JP2007019579A - Digital broadcast receiver, digital broadcast receiving method, and digital broadcast receiving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a storage area of a large capacity is required to repeat processing because processing for forming a pseudo inter-carrier interference component and eliminating it from a reception signal is repeated, in order to suppress deterioration in reception performance caused by inter-carrier interference generated in a mobile reception environment where a propagation path varies. <P>SOLUTION: A quadrature demodulator performs quadrature demodulation for an input signal to generate a quadrature-demodulated signal. A storage area stores and holds the quadrature-demodulated signal. A propagation path estimator estimates a propagation path from the quadrature demodulated signal and an expected value signal. A replica eliminator eliminates the inter-carrier interference from the quadrature-demodulated signal. An error corrector corrects an error of a demodulated signal by soft decision processing. A hard decision device applies hard decision processing to the demodulated signal. A determination switching device selects results of hard and soft decisions. A replica creating device creates a replica of an inter-carrier interference component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital broadcast receiver that can receive a digital broadcast signal and perform good demodulation processing not only on a stationary digital broadcast receiver but also on a mobile body such as an automobile.

  In addition to fixed reception by a stationary receiver, terrestrial digital broadcasting can be received by a receiver mounted on a mobile object. In the mobile reception environment, it is possible that the demodulator does not show a good reception result due to fading. This is because, in multi-carrier transmission such as OFDM (Othonal Frequency Division Multiplexing), Doppler shift occurs due to movement in each carrier, the orthogonality of the carrier arrangement collapses, and adjacent carriers overlap each other and cause interference between carriers. This is because interference (ICI: Inter Carrier Interference) occurs.

  For example, Patent Document 1 discloses a conventional technique for preventing deterioration of reception characteristics in demodulation processing due to the occurrence of inter-carrier interference due to the Doppler shift as described above. FIG. 9 is a block diagram showing the configuration of the conventional receiver. The conventional receiver includes an orthogonal demodulator 101, a transmission path estimator 102, a replica creator 103, a replica remover 104, and an error corrector 105.

  The quadrature demodulator 101 demodulates the signal input from the antenna and supplies the quadrature demodulated signal to the transmission path estimator 102 and the replica remover 104. The transmission path estimator 102 estimates the transmission path state from the quadrature demodulated signal and the expected value signal, and supplies the transmission path estimation signal to the replica creator 103 and the replica remover 104. The replica creator 103 creates an ICI replica signal from the expected value signal and the transmission path estimator signal, and supplies the ICI replica signal to the replica remover 104. The replica remover 104 generates a demodulated signal (time axis) obtained by removing the ICI replica component from the quadrature demodulated signal and the ICI replica signal, and suppresses the ICI residual and performs the time-frequency conversion of the demodulated signal using the transmission path estimation signal. The demodulated signal (frequency axis) is supplied to the error corrector 105. The error corrector 105 performs error correction on the demodulated signal (frequency axis) to generate an expected value signal, supplies the signal to the replica generator 103 and the transmission path estimator 102, and returns to the back end not added as an output of the digital broadcast receiver. Supply.

  The operation of the digital broadcast receiver will be described. The orthogonal demodulator 101 converts the signal input from the antenna into an IQ complex signal by performing orthogonal demodulation processing. Further, after synchronization of the complex signal is established, the guard interval is removed and supplied to the transmission path estimator 102 and the replica remover 104.

  FIG. 2 shows the configuration of the transmission path estimator 102. The transmission path estimator 102 includes a tap coefficient generation unit 201, a transmission path response matrix generation unit 202, a delay unit 203, a weighting unit 204, an addition unit 205, and a subtraction unit 206. The delay unit 203 delays the input expected value signal for each processing time unit, and supplies it to the weighting unit 204. The weighting unit 204 multiplies the delay signal supplied from the delay unit 203 by the tap coefficient supplied from the tap coefficient generation unit 201 and supplies the multiplication result as an output to the addition unit 205. The adding unit 205 calculates the sum of the multiplication results of the taps supplied from the weighting unit 204 and supplies the sum to the subtracting unit 206. The subtraction unit 206 calculates an error between the orthogonal demodulated signal and the signal supplied from the addition unit 205 and supplies the error to the tap coefficient generation unit 201. The tap coefficient generation unit 201 calculates a tap coefficient from the error signal supplied from the subtraction unit 206, supplies the tap coefficient to the weighting unit 204 to make a new tap coefficient, and supplies it to the transmission line response matrix generation unit 202. The transmission channel response matrix generation unit 202 generates a transmission channel response matrix based on the tap coefficients supplied from the tap coefficient generation unit 201, and uses the transmission channel response matrix (transmission channel estimation signal) as an output of the transmission channel estimator 102. This is supplied to the replica creator 103 and the replica remover 104. The calculation of the tap coefficient in the transmission path estimator 102 is performed using an RLS (Recursive Last Square) algorithm for each processing time. That is, processing is performed to minimize an absolute value square error between a received signal at a certain time and a replica signal of the received signal at a certain time obtained from an expected value.

  FIG. 3 shows the configuration of the replica remover 104. The replica remover 104 includes a subtractor 301 and a residual removal filter 302. The subtraction unit 301 performs subtraction between the quadrature demodulated signal supplied from the quadrature demodulator 101 and the ICI replica signal supplied from the replica creator 103, and supplies the result to the residual removal filter 302. The residual removal filter 302 suppresses the ICI residual after removing the ICI replica by using the quadrature demodulated signal after removal of the replica and the transmission path estimation signal, performs linear synthesis to perform Fourier transform, and outputs an error as an error. Supply to the corrector 105.

  The error corrector 105 performs error correction processing on the signal supplied from the residual removal filter 302. As one of error correction processes, there is a method of using a log likelihood ratio of a probability that each encoded bit is +1 and a probability that is -1. Maximum a posteriori probability (MAP) decoding is performed using the log likelihood ratio of the residual removal filter output as a priori information, and the log likelihood ratio between the sign bit and the information bit is calculated. The received bit sequence is determined by the log-likelihood ratio of the information bits. If there is an error, the log-likelihood ratio of the code bits is interleaved to generate an expected value, and this expected value is used as a replica generator and transmission path estimator. Supplied to. In this way, iterative equalization and decoding are performed to improve the error rate. The operation of MAP decoding is described in detail in Non-Patent Document 1. As another method, there is an error correction process in which Viterbi decoding and RS decoding are performed after the output of the residual removal filter is deinterleaved, and decoded bits are generated by soft decision. In addition to bit deinterleaving and carrier deinterleaving, deinterleaving includes time deinterleaving with a large processing delay in domestic terrestrial digital broadcasting.

As described above, in order to eliminate inter-carrier interference caused by mobile reception, the digital broadcast receiver once decodes a received signal and performs transmission path estimation based on decoded data of all carriers. At the same time, an ICI component is artificially created and removed from the received signal. By repeating the above operations, it is possible to gradually reduce the influence of ICI and realize good reception performance.
JP 2004-211702 A P. Robertson E. Villebrun P. Hoecher, “A comparison of optimal and sub-optimal MAP decoding algorithms in the log domain”, Proc. of ICC95, 1995. June, p. 1009-1003 Masafumi Ito, Satoshi Suyama, Kazuhiko Fukawa, Hiroshi Suzuki, “OFDM turbo interference cancellation reception for scattered pilot signals to remove ICI due to high-speed fading”, IEICE Technical Report, NS2003-51, RCS2003-74 Kenichiro Hayashi, Tomohiro Kimura, Seiji Kageyama, Yasuo Harada, Satoshi Kishida, Seiji Sakashita, “Examination of Adaptive Equalization Scheme in OFDM Demodulation”, Television Society Technical Report, ITE Technical Report Vol. 20. No. 53, PP. 55

  However, in domestic terrestrial television broadcasting, since error correction processing includes time deinterleave processing (processing delay of a maximum of 408 symbols), it takes more than one symbol, and transmission path estimation, replica removal, and error correction processing are performed N times. When (N ≧ 2) is repeated, a delay of N × 408 symbols occurs after data of a certain symbol is inputted and outputted. Since TV broadcast waves are non-intermittent continuous signals, it is necessary to continuously process and output received signals. In a conventional digital broadcast receiver, data of a certain symbol occupies each block during repeated processing of channel estimation, replica removal, and error correction, and data of the next symbol cannot be processed. As a result, the output data is lost, and the intermittent TV signal cannot be reproduced continuously. As a method of solving this problem, there is a method of providing a storage area after the quadrature demodulator. In this method, while data of one symbol is fed back and repeatedly processed, the data series received from the antenna is stored in the previous stage of the iterative process, that is, after the quadrature demodulator so that no signal is lost, Processing is performed sequentially. In the above method, the storage area for storing the data series increases with the number of repetitions and the symbol length. Furthermore, since the above method includes error correction processing including interleaving / deinterleaving, it causes an increase in cost due to an increase in storage capacity due to processing delay.

  Accordingly, the present invention has been made in order to solve the above-mentioned problems, and suppresses the deterioration in reception performance due to inter-carrier interference caused by mobile reception or the like, and a digital memory that does not require a large storage area for repeated processing. The purpose is to realize a broadcast receiver.

  In order to solve the above problems, a digital broadcast receiver according to the present invention includes an orthogonal demodulator that orthogonally demodulates an input signal to generate an orthogonal demodulated signal, a storage area that stores the orthogonal demodulated signal, and a storage area that stores the orthogonal demodulated signal. A transmission path estimator that estimates transmission path characteristics from the orthogonal demodulated signal and the expected value and generates a transmission path estimation signal; and removes ICI components from the stored orthogonal demodulation signal, transmission path estimation signal, and ICI replica signal A replica remover that generates the demodulated signal, an error corrector that performs error correction by soft decision processing of the demodulated signal from the replica remover, and a hard decision that performs a hard decision process on the demodulated signal from the replica remover A decision switching unit for selecting a hard decision result by the hard decision unit and a soft decision result by the error correction unit, an expected value from the decision change unit, and a transmission path estimator Comprising a replica generator for generating a ICI replica signal sending passage estimation signal based.

  According to the above configuration, when the process of creating the ICI replica signal and removing it from the quadrature demodulated signal is repeated, the signal source that generates the expected value by the determination switch is determined from the soft decision result during the process. By switching to the result, the capacity of the storage area can be reduced.

  As described above, the digital broadcast receiver according to the present invention can suppress deterioration of reception performance mainly due to inter-carrier interference during mobile reception only by mounting a small storage area.

(Embodiment 1)
A digital broadcast receiver according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of Embodiment 1 of a digital broadcast receiver according to the present invention. The configuration shown in FIG. 1 is obtained by adding a storage area 106, a hard decision unit 107, and a decision switching unit 108 to the conventional digital broadcast receiver shown in FIG.

  The hard decision unit 107 generates an expected value of the signal by demapping the demodulated signal from which the ICI replica signal supplied from the replica remover 104 is removed to a mapping point according to the modulation method, and switches the decision as a hard decision expected value signal. To the vessel 108. The decision switcher 108 selects either the hard decision expected value signal supplied from the hard decision device 107 or the soft decision expected value signal supplied from the error corrector 105, and the expected value used for replica creation and transmission path estimation The signals are supplied to the replica generator 103 and the transmission path estimator 102 as signals. The storage area 106 buffers the quadrature demodulated signal supplied from the quadrature demodulator 101 while iterating the process of transmission path estimation, replica creation, and replica removal, and at the same time the above process is completed, the next signal is estimated for each symbol. And supply to the replica 102 and the replica remover 104.

  As shown in FIG. 4, the determination switch 108 includes a counter 401, a repetition count determination unit 402, and a switching unit 403. The counter 401 starts (resets) the operation in response to a symbol switching signal indicating symbol switching that is not appended, and supplies the count value to the repetition count determination unit 402. The repetition number determination unit 402 compares the count value supplied from the counter 401 with a preset threshold value and supplies a repetition number determination signal to the switching unit 403. The switching unit 403 receives the hard decision expected value signal supplied from the hard decision unit 107 based on the repetition number decision signal supplied from the repetition number decision unit 402 or the soft decision expected value signal supplied from the error corrector 105. The selected value is supplied to the replica generator 103 and the transmission path estimator 102 as an expected value signal. Other configurations are the same as those shown in FIG. Description of the same components is omitted.

  In general, an expected value (hard decision expected value signal) by hard decision is less accurate and less reliable than an expected value (soft decision expected value signal) by soft decision. That is, in a state where many unnecessary components are included in the signal, the hard decision expected value signal often causes erroneous determination. Even if a transmission path estimation signal and an ICI replica signal are generated from a hard decision expected value signal containing a large amount of unnecessary components, the transmission path characteristics with low reliability are estimated, and the ICI has a large error from the ICI component that is originally desired to be removed. A replica signal is created. Even if it repeats using such a signal with insufficient accuracy, the accuracy cannot be further improved.

  However, according to Non-Patent Document 2, it has been reported that if ICI removal using a soft decision expected value signal is performed even once, the error rate indicating good or bad reception performance is greatly improved. Therefore, it is considered that ICI removal mainly using the hard decision expected value signal becomes possible by incorporating ICI removal using the soft decision expected value signal into ICI removal using the hard decision expected value signal. Specifically, at the initial movement when the transmission path state and ICI component are not well understood, the transmission path is estimated using the soft decision expected value signal and an ICI replica is created. If the reliability of the transmission path exceeds a certain level, a hard decision expectation is made. Switching is performed to perform transmission path estimation using a value signal and ICI replica creation. Switching between soft decision and hard decision is performed as follows. The number of iterations using the soft decision expected value signal at which the reliability of the transmission line is equal to or higher than a certain level is obtained in advance, and the soft decision is performed for the number of times described above. Next, the processing by the hard decision is repeated a predetermined number of times or until the symbol is switched to improve the accuracy of ICI replica removal.

  The reason why the accuracy of removing the ICI component is increased by the above operation will be described below. In the initial state, the transmission path estimation signal uses a certain value (initial value) that does not depend on the transmission path state, but if the transmission path estimation is updated at least once using the soft decision expected value signal. The transmission path estimation signal can take a value according to the state of the transmission path. The high accuracy of the transmission path estimation signal increases the accuracy of the ICI replica signal created using this. From the above, it is necessary to perform replica removal using the soft decision expected value signal at least once. Even when switching from processing using the soft decision expected value signal to processing using the hard decision expected value signal, it is after creating a highly accurate transmission path estimation signal once using the soft decision expected value signal, The deviation between the actual transmission path and the estimated transmission path does not increase. Therefore, the accuracy of the ICI replica signal created from the transmission path estimation signal can be kept high, and it can be said that no problem occurs even if the process using the hard decision expected value signal is repeated.

  FIG. 5 is a signal timing chart of the digital broadcast receiver of the present invention. This timing chart is shown as a model in which the replica removal process using the hard decision expected value signal is repeated after the replica removal process using the soft decision expected value signal is performed only once. Thereafter, the signal supplied from the storage area 106 is subjected to transmission path estimation, ICI replica creation, and replica removal processing in symbol units.

  The above operation will be described. The orthogonal demodulated signal is accumulated in the storage area 106 over time, and the storage area 106 supplies the data of the next symbol number i + 1 to the transmission path estimator 102 and the replica remover 104 block after the repetition of the symbol number i is completed. To do. Since the orthogonal demodulated signals are sequentially stored in the storage area 106 even during a series of processing of transmission path estimation, ICI replica creation, and replica removal after the storage area 106, in order to store in a certain finite memory, 1 A memory size (M × N) that is N times the number of repetitions of the data amount M that flows while removing the replica from the data for the symbol only once is required.

  At this time, the memory size can be reduced if a series of processes of channel estimation, ICI replica creation, and replica removal are performed within one symbol. Specifically, if a memory size of at least two symbols is secured, a series of processes of transmission path estimation, ICI replica creation, and replica removal can be performed a plurality of times until all data of the next symbol is accumulated. . In the digital broadcast receiver of the present invention, the time required for a series of processing of transmission path estimation, ICI replica creation, and replica removal after switching to the hard decision expected value signal is one symbol time (about 1 ms) of terrestrial digital broadcasting. It can be said that it can be repeated several tens of times. Specifically, when the processing delay required for a series of processing of transmission path estimation, ICI replica creation, and replica removal is about 15 μsec, iterative processing can be performed up to 66 times.

(Embodiment 2)
A digital broadcast receiver according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram of Embodiment 2 of the digital broadcast receiver of the present invention. The configuration shown in FIG. 6 is obtained by adding a storage area 106, a hard decision unit 107, a decision switching unit 108, and a decision carrier selector 601 to the conventional digital broadcast receiver shown in FIG.

  The determination carrier selector 601 determines whether the expected value signal supplied from the determination switch 108 is valid / invalid according to the reliability, and supplies the determination result to the transmission path estimator 102 and the replica creator 103. Other configurations are the same as those shown in FIG. Description of the same components is omitted.

  The operation of the decision carrier selector will be described with reference to FIG. FIG. 7 is a diagram obtained by demapping the QPSK-modulated demodulated signal output from the replica remover 104. When the demodulated signal does not contain interference components such as white noise, multipath interference components, and ICI components generated during mobile reception, the signal points that have been demapped and rearranged on the IQ plane are arranged at the time of modulation. Overlapping points. However, in the demodulated signal including the interference component, the demapped rearrangement point does not overlap the point arranged at the time of modulation, and deviates from the mapping point at the time of modulation. The degree of deviation is determined by the magnitude of the disturbing component, and when the disturbing is large, rearrangement to adjacent mapping points may occur. In such a case, it is rearranged to a point different from the point that should be rearranged, and the reception performance is deteriorated due to erroneous determination. Since the digital broadcast receiver of the present invention is configured to gradually improve the signal quality by feedback control, demodulation using an ICI replica signal or transmission path estimation signal created using an erroneously determined low-reliability signal When the processing is performed, not only the improvement effect of the signal quality is suppressed, but also the deterioration of the signal quality may be caused. Therefore, the quality of the signal is determined, and control is performed while suppressing the influence of an expected value signal indicating a low-quality signal point.

  Specifically, the vicinity of the boundary between adjacent mapping points is regarded as a region that is easily misjudged (difficult region of determination), and the expected value signal of the signal point demapped to the region when the ICI replica signal is created Hold the ICI leakage component at zero. As a result, the carrier expressed by the expected value signal with low reliability can suppress the deterioration of the signal quality due to the generation of an unnecessary ICI component. Further, by using the ICI leakage component from the carrier demapped in the difficult-to-determine area while holding the leakage component of the previous symbol, it is possible to suppress deterioration in signal quality due to generation of an unnecessary ICI component. .

  Note that the width of the difficult-to-determine area does not need to be constant, and may be variable according to the modulation method, the moving speed, and the number of repetitions of feedback processing.

(Embodiment 3)
A digital broadcast receiver according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram of Embodiment 3 of the digital broadcast receiver of the present invention. The configuration shown in FIG. 8 includes a storage area 106, a hard discriminator 107, a judgment switch 108, a judgment carrier selector 601, an equalizer 801, and a transmission path estimator B802 in the conventional digital broadcast receiver shown in FIG. It is added.

  Transmission path estimator B 802 supplies transmission path estimation signal B to equalizer 801 using the demodulated signal supplied from replica remover 104. The equalizer 801 performs equalization processing using a pilot signal using the demodulated signal supplied from the replica remover 104 and the transmission path estimation signal B supplied from the transmission path estimator B 802, and the equalized signal Is supplied to the hard discriminator 107 and the error corrector 105. Other configurations are the same as those shown in FIG. Description of the same components is omitted.

  If the ICI leakage component from the expected value signal determined to be in the difficult determination area by the determination carrier selector 601 is held at 0, the error of the ICI component can be suppressed, but the accuracy of transmission path estimation is improved. It is not possible. Therefore, in order to correct signal quality degradation due to erroneous channel estimation results, ICI components are removed by replica remover 104, and then channel estimation using pilot signals and pilot signals described in Non-Patent Document 3 are used. Equalization processing using the transmission path estimation result is performed. The reliability of channel estimation using signal points in difficult-to-determine areas can be achieved by independent processing such as ICI replica removal processing using all carriers using hard decision expected value signals and equalization processing using channel estimation using pilot signals. It is impossible to cope with signal quality degradation due to deterioration of signal quality and mixing of ICI components. The digital broadcast receiver according to the present embodiment can solve the above two problems at the same time and obtain a great improvement effect on the reception performance during mobile reception. Note that the switching from the hard decision expected value signal to the soft decision expected value signal in the present embodiment may be switched according to the reception state such as C / N and error rate as well as the number of repetitions.

  Note that the difficult-to-determine area set by the decision carrier selector of the digital broadcast receiver described in the second to third embodiments of the present application can be applied not only to the QPSK modulation method but also to the multi-value QAM such as the 16QAM modulation method and the 64QAM modulation method. The modulation scheme can also be set, and the influence from a low-quality signal can be reduced as in QPSK modulation.

  In the digital broadcast receiver described in the first to third embodiments of the present application, replica removal is performed on the time axis, but the orthogonal demodulated signal is converted into a signal on the frequency axis by time-frequency conversion processing such as Fourier transform, An ICI replica signal on the frequency axis may be created and replica removal may be performed on the frequency axis.

  In the digital broadcast receiver described in the first to third embodiments of the present application, the number of repetitions refers to the number of repetitions after synchronization is established after channel selection, and it is not necessary to perform repetition processing before synchronization is established. .

  In the digital broadcast receiver described in the first to third embodiments of the present application, the hard decision expected value signal and the soft decision expectation value signal are switched and used. Since the influence of interference is small and the influence on reception performance is small, there is no need to intentionally switch from the soft decision expected value to the hard decision expected value. Further, when the reception environment changes from a state in which a transmission path fluctuation due to movement changes from a large state to a small state, switching from the hard decision expected value to the soft decision expected value may be performed. Changes in the transmission path due to movement are detected from changes in the time of external speedometers and position information detectors attached to the moving body.

  Furthermore, in the digital broadcast receiver described in Embodiment 2 of the present application, switching from the hard decision expected value signal to the soft decision expected value signal was performed by the number of repetitions, but the reception state such as C / N and BER deteriorated. It may be switched in some cases.

  The digital broadcast receiver described in the first to third embodiments of the present application need not be received by a single antenna, and can be combined with the diversity effect by multi-antenna reception.

  In addition, all the embodiments of the present invention described above can be realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include all or part of the structure.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The digital broadcast receiver of the present invention is useful as a receiver for mobile objects such as digital TV broadcast and digital radio broadcast.

The block diagram which shows the structure of Embodiment 1 of the digital broadcast receiver of this invention. Block diagram showing the internal structure of the transmission path estimator in FIG. The block diagram which showed the internal structure of the replica remover in FIG. The block diagram which showed the internal structure of the determination switching device in FIG. Timing chart of internal signals of digital broadcast receiver of FIG. The block diagram which shows the structure of Embodiment 2 of the digital broadcast receiver of this invention. Mapping diagram showing determination criteria in determination carrier selector in FIG. The block diagram which shows the structure of Embodiment 3 of the digital broadcast receiver of this invention. Block diagram showing the configuration of a conventional digital broadcast receiver

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Quadrature demodulator 102 Transmission path estimator 103 Replica creator 104 Replica remover 105 Error corrector 106 Storage area 107 Hard discriminator 108 Decision switcher 201 Tap coefficient generator 202 Transmission path response matrix generator 203 Delay unit 204 Weighting unit 205 Adder 206 Subtractor 301 Subtractor 302 Residual Removal Filter 401 Counter 402 Repetition Count Judgment Unit 403 Switching Unit 601 Judgment Carrier Selector 801 Equalizer 901 Channel Estimator B

Claims (18)

A quadrature demodulator that quadrature demodulates the signal input from the antenna, a storage area that stores and holds the quadrature demodulated signal, an expected value signal, and an output signal from the storage area to estimate the state of the transmission path and to estimate the transmission path A replica estimator that generates an inter-carrier interference component using the expected value signal and the transmission path estimation signal,
A replica remover that removes an inter-carrier interference component by using an orthogonal demodulated signal output from the storage area, the transmission path estimation signal, and an inter-carrier interference component created in a pseudo manner from the replica creator; and An error corrector that performs soft decision processing on the demodulated signal from which the generated inter-carrier interference component has been removed, a hard decision device that performs hard decision processing on the demodulated signal from which the pseudo-generated inter-carrier interference component has been removed, and the error corrector And a decision switch for selecting an expected value signal from a hard decision expected value signal by the hard decision device, and the hard decision expected value signal when generating an inter-carrier interference component. And a digital broadcast receiver that switches depending on the reception state between the soft decision expected value signal. Whether to select the soft decision expectation value signal or the hard decision expectation value signal in the decision switcher is determined based on the number of repetitions of the feedback process, a series of processes of channel estimation, replica creation, and replica removal. The digital broadcast receiver according to claim 1. The digital broadcast receiver according to claim 1, wherein the size of the storage area is determined based on the number of repetitions of a series of feedback processes of transmission path estimation, replica creation, and replica removal and a processing delay time of the series of feedback processes. A quadrature demodulator that quadrature demodulates the signal input from the antenna, a storage area that stores and holds the quadrature demodulated signal, a transmission path estimation signal by estimating the state of the transmission path from the expected value signal and the quadrature demodulated signal A transmission path estimator, a replica creator that artificially creates an inter-carrier interference component using the expected value signal and the transmission path estimation signal, and an inter-carrier interference component that is artificially created from the orthogonally demodulated signal. A replica remover to be removed, an error corrector for soft-decision processing of the demodulated signal from which the artificially generated inter-carrier interference component is removed, and a hard-decision processing of the demodulated signal from which the artificially generated inter-carrier interference component has been removed A hard decision device, a decision switch for selecting an expected value signal from a soft decision expectation value signal by the error corrector and a hard decision expectation value signal by the hard decision device, A decision carrier selector for selecting data used when creating a replica according to the reliability of the expected value signal; and a source signal for generating an inter-carrier interference component as the hard decision expected value signal and the soft decision expected value signal Digital broadcast receiver that switches according to reception status. 5. The digital broadcast receiver according to claim 4, wherein the determination carrier selector generates a replica of inter-carrier interference by setting a leakage component from a carrier demapped near a boundary between adjacent mapping points to zero. 5. The determination carrier selector generates a replica of inter-carrier interference by holding and using a leakage component of a previous symbol as a leakage component from a carrier demapped near a boundary with an adjacent mapping point. Digital broadcast receiver. The input signal is orthogonally demodulated, the orthogonally demodulated signal is stored and retained, the state of the transmission path is estimated from the expected value signal and the stored output signal, and a transmission path estimation signal is generated, and the expected value signal and the transmission Create an inter-carrier interference component using the path estimation signal,
A demodulated signal from which the inter-carrier interference component is removed by using the orthogonally demodulated signal, the transmission path estimation signal, and the artificially created inter-carrier interference component that have been stored, and the pseudo-generated inter-carrier interference component is removed. Is subjected to soft decision processing, hard decision processing is performed on the demodulated signal from which the inter-carrier interference component created in a pseudo manner is removed, and an expected value signal is selected from the soft decision expected value signal and the hard decision expected value signal, A digital broadcast receiving method for switching the expected value signal when generating an inter-carrier interference component between a hard decision expected value signal and a soft decision expected value signal according to a reception state. 8. The digital broadcast receiving method according to claim 7, wherein the selection of the soft decision expected value signal and the hard decision expectation value signal determines a series of processes of channel estimation, replica creation, and replica removal based on the number of repetitions of feedback processing. . 8. The digital broadcast receiving method according to claim 7, wherein the size of the storage area is determined based on the number of repetitions of a series of feedback processes of transmission path estimation, replica creation, and replica removal and a processing delay time of the series of feedback processes. The input signal is orthogonally demodulated, the orthogonally demodulated signal is stored and held, the state of the transmission path is estimated from the expected value signal and the orthogonally demodulated signal, and a transmission path estimation signal is generated, and the expected value signal and the transmission path An inter-carrier interference component is artificially created using the estimated signal, and the pseudo-inter-carrier interference component is removed from the orthogonally demodulated signal, and the pseudo-generated inter-carrier interference component is removed and the demodulated signal is softened. Apply hard decision processing to the demodulated signal from which the artificially generated inter-carrier interference component has been removed, and select an expected value signal from the soft decision expected value signal by the error corrector and the hard decision expected value signal Then, a decision carrier selection process for selecting data to be used at the time of replica creation is performed according to the reliability of the expected value signal, and the source signal for generating the inter-carrier interference component is Digital broadcast receiving method of switching in accordance with the reception state hard decision expected value signal and said soft decision expected value signal. The digital broadcast receiving method according to claim 10, wherein the determination carrier selection process creates a replica of inter-carrier interference by setting a leakage component from a carrier demapped near a boundary between adjacent mapping points to zero. 11. The determination carrier selection process creates a replica of inter-carrier interference by holding and using a leakage component of a previous symbol as a leakage component from a carrier demapped near a boundary with an adjacent mapping point. The digital broadcast receiving method as described. An orthogonal demodulator that orthogonally demodulates an input signal, a storage area that stores and holds the orthogonally demodulated signal, an expected value signal, and an output signal from the storage area are used to estimate the state of the transmission path and generate a transmission path estimation signal A transmission path estimator; and a replica creator that artificially creates an inter-carrier interference component using the expected value signal and the transmission path estimation signal;
A replica remover that removes an inter-carrier interference component by using an orthogonal demodulated signal output from the storage area, the transmission path estimation signal, and an inter-carrier interference component created in a pseudo manner from the replica creator; and An error corrector that performs soft decision processing on the demodulated signal from which the generated inter-carrier interference component has been removed, a hard decision device that performs hard decision processing on the demodulated signal from which the pseudo-generated inter-carrier interference component has been removed, and the error corrector And a decision switch for selecting an expected value signal from a hard decision expected value signal by the hard decision device, and the hard decision expected value signal when generating an inter-carrier interference component. And a digital broadcast receiving circuit that switches between the soft decision expected value signal according to the reception state. Whether to select the soft decision expectation value signal or the hard decision expectation value signal in the decision switcher is determined based on the number of repetitions of the feedback process, a series of processes of channel estimation, replica creation, and replica removal. The digital broadcast receiving circuit according to claim 13. 14. The digital broadcast receiving circuit according to claim 13, wherein the size of the storage area is determined based on the number of repetitions of a series of feedback processes of channel estimation, replica creation, and replica removal and a processing delay time of the series of feedback processes. An orthogonal demodulator that orthogonally demodulates the input signal, a storage area that stores and holds the orthogonally demodulated signal, and a transmission path that estimates the state of the transmission path from the expected value signal and the orthogonally demodulated signal and generates a transmission path estimation signal An estimator; a replica creator that artificially creates an inter-carrier interference component using the expected value signal and the transmission path estimation signal; and a replica removal that removes the inter-carrier interference component that is artificially created from the orthogonally demodulated signal. An error correction unit that performs soft decision processing on the demodulated signal from which the inter-carrier interference component created in a pseudo manner is removed, and a hard decision that performs hard decision processing on the demodulated signal from which the pseudo inter-carrier interference component is removed. A decision switch for selecting an expected value signal from a soft decision expected value signal by the error corrector and a hard decision expected value signal by the hard decision device, and a signal of the expected value signal A decision carrier selector for selecting data to be used at the time of replica creation according to the characteristics, and depending on the reception state of the hard decision expected value signal and the soft decision expected value signal as the source signal when creating the inter-carrier interference component Digital broadcast receiving circuit to switch. The digital broadcast receiving circuit according to claim 16, wherein the determination carrier selector generates a replica of inter-carrier interference by setting a leakage component from a carrier demapped near a boundary between adjacent mapping points to zero. 17. The determination carrier selector creates a replica of inter-carrier interference by holding and using a leakage component of a previous symbol as a leakage component from a carrier demapped near a boundary with an adjacent mapping point. Digital broadcasting receiver circuit.

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