KR100255812B1 - Restoration method for atm cell - Google Patents

Abstract

PURPOSE: A method for restoring an ATM cell structure is provided to restore a deformed structure of an ATM cell into a standard structure in order to easily carry out the next ATM cell processing. CONSTITUTION: A user sets up the current word number 'n' as '27'(S411). The user moves a higher-level byte of the nth word to a lower-level byte of the nth word(S412). The user moves a lower-level byte of the (n-1)th word to the higher-level byte of the nth word(S413). The user checks the current word number(n)(S414). If the current word number 'n' is not '4', the user decreases 'n' by '1'(S415). In case that the 'n' is '4', the user fills all the bits of a lower-level byte of the third word with a logic value '0'(S420) and finalizes the ATM cell restoration procedures(S430).

Description

Method of recovering ATM cell structure

The present invention relates to a method for recovering an ATM cell structure for recovering an ATM cell of a modified structure into an ATM cell of a standard structure, and in particular, a demand dense optical subscriber carrier (Fiber Loop Carrier-Curb System: hereinafter referred to as a FLC-C system). It is used for.) And is an optical transceiver device that transmits multiple signals by receiving ATM cell-based electrical digital signals, converts electrical signals into optical signals and transmits them through optical cables (Optical Transmit / Receive Unit: OTRU), when the ATM cell-based signal multiplexed by the multiplexer is different from the standard ATM cell structure, the ATM cell structure recovery method for converting back to the standard structure will be.

Conventionally, since the digital signal multiplexed by the multiplexer of the OTRU has an ATM cell of a modified structure, the design of a device connected to the multiplexer is inconvenient.

Accordingly, the present invention has been made to solve the above problems, when the structure of the ATM cell is different from the standard structure, in order to facilitate the processing of the ATM cell of the next step, the modified ATM cell of the standard structure Its purpose is to provide a method for recovering an ATM cell.

In order to achieve the above object, the ATM cell structure recovery method according to the present invention comprises the steps of moving all the bytes from the lower byte of the third word of the ATM cell to the upper byte of the 27th word downward by one byte; And filling all of the lower bytes of the third word of the ATM cell with the logical value '0'.

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

2 is a structural diagram of an OTRU;

3 is a structural diagram of a standard ATM cell;

4 is a diagram illustrating an ATM cell structure recovery operation.

FIG. 1 is a schematic diagram of a FLC-C system. The service providers 130 that provide various services such as home shopping, games, and movies are provided through the ATM switch 100 and the FLC-C system 200. Are connected to each other with optical subscribers 140 requiring them.

The FLC-C system 200 is installed in the telephone company, connects the DS1 (E) signal connected to the PSTN 110 and the broadband signal based on the ATM delivered from the broadband switching network, and integrates and multiplexes the synchronous digital hierarchy. Then, the optical signal received from the HDT 210 is installed in the distribution center of the dense area, such as the HDT 210 and the apartment complex that performs the optical transmission to the ONU 220 and the reverse function of the power device Is a FTTC (Fiber To The Curb) type service transmission platform consisting of ONU 220, which is a device that separates each subscriber signal according to a service and provides the subscriber with the function and performs the reverse function. The FLC-C system 200 transmits data related to the service from the HDT 210 to the ONU 220 through the optical path 230, and the existing telephone line from the ONU 220 to each subscriber 140. 150, standard telephone and digital services are transmitted.

The HDT 210 receives four STM-1 (Synchronous Transport Module-1) signals having a transfer rate of 155.52 Mbps from the ATM switch 100, processes the overhead included in the STM-1 signal, and provides an ATM cell. ATRU 211 for extracting the data, a cell bus 213 that is a transmission path of ATM cells, an OTRU 212 that is in charge of the connection between the HDT 210 and the ONU 220, and the like. The DS1E signal is connected and the digital video service is connected from the ATM switch 100. The digital video service signal connection is made by the STM-1 based on the ATM, and the ATM cell is transmitted at the time of transmission to the ONU 220. It is relocated and multiplexed to the STM-4.

The ONU 220 separates the subscriber signal from the STM-4 optical signal received from the HDT 210 according to the service and provides the subscribers 140 with the service 140 and the reverse operation. A management system is an operator terminal, and is a device that performs functions such as failure, charging, configuration, performance, and security management according to a TMN (Telecommunication Management System) method.

2 is a configuration diagram of the OTRU 212 according to the present invention, and performs an operation of connecting the OTRU 212 and the ATM cell bus 213 using cell bus switching, and total eight cell bus switching units 311. UTOPIA of 622.08 Mbps by multiplexing four 155.52 Mbps Universal Test and Operations PHY Interface for ATM (UTOPIA) Level 1 signals transmitted from the cell bus connection 310 and the cell bus connection 310 to 4: 1 The multiplexer that transmits the level 2 signal to the ATM / UNI unit 340 and the virtual path identifier (VPI) value of the ATM cell among the UTOPIA level 2 signals transmitted from the ATM / UNI unit 340. Once the port is addressed, two multiplexing / demultiplexing units 320 and multiplexing / demultiplexing units 320 constituted by a demultiplexer for demultiplexing by transmitting one of four UTOPIA level 1 signals to an addressed port are provided. Port number to the demultiplexer, corresponding ATM cell Apparatus for controlling the transmission of the signals, the addressing unit 330 for translating the VPI of the UTOPIA level 2 signal cells from the ATM / UNI unit 340 to designate the port address of the demultiplexer, and 8 bits from the clock processing unit 350. Two ATM / UNI units 340 for converting the STM-4c-class signals transmitted through the data bus into UTOPIA level 2 signals through the 16-bit data bus and transmitting the data to the addressing unit 330 at the ATM cell level. By using a clock of 19.44Mhz supplied from the clock supply unit 301, a clock of 77.76Mhz is generated and the clock synthesizing unit 351, which supplies the main clock in the ATM / UNI unit 340, between the parallel signal and the serial signal. Two clock processing units 350 comprising a parallel / serial signal converting unit 352 for converting and a clock recovering unit 353 for restoring the original clock from the received signal. Optical transmission that performs optical conversion before reception The bride 360 and the cell bus connection 310 have a clock rate of 25.92Mhz, and the demultiplexer of the multiplexer / demultiplexer 320 has a clock rate of 25Mhz so that these two devices can correctly exchange data with each other. FIFO (First Input First Output) unit 370, which enables the inter-processor serial communication, the MC68302 16-bit microprocessor 382, the OTRU 212 operating program permanently stored When the ROM 383 and the OTRU 212 start to operate, the RAM 384 is configured to move an operation program in the ROM and to execute the program, thereby controlling, alarming, monitoring, and managing each device. A microprocessor unit 380 that performs a function and a power source and a power failure detection unit 390 that operate to supply power to the OTRU 212 or detect a failure of the power source.

3 is a structural diagram of a standard ATM cell, which has a total size of 27 words (16 bits), and the third to third words are overheads used to check the normality of data transmission, and the remaining words are payload. Data.

However, the multiplexer included in the multiplexer / demultiplexer 320 of FIG. 2 multiplexes four 155.52Mhz UTOPIA (Universal Test & Operations PHY Interface for ATM) level 1 data signals inputted from the cell bus connector 310 into one. Thus, when transmitting to the ATM / UNI unit 340 through a 16-bit data bus, the ATM structure changes. That is, in the ATM standard structure, the HCS (Header Check Sequence) is located in the lower byte 510 of word 3 and the payload is located in the lower byte 520 of word 27, but this HCS byte is the lower byte of word 27. It is located at 520.

4 is a flowchart illustrating a recovery operation of the modified ATM cell structure, and includes a byte shifting process (S410) for moving the changed bytes to an in-place position and an HCS insertion step (step S420) for filling HCS bytes.

In the byte shifting process S410, first, setting the current word number n to be related to the shift to 27 (step S411), and shifting the upper byte of the nth word to the lower byte of the nth word (step S412). ), shifting the lower byte of the n-1th word to the upper byte of the nth word (step S413), checking the current word number n (step S414), and determining the result n in step S414 by 4 If not, it decreases n by 1 and proceeds to step S412 again (step S415).

If the check result n in step S414 is 4, the process proceeds to the HCS insertion step (step S420) of filling all bits of the lower byte of the third word with the logic value "0", and ends the ATM cell recovery process (step S430). In the HCS insertion step (step S420), the reason for filling all bits of the lower byte of the third word with the logical value "0" is that the HCS bits contain information for checking a header error. 0 ".

Using the method according to the present invention, when the ATM cell structure is changed in the process of processing the signal based on the ATM cell, it is possible to restore to the standard structure of the ATM cell, so that subsequent ATM cell processing is easy. There is a repelling effect.

Claims (1)

Moving all bytes from the lower byte of the third word of the ATM cell to the upper byte of the 27th word downward by one byte; And And filling all lower bytes of the third word of the ATM cell with a logical value of '0'.

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