KR100411594B1 - ATM Cell Transmission Apparatus and there of Payload Error Detection Method - Google Patents

Abstract

The present invention relates to a cell transmission apparatus and a payload error detection method thereof.

In a conventional cell transmitter, when a ATM cell is transmitted / received to an ATM exchanger upper interface device, a HEC (Header Error Control) code is inserted into a header of an ATM cell to detect only an ATM cell header error. There is a problem in that the transmission quality of the ATM cell is degraded because the payload cannot be detected even if an error occurs in the payload because the error is not checked.

According to the present invention, an ATM cell using an unused portion of an ATM cell format of a UTOPIA level 2 interface in a cell transmission device converting an E1 / T1 frame into an ATM cell and transmitting the same to an ATM switch and converting the ATM cell into an E1 / T1 frame. Since the CRC is performed on the payload of, the reliability of ATM cell transmission is improved.

Description

Cell transmission device and its payload error detection method

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cell transmission apparatus. In particular, UTOPIA (Universal Test Operations) is used in a cell transmission apparatus that converts an E1 / T1 frame into an Asynchronous Transfer Mode (ATM) cell for transmission to an ATM switch and converts an ATM cell into an E1 / T1 frame. PHY Interface for ATM (CHY) A cell transmission apparatus for improving reliability in ATM cell transmission by performing a cyclic redundancy check (CRC) on an ATM cell payload using an unused portion of a format of a level 2 interface; It relates to a payload error detection method thereof.

In general, when transmitting subscribers to an E1 / T1 line, a cell signal transmitting the ATM signal from the E1 / T1 frame into an ATM cell and converting an ATM cell applied from the ATM switch into an E1 / T1 frame transmits the ATM cell. In order to increase the reliability of the image, a process of detecting an error is performed.

Such a conventional cell transmission apparatus includes an ATM switch interface unit 11, an AAL2 processor 12, and an E1 / T1 framer 13 as shown in FIG. The E1 / T1 framer 13 converts the line level information of the E1 / T1 frame into PCM data using a framer that also serves as E1 / T1, but in synchronization with the frame synchronization signal FS as shown in FIG. The data is converted into frame data and transmitted to the AAL2 processor 12, and the frame data applied from the AAL2 processor 12 is converted into line level information of the E1 / T1 frame.

In addition, the AAL2 processor 12 compresses the audio signal of 64 Kbps for each channel to 32 Kbps according to Recommendation G.726 (ADPCM) according to the recommendation G.726 (ADPCM). In the AAL2 packet payload portion, a compressed voice signal is loaded. In FIG. 3, the CID (Channel Identifier) is composed of 8 bits, the LI (Length Indicator) is composed of 6 bits, and the UUI (User to User Indication) is composed of 5 bits. HEC (Header Error Control) consists of 5 bits and Payload consists of 1-45 or 1-64 octets. In addition, the AAL2 packet as shown in FIG. 3 is assembled into an ATM cell by the AAL2 processor 12. As described above, the process of converting the AAL2 packet into the ATM cell is performed as shown in FIG. 4. The payload of each ATM cell is made into 48 octets. A start field (SF) is attached, and the start field SF includes a 6-bit offset field (OSF), a 1-bit sequence number (SN), and a 1-bit parity (P). The assembled ATM cells as shown in FIG. 4 are transmitted to the ATM switch interface unit 11, where the interface operates at UTOPIA level 2. In addition, the AAL2 processor 12 conversely decomposes the process of FIG. 4 to the AAL2 packet for ATM cells received from the ATM exchanger, converts the corresponding AAL2 packet into the voice signal of the corresponding channel, and converts the E1 / T1 framer 13 To send.

Meanwhile, the ATM switch interface unit 11 transmits the ATM cell received from the AAL2 processor 12 to the ATM switch, and transmits the cell received from the ATM switch to the AAL2 processor 12.

In the conventional cell transmitter as described above, when the ATM switch interface unit 11 transmits and receives an ATM cell with respect to the ATM switch upper interface device, as shown in FIG. 5, a header error control (HEC) code is applied to the header of the ATM cell. Since only the ATM cell header error is detected by inserting the snippet, it does not check for the payload of the ATM cell. However, even if an error occurs in the payload, the transmission quality of the ATM cell is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its object is to convert an E1 / T1 frame into an ATM cell and transmit it to the ATM switch and to convert the ATM cell into an E1 / T1 frame. Cell transmission device and its payload error detection, which improves reliability of ATM cell transmission by performing cyclic redundancy check (CRC) on ATM cell payload using unused portion of ATM cell format of 2 interface To provide a method.

1 is a block diagram of a conventional cell transmission apparatus.

2 is a timing diagram for explaining the operation of the E1 / T1 framer.

3 is a frame diagram for explaining an operation in an AAL2 processor;

4 illustrates an ATM cell assembly in an AAL2 processor.

5 illustrates a UTOPIA level 2 cell format.

6 is a block diagram of a cell transmission apparatus according to the present invention.

7 is a configuration diagram of the CRC insertion and inspection unit shown in FIG.

8 illustrates an ATM cell format used in the present invention.

9 is a flowchart of a process of inserting a CRC into an ATM cell in the present invention.

10 is a flowchart of a process for checking a CRC error of an ATM cell in the present invention.

Explanation of symbols on the main parts of the drawings

60: ATM switch interface 70: CRC insertion and inspection unit

71: Payload extraction / CRC insertion unit 72: CRC generation / error detection unit

73: payload / CRC extraction unit 80: AAL2 processor

90: E1 / T1 Framer

A feature of the present invention for achieving the above object is, in a cell transmission apparatus for converting a subscriber's signal to an ATM cell and transmitting it to the ATM switch side, and converts the ATM cell received from the ATM switch into a subscriber's signal, Inserting a CRC code for detecting an error in the payload into the ATM cell transmitted to the ATM switch, and checking whether there is an error in the payload of the ATM cell based on the CRC code included in the ATM cell received from the ATM switch. The method further includes a CRC insertion and checking unit for transmitting the error information to the upper processor when an error is detected by checking the error.

The CRC insertion and checker delivers an ATM cell transmitted to the ATM switch, extracts payload information from the ATM cell, and extracts a payload for inserting the received CRC code into the UDF region of the ATM cell. A CRC insert; A payload / CRC extraction unit for delivering an ATM cell received from the ATM switch, extracting payload information from the corresponding ATM cell, and extracting a CRC code in the UDF region of the ATM cell; Receives payload information from the payload extraction / CRC insertion unit, generates a CRC code corresponding to the payload information, and outputs the CRC code to the payload extraction / CRC insertion unit, and payload information from the payload / CRC extraction unit. And a CRC-6 code, and calculates a corresponding CRC code based on the payload information to determine whether the corresponding CRC code matches the CRC code applied from the payload / CRC extractor. And an CRC generation / error detection unit that detects an error and informs an upper processor of the error information.

In addition, another aspect of the invention, the process of extracting the payload of the ATM cell transmitted to the ATM switch side to generate a CRC code corresponding to the payload; Inserting the CRC code into a UDF region of the transmitting ATM cell; Extracting the payload of the ATM cell received from the ATM switch and extracting a CRC code in the UDF region of the ATM cell; Generating a CRC corresponding to the payload extracted from the receiving ATM cell, checking whether the generated CRC is identical to the CRC extracted from the receiving ATM cell, detecting an error on the payload of the receiving ATM cell, and reporting the error to the higher processor; To include the process.

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

The cell transmission apparatus according to the present invention comprises an ATM switch interface unit 60, a CRC insertion and inspection unit 70, an AAL2 processor 80 and an E1 / T1 framer 90 as shown in FIG. . The E1 / T1 framer 90 converts the line level information of the E1 / T1 frame into PCM data by using a framer that also serves as E1 / T1. 80), and converts frame data applied from the AAL2 processor 80 into line level information of the E1 / T1 frame.

The AAL2 processor 80 generates an AAL2 packet with PCM data applied from the E1 / T1 framer 90, assembles the AAL2 packet into an ATM cell, and transmits the AAL2 packet to the CRC insertion and inspection unit 70. Use UTOPIA Level 2. In addition, the AAL2 processor 80 decomposes an ATM cell received from the CRC insertion and check unit 70 into an AAL2 packet, converts the AAL2 packet into PCM data, and transmits the AAL2 packet to the E1 / T1 framer 90.

Meanwhile, the CRC inserting and checking unit 70 inserts a CRC-6 code for detecting an error of payload in an ATM cell received from the AAL2 processor 80 and transmits the CRC-6 code to the ATM switch interface unit 60. The CRC-6 code included in the ATM cell received from the ATM exchanger interface unit 60 is extracted to check whether there is an error in the payload, and when an error of the payload is detected, the corresponding error information is transmitted to the upper processor to transmit quality. To judge. When the CRC insertion and checking unit 70 inserts the CRC-6 code into the ATM cell transmitted to the ATM switch interface unit 60, the UDF not used in the ATM cell format of the UTOPIA level 2 interface shown in FIG. The CRC-6 code for detecting a payload error is inserted in the user defined area (see FIG. 8) and transmitted to the ATM switch side through the ATM switch interface unit 60 to the payload of the ATM cell. Check the CRC for errors. In addition, when the CRC insertion and checking unit 70 receives an ATM cell transmitted from the ATM exchanger through the ATM exchanger interface unit 60, the CRC-6 code inserted in the ATM cell is checked to check the ATM cell's pay. If an error occurs by determining whether an error occurs on a load, error information is transmitted to a higher processor to determine transmission quality.

The ATM switch interface unit 60 transmits the ATM cell received from the CRC insertion and check unit 70 to the ATM switch, and transmits the cell received from the ATM switch to the CRC insertion and check unit 70.

As described above, the CRC insertion and inspection unit 70 includes a payload extraction / CRC insertion unit 71, a CRC generation / error detection unit 72, and a payload / CRC extraction unit 73. It is composed. The payload extraction / CRC insertion unit 71 delivers the ATM cell applied from the AAL2 processor 80 to the ATM switch interface unit 60, extracts the payload from the corresponding ATM cell, and generates the CRC information / error. The CRC-6 code applied to the detection unit 72 side and applied from the CRC generation / error detection unit 72 is inserted into the UDF area of the ATM cell as shown in FIG. 8 and output to the ATM switch interface unit 60 side. The payload / CRC extractor 73 delivers the ATM cell applied from the ATM switch interface unit 60 to the AAL2 processor 80, extracts the payload from the corresponding ATM cell, and generates the corresponding payload information in CRC generation / At the same time as the output to the error detection unit 72, the CRC-6 code in the UDF area is extracted and output to the CRC generation / error detection unit 72. In addition, when the payload information is input from the payload extraction / CRC insertion unit 71, the CRC generation / error detection unit 72 generates a CRC-6 code corresponding to the payload information to generate the payload extraction / CRC insertion unit ( 71), and upon receiving the payload information and the CRC-6 code applied from the payload / CRC extractor 73, the corresponding CRC-6 code is calculated based on the payload information, and the corresponding CRC- By determining whether the 6 code matches the CRC-6 code applied from the payload / CRC extraction unit 73, it detects whether there is an error in the payload of the ATM cell received from the ATM switch interface unit 60, and the corresponding error information. Inform the upper processor to determine the transmission quality of the ATM cell.

In the cell transmission apparatus according to the present invention configured as described above, a process of inserting a CRC to detect an error on a payload of an ATM cell is performed as shown in FIG.

First, when an ATM cell is input from the AAL2 processor 80 (step S11), the payload extraction / CRC inserting unit 71 extracts the payload from the corresponding ATM cell and converts the information into a CRC generation / error detection unit 72. (Step S12), the CRC generation / error detection unit 72 receives the payload information from the payload extraction / CRC insertion unit 71 and generates a CRC-6 code corresponding to the payload information. It outputs to the load extraction / CRC insertion part 71 side (step S13). Accordingly, the payload extraction / CRC insertion section 71 inserts the CRC-6 code applied from the CRC generation / error detection section 72 into the UDF area of the ATM cell as shown in Fig. 8 (step S14), and the ATM switch interface section. It transfers to the 60 side (step S15). Thus, by inserting the CRC-6 code into the UDF area of the ATM cell and transmitting the ATM cell through the ATM switch interface unit 60, the upper exchange determines whether the ATM cell payload is error based on the corresponding CRC-6 code. Make it.

On the other hand, in the cell transmission apparatus according to the present invention, a process of detecting an error on the payload of the ATM cell applied from the ATM switch is performed as shown in FIG.

First, when an ATM cell is input from the ATM switch via the ATM switch interface unit 60 (step S21), the payload / CRC extractor 73 extracts the payload from the corresponding ATM cell and extracts the payload information. While outputting to the CRC generation / error detection unit 72, the CRC-6 code in the UDF area is extracted and output to the CRC generation / error detection unit 72 (step S22). At this time, when the CRC generation / error detection unit 72 receives the payload information and the CRC-6 code applied from the payload / CRC extraction unit 73, the CRC generation / error detection unit 72 generates a corresponding CRC-6 code based on the payload information. (Step S23), it is determined whether the corresponding CRC-6 code matches the CRC-6 code applied from the payload / CRC extraction section 73 to the payload of the ATM cell received from the ATM switch interface section 60. If an error is detected by checking whether there is an error (step S24), the corresponding error information is notified to the upper processor so as to grasp the transmission quality of the ATM cell (step S25).

As described above, in the present invention, a portion of the cell transmission apparatus that converts an E1 / T1 frame into an ATM cell and transmits the same to an ATM switch and converts the ATM cell into an E1 / T1 frame is not used in the ATM cell format of the UTOPIA level 2 interface. Since CRC is performed on the payload of the ATM cell, the reliability of the ATM cell transmission is improved.

Claims (3)

A cell transmission device for converting a subscriber's signal into an ATM cell and transmitting the signal to an ATM switch, and converting an ATM cell received from the ATM switch into a subscriber's signal, wherein the payload error is transmitted to the ATM cell transmitted to the ATM switch. Inserts a CRC code for detection and checks whether there is an error in the payload of the ATM cell based on the CRC code included in the ATM cell received from the ATM switch. And a CRC inserting and checking unit for transmitting. The method of claim 1, wherein the CRC insertion and inspection unit, A payload extraction / CRC insertion unit for delivering the ATM cell transmitted to the ATM switch, extracting payload information from the corresponding ATM cell, and inserting the received CRC code into the UDF region of the ATM cell; A payload / CRC extraction unit for delivering an ATM cell received from the ATM switch, extracting payload information from the corresponding ATM cell, and extracting a CRC code in the UDF region of the ATM cell; Receives payload information from the payload extraction / CRC insertion unit, generates a CRC code corresponding to the payload information, and outputs the CRC code to the payload extraction / CRC insertion unit, and payload information from the payload / CRC extraction unit. And a CRC-6 code, and calculates a corresponding CRC code based on the payload information to determine whether the corresponding CRC code matches the CRC code applied from the payload / CRC extractor. And a CRC generation / error detection unit for detecting an error and notifying the upper processor of the error information. Extracting a payload of an ATM cell transmitted to an ATM switch and generating a CRC code corresponding to the payload; Inserting the CRC code into a UDF region of the transmitting ATM cell; Extracting the payload of the ATM cell received from the ATM switch and extracting a CRC code in the UDF region of the ATM cell; Generating a CRC corresponding to the payload extracted from the receiving ATM cell, checking whether the generated CRC is identical to the CRC extracted from the receiving ATM cell, detecting an error on the payload of the receiving ATM cell, and reporting the error to the higher processor; Payload error detection method in a cell transmission device comprising a process.