JPH08237172A - Method and device for initial synchronization of spread spectrum communication - Google Patents

Abstract

PURPOSE: To surely and stably establish initial synchronization by integrating a correlation value with an integration time divided into a very short time based on a base band signal and a PN code obtained by demodulating a received signal and discriminating a maximum value of the integrated values. CONSTITUTION: A received signal from an antenna is frequency-converted by a converter 2, its base band signal is sampled and quantized by an A/D converter 3, and resulting digital data are given to n-stages of digital matched filters 4. The filters 4 receive digital data and a PN code from a PN code generator 5. The filters 4 obtain a correlation between the digital data and the PN code and provide an output of it to an integration device 6. Then a discrimination signal discriminating a maximum integration value is outputted. In this case, the integration device 6 the correlation values at each phase from the filters 4 by an integration time divided into a very small time. Then phases 'n-0' of the correlation data from the filters 4 are integrated with respect to blocks (1)-(3) with a very small integration time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in mobile communications and the like, and a spread spectrum (hereinafter referred to as SS) communication initial synchronization method for ensuring stable synchronization when the received signal level fluctuates greatly. And equipment.

[0002]

2. Description of the Related Art Conventionally, in SS communication, initial synchronization is established. In the process of establishing the initial synchronization, the received signal from the antenna is frequency-converted (down-converted) by the frequency conversion circuit (mixing circuit, local oscillation circuit). This frequency-converted baseband signal is sampled and quantized (digitized) by an A / D converter, and this digital data is input to an n-stage digital matched filter.

The digital matched filter receives the PN code from the PN code generator together with the digital data, and the digital matched filter obtains the correlation value between the digital data and the PN code. Correlation value data from the digital matched filter is input to an integrator, the integrated values are added up, and the added value is added up. Then, the maximum (peak) of the integrated value is determined by the integrator or the determination circuit, and this determination signal is output.

In the process of establishing the initial synchronization, for example, the digital matched filter uses the P from the PN code generator.
N code is latched, and the latched code 64 chips and the input baseband signal (I signal, Q signal) 6
Correlation values of four chips are calculated and output.
In the integrator, I signal from digital matched filter, Q
Each of the signals is integrated and summed. After this, further integration is performed.

FIG. 3 is a diagram showing such conventional correlation value data and the integration state for each phase. FIG.
The phases "n to 0" of the correlation value data from the digital matched filter shown in (a) are arranged in blocks (1) to (3) ... With an integrator as shown in FIG. 3 (b). That is,
M blocks for each phase "INT [PN code phase /
n] ”and add up. This accumulated (1) to (3)
The phase of the maximum integrated value is determined to be the synchronization establishment position by the integrator or the determination circuit from among the m blocks.

As a proposal for improving such an SS communication initial synchronization system, there is a "reception synchronization control system" proposed in Japanese Patent Laid-Open No. 2-100434. In this method, in the direct SS method, the larger the correlation between the received modulated signal and the random signal, the smaller the sliding width and the larger the sliding width in the asynchronous state where the correlation value is small. Then, when the correlation value continuously increases and approaches the synchronized state, it is determined that the synchronized state is maintained and the control of the sliding width is maintained. That is, the sliding width becomes smaller as the correlation value increases and approaches the synchronized state, so that the synchronized pull-in is performed at high speed.

[0007]

However, in the above-described conventional spread spectrum communication initial synchronization method, when initial synchronization is established, a multi-propagation (multipath) caused by a sudden movement of the transmitting side or the receiving side is caused. There is a case where the level of the received signal fluctuates (cuts) abruptly due to fading or the like, and establishment of the initial synchronization fails.

FIG. 4 is a diagram showing a state in which the level of the received signal greatly fluctuates. As shown in FIG. 4, when the level of the received signal fluctuates greatly, only the noise component is output from the digital matched filter at time Δt on the time axis (t) in FIG. Therefore, the integrated value in the integrator shown in FIG. 3B becomes an invalid value at time Δt1, and the phase of the correlation value data from the digital matched filter is “n to 0”.
Even if there is a synchronization code establishment phase in it, all of that data will be lost. That is, there is a drawback that the possibility of failing to establish synchronization increases.

The same is true for the example described in Japanese Patent Laid-Open No. 2-100434, and it is difficult to establish stable synchronization when the reception level changes abruptly (fading due to multiple propagation, etc.).

The present invention solves the above-mentioned drawbacks in the prior art, and the integrated time can be divided into short sections.
It is an object of the present invention to provide a spread spectrum communication initial synchronization method and apparatus capable of reducing the probability of failure to establish synchronization when the reception level changes abruptly and stably and reliably establishing the initial synchronization.

[0011]

In order to achieve the above object, the spread spectrum communication initial synchronization method according to claim 1 obtains a correlation value from a digitized baseband signal and a PN code, and then the correlation value. The integration time of the data is divided into shorter parts and integrated, and the determination of the maximum integrated value is made.

According to a second aspect of the spread spectrum communication initial synchronization device, digitized baseband data and PN.
A digital matched filter for obtaining a correlation value from the code, a PN code generating means for sending a PN code to the digital matched filter, an integrating means for integrating the integration time of the correlation value data from the digital matched filter by dividing it into short, The maximum integrated value of the means is determined, and a determination means for outputting the determination signal is provided.

[0013]

The spread spectrum communication initial synchronization method and apparatus according to claims 1 and 2 having such a configuration obtains a correlation value from the demodulated baseband signal and the PN code, and divides the integration time of this correlation value into shorter ones. Is being accumulated. Then, the maximum value in this integrated value is determined. That is, when the integration time is divided shortly, all of the correlation value data from the digital matched filter does not disappear, and there is a synchronization code establishment phase in the phase of the correlation value data,
Synchronization is established at that phase. In other words, the probability of failure to establish synchronization when the reception level changes abruptly becomes small.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of a spread spectrum communication initial synchronization method and apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a spread spectrum communication initial synchronization method and apparatus of the present invention. FIG.
In the above example, a frequency conversion circuit 2 that frequency-converts a reception signal from an antenna (not shown) is provided. The frequency conversion circuit 2 includes a mixing circuit 2a and a local oscillation circuit 2b.

Further, in this example, an A / D converter 3 which samples and quantizes (digitizes) the baseband signal whose frequency is converted by the frequency conversion circuit 2, and digital data from this A / D converter 3 N to calculate the correlation value with the PN code
And a digital matched filter 4 in stages.
Further, the PN code generator 5 that generates a PN code and sends it to the digital matched filter 4 and the integration time of the correlation value from the digital matched filter 4 are divided into shorter parts and integrated, and the maximum (peak) of the integrated value is calculated. And an integrator 6 that outputs a determination signal. The maximum determination may be performed by a determination circuit (not shown) instead of the integrator 6. Hereinafter, it is assumed that the maximum determination is performed by the integrator 6.

Next, the operation of this embodiment will be described. The received signal from the antenna is frequency-converted (down-converted) by the frequency conversion circuit 2 (mixing circuit 2a, local oscillation circuit 2b) to generate an A / D converter 3
Sampling and quantization (digitization) with. This digital data is input to the n-stage digital matched filter 4.

The digital matched filter 4 receives the PN code from the PN code generator 5 together with the digital data. The digital matched filter 4 finds the correlation value between the digital data and the PN code. Then, this correlation value data is output to the integrator 6 from the digital matched filter 4. The integrator 6 outputs a determination signal for determining the maximum integrated value. In this operation, the integrator 6
However, the integration time of the correlation value for each phase from the digital matched filter 4 is divided into shorter times for integration.

In such initial synchronization establishment processing, for example, the digital matched filter 4 latches the PN code from the PN code generator 5, and the latched code 64 chips and the input baseband signal (I signal) are input. , Q
For 64 chips of the signal), the correlation value is calculated and output.

Next, the integrator 6 integrates the I signal and Q signal from the digital matched filter 4. The integrated I signal and Q signal are added up and further added up.
In this case, the integration time is divided into shorter times for integration.

FIG. 2 is a diagram showing the correlation value data of such an embodiment and the integration state for each phase. Figure 2
The phase "n to 0" of the correlation value data from the digital matched filter 4 shown in (a) is divided into blocks (1) to (3) ... And add up. From the blocks (1) to (3), the phase of the maximum integrated value is determined by the integrator 6 or a determination circuit (not shown) to be the position for establishing synchronization, and the determination signal is output.

As described above, in this embodiment, as shown in FIG.
As shown in, when the level of the received signal suddenly fluctuates due to fading of multiple propagation (multipath) accompanying the movement of the transmitting side or the receiving side, the phase of the correlation value data from the digital matched filter 4 If there is a synchronization code establishment phase in “n to 0”, only the noise component is not output from the digital matched filter 4. That is, the integrated value data in the integrator 6 does not become an invalid value,
The probability of failure in synchronization establishment is reduced, and the establishment of the initial synchronization can be established stably and reliably.

[0022]

As is apparent from the above description, according to the spread spectrum communication initial synchronization method and apparatus of the first and second aspects, the received signal is demodulated into the baseband signal and P.
The integration time of the correlation value is divided into shorter parts from the N code and integrated, and the maximum value of the integrated values is determined. This allows
Since the integration time is divided shortly, if all the correlation value data from the digital matched filter does not disappear and there is a synchronization code establishment phase in the phase of the correlation value data, synchronization establishment is performed at that phase. . In other words, the probability of failure to establish synchronization when there is a sudden change in reception level is reduced,
It has an effect that the initial synchronization can be established stably and surely.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a spread spectrum communication initial synchronization method and apparatus of the present invention.

FIG. 2 is a diagram showing an integrated state in the embodiment. (A) is a figure which shows the correlation value data from a digital matched filter. (B) is a figure which shows the state which divides | segments an integration time into short and integrates.

FIG. 3A is a diagram showing conventional correlation value data.
(B) is a figure which shows the integrating | accumulating state for every phase of the data of (a).

FIG. 4 is a diagram showing a state in which the level of a received signal greatly changes.

[Explanation of symbols]

 2 frequency conversion circuit 2a mixing circuit 2b local oscillation circuit 3 A / D converter 4 digital matched filter 5 PN code generator 6 integrator

Claims (2)

[Claims] 1. A digitized baseband signal and PN.
An initial synchronization method for spread spectrum communication, characterized in that a correlation value is obtained from a code and then the integration time of the correlation value data is divided into short pieces and integrated, and further a determination is made to find the maximum of this integration value. 2. Digitalized baseband data and P
A digital matched filter for obtaining a correlation value from the N code, a PN code generating means for sending a PN code to the digital matched filter, and an integrating means for integrating by dividing the integration time of the correlation value data from the digital matched filter into short pieces. An initial synchronization device for spread spectrum communication, comprising: and a determination unit that determines the maximum integrated value of the integration unit and outputs the determination signal.