OLT and bandwidth allocation method

Abstract

This provides an OLT (Optical Line Terminal) capable of accommodating both IEEE-based PON (Positive On-Demand) ONUs and ITU-T-based PON (Positive On-Demand) ONUs. [Solution] An apparatus according to one aspect of the present disclosure is an OLT connected to a plurality of ONUs by a P2MP ODN, comprising: a first signal processing unit that performs the following first DBA; a second signal processing unit that performs the following second DBA; and a DBA cooperation unit that performs processing on the first and second signal processing units so as not to overlap the following first period and the following second period. First DBA: A DBA that targets the first ONU, which is an ONU of the IEEE-based PON. Second DBA: A DBA that targets the second ONU, which is an ONU of the ITU-T system PON. Period 1: Uplink reception period for IEEE permitted in the first DBA. Second period: Uplink reception period for ITU-T permitted in the Second DBA

Description

Technical Field

[0001] This disclosure relates to an OLT and a bandwidth allocation method.

Background Art

[0002] Patent Document 1 describes a PON system that enables coexistence of various PONs (Passive Optical Networks) with different systems. The PON system of Patent Document 1 includes a first OLT (Optical Line Terminal) and a second OLT, and a first ONU (Optical Network Unit) and a second ONU. The first and second OLTs share the allocation information of the upstream communication bandwidth of the first and second ONUs, and the first OLT allocates the upstream communication bandwidth to the first ONU while avoiding the upstream communication bandwidth of the second ONU.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the PON system of Patent Document 1, a plurality of OLTs (the first OLT and the second OLT) are required. Therefore, coexistence of ONUs of PONs with different communication systems in one OLT is not assumed in Patent Document 1. In particular, in IEEE-based PON and ITU-T-based PON, the upstream communication control methods are significantly different, so it has been difficult to accommodate ONUs of both PONs in one OLT.

[0005] In view of such conventional problems, an object of this disclosure is to provide an OLT that can accommodate ONUs of IEEE-based PON and ITU-T-based PON.

Means for Solving the Problems

[0006] An apparatus according to one aspect of the present disclosure is an OLT connected to a plurality of ONUs by a P2MP ODN, comprising: a first signal processing unit that performs the first DBA described below; a second signal processing unit that performs the second DBA described below; and a DBA cooperation unit that performs processing on the first and second signal processing units so as not to overlap the first period and the second period described below.

[0007] First DBA: A DBA that targets the first ONU, which is an ONU of the IEEE-based PON. Second DBA: A DBA that targets the second ONU, which is an ONU of the ITU-T system PON. Period 1: Uplink reception period for IEEE permitted in the first DBA. Second period: Uplink reception period for ITU-T permitted in the Second DBA

[0008] This disclosure can be implemented not only as a system and apparatus having the characteristic configuration described above, but also as a program for causing a computer to execute such characteristic configuration. Furthermore, this disclosure can be implemented as a semiconductor integrated circuit that implements part or all of the system and apparatus. [Effects of the Invention]

[0009] According to this disclosure, an IEEE-based PON ONU and an ITU-T-based PON ONU can be accommodated in a single OLT. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a network connection diagram showing an example of the overall configuration of a PON system. [Figure 2] Figure 2 is an explanatory diagram showing the recommended wavelength arrangement when GE-PON, 10G-EPON, and 25GS-PON are mixed together. [Figure 3] Figure 3 is an explanatory diagram illustrating the overview of uplink communication control for IEEE-based PON. [Figure 4] FIG. 4 is an explanatory diagram showing an overview of upstream communication control of an ITU-T type PON. [Figure 5] FIG. 5 is a block diagram showing an example of the internal configuration of an OLT. [Figure 6] FIG. 6 is an explanatory diagram showing an example of parameters related to the first DBA and the second DBA. [Figure 7] FIG. 7 is a sequence diagram showing an example of parameter setting processing based on a control signal. [Figure 8] FIG. 8 is an explanatory diagram showing an example of the first DBA performed by the first signal processing unit. [Figure 9] FIG. 9 is an explanatory diagram showing an example of the second DBA performed by the second signal processing unit.

MODE FOR CARRYING OUT THE INVENTION

[0011] <SUMMARY OF THE EMBODIMENTS OF THE PRESENT DISCLOSURE> The summary of the embodiments of the present disclosure will be listed and described below.

[0012] (1) An apparatus according to an aspect of the present embodiment is an OLT connected to a plurality of ONUs by a P2MP type ODN, and includes a first signal processing unit that executes the following first DBA, a second signal processing unit that executes the following second DBA, and a DBA cooperation unit that executes a process of not overlapping the following first period and the following second period in the first and second signal processing units.

[0013] First DBA: DBA targeting a first ONU that is an ONU of an IEEE type PON Second DBA: DBA targeting a second ONU that is an ONU of an ITU-T type PON First period: An upstream reception period for IEEE allowed in the first DBA Second period: An upstream reception period for ITU-T allowed in the second DBA

[0014] According to the OLT of this embodiment, since the DBA cooperation unit executes the process of not overlapping the first period and the second period on the first and second signal processing units, the reception time of the upstream frame from the first ONU and the reception time of the upstream frame from the second ONU are time-divisionally separated, and the OLT can appropriately receive both upstream frames. Therefore, an ONU of an IEEE-based PON and an ONU of an ITU-T-based PON can be accommodated in one OLT.

[0015] (2) In the OLT of (1) above, the non-overlapping process may include notifying the first and second signal processing units of the following first, second, and third parameters. First parameter: Information corresponding to the cycle length of the common cycle Second parameter: Synchronization information of the common cycle Third parameter: The time length of the first period or the second period within the common cycle In this way, by simply notifying each signal processing unit of the above parameters, the process of not overlapping the first period and the second period can be realized.

[0016] (3) In the OLT of (2) above, the first parameter may be a natural number multiplied by the time length of the upstream PHY frame for ITU-T. In this way, since the upstream PHY frame for ITU-T can be diverted to the common cycle, the operations of the first and second signal processing units can be synchronized more simply compared to the case where a cycle different from the upstream PHY frame is defined separately.

[0017] (4) In the OLT of (3) above, the second parameter may be the start time of the first common cycle synchronized with the start time of the upstream PHY frame. In this way, the first and second signal processing units can manage the progress of the common cycle based on the notified natural number and start time.

[0018] (5) In the OLT of (3) described above, the second parameter may be a reset signal that is released in synchronization with the start time of the up PHY frame. In this way, the first and second signal processing units can determine the time when the reset signal is released as the start time of the first common cycle, and then manage the progress of the common cycle based on the determined start time and the notified natural number.

[0019] (6) In the OLT of (3) described above, the second parameter notified to the second signal processing unit may include the number of delayed cycles from the boundary of the downlink PHY frame to the start of the first common cycle. In this way, the second signal processing unit can calculate the start time of the first common cycle from the notified number of delayed cycles and the phase difference between the uplink and downlink PHY frames, and manage the progress of the common cycle based on the calculated start time and the notified natural number.

[0020] (7) In the OLT described in (2) to (6) above, the third parameter may be calculated based on the contracted bandwidth and uplink speed of the first ONU and the contracted bandwidth and uplink speed of the second ONU. In this way, the third parameter (the duration of the first or second period) can be appropriately calculated according to the communication bandwidth to be guaranteed for the first and second ONUs.

[0021] (8) In the OLT described in (1) to (7) above, the first signal processing unit may determine the transmission start time and transmission time permitted to the first ONU such that the reception time of the uplink frame from the first ONU falls within the first period. In this way, the reception time of the uplink frame from the first ONU will not extend into the second period, thus enabling proper reception of the uplink frame.

[0022] (9) In the OLT described in (1) to (8) above, the second signal processing unit may determine the amount of transmission permission to allocate to the second ONU such that the reception time of the uplink frame from the second ONU falls within the second period. In this way, the reception time of the uplink frame from the second ONU will not exceed the first period, so that the uplink frame can be received properly.

[0023] (10) In the OLT described in (1) to (9) above, the first and second signal processing units may be able to send and receive control signals to each other to temporarily suppress the other DBA. In this way, for example, discovery or ranging in one signal processing unit can prevent the uplink communication control of the other signal processing unit from being disrupted.

[0024] (11) In the OLT described in (10) above, if the execution times of DBA suppression requested by each of the first and second signal processing units from the other party overlap, the first and second signal processing units may decide which DBA suppression to prioritize depending on at least one of the types of suppression causes, the length of the execution time, and the transmission speed. In this way, both signal processing units can appropriately determine the order of DBA suppression when execution times overlap.

[0025] (12) A method according to one aspect of this embodiment is a bandwidth allocation method performed in the OLT described in (1) to (11) above. Therefore, the bandwidth allocation method of this embodiment has the same effects as the OLT described in (1) to (11) above.

[0026] <Details of the embodiments of this disclosure> The embodiments of this disclosure will be described in detail below with reference to the drawings. At least some of the embodiments described below may be combined in any way.

[0027] [Definition of Terms] In this embodiment, among the upstream and downstream signals transmitted in the PON system 100, the upstream signal may be abbreviated as "US" and the downstream signal may be abbreviated as "DS".

[0028] In this embodiment, a set of multiple types of ONUs that comply with different PON communication protocols may be collectively referred to as "heterogeneous ONUs." PON communication protocols include, for example, IEEE-based PON and ITU-T-based PON. Note that "IEEE" is an abbreviation for "Institute of Electrical and Electronics Engineers." "ITU-T" is an abbreviation for the Telecommunication Standardization Sector of the International Telecommunication Union (ITU).

[0029] [Overall configuration of the PON system] Figure 1 is a network connection diagram showing an example of the overall configuration of the PON system 100. As shown in Figure 1, the PON system 100 is a multi-rate PON system in which multiple types of ONUs 20, 30, and 40 with different transmission speeds are connected to the OLT 10 by an ODN (Optical Distribution Network) 50 in a P2MP (Point To Multi Point) configuration. Although Figure 1 shows only one ONU20, multiple ONU20 connections are possible. The same applies to ONU30 and 40 with other transmission speeds.

[0030] The ODN50 includes multiple branch fibers 53 that branch off from the trunk fiber 51 via an optical splitter 52. The trunk fiber 51 is connected to the OLT 10, and the multiple branch fibers 53 are connected to the ONUs 20, 30, and 40, respectively. ONU20 is a GE-PON ONU, ONU30 is a 10G-EPON ONU, and ONU40 is a 25GS-PON ONU.

[0031] ONU20 and ONU30 are IEEE-based PON ONUs. ONU40 is an ITU-T-based PON ONU. Therefore, the three sets of ONU20, 30, and 40, which have different transmission speeds, constitute a "heterogeneous ONU." Hereafter, IEEE-based PON ONU20 and 30 may be referred to as "IEEE_ONU" or "First ONU," and ITU-T-based PON ONU40 may be referred to as "ITU-T_ONU" or "Second ONU."

[0032] Here, 25GS-PON is a method specified by the "25GS-PON multi-source agreement," one of the industry associations, and can be said to be neither strictly IEEE-based nor ITU-T-based; however, in this embodiment, it is included in the ITU-T-based PON. The reason is that 25GS-PON largely follows the ITU-T standard for XGS-PON in terms of its Transmission Convergence (TC) layer, which includes uplink bandwidth control. Therefore, from the perspective of uplink bandwidth control, it should be classified as an ITU-T standard.

[0033] [Wavelength arrangement when accommodating different types of ONUs] Figure 2 is an explanatory diagram showing the recommended wavelength arrangement when GE-PON ONU20, 10G-EPON ONU30, and 25GS-PON ONU40 are housed together. As shown in Figure 2, the US wavelength band of GE-PON can vary in the range of 1260–1360 nm depending on the operating temperature. This range interferes with the typical DS wavelength band of 25GS-PON (center wavelength 1300 nm).

[0034] To avoid interference, one could employ strategies such as narrowing the US wavelength band of GE-PON and assigning the DS wavelength of 25GS-PON as standard. However, narrowing the wavelength band requires limiting the temperature range or using distributed feedback (DFB) lasers. Therefore, in the PON system 100 of this embodiment, as shown in Figure 2, the bandwidth of the DS wavelength of 25GS-PON is shifted to, for example, the C / L band.

[0035] However, it is necessary to avoid interference between the DS wavelength band of 10G-EPON (1575-1580nm) and the RF (Radio Frequency) video wavelength band (1550-1560nm), and there is a guard band of approximately 15nm between the two. Therefore, it is preferable to shift the DS wavelength band of 25GS-PON to either 1530-1535 nm or 1595-1625 nm.

[0036] Taking the above into consideration, in this embodiment, the US wavelength and DS wavelength used in each ONU 20, 30, and 40 are set as follows, for example (see Figure 1). ONU20 US wavelength = 1260~1360nm DS wavelength=1480~1500nm ONU30:US wavelength=1260~1280nm DS wavelength=1575~1579nm ONU40: US wavelength = 1260~1280nm, 1290~1310nm, or 1284~1288nm DS wavelength=1530~1535nm

[0037] However, the above wavelength assignment is just one example; for example, the DS wavelength of ONU40 may be set to another wavelength included within the C / L band. As will be explained later, the IEEE-based 1G / 10G-EPON and the ITU-T-based 25GS-PON have fundamentally different methods for controlling uplink communication. For this reason, it was difficult to accommodate both the IEEE_ONU and the ITU-T_ONU in a single OLT.

[0038] In this embodiment, the OLT controls the reception time of the uplink frames received by the OLT from the IEEE_ONU and the ITU-T_ONU so that they are time-division multiplexed, thereby enabling the ONUs to be accommodated in a single ONU. The following describes the outlines of IEEE-based uplink communication control (Figure 3) and ITU-T-based uplink communication control (Figure 4), followed by a description of the internal configuration and control details of the OLT10 in this embodiment.

[0039] [Uplink communication control of IEEE-based PON] Figure 3 is an explanatory diagram illustrating the overview of uplink communication control for IEEE-based PON. As shown in Figure 3, the OLT sends gate frames 1, 2, and 3 to ONU #1, #2, and #3 respectively, instructing ONU #1, #2, and #3 to start transmitting. ONU #1, #2, and #3 transmit uplink signals 1, 2, and 3 according to the timing instructed by the OLT, so no collisions of uplink signals 1, 2, and 3 occur. In addition, a report frame for bandwidth request is transmitted for all or part of uplink signals 1, 2, and 3.

[0040] The OLT and ONUs #1, #2, and #3 each have a local clock (32 bits) in 16ns units. Since the gate frame contains a separate transmission start time for each ONU #1, #2, and #3, it is necessary to synchronize the time between the OLT and ONUs #1, #2, and #3. Therefore, when ONU #1, #2, and #3 receive a gate frame, they synchronize their own clocks with the OLT's clock (timestamp). The OLT also instructs ONU #1, #2, and #3 on the transmission start time (OLT's reception time - RTT (Round Trip Time)) and transmission time. The OLT measures the RTT during ONU discovery and updates it when it receives a report frame.

[0041] [ITU-T-based PON uplink communication control] Figure 4 is an explanatory diagram illustrating the overview of ITU-T-based PON uplink communication control. As shown in Figure 4, the OLT manages the progress of control for both up and down directions using "PHY (Physical Interface) frames" that progress in 125 μs cycles.

[0042] Specifically, the OLT manages the progress of uplink and downlink PHY frames in a one-to-one correspondence and in parallel. The time difference between the start times of the two frames is a fixed value determined by the communications administrator to ensure that reception from the furthest ONU (not shown) is completed in time. The header of the downlink PHY frame contains the ONU's "BWmap" (BandWidth map). The BWmap contains uplink transmission permission information.

[0043] Specifically, BWmap includes the "Alloc ID," "Start Time," and "Grant size." It is also possible to assign multiple Alloc IDs (in the example diagram, IDs X and Z) to a single ONU_X. ONU_X,Y stores the upstream buffer amount in the Dynamic Bandwidth Report Upstream (DBRu) of the upstream PHY frame. OLT performs Dynamic Bandwidth Allocation (DBA) based on the upstream buffer amounts of ONU_X,Y to determine the transmit permission amount for each ONU_X,Y.

[0044] ONU_X,Y calculates the start time for transmitting the uplink PHY burst based on the start time listed in BWmap, and when its local time reaches that transmission start time, it starts transmitting an uplink PHY burst containing user data (main signal) equivalent to the transmission permission amount in BWmap. Taking ONU_Y as an example, ONU_Y defines the start time of transmission for the uplink PHY burst as the point at which the response time Trsp, equivalent delay EqD_y, and start time Tsrt_y have elapsed from the time the beginning of the downlink PHY frame is received.

[0045] The response time Trsp and equivalent delay EqD_y are delay times specific to ONU_Y and are determined for each ONU based on the results of RTT measurement (ranging) by the OLT. Ranging is performed for each ONU_X,Y through the exchange of ranging requests and responses between the OLT and ONU_X,Y. The start time Tsrt_y is a delay time specific to ONU_Y, determined based on the uplink transmission order assigned to ONU_Y, and is indicated by the start time field in BWmap.

[0046] As described above, in ITU-T-based PON systems, the OLT specifies the transmission timing and transmission allowance to the ONU. This is the same as in IEEE-based PON systems. However, the transmission timing specified by the OLT (the start time Tsrt_y in the BWmap in Figure 4) is not an absolute time, but a relative time based on the boundary of the uplink PHY frame. For this reason, unlike the IEEE-based PON, the ITU-T system does not manage absolute time in uplink communication control.

[0047] [OLT Internal Configuration] Figure 5 is a block diagram showing an example of the internal configuration of OLT10. In Figure 5, solid arrows indicate "communication frames" exchanged within OLT10. Dashed arrows indicate "control signals" exchanged within OLT10. As shown in Figure 5, the OLT 10 comprises an optical transceiver 11, a first signal processing unit 12, a second signal processing unit 13, a DBA linkage unit 14, a switch unit 15, and a management control unit 16.

[0048] The optical transceiver 11 is a multi-rate optical transceiver capable of electro-optical conversion and photoelectric conversion at three or more different transmission speeds. The optical transceiver 11 includes a transmitting unit 11T that converts 1G / 10G / 25G electrical signals into optical signals of predetermined wavelengths as shown in the figure, and a receiving unit 11R that converts optical signals of predetermined wavelengths into 1G / 10G / 25G electrical signals.

[0049] Specifically, the transmitting unit 11T of the optical transceiver 11 converts the 1.25 Gbit / s electrical signal (downlink frame) input from the first signal processing unit 12 into, for example, a downlink optical signal of 1490 nm, and sends this downlink optical signal to the ODN 50. Similarly, the transmitting unit 11T of the optical transceiver 11 converts the 10.31 Gbit / s electrical signal (downlink frame) input from the first signal processing unit 12 into, for example, a downlink optical signal of 1577 nm, and sends this downlink optical signal to the ODN 50.

[0050] Similarly, the transmitting unit 11T of the optical transceiver 11 converts the 25.78 Gbit / s electrical signal (downlink frame) input from the second signal processing unit 13 into a downlink optical signal of, for example, 15XX nm, and sends this downlink optical signal to the ODN 50. The "15XXnm" mentioned above is set to any value that falls within the preferred numerical range of the DS wavelength for 25GS-PON as shown in Figure 1.

[0051] The receiving unit 11R of the optical transceiver 11 converts, for example, an uplink optical signal of 1260~1360nm into electrical signals of various rates and outputs them. In this case, only the electrical signals corresponding to the rates of the uplink optical signal are meaningful, and electrical signals corresponding to other rates become noise or are masked.

[0052] The first signal processing unit 12 includes a MAC chip capable of frame processing in accordance with GE-PON and 10G-EPON. This MAC chip is composed of, for example, a System on a Chip (SoC) that includes at least one CPU (Central Processing Unit) and memory. The MAC chip of the first signal processing unit 12 may include an integrated circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) in addition to or as a substitute for a CPU.

[0053] The second signal processing unit 13 includes a MAC chip capable of frame processing in accordance with 25GS-PON. This MAC chip is composed of, for example, an SoC that includes at least one CPU and memory. The MAC chip of the second signal processing unit 13 may include an integrated circuit such as an FPGA or ASIC in addition to, or as a substitute for, the CPU.

[0054] The DBA cooperation unit 14 is a controller that controls the operation of the first signal processing unit 12 and the second signal processing unit 13, etc. The DBA cooperation unit 14 may consist of, for example, at least one CPU and memory, but it may also include an integrated circuit such as an FPGA or ASIC in addition to or as a substitute for the CPU. The DBA linkage unit 14 can send and receive control signals S1 and S2 to and from the first signal processing unit 12 and the second signal processing unit 13, respectively, via serial communication such as I2C (Inter-Integrated Circuit).

[0055] The switch unit 15 is an integrated circuit, such as an LSI (Large Scale Integration), that has a Layer 2 relay function. The integrated circuit may also have a Layer 3 relay function. The switch unit 15 has multiple Ethernet ports ("Ethernet" is a registered trademark). A first signal processing unit 12 is connected to a predetermined port among the multiple Ethernet ports, and a second signal processing unit 13 is connected to another predetermined port. The switch unit 15 and the DBA cooperation unit 14 may be implemented on a single integrated circuit, such as an SoC.

[0056] The management control unit 16 is an integrated circuit, such as an LSI, that can communicate with the management device 17. The management device 17 is, for example, a computer operated by a communications administrator. The management device 17 may be connected to the OLT 10 via a management network such as a LAN (Local Area Network). The management control unit 16 can obtain predetermined setting information from the management device 17 via command line or the like, and performs various setting processes on the OLT 10 based on the obtained setting information.

[0057] For example, the management control unit 16 can perform tasks such as setting the QoS (Quality of Service) of the switch unit 15, setting the bandwidth of each port of the switch unit 15, and setting VLAN (Virtual LAN) settings. Furthermore, when the management control unit 16 acquires configuration information S0 (for example, contracted bandwidth) related to the ONUs 20, 30, and 40, it notifies the DBA cooperation unit 14 of the acquired configuration information S0.

[0058] The first signal processing unit 12 performs DBA (hereinafter referred to as "first DBA") related to the ONUs 20 and 30 under its control. The first DBA includes, for example, the following processes. Process P1: Calculates the transmission time to be allocated to ONU20 and 30 based on reports (bandwidth requests) from ONU20 and 30, QoS information, and the uplink communication speed of ONU20 and 30. Process P2: A gate frame containing the calculated transmission time is sent to the subordinate ONUs 20 and 30, respectively.

[0059] The second signal processing unit 13 performs DBA (hereinafter referred to as "second DBA") related to the ONU 40 under its control. The second DBA includes, for example, the following processes. Process Q1: Calculate the amount of transmit permission to allocate to ONU40 based on the report from ONU40 (DBRu uplink buffer size), QoS information, and the uplink communication speed of ONU40. Process Q2: The calculated transmission permission amount is recorded in the BWmap and the downlink PHY frame is broadcast to the subordinate ONU40.

[0060] By the way, if the reception time of the uplink frame transmitted according to the gate frame and the reception time of the uplink frame transmitted according to the BWmap overlap, the uplink optical signals will collide in the trunk fiber 51, which may cause the OLT 10 to fail to receive the uplink optical signals. Therefore, in this embodiment, the DBA linkage unit 14 generates parameters to prevent overlap between the uplink reception time allowed for the first ONU and the uplink reception time allowed for the second ONU, and transmits control signals S1 and S2, which include these parameters, to the respective signal processing units 12 and 13.

[0061] Specifically, two exclusive periods (D1 and D2 in Figure 6) are defined for IEEE and ITU-T within the "common cycle," which is a natural multiple of the length of the uplink PHY frame. Each signal processing unit 12 and 13 is then instructed to perform a first or second DBA to receive uplink frames during the periods D1 and D2 assigned to it. However, the signal processing units 12 and 13 share the unallocated period for discovery and ITU-T ranging, and give it priority over the DBA.

[0062] [Parameter Definitions] Figure 6 is an explanatory diagram showing an example of parameters related to the first and second DBAs. The meanings of the parameters in Figure 6 are as follows: tp: This is the time used to measure the progress of the common cycle. Hereinafter referred to as "progress time". i: This is the identification number for the common cycle. The identification number i is incremented each time the cycle length CL elapses.

[0063] Ui: This is the i-th common cycle. The method for synchronizing common cycles will be described later. uti: This is the start time of the common cycle UI. CL: This is the time length (cycle length) of the common cycle UI. N is the number of uplink PHY frames that make up the cycle length CL (a set natural number). Therefore, the cycle length CL is N times the time length of the uplink PHY frame, which is 125 μs, and the set natural number N is a type of information equivalent to the cycle length CL of the common cycle Ui.

[0064] D1: This is the uplink reception period for IEEE allowed in the first DBA. Hereinafter referred to as the "first period". The first period D1 is a time slot within the common cycle Ui. D2: This is the uplink reception period for ITU-T permitted in the second DBA. Hereinafter referred to as the "second period". The second period D2 is a time slot within the common cycle Ui. Whether each of the above periods D1 and D2 is placed in the first or second half of the common cycle Ui depends on the implementation, but in this embodiment, the first period D1 is placed in the first half.

[0065] j: This is the identification number of the first ONU (ONU20, 30). ONUj: This is the first ONU with identification number j. aj: This is the uplink reception time assigned to the first ONU with identification number j. CSj: This is the uplink communication speed of the first ONU with identification number j.

[0066] k: This is the identification number of the second ONU (ONU40). ONUk: This is the second ONU with identification number k. bk: This is the uplink reception time assigned to the second ONU with identification number k. CSk: This is the uplink communication speed of the second ONU with identification number k.

[0067] [Method for synchronizing common cycles] For example, the following methods can be used to synchronize the common cycle UI. (Synchronization Method 1) Synchronization method 1 is a type of time synchronization method in which the DBA cooperation unit 14 and each signal processing unit 12, 13 adopt a time based on a time distribution protocol such as PTP (Precision Time Protocol) as the progress time tp.

[0068] In this case, the DBA linkage unit 14 and each signal processing unit 12, 13 can, for example, use a 16ns granularity time obtained by converting the absolute time of the PTP using a predetermined conversion formula as the progress time tp. Alternatively, the DBA linkage unit 14 and each signal processing unit 12, 13 may initialize their own local time, which is counted up at a granularity of 16ns, using PTP and set it as the progress time tp.

[0069] (Synchronization Method 2) Synchronization method 2 is a type of time synchronization method in which the DBA cooperation unit 14 and each signal processing unit 12, 13 adopt a 32-bit time (hereinafter referred to as "IEEE time") that counts up in 16ns, such as that used in IEEE-based PON, as the progress time tp.

[0070] The clock that measures IEEE time (hereinafter referred to as the "IEEE clock") may be provided by the DBA cooperation unit 14 or by the first signal processing unit 12. If the DBA linkage unit 14 has an IEEE clock, each signal processing unit 12 and 13 should synchronize its own local clock to IEEE time. If the first signal processing unit 12 has an IEEE clock, the DBA linkage unit 14 and the second signal processing unit 13 should synchronize their own local clocks to IEEE time.

[0071] (Synchronization Method 3) Synchronization method 3 is a time synchronization method in which the first and second signal processing units 12 and 13 adopt the local time at which they begin to progress based on initialization using a reset signal as the progress time tp. In synchronization method 3, for example, the first signal processing unit 12 has a clock that progresses with the release of the reset signal as zero, and the second signal processing unit 13 has a clock that uses the release of the reset signal as the start timing of the ascending PHY frame.

[0072] The DBA linkage unit 14 associates the start timing of the uplink PHY frame with the local time of the first signal processing unit 12 by releasing the reset signals to both signal processing units 12 and 13 at a predetermined timing. The appropriate timing for releasing the reset signals can be determined experimentally.

[0073] (Synchronization method 4) Synchronization method 4 is a type of cycle synchronization method that synchronizes the start timing of the common cycle Ui with the start timing of the up PHY frame of the second signal processing unit 13. In synchronization method 4, for example, the DBA cooperation unit 14 has the function of snooping the downlink signal of the second signal processing unit 13 to detect the boundary of the downlink PHY frame.

[0074] In this case, the DBA cooperation unit 14 determines the number of delayed cycles from the detected boundary to the start of the first common cycle U1, and the phase difference (shift time) between the downlink PHY frame and the uplink PHY frame, and notifies the second signal processing unit 13 of the result. Alternatively, the DBA cooperation unit 14 may refer to the phase difference determined by the second signal processing unit 13. Furthermore, the DBA linkage unit 14 converts the start time U1 of the first common cycle into the clock of the first signal processing unit 12 and notifies the first signal processing unit 12 of the converted time value.

[0075] [Parameter setting process] Figure 7 is a sequence diagram showing an example of the parameter setting process based on control signals S0, S1, and S2. As shown in Figure 7, when the management control unit 16 detects the input of DBA-related setting information S0 by the OLT 10 (step S11), it notifies the DBA cooperation unit 14 of the detected setting information S0 (step S12).

[0076] Configuration information S0 may include the number of uplink PHY frames N, the contracted bandwidth Bj and uplink communication speed CSj of the first ONU, and the contracted bandwidth Bk and uplink communication speed CSK of the second ONU. The DBA linkage unit 14 determines the parameters to be notified to each signal processing unit 12 and 13 using the notified number of uplink PHY frames N, contracted bandwidths Bj and Bk, and uplink communication speeds CSj and CSK (step S13), and notifies each signal processing unit 12 and 13 of the determined parameters by including them in the control signals S1 and S2 (steps S14 and S15).

[0077] The parameters to be notified include, for example, the synchronization information SYN of the common cycle Ui, the number of up PHY frames N, and the duration of the first period D1. The content of the synchronization information SYN varies depending on the synchronization method of the common cycle Ui. For example, if the progress time tp of the first and second signal processing units 12 and 13 is synchronized in advance by synchronization method 1 and synchronization method 2, the start time ut1 of the first common cycle U1 is adopted as the synchronization information SYN.

[0078] When the progress time tp of the first and second signal processing units 12 and 13 is synchronized using synchronization method 3, the aforementioned reset signal is used as the synchronization information SYN. When synchronization with the uplink PHY frame is performed using synchronization method 4, the aforementioned delay cycle count and shift time are used as the synchronization information SYN for the second signal processing unit 13, and the aforementioned start time ut1 of the first common cycle U1 is used as the synchronization information SYN for the first signal processing unit 12.

[0079] The number of uplink PHY frames N is the value obtained from the management control unit 16 and is used as is. The length of the first period D1 is determined according to the service type of communication, based on the contracted bandwidth Bj and uplink speed CSj of the first ONU, and the contracted bandwidth Bk and uplink speed CSK of the second ONU. For example, if the service type of both the first and second ONUs is bandwidth guaranteed, the length of the first period D1 is determined based on the ratio of the sum of the contracted bandwidths Bj of the first ONU and the sum of the contracted bandwidths Bk of the second ONU (=ΣBj / ΣBk).

[0080] The DBA linkage unit 14 may determine the length of the first period D1 to be "0". For example, if the contracted bandwidth ΣBj of the first ONU is 0, the length of the first period D1 is set to 0. In this case, the time length of the second period D2 matches the cycle length CL of the common cycle Ui. Furthermore, if the number of first or second ONUs changes during operation, the DBA linkage unit 14 may recalculate the length of the first period D1 according to the ratio (=ΣBj / ΣBk) after the change.

[0081] Furthermore, the DBA linkage unit 14 can detect changes in the number of first ONUs or second ONUs based on notifications from the management control unit 16 or the respective signal processing units 12 and 13. Next, the first signal processing unit 12 uses the parameters (=SYN,N,D1) notified by the control signal S1 to perform a first DBA (Step S16) so that the reception time of the uplink frame from the first ONU (ONU20,30) falls within the first period D1. A specific example of this first DBA will be described later.

[0082] Similarly, the second signal processing unit 13 uses the parameters (=SYN,N,D1) notified by the control signal S2 to perform a second DBA (Step ST17) so that the reception time of the uplink frame of the second ONU (ONU 40) falls within the second period D2. A specific example of such a second DBA will be described later.

[0083] [Specific examples of a first-class DBA] Figure 8 is an explanatory diagram showing an example of the first DBA performed by the first signal processing unit 12. As shown in Figure 8, the first signal processing unit 12 calculates the cycle length CL of the common cycle Ui based on the number of up PHY frames N (step S21). Next, the first signal processing unit 12 sequentially adds the cycle length CL to the start time ut1 of the first common cycle U1 obtained from the notified synchronization information SYN, and manages the progress of each common cycle Ui (i=1,2...) (step S22).

[0084] Next, the first signal processing unit 12 determines the transmission start times t1, t2 and transmission time to allow the first ONU (ONU20,30) to transmit so that the reception times a1, a2 of the uplink frames from the first ONU (ONU20,30) fall within the first period D1 which is for IEEE (step S23). Therefore, in the first DBA, the reception times a1 and a2 of the uplink frames from the first ONU will not extend into the second period D2, which is for ITU-T.

[0085] [Specific examples of a second DBA] Figure 9 is an explanatory diagram showing an example of the second DBA performed by the second signal processing unit 13. As shown in Figure 9, the second signal processing unit 13 calculates the cycle length CL of the uplink common cycle Ui based on the number of uplink PHY frames N (step S31). Next, the second signal processing unit 13 sequentially adds the cycle length CL to the start time ut1 of the first common cycle U1 obtained from the notified synchronization information SYN, and manages the progress of each common cycle Ui (i=1,2...) (step S32).

[0086] Next, the second signal processing unit 13 determines the amount of transmission permission to allocate to the second ONU (ONU 40) such that the reception times b1 and b2 of the uplink frames from the second ONU (ONU 40) fall within the second period D2 which is for ITU-T (step S23). The start time of the second period D2 is determined, for example, by setting the first period D1 in the first half of the cycle as an allocation prohibition offset time. Therefore, in the second DBA, the reception times b1 and b2 of the uplink frames from the second ONU will not exceed the first period D1 which is for IEEE.

[0087] [Interrupt handling between signal processing units] As shown in Figure 5, the first signal processing unit 12 and the second signal processing unit 13 can send and receive predetermined control signals S3 to and from each other. These control signals S3 include, for example, a quiet window (hereinafter abbreviated as "QW") that temporarily suppresses the other party's DBA.

[0088] QW may consist of the following data, for example: tqs: Start time of DBA suppression Dq: DBA suppression execution time Tp: Type of suppression cause in the second signal processing unit 13 (discovery or ITU-T ranging) By adopting the above QW (Quick Wave) method, it is possible to prevent the other party's uplink communication control from being disrupted by one's own discovery or ranging.

[0089] For example, the first signal processing unit 12, which plans to perform discovery regarding the first ONU, notifies the second signal processing unit 13 of QW. Similarly, the second signal processing unit 13, which plans to perform discovery regarding the second ONU, notifies the first signal processing unit 12 of Tp=Discovery QW. Furthermore, the second signal processing unit 13, which plans to perform ranging for the second ONU, notifies the first signal processing unit 12 of the QW for ranging for Tp=ITU-T.

[0090] However, if discovery or ranging falls within the first period D1 or the second period D2, interrupt handling by QW is not necessary. Therefore, notification of QW should be performed when the first and second signal processing units 12 and 13 perform discovery or ranging beyond the first period D1 or the second period D2.

[0091] If the execution time Dq for DBA suppression requested by the first and second signal processing units 12 and 13 from the other party overlap, the following priority control should be performed. Priority control 1: If Tp is ranging, the QW of that ranging will take priority. Priority control 2: If Tp is discovery, the QW with the earlier start time tqs, the shorter execution time Dq, or the higher transmission speed will be given priority.

[0092] Alternatively, the execution periods for discovery performed by the first and second signal processing units 12 and 13 may be set in advance, and each unit may remember the other's execution period. In this case, by setting the discovery window intervals appropriately, excessive delays in the communication service can be avoided. However, even in this case, notification of the ranging QW by the second signal processing unit 13 is necessary. This is because in ITU-T-based PON systems, ranging must be performed separately from discovery.

[0093] [Other variations] The embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments described above, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0094] In the above-described embodiment, the time length of the second period D2 may be notified to the first and second signal processing units 12 and 13. In this case, the first signal processing unit 12 only needs to determine that the notified time length of the second period D2 is the offset time for which allocation is prohibited. In the above embodiment, the first signal processing unit 12 may be notified of the time length of the first period D1, and the second signal processing unit 13 may be notified of the time length of the second period D2. In this case, each signal processing unit 12 and 13 only needs to determine that the notified time lengths of periods D1 and D2 are the time during which the reception of uplink frames is permitted.

[0095] In the embodiments described above, the first ONU may be one of either a GE-PON ONU (ONU20) or a 10G-EPON ONU (ONU40). In the embodiments described above, the second ONU may be an XGS (10(X)G Symmetric)-PON ONU, an HSP (Higher Speed ​​PON) ONU, or a combination of at least two of the three types of ONUs described above, rather than a 25GS-PON ONU (ONU40).

[0096] In the embodiments described above, the PON system 100 is not limited to a multi-rate PON system. Specifically, for example, a 10G-EPON ONU (ONU40) may be used as the first ONU and an XGS-PON ONU may be used as the second ONU, so that the transmission speeds of the first ONU and the second ONU are equivalent.

[0097] In the above-described embodiment, the ODN 50 may be a circuit configuration in which, for example, a ROADM (Reconfigurable Optical Add / Drop Multiplexer) network, which is a type of core network, is interposed in the middle of the trunk fiber 51. In this case, different paths may be set within the ROADM network for the wavelength of the optical signal used in the PON system 100. [Explanation of symbols]

[0098] 10 OLT 11 Optical transceiver 11T Transmitter 11R Receiver 12 First Signal Processing Unit 13. Second Signal Processing Unit 14 DBA Collaboration Department 15 Switch section 16 Management and Control Unit 17 Management device 20 GE-PON ONU (IEEE_ONU, 1st ONU) 30 10G-EPON ONU (IEEE_ONU, 1st ONU) 40 25GS-PON ONU (ITU-T_ONU, 2nd ONU) 50 ODN 51 Trunk Fiber 52 Optical Splitter 53 Branch fiber 100 PON System

Claims

1. An OLT connected to multiple ONUs via a P2MP-type ODN, The first signal processing unit executes the first DBA described below, The second signal processing unit executes the second DBA described below, An OLT comprising a DBA linkage unit that executes a process on the first and second signal processing units to prevent the first period and the second period described below from overlapping. First DBA: A DBA targeting the first ONU, which is an ONU of an IEEE-based PON. Second DBA: A DBA targeting the second ONU, which is the ONU of the ITU-T system PON. Period 1: Uplink reception period for IEEE permitted in the first DBA Second period: Upstream reception period for ITU-T permitted in the second DBA

2. The aforementioned process to prevent duplication is: The OLT according to claim 1, comprising notifying the first and second signal processing units of the following first, second, and third parameters. Parameter 1: Information equivalent to the cycle length of the common cycle. Second parameter: Synchronization information for the common cycle Third parameter: The length of the first or second period within the common cycle.

3. The first parameter is, The OLT according to claim 2, which is a natural number multiplied by the time length of the up PHY frame for ITU-T.

4. The second parameter mentioned above is, The OLT according to claim 3, which is the start time of the first common cycle synchronized with the start time of the uplink PHY frame.

5. The second parameter mentioned above is, The OLT according to claim 3, which is a reset signal that is released in synchronization with the start time of the uplink PHY frame.

6. The second parameter notified to the second signal processing unit is: The OLT according to claim 3, including a number of delayed cycles from the boundary of a downlink PHY frame to the start of the first common cycle.

7. The third parameter mentioned above is, The OLT according to claim 3, calculated based on the contracted bandwidth and uplink speed of the first ONU and the contracted bandwidth and uplink speed of the second ONU.

8. The first signal processing unit is: The OLT according to any one of claims 1 to 7, which determines a transmission start time and transmission time to be permitted to the first ONU such that the reception time of the uplink frame from the first ONU falls within the first period.

9. The second signal processing unit is: The OLT according to any one of claims 1 to 7, which determines the amount of transmission permission to allocate to the second ONU such that the reception time of the uplink frames from the second ONU falls within the second period.

10. The first and second signal processing units are: The OLT according to any one of claims 1 to 7, which is capable of sending and receiving control signals to temporarily suppress the other party's DBA.

11. The first and second signal processing units are: The OLT according to claim 10, which determines which DBA suppression to prioritize if the execution times of DBA suppression requested by each party from the other party overlap, according to at least one of the following: the type of suppression cause, the length of execution time, and the length of transmission speed.

12. A bandwidth allocation method performed in an OLT connected to multiple ONUs via a P2MP configuration ODN, The first period and the second period below are processed to avoid overlap, The steps include performing the following first DBA so that the reception time of the uplink frame from the following first ONU falls within the first period, A bandwidth allocation method comprising the step of performing the second DBA described below so that the reception time of the uplink frame from the second ONU described below falls within the second period. First DBA: A DBA targeting the first ONU, which is an ONU of an IEEE-based PON. Second DBA: A DBA targeting the second ONU, which is the ONU of the ITU-T system PON. Period 1: Uplink reception period for IEEE permitted in the first DBA Second period: Upstream reception period for ITU-T permitted in the second DBA

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