Receiver and receiving method

Abstract

The transmitter (1) has a frequency repetition modulation unit (18) which generates a signal in which information symbols, whose time domain signal is non-zero, and null symbols, whose time domain signal is zero, appear periodically by generating a transmission spectrum in which the spectrum of the modulated signal is continuously arranged on the frequency axis, the same transmission symbols are arranged at regular subcarrier intervals in the spectrum of the modulated signal, and the spectrum on the high band side and the spectrum on the low band side are equal to a center frequency.

Description

[Technical field]

[0001] The present disclosure relates to a transmitter, a receiver, a transmitting method, a receiving method, a control circuit, and a program storage medium. [Background technology]

[0002] Unlicensed bands such as the ISM (Industry-Science-Medical) band used in wireless standards such as wireless LAN (Local Area Network) and Bluetooth (registered trademark) are widely used in various systems because no license is required for wireless communication. Since communication devices using unlicensed bands are installed in various indoor and outdoor locations, including offices and train stations, if the communication devices use the same frequency band as that used by other communication devices, signals from other systems including the other communication devices may cause significant interference to the system including the communication devices. Therefore, interference resistance is an important technology for stable communication using unlicensed bands.

[0003] One technique for improving interference resistance is interference avoidance technology. Interference avoidance technology is a technique for improving interference resistance by using a channel that is less susceptible to interference, and is a technique for switching the frequency channel used by a wireless system to a channel that is less susceptible to interference by measuring the degree of interference in advance or by detecting interference collisions. Patent Document 1 discloses a method for determining a channel that is less susceptible to interference as a channel to be preferentially used by the wireless system by measuring and evaluating the interference situation of each channel that the wireless system can use.

[0004] Patent document 2 discloses a method in which a processing circuit for measuring the interference situation of channels that can be used by a wireless system in the 5 GHz band is provided separately from the processing circuit for communications, so that when a signal from another system is detected in a channel being used for communications, the channel to be used for communications is switched to a channel that has been pre-evaluated by the processing circuit for measuring the interference situation as having less interference. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5895194 [Patent Document 2] Patent No. 4886814 Summary of the Invention [Problem to be solved by the invention]

[0006] By applying the above-mentioned interference avoidance technology, the probability of interference collisions can be reduced, and therefore the interference avoidance technology can improve the interference resistance of the wireless system. However, in an environment where interference is numerous, such as the ISM band, it is not rare that all channels used by the wireless system are subject to some kind of interference from other systems. In other words, in an environment where interference is numerous, interference collisions can occur even if interference avoidance technology is applied, and when interference collisions occur, the received packets that have been subjected to interference collisions cannot be demodulated due to the influence of the interference.

[0007] The present disclosure has been made in consideration of the above, and has an object to provide a transmitter capable of transmitting a signal that enables demodulation even in the event of interference collision. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object, the present disclosure relates to Receiver teeth, The receiver includes a frequency repetition synthesis selection unit that performs a frequency repetition synthesis process for generating one spectrum by synthesizing subcarriers containing the same symbol information for a received signal in which the same spectrum is arranged consecutively. When performing the frequency repetition synthesis process, the frequency repetition synthesis selection unit adjusts the amount of synthesis of each subcarrier by weighting the subcarriers when synthesizing them in response to the reception status of the received signal. The receiver according to the present disclosure further includes a reception quality measurement unit that extracts null symbols in any interval from the received signal, divides the extracted null symbols into intervals consisting of any number of null symbols, estimates the feature amount of the interference signal in each interval, compares the feature amounts of adjacent intervals to determine a change in the arrival status of the interference signal, and estimates the feature amount of the interference signal for each arrival status of the interference signal using the null symbol corresponding to the determined arrival status of the interference signal. Yes. Effect of the Invention

[0009] The transmitter according to the present disclosure advantageously transmits a signal that enables demodulation even in the event of interference collision. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 shows a configuration of a wireless system according to an embodiment. [Diagram 2] FIG. 1 is a diagram showing a configuration of a transmitter according to an embodiment; [Diagram 3] FIG. 13 is a diagram showing an example of a time waveform of a transmission signal when sampling is performed for each symbol time. [Figure 4] FIG. 1 shows a configuration of a receiver according to an embodiment. [Diagram 5] FIG. 2 is a diagram showing the configuration of a reception quality measurement unit included in a receiver according to an embodiment; [Figure 6] FIG. 1 is a diagram showing an image of processing by a signal separation unit included in a reception quality measurement unit of a receiver according to an embodiment; [Figure 7] FIG. 1 is a diagram for explaining the operation of an interference information estimation unit included in a reception quality measurement unit of a receiver according to an embodiment. [Figure 8] FIG. 8 is a diagram showing frequency spectrum characteristics in the interference arrival pattern of FIG. 7. [Figure 9] Average power diagram [Figure 10] FIG. 1 is a diagram showing a configuration of a frequency repetition synthesis selection unit included in a receiver according to an embodiment; [Figure 11] FIG. 1 is a diagram showing a processing circuit in the case where the functions of a transmitter and a receiver according to an embodiment are realized by the processing circuit; [Figure 12] FIG. 1 is a diagram showing a central processing unit (CPU) in the case where the functions of a transmitter and a receiver according to an embodiment are realized by the CPU; [Figure 13] FIG. 2 is a diagram showing a control circuit for controlling the operation of a transmitter according to an embodiment; [Figure 14] FIG. 1 is a diagram showing a program storage medium storing a program for controlling a transmitter according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A transmitter, a receiver, a transmitting method, a receiving method, a control circuit, and a program storage medium according to embodiments will be described in detail below with reference to the drawings. Note that in the following description, bold characters in mathematical expressions indicate vectors or matrices.

[0012] Embodiment 1 is a diagram showing a configuration of a wireless system according to an embodiment of the present invention. The wireless system according to the embodiment includes a transmitter 1 and a receiver 2.

[0013] 2 is a diagram showing a configuration of a transmitter 1 according to an embodiment. The transmitter 1 has a frequency repetition modulation unit 18 including a modulation unit 11, a frequency repetition unit 12, and an IFFT (Inverse Fast Fourier Transform) unit 13, a CP (Cyclic Prefix) adding unit 14, a transmission filter unit 15, a transmission RF (Radio Frequency) unit 16, and a transmission antenna 17.

[0014] The modulation unit 11 performs an OFDM (Orthogonal Frequency Division Multiplexing) modulation process on the data sequence to be transmitted. Here, the number of subcarriers in the OFDM signal is assumed to be N. In this case, the modulated symbol of the k-th subcarrier index is denoted by s k Then, the OFDM modulated signal spectrum s is expressed by the following equation (1): In the following description, the output of modulator 11 as expressed by equation (1), that is, the OFDM modulated signal spectrum, is referred to as a reference spectrum.

[0015]

number

[0016] The frequency repetition unit 12 performs frequency repetition processing on the reference spectrum generated by the modulation unit 11. The procedure of processing performed by the frequency repetition unit 12 is shown below. If the number of repetitions is M, the frequency repetition unit 12 executes frequency repetition processing so that M reference spectra are consecutively arranged on the frequency, as shown in the following formula (2). At this time, in the arrangement processing of each subcarrier performed by the frequency repetition unit 12, each subcarrier is arranged so that the same symbol is assigned at every N subcarrier interval, as shown in formula (2).

[0017]

number

[0018] Since the bandwidth of each subcarrier is the same as that of the reference spectrum, the bandwidth after repetition processing is expanded to M times the bandwidth of the reference spectrum. In the following description, the output of frequency repetition unit 12 is referred to as the transmission spectrum.

[0019] The IFFT unit 13 performs an inverse fast Fourier transform on the transmission spectrum and outputs one block of a time-domain transmission signal. The following equation (3) represents one block of the transmission signal after the inverse fast Fourier transform is performed.

[0020]

number

[0021] In formula (3), x n is the transmitted symbol at discrete time index n. In the following, the discrete time index is called the symbol time. Here, the time-domain transmitted signal x is expressed as x every symbol time interval M. n A symbol with ≠0 appears, and at other symbol times, x n=0, resulting in a transmission signal that forms a null in the time domain. FIG. 3 is a diagram showing an example of the time waveform of a transmission signal when sampling is performed every symbol time. As shown in FIG. 3, the time waveform of the transmission signal has a non-zero pulse that appears every M symbol times, and is null at other symbol times. At a null, both the I value and Q value are 0. In the following, the transmission symbol x n The symbols for which x is nonzero are called information symbols and transmitted symbols x n is called a null symbol.

[0022] The CP adding unit 14 adds a predetermined sample at the end of one block of the transmission signal converted into the time domain to the beginning of the time domain transmission signal as a guard interval. The transmission filter unit 15 performs filtering on the signal obtained by the CP adding unit 14 and outputs the generated transmission signal data to the transmission RF unit 16.

[0023] The transmission RF unit 16 performs digital to analog (DA) conversion on the generated transmission signal data, converts the baseband signal to a carrier frequency, amplifies the signal, and then outputs the signal to the transmission antenna 17 .

[0024] The transmitting antenna 17 radiates the signal from the RF transmitting unit 16 into the air.

[0025] More specifically, in the transmitter 1, the frequency repetition unit 12 generates a transmission spectrum in which the spectrum of the modulated signal is continuously arranged on the frequency axis, the same transmission symbol is arranged at a fixed subcarrier interval for the spectrum of the modulated signal, and the spectrum on the high band side and the spectrum on the low band side with respect to the center frequency are equal. The IFFT unit 13 converts the transmission spectrum generated by the frequency repetition unit 12 into a time domain signal, and generates and transmits a signal in which information symbols in which the time domain signal is non-zero and null symbols in which the time domain signal is zero appear periodically.

[0026] 4 is a diagram showing a configuration of a receiver 2 according to an embodiment. The receiver 2 includes a receiving antenna 21, a receiving RF unit 22, a receiving filter unit 23, a CP removal unit 24, a receiving quality measurement unit 25, an FFT (Fast Fourier Transformation) unit 26, a frequency repetition synthesis selection unit 27, and a demodulation unit 28.

[0027] The receiver 2 has one receiving antenna 21, and receives radio waves radiated from the transmitter 1 by the receiving antenna 21. In the embodiment, the number of receiving antennas 21 is one, but the number of receiving antennas 21 is not limited to one, and the receiver 2 may have multiple receiving antennas 21. When the receiver 2 has multiple receiving antennas 21, the following processing may be performed for each signal received by each of the multiple receiving antennas 21, or the multiple signals received by the multiple receiving antennas 21 may be combined and then the following processing may be performed.

[0028] The RF receiver 22 adjusts the gain of the signal received by the receiver antenna 21, converts the gain-adjusted signal into a baseband signal, and then performs AD conversion. The receiver filter 23 performs filtering on the AD-converted signal. The CP remover 24 removes the guard interval from the received signal processed by the receiver filter 23. It is assumed here that the transmitter 1 and receiver 2 are synchronized, and that the receiver 2 knows the arrival timings of information symbols and null symbols from among the desired signals received. Equation (4) shows one block of the time domain received signal after the CP removal by the CP remover 24.

[0029]

number

[0030] The received signal from which the guard interval has been removed by the CP removal unit 24 is output to a reception quality measurement unit 25 and an FFT unit .

[0031] 5 is a diagram showing a configuration of a reception quality measurement unit 25 included in the receiver 2 according to the embodiment. The reception quality measurement unit 25 includes a signal separation unit 251, an interference information estimation unit 252, an information interval estimation unit 253, and a reception quality information integration unit 254.

[0032] The signal separator 251 separates information symbols and null symbols in one block of the received signal to measure the feature of the information symbol and the feature of the interference signal. The feature is information on power, phase, and amplitude. The detailed operation will be described below. The signal separator 251 extracts an information symbol measurement section and an interference signal measurement section by taking into account the influence of multipath on the communication path and the like, and null symbols corresponding to the last several symbols of each information symbol in one block of the interference suppressed received signal, and by taking the remaining null symbols as the interference signal measurement section. The signal separator 251 outputs the extracted symbols corresponding to the information symbol measurement section to the information section estimation section 253, and outputs the extracted symbols corresponding to the interference signal measurement section to the interference information estimation section 252. FIG. 6 is a diagram showing an image of the processing of the signal separator 251 included in the reception quality measurement section 25 of the receiver 2 according to the embodiment. In FIG. 6, each information symbol and the following two null symbols are extracted from the received signal after CP removal as an information symbol measurement section, and the other null symbols are extracted as an interference signal measurement section.

[0033] The interference information estimation unit 252 estimates the feature quantity of the interference signal using the interference signal measurement section, and estimates whether there is any change in the interference arrival pattern. Fig. 7 is a diagram for explaining the operation of the interference information estimation unit 252 included in the reception quality measurement unit 25 of the receiver 2 according to the embodiment. The detailed operation of the interference information estimation unit 252 will be described in the following (i) to (iv) by taking as an example the case where interference A and interference B as shown in Fig. 7 arrive at different timings. Fig. 8 is a diagram showing frequency spectrum characteristics in the interference arrival pattern of Fig. 7.

[0034] (i) The interference information estimation unit 252 further divides the interference signal measurement period of one block of the received signal to measure the characteristic amount of interference. In the example of Fig. 7, the interference information estimation unit 252 divides the interference signal measurement period of one block of the received signal into a first interference signal measurement period to an eighth interference signal measurement period for each M symbol time, and estimates the average value of the characteristic amount of the interference signal in each period.

[0035] (ii) Next, the interference information estimation unit 252 estimates whether there is a change in the interference situation. The interference information estimation unit 252 judges whether there is a significant difference based on the difference in the feature amount of adjacent interference signal measurement sections to determine whether there is a change in the interference situation. In the embodiment, the average power of each measurement section is used as the feature amount, but the feature amount to be compared may be another feature amount such as phase. In the embodiment, the index used to determine the interference situation is the power difference, and the interference information estimation unit 252 determines that the interference situation has changed when the power difference is equal to or greater than a threshold. The interference information estimation unit 252 compares the feature amounts in order from the earliest section. The interference information estimation unit 252 determines that there is no change in the interference situation during the section in which the power difference is less than the threshold, and determines that the interference situation has changed during the section in which the power difference is equal to or greater than the threshold. FIG. 9 is an image diagram of the average power. In the example of FIG. 9, when the first part from the first interference signal measurement section to the fourth interference signal measurement section and the second part from the fifth interference signal measurement section to the eighth interference signal measurement section are compared, the power difference is less than the threshold in both the first and second parts, and it is determined that the interference situation is the same. On the other hand, when the fourth interference signal measurement section is compared with the fifth interference signal measurement section, the power difference is equal to or greater than the threshold, and it is determined that the interference situation has changed. In other words, in the example of FIG. 9, it is observed that two types of interference patterns have arrived regarding the observed interference arrival situation: a first interference pattern from the first interference signal measurement section to the fourth interference signal measurement section and a second interference pattern from the fifth interference signal measurement section to the eighth interference signal measurement section. In FIG. 9, P A means the average power value in the first interference signal measurement section and the second interference signal measurement section, and P B means the average power value of the third interference signal measurement section and the fourth interference signal measurement section, and P Cmeans the average power value in the fifth and sixth interference signal measurement sections, and P D means the average power value in the seventh interference signal measurement section and the eighth interference signal measurement section.

[0036] (iii) After estimating the interference state, the interference information estimation unit 252 estimates the feature amount of each interference pattern. When estimating the feature amount, the interference information estimation unit 252 estimates the average feature amount of all interference signal measurement intervals in which it is determined that the same interference has arrived. In the example of Fig. 9, the interference information estimation unit 252 estimates the average feature amount for the first interference pattern using the interference signal measurement interval of 0 to 4M symbol times, and estimates the average feature amount for the second interference pattern using the interference signal measurement interval of 4M to 8M symbol times.

[0037] (iv) After estimating the average feature value of each interference pattern, the interference information estimation unit 252 outputs information indicating the average feature value of each interference pattern and the interval of each interference pattern to the information interval estimation unit 253 and the reception quality information integrating unit 254.

[0038] The information interval estimation unit 253 measures the average power of the information symbols from the information symbol measurement interval. When measuring the average power of the information symbols, the information interval estimation unit 253 measures the average power of the information symbols assigned to the interval corresponding to each interference pattern notified by the interference information estimation unit 252. For example, in FIG. 6, when it is determined that the interference measurement interval from symbol time 3 to symbol time M-1 and the interference measurement interval from symbol time M+3 to symbol time 2M-1 have the same interference pattern, the information interval estimation unit 253 measures the average power using the information symbols corresponding to each interference measurement interval, that is, the information symbols of symbol time 0 and symbol time M. The information interval estimation unit 253 performs this process on the information symbols corresponding to all interference patterns estimated in one block of the received signal after interference suppression.

[0039] The reception quality information integrating unit 254 aggregates the interference information measured by the interference information estimating unit 252 and the information symbol information measured by the information interval estimating unit 253, and notifies the aggregated information to a subsequent module. The reception quality information integrating unit 254 judges the reception quality of the interference suppressed received signal based on the interference measured by the interference information estimating unit 252 and the average power of the information symbol measured by the information interval estimating unit 253. In the embodiment, the reception quality information integrating unit 254 judges the reception quality by comparing the average power of the information symbol with the average power of the interference signal for each interference arrival pattern measured by the interference information estimating unit 252. Hereinafter, the average power of the information symbol in a certain interference arrival pattern will be referred to as P d Let the average power of the interference signal be P i As an example of a method for determining reception quality in the embodiment, when an interference signal does not exist, the average power of the interference signal is relatively small compared to the average power of the information symbol. Therefore, when the power comparison result is P d >P i If so, the reception quality information integrating unit 254 judges the reception quality to be high. The "reception quality: high" means that the reception quality is relatively good. On the other hand, if a residual interference signal exists with a certain level or more, the power of the interference signal becomes equal to or greater than the average power of the information symbol. Therefore, if the power comparison result is P i >P d If so, the reception quality information integrating unit 254 determines that the reception quality is "low". "Low reception quality" means that the reception quality is relatively poor. After completing the determination of the reception quality, the reception quality information integrating unit 254 outputs the interference information, the information symbol information, and the reception quality information to a downstream module.

[0040] The FFT unit 26 performs a fast Fourier transform on one block of the received signal to convert the one block of the received signal into a frequency domain signal and outputs the frequency domain signal. The interference-suppressed received symbol of the k-th subcarrier after the fast Fourier transform process is denoted by r k The signal after fast Fourier transform is shown in the following equation (5): In the following explanation, the received signal converted into a frequency domain signal is called the received signal spectrum.

[0041]

number

[0042] 10 is a diagram showing the configuration of the frequency repetition synthesis selection unit 27 of the receiver 2 according to the embodiment. The frequency repetition synthesis selection unit 27 has a subcarrier selection unit 271 and a repetition synthesis unit 272. The frequency repetition synthesis selection unit 27 performs a repetition synthesis process that synthesizes spectra that are consecutively arranged in frequency by frequency repetition processing. When performing the repetition synthesis process, the frequency repetition synthesis selection unit 27 performs weighting taking into account the amount of interference of each subcarrier in order to reduce the influence of an interference signal, and then performs synthesis.

[0043] The subcarrier selection unit 271 determines the weight of each subcarrier when performing frequency repetition synthesis processing. In the embodiment, as an example, a process flow for determining the weight of the subcarrier during repetition synthesis using the reception quality information measured by the reception quality measurement unit 25 in the case of FIG. 8 is shown. In the example of FIG. 8, it is assumed that interference A and interference B exist, and the reception quality information in each interference pattern measured by the reception quality measurement unit 25 is both determined to be "reception quality: low". If there is even one signal determined to be "reception quality: low" in the measured interference pattern, the subcarrier selection unit 271 searches for whether interference is concentrated in any subcarrier in the reception signal spectrum. In the case of the embodiment, the subcarrier selection unit 271 compares the average power of all subcarriers with the power of each subcarrier, and determines that interference exists in the certain subcarrier when the power of the certain subcarrier is greater than the average power by a certain amount or more. In the example of Figure 8, the power of a subcarrier where only interference B exists and the power of a subcarrier where both interference A and interference B exist are greater than the average power, so subcarrier selection unit 271 determines that both the subcarrier where only interference B exists and the subcarrier where both interference A and interference B exist are subcarriers where interference exists.

[0044] Next, the subcarrier selection unit 271 determines the weight of each subcarrier. For the subcarriers determined to have interference, the subcarrier selection unit 271 determines the weight at the time of synthesis corresponding to the difference between the power of the subcarrier determined to have interference and the average power. In the example of FIG. 8, the subcarrier selection unit 271 determines the weight of the subcarrier where only interference B exists and the weight of the subcarrier where both interference A and interference B exist to be relatively small, and determines the weight of the subcarrier determined to have no interference to be relatively large. In the embodiment, when it is determined that the "reception quality: high", the search for interference is not performed, and the subcarrier selection unit 271 sets all the weights at the time of synthesis to be the same. After determining the weights of all the subcarriers, the subcarrier selection unit 271 outputs the weight of each subcarrier to the repetition synthesis unit 272.

[0045] The repetition synthesis unit 272 performs a repetition synthesis process that synthesizes spectra that are consecutively arranged in frequency by frequency repetition processing. At this time, the repetition synthesis unit 272 performs weighting using the weight determined by the subcarrier selection unit 271 and then performs synthesis processing. Since the same transmission symbol is arranged at every N subcarrier interval in the signal that has been subjected to frequency repetition processing according to equation (2), the repetition synthesis unit 272 synthesizes the same symbols when performing frequency repetition synthesis processing. In other words, the repetition synthesis unit 272 synthesizes the received symbols at every N subcarrier interval. The weight of the k-th subcarrier in the received signal spectrum before synthesis is set to v k Then, the received symbol R in the wth subcarrier after repetition synthesis is w is expressed by the following equation (6).

[0046]

number

[0047] In this embodiment, the output of repetition synthesis section 272 is referred to as the “repetition synthesis reception spectrum.” The number of subcarriers in the repetition synthesis reception spectrum is N, and the bandwidth of the repetition synthesis reception spectrum is the same as the bandwidth of the reference spectrum.

[0048] The demodulator 28 performs demodulation processing on the received spectrum after repetition synthesis, and outputs demodulated bits to a subsequent higher-level device.

[0049] More specifically, the receiver 2 has a frequency repetition synthesis selection unit 27 that performs frequency repetition synthesis processing for generating one spectrum by synthesizing subcarriers containing the same symbol information with respect to a received signal in which the same spectrum is arranged consecutively. When performing frequency repetition synthesis processing, the frequency repetition synthesis selection unit 27 adjusts the synthesis amount of each subcarrier by weighting the subcarriers when synthesizing them in response to the reception status of the received signal. For example, the reception quality measurement unit 25 extracts null symbols from the received signal in any section, divides the extracted null symbols into sections consisting of any number of null symbols, estimates the feature amount of the interference signal in each section, compares the feature amounts of adjacent sections to determine a change in the arrival status of the interference signal, and estimates the feature amount of the interference signal for each arrival status of the interference signal using the null symbol corresponding to the determined arrival status of the interference signal. For example, the reception quality measurement unit 25 extracts information symbols from the received signal in any section, estimates the feature amount of the information symbol using the extracted information symbol, and observes and evaluates the reception status using the estimated feature amount of the information symbol and the feature amount of the interference signal.

[0050] As described above, the transmitter 1 transmits a signal having such a characteristic that a null symbol appears in the time domain signal by performing frequency repetition processing on the modulated signal. That is, the transmitter 1 can transmit a signal that allows demodulation even in the case of interference collision. The receiver 2 can enable demodulation even in the case of interference collision by measuring the interference situation using the characteristics of the received signal and performing spectrum synthesis processing with weighting corresponding to the interference situation. That is, the receiver 2 can demodulate the received signal even in the case of interference collision.

[0051] Each component of the transmitter 1 and the receiver 2 is realized by a processing circuit. The processing circuit may be realized by a dedicated circuit or may be realized by a control circuit using a CPU. When the processing circuit is realized by a dedicated circuit, each of the transmitter 1 and the receiver 2 has a processing circuit 30 shown in FIG. 11, and each function of the transmitter 1 and the receiver 2 is realized by the processing circuit 30. FIG. 11 is a diagram showing the processing circuit 30 when each function of the transmitter 1 and the receiver 2 according to the embodiment is realized by the processing circuit 30. When the processing circuit is realized by a dedicated circuit, the processing circuit 30 is, 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.

[0052] When the processing circuit is realized by a CPU, each of the transmitter 1 and the receiver 2 has a CPU 31 and a memory 32 shown in FIG. 12, and each function of the transmitter 1 and the receiver 2 is described as a program, and the program is stored in the memory 32. The CPU 31 realizes a function corresponding to the program by reading and executing the program stored in the memory 32. FIG. 12 is a diagram showing the CPU 31 when each function of the transmitter 1 and the receiver 2 according to the embodiment is realized by the CPU 31. The CPU 31 may be replaced with a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor). The memory 32 is, for example, a non-volatile or volatile semiconductor memory such as a Random Access Memory (RAM), a Read Only Memory (ROM), a flash memory, an Erasable Programmable Read Only Memory (EPROM), or an Electrically Erasable Programmable Read-Only Memory (EEPROM (registered trademark)), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disk). Of the multiple functions possessed by each of the transmitter 1 and the receiver 2, some are realized by dedicated circuits, and the rest are realized by programs and a CPU. 31 This may be realized by:

[0053] 13 is a diagram showing a control circuit 33 that controls the operation of the transmitter 1 according to the embodiment. Specifically, the control circuit 33 causes the transmitter 1 to perform an operation of generating a transmission spectrum in which the spectrum of the modulated signal is continuously arranged on the frequency axis, the same transmission symbol is arranged at a constant subcarrier interval with respect to the spectrum of the modulated signal, and the spectrum on the high band side and the spectrum on the low band side are equal with respect to the center frequency, and an operation of transmitting a signal in which information symbols whose time domain signal is non-zero and null symbols whose time domain signal is zero appear periodically based on the generated transmission spectrum. The operation of the receiver 2 according to the embodiment may also be controlled by a control circuit equivalent to the control circuit 33. The control circuit that controls the operation of the receiver 2 causes the receiver 2 to perform an operation of frequency repetition synthesis processing for synthesizing subcarriers containing the same symbol information to generate one spectrum for a received signal in which the same spectrum is continuously arranged, and an operation of adjusting the synthesis amount of each subcarrier by weighting when synthesizing each subcarrier in response to the reception status of the received signal when performing the frequency repetition synthesis processing.

[0054] FIG. 14 is a diagram showing a program storage medium 34 storing a program for controlling the transmitter 1 according to the embodiment. The program causes the transmitter 1 to execute an operation of generating a signal in which information symbols in which the time domain signal is non-zero and null symbols in which the time domain signal is zero appear periodically by generating a transmission spectrum in which the spectrum of the modulated signal is continuously arranged on the frequency axis, the same transmission symbol is arranged at a constant subcarrier interval with respect to the spectrum of the modulated signal, and the spectrum on the high band side and the spectrum on the low band side are equal with respect to the center frequency. The receiver 2 according to the embodiment may also be controlled by a program stored in a program storage medium equivalent to the program storage medium 34. The program causes the receiver 2 to execute an operation of performing a frequency repetition synthesis process for synthesizing subcarriers containing the same symbol information to generate one spectrum for a received signal in which the same spectrum is continuously arranged, and an operation of adjusting the synthesis amount of each subcarrier by weighting when synthesizing each subcarrier in response to the reception status of the received signal when performing the frequency repetition synthesis process.

[0055] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0056] 1 transmitter, 2 receiver, 11 modulation section, 12 frequency repetition section, 13 IFFT section, 14 CP addition section, 15 transmission filter section, 16 transmission RF section, 17 transmission antenna, 18 frequency repetition modulation section, 21 reception antenna, 22 reception RF section, 23 reception filter section, 24 CP removal section, 25 reception quality measurement section, 26 FFT section, 27 frequency repetition synthesis selection section, 28 demodulation section, 30 processing circuit, 31 CPU, 32 memory, 33 control circuit, 34 program storage medium, 251 signal separation section, 252 interference information estimation section, 253 information interval estimation section, 254 reception quality information integration section, 271 subcarrier selection section, 272 repetition synthesis section.

Claims

1. A frequency repetition synthesis selection unit performs a frequency repetition synthesis process for generating a single spectrum by synthesizing subcarriers containing the same symbol information for a received signal in which the same spectrum is consecutively arranged, The frequency repetition synthesis selection unit, when performing the frequency repetition synthesis process, adjusts the amount of synthesis of each subcarrier by weighting the subcarriers in response to the reception status of the reception signal; a reception quality measuring unit that extracts null symbols in an arbitrary interval from the received signal, divides the extracted null symbols into intervals consisting of an arbitrary number of null symbols, estimates a feature value of an interference signal in each interval, compares the feature values ​​of adjacent intervals to determine a change in an arrival state of the interference signal, and estimates the feature value of the interference signal for each arrival state of the interference signal using the null symbol corresponding to the determined arrival state of the interference signal.

23. A receiver comprising:

2. The reception quality measurement unit extracts information symbols from the received signal in an arbitrary section, estimates a feature of the information symbol using the extracted information symbols, and observes and evaluates a reception state using the estimated feature of the information symbol and the feature of the interference signal.

2. The receiver according to claim 1 .

3. A step of performing a frequency repetition synthesis process for generating a single spectrum by synthesizing subcarriers containing the same symbol information for a received signal in which the same spectrum is consecutively arranged, In the step of performing the frequency repetition synthesis process, when performing the frequency repetition synthesis process, weighting is performed at the time of synthesis of each subcarrier in response to the reception status of the reception signal to adjust the synthesis amount of each subcarrier; The method further includes the steps of: extracting null symbols from the received signal in any interval; dividing the extracted null symbols into intervals consisting of any number of null symbols; estimating a feature value of the interference signal in each interval; comparing the feature values ​​of adjacent intervals to determine a change in an arrival state of the interference signal; and estimating the feature value of the interference signal for each arrival state of the interference signal using the null symbol corresponding to the determined arrival state of the interference signal. A receiving method comprising:

4. In the step of estimating the characteristic amount, an information symbol is extracted from the received signal in an arbitrary section, a characteristic amount of the information symbol is estimated using the extracted information symbol, and a receiving state is observed and evaluated using the estimated characteristic amount of the information symbol and a characteristic amount of the interference signal.

4. The receiving method according to claim 3.

Images