JP7221461B2 - Receiving device, communication system, interference measuring device, control circuit and storage medium - Google Patents

Description

The present disclosure relates to receivers, communication systems, interference measurement devices, control circuits and storage media.

In recent years, due to the full-scale arrival of IoT (Internet of Things) and M2M (Machine to Machine), the wireless communication system LPWA (Low Power Wide Area), which enables low power consumption, wide service area, and low cost, has attracted attention. ing. LPWA includes LoRa and SIGFOX, which are wireless communication standards for IoT, and Wi-SUN (Wireless Smart Utility Network), which is a wireless communication standard used for smart meters and the like.

Among these LPWA wireless communication standards, LoRa uses a spread spectrum system, and adopts CSS (Chirp Spectrum Spread) modulation that uses a chirp signal for spectrum spreading. Since the spread spectrum system obtains a spreading gain according to the spreading factor, the reception sensitivity is high and the communication distance can be lengthened. However, in the fields of IoT and M2M, since sensor information and the like are communicated, a low communication speed is sufficient, and the spread spectrum method can be said to be a wireless communication method suitable for IoT and M2M.

Since unlicensed bands such as the 920 MHz band are mainly used in the IoT and M2M frequency bands, resistance to interference waves such as other systems and interference waves is required. Since the spread spectrum system spreads the signal over a wide band, it will be affected by all interfering waves that exist within the spread signal band. However, in the spread spectrum system, interference waves are spread over a wide band by despreading processing in the receiver. Even so, depending on the magnitude of the interference wave power, the demodulation performance will be greatly affected.

In response to such a problem that the communication quality deteriorates due to the influence of the interference wave, in the wireless communication system described in Patent Document 1, in order to suppress the interference wave, the transmission side has a null signal which is a no-signal section in the transmission signal. Insert signal. The receiving side measures the interference wave from the null signal, and estimates the interference wave in the section corresponding to the data symbol by interpolating the interference wave measured with the null signal. After that, based on the estimated interference wave, processing for suppressing the interference wave intervening in the data symbol is performed.

Japanese Patent No. 6746029

In the wireless communication system described in Patent Document 1, since the interference wave corresponding to the data symbol is estimated by interpolating the interference wave measured by the null signal, if the number of null signals to be inserted into the transmission signal is small, the data symbol There is a problem that the accuracy of estimation of the interference wave corresponding to is degraded, and the transmission rate is lowered when the number of null signals to be inserted into the transmission signal increases.

The present disclosure has been made in view of the above, and it is an object of the present disclosure to obtain a receiver capable of improving estimation accuracy of an interference wave contained in a received signal and preventing a decrease in transmission rate.

In order to solve the above-described problems and achieve the object, the receiving device according to the present disclosure includes a despreading processing unit that despreads a directly spread received signal, and a despread received signal from a time domain signal to a frequency and a frequency component estimating unit for estimating a frequency component in which a communication wave exists in the received signal converted to the frequency domain signal. In addition, the receiving apparatus includes a null signal transforming unit that transforms frequency components of the received signal, which are transformed into frequency domain signals and are estimated to contain communication waves, into null signals based on the estimation result of the frequency component estimating unit; A respreading processing unit that restores an interference wave contained in a received signal before being despread by a despreading processing unit by respreading a received signal that has been converted by a signal conversion unit; a cyclic prefix removing unit for adding a cyclic prefix to the transmitted signal and removing the cyclic prefix from the transmitted signal . The despreading processor despreads the signal from which the cyclic prefix has been removed by the cyclic prefix remover. The frequency component estimator estimates the frequency component in which the communication wave is present, based on the maximum timing error, which is the maximum possible error in the timing at which the despreading processor performs the despreading process on the received signal. do.

The receiving device according to the present disclosure has the effect of being able to both improve the accuracy of estimating an interference wave contained in a received signal and prevent a decrease in transmission rate.

FIG. 2 is a diagram showing a configuration example of a transmission device that configures the communication system according to the first embodiment; FIG. 3 is a diagram showing a configuration example of a receiving device that configures the communication system according to the first embodiment; FIG. 3 is a diagram showing a configuration example of an interference measurement unit included in the receiving apparatus according to Embodiment 1; A diagram showing an example of a frequency spectrum before and after despreading of a received signal FIG. 4 is a diagram showing an example of a frequency spectrum before and after a null signal conversion unit executes conversion processing on a received signal; FIG. 4 is a diagram showing an example of the frequency spectrum of the received signal after the re-spreading processing unit has executed the re-spreading processing; FIG. 2 shows an example of a control circuit that implements the transmission device according to the first embodiment; FIG. 11 is a diagram showing a configuration example of a transmission device that configures a communication system according to a second embodiment; FIG. 10 is a diagram showing a configuration example of a receiving device that configures a communication system according to a second embodiment; FIG. 11 is a diagram showing a configuration example of an interference measurement unit included in a receiving apparatus according to Embodiment 2; A diagram showing the frequency spectrum of the received signal when there is no timing error and no delay wave A diagram showing the frequency spectrum of a received signal with a one-chip timing error and no delayed wave FIG. 10 is a diagram showing the frequency spectrum of a received signal when there is no timing error and there is a delayed wave with a delay amount of 2 chips; 1-chip timing error and delay A diagram showing the frequency spectrum of the received signal when there is a 2-chip delayed wave FIG. 10 is a diagram showing the relationship between the signal received by the receiver according to the second embodiment and the timing reference; FIG. 10 is a diagram for explaining the operation of the interference measuring unit of the receiving apparatus according to the second embodiment; FIG. 11 is a diagram for explaining the operation of the interference measurement unit of the receiving device according to the third embodiment;

A receiver, a communication system, an interference measurement device, a control circuit, and a storage medium according to embodiments of the present disclosure will be described below in detail with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram illustrating a configuration example of a transmission device that configures a communication system according to a first embodiment. FIG. 2 is a diagram showing a configuration example of a receiving device that configures the communication system according to the first embodiment. That is, the communication system according to the first embodiment is composed of a transmitter 1 shown in FIG. 1 and a receiver 2 shown in FIG. 2 that receives a signal transmitted from the transmitter 1. In FIG. In the communication system according to the first embodiment, a transmission device 1 directly spreads transmission data to generate a spread spectrum signal and transmits the signal. The receiver 2 receives the spread spectrum signal transmitted by the transmitter 1 .

The transmission device 1 will be described. As shown in FIG. 1 , transmitting apparatus 1 includes modulation section 100 , direct spreading processing section 101 , transmission filter section 102 , frequency conversion section 103 and transmission antenna 104 .

Modulation section 100 modulates input transmission data using a predetermined modulation scheme and outputs the modulated data to direct spreading processing section 101 . Direct spread processing section 101 performs spectrum spread processing on the transmission data modulated by modulation section 100 using a spreading sequence, and outputs the spread signal to transmission filter section 102 . Transmission filter section 102 filters the signal spectrum-spread by direct spreading processing section 101 using a transmission filter and outputs the filtered signal to frequency conversion section 103 . Frequency conversion section 103 frequency-converts the signal filtered by transmission filter section 102 and outputs the result to transmission antenna 104 . Transmitting antenna 104 transmits the signal frequency-converted by frequency converting section 103 .

The receiving device 2 will be explained. As shown in FIG. 2 , receiving apparatus 2 includes receiving antenna 200 , frequency converting section 201 , receiving filter section 202 , timing detecting section 203 , interference measuring section 204 , interference suppressing section 205 and demodulating section 206 .

Receiving antenna 200 receives a signal transmitted from transmitting apparatus 1 and outputs the signal to frequency converting section 201 . Frequency conversion section 201 frequency-converts a reception signal input from reception antenna 200 into a baseband signal, and outputs the baseband signal to reception filter section 202 . Reception filter section 202 filters the baseband signal input from frequency conversion section 201 into a communication wave band using a reception filter, and outputs the filtered signal. Reception filter section 202 outputs the filtered signal to timing detection section 203 , interference measurement section 204 and interference suppression section 205 . Timing detection section 203 performs timing detection processing using a matched filter method or the like on the signal filtered by reception filter section 202, and interference measurement section 204 and interference suppression section 205 despread the received signal. to detect the timing for Interference measurement section 204 estimates an interference wave contained in the filtered reception signal input from reception filter section 202 . Interference suppression section 205 uses the interference wave estimated by interference measurement section 204 to perform processing for suppressing the interference wave on the filtered reception signal input from reception filter section 202 . Demodulation section 206 performs demodulation processing on the received signal after interference waves have been suppressed by interference suppression section 205 .

Next, the details of the interference measuring section 204 that estimates the interference wave contained in the received signal in the receiving device 2 will be described.

FIG. 3 is a diagram showing a configuration example of the interference measuring section 204 included in the receiving device 2 according to the first embodiment. Interference measuring section 204 includes despreading processing section 210 , frequency domain transforming section 211 , frequency component estimating section 212 , null signal transforming section 213 and respreading processing section 214 . Note that the interference measurement unit 204 constitutes an interference measurement device.

Signals output from reception filter section 202 and timing detection section 203 are input to despreading processing section 210 . Despreading processing section 210 performs despreading processing by multiplying the received signal by despreading sequence β(n), which is the opposite phase of spreading sequence α(n) used in direct spreading processing section 101 of transmitting apparatus 1 . do. For example, the spreading sequence α(n) can be expressed by Equation (1).

In equation (1), N is the diffusion length and j is the imaginary unit. The spread sequence α(n) is a signal called a chirp signal, and has a constant envelope and a characteristic that the frequency changes with time. U in equation (1) means an integer representing the slope of the frequency in the chirp signal. The spreading sequence to be used is not limited to chirp signals, and may be M sequence, PN (Pseudorandom Noise) sequence, Gold sequence, Zadoff-Chu sequence, or the like.

A despreading sequence β(n), which is the opposite phase of the spreading sequence α(n), can be expressed by Equation (2).

The inverse modulation processing by despreading processing section 210 can be expressed by the following equation (3) using the despreading sequence β(n).

Here, r(n) represents the received signal in the time domain, which is the output of the receive filter section 202, and s(n) represents the received signal after despreading processing.

FIG. 4 is a diagram showing an example of the frequency spectrum of the received signal before and after despreading. In FIG. 4, communication wave 300 is the frequency spectrum of the communication wave included in the received signal before despreading (hereinafter sometimes referred to as "received signal after receiving filter") output from receive filter section 202. . An interference wave 301 is the frequency spectrum of the interference wave contained in the reception signal after reception filtering. The communication wave 300 is spectrally spread with a spreading factor N, and the bandwidth of the communication wave at this time is Bw [Hz]. The interference wave 301 exists within the bandwidth Bw [Hz] of the communication wave, and in FIG. 4, the center frequency of the interference wave 301 is f _I (−Bw/2≦f _I ≦Bw/2). When despreading processing is performed on the received signal after the reception filter, the communication wave 300 is converted into the frequency spectrum of the communication wave (after despreading) 302 . At this time, the bandwidth of the communication wave (after despreading) 302 is Bw/N [Hz]. Also, the interference wave 301 is converted into a frequency spectrum spread to a bandwidth of Bw [Hz] by despreading processing. This is because the despreading process is equivalent to the direct spreading process for the interference wave 301, and since the chip rate when performing the despreading process is Bw [Hz], it is spread over the bandwidth Bw [Hz]. . Here, since the despreading process is performed at a chip rate of Bw [Hz], if the sample rate of the input received signal is also Bw [Hz], the frequency band of the received signal is -Bw/2 [Hz] according to the sampling theorem. ] to Bw/2 [Hz]. Therefore, instead of the frequency component 304 below -Bw/2 [Hz], a frequency component 305 is added so as to fold back within the band.

Frequency domain transforming section 211 transforms the received signal despread by despreading processing section 210 from a time domain signal to a frequency domain signal. Frequency transform processing for transforming a time domain signal into a frequency domain signal is performed as shown in Equation (4) using DFT (Discrete Fourier Transform) processing.

where S(k) is the frequency domain representation of the received signal s(n) after despreading. k is a subcarrier number, k=0 represents the subcarrier with the lowest frequency, and k=N-1 represents the subcarrier with the highest frequency. Further, since the processing shown in Equation (4) is a processing of performing N-point DFT on the received signal s(n) of sample rate Bw [Hz], the subcarrier interval after DFT processing is Bw/N [Hz]. .

Frequency domain transforming section 211 outputs received signal S(k) transformed into a frequency domain signal to frequency component estimating section 212 and null signal transforming section 213 .

The frequency component estimating unit 212 estimates the frequency component of the received signal in the frequency domain input from the frequency domain transforming unit 211 in which the communication wave exists.

Null signal transforming section 213 performs a process of transforming frequency components in which communication waves are present in the received signal in the frequency domain input from frequency domain transforming section 211 into a null signal, based on the result of estimation by frequency component estimating section 212 . to run. That is, the null signal transforming section 213 transforms the frequency component in which the communication wave is present, which is estimated by the frequency component estimating section 212, into a null signal.

FIG. 5 is a diagram showing an example of the frequency spectrum before and after null signal conversion section 213 executes conversion processing on the received signal. In FIG. 5, communication wave (after despreading) 400 is the frequency spectrum of the communication wave included in the received signal after despreading, and interference wave (after despreading) 401 is the interference wave included in the received signal after despreading. is the frequency spectrum of Assuming that the communication wave (after despreading) 400 is detected at ideal timing, a frequency spectrum with a bandwidth Bw/N [Hz] appears centering on the frequency 0 [Hz]. That is, since the communication wave (after despreading) 400 exists at subcarrier number N/2, frequency component estimation section 212 outputs subcarrier number N/2 as the frequency component in which the communication wave exists. In this case, null signal conversion section 213 converts the subcarrier corresponding to subcarrier number N/2 into a null signal as shown in FIG. As a result, the communication wave (after despreading) 400 is removed. At the same time, an interference wave (after despreading) 401 existing in subcarrier number N/2 is also removed. Null signal conversion section 213 outputs the received signal after converting the communication wave to a null signal to respreading processing section 214 .

Respreading processing section 214 restores interference waves contained in the received signal by performing respreading processing on the received signal in the frequency domain after null signal conversion input from null signal conversion section 213 . The received signal here is the signal output from reception filter section 202 , that is, the received signal before being despread by despreading processing section 210 . FIG. 6 is a diagram showing an example of the frequency spectrum of the received signal after respreading processing has been performed by respreading processing section 214 . In FIG. 6, an interference wave (after re-spreading) 500 is a signal obtained by restoring the interference wave 301 in FIG. 4 by re-spreading processing. In other words, by removing the communication wave with the null signal converter 213, the interference wave within the communication wave band can be measured. However, with respect to the interference wave (after re-spreading) 500, an error occurs in restoration due to partial removal of the interference wave by the null signal converter 213. However, since only 1/N of the communication bandwidth is removed, the spreading factor As N increases, it is possible to restore the interference wave with higher accuracy.

The respreading processing section 214 performs respreading processing using the respreading sequence γ(k) in the respreading processing. Here, the respreading sequence γ(k) can be obtained by DFT processing the spreading sequence α(n) as shown in the following equation (5).

The respreading sequence γ(k) shown in Equation (5) is the frequency domain representation of the spreading sequence α(n).

That is, re-spreading processing section 214 uses γ(k) to perform re-spreading processing shown in Equation (6) below.

Here, S′(i) is a frequency domain signal obtained by converting a specific subcarrier of S(i) into a null signal by null signal conversion in null signal conversion section 213 . Equation (6) expresses the convolution integral of S′(i) and γ(k), and the convolution integral in the frequency domain is equivalent to the multiplication process in the time domain. Therefore, the time-domain signal for S'(i) is multiplied by the spreading sequence α(n), which is the time-domain representation of γ(k), which is equivalent to the direct spreading process for S'(i). means. B(k) is the frequency domain signal of the restored interference wave shown in FIG.

The respreading processing section 214 outputs the restored frequency domain signal B(k) of the interference wave to the interference suppression section 205 as an interference estimation value.

Interference suppression section 205 suppresses interference waves interposed in the received signal input from reception filter section 202 using frequency domain signal B(k) of interference waves restored by re-spreading processing section 214 by re-spreading processing. . Various methods can be considered for the interference suppression processing performed by the interference suppression unit 205, but the method is not limited to a specific method. For example, when there are multiple receiving antennas, the interference waves have spatial correlation among the receiving antennas. Therefore, by multiplying the weight vector that makes the interference waves included in the received signal of each receiving antenna uncorrelated, the interference Waves can be suppressed. In the interference suppression processing in this case, first, the received signal r(n) (see equation (3)) to be subjected to interference suppression is converted into a frequency domain signal. Here, let R _m (k) be a received signal represented in the frequency domain for a receiving antenna number m (0≦m<M) and a subcarrier number k (0≦k<N). Next, when the number of receiving antennas is M, interference suppression is performed on the received signal R _m (k) using the following equation (7).

Bold letters in equation (7) represent vectors. In the following description, a bold letter representing a vector is expressed as "letter + (bold letter)". For example, a bold A is described as "A (bold)".

In Equation (7), Q _k (bold) is the received signal vector (M×1) in the frequency domain representation after interference suppression for subcarrier number k, and Q _m (k) is for receive antenna number m and subcarrier number k. Fig. 3 is a received signal in frequency domain representation after interference suppression; R _k (bold) is a received signal vector (M×1) in frequency domain representation before interference suppression for subcarrier number k, and W _k (bold) is a weight vector (M×M) for subcarrier number k. W _m1,m2 (k) corresponds to receiving antenna number m1 (0≦m1<M) and receiving antenna m2 (0≦m2<M) for suppressing interference intervening in communication waves received with subcarrier number k is a weighted signal. Also, W ^H _k (bold) represents the complex conjugate transpose of W _k (bold).

A weight vector W _k (bold) is generated so as to satisfy the following equation (8).

Here, G _k (bold) is the covariance matrix of the frequency domain signal B _m (k) (0≦m<M) of the interference wave for subcarrier number k (B _m (k) is the receiving antenna m and subcarrier number k frequency domain signals of interference waves), I (bold) is the identity matrix (M×M). By performing interference suppression according to Equation (7) using the weight vector W _k (bold) that satisfies Equation (8), it is possible to convert the signals into uncorrelated interference waves between the receiving antennas.

Interference suppression section 205 outputs to demodulation section 206 the received signal in the frequency domain subjected to interference suppression according to Equation (7). The demodulator 206 demodulates the interference-suppressed received signal in the frequency domain. For example, the demodulation unit 206 converts the interference-suppressed received signal in the frequency domain into a time domain signal by IDFT (Inverse Discrete Fourier Transform) processing, and performs despreading processing in the time domain to extract communication waves from the received signal. demodulate.

As described above, according to the communication system according to the first embodiment of the present disclosure, the transmitting device 1 transmits a spread spectrum signal generated by directly spreading transmission data, and the receiving device 2 generates a communication wave from a received signal. In order to measure the interferer within the spread spectrum band, the received signal is despread to return the communication wave to the pre-spread signal, the interferer is spectrum spread, and the despread received signal is converted from the time domain signal to the frequency domain. From the received signal converted to the frequency domain, estimate the frequency component where the communication wave exists, convert the frequency component to a null signal, and re-spread the frequency domain signal after conversion to the null signal to interfere The signal is restored, and interference suppression and demodulation processing are performed using the restored interference signal. As a result, the higher the spreading factor N, the more accurately the interference wave within the spread spectrum band can be estimated. As a result, the receiving apparatus 2 can highly accurately suppress the interference wave intervening in the communication wave. In addition, it is not necessary for the transmission device 1 to insert a null signal for estimating the interference wave into the transmission signal, and it is possible to improve the estimation accuracy of the interference wave included in the received signal and prevent the transmission rate from decreasing. .

Next, hardware that implements each unit that performs signal processing in the transmitter 1 and hardware that implements each unit that performs signal processing in the receiver 2 will be described.

The modulation section 100, the direct sequence processing section 101, the transmission filter section 102, and the frequency conversion section 103 of the transmission device 1 can be realized by dedicated processing circuits operating as these sections or by processors executing programs. The dedicated processing circuit is, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit combining these. When modulating section 100, direct sequence processing section 101, transmission filter section 102, and frequency conversion section 103 are implemented by a processor, transmitting apparatus 1 includes a control circuit including processor 11 and memory 12 shown in FIG.

FIG. 7 is a diagram showing an example of a control circuit that implements the transmission device 1 according to the first embodiment. The processor 11 is a CPU (also referred to as a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP (Digital Signal Processor)). The memory 12 is, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), or the like.

Memory 12 stores a program describing the functions of modulation section 100 , direct sequence processing section 101 , transmission filter section 102 and frequency conversion section 103 . Processor 11 operates as modulation section 100 , direct spreading processing section 101 , transmission filter section 102 and frequency conversion section 103 by executing programs stored in memory 12 . Part of the modulation section 100, the direct spreading processing section 101, the transmission filter section 102, and the frequency conversion section 103 may be realized by a dedicated processing circuit, and the rest may be realized by the processor 11 and the memory 12 shown in FIG. . When some or all of the constituent elements of the transmitter 1 are realized by the processor 11 and the memory 12, the programs stored in the memory 12 are, for example, CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM It may be provided to a user or the like in a state in which it is written in a storage medium such as a storage medium, or may be provided via a network.

In addition, each unit that performs signal processing in the receiving device 2, that is, the frequency conversion unit 201, the reception filter unit 202, the timing detection unit 203, the interference measurement unit 204, the interference suppression unit 205, and the demodulation unit 206, is the same as each unit of the transmission device 1. Similarly, it can be implemented with dedicated processing or control circuitry as described above.

Similarly, each unit that performs signal processing in the transmission device and the reception device of the communication system according to Embodiments 2 and 3, which will be described later, can also be realized by the dedicated processing circuit or control circuit described above.

Embodiment 2.
In the first embodiment of the present disclosure described above, the transmission device 1 directly spreads the transmission data to generate a transmission signal, and the reception device 2 despreads the received signal and converts it into a frequency domain. By centering the spread spectrum band on the existing frequency component, the above frequency is converted to a null signal, and re-spreading restores the interference signal. However, when a timing error occurs in the receiving device 2 or when delayed waves are received due to multipath, communication waves remain even if only the center of the spread spectrum band is converted into a null signal after despreading. Interference waves cannot be restored with high accuracy.

On the other hand, in the present embodiment, a chirp signal is used as a spreading sequence, and a CP (Cyclic Prefix) is added after direct spreading to perform block transmission. As a result, even when a timing error occurs in the receiver 2 or when a delayed wave is received due to multipath, the CP length and timing detection position are adjusted so that the preceding wave and the delayed wave are contained within the CP. In addition to avoiding interfering interference, it is possible to restore the interference wave with high accuracy by implementing interference measurement according to the timing error amount and the delay amount of the delayed wave by using a chirp signal as the spreading sequence.

FIG. 8 is a diagram illustrating a configuration example of a transmitting device that configures the communication system according to the second embodiment. FIG. 9 is a diagram illustrating a configuration example of a receiving device that configures the communication system according to the second embodiment.

A transmitting apparatus 1a according to the second embodiment shown in FIG. 8 has a configuration in which a CP adding section 110 is inserted after the direct spreading processing section 101 of the transmitting apparatus 1 according to the first embodiment. In this embodiment, parts different from the transmitting apparatus 1 according to the first embodiment will be explained.

CP adding section 110 copies the last CP length N _cp (chips) of the directly spread transmission signal and adds it to the front of the transmission signal. Direct spreading processing section 101 uses a chirp signal as a spreading sequence.

In a receiver 2a according to the second embodiment shown in FIG. 8, a CP remover 220 is inserted after the timing detector 203 of the receiver 2 according to the first embodiment, and an interference measurement unit 204 is replaced with an interference measurement unit. 204a is replaced. In this embodiment, portions different from the receiving apparatus 2 according to the first embodiment will be explained.

A timing reference C, which will be described later, is input to the CP remover 220 . CP removal section 220 removes the CP from the received signal by the CP length N _cp (chips) based on the timing detected by timing detection section 203 and timing reference C. FIG.

As shown in FIG. 10, interference measuring section 204a has a configuration in which frequency component estimating section 212 of interference measuring section 204 of Embodiment 1 is replaced with frequency component estimating section 212a. FIG. 10 is a diagram showing a configuration example of the interference measuring section 204a included in the receiving device 2a according to the second embodiment.

The frequency component estimator 212a performs the same processing as the frequency component estimator 212 described in Embodiment 1, but the maximum timing error amount A (unit: chip, A≧0) and the maximum delay amount B ( Unit: chip, B≧0) are set, and processing is performed based on these, which is different from the frequency component estimating section 212 . Here, the maximum timing error amount A is the maximum timing error amount assumed to occur in the timing detection processing by the timing detection unit 203 . The maximum delay amount B is the maximum delay amount of delayed waves generated in an assumed multipath environment. Processing executed by the frequency component estimating unit 212a, that is, processing for estimating frequency components in which communication waves are present will be described below.

The frequency component estimator 212a uses the maximum timing error amount A and the maximum delay amount B to estimate the frequency component in which the communication wave exists. Since the chirp signal is used for the spreading sequence in the second embodiment, when a timing error occurs, a frequency offset remains in the communication wave according to the amount of the timing error.

11 to 14 show examples of frequency spectra of communication waves before and after despreading according to timing errors and delay amounts of delayed waves. 11 to 14, the timing reference C=-N _cp /2 is set. 11 shows the frequency spectrum of the received signal when there is no timing error and no delayed wave, FIG. 12 shows the frequency spectrum of the received signal when there is a one-chip timing error and no delayed wave, and FIG. FIG. 14 shows the frequency spectrum of the received signal when there is no timing error and there is a delayed wave with a delay amount of 2 chips. FIG. 14 shows the frequency spectrum of the received signal when there is a 1-chip timing error and a delayed wave with a delay amount of 2 chips. indicates 11 to 14, the frequency D in the frequency spectrum after despreading is the frequency corresponding to the timing reference C, and D=(Bw/N)×C×U. Note that U=1 in the illustrated example.

Now, the timing reference C will be described with reference to FIG. FIG. 15 is a diagram showing the relationship between the signal received by the receiver 2a and the timing reference C according to the second embodiment. As shown in FIG. 15, the reception signal 700 has a structure in which the CP is added to the data, so the ideal timing is the chip at the boundary between the CP and the data. However, the result of the timing detection unit 203 may have an error depending on the communication environment, and delay waves may occur in a multipath environment. In order to avoid inter-block interference based on these influences, it is necessary that the head timings of the leading wave and the delayed wave fall within the CP. In an environment with timing errors and delay waves, inter-block interference occurs if demodulation is performed at ideal timing, so it is necessary to intentionally shift the timing position within the CP. The timing reference C is this timing amount that is intentionally shifted. The CP removal unit 220 intentionally shifts the timing from the ideal timing of the 0th chip to the Cth chip when removing the CP. That is, the CP removal section 220 removes the CP by shifting the timing by C chips from the timing detected by the timing detection section 203 . Since C=-N _cp /2 in the examples shown in FIGS. 11 to 14, this means that the timing is shifted to the center of CP.

If a timing error occurs when a chirp signal is used in the spreading sequence, despreading will leave a frequency offset corresponding to the amount of the timing error. Here, consider the case of using a chirp signal that linearly increases up to the spread spectrum bandwidth Bw [Hz] with a spreading length of N [chips] as shown in FIG. Chirp signal 800 is the ideal timing of the received chirp signal, and despreading at this timing leaves no frequency offset. Chirp signal 801 is a chirp signal at an error of +1 chip from the ideal timing, and when despreading with the error of +1 chip, the frequency difference amount +Bw/N [Hz] from chirp signal 800 at ideal timing becomes frequency offset 810 (plus frequency offset ). If this is represented by the subcarrier number of the frequency spectrum appearing after despreading, if the ideal timing is subcarrier number N/2, the error +1 chip is subcarrier number N/2+1. Similarly, the chirp signal 802 is a chirp signal with an error of -1 chip from the ideal timing, and when despread with an error of -1 chip, the frequency difference amount -Bw/N [Hz] from the ideal timing chirp signal 800 is the frequency offset. The subcarrier number of the frequency spectrum remaining as 811 (negative frequency offset) and appearing after despreading is N/2-1.

Therefore, if a timing error T _d (T _d ≧0) occurs at timing reference C, the subcarrier number of the frequency spectrum appearing after despreading is (N/2)+C+T _d .

Next, consider the case of despreading when there is a delayed wave. The delayed wave is received with a delay of T _m (T _m ≧0) from the preceding wave. At this time, since despreading is performed at the timing of the preceding wave, the despreading is performed with a timing error of -T _m from the ideal timing of the delayed wave. Therefore, in the delayed wave after despreading, the frequency spectrum appears at a position shifted by -T _m in subcarrier number from the preceding wave. That is, if the subcarrier number of the preceding wave is (N/2)+C+ _Td , the subcarrier number of the delayed wave can be expressed as (N/2)+C+ _Td - _Tm (see FIGS. 13 and 14).

When the maximum timing error amount A and the maximum delay amount B are set, the timing error is in the range from -A to A, and the delay amount is in the range from 0 to B. Therefore, the subcarrier number V is in the range shown by the following formula (9).

Also, the condition for A, B, and C under which inter-block interference does not occur in Equation (9) is given by Equation (10) below.

The frequency component estimator 212a determines all subcarrier numbers that satisfy the above equation (9) as subcarrier numbers in which communication waves exist, and outputs the determined subcarrier numbers. The number of subcarrier numbers output at this time is 2A+B+1.

Null signal transforming section 213 transforms frequency components of each of 2A+B+1 subcarriers output from frequency component estimating section 212a into null signals. As a result, the frequency spectrum of communication waves (including leading waves and delayed waves) appearing after despreading can all be replaced with nulls, making it possible to restore interference waves with high accuracy.

As described above, according to the communication system according to the second embodiment of the present disclosure, the transmitting apparatus 1a uses a chirp signal as the spreading sequence to be used, adds a CP after direct spreading, and performs block transmission. In 2a, the maximum timing error amount A and the maximum delay amount B are set by the frequency component estimation unit 212a of the interference measurement unit 204a. Inter-block interference is avoided by setting a value that satisfies the above, and a subcarrier number corresponding to the frequency spectrum of a communication wave that appears after despreading is derived according to the set values A, B, and C. This makes it possible to remove the communication wave from the received signal even in an environment with timing errors and delay waves, and as a result, it is possible to restore the interference wave with high accuracy.

Embodiment 3.
In the second embodiment of the present disclosure described above, the maximum timing error amount A, the maximum delay amount B, and the timing reference C for removing the CP are used in the receiving device 2a, and the preceding wave and the delayed wave fit within the CP. By setting A, B, and C above to avoid inter-block interference and deriving the subcarrier number corresponding to the frequency spectrum of the communication wave that appears after despreading, even in an environment with timing errors and delayed waves To remove a communication wave from a received signal and restore an interference wave with high accuracy. However, considering an environment where the reception level of the delayed wave is much lower than that of the preceding wave and interference waves, null signal conversion is performed according to the maximum delay amount B in order to remove the delayed wave, so subcarriers are used more than necessary. As the number of subcarriers that are converted into null signals and the number of subcarriers for which interference waves are also converted into null signals increases, the restoration accuracy of the interference waves deteriorates.

On the other hand, in the receiving apparatus 2a according to the third embodiment, the reception level of each subcarrier is calculated for only the subcarrier number where the preceding wave and the delayed wave are expected to appear from the frequency spectrum after despreading. Only subcarriers exceeding a certain threshold are converted to null signals. As a result, communication waves can be efficiently removed, and the number of subcarriers to be converted into null signals can be reduced, so that it is possible to suppress deterioration in restoration accuracy of interference waves due to null signal conversion.

The restoration processing of the interference wave in this embodiment will be described in detail below. The configurations of the transmission device and the reception device of the communication system according to this embodiment are the same as those of the second embodiment. The difference between Embodiment 2 and this embodiment is the operation of frequency component estimator 212a constituting interference measuring section 204a of receiving apparatus 2a. Therefore, the operation of the frequency component estimation unit 212a will be mainly described below.

FIG. 17 is a diagram for explaining the operation of the interference measuring section 204a of the receiving device 2a according to the third embodiment. FIG. 17 shows the despread frequency spectrum input to the frequency component estimation section 212a included in the interference measurement section 204a. In FIG. 17, the predecessor (after despreading) 900 is the predecessor detected by timing reference C. FIG. A delayed wave 1 (after despreading) 901 is a delayed wave with a delay amount of T _x1 , and a delayed wave 2 (after despreading) 902 is a delayed wave with a delay amount of T _x2 . An interference wave (after despreading) 903 is an interference wave spread over the spread spectrum band Bw after despreading. Here, the frequency component estimator 212a performs threshold determination on the received level of subcarriers only for subcarrier numbers that are expected to contain communication waves and satisfy the above equation (9). When the reception level exceeds the threshold value σ, the frequency component estimator 212a assumes that a communication wave exists in the corresponding subcarrier number, and outputs the subcarrier number assumed to have a communication wave. In the example of FIG. 17, since the leading wave (after despreading) 900 and the delayed wave 1 (after despreading) 901 exceed the threshold, the frequency component estimator 212a uses the corresponding subcarrier numbers N/2+C, N/2+C- Output only T _x1 .

Here, the threshold σ used for the above threshold determination can be generated, for example, from the following equation (11).

Here, ρ is a weighting factor, _Pn is the power of subcarrier number n, and χ is a set of powers of subcarrier numbers that are not included in the range shown by equation (9).

From Equation (11), the threshold σ can be obtained by multiplying the average power of subcarriers not containing communication waves by the weighting factor ρ. The weighting factor ρ is a fixed value, and an appropriate value is set according to the communication environment. When using the threshold σ generated from Equation (11), the frequency component estimator 212a calculates the power of each subcarrier number that satisfies Equation (9) above and compares it with the threshold σ to perform threshold determination. .

Note that the threshold value σ may be generated by a method other than the above, and the generation method is not limited to a specific method.

As described above, according to the communication system according to the third embodiment of the present disclosure, in the interference measurement unit 204a of the receiving device 2a, the subcarrier number (specifically, is the subcarrier number that satisfies the equation (9), the reception level of each subcarrier is calculated, and only subcarriers exceeding the threshold value σ are determined to contain communication waves and converted to null signals. This makes it possible to accurately estimate subcarriers in which communication waves exist. As a result, the number of subcarriers to be converted into null signals can be made smaller than that of the interference measuring unit 204a of the receiving apparatus 2a according to the second embodiment, and the null signal conversion does not degrade the accuracy of restoration of interference waves. can be suppressed.

In the present embodiment, the interference measurement unit 204a of the receiving apparatus 2a according to the second embodiment performs threshold determination of the subcarrier reception level to determine subcarriers in which communication waves exist. The interference measurement section 204 of the receiving apparatus 2 according to the first embodiment may perform this.

The configurations shown in the above embodiments are only examples, and can be combined with other known techniques, or can be combined with other embodiments, without departing from the scope of the invention. It is also possible to omit or change part of the configuration.

Reference Signs List 1, 1a transmitting device, 2, 2a receiving device, 100 modulating section, 101 direct spreading processing section, 102 transmitting filter section, 103, 201 frequency converting section, 104 transmitting antenna, 110 CP adding section, 200 receiving antenna, 202 receiving filter section 203 timing detection section 204, 204a interference measurement section 205 interference suppression section 206 demodulation section 210 despreading processing section 211 frequency domain conversion section 212, 212a frequency component estimation section 213 null signal conversion section 214 Rediffusion processor, 220 CP remover.

Claims (20)

a despreading processor that despreads the directly spread received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms into a null signal a frequency component of the received signal, which is transformed into a frequency domain signal and is estimated to contain a communication wave, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimating unit estimates the frequency at which the communication wave exists, based on a maximum timing error amount that is the maximum value of the error assumed in the timing at which the despreading processing unit performs despreading processing on the received signal. to estimate the components,
A receiving device characterized by: a despreading processor that despreads the directly spread received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms into a null signal a frequency component of the received signal, which is transformed into a frequency domain signal and is estimated to contain a communication wave, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimator estimates the frequency component in which the communication wave exists, based on the maximum delay amount of delayed waves occurring in an assumed multipath environment.
A receiving device characterized by: a despreading processor that despreads the directly spread received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms into a null signal a frequency component of the received signal, which is transformed into a frequency domain signal and is estimated to contain a communication wave, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimating unit calculates a maximum timing error amount, which is the maximum value of errors assumed in the timing at which the despreading processing unit performs despreading processing on the received signal, and a delay that occurs in an assumed multipath environment. estimating the frequency component in which the communication wave exists, based on the maximum delay amount of the wave;
A receiving device characterized by: a despreading processor that despreads the directly spread received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms into a null signal a frequency component of the received signal, which is transformed into a frequency domain signal and is estimated to contain a communication wave, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
with
The frequency component estimator calculates the power of each frequency component of the received signal converted into a frequency domain signal, and detects the frequency component whose calculated power exceeds a predetermined threshold as the frequency component in which the communication wave exists. determine that
A receiving device characterized by: The received signal despread by the despreading processor is a signal directly spread using a chirp signal.
5. The receiver according to any one of claims 1 to 4, characterized in that: The frequency component estimator determines that a certain range including the center frequency of the received signal converted into a frequency domain signal is the frequency component in which the communication wave exists.
6. The receiver according to any one of claims 1 to 5 , characterized in that: The power value obtained by multiplying the average power of the frequency component of the received signal converted to the frequency domain signal in which no communication wave exists is multiplied by a predetermined coefficient as the threshold;
5. The receiving apparatus according to claim 4 , characterized by: a transmission device that transmits a spread spectrum signal generated by directly spreading transmission data;
The receiving device according to any one of claims 1 to 7 , which receives the spread spectrum signal transmitted from the transmitting device;
A communication system comprising: An interference measurement device for estimating an interference wave contained in a received signal in a receiving device that receives a directly spread signal,
a despreading processing unit that despreads the received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms, into a null signal, a frequency component in which a communication wave of the received signal transformed into a frequency domain signal is estimated to exist, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimating unit estimates the frequency at which the communication wave exists, based on a maximum timing error amount that is the maximum value of the error assumed in the timing at which the despreading processing unit performs despreading processing on the received signal. to estimate the components,
An interference measurement device characterized by: An interference measurement device for estimating an interference wave contained in a received signal in a receiving device that receives a directly spread signal,
a despreading processing unit that despreads the received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms, into a null signal, a frequency component in which a communication wave of the received signal transformed into a frequency domain signal is estimated to exist, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimator estimates the frequency component in which the communication wave exists, based on the maximum delay amount of delayed waves occurring in an assumed multipath environment.
An interference measurement device characterized by: An interference measurement device for estimating an interference wave contained in a received signal in a receiving device that receives a directly spread signal,
a despreading processing unit that despreads the received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms, into a null signal, a frequency component in which a communication wave of the received signal transformed into a frequency domain signal is estimated to exist, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
a cyclic prefix removing unit that removes the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
with
The despreading processing unit despreads the signal after the cyclic prefix has been removed by the cyclic prefix removing unit,
The frequency component estimating unit calculates a maximum timing error amount, which is the maximum value of errors assumed in the timing at which the despreading processing unit performs despreading processing on the received signal, and a delay that occurs in an assumed multipath environment. estimating the frequency component in which the communication wave exists, based on the maximum delay amount of the wave;
An interference measurement device characterized by: An interference measurement device for estimating an interference wave contained in a received signal in a receiving device that receives a directly spread signal,
a despreading processing unit that despreads the received signal;
a frequency domain transform unit that transforms the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimator for estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming unit that transforms, into a null signal, a frequency component in which a communication wave of the received signal transformed into a frequency domain signal is estimated to exist, based on an estimation result by the frequency component estimating unit;
a respreading processing unit that restores an interference wave included in the received signal before being despread by the despreading processing unit by respreading the received signal that has been converted by the null signal conversion unit;
with
The frequency component estimator calculates the power of each frequency component of the received signal converted into a frequency domain signal, and detects the frequency component whose calculated power exceeds a predetermined threshold as the frequency component in which the communication wave exists. determine that
An interference measurement device characterized by: A control circuit for controlling a receiving device that receives a directly spread signal,
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimating step, the frequency component in which the communication wave exists is calculated based on a maximum timing error amount that is the maximum value of the error assumed in the timing at which the despreading process is performed on the received signal in the despreading step. to estimate
A control circuit characterized by: A control circuit for controlling a receiving device that receives a directly spread signal,
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimating step, the frequency component in which the communication wave exists is estimated based on the maximum amount of delay of delayed waves occurring in an assumed multipath environment.
A control circuit characterized by: A control circuit for controlling a receiving device that receives a directly spread signal,
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimation step, in the despreading step, a maximum timing error amount that is the maximum value of errors assumed in the timing of performing despreading processing on the received signal, and a delay wave generated in an assumed multipath environment estimating the frequency component in which the communication wave exists, based on the maximum delay amount of
A control circuit characterized by: A control circuit for controlling a receiving device that receives a directly spread signal,
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
causes the receiving device to execute
In the frequency component estimating step, the power of each frequency component of the received signal converted into a frequency domain signal is calculated, and the frequency component in which the calculated power exceeds a predetermined threshold is detected as the frequency component in which the communication wave exists. determine that
A control circuit characterized by: A storage medium storing a program for controlling a receiving device that receives a directly spread signal,
Said program
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimating step, the frequency component in which the communication wave exists is calculated based on a maximum timing error amount that is the maximum value of the error assumed in the timing at which the despreading process is performed on the received signal in the despreading step. to estimate
A storage medium characterized by: A storage medium storing a program for controlling a receiving device that receives a directly spread signal,
Said program
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal, which is estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimating step, the frequency component in which the communication wave exists is estimated based on the maximum amount of delay of delayed waves occurring in an assumed multipath environment.
A storage medium characterized by: A storage medium storing a program for controlling a receiving device that receives a directly spread signal,
Said program
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
a cyclic prefix removal step of removing the cyclic prefix from a signal transmitted by adding a cyclic prefix to a signal directly spread by a transmitting device;
causes the receiving device to execute
The despreading step despreads the signal from which the cyclic prefix has been removed in the cyclic prefix removal step,
In the frequency component estimation step, in the despreading step, a maximum timing error amount that is the maximum value of errors assumed in the timing of performing despreading processing on the received signal, and a delay wave generated in an assumed multipath environment estimating the frequency component in which the communication wave exists, based on the maximum delay amount of
A storage medium characterized by: A storage medium storing a program for controlling a receiving device that receives a directly spread signal,
Said program
a despreading step of despreading the received signal;
a frequency domain transformation step of transforming the despread received signal from a time domain signal to a frequency domain signal;
a frequency component estimating step of estimating a frequency component in which a communication wave of the received signal converted into a frequency domain signal exists;
a null signal transforming step of transforming into a null signal a frequency component of the received signal transformed into a frequency domain signal estimated to contain a communication wave, based on the estimation result of the frequency component estimating step;
a re-spreading step of re-spreading the received signal after conversion in the null signal conversion step to restore an interference wave contained in the received signal before being de-spread in the de-spreading step;
causes the receiving device to execute
In the frequency component estimating step, the power of each frequency component of the received signal converted into a frequency domain signal is calculated, and the frequency component whose calculated power exceeds a predetermined threshold is detected as the frequency component in which the communication wave exists. determine that
A storage medium characterized by:

Images