JPS63283248A - Method for sampling bit synchronization - Google Patents

Abstract

PURPOSE:To correctly sample information data even when code distortion exists, by finding the central position of a synchronizing code at the rear side of a synchronizing pattern, and performing the sampling of the data setting the position as reference. CONSTITUTION:The sampling of the information data is performed by finding the central position of the synchronizing code by measuring the width of the synchronizing code at the rear side of the synchronizing pattern, and setting a sampling point for bit synchroni zation hereafter based on the central position. In other words, the leading point to of the synchronizing code 1B' is found, and next, the length(width) of the code T-DELTAT is found. Next, the central position Po' is found by multiplying the value(=T-DELTAT) by 1/2, and a first sampling point P1' is decided by setting the central point as reference, and hereafter, the sampling of the data is performed according to a sampling cycle. Therefore, the sampling point coincides with a code center.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sampling method for bit synchronization in a frame-synchronized cyclic digital information transmission system used in a centralized supervisory control system or the like.

[Conventional technology]

Conventionally, in a frame-synchronized data transmission system, bit synchronization between transmitting and receiving devices is performed independently of each other, and frame divisions are matched using a synchronization pattern (synchronization word). The synchronization pattern is 1/2 as shown in Figure 3.
A string of 'O's (usually 42) longer than the word length with 1's before and after (synchronization code IA).

1B). Then, the bit synchronization between the transmitting and receiving devices is as shown in FIG.
1'', that is, the rising time t0 of the synchronization code IB, is determined based on the internal transmission loss of the receiving device, and the next sampling point Pl is set after a long time of (T+1) bits has elapsed since this time t. This is done by sampling over a long period.

[Problem that the invention seeks to solve]

However, in this method, if the line distortion is the same amount before and after the synchronization code divided by the isochronous distortion that occurs, then the distortion of the later synchronization code IB (reference code) is equal to the sampling deviation. Become.

Since this is added to the internal transmission lock deviation between the transmitting and receiving devices, there is a problem in that line distortion directly affects bit synchronization.

That is, when there is no code distortion in the synchronization code IB, as shown in FIG. 4, the data sampling point P1. P2 coincides with the code center, but if the synchronous code IB becomes like IB in FIG. 5 due to code distortion, its sampling point will also shift like Pl. This relationship is expanded and explained in Fig. 6. For the synchronous code IB, which has an isochronous distortion of ΔT/2 before and after the synchronous code IB, Po is the first sampling point P1. This is called the reference position, and it can be seen that there is a deviation of ΔT from the original position (Po).

Although the case where the synchronization code becomes narrow due to isochronous distortion has been described above, it goes without saying that the same problem occurs when the synchronization code becomes wide.

Therefore, an object of the present invention is to provide a sampling method that can minimize the influence of code distortion.

[Means for solving problems]

In order to achieve bit synchronization in a frame-synchronized digital information transmission system, the width of the synchronization code on the rear side of the synchronization pattern is measured to find its center position, and based on that center position, the sampling point for subsequent bit synchronization is determined. Configure and sample information data.

[Effect]

By taking advantage of the fact that line distortion is isochronous distortion and determining the center of the reference code from the length and width of the reference code, the influence of code distortion on bit synchronization sampling is eliminated. In other words, the distortion of the reference symbol is ±ΔT
If so, this is the leading edge.

1/2 is added to the trailing edge, and the total amount is T±ΔT. According to the conventional sampling point determination method, 1
Since the bit length is T, the sampling point is 1/2T, and the correct sampling point is 1T-
1 knee! -A deviation occurs with respect to ΔT. however,
In the above manner, since the length of the reference code is T±ΔT, the sampling point becomes 1 (T±ΔT), which coincides with the correct sampling point. Therefore, the deviation of the sampling point due to the apparent sign distortion is corrected.

〔Example〕

FIG. 1 is an explanatory diagram for explaining the invention in detail.

This is an example where the synchronization code is narrowed like IB due to code distortion ΔT, and the sampling points are set as follows.

That is, first, the rising point t of the synchronization code IB.

Then, find its length (length and width) T - ΔT.

Next, this value (-T-ΔT) is halved to obtain the center position [Po, and using this as a reference point, the first sampling point PI is determined. From then on, data is sampled according to the sampling period. In other words, in the past, the next sampling position was determined based on the rising position of the synchronization code, resulting in a deviation as shown in Figures 5 and 6; Since the center position is determined and the sampling point is set using this as a reference point, the sampling point and the code center coincide as shown in Figure @1.

Note that although the case where the synchronization code becomes narrower due to isochronous distortion has been described above, the same applies to the case where the synchronization code becomes wider.

FIG. 2 is an explanatory diagram for explaining an example of applying the method according to the invention by setting a sampling window.

Here, 2 is a sampling window, and the sampling point in this case is represented by a relative significance interval (relative position) A within this sampling window 2. That is, first, the reference code IB rises t. is detected and the relative position A within the sampling window is stored.

Next, measure the length and width of the reference code) T - ΔT, and
Add 1/2 of ΔT to the first relative position (A+ -)
.

If the size of the sampling window is set to one bit length, the obtained relative position coincides with the sampling point Pl of bit synchronization. Therefore, transmission data can be obtained by sampling bit data based on this relative position.

〔Effect of the invention〕

According to this invention, the center position of the synchronization code on the rear side of the synchronization pattern is found and the data is sampled based on this position, so even if there is code distortion, information data can be sampled correctly. This provides the advantage of being able to obtain a transmission device that is resistant to line distortion.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the invention in detail, and FIG.
The figure is an explanatory diagram to explain an example of applying the method according to the present invention by setting a sampling window, Figure 3 is a waveform diagram to explain a synchronization pattern, and Figure 4 is a diagram to explain a conventional sampling method. FIG. 5 is an explanatory diagram for explaining the conventional sampling method when sign distortion occurs, and FIG. 6 is an enlarged diagram showing a part of FIG. 5. Code explanation 1... Synchronization pattern (synchronization word), IA, 1
2゜B...Synchronization code, 2A, 2B...Sampling window, to...Rising point of synchronization code, PotP1tP2...Code center, Po.
...Sampling reference position, Pl, P2...
...Sampling point. Agent Patent Attorney Akio Namiki Agent Patent Attorney Seimei Matsuzaki 1 Figure 2 Figure 31! ! ! No. AvA, to po' p, / p2

Claims (1)

[Claims] In order to achieve bit synchronization in a frame-synchronized digital information transmission system, the width of the rear synchronization code in the synchronization pattern for bit synchronization is measured and its center position is determined, and the center position is determined. A sampling method for bit synchronization characterized by sampling information data by setting sampling points for subsequent bit synchronization based on the following.