CN101902319B - Method for synchronizing network clock stamps - Google Patents
Method for synchronizing network clock stamps Download PDFInfo
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- CN101902319B CN101902319B CN 200910057339 CN200910057339A CN101902319B CN 101902319 B CN101902319 B CN 101902319B CN 200910057339 CN200910057339 CN 200910057339 CN 200910057339 A CN200910057339 A CN 200910057339A CN 101902319 B CN101902319 B CN 101902319B
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Abstract
The invention discloses a method for synchronizing network clock stamps. The method comprises the following steps: firstly local end equipment sends beacon frame to customer premise equipment in the fixed time position of the downlink time period of one period, the local end equipment, wherein the time from sending beacon frame to the customer premise equipment by the local end equipment to receiving beacon frame by the customer premise equipment is tds and beacon frame is different to GATE frame; the customer premise equipment sends REPORT frame to the local end equipment in the uplink time period of the period, wherein the time from sending REPORT frame to the local end equipment by the customer premise equipment to receiving REPORT frame is tus; calculating round trip time (RTT) which is equal to the sum of tds and tus, and synchronizing the clock stamps of the local end equipment and the customer premise equipment according to the calculated RTT. In the method of the invention, a beacon frame is inserted in the fixed time position of the downlink time period of the local end equipment, thus the difference of the RTTs obtained by calculations is greatly decreased. Therefore, the vibration of RTT can be greatly reduced, the occupied bandwidth can be lowered and accurate clock synchronization can be realized.
Description
Technical field
The present invention relates to the synchronous method of a kind of network clock stamps.
Background technology
EOC (Ethernet Over COAX, Ethernet transmits by coaxial cable) be based on the point-to-point configuration of coaxial cable transmission ethernet frame, comprise a main equipment, a plurality of from equipment, main equipment and from also having one or more splitters or distributor between the equipment, perhaps at main equipment with from comprising splitter and distributor between the equipment simultaneously.By splitter or distributor, main equipment is connected from equipment with a plurality of with tree.The uplink communication of EOC network using TDM (Time Division Multiplexing, time division multiplexing) a plurality of ustomer premises access equipments of mode control and management.One or more splitters or distributor are arranged between local side apparatus and the ustomer premises access equipment.Local side apparatus is down direction to the direction that ustomer premises access equipment sends packet; Ustomer premises access equipment is up direction to the direction that local side apparatus sends packet.Fig. 1 has provided an example, and wherein system is made up of a local side apparatus (Central OfficeDevice) and 5 ustomer premises access equipments (Subscriber Device):
The uplink communication of EOC network using TDM (Time Division Multiplexing, time division multiplexing) a plurality of ustomer premises access equipments of mode control and management.Be that local side apparatus is that a plurality of ustomer premises access equipments distribute up timeslice separately, each ustomer premises access equipment can only carry out transmitting uplink data in distributing to the up timeslice of oneself.In most systems, local side apparatus is notified its up timeslice of distributing to client by sending the MPCP protocol massages to client, and client is by sending REPORT protocol massages application last line time next time.Therefore, local side apparatus stabs consistent by the clock that calculates RTT (round trip time, loop time delay) and keep the timestamp of all user sides and local side so that a plurality of user side timeslice distribute correctly.
This basic scheme has following shortcoming at the clock synchronization aspects: in the bursty data flow network, the uncertainty of MPCP protocol package position in the data flow of burst causes that local side apparatus carries out RTT and calculates, and can produce very big shake.
Summary of the invention
Technical problem to be solved by this invention provides the synchronous method of a kind of network clock stamps, makes the EOC network under the situation of using the burst transfers of data technology, under the prerequisite of not using extra bandwidth, realizes that clock is synchronous accurately.
For solving the problems of the technologies described above, the technical scheme of the method that network clock stamps of the present invention is synchronous is, the fixed time position of the descending period of local side apparatus in one-period is sent a beacon frame earlier to ustomer premises access equipment, send the beacon frame from local side apparatus and receive that to ustomer premises access equipment the time of beacon frame is tds, described beacon frame is distinguished mutually with the GATE frame, ustomer premises access equipment sends the REPORT frame to local side apparatus in the up period in this cycle, send the REPORT frame from ustomer premises access equipment and receive that to local side apparatus the time of REPORT frame is tus, RTT is calculated, RTT=tds+tus stabs according to the clock of the local side apparatus of the RTT that calculates and ustomer premises access equipment and to carry out synchronously.
The present invention inserts a beacon frame by the fixed time position in the descending period of local side apparatus, the difference of the feasible RTT that at every turn calculates reduces greatly, thereby greatly reduce the shake of RTT, reduced the taking of bandwidth, realized that clock is synchronous accurately.
Description of drawings
The present invention is further detailed explanation below in conjunction with drawings and Examples:
Fig. 1 is the structural representation of EOC system;
Fig. 2 is for carrying out the schematic diagram of dividing processing to message;
Fig. 3 is the schematic diagram of existing network data transmission form;
Fig. 4 is the schematic diagram of the transmission course of existing inter-network data;
Fig. 5 is beacon frame of the present invention and GATE frame structure schematic diagram relatively;
Fig. 6 is the schematic diagram of the transmission course of inter-network data of the present invention.
Embodiment
The invention provides the synchronous method of a kind of network clock stamps, the fixed time position of the descending period of local side apparatus in one-period is sent a beacon frame earlier to ustomer premises access equipment, send the beacon frame from local side apparatus and receive that to ustomer premises access equipment the time of beacon frame is tds, described beacon frame is distinguished mutually with the GATE frame, ustomer premises access equipment sends the REPORT frame to local side apparatus in the up period in this cycle, send the REPORT frame from ustomer premises access equipment and receive that to local side apparatus the time of REPORT frame is tus, RTT is calculated, RTT=tds+tus stabs according to the clock of the local side apparatus of the RTT that calculates and ustomer premises access equipment and to carry out synchronously.Described beacon frame is Duoed a beacon territory than the GATE frame in the data flow is middle.
The communication at existing EOC system two ends generally is periodic, can have special protocol massages to provide time-interval distribution information to use for local side and user side in each cycle, as GATE message and REPORT message.The EOC system realizes the synchronous of local side and user side clock by the particularity of these messages.
Usually local side apparatus can send the GATE message at each downstream cycle, but the time that the time of sending begins with respect to downstream cycle is uncertain, for the PHY (physical layer device) that transmits by message, PHY only can introduce very little and stable shake, carries out can not producing synchronously very big RTT shake so ustomer premises access equipment goes out timestamp from the GATE packet parsing with local side apparatus.But concerning some were not the PHY that transmits by message, the uncertain of GATE literary composition transmitting time will bring unsettled RTT shake, and local side apparatus will dispose maximum RTT and satisfy upward that line time does not conflict like this, thereby seriously reduce system bandwidth.
As shown in Figure 2, MII (Media Independent Interface, Media Independent Interface) and be PHY between the Cable (cable), message is some processing of process in PHY, at first PHY is by monitoring TX_EN (MII transmit enable, transmission enables) the interval, after at interval greater than a certain threshold value, can restart the frame of a PHY so at next TX_EN rising edge, it is the PN_H of several bytes that the frame of each PHY begins, and then descending all messages is divided into the cell of several whole N bytes and M (cell of byte of M＜N); Each cell adds the head of 2 bytes and the parity of 16 bytes then, as the P among Fig. 2 and H, and the last PN_E that goes up some bytes that adds again.
Fig. 3 represents the cell form that message is propagated at physical link with chained list after PHY handles, wherein I and P are exactly the H shown in Fig. 2.
Suppose that the GATE message is first message of downstream cycle, then first arrives ustomer premises access equipment to the GATE message through PHY, and required time delay is:
T
dly＝T
PN_H+T
PHY+2*T
IP；
Wherein,
T
PN_H: the transmission time of PN_H;
T
PHY: uncertain time-delay among the PHY;
T
IP: the transmission time of I and P.
Suppose that the GATE message is M message of downstream cycle, then cutting apart again of the message of process PHY, the GATE message may be in K cell, and required time-delay this moment is:
T
dly＝T
PN_H+T
PHY+(K+M)*T
IP+(M-1)*T
IPG+(K-1)*T
P；
Wherein,
T
IPG: the transmission time of IPG;
T
P: the transmission time of 16 byte parity.
The transmission course of inter-network data as shown in Figure 4, existing assumption period Cycle1 (timeslice of the TDM) time started is 0, local side apparatus sends the GATE1 message to ustomer premises access equipment constantly at the t0 of descending period, suppose that the GATE1 message is m downlink message, after cutting apart, PHY is positioned at i cell, ustomer premises access equipment is received GATE1 through the time-delay of tds1 and is own local update of time stamp t0, the clock of ustomer premises access equipment and local side apparatus is with regard on synchronous like this, ustomer premises access equipment sends the REPORT message that has local time stamp t1 through the tw1 time toward local side apparatus, local side apparatus is received this REPORT message at t2, calculates RTT1 then.
RTT1＝tds1+tus1；
tds1＝T
PN_H+T
PHY+(i+m)*T
IP+(m-1)*T
IPG+(i-1)*T
P。
During next cycle Cycle2, local side apparatus sends the GATE2 message to ustomer premises access equipment constantly at the t3 of downstream cycle, supposes that the GATE2 message is n downlink message, and GATE2 is positioned at j cell after PHY is cut apart; Ustomer premises access equipment is received GATE2 through the time-delay of tds2 and is own local update of time stamp t3, the clock of ustomer premises access equipment and local side apparatus is with regard on synchronous like this, ustomer premises access equipment sends the REPORT message that has local time stamp t4 through the tw2 time toward local side apparatus, local side apparatus is received this REPORT message at t5, calculates RTT2 then.
RTT2＝tds2+tus2；
tds2＝T
PN_H+T
PHY+(j+n)*T
IP+(n-1)*T
IPG+(j-1)*T
P。
Usually tw1 is the same substantially with tw2, and tus1 is the same substantially with tus2, can ignore.Therefore the difference of RTT is mainly caused by tds, and each Cycle sends the different i that causes of GATE time point, j and m, n are widely different, so tds difference is also very big, so just local side apparatus is carried out the RTT compensation and cause great influence, can only compensate with maximum, thereby reduce the bandwidth of system greatly.
The embodiment of the invention is compared with above-mentioned existing RTT computational methods, by introducing the beacon frame, in the time that each downstream cycle begins, first sends the beacon frame, ustomer premises access equipment only just carries out the calculating of RTT when receiving the beacon frame, come that to carry out clock synchronous with local side apparatus thereby upgrade local timestamp.
As shown in Figure 5, the left side is former GATE frame format, and the right is compared with former GATE frame for beacon frame format among the present invention, and the beacon frame has increased a territory (beacon territory) that expression is the beacon frame.
The transmission course of inter-network data of the present invention as shown in Figure 6, local side apparatus sends the beacon frame at Cycle1 time started t0, receives the REPORT frame that ustomer premises access equipment feeds back at t2 then, the RTT1 that this moment, local side apparatus calculated:
RTT1＝tds1+tus1；
tds1＝T
PN_H+T
PHY。
Send the beacon frame at Cycle2 time started t3, receive the REPORT frame that ustomer premises access equipment feeds back at t5 then, the RTT2 that this moment, local side apparatus calculated:
RTT2＝tds2+tus2
tds2＝T
PN_H+T
PHY
So RTT1 is consistent with RTT2 substantially, has only the intrinsic very little shake of PHY and ustomer premises access equipment itself.
In sum, the present invention inserts a beacon frame by the fixed time position in the descending period of local side apparatus, and the difference of the feasible RTT that at every turn calculates reduces greatly, thereby greatly reduces the shake of RTT, reduced the taking of bandwidth, realized that clock is synchronous accurately.
Claims (1)
1. method that network clock stamps is synchronous, it is characterized in that, the fixed time position of the descending period of local side apparatus in one-period is sent a beacon frame earlier to ustomer premises access equipment, send the beacon frame from local side apparatus and receive that to ustomer premises access equipment the time of beacon frame is tds, described beacon frame is distinguished mutually with the GATE frame, ustomer premises access equipment sends the REPORT frame to local side apparatus in the up period in this cycle, send the REPORT frame from ustomer premises access equipment and receive that to local side apparatus the time of REPORT frame is tus, RTT is calculated, RTT=tds+tus, clock stamp according to the local side apparatus of the RTT that calculates and ustomer premises access equipment carries out synchronously, wherein
Described beacon frame is Duoed a beacon territory than the GATE frame in the data flow is middle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910057339 CN101902319B (en) | 2009-06-01 | 2009-06-01 | Method for synchronizing network clock stamps |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910057339 CN101902319B (en) | 2009-06-01 | 2009-06-01 | Method for synchronizing network clock stamps |
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| CN101902319A CN101902319A (en) | 2010-12-01 |
| CN101902319B true CN101902319B (en) | 2013-07-17 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103178918B (en) * | 2011-12-26 | 2016-08-03 | 中国科学院沈阳自动化研究所 | Factory automation wireless network time synchronous method based on TDMA |
| CN103457685B (en) * | 2012-05-29 | 2015-09-09 | 中国科学院沈阳自动化研究所 | Based on the industry wireless network high-precision time synchronization method of predictive compensation |
| CN103346917B (en) * | 2013-07-10 | 2016-03-23 | 中磊电子（苏州）有限公司 | EoC system transfers delay time and jitter computational methods and link failure diagnostic method |
| WO2016125081A1 (en) * | 2015-02-03 | 2016-08-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Signaling interface to support real-time traffic steering networks |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1947384A (en) * | 2004-05-05 | 2007-04-11 | 艾利森电话股份有限公司 | Hsdpa flow control, control frames rtt measurement |
| CN101335587A (en) * | 2008-07-23 | 2008-12-31 | 重庆邮电大学 | Accurate time synchronization method for industrial wireless network |
| CN101399653A (en) * | 2007-09-25 | 2009-04-01 | 普然通讯技术(上海)有限公司 | Time clock synchronization implementation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1947384A (en) * | 2004-05-05 | 2007-04-11 | 艾利森电话股份有限公司 | Hsdpa flow control, control frames rtt measurement |
| CN101399653A (en) * | 2007-09-25 | 2009-04-01 | 普然通讯技术(上海)有限公司 | Time clock synchronization implementation method |
| CN101335587A (en) * | 2008-07-23 | 2008-12-31 | 重庆邮电大学 | Accurate time synchronization method for industrial wireless network |
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