JPH06311145A - Pointer reception abnormality judgement method - Google Patents

Abstract

PURPOSE:To enlarge an error detection time interval and to reduce an abnormal error detection probability by means of few number of protection steps by dividing a pointer into plural pointers in an SDH transmission system, synthesizing the detection result of the received abnormality of the respective divided pointers and judging received abnormality. CONSTITUTION:An input signal is processed in an SOH processing part 2, and a separation part 3 divides an added AU-4-4C pointer into the four divided pointers being the unit of size equivalent to an AU-4 pointer. A pointer collation part 4 and a CI collation part 5 sequentially collate bit patterns from a head divided pointer. A detection protection part 6 detects and protects a prescribed value as to the respective divided pointers, and outputs an abnormal signal when abnormality continues for the number of times for protection steps. Then, an OR circuit 7 takes the OR of the abnormal signal, and outputs a pointer loss detection signal LOP. The error detection time interval T at that time becomes considerably large and the abnormal error detection probability being the reciprocal of T can be made small.

Description

Detailed Description of the Invention

[0001]

The present invention relates to SDH (Synchronous Dielectric).
(Gital Hierarchy) The present invention relates to a pointer reception abnormality determination method in the SDH transmission method for transmitting information using a transmission frame.

[0002]

2. Description of the Related Art CCITT (International Telegraph and Telephone Consultative Committee)
Recommendation G. S specified by 707, 708, and 709
In the DH transmission method, a block position specifying method called a pointer is adopted. This pointer indicates the start position of blocked information called a virtual container in bytes as a distance from the pointer value accommodating time slot.

Further, a method is defined in which a plurality of virtual containers are connected to send more information than the capacity of one virtual container. At this time, only one pointer is defined for the plurality of connected virtual containers, and a concatenation indication bit indicating the connection of the plurality of virtual containers is stored in the other pointer areas. For example, when connecting X virtual containers-4, the AU-4-Xc pointer is stored in the first part of the corresponding pointer area, and the concatenation indication bit is stored in the other part of the pointer area. It

FIG. 2 shows the AU- in the STM-4 frame.
It is a figure which shows a 4-4c pointer. As shown in the figure, in the pointer value accommodating time slots H1 and H2, there is a pointer value PTR indicating the start position of the virtual container VC-4.
In addition, the new data flag bit NDF and the size designation bit SS are stored, and the pointer value PTR, the new data flag bit NDF, and the size designation bit SS form an AU-4-4c pointer.

A method for determining the reception abnormality of the pointer value of the AU-4 pointer is described in CCITT Recommendation G.264. As described in 783, when the pointer value does not exceed 782, it is regarded as a normal value. Further, the concatenation indication bit CI has a transmission signal of AU-4-
Since it indicates a 4c pointer, AU-
It is necessary to constantly monitor the normality of the 4-4c pointer during transmission.

[0006]

However, conventionally, a method of determining the reception abnormality of the AU-4-Xc pointer including the monitoring of the concatenation indication bit CI has not been defined. In the pointer reception abnormality determining method, it is desirable that the abnormality erroneous detection probability can be suppressed to be small even with a short abnormality detection time, that is, a short number of protection steps.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a pointer reception abnormality determination method which has a small probability of abnormality error detection even with a short number of protection steps.

[0008]

In order to achieve this object, according to the present invention, a plurality of virtual containers are
In the pointer reception abnormality determination method in the SDH transmission method in which 4 are concatenated and a 6X-byte AU-4-Xc pointer is added and transmitted, the AU-4-Xc pointer is
X in units of 6 bytes, which is the size of a U-4 pointer
The divided pointer is divided into a plurality of divided pointers, a fixed value is independently protected for each divided pointer, and the reception abnormality of the divided pointer is detected.
-4-A judgment is made as to the reception abnormality of the Xc pointer.

[0009]

In this pointer reception abnormality determining method, the erroneous detection time interval based on the transmission path error can be increased.

[0010]

1 is a diagram showing an apparatus for carrying out a pointer reception abnormality judging method according to the present invention. As shown in the figure, the signal received by the optical receiving unit 1 is frame-synchronized by the SOH processing unit 2, and each overhead byte is processed. Next, the virtual container and the pointer value accommodating time slot connected by the separating unit 3 are separated. That is, in STM-4, it is possible to connect up to four virtual containers VC-4, and the AU-4-4c pointer added at this time has a length of 24 bytes. AU
4 bytes are divided into 4 divided pointers in units of 6 bytes, which is a size equivalent to 4 pointers. Next, the pointer collating unit 4 collates the first divided pointer, and the CI collating units 5a to 5c for the subsequent three divided pointers.
Check the bit pattern at. Next, the detection protection units 6a to 6d independently perform detection protection of a fixed value for each of the divided pointers, and if an abnormality continues for the number of protection stages, the detection protection units 6a to 6d output an abnormality signal. Next,
The OR circuit 7 takes the logical sum, and when at least one of the detection protection units 6a to 6d outputs an abnormal signal, the OR circuit 7 outputs a LOP (Loss of Pointer) detection signal.

Here, the abnormality erroneous detection probability when making the LOP determination is the reciprocal of the erroneous detection time interval. Then, assuming that the number of protection stages for transmission path errors is n, the frame period is t, and the pointer error probability is P, the error detection time interval T based on transmission path errors can be evaluated by the following equation.

[0012]

[Equation 1]

If the number of pointer matching bits is r and the transmission path error rate frame period is Pe, then P = r · Pe.

Therefore, the erroneous detection time interval T of the AU-4 pointer is 38 in the pointer collation bit number r in the AU-4 pointer, and the frame period t is 125 μsec. Road error rate Pe is 10 ~ ⁴
Under this condition, the false detection time interval is 5 years.

Further, when the abnormality is detected without dividing the AU-4-4c pointer, the number r of pointer collation bits is 155, so the erroneous detection time interval T is 0.004.
It will be the year.

On the other hand, when the AU-4-Xc pointer is divided into X pieces (the number of connections), the false detection time interval T based on the transmission path error can be evaluated by the following equation.

[0017]

[Equation 2]

When the number of pointer collation bits before concatenation is m, P = m · Pe and the number of pointer collation bits m is 38. Therefore, when the number of concatenation X is 4, the frame period t and the number of protection stages are set. If n and the transmission line error rate Pe are the same as those described above, the false detection time interval T is 1.25 years.

Thus, the AU-4-4c pointer is set to 4
When the abnormality detection is performed by dividing the pointer into the divided pointers, the erroneous detection time interval T becomes very large as compared with the case where the abnormality detection is performed without dividing the AU-4-4c pointer. Therefore, even if the number of protection steps is short, it is possible to perform pointer reception abnormality determination with a small abnormality erroneous detection probability.

In the above embodiment, the case where the number of connections X is 4 has been described, but it is obvious that the present invention can be applied to the case where the number of connections is other.

[0021]

As described above, in the pointer reception abnormality determining method according to the present invention, since the error detection time interval based on the transmission path error can be increased, the error error detection probability can be reduced even with a short number of protection steps. can do. As described above, the effect of the present invention is remarkable.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus for implementing a pointer reception abnormality determination method according to the present invention.

FIG. 2 is a diagram showing an AU-4-4c pointer in STM-4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical receiving part 2 ... SOH processing part 3 ... Separation part 4 ... Pointer collation part 5 ... CI collation part 6 ... Detection protection circuit 7 ... OR circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Hiromi Ueda 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. Connecting a plurality of virtual containers-4,
In the pointer reception abnormality determination method in the SDH transmission method in which a 6X-byte AU-4-Xc pointer is added and transmitted, the AU-4-Xc pointer is divided into X units in units of 6 bytes which is the size corresponding to the AU-4 pointer. The divided pointer is divided into a plurality of divided pointers, a fixed value is independently protected for each divided pointer, and the reception abnormality of the divided pointer is detected. Then, the logical sum of the results is used to receive the AU-4-Xc pointer. A pointer reception abnormality determination method characterized by determining abnormality.