Interference removal device, control circuit, storage medium, and interference replica weight setting method

Abstract

Provided is an interference removal device (1) capable of inhibiting deterioration due to noise emphasis. The interference removal device comprises: a data symbol extraction unit (11) for outputting a data symbol signal (101); a null symbol extraction unit (12) for outputting a null symbol signal (102); a data symbol power calculation unit (14) for calculating a data symbol power calculation estimation value (104); a null symbol spectrum calculation unit (15) for calculating a null symbol spectrum (105); an interference center frequency estimation unit (16) for outputting an interference center frequency estimation value (106); an interference bandwidth estimation unit (17) for outputting an estimation interference bandwidth (107); and an interference removal unit (18) for generating an interference replica signal and multiplying the interference replica signal by a weight factor for each frequency in accordance with the ratio of a noise power component and an interference power component included in the interference replica signal to thereby inhibit deterioration due to noise emphasis.

Description

Interference cancellation device, control circuit, storage medium, and interference replica weight setting method

[0001] The present disclosure relates to an interference cancellation device, a control circuit, a storage medium, and an interference replica weight setting method for canceling interference from a received signal.

[0002] Conventionally, interference removal using intermittent symbol transmission has been used as a method for removing interference from a received signal in a receiving device. In interference removal using intermittent symbol transmission, a transmitting device transmits a signal by inserting non-transmission intervals, so-called null symbols, between transmitted symbols. The receiving device removes interference by subtracting from the received signal an interference replica signal that regenerates interference superimposed on the data portion from interference components superimposed on the null symbol portion of the received signal. For example, Patent Document 1 discloses a technology that improves the efficiency of interference suppression and reduces the number of iterations by varying a weighting coefficient that is multiplied by the interference replica according to the remaining interference power for each iteration.

[0003] Patent No. 6746029

[0004] When the technology described in Patent Document 1 is applied to an interference cancellation method using intermittent symbol transmission, interference cancellation is performed by directly subtracting the interference replica signal from the received signal, regardless of the ratio between the interference power component and the noise power component contained in the interference replica signal. In this case, if the interference power is small compared to the noise signal in the interference replica signal, the degradation due to noise enhancement becomes more significant than the improvement effect of interference cancellation. However, Patent Document 1 does not disclose how to suppress the degradation due to noise enhancement.

[0005] The present disclosure has been made in view of the above, and aims to provide an interference removal device that can suppress degradation due to noise enhancement.

[0006] In order to solve the above-mentioned problems and achieve the object, the present disclosure is characterized by comprising: a data symbol extraction unit that outputs a data symbol signal extracted from a received signal in which null symbols are inserted into data symbols; a null symbol extraction unit that outputs a null symbol signal extracted from the received signal; a calculation unit that calculates a data symbol power estimate indicating the power of the data symbol signal and a null symbol spectrum from the null symbol signal; an interference center frequency estimation unit that outputs an estimated interference center frequency estimate using the data symbol signal, the data symbol power estimate, and the null symbol spectrum; an interference bandwidth estimation unit that outputs an estimated interference bandwidth estimated from the null symbol spectrum; and an interference cancellation unit that generates an interference replica signal using the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth, and multiplies the interference replica signal by a weighting coefficient for each frequency according to the ratio between the interference power component and the noise power component included in the interference replica signal, thereby suppressing degradation due to noise emphasis.

[0007] The interference removal device of the present disclosure has the effect of suppressing degradation due to noise enhancement.

[0008] FIG. 1 is a block diagram showing an example of the configuration of an interference cancellation device according to an embodiment; FIG. 2 is a flowchart showing the operation of the interference cancellation device according to an embodiment; FIG. 3 is a block diagram showing an example of the configuration of an interference cancellation unit according to an embodiment; FIG. 4 is a flowchart showing the operation of the interference cancellation unit according to an embodiment; FIG. 5 is a diagram showing an example of a signal oversampled on the frequency axis in an interference replica signal generation unit according to an embodiment; FIG. 6 is a diagram showing a frequency spectrum obtained by extracting only the frequency region specified by the interference center frequency estimate and the estimated interference bandwidth by the interference replica signal generation unit according to an embodiment, i.e., an interference replica signal; FIG. 7 is a diagram showing an example of the configuration of a processing circuit when the processing circuit realizing the interference cancellation device according to an embodiment is realized by a processor and a memory;

[0009] Hereinafter, an interference cancellation device, a control circuit, a storage medium, and an interference replica weight setting method according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0010] 1 is a block diagram showing an example of the configuration of an interference cancellation device 1 according to this embodiment. The interference cancellation device 1 is a device mounted on a receiving device (not shown) or the like. The interference cancellation device 1 removes interference added in a propagation path between a transmitting device (not shown) that is the signal source and the receiving device from a received signal 100 that is a signal received by the receiving device. In this embodiment, the transmitting device inserts null symbols to data symbols in a one-to-one ratio in the transmitted signal, that is, inserts data symbols and null symbols alternately. In the received signal 100 received by the receiving device, null symbols are inserted between data symbols.

[0011] The following describes the configuration and operation of the interference cancellation device 1. As shown in Fig. 1, the interference cancellation device 1 includes a data symbol extraction unit 11, a null symbol extraction unit 12, a null symbol power calculation unit 13, a data symbol power calculation unit 14, a null symbol spectrum calculation unit 15, an interference center frequency estimation unit 16, an interference bandwidth estimation unit 17, and an interference cancellation unit 18. Fig. 2 is a flowchart showing the operation of the interference cancellation device 1 according to this embodiment.

[0012] The data symbol extractor 11 extracts only the data symbol portion from the received signal 100 in accordance with the timing of the data symbol (step S11). The data symbol extractor 11 outputs the extracted data symbol portion as a data symbol signal 101.

[0013] The null symbol extractor 12 extracts only the null symbol portion from the received signal 100 in synchronization with the null symbol timing (step S12). The null symbol extractor 12 outputs the extracted null symbol portion as a null symbol signal 102.

[0014] The null symbol power calculation unit 13 calculates the power P of the null symbol signal 102. １ (Step S13). The l-th signal of the null symbol signal 102 is calculated as r Ｎ (l), then the power P １ is expressed as in equation (1): In equation (1), L is the number of symbols used in power calculation.

[0015]

[0016] Here, the null symbol signal 102 contains interference and noise. That is, if I is the interference power and N is the noise power, then P １ = I + N. The null symbol power calculation unit 13 calculates P １ = null symbol power estimate 103, and calculate null symbol power estimate 103.

[0017] The data symbol power calculation unit 14 calculates the power P ０ , and the power P １ (Step S14) where the data symbol signal 101 includes data symbols, interference, and noise. That is, if D is the transmission data symbol power, then P ０ = D + I + N. Therefore, the data symbol power calculation unit 14 calculates D = P ０ -P １ = data symbol power estimate 104, and calculate the data symbol power estimate 104 as the data symbol power included in the data symbol signal 101. The k-th symbol of the data symbol signal 101 is expressed as r Ｄ (k), the power P ０ is expressed as in equation (2): In equation (2), K is the number of symbols used in power calculation.

[0018]

[0019] The null symbol spectrum calculation unit 15 calculates the null symbol spectrum 105 from the null symbol signal 102 (step S15). The null symbol spectrum calculation unit 15 calculates the null symbol spectrum 105 using, for example, a fast Fourier transform (FFT). The null symbol power calculation unit 13, the data symbol power calculation unit 14, and the null symbol spectrum calculation unit 15 may be simply referred to as calculation units. One calculation unit may also perform multiple of the above calculations.

[0020] The interference center frequency estimation unit 16 estimates the center frequency of the interference signal using the data symbol signal 101, the data symbol power estimation value 104, and the null symbol spectrum 105, and calculates the interference center frequency estimation value 106 (step S16). The interference center frequency estimation unit 16 outputs the calculated, i.e., estimated, interference center frequency estimation value 106.

[0021] The interference bandwidth estimation unit 17 determines that a null symbol spectrum 105 that exceeds a predefined threshold is an interference band, and calculates an estimated interference bandwidth 107. That is, the interference bandwidth estimation unit 17 estimates the interference bandwidth of the interference signal from the null symbol spectrum 105, and outputs the estimated interference bandwidth 107 (step S17).

[0022] The interference canceller 18 cancels interference from the received signal 100 using an interference replica signal recovered based on the information of the data symbol power estimate 104, the null symbol spectrum 105, the interference center frequency estimate 106, and the estimated interference bandwidth 107 (step S18). The interference canceller 18 outputs an interference-canceled received signal 108, which is a signal obtained by removing interference from the received signal 100. In this embodiment, the interference canceller 18 generates an interference replica signal using the received signal 100, the data symbol power estimate 104, the null symbol spectrum 105, the interference center frequency estimate 106, and the estimated interference bandwidth 107, and multiplies the interference replica signal by a weighting coefficient for each frequency in accordance with the ratio between the interference power component and the noise power component contained in the interference replica signal, thereby suppressing degradation due to noise emphasis.

[0023] Next, a detailed configuration and operation of the interference removal unit 18 included in the interference removal device 1 will be described. Fig. 3 is a block diagram showing an example configuration of the interference removal unit 18 according to this embodiment. As shown in Fig. 3, the interference removal unit 18 includes an interference replica signal generation unit 21, a subtraction unit 22, a time domain transformation unit 23, a residual noise estimation unit 24, and a weighting coefficient calculation unit 25. Fig. 4 is a flowchart showing the operation of the interference removal unit 18 according to this embodiment.

[0024] The interference replica signal generator 21 generates an interference replica signal 201 using the null symbol spectrum 105, the interference center frequency estimate 106, and the estimated interference bandwidth 107 (step S21). The interference replica signal generator 21 oversamples the null symbol spectrum 105 on the frequency axis to set the null symbol spectrum 105 to the same sampling period as the received signal 100. The interference replica signal generator 21 performs oversampling on the frequency axis by repeatedly copying the null symbol spectrum 105 in the frequency direction. The interference replica signal generator 21 extracts only a frequency region specified by the interference center frequency estimate 106 and the estimated interference bandwidth 107 from the oversampled null symbol spectrum 105, and generates the interference replica signal 201 by setting the gain of signal components in frequency regions other than the extracted frequency region to zero.

[0025] FIG. 5 is a diagram showing an example of a signal oversampled on the frequency axis by the interference replica signal generator 21 according to this embodiment. Assume that the null symbol spectrum 105 is composed of interference 301 and noise 302. FIG. 5 also shows interferences 303a, 303b, and 303c, which are copies of the null symbol spectrum 105, and noises 304a, 304b, and 304c. FIG. 6 is a diagram showing a frequency spectrum obtained by the interference replica signal generator 21 according to this embodiment by extracting only the frequency region specified by the interference center frequency estimate 106 and estimated interference bandwidth 107, i.e., the interference replica signal 201. Signal components in frequency regions other than the extracted frequency region are forced to zero, leaving only the interference 303a and a portion of the noise 304a. Of course, the remaining frequency components vary depending on the specific values ​​of the interference center frequency estimate 106 and estimated interference bandwidth 107.

[0026] The subtractor 22 performs interference cancellation using the weighting coefficient 203, the interference replica signal 201, and the received signal 100 to generate a frequency-domain interference-canceled received signal 204 (step S22). The subtractor 22 subtracts the result of multiplying the interference replica signal 201 by the weighting coefficient 203 from the frequency-domain received signal obtained by converting the received signal 100 from a time-domain signal to a frequency-domain signal, thereby generating the frequency-domain interference-canceled received signal 204. The subtractor 22 uses, for example, a fast Fourier transform (FFT) for the conversion to the frequency domain. Here, if W(n) is the weighting coefficient 203, W(n) is the weighting coefficient by which the frequency-domain signal is multiplied, and n is the frequency number. Since W(n) is calculated based on the output of the subtractor 22, the initial value is set to W(n) = 1 for all n. However, this initial value setting is not necessarily required. Similarly, if the interference replica signal 201 is Rep(n), the frequency domain received signal is R(n), and the frequency domain interference-removed received signal 204 is R(~)(n), then R(~)(n) is calculated using equation (3).

[0027]

[0028] In the specification, it is not possible to express the state where ~ is added above R, so here, the state where ~ is added above R will be expressed as R(~).

[0029] The time domain transform unit 23 transforms the frequency domain interference-removed received signal 204 from a frequency domain signal to a time domain signal, and generates the interference-removed received signal 108 converted into a time domain signal (step S23). The time domain transform unit 23 uses, for example, an inverse fast Fourier transform (IFFT) for the transformation into the time domain.

[0030] The residual noise estimator 24 calculates the residual noise power 205 using the frequency-domain interference-removed received signal 204 and the data symbol power estimate 104 (step S24). ｒ０ (n) is calculated by equation (4). The power P of the received signal 204 after frequency domain interference cancellation is ｒ０ Ideally, (n) is the sum of the transmission data symbol power D at each frequency and the residual noise contained in the signal band after interference removal. Note that in equation (4), n is the frequency number.

[0031]

[0032] The residual noise estimation unit 24 further calculates the power P ｒ０ By subtracting the power per frequency of the data symbol power estimate 104 from (n) as in equation (5), the residual noise power per frequency 205 remaining in the subtractor 22 is obtained as N ｒ (n) is calculated. In equation (5), B is the signal bandwidth.

[0033] N ｒ (n) = P ｒ０ (n)-D / B...(5)

[0034] The weighting factor calculation unit 25 calculates the weighting factor 203 using the null symbol spectrum 105 and the residual noise power 205 (step S25). Since the null symbol is composed of an interference signal and a noise signal, the null symbol spectrum 105 is a one-dimensional vector with n as the frequency number. ｎｕｌｌ (n), the null symbol power spectrum is expressed by equation (6). Note that the null symbol power spectrum is calculated by subtracting the interference power I ｓｐ (n) and noise power N ｓｐ (n), that is, I ｓｐ (n) + N ｓｐ (n).

[0035] I ｓｐ (n) + N ｓｐ (n) = |R ｎｕｌｌ (n) | ２ …(6)

[0036] Here, the weighting coefficient 203 is a weighting coefficient for preventing unnecessary noise enhancement due to the interference replica signal 201 in the subtractor 22. As a feature of the weighting coefficient, the noise power N ｓｐ (n) is the interference power I ｓｐ (n), the weighting coefficient approaches 0 because subtracting the interference replica signal 201 adds unnecessary noise. ｓｐ (n) is the interference power I ｓｐ When I is much smaller than (n), complete removal of the interference signal by the interference replica signal 201 becomes important, so the weighting coefficient approaches 1. Taking this characteristic into consideration, the weighting coefficient 203 is calculated as shown in equation (7). In equation (7), I ｅｓｔ (n) is the estimated interference power I calculated by subtracting the residual noise power 205 from the null symbol power spectrum. ｅｓｔ (n) = I ｓｐ (n) + N ｓｐ (n)-N ｒ (n).

[0037] W(n) = I ｅｓｔ (n) / (I ｓｐ (n) + N ｓｐ (n)) ... (7)

[0038] In this way, the interference removal unit 18 uses the received signal 100, the data symbol power estimate 104, the null symbol spectrum 105, the interference center frequency estimate 106, and the estimated interference bandwidth 107 to calculate, for each frequency, a weighting coefficient 203 corresponding to the ratio between the residual noise power component and the interference power component contained in the received signal after interference removal, and subtracts from the received signal 100 a weighted interference replica signal obtained by multiplying the interference replica signal 201 by the weighting coefficient 203 for each frequency, thereby suppressing degradation due to noise emphasis.

[0039] As described above, according to this embodiment, the interference cancellation device 1 sets the weighting coefficient 203 for each frequency, thereby avoiding unnecessary noise enhancement at frequencies with a low INR (Interference to Noise power Ratio) and simultaneously achieving reliable interference cancellation at frequencies with a high INR. This allows the interference cancellation device 1 to efficiently remove interference signals contained in the received signal 100 and reduce degradation of reception quality, for example, bit error rate. The interference cancellation device 1 can suppress degradation due to noise enhancement. Furthermore, the interference cancellation device 1 can also minimize degradation due to noise enhancement.

[0040] The interference cancellation device 1 of this embodiment improves interference resistance, making it possible to realize stable wireless communication against various interference spectra on the frequency axis.

[0041] Next, a description will be given of the hardware configuration of the interference cancellation device 1. In the interference cancellation device 1, the data symbol extraction unit 11, the null symbol extraction unit 12, the null symbol power calculation unit 13, the data symbol power calculation unit 14, the null symbol spectrum calculation unit 15, the interference center frequency estimation unit 16, the interference bandwidth estimation unit 17, and the interference cancellation unit 18 are realized by processing circuits. The processing circuit may be a processor and memory that executes a program stored in a memory, or may be dedicated hardware. The processing circuit is also called a control circuit.

[0042] FIG. 7 is a diagram showing an example of the configuration of a processing circuit 90 when the processing circuit for implementing the interference removal device 1 according to this embodiment is implemented by a processor 91 and a memory 92. The processing circuit 90 shown in FIG. 7 is a control circuit and includes a processor 91 and a memory 92. When the processing circuit 90 is configured with the processor 91 and the memory 92, each function of the processing circuit 90 is implemented by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 92. The processing circuit 90 realizes each function by having the processor 91 read and execute the program stored in the memory 92. That is, the processing circuit 90 includes the memory 92 for storing a program that results in the processing of the interference removal device 1 being executed. This program can also be said to be a program that causes the interference removal device 1 to execute each function implemented by the processing circuit 90. This program may be provided by a storage medium on which the program is stored, or by other means such as a communication medium.

[0043] The program includes a first step in which a data symbol extraction unit 11 extracts a data symbol portion from a received signal 100 in which null symbols have been inserted into the data symbols, and outputs a data symbol signal 101; a second step in which a null symbol extraction unit 12 extracts a null symbol portion from the received signal 100, and outputs a null symbol signal 102; a third step in which a null symbol power calculation unit 13 calculates a null symbol power estimate 103 indicating the power of the null symbol signal 102; a fourth step in which a data symbol power calculation unit 14 calculates a data symbol power estimate 104 indicating the power of the data symbol signal 101; a fifth step in which a null symbol spectrum calculation unit 15 calculates a null symbol spectrum 105 from the null symbol signal 102; It can also be said that this is a program that causes the interference removal device 1 to execute the following steps: a sixth step in which the interference bandwidth estimation unit 17 estimates the center frequency of the interference signal using the data symbol power estimate 104 and the null symbol spectrum 105 and outputs an interference center frequency estimate 106; a seventh step in which the interference bandwidth estimation unit 17 estimates the interference bandwidth of the interference signal from the null symbol spectrum 105 and outputs an estimated interference bandwidth 107; and an eighth step in which the interference removal unit 18 generates an interference replica signal 201 using the received signal 100, the data symbol power estimate 104, the null symbol spectrum 105, the interference center frequency estimate 106, and the estimated interference bandwidth 107, and multiplies the interference replica signal 201 by a weighting coefficient 203 for each frequency in accordance with the ratio between the interference power component and the noise power component contained in the interference replica signal 201, thereby suppressing degradation due to noise emphasis.

[0044] Here, the processor 91 may be a CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor), etc. The memory 92 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a DVD (Digital Versatile Disc).

[0045] Fig. 8 is a diagram showing an example in which the processing circuit 93 that realizes the interference cancellation device 1 according to this embodiment is configured with dedicated hardware. When the processing circuit 93 is configured with dedicated hardware, the processing circuit 93 shown in Fig. 8 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each function of the interference cancellation device 1 may be realized by the processing circuit 93 separately, or all functions may be realized collectively by the processing circuit 93.

[0046] It should be noted that some of the functions of the interference removal device 1 may be realized by dedicated hardware and some by software or firmware. In this way, the processing circuit can realize each of the above-described functions by dedicated hardware, software, firmware, or a combination of these.

[0047] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0048] 1 Interference removal device, 11 Data symbol extraction unit, 12 Null symbol extraction unit, 13 Null symbol power calculation unit, 14 Data symbol power calculation unit, 15 Null symbol spectrum calculation unit, 16 Interference center frequency estimation unit, 17 Interference bandwidth estimation unit, 18 Interference removal unit, 21 Interference replica signal generation unit, 22 Subtraction unit, 23 Time domain transformation unit, 24 Residual noise estimation unit, 25 Weighting coefficient calculation unit, 90, 93 Processing circuit, 91 Processor, 92 Memory.

Claims

1. An interference cancellation device comprising: a data symbol extraction unit that outputs a data symbol signal extracted from a received signal in which null symbols have been inserted into data symbols; a null symbol extraction unit that outputs a null symbol signal extracted from the received signal; a calculation unit that calculates a data symbol power estimate indicating the power of the data symbol signal and a null symbol spectrum from the null symbol signal; an interference center frequency estimation unit that outputs an estimated interference center frequency estimate using the data symbol signal, the data symbol power estimate, and the null symbol spectrum; an interference bandwidth estimation unit that outputs an estimated interference bandwidth estimated from the null symbol spectrum; and an interference cancellation unit that generates an interference replica signal using the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth, and multiplies the interference replica signal by a weighting coefficient for each frequency in accordance with the ratio between the interference power component and the noise power component contained in the interference replica signal, thereby suppressing degradation due to noise emphasis.

2. The interference cancellation device according to claim 1, characterized in that the interference cancellation unit uses the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth to calculate, for each frequency, a weighting coefficient corresponding to the ratio between the residual noise power component and the interference power component contained in the received signal after interference cancellation, and subtracts from the received signal a weighted interference replica signal obtained by multiplying the interference replica signal by the weighting coefficient for each frequency, thereby suppressing degradation due to noise emphasis.

3. A control circuit for controlling an interference cancellation device, the control circuit causing the interference cancellation device to perform the following: extracting a data symbol portion from a received signal in which null symbols have been inserted into data symbols, and outputting a data symbol signal; extracting a null symbol portion from the received signal, and outputting a null symbol signal; calculating a null symbol power estimate indicating the power of the null symbol signal; calculating a data symbol power estimate indicating the power of the data symbol signal; calculating a null symbol spectrum from the null symbol signal; estimating a center frequency of an interference signal using the data symbol signal, the data symbol power estimate, and the null symbol spectrum, and outputting an interference center frequency estimate; estimating an interference bandwidth of the interference signal from the null symbol spectrum, and outputting an estimated interference bandwidth; generating an interference replica signal using the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth, and multiplying the interference replica signal by a weighting coefficient for each frequency according to the ratio between the interference power component and the noise power component contained in the interference replica signal, thereby suppressing degradation due to noise emphasis.

4. A storage medium storing a program for controlling an interference cancellation device, wherein the program causes the interference cancellation device to perform the following: extracting a data symbol portion from a received signal in which null symbols have been inserted into data symbols, and outputting a data symbol signal; extracting a null symbol portion from the received signal, and outputting a null symbol signal; calculating a null symbol power estimate indicating the power of the null symbol signal; calculating a data symbol power estimate indicating the power of the data symbol signal; calculating a null symbol spectrum from the null symbol signal; estimating a center frequency of an interference signal using the data symbol signal, the data symbol power estimate, and the null symbol spectrum, and outputting an interference center frequency estimate; estimating an interference bandwidth of the interference signal from the null symbol spectrum, and outputting an estimated interference bandwidth; generating an interference replica signal using the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth, and multiplying the interference replica signal by a weighting coefficient for each frequency according to the ratio between the interference power component and the noise power component contained in the interference replica signal, thereby suppressing degradation due to noise emphasis.

5. A first step in which a data symbol extraction unit extracts a data symbol portion from a received signal in which null symbols have been inserted into data symbols, and outputs a data symbol signal; a second step in which a null symbol extraction unit extracts a null symbol portion from the received signal, and outputs a null symbol signal; a third step in which a null symbol power calculation unit calculates a null symbol power estimate indicating the power of the null symbol signal; a fourth step in which a data symbol power calculation unit calculates a data symbol power estimate indicating the power of the data symbol signal; a fifth step in which a null symbol spectrum calculation unit calculates a null symbol spectrum from the null symbol signal; a sixth step in which an interference center frequency estimation unit estimates a center frequency of an interference signal using the data symbol signal, the data symbol power estimate, and the null symbol spectrum, and outputs an interference center frequency estimate; a seventh step in which an interference bandwidth estimation unit estimates the interference bandwidth of the interference signal from the null symbol spectrum, and outputs an estimated interference bandwidth; an eighth step in which an interference canceller generates an interference replica signal using the received signal, the data symbol power estimate, the null symbol spectrum, the interference center frequency estimate, and the estimated interference bandwidth, and multiplies the interference replica signal by a weighting coefficient for each frequency in accordance with a ratio between an interference power component and a noise power component contained in the interference replica signal, thereby suppressing degradation due to noise emphasis.

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