JP2005039570A - Method for preventing synchronization pull-in to interference wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing acquisition of synchronization with an interference wave, which enhances the holding capability of a synchronous position based on window ranges and thresholds not to acquire synchronization with the interference wave. <P>SOLUTION: In the method for preventing synchronization pull-in to an interference wave, correlation values between a preliminarily prepared synchronizing word and a received synchronizing word are calculated, a maximum correlation value of calculated correlation values is defined as a first maximum correlation value, a prescribed window range is provided before and after the first maximum correlation value, and the first maximum correlation value is compared with a first prescribed threshold. The first maximum correlation value is defined as a synchronous position when the former is the larger. When the former is equal to or larger than the first prescribed threshold, maximum one of calculated correlation values on the outside of window ranges is defined as a second maximum correlation value, and the second maximum correlation value is compared with a second prescribed threshold. When the former is the larger, the first maximum correlation value is defined as a synchronous position. When the second maximum correlation value is equal to or larger than the second prescribed threshold, the end of reception of the received synchronizing word is decided to perform synchronization terminating processing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a synchronization pull-in method for synchronizing a receiver with a transmitter in transmission of digital information.

Frame synchronization schemes that reduce the amount of frame timing offset due to delayed waves have also been proposed under Rayleigh fading and multipath fading environments. If a window of a certain range is set as the correlation value and the maximum correlation value is continuously detected within the range, it is determined that synchronization is maintained (see, for example, Patent Document 1).
JP-A-8-56218 (page 4, paragraph 0013)

A conventionally used synchronization method is a digital modulation signal, for example, FDM-DPSK (frequency division multiplex-differential phase), in the modulator 331 and the demodulator 332 included in the modem 330 of the data transmission apparatus shown in the block diagram of FIG. It is used as a synchronization method in demodulation in a modulation scheme such as shift keying) and 16QAM (quadture amplitude modulation).
As shown in the waveform diagram of the correlation value calculation result in FIG. 4, the synchronization processing in the demodulation processing when the modulated wave is received as a synchronization method is conventionally calculated as shown in FIG. When the above result is detected as the threshold value 41 or more in the window range 44, the position of the maximum correlation value 42 is set as the synchronization position 43, and a predetermined synchronization pull-in process is performed as if there is no interference.
On the other hand, by providing the window range 44, even if a maximum correlation value that is less than or equal to the threshold value 41 appears in the outside window range due to interference or the like, an erroneous synchronization position is detected for the maximum correlation value in such an outside window range However, as shown in FIG. 4J, a large level of interference occurs, the threshold value 41 is exceeded in the out-of-window range, and When the maximum correlation value 45 that is detected as a level equal to or greater than the maximum correlation value 42 is calculated as the correlation value, the position of the maximum correlation value of the interference wave is synchronized as the synchronization position 46 that is regarded as a predetermined synchronization position. It was like pulling in.

  In the initial synchronization pull-in, interference occurs after the synchronous pull-in process is performed with the position of the predetermined maximum correlation value as the synchronization position. Due to the interference, the predetermined threshold is exceeded and the predetermined maximum correlation is exceeded in the out-of-window range. When the maximum correlation value due to the interference wave, which is detected as a value exceeding the value, is calculated, the synchronization is drawn so that the position of the maximum correlation value due to the interference wave is erroneously regarded as a predetermined synchronization position. There was a problem.

  The object of the present invention is to solve the above-mentioned problem and to obtain the synchronization reliability of the data transmission apparatus, and to enhance the synchronization position holding ability by the window range and the threshold value, and to synchronize with the interference wave at the time of interference. An object of the present invention is to provide a method for preventing synchronization pull-in to interference waves that are not pulled in.

  The method of preventing synchronization pull-in to an interference wave of the present invention is provided in advance in order to perform synchronization processing between a synchronization word provided in advance on the receiving side for receiving and demodulating a digital modulation signal and the received synchronization word. The correlation value between the received synchronization word and the received synchronization word is calculated, the maximum correlation value among the calculated correlation values is set as the first maximum correlation value, and before and after the first maximum correlation value Providing a predetermined window range, comparing the first maximum correlation value with a first predetermined threshold, and if the first maximum correlation value is greater than the first predetermined threshold, When the first maximum correlation value is a synchronization position, and the first maximum correlation value is equal to or less than the first predetermined threshold, the maximum correlation value out of the calculated correlation values outside the window range is A second maximum correlation value, and the second maximum correlation value and a second predetermined threshold. When the second maximum correlation value is greater than the second predetermined threshold value, the first maximum correlation value is set as a synchronization position, and the second maximum correlation value is the second maximum correlation value. In the case where it is equal to or less than a predetermined threshold value, the above problem is solved by providing that the synchronization end processing is performed by regarding the reception end of the received synchronization word.

  By implementing the present invention, it is possible to prevent erroneous synchronization pull-in with respect to the interference wave at the time of interference, and a predetermined synchronization position is ensured even during and after interference, thereby improving synchronization reliability in the data transmission apparatus. Can be achieved.

  As shown in the flowchart of FIG. 1, the embodiment of the present invention is based on a correlation operation between a predetermined synchronization word and a received synchronization word provided in advance on the receiving side for receiving and demodulating a digital modulation signal. For the synchronization process for establishing synchronization, there is first a step 10 for starting the synchronization process, and then a step 11 for calculating a correlation value between a predetermined synchronization word provided in advance and the received synchronization word. Next, a window internal range having a predetermined timing range is provided at positions before and after the first maximum correlation value searched and detected from the correlation value calculation results. There is a correlation value search step 12, and then a “first maximum correlation value> threshold value” determination step 13 for determining whether or not the first maximum correlation value exceeds a first predetermined threshold value. Yes, here If the result of the determination step 13 of “maximum correlation value of 1> threshold value” is true (Y), then, the dependent synchronization pull-in control is performed so that the timing position of the first maximum correlation value is the synchronization position. On the other hand, if the result of the determination step 13 of “first maximum correlation value> threshold value” is false (N), the maximum correlation value of the out-of-window range that exists outside the in-window range is next There is a step 15 for searching, and then it is determined whether or not the second maximum correlation value detected in the maximum correlation value searching step 15 for the out-of-window range exceeds a second predetermined threshold value. There is a step 16 of “correlation value> threshold” determination, and if the result of the “second maximum correlation value> threshold” determination step 16 is true (Y), the second maximum correlation value is interference. The synchronization position obtained from the first maximum correlation value, assuming that it is due to the influence of the wave There is a step 17 in which control is performed to switch to independent synchronization, and if the result of the determination of “second maximum correlation value> threshold value” is false (N), the received synchronization word This is step 18 in which the synchronization processing is terminated by regarding the end of reception.

Next, FIG. 2 shows waveform diagrams (A) to (G) of the correlation value calculation results. Here, each correlation value waveform obtained as a result of calculating a correlation value according to the situation of a predetermined received wave and interference wave will be described.
First, FIG. 2A shows a waveform of a correlation value calculation result that does not cause interference and can perform a predetermined synchronization control operation. The predetermined synchronization control operation is the same as in the description of the prior art, and a maximum correlation value 22 exceeding the first predetermined threshold value 21 is detected at a substantially central position of the window range 24, and the synchronization position is determined by this maximum correlation value 22. Dependent synchronization in which synchronization pull-in is performed to obtain 23.
Next, as shown in FIGS. 2B and 2C, a maximum correlation value 22 that exceeds the first predetermined threshold value 21 is preliminarily provided at approximately the center position of the window range 24. First, (B) is a result of the correlation value calculation, due to interference in a range other than the window range 24 (outside window range) and not exceeding the second predetermined threshold value 21. 6 is a waveform diagram having a maximum correlation value 25. FIG. Next, (C) shows that the maximum correlation value in the out-of-window range generated by strong interference exceeds the second predetermined threshold value 21 and has a level equal to or higher than the maximum correlation value 22 at the predetermined synchronization position. It is a waveform diagram at the time of strong interference such that the maximum correlation value 26 appears. Here, a synchronous pull-in control operation for subordinate synchronization is performed so that the maximum correlation value position in the initial synchronization is set as the synchronization position so that the synchronization position 23 is secured.
Next, FIG. 2 (D) shows that the maximum correlation value 28 in the window range 24 is subjected to level suppression due to interference, etc. due to the strong interference, and the level falls below the first predetermined threshold value 21. It is a waveform diagram that results in the presence of a maximum correlation value 30 that exceeds the second predetermined threshold value 21 due to interference waves in the outer range 29.
In this case, the control is performed so that the synchronization position 23 can be held by the window range 24 from the initial synchronization, and then the window range is set and the window inner range 27 and the first predetermined threshold value are set. Although the maximum correlation value search is continued even when the value is 21 or less, since the maximum correlation value 28 is provided even when the value is equal to or less than the first predetermined threshold value 21, the second predetermined value generated in the outside window range 29 is obtained. The synchronization position holding control operation called independent synchronization that operates so as to hold the synchronization position 23 of the initial synchronization is not drawn into the maximum correlation value 30 by the interference wave exceeding the threshold value 21 as the synchronization position. is there.
Next, FIG. 2E shows the maximum of both the maximum correlation value 31 due to interference that is equal to or less than the second predetermined threshold value 21 in the outside window range 29 and the maximum correlation value 28 in the window range 27. It is a waveform diagram in which a correlation value exists. In particular, the maximum correlation value 28 in the in-window range 27 is further reduced below the first predetermined threshold value 21 and can be regarded as the end of reception of the synchronization word. Control at this time is the synchronization of synchronization control. The control is to end the position holding.
Finally, as shown in FIGS. 2 (F) and 2 (G), when the transmission of the transmission signal of the modulated wave is stopped and the reception signal disappears, first, (F) The correlation value calculation waveform 32 near the synchronization position timing is a waveform diagram in which the maximum value is not detected and the window range is not formed. The control is an operation of waiting for the start of the initial synchronization processing because the end of modulated wave transmission is detected even if the maximum correlation value 33 in interference exceeds the second predetermined threshold value 21.
Similarly, (G) is a waveform diagram when the modulation wave transmission has been completed, the window range is not formed, there is no interference, and the maximum correlation value between the two cannot be obtained. In the control, the correlation value calculation waveforms 32 and 34 are in a standby state for a reception signal because a predetermined reception signal is not received. This is a control operation for waiting for the start of the initial synchronization processing.
As described above, the present invention is based on the correlation calculation result between a predetermined synchronization word provided in advance on the receiving side and the received synchronization word, and determines whether or not there is an interference wave. The maximum correlation value in the window inner range and the window outer range is searched while distinguishing from the transmission time, and the first predetermined or second predetermined threshold value or more, the first predetermined or second This is a control method in which determination below a predetermined threshold value can be performed individually in the window inner range and the window outer range.
In addition, after the initial synchronization is established, even when the maximum correlation values that exceed the respective threshold values occur in both the in-window range and the outside-window range, it is determined that the maximum correlation value is on the interference side. Thus, it is possible to perform control such that the initial synchronization holding is continued. Further, when the maximum correlation value is equal to or smaller than the second predetermined threshold value in the outside window range, the synchronization holding is terminated.

In each processing step of processing steps 10 to 18 in the flowchart of FIG. 1, which correlation value waveform of correlation value waveforms (A) to (G) of FIG. 2 correlation value calculation result corresponds to which processing step will be described. The control operation of the present invention will be further clarified.
First, in step 10 “start synchronization process”, the received word input process is started. In step 11 “correlation value calculation”, all correlation value calculation waveforms (A) to (G) correspond to the processing results, and then In the processing of step 12 “maximum correlation value search within the window range”, the maximum correlation value waveforms (F) and (G) calculated and detected in the outside window range are excluded, and the correlation waveforms (A) to ( If the correlation value calculation waveform narrowed down to E) corresponds, and further proceeds to determination step 13 “maximum correlation value> threshold value”, and this determination processing result is true (Y), (A), (B ) And (C) correspond to each other, and thereafter, the process proceeds to the process of step 14 “the position of the maximum correlation value is the synchronization position”, while in the determination step 13 “maximum correlation value> threshold value”. If the result of the determination process is false (N), the maximum correlation value waveforms of (D) and (E) Then, the process proceeds to step 15 “maximum correlation value search within window range” and determination step 16 “maximum correlation value> threshold value”. If this result is true (Y), the maximum of (D) The correlation value waveform corresponds, and then the process proceeds to step 17 “synchronization position maintenance”. If the previous determination processing result is false (N), the maximum correlation value waveform of (E) corresponds, and finally step 14 At the same time as the process of step 17 and proceeding to step 18 “end of synchronization process”, the synchronization control process is completed.

The synchronization method at the time of demodulation in the modulation schemes of FDM-DPSK and 16QAM replaces each maximum correlation value search of the in-window range and the out-of-window range by calculating the correlation value and obtains the phase change amount between one symbol of the received signal. A method for searching for each maximum phase change amount in the inner range and the outside window range, that is, a phase change calculation method instead of the correlation value calculation method may be used.
Needless to say, the process of determining the window range is not limited to the demodulator 332 (see FIG. 3), but can be performed by the sign changer 320.

  The present invention is used in a communication business using a data transmission apparatus in wireless communication accompanied by radio wave propagation disturbance.

It is a flowchart figure showing the processing step of the method of this invention. It is a wave form diagram showing the correlation value calculation result of the method of the present invention. It is a block diagram of a data transmission apparatus. It is a wave form diagram showing the correlation value calculation result of the conventional method.

Explanation of symbols

10 to 18 processing steps 21 first predetermined or second predetermined threshold value 41 threshold value 22, 25, 26, 28, 30, 31, 33, 42, 45 maximum correlation value 23, 43, 46 synchronization Position 24, 44 Window range 27 Window range 29 Window outside range 310 Data input / output unit 320 Transformer 330 Modem 331 Modulator 332 Demodulator 340 Transmitter, receiver

Claims (1)

In order to perform synchronization processing between the synchronization word provided in advance on the receiving side for receiving and demodulating the digital modulation signal and the received synchronization word,
Calculating a correlation value between the synchronization word provided in advance and the received synchronization word;
The maximum correlation value among the calculated correlation values is set as a first maximum correlation value,
Providing a predetermined window range around the first maximum correlation value;
Comparing the first maximum correlation value with a first predetermined threshold;
If the first maximum correlation value is greater than the first predetermined threshold, the first maximum correlation value is set as a synchronization position;
When the first maximum correlation value is equal to or less than the first predetermined threshold, the maximum correlation value out of the calculated correlation values outside the window range is set as a second maximum correlation value;
Comparing the second maximum correlation value with a second predetermined threshold;
If the second maximum correlation value is greater than the second predetermined threshold, the first maximum correlation value is set as a synchronization position;
When the second maximum correlation value is less than or equal to the second predetermined threshold value, the reception of the received synchronization word is regarded as the end of reception, and a synchronization end process is performed. Prevention method.

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