KR20160092858A - channel synchronization method for the tuning control in TWDM-PON and apparatus thereof - Google Patents

Abstract

A channel synchronization method and apparatus for wavelength management in a TWDM-PON are disclosed. The optical line terminal in the time and wavelength division multiplexing passive optical network according to an embodiment of the present invention includes a main processor, a plurality of MAC chips each having a local processor, And a chip selector for providing a chip selection signal to each MAC chip using the received address value and causing the main processor to simultaneously access each MAC chip to transmit a synchronized PHY frame at each port through each MAC chip .

Description

[0001] The present invention relates to a channel synchronization method for wavelength management in a TWDM-PON,

The present invention relates to wavelength management in Time and Wavelength Division Multiplexing-PON (TWDM-PON) (hereinafter referred to as TWDM-PON), which is a standard technology of Next Generation-Passive Optical Network 2 (NG-PON2) To a technique for maintaining synchronization between channels.

Time and wavelength division multiplexing-passive optical network (TDM) technology is called Time Division Multiplexing (TDMA) Is a method of transmitting through a passive distribution network by combining wavelength division multiplexing (WDM) technology and providing a transmission bandwidth of 40 Gbps or more. That is, a TDMA technique that provides a transmission rate of 10 Gbps is multiplexed using WDM technology and transmitted. To this end, an optical network unit (ONU) uses a wavelength tunable technique capable of selecting one WDM wavelength in the multiplexed WDM wavelengths.

At present, TWDM-PON technology can use up to 8 WDM wavelengths and can transmit TDMA signals providing 10Gbps downstream and 2.5Gbps or 10Gbps upstream bandwidth per WDM wavelength. Accordingly, the TWDM-PON technique can provide a transmission bandwidth of up to 80 Gbps up / down.

TWDM-PON technology provides registration and transmission services of ONUs using 10Gbps TDMA (10 Gigabit-capable Passive Optical Network) based TC (Transmission Convergence) layer frame transmission technology. Therefore, they transmit PHY frames with a cycle of 125us, which are transmitted through the WDM wavelength.

The TWDM-PON technology uses a PLOAM message exchange scheme to select and control wavelengths for wavelength-tunable ONUs in an optical line terminal (OLT). In order to manage the wavelength, the OLT transmits a channel identifier included in the PHY frame header of 125us cycles transmitted for each WDM channel, and the ONU recognizes the channel identifier in the PHY frame of 125us cycle, . When ONU receives more than one WDM wavelength from OLT, it changes the wavelength until it recognizes the number for all WDM wavelengths. When the number recognition for the downstream WDM wavelength is completed, the ONU recognizes the number for the upstream WDM wavelength. To this end, when the ONU transmits a response message to a WDM wavelength, the OLT informs the ONU of the number of the upstream WDM wavelength transmitted the response message. The ONU repeats the above-described process until the number recognition for the uplink WDM channel is completed. The wavelength used by the ONU is determined by the OLT. The ONU can use the downstream and upstream WDM wavelengths as a pair, and can use them differently.

The TWDM-PON technology uses the Tuning_Control, US_WLCH_INFO, and Complete_d PLOAM messages downward to control the wavelength of the ONU, and uses the Serial_Number_ONU PLOAM message including the Tuning_Response and Calibration mode upward. Provides a wavelength change of ONUs through PLOAM message exchange. In addition, the TWDM-PON technology can selectively change wavelengths of ONUs during operation of the OLT in order to provide load balancing service and power saving service.

For wavelength management, TWDM-PON technology should provide PHY frame synchronization of 125us cycles between WDM channels, and when changing wavelength, two WDM channels should be controllable simultaneously.

1 is a block diagram of a general TWDM-PON link.

Referring to FIG. 1, a typical TWDM-PON system 1 includes an OLT 10 for transmitting signals with a plurality of WDM wavelengths, ONUs 12-1 and 12-2 for selecting one WDM wavelength, And a splitter 14 as a distribution network.

The TWDM-PON OLT 10 includes Media Access Controllers (MACs) 100-1, 100-2, ..., 100-n and PHYs 102-1, 102-2, ..., 102- -n). The MACs 100-1, 100-2, ..., 100-n convert Ethernet frames input through an SNI (Service Network Interface) port into XGEM (10 Gbps GPON Encapsulation Method) And is transmitted on the payload of the PHY frame of the period.

The PHYs 102-1, 102-2, ..., and 102-n used in the TWDM-PON OLT 10 transmit and receive different WDM wavelengths and are multiplexed or demultiplexed through the WDM MUX / DEMUX 104. The multiplexed WDM wavelengths are transmitted to the respective TWDM-PON ONUs 12-1 and 12-2 via the passive splitter 14, and the TWDM-PON ONUs 12-1 and 12-2 receive one And transmits the selected WDM wavelengths to the MACs 122-1 and 122-2. The TWDM-PON ONUs 12-1 and 12-2 are capable of receiving all of the WDM wavelengths (? 1,? 2, ...,? N) multiplexed through a wavelength tuning technique. Each of the TWDM-PON ONUs 12-1 and 12-2 includes one wavelength variable PHY 120-1 and 120-2 and one MAC 122-1 and 122-2. After finding the PHY frame of 125us cycles Extracts the XGEM frame included in the payload, converts it into an Ethernet frame, and transmits it to the subscriber terminal through a UNI (User Network Interface) port.

2 is a flowchart illustrating a general wavelength conversion process using a PLOAM message exchange scheme in a TWDM-PON.

Specifically, FIG. 2 shows an embodiment in which the ONU 1 20 in which the TWDM-PON OLT is registered in the OLT-port 1 21 is changed to the OLT-port 2 22. The wavelength change process is as follows.

- ONU1 (20) is registered in OLT-port1 (21) and is provided with services.

When the OLT-port1 21 wants to change the ONU1 20 to the OLT-port2 22, the OLT-port1 21 transmits a Tuning Control (Request) PLOAM message to the ONU 20 in order to change the wavelength (200). The Tuning_Control PLOAM message includes wavelength change start information (Start Count) and wavelength change information (Tune to lambda 2).

Upon receiving the Tuning Control PLOAM message, the ONU 1 20 determines whether or not the wavelength change information can be moved, and transmits the result to the OLT-port 1 21 in the Tuning_Response PLOAM message. The determination result may be indicated as ACK when the wavelength can be changed and NACK when the wavelength can not be changed. Then, the wavelength control is started based on the provided wavelength change start information (Tuning Start) (220).

When the OLT-port1 21 receives the Tuning_Response PLOAM message including the ACK, it notifies (230) the ACK to the OLT-port2 22 and simultaneously transmits the Tuning_Control (Confirm) PLOAM message and the PLOAMu grant To the ONU1 20 (240).

Upon completion of the wavelength tuning in the wavelength variable PHY, the ONU 1 20 can receive the PHY frame of 125us period of the OLT-port 2 (22), and can recognize the Tuning Control (Confirm) PLOAM message and PLOAMu grant (250). ONU1 20 transmits a Tuning_Response (Complete_u) PLOAM message to OLT-port2 22 at a time allocated to PLOAMu grant (260).

When the OLT-port2 22 receives the Tuning_Response (Complete_u) PLOAM message, it stops transmission of the Tunig_Control (Confirm) PLOAM message and the PLOAM grant, and assigns a Complete_d PLOAM message and a data grant for the uplink data transmission to the ONU1 20 (270).

The above-described wavelength changing process with reference to FIG. 2 is performed by the TWDM-PON OLT control during service operation. The TWDM-PON OLT shall be able to transmit the Tuning_Control (Confirm) PLOAM message and the PLOAMu grant at the same interval in the source port and the destination port in order to perform the wavelength change.

3 is a signal flow diagram illustrating a process of transmitting PHY frames of 125us cycles for different WDM channels in a general TWDM-PON.

In the TWDM-PON, data can be transmitted and received at different wavelengths in the downward direction and the upward direction. In order to discover a new ONU, a Quite Window (301, 302) with a 250 us interval is set periodically. The service transmission of the other ONUs is not performed in the set Quite Window sections 301 and 302. However, when the OLT-port1 21 and the OLT-port2 22 transmit PHY frames of 125us periods different from each other as shown in FIG. 3, if the quite windows 301 and 302 are set at different times, The ONU 1 20 attempting to register 310 receives the OLT-port 1 wavelength? 1 downward and transmits 320 the OLT-port 2 wavelength? 2 upward to respond to the registration request 320, , It disturbs the transmission of services of other ONUs out of the Quite Window range (301, 302) of the OLT-port2 (22). This action causes the ONU to act as if it were a Rouge ONU.

To solve this problem, in the TWDM-PON, a PHY frame of 125us cycles must be transmitted simultaneously on all WDM channels, and a quit window section for ONU registration must be set.

Therefore, in order to perform the wavelength management function between the OLT and the ONU in the TWDM-PON, the following operation must be performed.

- In the TWDM-PON OLT, all channels shall transmit PHY frames of 125us period with the same time period to each other.

- In order to register a new ONU in the TWDM-PON OLT, the Quite Window section must be set to all channels at the same time.

- When changing wavelength in TWDM-PON OLT, two ports should allocate PLOAM message and grant at the same time.

In order to provide these requirements, the TWDM-PON needs to be able to control and configure each WDM channel.

4 is a diagram illustrating a communication method between a general main processor and a local processor.

Referring to FIG. 4, the main CPU processor 40 distinguishes local CPU processors by using a bit in a chip select signal 400 and an address 410. For example, as shown in FIG. 4, a 2-bit address value is used to control the four local CPU processors 42-1, 42-2, 42-3, and 42-4. If the Chip Select signal is 0 and the Address value is 00, the local CPU processor 42-2 is assigned to the local CPU processor 42-2. If the Chip Select signal is 00, the local CPU processor 42-2 is assigned to the local CPU processor 42-2. 11, they are respectively connected to the local CPU processor 4 (42-4). Each of the local CPU processors 42-1, 42-2, 42-3, and 42-4 includes a read signal 420, a write signal 430, an address (Nx: 0) 440, a data bus M : 0) 450, and executes a command of the main CPU processor 40. That is, the main CPU processor 40 performs connection to each local CPU processor using one Chip Select signal 400 and x bit Address value 410. Thus, the main CPU processor 40 can only be connected to one local CPU processor at a time, and as shown in FIG. 4, the main CPU processor 40 includes four local CPU processors 42-1, 42-2, 4, 4, or 4). Accordingly, the conventional local CPU processor connection method can not perform WDM channel-to-channel synchronization and wavelength change in the TWDM-PON.

According to one embodiment, in order to provide effective wavelength management in the TWDM-PON, a main CPU processor is provided for each WDM channel so that PHY frame transmission, simultaneous quite window setting, and PLOAM grant can be simultaneously performed for each WDM channel A channel synchronization method for wavelength management in a TWDM-PON that simultaneously or selectively provides a chip select signal to a local CPU processor for each WDM channel by using a certain CPU address value for simultaneous connection to a local CPU processor, Lt; / RTI >

The OLT in the TWDM-PON according to an exemplary embodiment includes a main processor, a plurality of MAC chips each having a local processor, and a plurality of MAC chips, each receiving a chip selection signal and an address value from the main processor, And a chip selector for allowing the main processor to simultaneously connect to each MAC chip and transmit the synchronized PHY frame at each port through each MAC chip.

According to one embodiment, simultaneous access between MAC chips in a TWDM-PON is enabled, thereby enabling PHY frame transmission and quite-window setting of 125us cycles simultaneously in different MAC chips, thereby enabling effective wavelength management.

In particular, it enables simultaneous access from one main processor to a channel-specific local processor, to initiate a PHY frame transmission of 125us cycles for frame synchronization between channels, to set a quasi-window of 250us interval for ONU registration, And a PLOAMu (Physical Layer Operation, Administration, and Management Upstream) grant time for receiving a response message. Thus, the TWDM-PON system has a synchronized frame transmission period for each channel, and ONUs can select different wavelengths in downward and upward directions when changing wavelengths.

1 is a block diagram of a general TWDM-PON link,
FIG. 2 is a flowchart showing a general wavelength conversion process using a PLOAM message exchange scheme in a TWDM-PON;
FIG. 3 is a signal flow diagram illustrating a process for transmitting PHY frames of 125 us cycles for each WDM channel in a general TWDM-PON.
4 is a diagram for explaining a communication method between a general main processor and a local processor,
5 is a configuration diagram of a TWDM-PON OLT that provides per-port PHY frame synchronization according to an embodiment of the present invention;
FIG. 6 illustrates a structure of an operation table for providing a chip select signal using a bitmap address value in a chip selector according to an exemplary embodiment of the present invention. FIG.
FIG. 7 is a structure diagram of an operation table for providing a Chip Select signal using an address value encoded in a Chip Selector according to an embodiment of the present invention. FIG.
8 is a configuration diagram of a TWDM-PON OLT capable of PHY frame synchronization per port in a TWDM-PON through a Chip Select control according to an embodiment of the present invention.
FIG. 9 is a flowchart illustrating a wavelength changing process in a TWDM-PON through a Chip Select control according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention of the user, the operator, or the custom. Therefore, the definition should be based on the contents throughout this specification.

5 is a configuration diagram of a TWDM-PON OLT that provides per-port PHY frame synchronization according to an embodiment of the present invention.

5, a TWDM-PON OLT for PHY frame synchronization for each port includes a main CPU processor 40, a chip selector (hereinafter referred to as a chip selector) 52, a MAC chip 50- 50-1, 50-2, 50-3, 50-4, SERDES (Serialize & Deserialize) 54-1, 54-2, 54-3, 54-4, and optical modules 56-1, 56-2, 56-3, 56-4).

Each of the MAC chips 50-1, 50-2, 50-3, and 50-4 includes local CPU processors 42-1, 42-2, 42-3, and 42-4, 40) and the local CPU interface. The local CPU interface includes a Chip Select signal 500 and an N bit address 510, and a Read signal, a Write signal, and an M bit data signal 520. The Chip Select signal 500 indicates the access status of each of the local CPU processors 42-1, 42-2, 42-3, and 42-4, and the Write signal is transmitted from the main CPU processor 40 to each local CPU processor 42 -1, 42-2, 42-3, 42-4). The Read signal indicates that the main CPU processor 40 reads data from each of the local CPU processors 42-1, 42-2, 42-3, and 42-4. The N-bit address and the M-bit data bus represent the internal register addresses and data values of the local CPU processors 42-1, 42-2, 42-3, and 42-4, respectively.

In order to simultaneously control the four MAC chips 50-1, 50-2, 50-3, and 50-4, a chip selector 52 (CPLD) or a field programmable gate array (FPGA) ) Is used. The Chip Selector 52 receives the Chip Select signal 500 and the (N: NY) bit address value 510 from the main CPU processor 40 and receives the MAC chip 50-1, 50-2, 50-3, 50-4 to provide Chip Select signals 520-1,520-2,520-3,520-4. The (N-Y: 0) bit address value 510 is simultaneously input to each of the MAC chips 50-1, 50-2, 50-3, and 50-4. Each of the MAC chips 50-1, 50-2, 50-3, and 50-4 receives a Read signal and a Write signal based on Chip Select signals 520-1, 520-2, 520-3, and 520-4 output from the Chip Selector 52, And reads / writes data of the local CPU processors 50-1, 50-2, 50-3, and 50-4 according to a signal input. The Chip Selector 52 may provide one Chip Select signal or two or all Chip Select signals to the corresponding local CPU processor according to the input address value.

The MAC chips 50-1, 50-2, 50-3, and 50-4 according to one embodiment perform the TC layer function of the TWDM-PON. The SERDES chips 54-1, 54-2, 54-3, and 54-4 convert a parallel PON signal to a serial PON signal downward and a serial burst mode PON signal To the parallel burst mode PON signal. The optical modules 56-1, 56-2, 56-3, and 56-4 convert electric signals into optical signals or optical signals into electric signals having different WDM wavelengths and transmit the signals.

6 is a structure diagram of an operation table for providing a chip select signal using a bit map assigned address value in a chip selector according to an embodiment of the present invention.

Referring to FIGS. 5 and 6, the Y bit value input to the Chip Selector 52 is encoded in a bitmap allocation format. That is, the least significant bit (LSB) of the Y bit means the MAC chip 1 (50-1), and the MSB (most significant bit) means the MAC chip 4 (50-4). Therefore, each bit of the Y-bit address value indicates whether or not the corresponding MAC chip is selected.

As shown in FIG. 6, the Y bit address value generates a Chip Select signal of the corresponding MAC chip when the value of each bit is 1. FIG. Chip Select signal can be operated as Low Active or High Active depending on the system. In the example shown in Fig. 6, the apparatus operates in the Low Active state, but the present invention is not limited thereto.

If all the Y bit address values are 1, all the MAC chips can be set. As described above with reference to FIG. 5, since all of the MAC chips share the data buses, the main CPU processor 40 transmits the data to the MAC chips 50-1, 50-2, 50-3, and 50-4 Data can be stored simultaneously, but data reading from each of the MAC chips 50-1, 50-2, 50-3, and 50-4 to the main CPU processor 40 can be performed by only one MAC chip. Accordingly, the main CPU processor 40 can write to all of the MAC chips 50-1, 50-2, 50-3, and 50-4 or a plurality of MAC chips at the same time through the Chip Selector 52, The operation is performed only on one MAC chip. As shown in FIG. 6, a plurality of MAC chips can be controlled through a Y bit address value.

7 is a structural diagram of an operation table for providing a Chip Select signal using an address value encoded in a Chip Selector according to an embodiment of the present invention.

Referring to FIGS. 5 and 7, the Chip Selector 52 according to an exemplary embodiment provides a Chip Select signal for connection of a MAC chip using an encoded Y bit address value. As shown in FIG. 7, if the Y bit address value is 1011, data can be set for all MAC chips. The method using the encoded address value enables more MAC chip connections with a smaller number of bits.

8 is a configuration diagram of a TWDM-PON OLT capable of synchronizing a PHY frame per port in a TWDM-PON through a Chip Select control according to an embodiment of the present invention.

Referring to FIG. 8, the main CPU processor 40 inputs the upper 4 bits to the Chip Selector 52 for the PHY frame transmission of 125us periods simultaneously in each port, 1111 is set as a value (810). The lower 12 bits indicate the Transmit Start register address value 820 in the MAC chip and are transmitted together with the Write signal. The data bus transfers a value of 1 to store the Transmit Start register. The Chip Selector 52 outputs a value of 0 for Chip Select1 to Chip Select4 according to the 1111 input address value (830-1, 830-2, 830-3, and 830-4). This is output only when the Chip Select signals 830-1, 830-2, 830-3, and 830-4 are generated in synchronization with the Chip Select signal 805 input to the Chip Selector 52. [ Each of the MAC chips 50-1, 50-2, 50-3, and 50-4 stores a value in the Transmit Start register in the MAC chip according to the corresponding Chip Select signal. Each of the MAC chips 50-1, 50-2, 50-3, and 50-4 can transmit PHY frames 840-1, 840-2, 840-3, and 840-4 of 125us cycles internally with the value setting.

FIG. 9 is a flowchart illustrating a wavelength changing process in a TWDM-PON through a Chip Select control according to an embodiment of the present invention.

9, in order to change the wavelength of the ONU1 20 from the OLT-port1 21 to the OLT-port2 22, the main CPU processor 40 transmits the OLT-port1 21 through the Chip Selector 52, Only the Chip Select signal is transmitted (900) and the Tuning_Control (Request) PLOAM message is transmitted (910). The OLT-port1 21 receives a Tuning_Response (ACK) PLOAM message from the ONU1 20 (920), and transmits it to the main CPU processor 40 (930). The main CPU processor 40 transmits a Chip Select1 signal and a Chip Select2 signal through the Chip Selector 52 so that the OLT-port1 21 and the OLT-port2 22 can simultaneously transmit the PLOAM grant, (950). This operation is repeated until the Tuning_Response (Complete_u) PLOAM message is received (960) from the ONU1 20. When the OLT-port2 22 receives the Tuning_Response (Complete_u) PLOAM message (960), it transfers it to the main CPU processor 40 (970) to stop the PLOAMu grant transmission.

The embodiments of the present invention have been described above. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (1)

Time and wavelength division multiplexing-optical line terminal in a passive optical network,
A main processor;
A plurality of MAC chips each having a local processor; And
The main processor receives a chip selection signal and an address value from the main processor, and provides a chip selection signal to each MAC chip using the received address value. Accordingly, the main processor simultaneously accesses each MAC chip, A chip selector for transmitting a synchronized PHY frame;
And an optical line terminal connected to the optical line terminal.

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