KR100260251B1 - Atmpon mac protocol - Google Patents

Abstract

PURPOSE: An ATMPON(ATM Passive Optical Network) MAC protocol is provided to define an upward/downward transfer frame between NT and OLT, then to make reservation previously by sending local queue information of NT1(Network Termination) for information transfer using the upward frame, and then to permit the reservation by using a cell band allocation algorithm for ensuring a quality service(QoS) of an ATM traffic. CONSTITUTION: An ATMPON MAC protocol includes the following steps. When an NT slot is transmitted to an OLT upwardly, the OLT judges what slot the transmitted slot is in S1. As the result of the judgment, if the NT slot is RG, transmission permit information for 9 NTs is determined, if the NT slot is URG, permit information on UBR cells is determined, or if the NT slot is an information slot, permit information is determined in consideration of preference and traffic characteristics in S2. The corresponding slots are allocated in S3. When the slot allocation is finished, permit information is transmitted and then the above steps S1¯S3 are repeated in S4.

Description

Asynchronous Transmission Method Passive Optical Communication Network (ATM PON) Media Access Control (MC) Protocol Implementation Method

The present invention relates to a method for implementing asynchronous transmission type passive optical communication network (hereinafter referred to as ATMPON) media access control protocol, to provide efficient use of network resources and various ATM services in a PON based on ATM. A technology for designing a medium access control (hereinafter referred to as MAC) technique for the present invention.

In general, a PON is a passive divider or wavelength division multiplexing (WDM) device between a FTTH (Fiber To The Home) or FTTC (Fiber To The Corner) subscriber access node and a network terminal (hereinafter referred to as NT). All nodes are distributed topology in the form of bus or tree structure.

The PON system is for accessing an optical subscriber network, and an optical network unit (hereinafter referred to as ONU) 1 installed inside a home and a company as shown in FIG. 1;

NT (2);

An optical line terminator (hereinafter referred to as an OLT) 3 connected to each of the ONU 1 and NT 2 by an optical cable;

Each OLT 3 receives various services such as an internet service, a telephone service, an interactive video service, and the like.

This PON method allows users to share exchange equipment and optical resources, low maintenance costs because the optical distribution network is passive, high flexibility for suppliers to easily add and remove splits, and Resource cost per subscriber is low.

However, in PON, since a plurality of users share optical resources, there is a problem of collision among users.

Accordingly, the PON needs a medium access control (MAC) technique that can transmit information without collision problems between users and efficiently use network resources.

In the present invention, in consideration of the conventional requirements as described above, define the up / down transmission frame between the NT and OLT, and then send the local queue information of NT1 (Network Termination) for information transmission using the uplink frame in advance It is an object of the present invention to provide a MAC method that uses a cell-based bandwidth allocation algorithm to guarantee a quality service (hereinafter referred to as QoS) of ATM traffic.

1 is a schematic block diagram illustrating a typical optical subscriber network access structure and corresponding location of a PON;

2 is a schematic block diagram of a PON having a tree structure to which the present invention is applied.

3 (a)-(f) are uplink frame structure diagrams defined by the present invention;

4 (a) to 4 (b) are diagrams of a downlink transmission frame structure defined by the present invention.

5 is a flow chart showing the overall flow of the MAC protocol implemented by the present invention.

6 is a flowchart illustrating a process of allocating slots in FIG. 5 in detail.

<Description of Symbols for Major Parts of Drawings>

1: Optical Network Unit (ONU) 2: Network Terminal (NT)

3: Telephone Station Optical Termination (OLT) 4: Optical Distribution Network (ODN)

5: Local Exchange

In the present invention to achieve the above object in the optical transmission protocol method between the subscriber side and the telephone station in an asynchronous transmission passive optical network (ATMPON),

Defining an upframe structure including a separate field for storing request information for UBR traffic so as to efficiently transmit a cell while avoiding collision for an unspecified bit rate (UBR) cell during optical transmission;

For an available bit rate (ABR) cell, an MCR value is set to guarantee a minimum cell rate (MCR), and a global counter is set to the inverse of this value;

Defining a structure of a downlink frame corresponding to the uplink frame to improve the utilization rate of an uplink transmission channel;

A cell is transmitted in a band allocation manner.

The above objects, features, and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a structural diagram showing a tree structure of a PON structure to which the present invention is applied. The PON system is located at the root of the tree structure and plays a central role to provide information to each subscriber in an access network. Wow;

An optical distribution network (ODN) 4 located between the ONU and the OLT and having a tree topology structure;

An ONU (1) connected to the ODN (4) to connect a plurality of NT (2) to the OLT (3); And

It is configured to include a local area exchange (5) connected to the OLT (3) to switch each service node provided by the ATMPON.

In this case, the OLT 3 performs a bandwidth allocation algorithm in consideration of various ATM traffics.

Briefly describing the implementation form of the protocol implemented in the present invention in the above structure, when applying for reservation through the uplink frame, the permission information generated through the cell allocation algorithm for guaranteeing the QoS of ATM traffic is global (global) is stored in the queue, and then the downlink frame informs the corresponding NT (2) of the multiple NTs.

The NT 2 receiving the permission for the request transmits the information by referring to the received permission information.

Here, one permission information means that one slot of an uplink frame can be used by the corresponding NT (2), and a local queue in NT (2) as well as an ATM cell through one slot of the uplink frame. By sending information together, you can make reservations and send information at the same time.

And the bandwidth allocation for the uplink frame is dynamically allocated with priority (CBR> VBR> ABR> UBR) to satisfy the QoS considering the characteristics of ATM traffic.

Hereinafter, the up / down frame structure defined in the present invention will be described in detail. FIG. 3 shows the structure for the uplink frame, and the uplink frame is divided into three parts.

A first area is a 462-bit slot in which ATM cells and request information are transmitted together, and the slot is a 17-bit physical layer preamble PL;

'QLCBR, QLVBR, QLABR (Queue Lenght CBR / VBR / ABR)' of 7 bits indicating local queue information of NT 2 for reserving a slot of a next uplink frame;

It consists of a cell corresponding to an ATM cell, which is an actual information part.

At this time, NT (2) operates four types of local queues for identity bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR) traffic. The value of the 'QLUBR' area represents the number of cells that arrived in each queue. In this case, QLUBR represents the number of UBR cells that arrive in the local queue of NTs by using the U_RG slot described later. ---- Refer to (a), (d) of FIG.

In addition, the slot alone does not allow the OLT 3 to send the request information for the first NT 2 attempting transmission.

Therefore, in order to solve this problem, a request group (referred to as RG), which is the second area of the uplink frame, is defined, and the use of this RG has the effect of adapting to the change of traffic more quickly.

This RG is shown in detail in FIG. 3 (c), and has a form incorporating request information for nine NTs (2), and has nine request fields REQi to the same length (50 bits). REQi + 8).

In the present invention, the number of NT1 is assumed to be 81, and by placing 9 RGs in one frame, it is possible to accommodate all the request information for 81 NT (2).

In addition, each request field includes a 17-bit physical layer preamble (PL) as shown in FIG.

7-bit 'QLCBR, QLVBR, QLABR (queue length of CBR, queue length of VBR, queue length of ABR)' representing arrival information for cells 'CBR, VBR, ABR';

It consists of CRC for error search.

Subsequently, the third U_RG (UBR Request Group) part of an uplink frame is a part of transmitting request information for UBR traffic as shown in (d) of FIG. As shown in FIG. 3 (f), each request field includes a 17-bit physical layer preamble PL;

QLUBR indicating arrival information for the UBR cell;

It consists of CRC for error search.

Spare bits defined in the last bit in each structure are bits used for extension, and the entire frame structure including the above structures is shown in FIG.

On the other hand, the structure of the downlink frame is shown in Figure 4 (a), which consists of a plurality of slots of 462 bits, and transmits the permission information for the transmission request of the NT (2) through each slot.

This permission information is determined by a band allocation algorithm in the OLT 3.

The detailed structure of each slot is shown in Fig. 4B, and includes a 17-bit physical layer preamble;

A 3-bit Class (hereinafter referred to as CL) field;

A 7-bit NT address for storing the address of the NT 2;

An ATM cell for storing information;

Consists of a spare for expansion.

The CL field values are CBR cell when CL = 0, VBR cell when CL = 1, ABR cell when CL = 2, UBR when CL = 3, RG when CL = 4, and U_RG when CL = 5. Indicates permission information for.

The permission information for the RG allows the RG grouping request information for the NT (2) s to be sent upward, and is generated periodically for every d time slots (which is set to about 17 in the present invention).

The overall MAC algorithm is shown in FIG. 5 based on the uplink / downlink transmission frame described above.

As mentioned above, this algorithm is a band allocation algorithm performed by the OLT (3).

First, when the NT slot is transmitted to the OLT 3 upward, the OLT 3 determines which slot is transmitted ---- the first step S1;

After the determination result, the grant information is determined for the nine NTs if RG, the grant information for the UBR cells if URG, and the allowance information in consideration of the priority and traffic characteristics if the information slot is used (second step (S2)). Assign slots corresponding thereto ---- the third step (S3);

When the slot allocation is completed, the permission information is transmitted, and then the steps S1 to S3 are repeatedly performed ---- the fourth step (S4);

At this time, in addition to allocating the slot for the information and the information slot, the permission information of the URG slot of each of the RG slot transmitted from the upstream in step S3 of the permission information allocation permission information for transmitting the RG slot from the upstream Slot allocation for is initialized to the d value corresponding to the period of the initial RG (in the present invention set to the 'd' value shown in Figure 3) and then each time permission information is transmitted using an internal counter (using the down counter) 1 Decremented by zero and assigned when the counter value reaches zero.

In addition, a separate counter for allocating the permission information on the ABR traffic to satisfy the minimum cell rate (hereinafter referred to as MCR) value is allocated.

Hereinafter, the above-described processes will be described in more detail.

The permission information for the ATM traffic cell, RG and U_RG is determined and stored in the global FIFO queue, and transmitted to each NT (2) through the downlink frame. This means that the NT can transmit one slot (one of Slot, RG, or U_RG) through the uplink frame, and when receiving permission information for the RG, one RG slot including the required information of the nine NTs can be transmitted. It means that there is.

The grant information is allocated in order of CBR> VBR> ABR> UBR in order of priority to guarantee QoS for each traffic.

At this time, the minimum cell rate is guaranteed for ABR traffic.

Before describing the band allocation algorithm for the UBR traffic, which is one of the key points of the present invention, the band allocation algorithm for the existing UBR traffic will be briefly described.

In the past, a global counter is provided to give NTs a chance to send only this value, and when a UBR is sent, the counter value is increased to give NTs a chance to send a sequence. Gave the opportunity for UBR cell transmission.

However, this method transmits permission information even when there is no UBR cell waiting for the corresponding NT. Therefore, the corresponding slot is transmitted to the empty slot within the next uplink frame, thereby preventing the use of the uplink channel efficiently.

In order to solve this problem, in the present invention, when the global PIPO queue storing permission information for CBR, VBR, and ABR is empty, the OLT (3) allows the NT to allow U_RG to know the waiting UBR traffic information. Information is transmitted through a downlink frame.

On the NT side, request information for the UBR cells of 15 NTs is composed of one U_RG and transmitted to the OLT (3).

In OLT (3), U_RG is viewed and permission information for UBR cells of each NT is stored in a separate global PIPO queue for UBR, and then a global PIPO queue storing permission information for ATM cells and RG is stored. The UBR cell is transmitted only when empty to avoid collision problems and to improve the utilization of the transmission channel.

The detailed bandwidth allocation procedure considering the ATM traffic characteristics by applying the above theory will be described in detail with reference to FIG. 6.

First, CBR and VBR traffic for NT _i (i = 1 ... N) are assigned to CBR cells if QLCBR _i ≠ 0 according to priority. If QLCBR _i = 0 and QLVBR _i ≠ 0, it is allocated to the VBR cell.

For ABR traffic for NT _i , first, QLCBR _i = 0 and QLVBR _i = 0, and when QLABR _i ≠ 0, allocate a slot for the ABR cell.

In addition, in order to guarantee MCR for ABR traffic, the MAC controller in the OLT 3 operates a countdown counter CNT_D (i) and a request counter R_CNT (i), and this value changes under the following conditions.

The CNT_D (i) value of each NT _i is initialized to m _i = 1 / MCR _{i, which} is the inverse of the MCR value when the permission information for the initial NT _i ABR cell is added to the global PIPO queue.

The value of CNT_D (i) decreases by one every time a slot goes down in the global pipeo. If CNT_D (i) ≤ 0, the permission information for the ABR cell of NT _i is inserted into the global pipeo queue and CNT_D (i Reset the value back to m _i .

Also, R_CNT (i) is a permission information for each NT _i most recently was initialized with the required number of the ABR cell the slot sent to, the value NT _i ABR cells of the global pie port queue via uplink frame from Decreases by 1 each time it is added.

A band allocation procedure for allocating ABR traffic using the above two counter information is as follows.

The allocation is made first for CBR and VBR traffic, but can also be allocated for ABR traffic under the following conditions to ensure the MCR value of ABR traffic.

First, when CNT_D (i) ≤ 0 and R_CNT (i) ≠ 0, permission information for NT _i is inserted into the global PIPO queue.

At this time, the value of CNT_D (i) is set back to the value of m _{i, and the} value of R_CNT (i) is decreased by 1 because the permission information for the ABR cell is generated.

Second, if the global PIPO queue is empty, if NT _i with R_CNT (i) ≠ 0, permission information for the ABR cell of the corresponding NTi is inserted into the global PIPO queue.

However, when all R_CNT (i) = 0, it allocates for UBR traffic.

Meanwhile, band allocation conditions and procedures for UBR traffic are as follows.

If the global PIPO queue is empty and there is no request for ABR traffic, i.e. if R_CNT (i) = 0 for all i, then band allocation for UBR traffic is made.

OLT (3) inserts permission information for U_RG into the global pipeo queue.

The 15 NTs receiving this authorization information send the number of pending UBR cells to OLT (3) via U_RG, which is the request group information for UBR cells.

The OLT (3) receiving the above information inserts the permission information for the UBR cell into the global PIPO queue for a separate UBR, and the actual transmission for the UBR cell is a global pie that stores the permission information for the ATM cell and the RG. If the forque is empty and there is a permit in the global PIPO queue for a separate UBR traffic, the permission is taken from the NT that received the permit.

The flow of allocation based on the theory as described above will be described below with a flowchart.

If the slot is allocated from the NT, first searching whether the global PIPO queue is empty, and if the global PIPO queue is empty, transmitting permission information for UBR traffic (T1);

If the global PIPO queue is not empty, searching whether it is a permission information transmission period for RG traffic and if so, transmitting RG traffic permission information (T2);

If the result of the search is not a processing period for RG traffic, search for m <= 0 NT among NT (where m = 1 / MCR, m sends an ABR cell to satisfy a minimum cell rate, and then sends a next ABR cell) Indicating a maximum interval of slots, that is, a maximum ABR cell transmission interval value, and transmitting permission information for ABR traffic (T3);

After the preparation process for sending the RG traffic and ABR traffic permission information and if there is no NT with m <= 0, it is determined whether the slot information received from the upstream corresponds to the information slot or the RG slot. If it is a slot, determining the traffic to be transmitted and preparing to transmit (T4);

As a result of the determination, if the slot is an RG slot, a slot T5 is allocated to transmit permission information for RG traffic incorporating nine NTs.

In the process of transmitting the permission information for the UBR traffic (T1), if the condition is not satisfied by determining R_CNT <= 0 for all NTs, a process of allocating slots for transmitting permission information for the ABR traffic (T11) )and;

In the above process, if the condition is satisfied, the global PIPO queue for UBR traffic is searched for empty, and if not empty, permission information is not sent. If empty, slot is allocated to transmit permission information for URG traffic. T12).

In the case of the NT slot, the process of preparing the transmission by determining the traffic to be transmitted (T4) determines whether the slot to be allocated currently is a slot for the URG traffic, and transmits permission information of 15 UBR traffic when the condition is satisfied. Allocating a slot (T41);

Determining whether QLCBR> 0 of the information cells is satisfied when the determination result is not satisfied, and allocating slots for transmitting permission information for CBR traffic (T42);

Determining whether QLVBR> 0 is equal when QLCBR is 0 and allocating slots for transmitting permission information for VBR traffic when the condition is satisfied (T43);

If the QLVBR is 0, the process includes allocating a slot (T44) to transmit permission information for ABR traffic.

As described in detail above, the present invention provides a medium access control (MAC) scheme in an ATM PON for accessing an optical subscriber network, thereby ensuring at least an MCR value for an ABR cell and avoiding collision for a UBR cell. In addition, it provides the advantage of efficient transmission while increasing the utilization rate of the uplink transmission channel, and can also provide a variety of multimedia services, a large number of users can use the cost-effective optical resources in the form of efficient and economical sharing There is an economic effect.

In addition, a preferred embodiment of the present invention is disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the following claims You will have to look.

Claims (15)

Asynchronous transmission method In the optical transmission protocol method between subscriber side and telephone station side in ATMPON, Defining an upframe structure including a separate field for storing request information for UBR traffic so as to efficiently transmit a cell while avoiding collision for an unspecified bit rate (UBR) cell during optical transmission; For an available bit rate (ABR) cell, an MCR value is set to guarantee a minimum cell rate (MCR), and a global counter is set to the inverse of this value; Defining a structure of a downlink frame corresponding to the uplink frame to improve the utilization rate of an uplink transmission channel; A method of implementing an ATMPON medium access control (MAC) protocol, comprising transmitting a cell in a band allocation scheme. The method of claim 1, As a method for avoiding collision with the UBR cell, when the global PIPO queue storing permission information about the identity bit rate (CBR), the variable bit rate (VBR), and the available bit rate (ABR) is empty, Transmitting permission information for the UBR request group (U_RG) from the terminating device (OLT) to the subscriber station network terminal (NT) through a downlink frame; The NT side constructs a corresponding U_RG and sends it to the OLT; Subsequently, in the OLT, the permission information for the UBR cells of the respective NTs is stored in a separate global PIPO queue for the UBR with reference to the U_RG; A method of implementing the ATMPON Media Access Control (MAC) protocol, wherein the UBR cell is transmitted only when the global PIPO queue storing the permission information of the ATM cell and the RG is empty. The method of claim 1, The uplink frame structure includes a slot field in which ATM cells and request information are transmitted together; A request group (RG) field for quickly adapting to traffic changes and storing reservation information of network terminals NT; A method for implementing ATMPON medium access control (MAC) protocol, comprising a UBR request group (U_RG) field for storing request information for UBR traffic. The method of claim 3, The slot field of the uplink frame structure may include a physical layer preamble (PL); A length of the CBR queue indicating the local queue information of NT for reserving the slot of the next uplink frame, a length of the VBR queue, and a length of the ABR queue; A method for implementing an ATMPON medium access control (MAC) protocol, comprising a cell bit storing actual ATM cell information. The method of claim 4, wherein The method of the QLCBR, QLVBR, QLABR bits in the frame structure indicates the number of cells arriving in each queue, ATMPON medium access control (MAC) protocol implementation method. The method of claim 3, The RG field of the uplink frame structure includes a plurality of request fields having the same length in a form in which the request information for the plurality of NTs is integrated; A method for implementing the ATMPON Media Access Control (MAC) protocol, which distinguishes the CBR bit from the VBR bit in each request field. The method of claim 3, The U_RG field of the uplink frame structure comprises a plurality of request fields having the same length in a form in which UBR cell request information for a plurality of NTs is integrated. The method of claim 7, wherein Each request field of the plurality of request fields includes: a physical layer preamble (PL); QLUBR indicating arrival information for the UBR cell; Method for implementing ATMPON medium access control (MAC) protocol, characterized in that the structure including a CRC for error detection. The method of claim 1, The downlink frame structure is a structure comprising a class (CL) field for distinguishing between CBR and VBR ATMPON medium access control (MAC) protocol implementation method. The method of claim 9, If CL = 0 in the class field, permission information for the CBR cell is obtained. If CL = 1, the permission information for the VBR cell is If CL = 2, the permission information for ABR cell, If CL = 3, the permission information for the UBR cell is If CL = 4 then the permission information for RG is If CL = 5, the ATMPON medium access control (MAC) protocol implementation method characterized in that indicating the permission information for U_RG. The method of claim 1, The uplink frame transmission process in the bandwidth allocation process includes: determining whether the information is available if the permission information is to be transmitted by the telephone station and transmitting the information through the corresponding slot; As a result of the determination, if the information corresponding to the RG is transmitted through the RG slot, and if the cell is related to the information, if there is a slot in the queue for each of the CBR, VBR, and ABR, it is transmitted through the corresponding traffic slot considering the priority and traffic characteristics And preparing information to be transmitted through the URG slot if the information corresponds to the URG; Allocating slots corresponding to the slots to be transmitted through the process; And if the slot allocation is completed, transmitting the permission information and then performing the above steps again. The method of claim 11, In the case of the information about the RG slot in the process of preparing to transmit each slot, the down counter value is set every time the permission information is transmitted from the OLT, and then inserted when the value of the down counter is 0 Method for implementing the ATMPON Media Access Control (MAC) protocol, characterized in that for transmitting. The method of claim 11, The step of allocating slots may include: receiving slots from NT and transmitting permission information for UBR traffic when the global PIPO queue is empty; Then, if the global PIPO queue is not empty, searching whether the permission information transmission period for the RG traffic is transmitted and transmitting the RG traffic permission information; Then transmitting the permission information for the ABR traffic if there is an NT whose 'Maximum ABR cell transmission interval value' (m = 1 / MCR) is less than 0 among the NTs unless the processing period for the RG traffic is performed; After preparing the RG traffic and ABR traffic permission information, and if the 'maximum ABR cell transmission interval value' for all NT is greater than 0, the slot received from the upstream is determined. Performing a process; And if the result of the determination is an RG slot, allocating a slot to transmit permission information for RG traffic incorporating nine NTs. The method of claim 13, The transmitting of the permission information for the UBR traffic may include: allocating a slot for transmitting permission information for ABR traffic if a counter value for counting the number of request information for all NTs is greater than zero; In the above process, if the condition is satisfied, the global PIPO queue for UBR traffic is searched for empty, and if not empty, permission information is not sent. If empty, slot is allocated to transmit permission information for URG traffic. Method for implementing the ATMPON medium access control (MAC) protocol, characterized in that performed. The method of claim 13, The process of preparing the transmission by determining the traffic to be transmitted when the slot is determined as the information slot includes: allocating a slot for transmitting permission information of the UBR traffic when the slot to be allocated is the slot for the URG traffic; Allocating slots to transmit permission information for CBR traffic when QLCBR is greater than zero if the result is not a URG slot; Allocating slots for transmitting permission information for VBR traffic when QLVBR is 0 when the result of the determination is QLCBR; And if the QLVBR is 0, allocating slots to transmit the permission information for the ABR traffic.