Measuring device and program

Abstract

To accurately measure the quality of a reception signal even in an inferior reception environment in which a symbol error rate is large.SOLUTION: A measuring apparatus 1 comprises a quantization part 10 which quantizes constellation data of a measured signal to generate quantized data, an occurrence probability calculation part 20 which finds an occurrence probability of each of areas on a complex plane of the quantized data, a cumulative probability calculation part 30 which calculates a cumulative probability by cumulating occurrence probabilities by the areas, a reference signal generation part 40 which estimates and generates, for each carrier-to-noise power ratio, a cumulative probability obtained by cumulating occurrence probabilities of each area of the measured signal in advance as a reference signal, and a square error calculation part 70 which calculates a square error between the reference signal and the cumulative probability calculated by the cumulative probability calculation part 30, and outputs a carrier-to-noise power ratio corresponding to a reference signal with which the square error becomes minimum as a carrier-to-noise power ratio of the measured signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of terrestrial broadcasting and fixed and mobile communications, and in particular to a measuring device and program for assessing signal quality in the transmission of digital signals. [Background technology]

[0002] In digital transmission, multilevel modulation is often used to transmit more information within the available frequency bandwidth for each service. Increasing the number of bits allocated per symbol of the modulated signal (modulation order) is an effective way to improve spectral efficiency. However, the relationship between the upper limit of the information rate that can be transmitted per Hz of frequency and the signal-to-noise ratio is restricted by the Shannon limit. In currently used terrestrial digital broadcasting, information is corrected in the receiver using error-correcting codes. Adding redundant signals called parity bits to the information to be transmitted controls the signal redundancy (coding rate) and increases noise resistance. Error-correcting codes and modulation methods are closely related, and the theoretical upper limit of spectral efficiency relative to the signal-to-noise ratio is called the Shannon limit. In 1962, Gallagher proposed the LDPC (Low Density Parity Check) code as a powerful error-correcting code with performance approaching the Shannon limit (see Non-Patent Document 1).

[0003] Furthermore, instead of arranging signal points in a grid pattern, the distance between signal points is not uniform, but is arranged unevenly. In addition, by combining this with highly efficient error correcting codes such as LDPC codes and bit interleaving, noise resistance can be improved (see Non-Patent Document 2). Therefore, error-free transmission can be achieved even in poorer reception environments.

[0004] On the other hand, when transmitting digital signals, it is important to evaluate the signal quality when receiving them. For example, in the case of two-way communication, high throughput can be achieved by changing the transmission parameters according to the quality of the received signal. Even when transmission errors occur, information transmission can be achieved even at low throughput by changing the transmission parameters. Even in one-way communication, broadcasting, evaluating the quality of the received signal is important in that it not only allows us to know the reception margin, but also allows us to understand how much further improvement is needed in the quality of the received signal, even when error-free transmission is not possible.

[0005] When evaluating the quality of a received digital signal, in addition to basic information related to radio wave propagation such as received field strength, the modulation error ratio (MER) and error vector magnitude (EVM) are used as evaluation indices for the digital signal (see Non-Patent Document 3). MER is defined by equation (1). Here, N is the number of symbols used in the calculation, (I k ,Q k ) is the reference signal, (δI k ,δQ k ) denotes the error vector.

[0006]

number

[0007] The reference signal and the error vector are related by the following equation (2): k ,Q~ k ) is the received signal.

[0008]

number

[0009] [Non-Patent Document 1] R. G Gallager. Low density parity check codes. Research Monograph series Cambridge, MIT Press, 1963 [Non-patent document 2] NS Loghin, J. Zollner, B. Mouhouche, D. Ansorregui, J. Kim and S. Park, "Non-Uniform Constellations for ATSC 3.0," in IEEE Transactions on Broadcasting, vol. 62, no. 1, pp. 197-203, March 2016, doi: 10.1109 / TBC.2016.2518620. [Non-patent document 3] ETSI technical report ETR 290: "Measurement guidelines for DVB systems", Errata 1, May 1997 Summary of the Invention [Problem to be solved by the invention]

[0010] For example, if the receiver can use the transmitted signal as a reference signal by transmitting a known signal, the MER accurately indicates the quality of the received signal. However, when transmitting information, the transmitted signal is not known at the receiver, so the reference signal is the result of hard symbol decision. In such a case, in a poor reception environment, many symbol decisions will be made incorrectly, and the MER will no longer accurately indicate the quality of the received signal. This is particularly true when using the LDPC code or non-uniform digital modulation. Note that EVM is closely related to MER, and generally one can be calculated from the other. Since the above properties are identical, a detailed explanation is omitted.

[0011] In other words, the MER and EVM, which are indicators used to evaluate the transmission signal quality of conventional digital signals, have the problem that they do not provide accurate evaluation values ​​due to judgment errors during symbol judgment, especially when the reception environment is poor.

[0012] SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a measuring device and a program that can accurately measure the quality of a received signal even in a poor reception environment with a high symbol error rate. [Means for solving the problem]

[0013] In order to solve the above problem, a measurement device according to one embodiment includes a quantization unit that quantizes constellation data of a signal under measurement to generate quantized data; an occurrence probability calculation unit that calculates an occurrence probability for each region on a complex plane of the quantized data; a cumulative probability calculation unit that calculates a cumulative probability by accumulating the occurrence probabilities for each of the regions; a reference signal generation unit that estimates, for each carrier-to-noise power ratio, the cumulative probability by accumulating the occurrence probabilities for each of the regions of the signal under measurement, and generates the reference signal; and a squared error calculation unit that calculates the squared error between the reference signal and the cumulative probability calculated by the cumulative probability calculation unit, and outputs, as the carrier-to-noise power ratio of the signal under measurement, the carrier-to-noise power ratio corresponding to the reference signal when the squared error is minimized.

[0014] Furthermore, the measurement device according to one embodiment may further include a selector that outputs, as the carrier to noise power ratio, the carrier to noise power ratio that corresponds to the reference signal when the squared error is minimized.

[0015] Furthermore, the measurement device according to one embodiment may include a first weighting unit that weights the carrier-to-noise power ratio corresponding to the reference signal when the squared error is smallest and the carrier-to-noise power ratio corresponding to the reference signal when the squared error is second smallest by the respective squared errors, and outputs the weighted carrier-to-noise power ratios as the carrier-to-noise power ratios.

[0016] Furthermore, in one embodiment of the measuring device, the reference signal generation unit may include a bit string generation unit that outputs a random bit string, a carrier modulation unit that digitally modulates the bit string using a predetermined carrier modulation method to generate a digitally modulated signal, a noise generation unit that generates noise in accordance with a carrier-to-noise power ratio, an adder unit that adds the noise to the digitally modulated signal to generate an added signal, a reference signal quantization unit that quantizes constellation data of the added signal to generate reference signal quantized data, a reference signal occurrence probability calculation unit that calculates a reference signal occurrence probability for each region on a complex plane of the reference signal quantized data, and a reference signal cumulative probability calculation unit that accumulates the reference signal occurrence probability for each region to calculate the reference signal.

[0017] Furthermore, in one embodiment of the measurement device, the reference signal generation unit may include a reference signal quantization unit that quantizes constellation data of a signal under measurement having a known carrier-to-noise power ratio to generate quantized data for a reference signal, a reference signal occurrence probability calculation unit that calculates a reference signal occurrence probability for each region on a complex plane of the quantized data for the reference signal, and a reference signal cumulative probability calculation unit that calculates the reference signal by accumulating the reference signal occurrence probability for each region.

[0018] Furthermore, in one embodiment of the measurement device, the reference signal generation unit may include a reference signal occurrence probability calculation unit that calculates the reference signal occurrence probability for each region on a complex plane using a predetermined formula in accordance with the carrier-to-noise power ratio, and a reference signal cumulative probability calculation unit that calculates the reference signal by accumulating the reference signal occurrence probability for each region.

[0019] Furthermore, in one embodiment of the measurement device, the reference signal generation unit may further include a C / N degradation estimation unit that estimates the amount of C / N degradation for each frequency based on the frequency characteristics of the signal under measurement, a C / N degradation amount occurrence probability calculation unit that calculates the occurrence probability for each value of the amount of C / N degradation, and a second weighting unit that weights the reference signal calculated by the reference signal cumulative probability calculation unit with the occurrence probability calculated by the C / N degradation amount occurrence probability calculation unit and outputs the reference signal.

[0020] Moreover, a program according to one embodiment causes a computer to function as the measurement device. [Effects of the Invention]

[0021] According to the present invention, it is possible to accurately measure the quality of a received signal even in a poor reception environment with a high symbol error rate. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram showing an example of the configuration of a measurement device according to an embodiment; [Figure 2] 1 is a diagram showing an example of a constellation of a received signal input to a measurement device according to an embodiment; [Figure 3] FIG. 10 is a diagram illustrating an example of occurrence probabilities generated by a measurement device according to an embodiment. [Figure 4] FIG. 2 is a block diagram illustrating an example of the configuration of a cumulative probability calculation unit in the measurement device according to an embodiment. [Figure 5] FIG. 10 is a diagram showing an example of one-dimensional occurrence probability generated by a measurement device according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of cumulative probabilities generated by a measurement device according to an embodiment. [Figure 7] FIG. 10 illustrates an example of a squared error generated by a measurement device according to an embodiment. [Figure 8] FIG. 10 is a block diagram showing a modified example of the measurement device according to the embodiment. [Figure 9]FIG. 2 is a block diagram showing a first exemplary configuration of a reference signal generating unit according to an embodiment. [Figure 10] FIG. 10 is a block diagram showing a second exemplary configuration of a reference signal generating unit according to an embodiment. [Figure 11] FIG. 10 is a block diagram showing a third exemplary configuration of a reference signal generating unit according to an embodiment. [Figure 12] FIG. 10 is a block diagram showing a fourth exemplary configuration of a reference signal generating unit according to an embodiment. [Figure 13] FIG. 2 is a diagram illustrating an example of frequency characteristics of a received signal. [Figure 14] FIG. 10 is a diagram illustrating an example of the amount of C / N degradation of a received signal. [Figure 15] 10 is a diagram illustrating an example of the occurrence probability of the C / N degradation amount of a received signal. [Figure 16] FIG. 10 is a block diagram showing a fifth exemplary configuration of a reference signal generating unit according to an embodiment. [Figure 17] FIG. 1 is a diagram illustrating a computer simulation system. [Figure 18] FIG. 10 is a diagram illustrating a signal constellation of 256QAM NUC, R=12 / 16. [Figure 19] FIG. 10 is a diagram showing evaluation results of 256QAM NUC, R=12 / 16. [Figure 20] FIG. 10 is a diagram illustrating a signal constellation of 4096QAM NUC, R=4 / 16. [Figure 21] FIG. 10 is a diagram showing evaluation results of 4096QAM NUC,R=4 / 16. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0024] Fig. 1 is a block diagram showing an example of the configuration of a measurement device according to one embodiment of the present invention. The measurement device 1 shown in Fig. 1 includes a quantization unit 10, a first occurrence probability calculation unit 20, a cumulative probability calculation unit 30, a reference signal generation unit 40, a reference signal / C / N storage unit 60, a squared error calculation unit 70, and a selection unit 80.

[0025] The measurement device 1 receives the constellation of a received signal (signal under measurement) and outputs the carrier-to-noise power ratio (hereinafter referred to as C / N) of the received signal.

[0026] TIFF0007730288000003.tif53170

[0027] An example of constellation data is shown in Figure 2. This example shows the case where the carrier modulation is 256QAM NUC (Non-Uniform Constellation) and the error correction code coding rate is 12 / 16, and is represented as points on the complex plane. Figure 2(a) shows the case where the C / N is 0 dB, Figure 2(b) shows the case where the C / N is 20 dB, and Figure 2(c) shows the case where the C / N is 40 dB.

[0028] TIFF0007730288000004.tif84170

[0029] Fig. 3 shows an example of occurrence probabilities generated by the first occurrence probability calculation unit 20. Fig. 3 shows occurrence probabilities generated based on the constellation shown in Fig. 2, with Fig. 3(a) showing the case where the C / N is 0 dB, Fig. 3(b) showing the case where the C / N is 20 dB, and Fig. 3(c) showing the case where the C / N is 40 dB.

[0030] The cumulative probability calculation unit 30 calculates a cumulative probability by accumulating the occurrence probability for each region, and outputs the cumulative probability to the square error calculation unit 70.

[0031] 4 shows an example of the configuration of the cumulative probability calculation unit 30. The cumulative probability calculation unit 30 shown in FIG.

[0032] TIFF0007730288000005.tif27170

[0033]

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[0034] Fig. 5 shows an example of one-dimensional occurrence probabilities generated by the one-dimensionalization unit 31. Fig. 5 shows one-dimensional occurrence probabilities generated based on the occurrence probabilities shown in Fig. 3, with Fig. 5(a) showing the case where C / N is 0 dB, Fig. 5(b) showing the case where C / N is 20 dB, and Fig. 5(c) showing the case where C / N is 40 dB.

[0035] The sorting unit 32 rearranges the one-dimensional occurrence probabilities generated by the one-dimensionalization unit 31. Since the sorting can be in either ascending or descending order, ascending order should be used unless there is a particular reason not to do so. The output of the sorting unit 32 is P2(k) as shown in equation (4). The sorting unit 32 outputs the rearranged occurrence probabilities (sorted occurrence probabilities) to the accumulator 33.

[0036]

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[0037] The accumulator 33 accumulates the sorted occurrence probabilities generated by the sorter 32 and calculates the cumulative probability P3(k) using equation (5). The accumulator 33 outputs the calculated cumulative probability to the squared error calculator 70.

[0038]

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[0039] Alternatively, the accumulator 33 may calculate the cumulative probability P3(k) using equation (6).

[0040]

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[0041] Fig. 6 shows an example of cumulative probability generated by the accumulator 33. Fig. 6 shows cumulative probability generated based on the one-dimensional occurrence probability shown in Fig. 5, with Fig. 6(a) showing the case where C / N is 0 dB, Fig. 6(b) showing the case where C / N is 20 dB, and Fig. 6(c) showing the case where C / N is 40 dB. For example, when C / N is 0 dB, it can be seen that the cumulative probability does not reach 1. This is because the quantizer 10 outputs invalid data when it exceeds the representable range determined by the number of quantization bits.

[0042] The reference signal generating unit 40 estimates a cumulative probability for each C / N by accumulating the occurrence probability for each complex domain of the signal under measurement in advance, and generates the reference signal. The reference signal corresponds to the cumulative probability generated by the cumulative probability calculating unit 30. The reference signal generating unit 40 associates the reference signal with the C / N and stores it in the reference signal / C / N storage unit 60. A specific configuration of the reference signal generating unit 40 will be described later.

[0043] TIFF0007730288000010.tif59170

[0044] TIFF0007730288000011.tif27170

[0045]

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[0046] Fig. 7 shows an example of squared errors generated by the squared error calculation unit 70. Fig. 7 shows squared errors generated based on the cumulative probability shown in Fig. 6, with Fig. 7(a) showing the case where the C / N is 0 dB, Fig. 7(b) showing the case where the C / N is 20 dB, and Fig. 7(c) showing the case where the C / N is 40 dB.

[0047] The selection unit 80 outputs to the outside the C / N corresponding to the reference signal when the squared error input from the squared error calculation unit 70 is minimized as the measurement result (C / N of the signal under measurement) γ, as shown in equations (8) and (9).

[0048]

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[0049] (Modification of Measuring Device 1) Fig. 8 shows a modified example of the measurement device 1. The measurement device 2 shown in Fig. 8 includes a quantization unit 10, a first occurrence probability calculation unit 20, a cumulative probability calculation unit 30, a reference signal generation unit 40, a reference signal storage unit 60, a squared error calculation unit 70, and a first weighting unit 90. The measurement device 2 differs from the measurement device 1 shown in Fig. 1 in that it includes the first weighting unit 90 instead of the selection unit 80.

[0050] The squared error calculating section 70 outputs the calculated squared error to the first weighting section 90. As shown in equations (10) to (12), the first weighting section 90 weights the C / N corresponding to the reference signal when the squared error input from the squared error calculating section 70 is smallest and the C / N corresponding to the reference signal when the squared error is second smallest, by the respective squared errors, and outputs the result as the measurement result (C / N of the signal under measurement) γ.

[0051]

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[0052] Similarly, first weighting section 90 may perform weighting using a C / N of 3 or greater that corresponds to a reference signal with a small squared error. That is, measurement devices 1 and 2 output, as the C / N of the signal under measurement, the carrier-to-noise power ratio that corresponds to the reference signal with the smallest squared error.

[0053] Next, the reference signal generating unit 40 will be described in detail.

[0054] (First Configuration Example of Reference Signal Generator 40) Fig. 9 shows a first example configuration of the reference signal generation unit 40. The reference signal generation unit 40-1 shown in Fig. 9 includes a bit string generation unit 41, a carrier modulation unit 42, a noise generation unit 43, an addition unit 44, a quantization unit 45, a first occurrence probability calculation unit 46, and a cumulative probability calculation unit 47.

[0055] The bit string generator 41 generates a random bit string and outputs it to the carrier modulator 42 .

[0056] The carrier modulation unit 42 converts the random bit string input from the bit string generation unit 41 into an integer and then digitally modulates it using a predetermined carrier modulation method to generate a digitally modulated signal. The carrier modulation unit 42 outputs the digitally modulated signal to the addition unit 44.

[0057] The noise generator 43 generates a signal-to-noise ratio γ s The noise generating unit 43 outputs the white noise to the adding unit 44. That is, the noise generating unit 43 generates white noise with a power according to the C / N ratio.

[0058] The adder 44 generates an added signal by adding the white noise input from the noise generator 43 to the digitally modulated signal input from the carrier modulator 42. The adder 44 outputs constellation data of the added signal to the quantizer 45.

[0059] The processing of the quantizer 45, first occurrence probability calculator 46, and cumulative probability calculator 47 is the same as that of the quantizer 10, first occurrence probability calculator 20, and cumulative probability calculator 30 of the measurement device 1 shown in FIG. 1, so the explanation will be simplified. The quantizer 45 quantizes the constellation data of the added signal to generate quantized data for the reference signal. The first occurrence probability calculator 46 calculates the occurrence probability for the reference signal for each region on the complex plane of the quantized data for the reference signal. The cumulative probability calculator 47 accumulates the occurrence probability for the reference signal for each region to calculate the reference signal.

[0060] The noise generating unit 43 generates a signal-to-noise ratio γ sWhen S white noises are generated by changing the value of , S pairs of C / N and reference signal are ultimately generated, and these are stored in the reference signal and C / N storage unit 60.

[0061] The reference signal generating section 40-1 simulates the signal under measurement and uses it as a reference signal. Therefore, it is necessary to ensure the accuracy of the measurement results by collecting a sufficient number of samples to generate the reference signal.

[0062] (Second configuration example of the reference signal generating unit) 10 shows a second exemplary configuration of the reference signal generator 40. The reference signal generator 40-2 shown in FIG. 10 includes a demodulator 48, a quantizer 45, a first occurrence probability calculator 46, and a cumulative probability calculator 47.

[0063] The demodulator 48 receives an externally input signal under measurement with a known signal quality (C / N), demodulates the signal under measurement, and generates a demodulated signal. The demodulator 48 outputs constellation data of the demodulated signal to the quantizer 45. The quantizer 45 quantizes the constellation data of the demodulated signal.

[0064] The processing of the quantizer 45, first occurrence probability calculator 46, and cumulative probability calculator 47 is the same as that of the quantizer 10, first occurrence probability calculator 20, and cumulative probability calculator 30 of the measurement device 1 shown in FIG. 1, so the explanation will be simplified. The quantizer 45 quantizes the constellation data of the demodulated signal to generate quantized data for reference signal. The first occurrence probability calculator 46 calculates the occurrence probability for reference signal for each region on the complex plane of the quantized data for reference signal. The cumulative probability calculator 47 accumulates the occurrence probability for reference signal for each region to calculate the reference signal.

[0065] When S signals under measurement are input to the reference signal generating section 40-2, S pairs of C / N and reference signal are ultimately generated, and these are stored in the reference signal / C / N storage section 60.

[0066] The reference signal generating unit 40-2 requires the preparation of an externally measured signal with known signal quality, but serves the purpose of calibration by excluding characteristics of the analog signal processing and demodulation processing of the measuring devices 1 and 2 from the measurement results, and is therefore suitable for evaluating the quality of the measured signal itself.

[0067] (Third configuration example of the reference signal generator) Fig. 11 shows a third example configuration of reference signal generation unit 40. Reference signal generation unit 40-3 shown in Fig. 11 includes second occurrence probability calculation unit 49 and cumulative probability calculation unit 47. As described above, first occurrence probability calculation unit 46 included in reference signal generation unit 40-1 and reference signal generation unit 40-2 counts up input data and divides it by the total number of data to calculate the occurrence probability, whereas second occurrence probability calculation unit 49 calculates the occurrence probability using a formula.

[0068] The second occurrence probability calculation unit 49 calculates the occurrence probability by equation (13), where M is the number of signal points, (I m ,Q m ) indicates the coordinates of the mth signal point. 2 denotes the noise power, and when a given signal point is normalized, the signal-to-noise power ratio γ s That is, the second occurrence probability calculation unit 49 calculates the reference signal occurrence probability for each region on the complex plane using a predetermined formula according to the C / N.

[0069]

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[0070] When S C / Ns are input to the reference signal generating unit 40-3, S pairs of C / N and reference signal are ultimately generated, and these are stored in the reference signal / C / N storage unit 60.

[0071] The reference signal generator 40-3 calculates the occurrence probability according to a formula and generates a reference signal, which has the advantage of being able to generate a unique reference signal without collecting a large number of samples.However, since it is assumed that the noise added to the signal is white and follows a Gaussian distribution, if the noise added to the actual signal under measurement contains colored characteristics, errors will occur in the evaluation results of the signal quality.

[0072] (Fourth configuration example of the reference signal generator) 12 shows a fourth example configuration of the reference signal generator 40. The reference signal generator 40-4 shown in FIG. 12 includes a bit string generator 41, a carrier modulator 42, a noise generator 43, an adder 44, a quantizer 45, a first occurrence probability calculator 46, a cumulative probability calculator 47, a C / N degradation estimator 50, a third occurrence probability calculator 51, and a second weighting unit 52. The reference signal generator 40-4 differs from the reference signal generator 40-1 shown in FIG. 9 in that it receives frequency characteristics as input from an external device and includes the C / N degradation estimator 50, the third occurrence probability calculator 51, and the second weighting unit 52. A description of the components common to the reference signal generator 40-1 will be omitted. The reference signal generator 40-4 can be used when data related to frequency characteristics is available in addition to constellation data.

[0073] The frequency characteristics of the received signal at frequency f are expressed as H f If channel equalization is performed by dividing the received signal by the frequency characteristic, the noise components contained in the received signal are emphasized, causing degradation of signal quality after channel equalization as shown in equation (14). Therefore, the C / N degradation estimation unit 50 calculates the C / N degradation amount G for each frequency using equation (14) based on the frequency characteristic of the signal under measurement. f The C / N degradation estimation unit 50 estimates the estimated C / N degradation amount G f to the third occurrence probability calculation unit 51.

[0074]

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[0075] FIG. 13 shows an example of the frequency characteristics of the received signal, and FIG. 14 shows an example of the C / N degradation amount for each frequency of the received signal.

[0076] The third occurrence probability calculation unit 51 receives the C / N degradation amount G for each frequency from the C / N degradation estimation unit 50. f is input, and the C / N degradation amount G f Specifically, the third occurrence probability calculation unit 51 calculates the occurrence probability for each value of the C / N degradation amount G f quantize the amount of degradation Δγ and calculate the occurrence probability P G (Δγ) is output.

[0077] 15 shows an example of the occurrence probability of the C / N degradation amount generated by the third occurrence probability calculation unit 51. In this example, the occurrence probability of the C / N degradation amount being approximately -2 dB is the highest, followed by the occurrence probability of the C / N degradation amount being approximately 7 dB.

[0078] The second weighting unit 52 weights the cumulative probability calculated by the cumulative probability calculation unit 47 by the occurrence probability calculated by the third occurrence probability calculation unit 51 and outputs the weighted cumulative probability. Specifically, the second weighting unit 52 calculates the cumulative probability when frequency characteristics exist using equation (15) and outputs the cumulative probability to the reference signal / C / N storage unit 60.

[0079]

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[0080] (Fifth Configuration Example of Reference Signal Generator 40) Fig. 16 shows a fifth example configuration of the reference signal generator 40. The reference signal generator 40-5 shown in Fig. 16 includes a second occurrence probability calculator 49, a cumulative probability calculator 47, a C / N degradation estimation unit 50, a third occurrence probability calculator 51, and a second weighting unit 52. The reference signal generator 40-5 differs from the reference signal generator 40-3 shown in Fig. 11 in that it receives frequency characteristics as input from an external source and includes a C / N degradation estimation unit 50, a third occurrence probability calculator 51, and a second weighting unit 52. The reference signal generator 40-5 can be used when data related to frequency characteristics is available in addition to constellation data.

[0081] The second weighting unit 52 receives the cumulative probability from the cumulative probability calculation unit 47 and the occurrence probability for each value of the C / N degradation amount from the third occurrence probability calculation unit 51, calculates the cumulative probability when frequency characteristics exist using equation (15) as described above, and outputs the calculated cumulative probability to the reference signal / C / N storage unit 60. Note that the cumulative probability input to the second weighting unit 52 differs in that, in the case of the reference signal generation unit 40-4 shown in FIG. 12, it is the cumulative probability output by the cumulative probability calculation unit 47 in the reference signal generation unit 40-1 shown in FIG. 9, whereas in the case of the reference signal generation unit 40-5, it is the cumulative probability output by the cumulative probability calculation unit 47 in the reference signal generation unit 40-3 shown in FIG. 11. The description of each component is omitted as it has been described above.

[0082] Similarly, the reference signal generating section 40-2 shown in FIG. 10 may be further configured to include a C / N degradation estimating section 50, a third occurrence probability calculating section 51, and a second weighting section 52.

[0083] (Simulation results) Next, the results of a quality evaluation performed by simulation on the measurement device 2 including the reference signal generating unit 40-5 will be shown.

[0084] 17 shows a system diagram of the computer simulation. In simulation apparatus 100, measured signal generation unit 101 generates a measured signal that has been OFDM-modulated. After OFDM demodulation of the measured signal by OFDM demodulation unit 102, channel estimation unit 103 estimates a channel response of the measured signal, and channel equalization unit 104 generates an equalized signal by correcting (equalizing) signal distortion based on the channel response. MER calculation unit 105 calculates the MER of the equalized signal using the same method as in the conventional measurement apparatus. C / N estimation unit 106 performs the same processing as in measurement apparatus 2 equipped with reference signal generation unit 40-5, and estimates the C / N of the equalized signal.

[0085] Figure 18 shows a constellation with carrier modulation of 256 QAM (NUC) and an error correction code coding rate of 12 / 16. The lower limit of the C / N ratio (required C / N ratio) for error-free transmission is approximately 20 dB. Furthermore, OFDM with an FFT size of 16384 was used as the secondary modulation, and scattered pilots with a frequency spacing of 6 and a time spacing of 2 were used for channel estimation.

[0086] Figure 19 shows the evaluation results in an additive white Gaussian noise (AWGN) environment (Figure 19(a)) and a multipath environment (Figure 19(b)) when using the constellation shown in Figure 18. The small black circles indicate the MER when referring to the transmitted signal, the large black circles indicate the MER measurement results using the conventional measurement device, and the white circles indicate the C / N measurement results using measurement device 2. This figure shows that, in the measurement results using the conventional measurement device, the MER calculated using equation (1) is larger than the actual value when the C / N on the horizontal axis is smaller than approximately 25 dB, whereas the C / N estimated by measurement device 2 matches the C / N calculated using equation (1) using the transmitted symbol as a reference signal, indicating that accurate measurement results are obtained even in reception environments where the C / N is significantly lower than the required C / N of approximately 20 dB.

[0087] Figure 20 shows a constellation with carrier modulation of 4096 QAM (NUC) and an error correction code coding rate of 4 / 16. As in this case, when the modulation order is high, the symbol error rate is higher than when the modulation order is low, even if the reception environment is the same. Also, when the error correction code coding rate is low, the signal point arrangement generally becomes more non-uniform, and the symbol error rate also increases.

[0088] Figure 21 shows the evaluation results in an additive white Gaussian noise environment (Figure 21(a)) and a multipath environment (Figure 21(b)) when using the constellation shown in Figure 20. The small black circles indicate the MER when referring to the transmitted signal, the large black circles indicate the MER measurement results using the conventional measurement device, and the white circles indicate the C / N measurement results using measurement device 2. This figure shows that the measurement results using the conventional measurement device suffer from measurement errors of 3 dB or more even when the C / N is high due to the non-uniformity of the signal point arrangement, whereas the C / N estimated by measurement device 2 provides accurate measurement results even in a reception environment where the C / N is significantly lower than the required C / N of approximately 20 dB, as in the previous example.

[0089] (program) A computer capable of executing program instructions can be used to function as the above-described measuring devices 1 and 2. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a personal computer (PC), an electronic notepad, etc. The program instructions may be program code, code segments, etc. for performing the necessary tasks.

[0090] The computer includes a processor, a storage unit, an input unit, an output unit, and a communication interface. The processor may be a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), or an SoC (System on a Chip), and may be configured with multiple processors of the same or different types. The processor reads and executes programs from the storage unit to control the above components and perform various arithmetic processing. Note that at least a portion of these processing contents may be implemented by hardware. The input unit is an input interface that accepts user input operations and acquires information based on the user operations, such as a pointing device, keyboard, or mouse. The output unit is an output interface that outputs information, such as a display or speaker. The communication interface is an interface for communicating with external devices, such as a LAN (Local Area Network) interface.

[0091] The program may be recorded on a computer-readable recording medium. Using such a recording medium, the program can be installed on a computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a CD-ROM, a DVD-ROM, or a USB (Universal Serial Bus) memory. Furthermore, the program may be downloaded from an external device via a network.

[0092] For example, a program for causing the measuring devices 1 and 2 to function causes a computer to execute the following steps: quantizing constellation data of the signal under measurement to generate quantized data; determining the occurrence probability of each region on a complex plane of the quantized data; calculating a cumulative probability by accumulating the occurrence probability for each region; estimating the cumulative probability by previously accumulating the occurrence probability for each region of the signal under measurement for each carrier-to-noise power ratio and generating it as a reference signal; calculating the squared error between the reference signal and the cumulative probability; and outputting the carrier-to-noise power ratio corresponding to the reference signal when the squared error is minimum as the carrier-to-noise power ratio of the signal under measurement.

[0093] Furthermore, the measuring devices 1 and 2 may be configured with one or more semiconductor chips, and the semiconductor chip may be equipped with a CPU that executes a program that describes the processing content that realizes each function of the measuring devices 1 and 2.

[0094] As described above, in the present invention, the received signal is quantized to calculate the occurrence probability, and the cumulative probability is calculated. The squared error between the reference signal and the cumulative probability is also calculated, and the C / N ratio corresponding to the reference signal when the squared error is minimum is estimated as the received signal quality. Therefore, it is possible to accurately measure the received signal quality even in a poor receiving environment with a high symbol error rate.

[0095] Although the above-described embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications or alterations can be made without departing from the scope of the claims. For example, it is possible to integrate multiple building blocks shown in the block diagrams of the embodiments, or to divide one building block. [Explanation of symbols]

[0096] 1,2 Measuring equipment 10 Quantization section 20 First occurrence probability calculation unit 30 Cumulative Probability Calculation Unit 31 One-dimensionalization part 32 Sorting section 33 Accumulation Section 40,40-1,40-2,40-3,40-4,40-5 Reference signal generation section 41 Bit string generation unit 42 Carrier modulation section 43 Noise generating section 44 Addition section 45 Quantization section 46 First occurrence probability calculation unit 47 Cumulative Probability Calculation Unit 48 Demodulation section 49 Second occurrence probability calculation unit 50 C / N deterioration estimation section 51 Third occurrence probability calculation unit 52 Second weighting section 60 Reference signal / storage unit 70 Square error calculation unit 80 Selection section 90 First weighting section

Claims

1. a quantization unit that quantizes constellation data of the signal under test to generate quantized data; an occurrence probability calculation unit that calculates an occurrence probability for each region on a complex plane of the quantized data; a cumulative probability calculation unit that calculates a cumulative probability by accumulating the occurrence probability for each of the regions; a reference signal generating unit that estimates a cumulative probability obtained by previously accumulating occurrence probabilities for each of the regions of the signal under measurement for each carrier-to-noise power ratio and generates the cumulative probability as a reference signal; a square error calculation unit that calculates a square error between the reference signal and the cumulative probability calculated by the cumulative probability calculation unit, The measuring apparatus outputs the carrier-to-noise power ratio corresponding to the reference signal when the squared error is minimized as the carrier-to-noise power ratio of the signal under measurement.

2. The measurement device according to claim 1 , further comprising a selector that outputs, as the carrier to noise power ratio, a carrier to noise power ratio corresponding to a reference signal when the squared error is minimized.

3. 2. The measurement device according to claim 1, further comprising: a first weighting unit that weights a carrier-to-noise power ratio corresponding to a reference signal when the squared error is smallest and a carrier-to-noise power ratio corresponding to a reference signal when the squared error is second smallest, by the respective squared errors, and outputs the weighted carrier-to-noise power ratios as the carrier-to-noise power ratios.

4. The reference signal generation unit a bit string generator that outputs a random bit string; a carrier modulation unit that digitally modulates the bit string using a predetermined carrier modulation method to generate a digitally modulated signal; a noise generating unit that generates noise according to a carrier-to-noise power ratio; an adder unit that adds the noise to the digitally modulated signal to generate an added signal; a reference signal quantization unit that quantizes the constellation data of the addition signal to generate reference signal quantized data; a reference signal occurrence probability calculation unit that calculates a reference signal occurrence probability for each region on a complex plane of the reference signal quantized data; a reference signal cumulative probability calculation unit that calculates the reference signal by accumulating the reference signal occurrence probability for each of the regions; The measuring device according to claim 1 , comprising:

5. The reference signal generation unit a reference signal quantization unit that quantizes constellation data of a signal under test having a known carrier-to-noise power ratio to generate quantized reference signal data; a reference signal occurrence probability calculation unit that calculates a reference signal occurrence probability for each region on a complex plane of the reference signal quantized data; a reference signal cumulative probability calculation unit that calculates the reference signal by accumulating the reference signal occurrence probability for each of the regions; The measuring device according to claim 1 , comprising:

6. The reference signal generation unit a reference signal occurrence probability calculation unit that calculates a reference signal occurrence probability for each region on a complex plane using a predetermined calculation formula according to a carrier-to-noise power ratio; a reference signal cumulative probability calculation unit that calculates the reference signal by accumulating the reference signal occurrence probability for each of the regions; The measuring device according to claim 1 , comprising:

7. The reference signal generation unit a C / N degradation estimation unit for estimating a C / N degradation amount for each frequency based on the frequency characteristics of the signal under test; a C / N degradation amount occurrence probability calculation unit that calculates an occurrence probability for each value of the C / N degradation amount; a second weighting unit that weights the reference signal calculated by the reference signal cumulative probability calculation unit with the occurrence probability calculated by the C / N degradation amount occurrence probability calculation unit and outputs the weighted reference signal; The measurement device according to claim 4 , further comprising:

8. A program for causing a computer to function as the measurement device according to any one of claims 1 to 7.

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