JP2003032145A - Synchronization acquisition device for direct sequence spread spectrum signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synchronization acquisition device for direct sequence spread spectrum signals that detects mis-synchronization under a high C/N. SOLUTION: The synchoronization acquisition device for direct sequence spread spectrum signals is provided with a received spread code generating means that generates a received spread code, a correlation means that uses the received spread code to obtain a correlation with the received signal, a peak detection means that detects a peak of the obtained correlation value, a reception timing generating means that generates a timing for code synchronization based on the result of peak detection, and a peak value decision means that discriminates mis-synchoronization based on the correlation peak value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct-spread-spectrum signal synchronization capturing apparatus, and more particularly, to an improvement for detecting a code synchronization error in a receiving-side synchronization capturing apparatus in direct-spread spectrum communication. .

[0002]

2. Description of the Related Art In spread spectrum communication by a direct sequence (DS) system, a narrow band primary modulated signal is spread modulated (secondary modulated) on a transmitting side and transmitted as a wide band signal. This spread modulation is performed by multiplying the primary modulation signal by a spread code composed of a PN sequence (Pseudorandom Noise). At the receiving side, the received signal is despread using the same spreading code as at the transmitting side and the original 1
After returning to the next modulation signal, the demodulator reproduces the baseband waveform. Here, the spreading codes used on the transmitting side and the receiving side are unique and exactly the same.

In order to despread the received signal and obtain correct received data, the spreading code generation timing on the receiving side and the spreading code generation timing on the transmitting side must be matched. Here, a state in which the timing of the spread code of the transmitted signal and the timing of the spread code of the receiver match each other is called code synchronization, and reaching this state is called synchronization acquisition.

FIG. 5 is a block diagram showing a conventional structure of a synchronization acquisition device for performing synchronization acquisition in the direct spectrum spread system. 1 in the figure is a matched filter,
Reference numeral 2 is a reception spread code generation unit, 3 is an addition circuit, 4 is a peak detection unit, and 5 is a reception timing generation unit.

The receiving spread code generator 2 is given a spread code used for spread modulation on the transmitting side in advance, and generates the same spread code as this spread code. The matched filter 1 is a correlation circuit that finds the correlation between the reception spread code generated by the reception spread code generation unit 2 and the received signal that is a direct spectrum spread signal, and is configured as a digital matched filter circuit. The IF (intermediate frequency) signal obtained by down-converting the received spread spectrum signal is input to the matched filter 1, and the spread code from the reception spread code generation unit 2 is input to the matched filter 1 by multiplying them. The correlation value is calculated.

The adder circuit 3 is an arithmetic circuit for cyclically adding the correlation values output from the matched filter 1. The correlation value obtained by the matched filter 1 is added by the addition circuit 3 a predetermined number of times for each phase of the spread code to obtain an average value. That is, the correlation value is added for each phase over a period of n cycles (n is an arbitrary integer) of the spread code. The peak detector 4 determines the peak (maximum value) of the correlation value for each phase output from the adder circuit 3.
Is being detected.

The correlation value output from the matched filter 1 becomes large when the timings (phases) of the spread codes match, and becomes small when the timings of the spread codes do not match. Therefore, a peak of the correlation value appears for each cycle of the spread signal, and by detecting this peak, the timing shift between the spread code of the received signal and the spread code generated by the received spread code generation unit 2 is detected. be able to.
The reception timing generation unit 5 obtains the reception timing for code synchronization based on the detection result of the peak detection unit 4. In this way, the synchronization acquisition device synchronizes with the received spread spectrum signal.

[0008]

In direct spread spectrum communication, it is assumed that there is a certain level of noise, and in the presence of noise, despreading of the received signal spread by another code is performed. However, there is no peak in the correlation value. However, in a situation where the line condition is good and the noise level is low, a peak of the correlation value may occur with respect to a signal spread by another code, which may result in synchronization with an erroneous correlation peak.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a code synchronizer for a spectrum direct spread signal capable of detecting erroneous code synchronization. In particular, it is an object of the present invention to provide a code synchronizer for spread spectrum signals that can detect erroneous synchronization under a low noise level. Also,
An object of the present invention is to provide a code synchronizer for a direct spectrum spread spectrum signal which can establish code synchronization regardless of the line state.

[0010]

According to a first aspect of the present invention, there is provided a spread spectrum spread signal synchronization acquisition apparatus, wherein a spread spectrum code reception means for generating spread code for reception and a spread code for reception are used. Correlation means for obtaining a correlation value with a received signal, peak detection means for detecting a peak of the obtained correlation value, reception timing generation means for generating code synchronization timing based on the peak detection result, and correlation peak value And a peak value determining means for determining erroneous synchronization based on the above.

When the reception timing generating means generates the code synchronization timing based on the peak detection result of the correlation value by the peak detecting means, the peak value determining means determines the code synchronization error based on the correlation peak value. By determining, it is possible to detect the false synchronization.

According to a second aspect of the present invention, there is provided a spread spectrum signal synchronization acquisition apparatus according to the present invention, comprising spread code changing means for changing the receiving spread code to be supplied to the correlating means based on the judgment result of the peak value judging means. The peak value determination means is configured to determine false synchronization based on the peak detection result by the peak detection means after the spread code change.

The peak value judging means makes a primary judgment on false synchronization based on the correlation peak value, and the spreading code changing means changes the receiving spreading code to be supplied to the correlating means based on the result of the primary judgment. To do. The correlation means newly obtains a correlation value using the changed reception spreading code, and the peak value determination means makes a secondary determination regarding false synchronization based on the peak detection result by the peak detection unit. If it can be determined that there is an erroneous synchronization by the primary determination and the secondary determination, the erroneous synchronization detection accuracy can be improved. In particular, erroneous synchronization under high C / N can be accurately detected.

According to a third aspect of the present invention, there is provided a spread spectrum signal synchronization acquisition apparatus, wherein the spread code changing means changes the code sequence generated by the reception spread code generating means, and a peak is detected after the spread code is changed. If it is done, it is configured to determine the false synchronization. When the peak is detected even after the spreading code changing means changes the code sequence generated by the receiving spreading code generating means, the high C / N ratio is obtained.
It can be determined that the synchronization is below.

According to a fourth aspect of the present invention, there is provided a synchronization acquisition device for a direct spread spectrum signal according to the present invention, which is a timing offset multiplexing type synchronization supplement device, wherein the spread code changing means extends from the reception spread code generating means to the correlation means. The delay time of the spread code for reception is changed, and the peak value determination unit is configured to determine the false synchronization when the peak is not detected after the change of the spread code.

In the case of timing offset multiplex communication, the same spreading code is delayed and used for different channels. Therefore, if the receiving spreading code is delayed by a predetermined time, it is synchronized with the signal of another channel. be able to. Therefore, when the peak is not detected after the delay time of the spread code for reception is changed, it can be determined that the synchronization is low under high C / N.

According to a fifth aspect of the present invention, there is provided a synchronization acquisition device for a direct spectrum spread spectrum signal, wherein the peak value judging section comprises:
The detected correlation peak is compared with a predetermined threshold value, and false synchronization is determined based on the comparison result.
A peak that is erroneously detected under high C / N has a lower correlation peak value than a peak that is correctly detected. Therefore, by comparing the correlation peak value with a threshold value, false synchronization under high C / N is detected. be able to.

According to a sixth aspect of the present invention, there is provided a direct-spread-spectrum signal synchronization acquisition apparatus including peak averaging means for obtaining an average value of correlation peak values, and a peak value judging section correlates the detected correlation peaks. It is configured to compare with the average value of the peaks and to determine the false synchronization based on the comparison result. The detection accuracy can be further improved by comparing the detected peak value with the past peak average value.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing a configuration example of a synchronization acquisition device according to a first embodiment of the present invention. 1 in the figure is a matched filter (M
F) 2 is a reception spread code generation unit, 3 is an addition circuit, 4 is a peak detection unit, 5 is a reception timing generation unit, 6 is a peak value averaging unit, and 7 is a peak value determination unit. The blocks corresponding to the components of the conventional synchronization acquisition device are designated by the same reference numerals, and detailed description of the same configurations and operations will be omitted.

The matched filter 1 is a correlation circuit that multiplies the received spread spectrum signal by the reception spread code to obtain a correlation value. The reception spread code generation unit 2 generates a spread code for reception designated in advance to generate the matched filter 1
It is a circuit for generating a reception spread code that is output to. Adder circuit 3
Is a cyclic addition circuit that cyclically adds the correlation values output from the matched filter 1, and the peak detection unit 4 detects the peak of the correlation value based on the output of the addition circuit 3. The reception timing generation unit 5 generates a reception timing signal, that is, a spread code synchronization timing signal based on the correlation peak.

Further, the peak detecting section 4 outputs the correlation value of the detected peak as a peak value (correlation peak value) to the peak value averaging section 6 and the peak value determining section 7. The peak value averaging unit 6 stores the detected correlation peak value and obtains the average of the correlation peak values so far. The peak value determination unit 7 compares the correlation peak value from the peak detection unit 4 and the average value of the correlation peak values from the peak value averaging unit 6, and the newly detected peak is determined based on the comparison result. , It is determined whether it is normal reception or erroneous synchronization under high C / N. Therefore, it is possible to determine that the peak detection unit 4 has detected a peak different from the original peak observed at high C / N.

The result of this determination is output to the reception timing generator 5 as a false synchronization determination signal. The reception timing generation unit 5 generates a reception timing signal based on the false synchronization determination signal. That is, when the peak value determination unit 7 determines that the synchronization is incorrect, the reception timing signal is not output even if the peak detection result is output from the peak detection unit 4. Therefore, based on the false peak detection result,
It is possible to prevent or suppress the occurrence of false synchronization.

In this embodiment, a peak value averaging unit for obtaining an average value of the correlation peak values detected at the time of normal reception and a peak for comparing the correlation peak value newly detected by the peak detection unit with this average value. It is possible to determine whether or not the synchronization by the newly detected peak is erroneous synchronization based on the comparison result. In particular, false peak detection under high C / N can be discriminated. Therefore, it is possible to prevent or suppress the occurrence of false synchronization in the synchronization acquisition device. Further, it is possible to realize normal code synchronization even under high C / N.

Embodiment 2. FIG. 2 is a block diagram showing a configuration example of a synchronization acquisition device according to the second embodiment of the present invention. In the figure, 1 is a matched filter, 2 is a reception spread code generation unit, 3 is an adder circuit, 4 is a peak detection unit, 5 is a reception timing generation unit, 8 is a peak value determination unit, and 9 is a spread code change unit. Compared with FIG. 1, the peak value averaging unit 6
Is not provided, but the peak value determination unit 8 and the spread code changing unit 9 are provided.

The correlation peak value detected by the peak detection unit 4 is input to the peak value determination unit 8. The peak value determination unit 8 compares this correlation peak value with a predetermined threshold value and determines that the synchronization peak value is erroneous when the detected correlation peak value is smaller than the threshold value. That is, it is determined whether the newly detected correlation peak is normal reception or erroneous synchronization under high C / N based on the result of comparison with a predetermined threshold (primary determination). As a result, a peak different from the original peak observed at high C / N is detected by the peak detector 4.
It is possible to determine that there is a high possibility that it has been detected in.

The result of this determination is output to the spreading code changing section 9 as a spreading code changing signal. The spreading code changing unit 9
Based on the spread code change signal, the spread code generated by the reception spread code generation unit 2 is changed from the code (code sequence) originally used for reception to another code (code sequence).

After the spread code is changed, the reception spread code generator 2 generates a new spread code, the matched filter 1 obtains a correlation value using this new spread code, and the peak detector 3 detects the correlation peak. Detect. As a result, when a correlation peak is detected, the peak value determination unit 8 determines that the synchronization is high C / N (secondary determination). That is, the determination result of the primary determination can be confirmed. In this way
It is possible to determine that a peak observed at a high C / N different from the original peak is detected by the peak detection unit 4.

The result of this determination is output to the reception timing generator 5 as a false synchronization determination signal. The reception timing generation unit 5 generates a reception timing signal based on the false synchronization determination signal. Therefore, it is possible to prevent or suppress the occurrence of false synchronization based on the false peak detection result.

The present embodiment is provided with a peak value judging section for making a primary judgment and a secondary judgment of erroneous synchronization, and a spreading code changing section for changing the reception spreading code, and sets the newly detected peak value to a predetermined value. A primary judgment is performed by comparing with a threshold value, based on the result of the primary judgment, the spreading code generated by the reception spreading code generation unit is changed, and a secondary detection is performed based on whether a peak is detected after the spreading code is changed. Judging. Therefore, it is possible to accurately determine whether or not the synchronization based on the detected peak is erroneous synchronization. In particular, false peak detection under high C / N can be discriminated. Therefore, it is possible to prevent or suppress the occurrence of false synchronization in the synchronization acquisition device. Further, it is possible to realize normal code synchronization even under high C / N.

Embodiment 3. In the second embodiment, an example of comparing with a predetermined threshold value in the primary determination has been described, but in the present embodiment, the first comparison with the average value of the correlation peak values in the first determination is performed in the first embodiment. The case of using the determination method will be described.

FIG. 3 is a block diagram showing a configuration example of a synchronization acquisition device according to the third embodiment of the present invention. In the figure, 1 is a matched filter, 2 is a reception spread code generation unit, 3 is an addition circuit, 4 is a peak detection unit, 5 is a reception timing generation unit, 6 is a peak value averaging unit, 7'is a peak value determination unit, 9
Is a spread code changing unit. Compared with FIG. 1, a peak value determination unit 7 ′ and a spread code changing unit 9 are different, and compared with FIG. 2, a peak value averaging unit 6 is provided.

The peak averaging unit 6 obtains the average value of the correlation peak values detected by the peak detecting unit 4 up to the previous time, and the peak value judging unit 7'compares the newly detected correlation peak value with the average value. The operation to be performed is the same as in the case of the first embodiment (FIG. 1). The peak value determination unit 7'determines whether the reception is normal or erroneous synchronization under high C / N based on the comparison result (primary determination). As a result, when it is determined that there is a high possibility of erroneous synchronization under high C / N, the spread code change signal is output.

The subsequent operation is the same as in the case of the second embodiment. That is, when the spreading code generated by the reception spreading code generation unit 2 is changed from the originally used code to another code based on the spreading code change signal, and a correlation peak is detected after the change of the spreading code. Determines that the peak value determination unit 7'has a false C / N erroneous synchronization (secondary determination).

In the present embodiment, the primary judgment made by the correlation peak value is made based on the comparison result with the average value at the time of normal reception, so that the false synchronization under the high C / N and the low C / N can be achieved. The determination of normal synchronization below can be made more reliably than in the case of the second embodiment. Further, code synchronization can be performed more reliably under high C / N.

Fourth Embodiment In the second embodiment, an example in which the code of the spreading code is changed in the secondary determination has been described. However, in the present embodiment, in the timing offset multiplexing method, the spreading code is delayed by a predetermined time to perform the secondary determination. A case will be described. The timing offset multiplexing method is used to multiplex two or more channels by using the same spreading code for different channels at different timings, that is, with delays, when performing multiplex communication by the direct spectrum spreading method. It is a method to do. In this case, a spreading code having a sufficiently long code length is used, and a timing offset shorter than the code length is assigned to each channel.

FIG. 4 is a block diagram showing a configuration example of a synchronization acquisition device according to the fourth embodiment of the present invention. In the figure, 1 is a matched filter, 2 is a reception spread code generation unit, 3 is an adder circuit, 4 is a peak detection unit, 5 is a reception timing generation unit, 8'is a peak value determination unit, 9 is a spread code change unit, and 10 is a spread code change unit.
Is a spread code delay unit, and 11 is a spread code selection unit. Figure 2
The difference is that the spread code delay unit 10 and the spread code selection unit 11 are included.

The spreading code for reception generated by the reception spreading code generating section 2 is input to the spreading code selecting section 11 and the spreading code delaying section 10. The spread code delay unit 10 delays the spread code by a delay time that delays the spread code on the transmission side when using another channel, and outputs the delayed spread code to the spread code selection unit 11. Then, the spreading code selection unit 11
For the matched filter 1, either the spreading code from the reception spreading code generation unit 2 or the delayed spreading code from the spreading code delay unit 10 is selected and output.

The peak value determination unit 8'compares the newly detected correlation peak value with a predetermined threshold value to determine whether the reception is normal or erroneous synchronization under high C / N. Based on the result, the spread code change signal is transmitted to the spread code change unit 9
Is output to the same as in the second embodiment.

The spreading code changing section 9 controls the spreading code selecting section 11 based on the spreading code changing signal to change the spreading code input to the matched filter 1. The change of the spread code is not the change of the code of the spread code but the change of the timing offset, and the output of the reception spread code generation unit 2 is switched to the output of the spread code delay unit 10.

Peak detector 4 after changing the spreading code
The peak value determination unit 8 ′ determines whether or not there is an erroneous synchronization based on the peak detection result of 1. In the timing offset multiplexing method, signals spread by the same spreading code are transmitted at intervals delayed by a predetermined offset, and thus, when they are multiplexed, the delayed spreading code may be used. Correlation peaks can be detected. Therefore, if a peak is detected even after changing the spreading code,
The peak detected before the spread code change can be determined to be normal reception, and if the peak is not detected, it can be determined whether there is erroneous synchronization under high C / N. Based on this determination result, the peak value determination unit 8 ′
Outputs an erroneous synchronization determination signal to the reception timing generator 5.

In the present embodiment, in the synchronization complementation apparatus based on the timing offset multiplexing method, when the primary synchronization is judged to be erroneous synchronization, the spreading code is delayed by the delay time of the spreading code between the multiple channels to determine the correlation peak. Secondary detection is performed by detecting. Therefore, in the timing offset multiplexing method, it is possible to more reliably determine the false synchronization under high C / N and the normal synchronization under low C / N. Further, code synchronization can be performed more reliably under high C / N.

[0042]

In the apparatus for synchronously capturing a direct spread spectrum signal according to the present invention, the correlating means obtains the correlation value with the received signal using the receiving spread code, the peak detecting means detects the peak of the correlation value, and the peak The value determining means determines the false synchronization based on the correlation peak value. Therefore, the synchronization acquisition device can detect the false synchronization. In particular, it is possible to detect false synchronization under high C / N. In addition, code synchronization can be established regardless of the line status.

In the spread spectrum spread signal synchronization acquisition apparatus according to the present invention, the spread code changing means changes the receiving spread code based on the judgment result of the peak value judging means.
The peak value determination means determines false synchronization based on the peak detection result by the peak detection means after the spread code change. Therefore, false synchronization can be detected more reliably.
In particular, erroneous synchronization under high C / N can be accurately detected. In addition, code synchronization can be established regardless of the line status.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a synchronization acquisition device according to a first embodiment of the present invention, in which a detected correlation peak value and a correlation peak value at the time of past reception are compared to obtain a high C
A configuration for detecting false synchronization under / N is shown.

FIG. 2 is a block diagram showing a configuration example of a synchronization acquisition device according to a second embodiment of the present invention, in which a spread code is changed and confirmed when a detected correlation peak value is lower than a threshold value. , A configuration for detecting false synchronization under high C / N is shown.

FIG. 3 is a block diagram showing a configuration example of a synchronization acquisition device according to a third embodiment of the present invention, showing a configuration for changing a spreading code using a correlation peak value at the time of past reception. .

[Fig. 4] Fig. 4 is a block diagram showing a configuration example of a synchronization acquisition device according to a fourth embodiment of the present invention, in which a high C / A configuration for detecting false synchronization under N is shown.

FIG. 5 is a block diagram showing a conventional configuration of a synchronization acquisition device for performing synchronization acquisition in the direct spread spectrum system.

[Explanation of symbols]

1 Matched Filter, 2 Reception Spread Code Generator, 3
Adder circuit, 4 peak detection section, 5 reception timing generation section, 6 peak value averaging section, 7, 7 ', 8, 8'peak value determination section, 9 spreading code changing section, 10 spreading code delay section, 11 spreading code Selector.

Claims (6)

[Claims] 1. A reception spread code generation means for generating a spread code for reception, a correlation means for calculating a correlation value with a received signal using the spread code for reception, and a peak for detecting a peak of the calculated correlation value. A spectrum direct characterized by comprising a detection means, a reception timing generation means for generating code synchronization timing based on the peak detection result, and a peak value determination means for determining false synchronization based on the correlation peak value. Spread signal synchronization acquisition device. 2. A spread code changing means for changing the receiving spread code supplied to the correlating means based on the judgment result of the peak value judging means, wherein the peak value judging means uses the peak detecting means after changing the spreading code. The synchronization acquisition apparatus for a direct spread spectrum signal according to claim 1, wherein erroneous synchronization is determined based on a peak detection result. 3. The spread code changing means changes the code sequence generated by the reception spread code generating means, and determines a false synchronization when a peak is detected after changing the spread code. 2. A device for acquiring synchronization of a direct spread spectrum signal according to 2. 4. A timing offset multiplex synchronization supplementary device, wherein the spreading code changing means changes the delay time of the receiving spreading code from the receiving spreading code generating means to the correlating means, and the peak value judging section 3. The apparatus for acquiring synchronization of a direct spread spectrum signal according to claim 2, wherein when the peak is not detected after changing the spread code, it is determined as false synchronization. 5. The spectrum direct according to claim 2, wherein the peak value determination unit compares the detected correlation peak with a predetermined threshold value and determines false synchronization based on the comparison result. Spread signal synchronization supplementary device. 6. A peak averaging means for obtaining an average value of correlation peak values, wherein the peak value judging section compares the detected correlation peak with an average value of the correlation peaks, and erroneous synchronization is performed based on the comparison result. 3. The direct-spread-spectrum signal synchronization supplement device according to claim 1, wherein the determination is made as to.