JP2010272978A - Radio reception device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio reception device that is improved in reception performance by diversity effect even when a fault or error occurs to reliability information depending on states of a propagation path etc. <P>SOLUTION: The radio reception device includes a tentative hard determination unit provided by a plurality of antennas and making a hard determination on a reception signal received from the antenna by a multicarrier system, a selection unit which selects a synthesis method between a maximum ratio synthesis method or equal-gain synthesis method, and a selective synthesis method in accordance with determination results of tentative hard determination units, and a synthetic signal switching unit which outputs a signal synthesized from reception signals by the synthesis method selected by the selection unit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio reception apparatus that improves reception performance by reception diversity.

  In multicarrier communication using a plurality of antennas, a radio reception apparatus that suppresses a decrease in signal-to-noise ratio (Signal to Noise ratio) of a received signal due to reception diversity weights the received signal. The received signal is synthesized. As a received signal combining method, any one of a selection combining method (Selection Combining; SC), an equal gain combining method (EC), and a maximum ratio combining method (Maximum Ratio Combining; MRC) is used. The receiving device is communicating.

  In particular, the maximum ratio combining method has a higher effect of suppressing a decrease in the S / N ratio than the selective combining method and the equal gain combining method, and is often used in a radio receiving apparatus using reception diversity (Patent Document 1). . In the maximum ratio combining method, reliability information (CN ratio (Carrier to Noise ratio), channel response value, correlation value, etc.) is estimated, a weighting factor is calculated based on the estimated reliability information, and a plurality of antennas are calculated. Weighting is performed on the signals received from the respective weighting coefficients calculated, and the weighted signals are synthesized.

JP-A-11-205208

  However, reliability information (CN ratio, correlation value, etc.) used as a weighting factor used in the maximum ratio combining method is based on the maximum ratio combining method when an error or error occurs in the reliability information due to the condition of the propagation path of the received signal. There is a problem that the diversity effect may not be sufficiently obtained.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a radio reception apparatus that improves reception performance by a diversity effect even when an error or error occurs in reliability information due to a situation such as a propagation path. It is to provide.

  (1) In order to solve the above problem, the present invention is provided with each of a plurality of antennas, and performs a hard decision on a received signal received from the antenna by a multicarrier method, and the temporary hard decision unit A selection unit that selects a combination method from a maximum ratio combining method or equal gain combining method and a selection combining method according to the determination result of each determination unit, and a combination from the received signal by a combining method selected by the selecting unit And a combined signal switching unit that outputs the received signal.

  (2) Further, in the present invention described above, in the above-described invention, when the determination result of each of the provisional hard determination units does not match, the selection unit calculates the magnitude of the channel response estimation value calculated for each of the plurality of antennas. According to the method, a signal received from one of the plurality of antennas is selected.

  (3) Further, according to the present invention, in the above-described invention, the selection unit has a determination result of each of the plurality of antennas that does not match a determination result of each of the provisional hard determination units. When the difference between the values exceeds a predetermined reference value, the selective combining method is selected.

  (4) Further, in the present invention according to the present invention, the selection unit calculates a signal strength for each signal received from the plurality of antennas when the determination results of the temporary hard determination units do not match. In addition, a notch is detected, and a signal received from any one of the plurality of antennas is selected according to the calculated signal strength and the notch detection result.

  (5) Further, in the present invention described above, in the above-described invention, when the determination results of the temporary hard determination units do not match, the selection unit receives the received signal for each signal received from the plurality of antennas, etc. A difference between the post-equalization signal and the determination result of the temporary hard decision unit, that is, an equalization error is calculated, and a signal received from any one of the plurality of antennas is selected according to the calculated equalization error It is characterized by doing.

  (6) Further, according to the present invention, in the above-described invention, the selection unit does not match the determination results of the temporary hard determination units, and the magnitude of the equalization error calculated for each of the plurality of antennas When the difference between the two exceeds a predetermined reference value, the selective combining method is selected.

  According to the present invention, even if an error or error occurs in reliability information due to a situation such as a propagation path, it is possible to improve reception performance due to reception diversity effect by a plurality of antennas.

1 is a schematic block diagram showing a configuration of a wireless reception device 100 in a first embodiment. It is a flowchart which shows operation | movement of the radio | wireless receiver 100 in this embodiment. It is a schematic block diagram which shows the structure of the radio | wireless receiver 200 in 2nd Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless receiver 300 in 3rd Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless receiver 400 in 4th Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless receiver 500 in 5th Embodiment.

  Hereinafter, a wireless receiver according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, the radio reception apparatus will be described using an example in which reception is performed using an OFDM (Orthogonal Frequency Division M Multiplexing) scheme as a multicarrier scheme.

<First Embodiment>
FIG. 1 is a schematic block diagram illustrating the configuration of the wireless reception device 100 according to the first embodiment. As shown in FIG. 1A, a radio receiving apparatus 100 includes antennas 101 and 102, receiving units 103 and 104, FFT (Fast Fourier Transform) units 105 and 106, and a channel response estimating unit 107. , 108, coefficient multipliers 110, 111, 114, 115, MRC (Maximum Ratio Combining) coefficient calculator 109, spectrum combiner 112, and SC (Selection Combining) coefficient calculator. Unit 113, branch selection unit 116, combined signal switching unit 117, and selection unit 120.

The receiving unit 103 down-converts a signal received via the connected antenna 101 to a baseband frequency, and outputs a digital signal obtained by analog-digital conversion of the down-converted signal to the FFT unit 105. Similarly to the reception unit 103, the reception unit 104 converts a signal received via the connected antenna 102 into a digital signal and outputs the digital signal to the FFT unit 106. The FFT unit 105 performs FFT on the digital signal output from the receiving unit 103, converts a time domain signal into a frequency domain signal, calculates a modulation symbol, and uses the calculated modulation symbol as a coefficient multiplier 110, 114. Output to. Similar to FFT section 105, FFT section 106 calculates a modulation symbol from the digital signal output from receiving section 104, and outputs the calculated modulation symbol to coefficient multiplication sections 111 and 115.
Here, the modulation symbol is, for example, modulation data such as QPSK (Quadrature Phase Shift Keying) or 16QAM (16 Quadrature Amplitude Modulation) assigned to each subcarrier. That is.

Channel response estimation section 107 estimates the channel response for each subcarrier from the pilot symbols included in the signal output from FFT section 105, and estimates channel response estimation value H1 (k) for each subcarrier (k = 1, 2, ..., K; indicates a subcarrier number). Similarly to channel response estimation section 107, channel response estimation section 108 estimates the channel response for each subcarrier from the pilot symbols included in the signal output from FFT section 106, and estimates channel response estimation value H2 for each subcarrier ( k) is calculated.
Here, the channel response estimated values H1 (k) and H2 (k) are values represented by complex numbers indicating transmission path characteristics. In addition, the antenna 101, the reception unit 103, and the FFT unit 105, and the antenna 102, the reception unit 104, and the FFT unit 106 each form a branch in the wireless reception device 100. That is, the wireless reception device 100 according to the present embodiment has a configuration having two branches.

  The MRC coefficient calculation unit 109 uses the channel response estimation value H1 (k) calculated by the channel response estimation unit 107 and the channel response estimation value H2 (k) calculated by the channel response estimation unit 108 in the maximum ratio combining. In order to maximize the value, the weight coefficient Wmrc1 (k) for the modulation symbol output from the FFT unit 105 and the weighting coefficient Wmrc2 (k) for the modulation symbol output from the FFT unit 106 are subdivided using generally known methods. The calculation is performed for each carrier, the calculated weighting factor Wmrc1 (k) is output to the coefficient multiplier 110, and the calculated weighting factor Wmrc2 (k) is output to the coefficient multiplier 111.

Coefficient multiplying section 110 multiplies the modulation symbol output from FFT section 105 and the weighting coefficient Wmrc1 (k) output from MRC coefficient calculating section 109 for each subcarrier, and performs weighting modulated by weighting coefficient Wmrc1 (k). The symbol is output to spectrum synthesis section 112. Similar to coefficient multiplication section 110, coefficient multiplication section 111 multiplies the modulation symbol output from FFT section 106 and weighting coefficient Wmrc2 (k) output from MRC coefficient calculation section 109 for each subcarrier, and weighting coefficient Wmrc2 The modulation symbol weighted by (k) is output to spectrum synthesis section 112.
The spectrum combining unit 112 combines the weighted modulation symbols output from the coefficient multiplying units 110 and 111 by addition for each subcarrier, and outputs the combined modulation symbol to the combined signal switching unit 117.

The SC coefficient calculation unit 113 equalizes the received signal that is distorted due to frequency selective fading or the like in the propagation path, so that the channel response estimation values H1 (k) and H2 ( k), weighting factors Wsc1 (k) and Wsc2 (k) are calculated for each subcarrier. Further, the SC coefficient calculation unit 113 outputs the calculated weighting coefficient Wsc1 (k) to the coefficient multiplication unit 114, and outputs the calculated weighting coefficient Wsc2 (k) to the coefficient multiplication unit 115.
Here, the weight coefficient Wsc1 (k) calculated by the SC coefficient calculation unit 113 is the reciprocal (1 / H1 (k)) of the channel response estimated value H1 (k), and the weight coefficient Wsc2 (k) is the channel response. It is the reciprocal (1 / H2 (k)) of the estimated value H2 (k).

Coefficient multiplication section 114 multiplies the modulation symbol output from FFT section 105 and the weight coefficient Wsc1 (k) output from SC coefficient calculation section 113 for each subcarrier, and branches the equalization modulation symbol to branch selection section 116. Output to. Similar to coefficient multiplication section 114, coefficient multiplication section 115 multiplies the modulation symbol output from FFT section 106 and the weight coefficient Wsc2 (k) output from SC coefficient calculation section 113 for each subcarrier to equalize. The modulated symbols are output to the branch selection unit 116.
Under the control of the selection unit 120, the branch selection unit 116 selects either the modulation symbol output from the coefficient multiplication unit 114 or the modulation symbol output from the coefficient multiplication unit 115 for each subcarrier, and switches the combined signal. Output to the unit 117.
The combined signal switching unit 117 selects and selects one of the modulation symbol output from the spectrum combining unit 112 and the modulation symbol output from the branch selection unit 116 for each subcarrier under the control of the selection unit 120. The modulation symbol is output to a signal processing unit (not shown).

The selection unit 120 determines the maximum ratio according to the channel estimation response values H1 (k) and H2 (k) calculated by the channel response estimation units 107 and 108 and the modulation symbols equalized by the coefficient multiplication units 114 and 115. Control for determining whether to select a combining method or a selective combining method for each subcarrier, and selecting a modulation symbol output from the spectrum combining unit 112 when the maximum ratio combining method is selected. When the selective combining method is selected, control is performed to cause the combined signal switching unit 117 to select the modulation symbol output from the branch selecting unit 116.
Further, when selecting and combining the selection combining method, the selection unit 120 determines, for each subcarrier, which modulation symbol to be selected from the modulation symbols output from the FFT units 105 and 106 having different antennas receiving signals. Then, the branch selection unit 116 is controlled to select a modulation symbol according to the determination result.

FIG. 1B is a schematic block diagram illustrating the configuration of the selection unit 120. As illustrated, the selection unit 120 includes a channel response estimated value comparison unit 121, provisional hardness determination units 122 and 123, and a provisional hardness determination result comparison unit 124.
Channel response estimated value comparison section 121 determines the magnitudes of channel response estimated value H1 (k) calculated by channel response estimating section 107 and channel response estimated value H2 (k) calculated by channel response estimating section 107 as subcarriers. Compare each. Further, channel response estimation value comparison section 121 causes branch selection section 116 to select a modulation symbol output from coefficient multiplication section 114 when channel response estimation value H1 (k) is larger than channel response estimation value H2 (k). Take control.

Further, channel response estimation value comparison section 121 controls branch selection section 116 to select the modulation symbol output from coefficient multiplication section 115 when channel response estimation value H1 (k) is equal to or smaller than channel response estimation value H2 (k). do.
Here, the magnitudes of the channel response estimation values H1 (k) and H2 (k) are, for example, the channel response estimation values H1 (k) and H2 (k) represented by complex numbers multiplied by the respective complex conjugates. It is a value (real number).

The provisional hard decision unit 122 performs a hard decision on the modulation symbol output from the coefficient multiplication unit 114 and outputs a hard decision result to the provisional hard decision result comparison unit 124. Similarly to the temporary hard decision unit 122, the temporary hard decision unit 123 performs a hard decision on the modulation symbol output from the coefficient multiplication unit 115 and outputs the hard decision result to the temporary hard decision result comparison unit 124.
The temporary hardness determination result comparison unit 124 compares the hard determination result output by the temporary hardness determination unit 122 and the hard determination result output by the temporary hardness determination unit 123 for each subcarrier. When the modulation symbol output from the synthesis unit 112 is selected by the synthesis signal switching unit 117 and does not match, the modulation signal output from the branch selection unit 116 is selected by the synthesis signal switching unit 117.

FIG. 2 is a flowchart illustrating the operation of the wireless reception device 100 according to this embodiment.
First, in radio receiving apparatus 100, provisional hard decision units 122 and 123 make a hard decision for each equalized modulation symbol (step S101).
The temporary hardness determination result comparison unit 124 determines, for each subcarrier, whether or not the hard determination result of the temporary hardness determination unit 122 matches the hard determination result of the temporary hardness determination unit 123 (step S102).

When the determination results of the preliminary hardness determination units 122 and 123 match (step S102: Yes), the selection unit 120 selects reception diversity by the maximum ratio combining method, and the spectrum combining unit 112 is added to the combined signal switching unit 117. A modulation symbol to be output is selected (step S103).
When the determination results of the provisional hardness determination units 122 and 123 do not match (step S102: No), the selection unit 120 selects reception diversity by the selective combining method, and the branch selection unit 116 outputs to the combined signal switching unit 117. The modulation symbol to be selected is selected (step S104).

  The radio receiving apparatus 100 performs the above-described steps S101 to S104 for each subcarrier or for each predetermined frequency section, and uses one of the maximum ratio combining method and the selective combining method to receive the reception performance by the reception diversity effect. To improve.

  As described above, when the hard decision results of the two branches (reception systems) are different, that is, when an error or error occurs in the reliability information depending on the situation such as the propagation path, the wireless reception device 100 uses the maximum ratio combining method. Instead, diversity reception by the selective combining method is performed. In the reception state where the hard decision results of the two branches are different, the diversity effect by the maximum ratio combining method is significantly reduced due to the difference that occurs in the channel estimation response values of the two antennas. In such a case, the wireless reception device 100 can improve the reception performance by obtaining the diversity effect by the selective combining method that can improve the reception performance as compared with the maximum ratio combining method.

  In addition, when the radio reception apparatus 100 selects the selective combining method, which one of the two branches is selected depends on which of the channel response estimation values H1 (k) and H2 (k) of each branch is larger. Select a branch. By selecting according to the magnitude of the channel response estimation value, for example, it is possible to reduce the influence of noise power in selecting a branch as compared with the case where a signal having a high signal strength is selected.

<Second Embodiment>
FIG. 3 is a schematic block diagram illustrating a configuration of the wireless reception device 200 according to the second embodiment. As illustrated in FIG. 3A, the wireless reception device 200 includes antennas 101 and 102, reception units 103 and 104, FFT units 105 and 106, channel response estimation units 107 and 108, and an MRC coefficient calculation unit 109. A coefficient multiplier 110, 111, 114, 115, a spectrum synthesizer 112, an SC coefficient calculator 113, a branch selector 116, a synthesized signal switching unit 117, and a selector 220.

  Compared with the wireless reception device 100 (FIG. 1) of the first embodiment, the wireless reception device 200 includes a selection unit 220 instead of the selection unit 120, and the selection unit 220 includes FFT units 105 and 106. The difference is that the modulation symbols to be output and the equalized modulation symbols output from the coefficient multipliers 114 and 115 are input. Moreover, in the radio | wireless receiver 200, about the same structure as the radio | wireless receiver 100 of 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The selection unit 220 determines whether to select the maximum ratio combining method or the selection combining method according to the output signals of the FFT units 105 and 106 and the modulation symbols equalized by the coefficient multiplying units 114 and 115. Judge for each carrier. When the selection unit 220 determines to select the maximum ratio combining method, the selection unit 220 performs control to cause the combined signal switching unit 117 to select the modulation symbol output from the spectrum combining unit 112.

  If the selection unit 220 determines to select the selective combining method, the selecting unit 220 controls the combined signal switching unit 117 to select the modulation symbol output from the branch selecting unit 116. Further, when selecting and combining the selection combining method, the selection unit 220 determines which modulation symbol is selected for each subcarrier from among the modulation symbols output from the FFT units 105 and 106 having different antennas receiving signals. Control is performed so that the branch selection unit 116 selects a modulation symbol in accordance with the determination result.

  As illustrated in FIG. 3B, the selection unit 220 includes a notch detection unit 221, provisional hardness determination units 122 and 123, and a provisional hardness determination result comparison unit 124. The notch detection unit 221 calculates the signal strength for the modulation symbols output from the FFT units 105 and 106, and the modulation symbols of adjacent subcarriers for the modulation symbols output from the FFT units 105 and 106, respectively. , The notch that changes sharply due to frequency selective fading, in particular, sharply decreases, is detected. Here, the signal strength of a modulation symbol is, for example, a value (real number) obtained by multiplying a modulation symbol represented by a complex number by their complex conjugate.

  Further, when the notch detection unit 221 detects a notch in the modulation symbol output from the FFT unit 105, the notch detection unit 221 causes the branch selection unit 116 to select the modulation symbol output from the coefficient multiplication unit 115 for the subcarrier corresponding to the notch. Further, when the notch detection unit 221 detects a notch in the modulation symbol output from the FFT unit 106, the notch detection unit 221 causes the branch selection unit 116 to select the modulation symbol output from the coefficient multiplication unit 114 for the subcarrier corresponding to the notch.

  In addition, the notch detection unit 221 detects the signal strength of the modulation symbol output from the FFT unit 105 and the modulation symbol output from the FFT unit 106 when no notch is detected in any of the modulation symbols output from the FFT units 105 and 106. When the signal strength of the modulation symbol output from the FFT unit 105 is large, the modulation symbol output from the FFT unit 105 is selected by the branch selection unit 116 and the modulation symbol output from the FFT unit 106 is selected. When the signal strength of the symbol is high, the branch selection unit 116 is controlled to select the modulation symbol output from the FFT unit 106.

  With the above-described configuration, the radio reception apparatus 200 uses the maximum ratio combining method when the hard decision results of the two branches (reception systems) are different, that is, when an error or error occurs in the reliability information depending on the situation such as the propagation path. Instead, diversity reception by the selective combining method is performed. At this time, the notch detection unit 221 provided in the selection unit 220 detects whether or not a notch exists in the received signal spectrum of each branch, and selects a modulation symbol that does not correspond to the notch that degrades reception performance. Therefore, even when the selective combining method is used instead of the maximum ratio combining method, it is possible to prevent the diversity reception performance from being deteriorated.

In addition, when the hard decision results of the two branches (reception systems) are different, and when notches are not detected in all branches, the selection unit 220 selects a branch according to the reception intensity of each modulation symbol. Thereby, the radio | wireless receiver 200 can improve receiving performance by selecting a branch with high reliability.
Note that, in the wireless reception device 200, when notches are not detected, one of the two branches is selected depending on the signal strength. However, as in the wireless reception device 100 of the first embodiment, the channel response estimation value is selected. It is good also as a structure selected by.

<Third Embodiment>
FIG. 4 is a schematic block diagram illustrating a configuration of the wireless reception device 300 according to the third embodiment. As illustrated in FIG. 4A, the wireless reception device 300 includes a selection unit 320 instead of the selection unit 120 as compared to the wireless reception device 100 (FIG. 1) of the first embodiment, and the selection unit 120. The equalization modulation symbols output from the coefficient multiplication units 114 and 115 are input to the selection unit 320 provided instead of the channel response estimation values output from the channel response estimation units 107 and 108. Is different. Further, in the wireless reception device 300, the same reference numerals are given to the same components as those of the wireless reception device 100 of the first embodiment or the wireless reception device 200 of the second embodiment, and the description thereof is omitted.

The selection unit 320 determines, for each subcarrier, whether to select the maximum ratio combining method or the selection combining method according to the modulation symbols equalized by the coefficient multiplying units 114 and 115, and determines the maximum ratio combining method. When selecting, the control is performed to cause the combined signal switching unit 117 to select the modulation symbol output from the spectrum combining unit 112, and when selecting the selection combining method, the modulation symbol output from the branch selecting unit 116 is combined with the combined signal switching unit. The control which makes 117 select is performed.
Further, when selecting and combining the selection combining method, the selection unit 320 determines, for each subcarrier, which modulation symbol to be selected from the modulation symbols output from the FFT units 105 and 106 having different antennas that receive the signals. Then, the branch selection unit 116 is controlled to select a modulation symbol according to the determination result.

  As shown in FIG. 4B, the selection unit 320 includes a temporary hardness determination units 122 and 123, a temporary hardness determination result comparison unit 124, equalization error calculation units 321 and 322, and an equalization error comparison unit 323. Is provided. The equalization error calculation unit 321 receives the modulation symbol equalized from the coefficient multiplication unit 114, calculates the error included in the modulation symbol with respect to the hard decision result output from the temporary hard decision unit 122, and calculates the error The error is output to the equalization error comparison unit 323. Similar to the equalization error calculation unit 321, the equalization error calculation unit 322 receives the modulation symbol equalized from the coefficient multiplication unit 115 and outputs the modulation symbol corresponding to the hard decision result output from the temporary hard decision unit 123. The error included in is calculated, and the calculated error is output to the equalization error comparison unit 323.

  The equalization error comparison unit 323 compares the magnitudes of errors output from the equalization error calculation units 321 and 322, and if the error output from the equalization error calculation unit 321 is smaller, the coefficient multiplication unit 114 Control that causes the branch selection unit 116 to select the modulation symbol to be output, and causes the branch selection unit 116 to select the modulation symbol output from the coefficient multiplication unit 115 when the error output from the equalization error calculation unit 322 is smaller do. Here, the magnitude of the error is, for example, a value (real number) obtained by multiplying the difference (complex number) between the hard decision result and the equalization error signal by the complex conjugate thereof.

  With the above-described configuration, the wireless reception device 300 can perform maximum ratio combining when the hard decision results of the two branches (reception systems) are different, that is, when an error or error occurs in reliability information depending on the situation such as a propagation path. Diversity reception by the selective combining method is performed instead of the method. At this time, when the selection combining method is selected by the operation of the selection unit 320, the modulation symbol of the branch having a small difference (error) with respect to the hard decision result, that is, the equalization error is small. By selecting a modulation symbol, the diversity effect by the selective combining method can be improved.

<Fourth embodiment>
FIG. 5 is a schematic block diagram illustrating the configuration of the wireless reception device 400 according to the fourth embodiment. As illustrated in FIG. 5A, the wireless reception device 400 includes a selection unit 420 instead of the selection unit 120 as compared with the wireless reception device 100 (FIG. 1) of the first embodiment, and the selection unit 120. The selection unit 420 provided instead of is input with the equalized modulation symbols output from the coefficient multiplication units 114 and 115, and is not input with the channel response estimation values output from the channel response estimation units 107 and 108. Is different. In the wireless reception device 400, the same components as those of the wireless reception devices 100, 200, and 300 of the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted.

  As with the selection unit 320 of the third embodiment, the selection unit 420 determines whether to select the maximum ratio combining method or the selection combining method according to the modulation symbols equalized by the coefficient multiplication units 114 and 115. Judge for each carrier. In addition, when the selection unit 420 determines to select the maximum ratio combining method, the selection unit 420 controls the combined signal switching unit 117 to select the modulation symbol output from the spectrum combining unit 112.

  In addition, when the selection unit 420 determines to select the selection / combination method, the selection unit 420 performs control to cause the composite signal switching unit 117 to select the modulation symbol output from the branch selection unit 116. In addition, when the selection unit 420 determines to select the selective combining method, the selection unit 420 determines which modulation symbol is selected from among the modulation symbols output from the FFT units 105 and 106 having different antennas that receive the signals. A determination is made for each carrier, and control is performed so that the branch selection unit 116 selects a modulation symbol according to the determination result.

As illustrated in FIG. 5B, the selection unit 420 includes a temporary hardness determination units 122 and 123, an equalization error calculation unit 321 and 322, an equalization error comparison unit 423, and a temporary hardness determination result comparison unit 424. And a switching determination unit 425.
Similar to the equalization error comparison unit 323 (FIG. 4) of the third embodiment, the equalization error comparison unit 423 determines the equalization error output from the equalization error calculation units 321 and 322 for each subcarrier. If the error output from the equalization error calculation unit 321 is smaller, the modulation symbol output from the coefficient multiplication unit 114 is selected by the branch selection unit 116, and the error output from the equalization error calculation unit 322 When the value is smaller, control is performed to cause the branch selection unit 116 to select the modulation symbol output from the coefficient multiplication unit 115. Further, the equalization error comparison unit 423 calculates the difference in the magnitude of the equalization error output from the equalization error calculation units 321 and 322, and outputs the calculated difference to the switching determination unit 425.

The temporary hard decision result comparison unit 424 compares the hard decision result output from each of the temporary hard decision units 122 and 123 for each subcarrier, and generates a hard decision coincidence signal indicating whether or not they match. Output to.
The switching determination unit 425 receives the hard decision coincidence signal from the provisional hard decision result comparison unit 424 and the difference in the magnitude of the equalization error from the equalization error comparison unit 423. In addition, the switching determination unit 425 indicates that the hard determination match signal indicates that the hard determination results of the provisional hard determination units 122 and 123 do not match, and the difference in equalization error output from the equalization error comparison unit 423 is different. When the value is larger than the predetermined reference value, control is performed to cause the combined signal switching unit 117 to select the modulation symbol output from the branch selection unit 116. In other words, in this case, the switching determination unit 425 selects the selective synthesis method.

  Further, when the hard decision coincidence signal indicates that the hard decision results of the provisional hard decision units 122 and 123 match, the switching determination unit 425 converts the modulation symbol output from the spectrum synthesis unit 112 into the combined signal switching unit 117. When the hard decision coincidence signal indicates a mismatch of the hard decision results of the temporary hard decision units 122 and 123 and the difference in equalization error output by the equalization error comparison unit 423 is equal to or less than a predetermined reference, Control is performed to cause the combined signal switching unit 117 to select the modulation symbol output from the spectrum combining unit 112. That is, in this case, the switching determination unit 425 selects the maximum ratio combining method.

  As described above, when the hard decision results of the two branches (reception systems) are different, that is, when an error or error occurs in the reliability information depending on the situation such as the propagation path, the wireless reception device 400 uses the maximum ratio combining method. Instead, diversity reception by the selective combining method is performed. In the reception state where the hard decision results of the two branches are different, the diversity effect by the maximum ratio combining method is significantly reduced due to the difference that occurs in the channel estimation response values of the two antennas. In such a case, the wireless reception device 400 can improve the reception performance by obtaining the diversity effect by the selective combining method that can improve the reception performance than the maximum ratio combining method.

  Furthermore, when the selection unit 420 operates as described above, the wireless reception device 400 determines in advance a difference in error between the hard decision results of the two branches even if the hard decision results of the two branches are different. In other words, the error included in the modulation symbols of the two branches is small, and the reliability information used in the maximum ratio combining method is also small. Compared to the wireless reception device 300 of the third embodiment, It is possible to increase the opportunity to select the maximum ratio combining method and improve the reception performance due to the diversity effect.

<Fifth Embodiment>
FIG. 6 is a schematic block diagram illustrating a configuration of a wireless reception device 500 according to the fifth embodiment. As illustrated in FIG. 6A, the wireless reception device 500 is different from the wireless reception device 100 (FIG. 1) of the first embodiment in that a selection unit 520 is provided instead of the selection unit 120. In the wireless reception device 500, the same components as those of the wireless reception devices 100 to 400 already described are denoted by the same reference numerals and description thereof is omitted.

Similar to the selection unit 120 of the first embodiment, the selection unit 520 uses the channel estimation response values H1 (k) and H2 (k) calculated by the channel response estimation units 107 and 108, the coefficient multiplication units 114 and 115, and the like. Whether to select the maximum ratio combining method or the selective combining method is determined for each subcarrier according to the converted modulation symbol.
If the selection unit 520 determines that the maximum ratio combining method is to be selected, the selection unit 520 controls the combined signal switching unit 117 to select the modulation symbol output from the spectrum combining unit 112.

  When the selection unit 520 determines to select the selective combining method, the selecting unit 520 controls the combined signal switching unit 117 to select the modulation symbol output from the branch selecting unit 116. Further, when it is determined that the selection combining method is selected, the selection unit 520 determines whether one of the modulation symbols output from the FFT units 105 and 106 having different antennas receiving the signals is selected. A determination is made for each carrier, and control is performed so that the branch selection unit 116 selects a modulation symbol according to the determination result.

As illustrated in FIG. 6B, the selection unit 520 includes provisional hardness determination units 122 and 123, a provisional hardness determination result comparison unit 424, a channel response estimated value comparison unit 521, and a switching determination unit 525.
The channel response estimated value comparison unit 521 calculates a difference in magnitude between the channel response estimated values H1 (k) and H2 (k) output from the channel response estimation units 107 and 108, and the calculated difference is determined as a switching determination unit. Output to 525. Further, the channel response estimation value comparison unit 521 compares the channel response estimation values H1 (k) and H2 (k) output from the channel response estimation units 107 and 108 and compares the channel response estimation values H1 (k). Is larger, the modulation symbol output from the coefficient multiplier 114 is selected by the branch selector 116, and when the channel response estimation value H2 (k) is larger, the modulation symbol output from the coefficient multiplier 115 is selected. The branch selection unit 116 is controlled to select.

  The switching determination unit 525 includes a hard decision coincidence signal from the provisional hard decision result comparison unit 424 and a difference in magnitude between the channel response estimation value comparison unit 521 and the channel response estimation values H1 (k) and H2 (k). Entered. In addition, the switching determination unit 525 indicates that the hard determination position signal does not match the hard determination results of the provisional hard determination units 122 and 123, and the channel response estimated value comparison unit 521 outputs the channel response estimated value H1. When the difference in magnitude between (k) and H2 (k) is larger than a predetermined reference value, the combined signal switching unit 117 is made to select the modulation symbol output from the branch selection unit 116. In other words, in this case, the switching determination unit 525 selects the selective synthesis method.

Further, when the hard decision coincidence signal indicates that the hard decision results of the temporary hard decision units 122 and 123 match, the switching determination unit 525 outputs the modulation symbol output from the spectrum combining unit 112 to the combined signal switching unit 117. Channel response estimation values H1 (k), H2 output from the channel response estimation value comparison unit 521, and the hard decision match signal indicates that the hard decision results of the provisional hard decision units 122 and 123 do not match. (K) When the difference between the sizes is equal to or smaller than a predetermined reference value, control is performed to cause the combined signal switching unit 117 to select a modulation symbol output from the spectrum combining unit 112. That is, in this case, the switching determination unit 525 selects the maximum ratio combining method.

  As described above, when the hard decision results of the two branches (reception systems) are different, that is, when an error or error occurs in the reliability information depending on the situation such as the propagation path, the wireless reception device 500 uses the maximum ratio combining method. Instead, diversity reception by the selective combining method is performed. In the reception state where the hard decision results of the two branches are different, the diversity effect by the maximum ratio combining method is significantly reduced due to the difference that occurs in the channel estimation response values of the two antennas. In such a case, the wireless reception device 500 can improve the reception performance by obtaining the diversity effect by the selective combining method that can improve the reception performance than the maximum ratio combining method.

  Furthermore, when the selection unit 520 operates as described above, the wireless reception device 500 determines the difference in channel response estimation values between the two branches in advance even if the hard decision results of the two branches are different. When it is smaller than the reference value, that is, when the two branches are in the reception state with the same degree of reliability, the maximum ratio combining method is selected by selecting the maximum ratio combining method as compared with the radio receiving apparatus 100 of the first embodiment. Can increase the reception performance due to the diversity effect.

In the first to fifth embodiments described above, the wireless communication terminal has been described with the configuration including two antennas, but may be configured with three or more antennas.
In the first to fifth embodiments described above, the configuration using the maximum ratio combining method has been described. However, the equal gain combining method may be used instead of the maximum ratio combining method.

  In the first to fifth embodiments described above, either the maximum ratio combining method or the selective combining method is selected for each subcarrier. However, the frequency is configured by a plurality of adjacent subcarriers. A configuration may be made by selecting either the maximum ratio combining method or the selective combining method for each section. For example, when a frequency section is composed of N adjacent subcarriers, when the hard decision results of two branches (reception systems) differ for N / 2 or more subcarriers, the received spectrum in the corresponding frequency section One of the maximum ratio combining method and the selective combining method is selected according to the presence or absence of the notch, the channel response estimation value, and the equalization error.

  In the first to fifth embodiments described above, whether or not the hard decision results performed by the temporary hard decision result comparison units 124 and 424 match is determined by whether or not the modulation symbols match completely. For example, when 16QAM (16 Quadrature Amplitude Modulation), 16QAM, 256QAM, or the like is used, the same quadrant from the first quadrant to the fourth quadrant on the IQ plane is used. You may determine by the modulation symbol as a determination result mapping.

  The wireless reception device described above may have a computer system inside. In that case, the processing of the above-described coefficient multiplier, MRC coefficient calculator, SC coefficient calculator, spectrum synthesizer, branch selector, and selector is stored in a computer-readable recording medium in the form of a program. The above processing is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  A signal can be received by a plurality of antennas and applied to a movable or fixed receiving apparatus.

100, 200, 300, 400, 500 ... wireless receivers 101, 102 ... antenna 103, 104 ... receiving unit 105, 106 ... FFT unit 107, 108 ... channel response estimating unit 109 ... MRC coefficient calculating unit 110, 111, 114, DESCRIPTION OF SYMBOLS 115 ... Coefficient multiplication part 112 ... Spectrum synthesis part 113 ... SC coefficient calculation part 116 ... Branch selection part 117 ... Synthetic signal switching part 120, 220, 320, 420, 520 ... Selection part 121, 521 ... Channel response estimated value comparison part 122 , 123 ... Temporary hard decision unit 124, 424 ... Preliminary hard decision result comparison unit 221 ... Notch detection unit 321, 322 ... Equalization error calculation unit 323, 423 ... Equalization error comparison unit 425, 525 ... Switching judgment unit

Claims (6)

A provisional hard decision unit that is provided for each of a plurality of antennas and performs a hard decision on a received signal received from the antenna by a multicarrier scheme;
A selection unit that selects a synthesis method from a maximum ratio synthesis method or an equal gain synthesis method and a selection synthesis method according to the determination result of each of the temporary hard decision units,
A wireless signal receiving apparatus comprising: a combined signal switching unit that outputs a signal combined from the received signal by a combining method selected by the selecting unit. The selection unit includes:
If the determination results of the provisional hard decision units do not match, a signal received from one of the plurality of antennas is selected according to the magnitude of the channel response estimation value calculated for each of the plurality of antennas. The wireless receiver according to claim 1, wherein: The selection unit includes:
When the determination results of the temporary hardening determination units do not match and the difference in channel response estimation value calculated for each of the plurality of antennas exceeds a predetermined reference value, the selective combining method The radio reception apparatus according to claim 2, wherein the radio reception apparatus is selected. The selection unit includes:
When the determination results of the temporary determination units do not match, for each signal received from the plurality of antennas, the signal strength is calculated, the notch is detected, and the calculated signal strength and the notch detection result are determined. The radio reception apparatus according to claim 1, wherein a signal received from any one of the plurality of antennas is selected. The selection unit includes:
If the determination results of each of the temporary determination units do not match, for each signal received from the plurality of antennas, the difference between the equalized signal of the received signal and the determination result of the preliminary determination unit, that is, an equalization error The radio reception apparatus according to claim 1, wherein a signal received from any one of the plurality of antennas is selected according to the calculated equalization error. The selection unit includes:
When the determination results of the temporary hardening determination units do not match and the difference between the equalization errors calculated for each of the plurality of antennas exceeds a predetermined reference value, the selective combining method is performed. The radio reception apparatus according to claim 5, wherein the radio reception apparatus is selected.

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