CN101911557B - Reception processing method and reception device - Google Patents

Abstract

A reception device has the frequency outside the frequency band sandwiched between the highest frequency and the lowest frequency among the frequencies of subcarriers belonging to a first subcarrier group to which known signals are transmitted, respectively, performs a control of lowering the reliability of the signal after propagation path compensation for a first subcarrier belonging to a second subcarrier group to which the data signals to which propagation path compensation is applied on the basis of the known signals are transmitted, respectively than the reliability of the signal after propagation path compensation for a second subcarrier having the frequency inside the frequency band and belonging to the second subcarrier group, and corrects an error in the signal after the propagation path compensation for the first and second subcarriers.

Description

Receiving processing method and receiving device

technical field

The present invention relates to a receiving processing method and a receiving device. For example, the present invention can be used in multi-carrier communications such as OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiplexing Access, Orthogonal Frequency Division Multiplexing Access). the

Background technique

In wireless communication, a signal sent from a transmitter reaches a receiver through multiple propagation paths (multipath). Therefore, the signal observed by the receiver may be affected by multipath fading and become a waveform with a distorted amplitude or phase. One of means for correcting such distortion is coherent detection, which uses a pilot signal (also referred to as a reference signal), which is a known signal between a transmitter and a receiver. the

In a wireless communication system that performs coherent detection, a pilot signal is transmitted from a transmitter, the known received signal is used in a receiver to estimate (channel estimate) a propagation path response (propagation path value), and the propagation path estimated value is used The propagation path compensation of the data signal is performed. Therefore, when the error of the propagation path estimation value is large, the propagation path compensation of the data signal will be affected, and the error rate of the data signal will increase. the

In addition, as a type of wireless communication system in recent years, a system in which multi-carrier transmission such as OFDM and OFDMA capable of achieving high frequency utilization efficiency is known. the

OFDM (or OFDMA) is a technique for transmitting signals using a plurality of orthogonal subcarriers. In OFDM, channel estimation values are generated for each subcarrier, and channel compensation (equalization) of data signals is performed using the channel estimation values for data signals mapped to subcarriers. the

For example, in an OFDM receiver (hereinafter also referred to as an OFDM receiver), an effective symbol component is detected from a received signal, the detection timing is set as FFT (Fast Fourier Transform, Fast Fourier Transform) timing, and an FFT is performed on the effective symbol deal with. Thus, the received signal is converted from the time domain to a signal in the frequency domain. the

The OFDM receiver detects a pilot signal (mapped subcarrier) from the FFT-processed frequency domain signal, uses the pilot signal to perform propagation path estimation, and performs propagation path compensation for the data signal. the

Then, the OFDM receiver obtains, for example, a log likelihood ratio (LLR: Log Likelihood Ratio), which is one of reliability information of received signal symbols used for error correction, for the data signal after the propagation path compensation, and uses This information is used to correct errors in received signal symbols. the

Here, when the transmission environment is a multipath environment, usually due to frequency selective fading, the phase and amplitude of the propagation path estimation value differ for each subcarrier. In the following Patent Document 1, regarding the case where the amount of multipath delay spread is large, it is pointed out that the fading variation between adjacent subcarriers increases. The weighting of the likelihood ratio (LLR) is used to improve the effect of error correction. the

Patent Document 1: Japanese Patent No. 3594828

In the prior art described above, there is no consideration that there are subcarriers in the communication band (for example, subcarriers at the end of the communication band and its vicinity) that can be used to obtain propagation path estimation The number of pilot signals of the value is less than that of other subcarriers, and the accuracy of the obtained propagation path estimation value is more likely to deteriorate than that of other subcarriers. the

Contents of the invention

One of the objects of the present invention is to improve the error rate characteristics of received signals in consideration of the presence of such subcarriers. the

In addition, without being limited to the aforementioned object, another object of the present invention is to realize the effect derived from each structure shown in the best mode for carrying out the invention described later, that is, an effect that cannot be obtained by the prior art. the

For example, the scheme described below is employed. the

(1) A receiving processing method may be adopted. In the receiving processing method of a receiving device corresponding to multiple carriers, the receiving device receives a first subcarrier group and a second subcarrier group, and the first subcarrier group corresponds to Transmitting a plurality of subcarriers of a known signal for obtaining an estimated propagation path value, the second subcarrier group corresponds to transmitting a data signal subjected to propagation path compensation based on the estimated propagation path value obtained using the known signal, respectively. a plurality of subcarriers, the reception processing method is characterized in that it includes the following steps: performing control so that the reliability of the signal after propagation path compensation related to the first subcarrier is higher than the reliability of the signal after propagation path compensation related to the second subcarrier The reliability of the signal is low, the first subcarrier has a frequency other than a frequency band sandwiched between the highest frequency and the lowest frequency among frequencies of subcarriers belonging to the first subcarrier group, and belongs to the The second subcarrier group, the second subcarrier has a frequency within the frequency band and belongs to the second subcarrier group, based on the reliability of the control, for the first subcarrier and the The signal after propagation path compensation of the second subcarrier is subjected to error correction processing. the

(2) In addition, a reception processing method may also be adopted: generate an estimated propagation path value for each subcarrier according to a known received signal in a predetermined communication frequency band, and use the estimated propagation path value to map to any subcarrier Perform propagation path compensation on the received data signal, obtain the reliability information of the received data signal after the propagation path compensation, and perform weighting control, for the known received signal used to obtain the propagation path estimated value The number of subcarriers is smaller than that of other subcarriers, the weight of the reliability information obtained about these subcarriers is smaller than the weight of the reliability information obtained about other subcarriers, and the reliability information after the weight control is used to perform the Error correction of received data signals. the

(3) Wherein, the target of the weight control may be the reliability information obtained for the subcarrier at the end of the communication frequency band or the subcarrier and its nearby subcarriers. the

(4) In addition, the weight control may be such that the weight of subcarriers closer to the end of the communication band is reduced. the

(5) In addition, the weight control may be control such that the closer the subcarrier group is to the subcarrier at the end of the communication band, the lower the weight is. the

(6) Here, the number of subcarriers to be subjected to the weighting control may be controlled based on the measurement result of the multipath delay spread of the received signal. the

(7) In addition, the weighting coefficient used in the weighting control may be controlled based on the measurement result of the multipath delay spread amount of the received signal. the

(8) Furthermore, the weighting coefficient used in the weighting control may be controlled based on the measurement result of the reception quality information of the received signal. the

(9) In addition, in the case where the subcarriers mapped to the known received signal change with time, the subcarriers that are the object of the weight control can be controlled according to the respective mapping states and used in the weight control Either or both of the weighting coefficients. the

(10) Furthermore, when there are a plurality of subcarrier groups in the communication frequency band with one or more subcarriers not to be transmitted interposed therebetween, the weight control is performed for each subcarrier group. the

(11) In addition, a receiving device may be used. Among the receiving devices corresponding to multi-carriers, the receiving device receives the first subcarrier group and the second subcarrier group. The first subcarrier group corresponds to the The second subcarrier group corresponds to a plurality of subcarriers of a known signal from which a propagation path estimation value is obtained, and a plurality of subcarriers for transmitting a data signal subjected to propagation path compensation based on a propagation path estimation value obtained using the known signal, respectively. , the receiving apparatus includes: a control unit that performs control such that the reliability of a signal after propagation path compensation related to the first subcarrier is lower than the reliability of a signal after propagation path compensation related to the second subcarrier, the first subcarrier has a frequency other than a frequency band sandwiched between a highest frequency and a lowest frequency among frequencies of subcarriers belonging to the first subcarrier group, and belongs to the second subcarrier group, The second subcarrier has a frequency in the frequency band and belongs to the second subcarrier group; The signal after propagation path compensation of the second subcarrier is subjected to error correction processing. the

(12) Furthermore, it is also possible to employ a reception device including: a propagation path estimation unit that generates a propagation path estimation value for each subcarrier based on a known received signal in a predetermined communication frequency band; and a propagation path compensation unit that performing propagation path compensation on a received data signal mapped to any subcarrier using the propagation path estimated value; a reliability information generating unit that obtains reliability information of the received data signal after the propagation path compensation; A weighting control unit that performs weighting control such that, for subcarriers for which the number of known received signals used to obtain the channel estimation value is smaller than other subcarriers, the weight ratio of the reliability information obtained on these subcarriers is about The weights of the reliability information obtained by other subcarriers are small; and an error correction unit that performs error correction of the data signal using the reliability information after the weight control. the

(13) The weight control unit may set the target of the weight control to reliability information obtained for a subcarrier at an end of the communication frequency band or the subcarrier and its adjacent subcarriers. the

(14) Furthermore, the weight control unit may perform control such that the closer the subcarriers are to the subcarriers at the ends of the communication band, the lower the weights are. the

(15) In addition, the weight control unit may perform control such that the closer the subcarrier group is to the subcarrier at the end of the communication band, the lower the weight is. the

(16) Furthermore, the weight control unit may control the number of subcarriers to be controlled by the weight based on the measurement result of the multipath delay spread amount of the received signal. the

(17) In addition, the weight control unit may control the weight coefficient used in the weight control based on the measurement result of the multipath delay spread amount of the received signal. the

(18) Furthermore, the weight control unit may control a weight coefficient used in the weight control based on a measurement result of reception quality information of a received signal. the

(19) In addition, when the subcarriers to which the known received signals are mapped vary with time, the weight control unit may control the subcarriers targeted for the weight control and the Either or both of the weighting coefficients used in the above weighting control. the

(20) Furthermore, when there are a plurality of subcarrier groups in the communication frequency band with one or more subcarriers not to be transmitted interposed therebetween, the weight control unit performs weight control for each subcarrier group. the

The invention can improve the error rate characteristic of the received signal. the

Description of drawings

FIG. 1 is a block diagram showing a configuration example of an OFDM receiver according to the first embodiment. the

FIG. 2 is a schematic diagram illustrating an example of LLR weighting processing by the LLR correction unit shown in FIG. 1 . the

FIG. 3 is a schematic diagram illustrating a first modified example of LLR weighting processing by the LLR correction unit shown in FIG. 1 . the

FIG. 4 is a schematic diagram illustrating a second modified example of LLR weighting processing by the LLR correction unit shown in FIG. 1 . the

FIG. 5 is a schematic diagram illustrating a third modified example of LLR weighting processing by the LLR correction unit shown in FIG. 1 . the

FIG. 6 is a schematic diagram illustrating a fourth modified example of LLR weighting processing by the LLR correction unit shown in FIG. 1 . the

Fig. 7 is a block diagram showing a configuration example of an OFDM receiver according to the second embodiment. the

FIG. 8 is a schematic diagram illustrating an example of LLR weighting processing by the LLR correction unit shown in FIG. 7 . the

FIG. 9 is a schematic diagram illustrating a first modified example of LLR weighting processing by the LLR correcting unit shown in FIG. 7 . the

Fig. 10 is a block diagram showing a configuration example of an OFDM receiver according to the third embodiment. the

FIG. 11 is a schematic diagram illustrating an example of LLR weighting processing by the LLR correction unit shown in FIG. 10 . the

FIG. 12 is a schematic diagram illustrating an example of LLR weighting processing in the fourth embodiment. the

FIG. 13 is a schematic diagram illustrating an example of LLR weighting processing in the sixth embodiment. the

FIG. 14 is a schematic diagram illustrating an example of LLR weighting processing in the seventh embodiment. the

FIG. 15 is a schematic diagram illustrating an example of simulation. the

FIG. 16 is a graph showing an example of a simulation result. the

FIG. 17 is a schematic diagram showing how pilot signals and data signals are mapped to subcarriers in a communication frequency band. the

FIG. 18 is a schematic diagram showing an example of a received signal corresponding to the transmitted signal shown in FIG. 17 . the

FIG. 19 is a schematic diagram showing a situation in which propagation path estimation of a data signal is performed based on the pilot signal shown in FIG. 17 . the

FIG. 20 is a schematic diagram showing a case where propagation channel estimation is performed by averaging pilot signals of a plurality of subcarriers in the frequency domain of the communication band. the

Label description

10 OFDM receiver; 11 receiving antenna; 12 wireless section; 13 ADC (Analog to DigitalConverter, analog-to-digital converter); 14 timing synchronization section; 15 FFT (Fast FourierTransformer, Fast Fourier Transformer); 16 propagation path estimation section; 17 Propagation Path Compensation Section; 18 LLR Calculation Section; 19 LLR Correction Section; 20 Error Correction Section; 21 Delay Spread Measurement Section; 22 SNR (Signal to Noise Ratio, Signal to Noise Ratio) Measurement Section. the

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples, and should not be understood as excluding various modifications or technical applications not shown below. That is, the present invention can be implemented with various modifications (combination of the respective embodiments, etc.) without departing from the gist thereof. the

(A) Brief description

In a radio communication system utilizing multicarriers such as OFDM (or OFDMA), pilot signals may be mapped and transmitted while limiting a part of subcarriers (frequencies). For example, FIG. 17 shows that in a predetermined communication frequency band, a pilot signal is mapped every two subcarriers (in order to distinguish it from a data signal, an arrow is given to the pilot signal. The same applies hereafter), and the pilot signal Case where the signal is multiplexed with a data signal (no arrows) that does not contain a pilot signal. In this case, data signals may be mapped to subcarriers at the ends of the communication band instead of pilot signals. the

This multiplexed signal is received by the receiver as a signal whose phase and amplitude are changed as shown in FIG. 18, for example, from the transmitter through a multipath fading channel. the

In the receiver, as described above, in order to compensate the propagation path of the data signal, the propagation path estimation is performed using the pilot signal. As an example, FIG. 19 shows a case where propagation path estimation of a data signal (no arrow) is performed based on the pilot signal (arrow) shown in FIG. 17 . the

For example, the propagation path estimation value of the subcarrier to which the data signal is mapped can be obtained by performing linear interpolation on the propagation path estimation value obtained from two pilot signals mapped to adjacent subcarriers. the

Here, as shown in FIG. 19 , when the subcarrier mapped to the end of the communication band is not a pilot signal, the channel estimation value of the subcarrier can be obtained, for example, by extrapolation. the

However, since extrapolation uses a smaller number of pilot signals than interpolation, the accuracy of channel estimation values tends to deteriorate. Therefore, when a data signal is mapped to a subcarrier at the end of the communication band, as a result, channel estimation values that are less accurate than other channel estimation values are used for this channel compensation. As a result, the accuracy of the LLR of the data signal after propagation path compensation also deteriorates, resulting in an increase in the error rate at the time of error correction, and sometimes sufficient reception performance cannot be obtained. the

Also, even when the pilot signal is mapped to all subcarriers in the communication band, subcarriers at the ends of the communication band may not be able to obtain sufficient reception performance compared with other subcarriers. the

For example, as shown in FIG. 20 , consider a received signal in which pilot signals are mapped to all subcarriers in the communication band. When performing channel estimation for a certain subcarrier, channel estimation may be performed by averaging pilot signals of surrounding subcarriers. the

Its purpose is to obtain high-precision propagation path estimation by averaging a plurality of pilot signals by taking advantage of the tendency that the correlation of propagation path estimation values of surrounding subcarriers becomes high when the amount of multipath delay spread is small value. the

For example, it is considered that one subcarrier on each side of the subcarrier to be channel estimated is taken as an object of averaging (that is, the average of a total of three subcarriers is obtained). In this case, the average of 3 subcarriers can be performed for the center of the communication frequency band, and the average of only 2 subcarriers can be performed for both ends of the communication frequency band. the

In this case, the accuracy of channel estimation values for subcarriers at both ends of the communication band tends to be lower than the accuracy of channel estimation values for other subcarriers. Therefore, in this case, the error rate of the data signal also increases, and sometimes sufficient reception performance cannot be obtained. the

In other words, for subcarriers for which the number of pilot signals used to obtain channel estimation values is smaller than other subcarriers, the accuracy of LLR obtained therefrom is lower than that of other subcarriers. the

Therefore, in the present embodiment, for subcarriers whose number of pilot signals used for propagation path estimation is less than a predetermined number, such as subcarriers at the end of the communication band, or subcarriers at the end of the communication band and its vicinity, mapping to The reliability information (LLR) of the received data signal of the subcarrier is subjected to weight control weaker than other reliability information. the

Here, a group of subcarriers corresponding to a plurality of subcarriers for respectively transmitting pilot signals used to obtain channel estimation values is set as the first subcarrier group, and channel compensation (the channel compensation is based on The subcarrier group corresponding to the plurality of subcarriers of the data signal obtained by using the propagation path estimation value obtained by the pilot signal is set as the second subcarrier group, and the object of performing the weight control at this time will be related to the following the reliability of a signal after propagation path compensation of a subcarrier having a frequency other than a frequency band sandwiched between a highest frequency and a lowest frequency among subcarriers belonging to the first subcarrier group, And belong to the second subcarrier group. the

That is, the following control is performed so that the reliability of the channel-compensated signal related to the following first subcarrier is lower than the reliability of the channel-compensated signal related to the following second subcarrier. having a frequency other than a frequency band sandwiched between a highest frequency and a lowest frequency among subcarriers belonging to the first subcarrier group, and belonging to the second subcarrier group, the second subcarrier having all frequencies within the frequency band and belong to the second subcarrier group. the

As a result, it is possible to suppress the use of low-precision LLRs for error correction, and improve the error rate characteristics of the error-corrected data signal. In addition, the term "communication band end" hereinafter includes a subcarrier having the lowest or highest frequency in the communication band, and also includes one or more subcarriers in the vicinity of the subcarrier. the

(B) The first embodiment

FIG. 1 is a block diagram showing a configuration example of an OFDM receiver according to the first embodiment. the

The OFDM receiver shown in FIG. 1 (hereinafter also referred to simply as "receiver") 10, for example, has a receiving antenna 11, a wireless unit 12, an ADC (Analog to Digital Converter, analog to digital converter) 13, a timing synchronization unit 14, FFT (Fast Fourier Transformer, Fast Fourier Transformer) 15, propagation path estimation unit 16, propagation path compensation unit 17, LLR calculation unit 18, LLR correction unit 19 and error correction unit 20. In addition, the OFDM receiver 10 can be applied to a receiving system of a wireless base station, and can also be applied to a receiving system of a wireless terminal (mobile station). the

Among them, the reception antenna 11 receives signals (OFDM symbols) transmitted from an OFDM transmitter (not shown) via multi-carriers. the

The radio unit 12 performs reception processing such as low-noise amplification, frequency conversion (down-conversion) to a baseband frequency, band limitation by a roll-off filter, and the like on the signal received by the reception antenna 11 . the

The ADC 13 converts the reception signal subjected to the reception processing by the wireless unit 12 into a digital signal. The resulting digital signal is input to the timing synchronization section 14 and FFT 15. the

The timing synchronization unit 14 detects an effective symbol component from the received signal of the digital signal obtained by the ADC 13, and outputs the detected timing to the FFT 15 as FFT timing. the

The FFT 15 performs FFT processing on the digital signal (time-domain signal) from the ADC 13 at the FFT timing output from the timing synchronization unit 14, thereby converting it into a frequency-domain signal. the

The propagation path estimation unit 16 detects, from the frequency-domain signal after the FFT processing, a subcarrier frequency component to which a pilot signal, which is a known received signal, is mapped, and estimates a propagation path with the OFDM transmitter based on the pilot signal. path, to find the estimated value of the propagation path for each subcarrier. In addition, the channel estimation value of the subcarrier to which no pilot signal is mapped can be obtained by interpolation or extrapolation. Furthermore, the channel estimation value may be obtained by averaging a plurality of pilot signals as described above. the

The propagation path compensator 17 propagates the data signal component in any of the subcarriers mapped to the subcarriers of the FFT-processed frequency domain signal using the propagation path estimation value for each subcarrier obtained by the propagation path estimation section 16. path compensation. the

The LLR calculating unit (reliability information generating unit) 18 obtains the LLR per bit for the data signal after the channel compensation is performed by the channel compensating unit 17 (this is obtained after error correction by the error correcting unit 20 (soft decision decoding) ) is a type of reliability information used when ). the

The LLR correction unit (weight control unit) 19 corrects the LLR per bit obtained by the LLR calculation unit 18 by performing weight control corresponding to subcarriers. For example, when there is a subcarrier whose number of pilot signals is smaller than the number of pilot signals used by other subcarriers when extrapolation or the like is used to obtain the channel estimation value, such as at the end of the communication band, the LLR correction unit 19 For this subcarrier, make its LLR weight lower than the LLRs obtained for other subcarriers. the

The error correcting unit 20 performs error correction of the received signal using the LLR per bit corrected (weighted) by the LLR correcting unit 19 . Here, in the LLR correcting unit 19, the LLR of the data signal subjected to channel compensation using a channel compensation value based on extrapolation (generally, the accuracy of the extrapolation is lower than that of the interpolation) is weighted so that the weight is lower than that used. Since the weighting of the LLRs of the channel-compensated data signal is performed based on the interpolated channel compensation value, it is possible to suppress deterioration of the overall error rate characteristic and obtain desired reception performance. the

Next, the operations of the OFDM receiver 10 of this example configured as described above will be described with emphasis on the propagation path compensation unit 17, the LLR calculation unit 18, and the LLR correction unit 19. the

The number of sub-carriers in the communication frequency band is expressed as N _c , and the propagation path estimation value in sub-carrier #k (wherein, 0≤k≤N _c -1) is expressed as The reception data (FFT-processed data) of subcarrier #k in the receiver 10 is denoted as r(k).

In the channel compensator 17, the distortion received by the channel is compensated for the received data r(k) of each subcarrier #k as shown in the following equation (1). the

Formula 1)

$\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Then, in the LLR computing unit 18, the signal for which propagation path compensation has been performed is Find the LLR per bit. For example, Represented by N bits, when the nth bit is expressed as b _n (k)∈{−1,+1}, the LLR is represented by the following equation (2), which is obtained by the LLR calculation unit 18 .

Formula (2)

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{\mathrm{<span\; class="notranslate">\; PR</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; PR</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In addition, P _r (X|Y) represented by this formula (2) means the probability of conditional X in Y.

The LLR correction unit 19 multiplies the LLR per bit obtained by the above formula (2) by a weighting coefficient corresponding to subcarrier #k (hereinafter also referred to as an LLR weighting coefficient). the

For example, as shown in (1) of FIG. 2 , a pilot signal is mapped to every three subcarriers in the communication frequency band, and data signals are mapped to three subcarriers at both ends of the communication frequency band. The propagation channel estimation values of the data signals of the three subcarriers at the two ends are interpolated. the

Therefore, processing represented by the following equation (3) is performed in the LLR correction unit 19 . the

Formula (3)

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

_The above-mentioned formula (3) shows that, for example, as shown in ( ₂ ) of FIG _. , multiply the weighting coefficients α ₁ , α ₂ , and α ₃ by the LLR [λ ₁ (b _n (k))] calculated according to the above formula (2).

That is, in the example shown in (2) of FIG. 2 , three subcarriers #k=0, 1, 2 (K ₁ ) LLRs are multiplied by the weighting coefficient α ₁ respectively, and for the LLRs of the three subcarriers #k=N _c -3(K ₂ ), N _c -2, and N _c -1 included in the extrapolation interval on the high frequency side, Multiplied by the weighting coefficient α ₃ respectively, the subcarriers included in the frequency domain of the remaining non-extrapolation interval (for example, the frequency domain for obtaining the estimated value of the propagation path based on interpolation (hereinafter also referred to as the interpolation interval)) The LLR of #k is multiplied by the weighting coefficient α ₂ .

This is equivalent to performing control such that the reliability of the signal after propagation path compensation related to the first subcarrier (that is, the signal in the extrapolation interval) is higher than the reliability of the signal after propagation path compensation related to the second subcarrier. degree is low, the first subcarrier has a band other than the frequency band sandwiched between the highest frequency and the lowest frequency among subcarrier frequencies belonging to the first subcarrier group (which respectively transmit pilot signals) (extrapolation interval) frequency, and belongs to the second subcarrier group (which respectively transmits data signals subjected to propagation path compensation based on pilot signals), and the second subcarrier has frequency, and belongs to the second subcarrier group. the

Among them, regarding the relationship between the weighting coefficients α ₁ and α ₃ (wherein, 0≤α ₁ , 0≤α ₃ ) of the extrapolation interval and the weighting coefficient α ₂ (wherein, 0<α ₂ ) of the interpolation interval, for example It is assumed that α ₁ <α ₂ and α ₃ <α ₂ . That is, the LLR for the extrapolation interval is multiplied by the weighting coefficients α ₁ and α ₃ smaller than the weighting coefficient α ₂ of the interpolation interval. As an example, numerical values α ₁ =0.4, α ₂ =1, and α ₃ =0.3 are set in advance. In addition, the upper limit value of α ₂ does not need to be 1. In this example, the values α ₁ =0.4, α ₂ =1, α ₃ =0.3 are set in advance, but they can also be set to double these values, for example, α ₁ =0.8, α ₂ =2, α ₃ = 0.6.

In this way, λ ₂ (b _n (k)) obtained by weighting the LLR λ ₁ (b _n (k)) obtained by the LLR calculation unit 18 by the LLR correction unit 19 is input to the error correction unit 20, whereby the error can be improved. rate characteristics.

In addition, in the above example, α ₃ <α ₁ is set, but α ₃ =α ₁ may be set, or α ₃ >α ₁ may be set.

(b1) Modification 1

In (2) of FIG. 2 , only the extrapolation interval is multiplied by a weight factor smaller than that of the interpolation interval. However, in the case of averaging the pilot signals of a plurality of subcarriers in the frequency direction as described above with reference to FIG. 20 , may contain the LLR of subcarrier #k related to the extrapolation interval. the

Therefore, it may be preferable to perform the same weighting process as the extrapolation interval for not only the extrapolation interval but also a part of the interpolation interval (the interval closer to the center of the communication band than the extrapolation interval). For example, as shown in Fig. 3 , weighting coefficients α ₁ and α ₃ smaller than α ₂ may be multiplied to an interval including a part of the interpolation interval near the extrapolation interval.

In addition, in this example, the case where extrapolation and interpolation are performed when calculating the channel estimation value is described, but as described above with reference to FIG. In the case of , the weighting process by the LLR correcting unit 19 described above can also be applied in the same way, and this point is also the same in the following description. the

(b2) Second modified example

In addition, the above example is a case where extrapolation is performed at both ends of the communication band, but there is also a case, for example, as shown in FIG. Case. In this case, as shown in the following equation (4), only the subcarrier #k on the side of the communication band for extrapolation may be multiplied by a weighting coefficient α ₁ (<α ₂ ) smaller than that of the other subcarriers.

Formula (4)

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

(b3) The third modified example

In the above example, the LLR weighting coefficients α ₁ and α ₃ of the extrapolation interval are set to be fixed (same) in the interval, but it is also possible to multiply different LLR weighting coefficients for each subcarrier or subcarriers in the extrapolation interval alpha.

For example, as shown in FIG. 5 , consider a case where the extrapolation interval is relatively long in the frequency direction. As described above, the accuracy of the channel estimation value obtained by extrapolation tends to deteriorate as it gets closer to the end of the communication band, so the LLR correction unit 19 divides the extrapolation interval into a plurality of subcarrier blocks (groups), for example, LLRs are weighted differently in some or all blocks. the

In the example in FIG. 5 , three subcarriers are extrapolated at both ends of the communication band, and three LLR weighting coefficients α ₁ , α ₂ , and α ₃ different for each subcarrier are used for the left end (low frequency side). On the other hand, the right end (high frequency side) is divided into 1 subcarrier and 2 subcarriers, and different LLR weighting coefficients α ₅ and α ₆ are used respectively. Among them, the closer the subcarrier is to the end of the communication frequency band, the smaller the LLR weighting coefficient is (α ₁ <α ₂ <α ₃ <α ₄ , α ₄ >α ₅ >α ₆ ).

(b4) Fourth modified example

In addition, in the extrapolation period, instead of changing the LLR weighting coefficient for each subcarrier, the same LLR weighting coefficient may be applied to a part of a plurality of subcarriers. For example, as shown in FIG. 6 , in the LLR correction unit 19, the segment length (the number of subcarriers) multiplied by the LLR weighting coefficient is set to L _l at the left end of the communication band and L _r at the right end. In this example, it is assumed that extrapolation is performed according to these interval lengths L _l , L _r .

In addition, L _l is divided into M _l (M _l is an integer greater than or equal to 2), and the number of subcarriers in each section of M _l is represented as N _l (1) to N _l (M _l ) (both are 1 or more Integer), L _r is also divided into M _r (M _r is an integer greater than 2), and the number of subcarriers in each interval of M _r is expressed as N _r (1)～N _r (M _r ) (all is an integer greater than 1).

Wherein, the values of M _l , N _l (1)˜N _l (M _l ), M _r , N _r (1)˜N _r (M _r ) may be preset values. For example, as shown in FIG. 6, M _l = 3, N _l (1) = 2, N _l (2) = 2, N _l (3) = 1, M _r = 2, N _r ( 1) = 2, N _r (2) = 2 and so on.

In this example, the LLR weighting coefficient applied in the N _l (1) interval is α ₁ , the LLR weighting coefficient applied in the N _l (2) interval is α ₂ , and the LLR weighting coefficient applied in the N _l (3) interval is α 1 . The weighting coefficient is α ₃ , the LLR weighting coefficient applied in the N _r (1) section is α ₅ , the LLR weighting coefficient applied in the N _r (2) section is α ₆ , and the LLR weighting coefficient with respect to the band center side α ₄ , set (0≤)α ₁ <α ₂ <α ₃ <α ₄ , and (1≥)α ₄ >α ₅ >α ₆ .

That is, in this example, the LLR correction unit 19 sets (controls) the LLR weighting coefficient applied to subcarriers closer to the end of the communication band to a smaller value. This makes it possible to effectively improve the error rate characteristics even when the channel estimation values obtained at the subcarriers closer to the ends of the communication band tend to deteriorate. the

(C) Second Embodiment

When the amount of multipath delay spread is large, the propagation path value variation between subcarriers is large, so the accuracy of the propagation path estimation value by extrapolation tends to deteriorate. Taking this into consideration, the LLR correction unit 19 may also adaptively change the M _l , N _l (1)-N l (M ₁ ), M _r , N _r (1) _{-N r} ( M _r ) (that is, the number of divisions of the extrapolation interval, the number of subcarriers included in the division interval).

Therefore, in the OFDM receiver 10 of the present embodiment, for example, as shown in FIG. To measure the delay spread amount, the LLR correction unit 19 adaptively controls the LLR weighting coefficient to be applied based on the measurement result of the delay spread measurement unit 21. the

For example, when the delay spread amount is larger than the threshold value, since the channel value variation between subcarriers is large, the closer to the band edge of the extrapolation interval, the lower the accuracy of the channel estimation value. Therefore, in an extrapolation section with a large delay spread, it is preferable to increase the number of divisions of the section and apply different LLR weighting coefficients to the divisional sections. the

On the other hand, when the delay spread is small, the accuracy of the propagation path estimation value based on extrapolation is not as bad as when the delay spread is large, so compared with the case where the delay spread is large, the extrapolation interval can be reduced The number of divisions (or no divisions), reduce the object interval to weaken the weight of LLR. the

For example, when the delay spread amount measured by the delay spread measuring unit 21 is smaller than a certain threshold or greater than a certain threshold, in the LLR correcting unit 19, two types of M _l , N _l (1) to The values of N _l (M ₁ ), M _r , N _r (1) to N _r (M _r ) are stored in a memory or the like, and the LLR correction unit 19 adaptively Toggle these values. However, the values stored in the memory are not limited to the above two.

An example thereof is shown in FIG. 8 . In addition, (1) of FIG. 8 shows a case where pilot signals are mapped every five subcarriers in the communication band, and extrapolation is performed at the interval lengths L _l and L _r at both ends of the communication band. 8(2) shows the weighting of LLRs when the delay spread measured by the delay spread measuring unit 21 is larger than the threshold, and FIG. 8(3) shows that the delay spread measured by the delay spread measuring unit 21 is The weighting of LLRs below the threshold.

That is, when the delay spread is smaller than the threshold, for example, set M _l =1, M _r =1, and reduce the number of intervals to which the LLR weighting coefficient is applied. On the other hand, when the delay spread exceeds the threshold, the extrapolation interval is divided so that M _l =3 and M _r =2, and different LLR weighting coefficients are applied to each divided interval.

In this example, the delay spread amount is used as a reference, but instead or additionally, the same processing may be performed using the variation amount of propagation path estimation values between adjacent subcarriers as a reference. the

(c1) Modification 1

As described above, the accuracy of the channel estimation value at the time of extrapolation tends to deteriorate as the delay spread increases. In the above-mentioned second embodiment, an example of adaptively controlling the application target section of the LLR weighting coefficient according to the delay spread amount was shown. In this modified example, an example is shown in which the LLR weighting coefficient to be applied by the LLR correcting unit 19 is adaptively controlled based on the delay spread amount measured by the delay spread measuring unit 21 . the

An example thereof is shown in FIG. 9 . In addition, (1) of FIG. 9 shows a case where pilot signals are mapped every three subcarriers in the communication band, and extrapolation is performed in sections at both ends of the communication band. 9(2) shows the weighting of the LLR when the delay spread amount measured by the delay spread measuring unit 21 is larger than the threshold value, and FIG. 9(3) shows that the delay spread amount measured by the delay spread measuring unit 21 is The weighting of LLRs below the threshold. the

That is, a certain threshold value is set for the delay spread amount, and if the delay spread amount σ _s ² measured by the delay spread measurement unit 21 is smaller than the threshold value, the LLR correction unit 19 sets (α ₁ , α ₂ , α ₃ )=(A ₁ ⁽¹⁾ , A ₂ ⁽¹⁾ , A ₃ ⁽¹⁾ ), if σ _s ² is above the threshold, the LLR correction unit 19 is shown in (3) of FIG. 9 Let (α ₁ , α ₂ , α ₃ )=(A ₁ ⁽²⁾ , A ₂ ⁽²⁾ , A ₃ ⁽²⁾ ). Wherein, (0≤)A ₃ ⁽¹⁾ <A ₁ ⁽¹⁾ <A ₂ ⁽¹⁾ , (0≤)A ₃ ⁽²⁾ <A ₁ ⁽²⁾ <A ₂ ⁽²⁾ . Also, A ₁ ⁽¹⁾ , A ₂ ⁽¹⁾ , A ₃ ⁽¹⁾ , A ₁ ⁽²⁾ , A ₂ ⁽²⁾ , and A ₃ ⁽²⁾ may be preset values.

In other words, the LLR correcting unit 19 controls the LLR weighting coefficients so that when the delay spread amount σ _s ² is smaller than the threshold value, the ratio of the LLR weighting coefficients at both ends of the communication band to the LLR weighting coefficient at the center of the communication band is large, and the delay spread σ When _s ² is above the threshold, the ratio is small. Such control can be represented by, for example, the following formula (5).

Formula (5)

$\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ></span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ></span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In addition, the LLR correction unit 19 may also determine the LLR weighting coefficient as a function of the delay spread σ _s ² , for example, (α ₁ , α ₂ , α ₃ )=(f ₁ (σ _s ² ), f ₂ (σ _s ² ), f ₃ (σ _s ² )).

In addition, the above-mentioned weighting process may be performed with the variation amount of the channel estimation value between adjacent subcarriers as a reference instead of the delay spread amount or in addition. the

(D) The third embodiment

In the OFDM receiver 10, when the signal-to-noise ratio (SNR: Signal to Noise Ratio) of the received signal is low, compared with the case where the SNR is high, the accuracy of the propagation path estimation value varies over the entire communication frequency band. bad trend. In this case, LLR weighting may also not be performed. the

Therefore, in the OFDM receiver 10 of the present embodiment, for example, as shown in FIG. As for the SNR, the LLR weighting coefficient to be applied is adaptively controlled by the LLR correction unit 19 based on the SNR measured by the SNR measurement unit 22 . the

An example thereof is shown in FIG. 11 . In addition, (1) of FIG. 11 shows a case where pilot signals are mapped for every three subcarriers in the communication band, and extrapolation is performed in sections at both ends of the communication band. Moreover, (2) of FIG. 11 shows the weighting of the LLR when the SNR (γ) measured by the SNR measuring unit 22 is smaller than the threshold value, and (3) of FIG. 11 shows that the SNR (γ) measured by the SNR measuring unit 22 is The weighting of the LLR above the threshold. the

That is, a certain threshold is set for the reception SNR, and if the SNR(γ) measured by the SNR measuring unit 22 is smaller than the threshold, the LLR correcting unit 19 sets the LLR weighting coefficient to be applied as shown in (2) of FIG. 11 to be (α ₁ , α ₂ , α ₃ )=(Γ ₁ ⁽¹⁾ , Γ ₂ ⁽¹⁾ , Γ ₃ ⁽¹⁾ ), if the SNR(γ) is above the threshold, the LLR correction unit 19 as shown in FIG. 11 As shown in (3) above, it is assumed that (α ₁ , α ₂ , α ₃ )=(Γ ₁ ⁽²⁾ , Γ ₂ ⁽²⁾ , Γ ₃ ⁽²⁾ ). In addition, in the example shown in FIG. 11 , Γ ₂ ⁽¹⁾ > Γ ₁ ⁽¹⁾ > Γ ₃ ⁽¹⁾ (≥0), Γ ₂ ⁽²⁾ > Γ ₁ ⁽²⁾ > Γ ₃ ^{( 2)} (≥0). Also, Γ ₁ ⁽¹⁾ , Γ ₂ ⁽¹⁾ , Γ ₃ ⁽¹⁾ , Γ ₁ ⁽²⁾ , Γ ₂ ⁽²⁾ , Γ ₃ ⁽²⁾ may be preset values.

In other words, the LLR correction section 19 controls the LLR weighting coefficients to be applied so that the ratio of the LLR weighting coefficients on both end sides of the communication band to the LLR weighting coefficient on the center side of the communication band is large when the reception SNR is smaller than the threshold, and when the reception SNR is not less than the threshold , the ratio is small. Such control can be represented by, for example, the following formula (6). the

Formula (6)

$\frac{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ></span>\frac{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ></span>\frac{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&Gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In addition, the LLR correcting unit 19 may determine the LLR weighting coefficient to be applied as a function of SNR(γ), for example, (α ₁ , α ₂ , α ₃ )=(f ₁ (γ), f ₂ (γ), f ₃ (γ)).

(E) Fourth Embodiment

The LLR correction unit 19 may control the LLR weighting coefficient to be applied based on the measurement results of both the delay spread amount and the received SNR. The OFDM receiver 10 at this time is additionally provided with a delay spread measurement unit 21 shown in FIG. 7 and an SNR measurement unit 22 shown in FIG. 10 in addition to the configuration shown in FIG. 1 . the

In addition, in the LLR correcting unit 19, for example, the determination of the magnitude of the delay spread amount measurement result (threshold judgment) and the magnitude judgment of the SNR measurement result (threshold judgment) are performed separately, and for a total of four types [(delay spread, SNR)=(small , small), (small, large), (large, small), (large, large)] judgment results, pre-determined 4 kinds of LLR weighting coefficients (α ₁ , α ₂ , α ₃ ) values, stored in memory, etc. , multiply the LLR by the LLR weighting coefficient corresponding to any judgment result.

Fig. 12 shows an example thereof. Among them, (1) in FIG. 12 shows that in the communication band, the pilot signal is mapped every three subcarriers, and extrapolation is performed in the sections at both ends of the communication band. And, (2-1) of Fig. 12 represents that described determination result is (delay spread, SNR)=

In the case of LLR weighting when (small, small), (2-2) in FIG. 12 shows the case of LLR weighting when the determination result is (delay spread, SNR)=(small, large). Similarly, (2-3) of FIG. 12 represents the situation of LLR weighting when the determination result is (delay spread, SNR)=(large, small), and (2-4) of FIG. 12 represents that the determination result is ( The case of LLR weighting when delay spread, SNR) = (large, large). the

In addition, in the example of FIG. 12 , LLR weighting coefficients (α ₁ , α ₂ , α ₃ ) to be applied are defined as follows for the aforementioned four types of determination results.

(2-1) (delay spread, SNR) = (small, small) → (α ₁ , α ₂ , α ₃ ) = (A ₁ ⁽¹⁾ , A ₂ ⁽¹⁾ , A ₃ ⁽¹⁾ )

(2-2) (delay spread, SNR) = (small, large) → (α ₁ , α ₂ , α ₃ ) = (A ₁ ⁽²⁾ , A ₂ ⁽²⁾ , A ₃ ⁽²⁾ )

(2-3) (delay spread, SNR) = (large, small) → (α ₁ , α ₂ , α ₃ ) = (A ₁ ⁽³⁾ , A ₂ ⁽³⁾ , A ₃ ⁽³⁾ )

(2-4) (delay spread, SNR) = (large, large) → (α ₁ , α ₂ , α ₃ ) = (A ₁ ⁽⁴⁾ , A ₂ ⁽⁴⁾ , A ₃ ⁽⁴⁾ )

Among them, A ₁ ⁽ⁱ⁾ , A ₂ ⁽ⁱ⁾ , A ₃ ⁽ⁱ⁾ (i=any value in 1, 2, 3, 4) have a size relationship of A ₂ ⁽ⁱ⁾ > A ₁ ⁽ⁱ⁾ > A ₃ ⁽ⁱ⁾ (≥0).

Also, in this example, when the measured SNR is smaller than the threshold, the LLR weighting coefficient in the extrapolation section on the communication band end side is set to a slightly smaller value than the LLR weighting coefficient on the communication band center side. And, when both the measured delay spread and SNR are larger than the threshold value, the LLR weighting coefficient in the extrapolation section on the communication band end side is set to a weighting coefficient smaller than the LLR weighting coefficient on the communication band center side. the

In this way, according to this example, based on both the delay spread of the received signal and the SNR, more flexible and extremely detailed LLR weighting coefficient control can be realized, and appropriate LLR weighting control corresponding to the wireless communication environment can be realized. Improvements to the error rate feature. the

(F) Fifth Embodiment

It may be implemented by combining any of the examples in which the section to which the LLR weighting coefficient is applied is fixed/variable and any of the examples in which the above-mentioned LLR weighting coefficient is fixed/variable. the

(G) Sixth Embodiment

In an OFDM communication system, the arrangement (mapping) of pilot signals mapped to subcarriers may change over time, or the arrangement of pilot signals may differ for each cell. the

FIG. 13 shows an example of how the arrangement of pilot signals changes with time. 13 shows the following cases, (1) at a certain time T1, the pilot signal is mapped to both ends of the communication band, (2) at a certain time T2, the pilot signal is not mapped to the communication band. Both ends of the frequency band, (3) At a certain time T3, pilot signals are not mapped to both ends of the communication frequency band, and the arrangement interval of the pilot signals is also different from the time T1 and T2. the

In this way, when there are various pilot signal arrangements according to time changes, it is preferable that the LLR correction unit 19 determines (controls) the LLR weighting coefficient and any length of the section to which the LLR weighting coefficient is applied in each case as described above. one or both parties. the

For example, in the example of FIG. 13 , at time T1 of (1), since extrapolation is not performed, the LLR weighting coefficient is a fixed value in all subcarriers of the communication frequency band, and at time T2 of (2) and (3) and T3, for each extrapolation interval, different LLR weighting coefficients are applied for each subcarrier. the

In the example in Fig. 13, since the number of pilot signals in the communication frequency band at time T3 is smaller than that at time T2, and the extrapolation interval is longer, the ratio center is applied to more subcarriers at time T3 than at time T2. Small LLR weighting coefficients on the band side. the

Also, when the arrangement of the pilot signal is different for each cell, either or both of the LLR weight coefficient and the section length to which the LLR weight coefficient is applied are determined (controlled) for each cell as in the above case. the

In this way, according to this example, even when there are different pilot signal arrangements, appropriate LLR weighting control can be performed respectively, and desired reception performance can be easily ensured. the

(H) Seventh Embodiment

For example, as shown in FIG. 14, when there are one or more subcarriers that cannot be transmitted from the OFDM transmitter in the communication frequency band, and there are a plurality of subcarrier groups (blocks) across the subcarriers, each subcarrier The edge of the block, the accuracy of its propagation path estimation value is likely to be worse than that of the non-edge part. the

Therefore, the LLR correction unit 19 can independently apply and determine (control) either or both of the above-mentioned LLR weighting coefficients and the section lengths to which the LLR weighting coefficients are applied, in units of such subcarrier blocks. the

(I) Simulation results

FIG. 16 shows an example of the results of measuring the error rate characteristics by the LLR correction described above using computer simulation. The measurement results are based on the assumption that 2×2 MIMO (Multi-Input Multi-Output), 64QAM, coding rate (Coding Rate) = 3/4, and the transmission environment is a 6-ray Typical Urban Model (6-ray Typical Urban Model) measurement results. the

In this simulation, for example, the pilot arrangement shown in FIG. 15 is used, and pilot signals are inserted at intervals of 6 subcarriers. And, the pilot signal is inserted only in the first OFDM symbol and the fifth OFDM symbol within one slot (=7 OFDM symbols). In addition, an OFDM symbol refers to a signal unit in which a part of an effective symbol is cyclically copied and added as a guard interval (GI) (also referred to as a cyclic prefix (CP)) to the effective symbol. the

The interval for extrapolation is assumed as follows. For the 1st OFDM symbol, extrapolation is performed on 1 subcarrier on the left side (low frequency side) of the communication frequency band and 5 subcarriers on the right side (high frequency side) of the communication frequency band. For the 5th OFDM symbol , extrapolation is performed on 4 subcarriers on the left side of the communication frequency band and 2 subcarriers on the right side of the communication frequency band. the

Therefore, in this simulation, the above-described LLR weighting by the LLR correction unit 19 is performed for the four subcarriers on the left side of the band and the five subcarriers on the right side of the band. The LLR weighting coefficient is set to 1 for the center side of the frequency band and 0.3 for both ends. the

In this case, as for the OFDM symbols (the 2nd to 4th, 6th, and 7th OFDM symbols in the slot) that do not insert pilot signals, the estimation accuracy of the propagation path at the end of the communication band is also poor, so the Same LLR weighting factor. the

According to FIG. 16, by applying the LLR correction of this example, the SNR required when the frame error rate (FER: Frame Error Rate) = 0.1 can be improved by approximately 6 dB (refer to 200) compared to the conventional one (refer to 100). . the

Claims (16)

1. A reception processing method of a receiving device corresponding to multi-carriers, the receiving device receives a first subcarrier group and a second subcarrier group, the first subcarrier group corresponds to the signals respectively transmitted for obtaining propagation path estimation values A plurality of subcarriers of a known signal, the second subcarrier group corresponds to a plurality of subcarriers for respectively transmitting a data signal for which propagation path compensation is performed based on a propagation path estimated value obtained using the known signal, and the reception processing method is characterized by the following steps: Weighting control is performed so that the reliability of the channel-compensated signal related to the first subcarrier having a frequency band other than the following is lower than the reliability of the channel-compensated signal related to the second subcarrier frequency outside and belongs to the second subcarrier group, the second subcarrier has a frequency within the frequency band and belongs to the second subcarrier group, and the frequency band is sandwiched between the subcarriers belonging to the first subcarrier group The frequency band between the highest frequency and the lowest frequency among the frequencies of the subcarriers, based on the reliability of the weight control, performing error correction processing on the signal after propagation path compensation related to the first subcarrier and the second subcarrier, At least one of the number of subcarriers to be subjected to the weighting control and the weighting coefficient used in the weighting control is controlled based on a measurement result of a multipath delay spread amount of a received signal. 2. A method for receiving and processing in multi-carrier communication, characterized in that said method comprises the following steps: generating a propagation path estimation value for each subcarrier based on a known received signal in a predetermined communication frequency band, performing propagation path compensation on a received data signal mapped to any subcarrier using the propagation path estimated value, calculating reliability information of the received data signal after the propagation path compensation, performing weighting control such that, for subcarriers for which the number of known received signals used to obtain the propagation path estimation value is smaller than that of other subcarriers, the weight of the reliability information obtained on these subcarriers is higher than that on other subcarriers The weight of the obtained reliability information is small, performing error correction on the received data signal by using the reliability information after the weight control, The weighting coefficient used in the weighting control is controlled based on the measurement result of the reception quality information of the received signal. 3. A method for receiving and processing in multi-carrier communication, characterized in that said method comprises the following steps: generating a propagation path estimation value for each subcarrier based on a known received signal in a predetermined communication frequency band, performing propagation path compensation on a received data signal mapped to any subcarrier using the propagation path estimated value, calculating reliability information of the received data signal after the propagation path compensation, performing weighting control such that, for subcarriers for which the number of known received signals used to obtain the propagation path estimation value is smaller than that of other subcarriers, the weight of the reliability information obtained on these subcarriers is higher than that on other subcarriers The weight of the obtained reliability information is small, performing error correction on the received data signal by using the reliability information after the weight control, At least one of the number of subcarriers to be subjected to the weighting control and the weighting coefficient used in the weighting control is controlled based on a measurement result of a multipath delay spread amount of a received signal. 4. The reception processing method according to claim 3, wherein the object of the weight control is reliability information obtained for the subcarrier at the end of the communication frequency band or the subcarrier and its nearby subcarriers . 5 . The reception processing method according to claim 4 , wherein the weight control is control in which a subcarrier closer to a subcarrier at an end of the communication band is weighted smaller. 5 . 6. The reception processing method according to claim 4, wherein the weight control is control such that the closer the subcarrier group is to the subcarrier group at the end of the communication frequency band, the smaller the weight is. . 7. The reception processing method according to claim 3, characterized in that, in the case that the subcarriers mapped to the known received signal change with time, according to their respective mapping states, control Either or both of the subcarriers of and the weighting coefficients used in the weighting control. 8. The reception processing method according to claim 3, wherein when a plurality of subcarrier groups exist across the communication frequency band by one or more subcarriers not to be transmitted, the subcarrier group to implement the weighted control. 9. A receiving device corresponding to a multi-carrier, the receiving device receiving a first subcarrier group and a second subcarrier group, the first subcarrier group corresponding to the known signals used to obtain propagation path estimated values respectively transmitted a plurality of subcarriers, the second subcarrier group corresponds to a plurality of subcarriers for respectively transmitting data signals subjected to propagation path compensation based on propagation path estimation values obtained using the known signals, and the receiving apparatus is characterized in that : a weighting control unit that performs weighting control such that the reliability of a channel-compensated signal related to a first subcarrier is lower than the reliability of a channel-compensated signal related to a second subcarrier have a frequency other than the following frequency band and belong to the second subcarrier group, the second subcarrier has a frequency within the frequency band and belong to the second subcarrier group, and the frequency band is sandwiched between the a frequency band between the highest frequency and the lowest frequency among the frequencies of the subcarriers of the first subcarrier group; and an error correction unit that performs error correction processing on signals after propagation path compensation related to the first subcarrier and the second subcarrier based on the reliability of the weight control, The weighting control unit controls at least one of the number of subcarriers to be subjected to the weighting control and a weighting coefficient used in the weighting control based on a measurement result of a multipath delay spread amount of a received signal. 10. A receiving device in multi-carrier communication, the receiving device is characterized in that it has: a propagation path estimation section that generates a propagation path estimation value for each subcarrier based on a known received signal in a predetermined communication frequency band; a propagation path compensation section that performs propagation path compensation on a received data signal mapped to any one of the subcarriers using the propagation path estimated value; a reliability information generation unit that obtains reliability information of the received data signal after the propagation path compensation; a weighting control unit that performs weighting control such that, for subcarriers for which the number of known received signals used to obtain the channel estimation value is smaller than that of other subcarriers, the weights of reliability information obtained on these subcarriers are set to is less weighted than reliability information obtained on other subcarriers; and an error correction unit that performs error correction of the data signal using the reliability information after the weight control, The weighting control unit controls weighting coefficients used in the weighting control based on a measurement result of reception quality information of a received signal. 11. A receiving device in multi-carrier communication, the receiving device is characterized in that it has: a propagation path estimation section that generates a propagation path estimation value for each subcarrier based on a known received signal in a predetermined communication frequency band; a propagation path compensation section that performs propagation path compensation on a received data signal mapped to any one of the subcarriers using the propagation path estimated value; a reliability information generation unit that obtains reliability information of the received data signal after the propagation path compensation; a weighting control unit that performs weighting control to set the weight of reliability information obtained on these subcarriers for subcarriers for which the number of known received signals used to obtain the channel estimation value is smaller than that of other subcarriers is less weighted than reliability information obtained on other subcarriers; and an error correction unit that performs error correction of the data signal using the reliability information after the weight control, The weighting control unit controls at least one of the number of subcarriers to be subjected to the weighting control and a weighting coefficient used in the weighting control based on a measurement result of a multipath delay spread amount of a received signal. 12. The reception device according to claim 11, wherein the weight control unit sets the object of the weight control to a subcarrier at an end of the communication frequency band or the subcarrier and subcarriers in its vicinity. Reliability information obtained by the carrier. 13. The reception device according to claim 12, wherein the weight control unit performs control such that the weight of a subcarrier closer to a subcarrier at an end of the communication frequency band is reduced. 14. The reception device according to claim 12, wherein the weight control unit performs control such that the weight of a subcarrier group closer to a subcarrier at an end of the communication frequency band is reduced. . 15. The receiving device according to claim 11, wherein when the subcarriers to which the known received signals are mapped vary with time, the weight control unit controls the subcarriers as the Either or both of the subcarriers to be controlled by the weight and the weight coefficients used for the weight control. 16. The receiving apparatus according to claim 11, wherein, when a plurality of subcarrier groups exist in the communication frequency band via one or more subcarriers not to be transmitted, the weight control unit calculates the Weighting control is implemented using the subcarrier groups described above.