JPH06181471A - Transfer system in asynchronous transfer mode - Google Patents

Abstract

PURPOSE:To reduce a fault restoration time and to attain error correction and cell abort compensation with high reliability. CONSTITUTION:A virtual path VP1 is formed by adding control information based on an error correction code rule and a cell sequence number to each cell of input virtual line groups VC11-VC14 by a sender side virtual line switch VCH1, the virtual path is copied to generate a virtual path VP2 and the two virtual paths are connected to a receiver side virtual line switch VCH 2 via virtual line path cross connectors VPH1-VPH3 in a different route. The receiver side virtual line switch VCH2 applies buffering to cells of the virtual paths VP1,VP2 and implements cell abort compensation by a cell sequence number for error correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a transfer method of an asynchronous transfer mode. It is used for a transmission method that provides a high quality path by correcting failures of code errors and compensating for cell discards in a network in an asynchronous transfer mode, in which failure recovery is fast.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional automatic transmission switching control system for digital transmission. FIG. 6 is a diagram showing the principle of the cell loss compensation method (encoding process) of the transfer method of the asynchronous transfer mode of the conventional example. FIG. 7 shows a cell loss compensation method (2 in the conventional asynchronous transfer mode).
It is a figure which shows the principle of (dimensional array encoding).

Conventionally, the automatic switching control system (DSW, Digital Switcher) shown in FIG. 5 is the most well known in order to ensure the reliability of a digital transmission network. This system is basically a centralized control system, and is composed of a control unit CONT, a switching execution unit SV, and a switch MTX, and a switching pattern corresponding to a location where a failure has occurred is predetermined. After exchanging messages between the control unit CONT and the switching execution unit SV, a detour route is determined and switching control is performed in path units.

In addition, in a network based on the asynchronous transfer mode, information cells (fixed length blocks) are transmitted asynchronously as a unit, so that cell discard may occur due to buffer overflow at a relay node. Further, in order to prevent erroneous distribution of cells, the cells are discarded even when the error of the cell synchronization unit due to the transmission path error is severe. Attempts have been made to apply error correction codes as a compensation method for such transmission path errors and cell discard. As shown in FIG. 6, a fixed number of cells are arranged two-dimensionally, and two types of error correction codes are applied in the horizontal and vertical directions, respectively, to simultaneously compensate for transmission path errors and cell discard. Is what you are trying to do.

First, in the coding of the cell discard detection code, error correction coding is performed in the horizontal direction of the array using each cell as information.
The obtained inspection bit is used as a discard detection cell (Loss Det).
ecting cell). To encode the restoration code, several bits are extracted from one cell and error correction encoding is performed in the vertical direction of the array. The obtained check bit is stored in the parity cell. as a result,
Two-dimensional array coding as shown in FIG. 7 is configured.

From the viewpoint of error correction capability, the cell loss detection code is a BCH code (Bose-Chaudhuri-H).
An ocquengem code) and an RS code (Reed-Solomon code) are considered as the restoration code. The decoding process is basically possible by using the performance of these error correction codes, but for the detailed encoding process and decoding process, refer to the next paper. (Iwase et al., Compensation Method for Channel Code Error and Cell Discard in ATM Network, IEICE Transactions, B-IVol.J7
5-BI, NO. 1, pp. 1-11, 1992)

[0007]

However, in the transmission method of the asynchronous transfer mode of the conventional example, the automatic switching control system requires frequent exchange of control information between the control unit CONT and the switching execution unit SV, and There are problems in using this system as the recovery time is often tens of minutes due to its slow transfer information rate.

Further, the compensation method using the error correction code is certainly effective when cells are uniformly generated at a fixed bit rate, but it is premised that a two-dimensional matrix is created. In some cases, for example, when a burst of cells arrives, the matrix cannot be completely constructed and a desired cell loss compensation characteristic may not be obtained. For future services, of course bursty,
So-called time-varying cell transfer characteristics should be taken into consideration, and there is a problem in this point that the current technology cannot be used.

The present invention solves the above problems.
It is an object of the present invention to provide a high-quality asynchronous transfer mode transmission method capable of shortening the failure recovery time and performing highly reliable error correction and cell loss compensation.

[0010]

Means for Solving the Problem The present invention comprises means for forming a virtual path by adding control information and a cell sequence number based on an error correction coding rule to cells from a plurality of input virtual circuit groups, respectively. Copy this virtual path 2
A transmission side virtual circuit switch including means for creating virtual paths of the above series and connecting to different routes, and means for buffering cells of virtual paths of two or more series connected to the different routes respectively A receiving side virtual circuit switch including means for reading the contents of the buffering means, compensating for cell discard based on the cell sequence number, performing error correction, and outputting to a plurality of output virtual circuit groups. Characterize.

Further, the present invention comprises a plurality of virtual path cross connectors which are connected between the transmitting side virtual circuit switch and the receiving side virtual circuit switch and which set the two or more virtual paths to different routes. You can

[0012]

[Function] Since the virtual path has a redundant configuration, even if the cable is disconnected, it is possible to recover autonomously in a short time without inquiring to the control station, and the cells given to each virtual path can be restored. Since the cell discard compensation is performed with the sequence number of and the target of the error correction code is the information bit string,
The failure recovery time can be shortened, variable services can be handled without any changes, and highly reliable error correction and cell loss compensation can be performed.

[0013]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a transfer system in an asynchronous transfer mode according to an embodiment of the present invention.

In FIG. 1, a feature of the present invention is that a virtual path is created by adding control information and a cell sequence number based on an error correction code rule to cells from a plurality of input virtual circuit groups VC11 to VC14, respectively. As a means for configuring the above, a multiplexing circuit 11, a synchronizing circuit 12, a code forming circuit 13, and a virtual path forming circuit 14, and a means for copying this virtual path to create two or more series of virtual paths and connecting them to different routes. The transmission side virtual circuit switch VCH1 including the copy circuit 15 and the buffer 21 as a means for buffering cells of virtual paths of two or more series connected to the different routes, respectively.
Then, the contents of the buffer 21 are read out, cell discard compensation is performed based on the cell sequence number, error correction is performed, and the error is corrected and output to a plurality of output virtual circuit groups VC21 to VC24. Circuit 2
4 and a separation circuit 25, and a reception side virtual circuit switch VCH2.

Further, there are provided a plurality of virtual path cross connectors VPH1 to VPH3 which are connected between the transmission side virtual circuit switch VCH1 and the reception side virtual circuit switch VCH2 and which set the two or more virtual paths to different routes.

The operation of the transfer method in the asynchronous transfer mode having such a configuration will be described. FIG. 2 is a diagram showing the configuration of the (7,4) Hamming code in the asynchronous transfer mode transmission method of the present invention. FIG. 3 is a diagram showing a syndrome used for error correction of a (7,4) Hamming code in the transfer method of the asynchronous transfer mode of the present invention.

In FIG. 1, the simplest (7, 4) Humming code is used as an error correction code.
e) will be described as an example.

First, the (7, 4) Hamming code will be explained (for details, Hideki Imai, Information Theory, Shokodo Publishing, p.
138). First, the information bits (X1, X2, X3,
X4), a check bit C that satisfies the following relational expression
Create 1, C2 and C3.

C1 = X1 + X2 + X3 (+: exclusive OR) C2 = X2 + X3 + X4 C3 = X1 + X2 + X4 That is, the parity matrix H is And the transmitted code W is (X1, X2, X
3, X4, C1, C2, C3).

On the receiving side, using the parity matrix H,
By calculating the syndrome S according to S = YH ^T (Y: reception code, T: transposed matrix), error detection and correction are possible. Specifically, the code structure is as shown in FIG. 2, and the syndrome due to the error pattern is as shown in FIG.

Assuming that the error correction code is used, it is assumed that there are four input virtual circuits VC11 to VC14. As for the number of pieces of input information, it is sufficient to insert dummy bits in the unused input section, so that general characteristics are not impaired.

Transmitting side virtual circuit switch VCH shown in FIG.
In No. 1, the check bits are created for the input virtual circuits VC11 to VC14, the check bits are packed in the cells for each check bit, and then the check sequence (C1, C2, C3) is given to the cells, and the check codes are given to the cells. Virtual lines C1, C2, C3
Make up.

Next, a virtual path VP1 is constructed from the input virtual circuits VC11, VC12, VC13, VC14 composed of information series and the inspection virtual circuits C1, C2, C3. At that time, another virtual path VP2 having the same information as the virtual path VP1 is created by copying the virtual path VP1. One of the major characteristics of the asynchronous transfer mode is that the property of label multiplex is used, and the connection of a line or path and the amount that can be transferred on it can be made independent.
The connection status of the virtual path is not changed frequently, and once set, it is maintained for a long time. In this case, two virtual lines are already connected between the virtual circuit switches. Paths VP1 and VP2 are set, and information (VC11i, VC12i, VC13) is set as the capacity thereof.
i, VC14i) and inspection information (C1i, C2i, C3i) based on the calculation result are given. Therefore, the transmission side virtual circuit switch VCH1 is redundantly connected to the virtual path cross connector VPH1. With the virtual path cross connector VPH1,
According to the path route, as shown in FIG. 1, the virtual path V
P1 is directly connected to the virtual path cross connector VPH3,
The virtual path VP2 is a virtual path cross connector VPH2.
Via the virtual path cross connector VPH3.

The configuration of these paths changes according to the network topology and does not affect the essence of the present invention.
The important point is that multiple virtual paths are prepared for transferring the same information between the virtual circuit switches. In the receiving side virtual circuit switch VCH2, first, all information is stored in the buffer, and the virtual path VP1 and the virtual path VP2 are stored.
Ensure synchronization with and.

Next, among them, the cell sequence number forming each path is checked to confirm whether cell discard has occurred. It is possible to recover the discarded cell by using another cell received at the same time.

Then, the bit string is corrected by error correction, and even if there is a code error or cell discard on the transmission line, the original information series (VC11, VC1)
2, VC13, VC14) can be restored correctly.

In this system, when the cable is broken, the route is completely duplicated at the virtual path level, and the virtual line switch VCH2 on the receiving side is used to select a route in which no failure has occurred. It can be restored without switching.

In the embodiment N, the error correction code rule is described as the case of the (7, 4) Hamming code for simplification, but the code having a higher correction ability, for example, the code used for interplanetary communication is used. Is also possible.

Although the duplication of virtual paths has been described, it is possible to improve reliability by copying more virtual paths VP.

FIG. 4 is a block diagram of a transfer system of an asynchronous transfer mode according to another embodiment of the present invention. As shown in FIG. 4, a plurality of virtual path groups V carrying user information and control information
A method is also conceivable in which one spare virtual path VPc is prepared for P1 to VPn, and the receiving side virtual circuit switch VCH2 switches to a virtual path in which a failure or cell discard has occurred.
In this case, in the backup virtual path VPc, the virtual path number in which the failure is detected is notified to the transmission side virtual circuit switch VCH1 using the message communication means (MCM), and the path is copied and transferred. Take Here, the virtual path configuration circuit 14 adds the user information VC11k to VC14k (k = 1 to n) from the input virtual circuits VC11 to VC14 to the error correction control information C1k from the inspection virtual circuits C1 to C3.
~ C3k is added to the virtual path cell VPk (k = 1 to 1)
n) is output.

Further, since the virtual line for error correction control is configured independently of the information sequence, for example, when a large number of calls are generated, the virtual line for control is changed to
It is also possible to use by changing to the line for user information.

[0033]

As described above, according to the present invention, the recovery time can be shortened because the detour route is fixed in the redundant configuration, and the cell discard number is compensated by the cell sequence number to correct the error in the information bit string target. Since this is performed, there is an excellent effect that it is possible to deal with a service whose bit rate changes and highly reliable error correction and cell loss compensation.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a transfer system in an asynchronous transfer mode according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a (7, 4) Hamming code in a transfer method of an asynchronous transfer mode.

FIG. 3 is a diagram showing a syndrome used for error correction in a transfer method of an asynchronous transfer mode.

FIG. 4 is a block configuration diagram of a transfer system in an asynchronous transfer mode according to another embodiment of the present invention.

FIG. 5 is a block configuration diagram of a conventional automatic transfer control system of an asynchronous transfer mode transmission system.

FIG. 6 is a diagram showing the principle of a cell loss compensation method (encoding process) of a transfer method of an asynchronous transfer mode of a conventional example.

FIG. 7 is a diagram showing a principle of a cell loss compensation method (two-dimensional array coding) of a transfer method of an asynchronous transfer mode of a conventional example.

[Explanation of symbols]

11 Multiplexing circuit 12, 23 Synchronous circuit 13 Code configuration circuit 14 Virtual path configuration circuit 15 Copy circuit 21 Buffer 22 Virtual line configuration circuit 24 Error detection circuit 25 Separation circuit 26 Failure detection circuit C1 to C3 Inspection virtual line CONT control unit I / O Input / output unit LTE Terminal station relay unit MCM message communication means MTX switch (matrix unit) MUX multiplex conversion unit SV switching execution unit VC11 to VC14, VC11k to VC14k input virtual line VC21 to VC24, VC21k to VC24k output virtual line VCH1 transmission side Virtual circuit switch VCH2 Receiving side virtual circuit switch VP1 to VPn, VP2 Virtual path VPc Backup virtual path VPH1 to VPH3 Virtual path cross connector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kurakami 1-1-6, Saiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A means for forming a virtual path by adding control information and a cell sequence number based on an error correction code rule to cells from a plurality of input virtual circuit groups, respectively.
A transmission side virtual circuit switch including means for copying this virtual path to create two or more series of virtual paths and connecting them to different routes; and a virtual path of two or more series connected to the different routes. Means for buffering each cell,
A receiving side virtual circuit switch including means for reading out the contents of the buffering means, compensating for cell discard based on the cell sequence number, performing error correction, and outputting to a plurality of output virtual circuit groups. Asynchronous transfer mode transmission method. 2. A plurality of virtual path cross connectors which are connected between the transmission side virtual circuit switch and the reception side virtual circuit switch and which set the two or more virtual paths to different routes respectively. Asynchronous transfer mode transmission method.