DSSS parallel code phase capture judgment method based on noise threshold

Abstract

The invention provides a DSSS parallel code phase capture judgment method based on a noise threshold value, and the method comprises the steps: firstly carrying out the parallel code phase capture of a received signal, and obtaining a received signal code phase correlation value result # imgabs1 # of a # imgabs0 # point; points with the amplitude ranked in the front # imgabs3 # in the correlation value result # imgabs2 # are removed, and a total correlation value set # imgabs4 # about noise is obtained; calculating a noise correlation value mean value # imgabs6 # of a total correlation value set # imgabs5 # of the noise; extracting correlation values higher than the mean value # imgabs8 # in the total correlation value set # imgabs7 #, and counting the number # imgabs9 # of points of the total correlation value set # imgabs7 # to obtain a correlation value set # imgabs10 # of the high-noise region; counting the mean value of the correlation value set # imgabs11 # of the high-noise region to obtain a high-noise average correlation value # imgabs12 #; determining a capture threshold # imgabs13 # by using an average correlation value of high noise; when the highest peak value # imgabs14 # of the parallel code phase correlation value result is stably higher than a capture threshold # imgabs15 #, it is marked that capture succeeds. According to the invention, effective judgment of inconsistent interference signals between correct signals and noise and spreading codes can be completed, so that the capture effectiveness and reliability of a DSSS receiver are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct sequence spread spectrum communication, and specifically to a parallel code phase capture judgment method for a direct sequence spread spectrum (DSSS) communication receiver, and particularly to a direct sequence spread spectrum parallel code phase capture judgment method based on a noise threshold. Background Art

[0002] A direct sequence spread spectrum communication system expands the spectrum through spread spectrum modulation, and can effectively improve the anti-interference ability of the communication system, so it has been widely used.

[0003] In a direct sequence spread spectrum communication system, the transmitting end device spreads the digital signal through a spreading code, and then modulates the signal to the required frequency band through carrier modulation; the receiving end device receives and demodulates the signal through a receiving circuit and capture and tracking technologies. In the capture part, a parallel code phase capture method is usually adopted and the capture judgment is carried out by means of the correlation value of the received signal to determine whether the required signal exists currently and complete the capture process. An incorrect judgment will cause time loss to the receiver and seriously affect signal reception. In actual DSSS communication, the receiver will copy multiple received channels with different spreading codes. Each transmitting device uses a spreading code for signal modulation and transmission, and corresponds to a received channel of the receiver. When the transmitting device does not match the current channel, the spreading code of the transmitting end is inconsistent with the spreading code copied by the received channel. Since the spreading codes are not completely orthogonal to each other, there will be a relatively small correlation peak in the correlation result of the capture calculation. At this time, if the capture threshold is set too low, false capture is likely to occur, which will cause the receiver to wrongly switch from capture to tracking, and the tracking process and stage adjustment are relatively slow. If the correct signal of this channel arrives during the tracking process, it will not be received by the receiver, resulting in data loss. However, an overly large capture threshold will cause misjudgment of the capture of the correct signal and missed capture when the signal-to-noise ratio is small. The existing capture judgment methods mainly consider the situation when the signal is noise or a correct signal for judgment. When false capture occurs in the received channel, the communication of this time is abandoned and retransmitted at the next moment, but the judgment requirement for interference signals with inconsistent spreading codes cannot be met, affecting the success rate and timeliness of communication. Therefore, a new capture judgment method that can effectively cope with interference signals with different spreading codes is urgently needed. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art and achieve an accurate judgment of correct signals and interference signals with different spreading codes, the present invention provides a DSSS parallel code phase capture and judgment method based on a noise threshold. Through this method, an effective judgment of correct signals, noise, and interference signals with inconsistent spreading codes can be completed, thereby improving the effectiveness and reliability of DSSS receiver capture.

[0005] The steps of the technical solution adopted by the present invention to solve its technical problems are as follows:

[0006] Step 1: In DSSS communication, both the receiver and the transmitting device agree to use a spreading code of a certain length for spreading modulation; during reception, parallel code phase capture is performed on the received signal to obtain the received signal code phase correlation value results at points.

[0007] Step 2: Remove the points with the top magnitude rankings in the correlation value results to obtain the overall correlation value set regarding noise, where is the th overall correlation value in the set , and

[0008] is the number of points occupied by the peak value of the main peak in the received signal code phase correlation value; Step 3: Calculate the mean value

[0009]

[0010] of the noise correlation values in the overall correlation value set regarding noise: Step 4: Extract the correlation values in the overall correlation value set that are higher than the mean value and count the number of their points to form the correlation value set of the high-noise region, where is the th correlation value in the set

[0011] Step 5: Statistically calculate the mean value of the correlation value set

[0012]

[0013] :

[0014]

[0015] Among them is the false alarm rate, which represents the probability that when the receiver receives a correct DSSS signal but fails to capture the signal. The false alarm rate needs to be set before making the capture judgment the magnitude of the value;

[0016] Step 7: Perform parallel code phase capture on the received signal. If the peak value in the obtained parallel code phase correlation value result is stably higher than the capture threshold , it indicates that the capture is successful.

[0017] Furthermore, in step 1, according to different correlator spacings, generally required .

[0018] Furthermore, in step 2 , among which represents rounding up.

[0019] Furthermore, in step 7, perform parallel code phase capture on the received signal and adopt the Tong search method. Repeat the search multiple times within the set time and observe the peak value in the obtained parallel code phase correlation value result whether it is stably higher than the capture threshold , if so, it indicates that the capture is successful.

[0020] In addition, the present invention also proposes an electronic device and a readable storage medium:

[0021] An electronic device includes a processor and a memory. The memory is used to store one or more programs; when the one or more programs are executed by the processor, the above method is implemented.

[0022] A readable storage medium stores a computer program, and when the computer program is executed by a processor, the above method is implemented.

[0023] Beneficial effects:

[0024] The beneficial effects of the present invention are as follows: The magnitude of the high-noise correlation value, which has a greater impact on the judgment in the capture threshold calculation, is introduced into the capture calculation. Combining the noise distribution and the false alarm rate, the capture threshold calculation and judgment are completed. By removing the influence of the low-noise region in the noise on the threshold calculation, the calculated capture threshold is higher than the main peak correlation value of the interference signal (i.e., the signal with inconsistent spreading codes) with little difference from the noise peak, thereby effectively coping with the signal interference when the spreading codes are inconsistent, greatly improving the effectiveness and stability of the DSSS receiver capture, and realizing the parallel code phase capture judgment of the DSSS receiver. Description of the Drawings

[0025] Figure 1 is a flowchart for calculating the capture threshold value based on the noise threshold in the present invention. The signal correlation value obtained by the received signal through parallel code phase capture (implemented by inverse Fourier transform) , and then through de-peak filtering, the overall correlation value set of the noise is obtained ; subsequently, the mean value of the noise correlation value is obtained through integral-mean calculation ; the correlation value set of the high-noise region is obtained through a comparator ; the average correlation value of the high-noise is obtained through integral-mean calculation ; and then it is multiplied by the false alarm rate parameter to obtain the capture threshold value for the current parallel code phase capture.

[0026] Figure 2 is a schematic diagram of the noise region in the present invention. In the figure, the abscissa is the phase deviation PH, the ordinate is the correlation value of the signal, the curve in the figure is the signal correlation value obtained by parallel code phase capture, the lower region part is the low-noise region part, and the upper region part is the high-noise region part.

[0027] Figure 3 is a schematic diagram of the capture effect when the received signal is pure noise. The curve in the figure is the correlation value of the received signal, and the dashed line is the capture threshold value calculated by this method.

[0028] Figure 4 is a schematic diagram of the capture effect when the received signal is a received signal with inconsistent spreading codes. The curve in the figure is the correlation value of the received signal, and the dashed line is the capture threshold value calculated by this method. It can be seen that there is a relatively small correlation peak, and if the capture threshold is set inappropriately, mis-capture will occur.

[0029] Figure 5 is a schematic diagram of the capture effect when the received signal is a correct signal. The curve in the figure is the correlation value of the received signal, and the dashed line is the capture threshold value calculated by this method. Detailed Embodiment

[0030] The present invention will be further described below in conjunction with the drawings and embodiments.

[0031] The parallel code phase capture discrimination method based on the noise threshold proposed by the present invention combines the statistical advantages of noise distribution and the advantages of high-noise region discrimination, solves the problem of mis-capture when the spreading codes are inconsistent, reduces the resource overhead of the receiver, and improves its stability. The specific steps are as follows:

[0032] Step 1: In DSSS communication, both the receiver and the sending device agree to use Perform spread spectrum modulation on the spreading code; during reception, the receiver performs parallel code phase acquisition, and obtains the point inverse Fourier transform to obtain the point received signal code phase correlation value result ;

[0033] Step 2: Remove the top amplitude ranked points in the result to obtain the overall correlation value set about noise, where is the number of points occupied by the peak value of the main peak in the received signal code phase correlation value obtained through parallel code phase acquisition, take , where the symbol is rounding up;

[0034] Step 3: Calculate the mean value of the noise correlation values of the overall correlation value set :

[0035] (1)

[0036] Step 4: Extract the correlation values in the overall noise correlation value set that are higher than the mean value and count the number of their points to form the correlation value set of the high-noise region, is the th correlation value in the set , ;

[0037] Step 5: As Figure 2 shown, count the mean value of the correlation value set of the high-noise region to obtain the average correlation value of the high noise:

[0038] (2)

[0039] Step 6: Determine the acquisition threshold using the average correlation value of the high noise ; The acquisition threshold of the DSSS receiver is the standard for completing acquisition judgment.

[0040] When the receiver receives a correct DSSS signal but fails to acquire the signal, the probability is called the false alarm rate . In this embodiment, before performing acquisition judgment, the false alarm rate value is first set to 0.0001. And the acquisition threshold The distribution is Rayleigh distribution when no correct DSSS signal is received. Therefore, the false alarm rate is expressed as:

[0041] (3)

[0042] Where represents the exponential operation with the natural constant as the base. Then, according to formula (3), we get:

[0043] (4)

[0044] The difference between the peak value of the main peak of the correlation value and the remaining noise peak values is the core of the capture judgment. When using the average noise correlation value for calculation in the traditional method, the noise correlation values in the low-noise regions that are not concerned in the noise will participate in the calculation of the average noise correlation value, thus interfering with the calculation of the capture threshold, resulting in a relatively low final capture threshold, and thus causing the relatively low main peak of the correlation value when the spreading codes are inconsistent to exceed the capture threshold, leading to false capture. Therefore, this method uses the average correlation value of high noise to replace the overall correlation value to remove the interference of the low-noise regions on the calculation of the capture threshold, so as to realize the judgment of the interference signal with inconsistent spreading codes. Therefore, the present invention uses the average correlation value of high noise to determine the capture threshold :

[0045] (5)

[0046] Step 7: Adopt the Tong search method, repeat the search multiple times within the set time, and observe the peak value in the obtained parallel code phase correlation value results whether it is stably higher than the capture threshold . If so, mark the capture as successful

[0047] Performance analysis:

[0048] In the simulation analysis, the parallel code phase capture process uses a spreading code with a length of 255, and the Fourier transform points of 32768 are used for operation. As Figures 3 to 5 shown Figure 3 is the capture judgment situation under noise. At this time, there is no obvious main peak in the correlation value result. The capture threshold value of the method proposed by the present invention is higher than the overall correlation result, and the capture judgment is correct Figure 4 is the capture judgment situation of the interference signal with inconsistent spreading codes. At this time, the peak value of the correlation result does not exceed the capture threshold value of the method proposed by the present invention, and the capture judgment is correct without false capture Figure 5This is the capture judgment situation under the correct signal. At this time, there is an obvious main peak in the correlation value, and the peak value exceeds the capture threshold of the method proposed by the present invention, so the capture is successful. It can be seen that the method proposed by the present invention can meet the capture requirements in different situations, especially has good anti-interference ability for interference signals with inconsistent spreading codes, and can realize the stable capture of the receiver.

[0049] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A DSSS parallel code phase capture judgment method based on noise threshold, characterized by: The following steps are involved: Step 1: In DSSS communication, the receiver and the transmitter agree on the use of The length of the spread spectrum code is used for spread spectrum modulation; when receiving, the received signal is captured in parallel code phase to obtain The code phase correlation value result of the received signal at point ; Step 2: Remove the relevant value results Top mid-range ranking points, and obtain the overall correlation value set about the noise , For collection The The overall correlation value, , is the number of points occupied by the main peak value in the code phase correlation value of the received signal; Step 3: Calculate the overall correlation value set of the noise The mean noise correlation value of : Step 4: Extract the overall correlation value set Above average The correlation value of and count the number of points , which constitutes the set of correlation values ​​in the high noise region , For collection The The relevant values, ; Step 5: Count the correlation values ​​of the high noise area The average correlation value of high noise is obtained : Step 6: Determine the capture threshold using the average correlation value in high noise : in is the false alarm rate; Step 7: Perform parallel code phase capture on the received signal. If the peak value in the parallel code phase correlation value result is Stable above capture threshold , then the flag capture is successful.

2. The DSSS parallel code phase capture judgment method based on noise threshold according to claim 1, characterized in that: In step 1, the requirement .

3. The DSSS parallel code phase acquisition judgment method based on noise threshold according to claim 1, characterized in that: In step 2, ,in Indicates rounding up.

4. The DSSS parallel code phase acquisition judgment method based on noise threshold according to claim 1, characterized in that: In step 7, the received signal is captured in parallel code phase, and the Tong search method is used to repeat the search multiple times within the set time to observe the peak value in the parallel code phase correlation value result. Is it stable above the capture threshold? , if so, the flag capture is successful.

5. An electronic device, comprising a processor and a memory, wherein the memory is used to store one or more programs; characterized in that: When the one or more programs are executed by the processor, the method described in any one of claims 1 to 4 is implemented.

6. A readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method described in any one of claims 1 to 4 is implemented.

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