Measuring device, receiving device, and program

Abstract

To obtain a received signal quality index applicable to an advanced method.SOLUTION: A measuring device 10 according to the present invention includes an error correction decoding unit 18 that repeats LDPC decoding on a received signal until there is no error or until a predetermined maximum number of iterative decoding itrmax, and a calculation unit 19 that calculates a received signal quality index indicating the reception quality of the received signal on the basis of the number of iterative decoding itr of LDPC decoding and the maximum number of iterative decoding itrmax by the error correction decoding unit 18.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a measuring device, a receiving device, and a program. [Background technology]

[0002] In current terrestrial digital television broadcasting systems, several metrics such as BER (Bit Error Rate) or MER (Modulation Error Ratio) are used as indicators of received signal quality at the receiving end. However, these metrics are difficult to use as indicators of received signal quality in the next-generation terrestrial digital television broadcasting transmission system (hereinafter referred to as the "advanced system").

[0003] For example, in the advanced method, the slope of the BER with respect to C / N (Carrier-to-Noise Ratio) near the required C / N is even steeper compared to the current method (clear effect). Also, it is difficult to calculate an accurate BER unless the signal is known.

[0004] MER is a received signal quality index that can be measured even during broadcasting. In the current system, which employs 64QAM (Quadrature Amplitude Modulation) as the carrier modulation method, MER exhibits high linearity with respect to C / N in Gaussian noise environments and is widely used as a useful received signal quality index. On the other hand, in carrier modulation methods with high modulation levels of 256QAM or higher, which are used in advanced systems, the linearity of MER with respect to C / N near the required C / N is low (see Non-Patent Literature 1). This is because, in carrier modulation methods with high modulation levels of 256QAM or higher, the distance between signal points is close, and in noisy environments, judgment errors due to hard judgment increase, making it difficult to accurately estimate the amount of noise. Therefore, it is difficult to handle MER in advanced systems in the same way as in the current system. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Hirabayashi et al., "A Study on Received Signal Quality Indicators in Advanced Terrestrial Television Broadcasting Systems," Technical Report of the Institute of Image Information and Television Engineers, vol. 46, no. 1, pp. 41-44 (2022). [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As mentioned above, it is difficult to use BER or MER, which are used in the current system, as a received signal quality index in the advanced system as well, and there is a need for a received signal quality index that can be applied to the advanced system.

[0007] The object of the present invention is to solve the above-mentioned problems and to provide a measuring device, a receiving device, and a program that can determine a received signal quality index applicable to an advanced system. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a measuring device for calculating a received signal quality index that indicates the reception quality of a received signal that has been transmitted using LDPC (Low Density Parity Check) encoding, comprising: an error correction decoding unit that repeats LDPC decoding of the received signal until the errors are eliminated or until a predetermined maximum number of repeated decoding cycles is reached; and a calculation unit that calculates the received signal quality index based on the number of repeated decoding cycles of LDPC decoding by the error correction decoding unit and the maximum number of repeated decoding cycles. The calculation unit calculates the ratio of the number of repeated decodings to the maximum number of repeated decodings as the received signal quality index. ru.

[0010] Also, the receiving device according to the present invention is a receiving device that receives a signal transmitted after being LDPC (Low Density Parity Check) encoded, and includes an error correction decoder that repeats LDPC decoding on the received signal until there are no errors or until a predetermined maximum number of repeated decoding times is reached, and a calculation unit that calculates a received signal quality indicator indicating the received quality of the received signal based on the number of repeated decoding times of LDPC decoding by the error correction decoder and the maximum number of repeated decoding times. The calculation unit calculates the ratio of the number of repeated decodings to the maximum number of repeated decodings as the received signal quality index. is provided.

[0011] Also, in order to solve the above problems, the program according to the present invention causes a computer to operate as any of the above-described measuring devices.

Advantages of the Invention

[0012] According to the measuring device, receiving device, and program of the present invention, a received signal quality indicator applicable to an advanced system can be obtained.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing a configuration example of a measuring device according to an embodiment of the present invention. [Figure 2] It is a diagram showing a configuration example of the error correction decoder shown in FIG. 1. [Figure 3] It is a diagram for explaining LDPC encoding and LDPC decoding. [Figure 4] It is a diagram for explaining LDPC decoding. [Figure 5] It is a diagram showing the relationship between C / N and INR. [Figure 6] It is a diagram showing the simulation result of the calculation of INR by the calculation unit shown in FIG. 1 when the maximum number of repeated decoding times itrmax = 25. [Figure 7] It is a diagram showing the simulation result of the calculation of INR by the calculation unit shown in FIG. 1 when the maximum number of repeated decoding times itrmax = 10.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0015] Figure 1 shows an example of the configuration of a measuring device 10 according to one embodiment of the present invention. The measuring device 10 according to this embodiment calculates a received signal quality index, which is an index indicating the reception quality of a received signal received from a transmitting side in an advanced system. In the advanced system, LDPC (Low Density Parity Check) coding is used as an error correction code. That is, LDPC coding is applied to the transmission signal on the transmitting side. The measuring device 10 calculates a received signal quality index for a received signal that has been transmitted after being LDPC coded. In the current system (ISDB-T (Integrated Services Digital Broadcasting-Terrestrial)), hierarchical transmission is performed in which data signals of multiple layers with different transmission tolerance and transmission capacity are transmitted simultaneously within the same channel. Furthermore, in the advanced system, it is being considered to transmit emergency earthquake warnings, etc., on the same physical channel as the data signals of each layer, with lower latency (Low Latency) compared to the data signals of each layer. A transmission path through which such low-latency data signals are transmitted is called an LLch. In the following, it will be explained assuming that hierarchical transmission of two layers (layer A and layer B) and transmission on an LLch are performed. In this embodiment, the present invention will be explained using an example in which it is applied to a measuring device 10 that calculates a received signal quality index for a received signal. However, it is not limited to this, and can also be applied to receiving devices such as television receivers that receive broadcasts from broadcasters.

[0016] As shown in Figure 1, the measuring device 10 according to this embodiment includes an FFT unit 11, a channel response estimation unit 12, a noise estimation unit 13, a propagation path equalization unit 14, a frequency-time DIL unit 15, an LLR calculation unit 16, a bit DIL unit 17, an error correction decoding unit 18, and a calculation unit 19.

[0017] The FFT unit 11 receives a received signal, which is a signal transmitted from the transmitting side after being encoded using LDPC encoding. The FFT unit 11 performs an FFT (Fast Fourier Transform) on the input received signal and obtains the data signals (data carriers) of each layer, a pilot signal, a TMCC (Transmission and Multiplexing Configuration Control) signal, and an LLch data signal from the data signal after the FFT. The TMCC signal is a signal that contains control information regarding the transmission of data signals of each layer. The FFT unit 11 outputs the data signals (data carriers) of each layer to the propagation path equalization unit 14, the pilot signal to the channel response estimation unit 12, and the TMCC signal and LLch data signal to the noise estimation unit 13.

[0018] The channel response estimation unit 12 uses the pilot signal output from the FFT unit 11 to estimate the channel response and outputs the estimated value to the noise estimation unit 13 and the propagation path equalization unit 14.

[0019] The noise estimation unit 13 performs noise estimation on the TMCC signal and LLch data signal output from the FFT unit 11 based on the estimated channel response values ​​output from the channel response estimation unit 12, and outputs the estimated values ​​to the LLR calculation unit 16.

[0020] The propagation path equalization unit 14 corrects (equals) the signal distortion generated in the propagation path for each layer of data signals output from the FFT unit 11 based on the estimated channel response values ​​output from the channel response estimation unit 12, and outputs the equalized signal to the frequency-time DIL unit 15.

[0021] The frequency-time DIL unit 15 performs deinterleave (DIL) on the output signal of the propagation path equalization unit 14, which is the opposite of the frequency and time interleave (IL) performed on the transmitting side, and outputs the DIL-resolved signal to the LLR calculation unit 16.

[0022] The LLR calculation unit 16 calculates the LLR (Log Likelihood Ratio) bit by bit for the signal output from the frequency-time DIL 15 based on the noise estimation values ​​output from the noise estimation unit 13, and outputs it to the bit DIL unit 17.

[0023] The bit DIL unit 17 performs a deinterleaving (DIL) operation on the LLR output from the LLR calculation unit 16, in the opposite direction to the bit IL performed on the transmitting side, and outputs the DIL-processed signal to the error correction decoding unit 18.

[0024] The error correction decoding unit 18 performs error correction decoding on the signal output from the bit DIL unit 17 and outputs the error-corrected and decoded signal as received data. As described above, in this embodiment, LDPC coding is performed on the transmitting side. The error correction decoding unit 18 performs LDPC decoding, performs BCH decoding on the LDPC-decoded signal, and outputs the BCH-decoded signal as received data.

[0025] Figure 2 shows an example of the configuration of the error correction and decoding unit 18.

[0026] As shown in Figure 2, the error correction decoding unit 18 comprises an LDPC decoding unit 181 and a BCH decoding unit 182.

[0027] The LDPC decoding unit 181 performs LDPC decoding on the signal output from the bit DIL unit 17 and outputs the LDPC-decoded signal to the BCH decoding unit 182.

[0028] The BCH decoding unit 182 performs BCH decoding on the signal output from the LDPC decoding unit 181 and outputs the BCH-decoded signal as received data.

[0029] Next, the configuration of the LDPC decoding unit 181 will be explained with reference to Figure 2. First, the LDPC encoding on the transmitting side and the LDPC decoding on the receiving side will be explained with reference to Figure 3.

[0030] At the transmitting side, an encoder that performs LDPC encoding generates a transmission bit sequence w by adding a parity bit sequence p (p1, p2,,,, p k ) to the end of the data sequence C (C0, C1, C2,,,, C n-k ). n is the code length and k / n is the coding rate.

[0031] The encoder generates the parity bit sequence p such that wH T = 0. H is a known check matrix, and H T is the transpose matrix of H. When the code length = 7 and the parity length = 3, the check matrix H is a matrix represented by the code length (horizontal) × parity length (vertical) as shown in FIG. 3.

[0032] The transmission bit sequence w generated by the encoder is transmitted and received on the receiving side. For the received bit sequence r and H T , rH T = 0 should hold.

[0033] A decoder (in this embodiment, LDPC decoding unit 181) that performs LDPC decoding on the receiving side solves rH T = 0 by the sum-product algorithm. In the sum-product algorithm, error correction is performed by the probability propagation algorithm. In the sum-product algorithm, a series of algorithms are repeated, and the process ends when there are no more errors or when the predetermined maximum number of decoding repetitions is reached.

[0034] rH T = 0, the decoder outputs the data sequence C’0, C’1, C’2,,,, C’ k as the output bit sequence C’. When rH T ≠ 0, the decoder solves the system of simultaneous equations obtained from rH T as shown in FIG. 3.

[0035] FIG. 4 is a diagram showing an example of received points and ideal symbols when BPSK modulation is performed.

[0036] In the example shown in Figure 4, it is highly probable that C'0=0, C'2=1, p'0=1, and p'2=0. On the other hand, it is not possible to determine whether C'1 and C'3 are 0 or 1. Here, the decoder is rH T From the relationship C'0+C'2+C'3+p'0=0 in the system of equations obtained, we determine that the probability of C'3=0 is large. Also, the decoder is rH T From the relationship C'1+C'2+C'3+p'2=0 in the system of equations obtained, we determine that the probability of C'1=0 is large. In this way, the probability (likelihood) propagates in the sum-product method.

[0037] The decoder (LDPC decoding unit 181) performs row-direction likelihood exchange processing, which propagates probabilities in the row direction, and column-direction likelihood exchange processing, which propagates probabilities in the column direction. When the row-direction likelihood exchange processing and the column-direction likelihood exchange processing are completed, the decoder outputs the estimated word x of the transmitted bit sequence w (estimated word output), and xH T Determine whether the value is equal to 0 (parity check). Here, x is the estimated word of the transmitted bit sequence w.

[0038] xH T If it determines that the value is 0, the decoder considers the error to be 0 and terminates error correction. T If the decoder determines that the result is not equal to 0, it repeats the row-direction likelihood exchange process, the column-direction likelihood exchange process, and the estimated word output described above. As this process is repeated, the overall likelihood improves. Here, the maximum number of repeated decoding cycles (maximum number of repeated decoding cycles) is predetermined. The larger the maximum number of repeated decoding cycles, the better the error correction capability, but it saturates at a certain point.

[0039] Next, referring again to Figure 2, the configuration of the LDPC decoding unit 181 will be described.

[0040] As shown in Figure 2, the LDPC decoding unit 181 comprises a row processing / column processing unit 1811, a parity check unit 1812, and a repeatability determination unit 1813.

[0041] The row and column processing unit 1811 performs the row-direction likelihood exchange process and the column-direction likelihood exchange process described above on the signals output from the bit DIL unit 17 described above.

[0042] The parity check unit 1812 outputs an estimated word x from the signal that has undergone row-direction likelihood exchange processing and column-direction likelihood exchange processing by the row processing / column processing unit 1811, and xH T The system determines whether the value is equal to 0 or not, and repeatedly outputs the determination result to the determination unit 1813.

[0043] The repeat determination unit 1813 determines whether or not to repeat LDPC decoding based on the determination result output from the parity check unit 1812. The repeat determination unit 1813 determines whether or not to repeat LDPC decoding if the determination result indicating no error is output, or if the number of repeated decoding itr is the maximum number of repeated decoding itr max If this condition is reached, it is determined that LDPC decoding will not be repeated. In this case, the signal after LDPC decoding is output to the BCH decoding unit 182.

[0044] The repetition determination unit 1813 outputs a determination result indicating that there is an error, and the number of repeated decoding itr is the maximum number of repeated decoding itr max If it is determined that the value is less than the specified value, it is decided to repeat the LDPC decoding process. In this case, the row processing / column processing unit 1811 repeats the process described above.

[0045] Furthermore, the repeat determination unit 1813 determines the maximum number of repeated decoding itr max The number of repeated decoding itr at the point when it is determined that LDPC decoding should not be repeated is output to the calculation unit 19.

[0046] Referring again to Figure 1, the calculation unit 19 calculates the number of repeated decoding itr for LDPC decoding by the error correction decoding unit 18 (LDPC decoding unit 181) and the maximum number of repeated decoding itr max Based on this, the received signal quality index of the received signal from the measuring device 10 is calculated.

[0047] For example, the calculation unit 19 calculates the ratio between the number of iterative decoding times itr and the maximum number of iterative decoding times itr max as a reception signal quality indicator. Hereinafter, this reception signal quality indicator is referred to as INR (Iteration Number Ratio). The calculation unit 19 calculates INR based on the following formula.

[0048]

Equation

[0049] From its definition, the number of iterative decoding times itr satisfies 1 ≤ itr ≤ itr max Therefore, INR satisfies (1 / itr max ) ≤ INR ≤ 1.

[0050] INR takes values as shown in FIG. 5 according to the number of iterative decoding times itr in C / N. Therefore, by calculating INR, the quality of the reception signal can be grasped. Also, if C / N is in the range of (1 / itr max ) < INR < 1, by grasping in advance the value of INR at the required C / N, the margin of C / N can be estimated from the difference.

[0051] Next, the simulation results of the calculation of INR by the calculation unit 19 will be described with reference to FIGS. 6 and 7. In FIGS. 6 and 7, it is assumed that two-layer hierarchical transmission of the A layer (mobile reception) and the B layer (fixed reception) is performed, and the simulation results of the calculation of INR for the B layer are shown. The simulation parameters are shown in the following table. Each parameter corresponds to an advanced method. Also, as the decoding method of the LDPC code, the sum-product method is used.

[0052]

Table 1

[0053] FIG. 6 shows the maximum number of iterative decoding times itr maxThis figure shows the simulation results when =25. In Figure 6, the horizontal axis represents C / N, the left vertical axis represents BER, and the right vertical axis represents INR.

[0054] In Figure 6, the required C / N is 19.6 dB. As shown in Figure 6, in the region where the C / N is higher than the required C / N, the BER drops sharply, making accurate measurement difficult. On the other hand, the INR is 0.76 at C / N = 19.6 dB, and decreases gradually even in the region where the C / N is higher than 19.6 dB. From this, it can be seen that the quality of the received signal can be grasped by the INR. Furthermore, by knowing the relationship between C / N and INR in advance, the receiving margin at C / N can be calculated from the INR. For example, when INR = 0.20, C / N = 23 dB. The receiving margin can be calculated from the difference between these values ​​and the INR value at the required C / N (0.76).

[0055] Figure 7 shows the maximum number of repeated decoding itr max This figure shows the simulation results when = 10. In Figure 7, the horizontal axis represents C / N, the left vertical axis represents BER, and the right vertical axis represents INR.

[0056] In Figure 7, the required C / N is 21.2 dB. In Figure 7, too, in the region where the C / N is higher than the required C / N, the BER drops sharply, making accurate measurement difficult. On the other hand, the INR is 0.79 at C / N = 21.2 dB, and decreases gradually even in the region where the C / N is higher than 21.2 dB. This indicates that the quality of the received signal can be assessed using INR.

[0057] In this embodiment, the number of repeated decoding cycles itr and the maximum number of repeated decoding cycles itr max The present invention is not limited to the example in which INR, which is the ratio of to , is calculated as an index of received signal quality. The calculation unit 19 calculates an index that decreases linearly in the region where C / N is higher than the required C / N, using the number of repeated decoding cycles itr and the maximum number of repeated decoding cycles itrmax You may also calculate based on this.

[0058] Thus, the measuring device 10 according to this embodiment processes the received signal until the error is eliminated, or until a predetermined maximum number of repeated decoding cycles (itr) is reached. max Up to this point, the error correction decoding unit 18 (LDPC decoding unit 181) repeats LDPC decoding, and the number of repeated decoding itr and the maximum number of repeated decoding itr by the error correction decoding unit 18. max The system includes a calculation unit 19 that calculates a received signal quality index based on the above.

[0059] As explained with reference to Figures 6 and 7, the number of repeated decryptions itr and the maximum number of repeated decryptions itr max The received signal quality index (e.g., INR) calculated based on this index gradually decreases in the region where the C / N is higher than the required C / N, even when applied to an advanced system. Therefore, the quality of the received signal can be estimated based on this index. Accordingly, the measurement device 10 according to this embodiment can determine a received signal quality index applicable to an advanced system. Furthermore, by calculating the received signal quality index using a simple value such as INR, an increase in circuit size can be suppressed.

[0060] Although not specifically mentioned in the embodiments, a program may be provided to operate the computer as a measuring device 10 (receiving device). The program may also be recorded on a computer-readable medium. Using a computer-readable medium allows for installation on the computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may include, for example, a CD-ROM or DVD-ROM.

[0061] Alternatively, a chip may be provided that is mounted on the measuring device 10 (receiving device), comprising a memory for storing programs for executing each process performed by the measuring device 10 (receiving device), and a processor for executing the programs stored in the memory.

[0062] Although the embodiments described above are representative examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the embodiments described above, and various modifications and changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple component blocks shown in the configuration diagram of the embodiments into one, or to divide one component block. [Explanation of Symbols]

[0063] 10. Measuring device (receiving device) 11 FFT section 12 Channel Response Estimation Unit 13 Noise Estimation Unit 14. Propagation path equalization section 15 Frequency / Time DIL section 16 LLR Calculation Unit 17-bit DIL section 18 Error Correction and Decoding Unit 19 Calculation section 181 LDPC decoding section 182 BCH Decoding Unit 1811 Row processing / Column processing 1812 Parity Inspection Department 1813 Repeat determination unit

Claims

1. A measuring device that calculates a received signal quality index indicating the reception quality of a received signal that has been transmitted using LDPC (Low Density Parity Check) encoding, An error correction decoding unit that repeats LDPC decoding on the received signal until the error is eliminated or until a predetermined maximum number of repeated decoding cycles is reached. The system includes a calculation unit that calculates the received signal quality index based on the number of repeated decoding cycles of LDPC decoding by the error correction decoding unit and the maximum number of repeated decoding cycles, The calculation unit is a measuring device that calculates the ratio of the number of repeated decodings to the maximum number of repeated decodings as the received signal quality index.

2. A receiving device that receives signals transmitted using LDPC encoding, An error correction decoding unit that repeats LDPC decoding on the received signal until the error is eliminated or until a predetermined maximum number of decoding repetitions is reached. The system includes a calculation unit that calculates a received signal quality index indicating the received signal quality based on the number of repeated decoding cycles of LDPC decoding by the error correction decoding unit and the maximum number of repeated decoding cycles, The receiving device includes a calculation unit which calculates the ratio of the number of repeated decodings to the maximum number of repeated decodings as the received signal quality index.

3. A program that causes a computer to operate as the measuring device described in claim 1.

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