Receiving device and method

Abstract

To provide a reception device and a method, capable of calculating a noise variance with high accuracy.SOLUTION: The reception device according to an embodiment includes first obtaining means, second obtaining means, first calculating means, and second calculating means. The first obtaining means obtains a receiving point which is a point of a received signal subjected to a digital modulation. The second obtaining means obtains a plurality of ideal points corresponding to a modulation scheme of the digital modulation. The first calculating means calculates a pseudo-noise variance of the receiving point on the basis of the obtained receiving point and the plurality of obtained ideal points. The second calculating means calculates a noise variance of the receiving point on the basis of the calculated pseudo-noise variance of the receiving point. The pseudo-noise variance is a square value of a minimum difference among differences between the obtained receiving point and each of the plurality of obtained ideal points. The noise variance is calculated on the basis of a relation between the pseudo-noise variance and the noise variance in accordance with the modulation scheme of the digital modulation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to a receiving apparatus and method. [Background technology]

[0002] In order to achieve high-quality communication, it is useful to use the noise variance (value) which represents the degree of deviation between the signal received by the receiving device (received signal) and the data signal modulated by the sender of the received signal (transmitted signal).

[0003] Specifically, the higher the accuracy of the noise variance, the higher the accuracy of the likelihood (certainty) of the received signal, and as a result, high-quality communication with a small bit error rate after error correction decoding can be realized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-028607 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a receiving apparatus and method capable of calculating noise variance with high accuracy. [Means for solving the problem]

[0006] A receiving device according to an embodiment includes a first acquisition means, a second acquisition means, a first calculation means, and a second calculation means. The first acquisition means acquires a reception point, which is a point of a digitally modulated received signal. The second acquisition means acquires a plurality of ideal points, which are points of a plurality of ideal signals corresponding to the modulation method of the digital modulation. The first calculation means calculates a pseudo noise variance of the reception point from the acquired reception point and the acquired plurality of ideal points. The second calculation means calculates a noise variance of the reception point from the calculated pseudo noise variance of the reception point. The pseudo noise variance is the square value of the smallest difference between the acquired reception point and each of the acquired plurality of ideal points. The noise variance is calculated as follows: Using the probability density distribution of the reception points for each of the plurality of ideal points The relationship between the pseudo-noise variance and the noise variance according to the modulation method of the digital modulation or a conversion table in which a correspondence relationship between the pseudo noise variance and the noise variance calculated from the pseudo noise variance by the calculation formula is defined in advance. It is calculated. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a block diagram showing an example of the configuration of a receiving device according to the first embodiment. [Figure 2] 10 is a flowchart showing an example of a processing procedure of a receiving device. [Figure 3] FIG. 10 is a diagram for explaining an example of a process for calculating pseudo-noise variance and noise variance. [Figure 4] 10A and 10B are diagrams for explaining another example of the process of calculating pseudo-noise variance and noise variance. [Figure 5] FIG. 10 is a block diagram showing an example of the configuration of a receiving device according to a second embodiment. [Figure 6] 10 is a flowchart showing an example of a processing procedure of a receiving device. [Figure 7] FIG. 11 is a diagram conceptually showing a plurality of subcarriers that constitute an OFDM symbol in the third embodiment. [Figure 8] FIG. 10 illustrates a case where the power levels of multiple subcarriers are not the same. [Figure 9] 10 is a flowchart showing an example of a processing procedure of a receiving device according to the fourth embodiment. [Figure 10]FIG. 11 is a block diagram showing an example of the configuration of a receiving device according to a fifth embodiment. [Figure 11] 10 is a flowchart showing an example of a processing procedure of a receiving device. [Figure 12] FIG. 13 is a block diagram showing an example of the configuration of a receiving device according to a sixth embodiment. [Figure 13] 10 is a flowchart showing an example of a processing procedure of a receiving device. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, each embodiment will be described with reference to the drawings. (First embodiment) First, a description will be given of a first embodiment of the present invention, with reference to Fig. 1, which is a block diagram showing an example of the configuration of a receiving device according to the present embodiment.

[0009] As shown in FIG. 1, the receiving device 10 includes an AFE (Analog Front End) unit 101, a synchronization processing unit 102, an FFT (Fast Fourier Transform) processing unit 103, a transmission path estimation unit 104, a transmission path correction unit 105, a pseudo-noise variance calculation unit 106, a noise variance calculation unit 107, a likelihood ratio calculation unit 108, and an error correction decoding unit 109.

[0010] In this embodiment, the receiving device 10 is configured to receive, for example, a digitally modulated signal via an antenna (not shown). The signal received by the receiving device 10 (hereinafter referred to as the received signal) is a radio signal in which the modulation method of the primary modulation performed by the sender (transmitter) of the received signal is Phase Shift Keying (PSK) or Quadrature Amplitude Modulation (QAM), and the modulation method of the secondary modulation is Orthogonal Frequency Division Multiplexing (OFDM).

[0011] The AFE unit 101 has a function of inputting the above-described received signal and adjusting the received signal (analog signal). The AFE unit 101 is configured with a filter, an amplifier, an ADC (Analog-to-Digital Converter), etc. The AFE unit 101 removes out-of-band signal components contained in the received signal using, for example, a band-limiting filter, and amplifies the level of the received signal using an amplifier. The AFE unit 101 also converts the received signal into an analog baseband signal by down-converting the frequency of the received signal, and converts the analog baseband signal into a digital signal using the ADC. This digital signal includes OFDM symbols and is output from the AFE unit 101 to the synchronization processing unit 102.

[0012] The synchronization processing unit 102 receives the digital signal output from the AFE unit 101 and performs OFDM symbol timing synchronization processing such as amplitude control, frequency correction, timing correction, GI (Guard Interval) removal, etc. The synchronization processing unit 102 outputs the OFDM symbol that has undergone OFDM symbol timing synchronization processing to the FFT processing unit 103.

[0013] The synchronization processing unit 102 may have an I / F with other functional units. Specifically, the synchronization processing unit 102 may be configured to output a control value for controlling the gain of the received signal to the AFE unit 101, or may be configured to input a known pattern for timing synchronization used in timing correction from a storage unit (not shown).

[0014] The FFT processing unit 103 receives the OFDM symbols output from the synchronization processing unit 102 and performs a fast Fourier transform (FFT) on the OFDM symbols. This fast Fourier transform converts the OFDM symbols from time domain signals to frequency domain signals. The FFT processing unit 103 outputs the OFDM symbols converted into frequency domain signals in this manner to the transmission channel estimation unit 104 and the transmission channel correction unit 105.

[0015] Here, the OFDM symbol converted into a frequency domain signal is composed of a plurality of subcarriers including data subcarriers corresponding to data signals and pilot subcarriers corresponding to known signals (pilot signals). The transmission channel estimation unit 104 performs transmission channel estimation using pilot subcarriers included in the plurality of subcarriers constituting the OFDM symbol. The transmission channel estimation unit 104 performs transmission channel estimation based on amplitude fluctuations of the pilot subcarriers, etc. The transmission channel estimation unit 104 outputs a transmission channel estimate value (transmission channel correction value) obtained by the transmission channel estimation to the transmission channel correction unit 105.

[0016] The transmission path compensation unit 105 receives the OFDM symbol output from the FFT processing unit 103 and the transmission path estimation value output from the transmission path estimation unit 104, and performs transmission path compensation on the data subcarriers included in the multiple subcarriers that make up the OFDM symbol using the transmission path estimation value. The transmission path compensation unit 105 outputs the transmission path compensated data subcarriers to the pseudonoise variance calculation unit 106. Note that the data subcarriers output from the transmission path compensation unit 105 to the pseudonoise variance calculation unit 106 correspond to reception points, which are points on the received signal.

[0017] The pseudonoise variance calculation unit 106 receives (acquires) the data subcarriers output from the transmission path correction unit 105 and calculates the pseudonoise variance of the data subcarriers. Details of the processing by the pseudonoise variance calculation unit 106 will be described later. The pseudonoise variance calculation unit 106 outputs the calculated pseudonoise variance to the noise variance calculation unit 107.

[0018] The noise variance calculation unit 107 receives the pseudo noise variance output from the pseudo noise variance calculation unit 106 and calculates the noise variance from the pseudo noise variance. Details of the processing by the noise variance calculation unit 107 will be described later. The noise variance calculation unit 107 outputs the calculated noise variance to the likelihood ratio calculation unit 108.

[0019] The likelihood ratio calculation unit 108 receives the noise variance output from the noise variance calculation unit 107 and calculates a likelihood ratio for the noise variance. The likelihood ratio calculated by the likelihood ratio calculation unit 108 includes, for example, a log-likelihood ratio of each bit corresponding to the above-mentioned data subcarrier (reception point). The likelihood ratio calculation unit 108 outputs the calculated likelihood ratio to the error correction decoding unit 109.

[0020] The error correction decoding unit 109 receives the likelihood ratio output from the likelihood ratio calculation unit 108 and performs error correction decoding based on the likelihood ratio.

[0021] In this embodiment, it is assumed that each of the units 101 to 109 shown in FIG. 1 is realized by hardware, but some or all of the units 101 to 109 may be realized by software, or may be realized by a combination of hardware and software.

[0022] Next, an example of a processing procedure of the receiving device 10 will be described with reference to the flowchart of FIG.

[0023] First, the receiving device 10 (AFE unit 101) inputs the above-mentioned received signal (step S1). Note that the received signal is, for example, a radio signal that has been digitally modulated, but in the following description, it is assumed that the modulation method of the primary modulation is quadrature phase shift keying (QPSK), which is one form of phase shift keying (PSK). Note that the modulation method of the secondary modulation is OFDM as described above.

[0024] When the processing of step S1 is executed, multiple data subcarriers (multiple data subcarriers included in the OFDM symbol) are extracted from the received signal input in step S1 via the AFE unit 101, synchronization processing unit 102, FFT processing unit 103, transmission channel estimation unit 104, and transmission channel correction unit 105. The pseudo noise variance calculation unit 106 acquires the multiple data subcarriers extracted from the received signal (step S2). Note that the processing from step S3 onwards described below is executed for each of the multiple data subcarriers acquired in step S2, but for convenience, the following description will be given for one data subcarrier.

[0025] Next, the pseudo-noise variance calculation unit 106 calculates the pseudo-noise variance of the data subcarriers acquired in step S2 (step S3).

[0026] When the process of step S3 is executed, the noise variance calculation unit 107 calculates the noise variance from the pseudo-noise variance calculated in step S3 (step S4).

[0027] Hereinafter, the process of calculating the pseudo noise variance and noise variance will be described with reference to FIG.

[0028] First, when the modulation method of the primary modulation performed at the transmission source of the received signal is QPSK, a two-bit data signal can be transmitted with one symbol. In this case, the data signal corresponding to the data subcarrier acquired in the above-mentioned step S2 (i.e., the data signal modulated at the transmission source of the received signal) can be said to be one of four ideal mapping points: (A,A), (-A,A), (-A,-A), and (A,-A). These four ideal mapping points correspond to the two-bit data signals "11", "01", "00", and "10" modulated by QPSK.

[0029] The above-mentioned multiple ideal mapping points correspond to multiple ideal signal points and differ depending on the modulation method of the primary modulation (digital modulation) performed at the transmitter of the received signal, but the receiving device 10 can grasp the modulation method based on the control information by separately receiving control information indicating the modulation method of the primary modulation (here, QPSK) from the outside (for example, the transmitter of the received signal, etc.). In other words, by managing in advance within the receiving device 10 for each modulation method, (information indicating) the correspondence between the modulation method and the multiple ideal mapping points, the receiving device 10 can acquire the multiple ideal mapping points corresponding to the modulation method grasped based on the above-mentioned control information.

[0030] Here, the data subcarriers acquired in step S2 can be said to be reception points, which are points of the received signal, but the reception points (x, y) often deviate from the ideal mapping points due to the influence of noise, etc. Figure 3 shows an example of a constellation (signal space diagram) that represents the above-mentioned multiple ideal mapping points and reception points on a complex plane having a real part (I-ch) and an imaginary part (Q-ch).

[0031] In this embodiment, the noise variance indicates the degree of deviation between the reception point and the ideal mapping point, and is expressed by the following equation (1). σ 2 =(xx i ) 2 +(yy i ) 2 Formula (1)

[0032] In this equation (1), σ 2 represents the noise variance, and (x i ,y i ) represents the ideal mapping point.

[0033] Specifically, if the ideal mapping point corresponding to the data signal modulated at the transmitter (written as the ideal mapping point modulated at the transmitter) is (-A,-A), the noise variance σ 2 is (x+A)2 +(y+A) 2 This becomes:

[0034] For convenience, equation (1) assumes the case of one sample (i.e., one reception point), but in the case of multiple samples, the average value of the noise variance of each of the multiple samples may be used as the noise variance.

[0035] However, in order to obtain the data signal modulated by the sender of the above-mentioned received signal, the received signal must be demodulated. However, while the received signal is being demodulated, it is not possible to grasp the ideal mapping point modulated by the sender among the multiple ideal mapping points.

[0036] Therefore, in this embodiment, the distances on the constellation between the receiving point and multiple ideal mapping points are calculated, the shortest distance is selected from the distances, and the square value of the selected distance is calculated as the pseudo noise variance. That is, the ideal mapping point that is shortest from the receiving point is regarded as the ideal mapping point modulated on the transmitting side in a pseudo manner, and the square value of the shortest distance is used as the pseudo noise variance.

[0037] In the example shown in FIG. 3, the ideal mapping point at the shortest distance from the receiving point (x, y) is (A, -A), so the pseudo noise variance is (xA) 2 +(y+A) 2 is calculated.

[0038] Here, we have explained that the distance between the receiving point and multiple ideal mapping points is calculated, and then the square of the shortest distance among these distances is calculated as the pseudo noise variance. However, it is also possible to calculate the square of the distance for each ideal mapping point instead of the actual distance, and then use the smallest value among the squared values of the distances as the pseudo noise variance.

[0039] Incidentally, if the signal-to-noise ratio (SNR) of the received signal is sufficiently high and the reception point is close to the ideal mapping point modulated on the transmitting side, the pseudo-noise variance described above can be considered to be the noise variance itself.

[0040] However, for example, when the reception point is beyond the decision boundary (here, the real axis and the imaginary axis) on the constellation for the ideal mapping point modulated on the transmitting side, the pseudo noise variance described above differs from the actual noise variance, and the pseudo noise variance cannot be treated as the noise variance. Specifically, when the ideal mapping point (A, -A) shown in Figure 3 is the ideal mapping point modulated on the transmitting side, it is calculated as the pseudo noise variance (xA). 2 +(y+A) 2 can be used as the noise variance, but if the ideal mapping point (-A, -A) is the ideal mapping point modulated at the transmitting side (i.e., the receiving point is far from the ideal mapping point modulated at the transmitting side beyond the imaginary axis Q, which is the decision boundary), it is calculated as the pseudo noise variance (xA). 2 +(y+A) 2 It is not appropriate to treat as the noise variance.

[0041] For this reason, in this embodiment, the noise variance calculation unit 107 calculates the noise variance from the pseudo noise variance calculated in step S3, taking into consideration the case where the reception point exceeds the decision boundary.

[0042] In this case, assuming that the ideal mapping point modulated on the transmitting side (hereinafter referred to as the transmission point) is one of the four ideal mapping points (e.g., (A,A)) described above, the probability density distribution p(x,y) of the receiving point (x,y) for the transmission point (A,A) is expressed by the following equation (2).

number

[0043] However, the probability density distribution p(x, y) assumes that the transmission channel is AWGN (Additive White Gaussian noise).

[0044] Here, the quadrants in which the ideal mapping points (A,A), (-A,A), (-A,-A), and (A,-A) on the complex plane shown in Fig. 3 exist are defined as the first to fourth quadrants. In this case, the probability density distribution when the reception point (x, y) exists in each of the first to fourth quadrants is multiplied by the pseudo noise variance in that quadrant, and the sum of the multiplication results is calculated using the following equation (3), where the expected value (average value) of the pseudo noise variance (σ_p) is calculated statistically. 2 can be calculated.

number

[0045] The first term on the right side of equation (3) indicates that the probability density distribution and the pseudo noise variance are multiplied when the receiving point (x, y) is in the third quadrant. The second term on the right side of equation (3) indicates that the probability density distribution and the pseudo noise variance are multiplied when the receiving point (x, y) is in the fourth quadrant. The third term on the right side of equation (3) indicates that the probability density distribution and the pseudo noise variance are multiplied when the receiving point (x, y) is in the second quadrant. The fourth term on the right side of equation (3) indicates that the probability density distribution and the pseudo noise variance are multiplied when the receiving point (x, y) is in the first quadrant.

[0046] The expected value of the pseudo noise variance (σ_p) calculated statistically using the above formula (3) 2 is treated as the pseudo noise variance, the expected value (σ_p) of the pseudo noise variance calculated in step S3 2 It can be said that the noise variance can be calculated from

[0047] That is, if we substitute equation (2) for p(x,y) in equation (3), we get the expected value of the pseudo noise variance (σ_p) 2 and noise variance σ 2The relation between the pseudo noise variance calculated in step S3 and the expected value (σ_p) of the pseudo noise variance is obtained. 2 If we consider that and are equal, the noise variance σ 2 can be calculated.

[0048] Although the case where the transmission point is (A,A) has been described here, the pseudo noise variance can also be calculated statistically in the same way when the transmission point is (-A,A), (-A,-A), or (A,-A). Furthermore, if four transmission points (ideal mapping points) occur with equal probability, then due to symmetry, the above formula (3) can be said to be the relational expression between the pseudo noise variance and the noise variance (that is, the calculation formula that expresses the relationship between the pseudo noise variance and the noise variance).

[0049] That is, in this embodiment, even if the reception point exceeds the decision boundary, the noise variance can be calculated from the pseudo noise variance using the above-mentioned formula (3) (i.e., a calculation formula that expresses the relationship between the pseudo noise variance and the noise variance using the probability density distribution of the reception point for each of a plurality of ideal mapping points).

[0050] Here, we have explained that the modulation method of the primary modulation is quadrature phase shift keying (QPSK), but even if digital modulation based on other modulation methods is implemented, the noise variance can be calculated from the pseudo noise variance in the same way.

[0051] Hereinafter, a case will be described in which the modulation method of the primary modulation is binary phase shift keying (BPSK), which is one form of phase shift keying (PSK).

[0052] As described above, when the modulation method of the primary modulation performed at the transmitter of the received signal is BPSK, a 1-bit data signal can be transmitted with one symbol. In this case, the data signal corresponding to the data subcarrier acquired in step S2 (the data signal modulated at the transmitter of the received signal) can be said to be one of two ideal mapping points (A, 0) and (-A, 0). These two ideal mapping points correspond to 1-bit data signals "1" and "0" modulated by BPSK. In addition, the reception point (data subcarrier) in this case is expressed as (x, y).

[0053] Here, assuming that the transmission point (ideal mapping point modulated on the transmitting side) is one of the two ideal mapping points mentioned above (for example, (A, 0)), the probability density distribution p(x) of x among the reception points (x, y) for the transmission point (A, 0) is expressed by the following equation (4).

number

[0054] 4 shows a schematic diagram of the probability density distribution p(x) for the reception point x on the real axis I. When modulated by BPSK, the decision boundary is x=0. Therefore, the probability density distribution when the reception point x is in the region where x<0 and the region where x>0 are multiplied by the pseudo noise variance in the region, and the sum of the results of the multiplication is calculated using the following equation (5), which statistically calculates the expected value (average value) of the pseudo noise variance (σ_p) 2 can be calculated.

number

[0055] The first term on the right side of equation (5) indicates that the probability density distribution and the pseudo noise variance are multiplied when the reception point x is in the region where x<0. The second term on the right side of equation (5) indicates that the probability density distribution and the pseudo noise variance are multiplied when the reception point x is in the region where x<0.

[0056] The expected value of the pseudo noise variance (σ_p) calculated statistically using the above formula (5) 2 is treated as the pseudo noise variance, the expected value (σ_p) of the pseudo noise variance calculated in step S3 2 It can be said that the noise variance can be calculated from

[0057] That is, if we substitute equation (4) for p(x) in equation (5), we get the expected value of the pseudo noise variance (σ_p) 2 and noise variance σ 2 The relational expression is obtained, and the pseudo noise variance calculated in step S3 and the expected value of the pseudo noise variance (σ_p) 2 If we consider that and are equal, the noise variance σ 2 can be calculated.

[0058] Although the case where the transmission point is (A, 0) has been described here, the pseudo noise variance can also be calculated statistically in the same way when the transmission point is (-A, 0). Furthermore, if two transmission points (ideal mapping points) occur with equal probability, then due to symmetry, the above formula (5) can be said to be the relational expression between the pseudo noise variance and the noise variance (that is, a calculation formula that expresses the relationship between the pseudo noise variance and the noise variance).

[0059] That is, when the modulation method of the primary modulation is BPSK, the noise variance can be calculated from the pseudo-noise variance using the above equation (5).

[0060] In this embodiment, the case where the modulation method of the primary modulation is QPSK and BPSK has been mainly described. However, even if digital modulation based on a modulation method other than QPSK and BPSK is performed, the only difference is the number of bits of the data signal that can be transmitted in one symbol (i.e., the number of ideal mapping points), and the noise variance can be calculated from the pseudo noise variance by finding the calculation formula (relational formula) that expresses the relationship between the pseudo noise variance and the noise variance as described above.

[0061] Note that modulation methods other than QPSK and BPSK (i.e., phase shift keying) include, for example, amplitude shift keying (ASK) and frequency shift keying (FSK). In the case of ASK, the ideal amplitude is used as the ideal mapping point, and in the case of FSK, the ideal frequency is used as the ideal mapping point, thereby making it possible to obtain the above-mentioned calculation formula.

[0062] That is, in this embodiment, by preparing a calculation formula for each modulation method of digital modulation, it is possible to support various modulation methods.

[0063] When the process of step S4 is executed, the likelihood ratio calculation unit 108 calculates the likelihood ratio for the noise variance calculated in step S4 (step S5).

[0064] Next, the error correction decoding unit 109 performs error correction decoding based on the likelihood ratio calculated in step S5 (step S6).

[0065] When the above-described process shown in FIG. 2 is executed, the bits obtained by performing error correction decoding in step S6 (i.e., the data signal modulated at the transmission source of the received signal) are output from the receiving device 10.

[0066] As described above, in this embodiment, a data subcarrier (a reception point that is a point of the reception signal) is acquired from a digitally modulated reception signal, multiple ideal mapping points (multiple ideal points that are multiple ideal signal points) corresponding to the modulation method of the digital modulation (e.g., QPSK, etc.) are acquired, the pseudo noise variance of the reception point is calculated from the acquired reception point and the multiple acquired ideal mapping points, and the noise variance of the reception point is calculated from the calculated pseudo noise variance of the reception point. Note that in this embodiment, the pseudo noise variance is the square value of the smallest difference between the reception point and each of the multiple ideal mapping points, and the noise variance is calculated based on the relationship between the pseudo noise variance and the noise variance according to the modulation method of the digital modulation. Specifically, the noise variance is calculated using a formula that expresses the relationship between the noise variance and the probability density distribution of the reception point for each of the multiple ideal mapping points.

[0067] In this embodiment, the above-described configuration makes it possible to calculate noise variance with high accuracy.

[0068] Here, it is conceivable to estimate (calculate) the noise variance using, for example, a pilot signal, which is a known signal, but the noise variance of the pilot signal and the noise variance of the data signal are not necessarily the same, and it is preferable to use the noise variance of the data signal to achieve high-quality communication. Furthermore, in a configuration in which the noise variance is estimated using a pilot signal, there is a concern that the estimation accuracy of the noise variance may deteriorate (deteriorate) when the ratio of the pilot signal to the data signal is low.

[0069] In contrast to this, in this embodiment, the noise variance is calculated using data subcarriers corresponding to data signals, and therefore higher quality communication can be achieved compared to the configuration using the pilot signals described above.

[0070] Furthermore, a possible method for calculating noise variance using a data signal is to calculate the noise variance based on the SNR value in a section where the slope of a graph showing the correlation between the SNR and the Frame Error Rate (FER) in the constellation of the received data signal begins to change significantly. However, this method tunes and fixes the noise variance when the SNR of the received signal is in a specific section, and the calculation accuracy (estimation accuracy) of the noise variance deteriorates when the SNR deviates from the specific section. Furthermore, this method requires knowledge of the points of the constellation modulated on the transmitting side (i.e., the correct ideal mapping points), and therefore cannot be applied to calculating noise variance during demodulation of the received signal.

[0071] In contrast to this, in this embodiment, the noise variance can be calculated even during decoding of the received signal.

[0072] Furthermore, there are cases where noise variance is calculated by performing an inverse matrix operation, for example, but in this embodiment, noise variance can be calculated with a smaller amount of calculation compared to such an operation.

[0073] That is, in this embodiment, by using data subcarriers (data signals), noise variance can be calculated accurately with a small amount of calculation, and as a result, likelihood ratios can be calculated accurately, the bit error rate after error correction decoding can be reduced, and high-quality communication becomes possible (i.e., the reception characteristics for received signals can be improved).

[0074] In this embodiment, the noise variance is calculated from the pseudo noise variance using a calculation formula (relational formula) that represents the relationship between the pseudo noise variance and the noise variance. However, this embodiment may be configured to calculate the noise variance from the pseudo noise variance based on this relationship. For example, a conversion table that defines this relationship (i.e., the corresponding relationship between the pseudo noise variance and the noise variance) may be prepared in advance, and the noise variance corresponding to the pseudo noise variance may be calculated (obtained) by referring to this conversion table.

[0075] Furthermore, this embodiment is applicable to any receiving device that receives a digitally modulated radio signal, and the modulation method of the digital modulation may be PSK, QAM, ASK, FSK, or the like.

[0076] Furthermore, in this embodiment, the noise variance has been described as being used to calculate the likelihood ratio for error correction decoding, but the noise variance may also be used for other purposes, such as calculating the SNR for Maximal Ratio Combining (MRC).

[0077] Furthermore, although this embodiment has been described as the receiving device 10 receiving a wireless signal (i.e., performing wireless communication), this embodiment may also be applied to the case where the receiving device 10 receives a wired signal (i.e., performing wired communication).

[0078] (Second embodiment) Next, a second embodiment will be described. In this embodiment, detailed descriptions of the same parts as in the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0079] Fig. 5 is a block diagram showing an example of the configuration of a receiving device according to this embodiment. In Fig. 5, the same parts as those in Fig. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0080] The receiving device 10 of this embodiment differs from the first embodiment described above in that it does not include the noise variance calculation unit 107 in the first embodiment described above, and includes an LDPC (Low Density Parity Check) decoding unit 110 instead of the error correction decoding unit 109 in the first embodiment.

[0081] In this embodiment, the pseudonoise variance calculation unit 106 outputs the calculated pseudonoise variance to the likelihood ratio calculation unit 108 and the LDPC decoding unit 110. The likelihood ratio calculation unit 108 receives the pseudonoise variance output from the pseudonoise variance calculation unit 106 and calculates a likelihood ratio for the pseudonoise variance. The likelihood ratio calculation unit 108 outputs the calculated likelihood ratio to the LDPC decoding unit 110.

[0082] The LDPC decoding unit 110 receives the pseudo noise variance output from the pseudo noise variance calculation unit 106 and the likelihood ratio output from the likelihood ratio calculation unit 108, and performs LDPC decoding.

[0083] Next, an example of a processing procedure of the receiving device 10 will be described with reference to the flowchart of FIG.

[0084] First, the processes of steps S11 to S13, which correspond to the processes of steps S1 to S3 shown in FIG. 2, are executed.

[0085] Next, the likelihood ratio calculation unit 108 calculates a likelihood ratio for the pseudo noise variance calculated in step S13 (step S14). Note that in the first embodiment described above, the likelihood ratio calculation unit 108 calculates a likelihood ratio for the noise variance calculated by the noise variance calculation unit 107, but the processing in step S14 is the same as that in step S5 shown in Fig. 2 described above, except that the likelihood ratio for the pseudo noise variance is calculated instead of the noise variance.

[0086] After the process of step S14 is executed, the LDPC decoding section 110 performs LDPC decoding based on the likelihood ratio calculated in step S14 (step S15).

[0087] The following describes in detail the processing of the LDPC decoding unit 110. There are various LDPC decoding algorithms, but here we will explain a case where LDPC decoding is performed using an algorithm based on the offset UMP (Uniformly Most Powerful) BP method, which is a type of BP (Belief Propagation) decoding method.

[0088] This offset UMP BP method is a technique that reduces the amount of calculation by applying an approximation to the function used in the BP decoding method, and obtains the data signal modulated at the sender of the received signal by subtracting an offset value (parameter β) from the approximation to correct it.

[0089] Here, the offset value used in the offset UMP BP method is set to a different value for each modulation method because the optimal value differs for each modulation method, but if the noise variance (value) is not accurate, it may not be possible to obtain (decode) an appropriate data signal even if the set value is used. In other words, the offset value is affected by the noise variance in addition to the modulation method.

[0090] Therefore, in this embodiment, an offset value suitable for the combination of the pseudo-noise variance calculated in step S13 and the modulation method of the primary modulation performed at the transmitter of the received signal is selected, and LDPC decoding (decoding based on the offset UMP BP method) is performed.

[0091] In this embodiment, the offset value can be selected by preparing a table in which offset values suitable for the combinations of the pseudo noise variances and modulation methods are preset and referencing the table. In this case, the offset values set in the table are values that take into consideration the possibility that the pseudo noise variance may differ from the actual noise variance, as explained in the first embodiment, for example.

[0092] Furthermore, the modulation method of the primary modulation performed at the source of the received signal can be determined based on control information received from the outside, as explained in the first embodiment above.

[0093] As described above, in this embodiment, data subcarriers are acquired from a received signal that has been digitally modulated, multiple ideal mapping points corresponding to the modulation method of the digital modulation (e.g., QPSK, etc.) are acquired, the pseudo-noise variance of the received point is calculated from the acquired reception point and the multiple acquired ideal mapping points, a likelihood ratio for the calculated pseudo-noise variance is calculated, and LDPC decoding (error correction decoding) is performed based on the calculated likelihood ratio, the calculated pseudo-noise variance, and a parameter (offset value) suitable for the modulation method of the digital modulation implemented at the transmitter of the received signal.

[0094] In this embodiment, the above-mentioned configuration enables the noise variance to be calculated accurately using data subcarriers with a small amount of calculation, and as a result, the likelihood ratio can be calculated accurately, reducing the bit error rate after error correction decoding and enabling high-quality communication.

[0095] In this embodiment, since a likelihood ratio calculated based on the pseudo-noise variance is used, there is a concern that the quality of communication may be reduced compared to the first embodiment described above. However, this embodiment is configured to select an offset value suitable for the pseudo-noise variance and modulation method, thereby enabling decoding that reduces the difference (error) between the pseudo-noise variance and the actual noise variance.

[0096] (Third embodiment) Next, a third embodiment will be described. In this embodiment, detailed descriptions of the same parts as those in the first embodiment will be omitted, and differences from the first embodiment will be mainly described. Note that the configuration of the receiving device according to this embodiment is the same as that of the first embodiment, and therefore will be described with reference to FIG. 1 as appropriate.

[0097] Here, in the first embodiment described above, the multiple data subcarriers (corresponding data signals) that make up the OFDM symbol (received sequence) were mainly described as being modulated, for example, by QPSK. However, this embodiment differs from the first embodiment in that it assumes a case in which the multiple data subcarriers are modulated, for example, by QPSK and 16QAM.

[0098] As mentioned above, when the modulation method of the primary modulation is QPSK, a two-bit data signal can be transmitted with one symbol, whereas when the modulation method of the primary modulation is 16QAM, a four-bit data signal can be transmitted with one symbol. In other words, 16QAM is a modulation method with a higher modulation multi-level number (the number of bits of the data signal that can be transmitted with one symbol) than QPSK.

[0099] In this case, the pseudonoise variance calculation unit 106 calculates the pseudonoise variance of the data subcarriers modulated by QPSK from the data subcarriers and a plurality of ideal mapping points corresponding to the QPSK. The pseudonoise variance calculation unit 106 also calculates the pseudonoise variance of the data subcarriers modulated by 16QAM from the pseudonoise variance of the data subcarriers modulated by QPSK. The pseudonoise variance calculation unit 106 outputs the calculated pseudonoise variance of each data subcarrier to the pseudonoise variance calculation unit 107.

[0100] The noise variance calculation unit 107 calculates the noise variance of each data subcarrier from the pseudo noise variance of that data subcarrier output from the pseudo noise variance calculation unit 106 .

[0101] As described above, the fact that the multiple subcarriers constituting the OFDM symbol include data subcarriers modulated by QPSK and data subcarriers modulated by 16QAM (i.e., the modulation schemes for primary modulation are QPSK and 16QAM) can be understood based on the control information received from the outside, as explained in the first embodiment above.

[0102] An example of the processing procedure of the receiving device 10 according to this embodiment will be described below with reference to the flowchart of FIG.

[0103] First, the receiving device 10 receives the above-described received signal (step S1). The process of step S1 is the same as that of the first embodiment, but in this embodiment, it is assumed that radio signals modulated by a plurality of modulation methods with different modulation multi-level numbers are input as the received signal.

[0104] When the process of step S1 is executed, a plurality of data subcarriers that have been subjected to transmission path correction are extracted from the received signal input in step S1, and the pseudo noise variance calculation unit 106 acquires the plurality of data subcarriers. The process of step S2 is the same as in the first embodiment, but in this embodiment, the pseudo noise variance calculation unit 106 acquires data subcarriers modulated by each of the plurality of modulation methods (e.g., QPSK and 16QAM) described above.

[0105] Here, Fig. 7 conceptually shows multiple subcarriers constituting an OFDM symbol in this embodiment. In the example shown in Fig. 7, multiple subcarriers 201 to 213 are shown, and of the multiple subcarriers 201 to 213, subcarriers 202 to 206 and 208 to 212 are assumed to be data subcarriers. Furthermore, of data subcarriers 202 to 206, data subcarriers 202, 203, 205, and 206 are assumed to be data subcarriers modulated by QPSK (hereinafter referred to as QPSK data subcarriers), and data subcarrier 204 is assumed to be a data subcarrier modulated by 16QAM (hereinafter referred to as 16QAM data subcarrier). Similarly, of data subcarriers 208 to 212, data subcarriers 208, 209, 211, and 212 are assumed to be QPSK data subcarriers, and data subcarrier 210 is assumed to be a 16QAM data subcarrier. In the example shown in Fig. 7, subcarriers 201, 207, and 213 are pilot subcarriers. Also, Fig. 7 assumes that the power level of each subcarrier is the same (constant).

[0106] In this case, in step S2, a plurality of data subcarriers 202 to 206 and 208 to 212 are extracted from the OFDM symbol.

[0107] Next, the pseudo-noise variance calculation unit 106 calculates the pseudo-noise variance of each of the plurality of data subcarriers acquired in step S2 (step S3).

[0108] The process of step S3 will be specifically described below with reference to the above-mentioned Fig. 7. Here, the pseudo-noise variances of the data subcarriers 202 to 206 and 208 to 212 acquired in step S2 are denoted as σ1' to σ 10 ´.

[0109] First, the pseudo noise variance calculation unit 106 calculates the pseudo noise variances σ1′, σ2′, σ4′, σ5′, σ6′, σ7′, σ9′ and σ of the QPSK data subcarriers 202, 203, 205, 206, 208, 209, 211 and 212 among the plurality of data subcarriers 202 to 206 and 208 to 212 acquired in step S2. 10 ' is calculated. Note that the pseudo noise variances σ1', σ2', σ4', σ5', σ6', σ7', σ9' and σ 10 The calculation process for ' is the same as that explained in the first embodiment, and therefore a detailed explanation thereof will be omitted here.

[0110] Next, the pseudo noise variance calculation unit 106 calculates the pseudo noise variances σ3' and σ8' of the 16QAM data subcarriers 204 and 210 out of the multiple data subcarriers 202 to 206 and 208 to 212 acquired in step S2. In this case, the pseudo noise variances σ3' and σ8' are calculated from the pseudo noise variances σ2', σ4', σ7' and σ9' of the QPSK data subcarriers 203, 205, 209 and 211 described above.

[0111] Specifically, the pseudo noise variance σ 3′ of the 16QAM data subcarrier 204 is calculated using the following equation (6): σ3´=(σ2´+σ4´) / 2 Equation (6)

[0112] Similarly, the pseudo noise variance σ 8 ′ of the 16QAM data subcarrier 210 is calculated using the following equation (7): σ8´=(σ7´+σ9´) / 2 Equation (7)

[0113] That is, in this embodiment, the pseudo noise variance of the QPSK data subcarrier is calculated in the same manner as in the first embodiment described above, and the pseudo noise variance of the 16QAM data subcarrier is calculated based on the pseudo noise variance of the QPSK data subcarrier adjacent to the 16QAM data subcarrier on the frequency axis.

[0114] When the process of step S3 is executed, the noise variance calculation unit 107 calculates the noise variance of each data subcarrier from the pseudo noise variance of that data subcarrier calculated in step S3 (step S4).

[0115] In step S4, the noise variance of the QPSK data subcarriers is calculated from the pseudo noise variance of the QPSK data subcarriers, as in the first embodiment described above. On the other hand, although 16QAM differs from QPSK in the number of bits of a data signal that can be transmitted per symbol (i.e., the number of ideal mapping points), the noise variance of the 16QAM data subcarriers can be calculated using a calculation formula obtained from the same perspective as the noise variance of the QPSK data subcarriers, or a conversion table that defines the relationship represented by the calculation formula (the correspondence relationship between pseudo noise variance and noise variance).

[0116] After the process of step S4 is executed, the processes of steps S5 and S6 are executed. The processes of steps S5 and S6 are the same as those described in the first embodiment, and therefore detailed description thereof will be omitted here.

[0117] As described above, in this embodiment, for example, QPSK data subcarriers (first reception point) modulated with QPSK (first modulation method) and 16QAM data subcarriers modulated with 16QAM (second modulation method) are obtained from a received signal (OFDM symbol), the pseudo noise variance of the QPSK data subcarriers is calculated from the QPSK data subcarriers and a plurality of ideal mapping points corresponding to QPSK, and the pseudo noise variance of the 16QAM data subcarriers is calculated from the calculated pseudo noise variance of the QPSK data subcarriers. Note that the noise variance of the QPSK data subcarriers is calculated from the pseudo noise variance of the QPSK data subcarriers calculated as described above, and the noise variance of the 16QAM data subcarriers is calculated from the pseudo noise variance of the 16QAM data subcarriers calculated as described above.

[0118] Here, the accuracy of the noise variance calculated from the pseudo noise variance decreases when the data subcarriers are modulated using a modulation scheme with a large number of modulation levels. Also, among the multiple subcarriers (multiple data subcarriers) that make up an OFDM symbol, there is a high correlation between adjacent data subcarriers on the frequency axis.

[0119] Therefore, in this embodiment, the pseudo noise variance of 16QAM data subcarriers with a large number of modulation levels is calculated from the pseudo noise variance of QPSK data subcarriers with a small number of modulation levels, thereby improving the accuracy of the pseudo noise variance of the 16QAM data subcarriers, and as a result, it is possible to calculate noise variance with high accuracy.

[0120] In this embodiment, the pseudo-noise variance of the 16QAM data subcarriers is calculated from the pseudo-noise variance of the QPSK data subcarriers, and the noise variance of the 16QAM data subcarriers is calculated from the pseudo-noise variance of the 16QAM data subcarriers. However, this embodiment may be configured to calculate the noise variance of the 16QAM data subcarriers from the noise variance of the QPSK data subcarriers without calculating the pseudo-noise variance of the 16QAM data subcarriers.

[0121] Specifically, for example, the noise variance σ3 of the 16QAM data subcarrier 204 shown in FIG. 7 may be calculated using the following equation (8). σ3=(σ2+σ4) / 2 Equation (8)

[0122] In equation (8), σ2 is the noise variance of the QPSK data subcarrier 203 calculated from the pseudo noise variance σ2' of the QPSK data subcarrier 203, and σ4 is the noise variance of the QPSK data subcarrier 205 calculated from the pseudo noise variance σ4' of the QPSK data subcarrier 205.

[0123] Similarly, the noise variance σ 8 of, for example, 16QAM data subcarriers 210 may be calculated using equation (9) below: σ8=(σ7+σ9) / 2 Equation (9)

[0124] In equation (9), σ7 is the noise variance of the QPSK data subcarrier 209 calculated from the pseudo noise variance σ7' of the QPSK data subcarrier 209, and σ9 is the noise variance of the QPSK data subcarrier 211 calculated from the pseudo noise variance σ9' of the QPSK data subcarrier 211.

[0125] In this embodiment, even in a configuration in which the noise variance of 16QAM data subcarriers is calculated from the noise variance of QPSK data subcarriers, the accuracy of the noise variance of the 16QAM data subcarriers can be improved.

[0126] In this embodiment, it is assumed that the pseudo-noise variance or noise variance of a 16QAM data subcarrier is calculated by assigning equal weights to the pseudo-noise variances or noise variances of two adjacent QPSK data subcarriers, but the weights assigned to the pseudo-noise variances or noise variances of the two adjacent QPSK data subcarriers may be changed as appropriate.

[0127] Furthermore, in this embodiment, the pseudo noise variance or noise variance of the 16QAM data subcarrier is calculated using the pseudo noise variance or noise variance of two adjacent QPSK data subcarriers, but it is not necessarily two adjacent QPSK data subcarriers, and the pseudo noise variance or noise variance of non-adjacent QPSK data subcarriers may also be used.

[0128] Furthermore, in this embodiment, different data subcarriers on the frequency axis (QPSK data subcarriers constituting an OFDM symbol) are used to calculate the pseudo-noise variance or noise variance of other data subcarriers (16QAM data subcarriers constituting an OFDM symbol), but different data subcarriers on the time axis may be used to calculate the pseudo-noise variance or noise variance of other data subcarriers.

[0129] Incidentally, in this embodiment, it is assumed that the multiple data subcarriers constituting the OFDM symbol have the same power level as shown in FIG. 7. However, if the power levels of the multiple data subcarriers are not the same as shown in FIG. 8, the pseudo-noise variance may be calculated taking into account the ratio of the power levels (power ratio).

[0130] In this case, the pseudo noise variance σ3′ of the 16QAM data subcarrier 204 is calculated using the following equation (10) instead of the above equation (6). σ3´=γ(σ2´+σ4´) / 2 Equation (10)

[0131] In addition, γ in equation (10) is a correction value calculated as the ratio between the power level of QPSK data subcarriers 203 and 205 and the power level of 16QAM data subcarrier 204. For example, if the power level of 16QAM data subcarrier 204 is 3 dB lower than the power level of QPSK data subcarriers 203 and 205, then γ=2.

[0132] Moreover, the pseudo noise variance σ8′ of the 16QAM data subcarriers 210 is calculated using the following equation (11) instead of the above equation (7). σ8´=γ(σ7´+σ9´) / 2 Equation (11)

[0133] In addition, γ in equation (11) is a correction value calculated as the ratio between the power level of the QPSK data subcarriers 209 and 211 and the power level of the 16QAM data subcarrier 210. For example, if the power level of the 16QAM data subcarrier 210 is 3 dB lower than the power level of the QPSK data subcarriers 209 and 211, then γ=2.

[0134] In this embodiment, as described above, the pseudo noise variance of a 16QAM data subcarrier is calculated from the pseudo noise variance of the QPSK data subcarrier and the power ratio between the QPSK data subcarrier and the 16QAM data subcarrier. Therefore, even if a power level difference is set between the data subcarriers that make up an OFDM symbol (received signal), the pseudo noise variance is calculated taking into account the power level difference, thereby making it possible to calculate the noise variance with high accuracy.

[0135] Although the pseudo noise variance is calculated using the power ratio between data subcarriers in the above description, the noise variance may be calculated using the power ratio.

[0136] In this case, the noise variances σ3 and σ8 of the 16QAM data subcarriers 204 and 210 are calculated using the following equations (12) and (13) instead of the above equations (8) and (9). σ3=γ(σ2+σ4) / 2 Equation (12) σ8=γ(σ7+σ9) / 2 Equation (13)

[0137] That is, in this embodiment, as described above, it is also possible to configure the noise variance of the 16QAM data subcarrier to be calculated from the noise variance of the QPSK data subcarrier and the ratio between the power level of the QPSK data subcarrier and the power level of the 16QAM data subcarrier.

[0138] For example, as shown in Fig. 8, if a specific data subcarrier (reception point) is modulated with a larger power ratio than other data subcarriers, and the noise variance is calculated assuming the same SNR, the accuracy of the noise variance may be reduced (degraded) due to the influence of the power ratio, but in this embodiment, the accuracy of the noise variance can be improved by calculating the noise variance taking into account the influence of the power ratio. Note that by configuring the receiver 10 to be able to handle data subcarriers with different power ratios, it is also possible to improve the reception performance of the receiver 10.

[0139] Although the difference in power level between the QPSK data subcarriers and the 16QAM data subcarriers has been described as being 3 dB, the difference in power level may be other than 3 dB.

[0140] In addition, the example shown in FIG. 8 assumes that the multiple data subcarriers constituting the OFDM symbol have two different power levels, but the multiple data subcarriers may have three or more different power levels.

[0141] Furthermore, although the example shown in FIG. 8 assumes that the modulation method and the power level are linked (i.e., a different power level is set for each modulation method), it is also possible to have a configuration in which the modulation method and the power level are not linked (i.e., different power levels are set for the same modulation method).

[0142] In this embodiment, it is assumed that the received sequence, which is a collection of multiple data subcarriers (reception points), is an OFDM symbol, but other examples of the received sequence include blocks of multiple single-carrier signals and single-carrier signals with cyclic prefixes (CPs). In such received sequences, the modulated signals may be different (i.e., modulated by different modulation methods), and this embodiment improves the accuracy of the noise variance at reception points with a large number of modulation levels by using the pseudonoise variance or noise variance calculated at reception points with a small number of modulation levels in such received sequences.

[0143] (Fourth embodiment) Next, a fourth embodiment will be described. In this embodiment, detailed descriptions of the same parts as those of the first and third embodiments will be omitted, and the description will mainly focus on the parts that are different from the first and third embodiments. Note that the configuration of the receiving device according to this embodiment is the same as that of the first and third embodiments, and therefore will be described with reference to FIG. 1 as appropriate.

[0144] In this embodiment, similarly to the third embodiment described above, it is assumed that a plurality of data subcarriers constituting an OFDM symbol (received sequence) are modulated by, for example, QPSK and 16QAM.

[0145] In this embodiment, the pseudonoise variance calculation unit 106 calculates the pseudonoise variance of a data subcarrier modulated with QPSK (QPSK data subcarrier) from the QPSK modulated data subcarrier and a plurality of ideal mapping points corresponding to the QPSK modulated data subcarrier. The pseudonoise variance calculation unit 106 also calculates the pseudonoise variance of a 16QAM modulated data subcarrier from the 16QAM modulated data subcarrier and a plurality of ideal mapping points corresponding to the 16QAM modulated data subcarrier. The pseudonoise variance calculation unit 106 outputs the calculated pseudonoise variance of each data subcarrier to the pseudonoise variance calculation unit 107.

[0146] The noise variance calculation unit 107 calculates the noise variance of the QPSK data subcarrier from the pseudo noise variance of the QPSK data subcarrier output from the pseudo noise variance calculation unit 106. The noise variance calculation unit 107 also calculates the noise variance of the 16QAM data subcarrier from the pseudo noise variance of the 16QAM data subcarrier output from the pseudo noise variance calculation unit 106. Furthermore, the noise variance calculation unit 107 corrects the calculated noise variance of the 16QAM data subcarrier based on the noise variance of the QPSK data subcarrier.

[0147] An example of the processing procedure of the receiving device 10 according to this embodiment will be described below with reference to the flowchart of FIG.

[0148] First, the processes of steps S21 and S22, which correspond to the processes of steps S1 and S2 shown in FIG. 2 and described in the third embodiment, are executed.

[0149] Next, the pseudo-noise variance calculation unit 106 calculates the pseudo-noise variance of each of the plurality of data subcarriers acquired in step S22 (step S23).

[0150] In this case, the pseudo noise variance calculation unit 106 calculates the pseudo noise variance of the QPSK data subcarriers among the multiple data subcarriers acquired in step S22. Note that the pseudo noise variance of the QPSK data subcarriers may be calculated as described in the first embodiment.

[0151] Furthermore, the pseudonoise variance calculation unit 106 calculates the pseudonoise variance of 16QAM data subcarriers from among the multiple data subcarriers acquired in step S22. Note that although 16QAM has a different number of ideal mapping points from QPSK, the pseudonoise variance of 16QAM data subcarriers can be calculated based on the same perspective as the pseudonoise variance of the QPSK data subcarriers. In other words, the pseudonoise variance of 16QAM data subcarriers is calculated as the square of the shortest distance between the 16QAM data subcarrier (reception point) and multiple ideal mapping points (ideal points) corresponding to the 16QAM.

[0152] When the process of step S23 is executed, the noise variance calculation unit 107 calculates the noise variance of the data subcarrier from the pseudo noise variance of each data subcarrier calculated in step S23 (step S24).

[0153] 2 described in the third embodiment, detailed description thereof will be omitted here. Note that in step S24, the noise variance of a QPSK data subcarrier is calculated from the pseudo noise variance of the QPSK data subcarrier, and the noise variance of a 16QAM data subcarrier is calculated from the pseudo noise variance of the 16QAM data subcarrier.

[0154] As explained in the third embodiment, the accuracy of the noise variance calculated from the pseudo noise variance decreases when the data subcarriers are modulated by a modulation scheme with a large number of modulation levels (for example, 16QAM). Therefore, in this embodiment, the noise variance calculation unit 107 corrects the noise variance of the 16QAM data subcarriers (step S25).

[0155] The processing of step S25 will be specifically described below with reference to the aforementioned Fig. 7. Here, the noise variance of the 16QAM data subcarrier 204 calculated from the pseudo noise variance σ3' of the 16QAM data subcarrier 204 shown in Fig. 7 is denoted as σ3, the noise variance of the QPSK data subcarrier 203 calculated from the pseudo noise variance σ2' of the QPSK data subcarrier 203 adjacent to the 16QAM data subcarrier 204 is denoted as σ2, and the noise variance of the QPSK data subcarrier 203 calculated from the pseudo noise variance σ4' of the QPSK data subcarrier 205 adjacent to the 16QAM data subcarrier 204 is denoted as σ4.

[0156] In this case, the noise variance σ3 of the 16QAM data subcarrier 204 is corrected to noise variance σ3″ using the following equation (14). σ3´´=σ3 / 2+(σ2+σ4) / 4 Equation (14)

[0157] Similarly, the noise variance of the 16QAM data subcarrier 210 calculated from the pseudo noise variance σ8' of the 16QAM data subcarrier 210 shown in Figure 7 is σ8, the noise variance of the QPSK data subcarrier 209 calculated from the pseudo noise variance σ7' of the QPSK data subcarrier 209 adjacent to the 16QAM data subcarrier 210 is σ7, and the noise variance of the QPSK data subcarrier 211 calculated from the pseudo noise variance σ9' of the QPSK data subcarrier 211 adjacent to the 16QAM data subcarrier 210 is σ9.

[0158] In this case, the noise variance σ8 of the 16QAM data subcarriers 210 is corrected to noise variance σ8″ using the following equation (15). σ8´´=σ8 / 2+(σ7+σ9) / 4 Equation (15)

[0159] After the process of step S25 is executed, the processes of steps S26 and S27, which correspond to the processes of steps S4 and S5 shown in FIG. 2, are executed.

[0160] As described above, in this embodiment, for example, QPSK data subcarriers (first reception point) modulated with QPSK (first modulation method) and 16QAM data subcarriers modulated with 16QAM (second modulation method) are obtained from a received signal (OFDM symbol), the pseudo noise variance of the QPSK data subcarriers is calculated from a plurality of ideal mapping points corresponding to the QPSK data subcarriers and QPSK, and the pseudo noise variance of the 16QAM data subcarriers is calculated from a plurality of ideal mapping points corresponding to the 16QAM data subcarriers and 16QAM. Also, in this embodiment, the noise variance of the QPSK data subcarriers is calculated from the pseudo noise variance of the QPSK data subcarriers, the noise variance of the 16QAM data subcarriers is calculated from the pseudo noise variance of the 16QAM data subcarriers, and the calculated noise variance of the 16QAM data subcarriers is corrected based on the calculated noise variance of the QPSK data subcarriers.

[0161] With this configuration, the noise variance of 16QAM data subcarriers with a large modulation level can be corrected based on the noise variance of QPSK data subcarriers with a small modulation level, thereby improving the accuracy of the noise variance of the 16QAM data subcarriers.

[0162] In this embodiment, it is assumed that the noise variance of the 16QAM data subcarriers is corrected by assigning equal weights to the first and second terms of the above-described equations (14) and (15), but the weights assigned to the first and second terms may be changed as appropriate. Furthermore, different weights may be assigned to the noise variances of two adjacent QPSK data subcarriers used in equations (14) and (15).

[0163] Furthermore, in this embodiment, the noise variance of the 16QAM data subcarriers is corrected using the noise variance of two adjacent QPSK data subcarriers, but it is not necessarily necessary for these to be two adjacent QPSK data subcarriers, and the noise variance of non-adjacent QPSK data subcarriers may also be used.

[0164] Furthermore, in this embodiment, different data subcarriers on the frequency axis (QPSK data subcarriers constituting the OFDM symbol) are used to correct the noise variance of other data subcarriers (16QAM data subcarriers constituting the OFDM symbol), but different data subcarriers on the time axis may also be used to correct the noise variance of other data subcarriers.

[0165] Furthermore, in this embodiment, a configuration has been described in which the noise variance of data subcarriers with a large number of modulation levels is corrected based on the noise variance of data subcarriers with a small number of modulation levels, but it is also possible to configure the noise variance of data subcarriers with a small number of modulation levels to be corrected based on the noise variance of data subcarriers with a large number of modulation levels.

[0166] Furthermore, in this embodiment, a configuration in which noise variance is corrected has been described, but it is also possible to configure the configuration in which the pseudo-noise variance of 16QAM data subcarriers is corrected based on the pseudo-noise variance of QPSK data subcarriers, and the noise variance of the 16QAM data subcarriers is calculated from the corrected pseudo-noise variance.

[0167] (Fifth embodiment) Next, a fifth embodiment will be described. In this embodiment, detailed descriptions of the same parts as those in the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0168] Fig. 10 is a block diagram showing an example of the configuration of a receiving device according to this embodiment. In Fig. 10, the same reference numerals are used to designate the same parts as in Fig. 1, and detailed descriptions thereof will be omitted.

[0169] In this embodiment, similarly to the third embodiment described above, it is assumed that a plurality of data subcarriers constituting an OFDM symbol (received sequence) are modulated by, for example, QPSK and 16QAM.

[0170] The receiving device 10 according to this embodiment differs from the first embodiment described above in that it includes a threshold value storage unit 111 .

[0171] The threshold value storage unit 111 is realized by, for example, a nonvolatile memory provided in the receiving device 10, and stores a threshold value that is set in advance for each modulation method of the primary modulation performed at the transmission source of the received signal.

[0172] In this embodiment, the noise variance calculation unit 107 refers to the threshold stored in the threshold storage unit 111 for each modulation method and calculates the noise variance from the pseudo-noise variance of the data subcarriers modulated by QPSK and 16QAM (QPSK data subcarriers and 16QAM data subcarriers).

[0173] Next, an example of a processing procedure of the receiving device 10 according to this embodiment will be described with reference to the flowchart of FIG.

[0174] First, the processes of steps S31 and S32, which correspond to the processes of steps S1 and S2 shown in FIG. 2 and described in the third embodiment, are executed.

[0175] Next, the process of step S33 is executed, which corresponds to the process of step S23 shown in Fig. 9. That is, in step S33, the pseudo noise variance of each of the QPSK data subcarriers and the 16QAM data subcarriers is calculated.

[0176] As described in the first embodiment, the modulation scheme of the primary modulation (digital modulation) performed at the transmission source of the received signal can be determined based on control information received from outside. Therefore, the noise variance calculation unit 107 acquires thresholds set for the modulation schemes (here, QPSK and 16QAM) determined based on the control information received from outside from the threshold storage unit 111. Hereinafter, of the thresholds acquired from the threshold storage unit 111, the threshold set for QPSK will be referred to as the QPSK threshold, and the threshold set for 16QAM will be referred to as the 16QAM threshold.

[0177] When the pseudo noise variance of the QPSK data subcarriers is calculated in step S33, the noise variance calculation unit 107 determines whether the pseudo noise variance of the QPSK data subcarriers is equal to or greater than the QPSK threshold value (step S34).

[0178] If it is determined that the pseudo noise variance of the QPSK data subcarrier is equal to or greater than the QPSK threshold (YES in step S34), the noise variance calculation unit 107 calculates the noise variance of the QPSK data subcarrier from the pseudo noise variance of the QPSK data subcarrier (step S35).

[0179] On the other hand, if it is determined that the pseudo noise variance of the QPSK data subcarrier is not greater than the QPSK threshold (i.e., the pseudo noise variance of the QPSK data subcarrier is smaller than the QPSK threshold) (NO in step S34), the noise variance calculation unit 107 outputs the pseudo noise variance of the QPSK data subcarrier as the noise variance of the QPSK data subcarrier (step S36).

[0180] While the case where the pseudonoise variance of the QPSK data subcarrier is calculated in step S33 has been described above, the same applies when the pseudonoise variance of the 16QAM data subcarrier is calculated in step S33. Specifically, if the pseudonoise variance of the 16QAM data subcarrier is equal to or greater than the 16QAM threshold, the noise variance of the 16QAM data subcarrier is calculated from the pseudonoise variance of the 16QAM data subcarrier in step S35. On the other hand, if the pseudonoise variance of the 16QAM data subcarrier is not equal to or greater than the 16QAM threshold, the pseudonoise variance of the 16QAM data subcarrier is output as the noise variance of the 16QAM data subcarrier in step S36.

[0181] That is, in this embodiment, if the pseudo noise variance is equal to or greater than the threshold, it is estimated that the reception point (data subcarrier) is far from the ideal mapping point and may exceed the decision boundary described above, and the noise variance is calculated from the pseudo noise variance. On the other hand, if the pseudo noise variance is not equal to or greater than the threshold, it is estimated that the reception point (data subcarrier) is sufficiently close to the ideal mapping point and will not exceed the decision boundary, and the pseudo noise variance is treated as the noise variance. Note that the process of calculating the noise variance from the pseudo noise variance is the same as that described in the other embodiments described above, and therefore a detailed description thereof will be omitted here.

[0182] When the processes of steps S35 and S36 are executed, the processes of steps S37 and S38 are executed, which correspond to the processes of steps S5 and S6 shown in Fig. 2. When the process of step S35 is executed, a likelihood ratio for the noise variance calculated by the noise variance calculation unit 107 is calculated in step S37. On the other hand, when the process of step S36 is executed, a likelihood ratio for the pseudo noise variance output as the noise variance from the noise variance calculation unit 107 is calculated in step S37.

[0183] Although the case where multiple data subcarriers constituting an OFDM symbol are modulated (primary modulation) using multiple different modulation methods has been described here, this embodiment may also be applied to a configuration in which the multiple data subcarriers are modulated using a single modulation method.

[0184] As described above, in this embodiment, if the pseudo noise variance of a data subcarrier (receiving point) is greater than or equal to a threshold value (a predetermined value), the noise variance of the data subcarrier is calculated from the pseudo noise variance of the data subcarrier, and if the pseudo noise variance of the data subcarrier is smaller than the threshold value, the pseudo noise variance of the data subcarrier is output as the noise variance of the data subcarrier.

[0185] In this embodiment, the above-mentioned configuration makes it possible to omit the process of calculating the noise variance when the pseudo-noise variance is smaller than a threshold value, thereby reducing the amount of calculation in the receiving device 10 (noise variance calculation unit 107) and realizing low power consumption in the receiving device 10.

[0186] Furthermore, in this embodiment, for example, if the pseudo noise variance of the QPSK data subcarrier is calculated from a plurality of ideal mapping points corresponding to the QPSK data subcarrier (first reception point) and QPSK (first modulation method), the noise variance is calculated from the pseudo noise variance if the pseudo noise variance is equal to or greater than the QPSK threshold value (first value), and the pseudo noise variance is output as the noise variance if the pseudo noise variance is smaller than the QPSK threshold value. Also, in this embodiment, for example, if the pseudo noise variance of the 16QAM data subcarrier is calculated from a plurality of ideal mapping points corresponding to the 16QAM data subcarrier (second reception point) and 16QAM (second modulation method), the noise variance is calculated from the pseudo noise variance if the pseudo noise variance is equal to or greater than the 16QAM threshold value (second value), and the pseudo noise variance is output as the noise variance if the pseudo noise variance is smaller than the QPSK threshold value.

[0187] In this case, the threshold value set for each modulation scheme may be different depending on the modulation level of the modulation scheme. Specifically, the threshold value set for a modulation scheme with a small modulation level (for example, a QPSK threshold value) is set to be larger than the threshold value set for a modulation scheme with a large modulation level (for example, a 16QAM threshold value). This makes it possible to omit the process of calculating the noise variance more efficiently (i.e., avoid performing unnecessary calculations) in consideration of the fact that, even if the pseudo noise variance (or SNR) has the same value, the probability of exceeding the decision boundary is higher in a modulation scheme with a large modulation level (the number of ideal mapping points) than in a modulation scheme with a small modulation level.

[0188] The threshold value used in this embodiment may be a value that is predetermined taking into consideration the possibility of exceeding the above-mentioned decision boundary, but may also be set based on, for example, a calculation formula (relational formula) used to calculate the noise variance. Specifically, for example, a range of pseudonoise variance within which the difference between the pseudonoise variance and the noise variance when the noise variance is calculated from the pseudonoise variance using the calculation formula is specified in advance, and a threshold value may be set to determine whether the pseudonoise variance calculated by the pseudonoise variance calculation unit 106 falls within that range. In this way, if the pseudonoise variance calculated by the pseudonoise variance calculation unit 106 falls within the predetermined range (a range within which the difference from the actual noise variance is estimated to be equal to or greater than the predetermined value), the noise variance is calculated from the pseudonoise variance, and if the pseudonoise variance calculated by the pseudonoise variance calculation unit 106 does not fall within the predetermined range, the pseudonoise variance is output as the noise variance.

[0189] Furthermore, in this embodiment, for example, when the pseudo-noise variance of a 16QAM data subcarrier is equal to or greater than the 16QAM threshold, the noise variance of the 16QAM data subcarrier is calculated from the pseudo-noise variance of the 16QAM data subcarrier. However, the process for calculating the noise variance of the 16QAM data subcarrier may be the process described in the other embodiments (for example, the third and fourth embodiments) described above.

[0190] (Sixth embodiment) Next, a sixth embodiment will be described. In this embodiment, detailed descriptions of the same parts as those in the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0191] Fig. 12 is a block diagram showing an example of the configuration of a receiving device according to this embodiment. In Fig. 12, the same reference numerals are used to designate the same parts as in Fig. 1, and detailed descriptions thereof will be omitted.

[0192] The receiving device 10 according to this embodiment differs from the first embodiment in that it includes a combining and transmission path compensation unit 112 instead of the transmission path compensation unit 105 shown in Fig. 1. Note that, although this embodiment assumes that the combining and transmission path compensation unit 112 is realized by hardware, part or all of the combining and transmission path compensation unit 112 may be realized by software, or may be realized by a combination of hardware and software.

[0193] In this embodiment, it is assumed that, for example, in order to improve the reliability of the received signal, multiple data subcarriers (multiple reception points corresponding to the same data signal) transmitting the same data signal are repeated in part or all of the received signal (i.e., part or all of the received signal is a repeated signal that has been repeatedly transmitted multiple times). In this case, the combining and transmission path correction unit 112 generates a combined data subcarrier by combining multiple data subcarriers transmitting the same data signal (e.g., multiple data subcarriers constituting an OFDM symbol), and performs transmission path correction on the combined data subcarrier. The combining and transmission path correction unit 112 outputs the transmission path corrected combined data subcarrier to the pseudonoise variance calculation unit 106.

[0194] The pseudonoise variance calculation unit 106 calculates the pseudonoise variance of the combined data subcarriers from the combined data subcarriers output from the combining and transmission path correction unit 112 and a plurality of ideal mapping points corresponding to the modulation scheme of the primary modulation implemented at the transmission source of the received signal. The pseudonoise variance calculation unit 106 outputs the calculated pseudonoise variance of the combined data subcarriers to the noise variance calculation unit 107.

[0195] The noise variance calculation unit 107 calculates the noise variance of the composite data subcarrier from the pseudonoise variance of the composite data subcarrier output from the pseudonoise variance calculation unit 106, the modulation method of the primary modulation performed at the transmitter of the received signal, and the number of multiple data subcarriers combined when the composite data subcarrier is generated.

[0196] An example of the processing procedure of the receiving device 10 according to this embodiment will be described below with reference to the flowchart of FIG.

[0197] First, the process of step S41, which corresponds to the process of step S1 shown in FIG. 2, is executed.

[0198] When the processing of step S41 is executed, a composite data subcarrier is extracted from the received signal input in step S41 via the AFE unit 101, synchronization processing unit 102, FFT processing unit 103, transmission channel estimation unit 104, and synthesis and transmission channel correction unit 112. The pseudo noise variance calculation unit 106 acquires the composite data subcarrier extracted from the received signal (step S42). Note that in this embodiment, the composite data subcarrier is generated by synthesizing and performing transmission channel correction on a plurality of data subcarriers that transmit the same data signal, as described above.

[0199] Here, a known method for combining multiple data subcarriers is, for example, Maximum Ratio Combining (MRC). For example, if the first of the two data subcarriers to be combined is the first data subcarrier, the first data subcarrier y1 (received signal) at the time of reception is expressed by the following equation (16) using the first data subcarrier x1 (transmitted signal) at the time of transmission. y1=h1x+n1 formula (16)

[0200] In equation (16), h1 represents the transmission path of the first data subcarrier, and n1 represents noise for the first data subcarrier.

[0201] On the other hand, if the second data subcarrier of the two data subcarriers to be combined is the second data subcarrier, the second data subcarrier y2 (received signal) at the time of reception is expressed by the following equation (17) using the second data subcarrier x2 (transmitted signal) at the time of transmission. y2=h2x+n2 formula (17)

[0202] In equation (17), h2 represents the transmission path of the second data subcarrier, and n2 represents noise for the second data subcarrier.

[0203] In this case, the maximum ratio combining of the first and second data subcarriers (that is, the data signal modulated at the transmission source of the received signal) x' is expressed by the following equation (18). x´=(h * 1y1+h * 2y2) / (|h1| 2 +|h2| 2 ) Formula (18)

[0204] However, in equation (18), h * 1 is the complex conjugate of h1, h * 2 represents the complex conjugate of h2.

[0205] In this embodiment, the result of the above-described maximum ratio combining can be used as the combined data subcarrier.

[0206] Next, the pseudo-noise variance calculation unit 106 calculates the pseudo-noise variance of the combined data subcarriers acquired in step S42 (step S43). Note that the process of step S43 corresponds to the process of step S3 shown in Fig. 2, and therefore a detailed description thereof will be omitted here.

[0207] When the process of step S43 is executed, the noise variance calculation unit 107 calculates the noise variance of the combined data subcarrier from the pseudo noise variance of the combined data subcarrier calculated in step S43 (step S44).

[0208] In this case, the noise variance calculation unit 107 calculates the noise variance from the pseudo-noise variance of the composite data subcarrier calculated in step S43 using a calculation formula corresponding to the modulation method of the primary modulation performed at the sender of the received signal, which is determined based on control information received from outside, for example, and performs processing to adjust the calculated noise variance according to the number of multiple data subcarriers combined when the composite data subcarrier is generated (the combined number of data subcarriers).

[0209] Specifically, for example, when the composite number is 1, the noise variance calculation unit 107 outputs the noise variance calculated from the pseudo noise variance using a calculation formula according to the modulation method. On the other hand, for example, when the composite number is greater than 1, the noise variance calculation unit 107 outputs a value greater than the noise variance calculated from the pseudo noise variance using a calculation formula according to the modulation method. That is, in this embodiment, even if the pseudo noise variance and modulation method are the same, for example, the larger the composite number, the larger the calculated noise variance.

[0210] Although the noise variance calculated from the pseudo noise variance using a calculation formula according to the modulation method has been described here as being adjusted according to the number of combined data subcarriers, the noise variance calculation unit 107 may be configured to previously store a conversion table that defines the relationship (correspondence) between the pseudo noise variance, modulation method, and the combined number of data subcarriers as described above. In this way, the noise variance calculation unit 107 can output the noise variance obtained by referring to the conversion table using as parameters the pseudo noise variance of the combined data subcarrier, the modulation method of the primary modulation implemented at the transmitter of the received signal, and the number of multiple data subcarriers combined when the combined data subcarrier is generated (i.e., the noise variance converted from these parameters).

[0211] After the process of step S44 is executed, the processes of steps S45 and S46 are executed. The processes of steps S45 and S46 are the same as the processes of steps S5 and S6 shown in Figure 2, except that the noise variance of the data subcarriers is set to the noise variance of the composite data subcarriers.

[0212] As described above, in this embodiment, a composite data subcarrier (composite reception point) is generated by combining multiple data subcarriers (multiple reception points corresponding to the same data signal) that transmit the same data signal, and the pseudo noise variance of the composite data subcarrier is calculated from the generated composite data subcarrier and multiple ideal mapping points. Also, in this embodiment, the noise variance of the composite data subcarrier is calculated from the pseudo noise variance of the composite data subcarrier, the modulation method of the digital modulation performed on the received signal (i.e., performed at the transmitter of the received signal), and the number of multiple data subcarriers combined when the composite data subcarrier is generated.

[0213] In this embodiment, the above-described configuration makes it possible to calculate the noise variance with high accuracy, taking into consideration that the relationship between the pseudo-noise variance based on the calculation formula and the noise variance changes depending on the number of combined data subcarriers. Also, by configuring the data subcarriers to be combined, it is possible to improve the reception performance of the receiving device 10.

[0214] In this embodiment, maximum ratio combining has been described as an example of a method for combining multiple data subcarriers, but the method for combining multiple data subcarriers may be other methods such as equal gain combining.

[0215] Furthermore, in this embodiment, for convenience, a case has been described in which multiple data subcarriers (repeated signals) constituting an OFDM symbol are combined, but this embodiment may also be applied to a configuration in which signals received via different antennas are combined.

[0216] Furthermore, although the present embodiment has been mainly described with respect to the differences from the first embodiment, this embodiment may be combined with the other embodiments described above. Specifically, for example, by combining this embodiment with the second embodiment described above, a configuration may be adopted in which the offset value in the LDPC decoding described in the second embodiment is changed (adjusted) according to the composite number. Furthermore, by combining this embodiment with the fifth embodiment described above, the receiving device 10 according to this embodiment may further include the threshold value storage unit described in the fifth embodiment and operate as described in the fifth embodiment.

[0217] According to at least one of the above-described embodiments, it is possible to provide a receiving device and a receiving method capable of calculating noise variance with high accuracy.

[0218] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0219] 10...receiving device, 101...AFE unit, 102...synchronization processing unit, 103...FFT processing unit, 104...transmission path estimation unit, 105...transmission path correction unit, 106...pseudo noise variance calculation unit, 107...noise variance calculation unit, 108...likelihood ratio calculation unit, 109...error correction decoding unit, 110...LDPC decoding unit, 111...threshold value storage unit, 112...synthesis and transmission path correction unit.

Claims

1. a first acquisition means for acquiring a reception point, which is a point of a received signal that has been digitally modulated; a second acquisition means for acquiring a plurality of ideal points, which are a plurality of ideal signal points corresponding to a modulation method of the digital modulation; a first calculation means for calculating a pseudo noise variance of the reception point from the acquired reception point and the acquired plurality of ideal points; a second calculation means for calculating a noise variance of the reception point from the calculated pseudo noise variance of the reception point; Equipped with the pseudo noise variance is a square value of the smallest difference between the acquired reception point and each of the acquired plurality of ideal points; The noise variance is calculated using a formula expressing the relationship between the pseudo noise variance and the noise variance according to the modulation method of the digital modulation using a probability density distribution of the reception point for each of the plurality of ideal points, or using a conversion table in which a correspondence relationship between the pseudo noise variance and the noise variance calculated from the pseudo noise variance by the formula is predefined. Receiving device.

2. The first acquisition means acquires, from the received signal, a first reception point modulated by a first modulation method and a second reception point modulated by a second modulation method having a modulation multi-level number different from that of the first modulation method, the first calculation means calculates a pseudo noise variance of the first reception point from the acquired first reception point and a plurality of ideal points corresponding to the first modulation method, and calculates a pseudo noise variance of the acquired second reception point from the calculated pseudo noise variance of the first reception point; The second calculation means calculates the noise variance of the first receiving point from the calculated pseudo noise variance of the first receiving point, and calculates the noise variance of the second receiving point from the calculated pseudo noise variance of the second receiving point.

2. The receiving device according to claim 1.

3. 3. The receiving device according to claim 2, wherein the first calculation means calculates the pseudo noise variance of the second receiving point from the pseudo noise variance of the first receiving point and a ratio of the power level of the first receiving point to the power level of the second receiving point.

4. The first acquisition means acquires, from the received signal, a first reception point modulated by a first modulation method and a second reception point modulated by a second modulation method having a modulation multi-level number different from that of the first modulation method, the first calculation means calculates a pseudo noise variance of the first reception point from the acquired first reception point and a plurality of ideal points corresponding to the first modulation method; The second calculation means calculates the noise variance of the first receiving point from the calculated pseudo noise variance of the first receiving point, and calculates the noise variance of the acquired second receiving point from the calculated noise variance of the first receiving point.

2. The receiving device according to claim 1.

5. 5. The receiving device according to claim 4, wherein the second calculation means calculates the noise variance of the second receiving point from the noise variance of the first receiving point and a ratio of the power level of the first receiving point to the power level of the second receiving point.

6. The first acquisition means acquires, from the received signal, a first reception point modulated by a first modulation method and a second reception point modulated by a second modulation method having a modulation multi-level number different from that of the first modulation method, the first calculation means calculates a pseudo noise variance of the first reception point from the acquired first reception point and a plurality of ideal points corresponding to the first modulation method, and calculates a pseudo noise variance of the second reception point from the acquired second reception point and a plurality of ideal points corresponding to the second modulation method; the second calculation means calculates a noise variance of the first receiving point from the calculated pseudo noise variance of the first receiving point, and calculates a noise variance of the second receiving point from the calculated pseudo noise variance of the second receiving point; The calculated noise variance of the second receiving point is corrected based on the calculated first noise variance.

2. The receiving device according to claim 1.

7. 7. The receiving device according to claim 2, wherein the modulation level of the first modulation method is smaller than the modulation level of the second modulation method.

8. 2. The receiving device according to claim 1, wherein the second calculation means calculates the noise variance of the reception point from the pseudo noise variance of the reception point when the calculated pseudo noise variance of the reception point is equal to or greater than a predetermined value, and outputs the pseudo noise variance of the reception point as the noise variance of the reception point when the calculated pseudo noise variance of the reception point is smaller than the predetermined value.

9. The first acquisition means acquires, from the received signal, a first reception point modulated by a first modulation method and a second reception point modulated by a second modulation method having a modulation multi-level number different from that of the first modulation method, the first calculation means calculates a pseudo noise variance of the first reception point from the acquired first reception point and a plurality of ideal points corresponding to the first modulation method, and calculates a pseudo noise variance of the second reception point from the acquired second reception point and a plurality of ideal points corresponding to the second modulation method; The second calculation means If the calculated pseudo noise variance of the first reception point is equal to or greater than a predetermined first value, calculate the noise variance of the first reception point from the pseudo noise variance of the first reception point, and if the calculated pseudo noise variance of the first reception point is smaller than the first value, output the pseudo noise variance of the first reception point as the noise variance of the first reception point; if the calculated pseudo noise variance of the second reception point is equal to or greater than a predetermined second value, calculate the noise variance of the second reception point from the pseudo noise variance of the second reception point, and if the calculated pseudo noise variance of the second reception point is smaller than the second value, output the pseudo noise variance of the second reception point as the noise variance of the second reception point; When the modulation multi-level number of the first modulation method is smaller than the modulation multi-level number of the second modulation method, the first value is larger than the second value.

9. The receiving device according to claim 8.

10. further comprising a combining means for generating a combined reception point by combining a plurality of reception points corresponding to the same data signal; the first calculation means calculates a pseudo noise variance of the synthetic reception point from the generated synthetic reception point and the acquired plurality of ideal points; The second calculation means calculates the noise variance of the composite reception point from the calculated pseudo noise variance of the composite reception point, the modulation method of the digital modulation performed on the reception signal, and the number of multiple reception points combined when the composite reception point is generated.

2. The receiving device according to claim 1.

11. a first acquisition means for acquiring a reception point, which is a point of a received signal that has been digitally modulated; a second acquisition means for acquiring a plurality of ideal points, which are a plurality of ideal signal points corresponding to a modulation method of the digital modulation; a first calculation means for calculating a square value of the smallest difference among differences between the acquired reception point and each of the acquired plurality of ideal points as a pseudo noise variance; second calculation means for calculating a likelihood ratio for the calculated pseudo-noise variance; a decoding means for performing error correction decoding based on the calculated likelihood ratio, the calculated pseudo noise variance, and an offset value suitable for a combination of the modulation scheme of the digital modulation; Equipped with The offset value is selected by referring to a table in which offset values suitable for each combination of pseudo noise variance and digital modulation method are set in advance. Receiving device.

12. A method performed by a receiving device, comprising: obtaining a reception point, which is a point of the received signal on which digital modulation has been performed; acquiring a plurality of ideal points, which are a plurality of ideal signal points corresponding to a modulation format of the digital modulation; calculating a pseudo noise variance of the received point from the acquired received point and the acquired plurality of ideal points; calculating a noise variance of the reception point from the calculated pseudo noise variance of the reception point; Equipped with the pseudo noise variance is a square value of the smallest difference between the acquired reception point and each of the acquired plurality of ideal points; The noise variance is calculated using a formula expressing the relationship between the pseudo noise variance and the noise variance according to the modulation method of the digital modulation using a probability density distribution of the reception point for each of the plurality of ideal points, or using a conversion table in which a correspondence relationship between the pseudo noise variance and the noise variance calculated from the pseudo noise variance by the formula is predefined. method.

13. A method performed by a receiving device, comprising: obtaining a reception point, which is a point of the received signal on which digital modulation has been performed; acquiring a plurality of ideal points, which are a plurality of ideal signal points corresponding to a modulation format of the digital modulation; calculating a square value of the smallest difference among differences between the acquired reception point and each of the acquired plurality of ideal points as a pseudo noise variance; calculating a likelihood ratio for the calculated pseudo-noise variance; performing error correction decoding based on the calculated likelihood ratio, the calculated pseudo noise variance, and an offset value appropriate for a combination of a modulation scheme of the digital modulation; Equipped with The offset value is selected by referring to a table in which offset values suitable for each combination of pseudo noise variance and digital modulation method are set in advance. method.

Images