JP2006180365A - Ofdm demodulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce signal throughput, and to improve the equalizing processing performance. <P>SOLUTION: When L-th sub-carriers are determined as pilot sub-carriers, two pilot sub-carriers of the highest and the second highest signal quality are selected from among M pieces of the L-th sub-carriers through a first selection means 302. One data sub-carrier of the highest signal quality is selected from among M pieces of (L-1)-th data sub-carriers through a second selection means 301. One data sub-carrier of the highest signal quality is selected from among M pieces of (L+1)-th data sub-carriers through a third selection means 303. The selected pilot sub-carrier and the selected data sub-carrier are multiplied by weights through a multiplying means, the pilot sub-carrier and the data sub-carrier multiplied by weights are synthesized by a synthesizing means, and a weight which makes the difference between the synthesized signals and the given signals the smallest is calculated through a calculating means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) demodulator that performs diversity reception, and more particularly to an OFDM demodulator that reduces inter-subcarrier interference due to Doppler shift.

Conventionally, an equalizer as a countermeasure against Doppler shift reduces inter-subcarrier interference in the frequency domain (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 6-261019

  However, the conventional technology does not consider diversity. Therefore, when diversity is simply applied to the conventional technology, the received signal received by each antenna is Fourier transformed, individually equalized, and then diversity combined. When the L-th subcarrier is determined as a symbol, equalization processing is individually performed by each antenna, and the equalizer outputs D1 (L), D2 (L), and D3 (L) are diversity combined.

  In such a configuration, there is a problem that the amount of processing of the equalizer increases in proportion to the number of antennas. Further, since equalization processing and diversity combining processing are performed independently, optimal equalization combining processing cannot be performed.

  The present invention has been made to solve the above-described problems in the prior art, and an object thereof is to provide an OFDM demodulator capable of reducing the processing amount and improving the equalization performance.

According to the OFDM demodulator of the present invention, in an OFDM demodulator that demodulates an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more), M (M is 2) that receives the OFDM signal. (An integer above) antennas and M Fourier transform units connected to the M antennas in a one-to-one correspondence, each Fourier transform unit receiving signals received by the corresponding antennas And M Fourier transform units for extracting K subcarriers from L and determining whether L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier When the determination unit and the determination unit determine that the Lth subcarrier is a data subcarrier, equalization processing is performed on the Lth data subcarrier. As weights because, setting means for setting the same value as the weight for performing equalization processing on the pilot subcarriers disposed in a position closest to the L-th data subcarrier,
When the determination means determines that the Lth subcarrier is a pilot subcarrier, from the M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units, Pilot subcarrier selection means for selecting at least two pilot subcarriers from the higher signal quality, and M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units First subcarrier selection means for selecting one data subcarrier having the highest signal quality, and M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units Second subcarrier selecting means for selecting one data subcarrier having the highest signal quality from the above, Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight; Combining means for combining the multiplied pilot subcarriers and data subcarriers, and calculating means for calculating the weight so that an error between the combined signal combined by the combining means and a certain known signal is minimized. It is characterized by comprising.

In addition, according to the OFDM demodulator of the present invention, in the OFDM demodulator that demodulates an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more), M (M Is an integer of 2 or more) and M Fourier transform units connected to the M antennas in a one-to-one correspondence, each Fourier transform unit received by the corresponding antenna M Fourier transform units that extract K subcarriers from the received signal, and whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier A determination unit for determining, and when the determination unit determines that the Lth subcarrier is a data subcarrier, equalization processing is performed on the Lth data subcarrier. As wait for performing a setting means for setting the same value as the weight for performing equalization processing on the pilot subcarriers disposed in a position closest to the L-th data subcarrier,
When the determination means determines that the Lth subcarrier is a pilot subcarrier, from the M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units, Pilot subcarrier selection means for selecting at least two pilot subcarriers from the higher signal quality, and M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units First subcarrier selection means for selecting one data subcarrier having the highest signal level, and M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units Second subcarrier selection means for selecting one data subcarrier having the highest signal level, Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight. , A combining means for combining the multiplied pilot subcarriers and data subcarriers, and a calculation for calculating the weight so that an error between the combined signal combined by the combining means and a known signal is minimized. And means.

Furthermore, according to the OFDM demodulator of the present invention, in the OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more), M (M Is an integer of 2 or more) and M Fourier transform units connected to the M antennas in a one-to-one correspondence, each Fourier transform unit received by the corresponding antenna M Fourier transform units that extract K subcarriers from the received signal, and whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier A determination unit that performs equalization on the Lth subcarrier when the determination unit determines that the Lth subcarrier is a data subcarrier. As wait for, and setting means for setting the same value as the weight for performing equalization processing on the pilot subcarriers disposed in a position closest to the L-th sub-carrier,
When the determination means determines that the Lth subcarrier is a pilot subcarrier, the signal generation means for generating a known signal to be mapped to the Lth pilot subcarrier, and the M Fourier transform units Pilot subcarrier selection means for selecting at least two pilot subcarriers from M Lth pilot subcarriers included in the output subcarriers in order of least error with the known signal; and the M number of pilot subcarriers First subcarrier selection means for selecting one data subcarrier having the highest signal quality from M L-1 th data subcarriers included in the subcarrier output from the Fourier transform unit; M L + 1th data subcarriers included in subcarriers output from Fourier transform units Second subcarrier selecting means for selecting one data subcarrier having the highest signal quality, each pilot subcarrier selected by the pilot subcarrier selecting means, and the first and second subcarriers Multiplying means for multiplying each data subcarrier selected by the selecting means by a predetermined weight, combining means for combining the multiplied pilot subcarriers and data subcarriers, and combining means And calculating means for calculating the weight so that an error between the synthesized signal and a certain known signal is minimized.

Still further, according to the OFDM demodulator of the present invention, in the OFDM demodulator that demodulates an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more), M ( M is an integer of 2 or more) and M Fourier transform units connected to the M antennas in a one-to-one correspondence, and each Fourier transform unit receives the corresponding antenna. M Fourier transform units for extracting K subcarriers from the received signal and whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier And when the Lth subcarrier is determined to be a data subcarrier by the determination means, the Lth data subcarrier, etc. Treated as weights for performing a setting means for setting the same value as the weight for performing equalization processing on the pilot subcarriers disposed in a position closest to the L-th data subcarrier,
When the determination means determines that the Lth subcarrier is a pilot subcarrier, the signal generation means for generating a known signal to be mapped to the Lth pilot subcarrier, and the M Fourier transform units Pilot subcarrier selection means for selecting at least two pilot subcarriers from M Lth pilot subcarriers included in the output subcarriers in order of least error with the known signal; and the M number of pilot subcarriers Of M pilot subcarriers, the pilot subcarrier having the smallest error from the known signal is determined from the M Lth pilot subcarriers included in the subcarrier output from the Fourier transform unit. From information generating means for generating specified information to be specified and the M Fourier transform units A first data subcarrier corresponding to the pilot subcarrier having the smallest error is selected based on the designation information from M L-1th data subcarriers included in the received subcarrier. Corresponding to the pilot subcarrier having the smallest error based on the designation information, from subcarrier selection means and M L + 1st data subcarriers included in the subcarriers output from the M Fourier transform units Second subcarrier selection means for selecting one data subcarrier, each pilot subcarrier selected by the pilot subcarrier selection means, and each selected by the first and second subcarrier selection means Multiplication means for multiplying a data subcarrier by a predetermined weight, and the multiplication Combining means for combining each pilot subcarrier and each data subcarrier, and calculating means for calculating the weight so that an error between the combined signal combined by the combining means and a certain known signal is minimized. It is characterized by comprising.

  Furthermore, according to the OFDM demodulator of the present invention, in the OFDM demodulator that demodulates an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more), M ( M is an integer of 2 or more) and M Fourier transform units connected to the M antennas in a one-to-one correspondence, and each Fourier transform unit receives the corresponding antenna. M Fourier transform units for extracting K subcarriers from the received signal and whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier And the M Fourier transform units determine that the L-th subcarrier is a data subcarrier. First determination means for determining temporary symbols of M L-th data subcarriers included in the subcarriers, and M L included in the subcarriers output from the M Fourier transform units Second determination means for determining a tentative symbol of the −1st data subcarrier, and tentative symbols of the M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units; A third determination means for determining the Lth data subcarriers from the M Lth data subcarriers included in the subcarriers output from the M Fourier transform units; First subcarrier selection means for selecting at least two data subcarriers from the one with the smallest error, and subcarriers output from the M Fourier transform units. 2nd subcarrier selection for selecting one data subcarrier having the smallest error from the provisional symbol of the L-1st data subcarrier from M L-1th data subcarriers included in And the L + 1th data subcarrier included in the subcarriers output from the M Fourier transform units, and the one error with the smallest error between the L + 1th data subcarrier provisional symbol Selected by the third subcarrier selection means for selecting the data subcarrier, each first subcarrier selected by the first subcarrier selection means, and the second and third subcarrier selection means Multiplication means for multiplying each data subcarrier by a predetermined weight, and synthesis means for combining the multiplied data subcarriers And calculating means for calculating the weight so that an error between the synthesized signal synthesized by the synthesizing means and the provisional symbol of the L-th data subcarrier is minimized.

  According to the OFDM demodulator of the present invention, the amount of processing can be reduced and the equalization performance can be improved.

Hereinafter, an OFDM demodulator according to an embodiment of the present invention will be described in detail with reference to the drawings.
An outline of an OFDM demodulator according to an embodiment of the present invention will be described with reference to FIG.
An OFDM demodulator according to an embodiment of the present invention includes a plurality of antennas (here, the number of antennas M is three as an example) 101, 102, 103, FFT (fast Fourier transformer) 104, 105, 106, equalization synthesis. Unit 107 and determination unit 108. Each FFT 104, 105, 106 is connected to each antenna in a one-to-one correspondence. In the example of FIG. 1, the FFT 104 is connected to the antenna 101, the FFT 105 is connected to the antenna 102, and the FFT 106 is connected to the antenna 103.

  Antennas 101, 102, and 103 receive the OFDM signal. Each received OFDM signal is amplified by an LNA (not shown). The amplified OFDM signal is converted into an IF frequency band by a frequency converter (not shown). The frequency-converted signal is adjusted to an appropriate signal level by a variable gain amplifier (not shown). The signal whose signal level is adjusted is quadrature demodulated into a baseband signal by an orthogonal demodulator (not shown), and then converted into a digital signal by an A / D converter (not shown). An apparatus portion not shown in the drawings has been conventionally present and is obvious to those skilled in the art, so only a brief description has been given.

  Each FFT 104, 105, 106 extracts K subcarriers from the digital signal which is the output signal of the A / D converter.

The equalization combining unit 107 receives K subcarriers from the FFTs 104, 105, and 106, and performs equalization processing and diversity combining processing for each subcarrier. The equalization synthesis unit 107 performs equalization processing and diversity synthesis processing by feedback. Here, equalization processing combines multiple received signals weighted by weights and calculates and sets a weight that minimizes the error between the combined signal and the known signal, thereby improving the signal quality of the combined signal. It is a process to improve. The equalization / combination unit 107 receives the signal subjected to the diversity combining process again, and performs equalization processing and diversity combining processing based on the input signal. Thus, in the embodiment of the present invention, equalization processing and diversity combining processing are performed in cooperation. Weights calculated when the equalization combining unit 107 performs diversity combining processing will be described later with reference to FIG.
The determination unit 108 performs symbol determination on the output signal of the equalization synthesis unit 107.

Next, the format of the OFDM signal used in the embodiment of the present invention will be described with reference to FIG.
In the OFDM signal according to the embodiment of the present invention, pilot subcarriers, which are known signals, are arranged on every four subcarriers on the frequency axis as shown in FIG. That is, in the case of the example of FIG. 2, pilot subcarriers are arranged at the first, fifth, and ninth positions in FIG. Called subcarriers).

The equalization combining unit 107 performs equalization processing on the Lth subcarrier when the Lth subcarrier is a data subcarrier and the pilot subcarrier is adjacent to the data subcarrier. Is set to the same weight as the weight for performing equalization processing on adjacent pilot subcarriers. For example, in the example of FIG. 2, the equalization combining unit 107 performs equalization processing on the adjacent fifth pilot subcarrier as a weight for performing equalization processing on the fourth and sixth data subcarriers. Set the same value as the weight of.
On the other hand, if the Lth subcarrier is a data subcarrier and the pilot subcarrier is not adjacent to this data subcarrier, the equalization combiner 107 performs equalization processing on the Lth subcarrier. As a weight for performing, the same value as the weight for performing equalization processing is set for the pilot subcarrier arranged at a position closest to the Lth subcarrier. For example, in the example of FIG. 2, the equalization combining unit 107 uses the first or fifth pilot subcarrier closest to the third data subcarrier as a weight for performing equalization processing on the third data subcarrier. The same weight as the weight for performing equalization processing is set in
Also, equalization combining section 107 determines whether the Lth subcarrier is a pilot subcarrier or a data subcarrier. That is, equalization combining section 107 can obtain information on what number pilot subcarriers are located and what number data subcarriers are arranged.

Hereinafter, a method for calculating a weight for performing equalization processing on the Lth subcarrier when the Lth subcarrier is a pilot subcarrier will be described. Embodiments of the equalizing and synthesizing unit 107 that performs this method will be described as first to seventh embodiments with reference to the drawings. That is, in the following embodiment, the L-th subcarrier is a pilot subcarrier.
(First embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIG.
The equalization synthesis unit 107 of this embodiment includes selection units 301, 302, and 303, weight multiplication units 304, 305, 306, and 307, and a synthesis unit 308.
The selection unit 301 inputs M L−1th data subcarriers corresponding to the number of antennas. Since M = 3 in this embodiment, X1 (L-1), X2 (L-1), and X3 (L-1) are input. For example, the selection unit 301 measures the signal quality of the input data subcarriers, and selects at least one of the data subcarriers having the highest signal quality in descending order of signal quality. In the example of FIG. 3, the selection unit 301 selects one data subcarrier (for example, X1 (L−1)) with high signal quality. Here, the selection unit 301 measures the signal quality and selects the data subcarrier based on this signal quality, but other examples will be described later in the fifth and sixth embodiments.

  Selection section 302 inputs M Lth pilot subcarriers corresponding to the number of antennas. In the present embodiment, the selection unit 302 inputs X1 (L), X2 (L), and X3 (L). The selection unit 302 measures the signal quality of the input pilot subcarriers, and among these pilot subcarriers, those having high signal quality (for example, X1 (L), X2 (L)) are at least in order of high signal quality. Select two. In the example of FIG. 3, the selection unit 302 selects two pilot subcarriers with high signal quality.

The selection unit 303 inputs M L + 1-th data subcarriers corresponding to the number of antennas. In this embodiment, since M = 3, X1 (L + 1), X2 (L + 1), X3 (L
Enter 1). For example, the selection unit 303 measures the signal quality of the input data subcarriers, and selects at least one of the data subcarriers having the highest signal quality in descending order of signal quality. In the example of FIG. 3, the selection unit 303 selects one data subcarrier (for example, X2 (L + 1)) with high signal quality. Here, the selection unit 303 measures the signal quality and selects the data subcarrier based on this signal quality. Other examples will be described later in the fifth and sixth embodiments.

  Each of the weight multipliers 304, 305, 306, and 307 receives the information on the weight output from the weight calculator 309, and multiplies the input subcarrier by the weight corresponding to each information. Each weight multiplier 304 and 307 inputs data subcarriers from selectors 301 and 303, respectively. Each weight multiplication section 305 and 306 inputs a pilot subcarrier from selection section 302.

  The combining unit 308 combines the signals output from the weight multiplying units 304, 305, 306, and 307. The synthesis unit 308 outputs the synthesized signal to the determination unit 108 and feeds back the synthesized signal to the weight calculation unit 309.

The weight calculation unit 309 compares the input combined signal with a known signal and calculates a weight that minimizes the error between the combined signal and the known signal. The error _{E L} is, L th a composite signal _X L pilot subcarriers, the known signal of the L-th pilot subcarrier and _{S L,} is expressed as E _{L =} X L -S _L. Further, the weight calculation unit 309 may calculate a weight such that an error between the combined signal and the known signal is smaller than a predetermined threshold value. Further, the weight calculation unit 309 outputs a weight prepared in advance to each of the weight multiplication units 304, 305, 306, and 307 in an initial state where no combined signal is input.

According to the first embodiment described above, at least two pilot subcarriers out of M L-th pilot subcarriers corresponding to the number of antennas are selected, and each is multiplied by a weight and multiplied by a weight. Diversity combining processing is performed by combining the subcarriers and setting weights that reduce the error of the combined signal. In addition, according to the present embodiment, at least one subcarrier of M L−1 subcarriers is selected and multiplied by a weight, and at least one of M L + 1 subcarriers is selected. Equalization processing is performed by selecting a number of subcarriers, multiplying the weights, combining the subcarriers multiplied by the weights, and setting a weight that reduces the error of the combined signal.
Therefore, according to the present embodiment, equalization processing and diversity combining processing can be performed in cooperation, and in the equalization processing for removing interference between adjacent subcarriers, only one adjacent subcarrier having high signal quality is selected. By doing so, compared with the case where M adjacent subcarriers are used regardless of the signal quality, it is possible to reduce the processing amount and to improve the equalization performance by reducing the weight.

(Second Embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIG. In addition, the same device parts as those described in the first embodiment with reference to FIG. 1 or FIG.
The equalizing / combining unit 107 of this embodiment removes the selecting unit 302 from the equalizing / combining unit 107 of the first embodiment, and adds a weight multiplying unit 401. With the addition of the weight multiplier 401, the output of the weight calculator increases by one.

  Each of the weight multipliers 401, 305, and 306 inputs M L-th pilot subcarriers corresponding to the number of antennas, inputs information about the weights output from the weight calculator 402, and corresponds to each information The input pilot subcarrier is multiplied by the weight to be transmitted.

  According to the second embodiment described above, in addition to the effects obtained in the first embodiment, the selection process is omitted by using all M L-th pilot subcarriers. The amount of processing can be reduced.

(Third embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIGS. 5 and 6. In addition, the same device parts as those described in the first embodiment with reference to FIG. 1 or FIG.
The equalization / synthesis unit 107 of this embodiment is obtained by changing the selection unit 302 of the first embodiment to the minimum error selection unit 501. Along with this, an Lth Pilot known signal generation unit 502 is added.

Minimum error selection section 501 inputs M Lth pilot subcarriers and Lth pilot known signals corresponding to the number of antennas. In the present embodiment, the minimum error selection unit 501 inputs X1 (L), X2 (L), and X3 (L). Minimum error selection section 501 compares the input pilot subcarrier and the known pilot signal input from Lth pilot known signal generation section 502, and selects at least two pilot subcarriers in which the error is reduced in ascending order. In the example of FIG. 5, the minimum error selection unit 501 selects two pilot subcarriers (for example, X1 (L) and X2 (L)) having the smallest error and the pilot subcarrier having the second smallest error. ing. The smaller the error, the better the signal quality referred to in the first embodiment.
L-th pilot known signal generation section 502 generates a known signal mapped to the L-th pilot subcarrier and outputs the known signal to minimum error selection section 501.

Next, details of the minimum error selection unit 501 will be described with reference to FIG.
The minimum error selection unit 501 includes an error calculation unit 601, a minimum error detection unit 602, and a selector 603.

Error calculation section 601 compares the known signal of the Lth pilot subcarrier and each pilot subcarrier X1 (L), X2 (L), X3 (L) to calculate an error.
The minimum error detection unit 602 receives a plurality of errors detected by the error calculation unit 601, and detects a pilot subcarrier corresponding to the smallest error among these. Next, the minimum error detection unit 602 detects the smallest error among the errors corresponding to the pilot subcarriers excluding the pilot subcarrier corresponding to the smallest error. As a result, the minimum error detection unit 602 can detect two pilot subcarriers (for example, X1 (L) and X2 (L)) having the smallest error and the pilot subcarrier having the second smallest error. .

  The selector 603 selects the two pilot subcarriers detected by the minimum error detection unit 602 and outputs them to the weight multiplication units 305 and 306, respectively.

  According to the third embodiment described above, in addition to the effects obtained in the first embodiment, since a known signal is used, it is possible to perform equalization processing and diversity combining processing with high accuracy. .

(Fourth embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIG. In addition, the same device parts as those described in the first embodiment with reference to FIG. 1 or FIG.
The equalization synthesis unit 107 of this embodiment is obtained by adding an L-th pilot known signal generation unit 701 to the equalization synthesis unit 107 of the first embodiment. With the addition of the L-th pilot known signal generation unit 701, the input of the weight calculation unit increases by one.

  The Lth pilot known signal generation unit 701 generates a known signal of the Lth pilot signal and outputs the known signal to the Lth pilot known signal generation unit 701.

  The weight calculation unit 702 generates the known signal mapped to the Lth pilot subcarrier generated by the Lth Pilot known signal generation unit 701 and the combined signal D (L (L) when the Lth subcarrier is a pilot subcarrier. ) Is set to reduce the error. The weight calculation unit 702 outputs the set weights to the weight multiplication units 304, 305, 306, and 307.

  According to the fourth embodiment described above, in addition to the effects obtained in the first embodiment, it is possible to perform equalization processing and diversity combining processing with high accuracy because a known signal is used. . Further, according to the fourth embodiment, by setting a weight that reduces an error from a known signal, it is possible to simultaneously correct the transmission path response.

(Fifth embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIGS. In addition, the same parts as those described in the first embodiment with reference to FIG. 1 or FIG. 3 and the third embodiment with reference to FIG.
The equalization / synthesis unit 107 of this embodiment is different from the equalization / synthesis unit 107 of the first embodiment in that the selection units 3-1 and 3-2 are different and the L-th pilot known signal generation unit 502 is newly added. It is different to have.

The selection unit 802 inputs M Lth pilot subcarriers and Lth pilot known signals corresponding to the number of antennas. In the present embodiment, the selection unit 802 inputs X1 (L), X2 (L), and X3 (L). The selection unit 802 compares the input pilot subcarrier with the pilot known signal input from the L-th pilot known signal generation unit 502, and selects at least two pilot subcarriers in which the error is reduced in ascending order. In addition, selection section 802 outputs designation information designating which pilot subcarrier having the smallest error is one of M L-th pilot subcarriers to selection sections 801 and 803. In the example of FIG. 8, the selection unit 802 selects two pilot subcarriers (for example, X1 (L) and X2 (L)) having the smallest error and the pilot subcarrier having the second smallest error. . The smaller the error, the better the signal quality referred to in the first embodiment.
The selection units 801 and 803 receive the designation information from the selection unit 802 and select the data subcarrier corresponding to the number indicated by the designation information.

  Specifically, the selection unit 802 receives signals with the Nth (for example, N = 1) antenna among M = 3 Lth pilot subcarriers X1 (L), X2 (L), and X3 (L). When it is detected that the error from the known signal of the L-th pilot subcarrier is the smallest, the designation information of N = 1 is output to selection sections 801 and 803. Selection section 801 selects subcarrier X1 (L-1) received by N = 1st antenna among M = 3 L-1st subcarriers, and selection section 801 selects M = 3. The subcarrier X1 (L + 1) received by the N = 1st antenna among the (L + 1) th subcarriers is selected.

Next, details of the selection unit 802 will be described with reference to FIG. Device parts similar to those described with reference to FIG. 6 in the third embodiment are assigned the same reference numerals, and description thereof is omitted.
The selection unit 802 includes an error calculation unit 601, a minimum error detection unit 901, and a selector 603.

  Minimum error detection section 901 receives a plurality of errors detected by error calculation section 601, and detects a pilot subcarrier corresponding to the smallest error among these. Next, the minimum error detection unit 901 detects the smallest error among the errors corresponding to the pilot subcarriers excluding the pilot subcarrier corresponding to the smallest error. As a result, the minimum error detection unit 901 can detect two pilot subcarriers (for example, X1 (L) and X2 (L)) having the smallest error and the pilot subcarrier having the second smallest error. . Further, minimum error detection section 901 outputs information indicating the detected two pilot subcarriers to selector 603. Further, minimum error detection section 901 outputs information indicating pilot subcarriers corresponding to the smallest error to selection sections 801 and 803.

  In the fifth embodiment described above, in addition to the effects obtained in the first embodiment, since a known signal is used, it is possible to perform equalization processing and diversity combining processing with high accuracy. Further, according to the fifth embodiment, since the signal quality of adjacent subcarriers is close, the data quality of data subcarriers with high signal quality can be changed by substituting the signal quality of data subcarriers with the signal quality of adjacent pilot subcarriers. It becomes possible to select.

(Sixth embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIG. In addition, the same device parts as those described in the first embodiment with reference to FIG. 1 or FIG.
The equalization / synthesis unit 107 of this embodiment is different from the equalization / synthesis unit 107 of the first embodiment in that it includes maximum level selection units 1001 and 1002 instead of the selection units 301 and 303.

  Maximum level selection section 1001 inputs M L−1th data subcarriers corresponding to the number of antennas. Since M = 3 in this embodiment, X1 (L-1), X2 (L-1), and X3 (L-1) are input. Maximum level selection section 1001 measures the signal level of the input data subcarrier, and selects at least one of the data subcarriers having the maximum signal level. In the example of FIG. 10, the maximum level selection unit 1001 selects one data subcarrier (for example, X1 (L−1)) having a high signal level.

  Maximum level selection section 1002 inputs M L + 1-th data subcarriers corresponding to the number of antennas. In this embodiment, since M = 3, X1 (L + 1), X2 (L + 1), and X3 (L + 1) are input. Maximum level selection section 1002 measures the signal level of the input data subcarrier, and selects at least one of the data subcarriers having the maximum signal level. In the example of FIG. 10, the maximum level selection unit 1002 selects one data subcarrier (for example, X1 (L + 1)) having a high signal level.

  According to the sixth embodiment described above, in addition to the effects obtained in the first embodiment, when a specific subcarrier is selected from M predetermined subcarriers in other embodiments. Since the processing required for selection is easier than this, the amount of processing can be reduced.

(Seventh embodiment)
The equalization synthesis unit 107 of this embodiment will be described with reference to FIG. In addition, the same device parts as those described in the first embodiment with reference to FIG. 1 or FIG.
The equalization synthesis unit 107 of this embodiment is different from the equalization synthesis unit 107 of the first embodiment in place of the selection units 301, 302, and 303, and the minimum error selection units 1101, 1102, 1103, and the (L-1) th. A difference is that a data temporary determination signal generation unit 1104, an Lth data temporary determination signal generation unit 1105, and an L + 1th data temporary determination signal generation unit 1106 are newly provided.

  The (L-1) th data provisional determination signal generation unit 1104 receives the output signal X1 (L-1) of the FFT 104, and provisionally determines the symbol of the (L-1) th data subcarrier. Then, the (L-1) th data tentative determination signal generation unit 1104 outputs the tentatively determined symbol to the minimum error selection unit 1101.

  The Lth data temporary determination signal generation unit 1105 receives the output signal X1 (L) of the FFT 105, and temporarily determines the symbol of the Lth data subcarrier. Then, the Lth data provisional determination signal generation unit 1105 outputs the provisionally determined symbol to the minimum error selection unit 1102.

  The (L + 1) th data provisional determination signal generation unit 1106 receives the output signal X1 (L + 1) of the FFT 106, and provisionally determines the symbol of the (L + 1) th data subcarrier. Then, the (L + 1) th data provisional determination signal generation unit 1106 outputs the provisionally determined symbol to the minimum error selection unit 1103.

  Minimum error selection section 1101 receives M L−1th data subcarriers corresponding to the number of antennas. Since M = 3 in this embodiment, X1 (L-1), X2 (L-1), and X3 (L-1) are input. The minimum error selection unit 1101 calculates an error between the tentatively determined symbol input from the L−1th data tentative determination signal generation unit 1104 and each of the M L−1th data subcarriers. At least one data subcarrier is selected from the smallest. The minimum error selection unit 1101 is, for example, M = 3 L−1th data subcarriers X1 (L−1), X2 (L−1), and X3 (L−1) and the temporarily determined symbols. The error is calculated, and at least one data subcarrier (for example, X1 (L-1)) is selected from the one with the smallest error.

  Minimum error selection section 1102 inputs M Lth pilot subcarriers corresponding to the number of antennas. In this embodiment, since M = 3, X1 (L), X2 (L), and X3 (L) are input. Minimum error selection section 1102 calculates an error between the tentatively determined symbol input from Lth data tentative determination signal generation section 1105 and each of the M Lth pilot subcarriers, and the error is the smallest. At least two pilot subcarriers are selected. For example, the minimum error selection unit 1102 calculates an error between M = 3 L-th pilot subcarriers X1 (L), X2 (L), and X3 (L) and the tentatively determined symbol. At least two data subcarriers (for example, X1 (L), X2 (L)) are selected from the smallest.

  Minimum error selection section 1103 inputs M L + 1-th data subcarriers corresponding to the number of antennas. In this embodiment, since M = 3, X1 (L + 1), X2 (L + 1), and X3 (L + 1) are input. The minimum error selection unit 1103 calculates an error between the tentatively determined symbol input from the L + 1th data tentative determination signal generation unit 1106 and each of the M L + 1th data subcarriers, and the error is the smallest. At least one data subcarrier is selected. For example, the minimum error selection unit 1103 calculates an error between M = 3 L + 1-th data subcarriers X1 (L + 1), X2 (L + 1), and X3 (L + 1) and the tentatively determined symbol. At least one data subcarrier (for example, X1 (L + 1)) is selected from the smallest.

  The weight calculation unit 1107 compares the input combined signal with the tentatively determined symbol generated by the Lth data tentative determination signal generation unit 1104 so that the error between the combined signal and the tentatively determined symbol is minimized. Calculate the weight. Further, the weight calculation unit 1107 may calculate a weight such that an error between the synthesized signal and the tentatively determined symbol is smaller than a predetermined threshold value. Further, the weight calculation unit 1107 outputs weights prepared in advance to the respective weight multiplication units 304, 305, 306, and 307 in the initial state in which no combined signal is input.

  According to the seventh embodiment described above, in addition to the effects obtained in the first embodiment, a provisional symbol determination signal generation unit is newly provided to accurately calculate the weight corresponding to the data subcarrier. Therefore, equalization performance can be improved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The block diagram which shows the outline of the OFDM demodulation apparatus concerning embodiment of this invention. The figure for demonstrating the format of the OFDM signal used by embodiment of this invention. The block diagram of the equalization synthetic | combination part of the OFDM demodulation apparatus concerning the 1st Embodiment of this invention. The block diagram of the equalization synthetic | combination part of the OFDM demodulation apparatus concerning the 2nd Embodiment of this invention. The block diagram of the equalization synthetic | combination part of the OFDM demodulator concerning the 3rd Embodiment of this invention. FIG. 6 is a block diagram of a minimum error selection unit in FIG. 5. The block diagram of the equalization synthetic | combination part of the OFDM demodulator concerning the 4th Embodiment of this invention. The block diagram of the equalization synthetic | combination part of the OFDM demodulator concerning the 5th Embodiment of this invention. The block diagram of the selection part 3-2 of FIG. The block diagram of the equalization synthetic | combination part of the OFDM demodulator concerning the 6th Embodiment of this invention. The block diagram of the equalization synthetic | combination part of the OFDM demodulator concerning the 7th Embodiment of this invention.

Explanation of symbols

101, 102, 103 ... antenna, 104, 105, 106 ... FFT, 107 ... equalization synthesis unit, 108 ... determination unit, 301, 302, 303 ... selection unit, 304, 305, 306, 307 ... weight multiplication unit, 308 Synthesizer, 309 ... weight calculator, 401 ... weight multiplier, 402 ... weight calculator, 501 ... minimum error selector, 502 ... L-th pilot known signal generator, 601 ... error calculator, 602 ... minimum error detection , 603... Selector, 701... L-th pilot known signal generation unit, 702... Weight calculation unit, 801, 802, 803 ... selection unit, 901... Minimum error detection unit, 1001, 1002. , 1103... Minimum error selection unit, 1104... L−1th data tentative determination signal generation unit, 1105. Determination signal generating unit, 1106 ... L + 1 th data temporary decision signal generating unit, 1107 ... weight calculator.

Claims (7)

In an OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more),
M (M is an integer of 2 or more) antennas that receive the OFDM signal;
M Fourier transform units connected in a one-to-one correspondence with the M antennas, and each Fourier transform unit extracts K subcarriers from the received signal received by the corresponding antenna. M Fourier transform units;
Determination means for determining whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier;
When the Lth subcarrier is determined to be a data subcarrier by the determination means, the weight closest to the Lth data subcarrier is used as a weight for performing equalization processing on the Lth data subcarrier. Setting means for setting the same value as the weight for performing equalization processing on the arranged pilot subcarriers;
When the determination means determines that the Lth subcarrier is a pilot subcarrier,
Pilot subcarrier selection means for selecting at least two pilot subcarriers with higher signal quality from M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units;
First subcarrier selection means for selecting one data subcarrier having the highest signal quality from M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units. When,
Second subcarrier selection means for selecting one data subcarrier having the highest signal quality from M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units;
Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight. ,
Combining means for combining the multiplied pilot subcarriers and data subcarriers;
An OFDM demodulating apparatus comprising: a calculating unit that calculates the weight so that an error between a synthesized signal synthesized by the synthesizing unit and a certain known signal is minimized. In an OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more),
M (M is an integer of 2 or more) antennas that receive the OFDM signal;
M Fourier transform units connected in a one-to-one correspondence with the M antennas, and each Fourier transform unit extracts K subcarriers from the received signal received by the corresponding antenna. M Fourier transform units;
Determination means for determining whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier;
When the Lth subcarrier is determined to be a data subcarrier by the determination means, the weight closest to the Lth data subcarrier is used as a weight for performing equalization processing on the Lth data subcarrier. Setting means for setting the same value as the weight for performing equalization processing on the arranged pilot subcarriers;
When the determination means determines that the Lth subcarrier is a pilot subcarrier,
Pilot subcarrier selection means for selecting at least two pilot subcarriers with higher signal quality from M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units;
First subcarrier selection means for selecting one data subcarrier having the highest signal level from M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units. When,
Second subcarrier selecting means for selecting one data subcarrier having the highest signal level from M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units;
Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight. ,
Combining means for combining the multiplied pilot subcarriers and data subcarriers;
An OFDM demodulating apparatus comprising: a calculating unit that calculates the weight so that an error between a synthesized signal synthesized by the synthesizing unit and a certain known signal is minimized.   3. The pilot subcarrier selection means selects all of the M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units. The OFDM demodulator according to 1. In an OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more),
M (M is an integer of 2 or more) antennas that receive the OFDM signal;
M Fourier transform units connected in a one-to-one correspondence with the M antennas, and each Fourier transform unit extracts K subcarriers from the received signal received by the corresponding antenna. M Fourier transform units;
Determination means for determining whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier;
When the L-th subcarrier is determined to be a data subcarrier by the determination means, the weight is used to perform equalization processing on the L-th subcarrier, and is placed at a position closest to the L-th subcarrier. Setting means for setting the same value as the weight for performing equalization processing on the pilot subcarriers,
When the determination means determines that the Lth subcarrier is a pilot subcarrier,
Signal generating means for generating a known signal to be mapped to the Lth pilot subcarrier;
A pilot subcarrier that selects at least two pilot subcarriers having a smaller error from the known signal from M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units. A selection means;
First subcarrier selection means for selecting one data subcarrier having the highest signal quality from M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units. When,
Second subcarrier selection means for selecting one data subcarrier having the highest signal quality from M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units;
Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight. ,
Combining means for combining the multiplied pilot subcarriers and data subcarriers;
An OFDM demodulating apparatus comprising: a calculating unit that calculates the weight so that an error between a synthesized signal synthesized by the synthesizing unit and a certain known signal is minimized. In an OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more),
M (M is an integer of 2 or more) antennas that receive the OFDM signal;
M Fourier transform units connected in a one-to-one correspondence with the M antennas, and each Fourier transform unit extracts K subcarriers from the received signal received by the corresponding antenna. M Fourier transform units;
Determination means for determining whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier;
When the Lth subcarrier is determined to be a data subcarrier by the determination means, the weight closest to the Lth data subcarrier is used as a weight for performing equalization processing on the Lth data subcarrier. Setting means for setting the same value as the weight for performing equalization processing on the arranged pilot subcarriers;
When the determination means determines that the Lth subcarrier is a pilot subcarrier,
Signal generating means for generating a known signal to be mapped to the Lth pilot subcarrier;
A pilot subcarrier that selects at least two pilot subcarriers having a smaller error from the known signal from M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units. A selection means;
Of the M pilot subcarriers, the pilot subcarrier having the smallest error from the known signal is selected from the M Lth pilot subcarriers included in the subcarriers output from the M Fourier transform units. Information generating means for generating designation information for designating whether or not,
One piece of data corresponding to the pilot subcarrier having the smallest error based on the designation information, from the M L-1th data subcarriers included in the subcarriers output from the M Fourier transform units. First subcarrier selection means for selecting a subcarrier;
One data subcarrier corresponding to the pilot subcarrier having the smallest error based on the designation information from M L + 1th data subcarriers included in the subcarriers output from the M Fourier transform units Second subcarrier selection means for selecting
Multiplication means for multiplying each pilot subcarrier selected by the pilot subcarrier selection means and each data subcarrier selected by the first and second subcarrier selection means by a predetermined weight. ,
Combining means for combining the multiplied pilot subcarriers and data subcarriers;
An OFDM demodulating apparatus comprising: a calculating unit that calculates the weight so that an error between a synthesized signal synthesized by the synthesizing unit and a certain known signal is minimized. Signal generating means for generating a known signal mapped to the Lth pilot subcarrier;
6. The OFDM demodulator according to claim 4, wherein the calculating unit calculates the weight so that an error between the combined signal combined by the combining unit and the known signal is minimized. . In an OFDM demodulator for demodulating an OFDM signal including K subcarriers including pilot subcarriers (K is an integer of 2 or more),
M (M is an integer of 2 or more) antennas that receive the OFDM signal;
M Fourier transform units connected in a one-to-one correspondence with the M antennas, and each Fourier transform unit extracts K subcarriers from the received signal received by the corresponding antenna. M Fourier transform units;
Determination means for determining whether the L (L is an integer satisfying 1 ≦ L ≦ K) th subcarrier is a pilot subcarrier or a data subcarrier;
When the determination means determines that the Lth subcarrier is a data subcarrier,
First determination means for determining temporary symbols of M L-th data subcarriers included in the subcarriers output from the M Fourier transform units;
Second determination means for determining a temporary symbol of M L-1 th data subcarriers included in the subcarriers output from the M Fourier transform units;
Third determining means for determining a temporary symbol of M L + 1-th data subcarriers included in the subcarriers output from the M Fourier transform units;
From the M Lth data subcarriers included in the subcarriers output from the M Fourier transform units, at least two pieces of data from the one with the smaller error from the temporary symbol of the Lth data subcarrier. First subcarrier selection means for selecting a subcarrier;
One with the smallest error from the M-1 L-1th data subcarriers included in the subcarriers output from the M Fourier transform units to the temporary symbol of the L-1st data subcarrier Second subcarrier selection means for selecting the data subcarriers;
One data subcarrier having the smallest error from the M + 1 L + 1th data subcarrier included in the M subcarriers output from the M Fourier transform units with the provisional symbol of the L + 1th data subcarrier. Third subcarrier selection means for selecting
Multiply each first subcarrier selected by the first subcarrier selection means and each data subcarrier selected by the second and third subcarrier selection means by a predetermined weight. Multiplying means to
Combining means for combining the multiplied data subcarriers;
An OFDM demodulator comprising: a calculating unit that calculates the weight so that an error between a combined signal combined by the combining unit and a temporary symbol of the Lth data subcarrier is minimized. .

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