WO2014029253A1 - 一种otn网络中客户业务时钟提取的实现方法 - Google Patents

一种otn网络中客户业务时钟提取的实现方法 Download PDF

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Publication number
WO2014029253A1
WO2014029253A1 PCT/CN2013/079967 CN2013079967W WO2014029253A1 WO 2014029253 A1 WO2014029253 A1 WO 2014029253A1 CN 2013079967 W CN2013079967 W CN 2013079967W WO 2014029253 A1 WO2014029253 A1 WO 2014029253A1
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Prior art keywords
adjustment
clock
amount
frequency
data
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English (en)
French (fr)
Inventor
李光瑜
冯波
海增强
郑林
魏明
张睿
李剑峰
胡杰
郑哲文
沈羽纶
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Fiberhome Telecommunication Technologies Co Ltd
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Fiberhome Telecommunication Technologies Co Ltd
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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
    • H04J3/062—Synchronisation of signals having the same nominal but fluctuating bit rates, e.g. using buffers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
    • H04J3/1605—Fixed allocated frame structures
    • H04J3/1652—Optical Transport Network [OTN]

Definitions

  • the present invention relates to the field of optical transport network (OTN) communication technology, and more specifically to an implementation method for extracting a customer service clock (referring to a transmission clock of a customer service) in an 0TN network. This is especially true for the implementation of the transmit clock extraction for the GE, STM16, and 0TU1 client services in the 0TN network.
  • OTN optical transport network
  • 0TN has become the main optical transport network technology.
  • mainstream operators at home and abroad are very concerned about the development and application of 0TN technology.
  • Most operators' WDM transmission interfaces have realized 0TN functions.
  • the 0TN concept covers two layers of optical and electrical layers.
  • One of its key technical features is: a variety of customer signal packaging and transparent transmission.
  • the 0TN frame structure based on ITU-T G.709 can support mapping and transparent transmission of multiple client signals, such as SDH, ATM, Ethernet, etc.
  • the client when the client sends the service, it must extract the sending clock of the customer service (referred to as the customer service clock), and its clock frequency must be consistent with the service receiving clock before the 0TN bearer corresponds to the customer service.
  • the customer service clock the sending clock of the customer service
  • FIFO buffer redundancy control plus high-precision digital phase-locked loop
  • FIFO buffer redundancy control plus plug-in digital frequency synthesizer
  • FIFO buffer redundancy control plus high-precision digital phase-locked loop scheme is difficult to implement, clock tracking adjustment delay is long, high-precision digital phase-locked loop technology is too complicated, and the implementation cost is too high.
  • the FIFO buffer redundancy control plus the external digital frequency synthesizer scheme adjusts the clock only by the FIFO buffer state, which is limited by the judgment period and the adjustment step size of the external digital synthesizer. If the judgment period is short, the buffer redundancy error is large, and the clock adjustment is frequent, the clock jitter will be too large; the adjustment step size is too small or too large, and the tracking process
  • the cache is frequently empty or full. At this time, the cache redundancy value is unavailable, and the effective clock adjustment information cannot be extracted. When the device is cascading too much, the cache redundancy causes an iterative effect, resulting in excessive clock jitter.
  • the object of the present invention is to provide a method for implementing client service clock extraction in an OTN network, which is mainly used for clock extraction of a client-side service sender of an OTN device, and is used for implementing client services in a 0TN network. Transparent transmission, this method can recover high-performance customer service clock from 0TN anger and meet the jitter requirements of various customer services.
  • a method for realizing client service clock extraction in a 0TN network characterized in that: using statistical control plus a plug-in digital frequency synthesizer, the first step is to perform synchronous smoothing on the 0TN system clock for the customer service that is decrypted by the 0TN network.
  • the second step the clock extraction control process: statistically compare and compare the smoothed data volume with the amount of data sent by the customer service, and control the clock adjustment information by the weighting algorithm combined with the FIFO buffer redundancy
  • third, Clock extraction adaptation processing clock adjustment information provided by the clock extraction control processing, converted into accurate frequency adjustment information required by the external digital frequency synthesizer, and precise control of the external digital frequency synthesizer to generate a service transmission clock through the serial control interface .
  • Step 1 Set a smoothing time window, usually set according to the 0TN frame period of the 0TN line interface.
  • Step 2 Calculate the nominal data volume of the customer service in a smoothing time window.
  • Step 3 Calculate the amount of data that may be generated by the client service in a smooth time window according to the tolerance frequency offset of the customer service and the tolerance frequency offset of the 0TN interface. , the data volume package Include a larger value, an intermediate value, and a smaller value, and the amount of data is an integer.
  • Step 4 Detect the buffer status of the same RAM, and calculate the amount of data to be read by the smoothing time window, in a smoothed time window. The starting position is used to detect whether the readable space of the RAM is at the upper limit, the lower limit or the central area.
  • the amount of data to be read in the smoothing time window is a larger value calculated in step 3; for example, at the lower limit, the smoothing time
  • the amount of data to be read by the window is the smaller value calculated in step 3; as in the central area or abnormal condition, the amount of data to be read in the smoothing time window is the intermediate value calculated in step 3;
  • Step 5 According to the calculated amount of data to be read in a smoothing time window, a relatively uniform gap is generated, and the data is evenly read out from the synchronous RAM, and the customer business smoothing data can be obtained.
  • the second step includes the following specific steps:
  • Step 1 Calculate the 0-inch clock adjustment period T, one smoothing time window is a clock adjustment period ⁇ , the threshold value can be configured, the larger the threshold value, the statistical data volume is more accurate, but it cannot be infinitely large, if it is too large
  • the tracking time of the clock extraction will be long, and i needs a larger buffer
  • Step 2 Calculate the nominal amount of data of the customer service within a clock adjustment period T
  • Step 3 Calculate the smoothing of a clock adjustment period T
  • the amount of data that is, the amount of data received by the FIFO, FIR
  • the amount of data should be within the nominal value X (1+/-- (customer service tolerance maximum frequency offset +20ppm+redundant frequency offset)), otherwise the amount of data received by the FIFO should be Set to the nominal value, where 20ppm is the 0TN line tolerant frequency offset; the redundant frequency offset is set by itself to absorb the jitter and ensure that the circuit can tolerate a larger frequency offset, such as the jitter of the inlet data
  • Step 4 Statistically calculate the amount of data read by the FIFO in a clock adjustment period T, that is, the amount of data sent by the FIFO;
  • Step 5 Calculate the difference between the amount of FIFO received data and the amount of data sent by the FIFO in a clock adjustment period T.
  • the difference should be in the range of the nominal value X ((Customer Service Tolerance Maximum Frequency Offset + 20ppm + Redundant Frequency Offset)) If the difference is not within this range, it indicates that the line rate or the transmission clock frequency is incorrect. At this time, the alarm is reported and the difference is set to zero.
  • Step 6 Clock adjustment window setting, if there are both clock adjustments and advances in each cycle The decision will cause errors in the judgment. In order to avoid this situation, the current period adjustment is adopted, and the next period of the judgment is alternately processed to ensure that the clock is stable in the previous period of the judgment;
  • Step 7 Clock extraction control, clock extraction control The difference between the FIFO receiving and transmitting, and the FTF0 readable spatial information algorithm to calculate the clock adjustment direction and the adjustment byte amount.
  • the readable space information of the FIFO is used to generate clock fine-tuning control to ensure that the FIFO operates in a safe area.
  • the specific steps of generating the fine-tuning control of the day clock are: determining the FIFO readable space in the TO cycle judgment position, and giving a positive adjustment fine-tuning information when the readable space is greater than 256; when the readable space is less than 256 Give a negative adjustment fine-tuning information; when the readable space is 256, the positive adjustment fine-tuning information is generated in the above TO period, and the Bay U generates a negative fine-tuning information, and the negative adjustment information is generated in the TO period, and a positive adjustment fine-tuning is generated. Information, otherwise, does not produce any fine adjustment information.
  • the clock adjustment direction and the adjustment byte amount are generated including the following steps:
  • the difference between the amount of data received by the FIFO and the amount of data transmitted by the FIFO is outside the range of the nominal value X ( +/- - (Customer Service Tolerance Maximum Frequency Offset + 20ppm + Redundant Frequency Offset):). Adjust, adjust the byte amount to 0; if the difference B is within this range, the clock is adjusted as follows:
  • the difference B is 0, if there is positive adjustment fine adjustment information, the clock adjustment direction is positive adjustment, the adjustment amount is 1; if there is negative adjustment fine adjustment information, the clock adjustment direction is negative adjustment, the adjustment amount is 1; if there is no fine adjustment Information, then no adjustment, the adjustment amount is 0;
  • the absolute value of the difference B is greater than 1, if the received byte amount is greater than the transmitted byte amount, the clock adjustment direction is positively adjusted, and the adjustment amount is: Receive byte amount - Send byte amount ⁇ + Positive adjustment fine adjustment information - Negative adjustment Fine-tuning information; if the amount of received bytes is less than the amount of transmitted bytes, the clock The adjustment direction is negative adjustment, and the adjustment amount is: Send byte amount - Receive byte amount - Positive adjustment fine adjustment information + Negative adjustment fine adjustment information;
  • the difference B is equal to 1, if there is positive adjustment fine adjustment information, the clock adjustment direction is positive adjustment, the adjustment amount is 2; if there is negative adjustment fine adjustment information, the clock is not adjusted, the adjustment amount is 0; if there is no micro adjustment information, the clock The adjustment direction is positive adjustment, and the adjustment amount is 1;
  • the third step includes the following specific steps: Step 1: Converting the adjustment amount of the day t clock extraction control into the adjustment step of the frequency adjustment control word or the frequency offset offset required by the external digital frequency synthesizer Long; the minimum unit of adjustment of the clock extraction control is byte, and the adjustment step of the frequency adjustment control word or the frequency offset offset is small, and the adjustment of the clock extraction control is gradually reduced to 0 near a plurality of adjustments; 2 : Generate accurate frequency adjustment information required by the external digital frequency synthesizer: First set a customer service nominal frequency adjustment control word or frequency offset offset, the frequency adjustment control word or frequency offset offset is configured to the plug-in through the serial interface The digital frequency synthesizer generates a reference customer service clock; then, when there is positive adjustment information, the output frequency adjustment control word or frequency offset offset is the last configured adjustment control word or frequency offset offset + adjustment step size When there is negative adjustment information, the output frequency adjustment control word or frequency offset offset is the last configured adjustment control A word offset or the frequency offset adjustment step; when no
  • Step 3 Configure the calculated frequency adjustment control word or frequency offset offset to the external digital frequency synthesizer chip through a serial interface suitable for the external digital frequency synthesizer, and the external digital frequency synthesizer chip can output accurate customer service.
  • Send the clock On the basis of the above technical solution, when the adjustment amount of the clock extraction control is larger, the adjustment step of the frequency adjustment control word or the frequency offset offset is set larger; when the adjustment amount of the clock extraction control is small, the frequency adjustment control Adjust the step size of the word or frequency offset offset.
  • a frequency adjustment control word or a frequency offset offset maximum value and a minimum value are set, and when the clock adjustment is performed, if the calculated frequency adjustment control word or the frequency offset offset exceeds the maximum value or the minimum value When the value is used, the output frequency adjustment control word or the frequency offset offset is the set maximum or minimum value;
  • the maximum and minimum values are calculated according to the customer service tolerance frequency offset plus a redundant frequency offset of 15 ⁇ ⁇ ⁇ .
  • the method for implementing customer service clock extraction in the 0TN network uses a statistical method to predict the service clock rate of the bearer customer service, and supplements the cache redundancy to fine-tune the clock to ensure that the cache works in a secure area.
  • the method is difficult to implement and low in implementation cost; the clock extraction process is mainly controlled by statistics, and does not depend on the cache working state, and is safe and reliable; the abnormality in the statistical process will be filtered in time, and the device cascade time does not cause an iterative effect.
  • the extracted day clock is of better quality.
  • Figure 1 shows the mapping of customer services to the 0TN network structure
  • Figure 2 is a trend diagram of customer service in the 0TN network
  • FIG. 3 is a functional diagram of a clock extraction system provided by the present invention.
  • Figure 4 is a clock decision cycle diagram
  • Figure 5 is a flow chart of clock fine-tuning
  • Figure 6 shows the flow chart of the clock adjustment.
  • the method for realizing the extraction of the customer service clock in the OTN network of the present invention is applicable to the clock recovery of the client service transparently transmitted in the 0TN network, and can effectively filter the jitter generated by the mapping and demapping process of the customer service, and generate accurate
  • the clock control information recovers the high-performance customer service transmission clock through the external digital frequency synthesizer.
  • the 0TN frame structure based on ⁇ ---TG, 709 can support mapping and transparent transmission of multiple client signals.
  • the present invention mainly supports low-speed customer services of GE, STM16 and 0TU1.
  • Figure 1 shows the mapping of customer services to the 0TN network structure. After the customer service passes through various mapping paths, a high-order 0TN frame is formed to be transparently transmitted on the 0TN network, and various client services are deframed from the 0TN network.
  • FIG. 2 shows the trend of customer service in the 0TN network.
  • the client A forms a high-order 0TN frame transparently transmitted on the 0TN network.
  • the site B de-frames various customer services from the 0TN network.
  • the client service extracted from the site B itself does not carry any timing information.
  • the transmission date of the site B client service must be restored, so that the service is sent at the rate received from the site A.
  • FIG. 3 is a functional diagram of a system design provided by the present invention.
  • the method for implementing the client service clock extraction in the 0TN network is: using statistical control plus a plug-in digital frequency synthesizer, the first step is to perform synchronous synchronization on the 0TN system de-framed client service under the 0TN system clock.
  • the second step the clock extraction control process: statistically compare and compare the smoothed data volume with the amount of data sent by the customer service, and control the clock adjustment information by the weighting algorithm combined with the FIFO buffer redundancy
  • the third step Clock extraction adaptation processing The clock adjustment information provided by the clock extraction control processing is converted into the precise frequency adjustment information required by the external digital frequency synthesizer, and the external digital frequency synthesizer is accurately controlled by the serial control interface to generate the service transmission. Day clock.
  • the smoothing of the customer service includes the following steps:
  • Step h Set a smoothing time window, which is usually set according to the 0TN frame period of the 0TN line interface. If the line side is () TU1, the smoothing time window is determined according to the time of a 0TU1 frame in the system clock domain of 0TU1; The line side is 0DU2, then according to 0DU2 The system clock domain under an 0DU2 indignation time to determine the smoothing time window;
  • Step 2 Calculate the nominal data volume of the customer service in a smoothed time window, such as a 0TU1 instalment cycle time, GE's nominal data volume is 6121. 4, STM16's nominal data volume is 7616; - 0DU2 frame period Time, GE's nominal data volume is 1523. 9, STM16's nominal data volume is 1896;
  • Step 3 Calculate the amount of data (required as an integer) that may be generated by the client service in a smoothed time window according to the tolerated frequency offset of the customer service and the tolerance of the 0TN interface tolerance.
  • the data volume includes a larger value and an intermediate value. Value and a smaller value, such as a 0TU1 frame cycle time, the smoothed GE data volume may be 6120, 6121 or 6122, and the STM16 data volume may be 7615, 7616 or 7617;
  • Step 4 Detect the buffer state of the synchronous RAM, calculate the amount of data to be read in the smoothing time window, and detect whether the readable space of the RAM is at the upper limit, the lower limit, or the central area at a start position of a smoothed time window, such as at the upper limit.
  • the amount of data to be read in the smoothing interval window is the larger value calculated in step 3; if at the lower limit, the amount of data to be read in the smoothing time window is the smaller value calculated in step 3; as in the center area or the abnormality
  • the amount of data to be read by the smoothing time window is the intermediate value calculated in step 3;
  • Step 5 According to the calculated amount of data to be read in a smooth inter-day window, a relatively uniform gap is generated, and the data is evenly read out from the synchronous MM, and the customer business smooth data is obtained.
  • the client service is mapped to the 0TN network through one or more levels.
  • the client service introduces jitter during the mapping and demapping process. After the i client service is solved, it is in the clock domain of 0TN, and there will be data bursts, which will cause The customer service clock extraction difficulty is increased, and the clock performance index is not good.
  • the client data decoded by 0TN needs to be smoothed, and the smoothing process is composed of a synchronous cache RAM and a control logic.
  • the second step the statistics and the amount of data sent by the client are compared and compared, and the clock adjustment information is controlled by the weighting algorithm combined with the FIFO buffer redundancy, that is, the clock extraction control process, and the day clock extraction control process is performed by an asynchronous
  • the cache FIFO and a clock extraction control processing logic are formed.
  • Step h Calculate the clock adjustment period T.
  • One smoothing time window is a clock adjustment period ⁇
  • the threshold value can be configured. The larger the threshold value is, the statistical data volume is more accurate, but it cannot be infinitely large. If it is too large, the clock is extracted.
  • Step 2 ' Calculate the nominal amount of data for the customer's service within a clock adjustment period T
  • Step 3 Calculate the amount of smoothed data within a clock adjustment period T, That is, the amount of data received by the FIFO, the amount of data received by the FIFO should be within the nominal value X (I - (Customer Service Tolerance Maximum Frequency Offset + 20ppm + Redundant Frequency Offset)), otherwise the amount of data received by the FIFO should be set to the nominal value, where 20ppm is the 0TN line tolerant frequency offset; the redundancy frequency offset can be set by itself to absorb the jitter and ensure that the circuit can tolerate a larger frequency offset, such as the jitter of the inlet data amount is too large, and the statistical average is required;
  • Step 4 Statistically calculate the amount of data read by the FIFO in a clock adjustment period T, that is, the amount of data sent by the FIFO;
  • Step 5 Calculate the difference between the amount of FIFO received data and the amount of data sent by the FIFO in a clock adjustment period T.
  • the difference should be at the nominal value X ((Customer Service Tolerance Maximum Frequency Offset + +20ppm + Redundant Frequency Offset) Within the range, the difference is not within this range, indicating that the line rate or the transmission clock frequency is incorrect. At this time, the alarm is reported and the difference is set to zero.
  • Step 6 The clock adjustment window is set. If there are both clock adjustment and judgment in each cycle, an error will be caused to the decision. To avoid this situation, the current cycle adjustment is adopted, and the next cycle is judged alternately. The clock is stable in the previous cycle when the decision is guaranteed;
  • Figure 4 is the clock decision cycle diagram, the TO cycle is judged, the T1 cycle is counted, and the TO cycle is also counted, but not used;
  • Step 7 Clock extraction control, clock extraction control The difference between the FIFO receiving and transmitting, and the FIFO readable spatial information algorithm to calculate the clock adjustment direction and the adjustment byte amount.
  • the readable space information of the FIFO is used to generate the fine-tuning control of the day clock to ensure that the FIFO works in a safe area.
  • Figure 5 is a flow chart of clock fine tuning. The specific steps for generating the fine-tuning control of the day clock are as follows: the position judgment FIFO is readable in the TO cycle.
  • the difference B between the received data amount and the FIFO transmitted data amount in the TO cycle decision position FTF0 is in the range of the nominal value X ( ⁇ / ⁇ (customer service tolerates maximum frequency offset + 20 ⁇ + redundant frequency offset))
  • the clock is not adjusted, and the adjustment byte amount is 0. If the difference B is within this range, the day clock is adjusted as follows:
  • the adjustment amount is 1; if there is negative adjustment fine adjustment information, the clock adjustment direction is negative adjustment, the adjustment amount is 1; If the information is finely adjusted, it will not be adjusted, and the adjustment amount is 0 ;
  • the adjustment amount is: Receive byte amount - Send byte amount + Positive adjustment fine adjustment information - Negative adjustment fine adjustment Information; If the received byte amount is less than the transmitted byte amount, the clock adjustment direction is negative adjustment, the adjustment amount is: Send byte amount - Receive byte amount - Positive adjustment fine adjustment information + Negative adjustment fine adjustment information;
  • the third step includes the following specific steps: Step 1: Converting the adjustment amount of the day t clock extraction control into a plug-in digital frequency synthesizer The required frequency adjustment control word or the adjustment step of the frequency offset offset; the minimum unit of the adjustment amount of the clock extraction control is byte, and the adjustment step of the frequency adjustment control word or the frequency offset offset is small (the adjustment step assembly causes The clock has a large jitter.
  • the frequency adjustment control word or The adjustment step size of the frequency offset offset is set larger; when the adjustment amount of the clock extraction control is small, the adjustment step of the frequency adjustment control word or the frequency offset offset is set smaller;
  • Step 2 Generate accurate frequency adjustment information required by the external digital frequency synthesizer: First set a customer service nominal frequency adjustment control word or frequency offset offset, the frequency adjustment control word or frequency offset offset is configured through the serial interface to The plug-in digital frequency synthesizer generates a reference customer service clock; then, when there is positive adjustment information, the output frequency adjustment control word or frequency offset offset is the last configured adjustment control word or frequency offset offset ⁇ + ⁇ Adjusting the step size, when there is negative adjustment information, the output frequency adjustment control word or frequency offset offset is the last configured adjustment control word or frequency offset offset by one adjustment step; when there is no adjustment information, the output is not updated. Frequency adjustment control word or frequency offset offset;
  • the output frequency adjustment control word or frequency offset offset should be within the normal range; set a frequency adjustment control word or frequency offset offset maximum value and a minimum value, in the clock adjustment In the calculation, if the calculated frequency adjustment control word or frequency offset offset exceeds the maximum or minimum value (the maximum and minimum values are calculated according to the customer service tolerance frequency offset plus 15ppm redundant frequency offset), the output frequency Adjust the control word or frequency offset to the set maximum or minimum value;
  • Step 3 Configure the calculated frequency adjustment control word or frequency offset offset to the external digital frequency synthesizer chip through a serial interface suitable for the external digital frequency synthesizer, and the external digital frequency synthesizer chip can output accurate customer service.
  • Send the clock the clock extraction method provided by the present invention can effectively extract the client service transmission clock in the 0TN system, so as to implement transparent transmission of the 0TN bearer client service.
  • the foregoing embodiment only describes the implementation method of the client service sending clock extraction in the 0TN system. Other similar service clock extraction methods may also adopt the method, and the present invention is not limited thereto. Set.
  • the above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, substitutions, improvements, etc., which are within the spirit and scope of the present invention, should be included in the scope of the present invention. within. Content not described in detail in this specification is well known to those skilled in the art.

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Description

一种 OTN网络中客户业务时钟提取的实现方法
本发明涉及光传送网络 (OTN, Optical Transport Network) 通 信技术领域， 具体说是一种 0TN网络中客户业务时钟（指客户业务的 发送时钟）提取的实现方法。尤指 0TN网络中承载 GE、 STM16和 0TU1 客户业务的发送时钟提取的实现方法。
近年来， 通信网络所承载的业务发生了巨大的变化， 0TN已是主 要的光传送网技术。 目前， 国内外主流运营商都非常关注 0TN技术的 发展和应用， 多数运营商的 WDM传输接口已经实现 0TN功能。 0TN概 念涵盖了光层和电层两层网络， 其关键技术特征之一体现为： 多种客 户信号封装和透明传输。 基于 ITU— T G. 709的 0TN帧结构可以支持 多种客户信号的映射和透明传输， 如 SDH、 ATM, 以太网等。 为实现 0TN承载客户业务的透明传输， 在客户侧发送业务时必须要提取出客 户业务的发送时钟 （简称客户业务时钟）， 其时钟频率要与 0TN承载 对应客户业务之前的 务接收时钟一致。
对于客户业务时钟的提取， 目前主要通过两种方案来实现： FIFO 缓存冗余度控制加上高精度数字锁相环和 FIFO缓存冗余度控制加上 外挂数字频率合成器。
FIFO 缓存冗余度控制加上高精度数字锁相环方案实施起来难度 大， 时钟跟踪调整延时长， 高精度数字锁相环工艺太复杂， 实现成本 过高。 FIFO 缓存冗余度控制加上外挂数字频率合成器方案中仅靠 FIFO 缓存状态来调整时钟， 其受到判断周期以及外挂数字频率合成 器调整步长的限制。 如判断周期短， 缓存冗余度误差大， 而且时钟调 整频繁， 会导致时钟抖动过大； 调整步长设置过小或过大， 跟踪过程 中缓存频繁空或满， 此时缓存冗余度值不可用， 无法提取有效时钟调 整信息； 设备级联过多时， 缓存冗余度会引起迭代效应， 导致时钟抖 动过大。
针对现有技术中存在的缺陷，本发明的目的在于提供一种 0TN网 络中客户业务时钟提取的实现方法，主要定位于 0TN设备客户侧业务 发送端的时钟提取， 用于实现客户业务在 0TN网络中透明传输， 该方 法能够从 0TN愤中恢复出高性能的客户业务时钟，满足各种客户业务 对抖动的要求。
为达到以上目的， 本发明采取的技术方案是：
一种 0TN网络中客户业务时钟提取的实现方法， 其特征在于： 采 用统计控制加上外挂数字频率合成器， 第一步， 对 0TN网络解喊出的 客户业务在 0TN系统时钟下进行同步平滑处理，使客户业务数据比较 均匀； 第二步， 时钟提取控制处理： 统计并比较平滑后数据量与客户 业务发送数据量， 通过加权算法结合 FIFO缓存冗余度来控制时钟调 整信息， 第三歩， 时钟提取适配处理： 通过时钟提取控制处理提供的 时钟调整信息，将其转化为外挂数字频率合成器需要的精确频率调整 信息，并通过串行控制接口精准控制外挂数字频率合成器产生业务发 送时钟。 在上述技术方案的基础上， 所述对客户业务的平滑处理， 包括以 下步骤：
步骤 1 : 设定一个平滑时间窗口， 通常按照 0TN线路接口的 0TN 帧周期来设定，
步骤 2 : 计算在一个平滑时间窗口内客户业务的标称数据量， 步骤 3 : 根据客户业务的容忍频偏和 0TN接口容忍频偏， 计算在 一个平滑时间窗口平滑出客户业务可能出现的数据量，所述数据量包 括一个较大值、 一个中间值和一个较小值， 且该数据量为整数， 步骤 4: 检测同歩 RAM的缓存状态， 计算本平滑时间窗口要读出 的数据量，在一个平滑时间窗口起始位置进行检测 RAM的可读空间在 上限、 下限还是在中心区域， 如在上限， 本平滑时间窗口要读出的数 据量为歩骤 3计算的较大值； 如在下限， 本平滑时间窗口要读出的数 据量为步骤 3计算的较小值； 如在中心区域或异常情况， 本平滑时间 窗口要读出的数据量为歩骤 3计算的中间值；
步骤 5 : 按照计算好的一个平滑时间窗口要读出的数据量， 产生 比较均匀的缺口， 将数据均匀的从同步 RAM读出去， 即可得到客户业 务平滑数据。 在上述技术方案的基础上， 第二步包括以下具体步骤：
步骤 1 : 计算 0寸钟调整周期 T， Ν个平滑时间窗口为一个时钟调 整周期 Τ， Ν值可配置， Ν值越大， 统计的数据量更准， 但也不能无 限大，若 Ν太大，时钟提取的跟踪时间会很长，而 i需要更大的缓存； 步骤 2 : 计算在一个时钟调整周期 T内客户业务的标称数据量； 步骤 3 : 统计计算一个时钟调整周期 T内的平滑数据量， 即 FIFO 接收数据量， FIR)接收数据量应在标称值 X ( 1+/-- (客户业务容忍最 大频偏 +20ppm+冗余频偏）） 之内， 否则 FIFO接收数据量应设为标 称值， 其中， 20ppm为 0TN线路容忍频偏； 冗余频偏自行设置， 用来 吸收抖动和保证电路可以忍受更大的频偏， 如入口数据量抖动太大， 还需进行统计平均；
步骤 4: 统计计算一个时钟调整周期 T内的 FIFO读出数据量， 即 FIFO发送数据量；
步骤 5 : 计算一个时钟调整周期 T内的 FIFO接收数据量和 FIFO 发送数据量的差值， 差值应在标称值 X ( (客户业务容忍最大频偏 + 20ppm+冗余频偏））范围之内， 差值不在此范围之内， 表示线路速 率或发送时钟频率出错， 此时上报告警， 并将差值设为零；
步骤 6 : 时钟调整窗口设定， 如果每个周期既有时钟调整又有进 行判决， 会给判决造成误差， 为避免这种情况， 采用当前周期调整， 下一周期判决交替进行的处理方式，保证判决时的前一个周期里时钟 是稳定的；
步骤 7: 时钟提取控制， 时钟提取控制通过 FIFO接收和发送的 差值， 以及 FTF0的可读空间信息的加全算法计算出时钟调整方向和 调整字节量。
在上述技术方案的基础上， FIFO 的可读空间信息用来产生时钟 微调控制， 用来保证 FIFO工作在安全区域。 在上述技术方案的基础上， 产生日寸钟微调控制的具体步骤为： 在 TO周期判决位置判断 FIFO可读空间， 可读空间大于 256时， 给一个正调整微调信息； 可读空间小于 256 时给一个负调整微调信 息； 可读空间为 256时， 如上个 TO周期有正调整微调信息产生， 贝 U 产生一个负微调信息， 如上个 TO周期有负调整微调信息产生， 则产 生一个正调整微调信息， 否则， 不产生任何微调整信息。 在上述技术方案的基础上，时钟调整方向和调整字节量的产生包 含以下步骤：
在 TO周期判决位置 FIFO接收数据量和 FIFO发送数据量的差值 B在标称值 X ( +/- - (客户业务容忍最大频偏 + 20ppm+冗余频偏)：) 范 围之外， 时钟不作调整， 调整字节量为 0; 如果差值 B在此范围之内， 时钟调整如下：
当差值 B为 0时， 如果有正调整微调信息， 时钟调整方向为正调 整， 调整量为 1 ; 如果有负调整微调信息， 时钟调整方向为负调整， 调整量为 1 ; 如果无微调整信息， 则不调整， 调整量为 0;
当差值 B绝对值大于 1时， 如果接收字节量大于发送字节量， 时 钟调整方向为正调整， 调整量为： 接收字节量一发送字节量 ·+正调整 微调信息一负调整微调信息； 如果接收字节量小于发送字节量， 时钟 调整方向为负调整， 调整量为： 发送字节量一接收字节量一正调整微 调信息 +负调整微调信息；
当差值 B等于 1时， 如果有正调整微调信息， 时钟调整方向为正 调整， 调整量为 2; 如果有负调整微调信息， 时钟不调整， 调整量为 0； 如果无微调整信息， 时钟调整方向为正调整， 调整量为 1 ;
当差值 B等于 ····· ]_时， 如果有负调整微调信息， 时钟调整方向为 负调整， 调整量为 2; 如果有正调整微调信息， 时钟不调整， 调整量 为 0; 如果无微调整信息， 时钟调整方 为负调整。 在上述技术方案的基础上， 第三步包括以下具体步骤： 步骤 1 : 将日 t钟提取控制的调整量转换成外挂数字频率合成器所 需要的频率调整控制字或频偏偏移量的调整步长；时钟提取控制的调 整量最小单位是字节，而频率调整控制字或频偏偏移量的调整步长很 小， 需要多次调整后逐步将时钟提取控制的调整量降到 0 近； 步骤 2 : 产生外挂数字频率合成器需要的精确频率调整信息： 首 先设置一个客户业务标称的频率调整控制字或频偏偏移量，该频率调 整控制字或频偏偏移量通过串行接口配置到外挂数字频率合成器会 产生一个基准的客户业务时钟； 然后， 当有正调整信息时， 输出的频 率调整控制字或频偏偏移量为上一次配置的调整控制字或频偏偏移 量 +调整步长， 当有负调整信息时， 输出的频率调整控制字或频偏偏 移量为上一次配置的调整控制字或频偏偏移量一调整步长；当无调整 信息时， 不更新输出的频率调整控制字或频偏偏移量；
步骤 3 : 将计算好的频率调整控制字或频偏偏移量通过适合于外 挂数字频率合成器的串行接口配置到外挂数字频率合成器芯片，外挂 数字频率合成器芯片即可输出精准的客户业务发送时钟。 在上述技术方案的基础上， 当时钟提取控制的调整量较大日寸， 频 率调整控制字或频偏偏移量的调整步长设置大一点；当时钟提取控制 的调整量较小时，频率调整控制字或频偏偏移量的调整步长设置小一 在上述技术方案的基础上，设置一个频率调整控制字或频偏偏移 量最大值和一个最小值， 在时钟调整^算时， 如计算的频率调整控制 字或频偏偏移量超过最大值或最小值时，输出的频率调整控制字或频 偏偏移量为设定的最大值或最小值；
所述最大值和最小值按照客户业务容忍频偏加上 15ρΡίπ 的冗余 频偏计算得到。
本发明所述的 0TN网络中客户业务时钟提取的实现方法，采用统 计方法来预测承载客户业务速率提取业务时钟，并辅以缓存冗余度进 行微调时钟保证缓存工作在安全区域。本方法实现难度小， 实施起来 成本低；时钟提取过程主要通过统计来控制，不依赖于缓存工作状态， 安全可靠； 统计过程中遇到异常会及时过滤， 设备级联日寸不会引起迭 代效应， 提取的日寸钟质量更好。 附图说明
本发明有如下附图：
图 1为客户业务映射到 0TN网络结构图；
图 2为客户业务在 0TN网络中的走向图；
图 3为本发明提供的时钟提取系统设计功能图；
图 4为时钟判决周期图；
图 5为时钟微调流程图；
图 6为时钟调整流程图。
具体头藤万式
以下结合附图对本发明作进一步详细说明。 本发明所述的 OTN网络中客户业务时钟提取的实现方法，适用于 在 0TN网络中透明传输的客户业务的时钟恢复，能有效滤除客户业务 在映射和解映射过程中产生的抖动， 产生精准的时钟控制信息， 通过 外挂数字频率合成器恢复出高性能的客户业务发送时钟。 基于 ιτυ·- - - T G, 709的 0TN帧结构可以支持多种客户信号的映射和透明传输， 本 发明主要支持 GE、 STM16和 0TU1低速的客户业务。 图 1为客户业务 映射到 0TN网络结构图。 客户业务经过各种映射路径后形成高阶 0TN 帧在 0TN网络上透明传输， 同时从 0TN网络中解帧出各种客户业务。
图 2为客户业务在 0TN网络中的走向图。客户业务经过站点 A通 过各种映射路径后形成高阶 0TN帧在 0TN网络上透明传输，经过一级 或多级站点 C后到达站点 B， 站点 B从 0TN网络中解帧出各种客户业 务。从站点 B解^出的客户业务本身不带任何定时信息， 为保证业务 透明传输， 必须恢复出站点 B客户业务的发送日寸钟， 使业务按照从站 点 A接收的速率发送出去。 图 3为本发明提供的系统设计功能图。
本发明所述的 0TN网络中客户业务时钟提取的实现方法方案是： 采用统计控制加上外挂数字频率合成器， 第一步， 对 0TN网络解帧出 的客户业务在 0TN系统时钟下进行同步平滑处理，使客户业务数据比 较均匀； 第二步， 时钟提取控制处理： 统计并比较平滑后数据量与客 户业务发送数据量， 通过加权算法结合 FIFO缓存冗余度来控制时钟 调整信息， 第三步， 时钟提取适配处理： 通过时钟提取控制处理提供 的时钟调整信息，将其转化为外挂数字频率合成器需要的精确频率调 整信息，并通过串行控制接口精准控制外挂数字频率合成器产生业务 发送日寸钟。 在上述技术方案的基础上， 所述对客户业务的平滑处理， 包括以 下步骤：
步骤 h 设定一个平滑时间窗口， 通常按照 0TN线路接口的 0TN 帧周期来设定， 如线路侧为（)TU1， 则按照 0TU1的系统时钟域下一个 0TU1帧的时间来确定平滑时间窗口； 如线路侧为 0DU2 , 则按照 0DU2 的系统时钟域下一个 0DU2愤的时间来确定平滑时间窗口；
步骤 2 : 计算在一个平滑时间窗口内客户业务的标称数据量， 如 一个 0TU1愤周期时间， GE的标称数据量为 6121. 4， STM16的标称数 据量为 7616; —个 0DU2帧周期时间， GE的标称数据量为 1523. 9, STM16的标称数据量为 1896；
步骤 3: 根据客户业务的容忍频偏和 0TN接口容忍频偏， 计算在 一个平滑时间窗口平滑出客户业务可能出现的数据量（要求为整数）， 所述数据量包括一个较大值、一个中间值和一个较小值，如一个 0TU1 帧周期时间， 平滑处理后的 GE数据量可能为 6120、 6121或 6122， STM16的数据量可能为 7615、 7616或 7617;
步骤 4: 检测同步 RAM的缓存状态， 计算本平滑时间窗口要读出 的数据量，在一个平滑时间窗口起始位置进行检测 RAM的可读空间在 上限、 下限还是在中心区域， 如在上限， 本平滑日寸间窗口要读出的数 据量为步骤 3计算的较大值； 如在下限， 本平滑时间窗口要读出的数 据量为步骤 3计算的较小值； 如在中心区域或异常情况， 本平滑时间 窗口要读出的数据量为步骤 3计算的中间值；
步骤 5 : 按照计算好的一个平滑日寸间窗口要读出的数据量， 产生 比较均匀的缺口， 将数据均匀的从同步 MM读出去， 即可得到客户业 务平滑数据，
客户业务经过一级或多级映射上到 0TN网络，客户业务在映射和 解映射过程中会引入抖动， 而 i客户业务解^后处于 0TN 的时钟域 下， 会有数据突发现象， 这会造成客户业务时钟提取难度加大， 时钟 性能指标也不好。为解决此问题需要对 0TN解^出的客户数据进行平 滑处理， 平滑处理由一个同步缓存 RAM和一个控制逻辑构成。 第二步所述统计并比较平滑后数据量与客户业务发送数据量，通 过加权算法结合 FIFO缓存冗余度来控制时钟调整信息， 即时钟提取 控制处理过程， 日寸钟提取控制处理由一个异步缓存 FIFO和一个时钟 提取控制处理逻辑构成。 在上述技术方案的基础上， 第二步包括以下具体步骤：
步骤 h 计算时钟调整周期 T， Ν个平滑时间窗口为一个时钟调 整周期 Τ, Ν值可配置， Ν值越大， 统计的数据量更准， 但也不能无 限大，若 Ν太大，时钟提取的跟踪时间会很长，而且需要更大的缓存； 步骤2 ' : 算在一个时钟调整周期 T内客户业务的标称数据量； 步骤 3: 统计计算一个时钟调整周期 T内的平滑数据量， 即 FIFO 接收数据量， FIFO接收数据量应在标称值 X ( I - (客户业务容忍最 大频偏 + 20ppm+冗余频偏）） 之内， 否则 FIFO接收数据量应设为标 称值， 其中， 20ppm为 0TN线路容忍频偏； 冗余频偏可以自行设置， 用来吸收抖动和保证电路可以忍受更大的频偏，如入口数据量抖动太 大， 还需迸行统计平均；
步骤 4: 统计计算一个时钟调整周期 T内的 FIFO读出数据量， 即 FIFO发送数据量；
步骤 5: 计算一个时钟调整周期 T内的 FIFO接收数据量和 FIFO 发送数据量的差值， 差值应在标称值 X ( (客户业务容忍最大频偏 •+20ppm+冗余频偏））范 之内， 差值不在此范围之内， 表示线路速 率或发送时钟频率出错， 此时上报告警， 并将差值设为零；
步骤 6: 时钟调整窗口设定， 如果每个周期既有时钟调整又有进 行判决， 会给判决造成误差， 为避免这种情况， 采用当前周期调整， 下一周期判决交替迸行的处理方式，保证判决时的前一个周期里时钟 是稳定的； 图 4为时钟判决周期图， TO周期迸行判决， T1周期的统 计， TO周期也会统计， 但不采用；
步骤 7: 时钟提取控制， 时钟提取控制通过 FIFO接收和发送的 差值， 以及 FIFO的可读空间信息的加全算法计算出时钟调整方向和 调整字节量。 在上述技术方案的基础上， FIFO 的可读空间信息用来产生日寸钟 微调控制， 用来保证 FIFO工作在安全区域。 图 5为时钟微调流程图。 产生日寸钟微调控制的具体步骤为：在 TO周期判决位置判断 FIFO可读 空间， 可读空间大于 256时， 给一个正调整微调信息； 可读空间小于 256时给一个负调整微调信息； 可读空间为 256时， 如上个 TO周期 有正调整微调信息产生， 则产生一个负微调信息 （回调机制）， 如上 个 TO周期有负调整微调信息产生， 则产生一个正调整微调信息 （回 调机制）， 否则， 不产生任何微调整信息。 在上述技术方案的基础上，时钟调整方向和调整字节量的产生如 图 6所示。 时钟调整方向和调整字节量的产生以下步骤：
在 TO周期判决位置 FTF0接收数据量和 FIFO发送数据量的差值 B (见步骤 5 ) 在标称值 X ( ·/ · (客户业务容忍最大频偏 + 20ρρπι+冗 余频偏）） 范围之外， 时钟不作调整， 调整字节量为 0 ; 如果差值 B 在此范围之内， 日寸钟调整如下：
当差值 B为 0时， 如果有正调整微调信息， 日寸钟调整方向为正调 整， 调整量为 1 ; 如果有负调整微调信息， 时钟调整方向为负调整， 调整量为 1 ; 如果无微调整信息， 则不调整， 调整量为 0 ;
当差值 B绝对值大于 1时， 如果接收字节量大于发送字节量， 时 钟调整方向为正调整， 调整量为： 接收字节量一发送字节量 +正调整 微调信息一负调整微调信息； 如果接收字节量小于发送字节量， 时钟 调整方向为负调整， 调整量为： 发送字节量一接收字节量一正调整微 调信息 +负调整微调信息；
当差值 B等于 1日寸， 如果有正调整微调信息， 时钟调整方向为正 调整， 调整量为 2 ; 如果有负调整微调信息， 时钟不调整， 调整量为 0 ; 如果无微调整信息， 日寸钟调整方向为正调整， 调整量为 1 ;
当差值 B等于一 1时， 如果有负调整微调信息， 时钟调整方向为 负调整， 调整量为 2 ; 如果有正调整微调信息， 时钟不调整， 调整量 为 0; 如果无微调整信息， 时钟调整方向为负调整。 在上述技术方案的基础上， 第三步包括以下具体步骤： 步骤 1 : 将日 t钟提取控制的调整量转换成外挂数字频率合成器所 需要的频率调整控制字或频偏偏移量的调整步长；时钟提取控制的调 整量最小单位是字节，而频率调整控制字或频偏偏移量的调整步长很 小 （调整步长大会引起时钟有很大的抖动）， 需要多次调整后逐步将 时钟提取控制的调整量降到 0附近； 为加快时钟提取的跟踪时间， 当 时钟提取控制的调整量较大时，频率调整控制字或频偏偏移量的调整 步长设置大一点； 当时钟提取控制的调整量较小时， 频率调整控制字 或频偏偏移量的调整步长设置小一点；
步骤 2 : 产生外挂数字频率合成器需要的精确频率调整信息： 首 先设置一个客户业务标称的频率调整控制字或频偏偏移量，该频率调 整控制字或频偏偏移量通过串行接口配置到外挂数字频率合成器会 产生一个基准的客户业务时钟； 然后， 当有正调整信息时， 输出的频 率调整控制字或频偏偏移量为上一次配置的调整控制字或频偏偏移 量 ·+·调整步长， 当有负调整信息时， 输出的频率调整控制字或频偏偏 移量为上一次配置的调整控制字或频偏偏移量一调整步长；当无调整 信息日寸， 不更新输出的频率调整控制字或频偏偏移量；
为保证输出客户业务时钟的可靠，输出的频率调整控制字或频偏 偏移量要保证在正常的范围之内；设置一个频率调整控制字或频偏偏 移量最大值和一个最小值， 在时钟调整计算时， 如计算的频率调整控 制字或频偏偏移量超过最大值或最小值时 (：最大值和最小值按照客户 业务容忍频偏加上 15ppm的冗余频偏计算得到）， 输出的频率调整控 制字或频偏偏移量为设定的最大值或最小值；
步骤 3 : 将计算好的频率调整控制字或频偏偏移量通过适合于外 挂数字频率合成器的串行接口配置到外挂数字频率合成器芯片，外挂 数字频率合成器芯片即可输出精准的客户业务发送时钟。 综上所述，本发明提供的一种时钟提取方法能够有效提取 0TN系 统中客户业务发送时钟， 以实现 0TN承载客户业务的透明传输。上述 实施例只是对 0TN 系统中客户业务发送时钟提取的实现方法作了说 明， 其他类似的业务时钟提取也可以采用此方法， 本发明并不加以限 定。 以上所述仅为本发明的较佳实施例， 并不用以限制本发明， 凡在 本发明的精神和原则之内， 所作的任何修改、 替换、 改进等， 均应包 含在本发明的保护范围之内。 本说明书中未作详细描述的内容属于本领域专业技术人员公知

Claims

1 , 一种 OTN网络中客户业务时钟提取的实现方法， 其特征在于: 采用统计控制加上外挂数字频率合成器， 第一步， 对 0TN网络解帧出 的客户业务在 0TN系统时钟下进行同歩平滑处理，使客户业务数据比 较均匀； 第二步， 时钟提取控制处理： 统计并比较平滑后数据量与客 户业务发送数据量， 通过加权算法结合 FIFO缓存冗余度来控制时钟 调整信息， 第≡歩， 时钟提取适配处理： 通过时钟提取控制处理提供 的时钟调整信息，将其转化为外挂数字频率合成器需要的精确频率调 整信息，并遥过串行控制接口精准控制外挂数字频率合成器产生业务 发送 fi寸钟。
2 , 如权利要求 1所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于， 所述对客户业务的平滑处理， 包括以下步骤：
步骤 1 : 设定一个平滑时间窗口， 通常按照 0TN线路接口的 0TN 帧周期来设定，
步骤 2 : 计算在一个平滑时间窗口内客户业务的标称数据量， 歩骤 3 : 根据客户业务的容忍频偏和 0TN接口容忍频偏， 计算在 一个平滑时间窗口平滑出客户业务可能出现的数据量， 述数据量包 括一个较大值、 一个中间值和一个较小值， 且该数据量为整数，
步骤 4: 检测同步 RAM的缓存状态， 计算本平滑时间窗口要读出 的数据量，在一个平滑时间窗口起始位置进行检测 RAM的可读空间在 上限、 下限还是在中心区域， 如在上限， 本平滑时间窗口要读出的数 据量为步骤 3计算的较大值； 如在下限， 本平滑时间窗口要读出的数 据量为步骤 3计算的较小值； 如在中心区域或异常情况， 本平滑时间 窗口要读出的数据量为步骤 3计算的中间值；
步骤 5 : 按照计算好的一个平滑时间窗口要读出的数据量， 产生 比较均匀的缺口， 将数据均匀的从同步 RAM渎出去， 即可得到客户业 务平滑数据。
3 , 如权利要求 2所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于， 第二歩包括以下具体歩骤：
步骤 h 计算时钟调整周期 T， Ν个平滑时间窗口为一个时钟调 整周期 Τ, Ν值可配置， Ν值越大， 统计的数据量更准， 但也不能无 限大，若 Ν太大，时钟提取的跟踪时间会很长，而且需要更大的缓存； 步骤2 ' : 算在一个时钟调整周期 T内客户业务的标称数据量； 步骤 3: 统计计算一个时钟调整周期 T内的平滑数据量， 即 FIFO 接收数据量， FIFO接收数据量应在标称值 X ( I - (客户业务容忍最 大频偏 + 20ppm+冗余频偏）） 之内， 否则 FIFO接收数据量应设为标 称值， 其中， 20ρρίη为 0TN线路容忍频偏； 冗余频偏自行设置， 用来 吸收抖动和保证电路可以忍受更大的频偏， 如入口数据量抖动太大， 还需进行统计平均；
步骤 4: 统计计算一个时钟调整周期 Τ内的 FIFO读出数据量， 即 FIFO发送数据量；
步骤 5: 计算一个时钟调整周期 T内的 FIFO接收数据量和 FIFO 发送数据量的差值， 差值应在标称值 X ( (客户业务容忍最大频偏 •+20ppm+冗余频偏））范 之内， 差值不在此范围之内， 表示线路速 率或发送时钟频率出错， 此时上报告警， 并将差值设为零；
步骤 6: 时钟调整窗口设定， 如果每个周期既有时钟调整又有进 行判决， 会给判决造成误差， 为避免这种情况， 采用当前周期调整， 下一周期判决交替迸行的处理方式，保证判决时的前一个周期里时钟 是稳定的；
步骤 7: 时钟提取控制， 时钟提取控制通过 FIFO接收和发送的 差值， 以及 FIR)的可读空间信息的加全算法计算出时钟调整方向和 调整字节量。
4. 如权利要求 3所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于： FIFO 的可读空间信息用来产生时钟微调控制， 用 来保证 FIFO工作在安全区域。
5. 如权利要求 4所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于， 产生时钟微调控制的具体步骤为： 在 TO周期判决位置判断 FTF0可读空间， 可读空间大于 256时， 给一个正调整微调信息； 可读空间小于 256 时给一个负调整微调信 息； 可读空间为 256时， 如上个 TO周期有正调整微调信息产生， 则 产生一个负微调信息， 如上个 TO周期有负调整微调信息产生， 则产 生一个正调整微调信息， 否则， 不产生任何微调整信息。
6. 如权利要求 5所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于， 时钟调整方向和调整字节量的产生包含以下步骤： 在 TO周期判决位置 FIFO接收数据量和 FIFO发送数据量的差值 B在标称值 X ( +/· · (客户业务容忍最大频偏 + 20ppm+冗余频偏）） 范 围之外， 时钟不作调整， 调整字节量为 0; 如果差值 B在此范围之内， 时钟调整如下：
当差值 B为 0时， 如果有正调整微调信息， 时钟调整方向为正调 整， 调整量为 1 ; 如果有负调整微调信息， 时钟调整方向为负调整， 调整量为 1 ; 如果无微调整信息， 则不调整， 调整量为 0;
当差值 B绝对值大于 1时， 如果接收字节量大于发送字节量， 时 钟调整方向为正调整， 调整量为： 接收字节量一发送字节量 ·+正调整 微调信息一负调整微调信息； 如果接收字节量小于发送字节量， 时钟 调整方向为负调整， 调整量为： 发送字节量一接收字节量一正调整微 调信息 ·+·负调整微调信息；
当差值 B等于 1时， 如果有正调整微调信息， 时钟调整方向为正 调整， 调整量为 2 ; 如果有负调整微调信息， 时钟不调整， 调整量为 0； 如果无微调整信息， 时钟调整方向为正调整， 调整量为 1 ;
当差值 B等于一 1时， 如果有负调整微调信息， 时钟调整方向为 负调整， 调整量为 2 ; 如果有正调整微调信息， 时钟不调整， 调整量 为 0; 如果无微调整信息， 时钟调整方向为负调整。
7. 如权利要求 2所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于， 第三步包括以下具体步骤：
步骤 1 : 将时钟提取控制的调整量转换成外挂数字频率合成器所 需要的频率调整控制字或频偏偏移量的调整步长；时钟提取控制的调 整量最小单位是字节，而频率调整控制字或频偏偏移量的调整步长很 小， 需要多次调整后逐步将时钟提取控制的调整量降到 0刚近； 步骤 2 : 产生外挂数字频率合成器需要的精确频率调整信息： 首 先设置一个客户业务标称的频率调整控制字或频偏偏移量，该频率调 整控制字或频偏偏移量通过串行接口配置到外挂数字频率合成器会 产生一个基准的客户业务时钟； 然后， 当有正调整信息时， 输出的频 率调整控制字或频偏偏移量为上一次配置的调整控制字或频偏偏移 量 +调整步长， 当有负调整信息时， 输出的频率调整控制字或频偏偏 移量为上一次配置的调整控制字或频偏偏移量一调整步长；当无调整 信息时， 不更新输出的频率调整控制字或频偏偏移量；
步骤 3 : 将计算好的频率调整控制字或频偏偏移量通过适合于外 挂数字频率合成器的串行接口配置到外挂数字频率合成器芯片，外挂 数字频率合成器芯片即可输出精准的客户业务发送时钟。
8. 如权利要求 7所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于： 当时钟提取控制的调整量较大时， 频率调整控制字 或频偏偏移量的调整步长设置大一点；当时钟提取控制的调整量较小 时， 频率调整控制字或频偏偏移量的调整步长设置小一点。
9. 如权利要求 7所述的 0TN网络中客户业务时钟提取的实现方 法， 其特征在于： 设置一个频率调整控制字或频偏偏移量最大值和一 个最小值， 在时钟调整计算时， 如计算的频率调整控制字或频偏偏移 量超过最大值或最小值时，输出的频率调整控制字或频偏偏移量为设 定的最大值或最小值；
所述最大值和最小值按照客户业务容忍频偏加上 15ppm 的冗余 频偏计算得到。
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