JP2005286504A - Digital signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital signal receiver capable of reducing the memory capacity required for demodulating a received digital modulation signal. <P>SOLUTION: The digital signal receiver is provided with a pre-demapping section for generating pre-demapping data that denote a reference point on a corresponding constellation and a deviation from the reference point in response to a signal modulation system. A reliability determination/correction section 29# corrects the data denoting a deviation amount in response to reliability information on the basis of the pre-demapping data and the reliability information denoting the reliability of the data outputted from a pre-demapping section, carries out data conversion processing for including part of the reliability information to the pre-demapping data and provides an output of the result to a time de-interleave section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a configuration of a digital signal receiving apparatus for receiving and demodulating a signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) system used in terrestrial digital broadcasting or the like.

  In recent years, an OFDM (Orthogonal Frequency Division Multiplexing) scheme has been proposed as a modulation scheme that excels in high-quality transmission and frequency utilization efficiency for systems that transmit video signals or audio signals. .

  The OFDM method is a modulation method in which a large number of subcarriers are set in one channel band. For this reason, it is resistant to ghosting and can be made resistant to selective fading by devising a data structure for error correction. Therefore, it is an effective modulation method in terrestrial digital television broadcasting or the like.

  In the OFDM transmission, the following processing is performed. First, for example, an analog signal such as a television signal is converted into a digital signal and compressed by an MPEG (Moving Picture Experts Group) system. Subsequently, in order to disperse the cause of the error in the transmission path such as noise, the data signal is subjected to byte interleaving and bit interleaving processing, QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM. Mapping according to the modulation method is performed. Furthermore, in order to disperse the cause of errors in the transmission path such as fading and signal loss, time interleaving and frequency interleaving are performed, IFFT (Inverse Fast Fourier Transform) is performed, and after orthogonal modulation, the frequency is changed to RF frequency. Convert and send.

  FIG. 18 is a conceptual diagram for explaining the structure of OFDM data received by the terrestrial digital signal receiving apparatus.

  As shown in FIG. 18, one OFDM frame is composed of 204 OFDM symbols. An OFDM symbol is composed of a valid data section and an invalid data section (guard interval, null carrier).

  FIG. 19 is a diagram showing a configuration of the OFDM symbol shown in FIG.

  The effective data section in one OFDM symbol has a configuration in which 13 OFDM segments with pilot signals added to a data group (data segment) are arranged.

  According to the specifications of terrestrial digital broadcasting, it is possible to divide 13 segments into a maximum of three layers and specify a modulation method for each layer.

  FIG. 20 is a diagram for explaining the configuration of one OFDM segment in more detail.

  As shown in FIG. 19, one OFDM segment includes n carriers from 0th to (n-1) th.

  FIG. 21 is a diagram for explaining the mode dependency of the configuration of one OFDM segment.

  Referring to FIG. 21, the number of data signal carriers, the number of pilot signal carriers, and the like constituting one OFDM segment are determined for each mode, and the total number of carriers is set to n.

  There are four types of OFDM modulation, DQPSK (Differential QPSK), QPSK, 16QAM, and 64QAM, and mapping methods are different. The DQPSK method is called a differential modulation method, and the others are called synchronous modulation methods. The differential modulation method and the synchronous modulation method differ in the type and arrangement position of pilot signals inserted in the data signal of the OFDM segment, but the total number of pilot signals included in one OFDM segment is defined as shown in FIG. ing.

  A data signal modulated by the OFDM method is demodulated by processing in a procedure completely opposite to that of transmission.

  FIG. 22 is a schematic block diagram showing a configuration of a conventional OFDM receiving apparatus 3000.

  Referring to FIG. 22, tuner 11 is provided with a high-frequency signal input (RF signal input) captured by an antenna (not shown), and downconverts the frequency of a designated channel to obtain a baseband signal. . The analog / digital conversion circuit 12 converts an analog signal into a digital signal and uses a Hilbert transform or the like to generate a real axis (hereinafter referred to as “I axis”) component signal (in-phase detection axis signal) and an imaginary axis ( Hereinafter, a component signal (orthogonal detection axis signal) is generated. The I-axis signal and the Q-axis signal from the analog / digital conversion circuit 12 are subjected to synchronization processing in the synchronization unit 13 and output to a fast Fourier transform unit (hereinafter referred to as “FFT unit”) 14.

  The FFT unit 14 performs fast Fourier transform on the input signal to convert time axis data into frequency axis data. The demodulator 15 demodulates the output from the FFT unit 14 and outputs the result to the frequency deinterleaver 16.

  The frequency deinterleave circuit 16 performs reverse processing of frequency interleaving performed to compensate for the loss of a specific frequency signal due to radio wave reflection or the like. The time deinterleave circuit 17 performs reverse processing of time interleave performed for anti-fading.

  The demapping circuit 18 demaps the data after time deinterleaving from the I-axis data and the Q-axis data to obtain 2-bit (QPSK), 4-bit (16QAM) or 6-bit (64QAM) data. The bit deinterleave circuit 19 performs reverse processing of bit interleaving performed to increase error tolerance. A Viterbi decoding circuit 20 for performing Viterbi decoding, which is one of the maximum likelihood decoding processes, corrects errors while performing inverse processing of convolution performed between byte interleaving and bit interleaving. The byte deinterleave circuit 21 performs a reverse process of the byte interleave performed to increase error resilience in the same manner as the bit interleave. An RS (Reed-Solomon) decoding circuit 23 corrects an error while performing reverse processing of RS encoding performed before byte interleaving on the data subjected to the despread processing by the energy despreading unit 22. .

  The MPEG decoding circuit 24 performs reverse processing of compression by the MPEG method to decompress the data, and the digital / analog conversion circuit 25 converts the digital signal into an analog signal. In this way, the video signal and audio signal before being modulated by the OFDM method are reproduced and output for reproduction of video and audio.

  As described above, interleaving is frequently used in the OFDM system.

  In order to perform deinterleaving, it is necessary to temporarily store data. For this reason, the frequency deinterleaving circuit 16, the time deinterleaving circuit 17, the bit deinterleaving circuit 19, and the byte deinterleaving circuit 21 each store a memory. I have. However, of the four types of interleaving, the amount of data targeted by frequency interleaving and time interleaving is extremely large, and these deinterleaving requires a large amount of memory.

  For example, according to a report from the Telecommunications Technology Council for Digital Terrestrial Broadcasting in Japan on “Technical Conditions for Digital Terrestrial Television Broadcasting”, time deinterleaving uses memory to identify each carrier in a symbol. This is done by delaying symbols. The symbol delay amount is determined by the time interleave length given for each mode and layer and the carrier position in the segment. Time deinterleaving per segment requires 72,960 words of memory, and 13 segments require 948,480 words of memory.

  In addition, in the configuration shown in FIG. 22, time deinterleaving is performed on both the I-axis data and the Q-axis data, so the number of words is doubled, and the time deinterleaving circuit 15 is provided if each data is 9 bits. The capacity of the power memory is about 17 Mbits. Similarly, the frequency deinterleave circuit 14 requires a large capacity memory.

  Frequency interleaving and time interleaving bring about a great effect of ensuring high-quality transmission by distributing causes of error occurrence in the transmission path. However, the large memory capacity required for deinterleaving results in a significant increase in the circuit configuration of the receiving apparatus, which hinders improvement in manufacturing efficiency and cost reduction.

Accordingly, in a digital signal receiving apparatus for receiving a signal transmitted using the OFDM method such as terrestrial digital broadcasting, it is necessary to reduce the memory capacity required for such deinterleaving processing. is there. Various methods have been proposed to reduce the memory capacity. However, in Japanese Patent Application Laid-Open No. 2001-320345, a so-called pre-demapping process that performs demapping before deinterleaving is performed. It is possible to reduce the memory capacity required for the interleaving process.
JP 2001-320345 A

  FIG. 23 is a schematic block diagram for explaining the configuration of digital signal receiving apparatus 4000 that performs the above-mentioned “pre-demapping process” when reproducing a baseband signal from a received wave.

  As described below, by performing pre-demapping processing, it is possible to reduce the bit width of data subject to time deinterleaving processing without reducing the amount of information of the data signal, and thereby time deinterleaving processing. The required amount of memory required for this can be greatly reduced.

  In FIG. 23, the same components as those of digital signal receiving apparatus 3000 shown in FIG. 22 are denoted by the same reference numerals, and description thereof will not be repeated.

  Referring to FIG. 23, of the processes performed by digital signal receiving apparatus 4000, each process from the time when tuner 11 receives a signal from an antenna (not shown) until the demodulation process by demodulator 15 is performed. This is the same as the processing of the digital signal receiving device 3000 shown in FIG.

  In digital signal receiving apparatus 4000, frequency deinterleave circuit 16 calculates a demapping reference value according to the modulation scheme based on average value A of the pilot signal.

  FIG. 24 is a diagram illustrating an example of the distribution of SP signals within an OFDM frame.

  FIG. 25 is a diagram for explaining a procedure for calculating a demapping reference value in the frequency deinterleave circuit 16.

  In the OFDM frame, as shown in FIG. 24, for example, pilot signal SP is inserted once in 12 carriers and once in 4 symbols.

  The demapping reference value is obtained by converting the average value of such a pilot signal into a data signal level and multiplying by a coefficient for calculating a reference value determined for each modulation method as shown in FIG. .

  The pilot signal SP is 4/3 times that of the data signal on the modulation side, and the pilot signal is multiplied by 3/4 in order to convert the pilot average value to the level of the data signal. The minimum reference value of each modulation method is 1 / √2 times the pilot signal after level conversion for DQPSK and QPSK, 1 / √10 times the pilot signal after level conversion for 16QAM, and after the level conversion for 64QAM. Each is obtained by 1 / √42 times the pilot signal. That is, the demapping reference value is obtained by a constant multiple of the pilot average value.

  Referring back to FIG. 23, the pre-demapping circuit 26 determines which reference value on the constellation of each modulation method is the closest to the input I-axis data and Q-axis data for each carrier, and indicates the reference value. First, bit data of up to 6 bits is obtained.

  FIG. 26 is a conceptual diagram for explaining such a pre-demapping procedure.

  FIG. 26 shows the case of 64QAM. In FIG. 26, gray (GRAY) codes are assigned to both the I-axis direction and the horizontal axis direction.

  For example, in FIG. 26, white circles are 64QAM reference values, and black circles are received data. At this time, the black circle is closest to the reference point “011” in the I-axis direction and is closest to the reference point represented by “011” in the Q-axis direction. Therefore, in this case, the black circle is closest to the reference point represented by 6-bit data of the value “001111” obtained by alternately arranging the gray codes of the I axis and the Q axis.

  The pre-demapping circuit 26 further obtains the shift direction and distance in the I-axis and Q-axis directions from the reference point to the data viewed from the reference point, and adds them to the 6-bit bit data described above. That is, 1 bit is prepared as direction information, and the most significant bit is set to 1 if the direction of the data viewed from the reference point is plus, and the most significant bit is set to 0 if the direction is minus. The distance information is represented by 2-bit data following the information bits in this direction. The distance between two reference points that sandwich the data in each axis direction is divided into seven equal parts, and the magnitudes of the deviations “01”, “10”, “11” from the closest to the reference point closest to the data. It is expressed by three values.

  FIG. 27 is a diagram for explaining the procedure for obtaining the direction and distance of deviation in each of the I-axis and Q-axis directions from the reference point to the data viewed from the reference point, indicated by “001111” shown in FIG. It is a figure which expands and shows the relationship between the reference point (hatched circle) and the received signal shown with a black circle.

  As shown in FIG. 27, the received signal is shifted by +1 in the I-axis direction and shifted by +3 in the Q-axis direction. This can be expressed as a shift amount of “101” in the I-axis direction and expressed as a shift amount of “111” in the Q-axis direction when expressed in bit data.

  Accordingly, the pre-demapping data of the received signal as described with reference to FIGS. 26 and 27 can be expressed by 12-bit data “001111 101 111”.

  That is, the I-axis and Q-axis data supplied to the pre-demapping circuit 26 represents the 6-bit indicating the reference point closest to the data by the pre-demapping process, and the direction and distance of deviation in the I-axis direction viewed from the reference point. It is converted into bit data of 12 bits in total, 3 bits representing the direction and distance of deviation in the Q-axis direction.

  By performing the pre-demapping process as described above, in the configuration shown in FIG. 22, it is necessary to process 18-bit data in the time deinterleave circuit 17, whereas in the digital signal receiving apparatus 4000, It is sufficient to perform 12-bit data time deinterleaving.

  Note that in the later Viterbi decoding, when the hard decision process is performed instead of the soft decision process, the data of the direction of the deviation and the distance as described above can be omitted. However, if soft decision processing is performed, the correction capability by the convolutional code can be further enhanced in Viterbi decoding.

  That is, in the Viterbi decoding method, in addition to the method of setting the input data to “1” or “0”, the decoding process can be performed based on information including the accuracy of the value of the input data. .

  In this case, 1-bit input data is represented by 3 bits. When the 3-bit value is “111”, the data value is almost certainly “1”, and when it is “101”, the data value is “1”. Error correction can be performed assuming that there is a high possibility of being “1”, but there is also a possibility of being “0”.

  The data processed by the pre-demapping circuit 26 and the time deinterleaving circuit 17 can be converted by the bit conversion circuit 27 into a data format including the accuracy of the value of such input data.

  FIG. 28 is a diagram for explaining such bit conversion processing.

  Data output from the time deinterleave circuit 17 is indicated by white circles in FIG. In FIG. 28, a large black circle indicates a reference point, and a small black circle is a reference for indicating the accuracy of data.

  As described above, since a gray code is assigned to each reference point, the reference point closest to the reference point “001111” closest to the white circle data is only one bit from this “001111”. Different codes are assigned.

  Therefore, in the example shown in FIG. 27, among the data “001111” allocated by pre-demapping, the upper 2 bits “00” and the lower 2 bits “11” are surely “0” for both bits. Or “1”. Therefore, either “000” or “111” is assigned to each bit data.

  On the other hand, in the pre-demapping, among “001111” assigned to the closest reference point, for the middle two bits “11”, any of these two bits is surely “1”. It is a bit that cannot be said. Therefore, “110” is assigned to “1” corresponding to the data in the I-axis direction with reference to FIG. 28, and data “100” is assigned to “1” corresponding to the bit in the Q-axis direction. "Is assigned.

  As a result, the bit conversion circuit 27 outputs 18-bit data converted to “000 000 110 100 111 111” with respect to “001111”. The Viterbi decoding circuit 20 performs decoding processing on such 18-bit data by soft decision, so that error correction is performed.

[Configuration of Digital Signal Receiving Device that Performs Decoding Processing with Reliability Information Added]
Furthermore, in OFDM demodulation, by detecting the reliability of each carrier and applying the detected reliability information to error correction by Viterbi decoding, multipath may occur in the transmission path or co-channel interference may occur. It is possible to reduce the degradation of the data error rate after demodulation if it is mixed (Non-Patent Document (“Error Control Considering Terrestrial Transmission Line Characteristics”), 1998 Annual Conference of the Institute of Image Information and Television Engineers, 3-1. ).

  Therefore, if the structure is such that the reliability of each carrier is detected and Viterbi decoding is performed after adding information on the reliability of each carrier, more reliable data can be reproduced on the receiving device side. it can.

  FIG. 29 is a schematic block diagram for explaining the configuration of a digital signal receiving apparatus 5000 that can add such reliability information to decoded data.

  Also in FIG. 29, the same components as those of digital signal receiving apparatus 3000 shown in FIG. 22 are denoted by the same reference numerals, and description thereof will not be repeated.

  Referring to FIG. 29, in digital signal receiving device 5000, upon receiving the output from FFT unit 14, reliability detection unit 28 evaluates the reliability of the carrier according to the procedure described below, Such reliability data is added to the demodulated signal from the demodulator 15.

  That is, in the configuration shown in FIG. 29, the reliability R is obtained from the variance of the level of the SP signal periodically inserted among the pilot signals inserted in the data after the FFT processing. Based on the reliability R, a reliability information signal is calculated, added to the I-axis data and the Q-axis data, and supplied to the frequency deinterleave circuit 16. Such a procedure for obtaining the reliability R from the dispersion of the SP signal level is described in the above-mentioned non-patent document, and will be briefly described here.

  One method of obtaining the reliability R is obtained from the variance of the SP as described above. That is, the reliability R when the reception level of the reception SP is I (t, f) and Q (t, f) is determined from the following equation (1).

  However, A is a coefficient including a threshold value, and Iref (f) and Qref (f) are average values in the time direction of the received signals I (t, f) and Q (t, f). The numerator of Expression (1) indicates the average value of the reception level, and the reliability R increases as the reception amplitude increases. Further, the denominator of the equation (1) indicates dispersion, and the greater the disturbance, the smaller the reliability R.

  The reliability detection unit 28 pays attention to the SP signal periodically located in the symbol, calculates an average value of the SP signal level, and compares the level of each SP to detect the reliability of the SP signal. To do. The reliability detection unit 28 uses the reliability R as reliability information of the SP signal, and the carriers other than the SP use the reliability information of the SP signal closest to the carrier as the reliability information of the carrier. In this way, reliability information is added to all carriers in the hierarchy of synchronous modulation.

  FIG. 30 is a diagram for explaining the contents of the reliability information signal added in this way.

  That is, the information on the high reliability is a case where the erasure determination information that treats a carrier with extremely low reliability as erasure is assigned to the most significant bit, and the reliability is not so low as to be treated as erasure. However, 2 bits are further allocated as the reliability information corresponding to the weighting of the Viterbi decoding by the soft decision, and a total of 3 bits of data are added. Hereinafter, the bit data indicating whether the data is treated as erasure in the reliability information is referred to as “erasure determination information”, and the reliability information corresponding to the Viterbi decoding weighting by the soft decision is referred to as “reliability information” in the reliability information. It will be called “degree information”.

  However, when performing Viterbi decoding processing without weighting, it is also possible to add only one bit of erasure determination information to the data.

  Therefore, for example, when the reliability information is “1XX” (X is arbitrary bit data), it is assumed that the data to which such reliability information is added is unreliable, and lost data is used in subsequent processing. Are treated as

  On the other hand, when the reliability information signal is “011”, it is treated as the most reliable data. On the other hand, “000” is the data with the lowest reliability although it is not treated as lost data. Are treated as

  Therefore, if such a reliability information signal is added to the I-axis data and the Q-axis data demodulated by the demodulation circuit 15 after the FFT processing, the error correction capability during Viterbi decoding is further improved.

  However, if such a reliability information signal is added to the pre-demapping unit 26 in addition to the I-axis data and the Q-axis data converted to 12 bits, the time deinterleaving process can be performed on the data of a total of 15 bits. It becomes necessary.

  FIG. 31 is a schematic block diagram for explaining the configuration of a digital signal receiving apparatus 6000 having another configuration for adding reliability information to data to be decoded.

  In the digital signal receiving apparatus 6000 shown in FIG. 31, the variance of the deviation from the reference value of the pre-demapping data output from the pre-demapping unit 26 is obtained, and the reliability of the received data is evaluated from the level of the deviation.

  Corresponding to the result of the evaluation, a 3-bit reliability information signal is added to the pre-demapping data as in the digital signal receiving apparatus 5000 shown in FIG. Similarly to the case of FIG. 29, the time deinterleave circuit 17 performs time deinterleave processing on the input data to which the 3-bit reliability information signal is added to the 12-bit pre-demapping data.

  Therefore, in the configuration as shown in FIG. 31 as well, it is sufficient to process a smaller number of bits than 18 bits when the I-axis data and the Q-axis data are individually time-deinterleaved as shown in FIG. The addition of sex information will increase the number of bits.

  Therefore, in the digital signal receiving device 5000 shown in FIG. 29 or the digital signal receiving device 6000 shown in FIG. 31, a 3-bit reliability information signal is added to the 12 bits of data after the pre-demapping process by reliability detection. If a total of 15 bits of data are subjected to time deinterleave processing, the error correction capability itself can be improved, but it is not sufficient for reducing the amount of memory.

  The present invention has been made to solve the above-described problems, and its object is to further reduce the memory capacity required for demodulating the received digital modulation signal. A digital signal receiving apparatus is provided.

  A digital signal receiving apparatus according to the present invention is a digital signal receiving apparatus for receiving a digital modulation signal, and a frequency conversion processing means for frequency-converting the digital modulation signal, and a modulation method based on an output of the frequency conversion processing means. And a pre-demapping processing means for generating pre-demapping data having first data indicating a reference point on the corresponding constellation and second data indicating a deviation from the corresponding reference point, and for each pre-demapping data Based on the reliability detection means for adding reliability information for determining the reliability of the received signal and pre-demapping data and reliability information, and correcting the second data indicating the amount of deviation according to the reliability information Correction means for performing data conversion processing for including at least part of the reliability information in the pre-demapping data, and correction Based on the output stage comprises a demodulation processing means for performing demodulation processing through the memory, based on the output of the demodulation processing means, by the maximum likelihood decoding processing and a decoding processing unit for performing error correction. The second data includes deviation amount data indicating the magnitude of deviation and direction data indicating the direction of deviation. The correction means includes a plurality of points assigned to the pre-demapping data, the reference point on the constellation, a point shifted by a predetermined amount from the reference point, and a point where the shift direction to be corrected is indefinite according to the shift amount data. Data conversion means for converting into data expressed by numbers is included.

  Preferably, the digital modulated wave signal is modulated by an orthogonal frequency division multiplexing method, subjected to time interleaving processing, and transmitted. The demodulation processing means includes time deinterleaving processing means for performing time deinterleaving processing that is an inverse transformation of time interleaving processing.

  Preferably, the correction unit further includes a reliability correction processing unit that changes the deviation amount data in the direction indicated by the direction data in accordance with the reliability information.

  Preferably, in the data conversion unit, the correction point obtained by correcting the second data indicating the shift amount according to the reliability information is closer to another reference point adjacent to the reference point indicated by the first data. In some cases, the pre-demapping data is converted into a predetermined number of a plurality of numbers in order to indicate that the pre-demapping data is not a target of the maximum likelihood decoding process.

  Preferably, when the pre-mapping data is located at a point shifted outside the reference point located on the outermost side among the reference points on the constellation, the data conversion means sets the shift amount data to 0. Convert to assigned number.

  Preferably, a bit conversion unit that performs reverse conversion of the data conversion process is further provided between the demodulation processing unit and the decoding processing unit.

  In particular, the bit conversion means outputs bit data having a minimum number of bits necessary for representing data represented by a plurality of numbers.

  The present invention provides correction means for performing data conversion processing that includes at least part of the reliability information in the pre-demapping data, thereby reducing the bit width representing the data and reducing the memory capacity required for the processing. can do.

  Further, the correction means is expressed by a reference point on the constellation, a point shifted by a predetermined amount from the reference point, and a plurality of numbers assigned to points where the shift direction to be corrected is indefinite according to the shift amount data. By further including data conversion means for converting into converted data, the bit width of the data to be expressed can be further reduced, and the memory capacity required for processing can be further reduced. Further, it is considered that power consumption is reduced by reducing the memory capacity.

[Configuration of Digital Signal Receiving Apparatus 1000 that Performs Data Correction Processing on Data After Pre-demapping Processing]
FIG. 1 is a schematic block diagram for explaining the configuration of the digital signal receiving apparatus 1000.

  In digital signal receiving apparatus 1000, before time deinterleaving processing and after pre-demapping processing, in addition to reliability determination processing, data correction processing according to high reliability is performed. Thus, the number of bits of data to be subjected to the time deinterleaving process is reduced as compared with the digital signal receiving device 5000 shown in FIG. 29 or the digital signal receiving device 6000 shown in FIG.

  Also in FIG. 1, the same components as those of digital signal receiving apparatus 3000 shown in FIG. 22 are denoted by the same reference numerals, and description thereof will not be repeated.

  Referring to FIG. 1, in digital signal receiving apparatus 1000, reliability determination / correction unit 29 that performs erasure determination based on reliability information and correction of pre-demapping data between pre-demapping circuit 26 and time deinterleaving circuit 17. Is provided.

  In the reliability determination / correction unit 29, data conversion is performed so as to reduce the bit width of data input to the time deinterleave circuit 17.

  The digital signal receiving apparatus 1000 shown in FIG. 1 has a configuration in which reliability determination is performed based on the level of the SP signal, as in the case of the digital signal receiving apparatus 5000 shown in FIG.

  In FIG. 1, the same parts as those of FIG. 29 are denoted by the same reference numerals and description thereof will not be repeated.

  Referring to FIG. 1, reliability determination / correction unit 29 has reliability added for each carrier when reliability information input together with pre-demapping data is 3-bit data including reliability information. With reference to the information value, the reliability of the carrier is determined according to the rule shown in FIG.

  That is, first, the reliability determination / correction unit 29 performs erasure determination based on the erasure determination information expressed by the most significant bit of the reliability information.

  If the reliability of the data is not so low that it is necessary to perform erasure processing, the predemap data is converted into the pre-demapping data based on both the values of the deviation in the I-axis direction and the Q-axis direction with reference to the value of the reliability information. Apply corrections.

  That is, when the reliability information signal is “011”, since the data is sufficiently reliable, no particular correction is performed.

  On the other hand, when the reliability information signal is “010”, correction is performed on the assumption that the absolute value of the deviation is +1, as shown in FIG. Similarly, when the reliability information signal is “001”, correction is performed on the assumption that the absolute value of the deviation is +2, and when the reliability information signal is “000”, the absolute value of the deviation is +3. Corrections are made as if they exist.

  As a result, if the absolute value of the deviation in any of the I-axis direction and the Q-axis direction is 4 or more, it is treated as lost data because the reliability is extremely low.

  FIG. 2 is a diagram for explaining the processing performed by the reliability determination / correction unit 29 in more detail.

  In the example illustrated in FIG. 2, it is assumed that the reference point closest to the received data is determined to be “001111” in the pre-demapping process.

  Further, it is assumed that the deviation in the I direction is +2 and the deviation in the Q direction is determined to be +1 by the pre-demapping process.

  Therefore, as a result of the pre-demapping, the position on the constellation of the received signal is determined as the signal point MP0.

i) When the reliability information is “010” In this case, since the reliability information is “10”, it is assumed that the correction value is +1, and data is obtained for both the I-axis direction and the Q-axis direction. Make corrections.

  At this time, it is assumed that the direction in which correction is performed matches the direction of deviation in pre-demapping. That is, in this case, correction is performed in the + direction in both the I-axis direction and the Q-axis direction.

  Therefore, in this case, the pre-demapping data is corrected on the assumption that the deviation in the I-axis direction is +3 (= + 2 + 1) and the deviation in the Q-axis direction is +2 (= + 1 + 1) with respect to the reference point “001111”. . As a result of this correction, the corrected signal is a signal point MP1.

ii) When the reliability information is “001” In this case, the reliability information is “01”, and the correction value has an absolute value of +2.

  Therefore, in this case, with respect to the reference point “001111”, the deviation in the I-axis direction is +4 (= + 2 + 2), the deviation in the Q-axis direction is corrected to +3 (= + 1 + 2), and is corrected to the signal point MP2. Will be. However, the absolute value of the deviation becomes 4 or more, and it is corrected to a value closer to the adjacent reference point “000111” rather than the reference point “001111”, and the validity as data is lost. Therefore, when the absolute value of the deviation becomes 4 or more and approaches the adjacent reference point, this data is treated as lost data.

  FIG. 3 is a diagram for explaining another case where the reliability determination / correction unit 29 performs the correction process.

  As described with reference to FIG. 2, when the correction based on the reliability is performed, the correction is performed by further adding the absolute value indicated by the reliability information to the direction of the shift of the pre-demapping data.

  However, as shown in FIG. 3, when the deviation value is 0 in either the I-axis or the Q-axis of the pre-demapping data and the correction value is not 0, it is indeterminate in which direction the correction is applied. turn into.

  For example, as shown in FIG. 3, the reference point closest to the received data is determined to be “001111”, and the deviation in the I direction is ± 0 and the deviation in the Q direction is +2 by the pre-demapping process. Assume that it has been determined.

  At this time, if the reliability information is “010”, the reliability information is “10”, so the correction value is +1. In the Q-axis direction, correction may be performed assuming that the deviation is +3, but in which direction the correction is performed with respect to the I-axis direction is undefined.

  As a countermeasure against such an indefinite correction direction, the reliability determination / correction unit 29 performs the following processing.

  First, when the absolute value of the deviation of the pre-demapping is 0, in the result of the pre-demapping, the 3-bit bit data representing the deviation of each of the I-axis and Q-axis directions from the reference value is “000” or “100 "Can be represented.

  Therefore, the reliability determination / correction unit 29 sets the 3 bits to “000” when the absolute value of the deviation before correction is 0 and the deviation after correction is also the absolute value 0 in the correction process based on reliability. And set. On the other hand, although the absolute value before correction is 0, correction of 1 or more must be performed, and “100” is set when the direction of deviation becomes indefinite. As described above, the reliability determination / correction unit 29 includes, in the pre-demapping data, each 3-bit data representing a deviation in the I-axis direction or a deviation in the Q-axis direction and information related to the correction process based on the reliability. It shall be expressed again.

  Further, as described above, the reliability determination / correction unit 29 newly prepares 2 bits as information related to the reliability in response to the case where the correction direction may be indefinite. When the direction of any of the above becomes indefinite, the absolute value of the correction is expressed by the 2-bit data, and in other cases, the erasure determination information is expressed by the 2-bit.

  FIG. 4 is a diagram showing information on reliability newly added in this way.

  That is, if the deviation value of both the I axis and the Q axis is not “100”, the case where the two bits of the information related to reliability are “11”, “10”, and “01” corresponds. This indicates that the pre-demapping data is not the data subject to the erasure process, and when 2 bits of the newly added reliability information are “00”, the corresponding pre-demapping data is the object of the erasure process. Indicates.

  Similarly, when either the I-axis or the Q-axis has a deviation of “100” indicating that the absolute value is 0 but correction of 1 or more is required and the deviation direction itself is indefinite. Assume that newly added 2-bit information relating to reliability is “11”, “10”, and “01”, respectively, indicating that the correction values are +3, +2, and +1.

  In addition, when the deviation is “100” in any one of the I-axis and the Q-axis, and the newly added reliability information is “00”, the corresponding pre-demapping data is deleted. It shall be shown that it is the object of.

  By performing the data conversion process as described above in the reliability determination / correction unit 29, including the case where the direction of the shift is indefinite, the data information of the pre-demapping and the information amount of the reliability information are not reduced. The bit width of data input to the time deinterleave circuit 17 can be reduced from 15 bits to 14 bits.

  FIG. 5 is a schematic block diagram for explaining the internal configuration of the reliability determination / correction unit 29 described with reference to FIGS.

  Referring to FIG. 5, reliability determination / correction unit 29 is the highest of the 12-bit pre-demapping data from pre-demapping circuit 26 and the 3-bit reliability information added by reliability detection unit 28. Based on the bit erasure determination information, a reliability determination processing unit 292 for determining whether or not the pre-demapping data is data subject to erasure processing, and 12 output from the reliability determination processing unit 292 Reliability correction for performing the correction processing described in FIG. 2 and FIG. 3 based on the bit pre-demapping data, 1-bit erasure determination information, and 2-bit reliability information added by the reliability detection unit 28 The processing unit 294, the 12-bit corrected pre-demapping data from the reliability correction processing unit 294, and the reliability correction processing as described in FIG. Direction deviation of receiving an altered reliability information according to whether the exception processing such that indeterminate occurs in section 294, and a correction exception processing unit 296 for performing correction exception processing.

  That is, as described with reference to FIG. 2, the reliability correction processing unit 294 performs 12-bit pre-demapping when the direction of the shift is not indefinite and the corrected signal point does not shift to the range where it is treated as an erasure. Of the data, the result of correcting the deviation in the I-axis direction before correction and the deviation in the Q-axis direction before correction based on the reliability information is output. The reliability correction processing unit 294 changes the erasure determination information to a value designating erasure when the corrected signal point deviates to a range that is treated as erasure, although the direction of deviation is not indefinite. To do.

  On the other hand, as described with reference to FIG. 3, the reliability correction processing unit 294 has to make one or more corrections based on the reliability information, although the absolute value representing the deviation before the correction is 0. If the direction of deviation becomes indefinite, the three bits representing the deviation are reset to “100” for the axis direction indefinite among the I-axis and Q-axis directions. On the other hand, the reliability correction processing unit 294 determines whether the deviation before correction in the correction process based on reliability has an absolute value of 0 and the absolute value of the deviation after correction is also 0. The value of axial displacement is “000”.

  In response to the output from the reliability correction processing unit 294, the correction exception processing unit 296 corrects the newly added 2-bit information related to reliability as described with reference to FIGS. Append to data and output.

  Through the processing as described above, the reliability determination / correction unit 29, as a rule, displays the information related to the reliability detected by the reliability detection unit 28 in the data representing the deviation from the reference point in the pre-demap data. Convert to include.

  However, the reliability determination / correction unit 29 simultaneously performs the following processing as an exception in the process of including such reliability information in the data representing the deviation from the reference point in the pre-demapping data. Outputs a corresponding conversion result to the time deinterleave circuit 17.

  Exception processing 1) In the correction processing for including such reliability information in the data representing the deviation from the reference point in the pre-demapping data, the reference point assigned as the pre-demapping data as a result of the correction However, when approaching another adjacent reference point, the reliability correction processing unit 294 designates the loss of the data in the loss determination information in the reliability information.

  Exception processing 2) When the direction of the deviation to be corrected becomes indefinite, the correction exception processing unit 296 makes the axis indeterminate among the data representing the deviation from the reference point in the pre-demapping data. The direction data is changed to data (“100”) indicating that the direction is indefinite. At this time, the absolute value of the correction value is expressed by 2-bit information (“corrected reliability information”) regarding the corrected reliability that is newly added instead of the reliability information from the reliability detecting unit 28. .

  This post-correction reliability information specifies that the data is to be subject to erasure processing by a predetermined value (“00”) regardless of whether the correction direction is not indefinite or indefinite.

  Data for which erasure processing is designated is not subject to Viterbi decoding processing in the subsequent Viterbi decoding processing. This is because, when the Viterbi decoding is not performed on a carrier having a large error that is determined to be lost, it is possible to realize reproduction characteristics such as a good image as a whole.

  By performing such processing, it is possible to reduce the bit width of data input to the time deinterleave circuit 17 without reducing the information amount of pre-demapping data and reliability information.

  That is, in the above configuration, the reliability determination / correction unit 29 causes the reliability determination / correction unit 29 to perform the 12-bit post-correction predecoding based on the 12-bit pre-demapping data and the 3-bit reliability information. A total 14-bit data including mapping data and new 2-bit reliability information can be provided to the time deinterleave circuit 17, but it is not yet sufficient for reducing the amount of memory.

[Embodiment 1]
In the first embodiment of the present invention, a configuration capable of further reducing the amount of memory will be described.

  FIG. 6 is a schematic block diagram for illustrating a configuration of reliability determination / correction unit 29 # that performs pre-demapping data conversion processing according to the first embodiment of the present invention.

  Reliability determination / correction unit 29 # according to the first embodiment of the present invention has reliability correction processing unit 294 and correction exception processing unit 296 as reliability compared to reliability / correction unit 29 described in FIG. The difference is that the correction processing unit 294 # and the pre-demapping data conversion processing unit 298 are replaced. Since the other points are the same, detailed description thereof will not be repeated.

  Also in FIG. 6, the reliability information from the reliability detection unit 28 is composed of 3 bits including 2 bits of reliability information and 1 bit of erasure determination information.

  The reliability correction processing unit 294 # outputs the pre-demapping data after performing the above-described correction processing based on such disappearance determination information. Then, the pre-demapping data conversion processing unit 298 converts the corrected pre-demapping data or the erasure determination information as described below into numbers associated with each other, thereby correcting the pre-demapping data including reliability information. Convert to

  FIG. 7 is a diagram showing a reference point on the constellation and points indicating deviation from the reference point, that is, a distribution of pre-demapping data in 64QAM.

  Similarly to the reliability correction processing unit 294, the reliability correction processing unit 294 # also adds the absolute value indicated by the reliability information to the direction of deviation of the pre-mapping data as described in FIG. Make corrections.

  However, as described above, when the correction direction becomes indefinite by further adding the absolute value, the reliability information is output to the pre-demapping data conversion process 298 without being corrected. In addition, when the absolute value is further added to be a target of the erasure process, the erasure data is designated to be treated as erasure data in the erasure determination information.

  The pre-demapping data conversion processing 298 assigns numbers to the pre-demapping data for all possible states based on the pre-demapping data and reliability information given from the reliability correction processing unit 294 #.

  FIG. 8 is a diagram for explaining a state where the correction direction becomes indefinite by further adding the absolute value 1 of the correction deviation.

  As shown in FIG. 8, when the position of the pre-demapping data before the correction process is a black circle on the constellation of FIG. 8, when the absolute value of the deviation before correction is 1, the correction direction is indefinite. In this case, there are nine states.

  FIG. 9 is a diagram for explaining a state when the correction direction becomes indefinite by further adding the absolute value 2 of the correction deviation.

  As shown in FIG. 9, when the position of the pre-demapping data before the correction process is a black circle on the constellation in FIG. 9, when the absolute value of the deviation before correction is 2, the correction direction is indefinite. In this case, there are five states.

  FIG. 10 is a diagram for explaining a state when the correction direction becomes indefinite by further adding the absolute value 3 of the correction deviation.

  As shown in FIG. 10, when the position of the pre-demapping data before the correction process is a black circle on the constellation in FIG. 10, when the absolute value of the deviation before the correction is 3, the correction direction is indefinite. In this case, there are one state.

  Therefore, as shown in FIGS. 8 to 10, by adding the absolute value of the deviation of correction, the number of states in which the correction direction becomes indefinite becomes 9 + 5 + 1 = 15.

  The reliability determination / correction unit 29 # according to the first embodiment assigns a number to each of the states of the pre-demapping data subjected to the correction processing and all the states in the case of being indefinite.

  FIG. 11 is a conceptual diagram showing allocation of numbers to such pre-demapping data.

  As shown in FIG. 11, for example, there are 49 states of the corrected pre-demapping data, and therefore, numbers from 0 to 48 can be assigned one by one. Similarly, with respect to the state of pre-demapping data in the case of indefiniteness described with reference to FIGS. 8 to 10, if numbers are assigned, numbers from 0 to 63 can be assigned. In addition to the case of disappearance, a number from 0 to 64 can be assigned, and there are 65 different states. Therefore, these 65 patterns can be expressed by 7 bits, and can be expressed by 13 bits when combined with the 6-bit data representing the reference point described above.

  With such a configuration, it is possible to reduce the bit width of data to be subjected to time deinterleaving processing and to reduce the memory capacity required for processing. Further, it is considered that power consumption is reduced by reducing the memory capacity.

  However, when such data conversion is performed, the bit conversion circuit 27 performs inverse conversion of the conversion, that is, converts the converted data into bits again and outputs the result to the bit deinterleave circuit 19.

  Therefore, the reliability determination / correction unit 29 # can further reduce the amount of memory by providing 13-bit data to the time deinterleave circuit 17 in a format including reliability information.

  In the above description, the case of 64QAM as the modulation method has been described. For example, in the case of 16QAM, the state of the corrected pre-demapping data and the state in the case of indefiniteness do not change. When combined with 4-bit data, it is possible to represent data with 4 + 7 = 11 bits. Similarly, in QPSK (DQPSK), the data representing the reference point is 2 bits, so the data can be represented by 2 + 7 = 9 bits.

[Embodiment 2]
In the second embodiment of the present invention, a method for further reducing the number of bits than in the first embodiment will be described.

  FIG. 12 is a diagram illustrating rules according to the second embodiment of the present invention.

  Referring to FIG. 12, since there is no reference point in the region outside the reference point at the position of the outermost reference point on the constellation, the outward shift is estimated as zero.

  FIG. 13 is a diagram illustrating the state of pre-demapping data that has been corrected for the case where the position of the reference point is the outermost side.

  As shown in FIG. 13, assuming that the outer region, that is, the deviation in the Q direction is not taken into consideration, the number of states of the pre-demapping data subjected to the correction process is 4 × 7 = 28.

  As described in the first embodiment, there are 15 states when the correction direction becomes indefinite by further adding the absolute values 1 to 3 of the correction deviation.

  Therefore, the number of possible states of the pre-demapping data including the reliability information at the reference point located outside is 28 + 15 = 43.

  When all the reference points located outside the corner area are considered, 43 × 24 = 1032 patterns are obtained.

  FIG. 14 is a diagram for explaining the state of pre-demapping data obtained by correcting the reference points arranged in the corner regions at the position of the reference point on the constellation.

  As shown in FIG. 14, if the outer region, that is, the deviation in the I and Q directions is not taken into consideration, the number of states of the pre-demapping data subjected to the correction process is 4 × 4 = 16.

  As described in the first embodiment, there are 15 states when the correction direction becomes indefinite by further adding the absolute values 1 to 3 of the correction deviation.

  Therefore, the number of possible states of the pre-demapping data including the reliability information at the reference point of the corner region located outside is 16 + 15 = 31.

  Considering the reference points of all corner regions, there are 31 × 4 = 124 patterns.

  Then, considering the possible states of the reference points located in the inner area other than the outer area, there are 49 + 15 64 states for one reference point according to the same method as described above.

  Considering all the reference points in the inner region, there are 64 × 36 = 2304.

Therefore, when all these states are considered together, if one of the erased states is added, 1032 + 124 + 2304 + 1 = 3461 (<2 ¹² ).

  In the second embodiment, a number is assigned to each of these states. That is, as described in Embodiment 1, by assigning numbers one by one for all states, pre-demapping data including reliability information can be expressed as 12-bit data when the modulation scheme is 64QAM. it can.

  Therefore, with the configuration according to the second embodiment, it is possible to further reduce the bit width of data to be subjected to time deinterleaving processing, and to reduce the memory capacity required for processing. That is, the reliability determination / correction unit 29 # can further reduce the amount of memory by providing 12-bit data to the time deinterleave circuit 17 in a format including reliability information.

  FIG. 15 is a diagram for explaining reference points on the constellation of 16QAM.

  Also in 16QAM, if calculation is performed according to the same method, 43 × 8 = 344 patterns are obtained in consideration of all the possible states of the reference points located in the outer region excluding the corner region.

  Further, if all possible states of the reference points in the corner area are considered, 31 × 4 = 124.

  If all the reference points located in the inner region are considered in the same manner, 64 × 4 = 256 states can be mentioned.

Therefore, considering all the possible states, adding one way of the erased state gives 344 + 124 + 256 + 1 = 725 (<2 ¹⁰ ).

  Therefore, when the modulation scheme is 16QAM, the pre-demapping data can be expressed as 10-bit data in a format including reliability information.

  FIG. 16 is a diagram for explaining reference points on the QPSK constellation.

Also in QPSK, calculation according to the same method results in 31 × 4 = 124 patterns (<2 ⁷ ) because all are angular regions in this example.

  Therefore, when the modulation method is QPSK (the same applies to DQPSK), data can be expressed with 7 bits.

  By adopting such a method, it is possible to reduce the bit width of data to be subjected to time deinterleaving processing and to reduce the memory capacity necessary for processing. Further, it is considered that power consumption is reduced by reducing the memory capacity.

[Embodiment 3]
FIG. 17 is a schematic block diagram illustrating the configuration of digital signal receiving apparatus 2000 according to the third embodiment.

  In the digital signal receiving apparatus 1000 of the first embodiment shown in FIG. 1, the reliability detection unit 28 is configured to detect the reliability information from the level of the SP signal, but FIG. Similar to the configuration of the digital signal receiving device 6000 shown in the figure, the reliability detection unit 28 receives the output from the pre-demapping circuit 26 and based on the variance of the magnitude of the deviation between the pre-demapped data and the reference value. Reliability is determined and reliability information is added to pre-demapping data.

  In the configuration of FIG. 17, the reliability determination / correction unit 29 # receives the pre-demapping data to which the reliability information is added by the reliability detection unit 28 as described above, and receives the first or second embodiment. The corrected pre-demapping data is given to the time deinterleave circuit 17 by performing the same process as described in the above.

  Since other configurations are the same as those of digital signal receiving apparatus 6000 shown in FIG. 31, the same portions are denoted by the same reference numerals and description thereof will not be repeated.

  Even with such a configuration, it is possible to reduce the bit width of data to be subjected to time deinterleaving processing and to reduce the memory capacity required for processing. Further, it is considered that power consumption is reduced by reducing the memory capacity.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram for demonstrating the structure of the digital signal receiver 1000. FIG. It is a figure for demonstrating in more detail the process which the reliability determination / correction | amendment part 29 performs. It is a figure for demonstrating the other case where the reliability determination / correction | amendment part 29 performs a correction process. It is a figure which shows the information regarding the reliability newly added. FIG. 5 is a schematic block diagram for explaining an internal configuration of a reliability determination / correction unit 29 described with reference to FIGS. It is a schematic block diagram for demonstrating the structure of the reliability determination / correction | amendment part 29 # which performs the conversion process of the pre demapping data according to Embodiment 1 of this invention. It is a figure which shows distribution of pre demapping data in 64QAM. It is a figure explaining the state in case the direction of correction becomes indefinite by adding the absolute value 1 of the deviation of correction further. It is a figure explaining the state in case the direction of correction becomes indefinite by adding the absolute value 2 of the deviation of correction further. It is a figure explaining the state in case the direction of a correction becomes indefinite by adding the absolute value 3 of the deviation | shift of a correction | amendment further. It is a conceptual diagram which shows allocation of the number with respect to pre-demapping data. It is a figure explaining the rule according to Embodiment 2 of this invention. It is a figure explaining the state of the pre demapping data which carried out the correction process about the case where the position of a reference point is the outermost as an example. It is a figure explaining the state of the pre demapping data which carried out the correction process about the reference point arrange | positioned in a corner | angular area | region in the position of the reference point on a constellation. It is a figure explaining the reference point on the constellation of 16QAM. It is a figure explaining the reference point on the constellation of QPSK. 10 is a schematic block diagram illustrating a configuration of a digital signal receiving device 2000 according to Embodiment 3. FIG. It is a conceptual diagram for demonstrating the structure of the data of the OFDM system received with a terrestrial digital signal receiver. It is a figure which shows the structure of the OFDM symbol shown in FIG. It is a figure for demonstrating in more detail the structure of 1 OFDM segment. It is a figure for demonstrating the mode dependence of the structure of one OFDM segment. FIG. 10 is a schematic block diagram illustrating a configuration of a conventional OFDM receiving apparatus 3000. 4 is a schematic block diagram for explaining a configuration of a digital signal receiving device 4000. FIG. It is a figure which shows the example of distribution of SP signal in an OFDM frame. FIG. 10 is a diagram for explaining a procedure for calculating a demapping reference value in the frequency deinterleave circuit 16; It is a conceptual diagram for demonstrating the procedure of pre demapping. It is a figure for demonstrating the procedure which calculates | requires the direction and distance of each shift | offset | difference of I-axis and Q-axis direction to the data seen from the reference point. It is a figure for demonstrating a bit conversion process. It is a schematic block diagram for demonstrating the structure of the digital signal receiver 5000 which can add reliability information to the data decoded. It is a figure for demonstrating the content of the reliability information signal added. It is a schematic block diagram for demonstrating the structure of the digital signal receiver 6000 which has another structure which adds reliability information with respect to the data used as decoding object.

Explanation of symbols

  11 tuner, 12 A / D conversion circuit, 13 synchronization unit, 14 FFT unit, 15 demodulation unit, 16 frequency deinterleave circuit, 17 time deinterleave circuit, 18 demapping circuit, 19 bit deinterleave circuit, 20 Viterbi decoding circuit, 21 byte deinterleave circuit, 22 energy despreading unit, 23 RS decoding circuit, 24 MPEG decoding circuit, 25 D / A conversion circuit, 26 pre-demapping circuit, 28 reliability detection unit, 29, 29 # reliability determination / correction unit 292, reliability determination processing unit, 294,294 # reliability correction processing unit, 296 correction exception processing unit, 298 pre-demapping data conversion processing unit, 1000, 2000, 3000, 4000, 5000, 6000 digital signal receiving device.

Claims (7)

A digital signal receiving device for receiving a digital modulation signal,
Frequency conversion processing means for converting the frequency of the digital modulation signal;
Based on the output of the frequency conversion processing means, according to the modulation method, pre-decoding data having first data indicating a reference point on the corresponding constellation and second data indicating a deviation from the corresponding reference point. Pre-de-mapping processing means for generating mapping data;
Reliability detection means for adding reliability information that determines the reliability of the received signal for each pre-demapping data;
Based on the pre-demapping data and the reliability information, the second data indicating the shift amount is corrected according to the reliability information, and at least a part of the reliability information is included in the pre-demapping data. Correction means for performing a data conversion process including
Demodulation processing means for performing demodulation processing via a memory based on the output of the correction means;
Decoding processing means for performing error correction by maximum likelihood decoding processing based on the output of the demodulation processing means,
The second data includes deviation amount data indicating the magnitude of deviation and direction data indicating the direction of deviation,
The correction means sets the pre-demapping data to a reference point on the constellation, a point shifted by a predetermined amount from the reference point, and a point where the direction of shift to be corrected according to the shift amount data is indefinite. A digital signal receiving apparatus comprising data conversion means for converting data represented by a plurality of assigned numbers. The digital modulated wave signal is modulated by orthogonal frequency division multiplexing, subjected to a time interleaving process, and transmitted.
2. The digital signal receiving apparatus according to claim 1, wherein said demodulation processing means includes time deinterleaving processing means for performing time deinterleaving processing that is inverse transformation of said time interleaving processing.   The digital signal receiving apparatus according to claim 1, wherein the correction unit further includes a reliability correction processing unit that changes the deviation amount data in a direction indicated by the direction data in accordance with the reliability information.     In the data conversion means, a correction point obtained by correcting the second data indicating the amount of deviation according to the reliability information is set to another reference point adjacent to the reference point indicated by the first data. The pre-demapping data is converted into a predetermined number of the plurality of numbers to indicate that the pre-demapping data is not a target of the maximum likelihood decoding process when approaching. The digital signal receiving apparatus according to any one of claims.   In the case where the pre-mapping data is located at a point that is shifted to the outside of the reference point located on the outermost side among the reference points on the constellation, the data conversion means sets the shift amount data to 0. The digital signal receiving apparatus according to claim 1, wherein the digital signal receiving apparatus converts the number into a number assigned to the digital signal.   6. The digital signal receiving apparatus according to claim 1, further comprising a bit conversion unit that performs reverse conversion of the data conversion process between the demodulation processing unit and the decoding processing unit.   The digital signal receiving apparatus according to claim 6, wherein the bit conversion unit outputs bit data having a minimum number of bits necessary to represent data represented by the plurality of numbers.

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