JPH04100433A - Method for discriminating out-of-synchronism frame - Google Patents

Abstract

PURPOSE:To improve the discriminating probability of out-of-synchronism by finding the cumulative value of error rates at the time of frame synchronization and the cumulative value of the same pattern as that of the frame synchronizing time at the time of frame non-synchronization at every bit number and discriminating out-of-synchronism when the sum found at every bit number is small. CONSTITUTION:The bit number of a frame synchronizing signal is set to, for example, 16 bits. When the error rate is high in a frame synchronized state, the bit number of errors is found by Monte Carlo method and the values are summed from a 16-bit error. The then data and their characteristic line become Line A of the figure. Then the sum of the numbers of bits having the same patterns as that of frame synchronization is taken under a condition where frames are not synchronized and a characteristic line B is obtained. The lowest points of the lines A and B respectively represent the smallest synchronized and non-synchronized states. Therefore, when errors of 4 bits continue for (n) times, the occurrence of out-of-synchronism is discriminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a frame synchronization system in which frame synchronization is detected based on frame synchronization pattern matching rate in a digital communication system such as a satellite broadcasting signal that has frame synchronization. The present invention relates to a method for determining out-of-synchronization.

[Prior Art] In a digital communication system that uses a carrier wave having a frame synchronization signal, if the C/N ratio decreases, errors will also occur in the frame synchronization pattern. Furthermore, when the C/N ratio increases and frame synchronization is lost, the error rate of the frame synchronization pattern increases rapidly.

In the frame synchronization process, the following two points are important.

(1) In a state where the error rate is high, do not judge that frame synchronization is lost even though frame synchronization is established.

(2) It must be possible to immediately determine if frame synchronization is lost in a state with a high error rate.

However, in the conventional frame synchronization loss, if even one bit of the frame synchronization pattern is incorrect, it becomes an error frame, and when the number of consecutive error frames reaches a certain number, it is detected as a frame synchronization loss.

``Problem to be solved by the invention'' Therefore, in the conventional method, even when the error rate was high, it was necessary to set the consecutive number of times in order to prevent it from being mistakenly determined to be out of frame synchronization. .

Therefore, even if synchronization really occurred, the frame synchronization could not be detected.

An object of the present invention is to provide a method that can effectively detect frame synchronization even when the number of consecutive error frames is reduced as much as possible.

"Means to solve problems" The present invention provides an integrated value of error rates during frame synchronization.

This is a frame synchronization determination method in which an integrated value of the same pattern as frame synchronization when frames are out of synchronization is obtained for each number of bits, and out-of-synchronization is determined when the sum of each number of bits is small.

"Example" An embodiment of the present invention will be described below.

Assume that the number of bits of the frame synchronization signal is, for example, 16 bits.

(1) When frame synchronization is established and the error rate is high, use the Monte Carlo method to determine how many bit errors occur, and integrate the value from 16-bit errors. Then,
The data at that time and its characteristic line are shown as in FIG. 1(A).

(2) In a state where frame synchronization is not achieved, calculate how many bits have the same pattern as frame synchronization. Then, the data at that time and its characteristic line are shown as shown in FIG. 1(B).

The smallest points of these characteristic lines (A) and (B) are the smallest points of the synchronous state and the asynchronous state. Specifically, this occurs when the number of bits is 4 in FIG. Therefore, it is determined that frame synchronization has been lost when the number of times in which 4 or more bits are incorrect is consecutive n times.

"Effects of the Invention" As described above, in the present invention, it is determined that frame synchronization has been lost when the number of times of multiple focus errors is n times in a row. Therefore, the probability of determining that the frame is out of synchronization even though the frame is synchronized is 1 as in the conventional case.
This is significantly smaller than a method in which it is determined that frame synchronization has been lost when the number of bits or more is incorrect is n times in a row.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram based on data accumulated by the Monte Carlo method. same

Claims (1)

[Claims] (1) Calculate the integrated value of the error rate during frame synchronization and the integrated value of the same pattern as frame synchronization during frame asynchronization for each number of bits, and determine out-of-synchronization when the sum of each number of bits is small. A method for determining frame synchronization.