JP2021101518A - Radio communication device and radio communication method - Google Patents

Abstract

To provide a radio communication device and a radio communication method, capable of improving the interference resistance of a preamble.SOLUTION: A radio communication device transmits and receives a radio signal including a preamble signal and a data signal. The radio communication device on a transmission side sets a second no-signal section at any time before the start of transmission of the data signal, after the start of transmission of the preamble signal. The radio communication device on a receiving side includes: an antenna receiving the radio signal; an interference suppression part which measures interference in a first no-signal section and the second no-signal section before the preamble signal and suppresses interference based on the interference measurement result; and a demodulation part which demodulates the data signal after timing synchronization using a preamble signal suppressed in the interference.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wireless communication device that transmits and receives radio signals, and particularly relates to signal transmission / reception processing under the influence of interference.

An interference canceller is known as a technique for improving reception quality by suppressing the influence of interference from other radio stations and the like. According to Patent Document 1, in an OFDM signal transmission system, an OFDM signal transmitter inserts a training signal consisting of no signal and a known pattern into a data signal at regular intervals, and the OFDM signal receiver has two receiving antennas. Using the training signal included in the received signal received in, an interference canceller control signal for suppressing the interference signal in the received signal is generated, and the interference signal in the received signal is suppressed based on the interference canceller control signal. , An OFDM signal transmission method for correcting the transmission path based on the training signal for the output is described (see summary).

JP-A-2007-288263 International Publication 2016/162993

In the technique described in Patent Document 1, FFT (Fast Fourier Transform) for demodulating an OFDM signal is performed before interference suppression, and FFT timing (OFFT timing (OFDM) is performed using a preamble consisting of a known pattern. It is necessary to identify the boundary of the symbol). However, in a situation where the preamble is received with strong interference, it becomes difficult to capture the preamble. Therefore, it is an object of the present invention to improve the interference resistance of the preamble.

A typical example of the invention disclosed in the present application is as follows. That is, it is a wireless communication device that transmits and receives a radio signal including a preamble signal and a data signal, and the wireless communication device on the transmitting side is after the start of transmission of the preamble signal and before the start of transmission of the data signal. At any time, a second non-signal section is provided to transmit a signal, and the radio communication device on the receiving side has an antenna for receiving the radio signal and a first non-signal section prior to the preamble signal. And, after timing synchronization using the interference suppression unit that measures the interference in the second no-signal section and suppresses the interference based on the interference measurement result and the preamble signal in which the interference is suppressed, the data signal is transmitted. It is characterized by including a demodulator for demolishing.

According to one aspect of the present invention, communication is possible even in an environment where large interference exists. Issues, configurations and effects other than those mentioned above will be clarified by the description of the following examples.

It is a figure which shows the interference suppression method with respect to a preamble and a data signal in 1st Example. It is a figure which shows the structure of the receiver in 1st Example. It is a figure which shows the structure of the interference canceller with respect to the data signal in 1st Example. It is a figure which shows the operation of the interference canceller with respect to the preamble in the 1st Example. It is a figure which shows the structure of the antenna selection part in 1st Example. It is a figure which shows the interference suppression method with respect to a preamble and a data signal in a 2nd Example.

Hereinafter, examples of the present invention will be described with reference to the drawings.

<Example 1>
FIG. 1 shows an interference suppression method according to the first embodiment of the present invention. The present invention is premised on performing communication in synchronization with the time slot. For example, as shown in the lower part of FIG. 1, transmission 106 and reception 107 are alternately repeated according to a specified time slot. The transmitter transmits a transmission signal including a preamble signal 101 and a data signal 102. At this time, a non-signal section 100-2 for a predetermined time is provided between the preamble signal 101 and the data signal 102. The receiver measures the interference in the no-signal section 100-1 immediately before the start of the preamble 101 in the reception time slot. Interference is also measured in the non-signal section 100-2 provided between the preamble signal 101 and the data signal 102.

The preamble interference suppression coefficient calculation unit 104 calculates the interference suppression coefficient according to the measured interference, and suppresses the interference in the preamble section 101 according to the calculated interference suppression coefficient. At this time, in order to correspond to the propagation path fluctuation in the preamble 101, it is desirable to calculate the interference suppression coefficient interpolated in the time direction based on the interference measured in the non-signal sections 100-1 and 100-2. .. In the OFDM (Orthogonal Frequency Division Multiplex) data signal 102 transmitted following the preamble section 101, a plurality of non-signal symbols 103 are arranged. This method is disclosed in Patent Document 2, for example. Next, the interference is measured using the no-signal symbol 103. The interference of the OFDM data signal 102 is suppressed according to the interference suppression coefficient calculated by the data signal interference suppression coefficient calculation unit 105 using the measured interference.

The non-signal symbol disclosed in Patent Document 2 can be extracted via FFT according to the symbol delimiter of the OFDM signal. Therefore, it cannot be applied to the preamble signal for identifying the symbol delimiter of the OFDM signal. Therefore, as described above, it is necessary to insert the non-signal section by a method in which the position can be identified based on the time slot synchronization. Therefore, in this embodiment, the space between the preamble signal 101 and the data signal 102 is adopted as a specific position in the time direction that can be extracted by identifying an approximate temporal position.

FIG. 2 shows the configuration of the receiver of the first embodiment. In FIG. 2, components that are general to wireless communication devices such as RF (Radio Frequency) circuits and that are not related to the present invention are omitted. Antennas 201 and 202 receive the same signal transmitted from the transmitter. The signals received by the antennas 201 and 202 in the non-signal section 100-1, the preamble section 101, and the non-signal section 100-2 in FIG. 1 are overlapped FFT (Fast Fourier Transform) 203 and 204. Is converted into a signal in the frequency domain.

The operation of the overlap FFTs 203 and 204 will be described with reference to FIG. The input signal is divided into predetermined sample sections. For example, in FIG. 4, it is divided into sections of N / 2 samples. The two N / 2 sample intervals are combined to form an N sample interval, which is multiplied by the first window function to perform an FFT (Fast Fourier Transform) operation. At this time, in the next N sample, the signal behind the N / 2 sample is used to overlap the N / 2 sample with the immediately preceding N sample. The FFT calculation is also performed on the next N sample in the same manner to convert it into a signal in the frequency domain. Similarly, the window function processing and the FFT calculation are sequentially performed while shifting N / 2 samples at a time. The signal converted into the signal in the frequency domain by the overlap FFT 203 and 204 is input to the antenna selection unit 205.

The antenna selection unit 205 is configured as shown in FIG. 5, for example. The power comparison unit 500 compares the signal powers in the non-signal sections 100-1 and 100-2 from the plurality of antennas 201 and 202 (two in the figure), and selects the one having the larger average power via the selectors 501 and 502. Output from the upper side and the smaller one from the lower side.

After that, the phase calculation unit 206 calculates the upper phase (the one having the larger average power) of the received signals in the non-signal sections 100-1 and 100-2 output from the antenna selection unit 205. The phase rotation units 207 and 208 rotate the phase of the signal output from the antenna selection unit 205 in the direction opposite to the phase calculated by the phase calculation unit 206. The phase-rotated signals are averaged over multiple neighboring frequencies and multiple overlapping FFT sections within each non-signal section 100-1 and 100-2 by the averaging and interpolating units 209 and 210, and the non-signal section. The average results at 100-1 and 100-2 are interpolated in the time direction. For the interpolation, general first-order interpolation, LPF (Low Pass Filter), or the like can be used. Further, the interpolation result is held over the preamble section 101. Further, the delay units 222 and 223 delay the output of the antenna selection unit 205 by a predetermined time to match the timing with the interpolation result.

The multipliers 211 and 212 cross and multiply the retained interpolation results with the respective outputs of the delay portions 222 and 223 in the preamble section 101, and the adder 213 subtracts the other from one. As a result, a preamble signal in the frequency domain from which interference has been removed is obtained. After that, the overlapping IFFT (Inverse Fast Fourier Transform) 214 converts the preamble signal in the frequency domain from which the interference has been removed into a signal in the time domain.

The operation of the overlap IFFT 203 and 204 will be described with reference to FIG. The preamble signal in the frequency domain from which the interference has been removed is subjected to an IFFT calculation for each N sample, and is converted into a preamble signal in the time domain from which the interference of the N samples has been removed. The preamble signal in the time domain from which the interference of the N sample is removed is multiplied by the second window function to obtain the output of the N sample. The output of the N sample is sequentially added to the output of the next N sample while shifting by N / 2 sample to obtain a continuous signal in the time domain in which the interference is removed. The first window function and the second window function are functions that have a small value at the start and end of the N sample and a large value at the center, respectively, and are the first window function and the second window function. It is a function that becomes a constant value when the product of is sequentially added while shifting by N / 2 samples. For example, if sin ((i / N) * π) (i = 0 to N-1) is adopted as the first window function and the second window function, the product of the first window function and the second window function. Is sin2 ((i / N) * π) = (1-cos (2 * (i / N) * π)) / 2, and when this is added while shifting N / 2 samples, it becomes 1, and the above condition is satisfied. You can see that it meets.

Then, the preamble capture unit 215 detects the preamble in the preamble signal in the continuous time region in which the interference output from the overlap IFFT 214 is removed. The preamble capture unit 215 can employ a conventional method of configuring by cross-correlation calculation using a matched filter, or by autocorrelation calculation in the case of a preamble signal including repetition of the same pattern. Based on the preamble timing detected by the preamble capture unit 215, the FFT calculation units 216 and 217 perform FFT calculation of the OFDM data signal received by the antennas 201 and 202, respectively.

The data signal interference suppression coefficient calculation unit 105 calculates the interference suppression coefficient using the FFT calculation result. The interference suppression weight application unit 218 calculates the calculated interference suppression coefficient and the FFT calculation result, and outputs a signal in which interference is suppressed. A second interference suppression unit 232 that removes interference from the data signal is configured by the data signal interference suppression coefficient calculation unit 105 and the interference suppression weight application unit 218. The data signal interference suppression coefficient calculation unit 105 can be configured as shown in FIG. 3, for example. The signal separation unit 300 separates the outputs of the FFT calculation units 216 and 217 into symbols that do not include data signals (Null in FIG. 3), reference symbols (Reference in FIG. 3), and data symbols (Data in FIG. 3), respectively. .. The interference propagation path estimation unit 301 measures the interference of symbols that do not include a data signal. The first interference suppression unit 302 performs interference suppression on a symbol that does not include a data signal, based on the measured interference. As the calculation for interference suppression here, the same calculation as the interference suppression coefficient calculation method in the preamble interference suppression coefficient calculation unit 104 and the interference elimination calculation in the multipliers 211, 212 and the adder 213 can be adopted. Since only the interference and noise are received in the symbol that does not include the data signal, only the noise remains as a result of the interference suppression calculation. Therefore, the noise power can be estimated by measuring the power after the interference suppression calculation. The noise level is estimated by the noise level estimation unit 304.

Similarly, the interference suppression calculation is performed by the second interference suppression unit 303 with respect to the reference symbol. At this time, since at least one of the time and frequency of the reference symbol is different from that of the symbol that does not include the data signal, the interference propagation path estimation unit 301 interferes with the symbol other than the symbol that does not include the data signal by interpolation by moving average calculation or the like. It is necessary to estimate the propagation path. The signal propagation path estimation unit 305 estimates the signal propagation path using at least one of the reference symbol output from the signal separation unit 300 and the reference symbol that has undergone interference suppression processing. For example, when the interference of the received signal is small, the reference symbol output from the signal separation unit 300 may be used, and when the interference of the received signal is large, the reference symbol subjected to the interference suppression process may be used for estimation. Further, it is preferable to estimate the propagation path by changing the weighting coefficient of the reference symbol output from the signal separation unit 300 and the weighting coefficient of the reference symbol subjected to the interference suppression processing according to the magnitude of the interference of the received signal.

The output I of the interference propagation path estimation unit 301, the output N of the noise level estimation unit 304, and the output S of the signal propagation path estimation unit 305 are interpolated and output in the time and frequency directions. These outputs I, N, and S suppress interference with respect to symbols, reference symbols, and data symbols that do not include a data signal at the interference suppression weight application unit 218 (306, 307) as interference suppression coefficients. The calculation executed by the interference suppression weight application units 306 and 307 is preferably an MMSE (Minimum Mean Square Error) process. In this process, for example, when the signal propagation path estimation results are Sn1 and Sn2, the interference propagation path measurement results are Γn1 and Γn2, and the noise level estimation result is σ2, the equations (1) and (2) are used. This can be achieved by multiplying the calculated interference suppression coefficient Wn.

The interference suppression result of the symbol not including the data signal is input to the noise level estimation unit 308, and the noise level estimation unit 308 obtains the second noise level estimation result. Further, the interference suppression result of the reference symbol and the data symbol is input to the demodulation unit 220 together with the second noise level estimation result, and the demodulation unit 220 executes the demodulation process. The demodulation result output from the demodulation unit 220 is input to the decoding unit 221 and the decoding process is executed.

In the first embodiment, since the interference is measured using the non-signal section before and after the preamble and the interference suppression coefficient is calculated, the interference in the preamble signal can be suppressed even when the propagation path fluctuates during the preamble. ..

<Example 2>
Next, a second embodiment of the present invention will be described. The difference between the second embodiment and the first embodiment is the method of inserting the non-signal section. In the first embodiment, the non-signal section 100-2 is inserted between the preamble signal 101 and the data signal 102, but in the second embodiment, the non-signal section 100-3 is also inserted in the middle of the preamble signal 101. To do. In the second embodiment, the differences from the first embodiment will be mainly described, the same functions and processes as in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

FIG. 6 shows the interference suppression method of the second embodiment. The receiver measures the interference in the no-signal section 100-1 in the reception time slot, just before the start of the preamble 101-1. Similarly, the non-signal section 100-3 in the middle of the preamble 101 (that is, between the preamble 101-1 and the preamble 101-2), and the non-signal section 100 provided between the preamble 101-2 and the data signal 102. Interference is also measured at -2.

The preamble interference suppression coefficient calculation unit 104 calculates the interference suppression coefficient according to the measured interference, and suppresses the interference in the preamble section 101 according to the calculated interference suppression coefficient. At this time, in order to correspond to the propagation path fluctuation in the preamble 101, the interference suppression coefficient interpolated in the time direction is calculated based on the interference measured in the non-signal sections 100-1, 100-3 and 100-2. It is desirable to do. Further, in the receiver shown in FIG. 2, the preamble interference suppression coefficient calculation unit 104 measures the interference in the non-signal sections 100-1, 100-3 and 100-2, and calculates the interference suppression coefficient by these interpolations. To do. Since other operations are the same as those in the first embodiment, the description thereof will be omitted.

According to the second embodiment, the interference with the preamble can be suppressed even when the variation of the propagation path is faster than that of the first embodiment. In the second embodiment, the no-signal section is provided once in the middle of the preamble 101, but when the propagation path fluctuation is faster, it is preferable to provide a plurality of no-signal sections in the middle of the preamble 101. On the other hand, if the number of non-signal sections is increased, the signal transmission efficiency is lowered. Therefore, it is desirable to determine the insertion amount of the non-signal section in consideration of the balance between the speed of fluctuation of the propagation path and the transmission efficiency.

If the wireless communication device of the present invention needs to transmit and receive signals of an existing wireless standard and the configurations of the preamble signal and the data signal cannot be changed, a part of the preamble signal to be transmitted is set as a non-signal section. May be good. As a result, the preamble can be detected even in a conventional radio that does not assume that a part of the preamble is a non-signal section, and the influence on compatibility can be minimized.

Further, in inserting the non-signal section in the preamble, the non-signal section is inserted at the temporal position in the first and second embodiments, but it may be inserted at the frequency position. That is, in the frequency band used for wireless communication, a specific frequency band in the preamble may be set to no signal. Even in this case, as described above, a specific frequency in the specified preamble signal may be masked to be non-signaled in order to have compatibility with the existing wireless standard.

As described above, in the embodiment of the present invention, the radio communication device on the transmitting side has a second no signal at any time after the start of transmission of the preamble signal 101 and before the start of transmission of the data signal 102. A section 100-2 is provided to transmit a signal, and the radio communication device on the receiving side has antennas 201 and 202 for receiving the radio signal, and first non-signal sections 100-1 and a first signal section before the preamble signal 101. After timing synchronization using the interference suppression units 302 and 303 that measure the interference in the non-signal section 100-2 of 2 and suppress the interference based on the interference measurement result and the preamble signal 101 in which the interference is suppressed, the data Since it is provided with a demodulator 220 that demolishes the signal 102, communication is possible even in an environment where large interference exists.

Further, since the second non-signal section 100-2 is provided between the preamble signal 101 and the data signal 102, interference can be suppressed based on the interference suppression coefficient measured using the non-signal section before and after the preamble, and the preamble can be suppressed. Even when the propagation path fluctuates inside, the interference in the preamble signal can be suppressed.

Further, since the second non-signal section 100-2 is provided in the middle of the preamble signal 101 and between the preamble signal 101 and the data signal 102, interference with the preamble can be suppressed even when the propagation path fluctuates quickly.

Further, the interference suppression unit 302 is based on the interference measurement result obtained by interpolating the interference measured in the first non-signal section 100-1 and the interference measured in the second non-signal section 100-2. Since the interference is suppressed, the interference can be effectively suppressed by a simple calculation.

The present invention is not limited to the above-described embodiment, and includes various modifications and equivalent configurations within the scope of the attached claims. For example, the above-described examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the described configurations. Further, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Further, the configuration of another embodiment may be added to the configuration of one embodiment. In addition, other configurations may be added / deleted / replaced with respect to a part of the configurations of each embodiment.

Further, each of the above-described configurations, functions, processing units, processing units, etc. may be realized by hardware by designing a part or all of them by, for example, an integrated circuit, and the processor realizes each function. It may be realized by software by interpreting and executing the program to be executed.

Information such as programs, tables, and files that realize each function can be stored in a memory, a hard disk, a storage device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

In addition, the control lines and information lines indicate those that are considered necessary for explanation, and do not necessarily indicate all the control lines and information lines necessary for implementation. In practice, it can be considered that almost all configurations are interconnected.

100-1, 100-2, 100-3: No signal section 101, 101-1, 101-2: Preamble signal 102: OFDM data signal 103: No signal OFDM symbol 104: Interference suppression coefficient calculation unit for preamble 105: Data Signal interference suppression coefficient calculation unit 106: Transmission signal 107: Received signals 201, 202: Antenna 203, 204: Overlap Fourier unit 205: Antenna selection unit 206: Phase calculation unit 207, 208: Phase rotation calculation unit 209, 210: Average calculation unit 211, 212: Multiplier 213: Adder 214: Overlap IFFT unit 215: Preamble capture unit 216: 217: FFT calculation unit 218: Interference suppression weight application unit 219: Demodulation / decoding unit 220: Demodulation unit 221: Decoding section 222, 223: Delay section 300: Signal separation section 301: Interference propagation path estimation section 302, 303: First interference suppression section 304, 308: Noise level estimation section 305: Signal propagation path estimation section 306, 307: Interference Suppression weight application unit 400: Interference suppression unit 500: Power comparison unit 501, 502: Selector

Claims (8)

A wireless communication device that transmits and receives wireless signals including preamble signals and data signals.
The wireless communication device on the transmitting side transmits a signal by providing a second non-signal section at any time after the start of transmission of the preamble signal and before the start of transmission of the data signal.
The wireless communication device on the receiving side is
An antenna that receives the radio signal and
An interference suppression unit that measures interference in the first non-signal section and the second non-signal section prior to the preamble signal and suppresses the interference based on the interference measurement result.
A wireless communication device including a demodulation unit that demodulates the data signal after timing synchronization using the preamble signal in which the interference is suppressed. The wireless communication device according to claim 1.
The second non-signal section is a wireless communication device provided between the preamble signal and the data signal. The wireless communication device according to claim 1.
The wireless communication device is characterized in that the second non-signal section is provided in the middle of the preamble signal and between the preamble signal and the data signal. The wireless communication device according to claim 1.
The interference suppression unit suppresses interference based on the interference measurement result obtained by interpolating the interference measured in the first non-signal section and the interference measured in the second non-signal section. A wireless communication device featuring. A wireless communication method for transmitting and receiving wireless signals including preamble signals and data signals.
The wireless transmitter transmits the signal by providing a second non-signal section at any time after the start of transmission of the preamble signal and before the start of transmission of the data signal.
The wireless receiver is
Interference is measured in the first non-signal section and the second non-signal section prior to the preamble signal, and the interference is suppressed based on the interference measurement result.
A wireless communication method comprising demodulating the data signal after timing synchronization using the preamble signal in which the interference is suppressed. The wireless communication method according to claim 5.
The wireless communication method is characterized in that the wireless transmitter is provided with the second non-signal section between the preamble signal and the data signal. The wireless communication method according to claim 5.
The wireless communication method is characterized in that the wireless transmitter is provided with the second non-signal section in the middle of the preamble signal and between the preamble signal and the data signal. The wireless communication method according to claim 5.
The radio receiver suppresses the interference based on the interference measurement result obtained by interpolating the interference measured in the first no-signal section and the interference measured in the second no-signal section. A wireless communication method characterized by.

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