JP2003188769A - Synchronism capturing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synchronism capturing method in which accuracy for capturing the synchronism of a code stream having spread-spectrum codes or prescribed code patterns is improved and the time required for capturing synchronism can be shortened. <P>SOLUTION: A matched filter 1 detects a correlation over a plurality of observation cycles. A synchronous point candidate selecting part 3 selects an offset timing to apply first to Nth correlative values in each of the observation cycles. A synchronous point candidate comparing part 4 defines candidates in an Mth cycle as a comparison reference in order and defines the candidates less than the Mth cycle as a comparison target. The candidates are successively compared while making the order of comparison preferential as a candidate is closer to the Mth cycle and as the correlative value is greater. In the case of matching, the evaluation value of the comparison reference offset timing at that time point is counted up and the next comparison is performed. When the evaluation value exceeds a prescribed value, a synchronous point candidate evaluating part 5 decides the candidate as a synchronous point. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization acquisition method and apparatus for synchronizing a spread spectrum code generated by a spread code with a spread code generated on the receiving side, and a code sequence having a predetermined code pattern. The present invention relates to a synchronization acquisition method and apparatus for synchronizing a received signal that has been inserted into a target and a same code string generated on the receiving side.

[0002]

2. Description of the Related Art In a direct spread spectrum spread communication (DS-SS) receiver used in mobile communication, etc., a received signal spread by a spread code and a spread code generated on the receiving side are used. Must be synchronized (synchronization acquisition).
Figure 7 shows the direct sequence spread spectrum communication system (DS-SS).
3 is a block diagram showing a first example of a conventional synchronization acquisition method in FIG. 1 is a Matched Filter
That is, the correlation with the spread spectrum received signal is obtained.
The matched filter 1 uses the same spreading code as the spreading code on the transmitting side as the tap coefficient. The tap coefficient is usually
Codes of −1 and +1 are used corresponding to spread codes of 1 and 0. Reference numeral 21 is a maximum value selection and threshold comparison unit. The received spread spectrum signal r (t) is frequency-converted to a baseband band by quadrature demodulation of the received digital modulation signal and passed through a bandpass filter. Normally, IQ based on the carrier phase is used. It is input to the matched filter 1 as a component output.

FIG. 8 is a first explanatory diagram of the synchronization acquisition method in the prior art shown in FIG. Matched filter 1
Has a length (number of taps) equal to the spreading code period. For example, a binary PN (Pseudo Noise) code is used as the spreading code, and the transmission signal is modulated by the PN code, for example, BPSK modulation. The matched filter 1 selects the maximum value of the correlation value between the received spread spectrum signal r (t) and the PN code for each chip cycle or for each cycle in which the chip cycle is oversampled over one cycle of the spread code. It is output to the threshold comparison unit 21.

The maximum value selecting / threshold comparing section 21 observes the output of the matched filter 1 and extracts the code phase offset timing at which the correlation value becomes maximum. When the maximum value exceeds the predetermined threshold value, the offset timing is determined to be the synchronization point, and a signal indicating synchronization acquisition is output. When it does not exceed the threshold value, the observation of the correlation value output from the matched filter 1 for one cycle of the spreading code is repeated.

If the threshold value is fixed under the fading environment, it is impossible to deal with the fluctuation of the received power level. for that reason,
In the case of adaptively controlling the threshold value during the operation, as an example, there is a method in which the output average value of the matched filter 1 during the observation period is taken and γ ₁ obtained by multiplying this average value by a coefficient γ ₀ is used as the threshold value. However, the optimum value of γ ₀ is determined in advance by simulation. Alternatively, there is a method in which a matched filter using a code orthogonal to the spreading code as a coefficient is separately prepared, and γ ₃ obtained by multiplying the average value of the output by the coefficient γ ₂ is used as the threshold value. In this case as well, γ ₂ is fixed. In addition, the output of the matched filter 1 may be subjected to synchronous addition (also referred to as in-phase addition or ensemble averaging operation) with the cycle of the spreading code as one unit over a plurality of cycles of the spreading code. Since the time averaging process of the correlation value is performed, the influence of the correlation value due to fading distortion or noise is reduced, and the SN ratio is improved.

In the acquisition mode, when the threshold value is exceeded, the next confirmation mode is entered, and when the threshold value is not exceeded, the acquisition mode is restarted. In the confirmation mode, a sliding correlator multiplies the received spread spectrum signal and the spread code on the receiver side at the synchronization timing determined in the acquisition mode and integrates them to obtain a correlation output. The integration time is set to one to several cycles if the spreading code is a short code, and to a predetermined fraction of one cycle if the spreading code is a long code. This correlation detection is repeated multiple times. If the number of times the correlation value exceeds a certain threshold value is a predetermined number of times or more, it is determined that the synchronization point is correct, and the normal reception operation mode (operation mode) is entered. If not, start over from acquisition mode. The threshold value in this confirmation mode is also variable according to the power level of the received signal.

FIG. 9 is a second explanatory diagram of the synchronization acquisition method in the prior art shown in FIG. The illustrated example is suitable when the length of the matched filter 1 is shorter than the cycle of the spread code. As the coefficient of the matched filter 1,
Use part of the spreading code. In the illustrated example, the code having the number of chips corresponding to the length of the matched filter is taken out from the rear part of the spread code, but the coded place may be taken anywhere. Even in this case, as in the synchronization acquisition method shown in FIG. 8, synchronization is achieved by observing the output of the matched filter 1 for one cycle of the spreading code, with the chip cycle or the cycle of oversampling as a unit. Capturing can be done.

FIG. 10 is a block diagram showing a second example of a conventional synchronous acquisition method using a matched filter in direct sequence spread spectrum communication (DS-SS). In the figure,
Reference numerals 11 _{1 to} 11 _J denote a plurality of matched filters, which receive the spread spectrum signals r (t) spread by the spread code in common and perform the correlation detection in parallel. Reference numeral 31 is a maximum value selection and threshold comparison unit.
This conventional technique is provided with a plurality of matched filters 11 ₁ to ₁ 1.
This is a method of selecting the maximum value from 1 _J , and is suitable for detecting the correlation with the spreading code of the long code, and the synchronization acquisition time can be shortened to 1 / J (1 / J).

FIG. 11 is an explanatory diagram of the synchronization acquisition method in the prior art shown in FIG. The spread code is equally divided into a number according to the number (J) of the matched filters 11 _{1 to} 11 _J. The equally divided J divided spread codes are used as the coefficients of the matched filters 11 _{1 to} 11 _J , respectively. At this time, a further part of each divided spreading code is taken out in the same length and the matched filter 1
The coefficient may be _{1 to} 11 _J. The length of 11 _{1 to} 11 _J of each matched filter can be further shortened. FIG. 11 shows
This case is shown.

In the case of this synchronization acquisition method, the spread code period
Chip period or chips over 1 / J time
For every cycle that oversamples the cycle, all matched
Filter 11₁~ 11_JObserve the output of
Matched filter and its offset timing
Take out the ring. And if it exceeds the threshold,
Division spreading corresponding to the matched filter with the maximum value of
The sign is the offset of the matched filter with the maximum correlation value.
By determining that there is a synchronization point in the output timing,
A signal indicating synchronization acquisition is output. In the example shown, match
Defilter 11 ₂The maximum value is detected in the output of
The value is exceeded. Note that synchronous addition is also possible. For example,
Ched filter 11₁At the time of 1 / J of the spread code period of
Store all outputs over memory in memory and
Consider the advance of the received signal at 1 / J of the period
The value stored in the memory described above is
Filter 11₂The output of is added synchronously. Next spreading code cycle
The target of synchronous addition is 1 / J of the period
Next matched filter 11 ₃Will be output.

In a communication system such as mobile communication,
In addition to the above-described spread spectrum code, there is one that periodically inserts and transmits a code string having a predetermined code pattern at a predetermined time period (frame period). That is,
The known pattern used for initial synchronization acquisition and channel estimation during communication (channel estimation) is periodically inserted as a preamble. Even when the code sequence having such a predetermined code pattern is synchronously captured, the above-described code synchronous capture technique can be applied. The code string having the above-described predetermined code pattern is not necessarily the PN code.

FIG. 12 is an explanatory view showing a synchronization acquisition method by a conventional matched filter in a communication system in which preambles are periodically inserted. In this case, in order to detect the above-mentioned known code pattern and acquire the frame synchronization, the same configuration as that of the spreading code shown in FIG. 7 can be used. In that case, a code string having a predetermined code pattern may be used as the coefficient of the matched filter 1 of FIG. The illustrated example is an example in which a code string having a predetermined code pattern is a preamble, and a frame synchronization is acquired using a matched filter having the code string of the preamble as a coefficient.

In any of the above-mentioned conventional techniques,
By setting a threshold for the level of the correlation value, the maximum value exceeding the threshold is set.
It is determined that there is a synchronization point at the offset timing to be taken.
It Since this threshold follows the fading environment,
Mean value of matched filter output at
Then, calculate the average value of the power level by the coefficient γ₀Doubled γ₁Ai
Is a matched filter whose coefficient is a code orthogonal to the spreading code.
The average value of the output of ₂Doubled γ₃, Refer to the threshold
Had decided. However, the coefficient γ₀, Γ₂Is
The value must be determined by simulation and fixed.
Yes. However, the coefficient γ₀, Γ₂Is the signal-to-noise ratio at that time
(SNR) changes the optimum value. Therefore, improve performance
To obtain the coefficient γ depending on the signal-to-noise ratio at that time,₀, Γ₂
It is better to change. However, the estimation of the signal-to-noise ratio
In order to do so, you must first be able to acquire synchronization
And this is impossible. Therefore, the coefficient γ₀, Γ₂Is
Relatively characteristic over the expected signal-to-noise ratio
The compromise is to choose the best one. for that reason
Even if the threshold is set, the offset timing detection is
There is a problem of weak sound.

In the acquisition mode, when the threshold value is exceeded, the next confirmation mode is entered, and when the threshold value is not exceeded, the acquisition mode is restarted. If the threshold value is set too low, it is necessary to shift to the next confirmation mode, and then the synchronization point will be found to be wrong, and the acquisition mode will be restarted. Therefore, the overall synchronization acquisition time becomes long. On the contrary, if the threshold value is set too high, if the number of times of reacquisition of the synchronization reaches the limit, the maximum value at that time is output as the synchronization point even if the number of times of the synchronization acquisition has reached the limit. That is, it is the same as when no threshold is provided. The maximum value at this time is not necessarily guaranteed to be the correct synchronization point. If it is not correct, as in the case described above, the acquisition mode is restarted after shifting to the confirmation mode.

In the confirmation mode, the code phase which is the synchronization point in the acquisition mode is confirmed. It typically uses an active correlator to correlate the received signal with the spreading code generated in the receiving station over a period of time. This correlation value γ ₅
B is repeated B times, and if A times or more exceeds the threshold, acquisition is completed and normal reception operation starts. If not, return to acquisition mode. The threshold value γ ₅ here is a coefficient γ ₄ times the correlation value output at the synchronization point in the acquisition mode. Here, a state in which the normal reception operation is started even though it is not the synchronization point is called an erroneous alarm, and the time from when returning to the acquisition mode is called a penalty time. Since the penalty time is generally quite long, it is important to reduce the false alarm probability in the confirmation mode. Here again, in order to reduce the false alarm probability, it is sufficient to raise the threshold level, but the higher it is, the greater the probability that it will be false even though the synchronization is correct this time. . Therefore, the threshold coefficient γ ₄
Determines an appropriate value by the above trade-off.

As described above, in the prior art, it was necessary to set the threshold value for the output level of the correlation value in order to detect the maximum value. However, in practice, it is difficult to set this threshold optimally, so that the probability of erroneous synchronization acquisition is high due to noise or the like. On the other hand, the above-mentioned synchronous addition is effective as a measure for substantially lowering the signal-to-noise ratio.
When the synchronous addition is performed over a plurality of cycles, the peak waveform of the maximum value becomes steep. However, if the synchronous addition is continued for too long, the synchronous acquisition time becomes long. Then, not only it takes time to enter the operation mode, but also the propagation environment changes in mobile communication. That is, the optimum path of multipath changes or the optimum base station changes. In such a situation, not only the data that has been synchronously added until then is wasted, but it is rather harmful to the new environment.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has a high accuracy of synchronously capturing a spread spectrum code or a code string having a predetermined code pattern. An object of the present invention is to provide a synchronization acquisition method and device that can reduce the time required for acquisition. Without using the threshold value for the correlation output level for synchronization determination, the maximum output and several points subsequent thereto are set as synchronization point candidates, their timings are periodically observed twice or more times, and those The synchronization determination is performed depending on whether the timings are the same.

[0018]

In order to solve the above problems, in the invention described in claim 1, in the synchronization acquisition method, spectrum spreading is performed by a part or all of spreading codes and the spreading codes. Correlation detection with a received signal is performed by a predetermined M with the cycle of the spreading code as an observation cycle.
(M is an integer greater than or equal to 2) Correlation detection step performed during a period over the observation cycle, and based on the result of the correlation detection, from the first to the N-th (N is an integer greater than or equal to 2) in each observation cycle A synchronization point candidate selecting step of selecting the first to Nth offset timings as synchronization point candidates, which gives a correlation value of the magnitude; and the Mth period of the selected synchronization point candidates. The offset timings from the 1st to the Nth are used as comparison reference offset timings in descending order of correlation value, and the offset timings from the 1st to the Nth in each observation cycle of M-1th cycle or less As the comparison target offset timing, the closer to the M-th cycle, the higher the priority of comparison, and the correlation value within each observation cycle. When the comparison reference offset timing and the comparison target offset timing match, the evaluation value of the comparison reference offset timing at that time point is counted up and the next priority is given. And a comparison step of performing a comparison, and an evaluation step of determining that the comparison reference offset timing at the time point is a synchronization point when the evaluation value of each comparison reference offset timing exceeds a predetermined value during the comparison process. It is a thing. Therefore, since the synchronization point determination is performed in a plurality of observation cycles by using the information in the time axis direction, which has little fluctuation, more reliable synchronization determination can be performed. Further, since the offset timings for outputting the correlation values up to the Nth are used as the synchronization point candidates, the influence of noise on the correlation output is reduced. As a result, the synchronization acquisition can be performed with high accuracy. Therefore, it is possible to immediately shift to the normal reception operation mode after the synchronization acquisition. Further, even when the above-described synchronization acquisition is set as the acquisition mode and the confirmation mode is provided after that, the probability of returning from the confirmation mode to the acquisition mode again decreases. Therefore, the synchronization acquisition time as a whole can be shortened. The higher the probability of being the synchronization point at the moment is, the higher the comparison order is. Since there is a high possibility that a point will be determined, the synchronization point detection time is shortened by the time required for the remaining comparison.

According to a second aspect of the present invention, in the synchronization acquisition method, the correlation detection between a part or all of the spread codes and the received signal spectrum-spread by the spread codes is detected by using the cycle of the spread codes. Based on the correlation detection step performed during a predetermined M (M is an integer of 2 or more) observation cycle as an observation cycle, and the result of the correlation detection, the first to Nth observation cycles are performed in each observation cycle.
(N is an integer equal to or greater than 2) A synchronization point candidate selecting step for selecting a synchronization point candidate from the first offset timing to the Nth offset timing, which gives a correlation value up to the second correlation point, and the selected synchronization point Of the candidates, the first to Nth offset timings of the Mth cycle are set as comparison reference offset timings, and the first to Nth offsets in each of the observation cycles of M-1th cycle or less. Using the timing as a comparison target offset timing, a comparison step of comparing the comparison reference offset timing and the comparison target offset timing in all combinations, and evaluating the matching situation between the comparison reference offset timing and the comparison target offset timing By this, the comparison reference offset timing specific One but those having a determining evaluation step as a point synchronization. Therefore, since the synchronization point determination is performed in a plurality of observation cycles by using the information in the time axis direction, which has little fluctuation, more reliable synchronization determination can be performed. Further, since the offset timings for outputting the correlation values up to the Nth are used as the synchronization point candidates, the influence of noise on the correlation output is reduced. As a result, the synchronization acquisition can be performed with high accuracy. Therefore, it is possible to immediately shift to the normal reception operation mode after the synchronization acquisition. Further, even when the above-described synchronization acquisition is set as the acquisition mode and the confirmation mode is provided after that, the probability of returning from the confirmation mode to the acquisition mode again decreases. Therefore, the synchronization acquisition time as a whole can be shortened. The above-mentioned evaluation steps are not limited to those described in claims 3 and 4 described later. For example, when the comparison reference offset timing and the comparison target offset timing match, the evaluation value of the comparison reference offset timing at the time point is counted up, among all the combinations, the evaluation value is the maximum, and, It suffices to determine that the comparison reference offset timing at which the evaluation value exceeds a predetermined value is the synchronization point.

According to a third aspect of the present invention, in the synchronization acquisition method according to the second aspect, the evaluation step includes performing the correlation in each cycle with respect to each offset timing of the selected synchronization point candidate. When the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time point is added to the weight of the comparison target offset timing at the time point. Is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all the combinations, and the evaluation value exceeds the predetermined value. It is determined to be a point. Therefore, it is estimated that the probability of being a synchronization point is high, and the evaluation value becomes higher as the correlation value is larger, so that the determination of the synchronization point becomes more accurate and the synchronization acquisition can be performed with high accuracy. . The weight given in order does not necessarily have to be proportional to the order.

According to a fourth aspect of the present invention, in the synchronization acquisition method according to the second aspect, the evaluation step is performed from the first cycle to the first cycle with respect to each offset timing of the selected synchronization point candidate. When the comparison reference offset timing and the comparison target offset timing coincide with each other, the weight becomes larger as it reaches M cycles, and as the correlation value becomes larger in each cycle. A value obtained by adding the weight of the comparison target offset timing to the weight of the comparison reference offset timing is added to the evaluation value of the comparison reference offset timing, and in all the combinations, the evaluation value is the maximum, and, When the comparison reference offset timing at which the evaluation value exceeds a predetermined value is at the synchronization point It is intended to determine that that. Therefore, since the evaluation value is higher for the M-th cycle, which is estimated to have a higher probability of being the synchronization point at the present time, and for which the correlation value is larger, the determination of the synchronization point becomes accurate. , The synchronization acquisition of the synchronization point can be performed with high accuracy. The weight given according to the cycle and the weight given according to the correlation value may be given the same weight in order, or different weights may be given in order.

According to a fifth aspect of the present invention, in the synchronization acquisition method, some or all of the divided spread codes obtained by dividing the spread code into J and the received signal spectrum-spread by the spread code. And a correlation detection step of performing correlation detection with and in a period over a predetermined M (M is an integer of 2 or more) observation period with a division period of 1 / J of the spread code period as an observation period, and the result of the correlation detection. On the basis of the above, in each of the observation periods, a correlation value having a magnitude from the 1st to the Nth (N is an integer of 2 or more) is given, and the offset timings from the 1st to the Nth are given as synchronization point candidates. And a sync point candidate selecting step for specifying a part or all of the divided spread codes used for correlation detection at the time point, and the selected sync point Of the offset timing from the first th M cycles until the N-th, the comparison reference offset timing in order from the largest correlation value,
The first to N-th offset timings in each of the observation cycles equal to or less than the (M-1) th cycle are used as comparison target offset timings, and the closer to the M-th cycle, the more the comparison order is prioritized, and each observation is performed. Within the cycle, the larger the correlation value is, the higher the comparison priority is, and the successive comparison is performed, and the comparison reference offset timing and the comparison target offset timing match, and the correlation reference offset timing is used for correlation detection. Some or all of the divided spread codes and some or all of the divided spread codes used for correlation detection of the comparison target offset timing have continuity according to the difference in the observation cycle. If it has, count up the evaluation value of the comparison reference offset timing at that time. When the evaluation value of each of the comparison reference offset timings exceeds a predetermined value during the comparison process and the comparison step of performing the next priority comparison, the comparison reference offset timing at that time point is a synchronization point. It has an evaluation step for judging.

In the sixth aspect of the present invention, in the synchronization acquisition method, some or all of the divided spread codes obtained by dividing the spread code into J and the received signal spectrum-spread by the spread code. And a correlation detection step of performing correlation detection with and in a period over a predetermined M (M is an integer of 2 or more) observation period with a division period of 1 / J of the spread code period as an observation period, and the result of the correlation detection. On the basis of the above, in each of the observation periods, the correlation timings of the first to the Nth (N is an integer of 2 or more) -th degree are given, and the offset timings from the first to the N-th are given as synchronization point candidates. And a synchronization point candidate selecting step for specifying a part or all of the divided spread codes used for correlation detection at the time point, and the selected synchronization point Of the first to N-th offset timings of the M-th cycle as comparison reference offset timings, and the first to N-th offsets in each observation cycle of M-1th cycle or less. A comparison step of comparing the comparison reference offset timing and the comparison target offset timing in all combinations using timing as a comparison target offset timing, matching of the comparison reference offset timing and the comparison target offset timing, and the comparison Of a part or all codes of the divided spreading code used for correlation detection of the reference offset timing and a part or all codes of the divided spreading code used for correlation detection of the comparison target offset timing,
By evaluating the continuity situation according to the difference in the observation cycle, it is possible to determine the specific value of the comparison reference offset timing.
It has an evaluation step for determining that one is a synchronization point. The above-mentioned evaluation steps are not limited to those described in claims 7 and 8 described later. For example, the comparison reference offset timing and the comparison target offset timing are the same, and a part or all of the division spread codes used for correlation detection of the comparison reference offset timing and the comparison target offset timing When some or all of the divided spread codes used for correlation detection have continuity according to the difference in the observation cycle, the evaluation value of the comparison reference offset timing at that time point is counted up. Then, it is only necessary to determine that the comparison reference offset timing in which the evaluation value is the maximum and the evaluation value exceeds the predetermined value is the synchronization point among all the combinations.

In a seventh aspect of the present invention, in the synchronization acquisition method according to the sixth aspect, the evaluation step includes performing the correlation in each cycle with respect to each offset timing of the selected synchronization point candidate. The larger the value is, the larger the weight is given, and the comparison reference offset timing and the comparison target offset timing match each other, and a part of the divided spreading code used for correlation detection of the comparison reference offset timing or When all or a part or all of the divided spread codes used for correlation detection of the comparison target offset timing have continuity according to the difference in the observation period, The weight of the comparison reference offset timing is added to the weight of the comparison target offset timing at that time. The added value is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all the combinations, and the evaluation value exceeds the predetermined value. Is determined. The weight given in order does not necessarily have to be a weight proportional to the order.

According to an eighth aspect of the present invention, in the synchronization acquisition method according to the sixth aspect, the evaluation step is performed from the first period to the first period for each offset timing of the selected synchronization point candidate. The weight becomes larger as it reaches M cycles, and becomes larger as the correlation value becomes larger in each cycle, and the comparison reference offset timing and the comparison target offset timing match each other, and the comparison reference Part or all codes of the divided spread code used for correlation detection of offset timing and part or all codes of the divided spread code used for correlation detection of comparison target offset timing are the observation cycle. When there is continuity according to the difference of the Only, the value obtained by adding the weight of the comparison target offset timing at that time is added to the evaluation value of the comparison reference offset timing, and the evaluation value becomes the maximum among all the combinations, and the evaluation value is predetermined. The comparison reference offset timing exceeding the value is determined to be the synchronization point. The weight given according to the cycle and the weight given according to the correlation value may be given the same weight in order, or different weights may be given in order.

According to a ninth aspect of the present invention, in the synchronization acquisition method, some or all of the code strings having a predetermined code pattern and the code string having the predetermined code pattern are frame-based. A correlation detection step of performing the correlation detection with the periodically inserted received signal in a period over a predetermined M (M is an integer of 2 or more) observation period with the period of the frame as the observation period, and the correlation detection result. On the basis of the
A synchronization point candidate selecting step of selecting the first to Nth offset timings as synchronization point candidates, which gives a correlation value of a magnitude from the th to the Nth (N is an integer of 2 or more); Among the synchronization point candidates, the first to Nth offset timings of the Mth cycle are set as comparison reference offset timings in descending order of correlation value, and each observation is performed in the M-1th cycle or less. The first to N-th offset timings in the cycle are set as comparison target offset timings, and the closer to the M-th cycle, the more the comparison order is prioritized, and
Within each of the observation periods, the larger the correlation value is, the higher the comparison priority is, and the successive comparison is performed, and when the comparison reference offset timing and the comparison target offset timing match, the comparison reference offset timing at the time When the evaluation value of each of the comparison reference offset timings exceeds a predetermined value during the comparison step in which the evaluation value is counted up and the next priority is compared, the comparison reference offset timing at that time point Is an synchronization point.

According to a tenth aspect of the present invention, in the synchronization acquisition method, a part or all of the code strings having a predetermined code pattern and the code string having the predetermined code pattern are frame-based. A correlation detection step of performing the correlation detection with the periodically inserted received signal in a period over a predetermined M (M is an integer of 2 or more) observation period with the period of the frame as the observation period, and the correlation detection result. On the basis of the above, in each of the observation periods, the first to the N-th (N is an integer of 2 or more) correlation values of magnitudes are given, and the first to the N-th offset timings are used as synchronization point candidates. A step of selecting a synchronization point candidate to be selected, and M-th of the selected synchronization point candidates
The 1st to Nth offset timings of the cycle are set as comparison reference offset timings, and
A comparison step of comparing the comparison reference offset timing and the comparison target offset timing in all combinations, with the first to N-th offset timings in each observation cycle equal to or less than the cycle as comparison target offset timings; The method further includes an evaluation step of determining that one specific one of the comparison reference offset timings is a synchronization point by evaluating the state of coincidence between the comparison reference offset timings and the comparison target offset timings. The above-mentioned evaluation steps are not limited to those described in claims 11 and 12 described later. For example, when the comparison reference offset timing and the comparison target offset timing match, the evaluation value of the comparison reference offset timing at the time point is counted up, among all the combinations, the evaluation value is the maximum, and, It suffices to determine that the comparison reference offset timing at which the evaluation value exceeds a predetermined value is the synchronization point.

According to an eleventh aspect of the present invention, in the synchronization acquisition method according to the tenth aspect, the evaluation step includes performing the correlation in each cycle with respect to each offset timing of the selected synchronization point candidate. When the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time point is added to the weight of the comparison target offset timing at the time point. Is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all the combinations, and the evaluation value exceeds the predetermined value. It is determined to be a point. The weight given in order does not necessarily have to be proportional to the order.

According to a twelfth aspect of the present invention, in the synchronization acquisition method according to the tenth aspect, the evaluation step includes the first cycle to the first cycle with respect to each offset timing of the selected synchronization point candidate. When the comparison reference offset timing and the comparison target offset timing coincide with each other, a weight that increases as the number of M cycles increases and as the correlation value increases becomes greater in each cycle. A value obtained by adding the weight of the comparison target offset timing to the weight of the comparison reference offset timing is added to the evaluation value of the comparison reference offset timing, and in all the combinations, the evaluation value is the maximum, and,
The comparison reference offset timing when the evaluation value exceeds a predetermined value is determined to be the synchronization point. The weight given according to the cycle and the weight given according to the correlation value may be given the same weight in order, or different weights may be given in order.

The inventions described in claims 5 to 8 have the same effects as the inventions described in claims 1 to 4, respectively, and since the spreading code for synchronous detection is divided, the correlation detection is performed. The spreading code length used is reduced. as a result,
The processing load and circuit scale of each correlation detection can be reduced.
The inventions described in claims 9 to 12 have the same effects as those of the inventions described in claims 1 to 4 regarding the spreading code, respectively, with respect to the code string having the predetermined code pattern.

In the inventions described in claims 1, 5, and 9 and the inventions dependent on them, the synchronization point is detected even at the time of comparison with the final comparison target offset timing. If not, the correlation detection step advances the observation period by sliding one or more observation periods, and repeats the processing of the synchronization point candidate selection step, the comparison step, and the evaluation step. To do. In addition, claim 2, claim 6,
In the invention according to claim 10 and the inventions according to claims dependent thereon, when a synchronization point satisfying a condition cannot be detected, the correlation detecting step slides the observation period by a predetermined one or a plurality of observation periods. Then, the process of selecting the synchronization point candidate, the comparing step, and the evaluating step is repeated.

In the invention described in claims 1 to 12, the value of M, which is the number of observation cycles, and / or the value of N, which is the number of correlation values as synchronization point candidates in each observation cycle, use the present invention. It may be determined according to the SNR (signal-to-noise ratio) of the environment in which the SNR is changed, or the received power level that changes the SNR. The synchronization acquisition method according to any one of claims 1 to 12 described above includes a correlation detection step, a synchronization point candidate selection step,
The comparison step and the evaluation step can be realized by the synchronization acquisition device according to any one of claims 13 to 24, wherein the correlation detection means, the synchronization point candidate selection means, the comparison means, and the evaluation means respectively execute the comparison step and the evaluation step. The evaluation means has a weighting means, an evaluation value addition means, and a determination means. Claim 13-
In the synchronization acquisition device described in 16, a correlation detector can be used as the correlation detection means. Some or all of the spreading codes are set in the correlation detector.
In the synchronization acquisition device according to claims 17 to 20, a plurality of correlation detectors can be used as the correlation detection means. A code for a part or all of the divided spread codes obtained by dividing the spread code into J is set in each correlation detector. Some or all of the spreading codes are set. In the synchronization acquisition device according to the twenty-first to twenty-fourth aspects, a correlation detector can be used as the correlation detection means. A part or all of the code strings having a predetermined code pattern are set in the correlation detector.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the first embodiment of the present invention. In the figure, 1 is a matched filter, which is the same as that in FIG. 7, and the same spreading code as that on the transmitting side is set as its tap coefficient.
The matched filter 1 inputs the received signal r (t) that has been spectrum-spread by the spread code, detects the correlation between the received signal and the spread code, and uses the cycle of the spread code as the observation cycle to detect a plurality of observation cycles (first 1 to the Mth cycle), and outputs the correlation value for each chip cycle or for each cycle in which this chip cycle is oversampled. Reference numeral 2 denotes a determiner, which has a sync point candidate selection unit 3, a sync point candidate comparison unit 4, and a sync point candidate evaluation unit 5.

On the basis of the result of the correlation detection, the synchronization point candidate selection unit 3 gives the maximum correlation value in each observation cycle from the first first cycle to the last M-th cycle. In the following order, the first to the Nth offset timings that give the Nth correlation value are selected and stored as synchronization point candidates. Sync point candidate comparison unit 4
Reads out the selected synchronization point candidates, and selects the M-th candidate among them.
The offset timings from the 1st to the Nth in the cycle are set as comparison reference offset timings in descending order of correlation value. Further, offset timings less than the Mth cycle, that is, the first to Nth offset timings in the observation cycle from the (M-1) th cycle to the first cycle are set as comparison target offset timings.

At this time, the closer to the M-th cycle, and
In each cycle, the larger the correlation value, the higher the priority of comparison, and the successive comparison is performed. When the comparison reference offset timing and the comparison target offset timing match, the matching count of the comparison reference offset timing at that time point is counted up as an evaluation value and the next priority is compared. When the evaluation value of each comparison reference offset timing exceeds a predetermined value in the comparison process, the synchronization point candidate evaluation unit 5 determines that the comparison reference offset timing at that time point is the synchronization point. At this point, further operations of the matched filter 1 and the synchronization point candidate comparison unit 4 are unnecessary, so that the operations of the matched filter 1, the synchronization point candidate selection unit 3, or the synchronization point candidate comparison unit 4 may be stopped.

FIG. 2 is an explanatory diagram showing a concrete example of the synchronization acquisition method in the first embodiment shown in FIG. Here we see up to the third correlation value detected, ie N = 3
An example in the case of is shown. Also, an example will be described in which this is observed for M = 3 cycles and synchronization detection is performed when the comparison results match once. The matched filter 1 is sequentially observed. First, the synchronization point candidate selection unit 3 sets the code phase offset # 1-1 to the timing at which the correlation value output becomes the maximum value (first) in the first observation of the first cycle. Also, the timing when the correlation value output becomes the second and the third,
Code phase offsets # 1-2 and # 1-3, respectively. In this way, the timing is represented by the phase from the initial phase at the observation start timing of each observation cycle.

Next, the timings at which the correlation value output is the maximum value (first), second and third in the second observation are designated as code phase offsets # 2-1, # 2-2, # 2-3, respectively. To do. 3
Similarly for the second observation, code phase offset # 3-
Decide 1, # 3-2, # 3-3. In the sync point candidate comparison unit 4 and the sync point candidate evaluation unit 5, the last (third time in this example)
After the end of the observation period of, the synchronization point is identified. In the first embodiment, first, the code phase offset # 3-1 with the maximum correlation value in the last (third time in this example) observation cycle
(Value 33) is compared with the timing of code phase offset # 2-1 (value 19), which has the maximum correlation value in the previous (second) observation cycle.

In the case of this specific example, since the timings do not match, next, the code phase offset # 3-1 (value 33) and the code phase with the second correlation value at the previous (second) observation cycle Compare the timing of offset # 2-2 (value 25). This also does not match, so next, the code phase offset
# 3-1 (value 33) is compared with the timing of code phase offset # 2-3 (value 10), where the correlation value became the third during the previous (second) observation cycle. This also does not match, so next, the code phase offset # 3-1 (value 33) and the code phase offset # with the maximum correlation value during the first (first) observation period
Compare the timing of 1-1 (value 33). Since the timings match, this code phase offset # 3-1 (value 3
In 3), the timings match one or more times, so this is the synchronization point.

Assuming that the code phase offset # 3-1 (value 33)
As the comparison reference offset timing, until the timing of the last synchronization point candidate # 1-3 of the first (first) observation cycle is compared, if there is no match, the comparison reference offset timing is set to the last (this In the observation cycle of the third time in the example), the correlation value is the second code phase offset
Perform a similar comparison as # 3-2 (value 10). When they do not match even once, the comparison reference offset timing is set as the code phase offset # 3-3 (value 19) with the third correlation value in the last (third time in this example) observation cycle.
Make a similar comparison. Finally, the code phase offset # 3-3
Even if (value 19) is compared with the timing of the last sync point candidate # 1-3 in the first (first) observation cycle, there is a case where they do not match at all. At this time, I can't trust, so I'll have to start over.

That is, again, by observing the output of the matched filter 1 for one cycle of the spread code, the observation period is advanced by sliding for a predetermined observation cycle, for example, one cycle. From the beginning, the same comparison and evaluation shall be repeated. At this time, an observation period is newly added after the Mth period, and the synchronization point candidate in the first observation period is discarded. The original synchronization point candidates of the 2nd to Mth cycles become new synchronization point candidates of the 1st to (M-1) th cycles, respectively. Note that it is desirable to set a limit in advance on the number of times the correlation is detected again by advancing the observation period.

In the specific example described above, the synchronization point candidate evaluation unit 5
Has detected that the timings match one or more times, and has determined that it is the synchronization point. However, the same is true when the number of matches (evaluation value) is set multiple times. That is, if the code phase offset # 3-3 is not determined to be the synchronization point because the code phase offset # 3-3 does not match the predetermined number of times until it is compared with the code phase offset # 1-3, 2 of the last observation cycle is used. The same operation as described above is performed using the th code phase offset # 3-2 to find the synchronization point. If it is not found, the same operation is performed until the sync point is found at the last third code phase offset # 3-3 of the last observation cycle, and the sync point could not be found even then. In this case, the matched filter 1 advances the observation period by sliding a predetermined one or a plurality of observation periods, and repeats the processes of the synchronization point candidate selection step, the comparison step, and the evaluation step.

The acquisition mode described above can perform synchronization acquisition with high accuracy. Therefore, when it is determined that the synchronization is achieved, it is possible to immediately shift to the normal reception operation mode. Even if the confirmation mode is provided after the acquisition mode, the probability of returning from the confirmation mode to the acquisition mode again decreases. In the above description, all spreading code chips are used as the tap coefficients of the matched filter 1. However, the partial correlation may be detected as described with reference to FIG. 9 as the conventional technique. In this case, the tap coefficient of the matched filter 1 is a part of the spread code, for example,
The rear code sequence may be used.

The comparison of the offset timings described above is as follows.
Since the correlation detection is performed over a plurality of observation cycles, more reliable synchronization determination can be performed as compared with the maximum value selection in one observation cycle. In conventional synchronous addition, correlation detection is performed over a plurality of observation cycles, but in synchronous addition, noise components are reduced by averaging the output levels of correlation values. On the other hand, in the embodiment of the present invention,
It has been found that there is little variation in the correlation output in the time axis direction, and offset timings are compared based on this finding. In addition, not only the maximum value of the correlation output but also the code phase offsets that output up to a predetermined Nth correlation value are used as the synchronization point candidates, so that the influence of noise on the correlation output is reduced.

Next, another embodiment will be described with reference to FIGS. 1 and 2 again. The matched filter 1 and the synchronization point candidate selection unit 3 shown in FIG. 1 are the same as those in the first specific example. The synchronization point candidate comparison unit 4 sets the first to Nth offset timings of the last M-th cycle among the selected synchronization point candidates as comparison reference offset timings. On the other hand, the comparison target offset timings are the offset timings from the 1st to the Nth in the (M-1) th cycle to the 1st cycle. The comparison reference offset timing and the comparison target offset timing are compared in all combinations. The synchronization point candidate evaluation unit 5 determines that one particular comparison reference offset timing is a synchronization point by evaluating the state of coincidence between the comparison reference offset timing and the comparison target offset timing in all the combinations. When a synchronization point satisfying the conditions cannot be detected, the matched filter 1 advances the observation period by a predetermined one or a plurality of observation periods, and the like, and selects a synchronization point candidate step, a comparison step, and an evaluation. The processing of steps shall be repeated. It is desirable to set a limit in advance on the number of times the correlation period is detected again by advancing the observation period.

As a more specific method for evaluating the matching situation in all combinations, there are, for example, the following second to fourth specific examples. The second embodiment is
As the above-mentioned evaluation method, when the comparison reference offset timing and the comparison target offset timing match, the number of times the comparison reference offset timing matches at that time is counted up as an evaluation value, and the evaluation value becomes the maximum among all combinations. Moreover, it is determined that the comparison reference offset timing having the evaluation value in which this evaluation value exceeds the predetermined value is the synchronization point. This will be described using the specific example of FIG. Here, the correlation value
An example of looking up to the third, that is, when N = 3 is shown. Also, this is observed for M = 3 cycles, and here, the predetermined value is evaluated as twice or more. The synchronization point candidate comparison unit 4 and the synchronization point candidate evaluation unit 5 identify the synchronization point after the end of the last observation cycle.

In the second embodiment, first, the code phase offset # with the maximum correlation value in the last observation cycle
Looking at 3-1 (value 33), the code phase offsets # 2-1 (value 19) and # 2-2 that became sync point candidates in the previous observation cycle
Since there is no same timing in (value 25) and # 2-3 (value 10), the number of matches (score, evaluation value) is not counted up. The code phase offset # 3-1 (value 33) is changed to the code phase offset # 1-
Compared with 1 (value 33), # 1-2 (value 17), # 1-3 (value 10), it is equal to the timing of code phase offset # 1-1 (value 33), so code phase offset # 3- For 1, the score is 1. Similarly, the code phase offset # 3-2 (value 10) that became the second correlation value in the last observation cycle.
, The score is 2 because it coincides with the timing of code phase offset # 2-3 (value 10) and code phase offset # 1-2 (value 10). 3 in the last observation period
Code phase offset # 3-3 (value 1
Regarding 9), code phase offset # 2-1 (value 19)
Since it matches the timing of, the score is 1. As a result, the code phase offset # 3-2 (value 10) has the maximum score, and since this score is greater than or equal to the predetermined value 2, the timing of this code phase offset # 3-2 (value 10)
Is the synchronization point.

The third embodiment of the evaluation method is, as the evaluation method described above, a weight that becomes larger as the correlation value becomes larger in each cycle of the observation period with respect to each offset timing of the selected synchronization point candidate. Is to give. When the comparison reference offset timing and the comparison target offset timing match, the value obtained by adding the weight of the comparison reference offset timing at that time to the weight of the comparison reference offset timing at that time is counted as the evaluation value of the comparison reference offset timing. It is determined that the comparison reference offset timing having the evaluation value of which the evaluation value is the maximum and the evaluation value exceeds the predetermined value is the synchronization point among all combinations.

Description will be made with reference to the specific example of FIG. Here we look up to the third correlation value detected, ie N = 3
An example in the case of is shown. Also, this is observed for M = 3 cycles, and the weights are (N =) 3, (N−2 =) 2, (N
−2 =) 1. Further, the predetermined value (threshold value) is set to 4. The synchronization point candidate comparison unit 4 and the synchronization point candidate evaluation unit 5 identify the synchronization point after the end of the last observation cycle. First, looking at the code phase offset # 3-1 (value 33), which has the maximum correlation value in the last observation cycle, it is equal to the timing of the code phase offset # 1-1 (value 33). The score of the code phase offset # 3-1 and the score of the code phase offset # 1-1 are both 3, which is 6 in total.

Next, code phase offset # 3-2 (value 10)
, It coincides with the timing of code phase offset # 2-3 (value 10) and code phase offset # 1-2 (value 10). Code phase offset # 3-2 has a score of 2, code phase offset # 2-3 has a score of 1, code phase offset # 1-2
, The total score of the code phase offset # 3-2 is 2 + 1 + 2 = 5. Next, looking at the code phase offset # 3-3 (value 19), it coincides with the timing of the code phase offset # 2-1 (value 19). Code phase offset # 3-3 has a score of 1, code phase offset # 2-
Since the score of 1 is 3, the total score of the code phase offset # 3-3 is 1 + 3 = 4. As a result, the score 6 of # 3-1 becomes the maximum and exceeds the threshold value of 4, so this code phase timing # 3-1 (33) is set as the synchronization point. The larger the correlation value, the higher the probability of being the synchronization point, and accordingly, the higher the correlation value, the higher the evaluation value makes the determination of the synchronization point accurate. It should be noted that if the probability of being a synchronization point is known, the weight given in order is optimal if it is set to a value according to this probability, but if it becomes larger as the order becomes higher, it will not necessarily be described in the above-mentioned specific example. The weight does not have to be proportional to the order as described above.

The fourth embodiment of the evaluation method is the above-mentioned evaluation method, in which the offset timings of the selected synchronization point candidates are increased from the first cycle to the last Mth cycle of the observation period. In each observation, the larger the correlation value, the larger the weight. At the same time, when the comparison reference offset timing and the comparison target offset timing match, the value obtained by adding the weight of the comparison reference offset timing at that time to the weight of the comparison reference offset timing at that time is evaluated as the comparison reference offset timing. The value is counted up, and among all the combinations, the above-mentioned evaluation value is the maximum, and it is determined that the comparison reference offset timing having the evaluation value exceeding the predetermined value is the synchronization point.

This will be described with reference to the specific example of FIG. Here we look up to the third correlation value detected, ie N = 3
An example in the case of is shown. Also, this is observed for M = 3 cycles, and the weights are (N =) 3, (N-1 =) 2, (N-2
=) 1 Further, as weights in the time direction, from new observation to old one, (M =) 3, (M-1 =) 2, (M-2 =) 1
Shall be added. That is, for each sync point candidate,
6 to 1 are given as weights obtained by adding the weights according to the order of the magnitude of the correlation value and the weights according to the order of the observation period. The predetermined value (threshold value) is 10. The synchronization point candidate comparison unit 4 and the synchronization point candidate evaluation unit 5 identify the synchronization point after the end of the last observation cycle.

First, looking at the code phase offset # 3-1 (value 33) having the maximum correlation value in the last observation cycle, it is equal to the timing of the code phase offset # 1-1 (value 33). Code phase offset # 3-1 score is 3 + 3 = 6
Is. The score of the code phase offset # 1-1 is 1 + 3 = 4, and the total is 10. Then the code phase offset
Looking at # 3-2 (value 10), code phase offset # 2-
It matches the timing of 3 (value 10) and code phase offset # 1-2 (value 10). Code phase offset # 3-2 has a score of 3 + 2 = 5, code phase offset # 2-3 has a score of 2 + 1
= 3, the code phase offset # 1-2 has a score of 1 + 2 = 3, which is 11 when combined.

Next, code phase offset # 3-3 (value 19)
, It coincides with the timing of code phase offset # 2-1 (value 19). The code phase offset # 3-3 has a score of 3 + 1 = 4, and the code phase offset # 2-1 has a score of
2 + 3 = 5, and when added together, 4 + 5 = 9. in this case
Since the maximum score of # 3-2 is 11 and exceeds the threshold of 10, the timing of this code phase offset # 3-3 (value 1
9) is the synchronization point. The larger the correlation value, the higher the probability of being the synchronization point, and the higher the correlation probability at the present point in the Mth period. Therefore, the larger the correlation value, the more By increasing the evaluation value in the M-th cycle, the synchronization point can be accurately determined.

In the above description, the value obtained by adding the weight given according to the cycle and the weight given according to the correlation value is given to each synchronization point candidate. However, a value obtained by multiplying the weight given according to the cycle and the weight given according to the correlation value (for example, the correlation value itself) may be given to each synchronization point candidate. Weights are, for example, 1.2, 1.1, 1.0 from new observations to old ones.
, The weight given to each sync point candidate is the third
In the observation cycle, each correlation value is multiplied by 1.2, in the second observation cycle each correlation value is multiplied by 1.1, and in the first observation cycle each correlation value is multiplied by 1.0. It should be noted that if the probability of being the synchronization point at the present time is known, the weights given in order are optimally set to values according to this probability. However, as long as the order becomes higher, the weight does not necessarily have to be the weight according to the probability. The weight given according to the cycle and the weight given according to the correlation value may be given the same weight in order, or different weights may be given in order. Further, the weight may be given to each synchronization point candidate without dividing the weight according to the cycle and the weight according to the correlation value.

FIG. 3 is a block diagram showing the second embodiment of the present invention. In the figure, 11 _{1 to} 11 _J are matched filters, which are similar to the matched filter of FIG. A determiner 12 includes a sync point candidate selection unit 13, a sync point candidate comparison unit 14, and a sync point candidate determination unit 15. In this embodiment, similar to the conventional technique described with reference to FIG. 10, the correlation detection is performed using the division spread code. Each of the matched filters 11 _{1 to} 11 _J has a division spread code of equal length obtained by equally dividing the spread code into J pieces as a coefficient, and inputs the received signal spectrum-spread by the spread code. Then, the detection of the correlation between the received signal and each divided spread code is performed with a divided period of 1 / J of the period of the spread code as an observation period, and a unit period (chip period or Is repeatedly sampled in parallel every cycle).

The synchronization point candidate selection unit 13 selects the matched filters 11 ₁ to 11 _{1 for} each unit cycle in each observation cycle from the first cycle to the last M-th cycle (M is an integer of 2 or more).
The correlation values of 11 _J are compared to give the correlation values of the first to Nth magnitudes, and the first to Nth offset timings are selected as synchronization point candidates and The divided spread code used for correlation detection is specified and stored. The synchronization point candidate comparison unit 14 reads out the selected synchronization point candidates, and identifies a specific matched filter and a divided spreading code that outputs the maximum correlation value among them. That is, the division spread code set in the tap coefficient of this particular matched filter is identified.

Of the selected synchronization point candidates, the offset timings from the 1st to the Nth of the Mth cycle are
The comparison reference offset timing is set in order from the largest correlation value, and the first to Nth offset timings in the observation cycle less than the Mth cycle are set as comparison target offset timings.
In each cycle, the larger the correlation value is, the higher the priority of the comparison order is, the successive comparison is performed, and the first condition is that the comparison reference offset timing and the comparison target offset timing match. Secondly, the divided spreading code used for detecting the correlation of the comparison reference offset timing and the divided spreading code used for detecting the correlation of the comparison target offset timing have continuity according to the difference in the observation period. The condition of. The second condition is that the identified matched filter, in other words, the identified spread spectrum code moves with the progress of the received signal.

When these two conditions are satisfied,
The number of coincidences of the comparison reference offset timing at that point is counted up as an evaluation value and the next priority is compared. The synchronization point candidate evaluation unit 15
When the evaluation value of each comparison reference offset timing exceeds a predetermined value, it is determined that the comparison reference offset timing at that time point is the synchronization point. At this point, further operations of the matched filters 11 _{1 to} 11 _J , the synchronization point candidate selection unit 13, and the synchronization point candidate comparison unit 4 are unnecessary, so the matched filters 11 _{1 to} 11 _J and the synchronization point candidate selection unit 13 are not necessary. Alternatively, the operation of the synchronization point candidate comparison unit 14 may be stopped.

FIG. 4 is an explanatory view showing a concrete example of the synchronization acquisition method in the embodiment shown in FIG. In this example, look up to the second correlation value to be detected, ie N =
The case of 2 is shown. In addition, this is observed for M = 2 cycles, and the synchronization point is detected with one match. Matched filter 11
_{When 1} to matched filter 11 _J perform correlation detection over the time of 1 / J of the spreading code period, a synchronization point that is synchronized with the divided spreading code is detected. The synchronization point candidate selection unit 13 observes the outputs of all the matched filters 11 _{1 to} 11 _{J in} the first observation period (1 / J period of the spread code), and extracts the timing when the value becomes the maximum value from them. . In the illustrated example, it is assumed that the maximum value is found in the code phase offset # 1-1 of the matched filter (MF # 1) 11 ₁ . Further, the matched filter having the second correlation value output and the timing thereof are the matched filter (MF # 3) 11 ₃ and the code phase offset # 1-3, respectively.

Next, the matched filter and the timing at which the correlation value output becomes the maximum value in the second observation are set as the matched filter MF # 3 and the code phase offset # 2-1, respectively. Also, the matched filter whose correlation value output is the second and the timing are respectively matched filter MF # 2,
Set as code phase offset # 2-2. After the end (second time in this example) of the observation cycle, the synchronization point candidate comparison unit 14 and the synchronization point candidate evaluation unit 15 identify the synchronization point. (1) First, the code phase offset # 2-1 with the maximum correlation value in the last (second time in this example) observation cycle, and the maximum correlation value in the previous observation (first time in this example) Compare the timing of the lost code phase offset # 1-1 and whether the matched filter is continuous (matched filter, in other words, the specified spread spectrum code is moving as the received signal progresses). . In this case, both are different.

(2) Next, the timing of the code phase offset # 1-2, which has the second correlation value in the previous observation, and whether or not the matched filter is continuous are compared. In this case, both are different. (3) Next, the timing and matched filter of the code phase offset # 2-2 with the second highest correlation value in the last observation and the code phase offset # 1-1 with the highest correlation value in the previous observation Compare whether is continuous. In this example, since the matched filters are continuous, if the code phase offsets # 2-2 and # 1-1 match, this point is set as the synchronization point. If a sync point is not detected, the same operation is performed until the final comparison of priorities, and if no sync point is found there, the observation period is slid by one or more observation periods. The above operation is repeated from the beginning. It is desirable to set a limit in advance on the number of times the correlation period is detected again by advancing the observation period by one observation cycle.

In a certain matched filter, the received signal input each time one observation period (1 / J period of the spread code) elapses is spread with a code that follows the division period. Further, the plurality of divided spreading codes from the 1st to the Jth, which are created by equally dividing the original spreading code, are matched filters 11 _{1 to} 11 _{J in} order.
Is assigned as a coefficient of. Therefore, when the synchronization is correct, one observation period (1 / J of spreading code)
The cycle of the matched filter that outputs the maximum correlation value also advances by 1 every time (cycle). In this way, the synchronization point candidate comparison unit 14 compares not only the offset timings match but also the matched filter, in other words, whether or not the order of the divided spreading codes is continuous.

The above-mentioned offset timing is the offset timing based on the phase of the divided spread code,
It is a value that is repeated in the division cycle. Therefore, in other words, the offset timing based on the phase of the original spreading code before being divided (represented by the value repeated in the spreading cycle) is the offset timing obtained in each observation cycle. It is equivalent to determining that the synchronization is acquired when the signal is changing according to the progress of the signal.

Also in this embodiment, the same partial correlation as in the first embodiment may be performed. As a tap coefficient for each of the matched filters 11 _{1 to} 11 _J , a part of each divided spreading code, for example, a code sequence at the rear of each divided spreading code is used. In this case, the lengths of the code sequences extracted from the divided spread codes are the same. The extraction method from each divided spread code is also the same. When the extraction method is different, for example, a certain spreading code from the rear code sequence,
When the preceding code sequence is extracted from another divided spread code, the coincidence of the offset timing may be determined according to the phase difference between the extracted code sequences.

The above-described specific example corresponds to the first specific example in the first embodiment described with reference to FIGS. 1 and 2. Also in the second embodiment described with reference to FIGS. 3 and 4, the second, third, and fourth concrete examples can be applied as the evaluation method in the same manner as in the first embodiment. . That is, the synchronization point candidate comparison unit 14 selects, from among the selected synchronization point candidates, the first to Nth M-th cycles.
The offset timings up to the th are the comparison reference offset timings, and the offset timings from the first to the Nth in the (M-1) th period to the first period are the comparison target offset timings. The comparison reference offset timing and the comparison target offset timing are compared in all combinations. In all combinations, the synchronization point candidate evaluation unit 15 matches the comparison reference offset timing with the comparison target offset timing, and detects the correlation between the division spread code used for the correlation detection of the comparison reference offset timing and the comparison target offset timing. With the split spreading code used for
By evaluating the continuity situation according to the difference in the observation period, it is determined that one particular comparison reference offset timing is the synchronization point. If a synchronization point satisfying the conditions cannot be detected, the observation period is advanced by sliding the observation period by one or more observation periods, and the processes of the synchronization point candidate selection step and the comparison step are repeated.

In the second embodiment, the comparison reference offset timing matches the comparison target offset timing,
And, when the division spread code used for the correlation detection of the comparison reference offset timing and the division spread code used for the correlation detection of the comparison target offset timing has continuity according to the difference in the observation period, The number of coincidences of the comparison reference offset timing at that time is counted up as an evaluation value, the evaluation value becomes the maximum among all the combinations, and the evaluation value exceeds the predetermined value. Judge that there is.

Further, in the third embodiment, in all the combinations, each offset timing of the selected synchronization point candidates is given a weight which becomes larger as the correlation value becomes larger in each cycle, and the comparison criterion is set. The offset timing and the comparison target offset timing match, and the division spread code used for the correlation detection of the comparison reference offset timing and the division spread code used for the correlation detection of the comparison target offset timing have a difference in observation period. When there is continuity according to, a value obtained by adding the weight of the comparison target offset timing at that time to the weight of the comparison reference offset timing at that time,
Count up to the evaluation value of the comparison reference offset timing, the evaluation value becomes the maximum among all combinations,
Moreover, it is determined that the comparison reference offset timing whose evaluation value exceeds a predetermined value is the synchronization point.

In the fourth embodiment, with respect to weighting, in all combinations, the offset timings of the selected synchronization point candidates increase from the first cycle to the last M-th cycle, and In each cycle, the larger the correlation value is, the larger the weight is given, and the comparison reference offset timing is evaluated in the same manner as in the third embodiment.

FIG. 5 is an explanatory diagram showing a specific example of the synchronization acquisition method according to the third embodiment of the present invention. The frame format has the same configuration as the conventional one shown in FIG. As the block configuration, the one shown in FIG. 1 is used, and the code of the preamble described above is used as the coefficient of the matched filter 1. Similar to FIG. 12, the length of the matched filter is set equal to the code length of the preamble. In FIG. 1, the matched filter 1 has a preamble code of 1 which is a code string having a predetermined code pattern.
The received signal r (t) periodically inserted at the beginning of the frame is input, and the correlation between the received signal and the code of the preamble is detected. To the Mth period), and outputs the correlation value for each chip period or for each period in which this chip period is oversampled.

Based on the result of correlation detection, the synchronization point candidate selection unit 3 gives the maximum correlation value in each observation cycle from the first first cycle of observation to the last M-th cycle. In the following order, the 1st to Nth offset timings that give the correlation value of the Nth (N is an integer of 2 or more) magnitude are selected and stored as synchronization point candidates. The synchronization point candidate comparison unit 4 reads out the selected synchronization point candidates, and compares the offset timings from the first to the Nth of the M-th cycle, in order from the largest correlation value, with the comparison reference offset. Timing. Also,
The first to N-th offset timings in the observation cycle from the (M-1) th cycle to the first cycle are set as comparison target offset timings.

At this time, the closer to the M-th cycle, and
In each cycle, the larger the correlation value is, the higher the priority of comparison is, and the successive comparison is performed. When the comparison reference offset timing and the comparison target offset timing match, the matching count of the comparison reference offset timing at that time point is counted up as an evaluation value and the next priority is compared. When the evaluation value of each comparison reference offset timing exceeds a predetermined value in the comparison process, the synchronization point candidate evaluation unit 5 determines that the comparison reference offset timing at that time point is the synchronization point. At this point, the operations of the matched filter 1, the synchronization point candidate selection unit 3 or the synchronization point candidate comparison unit 4 may be stopped.

A concrete example of the synchronization acquisition method in the third embodiment of the present invention will be described with reference to FIG. Here, an example is shown in which up to the second correlation value to be detected is viewed, that is, N = 2. Also, an example will be described in which this is observed for M = 2 cycles, and synchronization detection is performed when the comparison results match once. The synchronization point candidate selection unit 3 makes sequential observations. First, at the first observation of the first cycle, the timing at which the correlation value output reaches the maximum value (first) is code phase offset # 1-1. And Also, the timing at which the correlation value output becomes the second is the code phase offset # 1-2.
Next, in the second observation, the correlation value output is the maximum value (first) and the second timing is the code phase offsets # 2-1 and # 2-2, respectively. The synchronization point candidate comparison unit 4 and the synchronization point candidate evaluation unit 5 identify the synchronization point after the end of the last (second time in this example) observation cycle.

In the first specific example, first, the code phase offset # 2-1 with the maximum correlation value in the last (second time in this example) observation cycle and the last (first time) observation cycle are used. Compare the timing of code phase offset # 1-1 with the maximum correlation value. In this specific example, the timings do not match, so next, the timing of code phase offset # 2-1 and the timing of code phase offset # 1-2 whose correlation value became the second during the previous (first) observation cycle To compare. Since this also does not match, next, the correlation value in the last (the second time in this example) observation cycle is the second code phase offset # 2-2 and the correlation value in the previous (first time) observation cycle is the maximum. Compare with the timing of sync point candidate # 1-1. Since this also does not match, the timing of the code phase offset # 2-2, which is the last possibility, is compared with the timing of the code phase offset # 1-2, which has the second correlation value in the previous observation. In the case of this specific example, since they match and they match once, the timing of this code phase offset # 2-2 is set as the synchronization point. If they do not match at this time as well, reliability cannot be obtained, so the observation period of the matched filter output is again advanced by one observation period, the above-described operation is performed from the beginning, and similar comparison and evaluation are repeated.

It is desirable to set a limit in advance on the number of times the observation period is advanced by one observation period and the correlation is detected again. The synchronization point candidate evaluation unit 5 may detect that the timings match a plurality of times and determine that the synchronization point is the synchronization point. As the tap coefficient of the matched filter 1,
Partial correlation may be detected using a part of the code of the preamble, for example, the code sequence of the rear part. The acquisition mode described above can perform synchronization acquisition with high accuracy. Therefore, when it is determined that the synchronization is achieved, it is possible to immediately shift to the normal reception operation mode. Even if the confirmation mode is provided after the acquisition mode, the probability of returning from the confirmation mode to the acquisition mode again decreases. As is clear from the above-described example, a method for acquiring synchronization of a received signal in which a code string having a predetermined code pattern is periodically inserted in a frame unit, and a method for acquiring a synchronization of a received signal spectrum-spread by a spread code. And are essentially the same,
Therefore, although detailed description is omitted, the second to fourth specific examples described with reference to FIGS. 1 and 2 can also be applied.

FIG. 6 is a diagram in which the synchronization point detection characteristic of the synchronization acquisition method of the first embodiment is evaluated by computer simulation in the second embodiment shown in FIG. That is, the correlation detection with the division spread code is performed, the offset timing of the last cycle is set as the comparison reference offset timing in order from the top, and the offset timing in the cycles less than that is the comparison target offset timing. In each cycle, the larger the correlation value, the higher the priority of the comparison order, and the successive comparison is performed to find a match. Code length 32 as spreading code
Spreading was done with BPSK using 768 PN codes. The number of matched filters J = 8, the matched filter tap length (code length) is 64, the penalty time is 10 ⁶ chips, and the synchronization point detection time (Total acquisition time) for SNR (signal-to-noise ratio) [dB] under Gaussian noise ) [Chips] is obtained.

Only the acquisition mode is used for the proposed method,
No confirmation mode is provided. The number of correlation values output was N = 16, 32, the number of observation cycles was M = 2, and the synchronization point was determined by one match. For comparison, the synchronous acquisition characteristics of the conventional system (acquisition mode: γ ₀ = 0, confirmation mode: γ ₄ = 0.5, A = 2, B = 4) are shown by dotted lines. Here, γ ₀ = 0 means that comparison is not performed, that is, the timing of the maximum value is unconditionally selected. It can be seen that the synchronization acquisition method of the present invention is superior to the synchronization acquisition method according to the conventional technique, particularly in a place where the SNR is poor.

The value of M, which is the number of observation cycles, and / or the value of N, which is the number of correlation values that are synchronization point candidates in each observation cycle, are the SNR (signal-to-noise ratio) or the received power that changes this SNR. It may be set in advance based on the estimated value such as the level. That is, in the propagation path environment where the SNR or the received power level is low, the values of M and / or N are set to be large. According to the simulation environment shown in FIG. 6, M = 2 is fixed and N = 32 is set in an environment where the received power level is smaller than the received power level corresponding to SNR of about 13 dB. Similar to the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 3, the third embodiment shown in FIG. 5 when a code pattern is used instead of the spread code. In the same manner, the values of M and N may be similarly set according to the environment of the propagation path.

In the above description, the case where the matched filter is operated with the chip cycle of the spreading code as a unit has been described. On the other hand, there is an oversampling operation in which the matched filter is operated at a time interval of 1 / (integer) of the chip cycle. The oversampling operation can be performed also in each of the embodiments of the present invention.
Correlation detection, sync point candidate selection, sync point candidate comparison,
And, the determination of the offset timing including the synchronization point candidate evaluation is performed at an integer multiple of the chip timing of the spread code,
It may be determined that the offset timings match when they are within a predetermined range.

Specifically, the number of stages of the matched filter is a
(Integer) times, tap output is taken out at 1-chip intervals to perform correlation detection. The correlation output is the chip timing a.
Since it is output at a time interval of one-half, correlation value detection including the maximum value is also performed at this interval. Regarding the maximum value detection, the code phase offset can be known at a time interval of 1 / (integer) of the chip timing. Therefore, there are two determination methods when comparing the offset timings. The first method is chip timing a
This is a method of looking for a match at a time interval of (integer) times.
The second method is a method of determining that the offset timings are coincident with each other if the offset timing deviation is within a predetermined range, for example, within a predetermined range of less than one chip. In this example, when a = 4 times, if there is a deviation of ± 2 timings or less, it is considered that they match.

As a matched filter for detecting correlation, an analog type or digital type transversal filter, a matched filter using a surface acoustic wave element (SAW), a filter having a function equivalent to a matched filter using a SAW convolver, etc. There is. It is also possible to use a sliding correlator. DSP (Di
The matched filter may be realized by using a digital signal processor). The determiners 2 and 12 can be realized by a logic circuit, and can also be realized by using a DSP or a general-purpose MPU (Micro Processing Unit).

[0081]

As is apparent from the above description, the present invention provides the timing information in the time axis direction of the correlation output with little fluctuation, instead of setting the threshold value at the level of the correlation value with large fluctuation as in the prior art. The matched filter is used to determine the offset timing at which the maximum value is output.
Therefore, the accuracy of synchronously capturing the spread spectrum code or the code string having the predetermined code pattern is higher than that of the conventional technique, and as a result, the time required for the synchronous capture can be shortened.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a specific example of the synchronization acquisition method in the first embodiment shown in FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a specific example of the synchronization acquisition method in the embodiment shown in FIG.

FIG. 5 is an explanatory diagram showing a specific example of a synchronization acquisition method according to the third embodiment of the present invention.

FIG. 6 is a diagram showing the first embodiment in the second embodiment shown in FIG.
FIG. 6 is a diagram in which the synchronization point detection characteristics of the synchronization acquisition method of the specific example are evaluated by computer simulation.

FIG. 7 shows a direct spread spectrum spread communication system,
It is a block diagram which shows the 1st example of the conventional synchronous acquisition method.

8 is a first explanatory diagram of the synchronization acquisition method in the conventional technique shown in FIG. 7. FIG.

FIG. 9 is a second explanatory diagram of the synchronization acquisition method in the conventional technique shown in FIG. 7.

FIG. 10 is a block diagram showing a second example of a synchronization acquisition method using a conventional matched filter in direct sequence spread spectrum communication.

11 is an explanatory diagram of a synchronization acquisition method in the conventional technique shown in FIG.

FIG. 12 is an explanatory diagram showing a synchronization acquisition method using a conventional matched filter in a communication system in which preambles are periodically inserted.

[Explanation of symbols]

1, 11 _{0 to} 11 _J ... Matched filter, 2, 12 ... Judgment device, 3, 13 ... Sync point candidate selection section, 4, 14 ... Sync point candidate comparison section, 5, 15 ... Sync point candidate evaluation section

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Claims (24)

[Claims] 1. Correlation detection between a code of a part or all of spread codes and a received signal spectrum-spread by the spread code is set to a predetermined M (M is an integer of 2 or more) with the cycle of the spread code as an observation cycle. ) Correlation detection step performed in the period over the observation cycle, and based on the result of the correlation detection, in each observation cycle, the correlation value of the size from the 1st to the Nth (N is an integer of 2 or more) A synchronization point candidate selection step of selecting the first to Nth offset timings as synchronization point candidates; and, from the selected synchronization point candidates, the first to Nth M-th cycles. Of the correlation values in descending order of correlation value, and the comparison reference offset timing is set in order from the first to the Nth in each of the observation periods of the M-1th period or less. The offset timings up to are used as comparison target offset timings, and the comparison order is prioritized for those closer to the M-th cycle, and the comparison order is prioritized for those with a larger correlation value within each observation cycle for successive comparison. At the same time, when the comparison reference offset timing and the comparison target offset timing match, a comparison step of counting up the evaluation value of the comparison reference offset timing at that time point and comparing the next priority order, and during the comparison process, And an evaluation step of determining that the comparison reference offset timing at that time point is a synchronization point when the evaluation value of each comparison reference offset timing exceeds a predetermined value. 2. Correlation detection between a part or all of spread codes and a received signal spectrum-spread by the spread codes is used as a predetermined M (M is an integer of 2 or more) with the cycle of the spread codes as an observation cycle. ) Correlation detection step performed in the period over the observation cycle, and based on the result of the correlation detection, in each observation cycle, the correlation value of the size from the 1st to the Nth (N is an integer of 2 or more) A synchronization point candidate selection step of selecting the first to Nth offset timings as synchronization point candidates; and, from the selected synchronization point candidates, the first to Nth M-th cycles. The offset timings of 1 to N are used as comparison reference offset timings, and As a comparison target offset timing, a comparison step of comparing the comparison reference offset timing and the comparison target offset timing in all combinations, and by evaluating the state of coincidence between the comparison reference offset timing and the comparison target offset timing. And an evaluation step of determining that one specific one of the comparison reference offset timings is a synchronization point. 3. The evaluation step assigns a greater weight to each of the offset timings of the selected synchronization point candidates as the correlation value is larger in each cycle, and further compares the offset timings with the comparison reference offset timings. When the comparison target offset timing matches, the value obtained by adding the weight of the comparison target offset timing at the time point to the weight of the comparison reference offset timing at the time point,
It is added to the evaluation value of the comparison reference offset timing, and among all the combinations, the evaluation value is the maximum, and it is determined that the comparison reference offset timing in which the evaluation value exceeds a predetermined value is a synchronization point. The synchronization acquisition method according to claim 2, wherein 4. The evaluation step increases from the first cycle to the Mth cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. When the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time is added to the weight of the comparison target offset timing at the time. The value
It is added to the evaluation value of the comparison reference offset timing, and among all the combinations, the evaluation value is the maximum, and it is determined that the comparison reference offset timing in which the evaluation value exceeds a predetermined value is a synchronization point. The synchronization acquisition method according to claim 2, wherein 5. The correlation detection between a part or all of the divided spread codes obtained by dividing the spread code by J and a received signal spectrum-spread by the spread code is detected by the J of the cycle of the spread code. Based on the result of the correlation detection step performed in a period over a predetermined M (M is an integer of 2 or more) observation cycle with the divided cycle of 1 / O as the observation cycle, the first detection period in each observation cycle. To Nth (N is an integer of 2 or more) correlation values of magnitudes from 1st to Nth are selected as synchronization point candidates and used for correlation detection at that time. And a sync point candidate selecting step for specifying a part or all of the divided spread codes, and among the selected sync point candidates, the first to N-th OFF of the Mth cycle. Set to the comparison reference offset timing in descending order of the correlation value, and the first to Nth offset timings in each of the observation periods of M-1th period or less are set as the comparison target offset timings. The order of comparison is prioritized as the number of M cycles is closer, and the order of comparison is prioritized as the correlation value is larger in each observation period, and the comparison reference offset timing and the comparison target offset timing are compared. And a part or all of the divided spread codes used for the correlation detection of the comparison reference offset timing and a part of the divided spread code used for the correlation detection of the comparison target offset timing. Or all the signs and continuity according to the difference of the observation period When it has, the comparison step of counting up the evaluation value of the comparison reference offset timing at that time point and comparing the next priority order, and the evaluation value of each comparison reference offset timing is a predetermined value during the comparison process. And a step of evaluating when the comparison reference offset timing at that time point is a synchronization point, the synchronization acquisition method. 6. The correlation detection between a part or all of the divided spread codes obtained by dividing the spread code by J and a received signal spectrum-spread by the spread code is detected by J of the cycle of the spread code. Based on the result of the correlation detection step performed in a period over a predetermined M (M is an integer of 2 or more) observation cycle with the divided cycle of 1 / O as the observation cycle, the first detection period in each observation cycle. To Nth (N is an integer of 2 or more) correlation values of magnitudes from 1st to Nth are selected as synchronization point candidates and used for correlation detection at that time. And a sync point candidate selecting step of specifying a part or all of the divided spread codes; and among the selected sync point candidates, the first to Nth M-th cycles. The offset reference timing is the comparison reference offset timing, the offset reference timing is the comparison reference offset timing, and the first to Nth offset timings are the comparison target offset timings in each of the observation periods that are equal to or less than the (M-1) th period. A comparison step of comparing the offset timing in all combinations, a match between the comparison reference offset timing and the comparison target offset timing, and a part of the divided spread code used for correlation detection of the comparison reference offset timing Or, by evaluating the situation of continuity according to the difference in the observation period, with all or a part of or all the codes of the divided spread code used for correlation detection of the comparison target offset timing, Comparison reference offset timing Acquisition Scheme particular one of the grayed characterized by having the evaluation step determines that the point synchronization. 7. The evaluation step assigns a greater weight to each of the offset timings of the selected synchronization point candidates as the correlation value is larger in each cycle, The comparison target offset timing matches, and the division spreading used for the correlation detection of the comparison target offset timing and a part or all of the division spreading codes used for the correlation detection of the comparison reference offset timing. When some or all of the codes have continuity according to the difference in the observation cycle, the weight of the comparison reference offset timing at the time is added to the weight of the comparison target offset timing at the time. The added value is added to the evaluation value of the comparison reference offset timing, The comparison reference offset timing when the evaluation value is the maximum and the evaluation value exceeds a predetermined value is determined to be a synchronization point among all combinations. Synchronization acquisition method. 8. The evaluation step increases from the first cycle to the Mth cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. A larger weight is given to the larger one, and the comparison reference offset timing and the comparison target offset timing match each other, and a part or all of the divided spread codes used for correlation detection of the comparison reference offset timing. When the code and a part or all of the divided spread codes used for the correlation detection of the comparison target offset timing have continuity according to the difference in the observation period, the comparison at the time point is performed. A value obtained by adding the weight of the reference offset timing to the weight of the comparison target offset timing at the time The comparison reference offset timing is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all combinations, and the comparison reference offset timing in which the evaluation value exceeds a predetermined value is determined to be the synchronization point. The synchronization acquisition method according to claim 6, wherein 9. A correlation detection between a part or all of a code string having a predetermined code pattern and a received signal in which the code string having the predetermined code pattern is periodically inserted in a frame unit. , A correlation detection step performed in a period over a predetermined M (M is an integer of 2 or more) observation period with the period of the frame as an observation period, and based on the result of the correlation detection, in each observation period, A synchronization point candidate selection step of selecting correlation timings up to the N-th (N is an integer of 2 or more) and selecting offset timings from the 1st to the N-th as synchronization point candidates; Among the synchronization point candidates, the first to Nth offset timings of the Mth cycle are set as comparison reference offset timings in order from the largest correlation value. The first to Nth offset timings in each of the observation cycles of the M-1th cycle or less are used as comparison target offset timings, and the closer to the Mth cycle, the higher the priority of comparison, and Within the cycle, the larger the correlation value is, the higher the comparison priority is, and the successive comparison is performed.When the comparison reference offset timing and the comparison target offset timing match, the evaluation value of the comparison reference offset timing at the time In the comparison step of counting up and comparing the next priority, and during the comparison process, when the evaluation value of each comparison reference offset timing exceeds a predetermined value, the comparison reference offset timing at that time point is the synchronization point. An acquisition step for determining that there is Method. 10. Correlation detection between a part or all of a code string having a predetermined code pattern and a received signal in which the code string having the predetermined code pattern is periodically inserted in units of frames. , A correlation detection step performed in a period over a predetermined M (M is an integer of 2 or more) observation period with the period of the frame as an observation period, and based on the result of the correlation detection, in each observation period, A synchronization point candidate selection step of selecting correlation timings up to the Nth (N is an integer of 2 or more) and selecting offset timings from the first to the Nth as synchronization point candidates; Of the synchronization point candidates, the first to Nth offset timings of the Mth cycle are set as comparison reference offset timings, and the respective views of the M−1th cycle and below are set. A comparison step of comparing the comparison reference offset timing and the comparison target offset timing in all combinations, with the first to Nth offset timings in a cycle as comparison target offset timing; and the comparison reference offset timing. A synchronization acquisition method comprising: an evaluation step of determining that a specific one of the comparison reference offset timings is a synchronization point by evaluating a state of coincidence with the comparison target offset timing. 11. The evaluation step assigns a greater weight to each of the offset timings of the selected synchronization point candidates as the correlation value is larger in each cycle, and the comparison reference offset timing and the comparison reference offset timings. When the comparison target offset timing matches, the value obtained by adding the weight of the comparison target offset timing at the time point to the weight of the comparison reference offset timing at the time point,
The comparison reference offset timing is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all combinations, and the comparison reference offset timing in which the evaluation value exceeds a predetermined value is determined to be the synchronization point. The synchronization acquisition method according to claim 10, wherein: 12. The evaluation step increases from the first cycle to the Mth cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. When the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time is added to the weight of the comparison target offset timing at the time. The value
The comparison reference offset timing is added to the evaluation value of the comparison reference offset timing, and the evaluation value is the maximum among all combinations, and the comparison reference offset timing in which the evaluation value exceeds a predetermined value is determined to be the synchronization point. The synchronization acquisition method according to claim 10, wherein: 13. Correlation detection means, synchronization point candidate selection means,
Comparing means, and evaluating means, the correlation detection means, the correlation detection of a part or all codes of the spread code and the received signal spectrum spread by the spread code, observe the cycle of the spread code The synchronization point candidate selection means is performed in a period over a predetermined M (M is an integer of 2 or more) observation cycle as a cycle, and the synchronization point candidate selection means, based on the result of the correlation detection, from the first to Nth (in each observation cycle). N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timings are selected as synchronization point candidates, and the comparison means selects the Mth out of the selected synchronization point candidates.
The offset timings from the 1st to the Nth in the cycle are set as comparison reference offset timings in order from the largest correlation value, and the 1st to the Nth in each observation cycle of the M-1th cycle or less. The offset timings up to are the comparison target offset timings,
The closer to the M-th cycle, the higher the priority of comparison, and within each of the observation cycles, the higher the correlation value, the higher the priority of comparison, and the successive comparison is performed, and the comparison reference offset timing and the comparison target are compared. When the offset timing coincides, the evaluation value of the comparison reference offset timing at that time point is counted up and the next priority is compared, and the evaluation unit evaluates each comparison reference offset timing during the comparison process. When the value exceeds a predetermined value, it is determined that the comparison reference offset timing at that time point is a synchronization point. 14. Correlation detection means, synchronization point candidate selection means,
Comparing means, and evaluating means, the correlation detection means, the correlation detection of a part or all codes of the spread code and the received signal spectrum spread by the spread code, observe the cycle of the spread code The synchronization point candidate selection means is performed in a period over a predetermined M (M is an integer of 2 or more) observation cycle as a cycle, and the synchronization point candidate selection means, based on the result of the correlation detection, from the first to Nth (in each observation cycle). N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timings are selected as synchronization point candidates, and the comparison means selects the Mth out of the selected synchronization point candidates.
The 1st to Nth offset timings of the cycle are set as comparison reference offset timings, and
The comparison reference offset timing and the comparison target offset timing are compared in all combinations, with the first to Nth offset timings in each observation cycle equal to or less than the cycle as comparison target offset timings, and the evaluation means The synchronization acquisition device is characterized in that a specific one of the comparison reference offset timings is determined to be a synchronization point by evaluating a state of coincidence between the comparison reference offset timings and the comparison target offset timings. . 15. The evaluation unit weights the offset timings of the selected synchronization point candidates to be larger as the correlation value is larger in each cycle, and the comparison reference offset timings. When the comparison target offset timing matches, a value obtained by adding the weight of the comparison target offset timing at the time point to the weight of the comparison reference offset timing at the time point,
Evaluation value adding means for adding to the evaluation value of the comparison reference offset timing, among all the combinations, the evaluation value is the maximum, and the evaluation value exceeds the predetermined value, the comparison reference offset timing is at the synchronization point. The synchronization acquisition device according to claim 14, further comprising: a determination unit that determines that there is. 16. The evaluation means increases from the first cycle to the Mth cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. A weighting means for giving a larger weight to a larger one, when the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time point is set to the weight of the comparison target offset timing at the time point. The added value is
Evaluation value adding means for adding to the evaluation value of the comparison reference offset timing, among all the combinations, the evaluation value is the maximum, and the evaluation value exceeds the predetermined value, the comparison reference offset timing is at the synchronization point. The synchronization acquisition device according to claim 14, further comprising: a determination unit that determines that there is. 17. Correlation detection means, synchronization point candidate selection means,
Comparing means and evaluating means, wherein the correlation detecting means includes a part or all of the divided spread codes obtained by dividing the spread code into J and a received signal spectrum-spread by the spread code. Correlation detection is performed in a period over a predetermined M (M is an integer of 2 or more) observation period with a division period of 1 / J of the period of the spreading code as an observation period, and the synchronization point candidate selecting means is Based on the detection result, in each of the observation periods, the first to Nth (N (N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timing are selected as synchronization point candidates, and a part or all of the division spread codes used for correlation detection at the time point are specified, and the comparison means Of the selected synchronization point candidates, the Mth
The offset timings from the 1st to the Nth in the cycle are set as comparison reference offset timings in order from the largest correlation value, and the 1st to the Nth in each observation cycle of the M-1th cycle or less. The offset timings up to are the comparison target offset timings,
The closer to the M-th cycle, the higher the priority of comparison, and within each of the observation cycles, the higher the correlation value, the higher the priority of comparison, and the successive comparison is performed, and the comparison reference offset timing and the comparison target. Offset timing is the same, and a part or all of the division spread code used for correlation detection of the comparison reference offset timing and the division spread code used for correlation detection of the comparison target offset timing When some or all of the codes have continuity according to the difference in the observation period, the evaluation value of the comparison reference offset timing at that time point is counted up and the next priority is compared, The evaluation means, when the evaluation value of each comparison reference offset timing exceeds a predetermined value during the comparison process. Determines that the comparison reference offset timing at that time point is a synchronization point. 18. Correlation detection means, synchronization point candidate selection means,
Comparing means and evaluating means, wherein the correlation detecting means includes a part or all of the divided spread codes obtained by dividing the spread code into J and a received signal spectrum-spread by the spread code. Correlation detection is performed in a period over a predetermined M (M is an integer of 2 or more) observation period with a division period of 1 / J of the period of the spreading code as an observation period, and the synchronization point candidate selecting means is Based on the detection result, in each of the observation periods, the first to Nth (N (N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timing are selected as synchronization point candidates, and a part or all of the division spread codes used for correlation detection at the time point are specified, and the comparison means Of the selected synchronization point candidates, the Mth
The 1st to Nth offset timings of the cycle are set as comparison reference offset timings, and
The comparison reference offset timing and the comparison target offset timing are compared in all combinations, with the first to Nth offset timings in each observation cycle equal to or less than the cycle as comparison target offset timings, and the evaluation means Is a match between the comparison reference offset timing and the comparison target offset timing, and a correlation between the comparison target offset timing and a part or all of the division spread codes used for correlation detection of the comparison reference offset timing. By evaluating the continuity situation according to the difference in the observation cycle with a part or all of the divided spread codes used for detection, a specific one of the comparison reference offset timings is a synchronization point. Synchronous capture characterized by determining that there is Capture device. 19. The evaluation means, to the offset timing of the selected synchronization point candidate, a weighting means for giving a greater weight to the offset value of the correlation point, the comparison reference offset timing. And the comparison target offset timing match, and the code used to detect the correlation between the comparison target offset timing and a part or all of the division spread codes used for the correlation detection of the comparison reference offset timing When a part or all of the divided spread codes have continuity according to the difference in the observation period, the weight of the comparison reference offset timing at the time point corresponds to the comparison target offset timing at the time point. The value added with the weight is added to the evaluation value of the comparison reference offset timing. Evaluation value adding means, and judgment means for judging that the comparison reference offset timing at which the evaluation value is maximum and the evaluation value exceeds a predetermined value is a synchronization point among all the combinations. The synchronization acquisition device according to claim 18, characterized in that: 20. The evaluation means increases from the first cycle to the Mth cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. Weighting means for giving a larger weight to the larger one, the comparison reference offset timing and the comparison target offset timing match, and a part of the divided spread code used for correlation detection of the comparison reference offset timing or When all or a part or all of the divided spread codes used for correlation detection of the comparison target offset timing have continuity according to the difference in the observation cycle, The weight of the comparison target offset timing is added to the weight of the comparison reference offset timing. The evaluation value adding means for adding to the evaluation value of the comparison reference offset timing, and in all the combinations, the evaluation value is the maximum, and the comparison reference offset timing the evaluation value exceeds a predetermined value. The synchronization acquisition device according to claim 18, further comprising: a determination unit that determines that the synchronization point is reached. 21. Correlation detection means, synchronization point candidate selection means,
Comparing means and evaluating means, the correlation detecting means, the code string having a predetermined code pattern part or all of the code string, and the code string having the predetermined code pattern is cycled in units of frames. The correlation detection with the received signal that has been inserted in a predetermined period (M is an integer of 2 or more) observation period with the period of the frame as an observation period, and the synchronization point candidate selecting means detects the correlation. Based on the result of the above, in each of the observation periods, the first to Nth (N (N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timings are selected as synchronization point candidates, and the comparison means selects the Mth out of the selected synchronization point candidates.
The offset timings from the 1st to the Nth in the cycle are set as comparison reference offset timings in order from the largest correlation value, and the 1st to the Nth in each observation cycle of the M-1th cycle or less. The offset timings up to are the comparison target offset timings,
The closer to the M-th cycle, the higher the priority of comparison, and within each of the observation cycles, the higher the correlation value, the higher the priority of comparison, and the successive comparison is performed, and the comparison reference offset timing and the comparison target are compared. When the offset timing coincides, the evaluation value of the comparison reference offset timing at that time point is counted up and the next priority is compared, and the evaluation unit evaluates each comparison reference offset timing during the comparison process. When the value exceeds a predetermined value, it is determined that the comparison reference offset timing at that time point is a synchronization point. 22. Correlation detection means, synchronization point candidate selection means,
Comparing means and evaluating means, the correlation detecting means, the code string having a predetermined code pattern part or all of the code string, and the code string having the predetermined code pattern is cycled in units of frames. The correlation detection with the received signal that has been inserted in a predetermined period (M is an integer of 2 or more) observation period with the period of the frame as an observation period, and the synchronization point candidate selecting means detects the correlation. Based on the result of the above, in each of the observation periods, the first to Nth (N (N
Is an integer greater than or equal to 2) and gives a correlation value up to
The first to the Nth offset timings are selected as synchronization point candidates, and the comparison means selects the Mth out of the selected synchronization point candidates.
The 1st to Nth offset timings of the cycle are set as comparison reference offset timings, and
The comparison reference offset timing and the comparison target offset timing are compared in all combinations, with the first to Nth offset timings in each observation cycle equal to or less than the cycle as comparison target offset timings, and the evaluation means The synchronization acquisition device is characterized in that a specific one of the comparison reference offset timings is determined to be a synchronization point by evaluating a state of coincidence between the comparison reference offset timings and the comparison target offset timings. . 23. The evaluation means, for each offset timing of the selected synchronization point candidate, a weighting means for giving a greater weight to the offset value of the correlation point, the comparison reference offset timing. When the comparison target offset timing and the comparison target offset timing match, a value obtained by adding the weight of the comparison target offset timing at the time point to the weight of the comparison reference offset timing at the time point,
Evaluation value adding means for adding to the evaluation value of the comparison reference offset timing, and in all the combinations, the evaluation value is the maximum, and the evaluation value exceeds the predetermined value, the comparison reference offset timing is the synchronization point. 23. The synchronization acquisition device according to claim 22, further comprising: a determination unit that determines that 24. The evaluation means increases from the first cycle to the M-th cycle with respect to each offset timing of the selected synchronization point candidate, and the correlation value of the correlation value is increased in each cycle. When the weighting means for giving a larger weight to the larger one and the comparison reference offset timing and the comparison target offset timing match, the weight of the comparison reference offset timing at the time point and the weight of the comparison target offset timing at the time point The value obtained by adding
Evaluation value adding means for adding to the evaluation value of the comparison reference offset timing, and in all the combinations, the evaluation value is the maximum, and the evaluation value exceeds the predetermined value, the comparison reference offset timing is the synchronization point. 23. The synchronization acquisition device according to claim 22, further comprising: a determination unit that determines that