JP4307308B2 - Digital signal receiver - Google Patents

Description

  The present invention relates to a digital signal receiving apparatus that receives and demodulates a digitally modulated signal. In particular, the present invention relates to a digital signal receiving apparatus having a function of receiving and demodulating a signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) system used in terrestrial digital broadcasting and a diversity combining function for mobile reception or mobile reception.

  In recent years, an OFDM system has been proposed as a modulation system excellent in high-quality transmission and frequency utilization efficiency for a system that transmits video signals or audio signals. The OFDM method is a modulation method in which a large number of subcarriers are set up in a band of one channel, and is resistant to interference by ghosts and multipaths, and can perform good mobile reception. There are four types of OFDM modulation: DQPSK (Differential Quadrature Phase Shift Keying), QPSK, 16QAM (Quadrature Amplitude Modulation), and 64QAM, each of which has a different mapping method. Further, DQPSK is called a differential modulation scheme, and others are called synchronous modulation schemes. In each scheme, the types and arrangement positions of pilot carriers inserted into OFDM symbols are different.

  On the transmission side of the OFDM system, modulation processing such as mapping by various modulation systems, time interleaving, and frequency interleaving is performed on a signal compressed to the MPEG system. On the demodulation side of the OFDM system, demodulation processing is basically performed in the completely reverse procedure to that on the transmission side. That is, as demodulation processing corresponding to the above three types of processing, reverse processing during modulation is performed in the order of frequency deinterleaving, time deinterleaving, and demapping.

  By the way, in mobile reception, transmitted radio waves are affected by fading, so that received power fluctuates greatly and it is difficult to maintain high-quality transmission. As a method for reducing quality deterioration due to fading, there is a technique called diversity reception. This technique receives a plurality of independent signals and appropriately uses them to reduce fading fluctuations and realize high-quality transmission. A means for reducing the fading fluctuation is called a diversity combining method, and there are basically three types: selective combining, equal gain combining, and maximum ratio combining. As an example, the selective combining is a combining method that selects and outputs a signal with the least deterioration among a plurality of received signals, and does not use other signals. The circuit configuration of selective synthesis is practical in that it is simpler than the other two synthesis methods.

In Japanese Patent Laid-Open No. 2003-60605, the reliability of a received signal is obtained based on a so-called AGC (automatic gain control) control amount for correcting the power of the received signal to a desired power value, and the signal is estimated to be a signal with little deterioration. A method for selecting a signal to be processed is disclosed.
JP 2003-60605 A

  In diversity reception, various methods have been proposed as selection conditions, and the received signal is affected in various ways by the characteristics of the propagation path of the received signal, the state of the receiving device, noise conditions, etc. It is preferable to select an appropriate signal in consideration of the above.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a digital signal receiving apparatus capable of selectively combining suitable received signals in diversity system signal reception.

  A digital signal receiving apparatus according to the present invention is a digital signal receiving apparatus that receives a signal transmitted by a digital modulation method including mapping processing, and includes a plurality of branches each receiving a signal independently, and a plurality of branches And a diversity circuit for synthesizing these signals. The diversity circuit acquires a plurality of selection information for selecting a reference point on the constellation that is closest to the received data input from each of a plurality of branches, and compares them to the comparison results of the comparison processing unit and the comparison processing unit. And a selection / synthesis unit that outputs data representing the selected reference point. The comparison processing unit indicates the reliability of reception generated according to the power level of the signal received in each branch when the most frequently selected reference point is not determined by comparing a plurality of selection information. Means for obtaining and comparing first reliability information for each received data. The selection / synthesis unit outputs data representing a reference point according to the most reliable received data based on a comparison result of the plurality of first reliability information when the most frequently selected reference point is not determined as one. To do.

  Preferably, the digital modulation scheme is an orthogonal frequency division multiplexing (OFDM) scheme.

  In particular, the comparison processing unit further includes means for acquiring and comparing the second reliability information detected from the dispersion of the SP for each received data using the SP signal included in the pilot signal inserted in the OFDM symbol. Including. The selection combining unit represents a reference point according to the reception data with the highest reliability based on the comparison result of the second reliability information when the reference point is not fixed to one by comparison of the first reliability information. Output data.

  Preferably, the comparison processing unit further includes means for acquiring and comparing the third reliability information detected from the variance of the deviation between the received data and the reference point on the constellation closest to the received data for each received data. And the selection / combination unit receives the most reliable received data based on the comparison result of the third reliability information when the reference point is not determined to be one by comparison of the first or second reliability information. Output data representing the reference point according to.

  Preferably, the selection combining unit selects and outputs any received data when the most frequently selected reference point is not determined as one.

  Preferably, when the reference point selected most frequently is not determined to be one, the selection / combination unit regards the received data as lost and outputs data indicating that it has been lost.

  Preferably, each branch includes a demodulation unit that measures the power level of the received signal, and an automatic gain control unit that controls the power level of the received signal to a desired power level based on the measurement result of the demodulation unit. . The demodulator has means for generating first reliability information based on a control amount for controlling the automatic gain controller.

  The digital signal receiving apparatus according to the present invention compares the reliability information after the reference point comparison process in the diversity combining process. That is, a plurality of conditions are set and compared, and the combining process is performed based on optimum information. Therefore, it is possible to improve reception performance corresponding to various transmission situations.

  The embodiment can be broadly divided into two types: diversity combining in a circuit configuration employing demapping processing and diversity combining in a circuit configuration employing pre-demapping processing. First, after describing a diversity combining process, a demapping process, a pre-demapping process, and a reliability detection process as premised technologies, these embodiments will be described.

  (Diversity Combining Process) FIG. 1 is a diagram for explaining an example of the diversity combining process when the modulation method is 16QAM. Here, a reference point selection method on a constellation will be described as an example. In the present embodiment, for received data received from a plurality of branches acquired by the diversity method, when the reference points on the constellation closest to the received data match all the received data of each branch Outputs its reference point. If all the reference points do not match, the most frequently selected reference point is output. If the reference point to be selected most often is not determined as one, if each branch has a reliability detection means for detecting the reliability of received data, which will be described later, the reliability representing the reliability added to the data Compare the height of information and select and output the most reliable data. When the reliability information cannot be determined or when the reliability information is not added, any input data is appropriately selected and output.

  For example, in FIG. 1, reference points r0 to r15 on a 16QAM constellation are shown. Here, when the reference point on the constellation is selected based on the received data A0 and B0 from the two branches, the reference point r13 is output as the reference point closest to the data A0 and B0. On the other hand, when the reference points r1 and r15 are cited as reference points close to the data A1 and B1, either one is selected according to the reliability information, or the reference point is output appropriately (randomly) And

  (Demapping Process) FIG. 2 is a diagram showing the reference point on the constellation and the degree of deviation between the reference point. The constellation 200 of FIG. 2 includes first to fourth reference points 202, 204, 206, and 208. In the demapping process, a reference point on the constellation corresponding to each modulation method described above is obtained, then the closest reference point is selected for each received data, and information for specifying the reference point is a maximum of 6 bits. Represented by data. The bit data is expanded to a maximum of 18 bits, 3 bits for each bit. Specifically, depending on the degree of deviation between the received data and the reference point closest to the received data, each bit is changed from the most probable one to “1” to the most probable one to “0”. 101, 100, 011, 010, 001, 000.

  For example, the point 210 is closest to the third reference point 206 among the four reference points, and has an uncertainty of about +2 in the I-axis direction and about -3 in the Q-axis direction. In the demapping process, this point 210 is represented by 18-bit data such as “000,000,000,000,101,011”. Constellation mapping is as shown in FIG. 3 for QPSK, FIG. 4 for 16 QAM, and FIG. 5 for 64 QAM.

  (Pre-demapping process) Regarding the above-described three types of demodulation processes such as frequency deinterleaving, time deinterleaving, and demapping, a method of changing the processing order and performing the demapping process before other processes is disclosed in Japanese Patent Laid-Open No. 2001-320345 Proposed in the Gazette. Performing the demapping process before the time deinterleaving process or before the frequency deinterleaving process is called a pre-demapping process. In the pre-demapping process, unlike normal demapping data, first data indicating a reference point on the constellation corresponding to the modulation method, and second data indicating the magnitude of deviation between the reference point and the data, To generate pre-demapping data. The pre-demapping data needs to be converted into demapping data after time deinterleaving, but the demapping data requires three times the amount of information (maximum 18 bits) as much as the data indicating the reference point (maximum 6 bits). On the other hand, the pre-demapping data has a maximum of 6 bits for the first data and 6 bits for the second data, and can be represented by a maximum of 12 bits in total. For example, the point 210 in FIG. 2 is represented by 12-bit data such as “000010, 110, 011”. Reducing the bit width of data by pre-demapping processing before frequency deinterleaving processing and time deinterleaving processing that require a large amount of memory has the advantage of reducing memory usage.

  (Reliability detection processing) In some cases, the received signal includes data with low reliability due to the influence of multipath, interference, noise, and the like. Therefore, the reception performance is improved by detecting the reliability information and treating the data as lost or correcting the data according to the high reliability. Here, three methods are shown as reliability detection methods.

  The first method is a method of detecting high reliability from the AGC control amount in AGC (automatic gain control) (hereinafter also referred to as the first method). The detection result is output as a signal of about 3 bits that can be reflected in the Viterbi soft decision weighting as shown in FIG.

  The second method is a method of detecting the reliability of each carrier from the dispersion of SP using SP (Scattered Pilot) signal among pilot signals after FFT (Fast Fourier Transform) (hereinafter referred to as the first method). (Also referred to as two systems) (Reference: "Error Control Considering Terrestrial Transmission Line Characteristics", 1998 Annual Conference of the Institute of Image Information and Television Engineers 3-1). However, since the SP is included only in the synchronous modulation unit, the reliability information is detected only by the synchronous modulation unit. The detection result is output as a signal of about 3 bits that can be reflected in the Viterbi soft decision weighting as shown in FIG. The reliability of the pilot signal carrier is also detected in the same manner as the data signal carrier. As shown in FIG. 7, the SP is inserted once in 12 carriers and once in 4 symbols in the synchronous modulation section.

  The third method is a method in which the variance is obtained from the magnitude of the data shift viewed from the reference point on the constellation and the reliability is detected from this variance (hereinafter also referred to as the third method) ( References: “Error Control Considering Terrestrial Transmission Line Characteristics”, 1998 Annual Conference of the Institute of Image Information and Television Engineers 3-2). As in the first method, the detection result is output as a signal of about 3 bits that can be reflected in the Viterbi soft decision weighting as shown in FIG.

  Reliability determination processing and correction processing are performed after demapping, and reliability information is reflected in the demapping data. That is, if the predetermined 1-bit data in the reliability information indicates “data lost”, the demapping data is determined to be lost and 0 is output. If it is not “data loss”, the reliability is judged from the data of about 2 bits of reliability information, and the amount of deviation between the received data and the reference point is corrected in proportion to the low reliability. Output.

(Embodiment 1)
FIG. 8 is a schematic block diagram showing a circuit configuration of the receiving apparatus 100 in the present embodiment that employs demapping processing. The receiving apparatus 100 includes two systems of demodulation processing circuits and a diversity circuit. The first branch 10 includes a first antenna 11, a first tuner 12, a first AGC control unit 22, a first A / D conversion unit 13, a first synchronization unit 14, and a first FFT unit 15. , And a first demodulator 16.

  The first tuner 12 receives the RF signal modulated by the OFDM modulation scheme via the first antenna 11 and down-converts it into a baseband signal. The first AGC control unit 22 sets the received signal to a desired power value according to the control signal based on the power of the signal measured by the demodulator 16 at the subsequent stage. The first A / D converter 13 converts an analog signal into a digital signal, and generates a real axis (I axis) component signal and an imaginary axis (Q axis) component signal using Hilbert transform or the like. To do. The first synchronization unit 14 performs synchronization processing, and the first FFT unit 15 performs fast Fourier transform to convert time axis data into frequency axis data. The first demodulator 16 performs various demodulation processes such as differential demodulation corresponding to the modulation method.

  The first branch 10 further includes a first reliability detection unit (first method) 23, a first reference point calculation unit 17, and a first reference point specification unit 18. The first reliability detection unit (first method) 23 receives AGC control amounts (to be described later) from the demodulation unit 16 to detect and output reliability information.

  The first reference point calculation unit 17 obtains a demapping reference point corresponding to each modulation method. This can be obtained by level-converting the average value of the pilot signal and multiplying by a coefficient for calculating a reference point determined for each modulation method as shown in FIG. Since the pilot signal is 4/3 times that of the data signal on the modulation side, 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 point 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 reference point for demapping is obtained by a constant multiple of the pilot average value.

  The first reference point specifying unit 18 selects, for each carrier, which reference point on the constellation of each modulation method is closest to the input frequency axis data. Selection information for specifying the selected reference point is output together with the input frequency axis data.

  The second branch 30 includes a second antenna 31, a second tuner 32, a second AGC control unit 42, a second A / D conversion unit 33, a second synchronization unit 34, and a second FFT unit 35. , A second demodulator 36, a second reliability detector (first method) 43, a second reference point calculator 37, and a second reference point specifying unit 38. These have the same functions as the blocks of the same name included in the first branch 10.

  In the demodulation process of the demodulator 16 of the receiving apparatus 100 according to the first embodiment, the power level of the input signal is detected together with various demodulation processes such as differential demodulation corresponding to the modulation method, and the input signal is detected based on the detection result. In order to obtain a desired power gain, a control amount to be fed back to the AGC control unit 22 is calculated and output. The reliability detection unit (first method) 23 outputs reliability information based on the AGC control amount that is the control amount. Specifically, the high reliability is detected by comparison with a predetermined threshold value based on the magnitude of the control amount, and the reliability information as described in FIG. Are added to each frequency axis data and output.

  Diversity circuit 50 includes a comparison processing unit 51 and a selection / combination unit 52. The comparison processing unit 51 acquires selection information for specifying the reference point on the constellation closest to the frequency axis data from each of the first and second branches 10 and 30 and compares them. When the closest reference points match, the selection / combination unit 52 outputs data representing the reference points. When the nearest reference points are different, the selection / combination unit 52 compares the reliability information based on the AGC control amount, and selects and outputs the frequency axis data with higher reliability. If there is no single output in either the reference point comparison or the reliability comparison, the selective combining unit 52 regards any received data as lost and outputs data indicating that fact. As a result, data whose reliability is unknown is deleted, and the reliability of the entire data is relatively improved. Alternatively, frequency axis data is selected at random and output.

  The data output from the selection / synthesis unit 52 is subjected to frequency deinterleaving processing by the frequency deinterleaving unit 60, time deinterleaving processing by the time deinterleaving unit 61, and then demapping processing by the demapping unit 62. The reliability determination unit 63 performs a data loss determination process based on reliability information and a correction process for the likelihood of demapping for the data demapped by the demapping unit 62. The data after the correction processing is bit deinterleaved by the bit deinterleaver 65. Further, after bit deinterleaving processing is performed by the bit deinterleaving unit 65, soft decision Viterbi decoding processing is performed by the Viterbi decoding unit 66 and output as decoded data.

  With the above configuration, high-quality transmission, that is, signal reception can be maintained even in various transmission situations in diversity combining processing. In particular, when AGC control is performed for each branch, there is a possibility that noise power of an antenna with low reception power may be excessively amplified, and there is a high possibility that the error rate characteristic is deteriorated. With the configuration in which reliability information is generated and compared based on this, inappropriate received data can be easily removed and highly reliable received data can be selected. Further, by using the reliability information, it is possible to reduce processing in later soft decision Viterbi decoding.

(Modification 1 of Embodiment 1)
In the first modification of the first embodiment, a case where reliability information detection processing by SP is also performed will be described.

  FIG. 10 is a schematic block diagram showing a configuration of receiving apparatus 110 according to the first modification of the first embodiment of the present invention.

  Referring to FIG. 10, the difference from receiving apparatus 100 in FIG. 8 is that first and second branches 10 and 30 are replaced with first and second branches 10a and 30a, respectively.

  The first and second branches 10a and 30a are different from the first and second branches 10 and 30 in that reliability detection units (second schemes) 24 and 44 are further provided, respectively. Since the other points are the same as those described in the first embodiment, detailed description thereof will not be repeated.

  The reliability detectors (second scheme) 24 and 44 detect the reliability of each carrier from the dispersion of the SP using an SP (Scattered Pilot) signal among the pilot signals, and based on the detection result, for example, FIG. 6 is generated, added with the information, and output to the diversity circuit 50.

  Diversity circuit 50 receives frequency axis data to which reliability information and selection information are added from first and second branches 10a and 30a, respectively. As a method of selective synthesis, first, a reference point closest to the frequency axis data is compared, and if they match, data representing this reference point is output. If they are different, the reliability information is compared, and the frequency axis data with higher reliability is selected and output. Here, for example, as described in the first embodiment, when the reliability information based on the control amount of the AGC is compared and the output is not determined by this reliability comparison, next, It is determined whether the output is determined to be one by comparing the reliability information based on the SP using the SP signal, and if the output is not determined to be one by either the reference point comparison or the reliability comparison, the selection / synthesis unit 52 is either The received data is regarded as lost, and data indicating that is output. As a result, data whose reliability is unknown is deleted, and the reliability of the entire data is relatively improved. Alternatively, frequency axis data is selected at random and output. Other processes are the same as those in the first embodiment.

  Therefore, in the combining process, a plurality of conditions are set and compared, and the combining process is performed based on the optimum information, so that the reception performance can be further improved.

(Modification 2 of Embodiment 1)
In the second modification of the first embodiment, there is also a reliability information detection process for obtaining a variance from the magnitude of the data shift viewed from the reference point on the constellation and detecting a higher reliability than this variance. The case where it performs is demonstrated.

  FIG. 11 is a schematic block diagram showing a configuration of receiving apparatus 120 according to the second modification of the first embodiment of the present invention.

  Referring to FIG. 11, the difference from receiving device 110 in FIG. 10 is that first and second branches 10a and 30a are replaced with first and second branches 10b and 30b, respectively.

  The first and second branches 10b and 30b are different from the first and second branches 10a and 30a in that reliability detection units (third system) 25 and 45 are further provided, respectively. Since the other points are the same as those described in the first modification of the first embodiment, detailed description thereof will not be repeated.

  The reliability detection units (third method) 25 and 45 use the reference point closest to the data obtained by the reference point calculation unit and the reference point specifying unit and the magnitude of the data shift, and the deviation between I and Q is determined. The variance of the deviation is obtained from the magnitude, and the reliability is detected from the magnitude of the variance. Based on the detection result, for example, the reliability information shown in FIG. 6 is generated, added with the information, and output to the diversity circuit 50.

  FIG. 12 is a diagram schematically illustrating processing in the comparison processing unit 51 and the selection combining unit 52 of the diversity circuit 50.

  The process in FIG. 12 will be described using the flowchart in FIG.

  Frequency axis data to which reliability information and selection information are added is input to the diversity circuit 50 from the first and second branches 10b and 30b, respectively, and synthesis processing is started (step S1). First, the reference point closest to the frequency axis data is compared (step S2). If they match, the process proceeds to the next step S3, and data representing this reference point is output (step S4). Then, the synthesis process is terminated (step S12). On the other hand, if the reference points do not match in step S2, the process proceeds to step S5 and the reliability information is compared. Specifically, the reliability information based on the AGC control amount is compared. Here, in the reliability comparison, when it is determined that the output is limited to one, that is, processing is possible, the process proceeds to step S6, and the process proceeds to step S4 described above based on the reliability information based on the AGC control amount. Output selected data. On the other hand, if the reliability information based on the control amount of the AGC is compared in step S5 and the output is not determined by this reliability comparison, the reliability information based on the SP is then used using the SP signal. It is determined whether the output is determined to be one by the comparison (step S7). Here, in the reliability comparison, when it is determined that the output is determined to be one, that is, processing is possible, the process proceeds to step S8, and the process proceeds to step S4 described above based on the reliability information based on the SP and is selected. Output data. In step S7, if the output of the reliability information based on the SP is not determined to be one, then the output is determined to be one by comparing the reliability information based on the variance of the data shift. Whether or not (step S9). Here, in the reliability comparison, when it is determined that the output is limited to one, that is, the processing is possible, the process proceeds to step S10, and the above-described reliability information based on the variance of the data deviation is used. In step S4, the selected data is output.

  In step S9, if the output is not determined to be one in either the reference point comparison or the reliability comparison, the selective combining unit 52 regards any received data as lost and outputs data indicating that fact. As a result, data whose reliability is unknown is deleted, and the reliability of the entire data is relatively improved. Alternatively, frequency axis data is selected at random and output (step S11).

  In the reliability comparison, the order of the comparison of reliability information based on the AGC control amount, the comparison of reliability information based on SP, and the comparison of reliability information based on the magnitude of variance of data shift is not limited to this. Of course, the order can be changed.

(Embodiment 2)
FIG. 14 is a schematic block diagram showing a configuration of receiving apparatus 300 according to Embodiment 2 of the present invention. The difference from Embodiment 1 is that the reference point on the constellation is obtained by the pre-demapping process.

  Referring to FIG. 14, receiving apparatus 300 according to the second embodiment of the present invention is different in that first and second branches 10 and 30 are replaced with first and second branches 10 # and 30 #. The first and second branches 10 # and 30 # are different from the first and second branches 10 and 30 in that the first and second branches 10 # and 30 # are replaced with the first and second branches 10 # and 30 #, instead of the reference point calculating units 17 and 37 and the reference point specifying units 18 and 38. The difference is that second pre-demapping units 19 and 39 and first and second reliability determination units 21 and 41 are provided. Since the other points are the same as those of the first and second branches 10 and 30 described in the first embodiment, detailed description thereof will not be repeated. The first and second pre-demapping units 19 and 39 first select a reference point closest to the frequency axis data. The selection information for specifying the reference point is represented by bit data having a maximum of 6 bits. This is the first pre-demapping data. Next, as viewed from the selected reference point, each axis meter with 1-bit direction and 2-bit degree of displacement indicates how much the data is displaced in the positive or negative direction in each of the I-axis and Q-axis directions. 3 bits, I and Q are combined to represent 6 bits of bit data. The degree of deviation is assumed to be performed in the same unit (four steps) as the degree of deviation during demapping. This is the second pre-demapping data. Combining the first data and the second data, the output of the pre-demapping is represented by bit data of a maximum of 12 bits.

  The first and second reliability determination units 21 and 41 are the reliability information described above, specifically, the reliability information generated by the reliability detection units (first method) 23 and 43 based on the AGC control amount. Based on the determination of disappearance, correction of the pre-demapping data is proportional to the low reliability.

  Two systems of pre-demapping data are input to the diversity circuit 50. As a method of selective synthesis, a reference point closest to the frequency axis data specified in the first data of the pre-demapping data is compared, and if they match, pre-demapping data indicating the reference point is selected and output. If they do not match, the selection combining unit 52 compares the reliability information based on the AGC control amount, and selects and outputs pre-demapping data indicating the reference point with the higher reliability. If there is no single output in either the reference point comparison or the reliability comparison, the selective combining unit 52 regards any received data as lost and outputs data indicating that fact. As a result, data whose reliability is unknown is deleted, and the reliability of the entire data is relatively improved. Alternatively, any pre-demapping data is selected at random and output.

  The bit conversion unit 64 converts time-deinterleaved data input in a maximum 12-bit pre-demapping data format into data of an 18-bit demapping data format. The converted data is subjected to bit deinterleaving processing by the bit deinterleaving unit 65. Other processes are the same as those in the first embodiment.

  With the above configuration, the same effect as described in the first embodiment can be obtained.

(Modification 1 of Embodiment 2)
In Modification 1 of Embodiment 2 of the present invention, a case where reliability information is further detected by SP will be described. The reliability information detection process by the SP is the same as that of the first modification of the first embodiment.

  FIG. 15 is a schematic block diagram showing a circuit configuration of receiving apparatus 310 according to the first modification of the second embodiment of the present invention.

  Referring to FIG. 15, receiving apparatus 310 of the first modification of the second embodiment of the present invention includes first and second branches 10 # and 30 # as compared with receiving apparatus 300 of the second embodiment. The difference is that the first and second branches 10 # a and 30 # a are replaced. The first and second branches 10 # a and 30 # a further include reliability detectors (second scheme) 24 and 44, respectively. Since the other points are the same, detailed description thereof will not be repeated.

  As described above, the reliability detectors (second scheme) 24 and 44 generate SP reliability information, add the reliability information, and output the reliability information.

  The first and second pre-demapping units 19 and 39 perform the above-described pre-demapping process and generate pre-demapping data. The first and second reliability determination units 21 and 41 perform erasure determination based on reliability information based on the AGC control amount or SP, and the reliability is low with respect to the magnitude of the pre-demapping data shift. A correction proportional to the height is applied.

  Two types of pre-demapping data after reliability determination and correction to which reliability information is added are input to the diversity circuit 50. As a selective combining method, first, the reference point closest to the frequency axis data specified in the first data of the pre-demapping data is compared, and if they match, the pre-demapping data of this reference point is selected and output. If they do not match, the reliability information is compared, and the input pre-demapping data with higher reliability is selected and output.

  The comparison of the reliability information is the same as that described in the first modification of the first embodiment. If there is no single output in either the reference point comparison or the reliability comparison, one of the input pre-demapping data is selected and output. Alternatively, the received data is regarded as lost, and data indicating that is output. As a result, data whose reliability is unknown is erased to improve the reliability of the entire data. Subsequent processing is the same as that described in the second embodiment.

(Modification 2 of Embodiment 2)
In the second modification of the second embodiment of the present invention, a case will be described in which the reliability information is detected from the variance of the pre-demapping shift. The method for detecting the reliability information by the dispersion of the pre-demapping shift is the same as that described in the second modification of the first embodiment.

  FIG. 16 is a schematic block diagram showing a circuit configuration of receiving apparatus 320 according to the second modification of the second embodiment of the present invention.

  Referring to FIG. 16, receiving apparatus 320 according to the second modification of the second embodiment of the present invention is compared with receiving apparatus 310 according to the second embodiment in the first and second branches 10 # a and 30 #. The difference is that a is replaced with the first and second branches 10 # b and 30 # b, respectively. The first and second branches 10 # b and 30 # b further include reliability detection units (third method) 25 and 45, respectively. Since the other points are the same, detailed description thereof will not be repeated. The first and second pre-demapping units 19 and 39 perform the above-described pre-demapping process and generate pre-demapping data. The reliability detection units (third method) 25 and 45 use the magnitude of the deviation between the reference point closest to the data obtained by pre-demapping and the data, and the variance of the deviation from the magnitude of the deviation of I and Q. The reliability is detected from the size of the variance, and the reliability information is added and output.

  The first and second reliability determination units 21 and 41 perform erasure determination based on reliability information based on the AGC control amount, SP, or the variance of the deviation, and then the magnitude of the deviation of the pre-demapping data. Therefore, a correction proportional to the low reliability is applied.

  The diversity circuit 50 compares the reference point closest to the frequency axis data specified in the first data of the pre-demapping data, and selects and outputs the pre-demapping data of the reference point if they match. If they do not match, the reliability information is compared, and the input pre-demapping data with higher reliability is selected and output.

  The comparison of reliability information is the same as that described in the second modification of the first embodiment. If there is no single output in either the reference point comparison or the reliability comparison, one of the input pre-demapping data is selected and output. Alternatively, the received data is regarded as lost, and data indicating that is output. As a result, data whose reliability is unknown is erased to improve the reliability of the entire data. Subsequent processing is the same as that described in the second embodiment.

  In each of the above embodiments, data reception by the OFDM method has been described as an example. However, as a modification, the present invention can be used for a transmission method by another modulation method capable of displaying a constellation.

  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 figure explaining the example of this diversity synthetic | combination process when a modulation system is 16QAM. It is a figure which shows the deviation | shift degree of the reference point on a constellation, and the reference point. It is a figure explaining the mapping of the constellation in the case of QPSK. It is a figure explaining the mapping of the constellation in the case of 64QAM. It is a figure explaining the mapping of the constellation in the case of 64QAM. It is a figure explaining the signal of about 3 bits which can be reflected in the weight of Viterbi soft decision. It is a figure explaining insertion of SP signal. It is a schematic block diagram which shows the circuit structure of the receiver 100 in this embodiment which employ | adopted the demapping process. It is a figure explaining the coefficient for the reference point calculation defined for every modulation system. It is a schematic block diagram which shows the structure of the receiver 110 according to the modification 1 of Embodiment 1 of this invention. It is a schematic block diagram which shows the structure of the receiver 120 according to the modification 2 of Embodiment 1 of this invention. It is a figure which illustrates roughly the process in the comparison process part 51 and the selection synthetic | combination part 52 of the diversity circuit 50. FIG. It is a flowchart figure explaining the process in FIG. It is a schematic block diagram which shows the structure of the receiver 300 according to Embodiment 2 of this invention. It is a schematic block diagram which shows the circuit structure of the receiver 310 according to the modification 1 of Embodiment 2 of this invention. It is a schematic block diagram which shows the circuit structure of the receiver 320 according to the modification 2 of Embodiment 2 of this invention.

Explanation of symbols

  10, 10a, 10b, 10 #, 10 # a, 10 # b, 30, 30a, 30b, 30 #, 30 # a, 30 # b branch, 11, 31 antenna, 12, 32 tuner, 13, 33 A / D conversion unit, 14, 34 synchronization unit, 15, 35 FFT unit, 16, 36 demodulation unit, 17, 37 reference point calculation unit, 18, 38 reference point identification unit, 19, 39 pre-demapping unit, 21, 41, 63 Reliability determination unit, 22, 42 AGC control unit, 23-25, 43-45 Reliability detection unit, 50 diversity circuit, 51 comparison processing unit, 52 selection synthesis unit, 60 frequency interleaving unit, 61 time deinterleaving unit, 62 Demapping unit, 64-bit conversion unit, 65-bit deinterleaving unit, 66 Viterbi decoding unit, 100, 110, 120, 300, 310, 320 Communication device.

Claims (5)

A digital signal receiving apparatus for receiving a signal transmitted by a digital modulation method including mapping processing,
A plurality of branches each receiving a signal independently; and a diversity circuit for combining signals from the plurality of branches,
The plurality of branches includes an AGC control unit that controls the power level of the received signal to a desired value, and first reliability detection that outputs first reliability information based on an AGC control amount of the AGC control unit. Part
The diversity circuit includes a comparison processing unit that acquires a plurality of selection information for selecting a reference point on the constellation that is closest to the received data input from each of the plurality of branches, and compares each of the comparison processing unit and the comparison processing unit A selection combining unit that outputs data representing the selected reference point based on the comparison result;
The selection / composition unit, when the reference point most frequently selected by the comparison processing unit is not fixed to one, the reference point according to the most reliable received data based on the first reliability information of each branch A digital signal receiving device that outputs data representing . Each branch includes a reference point calculation unit and a reference point specifying unit,
The reference point calculation unit calculates a demapping reference point, the reference point specifying unit specifies the calculated demapping reference point that is closest to the input frequency axis data, and determines the specified reference point. The digital signal receiving apparatus according to claim 1, wherein the first reliability information is added to the information to be expressed and output to the diversity circuit. Each branch includes a pre-demapping unit and a reliability determination unit,
The pre-demapping unit selects a reference point closest to the frequency axis data,
The reliability determination unit performs erasure determination based on the first reliability information, performs a correction proportional to the low reliability with respect to the magnitude of the deviation from the reference point, and adds the frequency axis data to the frequency axis data. 2. The digital signal receiving apparatus according to claim 1, wherein information indicating a degree of deviation from the reference point is added to information indicating the closest reference point and output to the diversity circuit. The digital modulation scheme is an orthogonal frequency division multiplexing (OFDM) scheme,
The comparison processing unit further includes means for acquiring and comparing the second reliability information detected from the dispersion of the SP for each received data using the SP signal included in the pilot signal inserted in the OFDM symbol. ,

The selection / combination unit, based on the comparison result of the first reliability information or the comparison result of the second reliability information, when the reference processing unit most frequently selected is not determined to be one. The digital signal receiving apparatus according to any one of claims 1 to 3, wherein data representing a reference point according to reception data having the highest reliability is output. The comparison processing unit further includes means for acquiring and comparing, for each received data, third reliability information detected from a variance of a deviation between the received data and a reference point on the constellation closest to the received data. ,
The selection / combination unit, when the reference point most frequently selected by the comparison processing unit is not determined as one, includes the first reliability information, the second reliability information, or the third reliability information. The digital signal receiving apparatus according to claim 4, wherein data representing a reference point according to the most reliable received data is output based on the comparison result.

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