Interference eliminating device, control circuit, storage medium, interference elimination method, and interference elimination system

Abstract

An interference eliminating device (304) comprises a null symbol extracting unit (401) for extracting a null symbol sequence from a received signal in which null symbols are inserted between data symbols, a received signal spectrum calculating unit (402) for converting the received signal into a frequency domain signal and calculating a received signal spectrum, which is the frequency spectrum of the received symbol sequence including the null symbols, an interference frequency range estimating unit (403) for estimating an interference frequency range from the null symbol sequence and the received signal spectrum, and an interference eliminating unit (404) for eliminating interference using the interference frequency range and the received signal spectrum and reproducing the received signal spectrum from which the interference has been eliminated, wherein the interference eliminating unit (404) eliminates interference signals from received signals in which the number of null symbols inserted between the data symbols is 2n-1, where n is an integer of 2 or more.

Description

Interference removal device, control circuit, storage medium, interference removal method, and interference removal system

[0001] This disclosure relates to an interference rejection device, control circuit, storage medium, interference rejection method, and interference rejection system for removing interference signals from a received signal.

[0002] Interference signals contained in wireless communication received signals significantly degrade communication performance; therefore, receiving devices are required to remove interference from the received signal.

[0003] In the wireless communication system described in Patent Document 1, the transmitting device transmits a signal by inserting null symbols between transmission symbols, and the receiving device extracts null symbols from the received signal and interpolates them to reconstruct the interference component in the section corresponding to the data symbol, and subtracts the interference component from the received signal.

[0004] Patent No. 6746029

[0005] However, in the technology described in Patent Document 1, the upper limit of the null symbol insertion rate is 50% of the symbol rate, and it is not possible to remove interfering signals with a bandwidth larger than 50% of the symbol rate from the received signal.

[0006] This disclosure has been made in view of the above, and aims to provide an interference rejection device that can remove interference signals having a bandwidth greater than 50% of the symbol rate from a received signal.

[0007] To solve the above-mentioned problems and achieve the objective, the interference removal device of this disclosure comprises a null symbol extraction unit that extracts a sequence of null symbols from a received signal in which null symbols are inserted between data symbols, and a received signal spectrum calculation unit that converts the received signal into a frequency domain signal and calculates a received signal spectrum, which is the frequency spectrum of the sequence of received symbols including null symbols. The interference removal device of this disclosure also comprises an interference frequency range estimation unit that estimates the interference frequency range by frequency-analyzing the sequence of null symbols to estimate the interference bandwidth and estimating the interference center frequency using the received signal spectrum. The interference removal device of this disclosure also comprises an interference removal unit that removes interference using the interference frequency range and the received signal spectrum and reconstructs the received signal spectrum from which interference has been removed, and a frequency-time domain conversion unit that converts the received signal spectrum from which interference has been removed into a time domain signal. When n is an integer of 2 or more, the number of null symbols inserted between data symbols in the interference removal unit is 2. n The interference signal is removed from the received signal, which is -1.

[0008] The interference rejection device described herein has the effect of removing interference signals with a bandwidth greater than 50% of the symbol rate from a received signal.

[0009] A functional block diagram showing an example configuration of a transmitting device according to the embodiment. A diagram showing a sequence of transmitted symbols output by the null insertion unit of the transmitting device according to the embodiment. A functional block diagram showing an example configuration of a receiving device according to the embodiment. A functional block diagram showing an example configuration of an interference rejection device included in the receiving device according to the embodiment. A diagram for explaining the received signal spectrum of a received signal received by the receiving device according to the embodiment. A diagram for explaining a first example of the process by which the interference rejection unit of the interference rejection device according to the embodiment removes interference. A diagram for explaining a second example of the process by which the interference rejection unit of the interference rejection device according to the embodiment removes interference. A diagram for explaining a third example of the process by which the interference rejection unit of the interference rejection device according to the embodiment removes interference. A flowchart showing the processing procedure of the process by which the interference rejection device according to the embodiment removes interference. A diagram showing an example configuration of a processing circuit when the processing circuit included in the control circuit of the interference rejection device according to the embodiment is implemented with a processor and memory. A diagram showing an example configuration of a processing circuit when the processing circuit included in the control circuit of the interference rejection device according to the embodiment is configured with dedicated hardware.

[0010] The interference removal device, control circuit, storage medium, interference removal method, and interference removal system according to embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0011] Embodiment. The interference rejection system comprises a transmitting device (transmitting device 1, described later) and a receiving device (receiving device 3, described later). Transmitting device 1 and receiving device 3 are separate devices, and transmitting device 1 communicates with receiving device 3 by transmitting a transmission signal to receiving device 3.

[0012] Figure 1 is a functional block diagram showing an example configuration of a transmitting device according to an embodiment. The transmitting device 1 comprises an encoding unit 100, a modulation unit 101, a null insertion unit 102, a waveform shaping filter unit 103, a DA (Digital to Analog) conversion unit 104, a transmission unit 105, and an antenna 106.

[0013] The encoding unit 100 performs error correction coding on the transmitted data. Examples of error correction coding include convolution coding, turbo coding, and LDPC (Low Density Parity Check). However, the error correction coding applied in this embodiment is not limited to these. The transmitting device 1 may also be configured not to perform error correction coding. The encoding unit 100 outputs the transmitted data that has undergone error correction coding to the modulation unit 101.

[0014] The modulation unit 101 applies primary modulation to the transmission data, converting it into a sequence of transmission symbols. Examples of modulation methods for primary modulation include PSK (Phase Shift Keying), FSK (Frequency Shift Keying), or QAM (Quadrature Amplitude Modulation). However, the modulation methods applied in this embodiment are not limited to these. The modulation unit 101 outputs the transmission data converted into a sequence of transmission symbols to the null insertion unit 102.

[0015] The null insertion unit 102 inserts null symbols into the time domain of the transmitted symbol sequence. A null is a signal with an amplitude of 0, and a null symbol is a symbol that is not transmitted. Details of the null insertion unit 102 will be described later. The null insertion unit 102 outputs the transmitted symbol sequence with the null symbols inserted to the waveform shaping filter unit 103.

[0016] The waveform shaping filter unit 103 upsamples the transmission symbol sequence. The waveform shaping filter unit 103 also applies bandwidth limiting to the transmission symbol sequence to generate a transmission digital signal, which is either a baseband signal or an IF (Intermediate Frequency) signal. The transmission digital signal is a digital signal intended for transmission.

[0017] The type of bandwidth limiting filter used by the waveform shaping filter unit 103 when performing bandwidth limiting on the transmission symbol sequence is not particularly limited, but it is effective to apply a Nyquist filter to prevent intersymbol interference between null symbols and data symbols during bandwidth limiting. The waveform shaping filter unit 103 outputs the generated transmission digital signal to the DA conversion unit 104.

[0018] The DA conversion unit 104 converts the transmitted digital signal into a transmitted analog signal. The transmitted analog signal is an analog signal for transmission. The DA conversion unit 104 outputs the converted transmitted analog signal to the transmission unit 105.

[0019] The transmitting unit 105 converts the DA-converted transmit analog signal into a radio frequency signal. The antenna 106 transmits the radio frequency signal as the transmit signal. The processing performed after the null insertion unit 102 is the same as that performed in a typical wireless transmission device, and is not particularly limited in this embodiment.

[0020] Here, the details of the operation of the null insertion unit 102 according to this embodiment will be described. The null insertion unit 102 receives a sequence of transmitted symbols as input. The null insertion unit 102 inserts null symbols in the time direction between data symbols. The number of null symbols that the null insertion unit 102 inserts between data symbols is one or more. The number of null symbols that the null insertion unit 102 inserts between data symbols is not particularly limited, but in this embodiment, n is an integer of 2 or more, so 2 n It is -1. Note that n may also be 1. For example, if n = 2, the number of null symbols that the null insertion unit 102 inserts between each data symbol is 3.

[0021] Figure 2 is a diagram showing the transmission symbol sequence output by the null insertion unit of the transmitting device according to the embodiment. In Figure 2, the horizontal axis represents time, and the vertical axis represents the amplitude of the signal. As shown in Figure 2, the null insertion unit 102 generates a transmission symbol sequence by inserting null symbols 201 between transmission symbol data 200 and outputs it to the waveform shaping filter unit 103.

[0022] The transmission time of one transmitted symbol data 200 is one symbol time (symbol interval), and the transmission time of one null symbol 201 is one null insertion time (null interval).

[0023] Figure 2 shows an example in which three null intervals (null symbols 201) are inserted between each transmission symbol data 200. Specifically, Figure 2 shows the case where three null symbols 201 are inserted after the transmission symbol data 200 indicated by "D0", three null symbols 201 are inserted after the transmission symbol data 200 indicated by "D1", and three null symbols 201 are inserted after the transmission symbol data 200 indicated by "D2".

[0024] Note that the insertion interval of the null interval is arbitrary, and the null interval is inserted periodically. For example, the null insertion unit 102 inserts a null interval every time X (X is a natural number) transmission symbol data 200 are transmitted (2 n A transmission symbol sequence is generated such that (1) null symbols 201 are transmitted. In this case, the null insertion unit 102 inserts (2) between X transmission symbol data 200 and X transmission symbol data 200. n -1) The process of inserting null symbols 201 is repeated. The following describes the case where X = 1. That is, each time one transmission symbol data 200 is transmitted, the null insertion unit 102 (2 n -1) Generate a sequence of symbols to send so that 1 null symbols 201 are sent.

[0025] Figure 3 is a functional block diagram showing an example configuration of a receiving device according to an embodiment. The receiving device 3 comprises an antenna 300, a receiving unit 301, an AD (Analog to Digital) conversion unit 302, a waveform shaping filter unit 303, an interference removal device 304, a demodulation unit 305, and a decoding unit 306.

[0026] Antenna 300 receives radio frequency signals. The radio frequency signals received by antenna 300 include the desired wave and interference waves. The receiving unit 301 frequency-converts the radio frequency signals received by antenna 300 into analog signals, which are IF signals or baseband signals, and outputs them to the AD conversion unit 302.

[0027] The AD conversion unit 302 converts the analog signal into a digital signal and outputs it to the waveform shaping filter unit 303. The waveform shaping filter unit 303 limits the bandwidth of the digital signal to remove noise and outputs it to the interference removal device 304.

[0028] The interference rejection device 304 suppresses interference by estimating interference from the received signal and removing it. The interference rejection device 304 estimates the interference frequency range, which is the frequency range of the interfering signal. The interference frequency range is the range of frequencies from frequency 0 to the symbol rate (symbol rate Fs, described later) in which the signal is interfering.

[0029] The interference rejection device 304 removes interference components by utilizing the characteristics of the frequency spectrum of the received symbol sequence, including null symbols, according to the interference frequency range. That is, the interference rejection device 304 removes interference components based on the interference frequency range and the received signal by utilizing the fact that the frequency spectrum of the transmitted symbols is repeated in the received signal spectrum, including null symbols. The interference rejection device 304 outputs the received symbols from which the interference components have been removed to the demodulation unit 305. Details of the operation of the interference rejection device 304 will be described later.

[0030] The demodulation unit 305 performs demodulation processing on the received symbols (data symbols) and outputs the demodulation result, which is the demapping result for error correction decoding. The decoding unit 306 receives the demapping result, performs error correction decoding, and outputs the decoded result. The processing performed by the antenna 300, receiving unit 301, AD conversion unit 302, waveform shaping filter unit 303, demodulation unit 305, and decoding unit 306 is the same as that performed in a typical wireless receiver, and is not particularly limited in this embodiment.

[0031] Figure 4 is a functional block diagram showing an example of the configuration of an interference rejection device included in the receiving device according to the embodiment. The interference rejection device 304 comprises a null symbol extraction unit 401, a received signal spectrum calculation unit 402, an interference frequency range estimation unit 403, an interference rejection unit 404, and a frequency-time domain conversion unit 406.

[0032] The null symbol extraction unit 401 and the received signal spectrum calculation unit 402 receive a digital signal (received signal) from the waveform shaping filter unit 303. The null symbol extraction unit 401 extracts the null symbols inserted by the null insertion unit 102 from the digital signal received from the AD conversion unit 302. In other words, the null symbol extraction unit 401 extracts a sequence of null symbols (the null symbol portion) from the received signal. The null symbol extraction unit 401 outputs the extracted sequence of null symbols to the interference frequency range estimation unit 403.

[0033] The received signal spectrum calculation unit 402 converts the digital signal received from the waveform shaping filter unit 303 into a frequency domain signal and calculates the received signal spectrum, which is the frequency spectrum of the received symbol sequence including null symbols. The received signal spectrum calculation unit 402 outputs the calculated received signal spectrum to the interference frequency range estimation unit 403 and the interference removal unit 404.

[0034] The interference frequency range estimation unit 403 estimates the interference frequency range by performing frequency analysis on the extracted null symbol sequence to estimate the interference bandwidth and by estimating the interference center frequency using the received signal spectrum. The interference bandwidth is the bandwidth of the interference frequency range, and the interference center frequency is the frequency at the center of the interference frequency range. The interference frequency range estimation unit 403 estimates the interference frequency range based on the interference bandwidth and the interference center frequency. The interference frequency range estimation unit 403 outputs the interference frequency range to the interference removal unit 404.

[0035] The interference removal unit 404 removes interference from the received signal spectrum using the estimated interference frequency range and the calculated received signal spectrum, and reconstructs the received signal spectrum from which the interference has been removed. The interference removal unit 404 outputs the received signal spectrum from which the interference has been removed to the frequency-time domain conversion unit 406.

[0036] A frequency-time domain converting unit 406 converts a received signal spectrum (frequency-domain signal) regenerated after interference is removed into a time-domain signal. The frequency-time domain converting unit 406 outputs the received symbol that has been subjected to interference removal and converted into a time-domain signal to a demodulation unit 305.

[0037] Here, the interference removing unit 404 will be described in detail. Characteristics of the received signal spectrum vary depending on the insertion rate of null symbols inserted by a null inserting unit 102. The insertion rate of null symbols is the ratio of the number of inserted null symbols to the number of data symbols.

[0038] When the number of symbols inserted between data symbols is 2 n -1, the received signal spectrum has a characteristic that the frequency spectrum formed only by a transmission symbol sequence excluding null symbols is repeated n times. That is, in the received signal spectrum which is a frequency-domain signal of a time signal sequence, the same frequency spectrum (the frequency spectrum formed only by the transmission symbol sequence) is repeated in the frequency direction.

[0039] For example, when n=2, the number of symbols inserted between data symbols is 3, and the frequency spectrum of the received signal spectrum is repeated 4 times.

[0040] Here, an example of the received signal spectrum of a reception signal received by the reception device 3 will be described. FIG. 5 is a diagram for explaining the received signal spectrum of a reception signal received by the reception device according to the embodiment. In FIG. 5, the horizontal axis represents frequency, and the vertical axis represents signal amplitude. In the following FIGS. 6 to 8, the horizontal axis also represents frequency, and the vertical axis also represents signal amplitude.

[0041] FIG. 5 shows a received signal spectrum 500 when n=2. Assuming that the frequency spectrum of only the transmission symbol sequence is a transmission signal spectrum 501, in the received signal spectrum 500, the same frequency spectrum as the transmission signal spectrum 501 is repeated 4 times on the frequency axis. Here, the repeated frequency regions are defined as a frequency region F0, a frequency region F1, a frequency region F2, and a frequency region F3 from the low frequency side.

[0042] When the symbol rate is symbol rate Fs, the frequency domain F0 is a frequency range from 0 to Fs / 4, and the frequency domain F1 is a frequency range from Fs / 4 to Fs / 2. Further, the frequency domain F2 is a frequency range from Fs / 2 to 3Fs / 4, and the frequency domain F3 is a frequency range from 3Fs / 4 to Fs.

[0043] The interference removal unit 404 performs the following copying process on the received signal spectrum 500 for each frequency bin obtained by M-dividing the range from frequency 0 to symbol rate Fs. The interference removal unit 404 sets m as the internal frequency bin number of the processing target, where m is a value from 0 to M-1.

[0044] The frequency domains F0 to F3 each have M / 4 frequency bins. If p0, p1, p2, and p3 are taken as the respective internal frequency bin numbers of the frequency domain F0, frequency domain F1, frequency domain F2, and frequency domain F3, each internal frequency bin number of the frequency domains F0 to F3 takes a value from 0 to ((M / 4)-1) in order from the lowest frequency.

[0045] When the internal frequency bin number m of the processing target is within the interference frequency range (interference frequency range 600 described later), the interference removal unit 404 copies the average value of the frequency components of the internal frequency bin numbers that are outside the interference frequency range 600 among the internal frequency bin numbers m mod (M / 4) of each of the frequency domains F0 to F3 as the frequency component of the internal frequency bin number m. Here, "%" is an operator indicating a remainder. That is, the interference removal unit 404 copies frequency components outside the interference frequency range 600 to the interference frequency range 600.

[0046] FIG. 6 is a diagram for explaining a first example of interference removal processing performed by the interference removal unit of the interference removal apparatus according to the embodiment. FIG. 6 shows a case where an interference signal having a bandwidth of 75% of the symbol rate Fs is present in the interference frequency range 600.

[0047] The interference frequency range 600 is the frequency range in the central region of the frequency range from frequency 0 to symbol rate Fs. Therefore, the frequency range outside the interference frequency range 600 is the frequency range that is not affected and becomes the frequency component of the copy source. The interference removal unit 404 uses the frequency range outside the interference frequency range 600 as the frequency component of the copy source and the frequency range inside the interference frequency range 600 as the frequency component of the copy destination.

[0048] The interference frequency range 600 includes, for example, a portion of the frequency domain F0 (the region on the symbol rate Fs / 4 side), frequency domains F1 and F2, and a portion of the frequency domain F3 (the region on the symbol rate 3Fs / 4 side).

[0049] When the interference rejection unit 404 applies the above copying process to a received signal spectrum in the interference frequency range 600, where the interference signal has a bandwidth of 75% of the symbol rate Fs, the relationship between the source and destination of the frequency components is as shown in Figure 6.

[0050] The source bandwidth F10 is a portion of the frequency domain F0 on the frequency 0 side. The source bandwidth F11 is a portion of the frequency domain F3 on the symbol rate Fs side. There is no overlap between the internal frequency bin numbers in source bandwidth F10 and source bandwidth F11, and the sum of the bandwidths of source bandwidth F10 and source bandwidth F11 is the same as the bandwidth of any of the frequency domains F0 to F3. That is, since the interference frequency range 600 has a bandwidth of 75% of the symbol rate Fs, the sum of the bandwidths of the non-interfering source bandwidths F10 and F11 is 25% of the symbol rate Fs, which is the same as the bandwidth of any of the frequency domains F0 to F3.

[0051] The combined frequency range of all destination bandwidths f20 and f21 is the same as the interference frequency range of 600. Destination bandwidth f20 is a portion of the frequency domains F1, F2, and F3 on the frequency 0 side, and the bandwidth of destination bandwidth f20 is the same as the bandwidth of source bandwidth F10. Destination bandwidth f21 is the remaining portion of the frequency domains F0, F1, and F2 on the symbol rate Fs side, and the bandwidth of destination bandwidth f21 is the same as the bandwidth of source bandwidth F11.

[0052] In this case, the internal frequency bin numbers within the source bandwidth F10 are the same as the internal frequency bin numbers within the destination bandwidth f20. Therefore, the interference rejection unit 404 copies the frequency components of the source bandwidth F10 to each destination bandwidth f20.

[0053] Similarly, the internal frequency bin numbers within the source bandwidth F11 are the same as the internal frequency bin numbers within the destination bandwidth f21. Therefore, the interference rejection unit 404 copies the frequency components of the source bandwidth F11 to each destination bandwidth f21.

[0054] In this way, the interference removal unit 404 copies the frequency components of the source band F10 to the destination band f20, and copies the frequency components of the source band F11 to the destination band f21. As a result, the entire interference frequency range 600 is replaced with the frequency components of the transmitted signal spectrum 501, and the interference is removed. In this way, the interference removal device 304 checks the number of null symbols inserted between data symbols. n Since the interference signal is removed from the received signal which is -1 (where n is an integer greater than or equal to 2), interference can be removed even if the interference signal has a bandwidth greater than 50% of the symbol rate Fs and is within the interference frequency range.

[0055] Figure 7 is a diagram illustrating a second example of the interference removal process performed by the interference removal unit of the interference removal device according to the embodiment. Figure 7 shows the case where an interference signal with a bandwidth of 50% to 75% of the symbol rate is in the interference frequency range 605.

[0056] The interference frequency range 605 is the central frequency range of the frequency range from frequency 0 to symbol rate Fs. Therefore, the frequency range outside the interference frequency range 605 is the frequency range that is not affected and becomes the source frequency component. The interference removal unit 404 uses the frequency range outside the interference frequency range 605 as the source frequency component and the frequency range inside the interference frequency range 605 as the destination frequency component. The interference frequency range 605 includes a part of the frequency domain F0 (the region on the symbol rate Fs / 4 side) and frequency domains F1 and F2.

[0057] When the interference rejection unit 404 applies the above copying process to a received signal spectrum in the interference frequency range 605 where an interference signal with a bandwidth of 50% to 75% of the symbol rate Fs is present, the relationship between the source and destination of the frequency components is as shown in Figure 7.

[0058] The source bandwidth F30 is a portion of the frequency domain F0 on the frequency 0 side. The source bandwidth F31 is a portion of the frequency domain F3 on the symbol rate Fs side, and the source bandwidth F32 is the remaining portion of the frequency domain F3 on the symbol rate 3Fs / 4 side. There is no overlap between the internal frequency bin numbers in source bandwidth F30 and source bandwidth F31, and the sum of the bandwidths of source bandwidth F30 and source bandwidth F31 is the same as the bandwidth of the frequency domain (any of frequency domains F0 to F3). Furthermore, although source bandwidth F32 is in a different frequency domain than source bandwidth F30, it has the same internal frequency bin numbers.

[0059] The combined frequency range of all destination bandwidths f40 and f41 is the same as the interference frequency range 605. Destination bandwidth f40 is a portion of the frequency 0 side of frequency domains F1 and F2, and its bandwidth is the same as the bandwidth of source bandwidth F30. Destination bandwidth f41 is the remaining portion of the frequency domains F0, F1, and F2 on the symbol rate Fs side, and its bandwidth is the same as the bandwidth of source bandwidth F31.

[0060] In this case, the internal frequency bin numbers within the source bandwidth F30 are the same as those within the destination bandwidth f40, and the internal frequency bin numbers within the source bandwidth F32 are the same as those within the destination bandwidth f40. Therefore, the interference removal unit 404 copies the average value of the frequency components of the source bandwidths F30 and F32 to each destination bandwidth f40.

[0061] Furthermore, the internal frequency bin numbers within the source bandwidth F31 are the same as those in the destination bandwidth f41. Therefore, the interference rejection unit 404 copies the frequency components of the source bandwidth F31 to each destination bandwidth f41.

[0062] In this way, the interference removal unit 404 copies the average value of the frequency components of the source bands F30 and F32 to the destination band f40, and copies the frequency components of the source band F31 to the destination band f41. As a result, the entire interference frequency range 605 is replaced with the frequency components of the transmitted signal spectrum 501, and the interference is removed.

[0063] Figure 8 is a diagram illustrating a third example of the interference removal process performed by the interference removal unit of the interference removal device according to the embodiment. Figure 8 shows the case where an interference signal with a bandwidth of 25% or less of the symbol rate Fs is in the interference frequency range 612.

[0064] The interference frequency range 612 is the central frequency range of the frequency range from frequency 0 to symbol rate Fs. Therefore, the frequency range outside the interference frequency range 612 is the frequency range that is not affected and becomes the source frequency component. The interference removal unit 404 uses the frequency range outside the interference frequency range 612 as the source frequency component and the frequency range inside the interference frequency range 612 as the destination frequency component. The interference frequency range 612 includes a portion of the frequency domain F0 (the region on the symbol rate Fs / 4 side).

[0065] When the interference rejection unit 404 applies the above copying process to a received signal spectrum in the interference frequency range 612 where an interference signal with a bandwidth of 25% or less of the symbol rate Fs is present, the relationship between the source and destination of the frequency components is as shown in Figure 8.

[0066] The destination bandwidth f60 has the same frequency range as the interference frequency range 612. The source bandwidths F50, F51, and F52 are parts of the symbol rate Fs side of the frequency domains F1, F2, and F3, respectively. The destination bandwidth f60 is a part of the symbol rate Fs side of the frequency domain F0, and the bandwidth of the destination bandwidth f60 is the same as the bandwidth of any of the source bandwidths F50, F51, or F52.

[0067] In this case, the internal frequency bin numbers in the source bandwidth F50, F51, and F52 are the same as the internal frequency bin numbers in the destination bandwidth f60. Therefore, the interference removal unit 404 copies the average value of the frequency components of the source bandwidths F50, F51, and F52 to the destination bandwidth f60. As a result, the interference frequency range 612 is entirely replaced by the frequency components of the transmitted signal spectrum 501, and the interference is removed.

[0068] Thus, the interference removal device 304 of this embodiment has a limit on the number of symbols inserted between data symbols. n When the value is -1, the frequency components of the non-interfering frequency range outside the interference frequency range 600 are copied into the interference frequency range 600. As a result, the interference rejection device 304 replaces the entire interference frequency range 600 with the frequency components of the transmitted signal spectrum 501 to remove the interference. Therefore, the interference rejection device 304 can remove interference signals with a bandwidth larger than 50% of the symbol rate Fs, and can suppress degradation due to noise enhancement.

[0069] Next, the processing procedure for the interference removal process performed by the interference removal device 304 will be described. Figure 9 is a flowchart showing the processing procedure for the interference removal process performed by the interference removal device according to the embodiment.

[0070] The null symbol extraction unit 401 of the interference removal device 304 extracts the null symbols inserted by the null insertion unit 102 from the digital signal received from the AD conversion unit 302 (step S10).

[0071] The received signal spectrum calculation unit 402 converts the digital signal received from the waveform shaping filter unit 303 into a frequency domain signal and calculates the received signal spectrum, which is the frequency spectrum of the received symbol sequence including null symbols (step S20).

[0072] The interference frequency range estimation unit 403 estimates the interference frequency range by performing frequency analysis on the extracted null symbol sequence to estimate the interference bandwidth and by estimating the interference center frequency using the received signal spectrum (step S30).

[0073] The interference removal unit 404 removes interference from the received signal spectrum using the estimated interference frequency range and the calculated received signal spectrum (step S40). As a result, the interference removal unit 404 reconstructs the received signal spectrum from which the interference has been removed.

[0074] The frequency-time-domain conversion unit 406 converts the received signal spectrum (frequency-domain signal), which has been regenerated after interference has been removed, into a time-domain signal (step S50). The frequency-time-domain conversion unit 406 outputs the received symbols, which have been converted into time-domain signals after interference has been removed, to the demodulation unit 305.

[0075] Next, the hardware configuration of the interference rejection device 304 will be described. The interference rejection device 304 is implemented by a processing circuit. The processing circuit may be a processor and memory that execute a program stored in memory, or it may be dedicated hardware.

[0076] Figure 10 is a diagram showing an example of the configuration of a processing circuit when the processing circuit of the control circuit of the interference removal device according to the embodiment is realized with a processor and memory. The processing circuit 90 shown in Figure 10 comprises a processor 91 and a memory 92. When the processing circuit 90 is composed of a processor 91 and a memory 92, each function of the processing circuit 90 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as an interference removal program and stored in the memory 92. In the processing circuit 90, each function is realized by the processor 91 reading and executing the interference removal program stored in the memory 92. That is, the processing circuit 90 includes a memory 92 for storing an interference removal program that will ultimately be executed by the processing of the interference removal device 304. This interference removal program can also be said to be a program that causes the interference removal device 304 to execute each function realized by the processing circuit 90. This interference removal program may be provided by a computer-readable storage medium that stores the interference removal program, or by other means such as a communication medium. The interference removal program can also be described as a program that causes the interference removal device 304 to execute the processes shown in steps S10 to S50 of Figure 9.

[0077] Here, the processor 91 is, for example, a CPU (Central Processing Unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor). The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Registered Trademark) (Electrically EPROM), magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0078] FIG. 11 is a diagram showing a configuration example of a processing circuit when the processing circuit included in the control circuit of the interference cancellation apparatus according to the embodiment is configured by dedicated hardware. The processing circuit 93 shown in FIG. 11 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. A part of the processing circuit 93 may be implemented by dedicated hardware, and another part may be implemented by software or firmware. As described above, the processing circuit 93 can implement each of the above functions by dedicated hardware, software, firmware, or a combination thereof. It should be noted that a part of the functions of the receiving apparatus 3 or the transmitting apparatus 1 may be implemented by the processing circuits 90 and 93 shown in FIG. 10 or FIG. 11.

[0079] When n is an integer of 2 or more, the interference cancellation apparatus 304 of the embodiment is configured such that the number of null symbols inserted between data symbols is 2 n -1, the interference cancellation apparatus 304 removes an interference signal from a received signal. Accordingly, the interference cancellation apparatus 304 can remove, from the received signal, an interference signal having a bandwidth larger than 50% of the symbol rate Fs.

[0080] The configuration described in the above embodiment is merely an example, and can be combined with another known technique, and a part of the configuration can be omitted or modified without departing from the scope of the invention.

[0081] 1 Transmitter, 3 Receiver, 90, 93 Processing Circuit, 91 Processor, 92 Memory, 100 Encoding Unit, 101 Modulation Unit, 102 Null Insertion Unit, 103 Waveform Shaping Filter Unit, 104 DA Conversion Unit, 105 Transmitting Unit, 106, 300 Antenna, 200 Transmitted Symbol Data, 201 Null Symbol, 301 Receiver, 302 AD Conversion Unit, 303 Waveform Shaping Filter Unit, 304 Interference Removal Device, 305 Demodulation Unit, 306 Decoding Unit, 401 Null Symbol Extraction Unit, 402 Received Signal Spectrum Calculation Unit, 403 Interference Frequency Range Estimation Unit, 404 Interference Removal Unit, 406 Frequency-Time Domain Conversion Unit, 500 Received Signal Spectrum, 501 Transmitted Signal Spectrum, 600, 605, 612 Interference Frequency Range, F0 to F3 Frequency domain: F10, F11, F30-F32, F50-F52. Source bandwidth: f20, f21, f40, f41, f60. Destination bandwidth: f60.

Claims

1. A null symbol extraction unit extracts a sequence of null symbols from a received signal in which null symbols are inserted between data symbols; a received signal spectrum calculation unit converts the received signal into a frequency domain signal and calculates a received signal spectrum which is the frequency spectrum of the received symbol sequence including the null symbols; an interference frequency range estimation unit estimates the interference frequency range by frequency analyzing the sequence of null symbols to estimate the interference bandwidth and estimating the interference center frequency using the received signal spectrum; an interference removal unit removes interference using the interference frequency range and the received signal spectrum and reconstructs the received signal spectrum from which the interference has been removed; and a frequency-time domain conversion unit converts the received signal spectrum from which the interference has been removed into a time domain signal, wherein the interference removal unit, when n is an integer of 2 or more, calculates the number of null symbols inserted between the data symbols as 2. n An interference removal device characterized by removing an interference signal from the received signal which is -1.

2. The interference removal device according to claim 1, characterized in that the interference removal unit removes the interference signal from the received signal by using the frequency components of the received signal spectrum outside the interference frequency range as the source band and the interference frequency range as the destination band, and copying frequency components with the same internal frequency bin number in the source band and the destination band from the source band to the destination band.

3. The interference removal device according to claim 2, characterized in that the interference removal unit removes the interference signal from the received signal by copying the average value of the frequency components of the internal frequency bins with the same internal frequency bin number as the interference frequency range from among the internal frequency bins outside the interference frequency range to the internal frequency bins within the interference frequency range.

4. The interference removal device according to claim 2 or 3, characterized in that the interference removal unit removes the interference signal from the received signal by copying the frequency components of the source band to the destination band for the received signal in which the frequency spectrum of the transmitted symbol is repeated n times in the received signal spectrum including the null symbol.

5. A control circuit for controlling an interference rejection device, comprising: extracting a sequence of null symbols from a received signal in which null symbols are inserted between data symbols; converting the received signal into a frequency domain signal; calculating a received signal spectrum which is the frequency spectrum of the received symbol sequence including the null symbols; estimating the interference frequency range by frequency analyzing the sequence of null symbols to estimate the interference bandwidth and estimating the interference center frequency using the received signal spectrum; removing interference using the interference frequency range and the received signal spectrum to reconstruct the received signal spectrum from which the interference has been removed; converting the received signal spectrum from which the interference has been removed into a time domain signal; and, when n is an integer of 2 or more, the number of null symbols inserted between the data symbols is 2. n A control circuit characterized by causing the interference removal device to remove an interference signal from the received signal which is -1.

6. A storage medium storing a program for controlling an interference removal device, wherein the program extracts a sequence of null symbols from a received signal in which null symbols are inserted between data symbols, converts the received signal into a frequency domain signal, calculates a received signal spectrum which is the frequency spectrum of the received symbol sequence including the null symbols, estimates the interference frequency range by frequency analyzing the sequence of null symbols to estimate the interference bandwidth and estimating the interference center frequency using the received signal spectrum, removes the interference using the interference frequency range and the received signal spectrum, reconstructs the received signal spectrum from which the interference has been removed, converts the received signal spectrum from which the interference has been removed into a time domain signal, and when n is an integer of 2 or more, the number of null symbols inserted between the data symbols is 2 n A storage medium characterized in that the interference removal device is made to remove an interference signal from the received signal which is -1.

7. The interference rejection device includes: a null symbol extraction step in which the interference rejection device extracts a sequence of null symbols from a received signal in which null symbols are inserted between data symbols; a received signal spectrum calculation step in which the interference rejection device converts the received signal into a frequency domain signal and calculates a received signal spectrum which is the frequency spectrum of the received symbol sequence including the null symbols; an interference frequency range estimation step in which the interference rejection device estimates the interference frequency range by frequency analyzing the sequence of null symbols to estimate the interference bandwidth and estimating the interference center frequency using the received signal spectrum; an interference rejection step in which the interference rejection device removes interference using the interference frequency range and the received signal spectrum and reconstructs the received signal spectrum from which the interference has been removed; and a frequency-time domain conversion step in which the interference rejection device converts the received signal spectrum from which the interference has been removed into a time domain signal, wherein in the interference rejection step, when n is an integer of 2 or more, the number of null symbols inserted between the data symbols is 2 n An interference removal method characterized by removing an interference signal from the received signal which is -1.

8. When n is an integer greater than or equal to 2, the number of null symbols between data symbols is 2. n A transmitting device transmits a transmission signal into which null symbols of -1 are inserted, and a receiving device receives the transmission signal as a receiving signal, wherein the receiving device comprises an interference removal device that removes interference signals from the received signal, the interference removal device comprises a null symbol extraction unit that extracts a sequence of null symbols from the received signal into which the null symbols are inserted, a received signal spectrum calculation unit that converts the received signal into a frequency domain signal and calculates a received signal spectrum which is the frequency spectrum of the received symbol sequence including the null symbols, an interference frequency range estimation unit that estimates the interference frequency range by frequency analysis of the sequence of null symbols and estimating the interference bandwidth and estimating the interference center frequency using the received signal spectrum, an interference removal unit that removes interference using the interference frequency range and the received signal spectrum and reconstructs the received signal spectrum from which the interference has been removed, and a frequency-time domain conversion unit that converts the received signal spectrum from which the interference has been removed into a time domain signal, wherein the interference removal unit, when n is an integer of 2 or more, determines that the number of null symbols inserted between the data symbols is 2 n An interference rejection system characterized by removing the interference signal from the received signal which is -1.

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