CN102347829A - Ethernet passive optical network (EPON) time synchronization method - Google Patents
Ethernet passive optical network (EPON) time synchronization method Download PDFInfo
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- CN102347829A CN102347829A CN2010102397760A CN201010239776A CN102347829A CN 102347829 A CN102347829 A CN 102347829A CN 2010102397760 A CN2010102397760 A CN 2010102397760A CN 201010239776 A CN201010239776 A CN 201010239776A CN 102347829 A CN102347829 A CN 102347829A
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Abstract
The invention discloses an Ethernet passive optical network (EPON) time synchronization method. An optical line terminal (OLT) side of an EPON realizes a peer to peer (PTP) sub clock. The method comprises the following steps that: a PTP timestamp counter is read through a central processing unit (CPU) at the OLT side; the CPU calculates the corresponding ToD and the PTP timestamp counter value corresponding to the latest one 1PPS; the obtained PTP timestamp counter value is set to a 1PPS PTP timestamp counter register; an OLT multipoint control protocol (MPCP) timestamp counter is latched into the 1PPS PTP timestamp counter register; the CPU reads the 1PPS PTP timestamp counter register; the CPU sends the information to an optical network unit (ONU) through operation and maintenance (OAM) messages; and the ONU side realizes the IPPS+ToD information output. The time synchronization method can simply and flexibly realize the time synchronization technology.
Description
Technical field
The present invention relates to a kind of EPON network field, the method for time synchronized in particularly a kind of EPON network.
Background technology
EPON EPON (Ethernet Passive OpticalNetworks) based on Ethernet is a point-to-point configuration.Among the EPON EPON based on Ethernet, a local side apparatus OLT (Optical Line Terminal) connects a plurality of ustomer premises access equipment ONU (Optical Network Unit) through tree-structure mode.Local side apparatus is a down direction to the communication of ustomer premises access equipment, and ustomer premises access equipment is a up direction to the communication of local side apparatus.Fig. 1 is the network topology sketch map of EPON system, and when EPON network during as the transmission network of mobile communication, the ability of transmission time synchronizing information becomes needs, can for the mobile base station time source be provided cheaply like this.
The EPON system realizes the clock synchronization between ONU and the OLT through the transmission of MPCP bag.After compensation downlink transfer time delay, can realize the transmission of time synchronized.Shown in Figure 2, in the time synchronized scheme based on EPON OAM, after the clock source inputed to OLT with 1PPS+ToD information, the PON time stamp that OLT is corresponding with 1PPS was transferred to each ONU, and ONU delays when the compensation downlink transfer, output 1PPS+ToD information.In this scheme, needing a clock source is that OLT provides 1PPS+ToD information.
Summary of the invention
The technical problem that the present invention will solve provides method for synchronizing time in a kind of EPON network, is used in the Ethernet of supporting the PTP agreement.
For solving the problems of the technologies described above, the method for time synchronized in the EPON network of the present invention, the OLT side of this EPON network has realized PTP from clock, and realizes that in the ONU side based on the 1PPS+ToD output of the Clock Synchronization Technology of EPON OAM, this method comprises the steps:
1) the OLT side is read PTP time stamp Counter Value through CPU;
2) CPU calculates the corresponding PTP time stamp Counter Value and the corresponding ToD information of the afterwards nearest 1PPS of PTP time stamp Counter Value of gained; If nearest 1PPS time corresponding distance is read the time of said PTP time stamp Counter Value less than a preset processing time, then calculate the corresponding PTP time stamp Counter Value of next 1PPS;
The PTP time stamp Counter Value that 3) will calculate gained places in the register of 1PPS PTP time stamp counter;
4) when OLT PTP time stamp Counter Value equals the register value of 1PPS PTP time stamp counter, OLT MPCP time stamp Counter Value is latched in the register of 1PPS MPCP time stamp counter, and produces interrupt notification OLT CPU;
5) the OLT side gets corresponding MPCP time stamp Counter Value of 1PPS and corresponding ToD information through the register that CPU reads 1PPS MPCP time stamp counter;
6) OLT side CPU is corresponding with above-mentioned 1PPS MPCP time stamp Counter Value and corresponding ToD information send to ONU through the OAM message;
7) the ONU side realizes the output of 1PPS+ToD information.
Adopt method for synchronizing time of the present invention; Can simple and flexible ground at the OLT that supports the PTP agreement with do not support the PTP agreement only to support between ONU based on the Time synchronization technique of EPON OAM; Realize Time synchronization technique, increase the flexibility of networking, reduce networking cost.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the present invention is done further detailed explanation:
Fig. 1 is the network topology sketch map of EPON system;
Fig. 2 is the time synchronized scheme sketch map based on EPON OAM;
Fig. 3 is a method for synchronizing time flow chart of the present invention.
Embodiment
In Ethernet, support the product of PTP (Precision Time Protocal, precision time protocol) time host-host protocol to increase gradually.If realize PTP from clock, and be converted into the 1PPS+ToD message transmission, then can realize more flexibly networking plan more cheaply to ONU in the OLT side.
The method of EPON network time synchronization of the present invention, applied environment are that the OLT side of EPON has realized PTP from clock, and realize the 1PPS+ToD information output based on EPON OAM Clock Synchronization Technology in the ONU side.The method of time synchronized of the present invention, concrete steps are:
1) the OLT side is read PTP time stamp Counter Value through CPU (also claiming software);
2) CPU calculates the corresponding PTP time stamp Counter Value and the corresponding ToD information of the afterwards nearest 1PPS of PTP time stamp Counter Value of gained; If the time that nearest 1PPS time corresponding distance is read said PTP time stamp Counter Value (can be through register configuration less than a preset processing time; Like 500ms), then calculate the corresponding PTP time stamp Counter Value of next 1PPS;
The PTP time stamp Counter Value that 3) will calculate gained places in the register of 1PPS PTP time stamp counter;
4) when OLT PTP time stamp Counter Value equals the register value of 1PPS PTP time stamp counter, OLT MPCP time stamp Counter Value is latched in the register of 1PPS MPCP time stamp counter, and produces interrupt notification OLT CPU;
5) the OLT side gets corresponding MPCP time stamp Counter Value of 1PPS and corresponding ToD information through the register that CPU reads 1PPS MPCP time stamp counter;
6) OLT side CPU is corresponding with above-mentioned 1PPS MPCP time stamp Counter Value and corresponding ToD information send to ONU through the OAM message;
7) the ONU side realizes the output of 1PPS+ToD information.
In the OLT side of the EPON that supports the PTP agreement, realize that PTP can be described as simply from clock: OLT initiates path delay and measures, obtain path delay; OLT receives after the PTP Sync message, and recorded message time of advent, OLT calibrates local zone time after compensation transmission delay and asymmetry.
And realize 1PPS+ToD output based on the Clock Synchronization Technology of EPON OAM in the ONU side, and specifically can be ONU and receive the MPCP time stamp Counter Value and corresponding ToD information that is calculated, export 1PPS+ToD information constantly at next 1PPS after the delay compensation.More specifically can be: the MPCP Counter Value that ONU is corresponding constantly with next 1PPS is arranged in the register, when the MPCP Counter Value equals this register value, and ONU output 1PPS rising edge of a pulse.After ONU output 1PPS pulse rising was prolonged, ONU hardware was changed to the corresponding MPCP Counter Value of next 1PPS with this register.ONU corresponding ToD information of (before 500ms) output in the stipulated time after output 1PPS rising edge of a pulse.After ONU receives through the next 1PPS information of OAM message transmission, behind the ONU compensation transmission delay, calculate the corresponding MPCP Counter Value of next 1PPS, and be placed in the above-mentioned register.
Adopt Time synchronization technique scheme of the present invention; Local side apparatus OLT need not the information such as GPS isochronon source input 1PPS+ToD; Only need realizing that PTP is from the basis of clock; Read PTP time stamp Counter Value through CPU, and calculate this PTP time stamp Counter Value a nearest 1PPS PTP time stamp Counter Value and corresponding ToD information afterwards, and be stored in the relevant register; When OLT PTP time stamp Counter Value equals the register value of above-mentioned 1PPS PTP time stamp counter; OLT MPCP time stamp Counter Value is latched in the register of 1PPS MPCP time stamp counter; Read the register of 1PPS MPCP time stamp counter subsequently through CPU; Obtain corresponding MPCP time stamp Counter Value of 1PPS and ToD information, give ONU through OAM message transmissions 1PPS+ToD information.Adopt method for synchronizing time of the present invention, can simple and flexible ground at the OLT that supports the PTP agreement with do not support the PTP agreement only to support to realize Time synchronization technique between ONU based on the Clock Synchronization Technology of EPON OAM, increase the flexibility of networking, reduce networking cost.
Claims (3)
1. the method for an EPON network time synchronization; The OLT side of said EPON network has realized that PTP is from clock; And realize it is characterized in that based on the 1PPS+ToD output of the Clock Synchronization Technology of EPON OAM said method comprises the steps: in the ONU of EPON network side
1) the OLT side is read PTP time stamp Counter Value through CPU;
2) CPU calculates the corresponding PTP time stamp Counter Value and the corresponding ToD information of the afterwards nearest 1PPS of PTP time stamp Counter Value of gained; If nearest 1PPS time corresponding distance is read the time of said PTP time stamp Counter Value less than a preset processing time, then calculate the corresponding PTP time stamp Counter Value of next 1PPS;
The PTP time stamp Counter Value that 3) will calculate gained places in the register of 1PPS PTP time stamp counter;
4) when OLT PTP time stamp Counter Value equals the register value of 1PPS PTP time stamp counter, OLT MPCP time stamp Counter Value is latched in the register of 1PPS MPCP time stamp counter, and produces interrupt notification OLT CPU;
5) the OLT side gets corresponding MPCP time stamp Counter Value of 1PPS and corresponding ToD information through the register that CPU reads 1PPS MPCP time stamp counter;
6) OLT side CPU is corresponding with above-mentioned 1PPS MPCP time stamp Counter Value and corresponding ToD information send to ONU through the OAM message;
7) the ONU side realizes the output of 1PPS+ToD information.
2. according to the described method of claim 1, it is characterized in that: the preset processing time in the said step 2 is passed through register configuration.
3. according to claim 1 or 2 described methods, it is characterized in that said step 7) is: the ONU side joint is received the information of sending in the step 6), after the delay compensation, exports 1PPS+ToD information constantly at next 1PPS.
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Citations (4)
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| US20080031283A1 (en) * | 2006-08-07 | 2008-02-07 | Martin Curran-Gray | Time synchronization for network aware devices |
| CN101213782A (en) * | 2005-06-29 | 2008-07-02 | 泰克诺沃斯公司 | Accommodating different clock frequencies in an Ethernet passive optical network |
| CN101431385A (en) * | 2008-08-26 | 2009-05-13 | 中兴通讯股份有限公司 | Frequency and time synchronization method for passive optical network |
| CN101615949A (en) * | 2008-06-27 | 2009-12-30 | 中国移动通信集团上海有限公司 | Realize method, system and the equipment of femtocell clock synchronization |
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- 2010-07-29 CN CN2010102397760A patent/CN102347829A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101213782A (en) * | 2005-06-29 | 2008-07-02 | 泰克诺沃斯公司 | Accommodating different clock frequencies in an Ethernet passive optical network |
| US20080031283A1 (en) * | 2006-08-07 | 2008-02-07 | Martin Curran-Gray | Time synchronization for network aware devices |
| CN101615949A (en) * | 2008-06-27 | 2009-12-30 | 中国移动通信集团上海有限公司 | Realize method, system and the equipment of femtocell clock synchronization |
| CN101431385A (en) * | 2008-08-26 | 2009-05-13 | 中兴通讯股份有限公司 | Frequency and time synchronization method for passive optical network |
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