JP2015035664A - Signal analyzer, signal analysis program, and signal analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress processing load for radio wave analysis.SOLUTION: A signal analyzer 10 obtains a correlation value between a signal containing a plurality of symbols and a replication signal of the signal by delaying the replication signal for a predetermined time width. The signal analyzer 10 divides a signal using an effective symbol length obtained from an amount of delay with a maximum correlation value and a set of GI length within GI lengths set to a plurality of lengths. For all sets, the signal analyzer 10 obtains correlation values between a segment and the replication signal by delaying the replication signal for a predetermined time width, for each divided segment. The signal analyzer 10 estimates an effective symbol length and a GI length from a histogram, generated based on an amount of delay having a peak correlation value, and a peak of averaged correlation value among each segment. The signal analyzer 10 estimates the number of subcarriers for a signal from a bandwidth obtained from a spectrum of the signal and a symbol rate obtained from the effective symbol length and the GI length obtained by the estimation.

Description

  The present invention relates to a signal analysis device, a signal analysis program, and a signal analysis method.

  As an example of a digital signal modulation method, an orthogonal frequency division multiplexing method, so-called OFDM (Orthogonal Frequency Division Multiplexing), is known. Such OFDM has advantages such as high-speed transmission, high frequency utilization efficiency, and strength against multipath, and is therefore used in various fields such as mobile communication and broadcast radio waves.

  The OFDM signal analysis technique can be used in the illegal radio wave monitoring field for searching and analyzing illegal radio waves and the software radio field in which parameters such as the carrier frequency and the modulation method are changed according to the surrounding radio environment.

  An example of such an analysis technique is a modulation scheme identification device. This modulation system identification device performs autocorrelation processing on an unknown communication signal after performing sliding processing for sliding a duplicate signal copied from the communication signal for correlation processing. Thereafter, the modulation scheme identification device determines whether or not OFDM modulation is performed based on the presence or absence of a peak of the guard interval symbol.

JP 2008-118619 A JP 2005-260921 A JP 2004-216961 A

  However, in the above technique, since a sliding process is performed on a communication signal that is unknown whether it is an OFDM modulation signal, an appropriate sample data length cannot be specified, and a sliding process is performed using sample data of an unnecessary length. As a result, the processing load increases.

  In one aspect, an object of the present invention is to provide a signal analysis device, a signal analysis program, and a signal analysis method that can suppress the processing load of radio wave analysis.

  The signal analysis apparatus according to one aspect performs a first correlation process for obtaining a correlation value by delaying a duplicate signal of the signal over a predetermined time width between a signal including a plurality of symbols and the duplicate signal of the signal. A first correlation processing unit to be executed is included. Further, the signal analysis device includes an effective symbol length obtained from a delay amount that takes a maximum correlation value among the correlation values calculated by the first correlation processing, and a guard interval length set to a plurality of lengths. A dividing unit that divides the signal using a set of one guard interval length. Further, the signal analysis apparatus may generate a duplicate signal of the segment between the segment and the duplicate signal of the segment for each segment into which the signal is divided for all the combinations of the effective symbol length and the guard interval length. A second correlation processing unit that executes a second correlation process for obtaining a correlation value with a delay over a predetermined time width; Further, the signal analysis device may generate a histogram generated based on a delay amount that takes a peak value of the correlation value calculated by the second correlation process and a peak of the correlation value averaged between the segments. A first estimation unit configured to estimate an effective symbol length and a guard interval length of the signal; Further, the signal analysis apparatus estimates the number of subcarriers of the signal from the bandwidth obtained from the spectrum of the signal and the symbol rate obtained from the estimated effective symbol length and guard interval length. Part.

  The processing load of radio wave analysis can be suppressed.

FIG. 1 is a block diagram illustrating a functional configuration of the signal analyzing apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating a functional configuration of the first estimation unit. FIG. 3 is a diagram illustrating an example of the delay amount. FIG. 4 is a diagram illustrating an example of an effective symbol length estimation method. FIG. 5 is a diagram illustrating an example of the relationship between the delay amount and the correlation value for each segment. FIG. 6 is a diagram illustrating an example of a histogram. FIG. 7 is a diagram illustrating an example of a subcarrier number estimation method. FIG. 8 is a diagram illustrating an example of a method for estimating the number of subcarriers. FIG. 9 is a flowchart illustrating a procedure of signal analysis processing according to the first embodiment. FIG. 10 is a diagram illustrating a hardware configuration example of the signal analysis apparatus.

  A signal analysis apparatus, a signal analysis program, and a signal analysis method according to the present application will be described below with reference to the accompanying drawings. Note that this embodiment does not limit the disclosed technology. Each embodiment can be appropriately combined within a range in which processing contents are not contradictory.

[Configuration of signal analyzer]
FIG. 1 is a block diagram illustrating a functional configuration of the signal analyzing apparatus according to the first embodiment. A signal analyzing apparatus 10 shown in FIG. 1 analyzes a radio wave whose various transmission parameters, for example, a symbol rate, a guard interval (GI) length, the number of subcarriers, and the like are unknown. As part of the radio wave analysis, the signal analysis apparatus 10 estimates transmission parameters related to a received signal determined to be an OFDM (Orthogonal Frequency Division Multiplexing) signal.

  As illustrated in FIG. 1, the signal analysis device 10 includes a reception unit 11, a storage unit 12, an analysis unit 13, a band limiting unit 14, a first estimation unit 15, and a second estimation unit 16. Note that the signal analysis device 10 may include various functional units included in known mobile terminal devices in addition to the functional units illustrated in FIG. 1.

  The receiving unit 11 is a processing unit that receives a signal via an antenna (not shown). As an aspect, the reception unit 11 amplifies a signal received via an antenna, and down-converts the amplified signal according to a clock generated by a predetermined oscillator. After that, the receiving unit 11 converts an analog signal into a digital signal by performing A / D (Analog-to-Digital) conversion on the down-converted signal. Thereafter, the receiving unit 11 stores the received signal subjected to amplification, down-conversion, and A / D conversion in the storage unit 12. At this time, the receiving unit 11 stores the received signal having a signal length that includes at least a plurality of effective symbols in the storage unit 12 so that the symbol rate can be estimated by the first estimating unit 15 described later. .

  The storage unit 12 is a storage device that stores various data. As an example, the storage unit 12 stores a reception signal received by the reception unit 11. As an aspect of the storage unit 12, a digital radio frequency memory (DRFM) can be employed. Note that the implementation example of the storage unit 12 is not limited to the DRFM, and a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), or the like may be employed.

  The analysis unit 13 is a processing unit that executes spectrum analysis of the received signal. As an aspect, the analysis unit 13 determines whether or not the received signal is an OFDM-modulated OFDM signal from the spectrum shape of the received signal stored in the storage unit 12 and the degree of dispersion of the spectrum phase. As a result, when it is determined that the received signal is an OFDM signal, the symbol length is estimated from the spectrum shape, and the estimated symbol length includes a plurality of symbols to be subjected to GI correlation processing as described below. A measure of the sampling length of the OFDM signal. The subsequent first estimation unit 15 and second estimation unit 16 perform processing for estimating the transmission parameter of the received signal.

  The band limiting unit 14 is a processing unit that limits the bandwidth of the received signal. As one aspect, the band limiting unit 14 reads out a reception signal that is determined to be an OFDM signal by the analysis unit 13 among the reception signals stored in the storage unit 12. In addition, the band limiting unit 14 performs fast Fourier transform, so-called FFT (Fast Fourier Transform), on the OFDM signal read from the storage unit 12. As a result, the bandwidth of the OFDM signal is limited. In the example of FIG. 1, the case where the band limitation is performed by adopting the band limitation unit 14 in the signal analysis device 10 is illustrated, but the band limitation is not necessarily performed.

  The first estimation unit 15 is a processing unit that estimates the effective symbol length of the OFDM signal. As one aspect, the first estimation unit 15 performs a GI correlation process on the OFDM signal including a plurality of symbols having a sampling length with the symbol length estimated by the analysis unit 13 as a guide, thereby performing OFDM correlation processing. After the effective symbol length is estimated, the OFDM signal is divided for each approximate effective symbol length. Then, the first estimation unit 15 performs a GI correlation process for each segment into which the OFDM signal is divided, and calculates a delay amount at which the GI correlation value reaches a peak for each segment. Then, the first estimation unit 15 estimates the effective symbol length from the delay amount histogram of each segment.

  FIG. 2 is a block diagram showing a functional configuration of the first estimation unit 15. As shown in FIG. 2, the first estimation unit 15 includes a distribution unit 150, GI setting units 151A to 151C, correlation processing units 152A-1 to 152A-x, and correlation processing units 152B-1 to 152B-x. And correlation processing units 152C-1 to 152C-x. Further, the first estimation unit 15 includes division units 153A to 153C, peak calculation units 154A to 154C, delay amount calculation units 155A to 155C, statistical processing units 156A to 156C, symbol length calculation units 157A to 157C, Determination units 158A to 158C and a symbol rate calculation unit 159 are included.

  Here, FIG. 2 illustrates a functional configuration of the first estimation unit 15 in the case where the effective symbol length is estimated in parallel assuming that the GI length is “A”, “B”, and “C”. ing. Of these three processing systems, a code including “A” is assigned to the functional part of the processing system A that executes the estimation of the effective symbol length assuming that the GI length is “A”. Similarly, the code | symbol containing "B" is provided to the functional part of the processing system B which performs estimation of an effective symbol length on the assumption that GI length is "B". Similarly, the code | symbol containing "C" is provided to the function part of the processing system C which performs estimation of an effective symbol length on the assumption that GI length is "C". In addition, although the case where three types of GI lengths are assumed is illustrated here, the number of GI lengths used for estimating the transmission parameter of the OFDM signal may be one or more.

  Distribution unit 150 is a processing unit that distributes OFDM signals. As an aspect, the distribution unit 150 uses the OFDM signal output by the band limiting unit 14 as the correlation processing unit 152A-x and the correlation processing unit 152B-x in order to execute parallel processing in the three processing systems. And distributed to the correlation processing unit 152C-x. Needless to say, the same OFDM signal is output to each correlation processing unit.

  The GI setting units 151A to 151C are all processing units that set the GI length. Of these, the GI setting unit 151A sets “A” as the GI length in the correlation processing units 152A-1 to 152A-x. In addition, the GI setting unit 151B sets “B” as the GI length in the correlation processing units 152B-1 to 152B-x. The GI setting unit 151C sets “C” as the GI length in the correlation processing units 152C-1 to 152A-x. For these GI lengths “A”, “B”, and “C”, it is possible to prepare a plurality of types of GI lengths that can be assumed to be used by an object that emits electromagnetic waves, such as an aircraft or a wiretap. it can.

  The correlation processing units 152A-1 to 152A-x, the correlation processing units 152B-1 to 152B-x, and the correlation processing units 152C-1 to 152C-x are processing units that perform GI correlation processing on OFDM signals. Hereinafter, the correlation processing units 152A-1 to 152A-x, the correlation processing units 152B-1 to 152B-x, and the correlation processing units 152C-1 to 152C-x are collectively referred to as “correlation processing unit 152”. There is a case.

  Here, the correlation processing unit 152 performs correlation processing of different GIs in the stage (1) of estimating the effective symbol length and the stage (2) of estimating the effective symbol length using the estimated effective symbol length. Execute.

  Of these, in the step (1), the OFDM signals distributed by the distribution unit 150 are collectively subjected to GI correlation processing. As described above, when the OFDM signal is subjected to GI correlation processing collectively, the target to be autocorrelated in any one of the correlation processing units 152 in each processing system is OFDM including a plurality of symbols. The entire signal is subjected to GI correlation processing. In the following description, the GI correlation process executed in step (1) is referred to as “first GI correlation process”, and the GI correlation process executed in stage (2) is referred to as “first GI correlation process”. 2 GI correlation processing ”.

  For example, the first GI correlation process will be described using the processing system A as an example. In the case of the processing system A, the first GI correlation process is executed by any one of the correlation processing units 152A-1 to 152A-x included in the processing system A. Here, the first GI correlation process will be described using the correlation processing unit 152A as an example, but the same processing is also executed in the correlation processing units 152B and 152C.

  Specifically, the correlation processing unit 152A calculates a correlation coefficient between the OFDM signal and the duplicate signal while delaying the entire duplicate signal of the OFDM signal in the time axis direction with respect to the OFDM signal including a plurality of symbols. Perform autocorrelation to calculate. At this time, the correlation processing unit 152A delays the duplicate signal with the resolution of the sampling clock period of the signal analyzing apparatus 10. The delay amount having the maximum correlation value among the correlation values of the OFDM signal and the replica signal repeatedly calculated for each delay amount while delaying the replica signal in this way is used as the approximate effective symbol length.

  FIG. 3 is a diagram illustrating an example of the delay amount, and FIG. 4 is a diagram illustrating an example of an effective symbol length estimation method. In the example of FIG. 3, for convenience of explanation, symbols and guard intervals included in an OFDM signal that is actually unknown are clearly shown. Also, the vertical axis of the graph shown in FIG. 4 indicates the correlation value, and the horizontal axis indicates the delay amount.

  In the OFDM signal, a signal in which a part of the data symbol, for example, tail data is duplicated, is added as a guard interval to the head of the data symbol. In the example of FIG. 3, a part of the data symbol that is painted out matches the GI signal added to the head of the data symbol. For this reason, as shown in FIG. 3, when the delay amount of the duplicate signal with respect to the OFDM signal becomes “τ”, the effective symbol tail of the OFDM signal and the GI of the duplicate signal match in each OFDM symbol, As shown in FIG. 4, the correlation value has a peak. The delay amount τ is highly likely to be equivalent to the delay amount when the duplicate signal is delayed by one effective symbol. Therefore, the delay amount τ with the highest correlation value can be estimated as the effective symbol length.

  The division units 153A to 153C are all processing units that divide the OFDM signal. Here, the processing executed by the dividing unit 153A on behalf of the dividing units 153A to 153C will be described, but the other processing contents having different GI lengths used for division are the same. As an aspect, the dividing unit 153A divides the OFDM signal distributed by the distributing unit 150 using the effective symbol length estimated by the correlation processing unit 152A and the GI length set by the GI setting unit 151A. For example, the dividing unit 153A demultiplexes the OFDM signal in the time axis direction for each signal length obtained by adding the estimated effective symbol length “τ” and the GI length “A”, that is, the length corresponding to the OFDM symbol length. Divide the signal into segments.

  Here, the second GI correlation process is executed for each segment by the correlation processing units 152A-1 to 152A-x. Among these, the correlation processing unit 152A-1 performs the following GI autocorrelation on the first received segment 1 among the segments 1 to x divided from the OFDM signal. That is, the correlation processing unit 152A-1 calculates the correlation coefficient between the segment 1 signal and the duplicate signal while delaying the duplicate signal of the segment 1 in the time axis direction for the segment 1 to be processed. Perform autocorrelation. Further, the correlation processing unit 152A-2 performs autocorrelation on the segment 2 received subsequent to the segment 1 in the same manner as the correlation processing unit 152A-1. Further, the correlation processing unit 152A- (x-1) performs autocorrelation similar to that of the correlation processing unit 152A-1 on the segment (x-1) received subsequent to the segment (x-2). Do. Similarly, the correlation processing unit 152A-x performs autocorrelation similar to the correlation processing unit 152A-1 on the segment x received subsequent to the segment (x-1). In this way, a correlation value for each delay amount in each segment 1 to x is calculated. Here, the case where the correlation processing units 152A-1 to 152A-x execute the second GI correlation processing has been described, but the correlation processing units 152B-1 to 152B-x and the correlation processing units 152C-1 to 152C are described. Similar autocorrelation is performed at -x.

  In this way, a correlation value is calculated for each segment 1 to x. Here, the case where the correlation processing units 152A-1 to 152A-x execute the second GI correlation processing is illustrated, but the correlation processing units 152B-1 to 152B-x and the correlation processing units 152C-1 to 152C are illustrated. Similar autocorrelation is performed at -x.

  The peak calculation units 154A to 154C are all processing units that calculate correlation value peaks. Here, the processing executed by the peak calculation unit 154A on behalf of the peak calculation units 154A to 154C will be described, but the same processing is executed for the other peak calculation units 154B and 154C. As an aspect, the peak calculation unit 154A calculates a correlation value that is a peak among the correlation values in the segment 1 calculated by the correlation processing unit 152A-1. The peak calculation unit 154A calculates a correlation value that is a peak among the correlation values in the segment 2 calculated by the correlation processing unit 152A-2. In this way, the peak calculation unit 154A calculates the peak of the correlation value for each of the segments 1 to x.

  FIG. 5 is a diagram illustrating an example of the relationship between the delay amount and the correlation value for each segment. FIG. 5 illustrates a graph of the delay amount and the correlation value in the segment 1 divided first time, and a graph of the delay amount and the correlation value in the segment 2 divided the second time from the front toward the depth direction. ing. The vertical axis of the graph shown in FIG. 5 indicates the correlation value, and the horizontal axis indicates the delay amount. As shown in FIG. 5, the peak of the correlation value of segment 1 divided at the first time is calculated, and the peak of the correlation value of segment 2 divided at the second time is calculated. In this way, the peak of the correlation value is calculated for each segment 1 to x. In the example of FIG. 5, it can be seen that the correlation value peaks are concentrated in N to N + 1 between the segments.

  Each of the delay amount calculation units 155A to 155C is a processing unit that calculates a delay amount corresponding to a correlation value peak for each segment. Here, the processing executed by the delay amount calculation unit 155A on behalf of the delay amount calculation units 155A to 155C will be described, but the same processing is also executed for the other delay amount calculation units 155B and 155C. As an aspect, the delay amount calculation unit 155A calculates the delay amount that takes the peak of the correlation value of the segment 1 calculated by the peak calculation unit 154A. Also, the delay amount calculation unit 155A calculates the delay amount that takes the peak of the correlation value of the segment 2 calculated by the peak calculation unit 154A. In this way, the delay amount calculation unit 155A calculates the delay amount that takes the peak correlation value for each of the segments 1 to x.

  Each of the statistical processing units 156A to 156C is a processing unit that statistically processes a delay amount that takes a peak correlation value. Here, the processing executed by the statistical processing unit 156A on behalf of the statistical processing units 156A to 156C will be described, but the same processing is executed for the other statistical processing units 156B and 156C. As one aspect, the statistical processing unit 156A histograms the delay amount that takes the peak of the correlation value calculated for each of the segments 1 to x by the delay amount calculation unit 155A. FIG. 6 is a diagram illustrating an example of a histogram. FIG. 6 shows a histogram generated from the delay amount that takes the peak of the correlation value shown in FIG. The vertical axis of the graph shown in FIG. 6 indicates the frequency, and the horizontal axis indicates the delay amount. As shown in FIG. 6, when the segments 1 to x are combined, it can be seen that the peak of the correlation value has the delay amount N as a peak and is concentrated in the vicinity thereof.

Each of the symbol length calculation units 157A to 157C is a processing unit that calculates a symbol length from a delay amount histogram. Here, the processing executed by the symbol length calculation unit 157A on behalf of the symbol length calculation units 157A to 157C will be described, but the same processing is executed for the other symbol length calculation units 157B and 157C. As an aspect, the symbol length calculation unit 157A calculates the expected value of the delay amount by using the frequency for each delay amount as a histogram by the statistical processing unit 156A as a sample. The delay amount at which the expected value calculated in this way takes the maximum value is estimated as the effective symbol length. For example, in the case of the delay amount histogram shown in FIG. 6, as shown in FIG. 6, “N _E ” is calculated as the expected value. In this case, the expected value “N _E ” of the delay amount is estimated as the effective symbol length.

  The determination units 158A to 158C are all processing units that determine the presence or absence of correlation. Here, the processing executed by the determination unit 158A on behalf of the determination units 158A to 158C will be described, but the same processing is executed for the other determination units 158B and 158C. As one aspect, the determination unit 158A averages the correlation value peaks calculated for each segment by the correlation processing units 152A-1 to 152A-x among the segments. Then, the determination unit 158A determines whether or not the correlation value peak averaged between the segments is equal to or greater than a predetermined threshold value. At this time, when the peak of the correlation value averaged between the respective segments is equal to or greater than a predetermined threshold, it is likely that the segment divided using the GI length set by the GI setting unit 151A is appropriate. Can be estimated to be high. In this case, determination section 158A causes effective symbol length calculated by symbol length calculation section 157A to be output to subsequent symbol rate calculation section 159. On the other hand, when the peak of the correlation value averaged between the segments is less than the predetermined threshold, it can be estimated that there is a high probability that the division by the GI length set by the GI setting unit 151A is inappropriate. In this case, the determination unit 158A does not cause the subsequent symbol rate calculation unit 159 to output the effective symbol length calculated by the symbol length calculation unit 157A.

  The symbol rate calculation unit 159 is a processing unit that calculates the symbol rate of the OFDM signal using the effective symbol length calculated by the symbol length calculation units 157A to 157C. Here, as an example, a case where the symbol rate is calculated from the effective symbol length calculated by the symbol length calculation unit 157A is illustrated. In this case, the symbol rate calculation unit 159 divides the unit time by the OFDM symbol length including the effective symbol length calculated by the symbol length calculation unit 157A and the GI length set by the GI setting unit 151A. The symbol rate of the OFDM signal is calculated.

  Returning to the description of FIG. 1, the second estimation unit 16 is a processing unit that estimates the number of subcarriers of the OFDM signal using the symbol rate of the OFDM signal estimated by the first estimation unit 15. As an aspect, the second estimation unit 16 estimates the number of subcarriers that differs depending on whether or not the OFDM unit has been subjected to band limitation by the preceding functional unit, that is, the band limitation unit 14. In the following, after explaining the estimation 1 of the number of subcarriers when the OFDM signal is not band-limited, it can be applied both when the OFDM signal is not band-limited and when the OFDM signal is band-limited. The subcarrier number estimation 2 will be described.

(1) Estimating the number of subcarriers 1
When the OFDM signal is not band-limited, attention is paid to the fact that the first side lobe appears at both ends of the OFDM spectrum, and the number of subcarriers of the OFDM signal is estimated.

  FIG. 7 is a diagram illustrating an example of a subcarrier number estimation method. FIG. 7 shows the waveform of the OFDM spectrum when the OFDM signal is not band-limited. The vertical axis of the graph shown in FIG. 7 indicates power, and the horizontal axis indicates frequency. As shown in FIG. 7, the second estimation unit 16 detects the peak point of the waveform of the OFDM spectrum in which the OFDM signal is converted into the frequency domain. Subsequently, the second estimation unit 16 performs the following process for each peak point of the waveform of the OFDM spectrum detected previously. That is, the second estimation unit 16 identifies points on the waveform of the OFDM spectrum that are separated from each other by a multiplication value obtained by multiplying the symbol rate estimated by the first estimation unit 15 by a predetermined coefficient α in the frequency axis direction from the peak point. To do. As an example of the coefficient α, 1.5 KHz can be adopted. Then, the second estimation unit 16 determines whether or not a point on the waveform of the previously specified OFDM spectrum is equivalent to an addition value obtained by adding a predetermined intensity β to the intensity of the peak point. . As an example of the intensity β, 1.4 dB can be employed. Here, “equivalent” means that a certain deviation, for example ± γ, can be allowed from the added value.

  At this time, if the point on the waveform of the OFDM spectrum is equal to the added value, it can be estimated that the peak point is the first side lobe. The estimation of the first side lobe is repeated for each peak point until two first side lobes are estimated in this way. After that, when two first side lobes are estimated, the second estimation unit 16 divides the bandwidth determined by the interval between the peak points of the first side lobe by the symbol rate estimated by the first estimation unit 15. Thus, the number of subcarriers is estimated.

  In this way, the second estimation unit 16 estimates the number of subcarriers by dividing the bandwidth determined by the interval between the peak points of the first side lobe by the symbol rate. As a result, the number of subcarriers can be estimated even when the reception level varies due to fading. That is, when an ideal OFDM signal is received, the spectrum shape is flat, so by measuring the bandwidth of 3 dB down from the intensity of the flat portion included in the waveform and dividing by the symbol rate Although the number of subcarriers can be estimated, when an actual spatially radiated radio wave is received, the reception level may vary due to fading. However, when the number of subcarriers is estimated using the first side lobe, it is possible to suppress a decrease in the estimation accuracy of the number of subcarriers even when the reception level fluctuates. Note that when estimation is performed in a wireless environment in which the variation in reception level is small, the number of subcarriers may be estimated by measuring a bandwidth of 3 dB down.

(2) Estimating the number of subcarriers 2
When the OFDM signal is band-limited, the number of subcarriers can be estimated from the bandwidth between the noise floor boundary points by executing high-resolution spectrum analysis. The “boundary point” here refers to a point on the waveform of the OFDM spectrum that is a predetermined value N (dB) higher than the noise floor level.

  FIG. 8 is a diagram illustrating an example of a method for estimating the number of subcarriers. FIG. 8 shows the waveform of the OFDM spectrum when band limiting is applied to the OFDM signal. The vertical axis of the graph shown in FIG. 8 indicates power, and the horizontal axis indicates frequency. As shown in FIG. 8, when the OFDM signal is band-limited, side lobes do not occur unlike the OFDM spectrum shown in FIG. For this reason, the boundary point of the noise floor is used for estimating the number of subcarriers instead of the side lobe. That is, the second estimation unit 16 calculates a noise floor level by calculating an average value of noise intensities other than the main components of the OFDM spectrum. Then, the second estimation unit 16 specifies a point NdB higher than the noise floor level among the points on the waveform of the OFDM spectrum as a boundary point. Then, the second estimation unit 16 estimates the number of subcarriers by dividing the bandwidth between the noise floor boundary points by the symbol rate estimated by the first estimation unit 15.

  In this way, the second estimation unit 16 estimates the number of subcarriers from the bandwidth between the noise floor boundary points. Thereby, similarly to the above estimation 1 of the number of subcarriers, the number of subcarriers can be estimated even when the reception level varies due to fading. In addition, in the case of estimation of the number of subcarriers 2, the number of subcarriers in the OFDM signal can be estimated both when the OFDM signal is band-limited and when the OFDM signal is not band-limited. .

  In addition, each said function part, ie, the 1st estimation part 15 and the 2nd estimation part 16, is realizable with hard wired logics, such as FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit), as an example. Each functional unit described above can also be realized by causing a MPU (Micro Processing Unit) such as a DSP (Digital Signal Processor) or a CPU (Central Processing Unit) to execute a signal analysis program.

[Process flow]
FIG. 9 is a flowchart illustrating a procedure of signal analysis processing according to the first embodiment. In this signal analysis process, for example, when the analysis unit 13 determines that the received signal is an OFDM signal, the OFDM signal is read from the storage unit 12 or the band is limited by the band limitation unit 14. The processing is started when the OFDM signal is input to the first estimation unit 15.

  As illustrated in FIG. 9, the correlation processing unit 152 of each processing system delays the entire duplicate signal of the OFDM signal in the time axis direction with respect to the OFDM signal including a plurality of symbols, A first GI correlation process for calculating an autocorrelation coefficient is executed (step S101).

  The delay amount having the maximum correlation value among the correlation values of the OFDM signal and the replica signal repeatedly calculated for each delay amount while delaying the replica signal in this way is used as the approximate effective symbol length.

  Thereafter, the dividing unit 153 of each processing system divides the OFDM signal distributed by the distributing unit 150 using the effective symbol length estimated in step S101 and the GI length set by the GI setting unit 151A (step S102). ).

  Subsequently, the correlation processing units 152-1 to 152-x of each processing system time-replicate the duplicate signal of the segment for the segment to be processed among the segments 1 to x divided from the OFDM signal in step S102. While delaying in the axial direction, a second GI correlation process for calculating the autocorrelation coefficient of the segment signal and the duplicate signal is executed (step S103).

  And the peak calculation part 154 of each processing system calculates the correlation value used as the peak among the correlation values calculated by step S103 for every segment 1-x (step S104). Furthermore, the delay amount calculation unit 155 of each processing system calculates a delay amount that takes the peak of the correlation value calculated in step S104 for each of the segments 1 to x (step S105).

  Subsequently, the statistical processing unit 156 of each processing system generates a histogram of the delay amount that takes the peak of the correlation value calculated for each of the segments 1 to x in step S105 (step S106). After that, the symbol length calculation unit 157 of each processing system estimates the delay amount corresponding to the highest expected value among the expected values calculated from the delay amount histogram generated in step S106 as the effective symbol length (step S107). ).

  Then, the symbol rate calculation unit 159 calculates the symbol rate of the OFDM signal from the effective symbol length calculated in step S107 and the GI length set by the GI setting unit 151A (step S108).

  Thereafter, the second estimation unit 16 estimates the number of subcarriers of the OFDM signal using the symbol rate of the OFDM signal estimated in step S108 and the bandwidth obtained from the spectrum of the OFDM signal (step S109). The process ends.

[Process flow]
As described above, the signal analyzing apparatus 10 according to the present embodiment approximates the effective symbol length by collectively performing GI correlation processing on OFDM signals including a plurality of symbols. Thereafter, the signal analysis apparatus 10 according to the present embodiment estimates the effective symbol length from the histogram of the delay amount obtained by performing the GI correlation processing for each segment obtained by dividing the OFDM signal using the approximate effective symbol length. In addition, the signal analyzing apparatus 10 according to the present embodiment estimates the number of subcarriers of the OFDM signal from the bandwidth obtained from the spectrum of the OFDM signal and the estimated effective symbol length.

  Therefore, according to the signal analysis apparatus 10 according to the present embodiment, the processing load of radio wave analysis can be suppressed. In addition, it is possible to accurately identify the object to be analyzed even in environments where the surrounding radio wave environment is unknown, and to detect and analyze radio waves that violate the Radio Law, the carrier frequency and It can be effectively used in the field of software defined radio that changes parameters such as modulation method.

  Although the embodiments related to the disclosed apparatus have been described above, the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, another embodiment included in the present invention will be described below.

[Distribution and integration]
In addition, each component of each illustrated apparatus does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. For example, the analysis unit 13, the band limiting unit 14, the first estimation unit 15, and the second estimation unit 16 may be connected as an external device of the signal analysis device 10 via a network. In addition, the analysis unit 13, the band limiting unit 14, the first estimation unit 15 and the second estimation unit 16 are provided in different devices, and are connected to the network to cooperate with each other, thereby functioning the signal analysis device 10 described above. It may be realized.

[Signal analysis program]
The various processes described in the above embodiments can also be realized by causing a processor to execute a program prepared in advance. Therefore, in the following, a hardware configuration example of the signal analysis apparatus according to the first embodiment will be described with reference to FIG.

  FIG. 10 is a diagram illustrating a hardware configuration example of the signal analysis apparatus 10. As shown in FIG. 10, an RF (Radio Frequency) circuit 101, a DRFM 102, a processor 103, and a memory 104 are included.

  As an example of the processor 103, a CPU or the like can be employed in addition to an MPU including a DSP. Further, as an example of the memory 104, a RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, or the like can be adopted.

  Under such a hardware configuration, as an example, a program corresponding to each process executed by the analysis unit 13, the band limiting unit 14, the first estimation unit 15, and the second estimation unit 16 is recorded in the memory 104. Each program is executed by the processor 103. The receiving unit 11 is realized by the RF circuit 101, and the storage unit 12 is realized by the DRFM 102.

  Moreover, you may implement | achieve a part of function part performed with the signal analysis apparatus 10 which concerns on Example 1 by making it execute with the other processor which the apparatus which mounts the signal analysis apparatus 10 has. For example, among the functional units included in the signal analysis apparatus 10 according to the first embodiment, the program corresponding to each process executed by the analysis unit 13 and the band limiting unit 14 is executed by another processor, and the first A program corresponding to each process executed by the estimation unit 15 and the second estimation unit 16 may be executed by the processor 103.

DESCRIPTION OF SYMBOLS 10 Signal analysis apparatus 11 Receiving part 12 Storage part 13 Analysis part 14 Band-limiting part 15 1st estimation part 150 Distribution part 151A-151C GI setting part 152A-1 to 152A-x, 152B-1 to 152B-x, 152C-1 -152C-x Correlation processing unit 153A-153C Dividing unit 154A-154C Peak calculation unit 155A-155C Delay amount calculation unit 156A-156C Statistical processing unit 157A-157C Symbol length calculation unit 158A-158C Determination unit 159 Symbol rate calculation unit 16th 2 Estimator

Claims (5)

A first correlation processing unit that executes a first correlation process for obtaining a correlation value between a signal including a plurality of symbols and a duplicated signal of the signal by delaying the duplicated signal of the signal over a predetermined time width; ,
A set of an effective symbol length obtained from a delay amount taking the maximum correlation value among the correlation values calculated by the first correlation process and one guard interval length among the guard interval lengths set to a plurality of lengths A dividing unit for dividing the signal using
For every set of effective symbol length and guard interval length, for each segment into which the signal is divided, the segment replica signal is delayed between the segment and the segment replica signal over a predetermined time width. A second correlation processing unit that executes a second correlation process for obtaining a correlation value of each other;
The effective symbol length and guard interval of the signal from the histogram generated based on the delay amount taking the peak value of the correlation value calculated by the second correlation process and the peak of the correlation value averaged between the segments A first estimation unit for estimating a length;
A second estimation unit that estimates the number of subcarriers of the signal from the bandwidth obtained from the spectrum of the signal and the symbol rate obtained from the estimated effective symbol length and guard interval length. Signal analysis device. The second estimation unit includes
The signal analysis apparatus according to claim 1, wherein the number of subcarriers of the signal is estimated from a bandwidth between peaks of two first side lobes obtained from the spectrum of the signal and the symbol rate. A band limiting unit that limits the band of the signal;
The second estimation unit includes
When band limiting is performed by the band limiting unit, a subcarrier of the signal is calculated from a bandwidth between boundary points having a signal strength that becomes a boundary of a noise floor on the waveform of the spectrum of the signal, and the symbol rate. The signal analyzing apparatus according to claim 1, wherein the number is estimated. On the computer,
Performing a first correlation process for delaying a duplicate signal of the signal between a signal including a plurality of symbols and the duplicate signal of the signal over a predetermined time width to obtain a correlation value of each other;
A set of an effective symbol length obtained from a delay amount taking the maximum correlation value among the correlation values calculated by the first correlation process and one guard interval length among the guard interval lengths set to a plurality of lengths To divide the signal using
For every set of effective symbol length and guard interval length, for each segment into which the signal is divided, the segment replica signal is delayed between the segment and the segment replica signal over a predetermined time width. Execute a second correlation process to obtain a correlation value between each other;
The effective symbol length and guard interval of the signal from the histogram generated based on the delay amount taking the peak value of the correlation value calculated by the second correlation process and the peak of the correlation value averaged between the segments Estimate the length,
Signal analysis characterized by executing a process of estimating the number of subcarriers of the signal from the bandwidth obtained from the spectrum of the signal and the symbol rate obtained from the estimated effective symbol length and guard interval length program. Computer
Performing a first correlation process for delaying a duplicate signal of the signal between a signal including a plurality of symbols and the duplicate signal of the signal over a predetermined time width to obtain a correlation value of each other;
A set of an effective symbol length obtained from a delay amount taking the maximum correlation value among the correlation values calculated by the first correlation process and one guard interval length among the guard interval lengths set to a plurality of lengths To divide the signal using
For every set of effective symbol length and guard interval length, for each segment into which the signal is divided, the segment replica signal is delayed between the segment and the segment replica signal over a predetermined time width. Execute a second correlation process to obtain a correlation value between each other;
The effective symbol length and guard interval of the signal from the histogram generated based on the delay amount taking the peak value of the correlation value calculated by the second correlation process and the peak of the correlation value averaged between the segments Estimate the length,
A signal analysis characterized by executing processing for estimating the number of subcarriers of the signal from the bandwidth obtained from the spectrum of the signal and the symbol rate obtained from the estimated effective symbol length and guard interval length Method.

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