CN102480415A - Method and device for recovering optical transport network clock by reference clock - Google Patents

Abstract

The invention discloses a method for recovering an optical transport network clock by a reference clock, which comprises the following steps: measuring the frequency information of an optical-channel data unit (ODUk) clock by a reference measurement clock; packaging the measured frequency information into the expenditure of a packet; and according to the reference measurement clock of the same frequency, frequency information analyzed from the expenditure of the packet and the length of the packet, restoring the ODUk clock of the same frequency in the de-packaging process for restoring ODUk from the packet. The invention also discloses a device for recovering the optical transport network clock by the reference clock. A processing module to ODUk from the packet is used for restoring the ODUk clock of the same frequency according to the reference measurement clock of the same frequency, the frequency information analyzed form the expenditure of the packet and the length of the packet. According to the method and the device disclosed by the invention, a favorable clock still can be restored after the ODUk is subjected to delayed and inconstant packet switching processing.

Description

A kind of method and device that recovers the optical transfer network clock through reference clock

Technical field

The present invention relates to the optical transfer network field, relate in particular to a kind of method and device that recovers the optical transfer network clock through reference clock.

Background technology

The optical transfer network standard is formulated by International Telecommunications Union (ITU-T), and G.709 and G.798 substance is defining, and requires to realize ODUk (k=0,1,2 in the standard; 2e, 3,3e1,3e2,4; 5,6, flex etc.) other cross scheduling of level, in scheduling, require to realize the ODUk clock transparent transmission.Here, so-called ODUk refers to the Optical Channel Data Unit-k in the optical transfer network.ODUk generally can't directly realize cross scheduling, and will convert another kind of signal format into, realizes cross scheduling again after for example converting SDH (SDH, SynchronousDigital Hierarchy) signal into or converting bag or packet signal etc. into.Wherein realize that based on bag or packet switching the mode of ODUk cross scheduling has very big technical advantage, can let the user on a physical platform, realize the function of data equipment and transmission equipment simultaneously.Yet; Because mode based on bag or packet switching realization ODUk cross scheduling; It is fixing in processing procedure, can to produce delay, and excursion is bigger, thereby the problem that causes is: through recovering very difficulty of high-quality ODUk clock after bag or the packet switching.If according to existing according to first in first out (FIFO; First Input First Output) or the buffer depth mode that produces recovered clock can't address this problem; Press for a solution at present, so that through postponing still to recover the enough good ODUk clock of quality and performance after indefinite bag or packet switching are handled.

Summary of the invention

In view of this, main purpose of the present invention is to provide a kind of method and device through reference clock recovery optical transfer network clock, makes ODUk still can recover the enough good clock of quality and performance through postponing after indefinite bag or packet switching are handled.

For achieving the above object, technical scheme of the present invention is achieved in that

A kind of method through reference clock recovery optical transfer network clock, this method comprises:

The encapsulation process that is transformed into bag from ODUk or divides into groups, measure the frequency information of ODUk clock in the optical transfer network, the frequency information of measuring is encapsulated in the expense of bag or grouping with the reference measurement clock; Going out the decapsulation processing of ODUk, recover the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from bag or packet recovery.

Wherein, said ODUk be specially ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex); The frequency of ODUk is specially Ck; The frequency of said reference measurement clock is Cm; The frequency of the ODUk clock that recovers is specially Cj, and Cj=Ck; The length of said bag or grouping is fixed value, and the said bag of fixed length or divide into groups in payload length be the B byte, comprise the ODUk information of B byte, comprise the said frequency information of measuring of 2bit in the said bag of fixed length or the expense of grouping at least;

The encapsulation process that is transformed into bag from ODUk or divides into groups; At every turn the ODUk information of B byte is encapsulated into the said bag of fixed length or when dividing into groups, this method also comprises: counting whenever receives the periodicity Nm of reference measurement clock process described in the B byte ODUk information process; Nm is the frequency information of the said ODUk clock of measuring with the reference measurement clock;

Under the prerequisite of frequency deviation of ODUk less than positive and negative 150ppm; The value of said Nm is specially Nms, Nms-1 or Nms+1; Wherein, said Nms adopts formula 1:

calculates; Wherein, Cks is the standard speed of ODUk.

Wherein, this method also comprises: Nms, Nms-1 or the Nms+1 that will represent with 2bit be as the frequency information of measuring, and is encapsulated in the expense of said bag or grouping of fixed length to transmit.

Wherein, going out the decapsulation processing of ODUk from bag or packet recovery, this method also comprises:

From the expense of the said bag of fixed length or grouping, parse the frequency information of measuring of 2bit;

The Nms that calculates according to frequency information of measuring and the said formula 1 of 2bit obtains Nm, and the value of said Nm is specially Nms, Nms-1 or Nms+1;

According to said Nm, calculate said Cj with another reference measurement clock and the said B of said reference measurement clock same frequency, calculating the formula that adopts is formula 2:

Wherein, calculate Cj after, this method also comprises: with the Cj input desynchronizer according to said formula 2 designs, obtain the clock that frequency is Cj according to said formula 2; Said frequency is that the clock of Cj is: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation processing.

Wherein, this method also comprises: calculate Cjk according to

, and it is imported the OTUk clock that said desynchronizer is restored out, its frequency is Cjk; Said OTUk is specially OTUk (k=1,2,2e; 3,3e1,3e2; 4,5,6).

A kind ofly recover the device of optical transfer network clock through reference clock, this device comprises: ODUk is to the processing module and the bag of bag or grouping or be grouped into the processing module of ODUk; Wherein,

Said ODUk is used for optical transfer network the encapsulation process that is transformed into bag from ODUk or divides into groups to the bag or the processing module of dividing into groups, and measures the frequency information of ODUk clock with the reference measurement clock, the frequency information of measuring is encapsulated in the expense of bag or grouping;

Said bag or be grouped into the processing module of ODUk; Be used for recovering the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from the decapsulation processing of wrapping or packet recovery goes out ODUk.

Wherein, said ODUk be specially ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex); The frequency of ODUk is specially Ck; The frequency of said reference measurement clock is Cm; The frequency of the ODUk clock that recovers is specially Cj, and Cj=Ck; The length of said bag or grouping is fixed value, and the said bag of fixed length or divide into groups in payload length be the B byte, comprise the ODUk information of B byte, comprise the frequency information of measuring of 2bit in the said bag of fixed length or the expense of grouping at least;

Said ODUk further comprises to the processing module of bag or grouping: first counter, second counter, first computing module, bag or grouping generation module; Wherein,

Said first counter is used to count the byte number of the ODUk information that receives, and maximum is B;

Said second counter is used to count the periodicity Nm that whenever receives reference measurement clock process described in the B byte ODUk information process; Nm is the frequency information of the said ODUk clock of measuring with the reference measurement clock; Wherein, Under the prerequisite of frequency deviation of ODUk less than positive and negative 150ppm; The value of said Nm is specially Nms, Nms-1 or Nms+1; Wherein, said Nms adopts formula 1:

calculates; Wherein, Cks is the standard speed of ODUk;

Said first computing module; Be used to receive that the B byte count of first counter finishes index signal and the resulting Nm of second rolling counters forward; The value of said Nm is specially Nms, Nms-1 or Nms+1, and Nms, Nms-1 or the Nms+1 that will represent with 2bit are as the frequency information of measuring;

Said bag or grouping generation module are used to generate said bag or the grouping that payload length is the fixed length of B byte, the frequency information of measuring of 2bit is encapsulated in the expense of said bag or grouping of fixed length transmits simultaneously.

Wherein, said bag or the processing module that is grouped into ODUk further comprise: parsing module, second computing module, desynchronizer; Wherein,

Said parsing module is used for from the said bag of the fixed length received or divides into groups to parse the frequency information of measuring of 2bit;

Said second computing module is used for the Nms that frequency information of measuring and said formula 1 according to 2bit calculate and obtains Nm, and the value of said Nm is specially Nms, Nms-1 or Nms+1; According to said Nm, calculate said Cj with another reference measurement clock and the said B of said reference measurement clock same frequency, calculating the formula that adopts is formula 2:

Said desynchronizer is used for obtaining the clock that frequency is Cj according to the Cj and the said formula 2 of input; Said frequency is that the clock of Cj is: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation processing.

The encapsulation process that is transformed into bag from ODUk or divides into groups, measure the frequency information of ODUk clock in the optical transfer network of the present invention, the frequency information of measuring is encapsulated in the expense of bag or grouping with the reference measurement clock; Going out the decapsulation processing of ODUk, recover the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from bag or packet recovery.

The present invention is applicable to that ODUk realizes the occasion of cross scheduling through bag or packet switching; The encapsulation process that is transformed into bag from ODUk or divides into groups; Measure the frequency information of ODUk clock with the reference measurement clock; And when ODUk being encapsulated into bag or dividing into groups, the frequency information of measuring is put in the expense of bag or grouping; The decapsulation that is going out ODUk from bag or packet recovery is handled, recover the ODUk clock of same frequency according to the length of the frequency information in the expense of reference measurement clock, bag or the grouping of same frequency and bag or grouping.Adopt the present invention, can ignore delay that bag or packet switching produce not stationarity the influence of recovered clock is recovered the enough good ODUk clock of quality and performance.

Description of drawings

Fig. 1 is the schematic flow sheet of the inventive method principle;

Fig. 2 is that apparatus of the present invention are having now based on the position view in the system of bag or packet switching realization ODUk cross scheduling;

Fig. 3 realizes the embodiment sketch map of ODUk to the encapsulation process of bag or grouping for apparatus of the present invention;

Fig. 4 realizes bag for apparatus of the present invention or is grouped into an embodiment sketch map of the decapsulation processing of ODUk.

Embodiment

Basic thought of the present invention is: the encapsulation process that is transformed into bag from ODUk or divides into groups, measure the frequency information of ODUk clock with the reference measurement clock in the optical transfer network, the frequency information of measuring is encapsulated in the expense of bag or grouping; Going out the decapsulation processing of ODUk, recover the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from bag or packet recovery.

Below in conjunction with accompanying drawing the enforcement of technical scheme is done further to describe in detail.

The present invention can ignore delay that bag or packet switching produce not stationarity the influence of recovered clock is recovered the enough good ODUk clock of quality and performance.And the recovery effects of ODUk clock and existingly separate the cbr (constant bit rate) (CBR that asynchronous mapping recovers from Optical Channel Transport Unit-k (OTUk); Constant Bit Rate) effect of signal is suitable, thereby the performance of feasible ODUk that recovers or OTUk clock can reach the requirement of optical transfer network relevant criterion.

Here it is to be noted: what originally will transmit is the frequency (frequency of ODUk is Ck) of ODUk; Because Ck is a frequency; Therefore, in fact the present invention need transmit Ck through the frequency information (this frequency information of measuring is Nm) of measuring the ODUk clock with the reference measurement clock, because the value of Nm may be greater than 1,000; Can't represent with 2bit; But because Nm can represent with the mode that Nms adds and subtracts deviant, and because Nms is that fixed value can be obtained through calculating, so only need to reach the purpose of transmission Nm with 2bit transmission deviation value.

A kind of method through reference clock recovery optical transfer network clock is with ODUk (k=0,1,2,2e, 3,3e1,3e2,4; 5,6, flex) set forth for example, ODUk is at least ODUk (k=0,1,2,2e, 3; 3e1,3e2,4,5,6, flex), be not limited to present example, mainly comprise following content:

The schematic flow sheet of method principle as shown in Figure 1 may further comprise the steps:

Step 101, the encapsulation process that is transformed into bag from ODUk or divides into groups, measure the frequency information of ODUk clock with the reference measurement clock, the frequency information of measuring is encapsulated in the expense of bag or grouping.

Step 102, the decapsulation that is going out ODUk from bag or packet recovery is handled, recover the ODUk clock of same frequency with the length of the reference measurement clock of same frequency, the frequency information that from the bag or the expense of dividing into groups, parses and bag or grouping.

For convenience, do following parameter-definition:

The frequency information of the ODUk clock that a1, reference measurement clock are measured, the frequency of promptly transferred ODUk are Ck.

A2, be Cj through the clock frequency of the ODUk that recovers after bag or the packet switching, Cj and Ck are very approaching, and can follow the variation of Ck and change.

The frequency of a3, reference measurement clock is Cm; The reference measurement clock is a plurality of; Same reference measurement clock is present in the present invention, and all are realized in the device that ODUk handle to bag or packet encapsulation, and all are realized bag or are grouped in the device that the decapsulation of ODUk handles also to be present in the present invention.Only require for all reference measurement clocks that frequency is consistent and get final product, do not require that phase place is consistent.

A4, whenever receive and form a bag behind the ODUk of B byte or divide into groups to send; The payload length that comprises ODUk in bag or the grouping is fixed as the B byte; Then the length of bag or grouping is fixed length, is fixing B+h byte, wherein the expense shared byte of h for wrapping or dividing into groups.

Called after CI0 (accounting for 2bit) and CI1 (accounting for 2bit) are distinguished in the proprietary territory that 4bit is arranged in a5, bag or the packet overhead, are used for transmitting the frequency information of the ODUk clock of mentioning among the a1 of measuring.The actual 2bit that only needs of frequency information; Just often get final product with CI0; Increase the frequency information that the CI1 expense also is used for transmitting the ODUk clock that a1 mentions; Its benefit is can guarantee to lose 1 bag or the back frequency information that divides into groups can not lost, thereby guarantees to recover according to the frequency information in the expense ODUk clock of same frequency.Support to lose continuously n bag back frequency information if desired and still do not lose, can further use the expense of 2 * (n+1) individual bit.That is to say; Behind the frequency information of the ODUk clock of in the a1 that has obtained 2bit, mentioning of measuring; For the bag that guarantees fixed length or be grouped in the exchange process; Lose the bag of continuous n this fixed length or divide into groups after the frequency information of this ODUk clock do not lose; Can the frequency information of this ODUk clock of above 2bit be copied to continuous n+1 (n for greater than 1 integer) fixed length bag or divide into groups, take the expense of 2 * (n+1) individual bit, thereby guarantee after the bag of losing n fixed length continuously or grouping, still can obtain the frequency information of this ODUk clock of 2bit.

The standard speed of a6, ODUk is Cks.

Here it is to be noted: consider bag and the realization principle basically identical that divides into groups, if below do not do specified otherwise, bag then will wrap and divide into groups all to be referred to as.

Definition is described below scheme of the present invention according to above-mentioned parameter:

Phase I: be transformed into from ODUk the encapsulation process of bag, the Ck clock whenever receives the ODUk of B byte, and it is the periodicity Nm of the reference measurement clock process of Cm that counting whenever receives B byte ODUk information process medium frequency, and Nm also can be described as the number of Cm clock.Frequency deviation at ODUk is no more than B less than positive and negative 150ppm and B _MaxPrerequisite under, the value of Nm only possibly be Nms, Nms-1 or Nms+1, wherein the value of Nms can calculate according to following formula 1:

Formula 1: $\mathrm{Nms}=\mathrm{Round}\left(\frac{\mathrm{Cm}\×B\×8}{\mathrm{Cks}}\right)$

In the top formula 1, the round numbers operation of round () for rounding up, Cks is the standard speed of ODUk.Consider that Nms+1 and Nms-1 must possess the adjustment capability of positive and negative at least 150ppm; Requirement Cm * B value can not be too big, supposes that Cm is 350MHz, only needs to guarantee that Nms is less than (1000000/150)-0.5; Can guarantee adjusting range, the maximum B of the B that obtains like this greater than positive and negative 150ppm _MaxAs shown in table 1 below, the corresponding B of each ODUk when table 1 is 350MHz for Cm _MaxMaximum tabulation.

The ODUk type	ODUk speed (Mbps)	B max
			ODU0	1244.16	2962.064
ODU1	2498.775	5949.018
			ODU2	10037.27	23896.48
ODU3	40319.22	95990.94
			ODU4	104794.4	249491.9

Table 1

Consider the B that ODU0 allows _MaxValue is minimum, so when Cm equals 350MHz, as long as keep B can guarantee that less than 2962 this scheme has the frequency deviation tolerance of positive and negative at least 150ppm to ODUk.If reduce the frequency of Cm, then B _MaxValue also can increase.

Second stage: Nms, Nms-1 or the Nms+1 that will utilize formula 1 to calculate converts the frequency information of the ODUk clock of mentioning among the a1 of 2bit of measuring into; Promptly respectively with corresponding 2 bit00 of Nms, Nms-1 or Nms+1, bit01, bit10; And the CI0 territory of the expense of the bag that the next B byte of being put into of these 2 bit ODUk is formed; Simultaneously these 2 bit are put into the CI1 territory of the expense of the bag that next but one B byte ODUk forms; Here, the said CI1 territory of unwrapping pin of putting into next but one B byte ODUk composition is meant: the frequency information of guaranteeing 2bit will be 2 bag backups continuously.

Phase III: the decapsulation that recovers ODUk from bag is handled; Under not having the situation of packet loss, from the CI0 territory of unwrapping pin, obtain the deviant of the frequency information of the corresponding 2bit of a bag; Can obtain the number Nm (value of Nm possibly be Nms, Nms-1 or Nms+1) of the corresponding clock Cm of a last bag B byte ODUk again according to top calculated value Nms; According to following formula 2; Nm, Cm and B input desynchronizer can be recovered the clock that frequency is Cj, and Cj will follow Ck and change, and this frequency is that the clock of Cj is: the ODUk clock of the same frequency that recovers after delayed indefinite bag of ODUk or packet switching are handled.

Formula 2: $\mathrm{Cj}=\frac{\mathrm{Cm}\×B\×8}{\mathrm{Nm}}$

Here it is to be noted: this desynchronizer be designed with different implementations, but its design principle and according to all from above-mentioned formula 2.

In above processing; If lost 1 bag; Then the CI1 territory of the next one bag of available lost package obtains the number Nm of the corresponding Cm clock of the bag of lost package front; And the value of filling B byte automatically is 0 byte, thereby guarantees under the situation of losing 1 bag, to have only some error codes and do not have frame head displacement phenomenon, and the effect of recovered clock is not affected simultaneously.If lost many bags continuously; Can think that the Cm number in the lost package is Nms; And to fill quantity automatically be that value that the bag number lost multiply by B byte is 0 byte, and the byte number in the ODUk frame that recovers like this will normal fully just some error code, can't produce the frame heads displacement and then produce of short duration frame losing mistake because of many or few byte; Though also can produce some influences to the synchronous effect of desynchronizer this moment; As long as but the bag of losing only can cause temporary time clock tracking property bad not too at most, can't cause clock information to be lost fully, clock will not recover synchronously very soon behind the packet loss.

Stage: on the basis of phase III, if hope to recover OTUk (k=1,2,2e; 3,3e1,3e2,4; 5,6) clock is because there is fixing proportionate relationship in the clock frequency of OTUk and ODUk; Therefore, only need following formula 3 is imported the OTUk clock that can be restored out in the desynchronizers, its frequency is Cjk.It is thus clear that: ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex) delayed indefinite bag or packet switching still can recover the enough good OTUk of quality and performance (k=1,2,2e, 3,3e1,3e2,4,5,6) clock after handling.Wherein, OTUk is at least OTUk (k=1,2,2e, 3,3e1,3e2,4,5,6), is not limited to present instance.

Formula 3:

A kind ofly recover the device of optical transfer network clock through reference clock, mainly comprise: ODUk is to the processing module and the bag of bag or grouping or be grouped into the processing module of ODUk.Wherein, ODUk is used for optical transfer network the encapsulation process that is transformed into bag from ODUk or divides into groups to the bag or the processing module of dividing into groups, and measures the frequency information of ODUk clock with the reference measurement clock, the frequency information of measuring is encapsulated in the expense of bag or grouping.The processing module of wrapping or be grouped into ODUk is used for recovering the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from the decapsulation processing of wrapping or packet recovery goes out ODUk.

Here, instance of said ODUk be ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex), but ODUk be at least ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex), be not limited to the instance here; The frequency of ODUk is specially Ck; The frequency of said reference measurement clock is Cm; The frequency of the ODUk clock that recovers is specially Cj, and Cj=Ck; The length of said bag or grouping is fixed value, and the said bag of fixed length or divide into groups in payload length be the B byte, comprise the ODUk information of B byte, comprise the said frequency information of measuring of 2bit in the said bag of fixed length or the expense of grouping at least;

ODUk further comprises to the processing module of bag or grouping: first counter, second counter, first computing module, bag or grouping generation module; Wherein,

First counter is used to count the byte number of the ODUk information that receives, and maximum is B;

Second counter is used to count the periodicity Nm that whenever receives reference measurement clock process described in the B byte ODUk information process; Nm is the frequency information of the ODUk clock measured with the reference measurement clock; Wherein, the frequency deviation at ODUk is no more than B less than positive and negative 150ppm and B _MaxPrerequisite under, the value of said Nm only possibly be Nms, Nms-1 or Nms+1, wherein, said Nms adopts formula 1: Calculate; Wherein, Cks is the standard speed rate of ODUk;

First computing module; Be used to receive that the B byte count of first counter finishes index signal and the resulting Nm of second rolling counters forward; The value of said Nm only possibly be Nms, Nms-1 or Nms+1, and Nms, Nms-1 or the Nms+1 that will represent with 2bit are as the frequency information of measuring;

Bag or grouping generation module are used to generate said bag or the grouping that payload length is the fixed length of B byte, the frequency information of measuring of 2bit is encapsulated in the expense of said bag or grouping of fixed length transmits simultaneously.

Here, the processing module of wrapping or be grouped into ODUk further comprises: parsing module, second computing module, desynchronizer; Wherein,

Parsing module is used for from the said bag of the fixed length received or divides into groups to parse the frequency information of measuring of 2bit;

Second computing module is used for the Nms that frequency information of measuring and said formula 1 according to 2bit calculate and obtains Nm, and the value of said Nm only possibly be Nms, Nms-1 or Nms+1; According to said Nm, calculate said Cj with another reference measurement clock and the said B of said reference measurement clock same frequency, calculating the formula that adopts is formula 2:

Desynchronizer is used for obtaining the clock that frequency is Cj according to the Cj and the said formula 2 of input; Said frequency is that the clock of Cj is: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation processing.

In sum, adopt the present invention, compared with prior art, can obtain following beneficial effect:

1, adopts method of the present invention and device; Solved ODUk through packet network after the ODUk clock problem that is difficult to recover; The delay of ODUk clock recovery effect and packet switch is uncertain irrelevant; That is to say can ignore delay that bag or packet switching produce not stationarity to the influence of recovered clock, so that recover quality and the enough good ODUk clock of performance.

2, the principle and existing of the inventive method and device recovered clock is separated asynchronous mapping to recover the principle of CBR similar from OTUk, and the clock recovery effect is also consistent.Because the frequency of Cm can be provided with the length of B, adopts method of the present invention and device,, even can reach than separate asynchronous mapping and recover the better effect of CBR from OTUk through selection appropriate C m and B.

3, adopt method of the present invention and device; The bag that obtains after ODUk encapsulated is the fixed length bag of regular length; And the length of bag can be provided with, and fixed length has higher efficient and littler delay when wrapping in through packet switching system, and feasible simultaneously general packet switching system is optimized becomes possibility; Make it only supporting ODUk can simplify significantly when intersecting, reduce the realization cost of packet switching system.

4, adopt method of the present invention and device; The bag that obtains after ODUk encapsulated is the fixed length bag; And the length of bag can be provided with; Through selecting suitable packet length, can be so that the parallel processing when from the fixed length bag, recovering ODUk be very simple, the operation of adjusting the ODUk width repeatedly of the complicacy of carrying out for the parallel processing that realizes ODUk when avoiding from elongated bag, recovering ODUk.

5, adopt method of the present invention and device; The packet loss phenomenon that occurs in the packet switch processing can be tolerated better, when using the 4bit expense, can under the situation of losing a bag, the frame head inconsistent phenomenon can be do not occurred; Some error codes only occur, the performance of recovered clock is not affected simultaneously; Under the situation of losing many bags continuously the frame head inconsistent phenomenon can not appear yet; Some error codes only appear; Simultaneously the following property of recovered clock can temporarily be affected, but the shake phenomenon that exceeds standard can not occur, and not behind the packet loss time clock tracking property will recover normal very soon; If use the expense of 2 * (n+1) bit, the performance of recovered clock is unaffected in the time of then guaranteeing to lose the n bag continuously.

Below to the present invention's elaboration of giving an example.

Fig. 2 is that apparatus of the present invention are having now based on the position view in the system of bag or packet switching realization ODUk cross scheduling.Existing realize the equipment of ODUk cross scheduling, wrap or be grouped into switching network adaptation unit (like the 101-1 to 101-n among Fig. 2) and switch fabric unit 103 is formed to the converting unit (shown in the 100-1 to 100-n among Fig. 2) of bag or grouping, n by n ODUk based on bag or packet switching.This system at first converts ODUk into bag or divides into groups, and will wrap or packet switched is unified backboard signal again, exchanges scheduling through switching network then, thus the cross scheduling of realization ODUk.The content that reference measurement clock (shown in the 104-1 to 104-n among Fig. 2) among Fig. 2 need increase for the present invention; Clock recovery when being used for assisting ODUk to pass switching network; Require reference measurement clock (shown in the 104-1 to 104-n among Fig. 2) to be necessary for the same frequency clock from same high precision reference clock source, the phase place of this n clock can be inconsistent, and frequency is Cm; Frequency range is recommended as 150M-350MHz, also can select other frequency values.Apparatus of the present invention are arranged in the conversion converting unit (as the 100-1 to 100-n of Fig. 2 shown in) of the ODUk of this system shown in Figure 2 to bag or grouping.

Device embodiment one: for apparatus of the present invention realize the embodiment of ODUk to the encapsulation process of bag or grouping; ODUk is to the processing module of bag or grouping; Consider bag and the realization principle basically identical that divides into groups, if below do not do specified otherwise, bag then will wrap and divide into groups all to be referred to as.

ODUk as shown in Figure 3 comprises to the bag or the processing module of dividing into groups: ODUk clock 105 (its frequency is Ck), ODUk data 113, first counter 106 (be used to calculate the ODUk byte number that receives, maximum is B), B byte count finish index signal 107 (being the index signal after the count value of first counter 106 reaches the B byte); Reference measurement clock 109 (frequency is Cm), second counter 108 (being used to calculate reference measurement clock 109 numbers), count value 110 are that current count value, first computing module 111 of second counter 108 (is used for finishing index signal 107 and count value 110 according to the B byte count of first counter 106; Produce CI0 and CI1 expense 112), CI0 and CI1 expense 112 (being CI0 and the CI1 expense that first computing module 111 produces), wrap generation module 114 and (be used to generate the bag that payload length is the B byte; It is the payload part that the ODUk of B byte is encapsulated into bag according to ODUk clock of importing 105 and ODUk data 113; Make that the length of payload is the B byte; Simultaneously CI0 and CI1 expense 112 are packed in the expense of bag), bag 115 (for the payload length that generates through bag generation module 114 is the bag of B byte, the switch fabric unit 103 among the final Fig. 2 of entering of this bag is done exchange and handled).

Device embodiment two a: embodiment who wraps or be grouped into the decapsulation processing of ODUk for apparatus of the present invention realization; Be specially the processing module of wrapping or being grouped into ODUk; Consider bag and the realization principle basically identical that divides into groups, if below do not do specified otherwise, bag then will wrap and divide into groups all to be referred to as.

After bag 115 (being that Fig. 3 is the bag of B byte through the payload length that bag generation module 114 generates) is done the exchange processing through the switch fabric unit 103 among Fig. 2; Get into bag as shown in Figure 4 or be grouped into the processing module of ODUk; As shown in Figure 4; Comprise: parsing module 120 (being used for parsing CI0 and CI1 expense 121), second computing module 122 (being used for parsing CI0 and CI1 expense 121 calculates Nm123), desynchronizer 125 (be used for recovering the ODUk clock 126 that frequency is Cj according to Nm123 and reference measurement clock 124, Cj will be consistent with the frequency Ck of ODUk clock 105 among Fig. 3) according to these from the bag 115 of B byte length.

Adopt above-mentioned device embodiment as shown in Figure 3; The processing procedure of corresponding method is: ODUk to the bag encapsulation process in; ODUk clock 105 (its frequency is Ck) gets into first counter 106, whenever count down to the B byte, produces 1 B byte count and finishes index signal 107; Second counter 108 calculates the number of reference measurement clock 109 (its frequency is Cm), and its counting number must guarantee greatly enough that count value can not overflowed between the sigtnal interval of two adjacent B byte counts end index signals 107; First computing module 111 calculates two adjacent B byte counts to be finished between the signal of index signal 107; The difference of the count value of second counter, 108 outputs; Thereby whenever received the clock number of reference measurement clock 109 in the B byte ODUk time, under the prerequisite of ODUk clock frequency deviation less than positive and negative 100ppm, an above clock numerical value can be Nms, Nms+1 or Nms-1 only; Wherein Nms is a constant, can be calculated by above-mentioned formula 1; First computing module produces CI0 and CI1 expense 112 according to the Nms that obtains, Nms+1 or Nms-1; Wrap generation module 114 simultaneously and whenever collect the ODUk of B byte and then the ODUk of this B byte is put into the payload of bag and produce a payload length bag 115 that is the B byte, the CI0 that bag generation module 114 calculates first computing module 111 simultaneously and CI1 expense 112 are put into and are wrapped 115 expense.

Adopt above-mentioned device embodiment as shown in Figure 4; The processing procedure of corresponding method is: in the decapsulation of wrapping ODUk is handled; Through the bag 115 among the Fig. 3 after switch fabric unit 103 processing, entering is wrapped in the decapsulation processing of ODUk, parse CI0 and CI1 expense 121 through parsing module 120 115 from wrapping; Send into second computing module 122 and obtain Nm123; The probable value of Nm123 only possibly be Nms, Nms+1 or Nms-1, and Nm123 and reference measurement clock 124 (its frequency is Cm) are sent into desynchronizer 125, and desynchronizer 125 will calculate Cj according to above-mentioned formula 2; And producing the ODUk clock 126 (its frequency is Cj) recover according to Cj, the frequency of the ODUk clock 126 that recovers will be consistent with the frequency of ODUk clock 105 among Fig. 3.In addition; In second computing module 122; Use the CI0 expense to produce Nm when not having packet loss; If detect 1 packet loss then use CI1,, more than handle making that the processing of recovered clock still can as far as possible correctly be carried out when packet loss was arranged if detect continuous many packet loss then force to export Nm=Nms.In addition, if hope to recover the clock of OTUk, then only need let top desynchronizer can recover the clock (its frequency is Cjk) of OTUk according to above-mentioned formula 3 work.

The above is merely preferred embodiment of the present invention, is not to be used to limit protection scope of the present invention.

Claims (9)

1. one kind is passed through the method that reference clock recovers the optical transfer network clock, it is characterized in that this method comprises:

The encapsulation process that is transformed into bag from ODUk or divides into groups, measure the frequency information of ODUk clock in the optical transfer network, the frequency information of measuring is encapsulated in the expense of bag or grouping with the reference measurement clock; Going out the decapsulation processing of ODUk, recover the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from bag or packet recovery.

2. method according to claim 1 is characterized in that, said ODUk be specially ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex); The frequency of ODUk is specially Ck; The frequency of said reference measurement clock is Cm; The frequency of the ODUk clock that recovers is specially Cj, and Cj=Ck; The length of said bag or grouping is fixed value, and the said bag of fixed length or divide into groups in payload length be the B byte, comprise the ODUk information of B byte, comprise the said frequency information of measuring of 2bit in the said bag of fixed length or the expense of grouping at least;

The encapsulation process that is transformed into bag from ODUk or divides into groups; At every turn the ODUk information of B byte is encapsulated into the said bag of fixed length or when dividing into groups, this method also comprises: counting whenever receives the periodicity Nm of reference measurement clock process described in the B byte ODUk information process; Nm is the frequency information of the said ODUk clock of measuring with the reference measurement clock;

Under the prerequisite of frequency deviation of ODUk less than positive and negative 150ppm; The value of said Nm is specially Nms, Nms-1 or Nms+1; Wherein, said Nms adopts formula 1:

calculates; Wherein, Cks is the standard speed of ODUk.

3. method according to claim 2 is characterized in that, this method also comprises: Nms, Nms-1 or the Nms+1 that will represent with 2bit be as the frequency information of measuring, and is encapsulated in the expense of said bag or grouping of fixed length to transmit.

4. method according to claim 3 is characterized in that, is going out the decapsulation processing of ODUk from bag or packet recovery, and this method also comprises:

From the expense of the said bag of fixed length or grouping, parse the frequency information of measuring of 2bit;

The Nms that calculates according to frequency information of measuring and the said formula 1 of 2bit obtains Nm, and the value of said Nm is specially Nms, Nms-1 or Nms+1;

According to said Nm, calculate said Cj with another reference measurement clock and the said B of said reference measurement clock same frequency, calculating the formula that adopts is formula 2:

5. method according to claim 4 is characterized in that, calculate Cj after, this method also comprises: with the Cj input desynchronizer according to said formula 2 designs, obtain the clock that frequency is Cj according to said formula 2; Said frequency is that the clock of Cj is: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation processing.

6. the described method of claim 4 is characterized in that, this method also comprises: calculate Cjk according to

; And it is imported the OTUk clock that said desynchronizer is restored out, and its frequency is Cjk, said OTUk is specially OTUk (k=1; 2,2e, 3; 3e1,3e2,4; 5,6).

7. one kind is recovered the device of optical transfer network clock through reference clock, it is characterized in that this device comprises: ODUk is to the processing module and the bag of bag or grouping or be grouped into the processing module of ODUk; Wherein,

Said ODUk is used for optical transfer network the encapsulation process that is transformed into bag from ODUk or divides into groups to the bag or the processing module of dividing into groups, and measures the frequency information of ODUk clock with the reference measurement clock, the frequency information of measuring is encapsulated in the expense of bag or grouping;

Said bag or be grouped into the processing module of ODUk; Be used for recovering the ODUk clock of same frequency according to the length of the reference measurement clock of same frequency, the said frequency information that from the expense of bag or grouping, parses and bag or grouping from the decapsulation processing of wrapping or packet recovery goes out ODUk.

8. device according to claim 7 is characterized in that, said ODUk be specially ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex); The frequency of ODUk is specially Ck; The frequency of said reference measurement clock is Cm; The frequency of the ODUk clock that recovers is specially Cj, and Cj=Ck; The length of said bag or grouping is fixed value, and the said bag of fixed length or divide into groups in payload length be the B byte, comprise the ODUk information of B byte, comprise the frequency information of measuring of 2bit in the said bag of fixed length or the expense of grouping at least;

Said ODUk further comprises to the processing module of bag or grouping: first counter, second counter, first computing module, bag or grouping generation module; Wherein,

Said first counter is used to count the byte number of the ODUk information that receives, and maximum is B;

Said second counter is used to count the periodicity Nm that whenever receives reference measurement clock process described in the B byte ODUk information process; Nm is the frequency information of the said ODUk clock of measuring with the reference measurement clock; Wherein, Under the prerequisite of frequency deviation of ODUk less than positive and negative 150ppm; The value of said Nm is specially Nms, Nms-1 or Nms+1; Wherein, said Nms adopts formula 1:

calculates; Wherein, Cks is the standard speed of ODUk;

Said first computing module; Be used to receive that the B byte count of first counter finishes index signal and the resulting Nm of second rolling counters forward; The value of said Nm is specially Nms, Nms-1 or Nms+1, and Nms, Nms-1 or the Nms+1 that will represent with 2bit are as the frequency information of measuring;

Said bag or grouping generation module are used to generate said bag or the grouping that payload length is the fixed length of B byte, the frequency information of measuring of 2bit is encapsulated in the expense of said bag or grouping of fixed length transmits simultaneously.

9. device according to claim 8 is characterized in that, said bag or the processing module that is grouped into ODUk further comprise: parsing module, second computing module, desynchronizer; Wherein,

Said parsing module is used for from the said bag of the fixed length received or divides into groups to parse the frequency information of measuring of 2bit;

Said second computing module is used for the Nms that frequency information of measuring and said formula 1 according to 2bit calculate and obtains Nm, and the value of said Nm is specially Nms, Nms-1 or Nms+1; According to said Nm, calculate said Cj with another reference measurement clock and the said B of said reference measurement clock same frequency, calculating the formula that adopts is formula 2:

Said desynchronizer is used for obtaining the clock that frequency is Cj according to the Cj and the said formula 2 of input; Said frequency is that the clock of Cj is: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation processing.

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