processing unit 121, the memory amount of the deinterleaving processing unit 121 is reduced. It is conceivable that the bit width is limited by quantization. As a result, when the signal quality is high, it is difficult to calculate the signal quality index value with high accuracy in the processing block subsequent to the deinterleave processing unit 121 due to the influence of the quantization error. On the other hand, if the MER value is calculated for the output signal of the equalization processing unit 113 before the deinterleaving processing unit 121 and the signal quality is higher than a certain value, the deinterleaving processing unit 121 If the value calculated in the previous stage is used as the signal quality index value and the signal quality is lower than a certain value, the “interference information per carrier” obtained from the inter-code distance calculation / accumulation processing unit 152 is used in the carrier direction. The averaged value is used as the signal quality index value.

  The second error correction unit 160 performs error correction processing based on the bit data obtained from the second demapping processing unit 153 and the reliability information, and generates an original signal sequence. Hereinafter, the operation of the second error correction unit 160 will be described in detail with reference to FIG.

  Similar to the first bit deinterleave processing unit 131, the second bit deinterleave processing unit 161 converts the bit data and reliability information obtained from the second demapping processing unit 153 according to the provisions of the ISDB-T standard. The original order is rearranged and output to the second decoding processing unit 162.

  Similar to the first decoding processing unit 132, the second decoding processing unit 162 obtains bit data and reliability information from the second bit deinterleaving processing unit 161, and receives the received bit data according to the reliability information. Then, the Viterbi decoding process is performed, and the data string of the Viterbi decoding result is output to the second byte deinterleave processing unit 163.

  Similarly to the first byte deinterleave processing unit 133, the second byte deinterleave processing unit 163 receives the Viterbi decoding result data sequence obtained from the second decoding processing unit 162 and rearranges it in the original order. And output the data string to the second energy despreading processing unit 164.

  Similar to the first energy despreading processing unit 134, the second energy spreading processing unit 164 performs energy spreading performed on the signal transmission side with respect to the data string obtained from the second byte deinterleaving processing unit 163. Processing to restore the processing is performed, and the converted data string is output to the second RS decoding processing unit 165.

  The second RS decoding processing unit 165 receives the data sequence obtained from the second energy spreading processing unit 164, performs a Reed-Solomon decoding process, and then performs a Reed-Solomon decoded transport stream packet data sequence. Is output to the TS reproduction processing unit 171.

  The TS reproduction processing unit 171 performs the same operation as the TS reproduction processing unit 671 in FIG. The Reed-Solomon-decoded data sequence is obtained from the second RS decoding processing unit 165 in FIG. 1, and the number of packets in the transport stream is supplemented with an appropriate number of null packets so as to be constant regardless of transmission parameters. Processing is performed, and the packet data of the transport stream after complementing the null packet is output for the TS decoding processing unit 172 to perform the TS decoding processing.

  Through the above processing, the multicarrier modulation signal receiving apparatus according to the first embodiment restores the transmission signal point generated at the signal transmission station from the data obtained by performing error correction processing once, and the transmission signal point and the demodulator The received signal points obtained from the above are compared in units of carriers, and the value obtained by integrating the Euclidean distance obtained from the comparison result for a certain period of time is regarded as the amount of interfering signals included in each carrier and the reliability information transmitted to the error correction unit is corrected. Therefore, it is possible to obtain higher reception performance as compared with the conventional method. In particular, when the received signal is affected by a frequency-selective interference signal, it is possible to more accurately calculate the amount of interference signal that is biased in units of carriers, so that a high effect can be obtained.

  By the way, in the description of the configuration of the multicarrier modulation signal receiving apparatus of the first embodiment, for example, the processing timing is adjusted for each layer as the signal is transmitted by a different carrier modulation method for each layer. Although not all procedures have been described for the processing defined in the ISDB-T standard, processing according to the ISDB-T standard is performed in an appropriate block unless otherwise specified. In addition, for example, OFDM transmission parameter information transmitted as a TMCC signal such as an error correction coding rate and the number of transmission layers may be required in each processing block. For information obtained from TMCC information, The illustration and detailed description are not performed on the assumption that the block is separately obtained from the block for decoding the TMCC signal.

  In the present embodiment, the error correction process is performed once in the second error correction unit 160 from the encoding unit 140 and output to the TS reproduction processing unit 171 as shown in FIG. The second error correction unit 160 may perform error correction processing a plurality of times, and output the result to the TS reproduction processing unit 171. In this case, as shown in FIG. 7, in order to count the number of times of error correction processing in the second error correction unit 160, an error correction count unit 166 for inputting the output signal of the second error correction unit 160 is provided. . For example, when the number of repetitions is 2, the error correction count unit 166 outputs a signal to the encoding unit 140 when the number of error correction processes in the second error correction unit 160 is 1, and error correction is performed. When the number of processes is two, the data is output to the TS reproduction processing unit 171. Further, for example, the signal processing from the error correction count unit 166 to the encoding unit 140 is repeated a plurality of times within the range where the operation speed of the second error correction processing unit 160 is increased and the output signal output time is not delayed, It is also possible to increase the error correction effect.

  In this embodiment, as shown in FIG. 1, two blocks for performing the same processing are provided, such as the first decoding processing unit 132 and the second decoding processing unit 162, but they may be shared. In this case, as shown in FIG. 8, the output signal from the second demapping processing unit 153 is input to the first error correction unit 130. In order to count how many times the error correction processing in the first error correction unit 130 is performed, an error correction count unit 136 for inputting an output signal of the first error correction unit 130 is provided. Then, the error correction count unit 136 outputs a signal to the encoding unit 140 when the number of error correction processes in the first error correction unit 130 is one, and the number of error correction processes reaches a specified number. A signal is output to the TS reproduction processing unit 171. In addition, for example, the operation speed of the first error correction processing unit 130 is set high, and the delay from the output time of the output signal does not increase so that the second demapping processing unit 153 transfers to the first error correction unit 130. It is also possible to increase the error correction effect by repeating this signal processing a plurality of times.

  A multicarrier modulation signal receiving apparatus according to the present invention restores a transmission signal point generated at a signal transmission station, compares the restored transmission signal point with a reception signal point obtained from a demodulation unit, in units of carriers, Since the value obtained by integrating the Euclidean distance obtained from the comparison result for a certain period of time is regarded as the amount of interference signal included in each carrier and the reliability information transmitted to the error correction unit can be corrected, the received signal is interfered with frequency selectivity. Higher receiving performance can be obtained when the signal is affected.

DESCRIPTION OF SYMBOLS 101 Antenna part 102 Tuner part 103 A / D conversion process part 110 Demodulation part 111 Quadrature detection process part 112 FFT process part 113 Equalization process part 121 Deinterleave process part 122 1st demapping process part 130 1st error correction part 131 First Bit Deinterleave Processing Unit 132 First Decoding Processing Unit 133 First Byte Deinterleaving Processing Unit 134 First Energy Spread Processing Unit 135 First RS Decoding Processing Unit 136 Error Correction Counting Unit 140 Encoding Unit 141 RS Code Processing Unit 142 Error Information Addition Processing Unit 143 Energy Spread Processing Unit 144 Byte Interleaving Processing Unit 145 Convolutional Code Processing Unit 146 Error Information Calculation Processing Unit 147 Bit Interleaving Processing Unit 151 Mapping Processing Unit 152 Inter-Code Distance Calculation / Accumulation Processing Unit 15 3 Second demapping processing unit 160 Second error correction unit 161 Second bit deinterleaving processing unit 162 Second decoding processing unit 163 Second byte deinterleaving processing unit 164 Second energy despreading processing unit 165 Second RS decoding processing unit 166 Error correction counting unit 171 TS reproduction processing unit 172 TS decoding processing unit 173 MPEG decoding processing unit

Claims (6)

A tuner unit that selects a multi-carrier signal of a predetermined frequency band from a signal received by the antenna unit;
An A / D conversion processing unit that samples a multi-carrier signal input from the tuner unit and converts it into a digital signal;
A demodulator that demodulates a multi-carrier signal from the signal input from the A / D conversion processor, and generates a data sequence of estimation results of reception symbol points and transmission path characteristics for each carrier;
A deinterleaving processing unit for rearranging the received symbol points input from the demodulating unit and a data sequence of estimation results of transmission path characteristics;
From the rearranged received symbol points and transmission path characteristic estimation results input from the deinterleave processing unit, and distance information between the received symbol points and the mapping point information obtained from the inter-code distance calculation / accumulation processing unit described later A first demapping processor for generating reliability information;
A first error correction unit that performs error correction processing based on reliability information of bit data input from the first demapping processing unit and restores a transmission signal sequence;
Was the encoding process performed on the data restored from the transmission signal sequence input from the first error correction unit, and in parallel with the encoding process, whether the signal after the encoding process was generated from a signal that could not be error corrected An encoding unit that generates a signal indicating an error-correctable range for determining whether or not;
A mapping processing unit for generating a signal indicating an error-correctable range and information on mapping points obtained by performing mapping according to a carrier modulation scheme on the data subjected to the encoding process input from the encoding unit;
The timing between the received symbol point input from the deinterleave processing unit, the mapping point information input from the mapping processing unit and the error presence / absence information of the mapping point, and the distance between the received symbol point and the mapping point information An inter-code distance calculation / accumulation processing unit for calculating
Information on mapping points and mapping point error presence / absence information input from the mapping processing unit, the rearranged received symbol points input from the deinterleaving processing unit and the estimation results of transmission path characteristics,
A demapping process is performed based on the distance information between the received symbol point and the mapping point information input from the inter-code distance calculation / accumulation processing unit and the estimation result of the transmission path characteristics input from the deinterleave processing unit. A demapping processing unit;
A second error correction unit that performs error correction processing based on the bit data and reliability information input from the second demapping processing unit and generates an original signal sequence;
A multicarrier modulation signal receiving apparatus comprising: When the error correction result data is encoded again, the mapping processing unit accurately calculates the error-corrected data range, and according to the information indicating the error-corrected data range, the signal point after the equalization process A signal point generated from the error-corrected signal and the information of the symbol point closest to the signal point after equalization processing are combined to generate a new signal point, and reliability information is generated according to the new signal point. The multicarrier modulation signal receiving apparatus according to claim 1. If the encoded signal is generated from an error-corrected signal,
The Euclidean distance between the signal point generated from the error-corrected signal and the demodulated received symbol point is integrated in carrier units,
If the encoded signal was generated from a signal that could not be error corrected,
The Euclidean distance between the received symbol point after demodulation and the transmission code point closest to the demodulated reception symbol point is integrated in carrier units,
If the encoded signal was generated from a signal that could not be corrected and a signal that could be corrected,
Among the code point candidates determined from the error corrected signal, the code point closest to the demodulated reception symbol point is regarded as the transmission code point, the demodulated reception symbol point, and the signal point regarded as the transmission code point And the Euclidean distance between
The multicarrier modulation signal receiving apparatus according to claim 2, wherein a value obtained by integrating the Euclidean distance in units of carriers is regarded as an interference signal amount and used as reliability information given to the error correction unit. If the encoded signal is generated from an error-corrected signal,
The Euclidean distance between the signal point generated from the error-corrected signal and the demodulated received symbol point is integrated in carrier units,
If the encoded signal was generated from a signal that could not be error corrected,
After correcting the Euclidean distance between the demodulated received symbol point and the transmission code point closest to the demodulated received symbol point, and adding up in units of carriers,
When the encoded signal is generated from a signal that could not be error-corrected and a signal that could be error-corrected, among the code point candidates determined from the signal that could be error-corrected, from the received symbol point after demodulation The closest code point is regarded as the transmission code point, the Euclidean distance between the received symbol point after demodulation and the signal point regarded as the transmission code point is integrated, and the value obtained by integrating the Euclidean distance in units of carriers, 4. The multicarrier modulation signal receiving apparatus according to claim 3, wherein the multicarrier modulation signal receiving apparatus is used as reliability information which is regarded as an interference signal amount and is given to an error correction unit. The input signal from the second error correction unit counts the number of error correction processes performed by the second error correction unit, and outputs a signal to the encoding unit when the number of error correction processes is less than a predetermined number The multicarrier modulation signal receiving apparatus according to claim 1, further comprising an error correction count unit configured to perform error correction. A tuner unit that selects a multi-carrier signal of a predetermined frequency band from a signal received by the antenna unit;
An A / D conversion processing unit that samples a multi-carrier signal input from the tuner unit and converts it into a digital signal;
A demodulator that demodulates a multi-carrier signal from the signal input from the A / D conversion processor, and generates a data sequence of estimation results of reception symbol points and transmission path characteristics for each carrier;
A deinterleaving processing unit for rearranging the received symbol points input from the demodulating unit and a data sequence of estimation results of transmission path characteristics;
From the rearranged received symbol points and transmission path characteristic estimation results input from the deinterleave processing unit, and distance information between the received symbol points and the mapping point information obtained from the inter-code distance calculation / accumulation processing unit described later A first demapping processor for generating reliability information;
A first error correction unit that performs error correction processing based on reliability information of bit data input from the first demapping processing unit and restores a transmission signal sequence;
The transmission signal sequence input from the first error correction unit counts the number of error correction processes performed by the first error correction unit, and signals to the encoding unit when the number of error correction processes is less than a predetermined number. An error correction count unit that outputs
Encoding processing is performed on the data obtained by restoring the transmission signal sequence input from the error correction count unit, and in parallel with the encoding processing, whether the signal after the encoding processing is generated from a signal that cannot be error-corrected. An encoding unit that generates a signal indicating an error-correctable range to be determined;
A mapping processing unit for generating a signal indicating an error-correctable range and information on mapping points obtained by performing mapping according to a carrier modulation scheme on the data subjected to the encoding process input from the encoding unit;
The timing between the received symbol point input from the deinterleave processing unit, the mapping point information input from the mapping processing unit and the error presence / absence information of the mapping point, and the distance between the received symbol point and the mapping point information An inter-code distance calculation / accumulation processing unit for calculating
Information on mapping points and mapping point error presence / absence information input from the mapping processing unit, the rearranged received symbol points input from the deinterleaving processing unit and the estimation results of transmission path characteristics,
Demap processing is performed from the distance information between the received symbol point and the mapping point information input from the inter-code distance calculation / accumulation processing unit and the estimation result of the channel characteristics input from the deinterleave processing unit, A second demapping processing unit for outputting to one error correction unit;
A multi-carrier modulation signal receiving apparatus that outputs a signal to a TS reproduction processing unit when the number of error correction processes counted by the error correction counting unit is a predetermined number or more.

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