KR0134433B1 - Method for receiving the cell reference signal of the cell header in the b-isdn - Google Patents

Abstract

The present invention relates to a method for recovering a cell reference signal, wherein when there is data to be transmitted in TAXI CHIP, when a sequence of synchronization signals, a cell starter, and a cell (53 bytes) is repeatedly transmitted before the cell transmission, By restoring the clock by using the cell start part as the reference signal, the clock of the signal can be easily restored with a simple circuit configuration using the function of TAXI CHIP.

Description

Cell Reference Signal Restoration Method in Cell Header in Broadband Telecommunication Network

1 is a block diagram for explaining a hierarchy of data applied to the present invention.

2 is a cell structure diagram of type 1 data applied to the present invention.

3 is a flowchart illustrating a cell reference signal recovery method of a cell header unit according to an embodiment of the present invention in a broadband integrated communication network;

4 is a block diagram of an apparatus for performing a cell reference signal recovery method of a cell header unit according to an embodiment of the present invention in a broadband integrated communication network;

5 is a signal timing diagram of each part in FIG.

* Explanation of symbols for main parts of the drawings

31 Inverter 32: D flip-flop

33: PLL

Detailed description of the invention

The present invention relates to an asynchronous transfer mode (abbreviated as ATM) suitable for implementing a broadband integrated services digital network (BISDN), and particularly for easily recovering a cell reference signal in an ATM cell structure. The present invention relates to a cell reference signal recovery method.

Recently, with the development of communication technology in various fields such as high-speed semiconductor technology, optical transmission technology, exchange technology, computer technology, and data compression technology, users' services are diverse and demand high quality. This change has led to the emergence of multimedia services in which all media are integrated in the voice, data, and image information transmission services provided by individual networks until now. Network providers can provide not only existing services but also new services and efficient network operation and management. Development of technology for this was inevitable.

According to this change of communication environment, network providers have accelerated concrete efforts to realize BISDN since the early 80s with the goal of integrating all communication related technologies such as transmission, exchange, and terminal. This was due to the fact that it was impossible to provide services with narrowband ISDN (NISDN) due to the nature of broadband services, and a new level of solution was needed. In the meantime, there has been a lot of research from telecommunication standards organizations and advanced telecommunications companies, mainly ITU-TS (formerly CCITT) for BISDN standardization.In the process, a new transmission method called ATM method was developed by CCITT as a base technology to realize BISDN. Was adopted.

ATM is a method that utilizes the advantages of the existing circuit-switched and packet-switched methods. It is a packet-type transmission method that uses statistical multiplexing. Its efficient use of transmission bands (channels), high-speed transmission, multimedia (voice, video, Data). In the existing circuit-switched system including NISDN, the channel is fixed in advance according to the service. Therefore, the channel is suitable for real-time service, but the channel cannot be efficiently used for a service having variable information characteristics. On the other hand, in the packet-switched system, efficient channel use is guaranteed, but it is not suitable for high-speed and real-time services due to problems of excessive processing and transmission delay due to complicated protocols.

However, the ATM method eliminates the complexity by simplifying the protocol and simplifying the routing, and by transmitting a cell of a certain size (53 bytes) in a slot on a high-speed transmission path, high-speed and real-time service is possible, and only when there is information to transmit a channel. It is possible to efficiently use the channel because it does not allocate a channel when there is no information to transmit. That is, the band can be efficiently managed by the statistical multiplexing method.

In the ATM method, a basic information unit in the form of a packet of 0g cell 0h having a size of 53 bytes is used, and the cell is composed of a header of 5 bytes and a user information part of 48 bytes. The cell header is used for channel identification, cell routing, traffic control and maintenance related functions in each channel, and the user information unit includes control information and pure user information for an ATM upper layer protocol. Since ATM is a connection type transmission method, a channel setup and release function must be performed during cell transmission, and a virtual path and a virtual channel (hereinafter referred to as VPI VCI) are used for channel identification and cell routing.

On the other hand, a communication system or switch using the ATM method as described above is connected to a plurality of subscriber stations to communicate the corresponding information and provide various services. Here, communication of such information and provision of service are possible because the terminal of each subscriber has a broadband communication terminal card having a plurality of processing modules as shown in FIG.

Referring to FIG. 1, in order for a terminal card in a subscriber station to transmit and receive text data between subscribers in a BISDN, an ATM Adaption Layer (AAL) layer processing module 10, an ATM layer processing module 20, and a physical layer processing module ( It can be seen that it has 30).

Therefore, in the case of transmission, data is read from the memory in which the subscriber's transmission data is stored and transmitted to the counterpart terminal through the AAL layer processing module 10, the ATM layer processing module 20, and the physical layer processing module 30. In the case of the reverse flow is made. At this time, the target data mainly processed at the time of transmission and reception are text data, and are classified into type 1, type 3/4, and type 5 according to the cell structure of the data.

On the other hand, looking at the functions of each layer, the AAL layer processing module 10 is responsible for improving the services provided by the ATM layer to support the functions required in the upper layer, in order to respond to the needs of different service users It is service dependent because it supports multiple protocols.

The function of the AAL layer consists of the disassembly and reassembly sublayers and the convergence sublayer. The ATM layer processing module 20 performs a multiplexing and demultiplexing function of a cell, a conversion function of a VPI VCI, a cell header generation and extraction function, and a GFC function. The physical layer processing module 30 performs cell rate decomposition, HEC header sequence generation and verification, cell illustration, transmission frame adaptation, and transmission frame generation and recovery.

2 is a cell structure diagram of Type 1 data, in which a header includes Generic Flow Control (GFC), Virtual Path Identifier (VPI), Virtual Channel Identifier (VCI), and Payload Type (PCI). Payload Type (PT), Cell Loss Priority (CLP), and Header Error Control (HEC). In the header, the GFC is applied when a plurality of subscriber stations are multiplexed to one interface, and 4 bits are allocated as a mechanism used to control the amount of information generated from the subscriber terminal in the network direction.

In addition, the VPI provides a path recognition method for finding a group of virtual channels transmitted through the same physical medium, and 8 bits are allocated, and the VCI provides a method for recognizing a virtual channel, and 16 bits are allocated. do. In addition, the PT indicates the type of payload and is used to indicate whether the cell includes user information or communication network information and is allocated about 3 bits. In addition, the CLP is used to indicate a priority for loss of a cell and is allocated about one bit. In addition, the HEC is used to control an error of a header, and one byte is allocated to correct an error of the entire cell information by a predetermined method.

Meanwhile, the 48-byte user information unit adds 1 byte of a SAR-PDU header to 47 bytes of segment-and-resembly-protocol data unit (SAR-PDU) payload data. Here, the 1-byte SAR-PDU header consists of 4 bits of SN and 4 bits of SNP. In addition, the 4-bit SN is composed of CSI 1 bit and SC 3 bits, and the 4-bit SNP is composed of CRC 3 bits and EP 1 bit. Among the English abbreviations used, SN is Sequence Number, SNP is Sequence Number Protection, CSI is Convergence Sublayer Indication, SC is Sequence Count, CRC is Cyclic Redundancy Check, and EP is Eeven Parity.

However, in the ATM cell structure as described above, a time stamp method or a synchronous frequency encoding method is conventionally used to restore a cell reference signal. However, in this case, there is a problem in that the circuit becomes complicated when implemented with real hardware.

Accordingly, an object of the present invention is to provide a cell reference signal recovery method for easily recovering a cell reference signal in the ATM cell structure as described above to solve the above problems.

In order to achieve the above object, a cell reference signal recovery method of a cell header unit in a broadband integrated communication network according to the present invention is a command mode for continuously transmitting a synchronization signal in a command mode for clock synchronization between TAXI CHIPs when there is no data to be transmitted. In the data transmission step, the data mode transmission step is repeated before the cell transmission in the data mode transmission step and the data mode transmission step is repeated. And a recovery step for recovering the clock using the cell start as a reference signal.

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

3 is a flowchart illustrating a method for recovering a cell reference signal of a cell header according to an embodiment of the present invention in a broadband integrated communication network. When there is no data to transmit, a command for continuously transmitting a synchronization signal in a command mode for clock synchronization between TAXI CHIPs is shown. The mode transmission step 30 and the data mode transmission step 32 and the data mode transmission step of switching to the data mode if there is data to be transmitted and repeatedly transmitting the synchronization signal, the cell starter, and the cell (53 bytes) in sequence. And a recovery step 34 for restoring the clock by using the cell start portion transmitted before the cell transmission as the reference signal at (32).

4 is a circuit diagram for explaining a cell reference signal recovery method of a cell header unit according to the present invention in a broadband integrated communication network, which comprises an inverter 41, a D flip-flop 42, and a phase locked loop (PLL) 43. As shown in FIG.

5 is a signal timing diagram of each part in FIG. 4, (a) shows a col signal applied to the inverter 41, and (b) shows an f_com signal output from the Q terminal of the D flip-flop 42. Indicates.

Next, a method of restoring a cell reference signal according to the present invention will be described with reference to FIGS. 4 and 5.

Broadband communication has various types of service according to transmission data. Among the constant bit rate service, information about the sender's clock must be transmitted to the receiver in order to receive data correctly.

TAXI CHIP used in broadband communication terminal card has data mode and command mode. When there is no data to transmit normally, JXI signal, which is a synchronization signal, is continuously transmitted in command mode for clock synchronization between TAXI CHIP. Here, in command mode, various commands can be transmitted by combining four command control inputs of TAXI CHIP.

However, if there is data to be transmitted, the data is transferred to the data mode. In the data mode, the command inputs are all set to '0' and the strobe signal STRB is applied. When transferring data, repeat the sequence JK → TT (cell start) → cell (53 bytes) → JK → TT → cell → ... In other words, the TT signal should be transmitted only once before cell transmission. Therefore, the clock can be restored on the receiving side using this signal as a reference signal.

On the other hand, the command output is '0000' when receiving the JK signal, and '0010' when receiving the TT signal. The command output also holds its value until the next command.

As described above, in the cell reference signal recovery method according to the present invention, when there is data to be transmitted in TAXI CHIP, the cell is switched to the data mode and repeatedly transmitted in the order of the synchronization signal, the start of the cell, and the cell (53 bytes). By restoring the clock by using the cell start transmitted as a reference signal before transmission, there is an advantage that the clock of the signal can be easily restored with a simple circuit configuration using the function of TAXI CHIP.

Claims (1)

A command mode transmission step of continuously transmitting a synchronization signal in a command mode for clock synchronization between TAXI CHIPs when there is no data to transmit; A data mode transmission step of switching to a data mode when there is data to be transmitted, and repeatedly transmitting a synchronization signal, a cell starter, and a cell (53 bytes) in sequence; And a recovery step for restoring a clock by using a cell start part transmitted before cell transmission as a reference signal in the data mode transmission step.