CN102480415B - A kind of method and device being recovered optical transport network clock by reference clock - Google Patents

Abstract

The invention discloses a kind of method being recovered optical transport network clock by reference clock, the method comprises: the frequency information measuring ODUk clock with reference measurement clock, is encapsulated into by the frequency information measured in the expense of bag or grouping; Going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.The invention also discloses and a kind ofly recover the device of optical transport network clock by reference clock, the processing module wherein wrapping or be grouped into ODUk recovers the ODUk clock of same frequency for the reference measurement clock according to same frequency, the frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.Adopt method of the present invention and device, make ODUk still can recover good clock after postponing indefinite bag or packet switching process.

Description

A kind of method and device being recovered optical transport network clock by reference clock

Technical field

The present invention relates to field of optical transport network, particularly relate to a kind of method and the device that are recovered optical transport network clock by reference clock.

Background technology

G.709 and G.798 optical transfer network standard is formulated by International Telecommunication Union (ITU-T), and substance is definition in, requires to realize ODUk (k=0 in standard, 1,2,2e, 3,3e1,3e2,4,5,6, flex etc.) cross scheduling of rank, require to realize ODUk clock transparent transmission while scheduling.Here, so-called ODUk refers to the Optical Channel Data Unit-k in optical transfer network.ODUk generally directly cannot realize cross scheduling, and another kind of signal format will be converted to, such as, realize cross scheduling again after being converted to SDH (Synchronous Digital Hierarchy) (SDH, SynchronousDigital Hierarchy) signal or being converted to bag or packet signal etc.The mode wherein realizing ODUk cross scheduling based on bag or packet switching has very large technical advantage, can allow user on a physical platform, realize the function of data equipment and transmission equipment simultaneously.But, owing to realizing the mode of ODUk cross scheduling based on bag or packet switching, can be delayed in processing procedure and not fix, and excursion is comparatively large, thus the problem caused is: after bag or packet switching, recover high-quality ODUk clock can be very difficult.If according to existing according to first in first out (FIFO, First Input First Output) or buffer depth produce the mode of recovered clock and cannot address this problem, at present in the urgent need to a solution, the enough good ODUk clock of quality and performance still can be recovered after postponing indefinite bag or packet switching process.

Summary of the invention

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

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

Recovered a method for optical transport network clock by reference clock, the method comprises:

In optical transfer network in the encapsulation process being transformed into bag or grouping from ODUk, measure the frequency information of ODUk clock with reference measurement clock, the frequency information measured is encapsulated in the expense of bag or grouping; Going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

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

In the encapsulation process being transformed into bag or grouping from ODUk, at every turn by the ODUk Information encapsulation of B byte to the described bag of fixed length or grouping time, the method also comprises: count the periodicity Nm often receiving reference measurement clock process described in B byte ODUk information process; Nm is the frequency information of the ODUk clock that described reference measurement clock is measured;

Be less than the prerequisite of positive and negative 150ppm in the frequency deviation of ODUk under, the value of described Nm is specially Nms, Nms-1 or Nms+1, and wherein, described Nms adopts formula 1: calculate; Wherein, Cks is the standard speed of ODUk.

Wherein, the method also comprises: using Nms, Nms-1 or Nms+1 of representing with 2bit as the frequency information measured, and is encapsulated in the described bag of fixed length or the expense of grouping and transmits.

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

The frequency information measured of 2bit is parsed from the described bag of fixed length or the expense of grouping;

Obtain Nm according to the Nms that the frequency information measured and the described formula 1 of 2bit calculate, the value of described Nm is specially Nms, Nms-1 or Nms+1;

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

Wherein, after calculating Cj, the method also comprises: Cj is inputted the desynchronizer designed according to described formula 2, obtain according to described formula 2 clock that frequency is Cj; Described frequency is the clock of Cj: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation process.

Wherein, the method also comprises: according to calculate Cjk, and inputted the OTUk clock that described desynchronizer is restored out, its frequency is Cjk, and described OTUk is specially OTUk (k=1,2,2e, 3,3e1,3e2,4,5,6).

Recover the device of optical transport network clock by reference clock, this device comprises: ODUk is to bag or the processing module of dividing into groups and bag or the processing module being grouped into ODUk; Wherein,

Described ODUk to bag or grouping processing module, in optical transfer network be transformed into from ODUk bag or grouping encapsulation process in, measure the frequency information of ODUk clock with reference measurement clock, the frequency information measured is encapsulated into bag or grouping expense in;

Described bag or be grouped into the processing module of ODUk, for going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

Wherein, described ODUk is specially ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex); The frequency of ODUk is specially Ck; The frequency of described reference measurement clock is Cm; The frequency of the ODUk clock recovered is specially Cj, and Cj=Ck; The length of described bag or grouping is fixed value, and the payload length in the described bag of fixed length or grouping is B byte, comprises the ODUk information of B byte, at least comprises the frequency information measured of 2bit in the described bag of fixed length or the expense of grouping;

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

Described first counter, for counting the byte number of the ODUk information received, maximum is B;

Described second counter, for counting the periodicity Nm often receiving reference measurement clock process described in B byte ODUk information process; Nm is the frequency information of the ODUk clock that described reference measurement clock is measured; Wherein, be less than the prerequisite of positive and negative 150ppm in the frequency deviation of ODUk under, the value of described Nm is specially Nms, Nms-1 or Nms+1, and wherein, described Nms adopts formula 1: calculate; Wherein, Cks is the standard speed of ODUk;

Described first computing module, B byte count for receiving the first counter terminates the Nm that index signal and the second rolling counters forward obtain, the value of described Nm is specially Nms, Nms-1 or Nms+1, using Nms, Nms-1 or Nms+1 of representing with 2bit as the frequency information measured;

Described bag or grouping generation module, for generating the described bag or grouping that payload length is the fixed length of B byte, being encapsulated into the frequency information measured of 2bit in the described bag of fixed length or the expense of grouping simultaneously and transmitting.

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

Described parsing module, for parsing the frequency information measured of 2bit from the described bag or grouping of the fixed length received;

Described second computing module, obtain Nm for the Nms calculated according to the frequency information measured and the described formula 1 of 2bit, the value of described Nm is specially Nms, Nms-1 or Nms+1; According to described Nm, calculate described Cj with another reference measurement clock of described reference measurement clock same frequency and described B, calculating the formula adopted is formula 2:

Described desynchronizer, for obtaining according to the Cj inputted and described formula 2 clock that frequency is Cj; Described frequency is the clock of Cj: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation process.

In optical transfer network of the present invention in the encapsulation process being transformed into bag or grouping from ODUk, measure the frequency information of ODUk clock with reference measurement clock, the frequency information measured is encapsulated in the expense of bag or grouping; Going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

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

Accompanying drawing explanation

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

Fig. 2 is apparatus of the present invention at the existing position view realized based on bag or packet switching in the system of ODUk cross scheduling;

Fig. 3 is that apparatus of the present invention realize the embodiment schematic diagram of ODUk to the encapsulation process of wrapping or divide into groups;

Fig. 4 is the embodiment schematic diagram that apparatus of the present invention realize the decapsulation process wrapping or be grouped into ODUk.

Embodiment

Basic thought of the present invention is: in optical transfer network in the encapsulation process being transformed into bag or grouping from ODUk, measure the frequency information of ODUk clock with reference measurement clock, is encapsulated into by the frequency information measured in the expense of bag or grouping; Going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

Be described in further detail below in conjunction with the enforcement of accompanying drawing to technical scheme.

The present invention can ignore bag or packet switching produce delay not stationarity on the impact of recovered clock, recover the ODUk clock that quality and performance is enough good.And the recovery effects of ODUk clock and existingly separate from Optical Channel Transport Unit-k (OTUk) cbr (constant bit rate) (CBR that asynchronous mapping recovers, Constant Bit Rate) effect of signal is suitable, thus make the performance of ODUk or the OTUk clock recovered 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 frequency, therefore, in fact the present invention needs the frequency information by measuring ODUk clock with reference measurement clock (this frequency information measured is Nm) to transmit Ck, because the value of Nm may be greater than 1,000, cannot represent with 2bit, but because Nm can represent by the mode that Nms adds and subtracts deviant, and due to Nms be fixed value can by calculate obtain, so only need with 2bit transmission deviation value can reach transmission Nm object.

A method for optical transport network clock is recovered, with ODUk (k=0,1,2,2e by reference clock, 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 current example, mainly comprise following content:

The schematic flow sheet of Method And Principle as shown in Figure 1, comprises the following steps:

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

Step 102, going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency by the reference measurement clock of same frequency, the frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

For convenience, the definition of following parameter is done:

The frequency information of the ODUk clock that a1, reference measurement clock are measured, the frequency of ODUk namely to be transmitted is Ck.

A2, the clock frequency of ODUk recovered after bag or packet switching be Cj, Cj and Ck closely, and the change of Ck can be followed and change.

The frequency of a3, reference measurement clock is Cm, reference measurement clock is multiple, same reference measurement clock is present in all ODUk that realizes of the present invention to wrapping or dividing into groups in the device of encapsulation process, is also present in all realization bags of the present invention or is grouped in the device of decapsulation process of ODUk.All reference measurement clocks are only required that frequency unanimously, does not require that phase place is consistent.

A4, often receive B byte ODUk after composition one bag or grouping send, bag or the payload length comprising ODUk in dividing into groups are fixed as B byte, then the length of bag or grouping is fixed length, is fixing B+h byte, wherein the byte of h shared by the expense of bag or grouping.

There is the proprietary territory of 4bit in a5, bag or packet overhead, respectively called after CI0 (accounting for 2bit) and CI1 (accounting for 2bit), be used for the frequency information of the ODUk clock measured mentioned in transmission a1.Frequency information reality only needs 2bit, with CI0 time normal, increase CI1 expense also for transmitting the frequency information of the ODUk clock mentioned in a1, its benefit to guarantee that loss 1 is wrapped or frequency information can not be lost after dividing into groups, thus guarantee to recover according to the frequency information in expense the ODUk clock of same frequency.If frequency information is not still lost after needing to support to lose n bag continuously, the expense of 2 × (n+1) individual bit can be used further.That is, after the frequency information of the ODUk clock measured mentioned in the a1 obtaining 2bit, in order to ensure the bag of fixed length or be grouped in exchange process, after losing the bag of continuous n this fixed length or grouping, the frequency information of this ODUk clock is not lost, the frequency information of this ODUk clock of above 2bit can be copied to continuous n+1 (n be greater than 1 integer) the bag of fixed length or grouping in, take the expense of 2 × (n+1) individual bit, thus guarantee the frequency information that still can obtain this ODUk clock of 2bit after the bag losing n fixed length continuously or grouping.

The standard speed of a6, ODUk is Cks.

Here it is to be noted: consider bag and grouping to realize principle basically identical, if below do not do specified otherwise, then by bag with divide into groups all to be referred to as bag.

According to above-mentioned parameter definition, the solution of the present invention is described below:

First stage: be transformed in the encapsulation process of bag from ODUk, Ck clock often receives the ODUk of B byte, counting often receives the periodicity Nm that B byte ODUk information process medium frequency is the reference measurement clock process of Cm, and Nm also can be described as the number of Cm clock.Positive and negative 150ppm is less than and B is no more than B in the frequency deviation of ODUk _maxprerequisite under, the value of Nm may be only Nms, Nms-1 or Nms+1, and wherein the value of Nms can calculate according to formula 1 below:

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

In formula 1 above, 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 at least positive and negative 150ppm, require that Cm × B value can not be too large, suppose that Cm is 350MHz, only need ensure that Nms is less than (1000000/150)-0.5, the adjusting range being greater than positive and negative 150ppm can be ensured, the maximum B of the B obtained like this _maxas shown in table 1 below, table 1 is B corresponding to ODUk each when Cm is 350MHz _maxmaximum list.

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 _maxbe worth minimum, so when Cm equals 350MHz, as long as keep B to be less than 2962 can ensure that this scheme has the frequency deviation tolerance of at least positive and negative 150ppm to ODUk.If reduce the frequency of Cm, then B _maxvalue also can increase.

Second stage: by the Nms utilizing formula 1 to calculate, Nms-1 or Nms+1 is converted to the frequency information of the ODUk clock measured mentioned in the a1 of 2bit, namely respectively by Nms, corresponding 2 bit00 of Nms-1 or Nms+1, bit01, bit10, and by the CI0 territory being put into the expense of the bag that next B byte ODUk forms of these 2 bit, these 2 bit are put into the CI1 territory of the expense of the bag that next but one B byte ODUk forms simultaneously, here, the described CI1 territory of unwrapping pin putting into next but one B byte ODUk composition refers to: guarantee that the frequency information of 2bit will 2 bag backups continuously.

Phase III: recovering in the decapsulation process of ODUk from bag, from the CI0 territory of unwrapping pin, the deviant of the frequency information of 2bit corresponding to a bag is obtained when there is no packet loss, (value of Nm may be Nms can to obtain the number Nm of clock Cm corresponding to a bag B byte ODUk according to calculated value Nms above again, Nms-1 or Nms+1), according to formula 2 below, by Nm, Cm and B inputs desynchronizer can recover the clock that frequency is Cj, Cj will follow Ck change, this frequency is the clock of Cj: the ODUk clock of the same frequency recovered after the delayed indefinite bag of ODUk or packet switching process.

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 the above process, if lost 1 bag, then the CI1 territory of the next one bag of available lost package obtains the number Nm of the Cm clock of the bag correspondence before lost package, and the value of an automatic filling B byte is the byte of 0, thus ensureing only have some error codes when loss 1 is wrapped and there is no frame head shifting phenomena, the effect of recovered clock is not affected simultaneously.If lost many bags continuously, can think that the Cm number in lost package is Nms, and the value that the bag number that automatic filling quantity is loss is multiplied by B byte is the byte of 0, byte number in the ODUk frame recovered like this will be completely normally some error code, can't frame head displacement be produced because of many or few byte and then produce of short duration frame losing mistake, although now also some impacts can be produced on the synchronous effect of desynchronizer, as long as but the bag lost only can cause temporary time clock tracking bad not too at most, clock information can't be caused to lose completely, after packet loss, clock will not recover synchronous very soon.

Fourth stage: on the basis of phase III, if wish to recover OTUk (k=1,2,2e, 3,3e1,3e2,4,5,6) clock, because the clock frequency of OTUk and ODUk exists fixing proportionate relationship, therefore, only formula 3 below need be inputted the OTUk clock that can be restored out in desynchronizer, its frequency is Cjk.Visible: after ODUk (k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex) delayed indefinite bag or packet switching process, still to recover the enough good OTUk of quality and performance (k=1,2,2e, 3,3e1,3e2,4,5,6) clock.Wherein, OTUk is at least OTUk (k=1,2,2e, 3,3e1,3e2,4,5,6), is not limited to current example.

Formula 3:

Recover the device of optical transport network clock by reference clock, mainly comprise: ODUk is to bag or the processing module of dividing into groups and bag or the processing module being grouped into ODUk.Wherein, ODUk to be used in optical transfer network, in the encapsulation process being transformed into bag or grouping from ODUk, measuring the frequency information of ODUk clock, be encapsulated into by the frequency information measured in the expense of bag or grouping with reference measurement clock to the processing module of bag or grouping.Bag or be grouped into ODUk processing module for going out in the decapsulation process of ODUk from bag or packet recovery, recover the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

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

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

First counter, for counting the byte number of the ODUk information received, maximum is B;

Second counter, for counting the periodicity Nm often receiving reference measurement clock process described in B byte ODUk information process; Nm is the frequency information of the ODUk clock measured with reference measurement clock; Wherein, positive and negative 150ppm is less than and B is no more than B in the frequency deviation of ODUk _maxprerequisite under, the value of described Nm may be only Nms, Nms-1 or Nms+1, and wherein, described Nms adopts formula 1: calculate; Wherein, Cks is the standard speed rate of ODUk;

First computing module, B byte count for receiving the first counter terminates the Nm that index signal and the second rolling counters forward obtain, the value of described Nm may be only Nms, Nms-1 or Nms+1, using Nms, Nms-1 or Nms+1 of representing with 2bit as the frequency information measured;

Bag or grouping generation module, for generating the described bag or grouping that payload length is the fixed length of B byte, being encapsulated into the frequency information measured of 2bit in the described bag of fixed length or the expense of grouping simultaneously and transmitting.

Here, to wrap or the processing module that is grouped into ODUk comprises further: parsing module, the second computing module, desynchronizer; Wherein,

Parsing module, for parsing the frequency information measured of 2bit from the described bag or grouping of the fixed length received;

Second computing module, obtains Nm for the Nms calculated according to the frequency information measured and the described formula 1 of 2bit, and the value of described Nm may be only Nms, Nms-1 or Nms+1; According to described Nm, calculate described Cj with another reference measurement clock of described reference measurement clock same frequency and described B, calculating the formula adopted is formula 2:

Desynchronizer, for obtaining according to the Cj inputted and described formula 2 clock that frequency is Cj; Described frequency is the clock of Cj: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation process.

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

1, method of the present invention and device is adopted, solve the problem that ODUk is difficult to by ODUk clock after packet network recover, the delay uncertainty of ODUk clock recovery effect and packet switch is irrelevant, that is can ignore bag or packet switching produce delay not stationarity on the impact of recovered clock, to recover the enough good ODUk clock of quality and performance.

2, the inventive method and device recovered clock principle and existingly from OTUk, separate asynchronous mapping to recover the principle of CBR similar, clock recovery effect is also consistent.Because the frequency of Cm and the length of B can be arranged, adopt method of the present invention and device, by selecting suitable Cm and B, even can reach and recovering the better effect of CBR than separating asynchronous mapping from OTUk.

3, method of the present invention and device is adopted, the bag obtained after encapsulating ODUk is the fixed length bag of regular length, and the length of bag can be arranged, fixed length wraps in by having higher efficiency and less delay during packet switching system, make to be optimized general packet switching system to become possibility simultaneously, it can be simplified significantly when only needing support ODUk to intersect, and that reduces packet switching system realizes cost.

4, method of the present invention and device is adopted, the bag obtained after encapsulating ODUk is fixed length bag, and the length of bag can be arranged, by selecting suitable packet length, parallel processing when recovering ODUk from fixed length bag can be made very simple, in order to realize the parallel processing of ODUk and the operation repeatedly adjusting ODUk width of complexity carried out when avoiding recovering ODUk from elongated bag.

5, method of the present invention and device is adopted, the packet loss phenomenon occurred in packet switch process can being tolerated better, when using 4bit expense, frame head inconsistent phenomenon can be there will not be when loss one is wrapped, only occur some error codes, the performance of recovered clock is not affected simultaneously; Also frame head inconsistent phenomenon is there will not be when losing many bags continuously, only there are some error codes, the followability of recovered clock can temporarily be affected simultaneously, but there will not be shake to exceed standard phenomenon, and not after packet loss time clock tracking will recover normal very soon, if use the expense of 2 × (n+1) bit, then when can ensure to lose n bag continuously, the performance of recovered clock is unaffected.

Carry out citing to the present invention below to set forth.

Fig. 2 is apparatus of the present invention at the existing position view realized based on bag or packet switching in the system of ODUk cross scheduling.Existingly realize the equipment of ODUk cross scheduling based on bag or packet switching, to be wrapped to bag or the converting unit (as shown in the 100-1 to 100-n in Fig. 2) of dividing into groups, n by n ODUk or be grouped into switching network adaptation unit (101-1 to 101-n as in Fig. 2) and switch fabric unit 103 forms.First ODUk is converted to bag or grouping by this system, then is unified backplane signal by bag or packet switched, then carries out exchange scheduling by switching network, thus realizes the cross scheduling of ODUk.Reference measurement clock (as shown in the 104-1 to 104-n in Fig. 2) in Fig. 2 for the present invention need increase content, for auxiliary ODUk through clock recovery during switching network, require that reference measurement clock (as shown in the 104-1 to 104-n in Fig. 2) is necessary for the same frequency clock from same high precision reference clock source, the phase place of this n clock can be inconsistent, 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 ODUk of this system shown in Fig. 2 to the conversion converting unit (as shown in the 100-1 to 100-n of Fig. 2) of wrapping or divide into groups.

Device embodiment one: for apparatus of the present invention realize the embodiment of ODUk to the encapsulation process of wrapping or divide into groups, ODUk is to the processing module of wrapping or divide into groups, consider bag and grouping to realize principle basically identical, if below do not do specified otherwise, then by bag with divide into groups all to be referred to as bag.

ODUk as shown in Figure 3 comprises to the processing module of bag or grouping: ODUk clock 105 (its frequency is Ck), ODUk data 113, first counter 106 (for calculating the ODUk byte number received, maximum is B), B byte count terminate index signal 107 count value of the first counter 106 (be reach the index signal after B byte), reference measurement clock 109 (frequency is Cm), second counter 108 (measuring clock 109 number for Calculation Basis), count value 110 is current count values of the second counter 108, first computing module 111 is (for terminating index signal 107 and count value 110 according to the B byte count of the first counter 106, produce CI0 and CI1 expense 112), CI0 and CI1 expense 112 (being CI0 and the CI1 expense that the first computing module 111 produces), bag generation module 114 is (for generating the bag that payload length is B byte, , according to the ODUk clock 105 inputted and ODUk data 113, the ODUk of B byte is encapsulated into the payload part of bag, the length of payload is made to be B byte, CI0 and CI1 expense 112 is loaded in the expense of bag) simultaneously, bag 115 is (for the payload length generated by bag generation module 114 is the bag of B byte, this bag switch fabric unit 103 finally entered in Fig. 2 does and exchanges process).

Device embodiment two: for apparatus of the present invention realize an embodiment of the decapsulation process wrapping or be grouped into ODUk, be specially the processing module wrapping or be grouped into ODUk, consider bag and grouping to realize principle basically identical, if below do not do specified otherwise, then by bag with divide into groups all to be referred to as bag.

Bag 115 (for Fig. 3 is the bag of B byte by the payload length that bag generation module 114 generates) is after the switch fabric unit 103 in Fig. 2 does and exchanges and process, enter bag as shown in Figure 4 or be grouped into the processing module of ODUk, as shown in Figure 4, comprise: parsing module 120 (for parsing CI0 and CI1 expense 121 from the bag 115 of B byte length), second computing module 122 (calculating Nm123 for parsing CI0 and CI1 expense 121 according to these), desynchronizer 125 is (for recovering according to Nm123 and reference measurement clock 124 the ODUk clock 126 that frequency is Cj, frequency Ck with the ODUk clock 105 in Fig. 3 is consistent by Cj).

Adopt above-mentioned device embodiment as shown in Figure 3, the processing procedure of corresponding method is: in the encapsulation process of ODUk to bag, ODUk clock 105 (its frequency is Ck) enters the first counter 106, often count down to B byte, produces 1 B byte count and terminates index signal 107; Second counter 108 Calculation Basis measures the number of clock 109 (its frequency is Cm), and it counts, and number is sufficiently large ensures that count value can not be overflowed between adjacent two sigtnal intervals that B byte count terminates index signal 107; First computing module 111 calculates two adjacent B byte counts and terminates between the signal of index signal 107, the difference of the count value that the second counter 108 exports, thus often received the clock number of reference measurement clock 109 in the B byte ODUk time, be less than the prerequisite of positive and negative 100ppm at ODUk clock frequency deviation under, an above clock numerical value can be Nms, Nms+1 or Nms-1 only, wherein Nms is constant, can be calculated by above-mentioned formula 1; First computing module produces CI0 and CI1 expense 112 according to Nms, Nms+1 or Nms-1 of obtaining, the ODUk of this B byte is then put into the payload of bag and produces the bag 115 that a payload length is B byte by the ODUk that bag generation module 114 often collects B byte simultaneously, CI0 and the CI1 expense 112 that the first computing module 111 calculates is put into the expense of bag 115 by bag generation module 114 simultaneously.

Adopt above-mentioned device embodiment as shown in Figure 4, the processing procedure of corresponding method is: at bag in the decapsulation process of ODUk, bag 115 in Fig. 3 after switch fabric unit 103 processes, to bag be entered in the decapsulation process of ODUk, from bag 115, CI0 and CI1 expense 121 is parsed by parsing module 120, send into the second computing module 122 and obtain Nm123, the probable value of Nm123 may be only Nms, Nms+1 or Nms-1, Nm123 and reference measurement clock 124 (its frequency is Cm) are sent into desynchronizer 125, desynchronizer 125 will calculate Cj according to above-mentioned formula 2, and the ODUk clock 126 (its frequency is Cj) recovered is produced according to Cj, frequency with the ODUk clock 105 in Fig. 3 is consistent by the frequency of the ODUk clock 126 recovered.In addition, in the second computing module 122, do not have to use CI0 expense to produce Nm during packet loss, if 1 packet loss detected, use CI1, if continuous many packet loss detected, force to export Nm=Nms, when above process makes packet loss, the process of recovered clock still can as far as possible correctly perform.In addition, if wish the clock recovering OTUk, then desynchronizer above only need be allowed can to recover the clock (its frequency is Cjk) of OTUk according to above-mentioned formula 3 work.

The above, be only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.

Claims (9)

1. recovered a method for optical transport network clock by reference clock, it is characterized in that, the method comprises:

In optical transfer network in the encapsulation process being transformed into bag or grouping from ODUk, measure the frequency information of ODUk clock with reference measurement clock, the frequency information measured is encapsulated in the expense of bag or grouping; Going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

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

In the encapsulation process being transformed into bag or grouping from ODUk, at every turn by the ODUk Information encapsulation of B byte to the described bag of fixed length or grouping time, the method also comprises: count the periodicity Nm often receiving reference measurement clock process described in B byte ODUk information process; Nm is the frequency information of the ODUk clock that described reference measurement clock is measured;

Be less than the prerequisite of positive and negative 150ppm in the frequency deviation of ODUk under, the value of described Nm is specially Nms, Nms-1 or Nms+1, and wherein, described Nms adopts formula 1: calculate; Wherein, Cks is the standard speed of ODUk, and described Nms equals by described Cm, described B byte and integer 8 product again divided by after described Cks, round.

3. method according to claim 2, is characterized in that, the method also comprises: using Nms, Nms-1 or Nms+1 of representing with 2bit as the frequency information measured, and is encapsulated in the described bag of fixed length or the expense of grouping and transmits.

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

The frequency information measured of 2bit is parsed from the described bag of fixed length or the expense of grouping;

Obtain Nm according to the Nms that the frequency information measured and the described formula 1 of 2bit calculate, the value of described Nm is specially Nms, Nms-1 or Nms+1;

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

5. method according to claim 4, is characterized in that, after calculating Cj, the method also comprises: Cj is inputted the desynchronizer designed according to described formula 2, obtain according to described formula 2 clock that frequency is Cj; Described frequency is the clock of Cj: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation process.

6. method according to claim 4, is characterized in that, the method also comprises: according to calculate Cjk, and inputted the OTUk clock that desynchronizer is restored out, its frequency is Cjk, and described OTUk is specially OTUk, wherein, and k=1,2,2e, 3,3e1,3e2,4,5,6.

7. recover the device of optical transport network clock by reference clock, it is characterized in that, this device comprises: ODUk is to bag or the processing module of dividing into groups and bag or the processing module being grouped into ODUk; Wherein,

Described ODUk to bag or grouping processing module, in optical transfer network be transformed into from ODUk bag or grouping encapsulation process in, measure the frequency information of ODUk clock with reference measurement clock, the frequency information measured is encapsulated into bag or grouping expense in;

Described bag or be grouped into the processing module of ODUk, for going out in the decapsulation process of ODUk from bag or packet recovery, recovering the ODUk clock of same frequency according to the reference measurement clock of same frequency, the described frequency information parsed from the expense of bag or grouping and bag or the length of dividing into groups.

8. device according to claim 7, is characterized in that, described ODUk is specially ODUk, wherein, and k=0,1,2,2e, 3,3e1,3e2,4,5,6, flex; The frequency of ODUk is specially Ck; The frequency of described reference measurement clock is Cm; The frequency of the ODUk clock recovered is specially Cj, and Cj=Ck; The length of described bag or grouping is fixed value, and the payload length in the described bag of fixed length or grouping is B byte, comprises the ODUk information of B byte, at least comprises the frequency information measured of 2bit in the described bag of fixed length or the expense of grouping;

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

Described first counter, for counting the byte number of the ODUk information received, maximum is B;

Described second counter, for counting the periodicity Nm often receiving reference measurement clock process described in B byte ODUk information process; Nm is the frequency information of the ODUk clock that described reference measurement clock is measured; Wherein, be less than the prerequisite of positive and negative 150ppm in the frequency deviation of ODUk under, the value of described Nm is specially Nms, Nms-1 or Nms+1, and wherein, described Nms adopts formula 1: calculate; Wherein, Cks is the standard speed of ODUk, and described Nms equals by described Cm, described B byte and integer 8 product again divided by after described Cks, round;

Described first computing module, B byte count for receiving the first counter terminates the Nm that index signal and the second rolling counters forward obtain, the value of described Nm is specially Nms, Nms-1 or Nms+1, using Nms, Nms-1 or Nms+1 of representing with 2bit as the frequency information measured;

Described bag or grouping generation module, for generating the described bag or grouping that payload length is the fixed length of B byte, being encapsulated into the frequency information measured of 2bit in the described bag of fixed length or the expense of grouping simultaneously and transmitting.

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

Described parsing module, for parsing the frequency information measured of 2bit from the described bag or grouping of the fixed length received;

Described second computing module, obtain Nm for the Nms calculated according to the frequency information measured and the described formula 1 of 2bit, the value of described Nm is specially Nms, Nms-1 or Nms+1; According to described Nm, calculate described Cj with another reference measurement clock of described reference measurement clock same frequency and described B, calculating the formula adopted is formula 2:

Described desynchronizer, for obtaining according to the Cj inputted and described formula 2 clock that frequency is Cj; Described frequency is the clock of Cj: the ODUk clock of the same frequency that ODUk recovers after encapsulation process and decapsulation process.