JP5226648B2 - Evaluation apparatus and evaluation method - Google Patents

Description

  The present invention relates to an evaluation technique, and more particularly to a technique for evaluating the performance of a digital signal receiver.

  When verifying the performance of an electronic device, the value of a control variable is changed, the index value is measured for each of these values, and the relationship between the value of the control variable and the index value is obtained.

  A raster method is known as a method for obtaining the relationship between the value of the control variable and the index value. In the raster method, first, the upper limit value and lower limit value of the control variable, the sweep step width, and the accumulation time are set. Then, the first measurement point, that is, the first value of the control variable is set. This first measurement point is set to either the upper limit value or the lower limit value of the control variable. Then, the sequential sweep of the control variable and the measurement of the index value are repeated from the first measurement point within the range of the upper limit value and the lower limit value, and the relationship between the control variable and the index value is obtained.

  The raster method can also be used when verifying digital signal transmission performance for a communication system. One of the indexes representing the transmission performance of digital signals is BER (Bit Error Rate). The relationship between C / N and BER by changing the value of a control variable such as C / N (Carrier to Noise Ratio) within the range of the upper limit and lower limit and measuring the BER for each C / N Can be requested.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a method for improving efficiency by reducing measurement points (that is, the number of values of control variables) when obtaining the relationship between control variables and BER.

  In general, the measurement of BER requires a large measurement parameter, and it takes a long measurement time to measure a low BER while maintaining a certain statistical reliability. This will be described with reference to FIG.

  FIG. 17 is Table 1 of Patent Document 1 and shows the relationship among BER (Error Rate), transfer bit rate (Bit Rate), and measurement time (Measurement Time). As illustrated, the lower the transfer bit rate and the lower the BER, the more measurement time is required. Therefore, the processing time can be shortened by reducing the measurement points.

  FIG. 18 is a flowchart in which step numbers are reassigned to FIG. 5 of Patent Document 1, and a procedure for obtaining a diagram showing the relationship between the control variable and the BER by the method disclosed in the Patent Document. is there.

  As shown in FIG. 18, first, a plurality of measurement points (initial measurement points) are given, and the BER is measured at each measurement point (S10). The plurality of measurement points are given by selecting a point with a large interval or selecting both the positive and negative sides of the diagram (corresponding to the upper limit value and the lower limit value of the control variable).

  Then, BER measurement at a new point is performed (S12). The points are stored and the measurement results are blotted on a diagram (S12, S14, S16).

  The process from the selection of a new point is repeated until the diagram meets the user's request (S18: No, S20, S12 ~). Note that selection of a new point (S20) includes reading of already measured points and selection using an optimization criterion (S22, S24), as shown on the right side of FIG. Optimization criteria include maximizing the distance between a new measurement point and a previously measured measurement point, minimizing the number of low BER measurements.

  Patent Document 2 discloses a technique for measuring the BER of a communication system such as CDMA. In this technique, synchronization is performed between transmission and reception of a spread spectrum code signal used for a pilot signal, and the BER is measured by demodulating the pilot signal. By doing so, the BER can be measured without frame synchronization.

On the other hand, in communication systems such as digital terrestrial television broadcasting, whether or not reception is possible is determined by whether or not the BER value is equal to or higher than a reference value (usually 2 × 10 ⁻⁴ ) in the output after Viterbi decoding. The In such a communication system, when evaluating the performance of a receiver, a technique for obtaining values corresponding to the BER reference value for various control variables is known. Specifically, the BER is measured while changing the value of the control variable, and the value of the control variable corresponding to the reference value of BER is obtained. Control variables include C / N (Carrier to Noise Ratio), input power of a desired wave, input power of an interference wave, and the like. Note that the value of the control variable corresponding to the reference value of BER is usually obtained as a range instead of one point. In the following description, “the value of the control variable corresponding to the BER reference value” includes “the range of the value of the control variable corresponding to the BER reference value”.

  When performing such an evaluation on the performance of the receiver, the raster method described above or the method of Patent Document 1 can be applied.

  When the raster method is applied, a processing procedure shown in FIG. 19 can be considered. First, the upper limit value and lower limit value of the control variable, the sweep step width, and the accumulation time are set (S30). Then, the first BER measurement point, that is, the first value of the control variable is set (S32). The first BER measurement point is set to either the upper limit value or the lower limit value of the control variable.

  Then, from the first BER measurement point, the BER measurement accompanying the sequential sweep of the control variable is repeated (S34). The measurement ends when the value of the control variable corresponding to the BER reference value is obtained (S36).

  FIG. 20 shows an example of a control variable and BER diagram obtained by the raster method. This is an example of a C / N and BER diagram at a constant sweep step width. In the example of FIG. 20, the measurement of BER is started from the lower limit value of the control variable C / N, and the measurement is completed when the C / N range corresponding to the reference value of BER is obtained. Further, as can be seen from FIG. 20, BER has a monotonically decreasing dependency on C / N.

  Further, when applying the method of Patent Document 1, step S18 in FIG. 18 may be replaced with “Is the value of the control variable corresponding to the BER reference value obtained?”.

  Moreover, when evaluating by the method mentioned above with respect to the receiver of communication systems, such as CDMA, the method of patent document 2 is applicable to the measurement of BER.

JP 2004-15807 A Japanese Patent Laid-Open No. 10-145339

ARIB STB-B31 1.7 edition Tadashi Shiomi and Mitsutoshi Hatori: “Digital Broadcasting”, Ohmsha (1998. 7)

  By the way, when the raster method is applied as shown in FIG. 19, the control variable is simply swept within the range between the upper limit value and the lower limit value, and therefore the value of the target control variable (corresponding to the reference value of BER). There is a possibility that many BER measurements will be performed at measurement points far away from the control variable). Since the measurement values at these measurement points are not used for obtaining the value of the target control variable, there is a possibility that a lot of waste occurs.

  When the method of Patent Document 1 is applied, when a new point is selected, for example, when an optimization criterion is applied so that the norm is maximized, that is, the distance from the previously measured point is maximized, the previous measurement is performed. One of the new points and the new point inevitably corresponds to a low BER, so that a low BER is measured, which takes time.

  Also, since the bit rate of the pilot signal is usually lower than the bit rate of the data signal, when the method of Patent Document 2 is applied to the BER measurement, the BER is measured at a low bit rate, and the measurement takes time. There is a problem that it takes.

  One aspect of the present invention provides a control that corresponds to a reference value of an index value by measuring an index value that represents the performance of the receiver for each of a plurality of values of a control variable for a receiver that receives a digital signal. This is an evaluation device for obtaining the value of a variable. The digital signal is modulated by a predetermined carrier modulation scheme, and includes a pilot signal modulated by a pilot modulation scheme that is a modulation scheme different from the carrier modulation scheme. The evaluation apparatus according to this aspect includes a synchronization determination unit and a measurement unit.

  The synchronization determination unit obtains the value of the control variable at the changing point at which the synchronization between the transmission and reception of the pilot signal included in the digital signal changes from the state where the synchronization is impossible to the state where the synchronization is possible.

  The measurement unit converts the value of the control variable obtained by the synchronization determination unit into a value corresponding to the carrier modulation method from the correlation of the index value with respect to the control variable between the pilot modulation method and the carrier modulation method. The index value is measured for the digital signal received by the receiver, with the later value as the first measurement point.

  Note that an apparatus in which the above aspect is replaced with a method or system, a program that causes a computer to operate as the apparatus, a recording medium that records the program, and the like are also effective as an aspect of the present invention.

  According to the technology of the present invention, it is possible to efficiently evaluate the performance of a digital signal receiver.

It is a figure which shows the basic composition on the transmission side of digital broadcasting. It is a figure which shows the transmission-line encoding part in the basic composition shown in FIG. It is a figure which shows the structure of the OFDM segment in the case of synchronous modulation. It is a figure which shows the structure of the OFDM segment in the case of differential modulation. It is a figure which shows the correlation of the BER characteristic in a different modulation system. It is a figure which shows the example of theoretical BER characteristic and measured BER characteristic. It is a figure which shows the evaluation apparatus concerning the 1st Embodiment of this invention. It is a flowchart which shows the example of the flow of a process by the synchronous determination part of the evaluation apparatus shown in FIG. 7 (the 1). It is a flowchart which shows the example of the flow of a process by the synchronous determination part of the evaluation apparatus shown in FIG. 7 (the 2). It is a figure for demonstrating the setting of the first BER measurement point by the measurement part of the evaluation apparatus shown in FIG. It is a flowchart which shows the flow of a process by the evaluation part of the evaluation apparatus shown in FIG. It is a figure for demonstrating the difference of the evaluation result resulting from the fluctuation | variation of a sample group. It is a figure which shows the parameter setting part in the evaluation apparatus of the 2nd Embodiment of this invention. It is a figure which shows the synchronous determination part in the evaluation apparatus of the 3rd Embodiment of this invention. It is a figure which shows the measurement part in the evaluation apparatus of the 4th Embodiment of this invention. It is a figure for demonstrating the first point correction | amendment part of the measurement part shown in FIG. It is a figure which shows the relationship between the measurement time of BER, the value of BER, and a bit rate. It is a figure for demonstrating the method of patent document 1. FIG. It is a flowchart at the time of applying a raster method when calculating | requiring the value of the control variable corresponding to the reference value of an index value. It is a figure which shows the example of the diagram of the control variable and BER obtained by the raster method.

  Embodiments of the present invention will be described below with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Each element described in the drawings as a functional block for performing various processes can be configured by a CPU, a memory, and other circuits in terms of hardware, and a program loaded in the memory in terms of software. Etc. Note that, in each drawing, the same element is denoted by the same reference numeral, and redundant description is omitted as necessary.

Prior to specific embodiments of the present invention, first, the principle of the present invention will be described.
The inventor of the present application has established an efficient evaluation method based on knowledge obtained through extensive research on receiver performance evaluation such as terrestrial digital broadcasting. Here, the transmission path encoding system will be described by taking the ISDB-T system adopted in Japan as a standard for terrestrial digital broadcasting as an example.

  The ISDB-T system is defined by ARIB STB-B31 (ARIB: Association of Radio Industries and Businesses). FIG. 1 shows a basic configuration of the transmission side determined by this method. In addition, this figure is FIG. 2-1 in P8 of nonpatent literature 1. FIG.

  As shown in FIG. 1, on the transmission side, one transport stream (TS) defined by MPEG2 Systems, or one TS obtained by remultiplexing a plurality of TSs, is transmitted to a plurality of transmission path coding units 10. Transmission path coding is performed and the signal is transmitted as one OFDM signal.

  FIG. 2 is a diagram of FIG. 3-2 in P16 of Non-Patent Document 1 and shows a basic configuration of the transmission path encoding unit 10. The transmission path encoding unit 10 converts the MPEG-2 TS into an OFDM signal and sends it to the transmission path. As shown in FIG. 10, in the transmission path encoding unit 10, after carrier modulation, frequency interleaving is finished, a pilot signal for assisting demodulation and decoding in the receiver, and a TMCC signal are added, and OFDM Frame configuration is performed.

  3 and 4 show the configurations of OFDM segments in the case of synchronous modulation and differential modulation, respectively. As shown in FIG. 3, in the case of synchronous modulation, Scattered Pilot (SP) distributed in carrier number order (frequency direction) and symbol direction (time direction) is inserted as a pilot signal. As shown in FIG. 4, in the case of differential modulation, Continuous Pilot (CP), which is a continuous carrier, is embedded. Further, in both cases of synchronous modulation and differential modulation, a TMCC signal including transmission control information and an auxiliary channel (AC) signal are added. The pilot signal (SP, CP) modulation method is BPSK modulation, and the TMCC and AC signal modulation method is DBPSK. On the other hand, any of QPSK, 16QAM, 64QAM, and DQPSK is adopted as the carrier modulation method.

  That is, the digital signal transmitted from the transmission side includes a data signal modulated by the carrier modulation scheme and a pilot signal modulated by a modulation scheme (BPSK) different from the carrier modulation scheme. The pilot signal is used as a synchronization signal on the receiving side, and the received data is reproduced based on the pilot signal.

  In addition to the ISDB-T system, in the DVB-T system adopted in Europe and the ASTC system adopted in North America, the carrier modulation system of the data signal is included in the digital signal transmitted by the transmission side. A pilot signal for synchronization modulated by a different modulation method is included. Hereinafter, a modulation method of a pilot signal such as BPSK is referred to as a “pilot modulation method”.

  The inventor of the present application paid attention to the fact that various modulation schemes have different transmission performance characteristics and the transmission performance characteristics correlate between the modulation schemes. Description will be made using BER as an example of an index value representing transmission performance characteristics and C / N as an example of a control variable.

When the signal energy-to-noise power ratio (E _b / N ₀ ) per bit is expressed by γ, the theoretical BER of each modulation method when performing absolute phase synchronous detection is expressed by the following equations (1) to (4 (Formula (3.7), Formula (3.9), Formula (3.12), Formula (3.13) of Non-Patent Document 2) “P” in the following formulas is BER. It is.

Further, the error complement function erfc (x) in the equations (1) to (4) is defined by the following equation (5).

Furthermore, γ (E _b / N ₀ ) can be converted into C / N by the following equation (6).

In equation (6), k is the amount of information (bits) per symbol, Bn is the equivalent noise bandwidth in the reception filter, and T is the symbol period. In the case of a matched filter, “BnT” becomes “1”. Therefore, in the case of BPSK, E _b / N ₀ matches C / N, and in the case of QPSK, E _b / N ₀ is 3 dB lower than C / N. FIG. 5 shows the BER characteristic of each modulation method given by the equations (1) to (4).

Thus, for each modulation method, the BER is theoretically expressed as a function of “E _b / N ₀ ” (or “C / N”). In actual measurement, a BER characteristic with deterioration due to noise in the communication line is observed. FIG. 6 shows a comparative example of a theoretical BER characteristic and a BER characteristic with deterioration. As shown in the figure, the BER in the case of deterioration is higher than the theoretical BER, but the tendency of dependence on the control variable “E _b / N ₀ ” (or “C / N”) is the same here. It is.

  The degradation is the same in the same measurement system. For this reason, in the same measurement system, a correlation is also established between BER characteristics with deterioration between different modulation methods. Therefore, the change point “C / N” at which the synchronization between the transmission and reception of the pilot signal included in the received digital signal changes from the disabled state to the enabled state is based on the correlation between the BER characteristics of the pilot modulation scheme and the carrier modulation scheme. Thus, if converted to “C / N” corresponding to the carrier modulation method, the converted “C / N” is a BER reference value for determining whether or not the data signal received by the receiver can be reproduced. Should be in the vicinity of “C / N” corresponding to. Therefore, by measuring the BER of the data signal with “C / N” after this conversion as the first measurement point, the value of “C / N” corresponding to the BER reference value can be obtained quickly.

  Here, the index value and the control variable for evaluating the performance of the receiver have been described by taking BER and C / N as examples, but the index for the control variable between the carrier modulation scheme and the pilot modulation scheme. The above can be said if the values are correlated. For example, the case where a modulation error rate (MER) that can be expressed as a C / N function is used as an index value, or the power of a desired wave, the power of an interference wave, or the like is used as a control variable. It is.

  Based on the above knowledge, the inventor of the present application, for a receiver that receives a digital signal including a data signal modulated by a carrier modulation scheme and a pilot signal modulated by a pilot modulation scheme, for each of a plurality of values of control variables. By measuring the index value representing the performance of the receiver, an efficient method for evaluating the performance of the receiver by obtaining the value of the control variable corresponding to the reference value of the index value was established.

  In this method, first, the value of the control variable at the change point at which the synchronization between the transmission and reception of the pilot signal included in the digital signal changes from the impossible state to the possible state is obtained. Next, from the correlation of the index value with respect to the control variable between the pilot modulation scheme and the carrier modulation scheme, the value of the control variable at the change point is converted into a value corresponding to the carrier modulation scheme. Then, using the converted value as the first measurement point, the index value is measured for the data signal in the digital signal received by the receiver.

  According to this method, since the first measurement point of the index value is in the vicinity of the value of the control variable corresponding to the reference value of the index value, the value of the control variable corresponding to the reference value of the index value can be quickly obtained. Can do.

Based on the above description, embodiments of the present invention will be described.
<First Embodiment>
FIG. 7 shows an evaluation apparatus 100 according to the first embodiment of the present invention. The evaluation apparatus 100 receives a digital signal including a data signal modulated by a predetermined carrier modulation scheme and a pilot signal modulated by a pilot modulation scheme that is a modulation scheme different from the carrier modulation scheme. Evaluation is performed by measuring an index value representing the performance of the receiver for each of a plurality of values of the control variable, and obtaining a value of the control variable corresponding to the reference value of the index value. As an example, it is assumed that the digital signal is an OFDM signal conforming to the ISDB-T system.

  In FIG. 7 and the following description, what is normally provided in this type of evaluation apparatus that performs clock supply and clock recovery is omitted.

  As illustrated in FIG. 7, the evaluation apparatus 100 includes a pattern generation unit 120 and an evaluation unit 130, and the receiver 110 to be evaluated is connected between the pattern generation unit 120 and the evaluation unit 130. The evaluation unit 130 includes a synchronization determination unit 132, a measurement unit 134, and a parameter setting unit 136.

  The pattern generation unit 120 generates and outputs a digital signal for evaluation. This digital signal includes a data pattern (data signal) and a pilot signal. The data pattern is a general PRBS (Pseudo Random Bit Sequence) or the like, and the pilot signal is for detecting the synchronization position of the data signal on the side receiving the digital signal. The pattern generation unit 120 uses various carrier modulation schemes defined by ISDB-T as a data pattern modulation scheme, and uses BPSK as a pilot signal modulation scheme. In addition, the pattern generation unit 120 can arbitrarily change values for various control variables.

In the following description, C / N and BER are used as examples of the control variable and the index value, and the reference value of the index value is 2 × 10 ⁻⁴ .

  The digital signal generated by the pattern generation unit 120 is received by the receiver 110 and input to the evaluation unit 130. Hereinafter, a signal input to the evaluation unit 130 via the receiver 110 is referred to as a received signal.

  The evaluation unit 130 measures the BER of the data pattern included in the received signal for each of a plurality of values of the control variable (here C / N), and obtains the C / N value corresponding to the reference value. Each functional block of the evaluation unit 130 will be described.

  The synchronization determination unit 132 sequentially designates a plurality of C / N values to the pattern generation unit 120, and for each of these C / N values, the pilot signal included in the digital signal output by the pattern generation unit 120 By determining whether or not the synchronization between transmission and reception can be established, the value of C / N at the change point at which the synchronization is disabled to the enabled state is obtained. Specifically, a signal similar to the pilot signal included in the digital signal transmitted by the pattern generation unit 120 is generated and synchronized with the pilot signal included in the reception signal from the receiver 110, and synchronization is achieved. The value of C / N at the time is obtained. The synchronization determination unit 132 changes the C / N value within the range between the upper limit value and the lower limit value of C / N set by the parameter setting unit 136, and determines whether synchronization is possible.

  As a method for obtaining the change point by the synchronization determination unit 132, any conventionally known method such as the raster method or the method of Patent Document 1 may be used. However, the synchronization determination unit 132 obtains a change point at which the synchronization between the transmission and reception of the pilot signal changes from an impossible state to a possible state, and does not measure the BER.

  FIG. 8 is a flowchart illustrating an example of processing of the synchronization determination unit 132 when the raster method is applied. First, the synchronization determination unit 132 sets the upper limit value and lower limit value of the C / N, the sweep step width, and the accumulation time from the parameter setting unit 136 (S100). Next, the synchronization determination unit 132 sets the higher BER of the upper limit value and the lower limit value as the first synchronization determination point, and instructs the pattern generation unit 120 on the C / N value. Here, since the control variable is C / N, the lower limit value is the higher BER. Since the BER tends to be higher as the input power of the desired wave is lower as a control variable when evaluating other control variables such as the minimum reception sensitivity, the lower limit value is set as the first synchronization determination point in this case as well. On the other hand, since the BER tends to be higher as the input power of the interference wave is higher, the upper limit value is set as the first synchronization determination point in this case.

  Then, the synchronization determination unit 132 determines whether synchronization between transmission and reception of the pilot signal included in the digital signal received signal output from the pattern generation unit 120 is possible or not according to the instructed C / N, and then C / N The sequential sweep and the determination of whether synchronization is possible are repeated (S104). Finally, the process ends when it is determined that there is a change point (C / N value) that changes from a state where synchronization is not possible to a state where synchronization is possible between two adjacent synchronization determination points (S106). .

  FIG. 9 is a flowchart illustrating an example of processing of the synchronization determination unit 132 when the method of Patent Document 1 is applied. First, the synchronization determination unit 132 sets an upper limit value and a lower limit value of C / N from the parameter setting unit 136 (S110). Next, the synchronization determination unit 132 sets a plurality of synchronization determination points within the range between the upper limit value and the lower limit value, sequentially instructs the pattern generation unit 120, and performs synchronization between transmission and reception of pilot signals at each synchronization determination point. It is determined whether or not it is possible (S112). Then, until the change point at which the synchronization between the transmission and reception of the pilot signal is changed from the disabled state to the enabled state is obtained, the setting of a new synchronization determination point and the determination of whether synchronization is possible are repeated (S114, S116: No, S114). ~). When the change point is obtained, for example, if it is determined that there is a change point between the synchronization determination points at a predetermined interval (S116: Yes), the process is terminated. In setting a new synchronization determination point, an optimization criterion such as a norm, that is, the distance between the new point and the previous point is maximized is applied.

  In this way, the synchronization determination unit 132 obtains a change point (a range of C / N values) of synchronization enable / disable between pilot signal transmission and reception and outputs the change point to the measurement unit 134.

First, the measurement unit 134 converts the change point from the synchronization determination unit 132 into a value corresponding to the carrier modulation scheme. Specifically, the change point obtained by the synchronization determination unit 132 is converted into a value corresponding to the carrier modulation method from the correlation of the BER characteristics with respect to C / N between the pilot modulation method (here, BPSK) and the carrier modulation method. To do. For example, when the carrier modulation method is QPSK, first, the C / N at the change point is converted to γ (E _b / N ₀ ) using Equation (6). In this case, because of pilot modulation, that is, BPSK, C / N and E _b / N ₀ are the same. Then, γ is substituted into equation (1) to obtain P _BPSK (BER). Next, γ is obtained by substituting the obtained P _BPSK into P _{QPSK into} equation (2). Finally, this γ is converted into C / N using equation (6). In this case, since the carrier modulation method is QPSK, C / N is 3 dB higher than γ.

The measurement unit 134 sets the C / N value obtained by such conversion as the first BER measurement point, and instructs the pattern generation unit 120. Then, the BER is measured for the data pattern included in the received digital signal generated by the pattern generation unit 120 according to the instructed C / N value. After that, the setting of the BER measurement point and the measurement of the BER are repeated using a conventional method such as the raster method or the method of Patent Document 1, and the processing is terminated when the BER reference value (2 × 10 ⁻⁴ ) is obtained. To do.

  When measuring the BER using the conventional method, the C / N sweep range is not between the upper limit value and the lower limit value set by the parameter setting unit 136. For example, when the BER measured at the first BER measurement point is larger than the reference value, the sweep is performed in the direction toward the lower limit set by the pattern generation unit 120, starting from the first BER measurement point. On the other hand, if the BER measured at the first BER measurement point is smaller than the reference value, the first BER measurement point is used as a starting point, and the sweep is performed in the direction toward the upper limit value set by the parameter setting unit 136.

  For example, as shown in FIG. 10, the first BER measurement point obtained by converting the change point obtained by the synchronization determination unit 132 into a C / N value corresponding to the carrier modulation scheme is the point A, and the point A The BER measured at is smaller than the reference value. In this case, the measurement unit 134 sets the next BER measurement point between the point A and the upper limit value. On the other hand, when the first BER measurement point is the point B and the BER measured at the point B is larger than the reference value, the measurement unit 134 sets the next BER measurement point between the point B and the lower limit value.

  Similarly, when the control variable is the input power of the desired wave, when the BER measured at the first BER measurement point is larger than the reference value, the sweep range of the control variable includes the first BER measurement point and the pattern. It is between the lower limits set by the generation unit 120. On the other hand, when the BER measured at the first BER measurement point is smaller than the reference value, the sweep range of the control variable is between the first BER measurement point and the upper limit value set by the parameter setting unit 136.

  Conversely, when the control variable is the input power of the interference wave, when the BER measured at the first BER measurement point is larger than the reference value, the sweep range of the control variable is the first BER measurement point and the pattern generation. This is between the upper limits set by the unit 120. On the other hand, when the BER measured at the first BER measurement point is smaller than the reference value, the sweep range of the control variable is between the first BER measurement point and the lower limit value set by the parameter setting unit 136.

  Further, a method other than the raster method or the method of Patent Document 1 may be used for setting the BER measurement points after the first BER measurement point. For example, the next BER measurement point may be set such that the larger the difference between the BER measured at the current BER measurement point and the reference value, the larger the step width, and the smaller the difference, the smaller the step width. . Of course, a large step width is set when the difference between the BER measured at the current BER measurement point and the reference value is equal to or larger than a predetermined threshold, and a small step width is used when the difference is smaller than the predetermined threshold. Also good. By these methods, the next BER measurement point can be brought closer to the reference value more efficiently.

  FIG. 11 shows a flowchart of receiver performance evaluation by the evaluation apparatus 100 of the present embodiment. First, the value of the control variable at the change point at which the state is changed from the state in which synchronization is not possible to the state in which synchronization is possible is determined by determining the synchronization between transmission and reception of pilot signals included in the digital signal (S120 to S124). Specifically, the upper limit value and the lower limit value of the change range of the control variable are set for the synchronization determination unit 132 (S120). Then, within the range of the upper limit value and the lower limit value, the synchronization determination unit 132 sets the synchronization determination point (control variable value) and determines whether synchronization is possible or not at the set point until the change point is obtained. Repeated (S122, S124).

  Next, the value of the control variable at the change point is converted into a value corresponding to the carrier modulation scheme by the data signal modulation scheme (S130).

  Then, the measurement unit 134 performs BER measurement on the data signal included in the digital signal, and obtains the value of the control variable corresponding to the BER reference value (S140 to S144). Specifically, the value obtained by the conversion in step S130 is set as the first BER measurement point, and BER measurement is performed (S140). Then, the setting of the BER measurement point and the BER measurement are performed until the value of the control variable corresponding to the BER reference value is obtained in the range between the first BER measurement point and the lower limit value or between the BER measurement point and the upper limit value. Repeated (S142, S144).

  Since the evaluation apparatus 100 of this embodiment sets the first BER measurement point to the value of the control variable near the BER reference value, the control variable corresponding to the BER reference value can be obtained with a small number of measurements.

  In general, a pilot signal modulated by a pilot modulation scheme has a smaller C / N necessary for reception than a data signal modulated by a carrier modulation scheme. Therefore, for the same C / N, it takes a short time to determine whether synchronization between transmission and reception is possible with a pilot signal. Therefore, although the process for obtaining the change point using the pilot signal is necessary to set the first BER measurement point, the time required for the entire evaluation process can be shortened.

  As a method of setting the first BER measurement point in the vicinity of the value of the control variable corresponding to the BER reference value, a method of setting the first BER measurement point to an average value obtained by past evaluation can be considered. For example, as shown in FIG. 12, the first BER measurement point can be set to an average value (average value of control variables corresponding to the BER reference value) Q0 obtained by past evaluation. However, due to variation in the variation of the sample population, the BER characteristics may vary lower (curve L1 in the figure) or higher (curve L2 in the figure) than the average BER characteristic (curve L0 in the figure). As shown in the lower part of FIG. 12, the variation range (degree of dispersion) of the value of the control variable corresponding to the BER reference value is considerably large.

  Therefore, when the BER characteristic at the time of measurement varies to the lower side as shown by the curve L1 in the figure, the average value Q0 obtained by the past evaluation is used as the first BER measurement point. In this case, the first BER measurement is performed, which may increase the measurement time.

  Also, when the BER characteristics at the time of measurement vary to the higher side as shown by the curve L2 in the figure, the time required for the first BER measurement does not increase, but it is useless for obtaining the final control variable value. There is a risk of measuring.

  On the other hand, in the evaluation apparatus 100 according to the present embodiment, a change point at which the synchronization between transmission and reception of pilot signals changes from the disabled state to the enabled state is obtained, and the first BER measurement point is set based on the change point. Even if there is a fluctuation that varies with the BER characteristics of the receiver or when there is a fluctuation in the time direction in the transmission line, the pilot signal and the data signal are affected to the same extent. An initial BER measurement point can be set near the value.

<Second Embodiment>
The second embodiment of the present invention is also an evaluation device. This evaluation apparatus is the same as the evaluation apparatus 100 according to the first embodiment shown in FIG. 1 except that the parameter setting unit is different. Therefore, only the parameter setting unit will be described for the evaluation apparatus according to the second embodiment. In the description, when it is necessary to refer to another functional block, the name and code of the functional block of the evaluation apparatus 100 are used.

  FIG. 13 shows a parameter setting unit 200 of the evaluation apparatus according to the second embodiment of the present invention. The parameter setting unit 200 includes a standard value storage unit 202, a measurement condition input unit 204, and a setting execution unit 206.

  The standard value storage unit 202 stores a range (upper limit value and lower limit value) in which the control variable is changed under standard measurement conditions.

  The measurement condition means a parameter that affects the BER characteristics, and can include environmental temperature, power supply voltage, process, and the like as examples. The standard value storage unit 202 stores a range of control variables when these parameters are standard state values.

  The measurement condition input unit 204 inputs actual values of the above measurement conditions to the setting execution unit 206. For example, it has an interface for the user to input and outputs the measurement condition input by the user to the setting execution unit 206, or a device for measuring the measurement condition such as a temperature sensor, and sets and executes the measured measurement condition This is input to the unit 206.

  The setting execution unit 206 corrects the upper limit value and lower limit value of the control variable stored in the standard value storage unit 202 according to the measurement condition input from the measurement condition input unit 204. Then, the upper limit value and the lower limit value are set in the synchronization determination unit 132 and the measurement unit 134 after correction. The correction may be performed according to, for example, a preset empirical formula or theoretical formula.

  Since the purpose is to obtain the value of the control variable corresponding to the BER reference value, it is necessary that the value of the control variable corresponding to the BER reference value is included in the sweep range of the control variable. On the other hand, the wider the sweep range of the control variable, the greater the possibility that measurement at an extra measurement point will be performed. The parameter setting unit 200 in the evaluation apparatus of the present embodiment corrects the upper limit value and the lower limit value of the control variable according to the measurement conditions, thereby appropriately setting the range of the control variable and reducing the measurement time. Can do.

<Third Embodiment>
The third embodiment of the present invention is also an evaluation device. This evaluation apparatus is the same as the evaluation apparatus 100 according to the first embodiment shown in FIG. 1 except that the synchronization determination unit is different. Therefore, only the synchronization determination unit will be described in the evaluation device according to the third embodiment. In the description, when it is necessary to refer to another functional block, the name and code of the functional block of the evaluation apparatus 100 are used.

  FIG. 14 shows a synchronization determination unit 300 of the evaluation apparatus according to the third embodiment of the present invention. The synchronization determination unit 300 includes a change point candidate measurement unit 302 and a change point determination unit 304.

  The change point candidate measurement unit 302 measures a change point that changes from a state in which synchronization between transmission and reception of pilot signals included in the digital signal from the pattern generation unit 120 is impossible to a state in which the change is possible, and performs each measurement. The change point (control variable value) is output to the change point determination unit 304 as a change point candidate. The specific measurement method for each time is the same as that of the synchronization determination unit 132 in the evaluation apparatus 100 except that measurement is performed a plurality of times and the measurement result is output to the change point determination unit 304.

  The change point determination unit 304 selects the change point with the highest reliability from the plurality of change points from the change point candidate measurement unit 302 and outputs the selected change point to the measurement unit 134. For example, a measurement result with the largest number of overlapping is selected from a plurality of measurement results by majority vote.

  Note that the number of measurements of the change point candidate measurement unit 302 may be an arbitrary fixed number of, for example, three or more, but may be changed according to the measurement result. For example, first, the change point candidate measurement unit 302 performs measurement twice and the change point determination unit 304 performs measurement. The change point determination unit 304 outputs the measurement result value (the value of the control variable at the change point) to the measurement unit 134 if the two measurement results are the same, and further changes if the two measurement results are different. You may make it make the point candidate measurement part 302 measure, and may determine the change point output to the measurement part 134 by majority vote after that.

  In a general measurement environment, erroneous measurement may occur due to sudden external noise. If the change point is erroneously measured, the first BER measurement point of the measurement unit 134 is separated from the point corresponding to the BER reference value, and the evaluation takes time. In particular, this problem becomes more serious when the first BER measurement point is shifted to a lower BER. The synchronization determination unit 300 in the evaluation apparatus according to the present embodiment performs measurement a plurality of times, obtains a highly reliable change point from a plurality of measurement results, and provides it to the measurement unit 134. Can be reduced. Multiple measurement of change points takes time by one measurement, but since measurement of change points is shorter by BER measurement, processing time for the entire evaluation can be shortened.

<Fourth embodiment>
The fourth embodiment of the present invention is also an evaluation device. This evaluation apparatus is the same as the evaluation apparatus 100 according to the first embodiment shown in FIG. 1 except that the measurement unit is different. Therefore, only the measurement unit of the evaluation apparatus according to the fourth embodiment will be described. In the description, when it is necessary to refer to another functional block, the name and code of the functional block of the evaluation apparatus 100 are used.

  FIG. 15 shows a measuring unit 400 of the evaluation apparatus according to the fourth embodiment of the present invention. The measurement unit 400 includes a change point conversion unit 402, an initial point correction unit 404, and a measurement execution unit 406.

  The change point conversion unit 402 converts the value of the control variable at the change point provided from the synchronization determination unit 132 into a value corresponding to the carrier modulation scheme. This conversion is the same as the conversion by the measurement unit 134 in the evaluation apparatus 100.

  The first point correction unit 404 corrects the converted value obtained by the changing point conversion unit 402, and sets the corrected value as the first BER measurement point. Specifically, a value obtained by shifting the value obtained by the change point conversion unit 402 so as to increase the BER is set as the first BER measurement point.

  The measurement execution unit 406 performs control variable sweep and BER measurement starting from the first BER measurement point set by the first point correction unit 404, and obtains the value of the control variable corresponding to the BER reference value. The control variable sweep and BER measurement by the measurement execution unit 406 are the same as these processes by the measurement unit 134 of the evaluation apparatus 100.

  FIG. 16 shows an example of correction by the first point correction unit 404. As shown in FIG. 16, it is assumed that the value obtained by converting the change point obtained by the synchronization determination unit 132 into a value corresponding to the carrier modulation scheme is A0. Therefore, as a result of the first point correction unit 404 shifting A0 toward the higher BER, A1 set as the first BER measurement point becomes higher than A0. As described above, the lower the BER, the longer the BER measurement takes. Therefore, by performing correction in this way, measurement at a high BER is expected, and the measurement time is shortened.

  In the example of FIG. 16, since the control variable is C / N, the first correction of the BER measurement point performed so as to increase the BER is a correction to reduce C / N. The same applies when the control variable is the input power of the desired wave. On the other hand, when the control variable is the input power of the interference wave, this correction is a correction to increase the input power of the interference wave.

  The present invention has been described above based on the embodiment. The embodiment is an exemplification, and various modifications, increases / decreases, and combinations may be made to the above-described embodiments without departing from the gist of the present invention. It will be understood by those skilled in the art that modifications in which these changes, increases / decreases, and combinations are also within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Transmission path encoding part 100 Evaluation apparatus 110 Receiver 120 Pattern production | generation part 130 Evaluation part 132 Synchronization determination part 134 Measurement part 136 Parameter setting part 200 Parameter setting part 202 Standard value memory | storage part 204 Measurement condition input part 206 Setting execution part 300 Synchronization Determination unit 302 Change point candidate measurement unit 304 Change point determination unit 400 Measurement unit 402 Change point conversion unit 404 First point correction unit 406 Measurement execution unit

Claims (5)

A plurality of control variables for a receiver that receives a digital signal including a data signal modulated by a predetermined carrier modulation scheme and a pilot signal modulated by a pilot modulation scheme that is a modulation scheme different from the carrier modulation scheme. An evaluation device for determining a value of a control variable corresponding to a reference value of the index value by measuring an index value representing the performance of the receiver for each value of
A synchronization determination unit for obtaining a value of a control variable at a change point at which the synchronization between transmission and reception of the pilot signal included in the digital signal is changed from a disabled state to a possible state;
From the correlation of the index value with respect to the control variable between the pilot modulation scheme and the carrier modulation scheme, the control variable value obtained by the synchronization determination unit is converted into a value corresponding to the carrier modulation scheme, An evaluation apparatus comprising: a measurement unit that measures the index value with respect to a data signal included in the digital signal received by the receiver with a later value as an initial measurement point.   The synchronization determination unit obtains the value of the control variable at the change point a plurality of times, and outputs the value of the change point with the highest reliability to the measurement unit from the result of the plurality of times. The evaluation apparatus according to 1. The index value is BER,
3. The evaluation according to claim 1, wherein the measurement unit further performs a correction for shifting the converted value toward a higher BER, and uses the corrected value as a first measurement point. 4. apparatus. A parameter setting unit for setting an upper limit value and a lower limit value for changing a control variable for the synchronization determination unit and the measurement unit;
The evaluation apparatus according to any one of claims 1 to 3, wherein the parameter setting unit is capable of changing the upper limit value and the lower limit value according to measurement conditions.   5. The evaluation apparatus according to claim 1, wherein the control variable is any one of a carrier-to-noise ratio, a desired wave input power, and an interference wave input power. .

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