JP7354297B2 - Timing detection method and wireless communication device - Google Patents

Description

The present invention relates to a timing detection method by a radio communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side.

In a wireless communication system, it is important that a receiving unit (receiver) of a wireless communication device synchronizes demodulation timing and demodulation frequency with a transmitting side. Generally, a method is adopted in which the transmitting side periodically transmits a known signal sequence together with transmission information, and the receiving side uses this known signal sequence to achieve synchronization. This known signal sequence is called a preamble signal. Specifically, by correlating the received signal and the preamble signal and finding the timing at which the maximum value (peak) of the amplitude is obtained, it is possible to accurately know the timing of the transmission signal included in the received signal.

On the other hand, especially in wideband communications, OFDM (Orthogonal Frequency Division Multiplex) is widely adopted. By combining OFDM and an appropriate error correction code, it is possible to realize a wireless communication system that has excellent resistance to transmission path distortion due to multipaths and narrowband interference signals.

Regarding OFDM, various inventions have been proposed in the past. For example, Patent Document 1 discloses an OFDM repeater that can optimize the position of an effective symbol extraction section and the transmission timing of interference waves according to the D/U value to prevent deterioration of reception quality due to looping transmission waves. Disclosed. Further, Patent Document 2 discloses an OFDM receiving device that enables transmission channel estimation with little error even when the reception timings of radio signals arriving from a plurality of multiple-connected transmitting devices are shifted.

Japanese Patent Application Publication No. 2013-098963 Japanese Patent Application Publication No. 2011-019057

In timing detection by correlation calculation between a received signal and a preamble signal, the correlation waveform is significantly impaired by narrow-band interference waves, and timing detection may become impossible. Therefore, in the conventional technology, timing synchronization cannot be ensured due to narrowband interference waves, and there are cases where OFDM transmission cannot exhibit interference wave resistance.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is an object of the present invention to ensure stable timing synchronization even in the presence of narrow band interference waves.

In order to achieve the above object, a timing detection method and a wireless communication device according to the present invention are configured as follows.
That is, the timing detection method according to the present invention is a timing detection method by a receiving side wireless communication device that performs synchronization processing using a preamble signal transmitted from a transmitting side, in which the receiving side wireless communication device A plurality of correlated signals, which are time domain signals of mutually different frequency parts, are stored in advance, and a correlation operation is performed on each of the plurality of correlated signals for the received signal, and a correlation calculation is performed for each of the correlated signals. The present invention is characterized in that the reception timing of the preamble signal is detected using at least one of the calculated correlation calculation results.

Here, as a configuration example, the wireless communication device on the receiving side calculates a moving average of each of the correlation calculation results obtained for each correlated signal, and uses the correlation calculation result with the smallest moving average value. Alternatively, the reception timing of the preamble signal may be detected.

As another configuration example, the wireless communication device on the receiving side calculates a moving average for each of the correlation calculation results obtained for each correlated signal, and weights each correlation calculation result according to the value of the moving average. The received timing of the preamble signal may be detected using the synthesized signal.

Further, in the wireless communication device according to the present invention, in a wireless communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side, a plurality of time domain signals of mutually different frequency portions of the preamble signal are provided. a memory storing correlated signals, a plurality of correlators that perform correlation calculations between the received signal and each of the plurality of correlated signals, and at least one of the plurality of correlation calculation results output from the plurality of correlators. The present invention is characterized in that it includes a detector that detects the reception timing of the preamble signal using a detector.

Here, as a configuration example, a wireless communication device on the receiving side includes a plurality of moving average calculators that calculate a moving average for each of the correlation calculation results for each correlated signal obtained by a plurality of correlators, and a plurality of Further comprising a comparator that compares the moving average values calculated by the moving average calculator, and a selector that selects the correlation calculation result that is found to have the smallest moving average value by comparison with the comparator, The detector may detect the reception timing of the preamble signal using the correlation calculation result selected by the selector.

In addition, as another configuration example, a wireless communication device on the receiving side includes a plurality of moving average calculators that calculate a moving average for each of the correlation calculation results for each correlated signal obtained by a plurality of correlators, and a plurality of A plurality of coefficient calculators calculate weighting coefficients for each correlated signal based on the moving average value calculated by the moving average calculator, and a correlation calculation result for each correlated signal obtained by a plurality of correlators. , further comprising a plurality of multipliers that multiply the weighting coefficients for each correlated signal calculated by the plurality of coefficient calculators, and an adder that synthesizes the multiplication results of the plurality of multipliers, and the detector performs the synthesis by the adder. The result may be used to detect the reception timing of the preamble signal.

According to the present invention, stable timing synchronization can be ensured even in the presence of narrowband interference waves. As a result, it becomes possible to effectively realize the interference wave resistance inherent in OFDM transmission including error correction, and wideband OFDM transmission with excellent interference wave resistance can be realized.

1 is a diagram illustrating a configuration example of a wireless communication device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating frequency band division of a preamble signal. FIG. 3 is a diagram showing the configuration of a test signal for simulation. FIG. 3 is a diagram showing an example of a frequency spectrum and a correlation output when no interference waves are present. It is a figure which shows an example of a frequency spectrum and correlation output when an interference wave exists. FIG. 2 is a diagram showing a first configuration example of the selection synthesizer shown in FIG. 1; 7 is a diagram showing an example of the output of a moving average calculator that constitutes the selector of FIG. 6. FIG. FIG. 2 is a diagram illustrating a second configuration example of the selection synthesizer in FIG. 1;

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of a wireless communication device according to an embodiment of the present invention. The wireless communication device of this example is a receiving side wireless communication device in a wireless communication system using OFDM, and includes an input terminal 101, correlators 102-1 and 102-2, and memories 103-1 and 103-2. , a selection synthesizer 104, a peak detector 105, and an output terminal 106.

A signal received by the wireless communication device of this example is input to the input terminal 101. The received signal input to the input terminal 101 is correlated with the correlated signals stored in the memories 103-1 and 103-2 by the correlators 102-1 and 102-2. That is, the correlator 102-1 performs a correlation operation on the input received signal with the correlated signal stored in the memory 103-1, and then calculates the correlation with the correlated signal stored in the memory 103-2. A correlation calculation with the signal is performed by the correlator 102-2. When the received signal at time n is r(n) and the correlated signal stored in the memory is x(k), the output value c(n) of the correlators 102-1 and 102-2 is expressed by the following (formula 1).

ここで、Ｌは被相関信号の長さであり、ｘ^* はｘの複素共役を表す。

Here, L is the length of the correlated signal and x ^* represents the complex conjugate of x.

The two correlation calculation results output from correlators 102-1 and 102-2 are input to selector 104. The selector 104 selects the one that is more appropriate from the two input correlation calculation results, that is, the one that is not affected by interference waves (or the one that is less affected), and outputs it to the peak detector 105. . The peak detector 105 detects the timing when the correlation calculation result gives the maximum value (peak). The timing detected by the peak detector 105 is outputted via the output terminal 106 as the reception timing of the preamble signal, and is used for timing control of the processing operation of the received signal.

The correlated signals stored in advance in the memories 103-1 and 103-2 will be explained using FIG. 2. A preamble signal 206, which is a known signal sequence used for synchronization with the transmitting side, is processed by IFFT (Inverse Fast Fourier Transform; The signal is converted into a time domain signal by performing an inverse fast Fourier transform (205).

In the present invention, as an example, the assignment indicated by reference numeral 201 is divided into a negative frequency component 202-1 (band A) and a positive frequency component 202-2 (band B), and IFFTs 203-1, 203- 2 to convert it into a time domain signal. The two signal sequences 204-1 and 204-2 generated in this way are stored as correlated signals in the memories 103-1 and 103-2 in FIG. 1, and are referenced when detecting the reception timing of the preamble signal. be done.

The effects of timing detection using the correlated signals 204-1 and 204-2 as described above will be explained using FIGS. 3 to 5. FIG. 3 shows the configuration of a test signal of a simulation performed for explanation. The test signal used in the simulation consists of a non-transmission period, a preamble symbol with a fixed known pattern, and a data symbol.

FIG. 4 illustrates each signal output when there is no interference wave. FIG. 4(a) shows the frequency spectrum of the test signal, which is a normal OFDM spectrum. FIG. 4(b) is a correlation output for the entire band of the preamble signal according to the prior art. A sharp peak corresponding to the final point of the preamble signal is obtained at time 512, and timing synchronization can be performed by detecting this peak timing. FIGS. 4(c) and 4(d) are correlation outputs for each of the divided bands A and B by the wireless communication device of this example, and mean the outputs of the correlators 102-1 and 102-2 in FIG. 1. Both of these correlation outputs show the same tendency as in FIG. 4(b), and it is possible to achieve timing synchronization by selecting either one or by adding both.

Next, the case where interference waves are present will be described using FIG. 5. FIG. 5A shows the frequency spectrum of the test signal, and it can be seen that in addition to the desired OFDM signal, there is a narrow band interference wave in the low frequency region. Note that this interference wave is GMSK (Gaussian-filtered Minimum Shift Keying) modulated. Even under such conditions, there is a high possibility that demodulation and decoding will be performed normally due to the effects of OFDM and error correction codes. However, there are strict conditions regarding synchronization for demodulation.

FIG. 5(b) shows the correlation output for the entire band of the preamble signal according to the conventional technology. Compared to FIG. 4(b), the level is higher overall, the original peak is almost buried, and the area near the peak is The waveform also contains distortion. Note that depending on the phase and amplitude of the interference wave, the peak may not be detected at all.

FIGS. 5(c) and 5(d) are correlation outputs for each of the divided bands A and B by the wireless communication device of this example, and mean the outputs of the correlators 102-1 and 102-2 in FIG. 1. The correlation output for divided band A shown in FIG. 5(c) is significantly affected by interference waves, as in FIG. 5(b). However, the correlation output for divided band B shown in FIG. 5(d) has almost no change compared to FIG. 4(d), and it can be seen that it is hardly affected by the interference waves.
As described above, by dividing the preamble signal into bands, performing correlation calculation on each band, and selecting an appropriate correlation calculation result from among them (in the example of FIG. 5, selecting the correlation calculation result for band B). , narrowband interference waves are suppressed from affecting the synchronization process, making it possible to achieve stable synchronization.

FIG. 6 shows a first configuration example of the selection/synthesizer 104 of FIG. 1 as one of the methods for providing the above selection criteria. The selection synthesizer 104 in FIG. There is.

The correlation calculation result by the correlator 101-1 in FIG. 1 is input to the input terminal 111-1, and the correlation calculation result by the correlator 101-2 in FIG. 1 is input to the input terminal 111-2. The moving average calculators 112-1 and 112-2 calculate moving averages of the input correlation calculation results over a time interval of a predetermined length. The calculation results by the moving average calculators 112-1 and 112-2 are input to the comparator 113. Comparator 113 compares the instantaneous magnitude of each moving average output from moving average calculators 112-1 and 112-2, and controls an input switching signal to selector 114 according to the result. Specifically, the selector 114 is controlled so that the correlation calculation result with the smaller moving average value is selected from the two correlation calculation results input to the input terminals 111-1 and 111-2. . The correlation calculation result selected by the selector 114 is output from the output terminal 115 and input to the peak detector 105.

FIG. 7 shows an example of the output of the moving averages 112-1 and 112-2. As shown in FIG. 7(b), the level of the moving average of divided band B where there is no interference wave is relatively low, whereas as shown in FIG. 7(a), the level of the moving average of divided band B where there is no interference wave is The moving average of is at a high level overall. Therefore, it can be seen that the influence of interference waves can be determined by taking a moving average and comparing the levels.

Note that in the configuration shown in FIG. 6, the reception timing of the preamble signal is detected using only the correlation calculation result with the smaller moving average value, but the configuration shown in FIG. 8 may also be used to weight and synthesize the correlation calculation results. It is possible. FIG. 8 shows a second configuration example of the selection/synthesizer 104 of FIG. 1. The selection synthesizer 104 in FIG. 8 includes input terminals 111-1, 111-2, moving average calculators 112-1, 112-2, coefficient calculators 116-1, 116-2, and a multiplier 117-1. , 117-2, an adder 118, and an output terminal 115.

The correlation calculation result by the correlator 101-1 in FIG. 1 is input to the input terminal 111-1, and the correlation calculation result by the correlator 101-2 in FIG. 1 is input to the input terminal 111-2. The moving average calculators 112-1 and 112-2 calculate moving averages of the input correlation calculation results over a time interval of a predetermined length. The calculation result by the moving average calculator 112-1 is input to the coefficient calculator 116-1, and the calculation result by the moving average calculator 112-2 is input to the coefficient calculator 116-1.

Coefficient calculator 116-1 calculates a weighting coefficient for subband A based on the moving average value output from moving average calculator 112-1, and outputs it to multiplier 117-1. For example, the coefficient calculator 116-1 is configured to output a larger weighting coefficient as the value of the moving average is smaller. Multiplier 117-1 multiplies the correlation calculation result input to input terminal 111-1 by the weighting coefficient output from coefficient calculator 116-1, and outputs the result to adder 118.

Similarly, coefficient calculator 116-2 calculates a weighting coefficient for divided band B based on the moving average value output from moving average calculator 112-2, and outputs it to multiplier 117-2. Multiplier 117-2 multiplies the correlation calculation result input to input terminal 111-2 by the weighting coefficient output from coefficient calculator 116-2, and outputs the result to adder 118. Adder 118 adds (synthesizes) the respective output values of multipliers 117-1 and 117-2.

The correlation calculation results weighted and combined in this manner are output from the output terminal 115 and input to the peak detector 105. Such a configuration also suppresses narrowband interference waves from affecting the synchronization process, making it possible to achieve stable synchronization. Note that if the weighting coefficient for the smaller moving average value is set to '1' and the weighting coefficient for the larger moving average value is set to '0', the same calculation result as in the first configuration example will be obtained.

As described above, in the wireless communication system of this example, the wireless communication device on the receiving side uses the memories 103-1 and 103 that store a plurality of correlated signals that are time-domain signals of mutually different frequency portions of the preamble signal. -2, correlators 102-1 and 102-2 that perform correlation calculations between the received signal and each of a plurality of correlated signals, and correlation calculation results obtained by the correlators 102-1 and 102-2. and a peak detector 105 that detects the reception timing of the preamble signal using at least one peak detector.

More specifically, the wireless communication device according to the first configuration example includes a moving average calculator that calculates a moving average for each of the correlation calculation results for each correlated signal obtained by the correlators 102-1 and 102-2. 112-1, 112-2 and a comparator 113 that compares the moving average values calculated by the moving average calculators 112-1, 112-2, and the comparison in the comparator 113 shows that the moving average value is smaller. The peak detector 105 is configured to use the correlation calculation result selected by the selector 114 to detect the reception timing of the preamble signal. ing.

The wireless communication device according to the second configuration example also includes a moving average calculator 112-1 that calculates a moving average for each of the correlation calculation results for each correlated signal obtained by the correlators 102-1 and 102-2; 112-2, and coefficient calculators 116-1 and 116-2 that calculate weighting coefficients for each correlated signal based on the moving average values calculated by the moving average calculators 112-1 and 112-2, A multiplier 117- that multiplies the correlation calculation results for each correlated signal obtained by the correlators 102-1 and 102-2 by the weighting coefficient for each correlated signal calculated by the coefficient calculators 116-1 and 116-2. 1,117-2 and an adder 118 for synthesizing the multiplication results of the multipliers 117-1, 117-2. It is configured to detect reception timing.

In this way, by band-dividing the preamble signal into multiple correlated signals and storing them in the receiving wireless communication device, and performing correlation calculations on the received signals with each correlated signal, narrowband Correlation calculation results can be obtained for frequency portions where there is no (or small) influence of interference waves. By performing timing detection by preferentially using the correlation calculation results for frequency parts where there is no (or small) influence from narrowband interference waves, stable timing can be achieved even in the presence of narrowband interference waves. It becomes possible to ensure synchronization. Thereby, it becomes possible to effectively realize the interference wave resistance that OFDM transmission including error correction originally has, and it is possible to realize wideband OFDM transmission having excellent interference wave resistance.

Here, in the above description, the number of band divisions of the preamble signal is two, but it is also possible to divide the preamble signal into three or more (that is, to divide the preamble signal into three or more correlated signals). In this case, the smaller the moving average value is given priority (that is, the smaller the moving average value is selected, or the smaller the moving average value is, the larger the weighting coefficient is), and the preamble signal is It is preferable to use it for detecting reception timing. Note that if the number of band divisions of the preamble signal is N, the processing load for correlation calculations and the required memory will increase by N times, but stable timing synchronization is possible even when multiple interference waves are scattered within the OFDM band. becomes.

Furthermore, in the above description, the preamble signal is evenly divided into bands to obtain a plurality of correlated signals, but the band may be divided in a biased manner. Furthermore, in the above explanation, a plurality of correlated signals are obtained by dividing the preamble signal into bands so that the frequency components do not overlap with each other, but the frequency components of each correlated signal may partially overlap. do not have.

Although the present invention has been described above based on one embodiment, it goes without saying that the present invention is not limited to the wireless communication system described herein, and can be widely applied to other wireless communication systems.
Further, the present invention can be provided, for example, as a method including technical procedures related to the above processing, a program for causing a computer to execute the above processing, and a storage medium that stores such a program in a computer-readable manner. is also possible.

This application claims priority benefit based on Japanese Patent Application No. 2020-010146 filed on January 24, 2020, and the entire disclosure thereof is incorporated herein by reference.

INDUSTRIAL APPLICATION This invention can be utilized for the wireless communication system which performs synchronization processing using a preamble signal.

101: Input terminal, 102-1, 102-2: Correlator, 130-1, 103-2: Memory, 104: Selection synthesizer: 105: Peak detector, 106: Output terminal, 111-1, 111-2 : input terminal, 112-1, 112-2: moving average calculator: 113: comparator, 114: selector, 115: output terminal, 116-1, 116-2: coefficient calculator, 117-2, 117- 2: Multiplier, 118: Adder

Claims (4)

In a timing detection method by a wireless communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side,
The wireless communication device stores in advance two correlated signals that are time domain signals of a negative frequency component and a positive frequency component of the preamble signal, and Perform a correlation calculation with each of the signals, calculate a moving average for each of the correlation calculation results for each correlated signal, compare the moving average values for each correlated signal, and calculate the correlation calculation results for each correlated signal. The present invention is characterized in that the correlation calculation result whose moving average value is found to be the minimum is selected from the above, and the timing at which the amplitude of the selected correlation calculation result reaches the maximum value is detected as the reception timing of the preamble signal . Timing detection method. In a timing detection method by a wireless communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side,
The wireless communication device stores in advance two correlated signals that are time domain signals of a negative frequency component and a positive frequency component of the preamble signal, and compares the two correlated signals with respect to the received signal. A moving average is calculated for each of the correlation calculation results for each correlated signal, and based on the moving average value for each correlated signal, the smaller the moving average value, the larger the moving average value. Calculate the weighting coefficient for each correlated signal, multiply the correlation calculation result for each correlated signal by the corresponding one of the weighting coefficients for each correlated signal, and make the multiplication results for each correlated signal in phase. A timing detection method characterized in that the preamble signal is synthesized without conversion and the timing at which the amplitude of the synthesis result reaches a maximum value is detected as the reception timing of the preamble signal. In a wireless communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side,
a memory storing two correlated signals that are time domain signals of a negative frequency component and a positive frequency component of the preamble signal;
a plurality of correlators that perform correlation calculations on the received signal with each of the two correlated signals;
a plurality of moving average calculators that calculate a moving average of each of the correlation calculation results for each correlated signal obtained by the plurality of correlators;
a comparator that compares moving average values for each correlated signal obtained by the plurality of moving average calculators;
a selector that selects, from among the correlation calculation results for each correlated signal, the correlation calculation result that is found to have the smallest moving average value through comparison in the comparator;
A wireless communication device comprising: a detector that detects the timing at which the amplitude of the correlation calculation result selected by the selector reaches a maximum value as the reception timing of the preamble signal. In a wireless communication device on a receiving side that performs synchronization processing using a preamble signal transmitted from a transmitting side,
a memory storing two correlated signals that are time domain signals of a negative frequency component and a positive frequency component of the preamble signal;
a plurality of correlators that perform correlation calculations on the received signal with each of the two correlated signals;
a plurality of moving average calculators that calculate a moving average of each of the correlation calculation results for each correlated signal obtained by the plurality of correlators;
A plurality of coefficient calculators that calculate weighting coefficients for each correlated signal such that the smaller the moving average value is, the larger the weighting coefficient is based on the moving average value for each correlated signal obtained by the plurality of moving average calculators. and,
A plurality of multiplications in which the correlation calculation results for each correlated signal obtained by the plurality of correlators are multiplied by corresponding weighting coefficients for each correlated signal obtained by the plurality of coefficient calculators. The vessel and
an adder that combines the multiplication results for each correlated signal obtained by the plurality of multipliers without converting them into in-phase;
A wireless communication device comprising: a detector that detects the timing at which the amplitude of the synthesis result by the adder reaches a maximum value as the reception timing of the preamble signal.

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