KR100287416B1 - Asynchronous Transmission Mode Cell Structure Conversion Method in Demand Dense Optical Subscriber Transmitter - Google Patents

Abstract

The present invention relates to a method for converting an asynchronous transmission mode cell structure in a demand dense optical subscriber transmitter, wherein a 27 word standard structure ATM cell processed in a demand dense optical subscriber transmitter is converted into an ATM cell having a predetermined other structure. It is to do it.

The present invention provides a predetermined ATM cell by swapping the position of the upper byte and the lower byte of every word with respect to a predetermined ATM cell having a standard structure, and counting from a start of cell (SOC) of the reverse standard ATM cell. Distinguishing the first word to the 27th word, and for each word from the fourth word to the 27th word among the divided words, the lower byte of the word is higher than the word having the number less than one by the current word number. After transferring to a byte, transferring the upper byte of the word to the lower byte of the word, and setting the upper byte of the 27th word to an arbitrary value.

Description

A method of changing a structure of Asynchronous Transfer Mode cells for Fiber Loop Carrier-Curb systems

The present invention relates to a method for converting an asynchronous transmission mode cell structure in a demand dense optical subscriber transmitter, and particularly used in a demand dense optical subscriber transmitter (hereinafter referred to as a Fiber Loop Carrier-Curb System). The present invention relates to a method for converting an ATM cell structure between devices for processing asynchronous transfer mode cells (ATM cells) using different ATM cell formats.

FIG. 1 is a block diagram of a FLC-C system 100, and service providers providing various services such as home shopping, games, movies, etc. are provided via a host digital terminal 110 through an ATM switch 10. And optical termination unit (120: Optical Network Unit) to provide services to optical subscribers.

At this time, the HDT 110 is a device installed in the telephone station, connects the DS1 and DS1E signals with the ATM-based broadband signals transmitted from the broadband switching network side, integrates and multiplexes them into the synchronous digital hierarchy, and then uses the ONU (international apparatus). 120) and the reverse function. In addition, the ONU 120 is installed in a distribution center of a dense residential area such as an apartment complex, and separates each subscriber signal from the optical signal received from the HDT 110 according to a service and provides each subscriber with its reverse function. Device to perform.

The FLC-C system 100 is a FTTC (Fiber To The Curb) service transmission platform. In order to provide telephone and video services to subscribers, the HDT 110 to the ONU 120 are connected to a service through an optical path. It transmits related data, and each subscriber from ONU 120 delivers standard telephone service and digital service using existing telephone line.

Meanwhile, the ONU 120 receives an STM-4 class optical signal having a transmission rate of 622.08 Mbps transmitted from the HDT 110, converts the optical signal into an ATM cell bus 123, and outputs the signal to the ATM cell bus 123. It is connected to the corresponding subscribers through a predetermined subscriber access device, such as 122, receives the signals of the ATM cell unit from the ATM cell bus 123 to make the STM-4 class optical signal to HDT (110) A clock and optical transceiver unit 121 that performs a function is used.

At this time, the clock and optical transmitting / receiving unit 121 (COTU) includes an ATM processor (not shown) for extracting signals of an ATM cell unit from the optical signal received from the HDT 110 to perform such a function, and from the ATM processor. A demultiplexer (not shown) is used to demultiplex the output ATM cell signals to any one of the four cell bus switching elements.

However, since the ATM processor and the demultiplexer are often implemented using a commercial chip that performs a corresponding function, the structure of an ATM cell may be different. That is, the ATM processor uses an ATM cell of a standard structure, but the demultiplexer uses an ATM cell having a different structure from that of the standard ATM cell. Therefore, in this case, it is necessary to convert the ATM cell output from the ATM processor into an ATM cell of a structure used by the demultiplexer.

Accordingly, the present invention has been made to meet the above needs, and a method for converting an ATM cell of a standard structure into an ATM cell structure used by the demultiplexer, that is, an asynchronous transmission mode in a demand dense optical subscriber transmission device. The purpose is to provide a cell structure conversion method.

In order to achieve the above object, the asynchronous transmission mode cell structure conversion method in the demand-density optical subscriber transmission device according to the present invention, the position of the upper byte and the lower byte of each word with respect to a predetermined ATM cell of the standard structure Switching to create a predetermined counterstandard ATM cell; Counting from a Start Of Cell (SOC) of the inverse standard ATM cell to distinguish each of the first word to the 27th word; For each word from the fourth word to the 27th word among the classified words, the lower byte of the word is moved to the upper byte of the word by one less than the current word number, and the upper byte of the word is Moving to lower byte; And setting the upper byte of the 27th word to an arbitrary value.

1 is a configuration diagram of an FLC-C system;

2 is a structural diagram of a standard ATM cell;

3 is a structural diagram of an ATM cell used in an ATM cell demultiplexing chip;

4 is a structural diagram of a standard ATM cell in which high byte and low byte positions are interchanged;

5 is a flow chart of a method according to the invention.

* Explanation of symbols for main parts of the drawings

10: ATM exchange 100: FLC-C system

110: host digital terminal (HDT) 120: optical termination (ONU)

121: clock and optical transceiver 122: ATM cell bus

123: video channel unit (VCU) 200: standard ATM cell

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a structural diagram of a standard ATM cell 200, which consists of a total of 27 words (word: 2 bytes).

In this case, the upper byte (Header1) of the first word is composed of 4 bits of Generic Flow Control (GFC) and 4 bits of Virtual Path Identifier (VPI), and the lower byte (Header2) is It consists of a 4-bit Virtual Path Identifier (VPI) and a 4-bit Virtual Channel Identifier (VCI).

In addition, the upper 12 bits of the second word (upper 4 bits of Header3 and Header4) are virtual channel identifiers (VCI), and the lower 4 bits of the lower byte (Header4) are 3 bits of payload type (PT) and payload type. 1 bit of cell loss priority (CLP: Cell Loss Priority), the upper byte (UDF1) of the third word is header error control (HEC: Header Error Control) information, the lower byte (UDF2) is the header check order ( HCS: Header Check Sequence (HCS) information.

In the remaining 24 word sections from the fourth word to the 27th word, a total of 48 bytes of payloads from the first payload byte Payload1 to the 48th payload byte Payload48 are sequentially filled.

3 is a structural diagram of the ATM cell 300 used in the demultiplexing chip. Compared to the standard ATM cell 200, the upper byte and the lower byte of the first word and the second word are interchanged with each other. The upper byte of the third word is the first payload byte Payload1, and the upper byte UDF1 of the third word of the standard ATM cell 200 is located in the lower byte.

The second payloads Payload2 to the 47th payloads 47 are shifted from the fourth word to the 26th word, and the upper byte of the last 48 bytes of the third word of the standard ATM cell 200 is located. The lower byte UDF2 is located and the 48 th payload byte Payload48 is located at the lower byte.

Therefore, the standard ATM cell 200 output from the ATM processor must be converted into the ATM cell 300 of the structure shown in FIG. 3 before being processed by the demultiplexing chip.

4 is a flow chart of a method according to the invention.

First, the ATM cell 200 having a standard structure output from the ATM cell processor is input (S410), and the positions of the upper byte and the lower byte of each word are interchanged (S420). This results in an ATM cell 500 having the structure as shown in FIG. 5, which will be referred to as an inverse standard ATM cell.

In step S430, the inverse standard ATM cell 500 is counted from a start point of a cell (SOC) to distinguish the first to twenty-seventh words (S430).

Then, using a predetermined memory element (eg, a D flip-flop), the lower byte of the word starting from the fourth word of the inverse standard ATM cell 500 and up to the twenty-seventh word is one word less than the current word number. After moving to the upper byte, the process of moving the upper byte of the word to the lower byte of the word is repeated (S440).

As an example, the processing for the fourth word will be described. After moving the lower byte Payload1 of the fourth word to the upper byte position of the third word, the upper byte Payload2 of the fourth word is lower than the fourth word. To move to the byte position.

Finally, the upper byte of the 27th word is set to an arbitrary value (S450). This byte is discarded during demultiplexing in the demultiplexing chip and can be set to any value.

As described above, the present invention can easily convert the ATM cell 200 having the standard structure into the ATM cell 300 having the structure shown in FIG. This has the effect of smoothly performing the interface.

Claims (1)

A method for converting a 27-word standard ATM cell processed by a predetermined demand density optical subscriber transmission device into an ATM cell having a predetermined other structure, For the standard ATM cell, swapping the high byte and low byte positions of every word to create a predetermined inverse standard ATM cell; Counting the inverse standard ATM cells from a start point of a cell (SOC) to distinguish first to twenty-seventh words; For each word from the fourth word to the 27th word among the classified words, the lower byte of the word is moved to the upper byte of the word by one less than the current word number, and the upper byte of the word is Moving to lower byte; And And setting the upper byte of the 27th word to an arbitrary value.