CN104717030B

CN104717030B - Method for synchronizing time and relevant device, system

Info

Publication number: CN104717030B
Application number: CN201310693681.XA
Authority: CN
Inventors: 李晗; 张德朝; 王世光; 韩柳燕; 耿亮; 程伟强
Original assignee: China Mobile Communications Group Co Ltd
Current assignee: China Mobile Communications Group Co Ltd
Priority date: 2013-12-17
Filing date: 2013-12-17
Publication date: 2017-11-03
Anticipated expiration: 2033-12-17
Also published as: CN104717030A

Abstract

The invention discloses a kind of method for synchronizing time and relevant device, system, including：Optical network unit ONU receives in the very first time sync message that the small base station of its second line of a couplet is sent, the very first time sync message and carries the time synchronizing signal that small base station is obtained from macro base station；In the time synchronizing signal that the very first time sync message received is carried, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the second line of a couplet；According to the reference synchronization source determined, time synchronized is carried out to each small base station of the second line of a couplet.Using technical solution of the present invention, can solve the problem that the synchronization accuracy between each small base station in the prior art is relatively low, and time synchronized reliability it is poor the problem of.

Description

Method for synchronizing time and relevant device, system

Technical field

The present invention relates to communication technical field, more particularly to a kind of method for synchronizing time and relevant device, system.

Background technology

Small base station is supplement and the extension of macro base station network, and it is mainly by being placed in subscriber household or office Small base station provide the user wireless access, to improve the in-door covering effect of user, lift the experience of user.Small base station Between need stringent synchronization in time, with avoid interference, and improve user link capacity and communication quality.

Wherein, small base station mainly includes miniature（Micro）Base station, nanometer（Nano）Base station, femto base station（Pico）, milli Slightly（Femto）Base station etc..

In Scaledeployment small base station, because deployed position is low, deployment quantity is big, therefore passive optical-fiber network （Passive Optical Network, PON）It is the preferable return network of small base station.

PON technologies are to realize intelligent acess（Fiber To The X, FTTx）Mainstream technology, typical PON system by Local side apparatus optical line terminal（Optical Line Terminal, OLT）, ustomer premises access equipment optical network unit（Optical Network Unit, ONU）And Optical Distribution Network（Optical Distribution Network, ODN）Composition.Such as Fig. 1 institutes Show, be PON system Organization Chart.Wherein, " passive " refers to not contain any active electronic device and electronic power supply in ODN, all It is made up of the Passive Optical Components such as optical fiber and light point/combiner.

The time synchronized between small base station can be realized using air interface synchronization mode at present, specifically, each small base station passes through Intercept the time synchronizing signal of macro base station around to adjust the internal clocking of itself, so as to realize the synchronization between each small base station. If but the time signal for not having macro base station or small base station to listen to around small base station is weaker, between each small base station just not Time synchronized can be realized.

But in Scaledeployment small base station, there are following defects in above-mentioned air interface synchronization mode：

1st, for concentrating only part small base station in the region disposed, usual region directly to be listened to by eating dishes without rice or wine The time synchronizing signal of macro base station, and other small base stations are then needed from the small of the time synchronizing signal that can listen to macro base station Time synchronizing signal is obtained in type base station, therefore, time synchronizing signal needs just to be delivered to by more synchronous hop count small Type base station, and synchronous hop count is more, error is bigger, therefore the synchronization accuracy between each small base station is relatively low.

2nd, for scattered deployment region, it is necessary to small base station can directly listen to the time synchronizing signal of macro base station, The deployment difficulty of small base station is added, if small base station can not directly listen to the time synchronizing signal of macro base station, it is necessary to Small base station uses global positioning system（GPS, Global Positioning System）To obtain time synchronizing signal, and In indoor small base station due to the influence of penetration loss, it is difficult to directly obtain GPS time synchronizing signal, thus it is each small-sized Synchronization accuracy between base station is relatively low.

If PON is the return network of small base station, 1588v2 time synchronizeds can be transmitted to small base station from PON and believed Number, but when the synchronous failure of single OLT or PON mouthfuls of time of occurrence, great quantity of small base station under the OLT or the PON mouthfuls is by nothing Method carries out time synchronized, the normal work of small base station is have impact on, hence in so that the reliability of the time synchronized between small base station It is poor.

The content of the invention

The embodiment of the present invention provides a kind of method for synchronizing time and relevant device, system, each in the prior art to solve Synchronization accuracy between small base station is relatively low, and time synchronized reliability it is poor the problem of.

Technical scheme of the embodiment of the present invention is as follows：

The embodiment of the present invention provides a kind of method for synchronizing time, including：

Optical network unit ONU receives the very first time sync message that the small base station of its second line of a couplet is sent, the very first time The time synchronizing signal that small base station is obtained from macro base station is carried in sync message；

In the time synchronizing signal that the very first time sync message received is carried, it is determined that to each small base station of the second line of a couplet Carry out the reference synchronization source of time synchronized；

According to the reference synchronization source determined, time synchronized is carried out to each small base station of the second line of a couplet.

Therefore, in technical scheme of the embodiment of the present invention, when PON is the return network of small base station, the ONU second lines of a couplet Small base station is got after the time synchronizing signal of macro base station, and the time synchronizing signal got is carried into synchronous in the very first time ONU is reported in message, ONU chooses reference synchronization source in the time synchronizing signal received, then according to the synchronization of selection Reference source carries out time synchronized to each small base station of the second line of a couplet.Therefore, when carrying out time synchronized between small base station, portion need to only be ensured Point small base station can well reception macro base station time synchronizing signal, significantly reduce the deployment hardly possible of small base station Degree, and adaptation scene is extended, can also even if part small base station can not directly receive the time synchronizing signal of macro base station The reference synchronization source chosen according to ONU carries out time synchronized, without obtaining time synchronized letter from other small base stations or from GPS Number, the timing tracking accuracy between small base station is effectively improved, further, since avoiding when OLT or PON mouthfuls of time of occurrence is same When walking failure, small base station can not carry out the situation of time synchronized, therefore improve the reliable of time synchronized between small base station Property.

It is preferred that, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each of the second line of a couplet Small base station carries out the reference synchronization source of time synchronized, specifically includes：

It is determined that the corresponding synchronous priority of time synchronizing signal that the very first time sync message received is carried；

In the time synchronizing signal that the very first time sync message received is carried, corresponding synchronous priority is chosen most High time synchronizing signal；

By the time synchronizing signal of selection, confirm as carrying out each small base station of the second line of a couplet reference synchronization of time synchronized Source.

By this embodiment scheme, reference synchronization source, Neng Gouti are used as according to synchronous priority access time synchronizing signal The accuracy in the reference synchronization source that height is chosen, so as to improve the precision of time synchronized.

It is preferred that, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each of the second line of a couplet Small base station is carried out before the reference synchronization source of time synchronized, in addition to：

ONU receives the second time synchronized message that the optical line terminal OLT of its first line of a couplet is sent, the second time synchronized report The time synchronizing signal of OLT acquisitions is carried in text；

In the time synchronizing signal that the very first time sync message received is carried, it is determined that to each small base station of the second line of a couplet The reference synchronization source of time synchronized is carried out, is specifically included：

The time synchronizing signal and the second time synchronized message carried in the very first time sync message received is carried Time synchronizing signal in, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the second line of a couplet.

By this embodiment scheme, ONU supports the not homologous time synchronizing signal bang path of two-way, all the way for OLT to Lower transmission, from upstream network side obtain time synchronizing signal, another road be small base station be communicated up, from macro base station The time synchronizing signal of acquisition, time synchronizing signal bang path breaks down all the way wherein or the time synchronized of transmission is believed During number exception, time synchronized between small base station can be effectively raised using time synchronizing signal bang path all the way in addition Reliability.

It is preferred that, the time synchronizing signal and the second time synchronized report carried in the very first time sync message received In the time synchronizing signal that text is carried, it is determined that carrying out the reference synchronization source of time synchronized, specific bag to each small base station of the second line of a couplet Include：

It is determined that the corresponding synchronous priority of time synchronizing signal that the very first time sync message that receives is carried and the The corresponding synchronous priority of time synchronizing signal that two time synchronized messages are carried；

The time synchronizing signal and the second time synchronized message carried in the very first time sync message received is carried Time synchronizing signal in, choose the time synchronizing signal of corresponding synchronous highest priority；

It is preferred that, it is determined that the corresponding synchronization of time synchronizing signal that the very first time sync message received is carried is preferential Level, is specifically included：

From the preset field of the very first time sync message received, very first time sync message carrying is extracted The corresponding synchronous priority of time synchronizing signal.

It is preferred that, the synchronous priority carried in very first time sync message is：

Small base station is got after time synchronizing signal from macro base station, according to the signal matter of the time synchronizing signal of acquisition What amount was determined；Or

The signal matter of time synchronizing signal that small base station is prestored, being obtained according to the small base station from macro base station What amount was determined.

In corresponding relation between the small base station prestored and synchronous priority, search and send very first time synchronization The corresponding synchronous priority of small base station of message, and by the synchronous priority found, confirm as the very first time and synchronously report The corresponding synchronous priority of time synchronizing signal that text is carried.

It is preferred that, the corresponding synchronous priority of small base station be previously according to the small base station obtained from macro base station when Between synchronizing signal signal quality determine.

It is preferred that, it is determined that the corresponding synchronization of time synchronizing signal that the second time synchronized message received is carried is preferential Level, is specifically included：

From the preset field of the second time synchronized message received, the second time synchronized message carrying is extracted The corresponding synchronous priority of time synchronizing signal.

It is preferred that, the synchronous priority carried in the second time synchronized message is：

OLT is got after time synchronizing signal, is determined according to the signal quality of the time synchronizing signal of acquisition；Or

What the signal quality of time synchronizing signal that OLT is prestored, according to acquisition was determined.

Obtain the corresponding synchronous priority of OLT prestore, described；

The synchronous priority of acquisition is confirmed as to the corresponding synchronization of time synchronizing signal of the second time synchronized message carrying Priority.

It is preferred that, the corresponding synchronous priority of the OLT is the signal matter previously according to the OLT time synchronizing signals obtained What amount was determined.

The embodiment of the present invention provides a kind of optical network unit, including：

Very first time sync message receiving unit, the small base station for receiving the optical network unit ONU second line of a couplet is sent Very first time sync message, the time that small base station obtains from macro base station is carried in the very first time sync message same Walk signal；

Reference synchronization source determining unit, for the time synchronizing signal carried in the very first time sync message received In, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the ONU second lines of a couplet；

Time synchronized unit, for the reference synchronization source determined according to reference synchronization source determining unit, under the ONU Each small base station of connection carries out time synchronized.

It is preferred that, reference synchronization source determining unit is specifically included：

First synchronous priority determination subelement, the time that the very first time sync message for determining to receive is carried is same Walk the corresponding synchronous priority of signal；

Very first time synchronizing signal chooses subelement, and the time for being carried in the very first time sync message received is same Walk in signal, choose the time synchronizing signal of corresponding synchronous highest priority；

First reference synchronization source determination subelement, the time for very first time synchronizing signal to be chosen to subelement selection is same Signal is walked, confirms as carrying out each small base station of the ONU second lines of a couplet reference synchronization source of time synchronized.

It is preferred that, the described first synchronous priority determination subelement, specifically for synchronously being reported from the very first time received In the preset field of text, the corresponding synchronous priority of time synchronizing signal of very first time sync message carrying is extracted.

It is preferred that, the described first synchronous priority determination subelement, specifically in the small base station prestored and together Walk in the corresponding relation between priority, search the corresponding synchronous priority of small base station for sending very first time sync message, And by the synchronous priority found, the corresponding synchronization of time synchronizing signal for confirming as very first time sync message carrying is excellent First level.

It is preferred that, the optical network unit also includes：

Second time synchronized message receiving unit, for being determined in reference synchronization source determining unit to the ONU second lines of a couplet Each small base station is carried out before the reference synchronization source of time synchronized, receive that the optical line terminal OLT of the ONU first line of a couplet sends the The time synchronizing signal of OLT acquisitions is carried in two time synchronized messages, the second time synchronized message；

Reference synchronization source determining unit, it is same specifically for the time in the very first time sync message carrying received Walk in the time synchronizing signal that signal and the second time synchronized message are carried, it is determined that to each small base station of the ONU second lines of a couplet Carry out the reference synchronization source of time synchronized.

Second synchronous priority determination subelement, the time that the very first time sync message for determining to receive is carried is same Walk the corresponding synchronous priority of signal；

3rd synchronous priority determination subelement, the time that the second time synchronized message for determining to receive is carried is same Walk the corresponding synchronous priority of signal；

Second time synchronizing signal chooses subelement, for the time synchronizing signal that is carried in very first time sync message with And second in the time synchronizing signal that carries of time synchronized message, the time synchronized letter of corresponding synchronous highest priority is chosen Number；

Second reference synchronization source determination subelement, the time for the second time synchronizing signal to be chosen to subelement selection is same Signal is walked, confirms as carrying out each small base station of the ONU second lines of a couplet reference synchronization source of time synchronized.

It is preferred that, the described second synchronous priority determination subelement, specifically for synchronously being reported from the very first time received In the preset field of text, the corresponding synchronous priority of time synchronizing signal of very first time sync message carrying is extracted.

It is preferred that, the described second synchronous priority determination subelement, specifically in the small base station prestored and together Walk in the corresponding relation between priority, search the corresponding synchronous priority of small base station for sending very first time sync message, And by the synchronous priority found, the corresponding synchronization of time synchronizing signal for confirming as very first time sync message carrying is excellent First level.

It is preferred that, the 3rd synchronous priority determination subelement, specifically for from the second time synchronized report received In the preset field of text, the corresponding synchronous priority of time synchronizing signal of the second time synchronized message carrying is extracted.

It is preferred that, the 3rd synchronous priority determination subelement, specifically for obtain it is prestoring, described OLT pairs The synchronous priority answered, the synchronous priority of acquisition is confirmed as the time synchronizing signal correspondence of the second time synchronized message carrying Synchronous priority.

The embodiment of the present invention provides a kind of small base station, including：

Time synchronizing signal acquiring unit, for obtaining time synchronizing signal from macro base station；

Time synchronized packet sending unit, the time synchronizing signal for time synchronizing signal acquiring unit to be obtained is carried Optical network unit ONU is sent in time synchronized message.

Therefore, in technical scheme of the embodiment of the present invention, when PON is the return network of small base station, the ONU second lines of a couplet Small base station is got after the time synchronizing signal of macro base station, and the time synchronizing signal got is carried into synchronous in the very first time ONU is reported in message, follow-up ONU chooses reference synchronization source in the time synchronizing signal received, then according to selection Reference synchronization source carries out time synchronized to each small base station of the second line of a couplet.Therefore, when carrying out time synchronized between small base station, only need to protect The time synchronizing signal for the reception macro base station that part small base station can be well is demonstrate,proved, the portion of small base station is significantly reduced Difficulty is affixed one's name to, and extends adaptation scene, even if part small base station can not directly receive the time synchronizing signal of macro base station, The reference synchronization source that can be chosen according to ONU carries out time synchronized, same without obtaining the time from other small base stations or from GPS Signal is walked, the timing tracking accuracy between small base station is effectively improved, further, since avoiding when occurring for OLT or PON mouthfuls Between synchronous failure when, small base station can not carry out the situation of time synchronized, therefore improve time synchronized between small base station Reliability.

It is preferred that, the small base station also includes：

Synchronous priority determining unit, for will be sent in time synchronized packet sending unit in time synchronized message Before ONU, the corresponding synchronous priority of time synchronizing signal that time synchronizing signal acquiring unit is obtained is determined；

The time synchronized packet sending unit, is additionally operable to the synchronous priority for determining synchronous priority determining unit Carrying is sent to ONU in the preset field of time synchronized message.

The embodiment of the present invention provides a kind of optical line terminal, including：

Time synchronizing signal acquiring unit, for obtaining time synchronizing signal；

It is preferred that, the optical line terminal also includes：

The embodiment of the present invention provides a kind of clock synchronization system, includes the small base station of optical network unit ONU and its second line of a couplet, Wherein：

Small base station, is carried for obtaining time synchronizing signal from macro base station, and by the time synchronizing signal of acquisition The ONU is sent in very first time sync message；

The ONU, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each small Type base station carries out the reference synchronization source of time synchronized, and according to the reference synchronization source determined, each small base station of the second line of a couplet is carried out Time synchronized.

It is preferred that, in addition to optical line terminal OLT；

The OLT, is carried in the second time synchronized for obtaining time synchronizing signal, and by the time synchronizing signal of acquisition The ONU is sent in message；

The ONU, specifically for the time synchronizing signal and second carried in the very first time sync message received In the time synchronizing signal that time synchronized message is carried, it is determined that carrying out the reference synchronization of time synchronized to each small base station of the second line of a couplet Source.

Brief description of the drawings

Fig. 1 is PON system configuration diagram in the prior art；

Fig. 2 be the embodiment of the present invention one in, method for synchronizing time schematic flow sheet；

Fig. 3 be the embodiment of the present invention three in, ONU internal structure schematic diagram；

Fig. 4 be the embodiment of the present invention three in, realize the principle schematic of time synchronized between Femto base stations；

Fig. 5 be the embodiment of the present invention four in, ONU structural representations；

Fig. 6 be the embodiment of the present invention four in, small base station structural representation；

Fig. 7 be the embodiment of the present invention four in, OLT structural representations；

Fig. 8 be the embodiment of the present invention four in, clock synchronization system structural representation.

Embodiment

In order that the object, technical solutions and advantages of the present invention are clearer, below in conjunction with accompanying drawing the present invention is made into One step it is described in detail, it is clear that described embodiment is only embodiment of the invention a part of, rather than whole implementation Example.Based on the embodiment in the present invention, what those of ordinary skill in the art were obtained under the premise of creative work is not made All other embodiment, belongs to the scope of protection of the invention.

In the prior art, the time synchronized between small base station is realized according to air interface synchronization mode, is then concentrating deployment Region, because the synchronous hop count of time synchronizing signal is relatively more, therefore causes synchronization accuracy relatively low, in the region of scattered deployment, Add the deployment difficulty of small base station.It is small-sized to realize to small base station transmission 1588v2 time synchronizing signals according to PON Time synchronized between base station, then it is a large amount of under the OLT or the PON mouthfuls when the synchronous failure of single OLT or PON mouthfuls of time of occurrence Small base station will be unable to carry out time synchronized, the normal work of small base station be have impact on, hence in so that the time between small base station Synchronous reliability is poor.

In view of this, the embodiment of the present invention is proposed, when PON is the return network of small base station, the small-sized base of the ONU second lines of a couplet Station is got after the time synchronizing signal of macro base station, and the time synchronizing signal got is carried in very first time sync message ONU is reported, ONU chooses reference synchronization source in the time synchronizing signal received, then according to the reference synchronization source of selection Time synchronized is carried out to each small base station of the second line of a couplet.Therefore, when carrying out time synchronized between small base station, only need guarantee section Small base station can be well reception macro base station time synchronizing signal, the deployment for significantly reducing small base station is difficult Degree, and adaptation scene is extended, can also even if part small base station can not directly receive the time synchronizing signal of macro base station The reference synchronization source chosen according to ONU carries out time synchronized, without obtaining time synchronized letter from other small base stations or from GPS Number, the timing tracking accuracy between small base station is effectively improved, further, since avoiding when OLT or PON mouthfuls of time of occurrence is same When walking failure, small base station can not carry out the situation of time synchronized, therefore improve the reliable of time synchronized between small base station Property.

The present invention program is described in detail below by specific embodiment, certainly, the present invention is not limited to following reality Apply example.

Embodiment one

As shown in Fig. 2 the method for synchronizing time flow chart proposed for the embodiment of the present invention one, its concrete processing procedure is such as Under：

Step 21, ONU receives the very first time sync message that the small base station of its second line of a couplet is sent, and the very first time is synchronous The time synchronizing signal that small base station is obtained from macro base station is carried in message.

The small base station mentioned in the embodiment of the present invention can be, but not limited to include Micro base stations, Nano base stations, Pico bases Stand, Femto base stations etc..

Several small base stations of the ONU second lines of a couplet, wherein may only have part small base station to listen to the time of macro base station Synchronizing signal, therefore the embodiment of the present invention one proposes that the small base station base station of the ONU second lines of a couplet gets time synchronized from macro base station After signal, the time synchronizing signal got is carried and is sent to ONU in very first time sync message.

Called time it should be noted that ONU can choose from each small base station of the second line of a couplet in advance at least one needs The time synchronizing signal for listening to macro base station is reported ONU by the small base station of synchronizing signal, the small base station of selection, and ONU is only The small base station of selection is intercepted, the time synchronizing signal that the small base station chosen is reported is received.In addition, small in order to avoid selection Type base station can not listen to the situation of the time synchronizing signal of macro base station, and ONU can also intercept all small base stations of the second line of a couplet, energy The time synchronizing signal listened to is reported ONU by all small base stations for enough listening to the time synchronizing signal of macro base station, So as to further increase the reliability of the time synchronized between small base station.

In the embodiment of the present invention one, small base station can periodically be reported according to report cycle set in advance to ONU The time synchronizing signal got from macro base station.

The time synchronizing signal that small base station is got from macro base station can be, but not limited to believe for 1588v2 time synchronizeds Number, now, above-mentioned very first time sync message is 1588v2 messages.It is same that small base station gets the 1588v2 times from macro base station Walk after signal, 1588v2 messages are generated according to the 1588v2 time synchronizing signals got, and the 1588v2 messages of generation are sent out ONU is given, ONU passes through Fast Ethernet/gigabit Ethernet（Fast Ethernet/Gigabit Ethernet, FE/GE）Connect Mouth is received after the 1588v2 messages of small base station transmission, the 1588v2 times is extracted from 1588v2 messages by ONU chips same Walk signal.

ONU in the embodiment of the present invention can be, but not limited to as FTTB type ONU.

Step 22, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each of the second line of a couplet Small base station carries out the reference synchronization source of time synchronized.

The detailed process that ONU chooses reference synchronization source will describe in detail in embodiment two.

Step 23, according to the reference synchronization source determined, time synchronized is carried out to each small base station of the second line of a couplet.

ONU is determined behind reference synchronization source, first with the reference synchronization source determined, adjusts the time of local clock, so The time generation time synchronized message based on the local clock after adjustment, the second line of a couplet is handed down to by the time synchronized message of generation afterwards Each small base station.If small base station can not obtain time synchronizing signal from macro base station, receiving, the time that ONU issues is same Walk after message, the time of local clock is adjusted according to the time synchronizing signal carried in the time synchronized message received, so that Realize the time synchronized between each small base station.

Wherein, the time synchronized message that ONU is handed down to small base station can be 1588v2 messages, and small base station is received After the 1588v2 messages that ONU is issued, 1588v2 time synchronizing signals are extracted from 1588v2 messages, when then according to 1588v2 Between synchronizing signal adjust local clock time.

, can be to the time synchronized message that receives if small base station can obtain time synchronizing signal from macro base station Do not deal with, can also by the time synchronizing signal carried in the time synchronized message received and obtained from macro base station when Between synchronizing signal verification is compared, if verify out the time synchronizing signal obtained from macro base station signal quality preferably, Then it is considered that abnormal information is reported ONU by the reference synchronization source exception that ONU chooses, small base station, ONU is receiving exception After information, reference synchronization source can be chosen again, and generates time synchronized message and is handed down to each small base station, so as to avoid It is abnormal that ONU chooses reference synchronization source so that the situation of precise synchronization is unable between small base station, further increases between small base station Timing tracking accuracy.

Therefore, when carrying out time synchronized between small base station, only need the reception that guarantee section small base station can be good The time synchronizing signal of macro base station, significantly reduces the deployment difficulty of small base station, even if part small base station can not Enough time synchronizing signals for directly receiving macro base station, the reference synchronization source that can also be chosen according to ONU carries out time synchronized, without Time synchronizing signal is obtained from other small base stations or from GPS, the timing tracking accuracy between small base station is effectively improved, Further, since avoiding when the synchronous failure of OLT or PON mouthfuls of time of occurrence, small base station can not carry out the situation of time synchronized, Therefore the reliability of the time synchronized between small base station is improved.

Embodiment two

After the time synchronizing signal that the small base station that ONU receives the second line of a couplet is reported, first determine that the very first time received is same The corresponding synchronous priority of time synchronizing signal that message is carried is walked, source algorithm is then selected by preset, in the received In the time synchronizing signal that one time sync message is carried, the time synchronizing signal of corresponding synchronous highest priority is chosen, will The time synchronizing signal of selection, confirms as carrying out each small base station of the second line of a couplet reference synchronization source of time synchronized.

Wherein, the synchronous priority of time synchronizing signal can be carried by small base station in very first time sync message ONU is offered, can also voluntarily be determined, both of these case is introduced respectively by ONU below.

Situation a, the synchronous priority of time synchronizing signal is carried by small base station to be reported in very first time sync message To ONU.

The embodiment of the present invention two proposes that small base station is got from macro base station after time synchronizing signal, during by first Between sync message be sent to before ONU, can be first according to the signal quality of time synchronizing signal got, it is determined that getting The corresponding synchronous priority of time synchronizing signal, then carries the synchronous priority determined in very first time sync message ONU is sent in preset field, ONU is received after the very first time sync message of small base station transmission, synchronous from the very first time In the preset field of message, the corresponding synchronous priority of time synchronizing signal of very first time sync message carrying is extracted.

Wherein, the signal quality of time synchronizing signal can be, but not limited to the synchronous hop count for time synchronizing signal, immediately Between synchronizing signal from the time server of network side（Such as 1588v2 time servers）The process for reaching small base station is undergone Synchronous hop count, the synchronous hop count of time synchronizing signal is more, and corresponding synchronous priority is lower, and synchronous hop count is fewer, correspondence Synchronous priority it is higher.

Small base station is got from macro base station after time synchronizing signal, according to the same of the time synchronizing signal got Hop count is walked, it is determined that the corresponding synchronous priority of the time synchronizing signal got.

In addition it is also possible to the signal quality of the time synchronizing signal obtained previously according to small base station from macro base station, really The fixed corresponding synchronous priority of the small base station, small base station stores itself corresponding synchronous priority, and small base station is from grand base Got in standing after time synchronizing signal, very first time sync message is sent to before ONU, the synchronization prestored is excellent First level is carried is sent to ONU in the preset field of very first time sync message, when ONU receives the first of small base station transmission Between after sync message, from the preset field of very first time sync message, extract very first time sync message carrying when Between the corresponding synchronous priority of synchronizing signal.

If the signal quality of time synchronizing signal is the synchronous hop count of time synchronizing signal, small base station pair is predefined , can be according to the deployment scenario of each small base station, when determining that each small base station is obtained from macro base station during the synchronous priority answered Between synchronizing signal when required synchronous hop count, then according to the synchronous hop count determined, determine the corresponding synchronization of each small base station Priority.

Situation b, the synchronous priority of time synchronizing signal is voluntarily determined by ONU.

The embodiment of the present invention two is proposed, is predefined the corresponding synchronous priority of each small base station of the ONU second lines of a couplet, is obtained small Corresponding relation between type base station and synchronous priority, ONU stores the corresponding relation, and ONU receives what each small base station was sent After very first time sync message, in the corresponding relation between the small base station and synchronous priority of storage, search and send first The corresponding synchronous priority of small base station of time synchronized message, and by the synchronous priority found, confirm as this first when Between sync message carry the corresponding synchronous priority of time synchronizing signal.

Wherein it is possible to the signal quality of the time synchronizing signal obtained previously according to small base station from macro base station, it is determined that The corresponding synchronous priority of the small base station.

Preferably, the embodiment of the present invention two also, it has been proposed that ONU not only the time can be obtained from the small base station of its second line of a couplet same Walk in signal, the OLT that can also join from it and obtain time synchronizing signal, OLT is got after time synchronizing signal, will be got Time synchronizing signal carry be sent to ONU in the second time synchronized message.ONU subsequently can be in the very first time received In the time synchronizing signal that the time synchronizing signal and the second time synchronized message that sync message is carried are carried, it is determined that to the second line of a couplet Each small base station carry out time synchronized reference synchronization source.That is, ONU supports the not homologous time synchronizing signal of two-way Bang path, time synchronizing signal being transmitted downwards for OLT all the way, being obtained from upstream network side, another road is small base station Time synchronizing signal being communicated up, being obtained from macro base station.

Wherein, OLT can issue the cycle according to set in advance, periodically issue what is got from network side to ONU Time synchronizing signal.This issues the cycle and small base station reports the report cycle of time synchronizing signal can be with equal.

OLT directly can obtain time synchronizing signal from the time server of network side, can also be set from other networks The time synchronizing signal of standby middle acquisition time server.

Above-mentioned time server can be, but not limited to as 1588v2 time servers, then the time synchronized that OLT is got Signal is 1588v2 time synchronizing signals, and above-mentioned second time synchronized message is 1588v2 messages.When OLT gets 1588v2 Between after synchronizing signal, 1588v2 messages are generated according to the 1588v2 time synchronizing signals got, and the 1588v2 of generation is reported The ONU chips that text is sent in ONU, ONU extract 1588v2 time synchronizing signals from 1588v2 messages.

Due to only having one to jump from small base station to ONU and from OLT to ONU, and time synchronizing signal is ripe height Precision 1588v2 time synchronizing signals, therefore, it is possible to ensure the timing tracking accuracy between small base station well, preferably meet The synchronisation requirement of small base station.

ONU is received after very first time sync message and the second time synchronized message, first determines the very first time received The time synchronized that the corresponding synchronous priority of time synchronizing signal and the second time synchronized message that sync message is carried are carried The corresponding synchronous priority of signal, then selects source algorithm by preset, is carried in the very first time sync message received In the time synchronizing signal that time synchronizing signal and the second time synchronized message are carried, corresponding synchronous highest priority is chosen Time synchronizing signal, the time synchronizing signal of selection is confirmed as carrying out the same of time synchronized to each small base station of the second line of a couplet Walk reference source.

The corresponding synchronization of time synchronizing signal that ONU determines that small base station is reported is had been described above in situation a and situation b The process of priority, therefore the mistake for the corresponding synchronous priority of time synchronizing signal that ONU determines that OLT is issued mainly is introduced below Journey.

The synchronous priority for the time synchronizing signal that OLT is issued can be under OLT be carried in the second time synchronized message ONU is issued, can also voluntarily be determined, both of these case is introduced respectively by ONU below.

Situation A, the synchronous priority of time synchronizing signal is carried by OLT is handed down to ONU in the second time synchronized message.

The embodiment of the present invention two proposes that OLT is got from network side after time synchronizing signal, first basis can get Time synchronizing signal signal quality, it is determined that the corresponding synchronous priority of the time synchronizing signal got, then will determine The synchronous priority gone out is carried is sent to ONU in the preset field of the second time synchronized message, and ONU receives OLT transmissions After second time synchronized message, from the preset field of the second time synchronized message, extract the second time synchronized message and take The corresponding synchronous priority of time synchronizing signal of band.

If the signal quality of time synchronizing signal is the synchronous hop count of time synchronizing signal, OLT gets time synchronized After signal, according to time synchronizing signal from the time server of network side（Such as 1588v2 time servers）Reach OLT's The synchronous hop count that process is undergone, it is determined that the corresponding synchronous priority of the time synchronizing signal got.

In addition it is also possible to previously according to the signal quality of the OLT time synchronizing signals obtained, determine the corresponding synchronizations of OLT Priority, OLT stores itself corresponding synchronous priority, and OLT is got after time synchronizing signal, by the synchronization prestored Priority is carried is sent to ONU in the preset field of the second time synchronized message, and ONU receives the second time of OLT transmissions After sync message, from the preset field of the second time synchronized message, the time of the second time synchronized message carrying is extracted The corresponding synchronous priority of synchronizing signal.

If the signal quality of time synchronizing signal is the synchronous hop count of time synchronizing signal, OLT is predefined corresponding , can be according to time synchronizing signal from the time server of network side during synchronous priority（Such as 1588v2 time servers）Arrive The synchronous hop count undergone up to OLT process, determines the corresponding synchronous priority of OLT.

If OLT directly obtains time synchronizing signal from time server, the synchronous jump of the time synchronizing signal obtained Number is jumped for 1, if OLT obtains the time synchronizing signal of time server from other network equipments, the time synchronized letter obtained Number synchronous hop count be more than 1 jump.

The embodiment of the present invention two is proposed, predefines the corresponding synchronous priority of OLT, and the synchronization that ONU storages are determined is excellent First level, ONU is received after the second time synchronized message of OLT transmissions, obtains the corresponding synchronizations of the OLT prestored preferential Level, the corresponding synchronization of time synchronizing signal that the synchronous priority of acquisition then is confirmed as into the carrying of the second time synchronized message is excellent First level.

Wherein it is possible to previously according to the signal quality of the OLT time synchronizing signals obtained, determine that the corresponding synchronizations of OLT are excellent First level.

The embodiment of the present invention two proposes that the time synchronized that the time synchronizing signal and OLT reported in small base station is issued is believed In number, if the time synchronizing signal only one of which of corresponding synchronous highest priority, ONU directly can believe the time synchronized Number reference synchronization source is chosen for, if the corresponding synchronous highest priority of at least two time synchronizing signals, ONU can be in correspondence Synchronous highest priority each time synchronizing signal in choose a time synchronizing signal as reference synchronization source, wherein, ONU A time synchronizing signal can be randomly selected as synchronization in each time synchronizing signal of corresponding synchronous highest priority Reference source.

Therefore, the not homologous time synchronizing signal bang path of ONU support two-way, being transmitted downwards for OLT all the way, From upstream network side obtain time synchronizing signal, another road be small base station be communicated up, obtained from macro base station when Between synchronizing signal, ONU chooses reference synchronization source according to selecting source algorithm from each time synchronizing signal received.Preferably, ONU can be decided whether to enable according to actual conditions select source algorithm picks reference synchronization source and select included in the algorithm of source when Between synchronizing signal source category, the time that the time synchronizing signal reported comprising small base station and OLT of time signal source are issued Synchronizing signal.When the time synchronizing signal that time synchronizing signal bang path breaks down or transmitted all the way wherein is abnormal, The reliability of time synchronized between small base station can be effectively raised using other time synchronizing signal bang path all the way.

In the normal mode of operation, ONU, which is enabled, selects source algorithm, and time synchronizing signal source includes the time that small base station is reported The time synchronizing signal that synchronizing signal and OLT are issued.The time synchronizing signal that OLT transmissions are detected when ONU chips it is abnormal or When the bang path that person OLT issues time synchronizing signal breaks down, ONU passes through using selecting source algorithm picks reference synchronization source When, the time synchronizing signal that reselection OLT is not issued.When the time synchronizing signal that ONU chips detect small base station transmission is different When normal or small base station reports the bang path failure of time synchronizing signal, deactivation selects source algorithm, directly using under OLT The time synchronizing signal of hair is used as reference synchronization source.

Embodiment three

The embodiment of the present invention three is proposed, can increase time synchronized module in ONU, to realize the He of the embodiment of the present invention one The method for synchronizing time that the embodiment of the present invention two is proposed.ONU internal structure is as shown in Figure 3.

If above-mentioned small base station is Femto base stations, based on the internal structure of the ONU shown in Fig. 3, Femto base stations are realized Between time synchronized principle as shown in figure 4, detailed process is as follows：

FE/GE interfaces in ONU obtain 1588v2 messages from the Femto base stations of the second line of a couplet, and 1588v2 messages are transferred into ONU Chip processing, ONU chips extract 1588v2 time synchronizing signals from 1588v2 messages, when then by the 1588v2 extracted Between synchronizing signal be sent to time synchronized module.Time synchronized module is by selecting source algorithm, and what is sent in Femto base stations is each Preferably go out a 1588v2 time synchronizing signal in 1588v2 time synchronizing signals as reference synchronization source, and by reference synchronization source It is supplied to ONU chips and CPU.

Reception optical module in ONU obtains 1588v2 messages in can also being received from the OLT of the first line of a couplet, and receiving optical module will 1588v2 messages transfer to ONU chips to handle, and ONU chips extract 1588v2 time synchronizing signals from 1588v2 messages, then The 1588v2 time synchronizing signals extracted are sent to time synchronized module.Time synchronized module by selecting source algorithm, Preferably go out a 1588v2 time synchronizing signal in each 1588v2 time synchronizing signals that Femto base stations and OLT are sent as same Reference source is walked, and reference synchronization source is supplied to ONU chips and CPU.

ONU chips are generated using the synchronous local clock in the reference synchronization source preferably gone out, and the time based on local clock 1588v2 messages, the 1588v2 messages of generation are passed down to all Femto base stations of this ONU second line of a couplet, each Femto base stations root Time synchronized is carried out according to 1588v2 messages.

The embodiment of the present invention three proposes that time synchronized module can realize that cooperate completion with ONU chips using independent chip Above-mentioned flow, in addition, time synchronized module can also be integrated into ONU chips.

Other small base stations（Such as Nano base stations or Micro base stations）Time synchronization process it is similar with said process, this In no longer repeat one by one.

Example IV

Corresponding with the method for synchronizing time that the embodiment of the present invention one is proposed, the embodiment of the present invention four proposes a kind of ONU, and it is tied Structure as shown in figure 5, including：

Very first time sync message receiving unit 51, for receive the ONU second lines of a couplet small base station send first when Between sync message, carry the time synchronizing signal that small base station is obtained from macro base station in the very first time sync message；

Reference synchronization source determining unit 52, for the time synchronizing signal carried in the very first time sync message received In, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the ONU second lines of a couplet；

Time synchronized unit 53, for the reference synchronization source determined according to reference synchronization source determining unit 52, to described Each small base station of the ONU second lines of a couplet carries out time synchronized.

It is preferred that, reference synchronization source determining unit 52 is specifically included：

It is preferred that, the optical network unit also includes：

Reference synchronization source determining unit 52, specifically for the time carried in the very first time sync message received In the time synchronizing signal that synchronizing signal and the second time synchronized message are carried, it is determined that to each small-sized base of the ONU second lines of a couplet Stand and carry out the reference synchronization source of time synchronized.

The embodiment of the present invention four also proposes a kind of small base station, its structure as shown in fig. 6, including：

Time synchronizing signal acquiring unit 61, for obtaining time synchronizing signal from macro base station；

Time synchronized packet sending unit 62, for the time synchronizing signal for obtaining time synchronizing signal acquiring unit 61 Carrying is sent to ONU in time synchronized message.

It is preferred that, the small base station also includes：

Synchronous priority determining unit, for will be sent in time synchronized packet sending unit 62 in time synchronized message Before ONU, the corresponding synchronous priority of time synchronizing signal that time synchronizing signal acquiring unit 61 is obtained is determined；

The time synchronized packet sending unit 62, the synchronization for being additionally operable to determine synchronous priority determining unit is preferential Level carries and is sent to ONU in the preset field of time synchronized message.

The embodiment of the present invention four also proposes a kind of OLT, its structure as shown in fig. 7, comprises：

Time synchronizing signal acquiring unit 71, for obtaining time synchronizing signal；

Time synchronized packet sending unit 72, for the time synchronizing signal for obtaining time synchronizing signal acquiring unit 71 Carrying is sent to ONU in time synchronized message.

It is preferred that, the OLT also includes：

Synchronous priority determining unit, for will be sent in time synchronized packet sending unit 72 in time synchronized message Before ONU, the corresponding synchronous priority of time synchronizing signal that time synchronizing signal acquiring unit 71 is obtained is determined；

The time synchronized packet sending unit 72, the synchronization for being additionally operable to determine synchronous priority determining unit is preferential Level carries and is sent to ONU in the preset field of time synchronized message.

The embodiment of the present invention provides a kind of clock synchronization system, its structure as shown in figure 8, including ONU81 and its second line of a couplet Small base station 82, wherein：

Small base station 82, is carried for obtaining time synchronizing signal from macro base station, and by the time synchronizing signal of acquisition The ONU is sent in very first time sync message；

The ONU81, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each Small base station carries out the reference synchronization source of time synchronized, and according to the reference synchronization source determined, each small base station of the second line of a couplet is entered Row time synchronized.

It is preferred that, in addition to OLT83；

It should be understood by those skilled in the art that, embodiments of the invention can be provided as method, system or computer program Product.The present invention can be used in one or more computer-usable storage mediums for wherein including computer usable program code （Including but not limited to magnetic disk storage, CD-ROM, optical memory etc.）The form of the computer program product of upper implementation.

The present invention is with reference to method according to embodiments of the present invention, equipment（System）And the flow of computer program product Figure and/or block diagram are described.It should be understood that can be by every first-class in computer program instructions implementation process figure and/or block diagram Journey and/or the flow in square frame and flow chart and/or block diagram and/or the combination of square frame.These computer programs can be provided The processor of all-purpose computer, special-purpose computer, Embedded Processor or other programmable data processing devices is instructed to produce A raw machine so that produced by the instruction of computer or the computing device of other programmable data processing devices for real The device for the function of being specified in present one flow of flow chart or one square frame of multiple flows and/or block diagram or multiple square frames.

These computer program instructions, which may be alternatively stored in, can guide computer or other programmable data processing devices with spy Determine in the computer-readable memory that mode works so that the instruction being stored in the computer-readable memory, which is produced, to be included referring to Make the manufacture of device, the command device realize in one flow of flow chart or multiple flows and/or one square frame of block diagram or The function of being specified in multiple square frames.

These computer program instructions can be also loaded into computer or other programmable data processing devices so that in meter Series of operation steps is performed on calculation machine or other programmable devices to produce computer implemented processing, thus in computer or The instruction performed on other programmable devices is provided for realizing in one flow of flow chart or multiple flows and/or block diagram one The step of function of being specified in individual square frame or multiple square frames.

Defined according to herein, computer-readable medium does not include the computer readable media of non-standing (transitory media), such as modulation data-signal and carrier wave.

, but those skilled in the art once know basic creation although preferred embodiments of the present invention have been described Property concept, then can make other change and modification to these embodiments.So, appended claims are intended to be construed to include excellent Select embodiment and fall into having altered and changing for the scope of the invention.

Obviously, those skilled in the art can carry out the essence of various changes and modification without departing from the present invention to the present invention God and scope.So, if these modifications and variations of the present invention belong to the scope of the claims in the present invention and its equivalent technologies Within, then the present invention is also intended to comprising including these changes and modification.

Claims

1. a kind of method for synchronizing time, it is characterised in that including：

Optical network unit ONU receives the very first time sync message that the small base station of its second line of a couplet is sent, and the very first time is synchronous The time synchronizing signal that small base station is obtained from macro base station is carried in message；

In the time synchronizing signal that the very first time sync message received is carried, it is determined that being carried out to each small base station of the second line of a couplet The reference synchronization source of time synchronized；

2. the method as described in claim 1, it is characterised in that same in the time that the very first time sync message received is carried Walk in signal, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the second line of a couplet, specifically include：

In the time synchronizing signal that the very first time sync message received is carried, corresponding synchronous highest priority is chosen Time synchronizing signal；

By the time synchronizing signal of selection, confirm as carrying out each small base station of the second line of a couplet reference synchronization source of time synchronized.

3. the method as described in claim 1, it is characterised in that same in the time that the very first time sync message received is carried Walk in signal, it is determined that before to the reference synchronization source of each small base station progress time synchronized of the second line of a couplet, in addition to：

ONU is received in the second time synchronized message that the optical line terminal OLT of its first line of a couplet is sent, the second time synchronized message Carry the time synchronizing signal of OLT acquisitions；

In the time synchronizing signal that the very first time sync message received is carried, it is determined that being carried out to each small base station of the second line of a couplet The reference synchronization source of time synchronized, is specifically included：

When the time synchronizing signal and the second time synchronized message of the very first time sync message carrying received are carried Between in synchronizing signal, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the second line of a couplet.

4. method as claimed in claim 3, it is characterised in that same in the time that the very first time sync message received is carried Walk in the time synchronizing signal that signal and the second time synchronized message are carried, it is determined that carrying out the time to each small base station of the second line of a couplet Synchronous reference synchronization source, is specifically included：

It is determined that when the corresponding synchronous priority of time synchronizing signal of the very first time sync message carrying received and second Between sync message carry the corresponding synchronous priority of time synchronizing signal；

When the time synchronizing signal and the second time synchronized message of the very first time sync message carrying received are carried Between in synchronizing signal, choose the time synchronizing signal of corresponding synchronous highest priority；

5. the method as described in claim 2 or 4, it is characterised in that it is determined that what the very first time sync message received was carried The corresponding synchronous priority of time synchronizing signal, is specifically included：

From the preset field of the very first time sync message received, the time of very first time sync message carrying is extracted The corresponding synchronous priority of synchronizing signal.

6. method as claimed in claim 5, it is characterised in that the synchronous priority carried in very first time sync message is：

Small base station is got after time synchronizing signal from macro base station, true according to the signal quality of the time synchronizing signal of acquisition Fixed；Or

The signal quality of time synchronizing signal that small base station is prestored, being obtained according to the small base station from macro base station is true Fixed.

7. the method as described in claim 2 or 4, it is characterised in that it is determined that what the very first time sync message received was carried The corresponding synchronous priority of time synchronizing signal, is specifically included：

In corresponding relation between the small base station prestored and synchronous priority, search and send very first time sync message The corresponding synchronous priority of small base station, and by the synchronous priority found, confirm as the very first time sync message and take The corresponding synchronous priority of time synchronizing signal of band.

8. method as claimed in claim 7, it is characterised in that the corresponding synchronous priority of small base station is small previously according to this What the signal quality for the time synchronizing signal that type base station is obtained from macro base station was determined.

9. method as claimed in claim 4, it is characterised in that it is determined that the time that the second time synchronized message received is carried The corresponding synchronous priority of synchronizing signal, is specifically included：

From the preset field of the second time synchronized message received, the time of the second time synchronized message carrying is extracted The corresponding synchronous priority of synchronizing signal.

10. method as claimed in claim 9, it is characterised in that the synchronous priority carried in the second time synchronized message is：

11. method as claimed in claim 4, it is characterised in that it is determined that the second time synchronized message received carry when Between the corresponding synchronous priority of synchronizing signal, specifically include：

Obtain the corresponding synchronous priority of OLT prestore, described；

The corresponding synchronization of time synchronizing signal that the synchronous priority of acquisition is confirmed as into the carrying of the second time synchronized message is preferential Level.

12. method as claimed in claim 11, it is characterised in that the corresponding synchronous priority of the OLT is previously according to OLT What the signal quality of the time synchronizing signal of acquisition was determined.

13. a kind of optical network unit, it is characterised in that including：

Very first time sync message receiving unit, for receiving the small base station of the optical network unit ONU second line of a couplet is sent the The time synchronized letter that small base station is obtained from macro base station is carried in one time sync message, the very first time sync message Number；

Reference synchronization source determining unit, in the time synchronizing signal that the very first time sync message that receives is carried, really Fixed each small base station to the ONU second lines of a couplet carries out the reference synchronization source of time synchronized；

Time synchronized unit, for the reference synchronization source determined according to reference synchronization source determining unit, to the ONU second lines of a couplet Each small base station carries out time synchronized.

14. optical network unit as claimed in claim 13, it is characterised in that reference synchronization source determining unit is specifically wrapped Include：

First synchronous priority determination subelement, the time synchronized letter that the very first time sync message for determining to receive is carried Number corresponding synchronous priority；

Very first time synchronizing signal chooses subelement, for the time synchronized letter carried in the very first time sync message received In number, the time synchronizing signal of corresponding synchronous highest priority is chosen；

First reference synchronization source determination subelement, for very first time synchronizing signal to be chosen into the time synchronized letter that subelement is chosen Number, confirm as carrying out each small base station of the ONU second lines of a couplet reference synchronization source of time synchronized.

15. optical network unit as claimed in claim 14, it is characterised in that the described first synchronous priority determination subelement, Specifically for from the preset field of the very first time sync message received, extracting very first time sync message carrying The corresponding synchronous priority of time synchronizing signal.

16. optical network unit as claimed in claim 14, it is characterised in that the described first synchronous priority determination subelement, Specifically in the corresponding relation between the small base station prestored and synchronous priority, searching and sending very first time synchronization The corresponding synchronous priority of small base station of message, and by the synchronous priority found, confirm as the very first time and synchronously report The corresponding synchronous priority of time synchronizing signal that text is carried.

17. optical network unit as claimed in claim 13, it is characterised in that also include：

Second time synchronized message receiving unit, for being determined in reference synchronization source determining unit to each small of the ONU second lines of a couplet Type base station is carried out before the reference synchronization source of time synchronized, receive that the optical line terminal OLT of the ONU first line of a couplet sends second when Between sync message, the time synchronizing signal of OLT acquisitions is carried in the second time synchronized message；

Reference synchronization source determining unit, believes specifically for the time synchronized carried in the very first time sync message received Number and the time synchronizing signal that carries of the second time synchronized message in, it is determined that being carried out to each small base stations of the ONU second lines of a couplet The reference synchronization source of time synchronized.

18. optical network unit as claimed in claim 17, it is characterised in that reference synchronization source determining unit is specifically wrapped Include：

Second synchronous priority determination subelement, the time synchronized letter that the very first time sync message for determining to receive is carried Number corresponding synchronous priority；

3rd synchronous priority determination subelement, the time synchronized letter that the second time synchronized message for determining to receive is carried Number corresponding synchronous priority；

Second time synchronizing signal chooses subelement, for the time synchronizing signal that is carried in very first time sync message and the In the time synchronizing signal that two time synchronized messages are carried, the time synchronizing signal of corresponding synchronous highest priority is chosen；

Second reference synchronization source determination subelement, for the second time synchronizing signal to be chosen into the time synchronized letter that subelement is chosen Number, confirm as carrying out each small base station of the ONU second lines of a couplet reference synchronization source of time synchronized.

19. optical network unit as claimed in claim 18, it is characterised in that the described second synchronous priority determination subelement, Specifically for from the preset field of the very first time sync message received, extracting very first time sync message carrying The corresponding synchronous priority of time synchronizing signal.

20. optical network unit as claimed in claim 18, it is characterised in that the described second synchronous priority determination subelement, Specifically in the corresponding relation between the small base station prestored and synchronous priority, searching and sending very first time synchronization The corresponding synchronous priority of small base station of message, and by the synchronous priority found, confirm as the very first time and synchronously report The corresponding synchronous priority of time synchronizing signal that text is carried.

21. optical network unit as claimed in claim 18, it is characterised in that the described 3rd synchronous priority determination subelement, Specifically for from the preset field of the second time synchronized message received, extracting the second time synchronized message carrying The corresponding synchronous priority of time synchronizing signal.

22. optical network unit as claimed in claim 18, it is characterised in that the described 3rd synchronous priority determination subelement, Specifically for obtaining the corresponding synchronous priority of OLT prestore, described, when the synchronous priority of acquisition is confirmed as into second Between sync message carry the corresponding synchronous priority of time synchronizing signal.

23. a kind of clock synchronization system, it is characterised in that the small base station including optical network unit ONU He its second line of a couplet, wherein：

Small base station, is carried first for obtaining time synchronizing signal from macro base station, and by the time synchronizing signal of acquisition The ONU is sent in time synchronized message；

The ONU, in the time synchronizing signal that the very first time sync message received is carried, it is determined that to each small-sized base Stand and carry out the reference synchronization source of time synchronized, according to the reference synchronization source determined, is carried out to each small base station of the second line of a couplet time It is synchronous.

24. system as claimed in claim 23, it is characterised in that also including optical line terminal OLT；

The OLT, is carried in the second time synchronized message for obtaining time synchronizing signal, and by the time synchronizing signal of acquisition In be sent to the ONU；

The ONU, specifically for the time synchronizing signal carried in the very first time sync message received and the second time In the time synchronizing signal that sync message is carried, it is determined that carrying out the reference synchronization source of time synchronized to each small base station of the second line of a couplet.