CN101252429B

CN101252429B - Method for enhancing clock synchronization accuracy in distributed network system

Info

Publication number: CN101252429B
Application number: CN2008100598607A
Authority: CN
Inventors: 韩晓霞; 张艳; 陈金龙; 廉玉平; 霍明旭; 韩雁
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2008-02-22
Filing date: 2008-02-22
Publication date: 2010-09-22
Anticipated expiration: 2028-02-22
Also published as: CN101252429A

Abstract

The invention relates to a method for improving the clock synchronization precision in a distributed network system. At present, the synchronized precision is relatively lower. Aiming at uncertainty and large disturbance, the invention only makes adjustment when the time offset between a local slave clock and a master clock is less than or equal to the offset value set through a register by the user; if the adjacent twice time offset is still more than the offset value, the invention adjusts the time of the local slave clock according to the time offset value. As the speed of a clock crystal oscillator is deviated, the time interval at which the local slave clock continuously twice sends sync synchronous messages to the master clock and the time interval at which the local slave clock continuously twice receives the sync synchronous messages from the master clock are compared, and then the difference between the two time intervals is evenly distributed within the synchronization interval. The method of the invention solves the problem of the decreasing of the clock synchronization precision to ensure the clock synchronization precision to reach microsecond level, through a filtering algorithm and the even adjustment of the offset of the crystal oscillator of the slave and the master clocks within the synchronization interval.

Description

A kind of method that improves clock synchronization accuracy in the distributed network system (DNS)

Technical field

The invention belongs to technical field of integrated circuits, relate to real-time synchronous method in the distributed network system (DNS), relate in particular to a kind of method that improves clock synchronization accuracy in the distributed network system (DNS) based on the IEEE1588 agreement.

Background technology

The IEEE1588 standard agreement has defined a clock synchronization protocol in measurement and automated system, be accurate clock synchronization protocol PTP (Precision Time Protocol), this agreement is suitable for distributed network system (DNS), can realize that microsecond level high accuracy clock is synchronous, make when distributing Control work, to need not to carry out again special synchronous communication, thereby reached the effect that call duration time pattern and application program time of implementation pattern are separated.Because high precision synchronous work, make ethernet technology intrinsic data transmission period fluctuation be reduced to acceptable, do not influence the scope of control precision.In all Network Synchronization algorithms, all will consider the influence that circuit delay causes synchro system, thereby the accuracy of circuit delay calculating has directly influenced the precision of synchro system.Circuit delay mainly is made up of the transmission delay on communication stack time-delay and the physical network, when data communicate in a network of not storing forwarding capability, by the circuit delay that physical network produced generally is stable, and communication stack software has very big uncertainty in the process of implementation, makes the time-delay of communication stack can produce bigger shake.There is deviation in speed owing to each equipment clock crystal oscillator in network in addition, and it is inaccurate to make that circuit delay also can cause in computational process, and these two kinds of reasons can cause real-time synchronization accuracy to reduce greatly.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, provide a kind of and improve the method for clock synchronization accuracy based on the IEEE1588 agreement, thus the consequence that the speed of the above-mentioned big perturbed problem that produces owing to network is uncertain and each equipment clock crystal oscillator of solving exists deviation to cause.

Particular content of the present invention comprises:

1. be directed to the uncertain big disturbance that produces of network, the inventive method has adopted following steps:

1-1. the deviate size of register configuration is passed through in this locality from time deviation between clock and the master clock and user relatively for the first time, if local from the time deviation between clock and the master clock greater than the deviate of user by register configuration, then do not consider as once the crossing large disturbance of chance in the network, promptly filtered deviation this time, this locality had not been adjusted from the time of clock; If this locality is less than or equal to the deviate of user by register configuration from the time deviation between clock and the master clock, adjust local time from clock according to this time deviation value;

If 1-2. the adjacent second time this locality from the time deviation between clock and the master clock still greater than the deviate of user by register configuration, judge that then present interference is not accidental the existence, record is this time local from the time deviation value between clock and the master clock, adjust local time according to this time deviation value, can improve local precision from the clock synchronization to the master clock from clock.Adjust local time method according to the time deviation value and adopt existing mature technology from clock.

2. there is deviation in the speed that is directed to each equipment clock crystal oscillator, and the present invention has adopted following steps:

2-1. local compare to time interval of the double transmission of master clock Sync sync message with from the double time interval that receives the Sync sync message that master clock sends of clock from clock, if both equate, then think and the crystal oscillator speed unanimity of two equipment do not have deviation; If the double transmission of master clock Sync sync message interval greater than from the double time interval that receives the Sync sync message that master clock sends of clock, then think local fast than master clock from the clock crystal oscillator operation, need slow down from the timing of clock system time, forward step 2-2 then to; If less than, then think local slow than master clock from the clock crystal oscillator operation, need accelerate timing from the clock system time, forward step 2-2 then to;

2-2., promptly on each point of mean allocation, adjust local system time from clock with time interval of the double transmission of master clock Sync sync message with within from the difference mean allocation at the interval in the double time interval that receives the Sync sync message that master clock sends of clock to sync interval.So promptly can guarantee to regulate the speed evenly, can also guarantee simultaneously this locality to be finished from the crystal oscillator compensation of clock within interval in synchronizing cycle.

Related operation (as register configuration, subtraction etc.) among the present invention is a basic fundamental general knowledge, adopts the routine techniques means.Inventive point of the present invention is to provide a kind of comparatively advanced real-time synchronization method.

The present invention is based on the IEEE1588 agreement and proposed a kind of method that improves the real-time synchronization accuracy of each equipment in the distributed network, this method has solved big disturbance and each the equipment crystal oscillator speed that the network uncertainty causes and has had the problem of deviation, thereby makes synchronization accuracy reach the microsecond level.

Description of drawings

Fig. 1 is the flow chart of adjusting at large disturbance in the inventive method;

Fig. 2 is the flow chart of adjusting at the crystal oscillator velocity deviation in the inventive method.

Embodiment:

The invention will be further described below in conjunction with accompanying drawing and embodiment.

As Fig. 1, the inventive method may further comprise the steps at the uncertain big perturbed problem embodiment that produces of network:

1, local from clock calculation go out and master clock between time deviation;

2, according to the time deviation in the above-mentioned steps 1, it is compared by the deviate of register configuration with the user, if greater than the deviate of user, then give up to fall the time deviation that is calculated specifically by register configuration, the while is the deviation-rectifying system time not.Simultaneously we can to analyze and draw this be because the once accidental big disturbance in the network causes such result.If be less than or equal to the deviate of user, then adjust local time from clock according to this time deviation value by register configuration;

3, adjacent second time this locality from the time deviation between clock and the master clock still greater than the deviate of user by register configuration, judge that then present interference is not accidental the existence, record is this time local from the time deviation value between clock and the master clock, adjust local time according to this time deviation value, can improve local precision from the clock synchronization to the master clock from clock.

As Fig. 2, the inventive method exists deviation to compensate embodiment at the speed of each equipment clock crystal oscillator to may further comprise the steps:

1, local from time interval that clock calculation goes out the double transmission sync message of master clock;

2, locally go out the double time interval that receives the sync message that master clock sends from clock calculation;

3, according to two time intervals that calculate in above-mentioned steps 1 and 2, deduct the double time interval that receives the sync message that master clock sends with time interval of double transmission sync message, if subtracting each other the result is 0, then show the crystal oscillator speed unanimity of two equipment, there is not deviation; If subtract each other the result greater than 0, then explanation is local very fast from the operation of clock crystal oscillator speed, and the timing of the system time that need slow down promptly reduces the frequency of timing enable signal, also promptly increases divide ratio, forwards step 4 simultaneously to; If subtract each other the result less than 0, then explanation is local slower from the operation of clock crystal oscillator speed, needs to accelerate the timing of system time, promptly the frequency of timing enable signal is increased, and also promptly reduces divide ratio, forwards step 4 simultaneously to;

4, poor according to the double transmission time interval that calculates in the above-mentioned steps 3 and double time of reception interval at interval, this difference mean allocation at interval within the sync interval, promptly only on each point of mean allocation, adjust local system time from clock, this improve one's methods promptly can guarantee to regulate the speed evenly, feasible adjustment is more stable, can also guarantee simultaneously this locality to be finished from the crystal oscillator compensation of clock within the interval in synchronizing cycle;

Method according to above-mentioned steps 4 is adopted specifically comprises:

4-1. at interval difference mean allocation within the sync interval, promptly on each point of mean allocation, adjust local system time from clock, then at first should calculate the time of each adjustment one-period and need adjust how many times;

4-2. according to the adjustment number of times that above-mentioned steps 4-1 calculates, calculate synchronizing cycle at interval in each point of mean allocation, promptly after the adjustment algorithm startup, every through how long adjusting once.

Claims

1. method that improves clock synchronization accuracy in the distributed network system (DNS) comprises at the adjustment of the uncertain big disturbance that produces of network with at the speed of each equipment clock crystal oscillator having the adjustment of deviation, it is characterized in that:

The method of adjustment that is directed to the uncertain big disturbance that produces of network comprises the steps:

A. the relatively for the first time more local deviate size of passing through register configuration from the time deviation between clock and the master clock and user, if local from the time deviation between clock and the master clock greater than the deviate of user by register configuration, then once cross large disturbance and do not consider, this locality was not adjusted from the time of clock as accidental in the network; If this locality is less than or equal to the deviate of user by register configuration from the time deviation between clock and the master clock, adjust local time from clock according to this time deviation value;

If the b. adjacent second time this locality from the time deviation between clock and the master clock still greater than the deviate of user by register configuration, judge that then present interference is not accidental the existence, record is this time local from the time deviation value between clock and the master clock, adjusts the local time from clock according to this time deviation value;

Speed at each equipment clock crystal oscillator exists the method for adjustment of deviation to comprise the steps:

C. locally compare to time interval of the double transmission of master clock Sync sync message with from the double time interval that receives the Sync sync message that master clock sends of clock from clock, if both equate, then think and the crystal oscillator speed unanimity of two equipment do not have deviation; If the double transmission of master clock Sync sync message interval greater than from the double time interval that receives the Sync sync message that master clock sends of clock, then think local fast than master clock from the clock crystal oscillator operation, need slow down from the timing of clock system time, forward steps d then to; If less than, then think local slow than master clock from the clock crystal oscillator operation, need accelerate timing from the clock system time, forward steps d then to;

D. with time interval of the double transmission of master clock Sync sync message with within, promptly on each point of mean allocation, adjust local system time from clock from the difference mean allocation at the interval in the double time interval that receives the Sync sync message that master clock sends of clock to sync interval; Specifically: the time that at first calculates each adjustment one-period need be adjusted how many times; Then according to the adjustment number of times that calculates, calculate synchronizing cycle at interval in each point of mean allocation, promptly after the adjustment algorithm startup, every through how long adjusting once.