JP7557159B2 - Bandwidth allocation device, subscriber line terminal device, and bandwidth allocation method - Google Patents

Description

The present invention relates to a bandwidth allocation device, a subscriber line terminal device, and a bandwidth allocation method.

In response to the growing need for faster access services, FTTH (Fiber To The Home) is becoming more widespread worldwide. In Japan, the main FTTH services include GE-PON (Gigabit Ethernet PON), which achieves gigabit-class transmission speeds, and 10G-EPON (10 Gigabit Ethernet PON).

In GE-PON and 10G-EPON, TDMA (Time Division Multiple Access) technology is used for upstream communications from the ONU to the OLT. In addition, one of the functions required for GE-PON and 10G-EPON to operate as a system is the DBA (Dynamic Bandwidth Allocation) function. The DBA function is a bandwidth control function that dynamically allocates bandwidth for upstream communications according to the amount of traffic. The DBA function realizes efficient upstream bandwidth without generating unused bandwidth by appropriately switching the allocated bandwidth according to the status of the upstream traffic flowing to each ONU.

JP 2003-087283 A

In the DBA function, the OLT uses a GATE frame to indicate the start time and amount of upstream data transmission so that each ONU can transmit upstream data without time collisions. Meanwhile, each ONU uses a REPORT frame to inform the OLT of the amount of upstream data waiting to be transmitted that is stored in its own ONU's buffer. The DBA function is realized through this exchange using GATE and REPORT frames.

In upstream communication, if the interval between the end of data transmission and the start time of the REPORT frame transmission is short, the ONU must calculate the amount of data to be written in the REPORT frame while transmitting data from the transmission reservation queue, which keeps the upstream data permitted to be transmitted waiting until the transmission start time. However, there may be ONUs that do not have a transmission reservation queue. An ONU that does not have a transmission reservation queue will calculate, in the normal queue, the amount of data reserved for transmission permitted to be transmitted by the OLT, and the remaining amount of data (i.e., the amount of upstream data waiting for a transmission request) after subtracting the amount of data reserved for transmission from the accumulated data amount.

However, in an ONU that does not have a transmission reservation queue, data transmission and the above two calculations (i.e., calculation of the amount of data reserved for transmission and calculation of the amount of data waiting to be transmitted) must be processed sequentially, which takes time to complete the calculations and may result in the calculations not being completed in time for the start time of the REPORT frame transmission. In this case, since the ONU does not transmit a REPORT frame, the OLT cannot grant permission to transmit upstream data. This creates the problem that the ONU may not be able to transmit upstream data.

In view of the above circumstances, the present invention aims to provide a bandwidth allocation device, a subscriber line terminal device, and a bandwidth allocation method that enable upstream data transmission in a PON system even if the system includes an ONU that does not have a transmission reservation queue.

One aspect of the present invention is a bandwidth allocation device that includes a detection unit that detects that a subscriber line termination device that does not have a transmission reservation queue for waiting upstream data permitted to be transmitted until a transmission start time has been connected to a passive optical network, and a setting unit that provides a calculation time during an operation period of upstream bandwidth control between the subscriber line termination device and a subscriber line terminal device, which is the time required for the subscriber line termination device to calculate the amount of upstream data to be transmitted out of the amount of upstream data permitted to be transmitted and to calculate the amount of upstream data to be requested to be transmitted.

One aspect of the present invention is a bandwidth allocation device that includes an acquisition unit that acquires identification information that identifies a subscriber line terminal connected to a passive optical network, a determination unit that determines, based on the identification information, whether the subscriber line terminal has a transmission reservation queue that keeps upstream data that has been permitted to be transmitted waiting until a transmission start time, and a setting change unit that, if it is determined that the subscriber line terminal does not have the transmission reservation queue, provides a predetermined calculation time between operating periods of upstream bandwidth control in the passive optical network.

One aspect of the present invention is a subscriber line termination device that includes a detection unit that detects that a subscriber line termination device that does not have a transmission reservation queue for waiting upstream data permitted to be transmitted until a transmission start time has been connected to a passive optical network, a setting unit that provides a calculation time during an operation period of upstream bandwidth control between the subscriber line termination device and the device itself, which is the time required for the subscriber line termination device to calculate the amount of upstream data to be transmitted out of the amount of upstream data permitted to be transmitted and the amount of upstream data to be requested to be transmitted, and a transmitting/receiving unit that transmits and receives data to and from the subscriber line termination device.

One aspect of the present invention is a subscriber line terminal device comprising: an acquisition unit that acquires identification information that identifies a subscriber line terminal device connected to a passive optical network; a determination unit that determines, based on the identification information, whether or not the subscriber line terminal device has a transmission reservation queue that keeps upstream data that has been permitted to be transmitted waiting until a transmission start time; a setting change unit that, if it is determined that the subscriber line terminal device does not have the transmission reservation queue, provides a predetermined calculation time between operating periods of upstream bandwidth control in the passive optical network; and a transmission/reception unit that transmits and receives data to and from the subscriber line terminal device.

One aspect of the present invention is a bandwidth allocation method having a detection step of detecting that a subscriber line termination device that does not have a transmission reservation queue for waiting upstream data permitted to be transmitted until a transmission start time has been connected to a passive optical network, and a setting step of setting a calculation time, which is the time required for the subscriber line termination device to calculate the amount of upstream data to be transmitted out of the amount of upstream data permitted to be transmitted and the amount of upstream data to be requested to be transmitted, during an operation period of upstream bandwidth control between the subscriber line termination device and a subscriber line terminal device.

One aspect of the present invention is a bandwidth allocation method having an acquisition step of acquiring identification information that identifies a subscriber line terminal connected to a passive optical network, a determination step of determining, based on the identification information, whether the subscriber line terminal has a transmission reservation queue that keeps upstream data that has been permitted to be transmitted waiting until a transmission start time, and a setting change step of providing a predetermined calculation time between operating periods of upstream bandwidth control in the passive optical network if it is determined that the subscriber line terminal does not have the transmission reservation queue.

The present invention makes it possible to transmit upstream data in a PON system even if the system includes ONUs that do not have a transmission reservation queue, thereby improving bandwidth utilization efficiency.

FIG. 1 is a block diagram showing the configuration of a typical PON. 11 is a diagram showing the flow of upstream data transmission when there is only one ONU 20. FIG. FIG. 13 is a diagram showing the flow of upstream data transmission when there are two ONUs 20. 11 is a schematic diagram for explaining a change in the amount of accumulated upstream data. FIG. FIG. 2 is a schematic diagram showing an example of the configuration of a granted queue. 2 is a diagram showing a flow of upstream data transmission by PON1 in an embodiment of the present invention. FIG. 1 is a diagram showing a flow of upstream data transmission by a conventional PON. 2 is a block diagram showing a functional configuration of an OLT 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of a pre-REPORT GAP database 105. 4 is a flowchart showing an operation of the OLT 1 in the embodiment of the present invention.

Below, an embodiment of the present invention is described in detail with reference to the drawings.

PON (Passive Optical Network) is an optical access system that provides fast and inexpensive FTTH services. PON does not perform optical-electrical conversion, but instead splits optical signals into multiple signals using an optical splitter, a low-cost passive element. This allows multiple users to share a single optical fiber, making it possible to realize an economical network. The main FTTH services in Japan include GE-PON, which achieves gigabit-class transmission speeds, and 10G-EPON, which has 10 times the bandwidth of GE-PON.

Figure 1 is a block diagram showing the configuration of a typical PON. As shown in Figure 1, PON 1 is composed of an OLT (Optical Line Terminal) 10, a plurality of ONUs (Optical Network Units) 20 (n units in Figure 1), an optical fiber 30, and an optical splitter 40.

The OLT 10 is installed in a telecommunications carrier's office, and the ONUs 20 are installed in a user's home or premises. The optical fiber 30 is laid between the telecommunications carrier's office and the user's home or premises, and the optical splitter 40 branches the optical fiber 30. By installing the optical splitter 40 between the OLT 10 and the ONUs 20, which multiplexes and splits optical signals, multiple ONUs 20 are connected to one OLT 10.

ONU 20 is responsible for converting optical signals from OLT 10 into electrical signals, and converting electrical signals from a user's terminal device (e.g., a PC, etc.) into optical signals and forwarding them to OLT 10. OLT 10 is responsible for forwarding optical signals from ONU 20 to a higher-level device/network (e.g., the Internet, etc.), forwarding signals from the higher-level device/network to ONU 20, and controlling and monitoring the PON section and ONU 20.

In PON1, TDM (Time Division Multiplexing) technology is used for communication from OLT 10 to ONU 20 (hereinafter referred to as "downstream communication"). TDM is a technology that multiplexes and transmits signals from multiple users without overlapping in time.

In downstream communication, the same signal (hereinafter referred to as the "downstream signal") is split by the optical splitter 40 and forwarded to all ONUs 20 connected to the same OLT 10. Therefore, data other than data addressed to the ONU 20 itself is also forwarded to each ONU 20. Therefore, each ONU 20 extracts only the data addressed to itself from the forwarded data, and discards the other data (addressed to other ONUs 20).

In addition, in PON1, TDMA technology is used for communication from ONU 20 to OLT 10 (hereinafter referred to as "upstream communication"). In upstream communication, signals from multiple ONUs 20 (hereinafter referred to as "upstream signals") are multiplexed by optical splitter 40. Therefore, if the upstream signals from each ONU 20 are transmitted in a disorderly manner, there is a possibility that collisions will occur on the transmission path. Therefore, TDMA controls the transmission timing of the upstream signals from ONU 20 and the transmission amount of upstream data so that the upstream signals from each ONU 20 are multiplexed without colliding on the transmission path.

The DBA function is one of the functions required for GE-PON and 10G-EPON to operate as a system. The DBA function is a bandwidth control function that dynamically allocates the bandwidth for upstream communication (hereinafter referred to as "upstream bandwidth") according to the amount of traffic. The DBA function can flexibly allocate the upstream bandwidth according to the upstream communication traffic (hereinafter referred to as "upstream traffic") from each ONU 20. The DBA function allocates the upstream bandwidth only to ONUs 20 through which upstream traffic is flowing, so the upstream bandwidth can be used without waste. The DBA function realizes efficient upstream bandwidth without generating unused bandwidth by appropriately switching the allocated bandwidth according to the status of the upstream traffic flowing through each ONU 20.

GE-PON and 10G-EPON use a protocol called MPCP (Multi Point Control Protocol) to control upstream signals. The OLT 10 uses a GATE frame to instruct each ONU 20 on the start time and amount of transmission so that each ONU 20 can transmit upstream signals without time collisions.

Meanwhile, each ONU 20 communicates the amount of upstream data awaiting transmission stored in the buffer of its own ONU 20 to the OLT 10 by a REPORT frame. The DBA function is realized by using this GATE frame and REPORT frame.

Below is a brief explanation of how the DBA function works. When ONU 20 receives upstream data, it first stores the upstream data in a buffer. ONU 20 writes the amount of stored upstream data in a REPORT frame and transmits the REPORT frame to OLT 10.

OLT 10 determines the amount of upstream data stored in ONU 20 from the received REPORT frame. OLT 10 calculates the upstream bandwidth to be allocated to ONU 20 based on the amount of stored data in that ONU 20 and the bandwidth used by other ONUs 20. Specifically, OLT 10 calculates the transmission start time and transmission amount of upstream data for ONU 20. OLT 10 writes the calculated values in a GATE frame and transmits the GATE frame to ONU 20.

ONU 20 transmits the upstream data at the specified transmission time according to the instructions written in the received GATE frame. At this time, ONU 20 may notify the amount of upstream data stored in the buffer again for the next allocation of upstream bandwidth.

By repeating the above procedure, the OLT 10 can know the upstream traffic situation in each ONU 20 and can appropriately allocate upstream bandwidth according to the situation.

In such upstream communication, if the interval between the transmission of the upstream data and the start time of transmitting the REPORT frame is short, it is desirable for ONU 20 to have a transmission reservation queue (hereinafter referred to as a "granted queue"), because in this case, ONU 20 can calculate the amount of data to be written in the REPORT frame (hereinafter referred to as "REPORT calculation") in parallel while transmitting data from the granted queue.

However, there may be ONUs 20 that do not have a granted queue. For example, PON1 may accommodate a mixture of ONUs 20 that have a granted queue and ONUs 20 that do not have a granted queue.

An ONU 20 that does not have a granted queue will calculate the amount of upstream data reserved for transmission (granted) based on the DATA grant of the GATE frame sent from OLT 10 in a normal queue (e.g., a priority queue), and calculate (REPORT calculation) the amount of upstream data remaining after subtracting the amount of upstream data reserved for transmission (granted) (i.e., the amount of upstream data waiting for a transmission request). Data grant indicates the amount of upstream data permitted to be transmitted by OLT 10.

However, in an ONU 20 that does not have a granted queue, it takes time to complete the above REPORT calculations, etc., due to sequential processing, and there is a possibility that the REPORT calculations will not be completed in time for the REPORT frame transmission start time. Sequential processing here means sequential processing of data transmission, calculation of the amount of data reserved for transmission, and calculation of the amount of data waiting to be transmitted. In this case, ONU 20 cannot communicate the amount of upstream data accumulated to OLT 10. As a result, OLT 10 cannot grant ONU 20 permission to transmit upstream data, and ONU 20 may not be able to transmit upstream data.

In the present embodiment, which will be described below, OLT 10 provides a gap (hereinafter referred to as "pre-REPORT GAP") between the operation cycles of the upstream bandwidth control to ensure that ONU 20 has time to calculate the transmission reservation of the DATA grant and the amount of upstream data waiting to be transmitted. This allows OLT 10 in this embodiment to complete these calculations in time for the start of transmission of the REPORT frame.

By providing a pre-REPORT GAP in this way, even an ONU 20 that does not have a granted queue can complete REPORT calculations and the like in time for the transmission timing of the REPORT frame. This enables upstream communication. Furthermore, according to the OLT 10 in this embodiment, upstream communication is possible even if there is a mixture of ONUs 20 with granted queues and ONUs 20 without granted queues.

The flow of transmitting upstream data will be explained below. To make the explanation easier to understand, we will first explain the case where there is only one ONU 20. Figure 2 is a diagram showing the flow of transmitting upstream data when there is only one ONU 20.

The OLT 10 transmits a GATE frame g1, for example as shown in Figure 2, to the ONU 20. The GATE frame g1 includes a Report block and a Data block.

2, for example, the Report block of the GATE frame g1 describes "Grant length: ▲ ₁ TQ". This means that the OLT 10 instructs the ONU 20 to allow ▲ ₁ TQ of transmission time for the REPORT frame. The ONU 20 transmits the REPORT frame to the OLT 10 during the allowed transmission time ▲ ₁ TQ in accordance with the instruction written in the GATE frame g1.

2, for example, the Data block of the GATE frame g1 describes "Grant length: 0 ₁ TQ". This means that the OLT 10 instructs the ONU 20 to transmit 0 ₁ TQ of DATA (upstream data). The ONU 20 transmits DATA (upstream data) to the OLT 10 during the transmission permission time of 0 ₁ TQ in accordance with the instruction written in the GATE frame g1.

Next, as shown in Figure 2, for example, while DATA (upstream data) is being transmitted from ONU 20 to OLT 10 based on instructions from GATE frame g1, OLT 10 transmits GATE frame g2 to ONU 20. GATE frame g2 also includes a Report block and a Data block.

2, for example, the Report block of the GATE frame g2 describes "Grant length: ▲ ₂ TQ". This means that the OLT 10 instructs the ONU 20 to allow ▲ ₂ TQ of transmission time for the REPORT frame. The ONU 20 transmits the REPORT frame to the OLT 10 during the allowed transmission time ▲ ₂ TQ in accordance with the instruction written in the GATE frame g2.

2, for example, the Data block of the GATE frame g2 describes "Grant length: 0 ₂ TQ". This means that the OLT 10 instructs the ONU 20 to transmit 0 ₂ TQ of DATA (upstream data). The ONU 20 transmits DATA (upstream data) to the OLT 10 during the transmission permission time of 0 ₂ TQ in accordance with the instruction written in the GATE frame g2.

Next, the flow of upstream data transmission when there are two ONUs 20 will be explained. Figure 3 is a diagram showing the flow of upstream data transmission when there are two ONUs 20. Note that the flow of upstream data transmission when there are three or more ONUs 20 is basically the same as the flow of upstream data transmission shown in Figure 3.

As shown in Figure 3, it is assumed here that two ONUs 20 ("ONU #1" and "ONU #2") are connected to the OLT 10. The OLT 10 receives a transmission request message (REPORT frame) sent from ONU #1 and a transmission request message (REPORT frame) sent from ONU #2 together ((1) in Figure 3).

In response to receiving a transmission request message (REPORT frame) from ONU #1 and ONU #2, respectively, OLT 10 transmits a transmission authorization message (GATE frame) to ONU #1 and ONU #2 together ((2) in Figure 3).

Specifically, OLT 10 determines the amount of upstream data stored in ONU #1 from a transmission request message (REPORT frame) received from ONU #1. Based on the determined amount of data, OLT 10 determines the transmission start time and transmission amount of the upstream data to be transmitted by ONU #1 in the next operating cycle. OLT 10 writes the determined transmission start time and transmission amount of the upstream data in ONU #1 in a transmission permission message (GATE frame).

In addition, OLT 10 determines the amount of upstream data stored in ONU #2 from a transmission request message (REPORT frame) received from ONU #2. Based on the determined amount of data, OLT 10 determines the transmission start time and transmission amount of the upstream data to be transmitted by ONU #2 in the next operating cycle. OLT 10 writes the determined transmission start time and transmission amount of the upstream data in ONU #2 in a transmission permission message (GATE frame).

As shown in Figure 3, OLT 10 transmits the above-generated permission to send messages (GATE frames) to ONU #1 and ONU #2 in bulk. ONU #1 and ONU #2 each receive the permission to send messages (GATE frames) transmitted from OLT 10.

From the contents described in the transmission permission message (GATE frame), ONU #1 and ONU #2 recognize the transmission start time and transmission amount of the upstream data specified for their own ONU 20. ONU #1 and ONU #2 each transmit the upstream data of the transmission amount specified by the transmission permission message (GATE frame) to OLT 10 at the transmission start time of the upstream data specified by the transmission permission message (GATE frame) ((3) in FIG. 3).

Below, we will explain the change in the amount of upstream data stored in the queue of ONU 20. Figure 4 is a schematic diagram for explaining the change in the amount of stored upstream data.

As shown in FIG. 4, which will be described below, ONU 20 may not have a granted queue (transmission reservation queue). FIG. 5 is a schematic diagram showing an example of the configuration of a granted queue. As shown in FIG. 5, for example, upstream data stored in queue #p and upstream data stored in queue #q are sequentially transferred to the granted queue (transmission reservation queue) under appropriate control by the scheduler.

If ONU 20 does not have a granted queue (transmission reservation queue), ONU 20 cannot simultaneously process the transmission of the granted DATA and the above two calculations (i.e., the data grant transmission reservation calculation and the REPORT calculation), so it performs the calculations sequentially. As a result, there is a possibility that the REPORT calculation will not be completed in time for the start of transmission of the transmission request message (REPORT frame) specified by the REPORT grant in the transmission authorization message (GATE frame).

If the REPORT calculation is not completed in time for the start time of the transmission of the transmission request message (REPORT frame), the transmission request message (REPORT frame) will not be transmitted from ONU 20 to OLT 10, and therefore no data grant will be assigned in the next transmission authorization message (GATE frame) transmitted from OLT 10 to ONU 20. This may result in ONU 20 being unable to transmit upstream data.

Figure 4 shows the amount of upstream data stored in the queue of ONU 20 at six points in time from time (a) to time (f). As shown in Figure 4, it is assumed here that ONU 20 has two queues ("queue #p" and "queue #q"). Here, queue #p is a queue in which high-priority upstream data is stored, and queue #q is a queue in which low-priority upstream data is stored.

First, in the column for time point (a), queue #p shows the amount of upstream data for which a transmission request has been reported (reported) and, of that, the amount of upstream data for which transmission has been reserved (granted). Similarly, queue #q shows the amount of upstream data for which a transmission request has been reported (reported) and, of that, the amount of upstream data for which transmission has been reserved (granted).

The upstream data volume for which a transmission request has already been reported (reported) here refers to the amount of upstream data that has already been reported by ONU 20 to OLT 10 via a transmission request message (REPORT frame). Also, the upstream data volume for which a transmission reservation has already been made (granted) here refers to the amount of upstream data that has been granted transmission permission by a transmission permission message (GATE frame) sent from OLT 10 to ONU 20 in response to the above-mentioned transmission request message (REPORT frame).

ONU 20 transmits the upstream data (granted DATA) of the amount of data reserved for transmission to OLT 10 at the transmission timing specified by the received transmission permission message (GATE frame). After that, the amount of upstream data stored in queue #p and queue #q changes from the state at time (a) shown in Figure 4 to the state at time (b).

Next, in the column for time point (b), queue #p shows the amount of upstream data for which a transmission request has been reported (reported) and the amount of upstream data for which a transmission request has not yet been requested (i.e., the amount of newly added upstream data). Queue #q also shows the amount of upstream data for which a transmission request has been reported (reported) and the amount of upstream data for which a transmission request has not yet been requested (i.e., the amount of newly added upstream data).

The amount of upstream data that has not yet been requested for transmission here refers to the amount of newly generated upstream data since the last REPORT calculation was performed.

As shown in the column for time (b) in Figure 4, the amount of upstream data (granted) that was reserved for transmission at time (a) has been removed from queue #p and queue #q as the transmission of the upstream data to OLT 10 has been completed.

ONU 20 calculates the amount of upstream data that can be transmitted in the relevant period in queue #p and queue #q (granted) from the amount of upstream data permitted for transmission (Data grant) written in the received transmission permission message (GATE frame), and sets it as reserved for transmission. The amount of upstream data stored in queue #p and queue #q changes from the state at time (b) shown in Figure 4 to the state at time (c).

Next, in the column for time point (c), queue #p shows the amount of upstream data that has been reserved for transmission (granted) and the amount of upstream data that has not yet been requested for transmission (i.e., the amount of newly added upstream data). Queue #q shows the amount of upstream data that has been reported for transmission (reported), and of that, the amount of upstream data that has been reserved for transmission (granted) and the amount of upstream data that has not yet been requested for transmission (i.e., the amount of newly added upstream data).

In addition, the time (c) column shows that, based on the amount of data (Data grant) of uplink data permitted for transmission written in the transmission permission message (GATE frame), the entire amount of data (reported) of uplink data for which a transmission request has been reported, shown in the time (b) column, for queue #p has changed to the amount of data (granted) of uplink data for which a transmission request has been reported. On the other hand, it shows that a part of the amount of data (reported) of uplink data for which a transmission request has been reported, shown in the time (b) column, for queue #q has changed to the amount of data (granted) of uplink data for which a transmission request has been reported.

That is, the column for time point (c) shows that for queue #p, which is a high-priority queue, all of the upstream data for which a transmission request has been made has been reserved for transmission, but for queue #q, which is a low-priority queue, some of the upstream data for which a transmission request has been made has not been reserved for transmission. This shows that the total amount of data (reported) of the upstream data for which a transmission request has been reported included in queue #p and the amount of data (reported) of the upstream data for which a transmission request has been reported included in queue #q is greater than the amount of data (Data grant) of the upstream data for which transmission permission has been granted, as written in the transmission permission message (GATE frame).

When the amount of upstream data reserved for transmission (granted) is determined, ONU 20 calculates the amount of accumulated upstream data to be written in the next transmission request message (REPORT frame) (i.e., the amount of upstream data to be requested for transmission). The amount of upstream data accumulated in queue #p and queue #q changes from the state at time (c) shown in Figure 4 to the state at time (d).

Next, in the column for time point (d), queue #p shows the amount of upstream data that has been reserved for transmission (granted) and the amount of upstream data that should be requested for transmission (i.e., the amount of upstream data waiting for a transmission request). Queue #q also shows the amount of upstream data that has been reserved for transmission (granted) and the amount of upstream data that should be requested for transmission (i.e., the amount of upstream data waiting for a transmission request).

As shown in the column for time (d) in Figure 4, the amount of upstream data to be requested for transmission contained in queue #p (for report in Figure 4) is the amount of data equivalent to the amount of upstream data that has not been requested for transmission at time (c) (i.e., the amount of newly added upstream data).

On the other hand, the amount of upstream data to be requested for transmission contained in queue #q (for report in Figure 4) is the total amount of data equivalent to the amount of unrequested upstream data at time (c) (i.e., the amount of newly added upstream data) and the amount of newly added upstream data for which a transmission request has been reported (reported) excluding the amount of upstream data reserved for transmission (granted).

ONU 20 generates a transmission request message (REPORT frame) indicating the sum of the amount of upstream data to be requested to be transmitted (for report in Figure 4) contained in queue #p and queue #q calculated above. ONU 20 transmits the generated transmission request message (REPORT frame) to OLT 10. The amount of upstream data stored in queue #p and queue #q changes from the state at time (d) shown in Figure 4 to the state at time (e).

Next, in the column for time point (e), queue #p shows the amount of upstream data for which a transmission request has been reported (reported), and of that, the amount of upstream data for which transmission has been reserved (granted). Queue #q also shows the amount of upstream data for which a transmission request has been reported (reported), and of that, the amount of upstream data for which transmission has been reserved (granted).

In addition, the data amount obtained by subtracting the data amount of upstream data for which a transmission request has been reported (reported) contained in queue #p and queue #q shown in the column for time (e) in Figure 4 from the data amount of upstream data for which a transmission request has been reported (granted) corresponds to the data amount of upstream data to be requested to be transmitted contained in queue #p and queue #q shown in the column for time (d) (for report in Figure 4), and is the data amount of upstream data whose state has changed due to the transmission of a transmission request message (REPORT frame) from ONU 20 to OLT 10.

ONU 20 transmits the upstream data (granted DATA) of the amount of data reserved for transmission to OLT 10 at the transmission timing specified by the received transmission permission message (GATE frame). After that, the amount of upstream data stored in queue #p and queue #q changes from the state at time (e) to the state at time (f) shown in FIG. 4.

Next, in the column for time point (f), queue #p shows the amount of upstream data (reported) for which a transmission request has been reported. Queue #q also shows the amount of upstream data (reported) for which a transmission request has been reported.

As shown in the column for time (f) in Figure 4, the amount of upstream data (granted) that had been reserved for transmission at time (d) has been removed from queue #p and queue #q as the transmission of the upstream data to OLT 10 has been completed.

Using the above procedure, the upstream data accumulated in the queue of ONU 20 is sequentially transmitted to OLT 10.

As mentioned above, ONU 20 needs to calculate the amount of upstream data reserved for transmission (granted) contained in queue #p and queue #q and calculate the amount of upstream data to be requested to be transmitted (i.e., REPORT calculation) between receiving a transmission permission message (GATE frame) and sending a transmission request message (REPORT frame) (i.e., between time (b) and time (d) in Figure 4).

In this embodiment, the OLT 10 provides a time (pre-REPORT GAP) between the operation cycles of the upstream bandwidth control for performing data grant transmission reservation calculation and REPORT calculation. This allows even an ONU 20 that does not have a granted queue (transmission reservation queue) to complete REPORT calculation etc. before the transmission start time of the transmission request message (REPORT frame).

Note that the above configuration is a configuration in which the operating period is changed by providing a pre-REPORT GAP between the operating periods, but is not limited to this configuration. For example, if it is not desired to change the operating period, the configuration may be such that the time equivalent to the operating period - pre-REPORT GAP is changed to be the new operating period.

Figure 6 is a diagram showing the flow of upstream data transmission by PON1 in an embodiment of the present invention. Figure 6 shows the flow of upstream data transmission when there are two ONUs 20. Note that the flow of upstream data transmission when there are three or more ONUs 20 is basically the same as the flow of upstream data transmission shown in Figure 3.

As shown in Figure 6, it is assumed here that two ONUs 20 ("ONU #1" and "ONU #2") are connected to the OLT 10. The OLT 10 receives a transmission request message (REPORT frame) sent from ONU #1 and a transmission request message (REPORT frame) sent from ONU #2 together ((1) in Figure 6).

In response to receiving a transmission request message (REPORT frame) from ONU #1 and ONU #2, respectively, OLT 10 transmits a transmission authorization message (GATE frame) to ONU #1 and ONU #2 together ((2) in Figure 6).

Specifically, OLT 10 determines the amount of upstream data stored in ONU #1 from a transmission request message (REPORT frame) received from ONU #1. Based on the determined amount of data, OLT 10 determines the transmission start time and transmission amount of the upstream data to be transmitted by ONU #1 in the next operating cycle. OLT 10 writes the determined transmission start time and transmission amount of the upstream data in a transmission permission message (GATE frame).

In addition, OLT 10 determines the amount of upstream data stored in ONU #2 from a transmission request message (REPORT frame) received from ONU #2. Based on the determined amount of data, OLT 10 determines the transmission start time and transmission amount of the upstream data to be transmitted by ONU #2 in the next operating cycle. OLT 10 writes the determined transmission start time and transmission amount of the upstream data in a transmission permission message (GATE frame).

At this time, OLT 10 writes in the transmission permission message (GATE frame) the transmission start time that takes into account the pre-REPORT GAP shown in Figure 6. Specifically, OLT 10 writes in the transmission permission message (GATE frame) the transmission start time of the REPORT frame and the transmission start time of the upstream data, which are delayed by the pre-REPORT GAP.

As shown in Figure 6, OLT 10 transmits the above-generated permission to send messages (GATE frames) to ONU #1 and ONU #2 all at once. ONU #1 and ONU #2 each receive the permission to send messages (GATE frames) transmitted from OLT 10. ONU #1 and ONU #2 recognize the transmission start time and transmission amount value of the upstream data specified for their own ONU 20 from the contents described in the permission to send message (GATE frame).

ONU #1 and ONU #2 transmit a transmission permission message (REPORT frame) at the transmission start time specified by the transmission permission message (GATE frame). As described above, the transmission start time specified by the transmission permission message (GATE frame) takes into account the pre-REPORT GAP, so even ONU #1 and ONU #2 that do not have a granted queue can complete the data grant transmission reservation calculation and REPORT calculation before the transmission start time of the transmission request message (REPORT frame).

ONU #1 and ONU #2 each transmit the amount of upstream data specified in the transmission permission message (GATE frame) to OLT 10 at the start time of transmission of the upstream data specified in the transmission permission message (GATE frame) ((3) in Figure 6).

Figure 7 is a diagram showing the flow of upstream data transmission by a conventional PON. As shown in Figure 7, the pre-REPORT GAP is not taken into account in a conventional PON. Therefore, for example, in Figure 7, the time from when ONU #2 receives a transmission permission message (GATE frame) to when it starts transmitting a transmission request message (REPORT frame) is much shorter than in Figure 6 described above.

As a result, if ONU #2 does not have a granted queue (transmission reservation queue), the REPORT calculation will not be completed in time for the start time of the transmission of the transmission request message (REPORT frame) specified by the Report grant in the transmission permission message (GATE frame). The Report grant indicates the start time of the transmission of the transmission request message (REPORT frame) that has been granted permission to transmit by OLT 10. If the REPORT calculation is not completed in time for the start time of the transmission, ONU #2 will not be able to transmit upstream data to OLT 10 in the next operating cycle.

[OLT Configuration]
An example of the functional configuration of the OLT 10 will be described below. Fig. 8 is a block diagram showing the functional configuration of the OLT 10 in the embodiment of the present invention.

As shown in FIG. 8, the OLT 10 comprises a signal transmission/reception unit 101, a MAC (Media Access Control) processing unit 102, an OAM (Operations, Administration, Maintenance) processing unit 103, an ONU (Optical Network Unit) identification and determination unit 104, a pre-REPORT GAP database 105, a dynamic bandwidth allocation operation unit 106, an MPCP (Multi-Point Control Protocol) processing unit 107, and a signal transmission/reception unit 108.

The signal transmission/reception unit 101 transmits and receives signals between each ONU and its own OLT 10. The MAC processing unit 102 performs priority control and forwarding processing. The OAM processing unit 103 executes maintenance and operation management functions. The OAM processing unit 103 also acquires ONU information.

The ONU identification determination unit 104 determines whether a pre-REPORT GAP is required based on the ONU identifier indicated by the ONU information. If the ONU identification determination unit 104 determines that a pre-REPORT GAP is required, it obtains the pre-REPORT GAP value corresponding to the ONU identifier from the pre-REPORT GAP database 105 and outputs it to the dynamic bandwidth allocation operation unit 106.

Figure 9 is a diagram showing an example of the configuration of the pre-REPORT GAP database 105. As shown in Figure 9, for example, the pre-REPORT GAP database 105 is data in which an ONU identifier is associated with a pre-REPORT GAP value. For example, it shows that no pre-REPORT GAP is required for ONU 20 with ONU identifier A, a pre-REPORT GAP of 10 [μs] is required for ONU 20 with ONU identifier B, and a pre-REPORT GAP of 15 [μs] is required for ONU 20 with ONU identifier C.

The dynamic bandwidth allocation operation unit 106 changes the setting of the operating period so as to provide a pre-REPORT GAP based on the value acquired above between the operating periods of the upstream bandwidth control.

The MPCP processing unit 107 recognizes multiple ONUs 20 connected to PON 1, and realizes functions such as measuring the RTT (Round Trip Time: round trip delay time from OLT 10 to ONU 20) required for communication between each ONU 20 and its own OLT 10, assigning LLIDs (Logical Link IDs), a multiplexing control function that assigns time slots to each ONU 20 and multiplexes upstream burst signals from each ONU 20 on the time axis, and a time synchronization function between the ONU 10 and its own OLT 10.

The signal transmission/reception unit 108 transmits and receives signals between the service network and its own OLT 10 via an SNI (Service Node Interface) port.

[OLT Operation]
An example of the operation of the OLT 10 will now be described. Fig. 10 is a flowchart showing the operation of the OLT 10 in the embodiment of the present invention.

The OAM processing unit 103 monitors the connection of a new ONU 20 to the PON 1 (step S01). When the OAM processing unit 103 detects that a new ONU 20 is connected to the PON 1 (step S01), it outputs the ONU information of the newly connected ONU 20 to the ONU identification determination unit 104.

The ONU identification determination unit 104 acquires the ONU information output from the OAM processing unit 103. The ONU identification determination unit 104 identifies the newly connected ONU 20 by specifying the ONU identifier from the acquired ONU information (step S02).

The ONU identification determination unit 104 determines whether the identified ONU 20 is an ONU 20 that requires a pre-REPORT GAP (step S03). Specifically, the ONU identification determination unit 104 determines whether the identified ONU 20 is an ONU 20 that has a granted queue (transmission reservation queue). Note that information for identifying whether the identified ONU 20 is an ONU 20 that requires a pre-REPORT GAP is stored in advance in a storage medium (not shown) or the like that the OLT 10 has. Alternatively, information for identifying whether the identified ONU 20 is an ONU 20 that requires a pre-REPORT GAP may be stored in the pre-REPORT GAP database 105 shown in FIG. 9, for example.

If it is determined that the identified ONU 20 is not an ONU 20 that requires a pre-REPORT GAP (step S03: NO), the process returns to step S01 above, and the OAM processing unit 103 continues to monitor the connection of a new ONU 20 to PON1.

If it is determined that the identified ONU 20 is an ONU 20 that requires a pre-REPORT GAP (step S03: YES), the ONU identification and determination unit 104 refers to the pre-REPORT GAP database 105 and acquires the pre-REPORT GAP value corresponding to the ONU identifier of the ONU 20 identified in step S02. The ONU identification and determination unit 104 compares the acquired pre-REPORT GAP value with the currently set pre-REPORT GAP value (step S04).

If the pre-REPORT GAP value corresponding to the ONU identifier of the identified ONU 20 is smaller than the currently set pre-REPORT GAP value (step S04: NO), the process returns to step S01 above, and the OAM processing unit 103 continues to monitor the connection of a new ONU 20 to PON1.

If the pre-REPORT GAP value corresponding to the ONU identifier of the identified ONU 20 is greater than the currently set pre-REPORT GAP value (step S04: YES), the ONU identification determination unit 104 outputs the pre-REPORT GAP value corresponding to the ONU identifier of the identified ONU 20 to the dynamic bandwidth allocation operation unit 106.

The dynamic bandwidth allocation operation unit 106 acquires the pre-REPORT GAP value output from the ONU identification and determination unit 104. The dynamic bandwidth allocation operation unit 106 changes the setting of the operation period so that the pre-REPORT GAP is suitable for the connected ONU 20. Specifically, the dynamic bandwidth allocation operation unit 106 changes the setting of the pre-REPORT GAP between the operation periods of the upstream bandwidth control so that it is the acquired value (step S05).

After that, the process returns to step S01, and the OAM processing unit 103 continues to monitor the connection of a new ONU 20 to the PON 1. Note that the operation of the OLT 10 shown in the flowchart of FIG. 10 ends, for example, when the PON 1 stops functioning.

As described above, in this embodiment, OLT 10 changes the operating cycle setting so as to provide sufficient time (pre-REPORT GAP) between operating cycles of upstream bandwidth control to perform data grant transmission reservation calculations and REPORT calculations.

With the above configuration, the OLT 10 in this embodiment can complete the calculations required to transmit upstream data before the transmission start time of the transmission request message (REPORT frame) even for ONUs 20 that do not have a granted queue (transmission reservation queue). This improves upstream throughput.

Note that the calculations required to transmit upstream data here are, as mentioned above, the calculation of the amount of upstream data reserved for transmission (granted) and the calculation of the amount of upstream data to be requested for transmission (i.e., REPORT calculation).

Furthermore, by having the above-mentioned configuration, the OLT 10 in this embodiment can enable upstream communication even in a PON 1 that accommodates a mixture of ONUs 20 with granted queues and ONUs 20 without granted queues.

According to the above-described embodiment, the bandwidth allocation device includes a detection unit and a setting unit. For example, the bandwidth allocation device is OLT1 in the embodiment, the detection unit is OAM processing unit 103 in the embodiment, and the setting unit is a dynamic bandwidth allocation operation unit in the embodiment.

The detection unit detects that a subscriber line termination device that does not have a transmission reservation queue that keeps the upstream data that is permitted to be transmitted waiting until the transmission start time has been connected to the passive optical network. For example, the passive optical network is PON1 in the embodiment, the upstream data that is permitted to be transmitted is granted DATA in the embodiment, the transmission reservation queue is granted queue in the embodiment, and the subscriber line termination device is ONU20 in the embodiment.

The setting unit provides a calculation time, which is the time required for the subscriber line termination device to calculate the amount of upstream data to be transmitted out of the amount of upstream data permitted for transmission, and to calculate the amount of upstream data to be requested for transmission, during the operation period of the upstream bandwidth control between the subscriber line termination device and the subscriber line termination device. For example, the subscriber line termination device is OLT 10 in the embodiment, and the calculation time is the pre-REPORT GAP in the embodiment.

According to the above-described embodiment, the bandwidth allocation device includes an acquisition unit, a determination unit, and a setting change unit. For example, the bandwidth allocation device is OLT 1 in the embodiment, the acquisition unit is OAM processing unit 103 in the embodiment, the determination unit is ONU identification determination unit 104 in the embodiment, and the setting change unit is dynamic bandwidth allocation operation unit 106 in the embodiment.

The acquisition unit acquires identification information that identifies a subscriber line terminal connected to the passive optical network. For example, the passive optical network is PON1 in the embodiment, the subscriber line terminal is ONU2 in the embodiment, and the identification information is an ONU identifier in the embodiment.

The determination unit determines, based on the identification information, whether the subscriber line termination device has a transmission reservation queue that keeps the upstream data that has been permitted to be transmitted waiting until the transmission start time. For example, the upstream data that has been permitted to be transmitted is the granted DATA in the embodiment, and the transmission reservation queue is the granted queue in the embodiment.

When the setting change unit determines that the subscriber line terminal does not have a transmission reservation queue, it sets a predetermined calculation time between the operating periods of the upstream bandwidth control in the passive optical network.

The setting change unit may change the operation period to include a calculation time, which is the time required for the subscriber line termination device to calculate the amount of uplink data to be transmitted out of the amount of uplink data permitted for transmission, and to calculate the amount of uplink data to be requested for transmission. For example, the calculation time is the pre-REPORT GAP in the embodiment.

The bandwidth allocation device may further include a memory unit. For example, the memory unit is the pre-REPORT GAP database 105 in the embodiment. The memory unit stores calculation time information in which the identification information and the calculation time are associated with each other. The setting change unit may change the operating period so that the calculation time specified based on the identification information and the calculation time information is included.

A part or all of the OLT 10 in each of the above-mentioned embodiments may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to realize the function. The term "computer system" here includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The term "computer-readable recording medium" may also include a medium that dynamically holds a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in that case. The above program may be a program for realizing a part of the above-mentioned function, or may be a program that can realize the above-mentioned function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment and also includes designs that do not deviate from the gist of the present invention.

1...PON, 30...optical fiber, 40...optical splitter, 101...signal transmission/reception unit, 102...MAC processing unit, 103...OAM processing unit, 104...ONU identification/determination unit, 105...pre-REPORT GAP database, 106...dynamic bandwidth allocation operation unit, 107...MPCP processing unit, 108...signal transmission/reception unit

Claims (8)

a detection unit that detects that a subscriber line termination device that does not have a transmission reservation queue for making upstream data that has been permitted to be transmitted wait until a transmission start time has been connected to the passive optical network;
a setting unit for setting a calculation time, which is a time required for calculating the amount of upstream data to be transmitted from the amount of upstream data permitted to be transmitted and the amount of upstream data to be requested to be transmitted, during an operation period of upstream bandwidth control between the subscriber line termination device and the subscriber line termination device;
A bandwidth allocation device comprising: an acquisition unit that acquires identification information that identifies a subscriber line unit connected to the passive optical network;
a determination unit that determines, based on the identification information, whether or not the subscriber line termination device has a transmission reservation queue for storing upstream data that has been permitted to be transmitted and that is kept waiting until a transmission start time;
a setting change unit that provides a predetermined calculation time between operation periods of upstream bandwidth control in the passive optical network when it is determined that the subscriber line terminal does not have the transmission reservation queue;
A bandwidth allocation device comprising: The bandwidth allocation device according to claim 2, wherein the setting change unit changes the operating period so as to include the calculation time, which is the time required for the subscriber line termination device to calculate the amount of upstream data to be transmitted out of the amount of upstream data permitted to be transmitted, and to calculate the amount of upstream data to be requested to be transmitted. a storage unit that stores calculation time information in which the identification information and the calculation time are associated with each other,
The bandwidth allocation device according to claim 3 , wherein the setting change unit changes the operation cycle so as to include the calculation time specified based on the identification information and the calculation time information. a detection unit that detects that a subscriber line termination device that does not have a transmission reservation queue for making upstream data that has been permitted to be transmitted wait until a transmission start time has been connected to the passive optical network;
a setting unit for setting a calculation time, which is a time required for calculating the amount of upstream data to be transmitted from the amount of upstream data permitted to be transmitted and the amount of upstream data to be requested to be transmitted, during an operation period of upstream bandwidth control between the subscriber line termination device and the own device;
a transmitting/receiving unit for transmitting and receiving data to and from the subscriber line termination device;
A subscriber line terminal device comprising: an acquisition unit that acquires identification information that identifies a subscriber line unit connected to the passive optical network;
a determination unit that determines, based on the identification information, whether or not the subscriber line termination device has a transmission reservation queue for storing upstream data that has been permitted to be transmitted and that is kept waiting until a transmission start time;
a setting change unit that provides a predetermined calculation time between operation periods of upstream bandwidth control in the passive optical network when it is determined that the subscriber line terminal does not have the transmission reservation queue;
a transmitting/receiving unit for transmitting and receiving data to and from the subscriber line termination device;
A subscriber line terminal device comprising: a detection step of detecting that a subscriber line terminal not having a transmission reservation queue for making upstream data permitted to be transmitted wait until a transmission start time is connected to the passive optical network;
a setting step of setting a calculation time required for calculating the amount of upstream data to be transmitted from the amount of upstream data permitted to be transmitted and the amount of upstream data to be requested to be transmitted, during an operation period of upstream bandwidth control between the subscriber line termination device and the subscriber line termination device;
The bandwidth allocation method includes the steps of: acquiring identification information identifying a subscriber line unit connected to the passive optical network;
a determination step of determining whether or not the subscriber line termination device has a transmission reservation queue for holding the upstream data permitted for transmission until a transmission start time based on the identification information;
a setting change step of providing a predetermined calculation time between operation periods of upstream bandwidth control in the passive optical network when it is determined that the subscriber line terminal does not have the transmission reservation queue;
The bandwidth allocation method includes the steps of:

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