JP5661665B2 - Branched optical access system and method - Google Patents

Description

  The present invention relates to a passive optical network (PON) in which a terminal device (OLT) on an office side and an optical network unit (ONU) on a user side are connected using an optical fiber and an optical splitter. : Passive Optical Network) In a system, the present invention relates to a branching optical access system and method for reducing delay when packetizing and transmitting a TDM signal in an ONU and further improving the efficiency of signal accommodation in a frame.

FIG. 10 shows a configuration example of the PON system.
In FIG. 10, the PON system has a configuration in which an OLT on the station side and a plurality of ONUs on the user side are connected via an optical fiber and an optical splitter.
The ONU includes a TDM-IF connected to the TDM terminal on the UNI side and an Ethernet (registered trademark) -IF connected to the data communication terminal, and a PON-IF connected to the OLT side PON-IF on the OLT side. TDM-IF, Ethernet-IF and PON-IF are connected via L2SW. L2SW transfers signals from TDM-IF and Ethernet-IF to PON-IF, and transfers signals from PON-IF to TDM-IF or Ethernet-IF.

  The OLT includes a TDM-IF connected to the circuit switching network on the NNI side and an Ethernet-IF connected to the packet switching network, and a PON-IF connected to the ONU side PON-IF on the ONU side. TDM-IF, Ethernet-IF and PON-IF are connected via L2SW. The L2SW transfers signals from the TDM-IF and Ethernet-IF to the destination PON-IF, and transfers the signal from the PON-IF to the TDM-IF or Ethernet-IF.

  A dynamic bandwidth allocation method for allocating bandwidth to each ONU according to the transmission frame amount of each ONU and a bandwidth allocation algorithm (DBA: Dynamic Bandwidth Allocation) between the ONU PON-IF and the OLT PON-IF (non-patent document) 1) Or, based on a fixed band allocation method (Non-patent Document 2) that allocates a fixed band to each ONU, the TDM signal and the Ethernet signal are each time-division multiplexed and transmitted in a band (time slot) allocated to each ONU. The

FIG. 11 shows a bandwidth allocation processing example of the dynamic bandwidth allocation method.
In FIG. 11, the OLT and the ONU exchange the DISCOVERY GATE frame and the RESISTER REQUEST frame to perform RTT measurement and time synchronization. The OLT assigns a unique LLID to the ONU that responded the RESISTER REQUEST frame, and Notify ONU. Subsequently, the OLT transmits a GATE frame in which the transmission start time (GST: Grant Start Time) of the next frame is described to the ONU, and the ONU that has received it transmits a RESISTER ACK frame to the GST. Is received by the OLT, the link between the OLT and the ONU is established. This is the DISCOVERY process.

  The OLT that has established a link with the ONU transmits a GATE frame in which the transmission start time GST0 of the upstream frame of the ONU is described. When the ONU receives the GATE frame, it waits for transmission until the designated GST0, packetizes the upstream data and stores it in the buffer. Then, the frame amount accumulated from the OLT to the designated GST0 is calculated, and when the GST0 is reached, the accumulated frame amount is notified to the OLT with a REPORT frame. This period is a delay required for packetization (“CES delay” described below).

  The OLT calculates the bandwidth (transmission start time GST1 and transmission permission amount GL) to be allocated to the ONU according to the DBA based on the accumulated frame amount notified by the REPORT frame from the ONU and the bandwidth used by other ONUs. Notify ONU with GATE frame. This period is a “DBA delay” required for bandwidth allocation. The ONU transmits the uplink frame accumulated based on the transmission start time GST1 specified in the GATE frame and the transmission permission amount GL. This period is a “buffer delay” required from bandwidth allocation to transmission of an upstream frame. At this time, a REPORT frame notifying the amount of accumulated frames after the transmission of the previous REPORT frame is transmitted to the OLT, and the next bandwidth allocation is requested.

FIG. 12 shows an example of bandwidth allocation processing in the fixed bandwidth allocation method.
In FIG. 12, each ONU is assigned a fixed time slot having a period of 125 μsec, and transmission is possible for each time slot. That is, the maximum delay due to transmission waiting in each ONU is 125 μsec.

IEEE802.3ah-2004 ITU-T G.984.3, “Gigabit-capable passive optical networks (GPON): Transmission convergence layer specification” RFC 5086, “Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)”

  In recent years, a technique for packetizing a TDM signal (CES: Circuit Emulation Service, Non-Patent Document 3) has been standardized and has begun to be adopted in a system employing a TDM system such as an STM (Synchronous Transfer Mode) dedicated line. However, compared to the TDM system, the CES system increases the delay by the CES conversion period (125 μsec to 8 msec) required for packetization, and delay fluctuation peculiar to packet transmission occurs. This is a problem in the case where the demand for low delay such as a dedicated line (eg, 10 msec or less for an end-to-end line) is used in a severe service.

  Therefore, when the dynamic band allocation method is applied to a PON system that transmits a TDM signal by converting it to CES, delays other than the CES delay must be reduced as much as possible. However, in general, a dynamic bandwidth allocation method in which a DBA delay of about 1 msec at the time of bandwidth allocation control or a buffer delay that cannot be transmitted until the transmission start time notified by the bandwidth allocation is reduced to a low delay like a dedicated line. Use for demanding services may be difficult.

  On the other hand, the fixed bandwidth allocation method is a method of allocating an upstream bandwidth in a fixed manner regardless of the presence or absence of upstream traffic, and repeatedly gives an upstream transmission opportunity to the ONU at a constant period. However, there are various CES conversion cycles for packetizing TDM signals, and in the case of 1 msec, which is longer than the fixed bandwidth of 125 μsec assigned, for example, the bandwidth is assigned as shown in ONU 1 shown in FIG. It is transmitted at a rate of once every eight time slots. That is, an unused time slot is generated, and the signal accommodation efficiency in the frame is lowered.

  The present invention suppresses an increase in delay due to DBA delay and buffer delay of a dynamic band allocation method in a PON system that transmits a TDM signal such as a dedicated line, which is required to reduce delay, in a CES, and further, a fixed band allocation method The present invention relates to a branching optical access system and method capable of improving a decrease in signal accommodation efficiency in a frame included in.

  According to a first aspect of the present invention, a plurality of terminal devices that convert a TDM signal into a packet signal at a CES period corresponding to each service type, and time slots that transmit packet signals to the plurality of terminal devices are assigned, In a branch optical access system including a terminal device that performs multiplexed transmission of packet signals with a terminal device, the terminal device transmits a packet signal at a period corresponding to the CES conversion period of the terminal device When a terminal device having a different CES cycle is allocated, adjacent time slots are allocated to the terminal device having the same CES cycle, and if there is a vacancy in a time slot shifted by the minimum CES cycle, Means for allocating, allocating adjacent time slots if there is no free space, and allowing transmission from the terminating device; End apparatus comprising means for transmitting at converts the TDM signal in the packet signal in synchronization with the cycle of the transmission permission is notified from the terminal device, the allocated time slot.

  According to a second aspect of the present invention, a plurality of terminal devices that convert a TDM signal into a packet signal with a CES conversion period corresponding to each service type, and a time slot that transmits the packet signal to the plurality of terminal devices, respectively, In a branch optical access system including a terminal device that performs multiplexed transmission of packet signals with a terminal device, the terminal device transmits a packet signal at a period corresponding to the CES conversion period of the terminal device When a terminal device having a different CES cycle is allocated, adjacent time slots are allocated to the terminal device having the same CES cycle, and if there is a vacancy in a time slot shifted by the minimum CES cycle, Means for allocating, allocating adjacent time slots if there is no free space, and allowing transmission from the terminating device; End device, in synchronization with the reference to the time slot assigned from the terminal equipment to the CES of cycle converts the TDM signal in the packet signal, comprising means for transmitting a synchronous time slot on the CES of cycle

  In the branch optical access system of the first or second invention, the terminal station device transmits a packet signal in a dynamic band whose band changes in addition to a terminal device that transmits a fixed-band packet signal converted from a TDM signal. When a terminating device to be connected is connected, a packet signal in the dynamic band is assigned to an empty time slot that is not assigned to another terminating device.

Further, the terminal device is already assigned when a time slot for transmitting a packet signal of a dynamic band is already allocated, and when a terminal device for transmitting a packet signal of a fixed band or a packet of a dynamic band is connected. In this configuration, a part of a time slot for transmitting a packet signal in a dynamic band is released and assigned to the packet signal.

  According to a third aspect of the present invention, a plurality of terminal devices each convert a TDM signal into a packet signal at a CES conversion period corresponding to a service type, and each time slot for transmitting a packet signal from a terminal device to a plurality of terminal devices is provided. In the branching optical access method in which packet signals are multiplexed and transmitted to and from a plurality of terminal devices, the terminal device assigns a time slot for transmitting a packet signal in a cycle corresponding to the CES conversion cycle of the terminal device. In addition, an adjacent time slot is assigned to a terminal device having a different CES conversion period, and a terminal device having the same CES conversion period is assigned to the corresponding time slot if there is an empty time slot shifted by the minimum CES conversion period. If there is not, the adjacent time slot is allocated and transmission from the terminating device is permitted. It converts the TDM signal in the packet signal in synchronization with the cycle of transmission permission to be known, to transmit at the assigned time slot.

  According to a fourth aspect of the present invention, there are provided time slots for converting a TDM signal into a packet signal at a CES conversion period corresponding to a service type at each of a plurality of terminal devices and transmitting the packet signal from the terminal station device to the plurality of terminal devices. In the branching optical access method in which packet signals are multiplexed and transmitted to and from a plurality of terminal devices, the terminal device assigns a time slot for transmitting a packet signal in a cycle corresponding to the CES conversion cycle of the terminal device. In addition, an adjacent time slot is assigned to a terminal device having a different CES conversion period, and a terminal device having the same CES conversion period is assigned to the corresponding time slot if there is an empty time slot shifted by the minimum CES conversion period. If there is not, the adjacent time slot is allocated and transmission from the terminating device is permitted. Ri against was time slot based on in synchronization with the CES of cycle converts the TDM signal in the packet signal, transmits a time slot synchronized with the CES of the period.

  In the branching optical access method of the third or fourth invention, the terminal station device transmits a packet signal of a dynamic band whose band changes in addition to a terminal device that transmits a fixed-band packet signal obtained by converting a TDM signal. When a terminating device to be connected is connected, a packet signal in the dynamic band is assigned to an empty time slot that is not assigned to another terminating device.

Further, the terminal device is already assigned when a time slot for transmitting a packet signal of a dynamic band is already allocated, and when a terminal device for transmitting a packet signal of a fixed band or a packet of a dynamic band is connected. A part of the time slot for transmitting the packet signal in the dynamic band is released and assigned to the packet signal.

  According to the present invention, ONU packet signals having different CES conversion periods are assigned to adjacent time slots, and ONU packet signals having the same CES conversion period are assigned to empty time slots or adjacent time slots shifted by the minimum CES conversion period. Thus, the packet signal of each ONU is multiplexed and accommodated. As a result, it is possible to improve a decrease in signal accommodation efficiency in a frame due to a mismatch between an allocated band and a CES conversion period that the conventional fixed band allocation scheme has.

  Also, when accommodating a dynamic band packet signal, an empty time slot is allocated, or a time slot allocated to an existing dynamic band packet signal is shared, so that the packet signal is transferred from the terminal device to the terminal station. Transfer to the device without delay.

It is a figure which shows the example of a bandwidth allocation process in the branch optical access system of this invention. It is a figure which shows the example of a bandwidth allocation process in the branch optical access system of this invention. It is a figure which shows the band allocation example 1 in the case of only a TDM line. It is a figure which shows the band allocation example 2 in case a TDM line and an Ether line coexist. It is a figure which shows the band allocation example 3 in case a TDM line and an Ether line coexist. It is a figure which shows the structural example of PON-IF of ONU and OLT in this invention. It is a figure which shows the example of DB with which PON-IF of OLT is provided. 5 is a flowchart illustrating an example of a bandwidth allocation processing procedure in a bandwidth allocation processing unit 26. It is a flowchart which shows the example of a calculation process sequence of CES conversion start time of ONU. It is a figure which shows the structural example of a PON system. It is a figure which shows the example of a bandwidth allocation process of a dynamic bandwidth allocation system. It is a figure which shows the example of a bandwidth allocation process of a fixed bandwidth allocation system.

FIG. 1 shows an example of bandwidth allocation processing in the branch optical access system of the present invention.
In FIG. 1, the OLT and the ONU establish a link by synchronizing time with a DISCOVERY process. The OLT refers to the database in the OLT based on the MAC address of the ONU that established the link, and the bandwidth such as the CES conversion cycle of the client signal and the service type (TDM system (LD / DA / HSD) or Ethernet system) in the ONU Get information for allocation. Further, when the service type of the ONU is a TDM system, the OLT transmits a transmission start time (GST: Grant Start Time) and a transmission permission amount (GL) that minimize the time buffered in the ONU according to the CES conversion period. : Grant Length). Here, GST1 is determined for a time slot that does not overlap with a time slot used by another ONU, and the CES conversion period and transmission permission including GST1 and GL are notified to the ONU.

  The ONU performs CES when the arriving client signal is a TDM signal. At this time, the CES conversion start time is determined by back-calculating the CES conversion period from the GST notified from the OLT, and the CDM conversion of the TDM signal is started. As a result, the CES completion time and GST are synchronized so that the buffer delay in the ONU is minimized, and the CES signal is transmitted upon completion of the CES. Thus, unlike the conventional dynamic bandwidth allocation method, the bandwidth allocation in the present invention does not cause a DBA delay unlike the OLT that performs bandwidth allocation upon receiving a notification of the amount of accumulated frames from the ONU. Delay is also minimized.

  The OLT sequentially updates GST2, GST3,... Shifted by the CES conversion period, and repeatedly notifies the ONU with the same transmission permission period as the CES conversion period. Accordingly, the ONU can repeatedly transmit a signal obtained by converting the TDM signal into a CES at a CES conversion period without performing dynamic band allocation control. Also for a plurality of ONUs connected to the OLT, as shown in FIG. 2, the CES conversion cycle and the transmission permission cycle of each ONU are synchronized, and a CES signal is transmitted from each ONU upon completion of CES conversion. When each ONU corresponds to a plurality of CES conversion cycles, the TDM signal is converted to CES at the CES conversion cycle notified from the OLT.

  It should be noted that the OLT does not repeatedly notify the ONU of transmission permission in the same cycle as the CES cycle, but instead, based on the CES cycle, GST, and GL first notified by the ONU, and then the CES cycle in the device clock And the next GST may be updated autonomously, and a signal obtained by converting the TDM signal into CES may be repeatedly transmitted to the OLT at a CES conversion period.

  As described above, the bandwidth allocation control in the present invention is close to the conventional fixed bandwidth allocation control because the transmission permission cycle is fixed, but since it is a transmission permission cycle according to the CES conversion cycle, the conventional fixed bandwidth allocation It is possible to improve a decrease in signal accommodation efficiency in a frame due to a mismatch between an allocated band and a CES conversion period that the method has. As shown in FIG. 2, this is made possible by assigning time slots that do not overlap with time slots used in other ONUs when performing bandwidth assignment according to the CES conversion cycle of each ONU. Hereinafter, a specific description will be given with reference to FIGS.

  In the present invention, it is assumed that both a packet signal having a fixed band obtained by converting a TDM signal into a CES at a constant period and a packet signal having a dynamic band in which traffic changes in a burst manner, such as an Ethernet signal, are handled. . Each ONU time-synchronized with the OLT transmits these client signals accommodated in the ONU in a band (GST, GL) allocated to the OLT. Here, the minimum unit of the bandwidth allocated to each ONU is defined as “time slot (TS)”. In the present embodiment, it is assumed that the size of each TS is fixed and about 12.5 μs necessary for transmitting a 1500-byte packet at 1 Gbps.

(Bandwidth allocation example 1)
FIG. 3 shows a band allocation example 1 in the case of only a TDM line. Here, a case is considered where a TDM line having CES conversion periods of 500 μs, 1 ms, and 2 ms is accommodated. Note that the CES cycle 500 μs is four times the specified minimum CES cycle 125 μs, and is the minimum CES cycle of this embodiment. It is assumed that ONU 1 having a CES conversion period of 500 μs is registered first, and added in the order of ONU 2, ONU 3 and ONU 4 having a CES conversion period of 1 ms, and ONU 5 having a CES conversion period of 2 ms. The procedure at this time is shown below.

(1) The ONU 1 is assigned to the first TS in the transmission permission period, and the TS is assigned every 500 μs of the ONU 1 CES conversion period. Here, GST is updated in the order of 0, 500 μs, 1000 μs,.
(2) When the ONU 2 is added, since it is different from the CES conversion cycle of the ONU 1 already accommodated, the TS of the ONU 2 is allocated to the TS adjacent to the TS allocated to the ONU 1 every 1 CES conversion cycle. Here, GST is updated in the order of 12.5 μs, 1012.5 μs, 2012.5 μs,.
(3) When the ONU 3 is added, since it is the same as the CES conversion period 1 ms of the already accommodated ONU 2, the TS of the ONU 3 is allocated with a shift from the GST of the ONU 2 by the minimum CES conversion period (500 μs). Here, GST is updated in the order of 512.5 μs, 1512.5 μs,.
(4) When ONU4 is added, it is the same as the CES conversion cycle 1ms of ONU2 and ONU3 that are already accommodated. There is no empty TS. In this case, for example, the TS of the ONU 4 is allocated to the TS adjacent to the TS allocated to the ONU 2 every CES conversion period 1 ms. Here, GST is updated in the order of 25 μs, 1025 μs, 2025 μs,.
(5) When adding ONU5, it is different from the CES conversion period of ONU1 to ONU4 already accommodated, so for example, assign TS of ONU5 to TS adjacent to TS allocated to ONU3 every CES conversion period . Here, GST is updated in the order of 525 μs, 2525 μs,.

  As described above, ONU client signals having different CES conversion periods are allocated to adjacent TSs, and ONU client signals having the same CES conversion period are allocated to the corresponding TS if the TS shifted by the minimum CES conversion period is an empty TS. Or, if the TS is not an empty TS, assigning it to an adjacent TS improves the reduction in the signal accommodation efficiency in the frame due to the mismatch between the allocated bandwidth and the CES cycle that the conventional fixed bandwidth allocation scheme has Can do.

  In addition, the CES conversion period and line / bandwidth management information such as GST and GL are managed in the OLT database, and are referred to later when a line is added.

(Bandwidth allocation example 2)
FIG. 4 shows a bandwidth allocation example 2 in the case where a TDM line and an Ethernet line coexist. Here, it is assumed that Ethernet ONU 6 is added to ONU 1 to ONU 5 similar to bandwidth allocation example 1 in FIG.

  Since Ethernet services may have a broadband service menu, many TSs may be used. A plurality of TSs can be continuously assigned to the ONU 6 according to the required bandwidth. At this time, if an uplink band is allocated by dividing each TS, transmission efficiency is reduced due to guard time, and therefore transmission permission is continuously given.

  In addition, since the generation of traffic is irregular in the Ethernet service, there is a concern that the buffer delay in the ONU may increase, but there is no delay when a free bandwidth that is not allocated to another ONU is allocated and a client signal arrives at the ONU. Transfer to OLT is possible. However, TS is regularly arranged for users who are sensitive to delay fluctuation. In addition, when the bandwidth is limited in the relay network, packet discarding does not occur, such as providing the same amount of bandwidth as the bandwidth secured in the relay network even in the access section, or restricting upstream transfer in the ONU. Measures shall be taken.

(Bandwidth allocation example 3)
FIG. 5 shows a bandwidth allocation example 3 in the case where a TDM line and an Ethernet line coexist. Here, it is assumed that an Ethernet ONU 7 is added to ONU 1 to ONU 6 similar to the bandwidth allocation example 2 in FIG.

  When a TDM system service is added, a part of the TS previously occupied by the Ethernet system service is released and allocated by the same method as the bandwidth allocation example 1 in FIG.

  On the other hand, when an Ethernet system service is added, a bandwidth is alternately allocated to the ONU 6 and the ONU 7 in order to reduce the buffer delay of packets that arrive in burst. At this time, the TS arrangement that satisfies the quality regulations such as SLA of the Ethernet system service is adopted.

  As described above, when a new line is added, the occupied band is temporarily released within a range satisfying the contracted band and the delay quality regulations, and additional lines can be accommodated.

(Configuration example of ONU and OLT PON-IF)
FIG. 6 shows a configuration example of the ONU and OLT PON-IF in the present invention. Here, the PON-IF of the ONU and OLT in the PON system shown in FIG. 10 is extracted and shown.

  In FIG. 6, the PON-IF on the ONU side includes a TDM line terminator 11 and an Ether line terminator 12 corresponding to main signal frames in downstream (NNI to UNI) and upstream (UNI to NNI) communications. Prepare. The main signal frame terminated at the TDM line termination unit 11 is subjected to CES processing at the CES conversion cycle specified by the OLT by the CES processing unit 13. The CES-converted main signal frame output from the Ether line termination unit 12 and the CES processing unit 13 is stored in the frame holding unit 14 and transmitted from the frame transmitting unit 15 to the OLT without delay with the GST designated by the OLT. . The ONU in-device time is synchronized with the OLT, and the frame can be accurately transmitted to the GST instructed by the transmission instructing unit 16 from the OLT.

  The main signal frame and the control signal frame (frames for transmitting the CES period, GST and GL) transmitted from the OLT are received by the frame receiving unit 17 and then stored in the frame holding unit 14. The control signal frame is processed by the control signal generation / processing unit 18 to control the CES processing unit 13 and the transmission instruction unit 16. The TDM main signal frame is converted from a packet signal into a TDM signal by the CES processing unit 13 and transferred from the TDM line termination unit 11 to the user terminal. The Ether main signal frame is transferred from the Ether line termination unit 12 to the user terminal.

  In the PON-IF on the OLT side, the main signal frame and the control signal frame received from the PON-IF on the ONU side are stored in the frame holding unit 22 via the frame receiving unit 21. The main signal frame is output to the L2SW via the frame processing unit 23.

  The control signal frame from the ONU is processed by the control signal generation / processing unit 25, and information necessary for the band allocation processing such as the ONU MAC address and time information is stored in the line information storage unit 27 of the DB via the band allocation processing unit 26. Remembered. The bandwidth allocation processing unit 26 searches for available TSs from the bandwidth management information storage unit 28 of the DB, and determines the CES conversion period, allocated bandwidth (GST, GL), and TS arrangement according to the service type. The control signal frame output from the control signal generation / processing unit 25 and the main signal frame input from the L2SW via the frame processing unit 23 are transmitted from the frame transmission unit 24 to the ONU via the frame holding unit 22.

  An example of the line information storage unit 27 is shown in FIG. The LLID, MAC address, service type, contract bandwidth, and CES conversion period corresponding to the ONU are set. An example of the bandwidth management information storage unit 28 is shown in FIG. LLID, RTT, GL, number of used TSs, and GST corresponding to the ONU are set.

FIG. 8 shows an example of a bandwidth allocation processing procedure in the bandwidth allocation processing unit 26 of the OLT.
In FIG. 8, the bandwidth allocation processing unit 26 reads line information such as service type, CES period, and contracted bandwidth from the line information storage unit 27 based on the MAC address of the ONU that has established a link through the DISCOVERY process (S1). Based on these line information, the required number of TS is calculated (S2), and the available TS is searched from the bandwidth management information storage unit 28 (S3).

  The presence / absence of an existing line is determined (S4), and if there is no existing line, an arbitrary TS is assigned (S5). This corresponds to the TS allocated to the ONU 1 in the bandwidth allocation example 1 of FIG. On the other hand, if there is an existing line, TS is allocated according to the service type of the existing line (S6).

  Here, if the existing line is only a TDM line, the service type of the additional line is determined (S7), and if the additional line is an Ether line, free TSs are continuously allocated (S8). This corresponds to the TS allocated to the ONU 6 in the bandwidth allocation example 2 of FIG.

  If the existing line is only a TDM line and the additional line is a TDM line, it is checked whether the CES conversion period is the same as that of the existing line (S9). When a TDM line having a CES conversion period different from that of an existing line is added, TSs before and after the TS assigned to the existing line are assigned (S10). In the bandwidth allocation example 1 in FIG. 3, this corresponds to the TS allocated to the ONU 2 and ONU 4.

  If the existing line is only a TDM line and the additional line is a TDM line and the CES conversion period is the same as that of the existing line, the minimum CES among the lines accommodated by the TS that accommodates the existing line is accommodated in the PON system. It is searched whether there is a vacancy in the TS shifted by the period (500 μs in the bandwidth allocation example 1 in FIG. 3) (S11). The search for the empty TS is performed over the maximum CES period (2 ms) while shifting by the minimum CES period. If there is a vacancy in the TS shifted by the minimum CES cycle, a TS shifted by the minimum CES cycle is assigned to the existing line having the same CES cycle from the assigned TS (S12). In the bandwidth allocation example 1 in FIG. 3, this corresponds to the TS allocated to the ONU 3 and ONU 5. On the other hand, if there is no vacancy in the TS shifted by the minimum CES cycle, TSs before and after the TS assigned to the existing line are assigned (S10).

  If the existing line is a TDM line and an Ether line, the service type of the additional line is determined (S13). If the additional line is an Ether line, a part of the TS occupied by the existing Ether line is released and the existing line is opened. TS is alternately allocated to the Ether line (S14). This corresponds to a TS assigned to the ONU 7 in the bandwidth allocation example 3 in FIG. If the existing line is a TDM line and an Ether line and the additional line is a TDM line, a part of the TS occupied by the existing Ether line is released (S15), and the processes after Step S9 are performed.

  If the existing line is only an Ether line, the service type of the additional line is determined (S16). If the additional line is an Ether line, a part of the TS occupied by the existing Ether line is released, and the existing Ether line is released. TS is allocated alternately with the line (S17). If the existing line is only an Ether line and the additional line is a TDM line, a part of the TS occupied by the existing Ether line is released and allocated (S18).

  In the above processing, the part of the Ether line TS is released only when the contracted bandwidth and quality regulations are not impaired.

  When TS allocation in steps S5, S8, S10, S12, S14, and S17 is completed, the GST and GL of the ONU are calculated from the TS allocated to the additional line (S19), and the bandwidth management information storage unit 28 is updated to update the bandwidth. End the allocation process. If the additional line is a TDM line, the ONU is notified of the CES cycle, GST, and GL. If the additional line is an Ether line, the ONU is notified of the GST and GL.

FIG. 9 shows an example of the processing procedure for calculating the ONU CES start time.
In FIG. 9, when the ONU is turned on and activated (S21), the Discovery process is executed to synchronize time with the OLT (S22). When the CES conversion period, GST, and GL are notified from the OLT (S23, S24), the ONU calculates the CES conversion start time by back calculating the CES conversion period from the GST (S25), and from the CES conversion start time The CES process is started (S26, S27). The packet generated by the CES process is transmitted to the OLT using the designated GST.

ONU terminator OLT Terminal station 11 TDM line terminator 12 Ether line terminator 13 CES conversion processing unit 14 Frame holding unit 15 Frame transmission unit 16 Transmission instruction unit 17 Frame reception unit 18 Control signal generation / processing unit 21 Frame reception unit 22 Frame holding unit 23 Frame processing unit 24 Frame transmission unit 25 Control signal generation / processing unit 26 Band allocation processing unit 27 Line information storage unit 28 Band management information storage unit

Claims (8)

A plurality of terminating devices each converting a TDM signal into a packet signal at a CES conversion period according to the service type;
A branch optical access system comprising: a terminal device that assigns time slots for transmitting the packet signals to the plurality of terminal devices, and performs a multiplexed transmission of the packet signals with the plurality of terminal devices. ,
When the terminal station allocates time slots for transmitting the packet signal at a period corresponding to the CES conversion period of the terminal apparatus, the terminal apparatus allocates adjacent time slots to terminal apparatuses having different CES conversion periods, and the same CES A terminating device having a conversion period is assigned to the time slot if the time slot shifted by the minimum CES period is empty; if there is no empty time slot, an adjacent time slot is assigned, and means for permitting transmission from the terminal device is provided. Prepared,
The terminating device includes means for converting the TDM signal into a packet signal in synchronization with a transmission permission period notified from the terminal device, and transmitting the packet signal in an assigned time slot. Access system. A plurality of terminating devices each converting a TDM signal into a packet signal at a CES conversion period according to the service type;
A branch optical access system comprising: a terminal device that assigns time slots for transmitting the packet signals to the plurality of terminal devices, and performs a multiplexed transmission of the packet signals with the plurality of terminal devices. ,
When the terminal station allocates time slots for transmitting the packet signal at a period corresponding to the CES conversion period of the terminal apparatus, the terminal apparatus allocates adjacent time slots to terminal apparatuses having different CES conversion periods, and the same CES A terminating device having a conversion period is assigned to the time slot if the time slot shifted by the minimum CES period is empty; if there is no empty time slot, an adjacent time slot is assigned, and means for permitting transmission from the terminal device is provided. Prepared,
The termination device converts the TDM signal into a packet signal in synchronization with the CES conversion cycle based on the time slot assigned from the terminal device, and transmits the packet signal in a time slot synchronized with the CES conversion cycle. A branch optical access system characterized by comprising: The branching optical access system according to claim 1 or 2,
When the terminal device that transmits a packet signal of a dynamic band whose band changes is connected to the terminal device that transmits a fixed-band packet signal obtained by converting the TDM signal, the terminal device is connected to the terminal device. A branching optical access system characterized in that a packet signal in a specific band is assigned to an empty time slot that is not assigned to another terminal device. The branched optical access system according to claim 3,
When the terminal station is already assigned a time slot for transmitting the packet signal of the dynamic band and is further connected to a terminal device for transmitting the packet signal of the fixed band or the packet signal of the dynamic band, A branching optical access system characterized in that a part of a time slot for transmitting a packet signal of the dynamic band already allocated is released and allocated to the packet signal . A plurality of terminal devices each convert a TDM signal into a packet signal at a CES conversion period corresponding to a service type, and assign a time slot for transmitting the packet signal from a terminal device to the plurality of terminal devices. In a branch optical access method for performing multiplexed transmission of the packet signal with a terminal device of
When the terminal station allocates time slots for transmitting the packet signal at a period corresponding to the CES conversion period of the terminal apparatus, the terminal apparatus allocates adjacent time slots to terminal apparatuses having different CES conversion periods, and the same CES If there is a vacant time slot shifted by the minimum CES period in a terminal device having a conversion period, the time slot is assigned to the time slot, and if there is no space, an adjacent time slot is assigned, and transmission from the terminal device is permitted,
The branched optical access method, wherein the terminating device converts the TDM signal into a packet signal in synchronization with a transmission permission period notified from the terminal device, and transmits the packet signal in an assigned time slot. A plurality of terminal devices each convert a TDM signal into a packet signal at a CES conversion period corresponding to a service type, and assign a time slot for transmitting the packet signal from a terminal device to the plurality of terminal devices. In a branch optical access method for performing multiplexed transmission of the packet signal with a terminal device of
When the terminal station allocates time slots for transmitting the packet signal at a period corresponding to the CES conversion period of the terminal apparatus, the terminal apparatus allocates adjacent time slots to terminal apparatuses having different CES conversion periods, and the same CES If there is a vacant time slot shifted by the minimum CES period in a terminal device having a conversion period, the time slot is assigned to the time slot, and if there is no space, an adjacent time slot is assigned, and transmission from the terminal device is permitted,
The terminating device converts the TDM signal into a packet signal in synchronization with the CES period based on the time slot allocated from the terminal station device, and transmits the packet signal in a time slot synchronized with the CES period. A branching optical access method characterized by the above. The branching optical access method according to claim 5 or 6,
When the terminal device that transmits a packet signal of a dynamic band whose band changes is connected to the terminal device that transmits a fixed-band packet signal obtained by converting the TDM signal, the terminal device is connected to the terminal device. A branching optical access method characterized by allocating a packet signal of a specific bandwidth to an empty time slot not assigned to another terminal device. The branched optical access method according to claim 7,
When the terminal station is already assigned a time slot for transmitting the packet signal of the dynamic band and is further connected to a terminal device for transmitting the packet signal of the fixed band or the packet signal of the dynamic band, A branching optical access method, wherein a part of a time slot for transmitting a packet signal of the dynamic band that has already been allocated is released and assigned to the packet signal .

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