JP2013172328A - Receiver and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of computation required for the detection of interference band.SOLUTION: A receiver comprises: a band suppressor for suppressing and outputting a signal of a part of subcarrier included in a received signal; a decoder for decoding output signal from the band suppressor and obtaining a received bit string; an error detector for detecting whether the received bit string decoded by the decoder has error or not; a replaced subcarrier setter for changing a subcarrier of which signal is suppressed by the band suppressor until the error detector does not detect an error in the received bit string; and an interference band detector for generating a received replica signal from the received bit string in which no error is detected, and detecting an interference band which is a frequency band where an interference wave exists within a frequency band of a desired wave, based on an error amplitude obtained by subtracting the received replica from the received signal. The band suppressor suppresses the signal of the subcarrier corresponding to the interference band when the interference band detector detects the interference band.

Description

  The present invention relates to a receiving apparatus and a receiving method.

  In recent years, the depletion of frequency resources has become a problem due to the widespread use of various wireless communication systems, and studies on superposition transmission techniques that improve frequency utilization efficiency by sharing frequencies with a plurality of wireless signals are underway.

FIG. 6 is a conceptual diagram illustrating an example of combining wireless communication systems that share a frequency band. In the figure, two wireless LAN (Local Area Network) systems with different frequency channels are shown. The wireless communication system shown in the figure includes wireless LAN base stations 91a and 91b and a receiving device 92a. The wireless LAN base station 91a communicates using the frequency band of the channel CH1 that is the center frequency fa. The wireless LAN base station 91b communicates using the frequency band of the channel CH5 having the center frequency fb (fa <fb).
The receiving device 92a is arranged at a position where the wireless signals of both the wireless LAN base stations 91a and 91b reach, and receives a signal in which the wireless signal of the center frequency fa and the wireless signal of the center frequency fb partially interfere with each other. .

Another example of sharing frequency bands with each other is a combination of a wireless LAN system, Bluetooth (registered trademark), and WiMAX (registered trademark), and systems of different wireless systems may share frequencies. .
Thus, for example, when the wireless LAN base station 91a is a communication target, the transmission frequency band of the desired wave having the center frequency fa and the transmission frequency band of the interference wave from the wireless LAN base station 91b having the center frequency fb Partially overlap (interfere). In other wireless communication in which such frequency sharing is performed, the receiving device 92a can detect the presence of an interference wave that overlaps the transmission frequency band of the desired wave in order to efficiently perform error correction and improve frequency use efficiency. It is necessary to detect accurately (Patent Document 1).

  In general, when there is an interference wave, the communication characteristics are remarkably deteriorated, but a technique for realizing accurate transmission by decoding distributed FEC (Forward Error Correction) blocks while suppressing the influence of this interference. Has been studied (Non-Patent Document 1). Specifically, before demodulating the desired wave, a filtering process is performed on a frequency component in which an interference wave is present in the received signal in an RF (Radio Frequency: radio frequency band) stage or an IF (Intermediate Frequency: intermediate frequency band) stage. Alternatively, the frequency component is weighted in the baseband so that the influence of the interference wave is suppressed and demodulated and decoded.

  In addition, a technique for detecting a frequency band in which an interference wave exists has been studied (Non-Patent Document 2). Specifically, in the technique described in Non-Patent Document 1, provisional demodulation decoding is performed by changing the filtering band or the weighting band on a trial basis, and the predetermined band, for example, the filtering band that minimizes the error rate or The weighting band is identified as the frequency band where the interference wave exists. In this case, it is possible to detect the interference band while performing desired wave communication.

JP 2007-282120 A

Masuno and Sugiyama, “Effects of improving frequency utilization efficiency by multi-carrier superimposed transmission”, Shingaku Techniques, vol. 108, no. 188, RCS2008-67, pp. 85-90, August 2008 Otsuki, Masuno, Sugiyama, “Interference wave detection method based on error rate using initial likelihood mask”, IEICE Tech. 111, no. 180, RCS 2011-119, pp. 45-49, August 2011

  However, in order to detect a frequency band in which an interference wave exists (hereinafter referred to as an interference band), it is necessary to repeatedly perform a filtering process, a weighting process, and the like for each of a plurality of combinations that determine a frequency and a frequency width. . Therefore, there is a problem that the amount of calculation required to detect the interference band becomes enormous and it takes time to detect the interference band.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a receiving apparatus and a receiving method capable of receiving a desired wave while reducing the amount of calculation required for detecting an interference band. There is.

  In order to solve the above problem, the present invention provides a receiving apparatus that receives a signal in which a desired wave transmitted using a multicarrier superimposed transmission scheme and an interference wave that interferes with the desired wave are superimposed. A band suppressor that suppresses and outputs a signal of some subcarriers included in the received signal, a decoder that obtains a received bit string by decoding the signal output from the band suppressor, and the decoder An error detector that detects whether or not an error is included in the received bit string decoded by the signal, and a subcarrier in which the band suppressor suppresses the signal is changed until the error detector no longer detects an error from the received bit string. A substitution subcarrier setter for generating a received replica signal from the received bit string in which no error is detected, and subtracting the received replica signal from the received signal. An interference band detection unit that detects an interference band that is a frequency band in which an interference wave exists in the frequency band of the desired wave, and the band suppressor detects the interference band by the interference band detection unit Then, the receiving apparatus is characterized by suppressing a signal of a subcarrier corresponding to the interference band.

  In the invention described above, the interference band detection unit may determine whether the error amplitude is greater than or equal to a predetermined threshold for each subcarrier, and the error amplitude greater than or equal to the threshold. It is characterized by identifying that an interference wave exists in the frequency band of the subcarrier having

  Further, the present invention is the above-described invention, wherein the interference band detection unit detects a subcarrier having a low frequency from the error amplitude of a subcarrier having a high frequency between adjacent subcarriers in the frequency band of the desired wave. A first deviation amount obtained by subtracting the error amplitude and a second deviation amount obtained by subtracting the error amplitude of a subcarrier having a high frequency from the error amplitude of a subcarrier having a low frequency are calculated. Is a frequency band equal to or higher than a subcarrier frequency at which the deviation amount is equal to or greater than a predetermined threshold, and a frequency band equal to or lower than the subcarrier frequency at which the second deviation amount is equal to or greater than the threshold is defined as an interference band. It is characterized by identifying.

  Further, the present invention provides the subcarrier according to the above-described invention, wherein the replacement subcarrier setting unit causes the band suppressor to suppress a signal in a period until the error detector no longer detects an error from the received bit string. Each time a subcarrier whose signal is suppressed by the band suppressor is selected, a different subcarrier is selected, and a subcarrier whose signal is suppressed by the band suppressor is selected according to the number of times the selection is repeated. It is characterized by reducing the number.

  In order to solve the above problem, the present invention provides a receiving apparatus that receives a signal in which a desired wave transmitted using a multicarrier superimposed transmission method and an interference wave that interferes with the desired wave are superimposed. A reception method for performing a band suppression step for suppressing and outputting a signal of some subcarriers included in the received signal, and a decoding for decoding a signal output in the band suppression step to obtain a received bit string An error detection step for detecting whether or not an error is included in the received bit string decoded in the decoding step, and a signal in the band suppression step until no error is detected from the received bit string in the error detection step. A replacement subcarrier setting step for changing a subcarrier to be suppressed, and the received bit string from which no error is detected. Interference for detecting an interference band that is a frequency band in which an interference wave exists in the frequency band of the desired wave based on an error amplitude obtained by generating a reception replica signal and subtracting the reception replica signal from the received signal A band detection step, wherein in the band suppression step, when an interference band is detected in the interference band detection step, a signal of a subcarrier corresponding to the interference band is suppressed. .

  Further, the present invention provides the above-described invention, wherein, in the interference band detection step, for each subcarrier, it is determined whether or not the error amplitude is greater than or equal to a predetermined threshold value, and the error amplitude greater than or equal to the threshold value. It is characterized by identifying that an interference wave exists in the frequency band of the subcarrier having

  Further, the present invention provides the above-described invention, wherein, in the interference band detecting step, the first deviation amount of the error amplitude between adjacent subcarriers in the frequency band of the desired wave is changed to a sub-frequency having a low frequency. The first deviation amount is calculated in ascending order from the carrier, and the second deviation amount of the error amplitude between the adjacent subcarriers is calculated in descending order from the subcarrier having the higher frequency. A frequency band that is equal to or higher than a frequency of a subcarrier that is equal to or higher than a threshold and that is equal to or lower than a frequency of the subcarrier that is equal to or higher than the threshold is identified as an interference band.

  Further, the present invention provides the subcarrier for suppressing signals in the band suppression step in the period until the error detector no longer detects an error from the received bit string in the replacement subcarrier setting step in the above-described invention. Each time a subcarrier for suppressing a signal is selected in the band suppression step, a different subcarrier is selected, and a subcarrier for suppressing a signal in the band suppression step is selected according to the number of times the selection is repeated. It is characterized by reducing the number.

  According to the present invention, every time a subcarrier for suppressing a signal is changed, a reception bit string that does not contain an error is detected from the received bit string without generating a reception replica signal or detecting an interference band. The interference band can be detected from the received replica signal and the received signal. Therefore, it is not necessary to repeatedly generate a reception replica signal and detect an interference band, so that a desired wave can be received while reducing the amount of calculation required for detecting the interference band.

It is a schematic block diagram which shows the structure of the receiver 1 in 1st Embodiment. It is a schematic block diagram which shows the structure of the interference band detection part 30 in the same embodiment. It is the schematic which shows the detection method of the interference band in the embodiment. It is a flowchart which shows the reception process which the receiver in the same embodiment performs. It is the schematic which shows the detection method of the interference band in 2nd Embodiment. It is a conceptual diagram which shows an example which combines the radio | wireless communications system which shares a frequency band.

  Hereinafter, a receiving apparatus and a receiving method in each embodiment according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic block diagram illustrating the configuration of the receiving device 1 according to the first embodiment. The receiving apparatus 1 transmits a signal in which a desired wave transmitted by a transmitting apparatus communicating with the own apparatus using a multicarrier superimposed transmission method and an interference wave that interferes with the desired wave are superimposed on the transmission path. Receive. The receiving device 1 detects an interference band for a desired wave included in the received signal. Further, the receiving apparatus 1 obtains a received bit string by suppressing the interference band detected in the received signal and performing demodulation and decoding. In the following description, a case where a signal transmitted using an OFDM (Orthogonal Frequency Division Multiplexing) transmission system is received as an example of a multicarrier superimposed transmission system will be described.

  As shown in the figure, the receiving apparatus 1 includes an antenna 11, a filter 12, an OFDM demodulator 13, a transmission path estimator 14, an amplitude and phase distortion corrector 15, a demodulator 16, a zero substitution device 17, and a parallel-serial converter 18. FEC decoder 19, CRC (Cyclic Redundancy Check) detector 20, permutation subcarrier setting unit 21, signal buffer 22, and interference band detection unit 30.

The filter 12 suppresses components other than the frequency band in which a desired wave including a signal to be demodulated and decoded is received from the received signal received via the antenna 11 and includes the component of the frequency band. Output a signal. As the filter 12, for example, a band pass filter may be used.
The OFDM demodulator 13 performs FFT (Fast Fourier Transform) on the signal output from the filter 12, converts the signal in the time domain to the signal in the frequency domain, and demodulates the signal for each subcarrier. .
The transmission path estimator 14 uses the signal of each subcarrier demodulated by the OFDM demodulator 13 to determine the characteristics of the transmission path (changes in amplitude, phase, etc.) between the transmission apparatus and the own apparatus for each subcarrier. Estimate the indicated channel coefficient. For example, the transmission path estimator 14 estimates a transmission path coefficient by applying a known technique to a known pattern (for example, a pilot signal or a training signal) included in each subcarrier signal.

The amplitude / phase distortion corrector 15 corrects amplitude and phase distortion generated in the transmission path with respect to the signal of each subcarrier using the transmission path coefficient of each subcarrier estimated by the transmission path estimator 14.
The demodulator 16 performs demodulation corresponding to the modulation scheme used in the transmission apparatus for each subcarrier signal corrected by the amplitude phase distortion corrector 15. The demodulator 16 outputs the signal of each subcarrier obtained by the demodulation to the zero substitution unit 17. Demodulation used in the demodulator 16 is demodulation corresponding to, for example, QPSK (Quadrature Phase Shift Keying), 16-QAM (Quadrature Amplitude Modulation), and the like.

The zero permutation unit 17 replaces the subcarrier signal designated by the permutation subcarrier setting unit 21 among the demodulated signals of each subcarrier input from the demodulator 16 with “0” and converts the subcarrier signal to the parallel-serial converter 18. Output. Of the demodulated signals of the subcarriers input from the demodulator 16, the zero permutator 17 outputs a subcarrier signal not designated by the permutation subcarrier setting unit 21 to the parallel-serial converter 18. The zero replacer 17 may be other than the one that replaces the signal with “0” as long as the signal of the subcarrier designated by the replacement subcarrier setting unit 21 is suppressed.
The parallel / serial converter 18 performs parallel-serial conversion on the signal sequence input from the zero substitution unit 17, converts the signal sequence into one signal sequence, and outputs the signal sequence to the FEC decoder 19.

The FEC decoder 19 restores the received bit string by performing error correction decoding on the signal string input from the parallel / serial converter 18, and outputs the restored received bit string to the CRC detector 20.
The CRC detector 20 performs a cyclic redundancy check on the received bit string input from the FEC decoder 19 and determines whether or not an error is included in the received bit string of the demodulated and decoded packet data. The CRC detector 20 outputs a CRC determination result indicating the determination result to the interference band detection unit 30. In addition, the CRC detector 20 outputs the received bit string to a host device (not shown) and the interference band detection unit 30.
The replacement subcarrier setting unit 21 selects a subcarrier whose signal is replaced with “0” in the zero replacement unit 17 based on the interference band information input from the interference band detection unit 30. The substitution subcarrier setting unit 21 controls the zero substitution unit 17 by outputting information indicating the selected subcarrier to the zero substitution unit 17.
The signal buffer 22 receives a signal in the frequency band of the desired wave that has passed through the filter 12 and stores the input signal. The signal buffer 22 outputs signals to the interference band detection unit 30 in the order of input.

  The interference band detection unit 30 receives a signal output from the filter 12, a transmission path coefficient estimated by the transmission path estimator 14, a CRC determination result output from the CRC detector 20, and a received bit string. The interference band detection unit 30 detects an interference band in the frequency band of the desired wave based on the input signal or the like. Moreover, the interference band detection unit 30 outputs interference band information indicating a subcarrier corresponding to the detected interference band to the replacement subcarrier setting unit 21.

FIG. 2 is a schematic block diagram showing the configuration of the interference band detection unit 30 in the present embodiment. As shown in the figure, the interference band detector 30 includes an FEC re-encoder 32, a serial-parallel converter 33, a re-modulator 34, an amplitude / phase distortion adder 35, an OFDM modulator 36, a subtractor 37, an absolute value. A calculator 38, an interference band detector 39, and an averager 40 are provided.
When the CRC determination result indicates that the received bit string input from the CRC detector 20 does not include an error, the FEC re-encoder 32 performs the same encoding as the FEC encoding used in the transmission apparatus. Is performed on the input received bit string, and the encoded bit string is output to the serial-to-parallel converter 33. On the other hand, the FEC re-encoder 32 does not perform FEC encoding and outputs the bit string to the serial-to-parallel converter 33 when the CRC determination result indicates that the input received bit string includes an error. Also do not.
When the CRC determination result indicates that the received bit string includes an error, when the operation of the interference band detection unit 30 is stopped or the FEC re-encoder 32 does not perform FEC encoding, In the interference band detection unit 30, processing subsequent to the series-parallel converter 33 is stopped. That is, the operation in the interference band detection unit 30 is switched between execution and stop according to the CRC determination result.

The serial / parallel converter 33 performs serial-parallel conversion on the bit string input from the FEC re-encoder 32, converts the bit string into a plurality of bit strings corresponding to the number of subcarriers, and outputs the bit string to the remodulator 34.
The remodulator 34 modulates each of the plurality of bit strings input from the serial / parallel converter 33 by using the same modulation method as that used in the transmission apparatus. The remodulator 34 outputs a signal corresponding to each subcarrier obtained by modulating a plurality of bit strings to the amplitude phase distortion adder 35.
The amplitude / phase distortion imparting unit 35 uses the transmission path coefficient of each subcarrier input from the transmission path estimator 14 for the signal of each subcarrier input from the remodulator 34, and transmits from the transmission apparatus to the own apparatus. Amplitude and phase distortion generated in transmission up to (receiving apparatus 1) is given. The amplitude / phase distortion adder 35 outputs a signal of each subcarrier to which distortion has been applied to the OFDM modulator 36.

The OFDM modulator 36 performs IFFT (Inverse Fast Fourier Transform) on the signal of each subcarrier input from the amplitude / phase distortion adder 35 to convert the frequency domain signal into the time domain signal. Convert. As a result, the OFDM modulator 36 generates a reception replica signal corresponding to the signal (desired wave) transmitted from the transmission device, and outputs the generated reception replica signal (D: Desired signal) to the subtractor 37.
The subtractor 37 subtracts the received replica signal corresponding to the signal and received from the OFDM modulator 36 from the signal stored in the signal buffer 21, and obtains the error signal obtained by the subtraction. It outputs to the absolute value calculator 38.
The absolute value calculator 38 calculates the absolute value (amplitude) of the signal level in each frequency band (each subcarrier) from the error signal input from the subtractor 37, and detects the calculated absolute value (amplitude) as an interference band. Output to the device 39.

Here, the reason why the amplitude in the error signal (hereinafter referred to as error amplitude) occurs is that there is an interference wave superimposed on the desired wave, and that there is an error in channel estimation in the interference band. In any case, since it is caused by the presence of an interference wave with respect to the desired wave, it can be identified that the interference wave exists in a frequency band in which the error amplitude exceeds a certain value (amplitude threshold).
The interference band detector 39 determines whether an interference wave exists for each subcarrier based on the error amplitude value of each subcarrier input from the absolute value calculator 38 and a predetermined amplitude threshold value. By performing the above, the interference band is detected. The interference band detector 39 outputs information indicating the detected interference band to the averager 40. Here, the amplitude threshold value is determined based on the actual measurement value, the result of the simulation, and the like and the reception performance of the own device (receiving device 1). The reception performance of the receiver 1 is determined by, for example, the symbol determination performance in the demodulator 16, the modulation method or coding rate used in communication, the estimation accuracy of the transmission path coefficient in the transmission path estimator 14, and the like.

  The averager 40 averages information input from the interference band detector 39 over a plurality of symbols (or packets). The averager 40 determines whether or not an interference wave exists in each subcarrier based on the averaged information, and outputs interference band information indicating the determination result to the replacement subcarrier setting unit 21. Here, the averaging performed by the averager 40 is performed by, for example, calculating the number of times that the interference band detector 39 detects the interference wave over a plurality of symbols (or packets) for each subcarrier, and the calculated number of times is predetermined. It is identified that the interference wave exists in the subcarriers exceeding the number of times (for example, the majority). Further, instead of the majority, it may be identified that the interference wave exists in the subcarrier exceeding the average number of times that the interference wave is detected in each subcarrier.

Here, an interference band detection method performed by the interference band detector 39 will be described.
FIG. 3 is a schematic diagram showing an interference band detection method in the present embodiment. In the figure, the horizontal axis indicates the frequency, and the vertical axis indicates the error amplitude. As shown in the figure, when the error amplitude value input from the absolute value calculator 38 is equal to or larger than the amplitude threshold value, the interference band detector 39 selects a frequency band (subcarrier) corresponding to the error amplitude as an interference wave. Is identified as an interference band.

FIG. 4 is a flowchart illustrating a reception process performed by the reception device 1 according to this embodiment.
In reception apparatus 1, when reception processing is started, permutation subcarrier setting unit 21 selects a permutation subcarrier that is a subcarrier whose signal is to be replaced with “0” in zero permutation unit 17 (step S101).
In step S101, the replacement subcarrier setting unit 21 selects a combination of subcarriers that are at least one subcarrier each time it is selected. For example, when performing communication using N subcarriers (SC1, SC2,..., SCN), SC1 to SCK, SC2 to SC (K + 1), SC3 to SC (K + 2),..., SC (N−K + 1) Different combinations of K subcarriers may be selected in order, such as ˜SCN. Further, the replacement subcarrier setting unit 21 may reduce the number of subcarriers to be selected according to the number of times the subcarrier selection is repeated.

The zero replacer 17 replaces the signal of the replacement subcarrier selected by the replacement subcarrier setting unit 21 with “0” for the signals demodulated by the filter 12 to the demodulator 16. The parallel-serial converter 18 and the FEC decoder 19 perform decoding on the signal in which the signal of the replacement subcarrier is replaced with “0” by the zero replacer 17, and decode the received bit string (step S102).
The CRC detector 20 determines whether or not an error is included in the decoded received bit string (step S103). If an error is detected (step S103: YES), the process returns to step S101 to perform a different replacement. The subcarrier is set in the replacement subcarrier setting unit 21. On the other hand, if no error is detected (step S103: No), a reception replica signal is generated by processing performed by the OFDM modulator 36 from the FEC re-encoder 32 (step S104), and the subtractor 37 calculates an error signal. Then, the absolute value calculator 38 calculates an error amplitude value in each subcarrier (step S105).

The interference band detector 39 detects a frequency band in which interference exists based on the error amplitude value calculated by the absolute value calculator 38, and the averager 40 detects the interference band detector 39 over a plurality of symbols (or packets). Based on the detection result, an interference band is identified, and interference band information indicating the interference band is output to replacement subcarrier setting unit 21 (step S106).
Replacement subcarrier setting unit 21 sets a subcarrier indicated by the interference band information as a replacement subcarrier (step S107).
Thereafter, the zero replacer 17 replaces the signal of the subcarrier set as the replacement subcarrier with “0”. The receiving device 1 obtains a received bit string from the received signal through the respective processes from the filter 12 to the CRC detector 20.

As described above, the receiving apparatus 1 according to the present embodiment demodulates and decodes the received bit string from the signal obtained by nulling (suppressing) the signal in the substitution subcarrier selected by the substitution subcarrier setting unit 21 by the zero substitution unit 17. The replacement subcarrier setting unit 21 changes the combination of replacement subcarriers in order until the received bit string can be decoded without error, that is, until the received bit string can be correctly decoded. When the interference band detecting unit 30 can decode the received bit string without error, the interference band detecting unit 30 generates a received replica signal of the desired wave from the received bit string and subtracts the received replica signal from the received signal including the desired wave and the interference wave. Wave (error signal) is extracted. Based on the extracted interference wave, the interference band detection unit 30 detects an interference band that is a frequency band in which the interference wave exists in the frequency band of the desired wave.
In the initial repetition of steps S101 to S103, the receiving apparatus 1 selects a subcarrier having a wide frequency band as a replacement subcarrier, and selects a replacement subcarrier by shifting the frequency band. Since the interference wave can be detected for the frequency band, the number of processes in the interference band detection unit 30 can be reduced, and the desired wave can be received while reducing the amount of calculation required for detecting the interference band. Can

  If the received bit string cannot be decoded correctly, the frequency band to be selected for the replacement subcarrier is narrowed, that is, the number of subcarriers to be selected for the replacement subcarrier is reduced, and the received substring is correctly decoded until the received bit string can be correctly decoded. Repeat the selection. Selection of replacement subcarriers, demodulation, and decoding are repeated, but there is no processing to generate a received replica signal from a received bit string, processing to detect an interference band, and the like, so that an increase in the amount of computation is suppressed. be able to.

For example, in the technique described in Non-Patent Document 2, the BER measurement value is used as the interference band identification criterion, and the subcarrier frequency band (subcarrier suppression band) in which the signal is suppressed when the minimum BER is obtained. ) Is an interference band. Therefore, it is necessary to repeatedly perform subcarrier band suppression, reception replica signal generation, and BER measurement for each of a plurality of subcarrier suppression bands. In addition, since the BER is minimized when the interference band and the replacement subcarrier coincide with each other, high accuracy is required for selection of the replacement subcarrier. As a result, the amount of calculation required to identify the interference band is enormous, and it takes time to identify the interference band.
On the other hand, if the reception apparatus 1 can select a replacement subcarrier so that an error is not included in the demodulated reception bit string as a result of error detection by the CRC detector 20, the interference band can be identified. That is, the replacement subcarrier may be selected with low accuracy. Therefore, the time required for identifying the interference band can be shortened. At this time, by selecting a plurality of subcarriers as the initial replacement subcarriers, the number of trials from step S101 to step S103 can be reduced, and the calculation and time required for identifying the interference band can be suppressed. .

(Second Embodiment)
In the first embodiment, the configuration in which the interference band detector 39 detects the interference wave by comparing the error amplitude calculated by the absolute value calculator 38 with the amplitude threshold value has been described. In the second embodiment, a deviation amount Δamp of error amplitude between adjacent subcarriers is used as a criterion. Hereinafter, the case where the subcarrier numbers in the desired wave are SC1, SC2, SC3,.

FIG. 5 is a schematic diagram illustrating an interference band detection method according to the second embodiment. In the figure, the horizontal axis indicates the frequency (subcarrier), and the vertical axis indicates the error amplitude.
The interference band detector 39 firstly shifts the error amplitude deviation Δamp (SC k → SC k + 1) (k = 1, 2,...) In adjacent subcarriers from the lower frequency to the higher frequency. 6) are measured in order (Process A). That is, the deviation amount Δamp (SC k → SC k + 1) is calculated by subtracting the error amplitude of the low-frequency subcarrier (SC k + 1) from the error amplitude of the high-frequency subcarrier (SC k + 1).
In the example shown in FIG. 5, the error amplitude deviation amount Δamp (SC1 → SC2) between the subcarrier SC1 and the subcarrier SC2 and the error amplitude deviation amount Δamp (SC2 → SC3) between the subcarrier SC2 and the subcarrier SC3. ) Etc. are almost zero. On the other hand, the deviation amount Δamp (SC3 → SC4) of the error amplitude between the subcarrier SC3 and the subcarrier SC4 is a large value. Further, the deviation amount Δamp (SC5 → SC6) of the error amplitude between the subcarrier SC5 and the subcarrier SC6 becomes a negative value.

Subsequently, the interference band detector 39 shifts the error amplitude deviation Δamp (SC k → SC k−1) (k = 7, 6) in the adjacent subcarriers from the higher frequency toward the lower frequency. ,..., 2) are measured in order (Process B). That is, the deviation amount Δamp (SC k → SC k−1) is calculated by subtracting the error amplitude of the high frequency subcarrier (SC k−1) from the error amplitude of the low frequency subcarrier (SC k−1).
In the example shown in FIG. 5, the error amplitude deviation amount Δamp (SC6 → SC5) between the subcarrier SC6 and the subcarrier SC5 becomes a large value, and the error amplitude deviation amount Δamp (subamp) between the subcarrier SC4 and the subcarrier SC3. SC4 → SC3) is a negative value.

  After performing the processing A and the processing B, the interference band detector 39 determines that an interference wave exists at the frequency in the measurement direction when the deviation amount Δamp is equal to or larger than a predetermined detection threshold. In the example shown in FIG. 5, it is determined from the result of process A that an interference wave exists in a frequency band equal to or higher than the frequency of subcarrier SC4, and from the result of process B, an interference wave exists in a frequency band equal to or lower than the frequency of subcarrier SC5. judge. The interference band detector 39 combines the determination based on the result of the process A and the determination based on the result of the process B to generate an “interference wave in a frequency band equal to or higher than the frequency of the subcarrier SC4 and lower than the frequency of the subcarrier SC5. Is present. "

  Further, for example, in process A, the displacement amount Δamp (SC2 → SC3) and the displacement amount Δamp (SC6 → SC7) are equal to or larger than the detection threshold value, and in process B, the displacement amount Δamp (SC4 → SC3) is above the detection threshold value. In this case, the interference band detector 39 identifies that “an interference wave exists in a frequency band that is equal to or higher than the frequency of the subcarrier SC3 and equal to or lower than the frequency of the subcarrier SC4 and a frequency band that is equal to or higher than the frequency of the subcarrier SC7”. .

As described above, in this embodiment, the interference band detector 39 detects the interference band, and the deviation amount Δamp of the error amplitude in the adjacent subcarrier is used. As a result, even when white noise with a high level is included in the frequency band of the desired signal in the received signal or when white noise with a high level is generated in the frequency band when generating the received replica signal, white The interference band can be identified without being affected by noise.
Also in the second embodiment, as in the first embodiment, in the initial stage of repeating steps S101 to S103, subcarriers having a wide frequency band are selected as replacement subcarriers, and the frequency band is shifted. By selecting replacement subcarriers, interference waves can be detected for a wide range of frequency bands in a single process, so that the number of processing times in the interference band detection unit 30 can be reduced, which is necessary for detecting the interference band. The desired wave can be received while reducing the amount of calculation.

  Note that a program for realizing the function of the receiving device 1 in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to perform reception processing. You may go. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The band suppressor described in the present invention corresponds to the zero replacer 17 in each of the above-described embodiments. The first deviation amount described in the present invention corresponds to the deviation amount Δamp calculated in the process A in the second embodiment described above. Further, the second displacement amount described in the present invention corresponds to the displacement amount Δamp calculated in the process B in the above-described second embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Receiver, 11 ... Antenna, 12 ... Filter, 13 ... OFDM demodulator, 14 ... Transmission path estimator, 15 ... Amplitude phase distortion corrector, 16 ... Demodulator, 17 ... Zero substitution device, 18 ... Parallel-serial conversion , 19 ... FEC decoder, 20 ... CRC detector, 21 ... replacement subcarrier setter, 22 ... signal buffer, 30 ... interference band detector, 32 ... FEC re-encoder, 33 ... serial-parallel converter, 34 ... Remodulator, 35 ... Amplitude / phase distortion adder, 36 ... OFDM modulator, 37 ... Subtractor, 38 ... Absolute value calculator, 39 ... Interference band detector, 40 ... Averager, 91a ... Wireless LAN base station 91b: Wireless LAN base station, 92a: Receiver

Claims (8)

A receiving apparatus that receives a signal in which a desired wave transmitted using a multicarrier superimposed transmission scheme and an interference wave that interferes with the desired wave are superimposed,
A band suppressor that suppresses and outputs a signal of some of the subcarriers included in the received signal;
A decoder for decoding a signal output from the band suppressor to obtain a received bit string;
An error detector for detecting whether an error is included in the received bit string decoded by the decoder;
A substitution subcarrier setting unit that changes a subcarrier in which the band suppressor suppresses a signal until the error detector no longer detects an error from the received bit string;
A frequency band in which an interference wave exists in the frequency band of the desired wave based on an error amplitude obtained by generating a received replica signal from the received bit string in which no error is detected and subtracting the received replica signal from the received signal An interference band detector for detecting an interference band of
The band suppressor is:
When the interference band detection unit detects an interference band, a signal of a subcarrier corresponding to the interference band is suppressed. The receiving device according to claim 1,
The interference band detector is
For each subcarrier, it is determined whether or not the error amplitude is greater than or equal to a predetermined threshold, and it is identified that an interference wave exists in a frequency band of a subcarrier having an error amplitude greater than or equal to the threshold. Receiver device. The receiving device according to claim 1,
The interference band detector is
A first deviation amount obtained by subtracting the error amplitude of a subcarrier having a low frequency from the error amplitude of a subcarrier having a high frequency between adjacent subcarriers in the frequency band of the desired wave, and a subcarrier having a low frequency A second deviation amount obtained by subtracting the error amplitude of a subcarrier having a high frequency from the error amplitude;
A frequency band equal to or higher than a subcarrier frequency at which the first deviation amount is equal to or greater than a predetermined threshold, and a frequency band equal to or lower than a subcarrier frequency at which the second deviation amount is equal to or greater than the threshold. A receiver characterized by being identified as an interference band. The receiving device according to any one of claims 1 to 3,
The replacement subcarrier setting device includes:
When selecting a subcarrier that causes the band suppressor to suppress a signal in a period until the error detector no longer detects an error from the received bit string,
Each time a subcarrier that causes the band suppressor to suppress a signal is selected, a different subcarrier is selected,
The receiving apparatus, wherein the number of subcarriers that cause the band suppressor to suppress a signal is reduced according to the number of times the selection is repeated. A reception method performed by a reception device that receives a signal in which a desired wave transmitted using a multicarrier superimposed transmission method and an interference wave that interferes with the desired wave are superimposed,
A band suppression step of suppressing and outputting a signal of some of the subcarriers included in the received signal;
A decoding step of decoding the signal output in the band suppression step to obtain a received bit string;
An error detection step of detecting whether or not an error is included in the received bit string decoded in the decoding step;
A substitution subcarrier setting step for changing a subcarrier for suppressing a signal in the band suppression step until no error is detected from the received bit string in the error detection step;
Generate a received replica signal from the received bit string in which no error is detected, and based on an error amplitude obtained by subtracting the received replica signal from the received signal, a frequency band in which an interference wave exists in the frequency band of the desired wave An interference band detecting step for detecting an interference band of
In the band suppression step,
When an interference band is detected in the interference band detection step, a signal of a subcarrier corresponding to the interference band is suppressed. The reception method according to claim 5, comprising:
In the interference band detection step,
For each subcarrier, it is determined whether or not the error amplitude is greater than or equal to a predetermined threshold, and it is identified that an interference wave exists in a frequency band of a subcarrier having an error amplitude greater than or equal to the threshold. Reception method. The reception method according to claim 5, comprising:
In the interference band detection step,
A first deviation amount obtained by subtracting the error amplitude of a subcarrier having a low frequency from the error amplitude of a subcarrier having a high frequency between adjacent subcarriers in the frequency band of the desired wave, and a subcarrier having a low frequency A second deviation amount obtained by subtracting the error amplitude of a subcarrier having a high frequency from the error amplitude;
A frequency band equal to or higher than a subcarrier frequency at which the first deviation amount is equal to or greater than a predetermined threshold, and a frequency band equal to or lower than a subcarrier frequency at which the second deviation amount is equal to or greater than the threshold. A receiving method characterized by identifying an interference band. The reception method according to any one of claims 5 to 7,
In the replacement subcarrier setting step,
When selecting a subcarrier for suppressing a signal in the band suppression step in a period until the error detector no longer detects an error from the received bit string,
Each time a subcarrier for suppressing a signal is selected in the band suppression step, a different subcarrier is selected,
A reception method characterized by reducing the number of subcarriers for suppressing signals in the band suppression step according to the number of times selection is repeated.

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