CN103916181A - Method for detecting SDH optical transmission network frequency synchronization performance - Google Patents
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Abstract
The invention discloses a method for detecting SDH optical transmission network frequency synchronization performance. The method comprises the following steps: obtaining pointer adjusting times in a preset time duration in an SDH optical transmission system; and according to the correspondence relation between the pointer adjusting times in the preset time duration and frequency offset, obtaining the network frequency offset value, and judging the network frequency synchronization performance. According to the technical scheme, an existing pointer adjustment mechanism and a statistics function of a network management system of an SDH network are utilized, and based on the correspondence relation between the pointer adjusting times and phase offset as well as the frequency offset, the network frequency offset value is obtained, so that the high precision detection of the network synchronization performance can be realized; the method is convenient and practical, and can be generally used in the actual engineering practice and network operation maintenance conveniently; and costly high-precision instruments and complex and tedious test processes can be omitted.
Description
Technical field
The present invention relates to light velocity transmission communication technology field, relate in particular to a kind of method of the SDH of detection optical transport network Frequency Synchronization performance.
Background technology
In SDH optical transport network, clock synchronous quality is the effectively important indicator of work of assurance system, and according to relevant ITU standard and home communications industry standard, the method for the necessary code requirement of the clock synchronous quality of SDH network, and realize quantitatively and detecting by special instrument.For example, conventionally can adopt SDH/PDH synthesis analyzer, use the method for ITU-0.172 regulation, by detecting the clock drift of E1, (precision is ppm=10 to calculate the relevant frequency departure of acquisition
-6).
In existing wireless communication networks, the Frequency Synchronization quality of network has very important impact for network technology performance.Take gsm system as example, owing to conventionally needing SDH net connection between base station and base station controller, in realizing relevant service channel function, also realize the synchronization timing transmission (realizing master-slave synchronisation with the reference clock of base station controller and upstream) that base station needs.
But because wireless base station is for the synchronous requirement of clock frequency very high (being better than 0.05ppm), for whether reaching this requirement, at present must be by professional detection means, need high-caliber technical staff, and rely on high-precision instrument and longer time can complete relevant performance test, not only cost is high, and efficiency is lower.
Summary of the invention
For solve prior art detecting that cost in SDH optical transport network Frequency Synchronization performance process is high, efficiency is low, be not easy to the problem of operation, the present invention proposes a kind of method of the SDH of detection optical transport network Frequency Synchronization performance, the high accuracy that can realize network net synchronization capability detects, convenient and practical.
A kind of method that the invention provides the SDH of detection optical transport network Frequency Synchronization performance, comprises the following steps:
Obtain the number of times that the pointer in SDH optical transmission is adjusted in default duration;
According to the corresponding relation between number of times and the frequency departure of pointer adjustment in described default duration, obtain the numerical value of network deviation, judge network net synchronization capability.
Preferably, the pointer in described SDH transmission system comprises Administrative Unit Pointer, i.e. AU pointer, and Tributary unit pointer, i.e. and TU pointer, corresponding pointer adjustment comprises the adjustment of AU pointer and the adjustment of TU pointer.
Preferably, default duration is 15 minutes, 1 hour or 24 hours.
Preferably, AU pointer is AU-4 or AU-3 pointer.
Preferably, TU pointer is TU-12 pointer, TU-11 pointer, TU-3 pointer or TU-4 pointer.
Preferably, if network A U-4 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be N time, judge that VC-4 frequency and system frequency deviation are 1.767N × 10
-10, wherein N is positive integer; If network A U-4 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be M time, judge that VC-4 frequency and system frequency deviation are 4.417M × 10
-11, wherein M is positive integer; If network A U-4 pointer continued unidirectional adjustment in 24 hours, and adjust number of times while being L time, judge that VC-4 frequency and system frequency deviation are 1.841L × 10
-12.Wherein L is positive integer.
Preferably, if network TU-12 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be R time, judge that VC-12 frequency and system frequency deviation are 3.858R × 10
-9, wherein R is positive integer; If network TU-12 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be S time, judge that VC-12 frequency and system frequency deviation are 9.64S × 10
-10, wherein S is positive integer; If network TU-12 pointer in 24 hours continue unidirectional adjustment, and adjust number of times be T time, judge that VC-12 frequency and system frequency deviation are 4.019T × 10
-11, wherein T is positive integer.
Technical solution of the present invention is because the existing pointer of the network management system of utilizing SDH network is adjusted mechanism and statistical function, corresponding relation (the easy judgement constant in different duration situations is provided) between number of times and phase deviation and the frequency departure of adjusting according to pointer, can obtain the numerical value of network deviation, thereby the high accuracy that realizes Network Synchronization performance detects, convenient and practical, be convenient to generally adopt in Practical Project practice and network operation maintenance, can save valuable high-precision meter and complicated loaded down with trivial details test process.
Accompanying drawing explanation
Fig. 1 is the flow chart of Sampling network Frequency Synchronization performance in the embodiment of the present invention one.
Fig. 2 is the flow chart of Sampling network Frequency Synchronization performance in the embodiment of the present invention two.
Embodiment
Below in conjunction with accompanying drawing, specifically describe the specific embodiment of the present invention:
SDH optical transmission is in the time of Network Synchronization normal operating conditions, all network element clocks (SEC) are all locked in the primary resource clock of upstream, generally do not have in the case pointer adjustment, but the impact of intrasystem noise and generation thereof is inevitably, thereby may produce a small amount of random Pointer Justification Event.In actual SDH network application, be generally that the acting in conjunction of frequency deviation and noise affects the adjustment of respective pointer, thereby make pointer adjustment there is certain uniformity and the feature of randomness, be embodied in respectively one direction variation or two-way variation that pointer is adjusted.
Pointer effect in SDH mainly contains 3 points:
The one, in the time transmitting network in synchronous working state, pointer is used for carrying out the phase alignment of synchronizing signal.
The 2nd, when network is during in synchronous abnormal operating state, pointer is as frequency-tracking calibration.
The 3rd, frequency jitter and the drift of the design mechanism that pointer is adjusted in can capacity network.
Pointer in SDH optical transmission comprises Administrative Unit Pointer (Administration Unit Pointer, be called for short AU pointer) and Tributary unit pointer (Tributary Unit Pointer is called for short TU pointer), corresponding pointer adjustment comprises the adjustment of AU pointer and the adjustment of TU pointer.AU pointer is set and can provides a kind of flexible and dynamic method for the location of VC in AU frame.TU pointer is set and can provides a kind of means for the flexible and dynamic location of VC in TU frame.
In SDH optical transport network, the synchrone mechanism of tributary signal is to adopt pointer adjustment, utilize the increase and decrease adjustment of pointer value to compensate phase place variation and the frequency change of low speed tributary signal, pointer is adjusted in signal synchronous multiplexing and permissive signal time delay and slip and plays critical effect.But in the situation that synchronization timing is undesirable, the frequency shift (FS) of clock is the main cause that pointer is adjusted, because pointer adjustment is that unit carries out by byte.For example, be embodied in the adjustment of TU-12 pointer once, cause a byte adjustment, will produce the phase jump of 8UI; The adjustment of AU-4 pointer once, causes that 3 bytes change, and will produce 24UI phase place and change, and this is also the one of the main reasons that SDH shake produces.
The drift of clock system comprises two contents conventionally: accumulation drift and the transmission drift in time of clock frequency difference.This two classes drift form difference, but be but equivalent on the impact of network synchronous system.Therefore, need to represent this two classes drift by unified expression way.The amount that this unified drift is expressed is exactly time interval error (TIE).TIE refers in t observation cycle second, and clock signal is with respect to the variation (time delay) of its ideal position.
Adjust the relation between number for quantitative analysis SDH network clocking frequency departure and AU, TU pointer, carry out following derivation and computing:
If f is clock frequency (unit is Hz), T is that clock-unit's signal period, (unit was s).F=1/T; To this formula differentiation,
df＝-(1/T
2)dT＝-f(dT/T)
So df/f=-dT/T
Right side molecule denominator is multiplied by n simultaneously, and the expression testing time is equivalent to n cycle: df/f=-ndT/nT=-Δ T/t
Be df/f=-Δ T/t (1)
Δ T is the time interval error measuring in the interval of testing time t, also can be called TIE;
If being the AU-4 pointer producing, m adjusts number of times, because each AU-4 pointer is adjusted 3 bytes, and 8 bits of each byte, the adjustment of an AU-4 pointer is equivalent to produce the phase hit of 24UI, and the relation between pointer adjustment number and time interval error is as follows:
m＝ΔT/(24UI)
1UI＝1/f
For AU-4 (150.912Mbit/s), 1UI=6.626ns
After arrangement:
m＝ΔT×f/24 (2)
Enter (2) formula for (1) formula, after arrangement,
m＝-(f/24)(df/f)t (3)
Wherein, f is clock signal frequency, and df/f is clock signal frequency accuracy, and t is test period.
If the TU-12 pointer adjustment number of times that m ' produces for SDH network, because each TU-12 pointer is adjusted 1 byte, 8 bits of each byte, the adjustment of a TU-12 pointer is equivalent to produce the phase hit of 8UI, and the pass that pointer is adjusted between number and time interval error is:
m’＝ΔT×f/8
Enter (2) formula for above formula, can calculating TU-12 pointer, to adjust number and clock signal frequency accuracy, test period relation as follows:
m’＝-(f/8)(df/f)t (4)
Adjust number of times by pointer and carry out determination frequency synchronism deviation:
According to above theoretical foundation and computing formula, can be further adjust number of times and analyze the net synchronization capability of SDH network by pointer.
For example, by f=150.912Mbit/s, df/f=1 × 10
-11, t=86400s substitution (3) formula, can obtain: m ≈ 5.433.
The physical interpretation of this result of calculation is: for being 1 × 1 with respect to reference clock frequency departure
-11sDH network element, in 24 hours, the AU pointer of generation is adjusted to number and is about 5.433 times.
If take 15 minutes as watch window, be located at AU pointer in 15 minutes and adjusted N time, can calculate corresponding network frequency deviation and be: N × 6.626 × 3 × 8/ (15 × 60 × 10
9) ≈ 1.767N × 10
-10.
So, there is Pointer Justification Event N time when find 15 minutes on webmaster, just can indirectly converse according to above formula the frequency deviation of this network.
In like manner, if pointer adjustment per hour once, corresponding network deviation is 4.417 × 10
-11; If pointer adjustment every day once, corresponding network deviation is 1.841 × 10
-12.
In order to verify the correctness of the method, we adopt another kind of computational methods (interval method), have obtained identical result.
The adjustment of AU-4 pointer once affects 3 bytes that transmit digital signal, and the time interval deviation TIE producing can calculate.For AU-4 transmission rate 150.912Mbit/s, 1UI=6.626ns.Pointer adjustment once causes that 3 bytes change, and phase place is changed to 3 × 8=24UI.Therefore, TIE=6.626 × 24=159.024ns.
If every day, AU pointer was adjusted 5.433 times, TIE=5.433 × 159.024=863.977ns, the clock signal phase TIE that is equivalent to every day changes; The frequency departure that can be scaled thus this system is 863.977./(86400 × 10
9)=1.00 × 10
-11.
If every day, AU pointer was adjusted 5 times, TIE=5 × 159.024=795.12ns, the clock signal phase TIE that is equivalent to every day changes; The frequency departure that can be scaled thus this system is
795.12/(86400×10
9)＝0.92×10
-11。
If AU pointer per hour is adjusted 225 times, clock signal phase per hour changes TIE=225 × 159.024=35780.4ns; The frequency departure that is scaled this system is: 35780.4/ (60 × 60 × 10
9)=9.939 × 10
-9.
Suppose that SEC is in free oscillation situation, when frequency accuracy is 4.6ppm, phase deviation per second is 4.6 microseconds; TIE=4.6 × 60 × the 15=4140 of every 15 minutes (μ s),, if ignore other factors impacts, can convert and should be for corresponding AU Pointer Justification Event: 4140/0.159024=26033.8 (inferior).
If within every 15 minutes, TU12 pointer is adjusted 1 time, corresponding 2.304Mbit/s, 1UI=434ns.Can calculate frequency departure is: (8 × 434)/(15 × 60 × 10
9) ≈ 3.858 × 10
-9; If TU12 pointer per hour adjustment once, corresponding frequency departure is: 3472/ (60 × 60 × 10
9) ≈ 9.64 × 10
-10; If pointer adjustment every day once, corresponding frequency departure is: 3472/ (60 × 60 × 24 × 10
9) ≈ 4.019 × 10
-11.
Based on above-mentioned principle, the embodiment of the present invention one provides a kind of method of Sampling network Frequency Synchronization performance, and as shown in Figure 1, the flow process of this Sampling network Frequency Synchronization performance comprises the following steps:
Step 101, obtain the number of times of AU-4 pointer in SDH transmission system adjustment in default duration (15 minutes, 1 hour or 24 hours).Also can adopt AU-3 pointer.
Step 102, basis are preset the corresponding relation between number of times and the frequency departure that in duration, AU-4 pointer is adjusted, and obtain the numerical value of network deviation, judge network net synchronization capability.
If network A U-4 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be N time, judge that VC-4 frequency and system frequency deviation are 1.767N × 10
-10, wherein N is positive integer; If network A U-4 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be M time, judge that VC-4 frequency and system frequency deviation are 4.417M × 10
-11, wherein M is positive integer; If network A U-4 pointer continued unidirectional adjustment in 24 hours, and adjust number of times while being L time, judge that VC-4 frequency and system frequency deviation are
1.841L×10
-12。Wherein L is positive integer.
The embodiment of the present invention two provides the method for another kind of Sampling network Frequency Synchronization performance, and as shown in Figure 2, the flow process of this Sampling network Frequency Synchronization performance comprises the following steps:
Step 201, obtain the number of times of TU-12 pointer in SDH transmission system adjustment in default duration (15 minutes, 1 hour or 24 hours), also can adopt TU-11 pointer, TU-3 pointer or TU-4 pointer.
Step 202, basis are preset the corresponding relation between number of times and the frequency departure that in duration, TU-12 pointer is adjusted, and obtain the numerical value of network deviation, judge network net synchronization capability.
If network TU-12 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be R time, judge that VC-12 frequency and system frequency deviation are 3.858R × 10
-9, wherein R is positive integer; If network TU-12 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be S time, judge that VC-12 frequency and system frequency deviation are 9.64S × 10
-10, wherein S is positive integer; If network TU-12 pointer in 24 hours continue unidirectional adjustment, and adjust number of times be T time, judge that VC-12 frequency and system frequency deviation are 4.019T × 10
-11, wherein T is positive integer.
In the time that 2048kbit/s business adopts asynchronous mapping to enter VC-12, the frequency deviation of the frequency deviation of VC-12 and 2048kbit/s business is almost identical, so, can understand intuitively the 2048kbit/s business of SDH carrying with respect to the frequency departure of network clocking by Pointer Justification Count.
The corresponding relation of number of times and this system phase deviation and frequency departure listed respectively AU-4 pointer under representative condition and TU12 and adjusts by table 1 and table 2, contrasts reference when practical use.
The corresponding relation of the table unidirectional adjustment number of times of 1AU-4 pointer and phase deviation and frequency departure
The corresponding relation of the table unidirectional adjustment number of times of 2TU-12 pointer and phase deviation and frequency departure
In SDH plant engineering Acceptance Test index request in the past, although pointer is not adjusted to number of times requirement to some extent, in regular maintenance, can be by checking that on webmaster pointer adjusts number of times, and with reference to the data of table 1, carry out the synchronous situation of judgment device.
In actual test, reach 283 times if 15 minute indicators are adjusted number of times, according to the data of table 1, show that Network Synchronization deviation has reached 50ppb.
In like manner, if showing 15 minutes TU-12 pointers on webmaster adjusts number of times and reaches 13 times, show that this correspondence E1 frequency deviation exceedes 50ppb, if utilize passage (Abis) between this link bearer wireless base station and base station controller can not meet the clock synchronous standard of base station.
And for example, AU-4 pointer is adjusted number of times, must not exceed 56.3 times within 15 minutes, within 1 hour, must not exceed 225 times, within 24 hours, must not exceed 5400 times.For the situation that exceeds this index, just should be considered as Network Synchronization and extremely draw attention, analyze and search reason.Clock board fault, clock free oscillation etc. can cause the Pointer Justification Event of hundreds thousand of times every day.
A network carrying IP traffic example is proposed below.
The AU Pointer Justification Event that certain actual transmissions network produces is as table 3, within the time of 24 hours, AU pointer adjusted value reaches more than 340,000 time, through question blank 1 obtain this VC-4 frequency relatively and the frequency deviation of system clock at 500ppb between 1000ppb, the frequency departure that calculates this business payload VC-4 frequency and system clock from formula (3) is 641.91ppb.Be data service through investigating this business, router adopts internal clock source, does not obtain clock from Synchronization Network, so pointer adjustment quantity is very large.Router clock is synchronized to after line clock, and pointer adjustment disappears.
The AU Pointer Justification Event that certain actual transmissions network of table 3 produces
According to above analysis, can determine: under the prerequisite of ignoring noise effect, pointer is adjusted number of times and is had dull linear corresponding correlation with the clock phase Accumulated deviation of SDH optical transport network, and pointer adjustment number of times is proportional to the deviation between data load and system clock.Because the net synchronization capability of SDH light transmission has material impact for whole network index.Therefore in checking and accepting, SDH equipment new construction should note test and analysis that pointer is adjusted; In SDH network regular maintenance, can check pointer by webmaster and adjust situation, the net synchronization capability of indirect review equipment, thus guarantee better the transmission quality of equipment; Technical scheme in the embodiment of the present invention can replace high-precision synchronism detection instrument within the specific limits, convenient practical again.
It should be noted that: above embodiment is only unrestricted in order to the present invention to be described, the present invention is also not limited in above-mentioned giving an example, and all do not depart from technical scheme and the improvement thereof of the spirit and scope of the present invention, and it all should be encompassed in claim scope of the present invention.
Claims (7)
1. a method that detects SDH optical transport network Frequency Synchronization performance, is characterized in that, comprises the following steps:
Obtain the number of times that the pointer in SDH optical transmission is adjusted in default duration;
According to the corresponding relation between number of times and the frequency departure of pointer adjustment in described default duration, obtain the numerical value of network deviation, judge network net synchronization capability.
2. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 1, it is characterized in that, pointer in described SDH transmission system comprises Administrative Unit Pointer, it is AU pointer, and Tributary unit pointer, be TU pointer, corresponding pointer adjustment comprises the adjustment of AU pointer and the adjustment of TU pointer.
3. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 1, is characterized in that, default duration is 15 minutes, 1 hour or 24 hours.
4. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 2, is characterized in that, AU pointer is AU-4 or AU-3 pointer.
5. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 2, is characterized in that, TU pointer is TU-12 pointer, TU-11 pointer, TU-3 pointer or TU-4 pointer.
6. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 4, it is characterized in that, if network A U-4 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be N time, judge that VC-4 frequency and system frequency deviation are 1.767N × 10
-10, wherein N is positive integer; If network A U-4 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be M time, judge that VC-4 frequency and system frequency deviation are 4.417M × 10
-11, wherein M is positive integer; If network A U-4 pointer continued unidirectional adjustment in 24 hours, and adjust number of times while being L time, judge that VC-4 frequency and system frequency deviation are
1.841L×10
-12。Wherein L is positive integer.
7. a kind of method that detects SDH optical transport network Frequency Synchronization performance according to claim 5, it is characterized in that, if network TU-12 pointer in 15 minutes continue unidirectional adjustment, and adjust number of times be R time, judge that VC-12 frequency and system frequency deviation are 3.858R × 10
-9, wherein R is positive integer; If network TU-12 pointer in 1 hour continue unidirectional adjustment, and adjust number of times be S time, judge that VC-12 frequency and system frequency deviation are 9.64S × 10
-10, wherein S is positive integer; If network TU-12 pointer in 24 hours continue unidirectional adjustment, and adjust number of times be T time, judge that VC-12 frequency and system frequency deviation are 4.019T × 10
-11, wherein T is positive integer.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111665431A (en) * | 2020-04-26 | 2020-09-15 | 江西联智集成电路有限公司 | Method, device, equipment and medium for calibrating clock source in chip |
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