JPH09214401A - Random code synchronization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the synchronization state in a short time. SOLUTION: A history of (theoretical) correlation integration values between each spread code and each of all spread codes deviated sequentially by one tip each is calculated and stored in advance in a storage device 1-7, a multiplier 1-2 multiplies an input spectrum spread signal and an inverse spread code, the result of multiplication is integrated and a value (history) of the correlation integration for each tip period is stored in a 1 code length storage device 1-5. A comparison discrimination device 1-6 compares the correlation integration value history with each theoretical correlation integration value history and seeks the closest theoretical correlation integration value history and a phase difference of the history is set to an inverse spread code generator 1-4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for synchronizing a despreading code with a received spread signal in a direct spread spectrum spread communication receiver, for synchronizing a local random code with an input random code.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional sliding correlation device. Spread spectrum signal (input random code) 4-1
Is input to the correlation multiplication device 4-2, and the correlation multiplication device 4
-2, it is multiplied with the spreading code (local random code) generated by the despreading code generator (local random code generator) 4-4. The output signal of the correlation multiplication device 4-2 is input to the correlation integration device 4-3, and the correlation integration device 4-3.
The integrated value is obtained by integrating at 3. The correlation integral value obtained when the integration of one period of the spread code is completed is called a correlation value. The obtained correlation value is the correlation synchronization determination device 4-
5, the correlation code determination device 4-5 completes the spread code synchronization acquisition when the correlation value reaches the specified value. In other cases, the correlation synchronization determination device 4-5 despreads. Shift the phase of the spread code of the code generator 4-4, initialize the correlation integral value of the correlation integrator 4-3,
Repeat the correlation operation until the synchronization acquisition is completed.

[0003]

In the conventional sliding correlator, the correlation operation between the phase shift of the local random code (despreading code) and the integration of the correlation value is repeated until the synchronization of the input random code (spreading code) is acquired. Therefore, there is a drawback that the synchronization acquisition time is the longest and is the code length times the random code period, that is, the long time. It is an object of the present invention to provide a random code synchronizer capable of high-speed synchronization acquisition.

[0004]

The correlation integral values obtained by the sliding correlator have different correlation integral values history depending on the phase difference between the input random code and the local random code. In the present invention, the history of theoretical correlation integral values of various phase differences is stored in the storage device, and the history of these theoretical correlation integral values and the history of correlation integral values obtained from the correlation integral of the reception code and the local code are compared and determined. And the phase of the local code of the received code is estimated from the closest history of theoretical correlation integral values. The synchronization acquisition can be performed faster than the conventional sliding correlator. This is largely different from the conventional technique in that the history of the correlation integral value and the history of the theoretical correlation integral value are compared to estimate the phase of the input code.

[0005]

FIG. 1 shows an embodiment in which the present invention is applied to synchronization of a despreading code generator (local random code generator) in a spread spectrum communication receiver. The received spread spectrum signal 1-1 has a correlation multiplication device 1-2.
And is multiplied by the despreading code generated by the despreading code generation device 1-4 in the correlation multiplication device 1-2. The multiplied signal is integrated by the correlation integration device 1-3, and the correlation integrated value is output. The correlation integrated value history storage device 1-5 stores the time history of the correlation integrated value input from the correlation integration device 1-3. In the correlation integrated value history comparison / determination device 1-6, the value of the theoretical correlation integrated value history storage device 1-7, which stores the theoretical value of the correlation integrated value history of the spreading code used, and the correlation integrated value history storage device. The phase of the spreading code used for the spread spectrum signal is estimated by comparing all or a part of the output signals of 1-5.
The spread code of the despreading code generator 1-4 is set to the estimated phase based on the phase estimation value in the correlation integration value history comparison / determination device 1-6, and synchronization of the spread code is performed.

FIG. 2 shows an operation example of the correlation integration value history comparison / judgment apparatus based on the theoretical correlation integration value history and the correlation integration value history obtained from the spread spectrum signal. The vertical axis of the graph in FIG. 2 is the correlation integral value, and the horizontal axis is the correlation time standardized by one chip (chip) of the spread code. In this example, the code length (one cycle) of the spread code is 127 chips. . A thick solid line 20 in the graph is an example of data in the correlation integrated value history storage device 1-5, that is, an example of a value of the correlation integrated value for each one-chip passage, and the four solid lines with symbols 21 to 24 are theoretical correlation integrated values. It is an example of the data in the value history storage device 1-7. The theoretical correlation integral value history storage device 1-7 stores a theoretical correlation integral value history calculated in advance, that is, one chip each of the correlation values using the phase difference between the spreading code and the despreading code as a parameter. The integrated value for each passage is stored. Only four different theoretical correlation integral values 127 are shown in the storage device 1-7 in FIG. 2 corresponding to the phase difference of the spread code of the spread spectrum communication signal and the code for despreading for each chip unit. Have a history. The correlation integrated value history comparison / determination device 1-6 compares the data of the correlation integrated value history storage device 1-5 with the data of each phase difference of the theoretical correlation integrated value history storage device 1-7, and compares both data. Estimate the theoretical correlation integral history that minimizes the difference. In FIG. 2, since the error between the correlation integrated value history 20 and the theoretical correlation integrated value history 23 is the smallest, the correlation integrated value history comparison device 1-6
Outputs the phase corresponding to the theoretical correlation integral value history 23 and uses it as the phase estimation value of the spread code.

FIG. 3 shows a processing procedure of synchronization acquisition by the sliding correlation device of the present invention. The synchronization acquisition request 3-1 sets the initial value of the despreading code generator 1-4 (3-
2) and the correlation integrator 1-3 are initialized (3-3). Correlation and integration of received spread signal and despread code are performed (3-4), sampling point (occurs at chip cycle)
If so (3-5), the correlation integral value is sampled and stored (3-6). If the number of integrations is not the code length, the process returns to the correlation integration (3-4) and the same process is performed.
When the cycle integration is completed, it is determined whether the number of repeated integrations is less than or equal to the set number (3-8).
Returning to step 3-3, the correlation integration device 1-3 is initialized, the correlation integration (3-3) and the correlation integration value history are sampled (3-5). When the number of times of correlation integration reaches the set value in step 3-8, the sample values for each number of repetitions are averaged for each sampling point in step 3-5 (3-9). The value of each sampling point of the averaged correlation integrated value history is compared with the value at the corresponding time point of the theoretical correlation integrated value history, or the corresponding values at all sampling points are compared, The phase difference of the theoretical correlation integrated value history having a small error is determined and used as the estimated phase (3-10). By setting the phase of the despreading code generator (1-4) based on the estimated phase (3-11), code synchronization acquisition is completed (3-12).

In the above description, it is not always necessary to take the average of the correlation integrated value history, that is, the correlation integrated value history may be obtained only once, and this may be compared with the theoretical correlation integrated value history. When synchronizing with an input signal that has passed through a noisy environment such as spread spectrum communication, it is possible to synchronize without error by taking the average of the correlation integrated value history.
In a normal sliding correlator, the average synchronization time is the code period X (half of the number of code chips), so the effect of the present invention cannot be obtained unless the average number of histories is less than half the number of code chips. The average number of history records may be determined according to the noise environment.

Further, in the above description, the history is obtained by obtaining the integrated value at each sampling point, that is, the chip period. You may compare with the integrated value history. In this case, depending on the type of code used, a sampling point is selected in which the value of the correlation integral value at the sampling point changes as much as possible according to the phase difference. For example, if the number n of sampling points that take P or more correlation integration values that differ depending on the phase difference is taken, an n point that satisfies P ⁿ > m (m is the number of chips of the code length) is determined, and the correlation integration value history is only for this n point. It suffices to make a comparison determination by obtaining

According to the present invention, not only the synchronizing device of the despreading code generator of the spread spectrum communication receiving device but also the random code is used for measuring the bit error rate of the transmission line. It can also be applied to other random code synchronizers, such as when synchronizing a local random code generated on the side.

[0011]

As described above, according to the present invention, the phase estimation and the synchronization acquisition of the input code are performed by comparing the correlation integrated value history and the theoretical correlation integrated value history.
It is possible to acquire synchronization faster than the conventional sliding correlator.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a sliding correlation device of a spread spectrum receiving device.

FIG. 2 is a diagram showing an example of a history of correlation integral values and a history of theoretical correlation integral values.

3 is a flowchart showing an example of a processing procedure of synchronization acquisition by the apparatus of FIG.

FIG. 4 is a block diagram showing a conventional sliding correlation device.

Claims (3)

[Claims] 1. An input random code and a local random code generated by a local code generator are multiplied by a correlation multiplier,
The output signal of the multiplication is integrated by a correlation integration device to calculate a correlation integration value, the phase of the local random code of the local code generator is shifted using the correlation integration value, and the input random code is converted to the local random code. In a device for synchronizing a random code, a theoretical correlation integrated value history storage device for storing a theoretical correlation integrated value history of the random code and random codes of various relative phases thereof, and the correlation integrated value output from the correlation integration device. Of the correlation integrated value history storage device that stores the time history of, the respective theoretical correlation integrated value history and the correlation integrated value history are compared, and the phase of the input random code is estimated from the relative phase of the closest theoretical correlation integrated value history. And a correlation integration value history comparison / judgment device for performing random code synchronization. 2. A means for obtaining an average value of a plurality of times of the correlation integrated value history and using the averaged correlation integrated value history for comparison with the theoretical correlation integrated value history is provided. Item 2. The random code synchronizer according to Item 1. 3. The random code synchronizer according to claim 1, wherein the history of the correlation integral value and the history of the theoretical correlation integral value are compared only with respect to some chip points in the code length. .