JP2020113927A - Mmse equalization receiving device - Google Patents

Abstract

To obtain the accurate signal-to-noise ratio of a data signal to improve the channel equalization accuracy of the MMSE standard and reduce the required C/N when boost processing is performed on a pilot signal UW in a SC-FDE method.SOLUTION: An SN measuring unit 30 of a receiving device 2 measures S/NUW. A first configuration example of an SN correction unit 31 uses a preset known UW boost ratio bst to divide S/NUW by the boost ratio bst to correct S/NUW to S/NDATA. A frequency domain equalizer 32 performs MMSE standard channel equalization by using a channel characteristic estimated by a channel estimation unit 28, data symbol generated by a Fourier transform unit 29 and a frequency domain signal relating to a UW portion, and the S/NDATA generated by the SN correction unit 31.SELECTED DRAWING: Figure 3

Description

The present invention relates to a single-carrier type receiving apparatus that can be used in a wireless transmission system such as broadcasting or communication, and more particularly to a receiving apparatus that channel equalizes a single carrier in the frequency domain.

Conventionally, in a wireless transmission system of fixed transmission such as broadcasting or communication, a single carrier method using one carrier and a multicarrier OFDM (Orthogonal Frequency Division Multiplexing) method using a plurality of carriers have been widely used. There is.

In recent years, even in the single carrier system, SC-FDE (Single Carrier-Frequency Domain Equalization) that performs channel equalization (processing for undoing changes in amplitude and phase generated in a propagation path) in the frequency domain ) System has been proposed (see, for example, Patent Document 1 and Non-Patent Document 1).

In general, the single-carrier method has a smaller PAPR (Peak to Average Power Ratio), which is the ratio of the peak power to the average power of a transmission signal, as compared with the multi-carrier OFDM method. Therefore, the single carrier system has high resistance to distortion due to nonlinear characteristics in the power amplifier of the output stage of the transmission device, and when the same power amplifier is used, the transmission power can be made larger than that of the multicarrier OFDM system. It is possible to improve the reception quality.

Also, the SC-FDE system can follow high-speed channel fluctuations in mobile transmission by performing channel estimation and channel equalization in the frequency domain in block units like the multi-carrier OFDM system. Therefore, the SC-FDE system is more suitable for mobile transmission than the conventional single carrier system that performs channel equalization in the time domain. Further, in the SC-FDE system, a guard interval (GI) is provided as in the multi-carrier OFDM system to prevent interblock interference in a multipath environment.

That is, the SC-FDE system is a modulation system suitable for a mobile transmission device that is required to be small in size and low in power consumption because the power amplifier can be used for high efficiency operation and mobile transmission.

A receiving device using the SC-FDE system performs block synchronization for detecting the beginning of a block with respect to a received signal, and a UW (unique word, which is a fixed pattern known between the transmitting and receiving devices) used as a pilot signal for channel estimation from the received signal. Signal) and data.

Then, the receiving device performs a Fourier transform on the UW and the data from the time domain to the frequency domain, and performs channel estimation and channel equalization processing. After that, the receiving device returns the data after the channel equalization to the signal in the time domain by the inverse Fourier transform, and performs processing such as symbol determination.

ZF (Zero-Forcing) standard or MMSE (Minimum Mean Square Error) standard is mainly used for the process of channel equalization.

ここで、Ｘ^_ZF（ｆ）は、ＺＦ基準によるチャネル等化後の信号、Ｘ^_MMSE（ｆ）は、ＭＭＳＥ基準によるチャネル等化後の信号を示す。ｆは、周波数領域のサンプリングポイント、Ｙ（ｆ）は、チャネル等化対象の受信信号、Ｈ（ｆ）は、推定したチャネル（伝送路特性）、Ｓ／Ｎは、ＳＮ比（信号対雑音比）を示す。 The channel equalization process based on the ZF standard is shown in formula (1), and the channel equalization process based on the MMSE standard is shown in formula (2).

Here, X^ _ZF (f) indicates a signal after channel equalization based on the ZF standard, and X^ _MMSE (f) indicates a signal after channel equalization based on the MMSE standard. f is a sampling point in the frequency domain, Y(f) is the received signal to be channel equalization target, H(f) is the estimated channel (transmission path characteristic), and S/N is the SN ratio (signal to noise ratio). ) Is shown.

The ZF standard performs equalization by dividing the received signal by the transmission line characteristic in the frequency domain, but simultaneously added noise is also divided by the transmission line characteristic. At this time, if the absolute value of the transmission line characteristic is a very small value, noise enhancement that causes noise to occur will occur.

The MMSE standard is an equalization method that also considers noise in order to reduce noise enhancement in the ZF standard, and exhibits equalization performance superior to the ZF standard. On the other hand, in the MMSE standard, it is necessary to obtain not only the transmission path characteristics but also noise power and signal power.

Further, for the pilot signal used for estimating the transmission path characteristic, the required C/N (carrier-to-noise ratio) can be obtained by performing processing (boost processing) for increasing the amplitude ratio, that is, the power ratio, compared to other signals. It is also known to improve (for example, see Non-Patent Document 2).

Japanese Patent No. 5624527

D. Falconer, et al., “Frequency domain equalization for single-carrier broadband wireless systems”, IEEE Commun. Mag., Vol. 40, pp. 58-66, April 2002. Yamagishi, Matsuzaki, Ito, Kamoda, Imamura, Hamazumi, "Study on boost ratio of pilot signal in SC-FDE system", Proc. of IEICE General Conference, B-5-94, 2018

Generally, when performing channel equalization based on MMSE, the SN ratio of the UW or the SN ratio of the entire transmission signal is used as the S/N of the above equation (2).

On the other hand, when the boost ratio of the pilot signal UW is greater than 1 in the amplitude ratio or the power ratio, that is, when the boost process is performed on the UW, the SN ratio of the data signal, the SN ratio of the UW, and the SN of the entire transmission signal. The ratios will be different values.

Therefore, when the UW is boosted and the channel equalization is performed using the SN ratio of the UW or the SN ratio of the entire transmission signal based on the MMSE standard, the accuracy of the channel equalization of the data signal is insufficient. become.

That is, when the boost process is performed on the UW, the SN ratio of the UW and the SN ratio of the entire transmission signal deviate from the SN ratio of the data signal that should be originally used. There was a problem that the effect was not sufficient.

Here, if an accurate SN ratio of a data signal can be used when performing channel equalization based on MMSE, the accuracy of channel equalization is improved, and as a result, a sufficient C/N reduction effect can be obtained. You can However, since it is difficult to directly calculate the SN ratio from the data signal, the SN ratio of the data signal cannot be used when performing channel equalization based on the MMSE standard.

Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide an accurate SN of a data signal when a boost process is performed on a pilot signal UW in the SC-FDE system. An object of the present invention is to provide an MMSE receiving apparatus capable of improving the channel equalization accuracy based on MMSE by obtaining the ratio and reducing the required C/N.

In order to solve the above-mentioned problems, the MMSE receiver according to claim 1 is a block including a UW (unique word) that is a boosted pilot signal, and is composed of the UW at the beginning, data, and the UW at the back. In the SC-FDE MMSE receiver that receives a modulated wave of the block series and performs channel equalization based on MMSE, the rear UW one block before and the UW at the beginning of a block continuous thereto are related. An SN measurement unit that measures the SN ratio of the UW based on a signal in the time domain; an SN correction unit that corrects the SN ratio of the UW measured by the SN measurement unit to the SN ratio of the data; The transmission line characteristic estimated based on the UW included in the reception signal of the modulated wave, the signal in the frequency domain calculated by the Fourier transform of the reception signal, and the SN ratio of the data corrected by the SN correction unit. A frequency domain equalization unit for performing channel equalization based on the MMSE standard, wherein the SN correction unit uses the preset boost ratio of the UW to change the SN ratio of the UW to the boost ratio. Alternatively, it is characterized by including a dividing means for dividing by the square value of the boost ratio to obtain the SN ratio of the data.

The MMSE receiver according to claim 2 is the MMSE receiver according to claim 1, wherein the SN correction unit uses the preset boost ratio to change the SN ratio of the UW to the boost ratio or the boost ratio. A division means for obtaining the SN ratio of the data by dividing by the square value of the ratio is provided, and the preset boost ratio is obtained from the boost ratio of each information when the data is composed of a plurality of types of information. When an average boost ratio of the data is used as the average boost ratio, a value obtained by dividing the known boost ratio of the UW by the average boost ratio of the data is used.

The MMSE receiver according to claim 3 is the MMSE receiver according to claim 1, wherein the data subjected to the channel equalization by the frequency domain equalizer is subjected to an inverse Fourier transform, and the inverse Fourier transform is performed. A symbol determination unit that determines the symbol of the time domain signal obtained by the conversion, calculates the deviation between the symbol obtained by the symbol determination and the ideal signal point, and converts the deviation into the distortion information of MER or EVM. When the distortion information converted by the symbol determination unit is the MER, the SN correction unit sets a boost ratio so that the MER becomes maximum, and when the distortion information is EVM, the EVM is Using the boost ratio setting means for setting the boost ratio so as to be the minimum and the boost ratio set by the boost ratio setting means, the SN ratio of the UW is set to the boost ratio or the square value of the boost ratio. And a dividing unit for obtaining the SN ratio of the data.

Further, an MMSE receiving device according to claim 4 is the MMSE receiving device according to any one of claims 1 to 3, wherein the SN measurement unit sets the UW located one block before as a first UW. , An average signal power and an average noise power per point from the time domain signals relating to the first UW and the second UW, with the UW at the beginning of a block continuing to this being the second UW. From the time domain signal relating to the first UW, the average power per point as the first average power, and the average power per point from the signal relating to the second UW in the time domain The power is calculated as a second average power, the average noise power is calculated based on the first average power and the second average power, and the average signal power is calculated based on the added power and the average noise power. Is calculated, and the SN ratio of the UW is calculated based on the average noise power and the average signal power.

As described above, according to the present invention, an accurate SN ratio of a data signal can be obtained in the SC-FDE method when boost processing is performed on UW that is a pilot signal. As a result, by performing channel equalization based on MMSE using the SN ratio of the data signal, the accuracy of channel equalization is improved, and as a result, the required C/N can be reduced.

It is a block diagram which shows the structural example of a transmitter. It is a figure explaining the structural example of a SC-FDE block. It is a block diagram which shows the structural example of the receiver by embodiment of this invention. It is a figure explaining the process which measures the SN ratio of UW with respect to the symbol of the time domain SC-FDE block distorted by fading. It is a block diagram which shows the 1st structural example of an SN correction|amendment part. It is a flow chart which shows the example of processing of the 1st example of composition of an SN amendment part. It is a block diagram which shows the 2nd structural example of an SN correction part. It is a flow chart which shows the example of processing of the 2nd example of composition of an SN amendment part. It is a block diagram which shows the 3rd structural example of an SN correction|amendment part. It is a flow chart which shows the example of processing of the 3rd example of composition of an SN amendment part. It is a figure which shows a simulation result.

Hereinafter, modes for carrying out the present invention will be described in detail with reference to the drawings. The present invention obtains the SN ratio of UW by utilizing the fact that UW, which is a pilot signal, is continuously transmitted, and obtains the SN ratio of a data signal based on the SN ratio of UW and a predetermined boost ratio. The channel equalization based on MMSE is performed using the SN ratio of

[Transmitting device]
First, the transmitter will be described. The transmission device is a device that uses a single carrier system in which channel equalization is performed in the frequency domain on the reception side. The modulation method of the data part includes BPSK (Binary Phase Shift Keying), DBPSK (Differential BPSK), QPSK (Quadrature Phase Shift Keying), 8PSK, 16APSK (16 Amplitude and Phase Shift Keying), 32APSK, 64APSK, 16QAM (16 Quadrature). Amplitude Modulation), 32QAM, 64QAM, or any other mapping is used. Further, it is assumed that boost processing is performed on UW which is a pilot signal.

FIG. 1 is a block diagram showing a configuration example of a transmission device. The transmitting device 1 is a device used in an SC-FDE wireless transmission system. The transmission device 1 includes a pre-transmission processing unit 11, a mapping unit 12, a UW (unique word) generation unit 13, an SC (single carrier) block configuration unit 14, a band limiting filter unit 15, a quadrature modulation unit 16, and a DA (digital analog). The conversion unit 17, the frequency conversion unit 18, the power amplification unit 19, and the transmission antenna 20 are provided.

The transmission preprocessing unit 11 inputs an information bit sequence (data) to be transmitted, performs preprocessing such as energy diffusion processing, error correction processing, and interleaving processing on the information bit sequence, and generates a coded bit sequence. Then, the transmission preprocessing unit 11 outputs the encoded bit sequence to the mapping unit 12. For this preprocessing, arbitrary energy spreading processing, error correction processing, interleaving processing, etc. can be applied.

The information bit sequence here is transmission control information, a video signal, an audio signal, and other arbitrary information, and the transmission preprocessing unit 11 may perform the same or different processing on these pieces of information. .. Further, the mapping unit 12 at the subsequent stage may select the same or different mapping method for each of these pieces of information.

The mapping unit 12 inputs the coded bit sequence from the transmission preprocessing unit 11, performs mapping such as 32APSK, and outputs the mapped data symbol (data signal) to the SC block configuration unit 14.

The UW generation unit 13 generates UW that is a pilot signal and outputs the UW to the SC block configuration unit 14. UW is fixed pattern data known between the transmitter 1 and a receiver 2 described later, and CAZAC (Constant Amplitude Zero Auto-) having a constant amplitude and excellent periodic autocorrelation characteristics in the time domain and frequency domain. Correlation: constant amplitude zero autocorrelation) sequence, for example, Zadoff-Chu sequence is used.

The SC block configuration unit 14 inputs the data symbol from the mapping unit 12 and the UW from the UW generation unit 13. Then, the SC block configuration unit 14 inserts a UW at a predetermined position of the data symbol, configures an SC-FDE block shown in FIG. 2 described later, and outputs the SC-FDE block sequence to the band limiting filter unit 15.

Here, the SC block composing unit 14 composes the SC-FDE block according to the preset boost ratio bst of the UW, on the basis of the average amplitude or the average power of the data symbols, the average amplitude or the average of the UW. Performs boost processing to increase power. By this means, it is possible to improve the channel estimation accuracy in receiving apparatus 2 described later.

For example, when a value of 1.4 is preset as the UW boost ratio bst on the basis of the amplitude, the SC block configuration unit 14 sets the average amplitude of the UW to be 1.4 times the average amplitude of the data symbols. , UW is boosted. As a result, the average amplitude of UW becomes 1.4 times the average amplitude of data symbols, and the average power of UW at that time becomes 1.4 ² times the average power of data symbols.

FIG. 2 is a diagram illustrating a configuration example of the SC-FDE block. The SC-FDE block is configured by inserting UWs before and after the data symbol, and has the order of the first UW, the data symbol, and the rear UW. In the SC-FDE block sequence in which the SC-FDE blocks are continuously formed, the rear UW included in the first SC-FDE block and the head UW included in the second SC-FDE block following the UW. Will be continuous in time. That is, two UWs are continuously inserted between two data symbols.

The length of the SC-FDE symbol is 2304 symbols, the length of the UW is 256 symbols, and the length of the data symbol is 1792 symbols. The equalization target is the data symbol and the rear UW, and its length is 2048 symbols. Here, the length of each symbol is an example, and the length of the UW and the length of the data symbol to be equalized and the length of the succeeding UW can be any length as long as they are powers of two. ..

Returning to FIG. 1, the band limitation filter unit 15 inputs the SC-FDE block sequence from the SC block configuration unit 14, performs waveform shaping on the SC-FDE block sequence by band limitation of filter processing, and SC-FDE. Upsampling the block sequence by a factor of 2. Then, band limiting filter section 15 outputs the SC-FDE block sequence after waveform shaping to quadrature modulation section 16. A root roll-off filter is generally used as the band limiting filter unit 15.

The quadrature modulation unit 16 inputs the waveform-shaped SC-FDE block sequence from the band-limiting filter unit 15, performs quadrature modulation processing on the waveform-shaped SC-FDE block sequence, and performs aperture correction processing. Then, the quadrature modulation unit 16 outputs the digital signal after quadrature modulation and aperture correction to the DA conversion unit 17. The aperture correction process is a process for correcting the aperture effect by the digital/analog conversion in the DA conversion unit 17 in the subsequent stage.

The DA converter 17 receives the digital signal after the orthogonal modulation and aperture correction from the orthogonal modulator 16, converts the digital signal into an analog signal, and outputs the analog signal to the frequency converter 18.

The frequency converter 18 receives the analog signal from the DA converter 17, converts the frequency of the analog signal into a radio frequency, and outputs the radio frequency modulated signal to the power amplifier 19.

The power amplification unit 19 inputs the radio frequency modulation signal from the frequency conversion unit 18, and amplifies the power of the radio frequency modulation signal to a predetermined power. Then, the amplified modulated signal of the radio frequency is transmitted via the transmitting antenna 20 as the radio signal of the modulated wave.

In this way, the radio signal of the modulated wave including the UW subjected to the boost process is transmitted from the transmission device 1 to the reception device 2 described later.

[Receiver]
Next, the receiving device according to the embodiment of the present invention will be described. The receiving device is a device that uses a single carrier system that performs channel equalization based on MMSE in the frequency domain. It is assumed that an arbitrary mapping is used as the modulation method of the data portion of the received signal, and that the received signal includes UW that has undergone boost processing.

FIG. 3 is a block diagram showing a configuration example of the receiving device according to the embodiment of the present invention. The receiving device 2 is an MMSE receiving device that performs MMSE standard channel equalization in a SC-FDE wireless transmission system. The reception device 2 includes a reception antenna 21, a frequency conversion unit 22, an AD (analog-digital) conversion unit 23, a quadrature demodulation unit 24, a band limiting filter unit 25, a block synchronization unit 26, a UW Fourier transform unit 27, a channel estimation unit 28, A Fourier transform unit 29, an SN measurement unit 30, an SN correction unit 31, a frequency domain equalization unit 32, an inverse Fourier transform unit 33, a symbol determination unit 34, and a decoding unit 35 are provided.

Although the number of reception branches is 1 here, it may be 2 or more. When the number of reception branches is 2 or more, it is assumed that diversity combining is possible.

The receiving device 2 receives the radio signal of the modulated wave transmitted from the transmitting device 1 shown in FIG. 1 via the receiving antenna 21. The radio signal of the modulated wave includes UW subjected to boost processing.

The frequency conversion unit 22 converts the radio frequency of the radio signal of the modulated wave received via the reception antenna 21 into an intermediate frequency, and outputs the intermediate frequency signal to the AD conversion unit 23.

The AD conversion unit 23 inputs the intermediate frequency signal from the frequency conversion unit 22, converts the analog signal of the intermediate frequency signal into a digital signal, and outputs the digital signal to the orthogonal demodulation unit 24.

The quadrature demodulation unit 24 receives the digital signal from the AD conversion unit 23, performs automatic frequency control on the digital signal, performs quadrature demodulation processing while correcting frequency deviation, and generates a quadrature-demodulated complex baseband signal. Then, the quadrature demodulation unit 24 outputs the frequency-corrected complex baseband signal to the band limiting filter unit 25.

The band limitation filter unit 25 inputs the frequency-compensated complex baseband signal from the quadrature demodulation unit 24, and performs band limitation by the filtering process on the frequency-compensated complex baseband signal. Then, the band limiting filter unit 25 outputs the band-limited complex baseband signal to the block synchronization unit 26. A root roll-off filter is generally used as the band limiting filter unit 25.

The block synchronization unit 26 inputs the band-limited complex baseband signal from the band-limiting filter unit 25, and based on the IQ signal of the UW portion, with respect to the band-limited complex baseband signal, of the SC-FDE block. Detect synchronization timing. Then, the block synchronization unit 26 extracts a time-domain signal related to the leading UW portion in the SC-FDE block, and extracts a subsequent data symbol and a time-domain signal relating to the rear UW portion.

In one SC-FDE block, the block synchronization unit 26 outputs the time domain signal regarding the head UW portion to the UW Fourier transform unit 27, and also performs the time domain signal regarding the data symbol and the rear UW portion by Fourier transform. Output to the conversion unit 29. The block synchronization unit 26 also outputs a signal in the time domain regarding the rear UW in the SC-FDE block that is one block before and the first UW (the same UW as the first UW to be output to the UW Fourier transform unit 27) subsequent thereto. Is output to the SN measuring unit 30.

The UW Fourier transform unit 27 inputs the time domain signal relating to the leading UW portion in the SC-FDE block from the block synchronization unit 26, and Fourier transforms the time domain signal relating to the leading UW portion into a frequency domain signal. To do. Then, the UW Fourier transform unit 27 outputs the frequency domain signal relating to the leading UW portion to the channel estimation unit 28.

The channel estimation unit 28 inputs from the UW Fourier transform unit 27 a signal in the frequency domain related to the leading UW portion in the SC-FDE block. Then, the channel estimation unit 28 performs channel estimation on the signal in the frequency domain using a signal in the known UW frequency domain as a reference signal, and obtains a transmission path characteristic. The channel estimation unit 28 outputs the transmission path characteristics to the frequency domain equalization unit 32.

The Fourier transform unit 29 inputs, from the block synchronization unit 26, the time domain signal relating to the data symbol and the rear UW portion in the SC-FDE block, and outputs the time domain signal relating to the data symbol and the rear UW portion in the frequency domain. Fourier transform to the signal. Then, the Fourier transform unit 29 outputs the signal in the frequency domain regarding the data symbol and the rear UW portion to the frequency domain equalization unit 32.

The SN measurement unit 30 inputs, from the block synchronization unit 26, a signal in the time domain regarding the UW one block before in the SC-FDE block and the UU portion following the UW. Then, the SN measurement unit 30 _obtains the average signal power S _UWave and the average noise power N _UWave of the UW based on the time-domain signals related to the two UW portions by utilizing the fact that the _UWs are _continuous . The S/N _UW which is the SN ratio of _UW is measured. Details will be described with reference to FIG. 4 described later. The SN measurement unit 30 outputs S/N _UW , which is the SN ratio of _UW, to the SN correction unit 31.

FIG. 4 is a diagram for explaining the process of measuring the UW SN ratio for the symbols of the SC-FDE block in the time domain distorted by fading. The upper figure shows the symbols of the SC-FDE block in the time domain distorted by fading, and the lower figure is an enlargement of the signal of the continuous UW part. UW-1 indicates the backward UW one block before, and UW-2 indicates the leading UW in the SC-FDE block. The horizontal axis represents time and the vertical axis represents power.

The SN measuring unit 30 extracts a signal for a point at a preset predetermined position from the signals of UW-1 and UW-2, calculates and adds the power at each point, and calculates the total power for the a point (S _UW + N _UW ) is calculated. Then, the SN measurement unit 30 divides the total power (S _UW +N _UW ) for a points by the number of points a as shown in the following formula, and the average signal power S _{UWave of} UW, which is the average power per point. _And the added power (S _UWave +N _UWave ) of the average noise power N _UWave .

The SN measurement unit 30 extracts a signal for b points at a predetermined position set in advance (a signal for b points of UW-1) from the UW-1 signal. Further, the SN measurement unit 30 extracts a signal at a position 512 points away from the position of the signal corresponding to b point of UW-1 (a signal corresponding to b point of UW-2) from the signal of UW-2. ..

Here, the number of points of each of UW-1 and UW-2 is 512. In the transmitter 1 shown in FIG. 1, the length of the UW included in the SC-FDE block formed by the SC block configuration unit 14 is 256 symbols as shown in FIG. Then, the SC-FDE block sequence is upsampled by a factor of 2 in the band limiting filter unit 15 in the subsequent stage, so that the UW length becomes 512 symbols. Therefore, in the SN measuring unit 30 of the receiving device 2, the number of points of each of UW-1 and UW-2 is 512.

The SN measuring unit 30 calculates the power of each point in the signal of b points of UW-1 and adds them to obtain the total power (S _1bUW +N _1bUW ) of b points. Then, the SN measurement unit 30 _divides the total power (S _1bUW +N _1bUW ) for b points by the number of points b to obtain the average power per point of UW-1.

The SN measurement unit 30 calculates the power of each point in the signal of b points of UW-2 and adds them to obtain the total power (S _2bUW +N _2bUW ) of b points. Then, the SN measuring unit 30 _divides the total power (S _2bUW +N _2bUW ) for b points by the number of points b to obtain the average power per point of UW-2.

The SN measurement unit 30 subtracts the average power per one point of the UW-2 from the average power per one point of the UW-1 according to the following equation, and _obtains a double value (2N) of the average noise power N _UWave of the UW. _UWave ).

The right side of the equation (4) is N _1bUW −N _2bUW . Since the noise power has a normal distribution, its variance corresponds to the noise power. The calculation result of the equation (4) becomes 2N _UWave =N _1bUW −N _2bUW because the variances of the subtraction results of the normal distributions that are uncorrelated with each other are different from each other due to the reproducibility of the normal distribution. This is because the added value is obtained. For reproducibility of normal distribution, refer to the following site.
"Statistics Supplementary Document 10. Regeneration of Normal Distribution", Sanyo Gakuen University/Sanyo Gakuen Junior College, [January 8, 2019 search], Internet <URL: www.sguc.ac.jp/i/st/ learning/statistics/hosoku/reproducibility of normal distribution.pdf>

The SN measurement unit 30 calculates the average signal power S _UWave and the average noise power N _UWave of the UW from the above equations (3) and (4), respectively, and as the following equation, the S/N _UW that is the SN ratio of the _UW. To calculate.

It should be noted that the position of the signal for the point a extracted from the signals of UW-1, 2 may be anywhere within the signals of UW-1, 2. It is desirable that the point number a be as large as possible within the total number of points in the UW-1, 2 signals. Further, the positions of the signals of b points extracted from the signals of UW-1 and UW-2 may be anywhere in the signals of UW-1 and UW as long as they are 512 points apart. Further, as described above, the length of each symbol is an example, and the length of the UW and the length of the data symbol to be equalized and the length of the succeeding UW may be any length as long as they are powers of two. It is possible, and the number of points of UW-1, 2 is twice the length of UW, and the position for extracting the signal of b points of UW-2 coincides with twice the length of UW.

Returning to FIG. 3, the SN correction unit 31 inputs the S/N _UW that is the SN ratio of UW from the SN measurement unit 30. In the case of a third configuration example described later, the SN correction unit 31 further inputs distortion information (MER (Modulation Error Ratio) or EVM (Error Vector Magnitude)) from the symbol determination unit 34. ..

The SN correction unit 31 uses the S/N _UW or the like (in the case of the third configuration example described later, the S/N _UW and the distortion information or the like) to obtain the SN ratio of the data symbol from the S/N _UW. Performs correction processing to S/N _DATA . Then, the SN correction unit 31 outputs S/N _DATA , which is the SN ratio of the data symbol, to the frequency domain equalization unit 32.

As the correction process, for example, the process according to the first configuration example, the process according to the second configuration example, or the process according to the third configuration example described later is performed. In the processing according to the first configuration example, the S/N _UW is divided by the boost ratio bst (or the squared value bst ² ) by using the preset known boost ratio bst of the _UW to obtain the S/N _UW by S. Correct to /N _DATA . The preset known UW boost ratio bst is a known value between the transmitter 1 and the receiver 2.

When the boost ratio bst is a power-based value, division is performed by the boost ratio bst, and when the boost ratio bst is an amplitude-based value, division is performed by a square value bst ² . Details of the first configuration example will be described later.

In the processing according to the second configuration example, a case where the data symbol is composed of a plurality of types of information (transmission control information, video signal, audio signal, and other arbitrary information), and the symbol of each information is boosted individually This is the assumed processing. In this process, S/N _UW is corrected to S/N _DATA by dividing S/N _UW by boost ratio bst' (or squared value bst' ² ) using a preset boost ratio bst'. To do.

The boost ratio bst' is obtained by dividing the preset UW known boost ratio bst by the preset known average boost ratio bsta of the data symbols. The preset boost ratio bst′ and the preset average boost ratio bsta of the data symbols are also known values between the transmitting device 1 and the receiving device 2, like the known boost ratio bst of the UW. ..

The SN correction unit 31 may calculate the boost ratio bst'. Specifically, the SN correction unit 31 sets the known boost ratio bst of the preset UW to the known average boost ratio of the preset data symbol (or the data symbol and the backward UW shown in FIG. 2). The known average boost ratio (boost ratio per point) in b) is divided by bsta to obtain the boost ratio bst'.

Further, the SN correction unit 31 does not use the preset known average boost ratio bsta when calculating the boost ratio bst′, but instead of using the average boost ratio of the data symbols (or the average of the data symbols and the backward UW). The boost ratio) bsta may be calculated. Specifically, the SN correction unit 31 has a known boost ratio of each piece of information forming the data symbol (or each piece of information forming the data symbol and a known boost ratio in the rear UW), and each piece of information. The average boost ratio of data symbols (or the average boost ratio of data symbols and backward UW) bsta is obtained based on the number of points (or each information and the number of points in the backward UW). Details of the second configuration example will be described later.

In the process according to the third configuration example, when the distortion information is MER, the boost ratio bst″ is obtained so that the MER becomes maximum, and when the distortion information is EVM, the boost ratio bst′ is obtained so that the EVM becomes minimum. Ask for. Then, S/N _DATA is obtained by dividing S/N _UW by the boost ratio bst″. Details of the third configuration example will be described later.

The frequency domain equalizer 32 inputs the channel characteristics from the channel estimator 28, and the Fourier transform unit 29 also inputs the data symbols in the SC-FDE block and signals in the frequency domain relating to the rear UW portion. Further, the frequency domain equalizer 32 inputs the S/N _DATA , which is the SN ratio of the data symbols in the SC-FDE block, from the S/N corrector 31.

The frequency domain equalizer 32 uses the transmission path characteristics, the data symbol and the frequency domain signal relating to the rear UW portion, and the S/N _DATA which is the SN ratio of the data symbol, and is expressed by the above equation (2). Perform MMSE standard channel equalization. Here, the channel equalization is performed by double up-sampling corresponding to the processing of the band limiting filter unit 15 of the transmission device 1 shown in FIG.

Further, the frequency domain equalization unit 32 down-samples the signal in the frequency domain relating to the data and the rear UW portion by half, that is, after the channel equalization by the double up-sampling, that is, the inverse Fourier transform is performed. Output to the conversion unit 33. Down-sampling by ½ can be realized by thinning out signals in the frequency domain or adding corresponding frequency points as the same frequency component.

The inverse Fourier transform unit 33 inputs the data after the channel equalization and the frequency domain signal regarding the rear UW portion from the frequency domain equalization unit 32, and outputs the frequency after the channel equalization and the frequency regarding the rear UW portion. Inverse Fourier transform of the domain signal into the time domain signal is performed. Then, the inverse Fourier transform unit 33 outputs the data and the signal in the time domain regarding the rear UW portion to the symbol determination unit 34.

The symbol determination unit 34 inputs the data and the time domain signal relating to the rear UW portion from the inverse Fourier transform unit 33, and outputs the time domain signal relating to the data portion from the time domain signal relating to the data and the rear UW portion. To extract. Then, the symbol determination unit 34 performs demapping and likelihood calculation on the time domain signal regarding the data portion, and performs symbol determination.

When the hard decision is made as the symbol decision, the symbol decision unit 34 generates a coded bit sequence (data that has been subjected to error correction coding) forming a symbol and outputs the coded bit sequence to the decoding unit 35. ..

On the other hand, when performing the soft decision as the symbol decision, the symbol decision unit 34 generates a likelihood sequence corresponding to the coded bit sequence and outputs the likelihood sequence to the decoding unit 35.

Here, when the SN correction unit 31 inputs the distortion information in the third configuration example illustrated in FIGS. 9 and 10, the symbol determination unit 34 calculates the deviation between the symbol determined as the symbol and the ideal signal point. Then, the shift is converted into distortion information of MER or EVM. Then, the symbol determination unit 34 outputs the distortion information to the SN correction unit 31.

The decoding unit 35 inputs the coded bit sequence or the likelihood sequence from the symbol determination unit 34 and corresponds to the coded bit sequence or the likelihood sequence to the pre-transmission processing unit 11 of the transmission device 1 illustrated in FIG. 1. Deinterleave processing, error correction decoding processing, energy despreading processing, etc. are performed. Then, the decoding unit 35 decodes and outputs the information bit sequence (data).

(First configuration example of the SN correction unit 31)
Next, a first configuration example of the SN correction unit 31 shown in FIG. 3 will be described in detail. FIG. 5 is a block diagram showing a first configuration example of the SN correction unit 31, and FIG. 6 is a flowchart showing a processing example of the first configuration example of the SN correction unit 31. The first configuration example of the SN correction unit 31 includes a division unit 41.

The dividing means 41 inputs the S/N _UW which is the SN ratio of the UW from the SN measuring section 30 (step S601). Then, when the boost ratio bst is the value of the power reference, the dividing unit 41 divides the S/N _UW by the preset boost ratio bst of the UW set in advance according to the following equation, and the SN of the data symbol is calculated. The ratio S/N _DATA is obtained (step S602).

On the other hand, when the boost ratio bst is the amplitude reference value, the dividing means 41 divides the S/N _UW by the squared value bst ² of the preset boost ratio bst of UW set in advance according to the following equation. Then, S/N _DATA which is the SN ratio of the data symbol is obtained.

The divider 41 outputs S/N _DATA , which is the SN ratio of the data symbol, to the frequency domain equalizer 32 (step S603).

As a result, the SN correction unit 31-1 corrects the S/N _UW, which is the SN ratio of the _UW , to the S/N _DATA , which is the SN ratio of the data symbol, by using the preset boost ratio bst of the UW set in advance. To be done.

(Second configuration example of SN correction unit 31)
Next, a second configuration example of the SN correction unit 31 shown in FIG. 3 will be described in detail. As described above, the second configuration example is an example in which each symbol is individually boosted for the transmission control information, the video signal, the audio signal, and other arbitrary information that form the data symbol.

FIG. 7 is a block diagram showing a second configuration example of the SN correction unit 31, and FIG. 8 is a flowchart showing a processing example of the second configuration example of the SN correction unit 31. The second configuration example of the SN correction unit 31 includes a division unit 42.

The dividing unit 42 inputs the S/N _UW , which is the SN ratio of the UW, from the SN measuring unit 30 (step S801).

Here, when the boost ratio bst' used in the process of step S803 to be described later is not preset, the dividing unit 42 performs a process for calculating the boost ratio bst' (step S802).

Specifically, the dividing unit 42 divides the preset boost ratio bst of the preset UW by the preset average boost ratio bsta of the preset data symbol (or the data symbol and the backward UW), Find the boost ratio bst'.

If the average boost ratio bsta of the data symbols is not preset, the dividing unit 42 presets each piece of information forming the data symbol (or each piece of information forming the data symbol and the rear UW). An average boost ratio bsta of the data symbol (or the data symbol and the rear UW) is calculated from the known boost ratio. As an example of the calculation process of the average boost ratio bsta, if the boost ratio of x symbols of the data symbols is bst _x and the boost ratio of the remaining 1792−x symbols is bst _1792-x , then bsta=(bst _x ×x+bst _{1792- x} ×(1792−x))/1792 (or bsta=(bst _x ×x+bst _1792−x ×(1792−x)+bst×256)/2048 including the rear UW) is calculated. Then, the divider 42 divides the preset boost ratio bst of the UW set in advance by the calculated average boost ratio bsta to calculate the boost ratio bst′.

The dividing means 42 divides the S/N _UW by a preset known boost ratio bst′ (or the calculated boost ratio bst′) when the boost ratio bst′ is a power reference value, and S/N _DATA which is the SN ratio is obtained (step S803).

The preset known boost ratio bst' is used when the receiving device 2 holds the average boost ratio bsta and the boost ratio bst' in advance.

On the other hand, when the boost ratio bst′ is a value based on the amplitude, the dividing unit 42 calculates the S/N _UW as the squared value bst′ ² of the preset known boost ratio bst′ ² (or the calculated boost ratio bst′. Then, S/N _DATA , which is the S/N ratio of the data symbol, is obtained by dividing by the squared value bst′ ² ).

The divider 42 outputs S/N _DATA , which is the SN ratio of the data symbol, to the frequency domain equalizer 32 (step S804).

Thereby, in the SN correction unit 31-2, the S/W that is the SN ratio of the UW is calculated by using the preset boost ratio bst of the UW and the boost ratio bst′ in which the average boost ratio bsta of the data symbols is reflected. N _UW is corrected to S/N _DATA which is the SN ratio of the data symbol.

(Third configuration example of the SN correction unit 31)
Next, a third configuration example of the SN correction unit 31 shown in FIG. 3 will be described in detail. As described above, the third configuration example is an example in which distortion information is used to correct S/N _UW , which is the SN ratio of _UW, to S/N _DATA , which is the SN ratio of data symbols.

FIG. 9 is a block diagram showing a third configuration example of the SN correction unit 31, and FIG. 10 is a flowchart showing a processing example of the third configuration example of the SN correction unit 31. The third configuration example of the SN correction unit 31 includes a boost ratio setting unit 43 and a dividing unit 44.

The boost ratio setting means 43 inputs the distortion information (MER or EVM) from the symbol determination unit 34 (step S1001).

In the initial processing, the boost ratio setting means 43 sets a known boost ratio bst of UW set in advance to the boost ratio bst″, and outputs the boost ratio bst″ to the dividing means 44.

The boost ratio setting means 43 sets a different boost ratio bst″ according to the distortion information input from the symbol determination section 34 and outputs it to the division means 44. In this case, the boost ratio setting means 43 sets the boost ratio bst″ so that the MER becomes maximum when the distortion information is MER, and sets the boost ratio bst so that the EVM becomes minimum when the distortion information is EVM. '' is set (step S1002). Then, the boost ratio setting means 43 outputs the boost ratio bst″ to the dividing means 44.

The dividing unit 44 inputs the S/N _UW which is the SN ratio of the UW from the SN measuring unit 30 (step S1003) and the boost ratio bst″ from the boost ratio setting unit 43.

When the boost ratio bst″ is the power reference value, the dividing unit 44 divides the S/N _UW by the boost ratio bst″ to obtain S/N _DATA which is the SN ratio of the data symbol (step S1004). ..

On the other hand, when the boost ratio bst″ is the amplitude reference value, the dividing means 44 divides S/N _UW by the square value bst″ ² of the boost ratio bst″ to obtain the S/N ratio of the data symbol. _Calculate /N _DATA .

The dividing unit 44 outputs S/N _DATA , which is the SN ratio of the data symbol, to the frequency domain equalization unit 32 (step S1005).

As a result, the SN correction unit 31-3 corrects the S/N _UW, which is the SN ratio of _UW , to the S/N _DATA , which is the SN ratio of the data symbol, using the boost ratio bst″ obtained from the distortion information. It

〔simulation result〕
Next, the simulation results by the transmitter 1 shown in FIG. 1 and the receiver 2 of the embodiment of the present invention shown in FIG. 3 will be described. FIG. 11 is a diagram showing the simulation result. The simulation result of FIG. 11 shows that the modulation method of the data part is 32APSK, the coding rate is 1/2, the UW boost ratio is 1.4, the noise is AWGN (additive white Gaussian noise), and the equalization standard is the MMSE standard. The data obtained under the above conditions. The error correction code uses a convolutional code, and the simulation result is obtained from the data after the soft decision Viterbi decoding.

The horizontal axis indicates the required C/N [dB], and the vertical axis indicates the BER (Bit Error Ratio). The dotted line shows the characteristics of the prior art in which MMSE-based channel equalization is performed using the SN ratio of UW, and the solid line shows the characteristics of the embodiment of the present invention.

It can be seen from FIG. 11 that when the required BER is 1×10 ⁻⁴ , the required CN is improved by about 0.15 dB in the embodiment of the present invention as compared with the conventional technique.

As described above, according to the receiving device 2 of the embodiment of the present invention, the SN measuring unit 30 measures the S/N _UW which is the SN ratio of _UW . The first configuration example of the SN correction unit 31 uses the preset known UW boost ratio bst to divide the S/N _UW by the boost ratio bst (or the squared value bst ² ) to obtain the S/N ratio. Correct _UW to S/N _DATA .

Further, the second configuration example of the SN correction unit 31 uses the boost ratio bst′ to divide the S/N _UW by the boost ratio bst′ (or the squared value bst′ ² ), so that the S/N _UW is S. Correct to /N _DATA .

As the boost ratio bst' in this case, a known preset boost ratio bst' is used. Alternatively, as the boost ratio bst', a value obtained by dividing the known boost ratio bst of the preset UW by the known average boost ratio bsta of the preset data symbol is used. Here, when the average boost ratio bsta of the data symbol is not set in advance, this average boost ratio bsta is calculated from a preset known boost ratio for each information or the like that constitutes the data symbol.

In addition, in the third configuration example of the SN correction unit 31, when the distortion information calculated by the symbol determination unit 34 is MER, the boost ratio bst″ is set so that the MER becomes maximum, and the distortion information is EVM. In this case, the boost ratio bst″ is set so that the EVM becomes the minimum. Then, in the third configuration example, the S/N _DATA is obtained by dividing the S/N _UW by the boost ratio bst″ (or the squared value bst″ ² ).

The frequency domain equalization unit 32 includes a transmission path characteristic estimated by the channel estimation unit 28, a frequency domain signal regarding the data symbol and the UW portion generated by the Fourier transform unit 29, and data generated by the SN correction unit 31. Using the S/N _DATA which is the SN ratio of the symbol, the channel equalization based on the MMSE shown in the equation (2) is performed.

Accordingly, when the boost ratio bst of the pilot signal UW is larger than 1 in the amplitude ratio or power ratio with the data symbol, the S/N _DATA that is the accurate SN ratio of the data symbol can be obtained. Therefore, by performing channel equalization based on MMSE using S/N _DATA , the accuracy of channel equalization is improved and the required C/N can be reduced. Therefore, the required C/N can be further reduced as compared with the case where MMSE-based channel equalization is performed using the SN ratio of UW or the SN ratio of the entire transmission signal.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the technical idea thereof.

INDUSTRIAL APPLICABILITY The present invention is useful for a wireless transmission system such as broadcasting or communication based on the SC-FDE system in which the boost ratio of UW that is a pilot signal is larger than 1 in terms of amplitude ratio or power ratio.

DESCRIPTION OF SYMBOLS 1 transmitter 2 receiver 11 transmission pre-processing unit 12 mapping unit 13 UW (unique word) generation unit 14 SC (single carrier) block configuration unit 15 band limiting filter unit 16 quadrature modulation unit 17 DA (digital-analog) conversion unit 18 frequency Conversion unit 19 Power amplification unit 20 Transmission antenna 21 Reception antenna 22 Frequency conversion unit 23 AD (analog digital) conversion unit 24 Quadrature demodulation unit 25 Band limiting filter unit 26 Block synchronization unit 27 UW Fourier transform unit 28 Channel estimation unit 29 Fourier transform unit 30 SN measurement section 31 SN correction section 32 Frequency domain equalization section 33 Inverse Fourier transform section 34 Symbol determination section 35 Decoding sections 41, 42, 44 Division means 43 Boost ratio setting means

Claims (4)

A block including a boosted pilot signal UW (unique word), which receives a modulated wave of a sequence of the block including the first UW, data, and rear UW, and channel equalization based on MMSE In the SC-FDE type MMSE receiver that performs
An SN measurement unit that measures the SN ratio of the UW based on the time-domain signal of the UW that is one block before and the UW that is the beginning of a block that follows the UW, and
An SN correction unit that corrects the SN ratio of the UW measured by the SN measurement unit to the SN ratio of the data,
Transmission path characteristics estimated based on the UW included in the received signal of the modulated wave, a frequency domain signal calculated by Fourier transform of the received signal, and an SN ratio of the data corrected by the SN correction unit. And a frequency domain equalizer that performs channel equalization based on the MMSE standard,
The SN correction unit is
A preset boost ratio of the UW is used to divide the SN ratio of the UW by the boost ratio or a squared value of the boost ratio to obtain a SN ratio of the data. MMSE receiver. The MMSE receiver according to claim 1,
The SN correction unit is
Using a preset boost ratio, the SN ratio of the UW is divided by the boost ratio or the square value of the boost ratio, the dividing means for obtaining the SN ratio of the data,
As the preset boost ratio,
When the average value obtained from the boost ratio of each information when the data is composed of a plurality of types of information is the average boost ratio of the data, the known boost ratio of the UW is the average boost of the data. An MMSE receiver characterized by using a value obtained by dividing by a ratio. The MMSE receiver according to claim 1,
Further, the data subjected to the channel equalization by the frequency domain equalizer is subjected to inverse Fourier transform, the time domain signal obtained by the inverse Fourier transform is subjected to symbol determination, and the symbol obtained by the symbol determination is used. A symbol determination unit for calculating a deviation from the ideal signal point and converting the deviation into MER or EVM distortion information,
The SN correction unit is
When the distortion information converted by the symbol determination unit is the MER, a boost ratio is set so that the MER is maximized, and when the distortion information is EVM, the boost ratio is minimized. Boost ratio setting means for setting
Division means for dividing the SN ratio of the UW by the boost ratio or the square value of the boost ratio using the boost ratio set by the boost ratio setting means to obtain the SN ratio of the data;
An MMSE receiving apparatus comprising: The MMSE receiver according to any one of claims 1 to 3,
The SN measurement unit
The UW that is one block before and behind is the first UW, and the UW at the beginning of a block that follows this is the second UW,
From the signals in the time domain regarding the first UW and the second UW, the average power per point is obtained as the added power of the average signal power and the average noise power,
From the time domain signal relating to the first UW, the average power per point is obtained as the first average power,
From the time domain signal relating to the second UW, the average power per point is determined as the second average power,
Determining the average noise power based on the first average power and the second average power,
Determining the average signal power based on the added power and the average noise power,
An MMSE receiver, wherein the SN ratio of the UW is obtained based on the average noise power and the average signal power.

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