JPS6238629A - Frame synchronizing method - Google Patents

Abstract

PURPOSE:To keep the periodicity of a transmission data even when a data with very high periodicity is sent and to improve the reliability of a synchronizing signal by arranging scatteringly synchronizing words to a position not losing the periodicity of the transmission data in each sub frame. CONSTITUTION:Suppose that one channel is required at each other word to send all animation data, let synchronizing words be two words S1, S2, then the sub frame constitution shown in figure (b) is attained. The rate of one channel in one sub frame is smaller in the constitution shown in figure (b). In order to avid it, in replacing one word of P-channel into I-channel as shown in the figure (b), number of words of I-channel in one sub frame is equal in both figures (a, b). Thus, a special circuit is needed for both the transmission and reception sides. In assigning the synchronizing words S1, S2 as shown in the figure (a) to each sub frame, the problem is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a frame synchronization method in digital data transmission, particularly when transmitting highly periodic information.

[Background of the invention]

In a transmission path that is divided into words with an equal number of bits determined for each subframe, a synchronization signal is required in order to synchronize each subframe at a receiving station. The conventional method, as described in Japanese Unexamined Patent Publication No. 59-204337, is to attach a synchronization word of the required number of bits to the beginning of each subframe and transmit it, and each receiving station is equipped with a synchronization detection device to detect synchronization. Word was detected and frame synchronization was detected. The number of synchronization words varies depending on the transmission system, but the greater the number of synchronization words, the fewer synchronization errors occur and the reliability of the system improves. However, if the number of synchronization words is increased and they are allocated consecutively in a subframe, other data cannot be transmitted while the synchronization word is being transmitted, so the periodicity cannot be maintained, especially when transmitting data with extremely high periodicity. The problem arises that the

[Purpose of the invention]

The present invention solves the above-mentioned problems and provides a frame synchronization method characterized by dispersing and attaching synchronization words at positions that do not impair the periodicity of transmitted data in each subframe. .

[Summary of the invention]

In a system that transmits highly periodic data that needs to be transmitted every other word, conventionally, when the synchronization word is one word or multiple words,
It was necessary to break the periodicity of highly periodic data.

The present invention prevents the transmission data from being deleted even in the case described above even if a plurality of synchronization words are used.

A feature of this method is that synchronization words are provided in subframes, avoiding the positions of words that transmit highly periodic data.

[Embodiments of the invention]

An example of a subframe configuration is shown in FIG. 1, which describes an embodiment of the present invention in a transmission system using a time division multiplex transmission path, which requires highly periodic data transmission. It is assumed that each subframe consists of M words, and one word consists of N bits. S1 and S2 are synchronization words, ■ is a channel for transmitting moving image data that needs to be transmitted periodically, and P is a channel for transmitting packet data. FIG. 1(a) shows an embodiment of the present invention. It is assumed that the I channel needs to be provided every other word in order to transmit all the moving image data. In this case, if the synchronization word is set to 2 words S1511 as in the conventional example, the subframe structure will be as shown in FIG. 1(b).

As is clear from comparing figures (a) and (b), the proportion of one channel in one subframe is (b)
is smaller. That is, the above-mentioned problem occurs because the synchronization word is two words and occupies the two-word transmission line consecutively. In order to avoid this, Figure 1 (b
), if one word of the P channel is replaced with an E channel, the number of E channel words in one subframe becomes equal in both (a) and (b). However, this method requires special circuits on both the transmitter and receiver sides. An embodiment of the present invention, as shown in FIG.
The above problem can be solved by allocating sff to each subframe.

Next, an embodiment of a device for detecting synchronization frames allocated as shown in FIG. 1(a) will be described. Second
The figure is a circuit diagram of an embodiment of a frame synchronization device under the above conditions. Now, the input pulse train e1 is led to the N-stage shift register 1゜2.3, and since the synchronization words appear one word apart, the outputs (2N bits) of the shift registers 1 and 3 are taken into the synchronization signal comparison circuit 4, and this If the signal matches the synchronization signal, the output of circuit 4 will be "0", thus the subframe synchronization position signal indicating the point at which the subframe synchronization pattern, which is the output of the subframe counter, should be checked. By ANDing the output of the circuit 4 and the output of the circuit 4, a subframe synchronization mismatch signal 77 is obtained at the output of the AND circuit 7. The synchronization protection circuit 5 is activated by this τ7, and when the frame synchronization is lost, the clock supplied to the subframe counter 6 is controlled by the gate 8.
An embodiment of a subframe synchronization detection device is one in which the subframe synchronization detecting device detects zero or more, delays the operating phase of the subframe counter, and performs hunting. An important feature of the device configuration compared to the conventional example is that a shift register circuit is provided for detecting synchronization words that are located apart in a subframe.

The method for allocating synchronization words under the above conditions and the subframe synchronization detection device have been described above. Than this,
The same applies when the number of synchronization words increases or decreases, or when more highly cyclic data transmission is required, such as in one channel.

It is easy to understand that it can be applied to

〔Effect of the invention〕

According to the present invention, the number of words of the synchronization signal can be set to a relatively large number, and the reliability of the synchronization signal can be improved. Furthermore, by increasing the number of words of the synchronization signal, data with extremely high periodicity can be processed. When transmitting, there was a problem that the periodicity of the transmitted data could not be maintained, but this can also be solved by the present invention, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a transmission subframe according to an embodiment of the present invention, and FIG. 2 is a block diagram of a frame synchronization detection device according to an embodiment of the present invention. 1.2.3...Shift register, 4...Synchronization signal comparison circuit, 5...Synchronization protection circuit, 6...Subframe counter, 7...AND circuit, 8...Gate circuit .

Claims (1)

[Claims] 1. N bits of information are encoded into one word, multiple words are made into one subframe, and each word in the subframe is divided into words that transmit information of different dimensions to transmit various information. A frame synchronization method in a time division multiplex data transmission system, characterized in that several synchronization words are distributed and allocated at the beginning of each subframe and at positions that do not impair the periodicity of various transmission information.