KR20030010138A - optical transferring system having a mini-slot frame structure and controlling method therefor - Google Patents

Abstract

PURPOSE: An optical transmitting system having a mini-slot frame structure and a control method therefor are provided to minimize the generation of CDV(Cell Delay Variation) by configuring the mini-slot frame structure in an upward frame using a MAC(Media Access Control) of an ATM(Asynchronous Transfer Mode) PON(Passive Optical Network), upward transmitting the mini-slot frame structure, and controlling a data transmission function of an ONU(Optical Network Unit) using configured information. CONSTITUTION: ONUs(2A-2N) inserts information signals inputted from a plurality of subscriber devices(1A-1N) into a mini-slot frame signal, upward transmits the mini-slot frame signal, and outputs an information signal transmitted from an upper equipment to the corresponding subscriber devices(1A-1N). An ODN(Optical Distribution Network)(3) distributes upward and downward information signals inputted and outputted to the ONUs(2A-2N) to the corresponding to ONUs(2A-2N). An OLT(Optical Line Terminal)(5) analyzes corresponding ONU state information included in the mini-slot frame signals of a plurality of ONUs(2A-2N), controls an upward data transmission function of the ONUs(2A-2N) according to a MAC protocol on the basis of analyzed information, and transmits an information signal transmitted from an external ATM switch(4) to the corresponding ONUs(2A-2N) through the ODN(3).

Description

Optical transfer system having a mini-slot frame structure and controlling method therefor}

The present invention relates to an optical transmission system having a mini-slot frame structure and a control method thereof. In particular, the present invention relates to a mini-slot frame structure containing subscriber information having priority in an uplink frame using a MAC protocol of an ATM PON network. And an optical transmission system having a mini-slot frame structure which significantly improves the transmission quality of an ATM cell by minimizing the occurrence of CDV by controlling the data transmission function of the ONU by using the configured information, and a control method thereof.

In general, the optical communication method is a technology that has been rapidly used in the field of the transmission network or international communication lines due to the rapid development of the technology and advantages such as low loss, broadband, light weight, induction of optical fiber. In particular, the optical communication method as described above uses an optical cable composed of an optical fiber. In this case, an optical transmission system is required to transmit a signal through the optical cable. Such an optical transmission system typically uses any one of wavelength division (WD), space division (SD), time division (TD), and free space division (FD), depending on the implementation method. For example, such a system may be configured with, for example, an Asynchronous Transfer Mode (ATM) Passive Optical Network (PON) network using a time division scheme. In addition, the optical transmission system using the ATM PON network as described above is equipped with devices for multiplexing and demultiplexing to transmit optical signals, and various protocols such as MAC (Media Access Control) protocol for such multiplexing and demultiplexing. The same specific protocol is used.

Then, referring to FIG. 1, the optical transmission system using the conventional MAC protocol as described above is connected to a plurality of subscriber stations 70A-N and transmits information signals inputted from the subscriber stations 70A-N upward and downward. ONU (optical network unit: 71A-N) for outputting the transmitted information signal to the subscriber terminal (70A-N), and the up and down information signal input and output to the ONU (71A-N) corresponding ONU (71A-N) ODN (optical distribution network: 72) to distribute the information, and the uplink information signal of the ONU (71A-N) input through the ODN (72) is controlled according to the MAC protocol to transmit to the destination device and the external ATM switch And an optical line terminal (OLT) 74 for transmitting the information signal transmitted from 73 to the ONU 71A-N via the ODN 72.

Here, the MAC protocol in the ATM PON network performs a function of efficiently multiplexing upstream data flows output from a plurality of ONUs 71A-N. Uplink data using the PON network is illustrated in FIG. 2. It is transmitted in a frame according to ITU-T G.983.1 (53 cells per frame). At this time, the frame is largely divided into guard time (GDT), preamble (pre), delimiter (DEL), and ATM CELL, of which GDT is data for preventing two consecutive cells from colliding, and PRE is OLT 74. It is used to extract the phase of the cell related to LOCAL TIMING of the cell. It is also used for bit synchronization and amplitude recovery. The DEL is used to indicate the starting point of an ATM cell through a specific pattern and to perform byte synchronization.

On the other hand, referring to the operation of the conventional optical transmission system as described above, OLT (74) in the first data transmission to prevent the collision of upstream data randomly input from a plurality of ONU (71A-N) PLOAM (physical layer operations, administration and maintenance) outputs the cell signal to the ODN 72. The ODN 72 then distributes the input PLOAM cell signal to each ONU 71A-N. Here, PON ID signals for setting ONUs 71A-N are stored in the PLOAM cell signal, and the ONUs 71A-N recognize this and transmit data upward in their ranks.

That is, the ONU 71A-N determines the PON ID of the PLOAM cell signal input from the ODN 72 and upwards the data input from each subscriber station 70A-N in its own sequence as shown in FIG. 2. It is carried in a frame (53 cells per frame) and is transmitted upward to the OLT (74) via the ODN (72). Then, the OLT 74 analyzes GDT (guard time), PRE (preamble), DEL (delimiter), etc. contained in the overhead of the input uplink frame, and analyzes ATM cell-type data in an ATM destination 73 of an external destination. To form a normal call.

However, in the optical transmission system using the conventional MAC protocol as described above, the OLT 74 cannot determine the information on the ONU 71A-N overloaded with the current uplink frame at the time of data uplink. Delay variation occurs, which causes a drawback of degrading transmission quality.

In addition, the optical transmission system has a problem in that it is not possible to determine whether real-time or non-real-time information on the uplink data from the uplink frame at all, the efficiency of the management of the transmission data is significantly reduced.

Accordingly, the present invention has been invented to solve the above conventional problems, and configures a minislot frame structure containing subscriber information having priority in an uplink frame using the MAC protocol of an ATM PON network and transmits the uplink. It is an object of the present invention to provide an optical transmission system having a mini-slot frame structure and a control method thereof, which minimizes the occurrence of CDV by controlling the data transmission function of the ONU by using information, thereby significantly improving the transmission quality of an ATM cell. .

Another object of the present invention is to accurately identify and process the information transmission state of the ONU through the information in the mini-slot frame structure OLT is transmitted upstream, so the optical transmission system having a mini slot frame structure to improve the transmission efficiency of the optical transmission system accordingly And a control method thereof.

The present invention for achieving the above object is carried in the mini slot frame signal to the processing information for the data signal input from the plurality of subscriber devices in the optical transmission system for transmitting a communication signal input from a plurality of subscriber devices through the optical signal Analyzes the ONU transmitted upward and the corresponding ONU state information included in the minislot frame signal outputted from the ONU, and generates information on the uplink data transmission priority of each ONU as a PLOAM cell signal according to the analysis information. It provides an optical transmission system having a mini-slot frame structure including an OLT to transmit to each of the.

According to another aspect of the present invention, in an uplink data transmission method of an optical transmission system using a MAC protocol, an uplink data including a PLOAM cell control signal including a transmission rank to an ONU and a minislot frame from a current ONU is transmitted according to the MAC protocol. The upstream data input confirmation step of confirming whether the data is input, and when the uplink data transmission is confirmed from the ONU during the upstream data input confirmation step, analyzes the minislot frame data generated by the ONU to determine the transmission priority of each ONU. Priority of transmitting the PLOAM cell control signal including the uplink data transmission priority data of the ONU determined according to the analysis of the minislot frame data of the ONU after the minislot frame analysis step of determining and the minislot frame analysis step. The control signal transmission step and the highest priority after the priority control signal transmission step The control method of the optical transmission system having a mini-slot frame structure comprising a mini-slot frame signal processing step of receiving a corresponding uplink data input in the ONU order to perform call processing and repeatedly analyzing the mini-slot frame signal transmitted from the ONU. to provide.

1 is an explanatory diagram illustrating a conventional optical transmission system.

FIG. 2 is an explanatory diagram for explaining an uplink frame structure applied to the apparatus of FIG. 1. FIG.

3 is an explanatory diagram illustrating a system of the present invention.

4 is an explanatory diagram illustrating a mini slot frame structure of the present invention.

5 (a) and 5 (b) are explanatory diagrams illustrating the structures of PID and CAI of a minislot frame;

6 is an explanatory diagram for explaining an uplink frame structure according to the present invention;

7 is a flowchart of the present invention.

<Detailed Description of Codes>

1A-N: Subscriber 2A-N: ONU

3: ODN 4: ATM Switch

5: OLT 6: FPGA

7: processor

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

As shown in FIG. 3, the present invention is connected to a plurality of subscriber stations 1A-N, and transmits information signals inputted from the subscriber stations 1A-N in mini-slot frame signals and transmits them upward. ONU (2A-N) for outputting downlink information signal transmitted from the upper level equipment to the corresponding subscriber device (1A-N), and the up and down information signal input and output to the ONU (2A-N) corresponding to the ONU (2A-N). ODN (3) to be distributed to the ODN (3), and the corresponding ONU state information included in the mini-slot frame signal of the plurality of ONU (2A-N) input through the ODN (3) is analyzed and the MAC protocol based on the analysis information According to the present invention, the OLT 5 controls the uplink data transmission function of the ONU 2A-N and transmits the information signal transmitted from the external ATM switch 4 to the corresponding ONU 2A-N through the ODN 3. .

Inside the ONU 2A-N, an FPGA 6 for generating a minislot frame signal and a processor 7 for controlling a minislot generation function of the FPGA 6 are provided. In addition, the FPGA structure may be configured of a field programmable gate array or an application-specific IC (ASIC).

Here, the frame is an ATM cell having a structure of 56 bytes, as shown in FIG. 6, wherein 37 cell slots are allocated for ATM cell transmission among a total of 53 cells, and the remaining 16 cell slots are allocated with an uplink bandwidth using a minislot. Allocate fixed time slots for request information and POTS services. At this time, the mini slot can be configured as 14 bytes per ONU, as shown in Figure 4, a total of 64 ONU can be allocated (14 byte * 64 (number of ONU) = 56 bytes * 16 cells).

In addition, the mini-slot frame structure is largely 4 bits GDT (guard time), PRE (preamble) 2 bytes, DEL (delimiter) 4 bits, PID (PON ID) 1 byte, CAI (Cell Available Information) 4 bytes, POT 5 bytes, CRC (Cyclic Redundancy) Check) It consists of a total of 14 bytes such as 1byt, of which GDT, PRE and DEL are OVERHEAD and perform the functions defined by the provisions of ITU-T G.983.1.

In the frame, GDT is data for preventing two consecutive cells from colliding, PRE is used to extract the phase of a cell related to LOCAL TIMING of OLT, and is also used for bit synchronization and amplitude recovery. It is used to indicate the starting point of a cell through a specific pattern and to perform byte synchronization.

Meanwhile, as shown in (a) of FIG. 5, the PID data format of the frame includes upper 2 bits as reserved bits and lower 6 bits as PON IDs to configure logical IDs of the ONUs (2A-N). It is actually used to distinguish 64 ONUs. The CAI data format of the frame is composed of a valid bit, a class bit, and a local time stamp bit, as shown in FIG. 5 (b), wherein the valid bit is a bit indicating whether data is valid, and the class bit is a real time data. A bit identifying whether data is non-real-time data, and a local time stamp bit is used to inform the OLT 5 of the arrival time of the cell signal in each ONU 2A-N.

The following describes the method of the present invention applied to such a system.

In the present invention, the OLT 5 of the optical transmission system using the MAC protocol initializes the system in the initial state S1 as shown in FIG. 7, and transmits the PLOAM cell control signal including the transmission rank to the ONU and the data discrimination step. Proceeding to S1A, it is determined whether the signal currently input to the OLT is data. If the OLT input signal is determined as data during the data discrimination step S1A, the process proceeds to an upstream data input determination step S2 and a downstream data input determination step S3. In this case, the upstream data input determination step (S2) determines whether upstream data including a mini slot frame is input from the current ONU. At this time, if the upstream data is not input from the ONU as a result of the determination during the upstream data determination step (S2), the process ends.

On the other hand, if it is determined during the downlink data input determination step S3, if downlink data is not input from the external exchange, the process proceeds to the end step. However, if it is determined during the downlink data input determination step (S3) that the downlink call data is input from the external exchange, the process proceeds to the downlink call data transmission step (S4) to transmit the downcall data input from the outside to the ONU to transmit the call. To form.

That is, the OLT 5 initializes the system and transmits an uplink data rank control signal of the ONU (2A-N) to the ODN 3 on the PLOAM cell signal using the MAC protocol. The ODN 3 then distributes the PLOAM cell signal of the OLT 5 to the processor 7 of the ONU 2A-N, respectively. At this time, if call data is input from the ATM exchanger 4 from the outside, for example, through an optical cable, the OLT 5 processes the call data signal by a certain signal and transmits the call data signal to the corresponding ONU 2A-N through the ODN 3. The processor 7 of the ONU 2A-N transmits the signal to the corresponding subscriber device 1A-N by analyzing the input call data signal.

On the other hand, if it is determined during the upstream data input determination step (S2), if upstream data is input from the ONU, the process proceeds to the minislot frame analysis step (S5) and analyzes the minislot frame data input from the ONU to prioritize the ONU. Decide After the minislot frame analysis step S5, the process proceeds to the priority control signal transmission step S6, and the PLOAM cell control signal including the upstream data transmission priority data of the ONU determined according to the analysis of the minislot frame data of the ONU. Is sent to each ONU. After the priority control signal transmission step (S6), the cell signal and the mini slot frame signal processing step (S7) proceed to receive the corresponding upstream data input in the ONU order having the highest priority, and perform call processing from the ONU. Analyze the transmitted mini slot frame signal.

In other words, the processor 7 of the ONU 2A-N of the optical transmission system receives the call data of this subscriber station 1A-N when the call data is input from a plurality of connected subscriber stations 1A-N. In this case, the OLT 5 transmits the ONU 2A-N according to the MAC protocol so that data of the plurality of ONUs 2A-N do not cause a collision during transmission. The PLOAM cell control signal including the rank is transmitted to the processor 7 of each ONU 2A-N via the ODN 3. Then, the processor 7 of each ONU 2A-N has an OLT 5 in the first 37 ATM cell frames of a total of 53 cell slots as shown in FIG. 6 via the FPGA 6 or the ASIC. As prioritized through the PLOAM cell control signal, data of the corresponding ONU (2A-N) are sequentially loaded and transmitted to the remaining 16 cell slots as shown in FIGS. 4 and 5 (a) and (b). Likewise, the transmission status information of each ONU (2A-N) is loaded into a mini slot frame and transmitted to the OLT (5) via the ODN (3).

For example, the FGPA 6 of each ONU 2A-N records its current transmission state information in a minislot frame, in which the PID of the minislot frame is shown in FIG. As described above, the reserved information is recorded in the upper 2 bits and the PON ID as the logical ID for identifying the corresponding ONU (2A-N) is set in the remaining lower 6 bits. In addition, the FPGA 6 of the OLT 5 writes a valid bit capable of determining whether or not the transmission data is valid in the most significant 1 bit of the CAI of the minislot frame. If it is recognized as a valid bit and if it is "1", it is recorded to be identified by a method such as not valid bit. The class bit, which is the upper second bit, carries information for identifying whether the current upstream data is real time data. In addition, the FPGA 6 of the ONU 2A-N uses an internal counter for the remaining 6 bits of the CAI, when the upstream data arrives at the ONU 2A-N from the subscriber device 1A-N. The time information is recorded as a time stamp, and the voice data signal of the actual subscriber is recorded in the POT of the mini slot frame. At this time, the FPGA 6 of the ONU 2A-N writes cell arrival information for four buffers separately in 4 bytes of each CAI, and transmits them to the OLT 5.

Then, the OLT 5 analyzes the 53 cell slots inputted from the ONUs 2A-N, as shown in FIG. 6, and then the OLT 5 performs the PLOAM cell signal in advance for the first 37 ATM cell signals. Since the upstream data sequentially input from the corresponding ONU (2A-N) as specified through, by processing a predetermined signal upstream of the sequentially input ONU (2A-N) and transmits to the ATM switch (4) of the destination To form a conventional arc.

In this case, the OLT 5 obtains upstream data priority information of the ONU 2A-N from the minislot frame signal of the remaining 16 cell slots of the 53 cell slots. For example, the OLT 5 is inputted. Information related to transmission signal control is obtained through overhead GDT, PRE and DEL among mini slot frame signals, and each ONU (2A-N) is identified through PID data, and then each ONU (2A-N) is identified. Search the most significant 1 bit of the CAI to determine whether the currently entered information is valid information. That is, the OLT 5 determines that the currently inputted information is valid when the most significant bit of the CAI of each ONU 2A-N is "0", and all other invalid data if it is other conditions. . After determining the most significant bit of the CAI, the OLT 5 searches the class bits of the CAI of each ONU (2A-N) to determine whether the currently input data is real time data, and if the currently input data is real time data. Then give priority to this data. In addition, after real-time data determination of the CAI, the OLT 5 determines the local time stamp of each ONU 2A-N, so that the value of the local time stamp is the smallest, that is, the first ONU 2A-N. Priority is given to the entered local time stamp value. Accordingly, the OLT 5 analyzes the mini-slot frame information through the above process to determine the priority of the information input from each ONU 2A-N, and the data of each ONU 2A-N according to the priority rank. The transmission sequence is loaded into the PLOAM cell signal and transmitted to each ONU (2A-N) via the ODN (3). Then, the respective ONUs 2A-N transmit their data to the OLT 5 via the ODN 3 in their own order according to the priority sequence recorded in the input PLOAM cell signal.

On the other hand, during the process, the OLT 5 reads voice data information of the actual subscriber recorded in POT 0-4 of the mini slot frame and transmits it to the destination of the corresponding telephone network to form a call. In this case, the POTO of the mini slot frame is used as a common signaling channel (CSC) and used for actual call control. In addition, 4 bytes of the POT 1-4 of the mini slot frame can be configured as shown in Table 1,

Dedicated subscribers (based on i mini-slot) Bit position Non compress mode 4 bit 7-0 32K ADPCM mode 8 bit 7 to 4, or 3 to 0 16K ADPCM mode 16 bit 7 to 6, 5 to 4, 3 to 2, or 1 to 0

For example, in non compress mode, all 1 byte of POT can be used to allocate up to 4 subscribers per minislot. In the 32K ADPCM mode, since a total of 1 byte is divided into 4 bit units to allocate subscribers, the POT is allocated to 8 subscribers twice as large as in the non compress mode. In addition, in the 16K ADPCM mode, since a total of 1 byte is divided into 2 bit units to allocate subscribers, a POT is allocated to 16 subscribers that are four times larger than in the non compress mode.

The CRC 1 byte of the mini slot frame may be generated as a polynomial of x ⁸ + x ² + x ¹ + ¹ as a checksum value of an error detection code value for a PON ID, a CAI, and a POT 10 byte.

Therefore, according to the present invention as described above, the OLT (5) is not overloaded because data is transmitted from a plurality of ONU (2A-N) according to the priority.

As described above, the present invention constructs a mini-slot frame structure containing subscriber information having priority in an uplink frame using the MAC protocol of an ATM PON network and transmits the uplink data using the configured information. By controlling, the occurrence of CDV is minimized, which has the advantage of significantly improving the transmission quality of ATM cells.

In addition, according to the present invention, since the OLT accurately grasps and processes the information transmission state of the ONU through the information in the minislot frame structure transmitted upward, there is also an effect of improving the transmission efficiency of the optical transmission system.

Claims (12)

In the optical transmission system for transmitting a communication signal input from a plurality of subscriber equipment through an optical signal, Analyzes the ONU which carries the processing information on the data signals inputted from the plurality of subscriber devices in a mini slot frame signal and transmits them upward, and the corresponding ONU state information included in the mini slot frame signals output from the ONU, respectively, and analyzing the analysis information. According to the optical transmission system having a mini-slot frame structure characterized in that it comprises an OLT for generating information on the uplink data transmission priority of each ONU as a PLOAM cell signal and transmits to each of the ONU. 2. The optical transmission system according to claim 1, wherein the ONU includes an FPGA for generating a minislot frame signal. 2. The optical transmission system according to claim 1, wherein the ONU includes an ASIC for generating a minislot frame signal. The optical transmission system according to claim 1, wherein the minislot frame structure is allocated transmission status information of ONU to 16 cell slots of a total of 53 ATM cell slots. The optical transmission system of claim 4, wherein the mini slot frame structure comprises GDT 4 bits, PRE 2 bytes, DEL 4 bits, PID 1 byte, CAI 4 bytes, POT 5 bytes, and CRC 1 byte. 6. The optical transmission system of claim 5, wherein the upper 2 bits are reserved bits and the lower 6 bits are PON IDs, which are configured as logical IDs of the ONUs. 6. The optical transmission system according to claim 5, wherein the POT is allocated for voice data information of a subscriber. 6. The optical transmission system according to claim 5, wherein the CAI comprises a valid bit, a class bit, and a local time stamp bit. In the ATM cell frame structure used by the MAC protocol in the optical transmission system, The ATM cell frame structure includes a mini slot frame for allocating ONU transmission status information to 16 cell slots among a total of 53 ATM cell slots. 10. The mini slot frame structure of claim 9, wherein the mini slot frame structure comprises GDT 4 bits, PRE 2 bytes, DEL 4 bits, PID 1 byte, CAI 4 bytes, POT 5 bytes, and CRC 1 byte. In the uplink data transmission method of the optical transmission system using the MAC protocol, According to the MAC protocol, during the uplink data input confirmation step of transmitting a PLOAM cell control signal including a transmission rank to the ONU and confirming whether uplink data including a minislot frame is input from the current ONU, When the transmission of the uplink data from the ONU is confirmed, the minislot frame analysis step of determining the transmission priority of each ONU by analyzing the minislot frame data generated by the ONU, and the minislot of the ONU after the minislot frame analysis step A priority control signal transmission step of transmitting a PLOAM cell control signal including the upstream data transmission priority data of the ONU determined according to the analysis of the frame data to each ONU, and then the ONU having the highest priority after the priority control signal transmission step Receives the corresponding upstream data inputted into the network and executes call processing. And a minislot frame signal processing step of repeatedly analyzing the slots frame signal. 12. The control method of claim 11, wherein the mini slot frame signal during the input checking step includes transmission state information of each ONU.