JP4175220B2 - Multicarrier demodulation method and multicarrier demodulation device - Google Patents

Description

  The present invention relates to a method and apparatus for compensating and demodulating a channel variation that varies with time in multicarrier communication. The present invention is particularly effective for a receiving apparatus on a moving body that moves at high speed with respect to transmission by an orthogonal frequency division multiplexing (OFDM) system.

  When receiving a transmission signal from a fixed station with a receiving device provided on a high-speed moving body, the propagation path characteristics change every moment. Taking a case where a broadcast signal is received by a vehicle traveling on a highway in an urban area, for example, there are a number of obstacles in the surrounding area, and the propagation path characteristics change very rapidly. When receiving a multi-carrier modulation signal such as an OFDM scheme, the change in the propagation path characteristic is different for each subcarrier. Such propagation path characteristics for each subcarrier that change at high speed lead to a significant reduction in communication quality. Specifically, the orthogonality between the subcarriers is broken and the intercarrier interference increases, so that interference with the pilot signal causes a decrease in channel estimation accuracy, which decreases the channel compensation accuracy.

Patent Documents 1 and 2 listed below are known as compensation for high-speed fluctuations in transmission path characteristics, and Patent Documents 3 and 4 listed below are methods for improving the estimation accuracy of transmission path characteristics.
JP 2000-286817 A JP-A-11-68630 JP 2001-44963 A The technique described in Japanese Patent Laid-Open No. 2002-261729 is a technique in which time domain equalization means is provided in an OFDM receiver at a stage before a Fast Fourier Transform (FFT). The technique described in Patent Document 2 performs distortion compensation before and after FFT in an OFDM receiver. In addition, the techniques described in Patent Documents 3 and 4 use the scattered pilot signal, and the channel characteristics of each symbol other than the symbol channel occupied by the pilot signal are used to determine the channel characteristics of the symbol occupied by the pilot signal. Interpolation is performed from channel propagation path characteristics. FIG. Like A, the pilot signal does not have to be included in all symbols, and can be arranged in different subcarriers as compared with other symbols including the pilot signal. Thus, the channel characteristics of each symbol channel other than the symbol channel occupied by the pilot signal are interpolated on the time / frequency plane by interpolation and extrapolation from the channel characteristics of the symbol channel occupied by the pilot signal. It is possible.

  The channel characteristic time / frequency interpolation using the scattered pilot signal will be described with reference to FIG. First, FIG. 7 shows a configuration in which only frequency fading by a normal pilot signal is compensated. Shown in A. FIG. A is a block diagram showing an outline of the configuration of the multicarrier demodulator 900. The received wave is demodulated by the quadrature demodulator 91 into a baseband signal and sampled. Next, a serial / parallel converter (S / P) 92 outputs each symbol length including the guard interval. This output is input to a guard interval (GI) remover 93, which removes the guard interval and outputs a 1-symbol length time-axis signal to an N-point fast Fourier transformer (N-point FFT) 94. The output of the N-point FFT 94 is a signal of N subcarriers. From this, a pilot symbol extractor 951 extracts a pilot signal. Next, channel characteristic estimator 952 estimates the channel characteristic of the subcarrier having the pilot signal. Next, channel characteristic frequency interpolator 953 interpolates the channel characteristics of all channels from the channel characteristics of the pilot signal. If a pilot signal is not provided for each symbol, the same channel characteristic is applied to each subcarrier until the next pilot signal is extracted. Thus, the frequency domain equalizer 97 outputs the N-point FFT 94 with N complex numbers indicating the channel propagation path characteristics output from the channel characteristic frequency interpolator 953 corresponding to the N complex numbers output from the N-point FFT 94. If the N complex numbers are divided, an output with compensated channel characteristics can be obtained.

  Next, Fig. 7 shows a configuration for time and frequency compensation using a scattered pilot signal. Shown in B. FIG. B is a block diagram showing an outline of the configuration of the multicarrier demodulator 950. FIG. B is a multi-carrier demodulator 950 and FIG. A is the difference in the configuration of the multicarrier demodulator 900 shown in FIG. B shows that the multi-carrier demodulator 950 is provided with a buffer (delay circuit, memory or shift register) 96 between the N-point FFT 94 and the frequency domain equalizer 97, and the channel characteristic instead of the frequency interpolator 953. A time / frequency interpolator 954 is provided.

  A 1-symbol length time-axis signal is input to an N-point FFT 94, and N subcarrier signals are obtained by FFT. From this, a pilot signal is extracted by a pilot symbol extractor 951, and a channel characteristic estimator 952 estimates the channel characteristic of a subcarrier having the pilot signal. Next, the channel characteristic time / frequency interpolator 954 interpolates the channel characteristics of all channels from the channel characteristics of the pilot signal, and sets the channel characteristics of all channels of symbols not provided with the pilot signal to the previous one. It calculates | requires by interpolation between the symbols which have the extracted pilot signal. At this time, the time occupied by the guard interval between symbols is also taken into consideration. Thus, in the frequency domain equalizer 97, N complex numbers indicating channel propagation path characteristics output from the channel characteristic time / frequency interpolator 954 corresponding to the N complex numbers output from the N-point FFT 94 via the buffer 96. By dividing N complex numbers that are the output of the buffer 96, an output with compensated channel characteristics can be obtained. This also compensates for time-varying channel characteristics.

  The technique described in Patent Document 1 uniformly compensates for each subcarrier, and thus is effective in a flat fading environment, but is not effective in a frequency selective fading environment. The technique described in Patent Document 2 ignores time fluctuations within an interval of one symbol length of OFDM. In addition, the techniques described in Patent Documents 3 and 4 cannot compensate for time fluctuations in a 1-symbol length section.

  Therefore, the present inventors have used channeled pilot signals as described in Patent Documents 3 and 4 above, and channel fluctuations that can compensate for temporal fluctuations within a one-symbol length section in a frequency selective fading environment. The invention relating to the compensation method and apparatus has been completed. That is, an object of the present invention is to compensate for time fluctuations of propagation path characteristics within a one-symbol length section in a frequency selective fading environment in a channel fluctuation compensation method and channel fluctuation compensation apparatus for a multicarrier modulation signal. It is.

  According to a first aspect of the present invention, in the multicarrier demodulation method, the received signal on the time axis is subjected to time / frequency division different from the time / frequency division pattern corresponding to the transmission side, and the divided temporary channels are divided. The estimated value of the corresponding propagation path characteristic is obtained by interpolation, the propagation path characteristic is compensated for each temporary channel, and the time of the temporary channel compensated for the propagation path characteristic and the time axis compensated from the signal on the frequency axis. And the compensated signal on the time axis is separated into subcarriers by a time / frequency division pattern corresponding to the transmission side.

  Further, according to a second aspect of the present invention, in the multicarrier demodulation method, the received signal on the time axis is subjected to time / frequency division different from the time / frequency division pattern corresponding to the transmission side. Estimate the propagation path characteristics corresponding to the channel by interpolation, compensate the propagation path characteristics for each tentative channel, and respond to the signal on the time and frequency axes of the tentative channel with compensated propagation path characteristics on the transmission side. It is characterized in that it is converted into a time-frequency division pattern and separated into subcarriers whose propagation path characteristics are compensated. The means according to claim 3 is characterized in that an estimated value of the propagation path characteristic corresponding to each temporary channel is obtained by interpolation based on the scattered pilot signal.

  According to a fourth aspect of the present invention, in the multicarrier demodulation method, the N complex signals on the time axis to be separated into each subcarrier by N-point discrete Fourier transform are divided into two or more groups, Each group is subjected to discrete Fourier transform by discrete Fourier transform with the number of complex signals as points, and divided into temporary channel groups, and N complex on the time axis to be separated into subcarriers by the N-point discrete Fourier transform. Determine the propagation path characteristics from the pilot signal obtained by separating the signal into subcarriers by N-point discrete Fourier transform, and interpolate the propagation path characteristics of each temporary channel in the time / frequency plane from the propagation path characteristics of the pilot signal. And each of the temporary channels is made to correspond to the time / frequency plane to compensate the propagation path characteristics of each temporary channel, and from the compensated signals of each temporary channel, N complex signals on the time axis compensated by inverse discrete Fourier transform by inverse discrete Fourier transform with corresponding points are obtained, and the N complex signals on the compensated time axis are N-point discrete Fourier transform To obtain a signal of each subcarrier whose propagation path characteristics are compensated. Further, according to a fifth aspect of the present invention, N is a power of 2, and N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform are obtained from a divisor of N. The discrete Fourier transform other than the N-point discrete Fourier transform is replaced with a discrete wavelet transform or wavelet packet transform with a corresponding number of points, and the inverse discrete Fourier transform is supported. It is characterized in that it is replaced with a point inverse discrete wavelet transform or inverse wavelet packet transform.

Also, the means described in claim 6, N is a power of 2 width, the N complex signal on the time axis to be separated into the subcarriers by N-point discrete Fourier transform, a divisor of the N It divides | segments into the 2 or more group which consists of the number of.

The means described in claims 7 to 12 is a multicarrier demodulator, and each has means for realizing the multicarrier demodulation method according to claims 1 to 6 .

  Considering one symbol as a rectangle on the time / frequency plane, this is not divided for each channel corresponding to each subcarrier including a null carrier, but is divided on the time / frequency plane by a different division method. Channel. At this time, the number of temporary channels generated by the division is made to match the number of original channels. Thus, the channel characteristics are not compensated for each channel corresponding to each subcarrier of one symbol length, but the channel characteristics are compensated for each temporary channel by different divisions on the time / frequency plane. As a result, compensation for fading on the frequency axis is reduced, but since it is divided on the time axis, compensation for fading on the time axis can be strengthened. Therefore, it is possible to compensate for fading on the time axis at a timing shorter than one symbol while compensating for frequency selective fading, and a multicarrier demodulating method or multicarrier demodulating device that follows a rapidly changing propagation path characteristic It can be.

  The discrete Fourier transform and the inverse discrete Fourier transform can be realized very easily because a fast Fourier transformer can be used for a factorial of 2 points. As for discrete Fourier transform, particularly fast Fourier transform, so-called partial discrete Fourier transform and partial fast Fourier transform have been studied. For example, N complex numbers are divided into two and obtained by N / 2 point discrete Fourier transform with a small number of points. It is also known to convert the original N complex numbers into N complex numbers obtained by N-point discrete Fourier transform from the two sets of N / 2 complex numbers (partial discrete Fourier transform). If this is used, the present invention can be easily realized.

First, the image of the present invention is shown in FIG. A, FIG. A description will be given using B. FIG. A is a conceptual diagram of a conventional channel fluctuation estimation method using scattered pilot signals described in Patent Documents 3 and 4. FIG. FIG. In A, the time at which each symbol arrives is plotted on the horizontal axis, and the frequency indicating the channel in each symbol is plotted on the vertical axis. FIG. A means that p + 1 OFDM symbols arrive sequentially in a time of p + 1 symbol length. FIG. In A, the scattered pilot signal occupies the four channels of the leftmost symbol and the four channels of the rightmost symbol. By demodulating these eight scattered pilot signals, the channel characteristics of each channel in the symbol occupied by the eight scattered pilot signals are calculated, and the eight channel characteristics in the symbol are calculated. Based on channel propagation characteristics, FIG. The channel characteristics of other channels of p + 1 symbols shown in A can be obtained by interpolation by interpolation or extrapolation. That is, when the propagation path characteristic is a function Z (ω, t) of the angular frequency ω and time t, from the measured eight Z (ω ₁ , t ₀ ),... Z (ω ₀ , t _p ). Thus, Z (ω, t) at an arbitrary point (ω, t) is obtained by interpolation calculation. Channel fluctuation can be compensated by dividing the value of each subcarrier after FFT by the propagation path characteristics of each channel of each symbol obtained in this way. This is channel fluctuation compensation in a time-varying frequency selective fading environment using a scattered pilot signal.

  On the other hand, the present invention is shown in FIG. It becomes a conceptual diagram like B. FIG. In the present invention shown in FIG. A multi-carrier modulation signal corresponding to A is received. First, a scattered pilot signal is analyzed by a normal demodulation method, for example, N-point FFT. Next, for example, the FFT score is N / 2 points, and the N point of one symbol length is divided into two parts, the first half and the second half, and all symbols are separately demodulated. The demodulated signal is shown in FIG. The number of channels in the frequency direction is halved and the carrier frequency interval is doubled in 2 (p + 1) FFT sections, which were originally p + 1 symbols, such as B. From the propagation path characteristics of each channel in the symbol occupied by the original eight scattered pilot signals obtained by analyzing the scattered pilot signal obtained by the normal N-point FFT, FIG. . The propagation path characteristic with respect to the output of each N / 2 point FFT at the position of the triangle B is calculated. After dividing the channel characteristic by the N / 2-point inverse fast Fourier transform (IFFT) and then performing the N-point FFT after dividing the channel characteristic by the propagation path characteristic, the multi-carrier modulation signal compensated for the propagation path characteristic is obtained. Data that should originally be obtained can be obtained.

  Wavelet transformation and wavelet packets that can be used in the present invention will be described. The detailed description is described in, for example, Hitoshi Kie, “Multi-rate Signal Processing”, Shosho-do, page 149 et seq. FIG. 2 is a diagram for explaining the wavelet series expansion in comparison with the Fourier series expansion. The division pattern on the time / frequency plane is developed with the same symbol length for each frequency in the Fourier series expansion, and there is no division in the time axis direction. However, in the wavelet series expansion, the time axis direction is also divided.

  FIG. 3 is an explanatory diagram for explaining the wavelet packet. FIG. A indicates “two-divided multirate filter bank”. In each figure of FIG. 3, HPF and LPF divide the band of the input signal from the preceding stage into two, and the passband characteristic is determined by the wavelet basis function. In the normal wavelet transform or wavelet packet transform, all the same HPFs have the same passband characteristics, but different passband characteristics may be used for each two-divided multirate filter bank. In addition, a downward arrow and 2 indicate thinning out of the digital signal.

  FIG. B is FIG. An example is shown in which a “two-divided multirate filter bank” of A is assembled in multiple stages to constitute a wavelet packet and a discrete wavelet transformer is constructed. FIG. C, FIG. In addition to discrete wavelet transformers and discrete Fourier transformers, D can be divided into one symbol on the time and frequency planes by arbitrarily constructing “two-divided multirate filter banks” in multiple stages. Indicates that the transducer can be configured. A filter using a complex number as a tap coefficient is called a complex multi-rate filter bank, and can realize various division patterns that cannot be realized by a real number coefficient.

Thus, FIG. 1 shows that one symbol can be divided on the time / frequency plane by performing N / 2-point Fourier transform on each of a plurality of symbols in the first half and the second half. Further, such division can be performed very easily and variously by assembling “two-division multi-rate filter banks” in multiple stages as shown in FIGS. In the following, when referred to as N / 2-point discrete wavelet transform, it is assumed to be a discrete wavelet transform corresponding to a “log-division multi-rate filter bank” having a maximum of log ₂ N / 2 stages in the horizontal direction. . For example, FIG. In B, the “two-divided multirate filter bank” has a maximum of three stages in the horizontal direction and is an 8-point discrete wavelet transform.

  FIG. 4 is a block diagram showing an outline of the configuration of a multicarrier demodulator 100 that is a specific embodiment of the present invention. The received wave is demodulated to a baseband signal by the quadrature demodulator 1 and sampled. Next, a serial-parallel converter (S / P) 2 outputs each symbol length including the guard interval. The guard interval (GI) remover 3 removes the guard interval and outputs N complex signals on the time axis of one symbol length to the N-point fast Fourier transform (N-point FFT) 41. The output of the GI remover 3 is input to the N / 2-point fast Fourier transformer (N / 2-point FFT) 511 as N / 2 complex signals in the first half of the time axis of one symbol length. N / 2 complex signals in the second half of the symbol length time axis are input to the N / 2 point FFT 521.

  The output of the N point FFT 41 is a signal of N subcarriers. From here, a pilot signal is extracted by a pilot symbol extractor 42. Next, the channel characteristic estimator 43 estimates the channel characteristic of the subcarrier having the pilot signal. Next, the channel characteristic time / frequency interpolator 44 calculates the N / 2 point FFT 511 and the N / 2 point from the channel characteristic of the pilot signal and the channel characteristic of the pilot signal in the symbol having the pilot signal extracted immediately before. The propagation channel characteristics of the temporary channel in the FFT 521 are obtained.

  Details of the calculation of “propagation channel characteristics of the temporary channel at the N / 2 point FFT 511 and the N / 2 point FFT 521” are as follows. First, the pilot signal of the channel corresponding to the N-point FFT will be described by assigning numbers as follows. The number of the symbol having the pilot signal extracted immediately before is set to 0, and the number of the symbol having the newly extracted pilot signal is set to p. However, p may be 1 or more. There is a symbol having no (p-1) pilot signals between symbol 0 and symbol p.

  The subcarrier number in the N-point FFT 41 is an integer from 0 to N-1. Assuming that pilot signals are present in symbol 0 and symbol p, a space consisting of a time axis, a frequency axis, and an axis of complex channel characteristics (amplitude and phase characteristics) is assumed. Interpolation of channel characteristics will be described using a space composed of a time axis, a frequency axis, and a complex channel characteristic axis.

  First, the location of the channel response based on the pilot signal is determined on the time / frequency plane. This is because each OFDM1 symbol has a horizontal length as a symbol length on the time axis, a vertical length as a frequency band (determined in an arbitrary unit), and a time axis of a gap from a rectangle indicating an adjacent OFDM1 symbol. The width of the direction is a rectangle with a guard interval length, and the area of each channel is divided into N in the frequency axis direction. Here, the location of the channel response based on the pilot signal is defined as the center of a rectangle indicating the channel region occupied by the pilot signal. Next, the channel response between the pilot signals included in the symbol p is determined linearly in the direction perpendicular to the time axis from the channel response based on the pilot signal. Next, for the symbol 0 having the previous pilot signal, the channel response determined linearly in the direction perpendicular to the time axis from the channel response based on the pilot signal, and the channel response based on the pilot signal for the symbol p To the channel response that is linearly determined in the direction perpendicular to the time axis is connected to the frequency axis in the direction perpendicular to the frequency axis to determine linearly. Thus, the channel response is determined for any point on the time / frequency plane.

  Next, in order to determine the propagation path characteristics of the temporary channel at the N / 2 point FFT 511 and the N / 2 point FFT 521, positions on the time / frequency plane are assigned as follows. A rectangle indicating each OFDM1 symbol (the width in the time axis direction between the rectangle indicating the adjacent OFDM1 symbol is a guard interval) and FIG. A is divided into N in the frequency axis direction. Like B, it is divided into N / 2 in the frequency axis direction and divided into 2 in the time axis direction. In this way, the provisional channel region occupied by each signal decomposed by N / 2 “coarse FFT” is determined. The region corresponding to subcarrier number 0 is set so that the center of the temporary channel region is located “on the time axis”. Thus, the provisional channel region occupied by each signal decomposed by “coarse FFT” is determined, and the channel response determined for any point on the time / frequency plane described above corresponds to the coordinate of the center. Thus, the channel response of the temporary channel region is obtained. Note that the channel responses of all necessary temporary channels are obtained using not only interpolation but also extrapolation as necessary.

  Thus, since the channel response of the provisional channel is determined, the channel response CFR1 corresponding to the first half of each of the symbols 1 to p and the channel response CFR2 corresponding to the second half are sequentially transmitted from the channel characteristic time / frequency interpolator 44 to the frequency. Output to the region equalizers 513 and 523. On the other hand, from the buffers 512 and 522, signals on the frequency axis corresponding to the first half and the second half of each of the symbols 1 to p are sequentially output from the channel characteristic time / frequency interpolator 44 to the frequency domain equalizers 513 and 523. . Thus, in the frequency domain equalizers 513 and 523, the signals on the frequency axis that compensate the channel responses corresponding to the first half and the second half of each of the symbols 1 to p are converted into N / 2 point IFFT 514 and N / 2 point IFFT 524. Is output. The N / 2 point IFFT 514 and the N / 2 point IFFT 524 generate a signal on the time axis by inverse fast Fourier transform (IFFT) and output it to the N point FFT 45. The signal on the frequency axis calculated by the N-point FFT 45 by the fast Fourier transform is a signal in which propagation path characteristics in the first half and the latter half of one symbol length are compensated. Thereafter, it is taken out as a signal string via a parallel / serial converter (P / S) 6.

  FIG. 5 is a block diagram showing an outline of the configuration of a multicarrier demodulator 200 that is a specific embodiment of the present invention. The configuration of multicarrier demodulation apparatus 200 in FIG. 5 is the same as that of multicarrier demodulation apparatus 100 in FIG. 4 except that N-point FFTs 41 and 45 and N / 2-point IFFT 514 and N / 2-point IFFT 524 are omitted. Converters 71 and 72 for converting the output of the N / 2 point FFT into the output of the N point FFT are provided. The multicarrier demodulator 200 in FIG. 5 obtains the same output as the output of the N-point FFT 41 in FIG. 1 by using the converter 71 from the outputs of the two N / 2-point FFT 511 and the N / 2-point FFT 521, the frequency domain, etc. The outputs of the generators 513 and 523 are obtained by the converter 72 to obtain the same output as that of the N-point FFT 45 in FIG. That is, compared with the multicarrier demodulator 100 of FIG. 4, two N-point FFTs and two N / 2 point IFFTs can be omitted, so that a smaller multicarrier demodulator can be obtained.

  FIG. 6 is a block diagram showing a schematic configuration of a multicarrier demodulator 300 which is a specific embodiment of the present invention. The configuration of multicarrier demodulation apparatus 300 in FIG. 6 is the same as that of multicarrier demodulation apparatus 100 in FIG. 4. N / 2 point FFT 511 and N / 2 point FFT 521, N / 2 point IFFT 514 and N / 2 point IFFT 524, and channels The characteristic time / frequency interpolator 44 is replaced with an N / 2 point WPT 551 and an N / 2 point WPT 561, an N / 2 point IWPT 554 and an N / 2 point IWPT 564, and a channel characteristic time / frequency interpolator 46.

  As described above, the N / 2 point WPT 551 and the N / 2 point WPT 561 are discrete wavelet transformers corresponding to the N / 2 point FFT, and the N / 2 point IWPT 554 and the N / 2 point IWPT 564 are the N / 2 point WPT 551 and the N / 2 point WPT 551, respectively. It is an inverse discrete wavelet transformer corresponding to N / 2 point WPT561. Of course, these may be formed by a multi-rate filter bank. The channel characteristic time / frequency interpolator 46 interpolates the position of the channel response to be interpolated corresponding to the channel position on the time / frequency plane of the outputs of the N / 2 point WPT 551 and the N / 2 point WPT 561. It is what you want to do. Similarly to the multicarrier demodulator 100 of FIG. 4, the multicarrier demodulator 300 of FIG. 6 can output a signal in which both the propagation path characteristics in the first half and the latter half of one symbol length are compensated. For the sake of understanding, the division of the time / frequency domain at each output is shown.

  For example, in the first embodiment, in order to enable parallel processing, an N / 2 point FFT, a buffer, a frequency domain equalizer, and an N / 2 point IFFT are provided in each of the first half and second half of the symbol processing sequence. However, even if the N / 2 point FFTs 511 and 521 are substituted with one N / 2 point FFT, the buffers 512 and 522 are set to 1 by providing a control system such as a CPU. N / 2-point IFFTs 514 and 524 can be substituted with one N / 2-point IFFT, even if one memory is substituted or frequency-domain equalizers 513 and 523 are substituted with one frequency-domain equalizer. Alternatively, the N point FFTs 41 and 45 may be replaced with one N point FFT. Also in the second and third embodiments, one arithmetic unit may be substituted by controlling two arithmetic units that perform the same arithmetic processing by providing a control system. At this time, adding a buffer (a delay circuit, a memory) to a necessary portion is also included in the present invention.

  In the above embodiment, the multi-carrier demodulator that always compensates the channel response in the first half and the second half of one symbol is exemplified, but the present invention is not limited to this. A device for separately monitoring the channel response is provided. When the variation in channel response is small, a normal demodulator that compensates the channel response in units of one symbol is used. When the variation in channel response is large, the above configuration is switched. In addition, when the fluctuation of the channel response is very large, one symbol is divided into 4 divisions, 8 divisions,..., And switched to the multicarrier demodulation apparatus that compensates the channel response in each divided time and frequency domain. To do. When one symbol is divided into four, the complex signal on the time axis of N points is processed by dividing it into four times by N / 4 point FFT. The same applies to a case where one symbol is divided into eight parts.

  There is also a multi-carrier demodulator that performs domain division of arbitrary time and frequency other than FFT and WPT using a complex multi-rate filter bank, and compensates the channel response in each divided time and frequency domain as in the present invention. The present invention is applied.

The conceptual diagram for demonstrating the outline of this invention. The conceptual diagram for demonstrating the outline of this invention. The conceptual diagram for demonstrating the outline of this invention. 1 is a block diagram illustrating an outline of a configuration of a multicarrier demodulation apparatus 100 according to a first embodiment. FIG. 6 is a block diagram illustrating a schematic configuration of a multicarrier demodulation apparatus 200 according to a second embodiment. FIG. 6 is a block diagram illustrating an outline of a configuration of a multicarrier demodulator 300 according to a third embodiment. The block diagram which shows the outline of a structure of the conventional multicarrier demodulation apparatus

Explanation of symbols

1: Quadrature double-tone 2: Serial-parallel converter (S / P)
3: GI remover 41, 45: N-point fast Fourier transform (FFT)
42: Pilot symbol extractor 43: Channel characteristic estimator 44, 46: Channel characteristic time / frequency interpolator 511, 521: N / 2-point fast Fourier transformer (FFT)
512, 522: Buffer 513, 523, 553, 563: Frequency domain equalizer 514, 524: N / 2-point inverse fast Fourier transform (IFFT)
551, 561: N / 2 point discrete wavelet transformer (WPT)
554, 564: N / 2 point inverse discrete wavelet transformer (IWPT)
6: Parallel to serial converter (P / S)
71, 72: FFT partial whole converter

Claims (12)

In the multicarrier demodulation method,
The received signal on the time axis is subjected to time / frequency division different from the time / frequency division pattern corresponding to the transmission side, and an estimated value of the propagation path characteristic corresponding to each divided temporary channel is obtained by interpolation, Compensates the propagation path characteristics for each channel, generates a signal on the time axis compensated from the time and frequency axis signals of the provisional channel compensated for the propagation path characteristics, and the compensated signal on the time axis A multicarrier demodulation method, characterized in that each subcarrier is separated by a time / frequency division pattern corresponding to the transmission side. In the multicarrier demodulation method,
The received signal on the time axis is subjected to time / frequency division different from the time / frequency division pattern corresponding to the transmission side, and an estimated value of the propagation path characteristic corresponding to each divided temporary channel is obtained by interpolation, The channel characteristics are compensated for each channel, and the channel characteristics are compensated by converting the time and frequency axis signals of the provisional channel compensated for the channel characteristics into a time / frequency division pattern corresponding to the transmission side. A multicarrier demodulation method characterized by separating each subcarrier. The multicarrier demodulation method according to claim 1 or 2, wherein an estimated value of a propagation path characteristic corresponding to each temporary channel is obtained by interpolation based on a scattered pilot signal. In the multicarrier demodulation method,
N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform are divided into two or more groups,
Each group is divided into provisional channel groups by discrete Fourier transform by discrete Fourier transform with the number of complex signals as points,
A propagation path characteristic is obtained from a pilot signal obtained by separating N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform into subcarriers by N-point discrete Fourier transform,
From the propagation path characteristics of the pilot signal, determine the propagation path characteristics of each temporary channel in the time / frequency plane by interpolation,
Each of the temporary channels is made to correspond to the time / frequency plane, and the propagation path characteristics of each temporary channel are compensated,
From the compensated signals of the provisional channels, N complex signals on the time axis that have been compensated by inverse discrete Fourier transform by inverse discrete Fourier transform of corresponding points are obtained,
Multicarrier demodulation characterized in that the N complex signals on the time axis compensated are separated into subcarriers by N-point discrete Fourier transform to obtain signals of subcarriers whose propagation path characteristics are compensated. Method. N is a power of 2,
Dividing N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform into two or more groups of divisors of N;
The discrete Fourier transform other than the N-point discrete Fourier transform is replaced with a discrete wavelet transform or wavelet packet transform with a corresponding number of points,
5. The multicarrier demodulation method according to claim 4, wherein the inverse discrete Fourier transform is replaced with an inverse discrete wavelet transform or inverse wavelet packet transform with a corresponding number of points. N is a power of 2,
N complex signal on the time axis to be separated into the subcarriers by N-point discrete Fourier transform, to claim 4, characterized in that divided into about two or more groups consisting of number of number of the N The multicarrier demodulation method described. In a multicarrier demodulator,
Temporary demodulation means for performing time / frequency division different from the time / frequency division pattern corresponding to the transmission side of the received signal on the time axis,
Channel propagation path characteristic estimation means for obtaining an estimated value of the propagation path characteristic corresponding to each temporarily demodulated temporary channel by interpolation;
Compensating means for compensating the propagation path characteristics for each temporary channel, and obtaining a signal on the time and frequency axes of the temporary channel compensated for the propagation path characteristics;
Provisional modulation means for generating a compensated time axis signal from the compensated time and frequency axis signal;
A multi-carrier demodulating apparatus comprising: a positive demodulating unit that separates the compensated signal on the time axis into subcarriers according to a time / frequency division pattern corresponding to a transmitting side. In a multicarrier demodulator,
Temporary demodulation means for performing time / frequency division different from the time / frequency division pattern corresponding to the transmission side of the received signal on the time axis,
Channel propagation path characteristic estimation means for obtaining an estimated value of the propagation path characteristic corresponding to each temporarily demodulated temporary channel by interpolation;
Compensating means for compensating the propagation path characteristics for each temporary channel, and obtaining a signal on the time and frequency axes of the temporary channel compensated for the propagation path characteristics;
Provisionally converting means for converting the compensated signal on the time and frequency axes into a time / frequency division pattern corresponding to the transmission side and separating the subcarriers whose propagation path characteristics are compensated. A multi-carrier demodulator characterized by the above. 9. The multicarrier demodulator according to claim 7 , wherein the compensation means obtains an estimated value of the propagation path characteristic corresponding to each temporary channel based on a scattered pilot signal by interpolation. In a multicarrier demodulator,
N-point discrete Fourier transform means for separating N complex signals on the time axis into subcarriers by N-point discrete Fourier transform;
Dividing means for dividing N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform into two or more groups;
Discrete Fourier transform means for performing discrete Fourier transform by discrete Fourier transform with the number of divided complex signals of each group as points, and converting the signals into signals of each temporary channel;
Pilot signal propagation path characteristic determining means for obtaining a propagation path characteristic of a pilot signal obtained by separating into subcarriers by the N-point discrete Fourier transform means;
Channel propagation path characteristic estimating means for determining the propagation path characteristics of each temporary channel in the time / frequency plane by interpolation from the propagation path characteristics of the pilot signal;
Compensation means for compensating the propagation path characteristics for each of the provisional channels, and obtaining a signal on the time and frequency axes of each provisional channel compensated for the propagation path characteristics;
Inverse discrete Fourier transform means for obtaining N complex signals on the time axis compensated by inverse discrete Fourier transform by inverse discrete Fourier transform of corresponding points from the compensated signals of the provisional channels,
An N-point discrete Fourier transform that separates the compensated N complex signals on the time axis into subcarriers by N-point discrete Fourier transform. N is a power of 2,
The dividing means divides N complex signals on the time axis to be separated into subcarriers by N-point discrete Fourier transform into two or more groups consisting of several divisors of N,
The discrete Fourier transform means other than the N-point discrete Fourier transform means is replaced with a discrete wavelet transform means or wavelet packet transform means with a corresponding number of points,
11. The multicarrier demodulator according to claim 10 , wherein the inverse discrete Fourier transform unit is replaced with an inverse discrete wavelet transform unit or an inverse wavelet packet transform unit with a corresponding number of points. N is a power of 2,
11. The multicarrier demodulating apparatus according to claim 10 , wherein the dividing means divides into two or more groups each consisting of a divisor of N.

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