JP6006629B2 - Multi-carrier modulation signal receiver - Google Patents

Description

  The present invention relates to a multi-carrier modulation signal receiving apparatus, and more particularly to a receiving apparatus that can correctly receive transmission data even in a multipath environment that causes problems when receiving radio waves in digital broadcasting, wireless LAN, and the like.

  There is OFDM (Orthogonal Frequency Division Multiplexing) as a multicarrier modulation system used for digital broadcasting, wireless LAN, and the like. In OFDM, a period called a guard interval (GI) or a cyclic prefix (CP) is provided in order to obtain resistance against multipath.

  On the other hand, Non-Patent Document 1 points out that OFDM is a kind of transmultiplexer. FIG. 13 is a block diagram showing a configuration of a general transmultiplexer. The transmultiplexer 100 includes a synthesis bank including M interpolators and M transmission filters, and an analysis bank including M reception filters and M decimators. The synthesis bank and the analysis bank are connected via a channel (transmission path).

  FIG. 14 is a block diagram showing a configuration when OFDM is expressed as a transmultiplexer. As can be seen from FIG. 14, OFDM is a DFT modulation transmultiplexer of a prototype filter whose filter coefficients are all 1 and whose filter length matches the number of subchannels. This is clear from the fact that the OFDM pulse forming filter uses a rectangular window function.

  However, the prototype filter in this OFDM has a first sidelobe level of about −13 dB and poor frequency characteristics. In order to cope with this, channel equalization is required using GI. Non-Patent Document 1 points out that the influence of the channel can be reduced by performing more ideal orthogonal frequency division multiplexing.

  Also, the DFT modulation filter bank (system in which the analysis bank and the synthesis bank of the DFT modulation transmultiplexer are dualized) uses an FFT (Fast Fourier Transform) pair for analysis and synthesis. Therefore, it is known to be useful in practical use.

  Non-Patent Document 2 describes that in a DFT modulation filter bank, correction is performed in two stages of decimation to satisfy a pseudo complete reconstruction condition. That is, it is described that the output signal is approximately equal to a constant multiple of the time delay of the input signal.

  FIG. 15 is a block diagram showing a configuration of the modified DFT modulation synthesis bank, and FIG. 16 is a block diagram showing a configuration of the modified DFT modulation analysis bank. In FIG. 15, the modified DFT modulation synthesis bank 101 receives M subchannel signals, extracts the real part component and the imaginary part component of the subchannel signal, performs the first-stage interpolation, and performs delay. The real part component and the imaginary part component are combined. Then, the second-stage interpolation is performed on the synthesized signal to perform filtering, and all the subchannel signals are synthesized to output an equivalent baseband signal. In FIG. 16, the modified DFT modulation analysis bank 102 receives an equivalent baseband signal, branches it into M equivalent baseband signals, respectively performs a filtering process to perform the first stage decimation, A second-stage decimation is performed on the delayed imaginary part component, and the real part component and the imaginary part component are combined to output M subchannel signals, respectively.

  When the modified DFT modulation synthesis bank 101 shown in FIG. 15 and the modified DFT modulation analysis bank 102 shown in FIG. 16 are viewed from the viewpoint of the multi-carrier modulation system, the modified DFT modulation synthesis bank 101 becomes a modulator, and the modified DFT modulation analysis bank 101 102 becomes a demodulator. That is, by using the modified DFT modulation synthesis bank 101 and the modified DFT modulation analysis bank 102 at the transmitting and receiving ends, signal transmission by the multicarrier modulation method can be realized. In this case, since a prototype filter having a filter length longer than the number of subchannels can be used, better frequency characteristics can be realized. However, if there is distortion due to multipath in the channel between transmission and reception, a channel equalizer is required.

  As a channel equalizer applicable to the DFT modulation transmultiplexer, for example, there is one described in Patent Document 1. Since this channel equalizer obtains the equalization coefficient by optimizing the pilot signal as a reference signal, there is a problem that the channel characteristic cannot be obtained directly.

JP 2010-98471 A

Ali N. Akansu, Pierre Dubamel, Xueming Lin, and Marc de Courville. “Orthogonal transmultiplexers in communications: A review.”, IEEE Trans. Signal Process., 46 (4): 979-995, April 1998. Tanja Karp and N. J. Fliege. “Modified DFT filter banks with perfect reconstruction.”, IEEE Trans. Circuits Syst. II, 46 (11): 1404-1414, November 1999.

  As described above, the conventional multi-carrier modulation signal receiving apparatus has a problem that the propagation path characteristic cannot be directly estimated although it is possible to obtain resistance against multipath without transmitting redundant information. Along with this problem, there has been a problem that the bit reliability cannot be obtained using the propagation path characteristics when performing error correction decoding. Therefore, the conventional multicarrier modulation signal receiving apparatus has a problem that the correction function of error correction decoding cannot be used effectively, particularly when the bit error is colored.

  Accordingly, the present invention has been made to solve the above-described problems, and its object is to obtain a bit error by obtaining a channel reliability using an equalization coefficient when a modified DFT modulation analysis bank is used. An object of the present invention is to provide a multicarrier modulation signal receiving apparatus having tolerance.

  In order to achieve the above object, a multicarrier modulation signal receiving apparatus according to claim 1 of the present invention is characterized in that an error correction coded signal is multicarrier modulated by a modified DFT modulation synthesis bank, and the multicarrier modulated signal is received. A multi-carrier modulation signal receiving apparatus for receiving, wherein a time-domain equivalent baseband signal obtained by orthogonally demodulating the received signal is converted into a frequency-domain equivalent baseband signal at a rate twice the maximum decimation rate, Equalized by the modified DFT modulation analysis bank for outputting the subchannel signal, the linear equalizer for the number of subcarriers for equalizing the subchannel signal output by the modified DFT modulation analysis bank, and the linear equalizer A log likelihood ratio calculation unit that calculates a log likelihood ratio from the subchannel signal after equalization, and the log likelihood ratio calculation unit Calculated by an error correction decoding unit that performs error correction decoding processing using a number likelihood ratio, an equalization coefficient calculation unit that calculates an equalization coefficient used in the linear equalizer, and an equalization coefficient calculation unit A transmission line reliability calculation unit that calculates transmission line reliability based on the equalization coefficient, and the transmission line reliability calculation unit calculates an amplitude sum of the equalization coefficients calculated by the equalization coefficient calculation unit. An amplitude calculation unit to be calculated, a normalization unit that normalizes the amplitude sum of the equalization coefficients calculated by the amplitude calculation unit so that an average is 1 for all subcarriers, and is normalized by the normalization unit Subtracting the sum of the amplitudes of the equalization coefficients from a predetermined value to obtain the transmission line reliability, and the subchannel signal after equalization equalized by the linear equalizer , Subchannel signal error after equalization, and transmission path signal Using transmission line reliability calculated by the degree calculation unit calculates a log likelihood ratio using at the error correction decoding unit, characterized in that.

  The multicarrier modulation signal receiving apparatus according to claim 2 is the multicarrier modulation signal receiving apparatus according to claim 1, wherein the log-likelihood ratio calculation unit equalizes from a known pilot symbol by the linear equalizer. The subtracter that subtracts the equalized subchannel signal and outputs the error of the equalized subchannel signal, and the error power that calculates the error power of the equalized subchannel signal output from the subtractor Equalization by a calculation unit, a first multiplier that multiplies the error power calculated by the error power calculation unit by the transmission channel reliability calculated by the transmission channel reliability calculation unit, and the linear equalizer A likelihood ratio calculation unit for calculating the log likelihood ratio based on the equalized subchannel signal and the error power of the equalized subchannel signal multiplied by the first multiplier; Having And features.

  The multicarrier modulation signal reception apparatus according to claim 3 is the multicarrier modulation signal reception apparatus according to claim 2, further comprising a second multiplier, wherein the log likelihood ratio calculation unit is configured to include the first log likelihood ratio calculation unit. Instead of the multiplier and likelihood ratio calculator, the logarithmic likelihood is calculated based on the equalized subchannel signal equalized by the linear equalizer and the error power calculated by the error power calculator. A likelihood ratio calculation unit for calculating a frequency ratio, and the second multiplier calculates the log likelihood ratio calculated by the log likelihood ratio calculation unit by the transmission channel reliability calculation unit. The transmission line reliability is multiplied, and the error correction decoding unit performs error correction decoding processing using the log likelihood ratio multiplied by the second multiplier.

  A multicarrier modulation signal receiving apparatus according to claim 4 is the multicarrier modulation signal receiving apparatus according to any one of claims 1 to 3, wherein the modified DFT modulation analysis bank is configured such that the received signal is orthogonal. The demodulated time domain equivalent baseband signal is subjected to decimating and filtering to generate a first signal, and the delayed equivalent baseband signal is subjected to decimating and filtering to obtain a second signal. Generating a signal, extracting a real part component and an imaginary part component from the second signal as first and second components, and extracting a third part by extracting the imaginary part component and the real part component from the first signal. And a fourth component, generating a real subchannel signal composed of the first to fourth components, and the fourth and third components of the real subchannel signal, The real part component and the imaginary part component are extracted as first and second components, and the real part component and the imaginary part component that are paired with the second and first components of the real part subchannel signal are extracted. Generating an imaginary part subchannel signal composed of the first to fourth components as the third and fourth components, and the amplitude calculation unit of the transmission line reliability calculation unit is configured by the equalization coefficient calculation unit. Of the calculated equalization coefficients, the sum of the amplitudes of the equalization coefficients corresponding to the first and fourth signals of the real and imaginary subchannel signals generated by the modified DFT modulation analysis bank is calculated. It is characterized by that.

  The multi-carrier modulation signal receiving apparatus according to claim 5 is the multi-carrier modulation signal receiving apparatus according to any one of claims 1 to 3, wherein the transmission line reliability calculation unit calculates the equalization coefficient. An amplitude calculation unit that calculates an amplitude sum of equalization coefficients calculated by the unit, and an amplitude calculation unit that normalizes the amplitude sum of the equalization coefficients calculated by the amplitude calculation unit so that an average is 1 for all subcarriers. 1 normalization unit, a third multiplier that multiplies a predetermined value by the amplitude sum of the equalization coefficient normalized by the first normalization unit, and the equalization coefficient calculation unit A variance calculating unit that calculates a variance of the equalized coefficients, and a second normalizing unit that normalizes the variance of the equalized coefficients calculated by the variance calculating unit so that an average is 1 for all subcarriers And normalization by the second normalization unit A fourth multiplier that multiplies the variance of the equalized coefficient by a predetermined value; and an amplitude sum of the equalized coefficient multiplied by the third multiplier is multiplied by the fourth multiplier. An adder for adding the variance of the equalization coefficient; and a subtractor for subtracting the addition result by the adder from a predetermined value to obtain the transmission line reliability.

  The multi-carrier modulation signal receiving apparatus according to claim 6 is the multi-carrier modulation signal receiving apparatus according to claim 5, wherein the modified DFT modulation analysis bank is an equivalent base in a time domain in which the received signal is orthogonally demodulated. The band signal is decimated and filtered to generate a first signal, the delayed equivalent baseband signal is decimated and filtered to generate a second signal, and the second signal is The real part component and the imaginary part component are extracted from the first signal as first and second components, the imaginary part component and the real part component are extracted from the first signal as third and fourth components, A real part subchannel signal composed of first to fourth components is generated, and a real part component and an imaginary part paired with the fourth and third components of the real part subchannel signal are generated. A component is extracted as first and second components, and a real component and an imaginary component that are paired with the second and first components of the real subchannel signal are extracted, and third and fourth components are extracted. And an imaginary part subchannel signal composed of the first to fourth components is generated, and the amplitude calculation unit of the transmission line reliability calculation unit includes the equalization coefficient calculated by the equalization coefficient calculation unit. Calculating the sum of amplitudes of equalization coefficients corresponding to the first and fourth signals of the real subchannel signal and the imaginary subchannel signal generated by the modified DFT modulation analysis bank, and the transmission line reliability calculation unit Of the real part subchannel signal and the imaginary part subchannel signal generated by the modified DFT modulation analysis bank among the equalization coefficients calculated by the equalization coefficient calculation unit. Corresponding to the signal Calculating the variance of the coefficients, characterized in that.

  As described above, according to the present invention, the channel reliability is obtained using the equalization coefficient used by the linear equalizer, and the error correction decoding is performed with the log likelihood ratio based on the channel reliability. I made it. As a result, the log likelihood ratio is calculated using the propagation path characteristics, so that the correction function by error correction decoding can be effectively used without estimating the propagation path characteristics, and the multi-carrier having bit error tolerance. A modulation signal receiving apparatus can be provided.

It is a block diagram which shows the structure of the 1st (Example 1) multicarrier modulation signal receiving apparatus by embodiment of this invention. It is a block diagram which shows the structure of the 2nd (Example 2) multicarrier modulation signal receiving apparatus by embodiment of this invention. FIG. 3 is a block diagram illustrating a configuration of a log likelihood ratio calculation unit according to the first embodiment. FIG. 10 is a block diagram illustrating a configuration of a log likelihood ratio calculation unit according to the second embodiment. It is a block diagram which shows the 1st structure of a transmission-line reliability calculation part. It is a block diagram which shows the 2nd structure of a transmission-line reliability calculation part. It is a block diagram which shows the 3rd structure of a transmission-line reliability calculation part. It is a block diagram which shows the structure of an analysis bank. It is a block diagram which shows the structure of a polyphase analysis bank. It is a block diagram which shows the structure of a subchannel process part. It is a block diagram which shows the structure of a linear equalizer. It is a block diagram which shows the structure of an equalizer. It is a block diagram which shows the structure of a general transmultiplexer. It is a block diagram which shows a structure when OFDM is expressed as a transmultiplexer. It is a block diagram which shows the structure of a correction DFT modulation synthesis bank. It is a block diagram which shows the structure of a correction DFT modulation analysis bank. It is a figure which shows the example of the BER characteristic calculated | required by computer simulation.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the multi-carrier modulation signal receiving apparatus using the modified DFT modulation analysis bank, the linear equalizer equalizes the received signal by multiplying the received signal by an equalization coefficient. In the equalization process of the linear equalizer, the amplitude is increased when the amplitude of the received signal is small, and the amplitude is decreased when the amplitude of the received signal is large, by multiplication of the equalization coefficient. On the other hand, in the received signal of the multicarrier modulation signal receiving apparatus, the reliability of data transmitted by a carrier having a large amplitude is high, and the reliability of data transmitted by a carrier having a small amplitude is usually low. . Therefore, when the amplitude of the equalization coefficient used in the linear equalizer is large, the received signal with a small amplitude is processed. Therefore, when the reliability of the received signal data is low and the amplitude of the equalization coefficient is small, Therefore, it can be said that the reliability of the data of the received signal is high. The present invention pays attention to the relationship between the equalization coefficient and the reliability of the data. When obtaining the transmission line reliability, if the amplitude of the equalization coefficient is large, the transmission line reliability is low. As described above, when the amplitude of the equalization coefficient is small, the logarithmic likelihood ratio reflecting the transmission line reliability is calculated based on the equalization coefficient so as to increase the transmission line reliability. And

  The multicarrier modulation signal receiving apparatus according to the first embodiment calculates the channel reliability from the equalization coefficient, calculates the log likelihood ratio by multiplying the amplitude of the error of the pilot symbol that is synchronously added by the channel reliability, Error correction decoding is performed using this log likelihood ratio. The multicarrier modulation signal receiving apparatus according to the second embodiment calculates a channel reliability from the equalization coefficient, multiplies the log likelihood ratio calculated from the equalized carrier symbol by the channel reliability, and calculates the logarithm of the multiplication result. Error correction decoding is performed using the likelihood ratio.

[Example 1]
First, the multicarrier modulation signal receiving apparatus according to the first embodiment will be described. FIG. 1 is a block diagram illustrating the configuration of the multicarrier modulation signal receiving apparatus according to the first embodiment. This multi-carrier modulation signal receiving apparatus 1-1 includes a frequency converter 2, an A / D (analog / digital) converter 3, an orthogonal demodulator 4, an analysis bank (modified DFT modulation analysis bank) 5, and a linear equalizer 6. , An equalization coefficient calculation unit 7, a log likelihood ratio calculation unit 8, and an error correction decoding unit 9.

  The frequency converter 2 converts the frequency of the received signal into an IF signal. The IF signal output from the frequency converter 2 is input to the A / D converter 3. The A / D converter 3 A / D converts the IF signal (analog IF signal) input from the frequency converter 2 into a digital IF signal. The digital IF signal output from the A / D converter 3 is input to the quadrature demodulator 4. The orthogonal demodulator 4 orthogonally demodulates the digital IF signal input from the A / D converter 3 into an equivalent baseband signal. The equivalent baseband signal output from the quadrature demodulator 4 is input to the analysis bank 5.

  The analysis bank 5 converts the time-domain equivalent baseband signal input from the quadrature demodulator 4 into a frequency-domain signal at a rate substantially twice the maximum decimation rate, and outputs an output signal in a normal analysis bank. In addition to the real part component and the imaginary part component, an imaginary part component and a real part component that are paired with a normal output signal are also output together. That is, the analysis bank 5 is composed of two real part components and two imaginary part components, and a real part subchannel signal vector consisting of a total of four real number signals, and two real part components and An imaginary part subchannel signal vector composed of two systems of imaginary part components and consisting of a total of four systems of real signals is output. The real part subchannel signal vector and the imaginary part subchannel signal vector (hereinafter collectively referred to as subchannel signal vectors) output from the analysis bank 5 are each divided into two parts, one being the linear equalizer 6 and the other being the same. It is input to the optimization coefficient calculation unit 7.

  The linear equalizer 6 equalizes the subchannel signal vector input from the analysis bank 5 using the equalization coefficient input from the equalization coefficient calculation unit 7, and performs the subchannel signal after equalization (after equalization) Output carrier symbol). The equalized subchannel signal output from the linear equalizer 6 is divided into two, one being input to the log likelihood ratio calculation unit 8 and the other being input to the equalization coefficient calculation unit 7.

  The equalization coefficient calculator 7 calculates and outputs an equalization coefficient using the subchannel signal vector input from the analysis bank 5 and the equalized subchannel signal input from the linear equalizer 6. The equalization coefficient output from the equalization coefficient calculation unit 7 is divided into two, one being input to the linear equalizer 6 and the other being input to the equalization coefficient calculation unit 7.

  The log likelihood ratio calculation unit 8 uses the equalized carrier symbol input from the linear equalizer 6 and the equalization coefficient input from the equalization coefficient calculation unit 7 to calculate the log likelihood ratio for each bit. Calculate and output. The log likelihood ratio for each bit output by the log likelihood ratio calculation unit 8 is input to the error correction decoding unit 9. The error correction decoding unit 9 performs an error correction decoding process using the log likelihood ratio for each bit input from the log likelihood ratio calculation unit 8, and outputs a bit string to the outside.

[Example 2]
Next, the multicarrier modulation signal receiving apparatus according to the second embodiment will be described. FIG. 2 is a block diagram illustrating a configuration of the multicarrier modulation signal receiving apparatus according to the second embodiment. The multicarrier modulation signal receiving apparatus 1-2 includes a frequency conversion unit 2, an A / D conversion unit 3, an orthogonal demodulation unit 4, an analysis bank 5, a linear equalizer 6, an equalization coefficient calculation unit 7, a transmission path reliability. A calculation unit 10, a log likelihood ratio calculation unit 11, a multiplier 12, and an error correction decoding unit 9 are provided. Comparing the multicarrier modulation signal receiving apparatus 1-1 of the first embodiment shown in FIG. 1 with this multicarrier modulation signal receiving apparatus 1-2, the multicarrier modulation signal receiving apparatus 1-2 is similar to the multicarrier modulation signal receiving apparatus 1-2 of the first embodiment. A difference is that a transmission line reliability calculation unit 10, a log likelihood ratio calculation unit 11, and a multiplier 12 are provided instead of the log likelihood ratio calculation unit 8 included in the carrier modulation signal receiving apparatus 1-1. The frequency conversion unit 2, the A / D conversion unit 3, the orthogonal demodulation unit 4, the analysis bank 5, the linear equalizer 6, the equalization coefficient calculation unit 7, and the error correction decoding unit 9 have been described in the first embodiment. Therefore, the description is omitted here.

  The equalized subchannel signal output from the linear equalizer 6 is divided into two, one being input to the log likelihood ratio calculation unit 11 and the other being input to the equalization coefficient calculation unit 7. The equalization coefficient output from the equalization coefficient calculation unit 7 is divided into two, one being input to the linear equalizer 6 and the other being input to the transmission line reliability calculation unit 10.

  The log likelihood ratio calculation unit 11 calculates and outputs a log likelihood ratio for each bit by using the equalized carrier symbol input from the linear equalizer 6. The log likelihood ratio for each bit output from the log likelihood ratio calculation unit 11 is input to the multiplier 12.

  The transmission line reliability calculation unit 10 calculates and outputs the transmission line reliability for each subcarrier using the equalization coefficient input from the equalization coefficient calculation unit 7. The transmission path reliability for each subcarrier output from the transmission path reliability calculation unit 10 is input to the multiplier 12.

  The multiplier 12 transmits the bit-wise log likelihood ratio input from the log-likelihood ratio calculation unit 11 and transmits the sub-carrier on which the bit is transmitted, which is input from the transmission line reliability calculation unit 10. Multiply the path reliability and output the log-likelihood ratio for each bit after multiplication. The log likelihood ratio for each bit after multiplication output from the multiplier 12 is input to the error correction decoding unit 9. The error correction decoding unit 9 performs error correction decoding processing using the log-likelihood ratio for each bit after multiplication input from the multiplier 12, and outputs the bit string to the outside.

[Analysis bank (polyphase composition)]
Next, the polyphase configuration of the analysis bank 5 shown in FIGS. 1 and 2 will be described. FIG. 8 is a block diagram showing the configuration of the analysis bank 5. The analysis bank 5 includes a delay unit 21, polyphase analysis banks 22-1 and 22-2, and subchannel processing units 23-0 to 23- (M-1). The analysis bank 5 receives an equivalent baseband signal from the quadrature demodulator 4 and receives subchannel signal vectors 0 to M-1 (real part subchannel signal vectors 0 to M-1 and imaginary part subchannel signal vectors 0 to M-). 1) is generated and output as subchannel signal vectors 0 to M-1.

  The equivalent baseband signal input from the quadrature demodulator 4 shown in FIGS. 1 and 2 is divided into two, one input to the delay unit 21 and the other input to the polyphase analysis bank 22-1. The delay unit 21 delays the equivalent baseband signal input from the quadrature demodulation unit 4 by M / 2 samples and outputs the delayed signal. The equivalent baseband signal output from the delay unit 21 is input to the polyphase analysis bank 22-2.

  The polyphase analysis bank 22-1 performs polyphase analysis on the equivalent baseband signal input from the quadrature demodulation unit 4 and generates first subchannel signals 0 to M-1. The first subchannel signals 0 to M-1 output from the polyphase analysis bank 22-1 are input to the corresponding subchannel processing units 23-0 to 23- (M-1).

  The polyphase analysis bank 22-2 performs polyphase analysis on the equivalent baseband signal input from the delay device 21, and generates second subchannel signals 0 to M-1. Second subchannel signals 0 to M−1 output from polyphase analysis bank 22-2 are input to corresponding subchannel processing units 23-0 to 23- (M−1).

  The subchannel processing units 23-0 to 23- (M-1) perform processing for each subchannel on the subchannel signals 0 to M-1 input from the polyphase analysis banks 22-1 and 22-2. Subchannel signal vectors 0 to M-1 (real part subchannel signal vectors 0 to M-1 and imaginary part subchannel signal vectors 0 to M-1), that is, real part subchannel signal vectors k and imaginary part subchannels. A signal vector k (subchannel signal vector k) is generated and output.

[Polyphase analysis bank]
Next, polyphase analysis banks 22-1 and 22-2 (hereinafter collectively referred to as polyphase analysis banks 22) shown in FIG. 8 will be described. FIG. 9 is a block diagram showing the configuration of the polyphase analysis bank 22. The polyphase analysis bank 22 includes delay units 24-1 to 24- (M-1), decimators 25-0 to 25- (M-1), polyphase filters 26-0 to 26- (M-1), An FFT unit 27 and multipliers 28-0 to 28- (M-1) are provided. The polyphase analysis bank 22 receives the equivalent baseband signal, generates and outputs subchannel signals 0 to M-1.

  The equivalent baseband signal input to the polyphase analysis bank 22 is divided into two, one input to the delay unit 24-1 and the other input to the decimator 25-0. The delay device 24-1 delays the input equivalent baseband signal by one sample. The equivalent baseband signal output from the delay unit 24-1 is divided into two, one input to the delay unit 24-2, and the other input to the decimator 25-1.

  Similarly, the delay unit 24-k (2 ≦ k <M−1) delays the equivalent baseband signal input from the preceding stage delay unit 24- (k−1) by one sample. The equivalent baseband signal output from the delay unit 24-k is divided into two, one input to the subsequent delay unit 24- (k + 1) and the other input to the decimator 25-k.

  The delay unit 24- (M-1) delays the equivalent baseband signal input from the preceding stage delay unit 24- (M-2) by one sample. The equivalent baseband signal output from the delay unit 24- (M-1) is input to the decimator 25- (M-1).

  A decimator 25-k (0 ≦ k ≦ M−1) receives an equivalent baseband signal and performs a decimation process with a ratio M on the equivalent baseband signal. The decimated equivalent baseband signal output from the decimator 25-k is input to the polyphase filter 26-k.

  The polyphase filter 26-k (0 ≦ k ≦ M−1) performs polyphase filter processing on the equivalent baseband signal after decimation input from the decimator 25-k. The equivalent baseband signal after the polyphase filter processing output from the polyphase filter 26-k is input to the FFT unit 27.

ここで、Ｎはプロトタイプフィルタのフィルタ長を、Ｍはサブチャネル数を示す自然数を、ｋは任意のサブチャネルをそれぞれ示す。 The polyphase filter E _k (z) is a polyphase component of Type 1 of the prototype filter p (n), and is represented by the following expression.

Here, N is the filter length of the prototype filter, M is a natural number indicating the number of subchannels, and k is an arbitrary subchannel.

  The FFT unit 27 performs FFT processing on each equivalent baseband signal after the polyphase filter processing input from the polyphase filter 26-k. The M subchannel signals output from the FFT unit 27 are respectively input to the multiplier 28-k.

The multiplier 28-k (0 ≦ k ≦ M−1) multiplies the subchannel signal input from the FFT unit 27 by j ^M−k . However, j is an imaginary unit. The subchannel signal k output from the multiplier 28-k is input to the subchannel processing unit 23-k illustrated in FIG.

  As described above, the polyphase analysis bank 22 receives the equivalent baseband signal, generates the subchannel signals 0 to M-1, and outputs the subchannel signals 0 to M-1 to the subchannel processing units 23-0 to 23- (M-1). Hereinafter, the subchannel signal output from the polyphase analysis bank 22-1 is k1, and the subchannel signal output from the polyphase analysis bank 22-2 is k2.

[Subchannel processing section of analysis bank (polyphase configuration)]
Next, the subchannel processing units 23-0 to 23- (M-1) illustrated in FIG. 8 will be described. FIG. 10 is a block diagram illustrating a configuration of the subchannel processing unit 23-k (0 ≦ k ≦ M−1). The subchannel processing unit 23-k includes real part extraction units 29-1 and 29-2, imaginary part extraction units 30-1 and 30-2, delay units 31-1 and 31-2, and a multiplier 32-1. 32-2 is provided. The subchannel processing unit 23-k receives the subchannel signal k1 from the polyphase analysis bank 22-1 and also receives the subchannel signal k2 from the polyphase analysis bank 22-2. A signal vector k (a real part subchannel signal vector k consisting of four elements and an imaginary part subchannel signal vector k consisting of four elements) is generated and output.

  The subchannel signal k2 input from the polyphase analysis bank 22-2 illustrated in FIG. 8 is divided into two, one input to the real part extraction unit 29-1 and the other input to the imaginary part extraction unit 30-1. The subchannel signal k1 input from the polyphase analysis bank 22-1 shown in FIG. 8 is divided into two, one input to the real part extraction unit 29-2 and the other input to the imaginary part extraction unit 30-2.

  The real part extraction unit 29-1 extracts a real part from the subchannel signal k2 input from the polyphase analysis bank 22-2, and generates a real number subchannel signal. The real subchannel signal output from the real part extraction unit 29-1 is divided into two, one is output from the subchannel processing unit 23-k as one element of the real part subchannel signal vector k, and the other is the delay unit 31-2. Is input.

  The imaginary part extraction unit 30-1 extracts an imaginary part from the subchannel signal k2 input from the polyphase analysis bank 22-2, and generates a real subchannel signal. The real number subchannel signal output from the imaginary part extraction unit 30-1 is divided into two, one is output from the subchannel processing unit 23-k as one element of the real part subchannel signal vector k, and the other is the delay unit 31-1. Is input.

  The imaginary part extraction unit 30-2 extracts an imaginary part from the subchannel signal k1 input from the polyphase analysis bank 22-1, and generates a real subchannel signal. The real subchannel signal output from the imaginary part extraction unit 30-2 is divided into two parts, one being one element of the real part subchannel signal vector k and the other being one element of the imaginary part subchannel signal vector k. 23-k.

  The real part extraction unit 29-2 extracts a real part from the subchannel signal k1 input from the polyphase analysis bank 22-1, and generates a real subchannel signal. The real subchannel signal output from the real part extraction unit 29-2 is divided into two, one is output from the subchannel processing unit 23-k as one element of the real part subchannel signal vector k, and the other is the multiplier 32-1. Is input.

  The multiplier 32-1 multiplies the real subchannel signal input from the real part extraction unit 29-2 by -1, and inverts the sign. The real subchannel signal with the inverted sign output from the multiplier 32-1 is output from the subchannel processing unit 23-k as one element of the imaginary part subchannel signal vector k.

  The delay device 31-1 delays the real subchannel signal input from the imaginary part extraction unit 30-1 by one sample. The real subchannel signal output from the delay unit 31-1 is output from the subchannel processing unit 23-k as one element of the imaginary part subchannel signal vector k.

  The delay unit 31-2 delays the real subchannel signal input from the real part extraction unit 29-1 by one sample. The real subchannel signal output from the delay unit 31-2 is input to the multiplier 32-2. The multiplier 32-2 multiplies the real subchannel signal input from the delay unit 31-2 by -1, and inverts the sign. The real subchannel signal with the inverted sign output from the multiplier 32-2 is output from the subchannel processing unit 23-k as one element of the imaginary subchannel signal vector k.

  As described above, the real subchannel signal output from the real part extraction unit 29-1, the real subchannel signal output from the imaginary part extraction unit 30-1, the real subchannel signal output from the imaginary part extraction unit 30-2, and the real number. The real subchannel signal output from the partial extraction unit 29-2 is output from the subchannel processing unit 23-k as a real subchannel signal vector k having each as an element. The real subchannel signal output from the imaginary part extraction unit 30-2, the real subchannel signal output from the multiplier 32-1, the real subchannel signal output from the delay unit 31-1, and the output of the multiplier 32-2. The real number subchannel signal to be output is output from the subchannel processing unit 23-k as an imaginary part subchannel signal vector k having each as an element.

とし、虚部抽出部３０−１により抽出される実数サブチャネル信号を

とし、虚部抽出部３０−２により抽出される実数サブチャネル信号を

とし、実部抽出部２９−２により抽出される実数サブチャネル信号を

とすると、実部サブチャネル信号ベクトルｋは、以下のようになる。

ここで、上付きのＴは転置を、下付きのｋはサブチャネルを、上付きのＲおよびＩはそれぞれ実部および虚部を、ｚ^Ｍは最大間引きレートであること、すなわちサンプル間隔がシンボル長の１／Ｍであることを示す。 The real subchannel signal extracted by the real part extraction unit 29-1 is

And the real subchannel signal extracted by the imaginary part extraction unit 30-1 is

And the real subchannel signal extracted by the imaginary part extraction unit 30-2 is

And the real subchannel signal extracted by the real part extraction unit 29-2 is

Then, the real part subchannel signal vector k is as follows.

Where the superscript T is the transpose, the subscript k is the subchannel, the superscripts R and I are the real and imaginary parts, respectively, and z ^M is the maximum decimation rate, ie the sample interval is a symbol Indicates 1 / M of the length.

On the other hand, the imaginary part subchannel signal vector k is as follows.

  8, 9, and 10, the delay units 21, 24-1 to 24-(M−1) provided in front of the decimators 25-0 to 25-(M−1) have the maximum thinning rate (samples). It operates at M times the rate at which the interval is 1 / M of the symbol length. Further, polyphase filters 26-0 to 26- (M-1), an FFT unit 27, and multipliers 28-0 to 28- (M-) provided at the subsequent stage of the decimators 25-0 to 25- (M-1). 1) Real part extraction units 29-1, 29-2, imaginary part extraction units 30-1, 30-2, delay units 31-1, 31-2 and multipliers 32-1, 32-2 Work at rate. However, the subchannel processing unit 23-k receives the subchannel signals k1 and k2 of the maximum thinning rate from the polyphase analysis banks 22-1 and 22-2, respectively, and branches into two signals without being thinned out. Then, processing is performed on the two branched subchannel signals at the same sampling rate (maximum thinning rate). Since the real part subchannel signal vector k and the imaginary part subchannel signal vector k are output, the subchannel processing unit 23-k as a whole operates at a rate substantially twice the maximum thinning rate.

  As described above, according to the analysis bank 5, the real part subchannel signal vector k is generated, and the imaginary part subchannel signal vector k is generated based on the real part subchannel signal vector k. Further, as shown in Equation (3), the conversion from the real part subchannel signal vector k to the imaginary part subchannel signal vector k is performed by a conversion matrix that is a constant. As a result, the linear equalizer 6 at the subsequent stage uses a common equalization coefficient for both vectors without using different equalization coefficients for the real subchannel signal vector k and the imaginary subchannel signal vector k. Therefore, it is preferable that linear equalization can be performed.

[Linear equalizer]
Next, the linear equalizer 6 shown in FIGS. 1 and 2 will be described. FIG. 11 is a block diagram showing the configuration of the linear equalizer. The linear equalizer 6 ′ includes equalizers 41-1, 41-2, a multiplier 42, and an adder 43. The linear equalizer 6 'receives the real part subchannel signal vector k and the imaginary part subchannel signal vector k from the analysis bank 5 shown in FIGS. 1 and 2, and the real part subchannel signal vector for each subchannel. k and the imaginary part subchannel signal vector k are equalized by the equalizers 41-1 and 41-2 using the equalization coefficient, respectively, and a complex carrier symbol composed of the real part and the imaginary part after the equalization is output. That is, the linear equalizer 6 shown in FIG. 1 and FIG. 2 includes the linear equalizer 6 ′ shown in FIG.

  The real part subchannel signal vector k output from the analysis bank 5 shown in FIGS. 1 and 2 is input to the equalizer 41-1, and the imaginary part subchannel signal vector k is input to the equalizer 41-2. . Although not shown, the equalization coefficient output from the equalization coefficient calculator 7 shown in FIGS. 1 and 2 is input to the equalizers 41-1 and 41-2. The equalizer 41-1 equalizes the real part subchannel signal vector k input from the analysis bank 5 with the equalization coefficient input from the equalization coefficient calculation unit 7, and the equalizer 41-2 analyzes The imaginary part subchannel signal vector k input from the bank 5 is equalized with the equalization coefficient input from the equalization coefficient calculation unit 7. The equalized real part subchannel signal k (the real part carrier symbol after equalization) output from the equalizer 41-1 is input to the adder 43 and is output from the equalizer 41-2. Imaginary part subchannel signal k (equalized imaginary part carrier symbol) is input to the multiplier 42.

  The multiplier 42 multiplies the imaginary part carrier symbol input from the equalizer 41-2 by 1j. The imaginary part carrier symbol multiplied by 1j output from the multiplier 42 is input to the adder 43.

  The adder 43 adds the real part carrier symbol input from the equalizer 41-1 and the imaginary part carrier symbol input from the multiplier 42 to generate a complex carrier symbol. The complex carrier symbols output from the adder 43 are supplied to the log likelihood ratio calculation unit 8 and the equalization coefficient calculation unit 7 in the case of the first embodiment shown in FIG. 1, and in the case of the second embodiment shown in FIG. Input to likelihood ratio calculation unit 11 and equalization coefficient calculation unit 7, respectively.

[Equalizer]
Next, the equalizers 41-1 and 41-2 (hereinafter collectively referred to as the equalizer 41) shown in FIG. 11 will be described. FIG. 12 is a block diagram showing the configuration of the equalizer 41. The equalizer 41 includes adaptive filters 44-1 to 44-4 and an adder 45. The equalizer 41 equalizes the real part subchannel signal vector k or the imaginary part subchannel signal vector k input from the analysis bank 5 with the equalization coefficient input from the equalization coefficient calculation unit 7 for each subchannel. , The equalized real part subchannel signal k (carrier symbol) or imaginary part subchannel signal k (carrier symbol) is output.

の要素、または虚部サブチャネル信号ベクトルｋである

の要素を、図１および図２に示した等化係数算出部７から入力される等化係数によりフィルタ処理する。適応フィルタ４４−１〜４４−４の出力するフィルタ処理後の実部サブチャネル信号ベクトルｋの要素または虚部サブチャネル信号ベクトルｋの要素は加算器４５へ入力される。 The adaptive filters 44-1 to 44-4 are real part subchannel signal vectors k input from the analysis bank 5.

Element or imaginary part subchannel signal vector k

Are filtered by the equalization coefficient input from the equalization coefficient calculation unit 7 shown in FIGS. 1 and 2. The elements of the real part subchannel signal vector k or the elements of the imaginary part subchannel signal vector k after the filtering process output from the adaptive filters 44-1 to 44-4 are input to the adder 45.

  The adder 45 adds the elements of the real part subchannel signal vector k or the elements of the imaginary part subchannel signal vector k after the filtering process input from the adaptive filters 44-1 to 44-4. The equalized real subchannel signal (carrier symbol) output from the adder 45 is input to the adder 43 shown in FIG. The equalized imaginary part subchannel signal (carrier symbol) output from the adder 45 is input to the multiplier 42 shown in FIG.

[Equalization coefficient calculator]
Next, the equalization coefficient calculation unit 7 shown in FIGS. 1 and 2 will be described. The equalization coefficient calculator 7 calculates an equalization coefficient by a known method using the subchannel signal vector input from the analysis bank 5 and the equalized subchannel signal input from the linear equalizer 6. Here, an RLS (Recursive Least Squares) algorithm having excellent convergence characteristics will be described as an example of a known method.

ここで、δは正の微小量（初期定数）を示し、Ｉは単位行列を示す。 The equalization coefficient at time n is w (n) and the correlation inverse matrix of the input signal is P (n), and initialization is performed as follows.

Here, δ represents a positive minute amount (initial constant), and I represents a unit matrix.

ここで、前記式（９）の右辺の第１項は、既知のパイロット信号ｄ（ｎ）を示し、第２項は、線形等化器６により出力された等化後のサブチャネル信号から抽出したパイロット信号を示す。また、ｋ（ｎ）はゲインベクトルを示し、Ｔｒｉ｛・｝は対角要素を対称軸とする対称行列化演算子を示す。また、λは忘却係数（０＜λ≦１）を示す。 An input signal vector that is a subchannel signal vector input from the analysis bank 5 is set to u (n), and the equalization coefficient is updated as follows.

Here, the first term on the right side of the equation (9) indicates a known pilot signal d (n), and the second term is extracted from the equalized subchannel signal output by the linear equalizer 6. The pilot signal is shown. Further, k (n) represents a gain vector, and Tri {•} represents a symmetric matrix forming operator having diagonal elements as symmetry axes. Λ represents a forgetting factor (0 <λ ≦ 1).

[Log Likelihood Ratio Calculation Unit]
Next, the log likelihood ratio calculation unit 8 provided in the multicarrier modulation signal receiving apparatus 1-1 of the first embodiment shown in FIG. 1 and the multicarrier modulation signal receiving apparatus 1- of the second embodiment shown in FIG. The log likelihood ratio calculation unit 11 provided in FIG. FIG. 3 is a block diagram illustrating a configuration of the log likelihood ratio calculation unit 8 according to the first embodiment. The log likelihood ratio calculation unit 8 includes a pilot symbol generation unit 51, a subtractor 52, an amplitude calculation unit 53, a synchronous addition unit 54, a transmission path reliability calculation unit 55, a subtractor 56, a multiplier 57, and a likelihood ratio calculation. A portion 58 is provided. As described above, the log likelihood ratio calculation unit 8 uses the equalized carrier symbol input from the linear equalizer 6 and the equalization coefficient input from the equalization coefficient calculation unit 7 to calculate the logarithm for each bit. A likelihood ratio is calculated.

  The equalized carrier symbols input from the linear equalizer 6 are divided into two, one input to the likelihood ratio calculation unit 58 and the other input to the subtractor 52. The pilot symbol generation unit 51 generates and outputs a known value for the carrier symbol assigned to the pilot symbol among the equalized carrier symbols input from the linear equalizer 6. The known pilot symbols output from the pilot symbol generator 51 are input to the subtractor 52. The subtractor 52 subtracts the equalized carrier symbol (pilot symbol) input from the linear equalizer 6 from the known pilot symbol input from the pilot symbol generator 51 to calculate and output an error. The error output from the subtractor 52 is input to the amplitude calculator 53.

  The amplitude calculator 53 calculates and outputs the error amplitude for each subcarrier input from the subtractor 52. The error amplitude for each subcarrier output from the amplitude calculator 53 is input to the synchronous adder 54. The synchronous adder 54 synchronously adds and outputs the error amplitude for each subcarrier input from the amplitude calculator 53. The synchronously added error amplitude output from the synchronous adder 54 is input to the multiplier 57. The error calculator 53 and the synchronous adder 54 constitute an error power calculator. The error power calculator obtains and outputs the error power for each subcarrier input from the subtractor 52. The error power output from the error power calculation unit is input to the multiplier 57 as the amplitude of the error subjected to synchronous addition.

  The equalization coefficient input from the equalization coefficient calculation unit 7 is input to the transmission line reliability calculation unit 55. The transmission path reliability calculation unit 55 obtains and outputs the transmission path reliability for each subcarrier from the equalization coefficient input from the equalization coefficient calculation unit 7. The transmission path reliability for each subcarrier output from the transmission path reliability calculation unit 55 is input to the subtractor 56. The subtracter 56 subtracts the transmission line reliability for each subcarrier input from the transmission line reliability calculation unit 55 from the constant 2 and outputs the result. The transmission line reliability subtracted from 2 output from the subtractor 56 is input to the multiplier 57.

  The multiplier 57 multiplies the amplitude of the synchronously added error input from the synchronous adder 54 by the transmission channel reliability input from the subtractor 56 for each subcarrier, and outputs the result. The amplitude of the error multiplied by the transmission line reliability output from the multiplier 57 is input to the likelihood ratio calculation unit 58.

ここで、Ｌ（ｋ，ｎ）は、サブキャリヤ番号ｋのｎ番目のビットに対する対数尤度比、Ｓ_n0およびＳ_n1は、ｎ番目のビットがそれぞれ０，１である信号点の集合、σ_k ²は、サブキャリヤ番号ｋの伝送路信頼度が乗算された誤差の振幅を示す。また、（ｘ，ｙ）は、線形等化器６から入力される等化後のキャリヤシンボルを示す。 The likelihood ratio calculation unit 58 uses the equalized carrier symbol input from the linear equalizer 6 and the error amplitude multiplied by the transmission line reliability input from the multiplier 57, by the following equation. A log likelihood ratio is calculated. The log likelihood ratio output from the likelihood ratio calculation unit 58 is input to the error correction decoding unit 9.

Where L (k, n) is a log likelihood ratio for the nth bit of subcarrier number k, S _n0 and S _n1 are a set of signal points whose nth bit is 0 and 1, respectively, σ _k ² represents the amplitude of the error multiplied by the transmission channel reliability of subcarrier number k. Further, (x, y) indicates a carrier symbol after equalization input from the linear equalizer 6.

  FIG. 4 is a block diagram illustrating a configuration of the log likelihood ratio calculation unit 11 according to the second embodiment. The log likelihood ratio calculation unit 11 includes a pilot symbol generation unit 51, a subtracter 52, an amplitude calculation unit 53, a synchronous addition unit 54, and a likelihood ratio calculation unit 58. As described above, the log likelihood ratio calculation unit 11 calculates the log likelihood ratio for each bit by using the equalized carrier symbol input from the linear equalizer 6. When the log likelihood ratio calculation unit 8 of the first embodiment shown in FIG. 3 and the log likelihood ratio calculation unit 11 are compared, the log likelihood ratio calculation unit 11 determines that the transmission channel reliability of the log likelihood ratio calculation unit 8 is the same. The difference is that the degree calculator 55, the subtractor 56, and the multiplier 57 are not provided. The transmission line reliability calculation unit 55 and the subtractor 56 that are not provided in the log likelihood ratio calculation unit 11 correspond to the transmission line reliability calculation unit 10 shown in FIG. 2, and the multiplier 57 is shown in FIG. These correspond to the multiplier 12 and are included in the upper configuration.

  That is, when the multicarrier modulation signal receiving apparatus 1-1 of the first embodiment shown in FIG. 1 is compared with the multicarrier modulation signal receiving apparatus 1-2 of the second embodiment shown in FIG. As described in the log likelihood ratio calculation unit 8 shown in FIG. 3, the modulation signal receiving apparatus 1-1 multiplies the error amplitude of the pilot symbol that has been synchronously added by the transmission line reliability to multiply the log likelihood ratio. And the error correction decoding is performed using the calculated log likelihood ratio, whereas the multicarrier modulation signal receiving apparatus 1-2 of the second embodiment multiplies the calculated log likelihood ratio by the transmission line reliability, The difference is that error correction decoding is performed based on the log likelihood ratio of the multiplication result. Both have different ways of obtaining the log-likelihood ratio, but give essentially the same meaning.

Since each component of the log likelihood ratio calculation unit 11 has been described in the log likelihood ratio calculation unit 8, a description thereof is omitted here. Note that the likelihood ratio calculation unit 58 of the log likelihood ratio calculation unit 11 uses the equalized carrier symbol input from the linear equalizer 6 and the error amplitude input from the synchronous addition unit 54. The log-likelihood ratio is calculated by the equation (12). In this case, σ _k ^{2 in the} equation (12) represents the amplitude of the error in the subcarrier number k.

[Transmission path reliability calculation unit]
Next, the transmission line reliability calculation unit 10 shown in FIG. 2 and the transmission line reliability calculation unit 55 shown in FIG. 3 will be described. FIG. 5 is a block diagram showing a first configuration of the transmission line reliability calculation unit 10. The transmission line reliability calculation unit 10 includes amplitude calculation units 61-1 to 61-4, an adder 62, a normalization unit 63, and a subtractor 64. 3 includes the subtractor 56 at the subsequent stage, and therefore does not include the subtracter 64 in the configuration illustrated in FIG. This is because the subtractor 64 corresponds to the subtractor 56. That is, the transmission line reliability calculation unit 55 includes amplitude calculation units 61-1 to 61-4 and an adder 62. The same applies to FIGS. 6 and 7 described later.

  As described above, the transmission line reliability calculation unit 10 calculates the transmission line reliability for each subcarrier using the four systems of equalization coefficients input from the equalization coefficient calculation unit 7. The four systems of equalization coefficients input from the equalization coefficient calculation unit 7 correspond to the coefficients of the adaptive filters used in the adaptive filters 44-1 to 44-4 of the equalizer 41 shown in FIG.

  Amplitude calculators 61-1 to 61-4 calculate and output, for each tap, the amplitudes of the equalization coefficients of the four systems input from equalization coefficient calculator 7 for each subcarrier. The amplitudes of the equalization coefficients output from the amplitude calculation units 61-1 to 61-4 are input to the adder 62. The adder 62 adds the amplitudes of the equalization coefficients input from the amplitude calculators 61-1 to 61-4 for each subcarrier and outputs the result. The sum of the amplitudes of the equalization coefficients, which is the addition result output from the adder 62, is input to the normalization unit 63.

  The normalizing unit 63 normalizes the amplitude sum of the equalization coefficients input from the adder 62 for each subcarrier so that the average of all subcarriers is 1, and outputs the result. The normalized amplitude sum of the normalized equalization coefficient output from the normalization unit 63 is input to the subtractor 64. The subtracter 64 subtracts the amplitude sum of the normalized equalization coefficient input from the normalization unit 63 from the constant 2, and outputs the subtraction result as the transmission path reliability. The transmission line reliability output from the subtractor 64 is input to the multiplier 12.

  FIG. 6 is a block diagram showing a second configuration of the transmission line reliability calculation unit 10. The transmission line reliability calculation unit 10 includes amplitude calculation units 61-1 and 61-4, an adder 62, a normalization unit 63, and a subtractor 64. When the first configuration of the transmission line reliability calculation unit 10 shown in FIG. 5 is compared with the second configuration, both transmission line reliability calculation units 10 include amplitude calculation units 61-1 and 61-4, addition The second configuration of the transmission path reliability calculation unit 10 is the same as the amplitude of the first configuration of the transmission path reliability calculation unit 10 except that the second unit 62, the normalization unit 63, and the subtractor 64 are provided. The difference is that the calculation units 61-2 and 61-3 are not provided. Since the amplitude calculation units 61-1 and 61-4, the adder 62, the normalization unit 63, and the subtractor 64 have already been described in the first configuration of the transmission line reliability calculation unit 10 illustrated in FIG. The description is omitted here.

  The second configuration of the transmission line reliability calculation unit 10 uses two equalization coefficients among the four equalization coefficients input from the equalization coefficient calculation unit 7 to use transmission line reliability for each subcarrier. Is calculated. Of the four systems of equalization coefficients input from the equalization coefficient calculation unit 7, the two systems of equalization coefficients used by the transmission line reliability calculation unit 10 are the adaptive filters 44- of the equalizer 41 shown in FIG. 1 corresponds to the coefficient of the adaptive filter used in 44-4.

  As described above, according to the second configuration of the transmission line reliability calculation unit 10 illustrated in FIG. 6, the amplitude calculation unit 61-is compared with the first configuration of the transmission line reliability calculation unit 10 illustrated in FIG. 5. 2 and 61-3 are not provided, there is an advantage that the circuit scale can be reduced. In the first configuration of the transmission line reliability calculation unit 10 illustrated in FIG. 5, the amplitudes of the equalization coefficients input to the amplitude calculation units 61-1 and 61-4 are the amplitude calculation units 61-2 and 61, respectively. Greater than the amplitude of the equalization coefficient input to -3. Therefore, the characteristic degradation of the transmission line reliability calculated by the second configuration of the transmission line reliability calculation unit 10 can be reduced. This is because the equalization coefficients input to the amplitude calculation units 61-1 and 61-4 are used to extract the main wave component of the transmission path, whereas the amplitude calculation units 61-2 and 61- are used. This is because the equalization coefficient input to 3 is used to suppress the interference component within the carrier and between the symbols when there is a transmission path distortion.

(Dispersion weighting)
FIG. 7 is a block diagram showing a third configuration of the transmission line reliability calculation unit 10. The transmission line reliability calculation unit 10 includes amplitude calculation units 61-1 to 61-4, dispersion calculation units 71-1 to 71-4, adders 62-1 and 62-2, and normalization units 63-1 and 63. -2, multipliers 72-1, 72-2, an adder 73, and a subtractor 64. When the first configuration of the transmission line reliability calculation unit 10 shown in FIG. 5 is compared with the third configuration, both transmission line reliability calculation units 10 include amplitude calculation units 61-1 to 61-4, and addition. The third configuration of the transmission line reliability calculation unit 10 is the same as that of the transmission line reliability calculation unit 10 except that the units 62 and 62-1, the normalization units 63 and 63-1, and the subtractor 64 are provided. In addition to the tenth first configuration, variance calculation units 71-1 to 71-4, an adder 62-2, a normalization unit 63-2, multipliers 72-1, 72-2, and an adder 73 are provided. It is different in point.

  The third configuration of the transmission line reliability calculation unit 10 calculates the transmission line reliability for each subcarrier using the four systems of equalization coefficients input from the equalization coefficient calculation unit 7. The four systems of equalization coefficients input from the equalization coefficient calculation unit 7 correspond to the coefficients of the adaptive filters used in the adaptive filters 44-1 to 44-4 of the equalizer 41 shown in FIG.

  Since the amplitude calculation units 61-1 to 61-4, the adder 62-1 and the normalization unit 63-1 have been described in the first configuration of the transmission line reliability calculation unit 10 illustrated in FIG. The description is omitted here. The amplitude sum of the normalized equalization coefficient output from the normalization unit 63-1 is input to the multiplier 72-1. The multiplier 72-1 multiplies the amplitude sum of the normalized equalization coefficient input from the normalization unit 63-1 by a predetermined constant and outputs the result. The multiplication result output from the multiplier 72-1 is input to the adder 73. Here, a constant in the multiplier 72-1 and a constant in a multiplier 72-2, which will be described later, are determined in advance so that the sum of these is 1.

  For each subcarrier, the variance calculation units 71-1 to 71-4 calculate and output the variance of the equalization coefficients of the four systems input from the equalization coefficient calculation unit 7 for each tap. The variances of the equalization coefficients output from the variance calculation units 71-1 to 71-4 are input to the adder 62-2. The adder 62-2 adds and outputs the variances of the equalization coefficients input from the variance calculation units 71-1 to 71-4 for each subcarrier. The variance sum of equalization coefficients, which is the addition result output from the adder 62-2, is input to the normalization unit 63-2.

  The normalizing unit 63-2 normalizes and outputs the dispersion sum of the equalization coefficients input from the adder 62-2 for each subcarrier so that the average of all the subcarriers becomes 1. The dispersion sum of the normalized equalization coefficients output from the normalization unit 63-2 is input to the multiplier 72-2. The multiplier 72-2 multiplies the dispersion sum of the normalized equalization coefficients input from the normalization unit 63-2 by a predetermined constant and outputs the result. The multiplication result output from the multiplier 72-2 is input to the adder 73. As described above, the constant in the multiplier 72-2 and the constant in the multiplier 72-1 are determined in advance so that the sum of these is 1.

  The adder 73 is a multiplication result of the amplitude sum of the normalized equalization coefficient input from the multiplier 72-1, and a multiplication result of the variance sum of the normalized equalization coefficient input from the multiplier 72-2. And are output. The addition result output from the adder 73 is input to the subtractor 64. The subtracter 64 subtracts the addition result of the normalized sum of amplitudes of the equalization coefficients and the multiplication result of the variance sum input from the adder 73 from the constant 2, and the subtraction result is transferred to the transmission line reliability. Output as degrees. The transmission line reliability output from the subtractor 64 is input to the multiplier 12.

  As described above, according to the third configuration of the transmission path reliability calculation unit 10 illustrated in FIG. 7, for example, when a received signal includes a frequency-dependent interference component other than transmission path distortion, Since the influence of the interference component on the equalization coefficient is white, equalization calculated by the dispersion calculation units 71-1 to 71-4, the adder 62-2, the normalization unit 63-2, and the multiplier 72-2. As a result, the transmission line reliability is lower than when no interference component is present. Thereby, the transmission path reliability is calculated with higher accuracy than the first configuration of the transmission path reliability calculation section 10 shown in FIG. 5 and the second configuration of the transmission path reliability calculation section 10 shown in FIG. can do.

  As a modification of the third configuration of the transmission line reliability calculation unit 10 shown in FIG. 7, according to the configuration shown in FIG. 6, the amplitude calculation units 61-2 and 61-3 and the dispersion calculation unit 71- 2, 71-3 may not be provided. Thereby, a circuit scale can be reduced rather than the 3rd structure of the transmission-line reliability calculation part 10. FIG.

〔Experimental result〕
FIG. 17 is a diagram illustrating an example of BER characteristics obtained by computer simulation. Digital data that has been subjected to error correction coding is converted into the multicarrier modulation signal receiving device 1-1 according to the first embodiment illustrated in FIG. The example of the BER characteristic at the time of transmitting via a multipath propagation path with the conventional multicarrier modulation signal receiver which does not use reliability is shown. However, the division number M is 1024, the symbol length is 126 μs, the propagation path is a multipath environment of D / U 3 dB, and the delay time 1 μs. The error correction code is an LDPC code (code length 64800) and a coding rate of 3/4.

From the BER characteristic shown in FIG. 17, when comparing the BER characteristic (2) of the multicarrier modulation signal receiving apparatus 1-1 of Example 1 with the BER characteristic (1) of the conventional multicarrier modulation signal receiving apparatus, for example, 1 × In order to obtain a BER of 10 ⁻⁷ , it can be seen that the multicarrier modulation signal receiving apparatus 1-1 of the first embodiment can improve about 2 dB.

  As described above, according to the multicarrier modulation signal receiver 1-1 of the first embodiment, the analysis bank 5, the linear equalizer 6, and the equalization coefficient calculation that operate at a rate substantially twice the maximum thinning rate. Unit 7, a log likelihood ratio calculation unit 8 including a channel reliability calculation unit 55 and a subtractor 56, and an error correction decoding unit 9, and the log likelihood ratio calculation unit 8 outputs the equalization coefficient calculation unit 7. The channel reliability is calculated from the equalization coefficient, and the log likelihood ratio is calculated using the equalized carrier symbol and the error of the equalized carrier symbol reflecting the channel reliability. did. As a result, the log-likelihood ratio is calculated using channel reliability without using channel characteristics, so that the correction function by error correction decoding can be used effectively, and multi-carrier modulation having bit error tolerance A signal receiving device can be realized.

  Further, according to the multicarrier modulation signal receiving apparatus 1-2 of the second embodiment, the analysis bank 5, the linear equalizer 6, the equalization coefficient calculation unit 7, which substantially operate at a rate twice the maximum thinning rate, A transmission line reliability calculation unit 10, a log likelihood ratio calculation unit 11, a multiplier 12, and an error correction decoding unit 9 are provided, and the transmission line reliability calculation unit 10 uses the equalization coefficient output from the equalization coefficient calculation unit 7. The transmission line reliability is calculated, the log likelihood ratio calculation unit 11 calculates the log likelihood ratio using the error of the carrier symbol after equalization, and the multiplier 12 adds the transmission line reliability to the log likelihood ratio. To obtain a new log-likelihood ratio used in error correction decoding. Thus, similar to the first embodiment, the log likelihood ratio is calculated using the transmission line reliability without using the propagation path characteristics, so that the correction function by error correction decoding can be used effectively, It becomes possible to realize a multicarrier modulation signal receiving apparatus having error tolerance.

DESCRIPTION OF SYMBOLS 1 Multicarrier modulation signal receiver 2 Frequency conversion part 3 A / D conversion part 4 Orthogonal demodulation part 5 Analysis bank 6 Linear equalizer 7 Equalization coefficient calculation part 8, 11 Log likelihood ratio calculation part 9 Error correction decoding part 10 55 Transmission path reliability calculation unit 12, 28, 32, 42, 57, 72 Multiplier 21, 24, 31 Delay 22 Polyphase analysis bank 23 Subchannel processing unit 25 Decimator 26 Polyphase filter 27 FFT unit 29 Real part Extraction unit 30 Imaginary part extraction unit 41 Equalizer 43, 45, 62, 73 Adder 44 Adaptive filter 51 Pilot symbol generation unit 52, 56, 64 Subtractor 53, 61 Amplitude calculation unit 54 Synchronous addition unit 58 Likelihood ratio calculation Unit 63 normalization unit 71 dispersion calculation unit 100 transmultiplexer 101 modified DFT modulation synthesis bank 102 modified DFT modulation analysis bank

Claims (6)

A multi-carrier modulation signal receiving apparatus for receiving an error-corrected encoded signal by multi-carrier modulation by a modified DFT modulation synthesis bank and receiving the multi-carrier modulated signal,
A modified DFT modulation analysis bank for converting a time domain equivalent baseband signal obtained by orthogonal demodulation of the received signal into a frequency domain equivalent baseband signal at a rate twice the maximum decimation rate and outputting a subchannel signal; ,
A linear equalizer for the number of subcarriers for equalizing the subchannel signal output from the modified DFT modulation analysis bank;
A log likelihood ratio calculator that calculates a log likelihood ratio from the equalized subchannel signal equalized by the linear equalizer;
An error correction decoding unit that performs error correction decoding processing using the log likelihood ratio calculated by the log likelihood ratio calculation unit;
An equalization coefficient calculator for calculating an equalization coefficient used in the linear equalizer;
A transmission line reliability calculation unit that calculates transmission line reliability based on the equalization coefficient calculated by the equalization coefficient calculation unit,
The transmission line reliability calculation unit,
An amplitude calculation unit that calculates an amplitude sum of the equalization coefficients calculated by the equalization coefficient calculation unit;
A normalization unit for normalizing the amplitude sum of the equalization coefficients calculated by the amplitude calculation unit so that the average is 1 for all subcarriers;
A subtractor that subtracts the amplitude sum of the equalization coefficients normalized by the normalization unit from a predetermined value and obtains the transmission line reliability;
Using the equalized subchannel signal equalized by the linear equalizer, the error of the equalized subchannel signal, and the transmission path reliability calculated by the transmission path reliability calculation unit, A multicarrier modulation signal receiving apparatus characterized in that a log likelihood ratio used in an error correction decoding unit is obtained. The multicarrier modulation signal receiving apparatus according to claim 1, wherein
The log likelihood ratio calculation unit
A subtracter that subtracts the equalized subchannel signal equalized by the linear equalizer from a known pilot symbol and outputs an error of the equalized subchannel signal;
An error power calculation unit for calculating the error power of the equalized subchannel signal output from the subtractor;
A first multiplier that multiplies the error power calculated by the error power calculation unit by the transmission channel reliability calculated by the transmission channel reliability calculation unit;
Based on the equalized subchannel signal equalized by the linear equalizer and the error power of the equalized subchannel signal multiplied by the first multiplier, the log likelihood ratio is calculated. A multi-carrier modulation signal receiving apparatus comprising: a likelihood ratio calculation unit for calculating. The multi-carrier modulation signal receiving apparatus according to claim 2,
A second multiplier;
The log-likelihood ratio calculation unit is replaced with the first multiplier and the likelihood ratio calculation unit.
A likelihood ratio calculator that calculates the log likelihood ratio based on the equalized subchannel signal equalized by the linear equalizer and the error power calculated by the error power calculator; ,
The second multiplier comprises:
Multiplying the log likelihood ratio calculated by the log likelihood ratio calculation unit by the transmission line reliability calculated by the transmission line reliability calculation unit,
The error correction decoding unit,
An apparatus for receiving a multicarrier modulation signal, wherein error correction decoding processing is performed using a log likelihood ratio multiplied by the second multiplier. In the multicarrier modulation signal receiving device according to any one of claims 1 to 3,
The modified DFT modulation analysis bank is
Decimating and filtering are performed on the time-domain equivalent baseband signal obtained by orthogonal demodulation of the received signal to generate a first signal, and decimating and filtering are performed on the delayed equivalent baseband signal. To generate a second signal, extract a real part component and an imaginary part component from the second signal to obtain first and second components, and imaginary part component and real part component from the first signal Is extracted as third and fourth components to generate a real subchannel signal composed of the first to fourth components, and is paired with the fourth and third components of the real subchannel signal. The real part component and the imaginary part component are extracted as first and second components, and the real part component and the imaginary part component that are paired with the second and first components of the real part subchannel signal are extracted. 3rd and A fourth component, to generate a imaginary part subchannel signal consisting of components from the first to the fourth,
The amplitude calculation unit of the transmission line reliability calculation unit,
Among the equalization coefficients calculated by the equalization coefficient calculation unit, equalization corresponding to the first and fourth signals of the real part subchannel signal and the imaginary part subchannel signal generated by the modified DFT modulation analysis bank A multicarrier modulation signal receiving apparatus characterized by calculating a sum of amplitudes of coefficients. In the multicarrier modulation signal receiving device according to any one of claims 1 to 3,
The transmission line reliability calculation unit,
An amplitude calculation unit that calculates an amplitude sum of the equalization coefficients calculated by the equalization coefficient calculation unit;
A first normalization unit that normalizes the amplitude sum of the equalization coefficients calculated by the amplitude calculation unit so that the average is 1 for all subcarriers;
A third multiplier for multiplying the amplitude sum of the equalization coefficients normalized by the first normalization unit by a predetermined value;
A variance calculation unit that calculates the variance of the equalization coefficient calculated by the equalization coefficient calculation unit;
A second normalization unit for normalizing the variance of the equalization coefficient calculated by the variance calculation unit so that the average is 1 for all subcarriers;
A fourth multiplier for multiplying the variance of the equalization coefficient normalized by the second normalization unit by a predetermined value;
An adder for adding the amplitude sum of the equalization coefficients multiplied by the third multiplier and the variance of the equalization coefficients multiplied by the fourth multiplier;
A multicarrier modulation signal receiving apparatus comprising: a subtractor for subtracting an addition result by the adder from a predetermined value to obtain the transmission path reliability. The multi-carrier modulation signal receiving device according to claim 5,
The modified DFT modulation analysis bank is
Decimating and filtering are performed on the time-domain equivalent baseband signal obtained by orthogonal demodulation of the received signal to generate a first signal, and decimating and filtering are performed on the delayed equivalent baseband signal. To generate a second signal, extract a real part component and an imaginary part component from the second signal to obtain first and second components, and imaginary part component and real part component from the first signal Is extracted as third and fourth components to generate a real subchannel signal composed of the first to fourth components, and is paired with the fourth and third components of the real subchannel signal. The real part component and the imaginary part component are extracted as first and second components, and the real part component and the imaginary part component that are paired with the second and first components of the real part subchannel signal are extracted. 3rd and A fourth component, to generate a imaginary part subchannel signal consisting of components from the first to the fourth,
The amplitude calculation unit of the transmission line reliability calculation unit,
Among the equalization coefficients calculated by the equalization coefficient calculation unit, equalization corresponding to the first and fourth signals of the real part subchannel signal and the imaginary part subchannel signal generated by the modified DFT modulation analysis bank Calculate the sum of the amplitudes of the coefficients,
The dispersion calculation unit of the transmission line reliability calculation unit,
Among the equalization coefficients calculated by the equalization coefficient calculation unit, equalization corresponding to the first and fourth signals of the real part subchannel signal and the imaginary part subchannel signal generated by the modified DFT modulation analysis bank A multicarrier modulation signal receiving apparatus characterized by calculating a variance of coefficients.

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