JPH04103235A - Frame pattern generating system - Google Patents

Abstract

PURPOSE:To reduce the probability of occurrence of pseudo synchronization without imposing a limit onto a main signal by generating a check code string having an error check or error correction function in response to processing function with respect to a bit string sent precedingly to a transmission line as a frame pattern. CONSTITUTION:A generating means 13 generates a frame pattern as a check code string having an error check or error correction function in response to processing function with respect to a bit string sent precedingly to a transmission line and a multiplexer means 11 multiplexes the main signal including the transmission information and the generated frame pattern in response to a prescribed frame structure and sends an obtained bit string to the transmission line. That is, the frame pattern of each frame is set variably in response to the bit string sent precedingly. Moreover, an opposite reception terminal equipment applies the bit arithmetic operation to the bit string received precedingly in response to the similar function to that of the generating means 13 to obtain the frame pattern. Thus, the probability of occurrence of pseudo synchronization is reduced without imposing a limit onto a bit pattern of a main signal and a frame pattern.

Description

[Detailed Description of the Invention] [Summary] Regarding a frame pattern generation method that generates a variable frame pattern for each frame sent to a transmission path in a digital multiplex transmission device, pseudo synchronization is achieved without imposing restrictions on the main signal. The aim is to realize a frame synchronization method that can reduce the probability of occurrence of , and detect deterioration in transmission quality.
In a transmission device equipped with a multiplexing means that multiplexes a main signal containing transmission information and a given frame pattern according to a predetermined frame configuration and sends out the obtained bit string to a transmission path, the transmission device transmits the bit string in advance of the transmission path. The apparatus is configured to include a generating means for generating a check code string having an error detection or error correction function according to a predetermined function from the bit string obtained by the process, and using the check code string as a frame pattern.

[Industrial application field]

The present invention relates to a frame pattern generation method for generating a variable frame pattern for each frame sent to a transmission path in a digital multiplexing transmission device.

[Prior Art] In a digital multiplex transmission device, bit strings of multiple channels including transmission information are multiplexed according to a predetermined frame structure and sent out to a transmission path.

In other words, each frame consists of dividing the bit string of each channel into a predetermined number of bits and synchronously arranging them in a predetermined order. ) is added. Further, as such a frame pattern, a specific repetitive bit pattern has conventionally been used.

On the other hand, at the receiving terminal, such a frame pattern is
It is used as a reference bit pattern for obtaining a reference position corresponding to each frame on a received bit string (establishing frame synchronization). Also, when frame synchronization is achieved,
In order to avoid being mistakenly recognized as being out of synchronization due to a single or temporary code error occurring on the transmission path,
A forward protection operation is performed to maintain the synchronization state until the number of consecutively detected errors in the received frame pattern reaches a predetermined number or more. Furthermore, in the process of establishing frame synchronization, in order to avoid false synchronization in which a bit string other than the frame pattern (for example, the main signal) is mistakenly recognized as a frame pattern and synchronization is detected, a frame pattern is detected consecutively more than a predetermined number of times. A backward protection operation is performed in which it is assumed that frame synchronization has been achieved under these conditions.

Note that word synchronization, which is performed to detect the first bit of transmission information when the number of channels to be transmitted is single, such as in a zero-order group, is considered to be a special case of the above-mentioned frame synchronization.

[Problem to be solved by the invention]

By the way, in such a conventional frame synchronization method using a frame pattern, if a bit string other than the frame pattern, such as a main signal, contains the same bit pattern as the frame pattern, the probability of pseudo synchronization occurring increases. In addition, methods for reducing the probability of occurrence of such pseudo synchronization include using a bit pattern with a low probability of being included in the main signal as a frame pattern, and limiting the main signal so that it does not contain the same bit pattern as the frame pattern. There is a way. However, both of these methods have limited applicability due to constraints imposed on frame patterns or information to be transmitted.

Furthermore, although the receiving terminal can recognize a fault in the transmission path by the occurrence of frame out-of-sync, it has not been possible to detect quality deterioration in the transmission path before frame out-of-sync occurs. Generally, such quality deterioration in a transmission path can be detected as a bit error by employing an error correction code, but to do so, redundant bits for error checking must be transmitted along with the main signal. .

That is, in order to transmit the main signal at a predetermined speed, the transmission speed must be increased, and if changing the transmission speed is not allowed, the number of bits of the main signal included per unit frame must be reduced. . Therefore, in any of these methods, the ratio of main signals included per unit frame (multiplexing efficiency) decreases.

An object of the present invention is to provide a frame pattern generation method that realizes a frame synchronization method that can reduce the probability of occurrence of pseudo synchronization and detect deterioration in transmission quality without imposing restrictions on the main signal.

[Means to solve the problem] FIG. 1 is a block diagram of the principle of the present invention.

In the figure, multiplexing means 11 of the transmission device multiplexes a main signal containing transmission information and a given frame pattern according to a predetermined frame configuration, and sends out the obtained bit string to a transmission path.

The generation means 13 of the frame pattern generation method generates a check code string having an error detection or error correction function according to a predetermined function in the bit string sent out in advance to the transmission path, and uses this check code string as a frame pattern. shall be.

[For production]

In the present invention, the generation means 13 generates a frame pattern as a check code sequence having an error detection or error correction function according to a predetermined function on the bit string sent out in advance to the transmission path, and the multiplexing means 11 transmits the frame pattern. The main signal containing information and the generated frame pattern are multiplexed according to a predetermined frame configuration, and the resulting bit string is sent to a transmission path. That is, the frame pattern of each frame is variably set according to the bit string sent out in advance. Furthermore, the receiving terminal facing the receiving terminal via the transmission path can perform bit operations on the previously received bit string according to a function similar to that of the generating means 13 to obtain a frame pattern to be received.

Therefore, the probability of pseudo synchronization occurring can be reduced without imposing restrictions on the main signal and the bit pattern of the frame pattern. Furthermore, since the receiving terminal can recognize a bit error that occurs on the transmission path before frame synchronization loss occurs as a bit error in the received frame pattern, it can detect deterioration in transmission quality.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, a transmitter 21 multiplexes the applied main signal according to a predetermined frame structure and sends it to a transmission path.
is connected to a receiving section 22 that extracts a main signal from a bit string received via a transmission path.

The transmitter 21 includes a counter 23 that determines the frame length according to the frame structure, a multiplexer 24 that multiplexes the main signal and the frame pattern that are applied, and sends the multiplexed signal to the transmission path. The frame pattern generation unit 25 is configured to generate the above-mentioned frame pattern according to the bit string obtained.

The receiving unit 22 includes a counter 26 that obtains a timing signal (hereinafter referred to as a "synchronization signal") corresponding to each frame on a bit string received via a transmission path (hereinafter referred to as a "received bit string"), and a received bit string. and a frame pattern (hereinafter referred to as “reference frame pattern”) according to the synchronization signal.
That's what it means. ), a comparison section 2B that compares the frame pattern included in the received bit string and a reference frame pattern according to the synchronization signal, and a synchronization protection section that performs backward protection and forward protection according to the comparison result. 29, an AND gate 30 that delays the counting operation of the counter 26 by a unit bit in accordance with the above comparison result and the out-of-sync detection signal output from the synchronization protection unit 29;
Similarly, it is composed of an anti-game 31 that detects code errors in a received bit string, and a separation section 32 that extracts a main signal included in the received bit string in accordance with a synchronization signal.

FIG. 3 is a diagram explaining the operation of this embodiment.

In the figure, the frame pattern sent out from the transmitter 21 is represented by adding a suffix number "1.2,..." to "F", and the frame pattern received by the receiver from the transmission path (regarded as a frame pattern (Including bit patterns.)
is expressed by adding a subscript number “l, 2, . . .” to “f”.

The operation of this embodiment will be described below with reference to FIGS. 2 and 3.

In this embodiment, as shown in FIG. 3, the frame pattern length ("N F ) and the number of bits included in the main signal (
=N,) are each set to a predetermined value, and each frame is composed of a main signal placed after the frame pattern on the time axis. Therefore, the frame length (=NY) is
It is given by NT = NF + NM.

In the transmitting unit 21, the frame pattern generating unit 25 performs a bit operation according to a predetermined function on the bit pattern of the frame previously sent to the transmission path to generate a bit pattern of N bits (see FIG. 3). ).Note that bit operations according to a predetermined function are, for example, CRC (Cyclic
C. Redundancy Check) refers to bit operations defined as a generation process for codes, Hamming codes, and others. The multiplexing unit 24 configures subsequent frames using the bit pattern thus generated as a frame pattern, and sends the resulting frame to the transmission path ((2) in FIG. 3).

The transmitter 21 repeats this operation for each frame.

In the receiving section 22, a counter 26 provides each section with reference timing synchronized with the received bit string every unit frame period. The frame pattern generation unit 27 generates N? The bit string of bits is subjected to the same bit operation as the frame pattern generation section 25 of the transmission section 21, and Nv
A bit pattern of bits (hereinafter referred to as "reference frame pattern") is generated (Fig. 3, ■). Comparison section 28
compares a bit string that is considered to be a frame pattern on a received bit string according to a given reference timing and a given reference frame pattern. If the result of this comparison is a mismatch, the counter 26 is controlled via the AND gate 30 to stop its counting operation by a unit bit. Therefore, from now on, the timing signal output from the counter 26 is output with a unit bit delay on the time axis, and the frame pattern generation section 27 and comparison section 28 perform frame pattern search operations at different timings (Fig. 3). ). Further, when the comparison section 28 detects a match between the frame patterns, the synchronization protection section 29 counts the number of matches, and the counter 26 continues the counting operation without the above-mentioned delay. Therefore, the frame pattern generation section 27 and the comparison section 28 continue the frame pattern search operation at the same timing (FIG. 3).

Furthermore, if frame pattern matching is detected a predetermined number of times or more, the synchronization protection unit 29 recognizes the completion of frame synchronization and outputs an inactive out-of-synchronization detection signal, so that the AND gate 30 is turned off. The state is set (■ in Figure 3).

Thereafter, the counter 26 continues counting without delay, and the separation unit 32 extracts the main signal of each frame from the received bit string in response to the synchronization signal (FIG. 3).

In addition, in such a synchronization pull-in completion state, the comparator 2
8 sequentially performs a comparison test between the received frame pattern and the corresponding reference frame pattern. The synchronization protection unit 29 detects a mismatch as the verification result (third
The forward protection operation is performed to maintain the synchronized state until a predetermined number or more of consecutive discrepancies are detected.

As described above, according to the present embodiment, the frame pattern of each frame sent from the transmitting section 21 is variably set for each frame according to the bit pattern of the preceding frame, but the receiving section 22 uses this frame pattern. It can take a frame pattern.

Therefore, the probability of pseudo synchronization occurring can be reduced without imposing restrictions on the bit pattern of the main signal.

Furthermore, when error correction code generation rules are used as the bit operations required to generate a frame pattern, the frame pattern is determined based on all bits (including the main signal) of the preceding frame. . That is, the receiving section 2
In No. 2, when a code error occurs in the transmission path, an error occurs in the reference frame pattern, so that the comparator 28 detects a mismatch of frame patterns, and furthermore, the AND gate 31 outputs a code error detection signal.

Therefore, before detecting out of synchronization (during forward protection operation)
Furthermore, it is possible to detect code errors due to deterioration in the transmission quality of the transmission path.

Note that the preceding frame in this embodiment is not limited to a frame sent out in advance by a unit frame period as shown in FIG. 3, but may also be a frame sent out in advance by two or more frame periods. Furthermore, multiple frames may be used. Furthermore, the object of the bit operation performed when generating a frame pattern is not limited to all bits of the preceding frame, but may also be, for example, the main signal of the NH bit included in the preceding frame or any other bit (sequence). Good too.

〔Effect of the invention〕

As described above, according to the present invention, by generating the frame pattern of the subsequent frame based on the bit pattern of the preceding frame, the probability of occurrence of suspicious synchronization can be calculated without imposing restrictions on the bit pattern of transmission information. A frame synchronization method that can reduce the number of frames can be realized.

Furthermore, by generating a frame pattern according to the error correction code generation rules, it is possible to detect deterioration in transmission quality during a period in which a synchronized state is maintained by forward protection without reducing multiplexing efficiency.

23.26 is the counter, 24 is a multiplexing unit; 25. 27 is a frame pattern generation section, 28 is a comparison section, 29 is a synchronization protection section, 30.31 is and gate, 32 is a separation section.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention. FIG. 2 is a diagram showing an embodiment of the present invention; FIG. 3 is a diagram explaining the operation of this embodiment. In the figure, 11 is a multiplexing means; 13 is a generation means; 21 is a transmitter; 22 is a receiving section;

Claims (1)

[Claims] (1) A transmission device comprising a multiplexing means (11) for multiplexing a main signal containing transmission information and a given frame pattern according to a predetermined frame configuration and sending the obtained bit string to a transmission path, generating means (13) for generating a check code string having an error detection or error correction function according to a predetermined function on the bit string sent out in advance on the transmission path, and for making the check code string the frame pattern; A frame pattern generation method characterized by: