WO2009026831A1

WO2009026831A1 - A system and a method for virtual concatenation synchronization in optical transport network

Info

Publication number: WO2009026831A1
Application number: PCT/CN2008/072069
Authority: WO
Inventors: Lei Shi; Juan Dong; Chen Wang; Xiuying Wang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-08-24
Filing date: 2008-08-20
Publication date: 2009-03-05
Also published as: CN101374030B; CN101374030A

Abstract

A system and method for virtual concatenation synchronization in optical transport network are disclosed in this invention, which is related to optical communication field. The said system comprises a synchronization module, a virtual concatenation delay compensation module, an asynchronous demapping module, a smoothed service obtaining module and a service data recovery module. The said method comprises: using OPUk fixed point floating in synchronization; recovering service data by combining virtual concatenation compensation and asynchronous demapping. The said technical scheme provided in this invention can suppress jitter caused by synchronization and virtual concatenation delay compensation and solve the problem of clock jitter target deterioration caused by fixed bit rate data transported by OTN virtual concatenation.

Description

Virtual cascaded peer system and method in optical transport network

Technical field

The present invention relates to the field of optical communications, and in particular, to a virtual cascade synchronization system and method in an optical transport network. Background technique

With the gradual commercialization of OTN (Optical Transport Network) devices, there is an increasing demand for using 0TN devices to carry large bandwidth. The 0TN device can be used to carry large bandwidth services, such as STM (Statistic Time-division Multiplexing) -64, 10G Ethernet, 40G POS (Packet Over SDH (Synchronous Digital Hierarchy) System)) and so on. OTN's virtual concatenation technology divides the large-bandwidth service into several network-supported granules for transmission, and only needs to support large-bandwidth processing at both the transmitting and receiving ends.

As shown in Figure 1, the structure of the OTN virtual concatenation. If the customer signal is X OPUk ( Optical Channel Payload

Unit, optical channel payload unit) to load (where k = l, 2, 3, corresponding to the rate level of 2.5G, 10G, 40G; X = l, ..., 256), then the virtual level used The union container is represented by OPUk_Xv (k=l, 2, 3; X=l, ..., 256). The frame structure of OPUk-Xv is a byte block frame structure with 4 rows and 3810X columns, which is composed of OPUk_Xv overhead area (OH, OverHead) and payload area (Payload).

On the sender side, the client data is encapsulated, mapped, framed, and sent to the receiver. The OPUk-Xv payload is mapped to IJX OPUk, and each OPUk is transmitted in an ODUk (Optical Channel Data Unit), and X ODUks form ODUk-Xv.

In the receiving direction, the OTN is deframed and demapped to recover the customer data. Since the OTN is an asynchronous system, the virtual channel transport unit (OTUk) is asynchronous, and the single container OPUk traverses in the OTN network in the form of OTUk. The element needs to perform the asynchronous mapping/demapping process. The OTUk from each network element will have a difference in rate and phase. Therefore, in the receiving direction, the asynchronous OTUk container needs to be synchronized to a system clock domain. In addition, since each ODUk in the ODUk-Xv is transmitted separately in the network, different ODUks have different delays when transmitting through the network, so there is sometimes a delay between the ODUks at the end, and thus a delay difference between the OPUks. . This delay difference must be compensated, so the virtual cascade delay compensation alignment is required, and finally the customer data is recovered by asynchronous demapping.

Constant Bit Rate (CBR) signals (STM-64, STM-256) can be asynchronous The way is mapped to OPUk-4v. The frame structure of OPUk-4v is shown in Figure 2. The OPUk-4v payload area consists of 4x4x3 808 bytes. Each line consists of 1 positive adjustment opportunity byte (PJO, Positive Justification Opportunity), 1 negative Negative Justification Opportunity (NJO) byte and 3 JC (Justification Control) bytes. The 7th and 8th bits of JC are used to control the NJO and PJO of the line. Since the OPUk-4v payload area is 4 times larger than the OPUk, the 10 Gbit I s signal can be loaded into the OPU1 - 4v, and the 40 Gbit / s signal can be loaded into the OPU 2 - 4v. In the process of loading, each line can be adjusted by one byte of positive/negative code rate; in the OPUk-4v frame, 4 times of positive/negative code rate adjustment can be made for 4 times.

Taking STM-64over OTUl-4V as an example, in the transmission direction, the mapping path of the OTN virtual concatenation standard is as follows: STM-64→OPUl-4v→4 X 0PU1→4 X ODU1→4 X OTU1.

As shown in FIG. 3, in the prior art 1, a scheme of OTN asynchronous virtual cascade delay compensation/demapping is provided. In the receive direction, the write clock of the synchronous FIFO (First In First Out) is the respective OTU1 clock, and the read clock of the synchronous FIFO is the OTU1 system clock, which is used to read 0PU1 from the FIFO. Selecting the four branches received, the FIFO is only the clock domain isolation, thus synchronizing the four OTU1 to one clock. The read control portion of the virtual cascade delay compensation is framed as shown in Fig. 2, and the aligned OPU1-4V structure is output, and the demapping portion recovers the STM-64 from the OPU1-4V.

The scheme directly selects one channel from the four OTU1 clocks as the system clock, and has higher requirements on the four OTU1 clocks, and requires four OTU1 clocks to be the same frequency. If the 4-channel OTU1 clock has a frequency difference, the position of OPU1 in OTU1 is fixed. When the system clock is used to synchronize the OPU1 container, the fixed position of the OPU1 in OTU1 cannot be guaranteed, and the virtual cascade delay compensation is performed. After that, the frame structure cannot be reproduced, thereby introducing random unmeasurable jitter. Asynchronous demapping is not able to effectively control the leakage of this part of the jitter, which is especially disadvantageous for services with strict jitter specifications such as STM64.

If the above system is a system with multiple virtual concatenation groups, such as a system that receives a total of eight OTU1s, but the eight paths belong to two different virtual concatenation groups, each of which is a virtual level from the same source node. In the case of a group, if one of the two groups is selected as the synchronous clock, the application scenario also needs to deal with the problem of introducing jitter into the service during the synchronization process. Moreover, once the selected path has severe clock degradation, another set of virtual concatenation groups will also be affected, and in such a system, the solution is even more undesirable.

As shown in FIG. 4, another scheme for the asynchronous virtual cascading delay compensation/demapping provided by the prior art 2 is provided. In this scheme, the read clock of the synchronous FIFO can be selected from the received four branches or from the local clock.

The same problem as in the prior art 1 is also generated when the 0TU1 system clock is selected from one of the four branches. When the 0TU1 system clock is selected from the local clock, since the 0TU1 system clock is different from the received 0TU1 clock of the four branches, although the write FIFO is 0TU1, the readout from the FIFO is 0PU1, but is read from the FIFO. 0PU1 The position in the OTU1 is not fixed, that is, the interval between the OPU1 frame and the frame is not fixed, that is, the OTU1 frame structure has been broken. The virtual cascade delay compensation unit aligns the four OPU1s, but the interval between the aligned OPU1-4V frames and the frames is also random, which is equivalent to providing a random tracking clock to the asynchronous demapping unit, which is not conducive to recovery. The jitter indicator meets the required clock. Therefore, although the scheme can synchronize the OTU1 of the branch to a system clock, the jitter amplitude introduced by the synchronization link cannot be measured, and the asynchronous demapping unit cannot perform effective filtering, and finally degrades the output service clock quality. Summary of the invention

In order to restore smooth service data when the OTN virtual concatenation is asynchronously demapped, an embodiment of the present invention provides a virtual concatenation synchronization system and method in an optical transport network. The technical solution is as follows:

A virtual cascade synchronization system in an optical transport network, the system comprising:

The synchronization module is configured to perform clock synchronization processing on each branch optical channel transmission unit, generate synchronization control information, and perform pointer adjustment on the synchronization control information of each branch according to the FIFO water line to generate a synchronized optical channel payload unit and Its corresponding gap clock;

a virtual cascade delay compensation module, configured to perform virtual cascade delay compensation on the synchronized optical channel payload units of all branches, according to the optical channel payload unit synchronized with each branch and its corresponding notch clock Obtaining an aligned optical channel payload unit virtual concatenation container and its corresponding notch clock;

An asynchronous demapping module, configured to extract a service payload from the aligned optical channel payload unit virtual concatenation container, and obtain a mapping according to the aligned optical channel payload unit virtual concatenation container and its corresponding gap clock respectively Positive and negative adjustment information and optical channel payload unit pointer adjustment information;

a smoothing service obtaining module, configured to select a scheduling pattern with a uniformly distributed gap according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, and obtain smoothing from the service payload according to the scheduling pattern uniformly distributed by the gap Business payload;

And a service data recovery module, configured to acquire a data clock by tracking a scheduling pattern uniformly distributed by the gap, and recover the service data from the smoothed service payload by using the data clock.

The embodiment of the invention further provides a virtual concatenation method in an optical transport network, the method comprising the following steps: performing clock synchronization processing on each branch optical channel transmission unit to generate synchronization control information, according to FIFO water The line adjusts the synchronization control information of each branch to generate a synchronized optical channel payload unit and its corresponding gap clock; performing virtual cascade delay compensation on the synchronized optical channel payload units of all branches, Obtaining an aligned optical channel payload unit virtual concatenation container according to the optical channel payload unit synchronized with each branch and its corresponding notch clock, according to the corresponding gap of the optical channel payload unit synchronized by each branch The clock obtains the optical channel payload unit virtual cascade container phase Shoulder clock

Extracting a service payload from the aligned optical channel payload unit virtual concatenation container, and obtaining the positive and negative adjustment information and light of the mapping according to the aligned optical channel payload unit virtual concatenation container and its corresponding notch clock respectively Channel payload unit pointer adjustment information;

And selecting a scheduling pattern uniformly distributed according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, and obtaining a smooth service payload from the service payload according to the scheduling pattern uniformly distributed by the gap;

Tracking the scheduling pattern of the gap uniformly distributed acquires a data clock and recovers the service data from the smoothed service payload using the data clock.

The technical solution in the embodiment of the present invention effectively suppresses the jitter introduced by the synchronization and the mapping by using the OPUk fixed-point floating and the virtual cascade delay compensation re-framing and the asynchronous demapping of the synchronization process, and solves the fixed bit rate through the OTN. The clock jitter indicator degradation caused by virtual concatenation transmission. DRAWINGS

1 is a structural diagram of an OPU-Xv in the prior art;

2 is a schematic diagram of a mapping structure of a CBR10G/CBR40G in the prior art;

3 is a structural diagram of OTN synchronization and virtual cascade delay compensation/asynchronous demapping in the prior art 1;

4 is a structural diagram of OTN synchronization and virtual cascade delay compensation/asynchronous demapping in prior art 2;

5 is a structural diagram of an OTN virtual concatenation synchronization system according to Embodiment 1 of the present invention;

6 is a schematic diagram of a fixed-point floating of an OPUk according to Embodiment 1 of the present invention;

7 is a structural diagram of a synchronization module according to Embodiment 1 of the present invention;

8 is a structural diagram of a virtual cascade delay compensation module according to Embodiment 1 of the present invention;

9 is a schematic diagram of a smooth service acquisition module according to Embodiment 1 of the present invention;

FIG. 10 is a flowchart of an OTN virtual concatenation synchronization method according to Embodiment 2 of the present invention. detailed description

The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

In a single virtual concatenation or multiple virtual concatenation group receiving system, all virtual concatenation group members are compensated by using system clock synchronization and virtual concatenation delay. The key steps of the OTN virtual concatenation receiving direction are synchronization and virtual concatenation delay compensation. The embodiment of the present invention effectively suppresses the jitter introduced by the synchronization by the OPUk fixed point floating and the virtual cascade delay compensation re-framing and the asynchronous demapping in the synchronization process, thereby solving the fixed bit rate (CBR) transmitted by the OTN virtual concatenation transmission. Clock jitter indicator degradation question.

In the embodiment of the present invention, the asynchronous mapping/demapping process of the STM-64 to 4 X OTU1 is taken as an example to describe the synchronization system and method of the OTN virtual concatenation, and other systems, such as the STM-2560TN virtual concatenation synchronization system, are similar. No longer.

Example 1

As shown in FIG. 5, an embodiment of the present invention provides an OTN virtual concatenation synchronization system. The system comprises five units, namely a synchronization module (201), a virtual cascade delay compensation module (202), an asynchronous demapping module (203), a smoothing service acquisition module (204) and a service data recovery module (205). Each unit will be specifically described below.

1, synchronization module (201)

The synchronization module (201) completes the clock synchronization processing of the four OTU1s, generates synchronous control information, and performs pointer adjustment on the synchronization control information of each branch according to the FIFO waterline, thereby generating a synchronized optical channel payload unit and the branch peer. The optical channel payload unit corresponds to the gap clock.

In the prior art, due to the difference between the system clock and the branch clock after synchronization, the position of the synchronized OPU1 in the OTU1 is not fixed, and such unfixed will introduce high-amplitude jitter to the output client service. Therefore, it is desirable that the difference between the floating OPU1 and the fixed OPU1 is measurable, so that the subsequent high-amplitude jitter is leaked out to the synchronization part, and the purpose of optimizing the customer service jitter index is achieved. In the embodiment of the present invention, the synchronization module (201) adopts a fixed-point floating mode, and allows the OPU to float in a fixed area of the OTU1.

As shown in Figure 6, the first row and the 14th byte of the OTU1 are defined as the OPU1 negative adjustment position; the first row and the fifteenth byte are defined as the OPU1 positive adjustment position. In the implementation process, the byte of the other location may be selected as the positive and negative adjustment position of the OPU1, as long as it is the OTU idle bit, and is not limited to the positive and negative adjustment position definition method of the embodiment.

According to the above definition, the OPU1 frequency deviation range that can be accommodated in the OPU1 area is calculated as follows:

OPU1 rate = 2.48832Gbps;

Maximum rate =2.48832GbpsX 15233/15232=2.488483Gbps;

Minimum rate = 2.48832GbpsX 15231/15232 = 2.4881566Gbps;

Adjustment range 2.4881566~2.488483Gbps;

Converted to ppm: -65.65ppm~65.65ppm;

That is, the structure can accommodate the reception of OPU1 fluctuating between -65.65 ppm and 65.65 ppm.

As shown in FIG. 7, it is a schematic structural diagram of the synchronization module (201). The peer module (201) includes four channels, each of which includes a synchronization sub-module (2012), a waterline detection sub-module (2012), and a fixed-point floating control sub-module (2013). The synchronization sub-module (2012) further includes an OPU1 write control unit (20121) and an OPU1 FIFO unit (20122) for performing clock synchronization processing on each of the branch optical channel transmission units to generate a synchronized optical channel payload unit. As shown in FIG. 7, the specific structure of the synchronization module (201) is as follows: The synchronization sub-module (2011) is used for clock synchronization processing of each branch optical channel transmission unit to generate synchronization control information. The OPU1 write control subunit receives the OTU1, extracts the OPU1 therefrom, writes the OPU1 into the OPU1 FIFO, and writes the clock to the OTU1 clock received by each channel. The OPU1FIFO receives OPU1 and isolates the clock domain.

The waterline detection sub-module (2012) is used to detect the watermark of each branch FIFO and send the detection result to the corresponding fixed-point floating control sub-module (2013).

The fixed-point floating control sub-module (2013) is used to set the positive adjustment position and the negative adjustment position at the fixed position of the optical channel transmission unit, and the synchronization sub-module is in the positive and negative adjustment position according to the detection result of the water line detection sub-module (2012) ( 2011) The generated synchronization control information is adjusted by the pointer. The fixed-point floating control sub-module (2013) generates a read control input to the OPU1FIFO unit (20122) as a read control. The OPU1 read control adopts the fixed-point floating mode. The read control is at a fixed position (that is, the defined positive and negative adjustment positions). According to the FIFO water line, it is determined whether the OPU1 is floating or not, and the read rate is adjusted. Specifically, the fixed-point floating control sub-module (2013) adjusts according to the detected result. If the FIFO water line is higher than the high water line, that is, the write rate of the OPU1 FIFO unit (20122) is greater than the read rate, the fixed-point floating control The module (2013) uses the negative adjustment OPU1 floating area to increase the read rate; if the FIFO water line is lower than the low water line, ie the write rate of the OPU1FIFO unit (20122) is less than the read rate, the positive adjustment OPU1 floating area is used. To reduce the read rate; if the FIFO water line is between the high and low water lines, the OPU1 does not float.

The read control generated by the fixed-point floating control sub-module (2013) may be equivalent to the gap clock, and the gap clock 1_1, the gap clock 1_2, the gap clock 1_3, and the gap clock 1_4 are respectively deducted from the overhead and padding information after each branch is synchronized. As a result, the gap clock acts as the write clock for the virtual cascaded delay compensation module (202).

OPU1 uses the same clock from the read clock of OPU1FIFO unit (20122) and the write clock of fixed-point floating control sub-module (2013). The source of this clock can be selected from each branch or local clock. The OPU1 outputted by the OPU1 FIFO unit (20122) is output to the next-stage imaginary delay delay compensation module (202) through the fixed-point floating control sub-module (2013).

2. Virtual cascade delay compensation module (202)

In the prior art, the virtual concatenation process only has the frame alignment function, that is, the slowest member in a virtual concatenation group is aligned after arrival, and the number of frames can be aligned. The disadvantage of this method is that the output data traffic after the alignment is random, and the synchronization process pointer adjustment cannot be transparently transmitted. In this embodiment, the output of the virtual concatenation buffer is added to the reframing unit, and the virtual concatenation delay compensation module (202) performs the virtual concatenation delay compensation on the four OPU1s, completes the alignment function, and transparently transmits the synchronization process. Introduced OPU1 pointer adjustment information.

In this embodiment, the virtual cascade delay compensation module (202) is configured to perform virtual cascade delay compensation on the synchronized optical channel payload units of all branches, and the synchronized light of each branch generated according to the synchronization module (201) The channel payload unit and its corresponding notch clock obtain the aligned optical channel payload unit virtual concatenation container and the optical channel payload unit virtual concatenation container corresponding Notch clock 2.

As shown in FIG. 8, the virtual concatenated delay compensation module (202) includes four virtual concatenated delay compensation buffer sub-modules (2021) 1, 2, 3, and 4, and the slowest channel identification sub-module (2022) and the virtual concatenation. Reframing the submodule (2023).

The virtual cascade delay compensation buffer sub-module (2021) 1, 2, 3 and 4 are used for receiving and buffering four OPU1s sent from the synchronization module (201), and the four OPUs respectively use the gap clocks 1_1, 1_2, 1_3 and 1_4 is written, and then sent to the virtual concatenation reframing sub-module (2023).

The input end of the slowest channel identification sub-module (2022) inputs the multi-frame number information and the gap clocks 1_1, 1_2, 1_3, and 1_4, and selects the channel number of the optical channel payload unit of the slowest path according to the multi-frame number information. The gap clock is used as a read control for the virtual concatenated delay compensation buffer. The slowest channel selection method can be implemented according to the minimum multiframe number decision. The multi-frame numbers of the four branches are compared, and the minimum multi-frame number is obtained by taking the minimum, and the channel number corresponding to the current minimum multi-frame number is the slowest channel. The gap clock corresponding to the slowest channel is the notch clock 2. Since the slowest path reading is used, it can ensure that the data of the corresponding multi-frames of other branches in the virtual concatenation group has arrived, that is, the data of other branches can be provided. , there will be no cases where other branches are empty. Since the virtual concatenation members are homologous, in the long run, the frequency of the positive and negative pointer adjustments in the aforementioned synchronization process is the same, and the short-term difference is compensated by the virtual concatenation delay buffer buffer, so the gap clock of the slowest branch is unified. Reading from the virtual cascade delay compensation buffer does not cause other branch buffers to overflow. The gap clock 2 that is selected at the same time includes the OPU1 pointer adjustment information introduced by the foregoing synchronization process. The pointer adjustment information is substantially due to the jitter introduced by different sources of the source and sink clocks, and needs to be processed by the subsequent smooth service acquisition module (204).

The virtual concatenation reframing sub-module (2023) receives the 4-way OPU1 sent by the virtual concatenated delay compensation buffer sub-module (2021) 1, 2, 3, and 4, and simultaneously inputs the notch clock 2 into the virtual concatenation and re-framing the sub-frame. The module (2023) obtains aligned OPUl-4v as a read control.

The contiguous OPU 1-4V generated by the imaginary delay compensation module (202) is input to the asynchronous demapping module (203), and the missing clock 2 is used as the write clock of the asynchronous demapping module (203).

3. Asynchronous demapping module (203)

As shown in FIG. 5, the asynchronous demapping module (203) includes a demapping submodule (2031) and a statistic submodule (2032). The demapping sub-module (2031) extracts the STM-64 service payload from the aligned OPU1-4V output by the imaginary cascading delay compensation module (202), and inputs the smoothing sub-module into the smoothing service acquisition module (204) (2042) The gap clock 3 is generated by deleting the overhead and the control information and padding information inserted in the asynchronous mapping, and is input to the smoothing submodule (2042) in the smoothing service obtaining module (204), which reflects the STM-64. Payload rate. The demapping sub-module (2031) also inputs the notch clock 2 and the aligned OPU 1-4V to the statistical subunit. In practical applications, the statistical subunit can also be used to obtain the notch clock 2 and the aligned OPU1-4V directly from the virtual concatenated delay compensation module (202).

When the customer service is transmitted in the OTN network, there will be multiple links to bring jitter. The mapping of the customer service into the OPUk-xV needs to be performed. Code rate adjustment, this process introduces mapping jitter. In addition, due to the asynchronous nature of the OTN, there is no synchronization between the virtual cascaded member clocks of different NEs on the sink node, and the synchronization process is required. The synchronization of the virtual cascaded member clocks also causes jitter damage to the service. The pointer of the SDH (Synchronous Digital Hierarchy) network adjusts the jitter, and the pointer adjustment jitter is also called combined jitter. Mapping jitter and combined jitter are required to be addressed in the sink nodes of the OTN network to ensure the performance of the customer's service.

In order to achieve the above purpose, the statistics sub-module (2032) can identify the OPU1 pointer adjustment information according to the difference between the gap clock 2 and the standard OPU1 clock, according to the OPU1-4W, the positive and negative adjustment information when the asynchronous mapping is performed, and the acquired OPU1 pointer. The adjustment information and the positive and negative adjustment information are provided for use by the clock smoothing sub-module (2041) in the smooth service acquisition module (204).

4. Smoothing service acquisition module (204)

The smoothing service obtaining module (204) implements smoothing of the clock gap caused by the mapping/demapping process and the synchronization process, that is, selecting a scheduling pattern with uniformly distributed gaps according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information. . And a smoothed service payload is obtained from the traffic payload sent by the heterogeneous demapping module (203) according to the obtained scheduling pattern in which the gaps are uniformly distributed. As shown in FIG. 9, the smoothing service acquisition module (204) includes a clock smoothing sub-module (2041) and a smoothing sub-module (2042).

The function of the clock smoothing sub-module (2041) is to customize the scheduling pattern, that is, to generate a scheduling pattern in which the gaps are evenly distributed (ie, the notch clock 4). The scheduling pattern is selected based on the positive and negative adjustment information of the asynchronous mapping and the OPU1 pointer adjustment information of the synchronization process.

The calculation method of the business smoothing scheduling pattern is as follows: Assume that three scheduling patterns MapA, MapB, and MapC are used, which correspond to positive adjustment, negative adjustment, and no adjustment, respectively, and the usage probability of MapA is Pl, and the usage probability of MapB is P2, then MapC The probability of use is 1-P1-P2, then the following formula holds:

V = SysFreq x [MapA x P\ + MapB x P2 + MapC x (1 - PI - P2)]x Width

V: STM-64 service rate;

SysFreq: OTU1 system clock;

P\ : probability of use of MapA;

P2: Probability of use of MapB;

Width-. Smooths the bit width of the FIFO.

For STM-64 to OPU1-4V mapping, the scheduling pattern can be designed as: MapA=(255, 237) (for 255 clock cycles, 237 active), MapB=(255, 239), MapC=(255, 238) .

As shown in FIG. 9, the clock smoothing sub-module (2041) includes an adding unit (2041 1 ), a leak rate control unit (20412), and a pattern selection control unit (20413). The adding unit (20411) adds the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, that is, the sum of the asynchronous mapping positive and negative adjustment values and the OPU1 pointer adjustment value to obtain a leakage value for selecting the scheduling pattern. And send the leak value to the leak rate control unit (20412).

The leak rate control unit (20412) can perform bit level leakage of the leak value through the leak rate control algorithm, control the leak rate of the leak value, and extend the low frequency high amplitude jitter to the high frequency low amplitude jitter, which will be controlled after the leak rate. The leak value is sent to the pattern selection control unit (20413). The pattern selection control unit (20413) is configured to select a scheduling pattern according to the leakage value sent by the leakage rate control unit (20412), if the leakage value is positive, and the absolute value is greater than or equal to one leakage unit (ie, the bit width of the FIFO), then selecting MapA; If the leak value is negative, and the absolute value is greater than or equal to one leak unit, select MapB; if the absolute value of the leak value is less than one leak unit, select MapC, and put the selected schedule pattern into a uniform gap, The clock with a uniform gap is selected as the notch clock 4. The gap clock 4 is input to a tracking buffer sub-module (2051) and a clock-tracking phase-locked loop (PLL) in the service data recovery module (205).

In an actual application, the scheme of adding the positive/negative adjustment information and the optical channel payload unit pointer adjustment information may not be adopted, but is separately sent to the subsequent one-stage leakage rate control unit and the pattern selection control unit (20413), and the pattern is adopted. The selection control unit (20413) selects a scheduling pattern in which the gaps are evenly distributed, thereby acquiring a service clock and recovering service data.

The function of the smoothing sub-module (2042) is to write the payload outputted by the demapping sub-module (2031) in the asynchronous demapping module (203) by the notch clock 3, according to the scheduling pattern of the gap uniformly distributed (ie, the notch clock 4) As a read clock, the service payload readout rate from the smoothing sub-module (2042) is controlled to obtain a smooth service payload, and the acceleration or delay of the phase-locked loop adjustment action is reduced by controlling the traffic flow, thereby reducing jitter. The smoothed service payload is sent to the service data recovery module (205).

The payload clock jitter caused by the OPU1 pointer adjustment causes a clock jitter if it is completely released in one pattern selection period at a time. Here, a low-frequency filter processing unit (20421) is added for performing leakage rate control on the statistical judgment of the leakage value. That is, the low-pass filtering link of the phase-locked loop filters out the short-term oscillation of the pointer, and the adjustment judgment of the OPU pointer is used as a parameter for controlling the leakage rate, and the bleed speed of the pointer adjustment is controlled, and the clock can be reduced. Instant shaking. The filtered leakage value is sent to the pattern selection control unit (20413). The use of each positive and negative adjustment opportunity is called a release, and the release control strategy of the release refers to the smooth use of the statistically adjusted adjustment opportunity.

5. Business data recovery module (205)

As shown in FIG. 5, the service data recovery module (205) is composed of a trace buffer sub-module (2051) and a clock-tracking phase-locked loop (PLL).

(2052) Composition. The clock tracking phase-locked loop (2052) is used to obtain a data clock for the scheduling pattern in which the notch is evenly distributed. The clock tracking phase locked loop can be an analog loop or a digital loop. In this embodiment, the reference clock is tracked, that is, the tracked object is the gap clock 4, and the acquired data clock is a continuous STM-64 clock.

The Trace Cache sub-module (2051) is configured to recover service data from the smoothed service payload using the service clock recovered by the clocked phase-locked loop (2052).

Example 2

As shown in FIG. 10, an embodiment of the present invention further provides a virtual concatenation synchronization method in an optical transport network. In this embodiment, the fixed-point floating mode is adopted. First, the two idle bytes of the OTU1 are respectively defined as positive and negative adjustment positions. For example, the first row and the 14th byte of the OTU1 are defined as the OPU1 negative adjustment position; The 1st line and the 15th byte are the OPU1 positive adjustment positions. In the implementation process, the bytes of other positions may also be selected as the positive and negative adjustment positions of the OPU1, and are not limited to the positive and negative adjustment position definition methods of the embodiment. The positive and negative adjustment positions are relatively fixed at the OTU1 position to allow the OPU1 to float at a fixed position.

After the positive and negative adjustment positions are defined, the five steps of synchronization, virtual cascade delay compensation, asynchronous demapping, smooth service acquisition, and service data recovery are performed in sequence. The specific operations are as follows:

First, clock synchronization processing is performed on each branch optical channel transmission unit in the OTN virtual cascade receiving direction, and each branch OPU1 is adjusted according to the FIFO water line to generate a synchronized OPU1. The specific steps are as follows:

Step 101: Each branch writes OPU1 to the FIFO using its own OTU1 clock.

Step 102: Using the system clock as a read clock, synchronizing the OPU1 of each branch to generate synchronous control information; wherein the system clock adopts the same clock, and the source of the clock may be selected from each branch or a local clock.

Step 103: Perform pointer adjustment on the synchronization control information of each branch according to the FIFO water line to generate the synchronized OPU1 and its corresponding gap clock.

The OPU1 read control adopts the fixed-point floating mode, that is, the read control determines whether the OPU1 is floating according to the FIFO water line at the fixed position of the OTU1 (that is, the defined positive and negative adjustment positions), that is, the read rate is adjusted.

Detect each branch FIFO water line, and adjust the 0PU1 floating area at the positive and negative adjustment positions according to the detection result of the FIFO water line. If the FIFO water line is higher than the high water line, use the negative adjustment OPU1 floating area to improve the readout. Rate; If the FIFO water line is lower than the low water line, use the positive adjustment OPU1 floating area to reduce the read rate; if the FIFO water line is between the high and low water lines, OPU1 does not float.

The read control of the OPU1 FIFO, that is, the read enable can be equivalent to the gap clock, and the four paths are the gap clock 1_1, the gap clock 1_2, the gap clock 1_3, and the gap clock 1_4. It is equivalent to using the notch clock 1_1 to the notch clock 1_4 as a read control to read the OPU1 of the corresponding channel. So far, the synchronization step is completed. The subsequent steps need to perform virtual cascade delay compensation on the OPU1 of all the branches of the OPU1-4V through the virtual cascade delay compensation, according to the OPU1 of each branch and its corresponding gap clock. The aligned OPU1 virtual concatenation container obtains the corresponding gap clock of the OPU1 virtual concatenation container according to the corresponding gap clock of the OPU1 synchronized by each branch.

Step 104: Write each branch OPU1 read in step 103 to the FIFO according to the respective gap clock. Step 105: Identify the notch clock of the slowest one of the branches as the gap clock 2, and read the aligned OPU1 according to the missing clock 2 to obtain the aligned OPU1-4v. The gap clock 2 is the corresponding gap clock of the OPU1 virtual concatenation container.

The above steps result in the aligned OPU1-4V and its corresponding gap clock 2. After alignment, the service payload needs to be extracted through the demapping step.

Step 106: Extract the STM-64 payload from the OPU1-4V obtained in step 105, and generate the gap clock 3 by deleting the overhead and the control information and padding information inserted during the asynchronous mapping.

Step 107: Identify the OPU1 pointer adjustment information according to the gap clock 2 obtained in step 105, and adjust the information according to the positive and negative values when the OPU1-4^ is asynchronously mapped.

Since the pointer adjustment information and the positive and negative adjustment information introduce low frequency and high amplitude jitter, it needs to be filtered out by a further smoothing step. Therefore, the following smoothing step is required to obtain a smooth gap clock, and the smoothed gap clock is used to read the smoothed service. Payload.

Step 108: Select a scheduling pattern in which the gaps are uniformly distributed according to the positive and negative adjustment information of the mapping obtained in step 107 and the OPU1 pointer adjustment information, and obtain a smooth service from the service payload obtained in step 106 according to the scheduling pattern uniformly distributed by the gap. Payload.

The payload is written to the FIFO by the gap clock 3, and the gap clock 4 is generated by the service smoothing algorithm to control the read rate of the service payload from the FIFO.

The scheduling pattern calculation method of the business smoothing algorithm is as follows: Assume that three scheduling patterns MapA, MapB, and MapC are used, which correspond to positive adjustment, negative adjustment, and no adjustment, respectively.

The OPU1 pointer adjustment information obtained in step 107 is added to the positive and negative adjustment information to obtain a leakage value, which can be bit-level leakage through the leakage rate control algorithm, and after the leakage rate control algorithm, the low-frequency high-amplitude jitter is obtained. Expand to high-frequency low-amplitude jitter and filter through the low-pass filter of the phase-locked loop; if the leakage value is positive, and the absolute value is greater than or equal to one leakage unit (ie, the bit width of the FIFO), select MapA; If the leakage value is negative, and the absolute value is greater than or equal to one leakage unit, then MapB is selected; if the absolute value of the leakage value is less than one leakage unit, MapC is selected to put a uniform gap on the selected scheduling pattern, and the selected gap is uniform. The clock is the notch clock 4. The gap clock 4 with the gap is used as the read clock, and the service payload in the smoothing sub-module (2042) is read to obtain a smooth industry. The net load. This achieves smoothing of the business.

For STM-64 to OPU1-4V demapping, the scheduling pattern can be designed as: MapA=(255, 237) (representing 255 clock cycles, 237 active), MapB=(255, 239), MapC=(255, 238 ).

The payload clock jitter caused by the OPU1 pointer adjustment will cause the clock jitter if it is completely released in one pattern selection period at a time. Here, a little low-frequency filtering processing is added, and the adjustment judgment of the OPU pointer is used as a parameter for controlling the leakage rate control. , Control the bleed speed of the pointer adjustment, which can reduce the instantaneous jitter of the clock.

Step 109: Track the scheduling pattern with evenly distributed gaps, and obtain a data clock. In this embodiment, the clock can be tracked through the phase-locked loop. The clock-tracking phase-locked loop can be an analog loop or a digital loop. The tracking reference clock, that is, the tracked object is the gap clock 4, and the acquired data clock. For continuous STM-64 clocks.

The service data is recovered from the smoothed service payload obtained in step 107 using the data clock acquired via the phase locked loop. The technical solution in the embodiment of the present invention solves the fixed bit rate and the OTN virtual concatenation by re-framing the OPUk fixed-point floating and virtual concatenated delay compensation, and combining the asynchronous de-mapping to effectively suppress the synchronization and the jitter introduced by the mapping. The clock jitter indicator degradation caused by the transmission. It is especially suitable for multi-virtual concatenation groups to be reorganized on one sink.

Some of the steps in the embodiment of the present invention may be implemented by software, and the corresponding software program may be stored in a readable storage medium such as an optical disk or a hard disk.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

Claim

A virtual cascade synchronization system in an optical transport network, characterized in that the system comprises:

The synchronization module (201) is configured to perform clock synchronization processing on each branch optical channel transmission unit, generate synchronization control information, and perform pointer adjustment on the synchronization control information of each branch according to the FIFO water line to generate a synchronized optical channel net. Charge unit and its corresponding notch clock;

The virtual cascade delay compensation module (202) is configured to perform virtual cascade delay compensation on the synchronized optical channel payload units of all branches, according to the optical channel payload unit synchronized by each branch and corresponding The notch clock obtains the aligned optical channel payload unit virtual concatenation container, and obtains the corresponding notch clock of the optical channel payload unit virtual concatenation container according to the corresponding notch clock of the optical channel payload unit of each branch synchronization ;

An asynchronous demapping module (203), configured to extract a service payload from the aligned optical channel payload unit virtual concatenation container, according to the aligned optical channel payload unit virtual concatenation container and its corresponding notch clock Obtaining the mapping of the positive and negative adjustment information and the optical channel payload unit pointer adjustment information respectively;

a smoothing service obtaining module (204), configured to select a scheduling pattern in which gaps are uniformly distributed according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, and the service payload is obtained according to the scheduling pattern uniformly distributed by the gap Get a smooth business payload;

The service data recovery module (205) is configured to acquire a data clock by tracking a scheduling pattern uniformly distributed by the gap, and recover the service data from the smoothed service payload by using the data clock.

2. The virtual concatenation synchronization system in the optical transport network of claim 1, wherein the synchronization module (201) specifically includes:

a synchronization sub-module (2011), configured to perform clock synchronization processing on each branch optical channel transmission unit to generate synchronization control information;

Waterline detection sub-module (2012) for detecting each branch FIFO waterline;

a fixed-point floating control sub-module (2013) for setting a positive adjustment position and a negative adjustment position at a fixed position of the optical channel transmission unit, according to the detection result of the waterline detection sub-module (2012) at the positive and negative adjustment position Pointer adjustment is performed on the synchronization control information of each branch to generate a synchronized optical channel payload unit and its corresponding notch clock.

3. The virtual concatenation synchronization system in the optical transport network of claim 1, wherein the virtual concatenation delay compensation module (202) specifically includes:

a virtual cascade delay compensation buffer sub-module (2021) for writing and buffering an optical channel payload unit of each branch synchronization; The slowest channel identification sub-module (2022) is configured to select, according to the multi-frame number information, a gap clock corresponding to the channel number of the slowest one optical channel payload unit;

a virtual concatenation reframing compensation sub-module (2023), configured to read each branch in the virtual concatenation delay compensation buffer according to a gap clock corresponding to a channel number of the slowest one-way optical channel payload unit The optical channel payload unit obtains the aligned optical channel payload unit virtual concatenation container, and uses the gap clock corresponding to the channel number of the slowest one-way optical channel payload unit as the optical channel payload unit virtual level The corresponding gap clock of the joint container.

4. The virtual concatenation synchronization system in the optical transport network of claim 1, wherein the smooth service acquisition module (204) specifically includes:

a clock smoothing sub-module (2041), configured to obtain a leakage value according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, and perform leakage rate control on the leakage value according to a leakage value after the leakage rate control Selecting a scheduling pattern in which the gaps are evenly distributed;

The smoothing submodule (2042) is configured to obtain a smooth service payload from the service payload according to a scheduling pattern uniformly distributed by the gap.

The virtual concatenation synchronization system in the optical transport network of claim 4, wherein the clock smoothing submodule (2041) further comprises:

The low frequency filter processing unit (20411) is configured to perform leakage rate control on the statistical judgment of the leakage value.

A virtual cascade synchronization method in an optical transport network, characterized in that the method comprises the following steps: performing clock synchronization processing on each branch optical channel transmission unit to generate synchronization control information according to a FIFO waterline pair The synchronization control information of each path is adjusted by pointers to generate synchronized optical channel payload units and their corresponding gap clocks; virtual cascade delay compensation is performed on the synchronized optical channel payload units of all branches, according to An optical channel payload unit synchronized with each branch and its corresponding notch clock obtains an aligned optical channel payload unit virtual concatenation container, which is obtained according to a corresponding notch clock of the optical channel payload unit synchronized by each branch The corresponding gap clock of the virtual channel cascading container of the optical channel payload unit;

And selecting, according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information, a scheduling pattern in which the gaps are uniformly distributed, and obtaining a smooth service payload from the service payload according to the scheduling pattern uniformly distributed by the gap; Tracking the scheduling pattern of the gap uniformly distributed acquires a data clock, and recovers the service data from the smoothed service payload by using the data clock.

7. The virtual concatenation synchronization method in an optical transport network according to claim 6, wherein the step of adjusting synchronization control information of each branch according to a FIFO waterline to generate a synchronized optical channel payload The steps of the unit and its corresponding gap clock specifically include:

Detect each branch FIFO waterline;

Setting a positive adjustment position and a negative adjustment position at a fixed position of the optical channel transmission unit, and performing pointer adjustment on the synchronization control information of each branch at the positive and negative adjustment positions according to the detection result, thereby generating a synchronized optical channel payload The unit and its corresponding notch clock.

8. The virtual concatenation synchronization method in an optical transport network according to claim 6, wherein the optical channel payload unit synchronized with each branch and its corresponding notch clock obtain aligned light The step of obtaining the corresponding gap clock of the virtual channel cascading container of the optical channel payload unit according to the corresponding gap clock of the optical channel payload unit of each of the branches is as follows:

Write and cache each branch optical channel payload unit;

Selecting a gap clock corresponding to the channel number of the slowest channel optical channel payload unit according to the multiframe number information;

Reading each branch optical channel payload unit according to the corresponding notch clock of the channel number of the slowest one-path optical channel payload unit, obtaining an aligned optical channel payload unit virtual concatenation container, and The corresponding notch clock of the channel number of the slow channel optical channel payload unit is used as the corresponding gap clock of the virtual channel cascading container of the optical channel payload unit.

9. The virtual concatenation synchronization method in an optical transport network according to claim 6, wherein the scheduling of the gap is uniformly distributed according to the positive and negative adjustment information of the mapping and the optical channel payload unit pointer adjustment information The steps of the pattern specifically include:

A leak value is obtained based on the positive/negative adjustment information of the map and the optical channel payload unit pointer adjustment information, and the leakage rate is controlled by the leakage rate, and the scheduling pattern in which the gap is uniformly distributed is selected according to the leakage value after the leakage rate control.

10. The virtual concatenation synchronization method in an optical transport network according to claim 9, wherein the method further comprises: adding a low frequency filtering process, and performing leakage rate control on the statistical judgment of the leakage value.