Receiving device

Abstract

To provide a receiving device capable of suppressing a rising of a BER of the receiving device without requiring likelihood information.SOLUTION: A receiving device comprises: a calculation part that calculates likelihood information of a data symbol contained in an error correction block by using the error correction block as an object; a decoding part that executes an error correction decoding of the data symbol contained in the error correction block on the basis of the likelihood information of the data symbol calculated; and a control part that executes a specific control for degenerating the likelihood information of the data symbol calculated when a reception state of the error correction block is in a specific state. The control part determines whether or not the receiving state of the error correction block is in the specific state on the basis of a fact that at least the specific condition defined by the number of repetition times of a calculation of an estimation value of the data symbol contained in the error correction block is satisfied.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a receiving apparatus.

Background Art

[0002] In recent years, as a high-performance error correction code, a Low-Density Parity-check Code (LDPC code) is known (Non-Patent Document 1).

[0003] Examples of broadcast systems using LDPC codes include an advanced wideband satellite digital broadcast system, DVB-S2, DVB-T2, DVB-NGH, etc. In Japan as well, LDPC codes are adopted in the advanced terrestrial broadcast system.

[0004] By the way, a system in which a relay device is provided between a transmitting device and a receiving device is known. The transmitting device may be referred to as a master station or a parent station. The receiving device may be referred to as a slave station or a child station. The relay device executes processing for equalizing the distortion of multipaths included in the radio wave received from the transmitting device (hereinafter, equalization processing), processing for determining the symbol received from the transmitting device (hereinafter, symbol determination processing), processing for remodulating the symbol after symbol determination (hereinafter, remodulation processing), and the like. According to such a system, deterioration of the quality of the received signal in the receiving device can be reduced.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when the symbol determination process of the relay device is a hard determination process, the likelihood information between the transmission device and the relay device is not propagated to the receiving device. Therefore, if the symbol transmitted by the transmission device is determined to be an incorrect symbol in the symbol determination process of the relay device, when the propagation environment between the relay device and the receiving device (for example, the C / N ratio (Carrier to Noise Ratio)) is good, it is determined that the likelihood of the incorrect symbol is high at the receiving device, and the BER ( Bit Error Rate) may increase at the receiving device.

[0007] On the other hand, when the symbol determination process of the relay device is a soft determination process, the likelihood information between the transmission device and the relay device can be propagated to the receiving device, but it is necessary to transmit the likelihood information from the relay device to the receiving device, which causes complication of the relay device and an increase in signaling load.

[0008] Therefore, an object of the present invention is to provide a receiving device that can suppress an increase in the BER of the receiving device without requiring likelihood information.

Means for Solving the Problems

[0009] A receiving device according to an aspect of the disclosure includes a calculation unit that calculates the likelihood of data symbols included in the error correction block for the error correction block, a decoding unit that performs error correction decoding of the data symbols included in the error correction block based on the calculated likelihood of the data symbols, and a control unit that performs specific control to degenerate the calculated likelihood of the data symbols when the reception state of the error correction block is a specific state. The decoding unit repeatedly calculates an estimated value of the data symbols included in the error correction block until the errors of the data symbols included in the error correction block are corrected, with the maximum number of repetitions as an upper limit. The control unit determines whether the reception state of the error correction block is a specific state based on whether a specific condition defined at least by the number of repetitions of the calculation of the estimated value of the data symbols included in the error correction block is satisfied.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a receiving apparatus that can suppress an increase in the BER of the receiving apparatus without requiring likelihood information.

Brief Description of the Drawings

[0011]

Figure 1

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Embodiments for Carrying Out the Invention

[0012] Next, embodiments of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the ratios of the respective dimensions are different from the actual ones.

[0013] Therefore, specific dimensions and the like should be determined with reference to the following description. Of course, the drawings also include portions where the dimensional relationships and ratios are different from each other.

[0014] [Summary of Disclosure] As a result of intensive studies, the inventors have found that there may be a case (specific state) where the number of repetitions reaches the maximum number of repetitions even though the C / N ratio (Carrier to Noise Ratio) of the received signal is good. Furthermore, the inventors have found that in a specific state, the BER (Block Error Rate) of the error correction block improves rather when the C / N ratio of the received signal is artificially deteriorated. Based on such new findings, the receiving apparatus according to the summary of the disclosure has the following configuration.

[0015] The receiving device according to the summary of the disclosure includes: a calculation unit that calculates the likelihood of data symbols included in the error correction block for the error correction block; a decoding unit that performs error correction decoding of the data symbols included in the error correction block based on the calculated likelihood of the data symbols; and a control unit that performs specific control to degenerate the calculated likelihood of the data symbols when the reception state of the error correction block is a specific state. The decoding unit repeatedly calculates an estimated value of the data symbols included in the error correction block until the errors of the data symbols included in the error correction block are corrected, with the maximum number of repetitions as the upper limit. The control unit determines whether the reception state of the error correction block is a specific state based on whether a specific condition defined at least by the number of repetitions of the calculation of the estimated value of the data symbols included in the error correction block is satisfied.

[0016] In the summary of the disclosure, the receiving device determines whether the reception state of the error correction block is a specific state based on whether a specific condition defined at least by the number of repetitions of the calculation of the estimated value of the data symbols included in the error correction block is satisfied. According to such a configuration, it is possible to appropriately determine whether the reception state of the error correction block is a specific state.

[0017] In the summary of the disclosure, the receiving device performs specific control to degenerate the calculated likelihood of the data symbols when the reception state of the error correction block is a specific state. According to such a configuration, it is possible to improve the BER in a specific state.

[0018] [Embodiment] (Digital Wireless Transmission System) Hereinafter, a digital wireless transmission system according to an embodiment will be described. FIG. 1 is a diagram showing a digital wireless transmission system 10 according to an embodiment. As shown in FIG. 1, the digital wireless transmission system includes a transmission device 100, a relay device 200, and a receiving device 300.

[0019] The transmission device 100 executes processes such as a process of generating an error correction block (block generation process) and a process of applying orthogonal modulation to a frame including the error correction block (orthogonal modulation process).

[0020] The relay device 200 relays the signal (frame) received from the transmission device 100 to the reception device 300. The relay device 200 executes processes such as a process of equalizing the distortion of multipath included in the radio wave received from the transmission device 100 (equalization process), a process of determining the symbol received from the transmission device 100 (symbol determination process), and a process of remodulating the symbol after symbol determination (remodulation process).

[0021] In the embodiment, the symbol determination process of the relay device 200 is a hard determination process. That is, the likelihood information between the transmission device 100 and the relay device 200 is not propagated to the reception device 300.

[0022] The reception device 200 executes processes such as a process of applying orthogonal demodulation to the frame received from the relay device 200 (orthogonal demodulation process) and a process of decoding the error correction block (decoding process). Details of the reception device 200 will be described later.

[0023] Here, in the digital wireless transmission system 10, an LDPC (Low-Density Parity-check Code) code may be used as the error correction code. Hereinafter, the error correction block is referred to as an LDPC block. In the digital wireless transmission system 10, as the MCS (Modulation and Coding Scheme), 64QAM, 256QAM, 1024QAM, 4096QAM, etc. may be used. As the QAM constellation, a uniform constellation in which signal points are uniformly arranged on the IQ plane may be used, or a non-uniform constellation (NUC) in which signal points are non-uniformly arranged on the IQ plane may be used.

[0024] (Reception device) Hereinafter, the receiving apparatus according to the embodiment will be described. As shown in FIG. 2, the receiving apparatus 300 includes a variable attenuator 301, an FFT processing unit 303, an equalization processing unit 305, a noise estimation unit 307, an LLR calculation unit 309, an LDPC decoding unit 311, and a control unit 313.

[0025] The variable attenuator 301 reduces (attenuates) the power of the received signal. The variable attenuator 301 operates according to a command from the control unit 313.

[0026] The FFT processing unit 303 applies FFT (Fast Fourier Transform) processing to the received signal (a signal in the time domain) and converts the signal in the time domain into a signal in the frequency domain.

[0027] The equalization processing unit 305 executes an equalization process for equalizing the signal in the frequency domain. For example, the equalization processing unit 305 may execute an equalization process based on a channel estimation result and noise (power). In the equalization process, the equalization weight for equalizing the signal in the frequency domain may be calculated using the minimum mean squared error (MMSE) method. The equalization process may include a maximum ratio combining process.

[0028] The noise estimation unit 307 estimates the noise of the received signal. Specifically, the noise estimation unit 307 estimates the noise based on known symbols included in the received signal. The known symbols are symbols known to the receiving apparatus 300 and may be any symbols used for noise estimation. The known symbols may include pilot symbols.

[0029] The LLR calculation unit 309 constitutes a calculation unit that calculates the likelihood of data symbols included in an LDPC block for the LDPC block. The likelihood may be a log-likelihood ratio (hereinafter, LLR (Log-Likelihood Ratio)). The LLR calculated by the LLR calculation unit 309 may be referred to as an initial LLR or a priori LLR. The LLR may be calculated based on the following options.

[0030]

Number

[0031] Note that Option 1 is the option to calculate the LLR precisely, and Option 2 is the option to calculate the LLR approximately.

[0032] The LDPC decoder 311 constitutes a decoder that performs error correction decoding of data symbols included in the LDPC block based on the initial LLR. The LDPC decoder 311 repeats the calculation of the estimated values of the data symbols (bits included therein) included in the LDPC block until the errors of the data symbols (bits included therein) included in the LDPC block are corrected, with the maximum number of repetitions as the upper limit.

[0033] Specifically, the LDPC decoder 311 updates the logarithm ratio from the variable node to the check node based on the initial LLR, and updates the logarithm ratio from the check node to the variable node based on the updated logarithm ratio, and calculates a temporary estimated word based on these probability values. Subsequently, the LDPC decoder 311 performs a parity check on the temporary estimated word to determine whether the errors of the data symbols included in the LDPC block have been corrected. The LDPC decoder 311 repeats the calculation of the temporary estimated word based on the probability values until the errors of the data symbols are corrected, with the maximum number of repetitions as the upper limit. Likelihood ratio, and calculates a temporary estimated word based on these probability values. Subsequently, the LDPC decoder 311 performs a parity check on the temporary estimated word to determine whether the errors of the data symbols included in the LDPC block have been corrected. The LDPC decoder 311 repeats the calculation of the temporary estimated word based on the probability values until the errors of the data symbols are corrected, with the maximum number of repetitions as the upper limit. Likelihood ratio, and calculates a temporary estimated word based on these probability values. Subsequently, the LDPC decoder 311 performs a parity check on the temporary estimated word to determine whether the errors of the data symbols included in the LDPC block have been corrected. The LDPC decoder 311 repeats the calculation of the temporary estimated word based on the probability values until the errors of the data symbols are corrected, with the maximum number of repetitions as the upper limit. Likelihood ratio, and calculates a temporary estimated word based on these probability values. Subsequently, the LDPC decoder 311 performs a parity check on the temporary estimated word to determine whether the errors of the data symbols included in the LDPC block have been corrected. The LDPC decoder 311 repeats the calculation of the temporary estimated word based on the probability values until the errors of the data symbols are corrected, with the maximum number of repetitions as the upper limit.

[0034] The control unit 313 constitutes a control unit that performs specific control to degenerate the initial LLR when the reception state of the LDPC block is a specific state. The control unit 313 determines whether the reception state of the LDPC is a specific state based on whether at least a specific condition defined by the number of repetitions of the calculation of the estimated values of the data symbols included in the LDPC block is satisfied.

[0035] Specifically, as shown in FIG. 3, the control unit 313 includes a storage unit 331, a determination unit 333, and a generation unit 335. The storage unit 331 stores the number of repetitions of the calculations executed by the LDPC decoder 311 for each LDPC block. The determination unit 333 determines whether the reception state of an LDPC block is a specific state based on whether a specific condition is satisfied. The generation unit 335 generates a control signal for executing specific control to degenerate the initial LLR.

[0036] In the embodiment, the specific control is control for reducing the power of the received signal. That is, the generation unit 335 generates a control signal for reducing the power of the received signal and inputs the generated control signal to the variable attenuator 301. Details of the specific state and the specific condition will be described later.

[0037] (Specific state) Hereinafter, the specific state according to the embodiment will be described. Here, a case where a relay device 200 is interposed between the transmission device 100 and the reception device 300 will be described. The symbol determination process of the relay device 200 is a hard determination process. A case where 256QAM is used as the MCS, NUC is used as the constellation, and the LDPC coding rate is 12 / 16 will be taken as an example. Further, the C / N ratio of the signal received by the relay device 200 from the transmission device 100 is 26 dB.

[0038] As shown in FIG. 4, as a result of intensive studies, the inventors focused on the fact that the reception state of the reception device 300 can be classified into four states (state A to state D).

[0039] State A is a state where the C / N ratio of the reception device 300 is lower than a required C / N ratio (for example, 20 dB), and since the number of repetitions always reaches the maximum number of repetitions, it is a state with a high BER.

[0040] State B is a state where the C / N ratio of the reception device 300 is near the required C / N ratio. Since the number of repetitions may reach the maximum number of repetitions or may not reach the maximum number of repetitions, the BER is in a variable state.

[0041] State C is a state where the C / N ratio of the receiving device 300 is higher than the required C / N ratio, and since the number of repetitions never reaches the maximum number of repetitions, it is a state where the BER is 0.

[0042] State D is a state where, although the C / N ratio of the receiving device 300 is higher than the required C / N ratio, the number of repetitions may reach the maximum number of repetitions, so the BER is higher than that in state C.

[0043] State D is considered to be caused by an event in which the symbol transmitted by the transmitting device is determined as an incorrect symbol in the symbol determination process (hard determination process) of the relay device 200.

[0044] Based on the new finding that state D occurs, the inventors have found that it is preferable to pseudo-transition state D to state C. State D may be considered an example of a specific state.

[0045] In the embodiment, the specific condition includes a first specific condition in which the number of repetitions may reach the maximum number of repetitions. Specifically, the first specific condition is a condition in which the number of repetitions may or may not reach the maximum number of repetitions. In other words, the first specific condition is a condition in which the condition that the number of repetitions never reaches the maximum number of repetitions and the condition that the number of repetitions always reaches the maximum number of repetitions are not satisfied.

[0046] Under such a premise, when the first specific condition is satisfied, it is assumed that the reception state of the receiving device 300 is state B or state D, and it is impossible to distinguish between state B and state D. Therefore, in the embodiment, when the first specific condition is satisfied, after executing specific control, it is determined again whether the BER becomes 0 (that is, whether the reception state transitions from state D to state C) to distinguish between state B and state D.

[0047] (Operation example) Hereinafter, an operation example according to an embodiment will be described.

[0048] As shown in FIG. 5, in step S10, the receiving device 300 resets the observation data. The observation data is data regarding the number of repetitions for each LDPC block.

[0049] In step S11, the receiving device 300 determines whether or not the number of stored observation data has reached a predetermined number. The receiving device 300 continues to store the observation data until the number of stored data reaches the predetermined number.

[0050] In step S12, the receiving device 300 determines whether or not a first specific condition is satisfied. The first specific condition is a condition under which the number of repetitions may reach the maximum number of repetitions. If the first specific condition is not satisfied, that is, if the condition that the number of repetitions never reaches the maximum number of repetitions and the condition that the number of repetitions always reaches the maximum number of repetitions are satisfied, the receiving device 300 ends a series of processes. If the first specific condition is satisfied, the receiving device 300 executes the process of step S13. It should be noted that state B and state D are not distinguished at the stage of step S12.

[0051] In step S13, the receiving device 300 executes specific control for degenerating the initial LLR. Specifically, the receiving device 300 executes control for reducing the power of the received signal by controlling the variable attenuator 301 with a control signal.

[0052] In step S14, the receiving device 300 determines whether or not the number of stored observation data has reached a predetermined number. The receiving device 300 continues to store the observation data until the number of stored data reaches the predetermined number.

[0053] In step S15, the receiving device 300 determines whether the first specific condition is satisfied. If the first specific condition is not satisfied, the receiving device 300 executes the process of step S16. If the first specific condition is satisfied, the receiving device 300 executes the process of step S13. That is, by further shrinking the initial LLR, a pseudo-transition from state B to state A or a pseudo-transition from state D to state C is promoted.

[0054] In step S16, the receiving device 300 determines whether the BER is 0. If the BER is 0, the receiving device 300 determines that a pseudo-transition from state D to state C has occurred and ends a series of processes. If the BER is not 0, the receiving device 300 determines that a pseudo-transition from state B to state A has occurred and executes the process of step S17.

[0055] In step S17, the receiving device 300 releases the specific control. As a result, the pseudo-transition from state B to state A is released, and the reception state of the receiving device 300 returns to (improves to) state B.

[0056] (Operation and Effect) In the embodiment, the receiving device 300 determines whether the reception state of the LDPC block is a specific state based on whether a specific condition defined at least by the number of repetitions of calculating the estimated value of the data symbol included in the LDPC block is satisfied. Specifically, the receiving device 300 determines whether the reception state of the LDPC block is a specific state based on whether the first specific condition that the number of repetitions may reach the maximum number of repetitions is satisfied. According to such a configuration, it is possible to appropriately determine whether the reception state of the LDPC block is state D.

[0057] In the embodiment, when the reception state of the LDPC block is in a specific state, the receiving device 300 executes specific control to degenerate the initial LLR. Specifically, the receiving device 300 executes control to reduce the power of the received signal by controlling the variable attenuator 301 with a control signal. According to such a configuration, the BER can be improved by a pseudo-transition from state D to state C.

[0058] In the embodiment, even without the likelihood information from the relay device 200, the BER can be improved by the control of the receiving device 300, so that the complication of the relay device 200 and the increase in the signaling load can be suppressed.

[0059] [Modification Example 1] Hereinafter, Modification Example 1 of the embodiment will be described. Hereinafter, the differences from the embodiment will be mainly described.

[0060] Specifically, in the embodiment, the specific control is control to reduce the power of the received signal. In contrast, in Modification Example 1, the specific control is control to add noise to the received signal.

[0061] As shown in FIG. 6, the receiving device 300 has a noise generator 351 instead of the variable attenuator 301.

[0062] The noise generator 351 generates noise. The noise generator 351 operates according to a command from the control unit 313.

[0063] The control unit 313 generates a control signal for generating noise and inputs the generated control signal to the noise generator 351. The noise generated by the noise generator 351 is added to the received signal.

[0064] (Operation and Effect) In Modification Example 1, as specific control, noise is added to the received signal. According to such a configuration, the initial LLR can be degenerated, so that the same effect as in the embodiment can be obtained.

[0065] [Modification Example 2] In the following, Modification Example 2 of the embodiment will be described. In the following, the differences from the embodiment will be mainly described.

[0066] Specifically, in the embodiment, the specific control is control for reducing the power of the received signal. In contrast, in Modification Example 2, the specific control is control for manipulating the noise variance value.

[0067] As shown in FIG. 7, the receiving apparatus 300 has a noise operation unit 353 instead of the variable attenuator 301.

[0068] The noise operation unit 353 manipulates the noise variance value estimated by the noise estimation unit 307. The noise operation unit 353 operates according to a command from the control unit 313.

[0069] The control unit 313 generates a control signal for manipulating the noise variance value, and inputs the generated control signal to the noise operation unit 353. The noise operation unit 353 manipulates the noise variance value so as to regress the initial LLR.

[0070] [Operation and Effect] In Modification Example 2, as the specific control, the noise variance value used for calculating the initial LLR is manipulated. According to such a configuration, since the initial LLR can be regressed, the same effect as that of the embodiment can be obtained.

[0071] [Modification Example 3] In the following, Modification Example 3 of the embodiment will be described. In the following, the differences from the embodiment will be mainly described.

[0072] Specifically, in the embodiment, the specific control is control for reducing the power of the received signal. In contrast, in Modification Example 3, the specific control is control for manipulating the initial LLR.

[0073] As shown in FIG. 7, the receiving apparatus 300 has an LLR operation unit 355 instead of the variable attenuator 301.

[0074] The LLR operation unit 355 operates on the initial LLR calculated by the LLR calculation unit 309. The LLR operation unit 355 operates according to the command of the control unit 313.

[0075] The control unit 313 generates a control signal for operating the initial LLR and inputs the generated control signal to the LLR operation unit 355. The LLR operation unit 355 operates on the initial LLR so as to degenerate the initial LLR.

[0076] (Function and Effect) In Modification 3, as a specific control, the initial LLR is directly operated. According to such a configuration, since the initial LLR can be degenerated, the same effects as those of the embodiment can be obtained.

[0077] [Modification 4] Hereinafter, Modification 4 of the embodiment will be described. Hereinafter, the differences from the embodiment will be mainly described.

[0078] Specifically, in the embodiment, the specific condition includes a first specific condition in which the number of repetitions may reach the maximum number of repetitions. In contrast, in Modification 4, the specific condition includes a second specific condition in which the variance of the number of repetitions is equal to or greater than a predetermined threshold.

[0079] As shown in FIG. 9, in state A, since the number of repetitions always reaches the maximum number of repetitions, the variance of the number of repetitions is smaller than the threshold (for example, 20). In state B, since the number of repetitions gradually changes, the variance of the number of repetitions is smaller than the threshold (for example, 20). In state C, since the number of repetitions is always small, the variance of the number of repetitions is smaller than the threshold (for example, 20). In contrast, in state D, although the number of repetitions is basically small, the number of repetitions sporadically reaches the maximum number of repetitions, so the variance of the number of repetitions is equal to or greater than the threshold (for example, 20).

[0080] Under such a premise, in Modification 4, as a specific condition, a second specific condition in which the variance of the number of repetitions is equal to or greater than a predetermined threshold is used.

[0081] (Operation example) Hereinafter, the operation example according to Modification 4 will be described.

[0082] As shown in FIG. 10, in step S30, the receiving device 300 resets the observation data. The observation data is data regarding the number of repetitions for each LDPC block.

[0083] In step S31, the receiving device 300 determines whether or not the number of stored observation data has reached a predetermined number. The receiving device 300 continues to store the observation data until the number of stored data reaches the predetermined number.

[0084] In step S32, the receiving device 300 determines whether or not a second specific condition is satisfied. The second specific condition is a condition that the variance of the number of repetitions is equal to or greater than a predetermined threshold. If the second specific condition is not satisfied, that is, if the reception state is any one of states A to C, the receiving device 300 ends a series of processes. If the first specific condition is satisfied, the receiving device 300 executes the process of step S33.

[0085] In step S33, the receiving device 300 executes specific control for degenerating the initial LLR. For example, the receiving device 300 executes control for reducing the power of the received signal by controlling the variable attenuator 301 with a control signal, as in the embodiment.

[0086] However, the receiving device 300 may add noise to the received signal by controlling the noise generator 351 with a control signal, as in Modification 1. The receiving device 300 may operate the noise variance value used for calculating the initial LLR by controlling the noise operation unit 353 with a control signal, as in Modification 2. The receiving device 300 may directly operate the initial LLR by controlling the LLR operation unit 355 with a control signal, as in Modification 3.

[0087] (Function and effect) In Modification Example 4, the specific condition includes a second specific condition that the variance of the number of repetitions is equal to or greater than a predetermined threshold. According to such a configuration, state D can be determined more directly than in the embodiment.

[0088] [Modification Example 5] Hereinafter, Modification Example 5 of the embodiment will be described. Hereinafter, the differences from the embodiment and Modification Examples 1 to 3 will be mainly described.

[0089] Specifically, in the embodiment, the specific condition includes a first specific condition that the number of repetitions may reach the maximum number of repetitions. In contrast, in Modification Example 5, the specific condition includes, in addition to the first specific condition, a third specific condition that the noise dispersion value is equal to or less than a predetermined threshold.

[0090] As shown in FIG. 11, the receiving apparatus 300 may have a configuration similar to the configuration shown in FIG. 2, except that the control unit 313 acquires the noise (or the noise dispersion value) estimated by the noise estimation unit 30 (see the embodiment). Alternatively, as shown in FIG. 12, the receiving apparatus 300 may have a configuration similar to the configuration shown in FIG. 6, except that the control unit 313 acquires the noise (or the noise dispersion value) estimated by the noise estimation unit 30 (see Modification Example 1). Alternatively, as shown in FIG. 13, the receiving apparatus 300 may have a configuration similar to the configuration shown in FIG. 7, except that the control unit 313 acquires the noise (or the noise dispersion value) estimated by the noise estimation unit 30 (see Modification Example 2). Alternatively, as shown in FIG. 14, the receiving apparatus 300 may have a configuration similar to the configuration shown in FIG. 8, except that the control unit 313 acquires the noise (or the noise dispersion value) estimated by the noise estimation unit 30 (see Modification Example 3).

[0091] As shown in FIG. 15, in state A, since the C / N ratio of the receiving device 300 is lower than the required C / N ratio (for example, 20 dB), the noise variance value of the received signal is larger than the threshold value (for example, 0.01). In state B, since the C / N ratio of the receiving device 300 is in the vicinity of the required C / N ratio, the noise variance value of the received signal is larger than the threshold value (for example, 0.01). In state C, since the C / N ratio of the receiving device 300 is higher than the required C / N ratio, the noise variance value of the received signal is equal to or less than the threshold value (for example, 0.01). In state D, since the C / N ratio of the receiving device 300 is higher than the required C / N ratio, the noise variance value of the received signal is equal to or less than the threshold value (for example, 0.01).

[0092] As described above, only under the first specific condition where the number of repetitions may reach the maximum number of repetitions, state B and state D cannot be distinguished. However, if the third specific condition that the noise variance value is equal to or less than a predetermined threshold value is used, state B and state D can be distinguished.

[0093] Under such a premise, in Modification 5, as the specific conditions, the first specific condition where the number of repetitions may reach the maximum number of repetitions and the third specific condition where the noise variance value is equal to or less than a predetermined threshold value are used.

[0094] (Operation Example) Hereinafter, the operation example according to Modification 5 will be described.

[0095] As shown in FIG. 16, in step S50, the receiving device 300 resets the observation data. The observation data is data regarding the number of repetitions for each LDPC block.

[0096] In step S51, the receiving device 300 determines whether or not the number of stored observation data has reached a predetermined number. The receiving device 300 continues to store the observation data until the number of stored data reaches the predetermined number.

[0097] In step S52, the receiving device 300 determines whether the first specific condition is satisfied. The first specific condition is a condition under which the number of repetitions may reach the maximum number of repetitions. When the first specific condition is not satisfied, that is, when the condition that the number of repetitions never reaches the maximum number of repetitions and the condition that the number of repetitions always reaches the maximum number of repetitions are satisfied, the receiving device 300 ends the series of processes. When the first specific condition is satisfied, the receiving device 300 executes the process of step S53. It should be noted that at the stage of step S52, state B and state D are not distinguished.

[0098] In step S53, the receiving device 300 determines whether the third specific condition is satisfied. The third specific condition is a condition that the noise dispersion value is equal to or less than a predetermined threshold value. When the third specific condition is satisfied, that is, when the reception state is state D, the receiving device 300 executes the process of step S54. When the third specific condition is not satisfied, that is, when the reception state is state B, the receiving device 300 ends the series of processes.

[0099] In step S54, the receiving device 300 executes specific control for degenerating the initial LLR. For example, similar to the embodiment, the receiving device 300 executes control for reducing the power of the received signal by controlling the variable attenuator 301 with a control signal.

[0100] However, similar to Modification Example 1, the receiving device 300 may add noise to the received signal by controlling the noise generator 351 with a control signal. Similar to Modification Example 2, the receiving device 300 may operate the noise dispersion value used for calculating the initial LLR by controlling the noise operation unit 353 with a control signal. Similar to Modification Example 3, the receiving device 300 may directly operate the initial LLR by controlling the LLR operation unit 355 with a control signal.

[0101] (Function and Effect) In Modification 5, the specific conditions include a third specific condition that the noise variance value is equal to or less than a predetermined threshold value, in addition to the first specific condition in which the number of repetitions may reach the maximum number of repetitions. According to such a configuration, state D can be determined more directly than in the embodiment.

[0102] [Other Embodiments] Although the present invention has been described by the above disclosure, the arguments and drawings that form a part of this disclosure should not be understood as limiting this invention. Various alternative embodiments, examples, and operation techniques will become apparent to those skilled in the art from this disclosure.

[0103] In the above disclosure, the case where an LDPC code is used as an error correction code has been described, but the above disclosure is not limited thereto. As the error correction code, a code other than the LDPC code may be used.

[0104] In the above disclosure, the case where the relay device 200 is interposed between the transmission device 100 and the reception device 300 has been described, but the above disclosure is not limited thereto. The relay device 200 may not be interposed between the transmission device 100 and the reception device 300.

[0105] Although not particularly mentioned in the above disclosure, a program for causing a computer to execute each process performed by the reception device 300 may be provided. Further, the program may be recorded on a computer-readable medium. By using a computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and for example, a recording medium such as a CD-ROM or a DVD-ROM may be used.

[0106] Alternatively, a chip including a memory for storing a program for executing each process performed by the reception device 300 and a processor for executing the program stored in the memory may be provided. [Description of Reference Numerals]

[0107] 10… Digital wireless transmission system, 100… Transmitter, 200… Relay device, 300… Receiver, 301… Variable attenuator, 303… FFT processing unit, 305… Equalization processing unit, 307… Noise estimation unit, 309… LLR calculation unit, 311… LDPC decoder, 313… Control unit, 331… Storage unit, 333… Judgment unit, 335… Generation unit, 351… Noise generator, 353… Noise operation unit, 355… LLR operation unit

Claims

Claim 1. A receiving apparatus comprising: a calculation unit that calculates likelihoods of data symbols included in an error correction block without using likelihood information in a relay apparatus that relays the error correction block, for the error correction block; a decoding unit that performs error correction decoding of the data symbols included in the error correction block based on the likelihoods of the data symbols; a control unit that does not perform specific control to degenerate the likelihoods of the data symbols when a reception state of the error correction block is not a specific state, and performs the specific control when the reception state of the error correction block is the specific state; wherein the decoding unit performs error correction decoding of the data symbols based on the likelihoods of the data symbols calculated by the calculation unit when the reception state of the error correction block is not the specific state, and performs error correction decoding of the data symbols based on the likelihoods of the data symbols to which the specific control has been applied when the reception state of the error correction block is the specific state; repeats calculation of estimated values of the data symbols included in the error correction block until errors of the data symbols included in the error correction block are corrected, with a maximum number of repetitions as an upper limit; wherein the control unit determines whether the reception state of the error correction block is the specific state based on whether at least a specific condition defined at least by the number of repetitions of the calculation of the estimated values of the data symbols included in the error correction block is satisfied; wherein the specific condition includes a first specific condition that at least one of the number of repetitions reaches the maximum number of repetitions. Claim 2. A receiving apparatus comprising: a calculation unit that calculates likelihoods of data symbols included in an error correction block without using likelihood information in a relay apparatus that relays the error correction block, for the error correction block; a decoding unit that performs error correction decoding of the data symbols included in the error correction block based on the likelihoods of the data symbols; a control unit that does not perform specific control to degenerate the likelihoods of the data symbols when a reception state of the error correction block is not a specific state, and performs the specific control when the reception state of the error correction block is the specific state; wherein the decoding unit When the reception state of the error correction block is not the specific state, error correction decoding of the data symbol is performed based on the likelihood of the data symbol calculated by the calculation unit, and when the reception state of the error correction block is the specific state, error correction decoding of the data symbol is performed based on the likelihood of the data symbol to which the specific control is applied. With the maximum number of repetitions as the upper limit, the calculation of the estimated value of the data symbol included in the error correction block is repeated until the error of the data symbol included in the error correction block is corrected. The control unit determines whether the reception state of the error correction block is a specific state based on whether at least a specific condition defined by the number of repetitions of the calculation of the estimated value of the data symbol included in the error correction block is satisfied. The specific condition includes a second specific condition that the variance of the number of repetitions is equal to or greater than a predetermined threshold value. The receiving device.

3. The receiving device according to claim 1, wherein the specific condition includes a third specific condition that a noise variance value estimated based on a known symbol is equal to or less than a predetermined threshold value in addition to the first specific condition.

4. The receiving device according to any one of claims 1 to 3, wherein the control unit performs control to reduce the power of the received signal as the specific control.

5. The receiving device according to any one of claims 1 to 4, wherein the control unit performs control to add noise to the received signal as the specific control.

6. The receiving device according to any one of claims 1 to 4, wherein the control unit performs control to operate a noise variance value estimated based on a known symbol so as to degenerate the likelihood of the data symbol as the specific control.

7. The receiving device according to any one of claims 1 to 4, wherein the control unit performs control to operate the likelihood of the data symbol so as to degenerate the likelihood of the data symbol as the specific control.

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