JP2006005764A - Optical subscriber line terminal equipment and band allocation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impartially allocate a band to a plurality of optical subscriber line terminal equipment in a congestion cycle. <P>SOLUTION: This optical subscriber line terminal equipment is optical subscriber line terminal equipment connectable to an optical subscriber terminator and is provided with a first receiving means for receiving a transmission request amount showing the amount of storage data stored for transmission in the optical subscriber terminator, a determining means for determining the maximum transmission allowable amount on the basis of the transmission request amount, a first transmitting means for transmitting the maximum transmission allowable amount, a second receiving means for receiving a predetermined transmission amount being the maximum data amount at which the storage data stored in the optical subscriber terminator can be transmitted in a frame unit within the maximum transmission allowable amount, and a second transmitting means for transmitting grant that includes the predetermined transmission amount as a transmission allowable amount and allows data transmission. The determining means includes a satisfaction calculating means for calculating satisfaction for each optical subscriber line terminator and determines the maximum transmission allowable amount to be a large value in the order of low satisfaction (S26) during a congestion cycle (S27). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a PON (Passive Optical Network) that is a medium-shared communication in which a plurality of home-side devices share a medium and transmit data, and in particular, an EPON that transmits data as an Ethernet (registered trademark) frame. The present invention relates to an OLT (optical subscriber line terminal equipment) that efficiently allocates an upstream band in (Ethernet (registered trademark) PON) and a band allocation program executed thereby.

  In recent years, the Internet has become widespread, and users can access various information on sites operated in various parts of the world and obtain the information. Along with this, the demand for broadband access such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) is also increasing rapidly.

  FIG. 11 is a block diagram showing a schematic configuration of a conventional PON system. This PON system mainly branches an OLT 101 installed in a telephone office or the like, a plurality of ONUs 102-1 to 102-n mainly installed in each home, and an optical signal transmitted from the OLT 101 to split the ONU 102-1. 102-n, a splitter 105 for converging optical signals sent from the ONUs 102-1 to 102-n and sending them to the OLT 101, and a user terminal 111 connected to each of the ONUs 102-1 to 102-n including. Note that the first ONU 102-1 to the n-th ONU 102-n have the same configuration.

  The OLT 101 sends the data received via the upper network 109 to the ONUs 102-1 to 102-n via the transmission path 104 and the splitter 105. Further, the OLT 101, based on the report 107 transmitted from the ONUs 102-1 to 102-n, transmits the transmission start time of data stored in the buffers 103-1 to 103-n in the ONUs 102-1 to 102-n and The grant permission amount is calculated, and the grant 106 into which the instruction signal is inserted is sent to the ONUs 102-1 to 102-n via the transmission path 104 and the splitter 105.

  For example, when the ONU 102-1 receives the uplink information frame 108 from the user terminal 111 via the lower network 110, the uplink information frame 108 is temporarily stored in the buffer 103-1. When the ONU 102-1 receives the grant 106 from the OLT 101, the ONU 102-1 notifies the OLT 101 with the report 107 of the data amount in the buffer 103-1 at the time designated by the grant 106. The uplink information frame 108 arrives in variable length packet units.

  When the ONU 102-1 receives the grant 106 in which the instruction signal is inserted from the OLT 101, the ONU 102-1 transmits the data in the buffer 103-1 to the OLT 101 together with the report 107 based on the instruction signal.

  FIG. 12 is a sequence diagram for explaining the operation procedure of the conventional PON system. This sequence diagram is for the operations of the OLT 101 and the ONU 102-1, but the same is true for the operations of the other ONUs 102-2 to 02-n.

  At the operation time start time T0, the OLT 101 has already calculated an RTT (Round Trip Time) for the ONUs 102-1 to 102-n. At time Ta1, the OLT 101 transmits a grant 121 including the report transmission start time Tb2 to the ONU 102-1, in order to notify the transmission request amount. This report transmission start time Tb2 is calculated so as not to collide with reports transmitted from other ONUs.

  When the ONU 102-1 receives the grant 121 for itself, the ONU 102-1 calculates the requested transmission amount by referring to the data amount stored in the buffer 103-1, and the OLT 101 receives the report transmission start time Tb2 included in the grant 121. A report 122 including the requested transmission amount is transmitted.

  When the OLT 101 receives the report 122, the OLT 101 calculates a value that is equal to or less than the fixed or variable maximum allowable transmission amount and can transmit as much data as possible in the buffer included in the report 122, and grants the calculation result as the allowable transmission amount. 123. When the transmission request amount included in the report 122 is zero, the operation result by the OLT 101 is zero and no bandwidth is allocated. However, since the ONU 102-1 needs to transmit the report, the OLT 101 causes the ONU 102-1 to send the report. The grant 123 is always transmitted.

  The transmission start time Tb4 included in the grant 123 uses the calculated scheduled ONU data reception time, the previous ONU transmission permission amount, the RTT related to the current ONU, and the guard time which is a fixed time, and data and reports. Is calculated so as not to collide with data or reports from other ONUs. The OLT 101 calculates a time Ta3 at which the grant 123 including the transmission permission amount and the transmission start time Tb4 is transmitted so that the grant 123 arrives at the ONU 102-1 by the transmission start time Tb4.

  When the ONU 102-1 receives the grant 123 for itself, the ONU 102-1 sends the data 124 corresponding to the transmission permission amount to the OLT 101 together with the report including the next transmission request amount at the transmission start time Tb4 included in the grant 123. This report is sent immediately before or after the data. When the report is sent immediately before the data, the value to be reported to the OLT 101 as the send request amount is the amount of data stored in the buffer 103-1 and the data amount. It is the difference from the amount of data.

  When the OLT 101 receives the data and the report 124, the OLT 101 sends the data to the upper network 109, and the report is processed in the same manner as the processing for the report 122. The processing described above is performed independently for all the ONUs 102-1 to 102-n, and the processing from time Ta3 to time Ta4 is repeated until the operation time ends.

  FIG. 13 is a diagram illustrating an example of a distributed allocation method. This diagram is a sequence diagram showing bandwidth allocation when the number of ONUs is 3, and transmission / reception of grants and reports between OLT-ONUs.

  The OLT 101 sequentially sends grants 131 to 133 to the ONUs 102-3, 102-2, and 102-1. When the OLT 101 receives the reports 134 to 136 from the ONUs 102-3, 102-2, and 102-1, it first sends a grant 137 to the ONU 102-3 that permits transmission of data.

  The OLT 101 receives the data 138 sent from the ONU 102-3 and sends a grant 139 to the ONU 102-2 in parallel with this. Thereafter, similar processing is repeated, and the OLT 101 sequentially allocates bands to the ONUs 102-1 to 102-3 and repeats data reception.

  As can be seen from FIG. 13, the waiting time from when the data sent from the user terminal 111 arrives at the ONU 102-1 until it is sent is the data corresponding to the report after the ONU 102-1 sends the report. Depends on the time to send That is, it varies depending on the amount of data transmitted from all ONUs 102-1 to 102-3.

  For example, if all the transmission request amounts by reports from the ONUs 102-1 to 102-n shown in FIG. 11 are permitted, the waiting time from the report transmission to the data transmission is greatly increased, which affects the service that requires real-time. As well as greatly affecting TCP (Transmission Control Protocol) throughput. Therefore, the OLT 101 needs to control the amount of data transmitted from the ONUs 102-1 to 102-n so that the waiting time in the buffer in the ONU can be suppressed within an allowable time.

  In order to solve this problem, after the OLT 101 receives a report from the ONUs 102-1 to 102-n, a credit (maximum transmission permission amount) is used to limit the transmission permission amount of the ONUs 102-1 to 102-n. The concept is introduced. If the total number of ONUs that can be transmitted is N, the line speed of the transmission path 104 is r [bps], and the allowable delay time is td [sec], the credit c [bit] is calculated by the following equation.

c = r × td / N (1)
As described above, the OLT 101 allocates a fixed amount of credit to each of the ONUs 102-1 to 102-n, and controls the amount of data transmitted from the ONUs 102-1 to 102-n. The data transmission waiting time in the buffers 103-1 to 103-n is suppressed within an allowable time.

  As a related prior art, “IPACT: A Dynamic Protocol for an Ethernet® PON” (Glen Kramer et al., Pp74-80, IEEE Commun, Feb. 2002.) (hereinafter referred to as the first prior art). ) And “Dynamic Bandwidth Allocation Algorithm Suitable for GE-PON” (Yoshihara et al., IEICE Technical Report, NS2002-17, pp1-4, 2002.04) (hereinafter referred to as second prior art).

  The first prior art relates to a dynamic allocation method in the EPON type FTTH service, in which the OLT sends a report to each ONU independently, and each time the OLT issues a grant to the corresponding ONU. It relates to the allocation method.

  The second prior art relates to a centralized allocation method, in which the ONU has a buffer amount up to the maximum data size that can be allocated per grant period, and a buffer amount that is less than or equal to the specified upper limit from the beginning of the buffer. Are sent as a report. The OLT permits a buffer amount equal to or less than the upper limit value in order from the first ONU, and reduces the allocation loss by giving the unallocated bandwidth as a grant only to the last ONU of the grant period.

  In the method of assigning the credit calculated by the equation (1) to each ONU, there is a problem that if the credit is small, even if only a small number of ONUs can monopolize the line, the uplink bandwidth cannot be used efficiently. there were.

  FIG. 14 is a diagram for explaining a problem in the first prior art. When the OLT recognizes only the transmission permission band for the transmission request amount (buffer declaration amount) included in the report received from the ONU # 1, the ONU # 1 uses the MAC (Media Access) for the transmission permission band. Control) frames 141, 142, and 143 are transmitted, but an allocation loss occurs because the MAC frame 144 cannot be transmitted within the permitted transmission band.

  Similarly, ONU # 2 cannot send MAC frame 153 within the transmission-permitted band, and ONU # 3 cannot send MAC frame 163 within the transmission-permitted band, so an allocation loss occurs. This allocation loss corresponds to the maximum MAC frame length in the worst case. Therefore, there is a problem that the uplink information frame cannot be efficiently transmitted.

In the second prior art, the number of ONUs to which the OLT gives a large permitted amount within the same period is one, and the other ONUs can only allocate a small permitted amount, so the uplink information frame is stored in the buffer. There was a problem that the time is long.
IPACT: A Dynamic Protocol for an Ethernet (R) PON (Glen Kramer et al., Pp74-80, IEEE Commun, Feb. 2002.) Dynamic bandwidth allocation algorithm suitable for GE-PON (Yoshihara et al., IEICE Technical Report, NS2002-17, pp1-4,2002.04)

  The present invention has been made to solve the above-described problems, and one of the objects of the present invention is to provide an optical network that can efficiently use the upstream bandwidth and can equally allocate the bandwidth to the congestion cycle. An object is to provide an optical subscriber line terminal apparatus and a bandwidth allocation program capable of providing a subscriber line terminal station apparatus.

  Another object of the present invention is to provide an optical subscriber line terminal apparatus that prevents a band from being allocated to a specific optical subscriber line terminator.

  In order to achieve the above object, according to one aspect of the present invention, an optical subscriber line terminal device is an optical subscriber line terminal device connectable to an optical subscriber line terminal device, wherein the optical subscriber line terminal device is an optical subscriber line device. A first receiving means for receiving from the optical subscriber line terminating device a transmission request amount indicating the amount of stored data accumulated for transmission at the subscriber line terminating device, and determining a maximum permitted transmission amount based on the transmission requested amount; Determining means; first transmission means for transmitting the determined maximum transmission permission amount to the optical subscriber line termination device; and stored data stored in the optical subscriber line termination device in units of frames within the maximum transmission permission amount. Second receiving means for receiving a scheduled transmission amount, which is the maximum amount of data that can be transmitted, from the optical subscriber line terminating device, and a grant that includes the planned transmission amount as a permitted transmission amount and that permits transmission of data. Second transmitting means for transmitting to the terminating device And the determination means includes satisfaction calculation means for calculating satisfaction for each optical subscriber line terminating device, and determines the maximum permitted transmission amount in descending order of satisfaction when the congestion cycle occurs. .

  According to the present invention, the maximum transmission permission amount determined based on the transmission request amount received from the optical subscriber line terminating device is transmitted, and the transmission is the maximum data amount that can be transmitted in frame units within the maximum transmission permission amount. The scheduled amount is received from the optical subscriber line terminating device, and the received scheduled amount is transmitted as the permitted transmission amount. Also, when in the congestion cycle, the maximum transmission permission amount is determined to be a large value in ascending order of satisfaction. Therefore, it is possible to provide an optical subscriber line terminal apparatus that can efficiently use the upstream bandwidth and can equally allocate the bandwidth to the congestion cycle.

  Preferably, the satisfaction degree calculation means determines the satisfaction degree from the transmission request amount and the maximum transmission permission amount.

  Preferably, the satisfaction degree calculation means sets the satisfaction level to a higher value when the requested amount of transmission is zero than when it is other than zero.

  Preferably, the satisfaction level calculation means sets the satisfaction level to a lower value as the transmission request amount is larger and the maximum transmission permission amount is smaller.

  Preferably, the satisfaction degree calculation means takes a value obtained by averaging the satisfaction degrees while the congestion cycle continues.

  According to the present invention, it is possible to allocate bandwidth fairly while the congestion cycle continues.

  Preferably, when in the congestion cycle, the determination unit sets the maximum transmission permission amount as the transmission request amount when the transmission request amount is equal to or less than a predetermined value, and sets the maximum transmission permission amount when the transmission request amount exceeds the predetermined value. Is first set to a predetermined value, and then is set to a value obtained by adding an additional value to the predetermined value in order from the optical subscriber line terminating device with the lower satisfaction level.

  Preferably, the determining means sets the maximum value of the additional value to a remaining bandwidth determined from a value obtained by subtracting the predetermined value from the transmission request amount, a congestion cycle period, and a maximum transmission permission amount before adding the additional value. Select from the values.

  Preferably, the determination means makes the maximum transmission permission amount and the predetermined value variable for each optical subscriber line terminating device, sets the maximum additional value to a value obtained by subtracting the predetermined value from the transmission request amount, and the congestion cycle period. And the remaining bandwidth value determined from the maximum transmission permission amount before adding the additional value, and the value obtained by subtracting a predetermined value from the maximum transmission permission amount.

  According to the present invention, it is possible to prevent a band from being unduly allocated to a specific optical subscriber line terminal station apparatus.

  Preferably, the determining means sets the maximum transmission permission amount as the transmission request amount when in the non-congestion cycle.

  Preferably, the determination unit sets the upper limit value of the maximum transmission permission amount as a second predetermined value.

  According to the present invention, since an upper limit is set for the maximum creation permission amount, it is possible to provide an optical subscriber line terminal station apparatus that prevents a band from being unduly allocated to a specific optical subscriber line termination apparatus.

  According to another aspect of the present invention, a bandwidth allocation program is a bandwidth allocation program executed by an optical subscriber line terminal device that can be connected to an optical subscriber line termination device, Receiving a transmission request amount indicating the amount of stored data accumulated for transmission from the optical subscriber line terminating device, determining a maximum transmission permission amount based on the transmission request amount, and determining the determined maximum transmission A step of transmitting the permitted amount to the optical subscriber line terminating device and a scheduled transmission amount that is the maximum amount of data that can be transmitted in units of frames within the maximum permitted transmission amount of the accumulated data stored in the optical subscriber line terminating device. And a step of transmitting a grant permitting data transmission to the optical subscriber line terminator including a scheduled transmission amount as a permitted transmission amount and a computer. The determining step includes a step of calculating a satisfaction level for each optical subscriber line terminating device, and a step of determining a maximum transmission permission amount to a large value in the order of decreasing satisfaction level in a congestion cycle. .

  According to the present invention, when in the congestion cycle, the maximum transmission permission amount is determined to be a large value in ascending order of satisfaction, so that a bandwidth is allocated fairly to a plurality of optical subscriber line terminal apparatuses in the congestion cycle. Therefore, it is possible to provide a bandwidth allocation program capable of performing

  FIG. 1 is a block diagram showing a schematic configuration of an OLT in one embodiment of the present invention. The OLT 1 receives an optical signal from the ONU and outputs a frame, a transmission unit 12 that transmits a data frame received from the reception unit 11 to a higher-level network, and a report frame received from the reception unit 11. A control frame processing unit 13 that generates a grant frame based on the received data and performs transmission control of a data frame received from the higher level network, a reception unit 14 that receives a frame from the higher level network, and the reception unit 14 It includes a buffer memory 15 that accumulates frames, and a transmission unit 16 that sends frames accumulated in the buffer memory 15 under the control of the control frame processing unit 13 to the ONU. The buffer memory 15 may be any memory that can store data, such as a register, a flip-flop circuit, or a latch circuit.

  The receiving unit 11 receives the optical signal from the ONU and reads the header portion of the frame to determine whether it is a data frame or a control frame such as a report frame. If the received frame is a data frame, the reception unit 11 transfers the data frame to the transmission unit 12. If the received frame is a control frame, the receiving unit 11 transfers the control frame to the control frame processing unit 13.

  When receiving the data frame from the reception unit 11, the transmission unit 12 transmits the data frame to the upper network.

  The control frame processing unit 13 includes a scheduled arrival time storage table, an RTT storage table, an active information storage table, and a satisfaction level storage table, which will be described later, and has a bandwidth allocation calculation function and a downlink control frame creation function. When receiving a report frame from the receiving unit 11, the control frame processing unit 13 creates a grant frame by a process described later and transfers it to the buffer memory 15. The control frame processing unit 13 also performs transmission control of frames stored in the buffer memory 15.

  The control frame processing unit 13 generates and sends out a control frame for periodically detecting whether or not there is a newly connected ONU, and a table such as an active information storage table according to the detection result. Rewrite the contents of. In addition, when the connected ONU is disconnected, the control frame processing unit 13 detects that and rewrites the contents of a table such as an active information storage table.

  The receiving unit 14 receives a frame from the upper network and transfers it to the buffer memory 15. The buffer memory 15 accumulates the control frames and data frames transferred from the control frame processing unit 13 and the receiving unit 14 in the queue, and transfers the frames accumulated in the queue to the transmission unit 16 under the control of the control frame processing unit 13. . The transmission unit 16 transmits the control frame and data frame transferred from the buffer memory 15 to the ONU.

  The OLT 1 can be mounted with a flash ROM 17. The flash ROM 17 stores a bandwidth allocation program that can be read and executed by a computer. Such a bandwidth allocation program is read by an external storage device included in the OLT 1, stored in a non-volatile manner in a random access memory (RAM) included in the OLT 1, and executed by the CPU. The band allocation program may be stored in advance in a read only memory (ROM) provided in the OLT 1 instead of being recorded in the flash ROM 17. Moreover, you may make it download from another computer via a high-order network.

  In addition to the flash ROM 17, the bandwidth allocation program includes a CD-ROM (Compact Disc Read Only Memory), an FD (Flexible Disc), a hard disk, a magnetic tape, a cassette tape, an optical disc (MO (Magnetic Optical Disc) / MD (Mini Discs / DVDs (Digital Versatile Discs), IC cards (including memory cards), optical cards, mask ROMs, EPROMs, EEPROMs, and other semiconductor memories may be used.

  The bandwidth allocation program here includes not only a program that can be directly executed by the CPU of the OLT 1, but also a source program format program, a compressed program, an encrypted program, and the like.

  FIG. 2 is a block diagram showing a schematic configuration of the ONU in the present embodiment. The ONU 2 receives an optical signal from the OLT 1 and outputs a frame addressed to itself, a transmission unit 22 that transmits a data frame received from the reception unit 21 to a terminal on the user side, and a reception unit 21. A control frame processing unit 23 that generates a report frame based on the received grant frame and controls transmission of a data frame received from the user terminal, and a receiving unit 24 that receives a frame from the user terminal. A buffer memory 25 for storing the data frame received by the receiving unit 24 and the control frame generated by the control frame processing unit 23, and a frame stored in the buffer memory 25 under the control of the control frame processing unit 23 in the OLT. Each data frame received by the transmitting unit 26 to be transmitted and the receiving unit 24 And a counter 27 for counting the length of the.

  The receiving unit 21 receives an optical signal from the OLT and reads the header portion of the frame to determine whether or not the frame is addressed to itself. The receiving unit 21 takes in the frame if the received frame is addressed to itself, and discards the frame if it is addressed to another ONU or a device connected to another ONU. In addition, the receiving unit 21 determines whether it is a data frame or a control frame such as a grant frame based on the header portion of the captured frame. If the received frame is a data frame, the reception unit 21 transfers the data frame to the transmission unit 22. If the received frame is a control frame, the receiving unit 21 transfers the control frame to the control frame processing unit 23.

  When receiving the data frame from the receiving unit 21, the transmitting unit 22 transmits the data frame to a link to which a user terminal or the like is connected.

  The control frame processing unit 23 includes a data length storage table for storing the length of the data frame transferred from the counter 27, and has a transmission request amount calculation function and an uplink control frame creation function. When the control frame processing unit 23 receives the grant frame from the receiving unit 11, the control frame processing unit 23 creates a report frame by a process described later and transfers it to the buffer memory 25. The control frame processing unit 23 also performs transmission control of frames stored in the buffer memory 25.

  In addition, the control frame processing unit 23 executes processing of control frames other than the grant frame from the OLT, stores the control frames in the buffer memory 25, and performs control frame transmission control.

  The receiving unit 24 receives a frame from a user terminal (link) and transfers the frame to the buffer memory 25. The buffer memory 25 temporarily accumulates the control frames and data frames transferred from the control frame processing unit 23 and the receiving unit 24 for each frame type, and transmits the frames accumulated in the queues under the control of the control frame processing unit 13. The data is transferred to the unit 26. The transmission unit 26 transmits the control frame and data frame transferred from the buffer memory 25 to the OLT.

  The counter 27 counts the length of the data frame received by the receiving unit 24 and notifies the control frame processing unit 23 of the length of each data frame.

  FIG. 3 is a diagram illustrating an example of a communication procedure between the OLT and the ONU in the present embodiment. In this communication procedure, three cycles are required from when the ONU 2 requests data transmission until data is transmitted. Here, these three cycles are indicated by cycle #i to cycle # i + 2 using variable i. The t-th ONU is indicated by ONU (t). However, 1 ≦ t ≦ N and N is the number of ONUs. As described above, the OLT 1 communicates with a plurality of ONUs (t) in one cycle.

<Cycle #i>
The ONU (t) transmits a request amount Rt (i + 2) indicating the amount of data requested to be transmitted to the OLT 1. This required amount Rt (i + 2) is usually the amount of data stored in the buffer memory 25 of the ONU (t). Further, an upper limit value may be provided instead of the data amount of all accumulated data. Further, the request amount Rt (i + 2) is used to determine a bandwidth to be allocated to ONU (t) in cycle # i + 2.

  In OLT 1, Rt (i + 2) is received from all ONUs (t) (1 ≦ t ≦ N) in cycle #i. Thereby, it is determined whether or not data transmission from the ONU 2 in the cycle # i + 2 is congested. Since the period of cycle # i + 2 is determined in advance, it is determined as a congestion cycle when the communication time determined from the sum of Rt (i) exceeds the period of cycle # i + 2, and when it does not exceed, the non-congestion cycle Is determined.

  The OLT 1 determines a credit Ct (i + 2) for each ONU (t). This credit Ct (i + 2) is used to determine the bandwidth to be allocated to ONU (t) in cycle # i + 2. The credit Ct (i + 2) determination process will be described later in detail.

<Cycle # i + 1>
The OLT 1 transmits the credit Ct (i + 2) to the ONU (t). In ONU (t), the credit Ct (i + 2) is received. Then, the ONU (t) notifies the OLT of the maximum data amount that can be transmitted in units of frames from the first data frame that is not more than credits and that is transmitted, as a transmission amount St (i + 2). Then, in the OLT 1, the transmission amount St (i + 2) is received from all the ONUs (t). This transmission amount St (i + 2) determines the bandwidth allocated to ONU (t) in cycle i + 2. As a result, the OLT 1 can recognize how much data is received from each ONU (t) in the cycle # i + 2 at the stage of the cycle i + 1. The OLT 1 determines the received transmission amount St (i + 2) as a permission amount Gt (i + 2) that permits transmission in the cycle i + 2.

<Cycle # i + 2>
The OLT 1 transmits the permitted amount Gt (i + 2) to the ONU (t). The ONU (t) receives the permission amount Gt (i + 2), and transmits only the permission amount Gt (i + 2) from the first data frame to be transmitted out of the data stored in the buffer memory 25 to the OLT 1.

  Here, for the sake of explanation, the procedure for determining the bandwidth allocated to the ONU (t) in cycle # i + 2 has been described, but in reality, the next data is transmitted / received in cycle #i.

(1) Data related to bandwidth allocation in cycle #i Data transmitted from OLT 1 to ONU (t): Allowable amount Gt (i)
Data transmitted from ONU (t) to OLT1: Data Dt (i) for permitted amount Gt (i)
(2) Data relating to bandwidth allocation in cycle # i + 1 Data transmitted from OLT 1 to ONU (t): Credit Ct (i + 1)
Data transmitted from ONU (t) to OLT1: Transmission amount St (i + 1)
(3) Data related to bandwidth allocation in cycle # i + 2 Data transmitted from ONU (t) to OLT1: Request amount Rt (i + 2)
Here, for the sake of explanation, the permitted amount Gt (i) and the credit Ct (i + 1) transmitted from the OLT 1 to the ONU (t) in the cycle #i are separated, but these are transmitted in one frame. Alternatively, it may be transmitted in another frame. Similarly, the request amount Rt (i + 2) and the transmission amount St (i + 1) transmitted from the ONU (t) to the OLT 1 in cycle #i are separated, but these may be transmitted in one frame. Alternatively, it may be transmitted in another frame. In the following description, the permitted amount Gt (i) and the credit Ct (i + 1) transmitted from OLT1 to ONU (t) in cycle #i are transmitted in one frame, and transmitted from ONU (t) to OLT1. The request amount Rt (i + 2) and the transmission amount St (i + 1) are described as being transmitted in one frame.

  For the sake of explanation, the OLT 1 transmits / receives data to / from all ONUs (t) in one cycle. However, the OLT 1 transmits / receives data to / from all ONUs (t) in a plurality of cycles. It may be.

  FIG. 4 is a flowchart for explaining the processing procedure of the control frame processing unit 13 of the OLT 1. First, when the control frame processing unit 13 receives a report frame from the ONU (t) received by the receiving unit 11 in cycle #i (step S11), the control frame processing unit 13 refers to the transmission source information in the header of the report frame, The ONU (t) information corresponding to the transmission source information is read from the storage table (step S12). The report frame includes a request amount Rt (i + 2) that ONU (t) desires to transmit in cycle # i + 2 and a transmission amount St (i + 1) that indicates the amount of data that ONU (t) transmits in cycle # i + 1. It is.

  FIG. 5 is a diagram illustrating an example of a storage table provided in the control frame processing unit 13. FIG. 5A shows an estimated arrival time storage table, in which the estimated arrival time of the frame is stored in correspondence with the number k of ONU (t) determined to be active at the current time. This estimated arrival time storage table is updated at the time of report / grant frame processing.

  FIG. 5B shows an RTT storage table, in which each RTT is stored corresponding to the numbers 1 to N of ONU (t) that can be transmitted. This RTT storage table is updated when measuring the distance to the ONU.

  FIG. 5C shows an active information storage table, which stores information indicating whether each ONU is active corresponding to the numbers 1 to N of the ONU (t) that can be transmitted. The This active information storage table is updated when a new ONU is detected, when an ONU disconnection is detected, and during a report / grant process.

  When a new ONU is detected, information corresponding to the ONU is added to the RTT storage table and the active information storage table. When the disconnection of the ONU is detected, information corresponding to the ONU is deleted from the RTT storage table and the active information storage table.

  When a new ONU is connected to the network, the ONU sends an uplink control frame in response to the downlink control frame periodically sent by the OLT 1. The OLT 1 recognizes that the ONU is connected by receiving the control frame from the ONU, and detects the round trip time between the OLT 1 and the ONU, that is, the RTT based on the response time.

  The OLT 1 determines that the ONU has been disconnected when a report frame is not returned for a certain period of time with respect to the grant frame transmitted to the ONU or when a control frame indicating a disconnection request is received from the ONU.

  FIG. 5D shows a satisfaction degree storage table, in which satisfaction levels of the respective ONUs (t) are stored corresponding to the numbers 1 to N of the ONUs (t) that can be transmitted. The satisfaction level is calculated and stored for every ONU for each congestion cycle. When the congestion cycle continues, the satisfaction level is stored as an average value for the duration. Furthermore, the satisfaction level is reset to the maximum value “1” when the congestion cycle ends.

  Returning to the description of the flowchart of FIG. Next, the control frame processing unit 13 reads the estimated arrival time and permitted amount Gt-1 (i + 1) of the ONU (t-1) processed immediately before the ONU (t) read from the storage table, From the RTT of the ONU (t), the arrival time and transmission start time of the next cycle # i + 1 of the ONU (t) are calculated (step S13). The permitted amount Gt-1 (i + 1) of ONU (t-1) is the transmission amount St-1 (i + 1) included in the report frame of ONU (t-1) received in step S11.

  Further, the control frame processing unit 13 calculates a credit Ct (i + 2) for bandwidth allocation of cycle # i + 2 from the request amount Rt (i + 2) (step S14). The calculation of the credit Ct (i + 2) will be described later.

  Next, the control frame processing unit 13 determines whether or not the ONU is active at the current time from the request amount Rt (i + 2). Then, the contents of the storage table are updated depending on whether or not the ONU (t) is active (step S15).

  Finally, the control frame processing unit 13 is configured by a transmission source address (address of OLT1), a transmission destination address (address of the ONU (t)), a transmission start time, a credit Ct (i + 2), and a permission amount Gt (i + 1). The grant frame is created and transferred to the buffer memory 15, and the transmission of the grant frame is instructed during the downlink data frame of cycle # i + 1 (step S16). As the permitted amount Gt (i + 1), the transmission amount St (i + 1) included in the report frame received in step S11 is assigned as it is.

  Thus, since the transmission amount St (i + 1) received from the ONU is directly assigned to the permitted amount Gt (i + 1), the bandwidth allocation loss can be minimized, and the upstream bandwidth can be efficiently used. .

  FIG. 6 is a flowchart showing the credit determination process executed in step S14 of FIG. Here, a case where a report frame is received from ONU (t) in cycle #i in step S11 of FIG. 4 will be described. In this case, the report frame includes a request amount Rt (i + 2) that ONU (t) desires to transmit in cycle # i + 2 and a transmission amount St (i + 1) indicating the amount of data that ONU (t) transmits in cycle # i + 1. And was included. Therefore, in the credit determination process, the credit Ct (i + 2) for allocating the band of cycle # i + 2 is determined.

  Referring to FIG. 6, it is first determined whether or not cycle # i + 2 is a congestion cycle (step S21). If it is determined that the cycle is a congestion cycle, the process proceeds to step S22; otherwise, the process proceeds to step S29. The OLT 1 receives Rt (i + 2) from all ONUs (t) (1 ≦ t ≦ N). On the other hand, since the period of cycle # i + 2 is determined in advance, it is determined as a congestion cycle when the total communication time of Rt (i + 2) exceeds the period of cycle # i + 2, and when it does not exceed, it is non-congested Judge as a cycle.

  In step S29, the satisfaction degree storage table is reset, and in the next step S30, the requested amount Rt (i + 2) is allocated as it is to the credit Ct (i + 2). Thereafter, the process ends. This is because in the non-congestion cycle, there is no ONU (t) that cannot be transmitted even if all transmission of the request amount Rt (i + 2) is permitted.

  In step S22, it is determined whether or not the required amount Rt (i + 2) exceeds a threshold value W [bit]. If so, the process proceeds to step S23, and if not, the process proceeds to step S24. The threshold value W may be a predetermined value. For example, a value determined from a period obtained by dividing the period of cycle # i + 2 by the total number N of ONU (t) can be used.

  In step S23, a threshold value W is assigned to credit Ct (i + 2), and the process proceeds to step S25. On the other hand, in step S24, the requested amount Rt (i + 2) is directly assigned to the credit Ct (i + 2), and the process proceeds to step S25.

  In step S25, it is determined whether there is a remaining bandwidth T (i + 2). The remaining bandwidth T (i + 2) is a value obtained by subtracting the total communication time of the previously assigned credit Ct (i + 2) from the period of cycle # i + 2. If the remaining bandwidth T (i + 2) exceeds zero, the process proceeds to step S26, and if not, the process proceeds to step S31.

  In step S26, referring to the satisfaction level storage table, the lowest satisfaction level is extracted from ONU (t) in which the required amount Rt (i + 2) exceeds the threshold value W in step S22. When there are a plurality of such ONUs, any one ONU may be determined as appropriate. Let the extracted ONU be ONU (S).

  Then, the credit Cs (i + 2) corresponding to the extracted ONU (S) is updated to a value obtained by adding the additional value B (i + 2) to the threshold value W (step S27). Here, the additional value B (i + 2) is a value within the lower range of the value obtained by subtracting the threshold value W from the requested amount Rs (i + 2) of the ONU (S) and the remaining bandwidth T (i + 2). Set to

0 ≦ B (i + 2) ≦ min (Rs (i + 2) −W, T (i + 2)) (2)
In the next step S28, the remaining bandwidth is updated. Since the additional value B (i + 2) is added to the credit Cs (i + 2), the remaining bandwidth T (i + 2) is subtracted by the additional value B (i + 2).

  Thereafter, the process returns to step S25, and the processes of steps S26 to S28 are repeated until the remaining bandwidth T no longer exists. Thereby, the ONU having the next lowest satisfaction is extracted, and the additional value B (i + 2) is added to the corresponding credit Cs (i + 2).

  When there is no remaining bandwidth T in step S25, the process proceeds to step S31, where the satisfaction levels of all ONUs (t) are calculated, and the satisfaction level storage table is updated. Thereafter, the process ends.

  In this way, since many bands are preferentially allocated to ONUs with low satisfaction, it is possible to effectively allocate bands while maintaining the fairness of a plurality of ONUs.

  FIG. 7 is a diagram illustrating an example of a satisfaction determination table used to determine satisfaction. Here, a case where the satisfaction level A (i) of cycle #i is determined will be described as an example. The satisfaction level A (i) is determined from the required amount Rt (i-1) and the credit Ct (i-1).

  (1) When the required amount Rt (i−1) is “0”, the satisfaction level A (i) is set to the maximum “1” regardless of the credit Ct (i−1).

(2) When the required amount Rt (i−1) is equal to or less than the threshold value W,
When the credit Ct (i−1) is zero, the satisfaction level A (i) is the lowest “0”.
When the credit Ct (i−1) exceeds zero, the satisfaction level A (i) is either a value obtained by dividing the credit Ct (i−1) by the requested amount Rt (i−1) or “1”. Small value. In other words, the credit Ct (i−1) is divided by the required amount Rt (i−1) with the maximum value “1” as a limit.

(3) When the request amount Rt (i-1) exceeds the threshold value W,
When the credit Ct (i−1) is zero, the satisfaction level A (i) is the lowest “0”.
When the credit Ct (i−1) exceeds zero, the satisfaction level A (i) is set to a value that is smaller of the value obtained by dividing the credit Ct (i−1) by the threshold W and “1”. The In other words, the credit Ct (i−1) is divided by the threshold value W with the maximum value “1” as a limit.

  The satisfaction level is determined for each congestion cycle using the satisfaction level determination table shown in FIG. The determined satisfaction level is stored in a satisfaction level storage table. When the congestion cycle continues, the satisfaction level is an average value. Furthermore, when the congestion cycle ends, the satisfaction levels stored in the satisfaction level storage table are all reset to the maximum “1”.

  FIG. 8 is a flowchart for explaining the processing procedure of the control frame processing unit 23 of the ONU. First, the control frame processing unit 23 receives a grant frame from the OLT 1 received by the receiving unit 21 in cycle #i (step S21). The grant frame received by ONU (t) in cycle # 1 includes a credit Ct (i + 1) for allocating the band of cycle # i + 1 and a grant amount Gt (i) indicating the band allocated for cycle #i. It is.

  The ONU (t) updates the contents of the data length storage table by the permitted amount Gt (i) and reads the credit Ci (t + 1) included in the grant frame (step S22).

  The buffer memory 25 is provided with a data length storage table. When the data frame is transferred from the receiving unit 24 to the buffer memory 25, the length of the data frame is detected by the counter 27, and the data frame is sequentially displayed from the top in an area where the data length of the data length storage table is not recorded. The data length of is written.

  When receiving the grant frame, the control frame processing unit 23 deletes the data length corresponding to the data of the permitted amount Gt (i) from the data length storage table, and transmits the corresponding data frame to the buffer memory 25. Instruct.

  Further, when creating the report frame, the control frame processing unit 23 reads the data length of the data frame. That is, the total value of the data length corresponding to the maximum amount of data that can be transmitted in units of frames from the first data frame that is less than or equal to the credit Ct (i + 1) included in the grant frame is the transmission amount St (i + 1). )

  In cycle #i, the permitted amount Gt (i) transmitted from the OLT 1 is the transmission amount St (i−1) itself transmitted by the ONU (t) in cycle # i−1. Therefore, the permitted amount Gt (i) has a data length corresponding to the maximum amount of data that can be transmitted in frame units. For this reason, the bandwidth allocated to the ONU (t) with the permitted amount Gt (i) is the maximum amount of data that can be transmitted in units of frames, so that data can be transmitted using the allocated bandwidth as much as possible. It becomes possible.

  Next, the control frame processing unit 23 refers to the credit Ct (i + 1) included in the grant frame received from the OLT, and transmits it in frame units from the first data frame that is equal to or less than the credit Ct (i + 1). The maximum possible data amount is calculated, and the value is set as the transmission amount St (i + 1) (step S23).

  Next, the control frame processing unit 23 sends a transmission source address (address of the ONU (t)), a transmission destination address (address of OLT 1), a request amount Rt (i + 2) for allocating a bandwidth of cycle # i + 2, and cycle #. A report frame constituted by the transmission amount S (i + 1) for allocating the band of i + 1 is created and transferred to the buffer memory 25 (step S24).

  The request amount Rt (i + 2) is a value obtained by subtracting the permission amount Gt (i) and the transmission amount St (i + 1) from the data amount of the data stored in the buffer memory 25.

  Finally, the control frame processing unit 23 instructs the buffer memory 25 and the transmission unit 26 to transmit the report frame and the data frame for the permitted amount Gt (i) at the transmission start time included in the grant frame (step S25). .

<First Modification of Credit Determination Process>
FIG. 9 is a flowchart showing the flow of another credit determination process executed in step S14 of FIG. In a modification of the credit determination process, an upper limit value Wmax is provided for the credit to be given. For this reason, step S29A and step S29B are added after step S29 of the credit determination process shown in FIG. 6, and step S27 is changed. The different points are mainly described below.

  In step S21, it is determined whether or not cycle # i + 2 is a congestion cycle. If it is determined that the cycle is not a congestion cycle, the process proceeds to step S29. In step S29, the satisfaction degree storage table is reset, and the process proceeds to step S29A.

  In step S29A, it is determined whether or not the required amount Rt (i + 2) exceeds the threshold value Wmax [bit]. If so, the process proceeds to step S29B. If not, the process proceeds to step S30. The threshold value Wmax may be a predetermined value.

  In step S29B, a threshold value Wmax as an upper limit value is assigned to the credit Ct (i + 2). Thereafter, the process ends. On the other hand, in step S30, the requested amount Rt (i + 2) is allocated as it is to the credit Ct (i + 2). Thereafter, the process ends. By limiting the credit to be given with the threshold value Wmax serving as the upper limit value, it is possible to prevent a wide band from being allocated to a specific ONU.

  In step S27A, the credit Cs (i + 2) corresponding to the extracted ONU (S) is updated to a value obtained by adding the additional value B (i + 2) to the threshold value W. Here, the additional value B (i + 2) is obtained from the value obtained by subtracting the threshold value W from the requested amount Rs (i + 2) of the ONU (S), the remaining bandwidth T (i + 2), and the threshold value Wmax serving as the upper limit value. The threshold value W is set to a value within a range equal to or lower than the value obtained by subtracting the threshold value W.

0 ≦ B (i + 2) ≦ min (Rs (i + 2) −W, T (i + 2), Wmax−W) (3)
<Second Modification of Credit Determination Process>
In the credit determination process in the second modification, a threshold value W and an upper threshold value Wmax are set for each ONU (t). Here, a description will be given assuming that a threshold value W (t) and an upper limit threshold value Wmax (t) are set for the t-th ONU (t).

  FIG. 10 is a flowchart showing the flow of still another credit determination process executed in step S14 of FIG. Here, a case where a report frame is received from ONU (t) in cycle #i in step S11 of FIG. 4 will be described. In this case, the report frame includes a request amount Rt (i + 2) that ONU (t) desires to transmit in cycle # i + 2 and a transmission amount St (i + 1) indicating the amount of data that ONU (t) transmits in cycle # i + 1. And was included. Therefore, in the credit determination process, the credit Ct (i + 2) for allocating the band of cycle # i + 2 is determined.

  Referring to FIG. 10, it is first determined whether or not cycle # i + 2 is a congestion cycle (step S21). If it is determined that the cycle is a congestion cycle, the process proceeds to step S22 '; otherwise, the process proceeds to step S29 if it is determined that the cycle is a non-congestion cycle.

  In step S29, the satisfaction degree storage table is reset, and the process proceeds to step S29A '. In step S29A ', it is determined whether or not the required amount Rt (i + 2) exceeds the threshold value Wmax (t) [bit]. If so, the process proceeds to step S29B '. If not, the process proceeds to step S30. This threshold value Wmax (t) may be a predetermined value.

  In step S29B ', a threshold value Wmax (t) serving as an upper limit value is assigned to the credit Ct (i + 2). Thereafter, the process ends. On the other hand, in step S30, the requested amount Rt (i + 2) is allocated as it is to the credit Ct (i + 2). Thereafter, the process ends. By restricting the credit to be given with the threshold value Wmax (t) serving as the upper limit value, it is possible to prevent a wide band from being allocated to a specific ONU.

  On the other hand, in step S22 ', it is determined whether or not the required amount Rt (i + 2) exceeds the threshold value W (t) [bit]. If so, the process proceeds to step S23 '. If not, the process proceeds to step S24. The threshold value W (t) may be a predetermined value.

  In step S23 ', a threshold value W (t) is assigned to credit Ct (i + 2), and the process proceeds to step S25. On the other hand, in step S24, the requested amount Rt (i + 2) is directly assigned to the credit Ct (i + 2), and the process proceeds to step S25.

  In step S25, it is determined whether there is a remaining bandwidth T (i + 2). The remaining bandwidth T (i + 2) is a value obtained by subtracting the total communication time of the previously assigned credit Ct (i + 2) from the period of cycle # i + 2. If the remaining bandwidth T (i + 2) exceeds zero, the process proceeds to step S26, and if not, the process proceeds to step S31.

  In step S26, referring to the satisfaction level storage table, the lowest satisfaction level is extracted from ONU (t) in which the requested amount Rt (i + 2) exceeds the threshold value W (t) in step S22. The When there are a plurality of such ONUs, any one ONU may be determined as appropriate. Let the extracted ONU be ONU (S).

  In the next step S27A ', the credit Cs (i + 2) corresponding to the extracted ONU (S) is updated to a value obtained by adding the additional value B (i + 2) to the threshold value W (s). Here, the additional value B (i + 2) is a threshold value obtained by subtracting the threshold value W (s) from the requested amount Rs (i + 2) of the ONU (S), the remaining bandwidth T (i + 2), and an upper limit value. It is set to a value within a range equal to or lower than a value obtained by subtracting the threshold value W (s) from the value Wmax (s).

0 ≦ B (i + 2) ≦ min (Rs (i + 2) −W (s), T (i + 2), Wmax (s) −W (s)) (4)
In the next step S28, the remaining bandwidth is updated. Since the additional value B (i + 2) is added to the credit Cs (i + 2), the remaining bandwidth T (i + 2) is subtracted by the additional value B (i + 2).

  Thereafter, the process returns to step S25, and the processes of steps S26 to S28 are repeated until the remaining bandwidth T no longer exists. Thereby, the ONU having the next lowest satisfaction is extracted, and the additional value B (i + 2) is added to the corresponding credit Cs (i + 2).

  When there is no remaining bandwidth T in step S25, the process proceeds to step S31, where the satisfaction levels of all ONUs (t) are calculated, and the satisfaction level storage table is updated. Thereafter, the process ends.

  As described above, according to the OLT 1 in the present embodiment, the credit assigned to the congestion cycle is added to the ONU (t) with a low satisfaction level by adding the additional value B (t) to other ONU (t). Therefore, the bandwidth can be effectively allocated while maintaining the fairness of a plurality of ONUs.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows schematic structure of OLT in one of the embodiments of this invention. It is a block diagram which shows schematic structure of ONU in this Embodiment. It is a figure which shows an example of the communication procedure between OLT and ONU in this Embodiment. It is a flowchart for demonstrating the process sequence of the control frame process part of OLT. It is a figure which shows an example of the storage table provided in the control frame process part. It is a flowchart which shows the flow of the credit determination process performed by FIG.4 S14. It is a figure which shows an example of the satisfaction determination table used in order to determine a satisfaction. It is a flowchart for demonstrating the process sequence of the control frame process part of ONU. It is a flowchart which shows the flow of another credit determination process performed by step S14 of FIG. It is a flowchart which shows the flow of another credit determination process performed by FIG.4 S14. It is a block diagram which shows schematic structure of the conventional PON system. It is a sequence diagram for demonstrating the operation | movement procedure of the conventional PON system. It is a figure which shows an example of a distributed allocation system. It is a figure for demonstrating the problem in 1st prior art.

Explanation of symbols

  1 OLT, 2 ONU, 11, 14, 21, 24 Receiver, 12, 16, 22, 26 Transmitter, 13, 23 Control frame processor, 15, 25 Buffer memory, 27 Counter, 104 Transmission path, 105 Splitter, 108 Information frame, 109 Upper network, 110 Lower network, 111 User terminal.

Claims (11)

An optical subscriber line terminal device connectable with an optical subscriber line termination device,
First receiving means for receiving, from the optical subscriber line termination device, a transmission request amount indicating an amount of stored data accumulated for transmission in the optical subscriber line termination device;
Determining means for determining a maximum permitted amount of transmission based on the requested amount of transmission;
First transmission means for transmitting the determined maximum transmission permission amount to the optical subscriber line terminating device;
Second reception for receiving, from the optical subscriber line termination device, a scheduled transmission amount that is the maximum amount of data that can be transmitted in units of frames within the maximum transmission permission amount of the accumulated data stored in the optical subscriber line termination device. Means,
Second transmission means for transmitting the grant for allowing transmission of data to the optical subscriber line terminating device, including the scheduled transmission amount as a permitted transmission amount;
The determining means includes satisfaction calculation means for calculating satisfaction for each optical subscriber line terminating device,
An optical subscriber line terminal apparatus that determines the maximum transmission permission amount to be a large value in the order of low satisfaction when in a congestion cycle.   The optical subscriber line terminal station apparatus according to claim 1, wherein the satisfaction degree calculation means determines a satisfaction degree from the transmission request amount and the maximum transmission permission amount.   3. The optical subscriber line terminal apparatus according to claim 2, wherein the satisfaction level calculation unit sets the satisfaction level to a higher value when the requested amount of transmission is zero than when it is other than zero.   3. The optical subscriber line terminal apparatus according to claim 2, wherein the satisfaction level calculation unit sets the satisfaction level to a lower value as the transmission request amount is larger and the maximum transmission permission amount is smaller.   2. The optical subscriber line terminal apparatus according to claim 1, wherein the satisfaction degree calculation means takes a value obtained by averaging the satisfaction degrees while a congestion cycle continues.   In the congestion cycle, the determining means sets the maximum transmission permission amount as the transmission request amount when the transmission request amount is equal to or less than a predetermined value, and sets the maximum when the transmission request amount exceeds a predetermined value. 2. The optical subscription according to claim 1, wherein a transmission permission amount is first set to the predetermined value, and then an additional value is added to the predetermined value in order from the optical subscriber line terminating device having a low satisfaction level. Line terminal equipment.   The determination means determines the maximum value of the additional value from a value obtained by subtracting the predetermined value from the transmission request amount, a congestion band period, and a remaining bandwidth value determined from a maximum transmission permission amount before adding the additional value. 7. The optical subscriber line terminal station apparatus according to claim 6, wherein the optical subscriber line terminal station apparatus is selected from the following.   The determining means makes the maximum transmission permission amount and the predetermined value variable for each optical subscriber line terminating device, and sets the maximum additional value to a value obtained by subtracting the predetermined value from the transmission request amount. And selecting a remaining bandwidth value determined from a congestion cycle period and a maximum transmission permission amount before adding an additional value, and a value obtained by subtracting the predetermined value from the maximum transmission permission amount. Optical subscriber line terminal equipment.   2. The optical subscriber line terminal apparatus according to claim 1, wherein the determination unit sets the maximum transmission permission amount as the transmission request amount when in a non-congestion cycle.   The optical subscriber line terminal station apparatus according to claim 9, wherein the determining means sets the upper limit value of the maximum transmission permission amount to a second predetermined value. A bandwidth allocation program executed by an optical subscriber line terminal device connectable to an optical subscriber line termination device,
Receiving from the optical subscriber line termination device a transmission request amount indicating an amount of stored data accumulated for transmission in the optical subscriber line termination device;
Determining a maximum permitted transmission amount based on the requested transmission amount;
Transmitting the determined maximum transmission permission amount to the optical subscriber line terminating device;
Receiving from the optical subscriber line termination device a scheduled transmission amount that is the maximum amount of data that can be transmitted in units of frames within the maximum transmission permission amount of the accumulated data stored in the optical subscriber line termination device; ,
Sending the grant to allow transmission of data to the optical subscriber line terminating device, including the scheduled transmission amount as a permitted transmission amount,
The determining step includes calculating satisfaction for each optical subscriber line terminating device; and
And a step of determining the maximum transmission permission amount to a larger value in the order from the lowest satisfaction level during the congestion cycle.

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