JP2007013587A - Transmission characteristic estimating unit and transmission characteristic estimating program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission characteristic estimating device and a transmission characteristic estimating program which are capable of estimating transmission error rate characteristics without using transmission signals. <P>SOLUTION: The transmission characteristic estimating device 100 is equipped with a CIR calculating unit 101, a P<SB>ave</SB>calculating unit 102, a noise statistics processing unit 103 performing statistics processing of a noise component through computer simulations, an amplitude distribution display unit 104 displaying the amplitude distribution of noise components, a threshold calculating unit 105, an SER estimating unit 106 estimating the symbol error rate characteristic of digital transmission signals, and an error rate display unit 107 displaying the transmission error rate of the digital transmission signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission characteristic estimation device and a transmission characteristic estimation program for estimating an error rate characteristic of a digital transmission signal.

  Conventionally, a bit error rate (hereinafter referred to as “BER”) characteristic evaluation test is known as a test for evaluating the performance of a system for transmitting a digital signal. This evaluation test is generally performed by installing a transmitter / receiver in an experimental environment simulating transmission line characteristics. For example, in a mobile communication system that uses radio waves, the transmission characteristics of the wireless transmission path vary depending on the environment. May be implemented. In this case, since costs are generated due to the introduction and transfer of the evaluation test device, a wireless transmission path simulation device that can reduce these costs and efficiently perform the evaluation test has been proposed (for example, patents). Reference 1).

JP-A-9-93210

  However, the conventional transmission characteristic estimation apparatus disclosed in Patent Document 1 cannot estimate the BER characteristic of a digital transmission signal including an intermodulation distortion component generated due to nonlinearity of an amplifier or a circuit element. This will be specifically described below.

  As a digital transmission signal in which intermodulation distortion is likely to occur due to non-linearity, for example, there is an OFDM (Orthogonal Frequency Division Multiplexing) signal used in terrestrial digital broadcasting, a wireless LAN (Local Area Network), or the like. Hereinafter, with reference to an OFDM signal as an example, intermodulation distortion will be described with reference to FIG. FIGS. 10A and 10B are schematic diagrams illustrating spectrum examples of OFDM signals in a linear region and a nonlinear region, respectively. FIG. 10C is a schematic diagram showing a spectrum example for explaining the principle of occurrence of intermodulation distortion.

For example, as shown in FIG. 10A, an OFDM signal used in terrestrial digital broadcasting is composed of a plurality of continuous waves with transmission bandwidths f _{L to} f _H , and a thermal noise component as a noise component in a linear region. Is included. It is known that the thermal noise component has a normal distribution of amplitude data, and a theoretical analysis method is well known. On the other hand, in the nonlinear region where the amplification factor of the OFDM signal is increased, an intermodulation distortion component is generated in addition to the thermal noise component as shown in FIG. The BER characteristic of the OFDM signal is deteriorated.

The intermodulation distortion is distortion that occurs when signals having a plurality of adjacent frequencies pass through a nonlinear circuit. For example, when signals of frequencies f ₁ and f ₂ pass through a nonlinear circuit, mf ₁ ± nf ₂ (m , N is an integer) signal appears, which interferes with the digital transmission signal. referred to m ± n the order of the intermodulation, as shown in FIG. 10 (c), an odd-order intermodulation distortion component appears in the vicinity of the frequency f ₁ and f ₂ of the signal.

As the non-linearity becomes more prominent, among the odd-order intermodulation distortion components, intermodulation distortion components (CTB) represented by a cubic function, that is, 2f ₁ -f ₂ in FIG. The degree of influence of the intermodulation distortion component of the frequency of 2f ₂ −f ₁ becomes large, and the BER characteristics of the digital transmission signals of the frequencies f ₁ and f ₂ are remarkably deteriorated.

In addition, the intermodulation distortion component not only deteriorates the BER characteristics of the transmission band, but also affects the frequency region adjacent to the transmission band. For example, influenced by intermodulation distortion component even if you set the transmission band of the cable TV frequency range higher than the frequency f _H, BER characteristics of the cable television transmission signal is deteriorated.

  As described above, the noise component including the intermodulation distortion component and the BER characteristic have a close relationship, and estimating the BER characteristic by analyzing the noise component estimates the transmission characteristic of the digital signal. Although it is an important problem above, the conventional transmission characteristic estimation device cannot estimate the BER characteristic of a digital transmission signal including an intermodulation distortion component. Therefore, conventionally, a method of using a transmission signal when estimating the BER characteristic has been adopted, and a technique for estimating the BER characteristic without using the transmission signal has not been realized.

  The present invention has been made in order to solve the conventional problems, and provides a transmission characteristic estimation apparatus and a transmission characteristic estimation program that can estimate a transmission error rate characteristic without using a transmission signal.

  The transmission characteristic estimation apparatus of the present invention calculates the ratio of the power of a digital transmission signal with a predetermined modulation scheme and carrier-to-noise power ratio and the sum of the powers of interference waves that interfere with the transmission of the digital transmission signal. Statistical processing for analyzing the statistical properties of the interference wave based on the calculation results of the ratio calculation means, the average power calculation means for calculating the average power of the digital transmission signal, and the power ratio calculation means and the average power calculation means Means, threshold calculation means for calculating a threshold for determining a symbol of the digital transmission signal based on the calculation results of the power ratio calculation means and the average power calculation means, and statistical analysis processing results of the interference wave And a symbol error rate estimating means for estimating a symbol error rate of the digital transmission signal based on the threshold value and the threshold value.

  With this configuration, the transmission characteristic estimation apparatus of the present invention can estimate the symbol error rate of a digital transmission signal based on the statistical properties and threshold values of jamming waves, so that the transmission error rate characteristic can be achieved without using a transmission signal. Can be estimated.

  Furthermore, the transmission characteristic estimation apparatus of the present invention has a configuration including a bit error rate calculation unit that calculates a bit error rate of the digital transmission signal based on the symbol error rate estimated by the symbol error rate estimation unit. is doing.

  With this configuration, the transmission characteristic estimation apparatus of the present invention can estimate the bit error rate of a digital transmission signal without using a transmission signal.

  Furthermore, the transmission characteristic estimation apparatus of the present invention includes a noise analysis apparatus that analyzes a noise component included in a digital transmission signal, a threshold calculation means that calculates a threshold for determining a symbol of the digital transmission signal, and the noise analysis. Symbol error rate estimation means for estimating a symbol error rate of the digital transmission signal based on a noise analysis result of the device and the threshold, and the noise analysis device acquires noise amplitude data acquisition for acquiring amplitude data of the noise component Means, a statistic calculating means for calculating a predetermined statistic relating to the amplitude data of the noise component, and normalizing the amplitude data of the noise component based on the statistic, and normalizing cumulative probability distribution of normalized amplitude And a cumulative probability distribution calculating means for calculating.

  With this configuration, the transmission characteristic estimation apparatus of the present invention can estimate the symbol error rate of a digital transmission signal without using a transmission signal, based on the statistical properties of noise components analyzed by the noise analysis apparatus.

  Also, the transmission characteristic estimation apparatus of the present invention is configured such that the noise analysis apparatus includes ratio calculation means for calculating a ratio between a cumulative probability distribution of normalized amplitudes of the noise component and a predetermined reference cumulative probability distribution. have.

  With this configuration, the transmission characteristic estimation apparatus of the present invention can calculate the ratio between the cumulative probability distribution of the normalized amplitude of the noise component and the predetermined reference cumulative probability distribution without using the transmission signal.

  Further, in the transmission characteristic estimation device of the present invention, the digital transmission signal includes a thermal noise component, the reference cumulative probability distribution is a cumulative probability distribution of the amplitude of the thermal noise component, and the ratio calculating means includes the ratio calculating means, It has a configuration for calculating the ratio between the cumulative probability distribution of the normalized amplitude of the noise component and the cumulative probability distribution of the amplitude of the thermal noise component.

  With this configuration, the transmission characteristic estimation apparatus of the present invention uses the transmission signal because the ratio calculation means calculates the ratio between the cumulative probability distribution of the normalized amplitude of the noise component and the cumulative probability distribution of the amplitude of the thermal noise component. Without compromising the disturbance characteristics of the thermal noise component.

  Further, in the transmission characteristic estimation apparatus of the present invention, the digital transmission signal includes an intermodulation distortion component, and the ratio calculation means includes the cumulative probability distribution of the normalized amplitude of the intermodulation distortion component and the amplitude of the thermal noise component. It has the structure which calculates ratio with cumulative probability distribution of.

  With this configuration, the transmission characteristic estimation apparatus according to the present invention calculates the ratio between the cumulative probability distribution of the normalized amplitude of the intermodulation distortion component and the cumulative probability distribution of the amplitude of the thermal noise component in the ratio calculating means. The ratio of the intermodulation distortion component to the interference of the digital transmission signal can be calculated without using, and the cumulative probability distribution of the normalized amplitude of the intermodulation distortion component with respect to the cumulative probability distribution of the amplitude of the thermal noise component can be calculated. Deviations can be shown quantitatively.

  Further, in the transmission characteristic estimation device of the present invention, the noise analysis device displays the data of the normalized amplitude cumulative probability distribution of the noise component and the reference cumulative probability distribution on a screen imitating a predetermined probability paper. It has the composition provided with.

  With this configuration, in the transmission characteristic estimation apparatus of the present invention, the display means displays the accumulated probability distribution of the normalized amplitude of the noise component and the data of the reference cumulative probability distribution on a screen imitating a predetermined probability sheet. The ratio between the cumulative probability distribution of the normalized amplitude of the noise component and the reference cumulative probability distribution can be quantitatively shown without using.

  In addition, the transmission characteristic estimation apparatus of the present invention has a configuration including a bit error rate calculation unit that calculates a bit error rate of the digital transmission signal based on the symbol error rate estimated by the symbol error rate estimation unit. is doing.

  With this configuration, the transmission characteristic estimation apparatus of the present invention can estimate the bit error rate of a digital transmission signal without using a transmission signal.

  The transmission characteristic estimation program of the present invention includes a step of predetermining a modulation method and a carrier-to-noise power ratio of a digital transmission signal; Calculating a signal-to-jamming wave power ratio indicative of the ratio of the digital transmission signal, calculating an average power of the digital transmission signal, and statistical characteristics of the jamming wave based on the signal-to-jamming wave power ratio and the average power Analyzing a threshold for determining a symbol of the digital transmission signal based on the signal-to-jamming wave power ratio and the average power, and statistical characteristics of the jamming wave and the threshold And a step of estimating a symbol error rate of the digital transmission signal based on the above.

  With this configuration, the transmission characteristic estimation program of the present invention can estimate the symbol error rate of a digital transmission signal without using a transmission signal, based on the statistical properties of the interference wave and the threshold value.

  In addition, the transmission characteristic estimation program of the present invention has a configuration including a step of calculating a bit error rate of the digital transmission signal based on the symbol error rate.

  With this configuration, the transmission characteristic estimation program of the present invention can estimate the bit error rate of a digital transmission signal without using a transmission signal.

  The present invention can provide a transmission characteristic estimation apparatus and a transmission characteristic estimation program that can estimate a transmission error rate characteristic without using a transmission signal.

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

(First embodiment)
First, the configuration of the transmission characteristic estimation apparatus according to the first embodiment of the present invention will be described. The transmission characteristic estimation apparatus of the present embodiment is configured by a computer, for example.

As shown in FIG. 1, a transmission characteristic estimation apparatus 100 according to the present embodiment includes a CIR calculation unit 101 that calculates a CIR (Carrier to Interference Ratio) described later, and a P _ave calculation unit 102 that calculates P _ave (described later). A noise statistical processing unit 103 that performs statistical processing of the noise component by computer simulation, an amplitude distribution display unit 104 that displays an amplitude distribution of the noise component, a threshold value calculation unit 105 that calculates a threshold value, and a symbol error in the digital transmission signal A SER estimation unit 106 that estimates rate (Symbol Error Rate, hereinafter referred to as “SER”) characteristics and an error rate display unit 107 that displays a transmission error rate of a digital transmission signal are provided.

The CIR calculation unit 101 and the _Pave calculation unit 102 constitute a power ratio calculation unit and an average power calculation unit of the present invention, respectively. Further, the noise statistical processing unit 103 and the threshold calculation unit 105 constitute a statistical processing unit and a threshold calculation unit of the present invention, respectively. The SER estimation unit 106 constitutes a symbol error rate estimation unit and a bit error rate calculation unit of the present invention.

  Next, a method for estimating the SER characteristic when the amplitude distribution of the noise component is known by analysis will be described.

When the cumulative probability distribution function of the noise component of the normalized amplitude x is p (x), the value of the distribution function P (δ) is a definite integral from the threshold value δ to infinity as shown in the equation (1). It becomes the value.

  The cumulative probability distribution p (x) of the thermal noise component is a normal distribution, and the distribution function P (δ) is indicated by an error function. On the other hand, for a noise component whose function is unknown, the value of the distribution function is indicated from the cumulative probability distribution of the amplitude. The distribution function is the probability that the amplitude of the noise component exceeds the threshold value, and becomes the SER characteristic of the digital transmission signal.

It is known that the SER characteristic is affected by the modulation scheme and the carrier-to-noise ratio (hereinafter referred to as “CNR”). In a QAM (Quadrature Amplitude Modulation) signal in which the constellation of the modulation signal is arranged in a grid, the distance between adjacent symbols is 2δ, that is, the distance from the symbol to the threshold is δ, and the interference wave power is σ ² Then, CNR is shown by (2) Formula.

Here, P _ave is the average power of the QAM signal when δ is 1. Table 1 shows a value of P _ave of a typical QAM signal in which symbols are arranged in a lattice pattern. For example, the average power of a 1024QAM signal when δ is 1 is 682.

The SER characteristic due to the thermal noise component is expressed by equation (3) according to the document “Modulation / demodulation of digital wireless communication,” edited by the Institute of Electronics, Information and Communication Engineers, p. 117. In equation (3), erfc represents a complementary error function.

Here, when equation (2) is solved for δ, equation (4) is obtained.

If noise data normalized with σ in equation (4) as 1 is handled, the threshold δ can be calculated using CNR and P _ave . From the above, it can be seen that the SER characteristic can be estimated from the value of the distribution function P (δ) of the normalized noise data if the modulation method and the CNR are assumed.

  Next, the operation of transmission characteristic estimation apparatus 100 according to the present embodiment will be described. Here, an example in which the BER characteristic of a QAM signal is estimated from a computer simulation of an amplitude distribution when the CNR is 44 dB and the CTB is −48 dB, −50 dB, and −52 dB, will be described.

First, the modulation method and CNR of a digital transmission signal are determined in advance. In terrestrial digital broadcasting, since the BER is preferably about 10 ⁻⁴ or less, the CNR is preferably set to about 36 dB or more from the data shown in FIG. 4 described later.

Next, the CIR calculation unit 101 calculates the CIR from the CNR and CTB according to the equation (5). CIR refers to the ratio of the desired wave power and the sum of the jamming wave power.

Then, based on the modulation scheme determined in _{advance, P ave} is calculated by _{P ave} calculator 102. For example, when a 1024QAM signal is used, 682 is obtained as P _ave from Table 1.

Subsequently, the noise statistical processing unit 103 separately generates 10 ⁷ pieces of amplitude data of the thermal noise component and data obtained by squaring the amplitude data of the OFDM signal used as CTB (hereinafter referred to as “CTB amplitude data”). The thermal noise component and the CTB amplitude ratio are calculated from the CNR and CTB values, respectively. Next, the respective amplitude ratios are used as the coefficients of the thermal noise component amplitude data and the CTB amplitude data.

  Furthermore, the noise statistics processing unit 103 adds the thermal noise component amplitude data multiplied by each coefficient and the CTB amplitude data, thereby adding statistics such as an average value, a variance value, and a standard deviation of the amplitude data. Is calculated. Since the amplitude of the OFDM signal is normally distributed in the same way as the amplitude of the thermal noise component, data obtained by cubeing the amplitude data of the thermal noise component can be used as the CTB.

  Next, amplitude distribution data is displayed by the amplitude distribution display unit 104. FIG. 2 shows an example of amplitude distribution data displayed on the amplitude distribution display unit 104. The calculator of the amplitude distribution of the interference wave when the CNR is 44 dB and the CTB is −48 dB, −50 dB, and −52 dB, respectively. It is a simulation result. In addition, since the data of amplitude distribution are positive / negative objects, only the negative polarity side is displayed in FIG.

Subsequently, the threshold value calculation unit 105 calculates the threshold value δ of the symbol. This threshold value δ is calculated based on the thermal noise component and the total sum of interference wave power including the CTB of the OFDM signal. When the CNR in the equation (4) is replaced with the CIR in the equation (5), the threshold δ is obtained by the equation (6).

  Next, in the amplitude distribution data displayed by the amplitude distribution display unit 104, an estimated value of the SER characteristic is acquired by the SER estimation unit 106 by obtaining the cumulative probability at the threshold value −δ calculated by the equation (6). The Here, the reason why the negative value is attached to the threshold value δ is that the amplitude distribution data shown in FIG. 2 displays only the negative polarity side as described above. The SER estimation unit 106 can also estimate the BER characteristic by a method described later based on the estimated SER characteristic.

  Then, the SER characteristic is displayed by the error rate display unit 107. The error rate display unit 107 can also display BER characteristics.

  Next, a method for converting the SER characteristic estimated by the SER estimation unit 106 into the BER characteristic will be described.

  The number of bits included in one symbol differs depending on the modulation method, and is, for example, 2 bits in the QPSK (Quadrature Phase Shift Keying) method and 10 bits in the 1024QAM method. Here, the 1024QAM system will be described as an example.

According to the document "" Development of 1024QAM transmission device for cable television, "Journal of the Institute of Image Information and Television Engineers Vol.58, No.10, pp.1421-1428 (2004)", BER when absolute synchronous detection is performed on the receiver side. The characteristic is expressed by equation (7).

Therefore, by substituting equation (3) into equation (7), the relationship between the SER characteristic and the BER characteristic is expressed by equation (8).

Table 2 shows a comparison between the SER characteristic and the BER characteristic estimated from the simulation result by the transmission characteristic estimation apparatus 100 and the actually measured value. The measured value and estimated value of the BER characteristic correspond well.

  Next, the influence of disturbance of the distortion component on the digital transmission signal was measured using a transceiver. Using the CTB size as a parameter, the BER characteristic with respect to the CNR of the QAM signal was measured. Here, a 1024 QAM signal is taken as an example of the QAM signal. As the 1024QAM signal, a signal having a Gray code arrangement is used.

  FIG. 3 is a block diagram illustrating a configuration example for measuring transmission characteristics of a QAM signal. As shown in FIG. 3A, a QAM modulator 31 as a transmitter that outputs a QAM signal, a non-linear distortion generator 32 that generates a signal including a non-linear distortion component, and an output signal and non-linearity of the QAM modulator 31 An adder 33 for adding the output signal of the distortion generator 32, a thermal noise generator 34 for generating a thermal noise signal, an adder 35 for adding the output signal of the adder 33 and the thermal noise signal, and a QAM signal QAM signal transmission characteristics were measured with a configuration including a QAM demodulator 36 as a receiver for demodulating the signal and a BER display 37 for displaying the BER characteristics.

  The nonlinear distortion generator 32 shown in FIG. 3B includes an OFDM signal generator 20, a band-pass filter 11 that passes a signal having a predetermined bandwidth, a local oscillator 13a that generates a local oscillation signal, and an amplified signal. A mixer 13b for mixing the noise component of the transmission band and the local oscillation signal is provided to generate a signal including a nonlinear distortion component. The OFDM signal generator 20 includes an OFDM signal generator 21 that generates an OFDM signal for terrestrial digital broadcasting, an attenuator 22 that sets an input level of an amplifier 23, and an amplifier 23 that amplifies the OFDM signal.

  Here, the non-linear distortion means intermodulation distortion generated by the non-linearity of an amplifier or a circuit element, and includes CTB. This CTB is the third-order intermodulation distortion of the OFDM signal generated in the vicinity of 620 MHz, and is input to the mixer 13b. The mixer 13b outputs an intermediate frequency band signal having a center frequency of 10 MHz and a bandwidth of 6 MHz.

  A nonlinear distortion component and a thermal noise component are added to the QAM signal from the QAM modulator 31 as interference waves and input to the QAM demodulator 36. A spectrum analyzer was connected to the input of the QAM demodulator 36, the noise power density (dBm / Hz) was measured with the spectrum analyzer, and the interference wave power was obtained by converting it with the bandwidth of the symbol rate of the QAM signal. The CTB value was a relative value of the interference wave power with respect to the average power of the QAM signal.

  FIG. 4 is a diagram showing the relationship between the CNR and the BER characteristic of the 1024QAM signal, and shows the influence of distortion generated from nine waves of the OFDM signal. In FIG. 4, the data plotted with the triangle mark, the square mark, and the X mark indicate the results of measuring the BER characteristics of the CNR versus 1024QAM signal using the CTB size as a parameter. Further, the data plotted with black circles show the measured values of the BER characteristics in the case of only the thermal noise component. The solid line shows the theoretical value of the BER characteristic of the 1024QAM signal.

  As shown in FIG. 4, when the CNR decreases and the ratio of the thermal noise component increases, the BER characteristic due to CTB approaches the BER characteristic due to the thermal noise component. This represents the statistical properties of the noise component when the thermal noise component and CTB are convoluted, and shows that the interference wave becomes closer to the normal distribution as the proportion of the thermal noise component increases.

  Note that, by programming each step of the operation of the transmission characteristic estimation apparatus 100 described above, a transmission characteristic estimation program for calculating at least one of the SER characteristic and the BER characteristic of the digital transmission signal can be produced.

  As described above, according to the transmission characteristic estimation apparatus 100 of the present embodiment, the noise statistical processing unit 103 performs the simulation of the amplitude distribution of the noise component in which the thermal noise component and the CTB are mixed, and the threshold calculation unit 105 Since the threshold of the symbol of the digital transmission signal is calculated, and the SER estimation unit 106 is configured to estimate the SER characteristic or the BER characteristic of the digital transmission signal based on the amplitude distribution of the noise component and the threshold, the transmission signal is not used. In addition, the transmission characteristics of the digital transmission signal can be estimated based on the statistical properties of the noise components.

  In the present embodiment, a 1024QAM signal has been described as an example. However, the present invention is not limited to this, and similar effects can be obtained even with other digital transmission signals.

(Second Embodiment)
First, the configuration of the transmission characteristic estimation apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram of the transmission characteristic estimation apparatus according to the present embodiment.

As shown in FIG. 5, the transmission characteristics estimation apparatus 200 of the present embodiment, a noise analyzer 10 to perform noise analysis, and CIR calculation section 201 that calculates a _CIR, and _{P ave} calculating unit 202 for calculating a _{P ave} A threshold calculation unit 203 that calculates a threshold, a SER estimation unit 204 that estimates SER characteristics, and an error rate display unit 205 that displays an error rate.

Note that the CIR calculation unit 201, the P _ave calculation unit 202, the threshold value calculation unit 203, the SER estimation unit 204, and the error rate display unit 205 are the transmission characteristic estimation device 100 (see FIG. 1) according to the first embodiment of the present invention. ) Correspond to the CIR calculation unit 101, the _Pave calculation unit 102, the threshold value calculation unit 105, the SER estimation unit 106, and the error rate display unit 107 in FIG.

  Next, the configuration of the noise analysis apparatus 10 will be described with reference to FIG.

  As shown in FIG. 6, the noise analysis apparatus 10 of the present embodiment receives a digital transmission signal including a measured noise component, a band pass filter 11 that passes a signal of a predetermined bandwidth, and amplifies the signal. An amplifier 12, a frequency conversion unit 13 that converts a frequency, an analog-digital conversion unit (hereinafter referred to as an "A / D conversion unit") 14 that converts frequency-converted analog signal data into digital signal data, and digital A recording unit 15 that records signal data, a calculation unit 16 that reads digital signal data from the recording unit 15 and calculates a predetermined statistic, and a display unit 17 that displays a calculation result are provided.

  The band pass filter 11 is configured to pass, for example, a noise component included in a signal in a frequency band (hereinafter referred to as “transmission band”) in which a terrestrial digital broadcast wave is transmitted by an OFDM signal. The amplifier 12 amplifies the noise component of the transmission band that has passed through the band-pass filter 11. Here, the noise component includes a thermal noise component in the linear region, and includes an intermodulation distortion component and a thermal noise component in the nonlinear region. The intermodulation distortion component and the thermal noise component are interference waves generated in the transmission system of the digital transmission signal.

  The frequency converter 13 includes a local oscillator 13a that generates a local oscillation signal, and a mixer 13b that mixes the amplified noise component of the transmission band and the local oscillation signal, and converts the noise component of the transmission band to an intermediate frequency (IF). It is designed to convert the signal.

  The A / D converter 14 acquires amplitude data of a noise component in the transmission band, which is an analog signal converted to an intermediate frequency, and converts the acquired amplitude data into a digital value. The A / D converter 14 constitutes noise amplitude data acquisition means of the present invention.

  The recording unit 15 is composed of, for example, a semiconductor memory, and records the amplitude data of the noise component converted into a digital value by the A / D conversion unit 14.

  The calculation unit 16 is configured by, for example, a CPU (Central Processing Unit), a ROM (Read-Only Memory), a RAM (Random-Access Memory), and the like, reads amplitude data of noise components from the recording unit 15, and averages the amplitude data. Statistical values such as variance values and standard deviations are calculated. The standard deviation is represented by the symbol σ.

  In addition, the calculation unit 16 normalizes the data of the noise component amplitude based on the statistic obtained by the calculation, obtains a cumulative probability distribution of the normalized amplitude (hereinafter referred to as “normalized amplitude”), and calculates the normalized amplitude. The ratio of the cumulative probability distribution to a predetermined reference cumulative probability distribution, for example, a normal distribution is calculated. The calculation unit 16 displays data such as the calculated statistic, the cumulative probability at a certain normalized amplitude, the ratio between the cumulative probability distribution of the normalized amplitude and the normal distribution, and the display unit 17 and the SER estimation unit 204 (FIG. 5). Output). The calculation unit 16 constitutes a statistic calculation unit, a cumulative probability distribution calculation unit, and a ratio calculation unit of the present invention.

  The display unit 17 is configured by a liquid crystal display, for example, and displays a screen that simulates a normal probability paper, for example, and displays data for comparing the cumulative probability distribution of the normalized amplitude with the normal distribution. Further, the display unit 17 can display data such as a statistic calculated by the calculation unit 16, a cumulative probability at a certain normalized amplitude, a ratio between a cumulative probability distribution of the normalized amplitude and a normal distribution, and the like. It has become. Note that the display unit 17 is not limited to displaying only a screen simulating normal probability paper, and may be configured to display a screen simulating probability paper corresponding to the statistic processed by the calculation unit 16. The display unit 17 constitutes a display unit of the present invention.

  Next, the operation of transmission characteristic estimation apparatus 200 according to the present embodiment will be described.

  First, the operation of the noise analysis apparatus 10 will be described with reference to FIGS.

  FIG. 7 shows the characteristics of intermodulation distortion components generated when the OFDM signal generator 20 as a signal source is connected to the noise analyzer 10 of the present embodiment and the OFDM signal of terrestrial digital broadcasting is nonlinearly amplified. It is a figure which shows an example. The OFDM signal generator 20 includes an OFDM signal generator 21 that generates an OFDM signal for terrestrial digital broadcasting, an attenuator 22 that sets an input level of an amplifier 23, and an amplifier 23 that amplifies the OFDM signal.

  FIG. 8 is a diagram showing the spectrum of an OFDM signal for digital terrestrial broadcasting used in the noise analysis. FIG. 8A shows the spectrum of the OFDM signal input to the amplifier 23, and FIG. These are figures which show the spectrum of the OFDM signal output from the amplifier 23, ie, the spectrum containing an intermodulation distortion component.

  First, an OFDM signal used for noise analysis will be described with reference to FIG. As shown in FIG. 8 (a), the OFDM signal of terrestrial digital broadcasting is a continuous 9 channel from 19ch (center frequency 509MHz) to 27ch (557MHz) of UHF (Ultra High Frequency) band used in terrestrial digital broadcasting. It is a wave signal.

  As shown in FIG. 8A, the power level of the OFDM signal input to the amplifier 23 is noise power in the channel band adjacent to the higher frequency side of the OFDM signal (hereinafter referred to as “right adjacent transmission channel”). The difference from the level was about 55 dB. The spectrum shown in FIG. 8B is obtained by changing the power level of the OFDM signal input to the amplifier 23 by the attenuator 22, and the difference from the noise power level in the right adjacent transmission channel is about 35 dB.

  The OFDM signal set as described above is input to the noise analysis apparatus 10 and input to the frequency conversion unit 13 via the band pass filter 11 and the amplifier 12. Here, the analyzed noise component analyzed by the noise analyzing apparatus 10 is a distortion component generated in the vicinity of 620 MHz, that is, a third-order intermodulation distortion (hereinafter referred to as “CTB”) of the OFDM signal, and a frequency. The frequency conversion unit 13 performs frequency conversion so that the output from the conversion unit 13 becomes a signal in an intermediate frequency band with a center frequency of 10 MHz and a bandwidth of 6 MHz.

Then, the signal of the analyzed noise component, based on the sampling theorem by the A / D converter 14 is converted into a digital signal, is acquired amplitude data, for example, 10 ⁷ of the analyzed noise component. This sample data is recorded by the recording unit 15.

  Subsequently, all the sample data of the amplitude data of the analyzed noise component is read out from the recording unit 15 by the calculation unit 16, and the average value, variance value, and standard of the amplitude data are obtained in order to grasp the statistical properties of the analyzed noise component. The deviation σ is acquired.

  Further, the calculation unit 16 normalizes all samples of the amplitude data of the noise component to be analyzed, and sets the average value of the amplitude data to 0 and the standard deviation σ to 1. By this normalization processing, it becomes possible to compare the statistical properties of the analyzed noise component and the normally distributed thermal noise component. Further, the arithmetic unit 16 calculates a cumulative probability distribution (hereinafter referred to as “amplitude distribution”) of the normalized amplitude of the noise component to be analyzed, and outputs amplitude distribution data to the display unit 17 and the SER estimation unit 204.

  Then, the display unit 17 displays a graph of the normalized amplitude amplitude distribution of the analyzed noise component and the normally distributed thermal noise component as shown in FIG. . In FIG. 9, the horizontal axis indicates the normalized amplitude, and the vertical axis indicates the cumulative probability. In addition, the solid line indicates data of a normally distributed thermal noise component, the broken line indicates a theoretical value obtained by analytically deriving the CTB of the OFDM signal, and the circle indicates a measured value of the CTB of the OFDM signal obtained by experiment and statistically processed.

  As shown in FIG. 9, the CTB measurement value is in good agreement with the analytically derived CTB theoretical value, and shows a large deviation from the normal distribution in the range where the absolute value of the normalized amplitude is large. . This means that even if the CTB of the OFDM signal has the same power as the thermal noise component that is normally distributed, the influence on the deterioration of the BER characteristic of the digital modulation signal is increased.

Next, returning to FIG. 5, the amplitude distribution data output from the noise analysis device 10 is input to the SER estimation unit 204. It is assumed that the modulation method and CNR of the digital transmission signal are predetermined. Next, the CIR calculation unit 201 calculates CIR from the CNR and CTB according to the equation (5). _Furthermore, the _{P ave} calculator _{202, P ave} is calculated.

  Subsequently, the threshold value calculation unit 105 calculates the threshold value δ of the symbol. This threshold value δ is calculated by the formula (6) based on the thermal noise component and the total sum of interference wave power including the CTB of the OFDM signal.

  Next, in the amplitude distribution data output from the noise analysis device 10, the estimated value of the SER characteristic is acquired by the SER estimating unit 204 by obtaining the cumulative probability at the threshold value −δ calculated by the equation (6). The Note that the SER estimation unit 204 can also estimate the BER characteristic from the estimated SER characteristic by the expressions (7) and (8).

  Then, the SER characteristic is displayed by the error rate display unit 205. The error rate display unit 205 can also display the BER characteristic when the SER estimation unit 204 estimates the BER characteristic.

  As described above, according to the transmission characteristic estimation apparatus 200 of the present embodiment, the noise analysis apparatus 10 acquires the amplitude distribution of the noise component in which the thermal noise component and the CTB interference are mixed, and the threshold calculation unit 203 Since the threshold of the symbol of the digital transmission signal is calculated and the SER estimation unit 204 is configured to estimate the SER characteristic or BER characteristic of the digital transmission signal based on the amplitude distribution of the noise component and the threshold, the transmission signal is not used. The transmission characteristic of the digital transmission signal can be estimated based on the statistical property of the noise component.

The block diagram of the transmission characteristic estimation apparatus which concerns on the 1st Embodiment of this invention The figure which shows the data example of the amplitude distribution displayed on the amplitude distribution display part of the transmission characteristic estimation apparatus which concerns on the 1st Embodiment of this invention (A) Block diagram showing a configuration example for measuring transmission characteristics of a QAM signal (b) Block diagram showing a configuration example of a nonlinear distortion generator The figure which shows the relationship between CNR and BER characteristic The block diagram of the transmission characteristic estimation apparatus which concerns on the 2nd Embodiment of this invention The block diagram of the noise analyzer which concerns on the 2nd Embodiment of this invention An OFDM signal generator as a signal source is connected to the noise analyzer according to the second embodiment of the present invention, and characteristics of intermodulation distortion components generated when nonlinearly amplifying an OFDM signal of digital terrestrial broadcasting are analyzed. Block diagram showing a configuration example The figure which shows the spectrum example of the OFDM signal in the OFDM signal generator connected to the noise analyzer which concerns on the 2nd Embodiment of this invention (a) Spectrum example of the OFDM signal input into the amplifier of an OFDM signal generator (B) Diagram showing an example of the spectrum of the OFDM signal output from the amplifier of the OFDM signal generator A screen imitating normal probability paper, a cumulative probability distribution of normalized amplitudes of analyzed noise components, and thermal noise components that are normally distributed, displayed by the display unit of the noise analysis apparatus according to the second embodiment of the present invention Figure showing and graph (A) Schematic diagram showing example spectrum of OFDM signal in linear region (b) Schematic diagram showing example spectrum of OFDM signal in non-linear region (c) Schematic diagram showing example spectrum for explaining generation principle of intermodulation distortion

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Noise analyzer 11 Band pass filter 12, 23 Amplifier 13 Frequency conversion part 13a Local oscillator 13b Mixer 14 A / D conversion part (noise amplitude data acquisition means)
15 recording unit 16 calculation unit (statistics calculation means, cumulative probability distribution calculation means, ratio calculation means)
17 Display section (display means)
DESCRIPTION OF SYMBOLS 20 OFDM signal generator 21 OFDM signal generator 22 Attenuator 31 QAM modulator 32 Nonlinear distortion generator 33, 35 Adder 34 Thermal noise generator 36 QAM demodulator 37 BER display device 100, 200 Transmission characteristic estimation device 101, 201 CIR calculation unit (power ratio calculation means)
102, 202 P _ave calculation unit (average power calculation means)
103 Noise statistical processing section (statistical processing means)
104 Amplitude distribution display unit 105, 203 Threshold calculation unit (threshold calculation means)
106, 204 SER estimation unit (symbol error rate estimation means, bit error rate calculation means)
107, 205 Error rate display

Claims (10)

A power ratio calculation means for calculating a ratio between the power of a digital transmission signal having a predetermined modulation scheme and carrier-to-noise power ratio and the sum of the power of interference waves that interfere with the transmission of the digital transmission signal; and the digital transmission signal Average power calculating means for calculating the average power of the interference wave, statistical processing means for analyzing the statistical properties of the disturbing wave based on the calculation results of the power ratio calculating means and the average power calculating means, the power ratio calculating means, Threshold calculation means for calculating a threshold for determining a symbol of the digital transmission signal based on the calculation result of the average power calculation means, and the digital based on the statistical analysis processing result of the interference wave and the threshold A transmission characteristic estimation apparatus comprising symbol error rate estimation means for estimating a symbol error rate of a transmission signal. The transmission characteristic estimation according to claim 1, further comprising bit error rate calculation means for calculating a bit error rate of the digital transmission signal based on the symbol error rate estimated by the symbol error rate estimation means. apparatus. Based on a noise analysis device that analyzes a noise component included in a digital transmission signal, a threshold calculation unit that calculates a threshold for determining a symbol of the digital transmission signal, a noise analysis result of the noise analysis device, and the threshold Symbol error rate estimating means for estimating a symbol error rate of the digital transmission signal,
The noise analysis device includes a noise amplitude data acquisition unit that acquires amplitude data of the noise component, a statistic calculation unit that calculates a predetermined statistic related to the amplitude data of the noise component, and the statistic based on the statistic A transmission characteristic estimation apparatus comprising: cumulative probability distribution calculating means for normalizing noise component amplitude data and calculating a normalized cumulative probability distribution of normalized amplitude. The transmission according to claim 3, wherein the noise analysis device includes ratio calculation means for calculating a ratio between a cumulative probability distribution of normalized amplitudes of the noise component and a predetermined reference cumulative probability distribution. Characteristic estimation device. The digital transmission signal includes a thermal noise component, the reference cumulative probability distribution is a cumulative probability distribution of the amplitude of the thermal noise component, and the ratio calculating means includes a cumulative probability distribution of a normalized amplitude of the noise component and The transmission characteristic estimation apparatus according to claim 4, wherein a ratio with the cumulative probability distribution of the amplitude of the thermal noise component is calculated. The digital transmission signal includes an intermodulation distortion component, and the ratio calculation means calculates a ratio between a cumulative probability distribution of normalized amplitude of the intermodulation distortion component and a cumulative probability distribution of amplitude of the thermal noise component. The transmission characteristic estimation apparatus according to claim 5. 4. The noise analysis apparatus includes a display unit that displays a cumulative probability distribution of normalized amplitudes of the noise component and data of the reference cumulative probability distribution on a screen imitating a predetermined probability sheet. The transmission characteristic estimation apparatus according to any one of claims 1 to 6. 8. A bit error rate calculating means for calculating a bit error rate of the digital transmission signal based on the symbol error rate estimated by the symbol error rate estimating means. The transmission characteristic estimation apparatus according to any one of claims. Predetermining a modulation method and a carrier-to-noise power ratio of a digital transmission signal, and a signal-to-jamming wave power indicating a ratio between the power of the digital transmission signal and the sum of the powers of jamming waves that interfere with transmission of the digital transmission signal A step of calculating a ratio, a step of calculating an average power of the digital transmission signal, a step of analyzing a statistical property of the interference wave based on the signal-to-interference wave power ratio and the average power, and the signal pair Calculating a threshold for determining a symbol of the digital transmission signal based on an interference wave power ratio and the average power; and a symbol error of the digital transmission signal based on a statistical property of the interference wave and the threshold A transmission characteristic estimation program including a step of estimating a rate. The transmission characteristic estimation program according to claim 9, further comprising a step of calculating a bit error rate of the digital transmission signal based on the symbol error rate.

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