JPH04124931A - Frame synchronizing system - Google Patents

Abstract

PURPOSE:To reduce the probability of falling into a pseudo synchronized state by constituting a synchronizing pattern of a first synchronizing pattern set at a fixed timing position and a second synchronizing pattern set at the timing position delayed by the portion of time varying for every frame in conformity to a predetermined rule. CONSTITUTION:One frame is constituted of 7-bytes, and a frame synchronizing patterns 11(F1), 12(F2) of 2-bytes are used for every frame. The first frame synchronizing pattern 11(F1) is sent by a leading byte of every frame synchronization. The second frame synchronizing pattern 12(F2) is sent k-bytes behind the frame synchronizing pattern 11(F1). The number (k) varies for every sending of the frame, and the frame synchronizing pattern 12(F2) is sent in conformity to the rule that k=1 and k=2 are repeated. At a receiving side, by confirming the regularity (repetition of k=1 and k=2) of the variation of the number (k) of the delayed bytes between the synchronizing patterns 11(F1) and 12(F2), the frame is synchronized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frame synchronization method for digital data transmission.

[Conventional technology]

Conventionally, as a frame synchronization method for digital data transmission, the transmitting side sets and transmits a multi-bit synchronization pattern at a fixed timing position for each frame synchronization, and the receiving side sets and transmits a synchronization pattern of multiple bits at a fixed timing position for each frame synchronization. There was a method in which synchronization was established when a match was detected with a pattern.

FIG. 2 shows an example of a frame structure (data string) of a conventional frame synchronization method. One frame consists of 7 bytes, and the first 2 bytes of the frame contain the frame synchronization pattern F1. Send F2.

The 2-byte overhead A 1 , A 2 following the frame synchronization pattern F2 is the same in each frame.

Data DIl to D13 and D to be transferred in the remaining 3 bytes
2 to D23 are sent out in order.

On the receiving side, the synchronization pattern F1F2 was detected from this data string and frame synchronization was established.

[Problem to be solved by the invention]

In the conventional frame synchronization method described above, there is a possibility that pseudo-synchronization may occur if data within a frame matches a synchronization pattern. In particular, when a fixed pattern other than the frame synchronization pattern, such as overhead within a frame, is sent out every frame period, there is a problem in that the probability of pseudo synchronization is high.

[Means to solve the problem]

The frame synchronization method of the present invention is a frame synchronization method that synchronizes frames by sending out a synchronization pattern consisting of multiple bits every frame period when transmitting digital data. It consists of a first synchronization pattern and a second synchronization pattern set at a timing position delayed from the timing position of the first synchronization pattern by a time varying from frame to frame according to a predetermined rule.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a diagram showing a frame structure of an embodiment of the present invention. One frame consists of 7 bytes, and each frame has a 2-byte frame synchronization pattern 11 (
F+), 12 (F2) is used. The first frame synchronization pattern 11 (Fl) is sent at the first byte of each frame period.

The second frame synchronization pattern 12 (F2) is sent one byte after the frame synchronization pattern 11 (Fl). k changes for each frame transmission, and k=1 and =2
Frame synchronization pattern 12 (F2) is transmitted according to the rule that repeats the above steps.

FIG. 1(b) shows a data string sent out according to the frame structure shown in FIG. The data is sent in 3 bytes of data, but usually different data 15 to 17 (D
Il-D13), 18-20 (D21-D23).

On the receiving side, from this data string, first synchronization pattern 11 (F
l>, and further detects synchronization pattern 12 (F2), and also detects each synchronization pattern 11 (Fl) and 12 (F2).
Frame synchronization is achieved by checking the regularity of changes in the number of delay bytes (repetition of k=1. to =2).

〔Effect of the invention〕

As explained above, the present invention has two frame synchronization patterns.
The first synchronization pattern exists at a fixed timing position for each frame period, but the second synchronization pattern exists at a position delayed in time from the first synchronization pattern, and k
Since the value of changes for each frame according to a predetermined rule, the same data in each frame will not be recognized as a synchronization pattern, and the probability of a pseudo-synchronization state is reduced compared to conventional technology. It has this effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the frame structure and data string of the present invention,
FIG. 2 (This is a diagram showing a conventional frame structure and data string. 2... Synchronization pattern, 3° 4... Overhead, 15-20... Data.

Claims (1)

[Claims] In a frame synchronization method that synchronizes frames by sending a synchronization pattern consisting of multiple bits every frame period when transmitting digital data, the synchronization pattern is connected to a first synchronization pattern set at a fixed timing position for each frame period, and A frame synchronization method comprising: a second synchronization pattern set at a timing position delayed by a time varying from frame to frame according to a predetermined rule from the timing position of the first synchronization pattern.