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CN102075277B - Method and system for synchronizing uplink transmission in passive optical network - Google Patents

Method and system for synchronizing uplink transmission in passive optical network Download PDF

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CN102075277B
CN102075277B CN200910178393.4A CN200910178393A CN102075277B CN 102075277 B CN102075277 B CN 102075277B CN 200910178393 A CN200910178393 A CN 200910178393A CN 102075277 B CN102075277 B CN 102075277B
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rtd
max
eqd
value
olt
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CN102075277A (en
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张伟良
耿丹
张德智
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ZTE Corp
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ZTE Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

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  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

The invention discloses a method and a system for synchronizing uplink transmission in a passive optical network (PON). The method comprises the following steps that: an optical line terminal (OLT) determines the maximum equalization delay (EqDmax) according to the maximum round trip delay (RTDmax) of all on-line optical network units (ONU) in a PON system, and calculates the values of the EqD of all the ONUs according to the EqDmax; when the RTDmax is updated, the OLT calculates EqD updating information according to the updated RTDmax; and the OLT sends EqD updating information to all on-line ONUs, and after updating the EqD according to the received EqD updating information, the ONUs synchronize uplink transmission according to the updated EqD. The OLT can update the RTDmax of all on-line ONUs timely and updates the EqD of each ONU according to the RTDmax dynamically, so that uplink transmission efficiency can be improved.

Description

Method and system for synchronous uplink transmission in passive optical network
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a method and a system for synchronous uplink transmission in a passive optical network.
Background
A Gigabit-Capable Passive Optical Network (GPON) technology is an important branch of a Passive Optical Network (PON) family, and similar to other PON technologies, GPON is also a Passive Optical access technology using a point-to-multipoint topology structure.
As shown in fig. 1, a topology structure of a GPON system is that a GPON is composed of an Optical Line Terminal (OLT) on an office side, an Optical Network Unit (ONU) on a user side, and an Optical Distribution Network (ODN), and generally adopts a point-to-multipoint Network structure. The ODN is composed of single-mode optical fibers, optical splitters, optical connectors, and other passive optical devices, and provides an optical transmission medium for physical connection between the OLT and the ONUs.
In the GPON system, the data transmission in the downstream direction (from OLT to ONU) adopts a broadcast mode, each ONU respectively receives all frames, and then acquires the frames belonging to the ONU according to the ONU-ID, the GEM-Port ID and the Allocation-ID. However, for data transmission in the upstream direction (from the ONUs to the OLT), each ONU should transmit upstream data in a time slot scheduled by the OLT for itself, since each ONU needs to share the transmission medium. The distances between each ONU and the OLT are different, in order to prevent uplink data sent by each ONU from reaching the OLT at the same time, the OLT needs to measure the distance of each ONU and send the equalization delay of each ONU obtained according to the distance measurement result to the corresponding ONU, and the ONU adjusts the clock for sending the data according to the equalization delay sent by the OLT, namely when the ONU prepares to send an uplink frame, the uplink frame is sent after a period of time corresponding to the own equalization delay is required to be delayed, thereby realizing the synchronization of uplink transmission of all ONUs.
In the related art for realizing uplink transmission synchronization of each ONU, the OLT first determines the farthest distance L from the ONU supported by the OLT itself (the farthest distance is a fixed value). The OLT measures a value RTD of a Round Trip Delay (RTD) of the ONU at the Lmax. Measuring RTD in the prior artmaxThe method comprises the following steps: the OLT encapsulates the ranging request and the value of the upstream data sending time StartTime of the ONU in a downstream frame and sends the downstream frame to the ONU, the OLT records the sending time T1 of the downstream frame containing the ranging request, the ONU sends a response message to the OLT in the upstream time allowed by the OLT after receiving the downstream frame containing the ranging request, and the OLT records the response cancellation received by the OLTTime of rest T2. The OLT obtains the RTD of the ONU according to the following formulamax：
RTDmax=T2-T1-StartTime/R
In the above formula, the R value is the uplink rate of the ONU, and the unit is words/μ s.
And according to the RTDmaxDetermining the value EqD of the maximum Equalization Delay (EqD for short) of all ONUmax. Maximum equalized time delay value EqDmaxIs greater than or equal to RTDmaxAnd (4) finishing. OLT selects one RTD greater than or equal tomaxeqD of valuemaxThe value of (c).
When an ONU is accessed into a PON system, the OLT measures the RTD of the ONUiThereby obtaining the EqD of the ONUiValue of (EqD)i=EqDmax-RTDi). In this technique, RTDmaxIs constant, so EqDmaxIs constant, each ONU is according to EqDmaxWhen the value of L in the PON system is large, the value of EqD of each ONU is also large, resulting in low efficiency of upstream transmission.
Therefore, it is necessary to provide a solution to solve the problem of low efficiency of uplink transmission when the L value is large in the PON system.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method and a system for synchronizing uplink transmission in a passive optical network, which improve uplink transmission efficiency while realizing uplink transmission synchronization.
In order to solve the above problem, the present invention provides a method for synchronous uplink transmission in a passive optical network, including:
an Optical Line Terminal (OLT) calculates a maximum loop delay (RTD) according to all on-line Optical Network Units (ONUs) in a Passive Optical Network (PON) systemmax) Determining maximum equalization delay (EqD)max) And according to said EqDmaxCalculating the value of EqD of all the ONUs;
when the RTD ismaxWhen the update occurs, the OLT according to the updated RTDmaxCalculating EqD updating information;
and the OLT sends the EqD updating information to all online ONUs, and the ONUs update the EqD according to the received EqD updating information and then synchronize uplink transmission according to the updated EqD.
Further, the RTDmaxThe step of generating the update specifically includes:
the OLT stores RTDs of all current online ONUs in the PON systemmaxA value;
the OLT regularly and/or irregularly measures the RTD of part or all of the on-line ONU in the PON system, and compares the measured RTD with the stored RTDmaxComparing the values, if the measured RTD value is larger than the RTD locally stored by the OLTmaxValue, then OLT updates the locally stored RTDmaxThe value is the value of the measured RTD.
Further, when the RTD is usedmaxWhen the update occurs, the OLT according to the updated RTDmaxValue update EqDmaxValue and according to the updated EqDmaxAnd after updating the EqD value of part or all of the on-line ONUs in the PON system, sending the updated EqD value to the corresponding ONUs as the EqD updating information.
Further, the RTDmaxThe step of generating the update specifically includes:
OLT stores RTDs of all online ONUs in all current PON systemsmaxA value;
when a new ONU or an ONU needing to recover PON service is accessed into the PON system, the OLT measures the distance of the ONU accessed into the PON system to obtain the RTD value of the ONU;
OLT compares RTD value of ONU with OLT local storageRTDmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxValue, then OLT updates the locally stored RTDmaxThe value is the value of the RTD of the ONU.
Further, the RTDmaxThe step of generating the update specifically includes:
OLT stores RTDs of all online ONUs in all current PON systemsmaxA value;
when an ONU in the PON system is offline or offline, the OLT measures the distance of the offline or offline ONU to obtain the RTD value of the ONU;
the OLT compares the RTD value of the ONU with the RTD locally stored by the OLTmaxValue if the RTD value of the ONU is equal to the RTD locally stored by the OLTmaxIf so, the OLT judges whether the maximum RTD value of all the on-line ONUs in the PON system is smaller than the RTD locally stored by the OLTmaxValue, if yes, OLT updates local storage RTDmaxThe value is the maximum RTD value of all online ONUs in the PON system.
Further, the OLT stores the RTDmaxWhile storing the value according to the RTDmaxEqD of value determinationmaxA value of (d);
when the RTD ismaxWhen updating happens, OLT according to the updated EqDmaxUpdating EqDmaxAnd according to the updated EqDmaxAnd after updating the EqD values of all online ONUs in the PON system, sending the updated EqD values to the corresponding ONUs as the EqD updating information.
Further, the OLT stores the RTDmaxWhile storing the value according to the RTDmaxEqD of value determinationmaxA value of (d);
when the RTD ismaxWhen updating happens, OLT according to the updated EqDmaxUpdating EqDmaxAnd stores the updated EqDmaxeqD before update stored with the OLTmaxAnd the difference value between the EqD difference values is used as the EqD updating information to be sent to all online ONUs.
Further, the OLT transmits the updated EqD value to the corresponding ONU through a Ranging _ Time message.
Further, the OLT sends the EqD difference to all on-line ONUs through an existing or newly created physical layer operation maintenance administration (PLOAM) message.
Further, the data field of the PLOAM message at least comprises the following contents:
the EqD difference value, a sign of the EqD difference value.
The invention also provides a system for synchronous uplink transmission in a passive optical network, which comprises an Optical Line Terminal (OLT) and an Optical Network Unit (ONU), wherein the OLT further comprises an RTD module and an EqD module,
the RTD module is used for storing the maximum loop delay (RTD) of all on-line ONUs in a Passive Optical Network (PON) systemmax) And sending the data to the EqD module; and when the RTD ismaxWhen update occurs, the updated RTD is usedmaxSending the data to the EqD module;
the eqD module is used for determining a maximum loop delay (RTD) of all on-line ONUs in a Passive Optical Network (PON) systemmax) Determining maximum equalization delay (EqD)max) And according to said EqDmaxCalculating the value of EqD of all the ONUs; and, based on the received updated RTDmaxCalculating EqD updating information and sending the EqD updating information to all online ONUs;
and the ONU is used for updating the EqD according to the received EqD updating information and then synchronously transmitting uplink according to the updated EqD.
Further, the RTD module is used for aligning the RTD in the following waymaxAnd (3) storage and updating:
locally storing at OLTRTDs of all current online ONUs in the PON systemmaxA value;
regularly and/or irregularly measuring RTDs of part or all of on-line ONUs in the PON system, and comparing the measured RTDs with stored RTDsmaxComparing the values, if the measured RTD value is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the value of the measured RTD.
Further, the RTD module is used for aligning the RTD in the following waymaxAnd (3) storage and updating:
locally storing RTDs of all online ONUs in all current PON systems by OLTmaxA value;
when a new ONU or an ONU needing to recover PON service is accessed into the PON system, the ONU accessed into the PON system is subjected to ranging to obtain the RTD value of the ONU, and the RTD value of the ONU is compared with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the RTD value of the ONU;
when the ONU in the PON system is off-line or off-line, the off-line or off-line ONU is subjected to ranging to obtain the RTD value of the ONU, and the RTD value of the ONU is compared with the RTD locally stored by the OLTmaxValue if the RTD value of the ONU is equal to the RTD locally stored by the OLTmaxIf so, judging whether the maximum RTD value of all the online ONUs in the PON system is smaller than the RTD locally stored by the OLTmaxValue, if so, updates the locally stored RTDmaxThe value is the maximum RTD value of all online ONUs in the PON system.
Further, the EqD module is configured to receive the updated RTDmaxAnd then, calculating the EqD updating information by adopting the following method:
according to the updated EqDmaxUpdating EqDmaxAnd according to the updated EqDmaxAfter updating the EqD values of all online ONUs in the PON system, sending the updated EqD values to the corresponding ONUs as the EqD updating information; or,
according to the updated EqDmaxUpdating EqDmaxAnd calculates the updated EqDmaxAnd eqD before updatemaxAnd the difference value between the EqD difference values is used as the EqD updating information to be sent to all online ONUs.
By adopting the technical scheme of the invention, the OLT dynamically updates the maximum RTDs of all the online ONUs, and dynamically updates the EqD of each ONU according to the maximum RTDs, so that the EqD of each ONU can be reduced, and the uplink transmission efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a topology of a GPON system;
fig. 2 is a schematic block diagram of a system for synchronous uplink transmission in a passive optical network according to an embodiment of the present invention.
Detailed Description
The core idea of the invention is as follows: OLT according to maximum RTD value (RTD) of RTDs of all on-line ONUs in PON systemmax) Determining maximum equalization delay EqDmaxAccording to EqDmaxCalculating the value of EqD for each ONU: EqDi=EqDmax-RTDi. When RTD in PON systemmaxWhen the change occurs, the OLT changes the new RTD according to the changemaxUpdating the maximum equalization time delay EqDmaxAnd updating the value of the EqD of each ONU. And then, the OLT sends the updated EqD information of each ONU or the difference value of the EqD required to be adjusted by each ONU to the corresponding ONU, and the ONU synchronously transmits uplink according to the updated EqD.
Specifically, the present invention can adopt at least the following two schemes:
scheme one
The OLT stores RTD values of all the ONUs in the PON system and stores the maximum RTD value RTD of all the ONUs in the PON systemmax；
The OLT regularly and/or irregularly measures RTD values of all on-line ONUs in the PON system and detects the RTDs in the PON system according to the measurement resultsmaxWhether a change has occurred, if so, based on the new RTDmaxAnd recalculating the EqD values of all the on-line ONUs according to the measured RTD values of the ONUs, and sending the updated EqD values to all the on-line ONUs.
Scheme two
The OLT stores RTD values of all the ONUs in the PON system, and stores the maximum RTD values of all the ONUs in the PON system and the maximum EqD determined according to the maximum RTD values;
when a new ONU or an ONU needing service recovery is added into a PON system, an OLT measures the RTD of the ONU and compares the RTD of the ONU with the maximum RTD locally stored by the OLT, if the RTD of the ONU is larger than the maximum RTD locally stored by the OLT, the OLT updates the maximum RTD value locally stored to be the RTD of the ONU, and calculates the maximum equalization time delay EqD according to the updated maximum RTD value, the OLT stores the updated maximum equalization time delay EqD, and the OLT stores the difference value of the maximum EqD before and after updating;
when a certain ONU in the PON system is offline or offline, the OLT compares the RTD of the ONU with the maximum RTD locally stored by the OLT, if the RTD of the ONU is equal to the maximum RTD locally stored by the OLT, the OLT compares the maximum RTD values of all the online ONUs with the maximum RTD locally stored by the OLT, if the maximum RTD values of all the online ONUs are smaller than the maximum RTD locally stored by the OLT, the OLT updates the locally stored maximum RTD value to be the maximum RTD value of the online ONUs in the PON system, and the OLT updates the maximum equalization time delay EqD according to the updated maximum RTD value, stores the updated maximum equalization time delay EqD, and stores the difference value between the maximum EqD before and after updating;
and after the OLT updates the locally stored maximum RTD and EqD values, calculating the EqD information of all online ONUs, sending the updated EqD information to the ONUs, updating the local EqD values by the ONUs receiving the updated EqD information, and synchronizing uplink transmission according to the updated EqD values.
The EqD information sent by the OLT to the ONUs may be an updated EqD value corresponding to each ONU, or an EqD difference value that the ONUs need to adjust.
The OLT may send the updated EqD value to each ONU, or send the EqD difference value that needs to be adjusted to all online ONUs at the same time.
Further, the OLT may send the EqD difference value that needs to be adjusted to all online ONUs simultaneously by creating a new Physical layer operation and management (PLOAM) message.
The following describes the implementation of the technical solution of the present invention in further detail with reference to specific examples.
Example one
The method for synchronous uplink transmission in the passive optical network provided by the embodiment mainly comprises the following steps:
step 101, when the OLT completes ranging for each ONU, the OLT stores RTD values of the ONUs, and the OLT stores RTD values of maximum RTDs of all currently online ONUs in the PON systemmax；
102, the OLT periodically and/or aperiodically measures RTDs of all on-line ONUs in the PON system, and compares the measured RTDs with stored RTDsmaxComparing, if the measured RTD value of ONU is larger than the RTD stored locally by OLTmaxIf so, the OLT updates the locally stored maximum RTD value to be the RTD value of the ONU;
103, the OLT updates the RTD according to the updated RTDmaxUpdating EqDmaxAnd according to the updatedEqDmaxAnd re-measured RTDiThe value of EqD for each ONU is updated using the following formula: EqDi=EqDmax-RTDi；
And step 104, the OLT sends the updated EqD value of each ONU to all the on-line ONUs, and the ONUs synchronously transmit uplink according to the updated EqD values.
In addition, in this embodiment, the OLT may also perform RTD measurement only on a part of the ONUs that need to perform ranging anew according to the aging period of each ONU, and the measurement step is completely the same as the above step, and is not described herein again.
Example two
When the OLT finishes ranging to an ONU, the OLT stores the RTD value of the ONU, and the OLT stores the RTD value of the maximum RTD of the ONUs on line in all the current PON systemsmaxAnd according to the RTDmaxDetermined EqDmaxThe value of (c).
When a new ONU or an ONU which needs to recover PON service is accessed to a PON system, the OLT and the ONU adopt the following main steps to complete the transmission synchronization of all uplink ONUs:
the method comprises the steps that firstly, an OLT measures the distance of an ONU newly accessed into a PON system to obtain the RTD of the ONU;
step two, the OLT stores the RTD value of the ONU and compares the RTD value of the ONU with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxIf so, the OLT updates the locally stored maximum RTD value to be the RTD value of the ONU and updates the maximum RTD value to be the RTD value of the ONU according to the updated RTD valuemaxUpdating EqDmaxAnd OLT stores the updated EqDmaxAnd may also store the updated EqDmaxeqD before update stored with the OLTmaxThe difference between them; if the RTD value of the ONU is less than or equal to the RTD locally stored by the OLTmaxIf so, the OLT and the ONU directly execute the step four;
step three, the OLT may update the EqD value of the ONU in the working state in the PON system by any one of the following manners:
1) OLT utilizing updated EqDmaxUpdating the eqD of all the ONUs in the working state, respectively sending the updated eqD of each ONU to the corresponding ONUs through a PLOAM message named Ranging _ Time, and updating local eqD values after the ONUs receive the PLOAM message named Ranging _ Time;
2) the OLT stores the updated EqD stored by the OLT in the step twomaxeqD before update stored with the OLTmaxThe difference between the ONUs, that is, the difference information of the EqD that each ONU needs to adjust, is sent to all the ONUs in operation through the PLOAM message shown in table 1, as shown in table 1, the PLOAM Message named EqD _ adjust comprises four parts, wherein the first part of ONU-ID (ONU identifier) has a value of 11111111, which indicates that the PLOAM Message is sent to all ONUs in working state, the second part of Message ID has a value of 10000000 (which is only an example and can take other values), which indicates that the type of the PLOAM Message is EqD adjustment, the third part of the PLOAM Message is a Data field of the PLOAM Message, which includes Data1 and Data2, Data1 indicates the EqD difference value that all ONUs in working state need to be adjusted, Data2 indicates the sign of the EqD difference value, when the value is 0 (1), the EqD difference value indicated by Data1 needs to be added to the EqD of the ONU, and when the value is 1 (0), the EqD difference value indicated by Data1 needs to be subtracted from the EqD of the ONU. The fourth part of the PLOAM message is a frame check sequence. After the ONU in the working state receives the PLOAM message named as EqD _ adjust, if the value of Data2 is 0, the ONU adds the EqD difference represented by Data1 to the local EqD value, and if the value of Data2 is 1, the ONU subtracts the EqD difference represented by Data1 from the local EqD value to complete the updating of the local EqD value;
table 1 PLOAM message (EqD _ adjust) format of EqD difference value to be adjusted
Step four, calculating the EqD value of the ONU newly accessed to the PON system, sending the EqD value of the ONU to the ONU, receiving and storing the EqD value sent by the OLT by the ONU, and entering a working state;
and step five, all the ONUs in the working state synchronously perform uplink transmission according to the locally updated EqD value.
Similarly, when there is an ONU in the PON system going offline, the OLT and the ONU complete transmission synchronization of all upstream ONUs by using the following method: the OLT compares the RTD value of the offline ONU with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is equal to the RTD locally stored by the OLTmaxIf so, the OLT compares the RTD values of all the ONUs in the working state with the RTD stored by the OLTmaxValue, if the maximum RTD value of all the ONUs in working state is smaller than the RTD stored locally by OLTmaxValue, then OLT updates the locally stored RTDmaxThe value is the maximum RTD value of all the current ONUs in the working state and is updated according to the updated RTDsmaxUpdating EqDmaxOptionally, the updated EqD may also be storedmaxeqD before update stored with the OLTmaxThe OLT and the ONU execute the second step and the fifth step according to the difference value between the OLT and the ONU; if the RTD value of the offline ONU is smaller than the RTD locally stored by the OLTmaxThe value or the maximum RTD value of all the ONUs in the working state at present is equal to the RTD locally stored by the OLTmaxValue, then OLT and ONU do not perform any operation.
As shown in fig. 2, an embodiment of the present invention further provides a system for synchronous uplink transmission in a passive optical network, including an OLT and an ONU, where the OLT further includes an RTD module and an EqD module, where:
the RTD module is used for storing the maximum loop delay (RTD) of all the on-line ONUs in a Passive Optical Network (PON) systemmax) And sending the data to an EqD module; and, when the RTD ismaxWhen update occurs, the updated RTD is usedmaxSending the data to an EqD module;
the eqD module is used for determining the maximum loop delay (RTD) of all ONUs on line in a Passive Optical Network (PON) systemmax) Determining maximum equalization delay (EqD)max) According to EqDmaxCalculating the value of EqD of all the ONUs; and, based on the received updated RTDmaxCalculating EqD updating information and sending the EqD updating information to all online ONUs;
and the ONU is used for updating the EqD according to the received EqD updating information and then synchronously transmitting uplink according to the updated EqD.
Wherein, the RTD module can adopt the following modes to the RTDmaxAnd (3) storage and updating:
RTD of all current online ONU in OLT local storage PON systemmaxA value;
regularly and/or irregularly measuring RTD of partial or all on-line ONU in PON system, and comparing the measured RTD value with stored RTDmaxComparing the values, if the measured RTD value is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the value of the measured RTD.
Alternatively, the RTD module can also be used for RTDs in the following mannermaxAnd (3) storage and updating:
locally storing RTDs of all online ONUs in all current PON systems by OLTmaxA value;
when a new ONU or an ONU needing to recover PON service is accessed into the PON system, the ONU accessed into the PON system is subjected to ranging to obtain the RTD value of the ONU, and the RTD value of the ONU is compared with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the RTD value of the ONU;
when an ONU in the PON system is off-line or off-line, ranging the off-line or off-line ONU to obtain the RTD value of the ONU, and comparing the RTD value of the ONURTD value and OLT locally stored RTDmaxValue if the RTD value of the ONU is equal to the RTD locally stored by the OLTmaxIf so, judging whether the maximum RTD value of all the on-line ONUs in the PON system is smaller than the RTD locally stored by the OLTmaxValue, if so, updates the locally stored RTDmaxThe value is the maximum RTD value of all online ONUs in the PON system.
Further, the eqD module is configured to receive the updated RTDmaxAnd then, calculating EqD updating information by adopting the following method:
according to the updated EqDmaxUpdating EqDmaxAnd according to the updated EqDmaxAfter updating the EqD values of all online ONUs in the PON system, sending the updated EqD values to the corresponding ONUs as EqD updating information; or,
according to the updated EqDmaxUpdating EqDmaxAnd calculates the updated EqDmaxAnd eqD before updatemaxAnd the difference value between the EqD and the ONU is used as EqD updating information to be sent to all online ONUs.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications may be effected herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

1. A method for synchronizing uplink transmission in a passive optical network, the method comprising:
an optical line terminal OLT according to the maximum loop time delay RTD of all on-line optical network units ONU in a passive optical network PON systemmaxDetermining maximum equalization delay EqDmaxAnd according to said EqDmaxCalculating the value of EqD of all the ONUs;
when the RTD ismaxWhen the update occurs, the OLT according to the updated RTDmaxCalculating EqD updating information;
the OLT sends the EqD updating information to all online ONUs, and the ONUs update the EqD according to the received EqD updating information and then synchronize uplink transmission according to the updated EqD;
the RTDmaxThe step of generating the update specifically includes:
OLT stores RTDs of all online ONUs in all current PON systemsmaxA value;
when a new ONU or an ONU needing to recover PON service is accessed into the PON system, the OLT measures the distance of the ONU accessed into the PON system to obtain the RTD value of the ONU;
the OLT compares the RTD value of the ONU with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxValue, then OLT updates the locally stored RTDmaxThe value is the value of the RTD of the ONU.
2. The method of claim 1,
the RTDmaxThe step of generating the update specifically includes:
the OLT stores RTDs of all current online ONUs in the PON systemmaxA value;
the OLT regularly and/or irregularly measures the RTD of part or all of the on-line ONU in the PON system, and compares the measured RTD with the stored RTDmaxComparing the values, if the measured RTD value is larger than the RTD locally stored by the OLTmaxValue, then OLT updates the locally stored RTDmaxThe value is the value of the measured RTD.
3. The method of claim 2,
when the RTD ismaxWhen the update occurs, the OLT according to the updated RTDmaxValue update EqDmaxValue and according to the updated EqDmaxAnd after updating the EqD value of part or all of the on-line ONUs in the PON system, sending the updated EqD value to the corresponding ONUs as the EqD updating information.
4. The method of claim 1,
the RTDmaxThe step of generating the update further comprises:
storing RTDs of all online ONUs in all current PON systems at OLTmaxAfter the value is reached,
when an ONU in the PON system is offline or offline, the OLT measures the distance of the offline or offline ONU to obtain the RTD value of the ONU;
the OLT compares the RTD value of the ONU with the RTD locally stored by the OLTmaxValue if the RTD value of the ONU is equal to the RTD locally stored by the OLTmaxIf so, the OLT judges whether the maximum RTD value of all the on-line ONUs in the PON system is smaller than the RTD locally stored by the OLTmaxValue, if yes, OLT updates local storage RTDmaxThe value is the maximum RTD value of all online ONUs in the PON system.
5. The method of claim 1 or 4,
the OLT stores the RTDmaxWhile storing the value according to the RTDmaxEqD of value determinationmaxA value of (d);
when the RTD ismaxWhen updating happens, OLT according to the updated EqDmaxUpdating EqDmaxAnd according to the updated EqDmaxAnd after updating the EqD values of all online ONUs in the PON system, sending the updated EqD values to the corresponding ONUs as the EqD updating information.
6. The method of claim 1 or 4,
the OLT stores the RTDmaxWhile storing the value according to the RTDmaxEqD of value determinationmaxA value of (d);
when the RTD ismaxWhen updating happens, OLT according to the updated EqDmaxUpdating EqDmaxAnd stores the updated EqDmaxeqD before update stored with the OLTmaxAnd the difference value between the EqD difference values is used as the EqD updating information to be sent to all online ONUs.
7. The method of claim 5,
and the OLT sends the updated EqD value to the corresponding ONU through a Ranging Time Ranging _ Time message.
8. The method of claim 6,
and the OLT transmits the EqD difference value to all online ONUs through the existing or newly-built physical layer operation maintenance management PLOAM message.
9. The method of claim 8,
the data field of the PLOAM message at least comprises the following contents:
the EqD difference value, a sign of the EqD difference value.
10. A system for synchronizing upstream transmission in a passive optical network, comprising an Optical Line Terminal (OLT) and Optical Network Units (ONU), wherein the OLT further comprises a RTD module and an EqD module,
the RTD module is used for storing the maximum loop time delay RTD of all on-line ONU in the passive optical network PON systemmaxAnd sending the data to the EqD module; and when the RTD ismaxWhen update occurs, the updated RTD is usedmaxSending the data to the EqD module;
the EqD module is used for delaying the RTD according to the maximum loop time of all on-line ONUs in the passive optical network PON systemmaxDetermining maximum equalization delay EqDmaxAnd according to said EqDmaxCalculating the value of EqD of all the ONUs; and, based on the received updated RTDmaxCalculating EqD updating information and sending the EqD updating information to all online ONUs;
the ONU is used for updating the EqD according to the received EqD updating information and then synchronously transmitting uplink according to the updated EqD;
the RTD module is used for aligning the RTD in the following waymaxAnd (3) storage and updating:
locally storing RTDs of all online ONUs in all current PON systems by OLTmaxA value;
when a new ONU or an ONU needing to recover PON service is accessed into the PON system, the ONU accessed into the PON system is subjected to ranging to obtain the RTD value of the ONU, and the RTD value of the ONU is compared with the RTD locally stored by the OLTmaxValue, if the RTD value of the ONU is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the value of the RTD of the ONU.
11. The system of claim 10,
the RTD module is used for aligning the RTD in the following waymaxAnd (3) storage and updating:
locally storing RTDs of all current online ONUs in the PON system at an OLT (optical line terminal)maxA value;
regularly and/or irregularly measuring RTDs of part or all of on-line ONUs in the PON system, and comparing the measured RTDs with stored RTDsmaxComparing the values, if the measured RTD value is larger than the RTD locally stored by the OLTmaxValue, then update the locally stored RTDmaxThe value is the value of the measured RTD.
12. The system of claim 10,
the RTD module is also used for aligning the RTD in the following waymaxAnd (3) storage and updating:
locally storing RTDs of all online ONUs in all current PON systems by OLTmaxAfter the value is reached,
when the ONU in the PON system is off-line or off-line, the off-line or off-line ONU is subjected to ranging to obtain the RTD value of the ONU, and the RTD value of the ONU is compared with the RTD locally stored by the OLTmaxValue of RTD if the ONURTD equal to OLT local storagemaxIf so, judging whether the maximum RTD value of all the online ONUs in the PON system is smaller than the RTD locally stored by the OLTmaxValue, if so, updates the locally stored RTDmaxThe value is the maximum RTD value of all online ONUs in the PON system.
13. The system of claim 12,
the eqD module is used for receiving the updated RTDmaxAnd then, calculating the EqD updating information by adopting the following method:
according to the updated EqDmaxUpdating EqDmaxAnd according to the updated EqDmaxAfter updating the EqD values of all online ONUs in the PON system, sending the updated EqD values to the corresponding ONUs as the EqD updating information; or,
according to the updated EqDmaxUpdating EqDmaxAnd calculates the updated EqDmaxAnd eqD before updatemaxAnd the difference value between the EqD difference values is used as the EqD updating information to be sent to all online ONUs.
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