KR19980017792A - Boundary Signal Extractor from Pointer with Structural Data Transfer Information in AAL Type 1 and Its Extraction Method - Google Patents

Abstract

According to the present invention, a boundary signal extraction from a pointer having structural data transfer information in AAL type 1 is adapted to extract a frame signal having boundary information of a user data structure from a pointer having information on a user data structure input from an ATM layer. An apparatus and a method of extracting the same, comprising: a first register (12); Second register 13; A counter for counting user data of the split-and-recombine protocol data unit (SAR-PDU) from a user clock from the ATM layer and outputting a count bit for the user data by the enable signal from the control means 15 ( 11); Comparison means (14) for comparing the count bits from the counter (11) with the pointer bits from the second register (13) and outputting a boundary signal; An AND gate 16 which blocks the boundary signal from the comparison means 14 by the control signal from the control means 15; Control means (15) for enabling the first and second registers (12, 13), the counter (11), and outputting a frame signal to the AND gate (16) by the cell loss signal. It is characterized by.

Description

Boundary Signal Extractor from Pointer with Structural Data Transfer Information in AAL Type 1 and Its Extraction Method

The present invention relates to an apparatus for extracting a boundary signal from a pointer having structural data transfer information in AAL type 1 and a method of extracting the same. In particular, the boundary of a user data structure from a pointer having information about a user data structure input from an ATM layer An apparatus for extracting a boundary signal from a pointer having structural data transfer information in AAL type 1 configured to extract a frame signal having information and a method of extracting the same.

In general, the ATM Adaptation Layer (ATM) adapts the service provided by the ATM layer to the requirements of the upper layer user. Therefore, the ATM adaptation layer must provide support between the ATM and non-ATM environments, as well as support the user plane, the higher levels of the control plane, and the management plane.

In addition, the ATM adaptation layer maps the protocol data unit (PDU) of the upper layer to the payload section of the ATM cell, handles transmission errors, processes and flows control of lost and inserted cells. It provides timing control. The ATM adaptation layer is divided into two sublayers: a segmentation and reassembly (SAR) sublayer and a convergence sublayer (CS).

The convergence sublayer (CS) performs a function related to a specific service, and the partitioning and recombination (SAR) processes a function related to service segmentation and recombination by processing a function that is not related to service termination. Therefore, at the transmitting side, the convergent sublayer (CS) is applied as user information from an upper layer, attaches a header and a trailer, forms a convergent sublayer protocol data unit (CS-PDU), and sends it to a split and recombination (SAR) sublayer. This split and recombine (SAR) sublayer cuts it into the size of an ATM cell, attaches a header and a trailer to form a split and recombine protocol data unit (SAR-PDU) and transmits it through the ATM layer.

On the receiving side, the segmentation and recombination (SAR) sublayer extracts only the payload interval among the segmentation and recombination protocol data units (SAR-PDU) received through the ATM layer to form a convergence sublayer protocol data unit (CS-PDU). After that, the information is transferred to the convergence sublayer CS, and the convergence sublayer CS extracts only upper layer user information among the received convergence sublayer protocol data units CS-PDUs and delivers the information to the upper layer.

At this time, the header and the trailer attached to each sub-layer in the transmission process are related to error processing, buffer management, and sequence preservation. Will be passed to the layer.

On the other hand, ITU-T classifies user services into four types of A, B, C, and D according to constant bit rate (CBR), real time, and connectivity, and AAL type to correspond to these various services. It is defined by dividing into 1 to 4. In addition, the June 1992 ITU-T Conference newly discussed AAL Type 5 to support high-speed data communications.

In the AAL type 1, a real-time equal bit rate service is provided in a connected manner, and a service provided to a user is largely equal bit rate (CBR) data transfer, timing information transfer, user data structure information transfer, error recovery capability, and cannot be recovered. Display of information about errors and losses.

Accordingly, in AAL type 1, when information of a user data structure for the user data is to be transferred, that is, when the boundary of the user data structure needs to be preserved, for example, in case of 8 kHz structured data, a converging sublayer ( In the CS), the start of the user data block is represented by a pointer, and structural data transfer using the pointer is performed.

On the other hand, when performing data transmission using the pointer including the information of the user data structure as described above, the frame signal for the boundary signal of the user data structure from the pointer containing the structural data transfer information input from the receiving ATM layer There is a need for a device for extracting the.

Accordingly, the present invention is to solve the above problems, the structural data transfer in the AAL type 1 to extract the frame signal having the boundary information of the user data structure from the pointer having information about the user data structure input from the ATM layer An object of the present invention is to provide an apparatus for extracting boundary signals from a pointer with information and a method of extracting the same.

According to an aspect of the present invention, a payload pointer of a split and recombination protocol data unit input from an ATM layer is extracted and stored, and a first output point is output by an enable signal from a control means. A register; A second register for shifting and storing the pointer from the first register and outputting pointer data by an enable signal from the control means; A counter for counting user data of the segmentation and recombination protocol data unit from the user clock from the ATM layer and outputting a count bit for the user data by the enable signal from the control means; Comparison means for comparing the count bit from the counter with the pointer bit from the second register and outputting a boundary signal; An AND gate which blocks the boundary signal from the comparing means by the control signal from the control means; And the control means for enabling the first and second registers and the counter by the cell loss signal and outputting a frame signal to the AND gate.

According to the present invention configured as described above, when a malfunction occurs from an external signal by extracting a frame signal having boundary information of a user data structure from a pointer having information on a user data structure input from an ATM layer, It is possible to provide a function of bit error detection and correction.

1 is a conceptual diagram illustrating a general ATM protocol reference model;

2A is a diagram illustrating a data format of an ATM cell;

2b is a diagram illustrating a header structure in a user network interface (UNI);

2c is a diagram illustrating a header structure at a network node interface (NNI);

3A is a diagram illustrating a data format for each layer in an ATM communication method;

3B is a view showing the SAR format of the AAL type 1 shown in FIG. 2A;

4A to 4C are diagrams illustrating a segmentation and recombination protocol data unit (SAR-PDU) and a pointer interval for structural data delivery;

FIG. 5 is a view showing an embodiment of a boundary signal extracting device from a pointer with structural data transfer information in AAL type 1 according to the present invention; FIG.

6 is a flowchart illustrating the operation of the boundary signal extraction method from the pointer with the structural data transfer information in AAL type 1 according to the present invention.

Explanation of symbols on the main parts of the drawings

10: FIFO, 11: 7 bit counter,

12, 13: first and second register, 14: comparator,

15: control unit, 16: AND gate.

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

First, the ATM scheme to which the present invention is applied will be briefly described to facilitate understanding of the present invention.

1 is a conceptual diagram illustrating an ATM protocol reference model, wherein the openness is composed of a management plane, a control plane, and a user plane, and the management plane is again hierarchical. It will consist of management and flat management. In addition, the plane management means the overall management of the system, and the hierarchical management manages resource and usage variables and OAM information management.

In addition, the control plane manages call control and connection control information, and the user plane transmits user information. The protocol of the control plane and the user plane is composed of a higher layer, an ATM adaptation layer, an ATM layer, and a physical layer.

As shown in FIGS. 2A to 2C, the user's long message is divided into ATM cells and transmitted, and the received ATM cell is reassembled into one message and transmitted to the upper user. .

FIG. 2A is a diagram illustrating a data format of an ATM cell, FIG. 2B is a diagram illustrating a header structure at a user network interface (UNI), and FIG. 2C is a diagram illustrating a header structure at a network node interface (NNI).

Here, the ATM cell is divided into a header section of 5 bytes (or octets) and a user information section of 48 bytes, and the header of 5 bytes is a user network interface (UNI) as shown in FIGS. 2B and 2C. Header structure in the user network interface (UNI), where the first byte is a 4-bit generic flow control (GFC) and a 4-bit virtual path identification number (VPI). identifier).

The second byte is composed of a 4-bit virtual path identification number (VPI) and a 4-bit virtual channel identifier (VCI), and the third byte is an 8-bit virtual channel identifier (VCI). The fourth byte consists of a 4-bit virtual channel identification number (VCI), a 3-bit payload type (PT), and a 1-bit cell loss priority (CLP). The byte consists of 8 bits of header error control (HEC).

Also, in the header structure of the network node interface (NNI) as shown in FIG. 2C, the general flow control (GFC) in the first byte of the user network interface (NNI) is converted into a virtual path identification number (VPI). Except for being used, it can be seen that it is identical to the header structure of NNI. This ATM communication method has a hierarchical structure as shown in Table 1 below and has standardized standards for each layer.

Hierarchy Tier function Upper hierarchy Higher layer function ATM Adaptation Layer Convergence (CS) sublayer Convergence function Cutting and Recombination (SAR) Cutting function and recombination function ATM layer General flow control and cell header processing Physical layer Transmission Convergence (TC) HEC signal generation and extraction function Physical medium Bit time information function

As shown in Table 1, the ATM communication method is divided into vertical structures such as a physical layer, an ATM layer, an ATM adaptation layer (AAL), and a higher protocol layer, and the AAL layer is a cut and recombination sublayer (SAR). It is divided into segmentation and reassembly sublayer (CS) and convergence (CS) sublayers, and the physical layer is divided into physical media (PM) and transmission convergence (TC) sublayers.

In addition, a service required by a user in an ATM communication method may be classified as shown in Table 2 below according to its characteristics.

Type of service End-to-end time relationship Bit rate Connection mode Example of service Class A Real time Identity Connectivity Video signal Class B Real time variable Connectivity Variable Rate Video Signal Class C Non-real-time variable Connectivity Connectivity data Class D Non-real-time variable Connectionless Connectionless data

The AAL protocol corresponding to the service is divided into AAL 1 to AAL 5 as shown in Table 3 below.

AAL form Typical feature AAL 1 Support class A service of equal bit rate AAL 2 Support real-time, variable bit rate Class B service AAL 3/4 Support class C and D services with variable bit rate AAL 5 High speed service by simplifying AAL 3/4 function

In Table 3, the AAL layer is divided horizontally as AAL 1, AAL 2, AAL 3/4, and AAL 5 to efficiently process the corresponding service according to the type of service.

Here, the AAL layer 1 is a convergent sub-layer (CS) that transparently transmits a Class A service data unit (U-SDU) having a constant bit rate, detects transmission errors, and performs information identification and clock synchronization functions. A split and recombination sublayer (SAR) that divides variable-length data received from the convergence sublayer (CS), creates an ATM cell, transfers it to the ATM layer, and receives and reassembles the ATM cell from the ATM layer to recover the CS-PDU. Will be divided into

In addition, the convergence (CS) sublayer is a common part convergence sublayer (CPCS) that performs functions common to the connectivity and connectionless services, and a service specific convergence sublayer for providing a specific AAL user service. (SSCS: service specific convergence layer).

3A is a diagram illustrating a data format for each layer in an ATM communication method, wherein an upper layer user service data unit (U-SDU) passes through an AAL service access point (AAL-SAP) and then AAL. It is formed as a service data unit (AAL-SDU) and stored in the AAL FIFO.In the AAL1 SAR layer, the CS-PDU is divided into 47 bytes according to the message to be transmitted by the user, and then 1-byte SAR header is added to divide and recombine. A protocol unit (SAR-PDU) is formed and sent down to the ATM layer via an ATM service access point (ATM-SAP). In the ATM layer, a 5-byte ATM header is attached to form a 53-byte ATM cell, and then transmitted to another terminal or ATM switch through an optical transmission path of the physical layer.

That is, AAL type 1 protocol transmits U-SDU of equal bit rate at the same bit rate along with related time information, so that clock information of information source can be extracted at the receiving side, and at the convergence part layer, the bit for high quality video or audio signal Error correction function is provided, and the division and reassembly sublayer divides the CS-PDU and adds a 1-byte header to send it to the ATM layer.

FIG. 3B illustrates the SAR format of the AAL Type 1 shown in FIG. 3A, wherein the transmitted message is divided into a 47-byte SAR-PDU payload and a 1-byte header, which is a 4-bit sequence number protection. (SNP: sequence number protection), which consists of a 1-bit convergence sublayer indicator (CSI) and a 3-bit sequence count (SC). Number protection (SNP) is composed of three bits of CRC and one bit of parity (P).

4A to 4C are diagrams illustrating a segmentation and recombination protocol data unit (SAR-PDU) and a pointer section for structural data transfer, wherein the pointer section is included in the segmentation and recombination protocol data unit (SAR-PDU) payload section. This is not possible for each segmentation and recombination protocol data unit (SAR-PDU), and the segmentation and recombination protocol data unit (SAR-PDU) payload interval is encoded according to the following rules.

First, the payload interval of a segmentation and recombination protocol data unit (SAR-PDU) is divided into a P format and a non-P format, as shown in FIGS. 4A and 4B. Is the pointer interval where the first byte of the segment-recombination protocol data unit (SAR-PDU) payload interval is the pointer interval, and its format is 93 bytes from the end of the pointer interval (94 in some cases, as shown in FIG. 4C). Is an offset value in octets of the distance from the beginning of the user data block in bytes). The binary value of this offset is aligned to the right, and the first bit of the pointer interval is used for odd and even check bits.

In addition, the P format is possible only when the sequence number of the split-and-recombine protocol data unit (SAR-PDU) header is an even number, for example, 0, 2, 4, and 6, and one cycle, that is, eight split-and-recombination protocol data units ( SAR-PDUs may only be used once during the transmission period. If there is no boundary information during the one cycle, a segmentation and recombination protocol data unit (SAR-PDU) having a header sequence number of 6 is formed in P format, and a dummy pointer having all bits of 1 is formed in the pointer section. Will be used.

If the split-recombination protocol data unit (SAR-PDU) is of type P, the convergence sublayer indicator (CSI) bit of the header is transmitted as 1, and in this case, the reception side merely receives the convergence sublayer identifier. It is possible to detect boundary information by checking only (CSI) bits.

FIG. 5 is a view showing an embodiment of an edge signal extracting device from a pointer with structural data transfer information in AAL type 1 according to the present invention. First, in the present embodiment, a signal including a boundary of a data structure from an ATM layer is shown. A pointer is used as a symbol, and an equal bit rate (CBR) data is used as an ATM-user data service unit (ATM-SDU).

In addition, the pointer of this embodiment is composed of 8 bits of data, 7 bits of which are offset fields, and 1 bit is a reserved bit, for example, a parity check bit.

In FIG. 5, the first register 12 extracts and stores the payload pointer of the segmentation and recombination protocol data unit (SAR-PDU) input from the ATM layer, and adds to the enable signal from the controller 15. The pointer is outputted, and the second register 13 outputs the pointer data by the enable signal from the controller 15 while the pointer from the first register 12 is shifted and stored.

In addition, the 7-bit counter 11 counts user data of the segmentation and recombination protocol data unit (SAR-PDU) from the user clock from the ATM layer, and adds the user data by the enable signal from the control unit 15. The comparator 14 outputs a boundary signal by comparing the count bit from the 7-bit counter 11 with the pointer bit from the second register 13.

In addition, the AND gate 16 blocks the boundary signal from the comparator 14 by the control signal from the controller 15. The controller 15 enables the first and second registers 12 and 13 and the counter 11 by the cell loss signal, and outputs a frame signal to the AND gate 16. Done.

On the other hand, the pointer includes information on the payload data, such as 93 bytes or 94 bytes. That is, since the pointer is generated only when the header of the split and recombine protocol data unit (SAR-PDU) is 0, 2, 4, 6, the counter 11 is 93 bytes (when a frame signal is detected) or 94 bytes ( Each time the frame signal is not detected) is reset to zero.

And, only one pointer occurs during one cycle, for example, sequence numbers 0 to 7, but if a frame signal occurs several times in one cycle due to a malfunction of the ATM layer, a problem is recognized and the pointer is not stored in a register. Will not.

On the other hand, while the data input from the ATM layer is input to the FIFO 10 by 8 bits and stored, the 7-bit counter 11 of the FIFO 10 and the boundary signal extractor 20 receives the user clock signal from the ATM layer. The cell loss signal is inputted to the controller 15 from the ATM layer. Accordingly, the control unit 15 detects a parity error by the parity bit, and at the same time, the 7-bit counter 11 counts the payload by the user clock signal.

On the other hand, after checking whether the pointer exists from the SAR header of the split-and-recombine protocol data unit (SAR-PDU) input to the FIFO 10, if the pointer exists, the pointer is stored in the first register 12. . Thereafter, the controller 15 checks whether a parity error has occurred by using a cell-loss signal input from the ATM layer by using the pointer stored in the first register 12, and if the error does not occur, The shift signal EN shifts the second register 13 to the second register 13.

Next, the comparator 16 compares the 7-bit count bits for the data output from the 7-bit counter 11 and the pointer bits from the second register 13 to generate a boundary signal, for example, a frame signal. If a cell loss occurs during the comparison, a stop signal generation signal of the boundary signal is output from the controller 15 in order to prevent generation of a false boundary signal.

After generating the frame signal, that is, the boundary signal, the standby state is reached until the end of the current cycle. After that, when the end of the current cycle is completed, the first state is extracted to extract a new pointer. When the frame signal is extracted, the frame signal is immediately generated without generating the frame signal.

FIG. 6 is a flowchart illustrating an operation of a method for extracting a boundary signal from a pointer with structural data transfer information in AAL type 1 according to the present invention. First, step S1 is divided into an input from an ATM layer. The payload pointer of the recombination protocol data unit (SAR-PDU) is extracted and stored in the first register 12.

In the second step S2, the controller 15 determines whether an error occurs in the pointer stored in the first register 12 or is a null pointer according to the cell loss signal. If there is an occurrence or a null pointer, the process moves to the seventh step S7 to maintain the standby state.

In the third step S3, when the pointer is not an error or the null pointer in the second step S2, a seven-bit count bit and the second bit of the data output from the seven-bit counter 11 are generated. The pointer bits from the register 13 are compared. In addition, the fourth step S4 determines whether or not cell loss has occurred as a result of the comparison in the third step S3. If the cell loss has occurred as a result of the determination, the fourth step S4 moves to the seventh step S7 and waits until it is finished. It becomes

In the fifth step S5, when the cell loss does not occur as a result of the determination in the fourth step S4, a seven-bit count bit for the data output from the seven-bit counter 11 and the second register 13 are generated. If it is determined that the pointer bits from the () are matched, and if they do not match, the process of step S3 is performed.

The sixth step S6 generates a frame signal when the result of the determination in the fifth step S5 matches, and the seventh step S7 is performed after the generation of the frame signal in the sixth step S6. The cycle will be idle until the end of the cycle.

In addition, the eighth step S8 determines whether the current cycle has ended after the waiting state of the seventh step S7, and when the determination is not finished, the eighth step S8 maintains the waiting state of the seventh step S7 and ends. In this case, the process moves to the first step S1.

On the other hand, the reference numerals written in the components of the claims of the present application to facilitate the understanding of the present invention, and are not written in the intention to limit the technical scope of the present invention to the embodiments shown in the drawings. Further, various modifications can be made without departing from the scope of the invention.

As described above, according to the present invention, when a malfunction occurs from an external signal by extracting a frame signal having boundary information of a user data structure from a pointer having information on a user data structure input from an ATM layer, It is possible to provide a function of bit error detection and correction.

Claims (3)

A first register 12 for extracting and storing the payload pointer of the segmentation and recombination protocol data unit (SAR-PDU) input from the ATM layer and outputting the pointer by the enable signal from the control means 15; ; A second register 13 for shifting and storing the pointer from the first register 12 and outputting pointer data by the enable signal from the control means 15; A counter for counting user data of the split-and-recombine protocol data unit (SAR-PDU) from a user clock from the ATM layer and outputting a count bit for the user data by the enable signal from the control means 15 ( 11); Comparison means (14) for comparing the count bits from the counter (11) with the pointer bits from the second register (13) and outputting a boundary signal; An AND gate 16 which blocks the boundary signal from the comparison means 14 by the control signal from the control means 15; Control means (15) for enabling the first and second registers (12, 13), the counter (11), and outputting a frame signal to the AND gate (16) by the cell loss signal. An apparatus for extracting boundary signals from a pointer having structured data transfer information in AAL type 1, comprising: 2. The structural data transfer information of claim 1, wherein the control means 15 does not generate a frame signal until the end of the current cycle if a cell loss occurs before generating the frame signal. Boundary signal extraction device from the pointer. A first step (S1) of extracting the payload pointer of the split-and-recombination protocol data unit (SAR-PDU) input from the ATM layer and storing it in the first register 12; The controller 15 determines whether an error occurs in the pointer stored in the first register 12 or is a null pointer according to the cell loss signal. A second step S2 of moving to a seventh step S7 to a standby state; In the second step S2, when the pointer is not an error or the null pointer, the third step S3 of comparing the count bit output from the counter 11 with the pointer bit from the second register 13; ; As a result of the comparison of the third step S3, it is determined whether the cell loss has occurred, and if the cell loss occurs as a result of the determination, the fourth step S4 goes to the seventh step S7 and is in a waiting state until the end. ; If the cell loss does not occur as a result of the determination in the fourth step S4, it is determined whether or not the count bit output from the counter 11 and the pointer bit from the second register 13 match. The fifth step (S5) to perform the process of the third step (S3); A sixth step S6 of generating a boundary signal when the determination result of the fifth step S5 is identical; A seventh step (S7) in which the standby state is reached until the current cycle ends after the generation of the alert signal in the sixth step (S6); After the waiting state of the seventh step S7, it is determined whether the current cycle has ended. If the determination is not completed, the standby state of the seventh step S7 is maintained. And an eighth step (S8) of moving to the boundary signal extraction method from the pointer with the structural data transfer information in the AAL type 1.