Measuring device and measuring method

Abstract

To provide a measuring apparatus and a measuring method capable of suppressing a decrease in the correlation between MER and a CN ratio.SOLUTION: A measuring apparatus includes a receiving unit that receives a signal modulated with a predetermined modulation multilevel number from a transmission device, an extraction unit that extracts a signal that satisfies a predetermined condition from among the received signals, and a calculation unit that calculates a modulation error ratio of the extracted signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measurement device and a measurement method. [Background technology]

[0002] In terrestrial digital broadcasting (e.g., Integrated Services Digital Broadcasting-Terrestrial (ISDB-T)), MER (Modulation Error Ratio) is known as an index representing the reception level of a broadcast signal. MER is an index representing the difference in phase and amplitude of the symbol coordinates of a received signal relative to ideal symbol coordinates on an In-phase Quadrature-phase (IQ) plane (e.g., Patent Document 1).

[0003] In 64QAM (Quadrature Amplitude Modulation) used in ISDB-T, the MER has a high correlation with the Carrier to Noise (CN) ratio in a region where the CN ratio is 20 dB or more.

[0004] As such, MER has a correlation with the CN ratio and can be measured using relatively simple measuring equipment, so it is used to measure the reception level of broadcast signals in situations such as in-home construction work. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-239750 Summary of the Invention [Problem to be solved by the invention]

[0006] As a result of careful consideration, the inventors have focused on the possibility that a modulation multi-level number higher than 64QAM will be introduced with the introduction of advanced terrestrial broadcasting standards, and have found that the correlation between MER and CN ratio decreases in low CN ratio regions.

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a measurement device and a measurement method that make it possible to suppress a decrease in the correlation between the MER and the CN ratio. [Means for solving the problem]

[0008] The disclosed measuring device includes a receiving unit that receives a signal modulated with a predetermined modulation multi-level number from a transmitting device, an extracting unit that extracts a signal that satisfies predetermined conditions from the received signals, and a calculating unit that calculates the modulation error ratio of the extracted signal.

[0009] The disclosed measurement method includes the steps of receiving a signal modulated with a predetermined modulation multi-level number from a transmitting device, extracting a signal that satisfies predetermined conditions from the received signal, and calculating a modulation error ratio of the extracted signal. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a measurement device and a measurement method that can suppress a decrease in the correlation between the MER and the CN ratio. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a digital wireless transmission system 10 according to an embodiment. [Figure 2] FIG. 2 is a diagram showing a measurement device 200 according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a constellation. [Figure 4] FIG. 4 is a diagram illustrating an example of a constellation. [Figure 5] FIG. 5 is a diagram showing a measurement device 200 according to the first modified example. [Figure 6] FIG. 6 is a diagram for explaining the experiment. [Figure 7] FIG. 7 is a diagram for explaining the experiment. [Figure 8] FIG. 8 is a diagram for explaining the experiment. [Figure 9] FIG. 9 is a diagram for explaining the experiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] Therefore, specific dimensions should be determined with reference to the following explanation. Of course, the dimensional relationships and ratios may differ between the drawings.

[0014] [Disclosure Summary] The measurement device according to the outline of the disclosure includes a receiving unit that receives a signal modulated with a predetermined modulation multi-level number from a transmitting device, an extracting unit that extracts a signal that satisfies predetermined conditions from the received signals, and a calculating unit that calculates a modulation error ratio of the extracted signal.

[0015] The measurement method according to the outline of the disclosure includes the steps of receiving a signal modulated with a predetermined modulation multi-level number from a transmitting device, extracting a signal that satisfies predetermined conditions from the received signal, and calculating a modulation error ratio of the extracted signal.

[0016] In the outline of the disclosure, the measurement device extracts signals that satisfy predetermined conditions from received signals, and then calculates the modulation error ratio of the extracted signals. With this configuration, it is possible to suppress a decrease in the correlation between the modulation error ratio (hereinafter referred to as MER; Modulation Error Ratio) and CNR (Carrier to Noise Ratio) in a low CNR region, compared to a case in which the modulation error ratio is calculated based on all received signals.

[0017] [Embodiment] (Digital Wireless Transmission System) A digital wireless transmission system according to an embodiment will be described below. Fig. 1 is a diagram showing a digital wireless transmission system 10 according to an embodiment. As shown in Fig. 1, the digital wireless transmission system includes a transmitting device 100 and a measuring device 200.

[0018] In the embodiment, the digital wireless transmission system may be an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) transmission system or an advanced terrestrial broadcasting transmission system.

[0019] The transmitting device 100 may transmit broadcast signals related to terrestrial digital television broadcasting and V-Low terrestrial multimedia broadcasting (e.g., TS (Transport Stream) signals, TMCC (Transmission and Multiplexing Configuration Control) signals, etc.). The transmitting device 100 may also transmit XMI (eXtensible Modulator Interface) signals related to the terrestrial broadcasting advanced standard.

[0020] The measurement device 200 receives a signal modulated with a predetermined modulation level from the transmission device 100. The measurement device 200 calculates (measures) an MER based on the signal received from the transmission device 100 (hereinafter referred to as the received signal). Although not particularly limited, the predetermined modulation level may be a modulation level greater than 64QAM (Quadrature Amplitude Modulation) used in ISDB-T.

[0021] For example, the predetermined modulation level may be 256QAM or 1024QAM. The predetermined modulation level may be a modulation level greater than 1024QAM (for example, 4096QAM).

[0022] The shape of the constellation related to the carrier modulation method (i.e., the shape of the constellation on the IQ (In-phase Quadrature-phase) plane) may be a circle centered on the origin on the IQ plane, or a rectangle centered on the origin on the IQ plane. The distribution of the constellation may be uniform or non-uniform.

[0023] (Measuring equipment) The measuring device according to the embodiment will be described below. Fig. 2 is a diagram showing a measuring device 200 according to the embodiment.

[0024] As shown in FIG. 2, the measurement apparatus 200 includes an FFT processing unit 201, an equalization processing unit 203, a deinterleaving unit 205, an extraction unit 207, a search unit 209, and a calculation unit 211.

[0025] The FFT processing unit 201 applies FFT (Fast Fourier Transform) processing to the received signal (time domain signal) to convert the time domain signal into a frequency domain signal.

[0026] The equalization processing unit 203 performs equalization processing to equalize the frequency domain signal. For example, the equalization processing unit 203 may perform equalization processing based on the channel estimation result and noise power.

[0027] The deinterleaving unit 205 applies deinterleaving to the equalization processing unit 203. The deinterleaving may include deinterleaving in the frequency domain or may include deinterleaving in the time domain.

[0028] Extraction section 207 extracts a signal that satisfies a predetermined condition from the received signal (here, the signal output from deinterleaving section 205). The predetermined condition is that the symbol coordinates of the received signal on the IQ plane exist outside a predetermined range including the origin. Extraction section 207 extracts the received signal having symbol coordinates that exist outside the predetermined range on the IQ plane.

[0029] In the embodiment, the information element defining the predetermined range may be included in a control signal (for example, TMCC) received from the transmitting device 100. The predetermined range may be set in the measuring device 200 in advance.

[0030] Here, the shape of the constellation may be circular, as shown in Fig. 3. In Fig. 3, a non-uniform constellation of 256QAM is illustrated as an example of a constellation related to ideal symbol coordinates. In such a case, the predetermined range may be defined by the distance from the origin (Euclidean distance). For example, the information element that defines the predetermined range is an information element that indicates the distance from the origin (Euclidean distance).

[0031] Alternatively, the shape of the constellation may be rectangular, as shown in Fig. 4. In Fig. 4, a non-uniform constellation of 1024QAM is illustrated as a constellation related to ideal symbol coordinates. In such a case, the predetermined range may be defined by the maximum value of the I axis and the maximum value of the Q axis. The maximum values ​​of the I axis and the Q axis may be the same value. For example, the information element that defines the predetermined range is an information element that indicates the maximum value of the I axis (or the maximum value of the Q axis).

[0032] As described above, when the shape of the constellation is circular, the predetermined range is determined by the distance from the origin (Euclidean distance), and when the shape of the constellation is circular, the predetermined range is defined by the maximum value of the I axis (or the maximum value of the Q axis). Therefore, the method for defining the predetermined range is determined by the shape of the constellation on the IQ plane.

[0033] Searching unit 209 searches for ideal symbol coordinates (nearest neighbor search) that are closest to the symbol coordinates of the received signal extracted by extraction unit 207. By the nearest neighbor search, the symbol coordinates of the received signal are associated with the ideal symbol coordinates that are closest to the symbol coordinates of the received signal.

[0034] The calculation unit 211 calculates the MER based on the result of the nearest neighbor search. It should be noted that the nearest neighbor search is performed on the received signal extracted by the extraction unit 207, and therefore the calculation unit 211 calculates the MER based on the extracted received signal.

[0035] Specifically, the calculation unit 211 may calculate the MER based on the following formula:

[0036]

number

[0037] Here, since the MER is calculated for received signals having symbol coordinates outside the predetermined range, the numerator of the above formula may become large, which may result in an unnaturally large MER. Therefore, the calculation unit 211 may calculate the MER based on the following formula:

[0038]

number

[0039] That is, the correction coefficient α is a coefficient for correcting the power of the extracted received signal by the power of the received signals present in the entire constellation (power of the received signals present in the entire constellation / power of the extracted received signal).

[0040] The symbol coordinates of the extracted received signal may be interpreted as symbol coordinates that exist outside a specified range in the constellation, and the symbol coordinates of all received signals may be interpreted as symbol coordinates that exist throughout the entire constellation.

[0041] (Action and effect) In the embodiment, the measurement apparatus 200 extracts signals that satisfy a predetermined condition from the received signals, and then calculates the modulation error ratio of the extracted signals. With this configuration, it is possible to suppress a decrease in the correlation between the modulation error ratio and the CNR in a low CNR region, compared to a case where the modulation error ratio is calculated based on all received signals.

[0042] [Change Example 1] Modification 1 of the embodiment will be described below, focusing mainly on the differences from the embodiment.

[0043] In the embodiment, a case has been exemplified in which a signal satisfying a predetermined condition is extracted by the extraction unit 207, and then a nearest neighbor search is performed by the search unit 209. In contrast to this, in Modification Example 1, a signal satisfying a predetermined condition is extracted by the extraction unit 207 after the search unit 209 performs a nearest neighbor search.

[0044] Specifically, as shown in FIG. 5, the order of the extraction unit 207 and the search unit 209 is reversed compared to the case shown in FIG.

[0045] In such a case, the search unit 209 performs a nearest neighbor search on all received signals, and the constellation of the received signals is identified by the nearest neighbor search.

[0046] The extraction unit 207 determines the predetermined range based on the constellation of the received signal. For example, the extraction unit 207 may determine the predetermined range so as to extract symbol coordinates that form the outer periphery of the constellation of the received signal. The outer periphery may be formed by a predetermined number (for example, one) of symbol coordinates counted from the outermost position in the constellation. The predetermined number may be two or more.

[0047] As in the embodiment, calculation unit 211 calculates the MER of the received signal extracted by extraction unit 207. The method of calculating the MER is the same as in the embodiment, and therefore the details thereof are omitted.

[0048] [experiment] An experiment on the correlation between MER and CNR will be described below. In the experiment, the correlation between MER and CNR was confirmed for a comparative example, example 1, and example 2. In the comparative example, the MER was calculated for all received signals. In example 1, the MER was calculated using the method according to the embodiment. In example 2, the MER was calculated using the method according to the comparative example. In examples 1 and 2, the MER was calculated using the above-mentioned correction coefficient.

[0049] First, experimental results for a non-uniform constellation of 256QAM will be described. The FFT size is 16k, and the coding rate is 12 / 16. As shown in Fig. 6, it was confirmed that the correlation (linearity) with MER is reduced in the low CNR region (around 20dB) in the comparative example, whereas the correlation with MER is improved in the low CNR region (around 20dB) in the examples 1 and 2 compared to the comparative example.

[0050] Secondly, experimental results for a non-uniform constellation of 1024QAM will be described. The FFT size is 16k and the coding rate is 9 / 16. As shown in Fig. 7, it was confirmed that the correlation (linearity) with MER is reduced in the low CNR region (around 20dB) in the comparative example, whereas the correlation with MER is improved in the low CNR region (around 20dB) in the examples 1 and 2 compared to the comparative example.

[0051] Thirdly, experimental results for a uniform constellation of 256QAM will be described. The FFT size is 16k, and the coding rate is 12 / 16. As shown in Fig. 8, it was confirmed that the correlation (linearity) with MER is reduced in the low CNR region (around 20dB) in the comparative example, whereas the correlation with MER is improved in the low CNR region (around 20dB) in the examples 1 and 2 compared to the comparative example.

[0052] Fourth, experimental results for a uniform constellation of 1024QAM will be described. The FFT size is 16k, and the coding rate is 9 / 16. As shown in Fig. 9, it was confirmed that the correlation (linearity) with MER is reduced in the low CNR region (around 20 dB) in the comparative example, whereas the correlation with MER is improved in the low CNR region (around 20 dB) in the examples 1 and 2 compared to the comparative example.

[0053] [Other embodiments] Although the present invention has been described by the above disclosure, the descriptions and drawings that form part of this disclosure should not be understood as limiting the present invention. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art.

[0054] In the above disclosure, the measurement device 200 has been mainly described. However, the above disclosure is not limited to this. The functions of the measurement device 200 may be implemented in a receiving device that receives a signal from the transmitting device 100. In such a case, the measurement device may be read as a receiving device.

[0055] In the above disclosure, 256QAM and 1024QAM have been mainly described. However, the above disclosure is not limited thereto. The predetermined modulation multi-level number may be a modulation multi-level number greater than 1024QAM (for example, 4096QAM).

[0056] In the above disclosure, a case has been described in which the predetermined range is defined so as to extract a received signal having a predetermined number of symbol coordinates counted from the outermost part of the constellation (symbol coordinates constituting the outer periphery of the constellation). However, the above disclosure is not limited to this. The predetermined number may vary depending on the modulation level applied to the transmission signal, the coding rate applied to the transmission signal, the shape of the constellation (e.g., circular or rectangular), or the distribution of the constellation (e.g., uniform or non-uniform). In other words, the predetermined range may be determined by at least one of the shape and distribution of the constellation, or by at least one of the modulation level and coding rate applied to the transmission signal.

[0057] Although not specifically mentioned in the above disclosure, a program may be provided that causes a computer to execute each process performed by the measurement device 200. The program may also be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0058] Alternatively, a chip may be provided that is configured by a memory that stores a program for executing each process performed by the measurement device 200 and a processor that executes the program stored in the memory. [Explanation of symbols]

[0059] 10... digital wireless transmission system, 100... transmitting device, 200... measuring device, 201... FFT processing unit, 203... equalization processing unit, 205... deinterleaving unit, 207... extraction unit, 209... search unit, 211... calculation unit

Claims

1. a receiving unit that receives a signal modulated with a predetermined modulation level from a transmitting device; an extraction unit that extracts signals that satisfy a predetermined condition from among the received signals; a calculation unit for calculating a modulation error ratio of the extracted signal, The calculation unit calculates a modulation error ratio of the extracted signal based on a correction coefficient that corrects the power of the extracted signal.

2. 2. The measurement apparatus according to claim 1, wherein the predetermined condition is a condition that a symbol coordinate of a received signal on an IQ plane is outside a predetermined range including an origin.

3. The measurement apparatus according to claim 2 , wherein the predetermined range is determined by at least one of a shape and a distribution of a constellation on the IQ plane.

4. The shape of the constellation is circular, The measurement apparatus of claim 3 , wherein the predetermined range is defined by a Euclidean distance from the origin.

5. 5. The measurement device according to claim 2, wherein the predetermined range is determined by at least one of a modulation level and a coding rate applied to the signal transmitted from the transmitting device.

6. 6. The measuring device according to claim 2, wherein the predetermined range is determined based on a control signal received from the transmitting device.

7. The measurement device according to claim 3 or 4, wherein the extraction unit determines the predetermined range based on the constellation related to the received signal.

8. Step A of receiving a signal modulated with a predetermined modulation level from a transmitting device; A step B of extracting signals that satisfy a predetermined condition from among the received signals; C. calculating a modulation error ratio of the extracted signal, The measurement method, wherein step C includes calculating a modulation error ratio of the extracted signal based on a correction factor that corrects a power of the extracted signal.

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