JPH07297816A - Data demodulation system - Google Patents

Abstract

PURPOSE:To easily settle synchronism by synchronizing word detection in the early stage after the time, when decoding is properly synchronized in accordance with the quality of the reception line, With a simple circuit constitution. CONSTITUTION:A control part 7 sets an initial value N to an error tolerance rate setting part 6 to prepare for input of a reception signal. When acquisition of synchronism based on synchronizing word detection is not reported from a synchronism discriminating part 5 within a prescribed time after a decoding synchronism detection part 3 detects decoding synchronism, the control part 7 sets the initial value N to larger one; and when acquisition of synchronism based on synchronizing word detection is not reported from the synchronism discriminating part 5 within a prescribed time, the set value to the error tolerance rate setting part 6 is changed to larger one in the same manner. A maximum value of the set value is preliminarily determined, but normally, synchronism is acquired by the synchronizing word before the maximum value is attained. Thus, communication is possible even if the line quality is considerably degraded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data demodulation system for demodulating frame-structured data using a sync word, and more particularly to a system for optimally detecting a sync word in accordance with the degree of deterioration of reception line quality.

[0002]

2. Description of the Related Art As a method for demodulating frame-structured data using a synchronization word, a method shown in FIG. 3 has been conventionally known. In FIG. 3, the reception signal applied to the input terminal is demodulated by the demodulation unit 1 and is separated by the separation unit 9 via the decoding unit 2.
In addition to the above, it is also input to the synchronization word detecting unit 4.

Various error tolerance rates are stored in the data storage section 8, and the error tolerance rate setting section 6 includes a data storage section 8.
A predetermined error tolerance N is taken out from and is given to the synchronization word detecting unit 4.

The synchronization word detection unit 4 detects a synchronization word from the output of the demodulation unit 1 on the basis of the error tolerance N for frame synchronization. The synchronization determination unit 5 determines whether or not the synchronization by the synchronization word has been established depending on whether the output of the synchronization word detection unit 4 is “detection of synchronization word” or “non-detection of synchronization word”.

When the output of the sync word detecting section 4 indicates "sync word detection" and the output of the sync determining section 5 indicates "synchronization by sync word", the separating section 9 decodes the decoding section 2 Received data is extracted from the output of and output to the output end.

Here, as the error tolerance rate of the sync word which gives the reference for frame synchronization, a value is used which can be regarded as the sync word even if the sync word has any error due to a bit error due to deterioration of the receiving line quality. In the method of FIG. 3 in which the error tolerance rate of the synchronization word is fixedly set to a certain value, the demodulation section and the decoding section are synchronized when the reception line quality significantly deteriorates during communication, but the synchronization word There is a possibility that the synchronization cannot be achieved due to the above. In such a case, the frame cannot be detected, so that it becomes impossible to receive the frame.

Therefore, conventionally, for example, as shown in FIG. 4, a receiving line quality measuring unit 10 and a control unit 11 are provided, and the receiving line quality measuring unit 10 measures the receiving line quality from the synchronization state of the decoding unit 2. Based on this, the control unit 11 changes the error allowance rate given to the error allowance rate setting unit 6 from the initial value N so that communication can be performed in a state suitable for the reception line quality (for example, Japanese Patent Laid-Open No. 63-33031). Issue).

[0008]

However, in the method of measuring the receiving line quality shown in FIG. 4, the receiving line quality measuring section must be composed of a counter or the like for the measurement, and the circuit becomes complicated. There is a problem of large scale. This method is also effective to prevent the synchronization from being lost after the synchronization is detected, but as a measure to establish the synchronization by the synchronization word detection in the initial stage after the decoding synchronization is obtained. There is also the problem that is not effective.

The present invention has been made in view of the above problems, and an object thereof is to easily perform synchronization by detecting a synchronization word in the initial stage after decoding synchronization is obtained according to the reception line quality with a simple circuit configuration. An object of the present invention is to provide a data demodulation method that can be established and thus enables optimum communication according to the reception line quality without directly measuring the reception line quality.

[0010]

In order to achieve the above object, the data demodulation system of the present invention has the following configuration. That is, the data demodulation method of the present invention is a data demodulation method for demodulating frame-structured data using a synchronization word;
A means for detecting the presence / absence of synchronization of the decoding unit; the presence / absence of decoding synchronization and the presence / absence of synchronization by the synchronization word detection based on the error tolerance are monitored, and the synchronization by the synchronization word detection is performed within a predetermined time after the decoding synchronization is obtained. When it is not possible, the control means for resetting the error tolerance rate from the initial value to a large value is provided.

Here, the control means can also be configured to repeatedly change the setting of the error tolerance rate within a range up to the maximum value at predetermined time intervals. It should be noted that the control means returns the setting value of the error tolerance rate to the initial value when the synchronization is lost after the synchronization by the synchronization word detection is obtained or when the decoding synchronization is lost after the decoding synchronization is obtained. .

[0012]

Next, the operation of the data demodulating system of the present invention configured as described above will be described. According to the present invention, a simple operation of monitoring the presence / absence of decoding synchronization and the presence / absence of synchronization by detecting a synchronization word based on an error tolerance rate allows early detection of the synchronization word after the decoding synchronization is properly obtained according to the reception line quality. It is easy to establish synchronization by. Therefore, since it is not necessary to provide a line quality measuring unit, the circuit can be simplified and downsized, and even if the reception line quality is significantly deteriorated, communication can be performed and optimum communication can be performed according to the reception line quality.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a data demodulation method according to an embodiment of the present invention. 1, in the present invention, a decoding synchronization detecting unit 3 for detecting the presence or absence of synchronization of the decoding unit 2 is provided in place of the reception line quality measuring unit 10 in FIG. 4, and a control unit 7 is provided in place of the control unit 11 for control. The output of the decoding synchronization detection unit 3 and the output of the synchronization determination unit 5 are given to the unit 7.

Although the control unit 7 takes out the initial value N of the error tolerance rate from the data storage unit 8 and gives it to the error tolerance rate setting unit 6 to prepare for input of the received signal, it is the same as the conventional one. According to the invention, the output of the decoding synchronization detecting unit 3 (presence or absence of decoding synchronization) and the output of the synchronization determining unit 5 (presence or absence of synchronization by detecting synchronization word) are monitored, and the synchronization word is detected within a predetermined time after the decoding synchronization is obtained. When the synchronization cannot be achieved due to, the error tolerance is reset from the initial value N to a large value.

Here, the number of times the setting value is changed is arbitrary, but it is arranged so that the synchronization can be achieved by the detection of the synchronization word at an early stage after the decoding synchronization is properly established in accordance with various levels of the receiving channel quality. 2 is suitable for the method shown in FIG.

As shown in FIG. 2 (a), the decoding synchronization detecting section 3 sets the output to a low level when the decoding section 2 is not synchronized, and outputs when the decoding section 2 is in the synchronization state. To a high level.

The control unit 7 outputs an initial value N of the error tolerance rate to the error tolerance rate setting unit 6 in preparation for the input of the received signal, and monitors whether the output of the decoding synchronization detection unit 3 rises to a high level. Next, when the output of the decoding synchronization detection unit 3 rises to a high level, the output content of the synchronization determination unit 5 is monitored for a predetermined time T ₀ thereafter, and the content is "synchronized by synchronization word detection". , The initial value N is held as it is, but when the output of the synchronization determination unit 5 does not indicate that “synchronization has been achieved by the detection of the synchronization word”, the error allowable rate setting unit is held for a predetermined time T ₁ thereafter. The error tolerance for 6 is the initial value N
To N + n ₁ (n ₁ ≧ 1), and the synchronization determination unit 5
Monitor the output content of.

Then, when the synchronization by the post-synchronization detection is not achieved during the predetermined time T ₁ , the control unit 7 further increases the error tolerance rate from N + n ₁ to a larger N + n ₂ (for a predetermined time T ₂ thereafter). The value of n is increased at predetermined time intervals such that the setting is changed to (n ₂ > n ₁ ). A maximum value N + M is set for N + n to be changed and set, which is normally 1/2 or less of the number of symbols of the synchronization word. Note that the time T _i (i
Needless to say, = 0, 1, 2, ...) And the value n _j (j = 1, 2, ...) Are appropriately determined according to the system.

In many cases, synchronization can be achieved by detecting the synchronization word within the range up to the maximum value N + M, but depending on the degree of deterioration of the receiving line quality, the synchronization word detection may not be achieved and the maximum value N + M can be reached. is there. In this case, communication cannot be performed and there is no choice but to wait for the recovery of the line quality. However, the range in which synchronization can be achieved by the detection of the synchronization word is considerably wider than in the conventional case where the initial value N is fixed. Even in a wide range, the synchronization can be properly established by detecting the synchronization word according to the reception line quality.

When the decoding unit 2 is in the synchronization state, the synchronization is lost by the detection of the synchronization word, that is, 1
If the quality of the receiving line deteriorates rapidly in the middle of the transmission frame, the error tolerance setting value is returned to the initial value N and the recovery of the receiving line product is waited. When the decoding synchronization is lost after the decoding synchronization is achieved, that is, when one transmission frame is completed, the setting value of the error tolerance rate is returned to the initial value N to prepare for the input of the next received signal.

[0021]

As described above, in the data demodulation method of the present invention, the presence or absence of decoding synchronization and the presence or absence of synchronization by the synchronization word detection based on the error tolerance are monitored, and the predetermined time after the decoding synchronization is obtained. If synchronization cannot be achieved due to the detection of the synchronization word, the error tolerance is reset from the initial value to a large value, so a simple operation can be performed early after decoding synchronization is properly established according to the reception line quality. It is possible to easily establish synchronization by detecting the synchronization word in. Therefore, since it is not necessary to provide a line quality measuring unit, the circuit can be simplified and downsized, and even if the reception line quality is significantly deteriorated, communication can be performed and optimum communication can be performed according to the reception line quality. is there.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a data demodulation method according to an embodiment of the present invention.

FIG. 2 is a time chart for explaining an operation of establishing synchronization by detecting a synchronization word at an early stage after the establishment of decoding synchronization of the present invention.

FIG. 3 is a configuration block diagram of a conventional data demodulation method.

FIG. 4 is a configuration block diagram of a conventional data demodulation method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 demodulation section 2 decoding section 3 decoding synchronization detection section 4 synchronization word detection section 5 synchronization determination section 6 error tolerance rate setting section 7 control section 8 data storage section 9 separation section

Claims (4)

[Claims] 1. A data demodulation method for demodulating frame-structured data using a synchronization word; a means for detecting the presence or absence of synchronization of a decoding unit; a presence or absence of synchronization by detection of a synchronization word based on the presence or absence of decoding synchronization and an error tolerance rate. And a control means for resetting the error tolerance rate from an initial value to a large value when the synchronization by the synchronization word detection cannot be established within a predetermined time after the decoding synchronization is established. Data demodulation method. 2. The data demodulation system according to claim 1, wherein the control means repeatedly changes the setting of the error tolerance rate within a range up to the maximum value every predetermined time. 3. The control means resets the setting value of the error tolerance rate to the initial value when the synchronization is lost after the synchronization by the synchronization word is obtained. Data demodulation method. 4. The control means resets the set value of the error tolerance rate to the initial value when the decoding synchronization cannot be established after the decoding synchronization is established.
Data demodulation method described in.