CN103181104B - For the method that in access network, the time is accurately distributed to receiver node - Google Patents

Abstract

A kind of equipment, described equipment includes client node, for being couple to access node, and for receiving Time of Day (TOD) value and corresponding sample index (SNUM) value by channel from described access node, wherein said TOD value and described SNUM value estimate second day time (TOD ') value in order to propagation delay based on described channel (L Delay), and wherein said TOD value and described TOD ' value are in order to estimate the 2nd SNUM (SNUM ') value based on L Delay and multiple parameter.

Description

For the method that in access network, the time is accurately distributed to receiver node

The cross reference of related application

Application claims on July 2nd, 2010 is by defending the invention that east (Dong Wei) et al. is submitted Entitled " for accurately distributing method (the Method for Accurate Distribution of of time The earlier application priority of the 61/361st, No. 259 U.S. Provisional Patent Application case Time) ", is somebody's turn to do The mode that the content of first to file introduces in full is expressly incorporated herein in this.

About the statement by the research and development of federal funding

Inapplicable.

With reference to microfiche appendix

Inapplicable.

Technical field

Nothing

Background technology

Mobile Communication Service is the most increasingly welcome by client all over the world.With tradition such as voice services Service is compared, the multiple clothes such as such as video request program (VOD), unification of three nets and other Information Mobile Services Business requires higher bit rate.Use the stable digital link of relative high quality, such as, it is provided that relatively High-caliber service quality (QOS) and the digital link of high bit rate, it is ensured that require higher Service.In order to reach this requirement, the base station (BS) being used for wireless system can be placed on indoor Rather than outdoor, in order to reduce aerial signal conveying length.This scheme also considerably increases and is disposed BS quantity.In order to meet above-mentioned trend, serve as mobile retransmission network (mobile backhaul) Access network can participate in the data stream of Information Mobile Service in conveying room.The example of access network comprises numeral use Family line (DSL) system and EPON (PON).Some data streams are transported permissible from indoor BS Reducing network cost, indoor BS is also referred to as miniature BS.The method may also require that moving back to of improvement The time/frequency passing network synchronizes, and such as, marks according to Institute of Electrical and Electronics Engineers (IEEE) Accurate 1588, this standard is expressly incorporated herein in this in the way of introducing.

Summary of the invention

In one embodiment, the present invention comprises a kind of equipment, and described equipment includes access node, For being couple to receiver node and relative Time of Day (TOD) value being sent to described receptor joint Point, wherein said relative TOD value is for adjusting the clock in client node by relative TOD ' value Frequency, and/or adjust receptor further by propagation delay L-Delay of TOD value and link The clock time of side, in order to Tong Bu with the clock in access node.

In another embodiment, the present invention comprises a kind of network components, and described network components includes connecing Clock in ingress, described clock is updated by network clock signal, such as, from network of network Timing reference (NTR) signal or Time of Day signal, and for being transferred to the signal of client node TOD value is provided when arriving the reference point of access node side, and/or obtains relative TOD value further, The value that wherein said relative TOD value obtains for TOD value mould fixed value (such as, 125 microsecond).

In another embodiment, the present invention comprises a kind of method, and described method includes: receive TOD Value and/or relatively TOD value；The ginseng at client node is arrived at the identical signal using described TOD value During examination point, obtain TOD ' value, and/or obtain relative TOD ' value, wherein said relative TOD ' further The value that value obtains for TOD ' value mould fixed value (such as, 125 microsecond)；Pass through received value and institute The value obtained adjusts the frequency of second clock in client node；And/or pass through received TOD value The time of second clock in client node is adjusted, in order to guarantor with propagation delay L-Delay of link Stay the clock at access node to synchronize.

In one embodiment, the present invention comprises a kind of equipment, and described equipment includes client node, For being couple to access node, and for receiving Time of Day (TOD) by channel from access node Value and corresponding sample index (SNUM) value, wherein said TOD value and described SNUM value are used The 2nd TOD (TOD ') value, Er Qieqi is estimated with propagation delay (L-Delay) based on link Described in TOD value and described TOD ' value in order to estimate the second sample based on L-Delay and multiple parameter This index (SNUM ') value.

In another embodiment, the present invention comprises a kind of network components, and described network components includes: Enumerator, for providing the SNUM value of the pulse corresponding to pulse per second (PPS) (PPS) signal；Clock, For offer shows that signal is transmitted at reference point when；And emitter, it is used for passing through copper Twisted wire transmits described SNUM value and described TOD value.

In another embodiment, the present invention comprises a kind of method, and described method includes: receive TOD Value and corresponding SNUM value；TOD ' value is obtained based on propagation delay；Based on described TOD value, Described TOD ' value, described SNUM value and multiple transmission parameter obtain SNUM ' value；And make Use adjusted clock, produce PPS ' signal pulse based on described TOD ' value and described SNUM ' value.

By combining accompanying drawing and appended claims is carried out described in detail below will be apparent from ground Understand these and other features.

Accompanying drawing explanation

In order to be more fully understood from the present invention, carry out with reference now to below in conjunction with accompanying drawing and detailed description Brief description, wherein same reference numerals represents same section.

Fig. 1 is the schematic diagram of an embodiment of PPS signal.

Fig. 2 is the schematic diagram of an embodiment of PPS Yu TOD Signal separator.

Fig. 3 is the signal of an embodiment of reference point and the generation of corresponding sample index SNUM Figure.

Fig. 4 is SNUM and the schematic diagram of an embodiment of TOD generation.

Fig. 5 is the schematic diagram of the embodiment that PPS signal recovers.

Fig. 6 is the schematic diagram of the embodiment that sampling clock cycle is estimated.

Fig. 7 is the schematic diagram of an embodiment of reference point and corresponding TOD generation.

Fig. 8 is the schematic diagram of the embodiment produced by the frequency of TOD value/time synchronized.

Fig. 9 is the embodiment produced by the Frequency Synchronization of relative TOD value (relative time) Schematic diagram.

Figure 10 is the schematic diagram of an embodiment of symbols at error.

Figure 11 is the schematic diagram of an embodiment of symbols at error estimation.

Figure 12 is the schematic diagram of the embodiment that twisted-pair feeder propagation delay is estimated.

Figure 13 is another schematic diagram of the twisted-pair feeder propagation delay estimation of Figure 12.

Figure 14 is the schematic diagram of the embodiment that analog circuit postpones.

Figure 15 is the schematic diagram of an embodiment of digital delay circuit.

Figure 16 is the schematic diagram of an embodiment of the estimation of FIR digital delay circuit.

Figure 17 is the protocol figure of an embodiment of time allocation method used therein accurately.

Figure 18 is the flow chart of an embodiment of time allocation method used therein accurately.

Figure 19 is the schematic diagram of an embodiment of emitter/receiver unit.

Figure 20 is the schematic diagram of an embodiment of general-purpose computing system.

Detailed description of the invention

Although first should be understood that the illustrative embodiment that one or more embodiment is provided below, But disclosed system and/or method can use any number of technology to implement, no matter this technology is to work as Front known or existing.The present invention should in no way be limited to illustrative embodiment described below, attached Figure and technology, comprise exemplary design illustrated and described here and embodiment, but can be Modify in the full breadth of the scope of the appended claims and equivalent thereof.

Have been proposed that a kind of current techique based on bag, in order to carry out correct time for network and divide Join, such as, as described in ieee standard 1588v2, described standard is expressly incorporated herein this in the way of introducing In, its asymmetrical delay based on link is assumed to use two way method.Clock carries in upper strata is wrapped, institute State upper strata bag and can distribute to the base station of all connections.Under using IEEE1588v2 to require at upper strata The symmetry that row postpones between upstream delay is at a relatively high, and the delay jitter in both direction is relative Relatively low.But, physical layer may belong to DSL system, in DSL system, descending (that is, from Central office (CO) arrive customer rs premise equipment (CPE)) with up (that is, from CPE to CO) it Between delay be asymmetric, and the unstable shake of several milliseconds may be introduced into.This makes it difficult to, Such as, when being realized accurately on DSL link by technology based on bag as IEEE 1588v2 Between distribute.If additionally, at clock and CPE, Frequency Synchronization between clock is poor at CO, then May more frequently being require time for synchronizing process, it is thus possible to require more system resource.Currently DSL system use ITU-T recommendation (such as, be all expressly incorporated herein in this in the way of introducing G.992.3 Network timing references (NTR) mechanism of regulation in, G.992.5 and G.993.2), this The Frequency Synchronization precision that the mechanism of kind realizes and may be unsatisfactory for the Frequency Synchronization essence required by mobile network Degree.Accordingly, it would be desirable to the Frequency Synchronization technology that a kind of accuracy is high.

Disclosed herein a kind of for providing frequency/time distribution the most accurately for access network System and method, described access network such as DSL system or PON system, mobile retransmission can be served as Network.Described method can be used to be reduced or eliminated because channel or propagation delay, sample clock frequency are inclined From or skew and symbols at error and the frequency/time distribution degradation that causes.Described system and method Go for the system with asymmetric link delay and jitter, such as, DSL system.

Described method may include that when pulse PPS signal being detected, obtains sample index value, Represent with SNUM；By sample index SNUM value and by using access node (such as, CO) The clock at place and the corresponding TO D value that obtains is sent to client node (such as, CPE).Described value with After can be received by client node and for obtaining the TOD ' value of estimation, wherein will in view of access Link propagation delay between node and client node, represents with L-Delay.Subsequently, can be based on TOD value and TOD ' value, sample clock time interval or cycle (T_s), propagation delay and symbol pair Quasi-error (Δ sym-align), obtains corresponding SNUM ' value.The clock recovered at client node can To be adjusted by the SNUM ' at process client node and TOD ', so that at client node Clock frequency/time synchronized at adjusted clock and access node.The PPS recovered at client node Signal PPS ' signal represents, it is the output of clock at client node, by process SNUM ' and TOD ' is adjusted, consequently, it is possible to the most accurate, in order to meet mobile retransmission network frequency/time Between distribute and synchronize requirement.

Additionally, described method can include from access node, such as, CO sends TOD value or phase To TOD value, wherein TOD value shows with relative TOD value to specify signal at access node respectively Appointment position on (such as, the U-O reference point of DSL system or the output of IDFT) transmit time Carve and relative instant.Described TOD value can use the clock at access node to obtain with relative TOD value Taking, described clock is Tong Bu with network clocking and is updated by PPS signal.At client node Clock can be adjusted by the value received, in order to the clock frequency/time synchronized at access node. If send is relative TOD value, then as same position (such as, the DSL at client node The U-R reference point of system or the input of DFT) when receiving identical appointment signal, client node The clock at place can be adjusted to identical relative TOD value, so that adjusted clock saves with accessing Clock rate synchronization at Dian.Relatively TOD value is the time, it relative to can by access node with What client node received is expressed as a value from third-party appointment signal.If that send is TOD Value, then the clock at client node can be based on the TOD value received and propagation delay L-Delay It is adjusted, in order to the clock frequency/time synchronized at access node.Recover at client node PPS signal PPS ' signal represents, adjusted clock be adjusted.It is described further below For calculating the additive method of above-mentioned various value and details and other relevant parameters.

Fig. 1 shows an embodiment of PPS signal 100.PPS signal 100 can be based on string Port communications method is transmitted by Time of Day interface, in order to update the clock at access node, thus TOD information is provided for communication system (such as, DSL system).When PPS signal and corresponding day Between information all can be sent by identical channel, such as, use identical interface, port or pin Send.PPS signal and corresponding ToD information can send in 1PPS Yu ToD signal 102, Described signal 102 represents a type of PPS signal.1PPS Yu ToD signal 102 may be with about 1,000,000 hertz (Hz) are transmitted.The trailing edge of 1PPS Yu ToD signal 102 and standard The rising edge alignment of PPS signal 101.When carrying Time of Day information on PPS signal, PPS signal 102 can include PPS section 103, wait section 104, serial information section 106 and idle section 108. Described Time of Day information can carry in serial information section 106, to show in the current PPS cycle The moment of the trailing edge of the PPS signal of transmission in section 103.PPS signal 102 can include about one Start bit and about stopping position, and verification and position can not be included.Low voltage transistor-transistor is patrolled Collect (LVTTL) to can be used to transmit 1PPS Yu ToD signal 102.

Fig. 2 shows an embodiment of PPS Yu ToD Signal separator 200, described Signal separator Can be in access node, such as, implement at CO.In order to make system have motility, from outside PPS Yu the ToD signal of clock sources is segmented into PPS signal and ToD information.PPS and ToD Signal separator 200 can be used to receive and transports Time of Day (ToD) information by single channel or interface PPS signal, is extracted PPS signal and ToD information, and is forwarded by different interfaces or port They.PPS Yu ToD Signal separator 200 can use S2P module separator 202, described module Separator for being converted into two parallel PPS signal and ToD letter by PPS Yu ToD serial signal Number, the two signal can forward each via single channel.PPS signal is at least 1PPS letter Number, i.e. a pulse per second (PPS).PPS signal can be used to the clock updated at access node.

Fig. 3 shows can be in access node, such as, and the reference point implemented at CO and correspondence Sample index SNUM produces an embodiment of 300.Reference point and corresponding sample index SNUM Produce 300 and can detect that every subpulse of PPS signal or specific pulse are (such as, shown in Fig. 1 The trailing edge of 1PPS Yu ToD signal 102) time, produce sample index SNUM.For CO Every subpulse of PPS signal that place occurs, i.e. the beginning in each PPS cycle, CO can be based on The location counter that may retain in system records sample index SNUM value.Such as, position meter Number devices potentially include multiple enumerator: synchronizing symbol enumerator (SSCLK), symbol counter (SCLK) And Sample Counter (CLK).CLK enumerator calculates the Discrete Multitone (DMT) of access node transmission The number of sample in symbol.SCLK enumerator calculates two neighbours showing the time (Showtime) The number of symbols transmitted by access node during nearly synchronizing symbol.SSCLK enumerator calculates the displaying time The number of period synchronizing symbol.When PPS signal pulse being detected at access node, according to position Put the value of enumerator, SNUM value can be obtained, as shown in Figure 3.

Fig. 4 shows can be in access node, such as, SNUM and TOD implemented at CO Produce an embodiment of 400.SNUM and TOD produces 400 can be based on reference point and correspondence Sample index SNUM produce 300.Such as, when DSL system (such as, ADSL2, ADSL2+, When VDSL2) entering the displaying time, when the location counter 402 at CO can start according to sampling Clock calculates the number of samples of access node transmission.Location counter 402 can include that SSCLK counts Device, SCLK enumerator, and/or CLK enumerator, as mentioned above.When a pulse is detected, position The value putting enumerator 402 can be by the SRecoder404 record in system, described value SNUM Represent.SNUM value subsequently can be via emitter by embedded operation channel (EOC) or expense (OH) frame is transferred to receptor, such as, and CPE.Additionally, simultaneously (i.e., when a pulse is detected), TOD value can be by TRecorder406 record, to show to detect the moment of current PRF, and It is sent to receptor by EOC or OH frame subsequently on emitter.TRecorder406 can make TOD value is obtained with the clock at access node.Described clock can Tong Bu with PPS signal and Updated by PPS signal.TOD value can be with SNUM value in identical EOC message or identical OH frame sends.

Fig. 5 shows that PPS signal recovers an embodiment of 500, and described signal recovers can be by Client node (such as, CPE) is implemented.PPS signal recovers 500 and can receive with CPE SNUM value and/or TOD value carry out the PPS signal of adjustment and recovery, and the PPS signal of described recovery is used PPS ' signal represents.Time of Day information can be supplied to other equipment by the PPS signal recovered.One Location counter can be retained at CPE, and it is Tong Bu with the location counter of CO side.At CPE Location counter can include SSCLK ' enumerator, SCLK ' enumerator, and/or CLK ' enumerator. The number of the synchronizing symbol that SSCLK ' counter records is received at displaying time period CPE. Being connect between the SCLK ' counter records two neighbouring synchronizing symbols at displaying time period CPE The number of symbols received.A CLK ' counter records DMT symbol at displaying time period CPE Middle received number of samples.When receiving SNUM value and corresponding TOD value at CPE, CPE can estimate moment TOD '.TOD ' value shows that next the PPS cycle of the PPS signal recovered opens The moment of beginning (such as, the pulse of the 1PPS signal shown in Fig. 1).Generally, due to except link Propagation delay outside, there is also other system postpone, therefore, TOD value and corresponding TOD ' value Between time difference can be more than EOC channel transmission time.PPS signal recovers 500 and can solve The time caused because of propagation delay, sample clock frequency deviation and symbols at error etc. distributes repeatedly Degradation, thus improve the precision of the PPS ' signal recovered at CPE.

Specifically, corresponding SNUM ' value may indicate that the sample that CPE receives with TOD ' value Index.Estimation to SNUM ' value can be based on the SNUM value received, the TOD received Value, the TOD ' value estimated, the propagation delay of link, and/or symbols at error are as follows:

SNUM+ (TOD '-TOD-L-Delay-(Δ sym-align)/Ts, (1)

Or as follows:

(TOD '-L-Delay-Δ sym-align)/Ts, (2)

Wherein L-Delay is the link propagation delay from CO to CPE, generally can depend on loop Length, digital circuit and analog circuit；Δ sym-align is symbols at error；And T_sBe by The cycle of the sample of access node transmission.

When CPE receives the sample with SNUM ', the output pulse of adjusted PPS ' signal. Recover PPS signal (that is, PPS ' signal) can by CPE based on SNUM ' value and TOD ' be worth into Row sum-equal matrix so that the PPS signal frequency/time at adjusted PPS ' signal and access node with Step.

Or, clock can be retained at CPE.The TOD ' that described clock can be estimated by CPE Value and SNUM ' value are updated.Described clock can export the PPS ' signal of recovery.When CPE connects When receiving SNUM ' sample, clock can export the PPS ' signal pulse of the recovery with TOD ' information.

Sampling clock at CPE can come Tong Bu with the sampling clock at CO by loop timing. But, agitator may introduce the skew of accumulation, in order to produces the sampling clock at CO and CPE. Agitator generally uses PPM (PPM), and therefore, deviation is probably several milliseconds.This may The error estimating TOD ' is increased to hundreds of nanosecond.Such as, if agitator is about 20PPM, And the difference between TOD ' and TOD is equal to about 20 milliseconds, then estimate that the error of TOD ' value may It is about 400 nanoseconds.For the time/frequency synchronization accuracy of mobile network, this is probably cannot Accept.In order to error is reduced or eliminated, it may be necessary to one sample clock frequency the most accurately Or phase estimate.

Fig. 6 shows that sampling clock cycle estimates an embodiment of 600, described sampling clock week Phase estimation can be in access node, such as, implements at CO.Sampling clock cycle estimates that 600 is permissible Use the enumerator 602 at CO, to calculate the sampling clock week between two neighbouring PPS cycles The number of phase, thus obtain sample clock frequency (F the most accurately_s) or cycle (T_s)。F_s Or T_sValue can be transferred to CPE by EOC or OH frame subsequently.This F the most accurately_sOr T_sEstimation can be used in equation (1), in order to eliminates or generally reduce the offset error of accumulation.

In another embodiment, in order to eliminate F_sOr T_sThe uncertainty of value or inaccuracy, CO Sampling clock can be Tong Bu with NTR.NTR can be Tong Bu with primitive network clock.Tong Bu with NTR CO sampling clock can generally accurately and stable.In this case, F_sValue for sampling time The frequency of clock.This scheme can be passed through equation (1) and improve the essence of the SNUM ' value estimated further Degree.

Fig. 7 shows can be in access node, such as, and the reference point implemented at CO and correspondence TOD produces an embodiment of 700.Reference point and corresponding TOD produce 700 can be at CO Place produces access node transmission and specifies the moment of sample.TOD can obtain according to the clock at CO. Clock can by NTR signal or Time of Day signal (such as, the 1PPS signal shown in Fig. 1) with Network clocking outside CO synchronizes, such as, Tong Bu with primitive network clock.Described clock can be by The network clock signal such as NTR signal or Time of Day signal update.For DSL system, it is intended that Sample can be the n-th sample of designated symbols, such as, the first time domain samples.Designated symbols is permissible Enter the m-th symbol of each unit of time after the displaying time for CO, or be phase displaying time Between the l-th symbol of each superframe, such as, the first data symbol of each superframe, or show Synchronizing symbol during time.

Pass when specifying sample (such as, the first time domain samples of the first data sample of each superframe) Time defeated, moment TOD can be obtained according to the clock being retained in CO side by CO.When specifying sample Arrive the output of the inverse discrete Fourier transformer inverse-discrete (IDFT) of CO or arrive the U-O reference of CO side During point, TOD value can be obtained.If TOD value is to obtain when concrete sample arrives U-O reference point Take, then propagation delay L-Delay of link can be the propagation delay of twisted-pair feeder, i.e. from U-O Reference point is to the propagation delay of U-R reference point.To specify sample may be CO and CPE it is known that because of This, can not be sent to CPE from CO for obtaining the sample for reference index of TOD value.CO is permissible Via EOC message or OH frame, TOD value is sent to CPE.Or, it is sent to the TOD of CPE Value can be relative value.TOD value may indicate that reference signal and CO transmission specify sample moment it Between time difference.Described reference signal can be the pulse the most recently of PPS signal, or NTR The pulse the most recently of signal.Or, one fixed value of die sinking when TOD value can be registered as.As Upper described, the described moment can be obtained.Described fixed value can be about 125 microseconds, or 125 is micro- The multiple of second.

Fig. 8 shows the embodiment producing 800 by the frequency of TOD value/time synchronized, institute Stating that frequency/time synchronized produces can be at client node, such as, and enforcement CPE at.By TOD value Frequency/time synchronized produces 800 can receive identical sample for reference (that is, CO acquisition at CPE The sample for reference of TOD value) time obtain TOD ' value, pass through received TOD value and the biography of link Broadcasting delay L-Delay to calculate the moment, and the frequency/time of the clock being retained CPE is carried out Adjust.The adjusted clock in CPE side can be retained in the clock frequency/time synchronized of CO side, from And make the adjusted clock in CPE side can be with network clock frequency/time synchronized.TOD value can be as Obtain as shown in Figure 7.TOD ' value can be used position similar when obtaining with CO by CPE Obtain, i.e. the input of discrete Fourier transform (DFT) (DFT) that arrives when same reference sample or arrive Obtain when reaching the U-R reference point of CPE side.If TOD value and TOD ' value are at u reference point Obtain, then the propagation delay of link is to the propagation delay of U-R reference point from U-O reference point. Produce 800 by the frequency of TOD value/time synchronized and can calculate the moment by TOD value and propagation delay TIME, is adjusted to TOD+L-Delay by the clock at CPE from TOD ' subsequently, so that CPE Clock frequency/time synchronized at the clock at place and CO.The recovery exported from adjusted clock PPS ' signal can be input to the PPS signal of access node, such as, the 1PPS letter shown in Fig. 1 Number frequency/time synchronized.

Fig. 9 shows the embodiment producing 900 by the Frequency Synchronization of relative TOD value, institute Stating Frequency Synchronization generation can be at client node, such as, implements at CPE.By relative TOD value Frequency/time synchronized generation 900 can obtain CPE and receive (that is, the CO acquisition of same reference sample The sample for reference of TOD value) moment, and the described moment is replaced by relative value TOD ', such as figure Shown in 7.With the frequency of relative TOD value/time synchronized produce 900 can calculate relative TOD ' value and Offseting in generation during the preceding superframe cycle to current super frame cycle between TOD Change, adjusts the clock frequency of CPE side with the change offset subsequently so that in CPE time Clock can be with the clock rate synchronization in CO.If obtained when CO transmits sample for reference Received by CPE, then producing 900 by the Frequency Synchronization of relative TOD value can will retain further Clock at CPE be adjusted to CO at clock time/Frequency Synchronization.Clock can export extensive Multiple PPS ' signal, the PPS signal time/frequency being allowed to being input to DSL system from network clocking Synchronize.

Figure 10 shows an embodiment of symbols at error 1000 (Δ sym-align), described Symbols at error may be at client node, such as, occurs at CPE.Symbols at error 1000 May occur in a case where: Discrete Multitone (DMT) symbol or frame are using DMT modulation DSL system is transmitted, described DSL system such as ADSL, ADSL2, ADSL2+, and VDSL2 system.DSL receptor at CPE can detect the border of DMT frame, and implements Symbol Timing or symbols at algorithm, with by the symbol sebolic addressing received start locking.Due to sampling Rate is limited, and therefore, except trueness error, symbols at algorithm is also possible to introduce other error.Gained Symbols at error 1000 (Δ sym-align) may affect clock synchronize accuracy.Such as figure Shown in 10, CO emitter can be with transmission symbol sequence, and described symbol sebolic addressing is with referred to as SINDEX0 The first sign-on.When CPE receives symbol sebolic addressing, CPE can be by after SINDEX0 Be referred to as SINDEXi another symbol rather than SINDEX0 is locked as the first symbol in this sequence. Difference between SINDEXi and SINDEX0 can correspond to Δ sym-align, and be probably by The accuracy error of the symbols at algorithm implemented and/or trueness error cause, because sample rate has Limit.

In a scheme of elimination or minimizing Δ sym-align, emitter (such as, is positioned at CO Place) local zone time can be recorded when starting to transmit symbol or symbol sebolic addressing.About simultaneously, emitter Special or predetermined sinusoidal signal can also be transmitted.Sinusoidal signal and other possible modulated sinusoidal letters Number can form sign pulse signal.Relative to the beginning of symbol, sinusoidal signal can have appointment or Predetermined phase offset.Such as, phase offset is equally likely to about zero degree (0 °).In receptor side's (example As, CPE) place, the starting point of symbol can determine in initialization procedure with symbolization alignment algorithm, And got off by stamp the actual time of correspondence.As it has been described above, this time stamp there may be symbol pair Quasi-error.Hence, it can be determined that away from time stamp point closest to the phase point of about 0 ° in special sinusoidal signal. 0 ° of skew between phase point and the starting point of symbol so can be provided.Described skew can be used to correct Receptor time stamp.If described skew is less than a circle (such as, 360 °) of sinusoidal signal, that Symbols at error may be easy to correction.Fast fourier transform (FFT) or relevant can be used Algorithm finds 0 ° of phase point.Owing to sample rate is limited, therefore, 0 ° of phase point is not likely to be buffer (buffer) real point in, but may be between two neighbor points in buffer.But, this can To use FFT or other related algorithms to solve.

For actual DSL system, the above-mentioned method for stamp correction time implements not Certain effective and/or possible relatively difficult.In the DSL system using multiple-frequency signal, in view of system Condition, can carry out some according to existing noise level and simplify.Such as, comprise analog circuit and In the actual channel of copper cash, phase response is generally linear in the certain limit of passband, such as, Wherein multiple-frequency signal is likely to be of the most identical group delay.Therefore, some or all in frequency range Signal can be used to obtain the delay skew caused by symbols at error.In initialization procedure, can To implement frequency domain equalizer (FEQ) algorithm, in order to providing may be by symbols at error and non-linear The phase-shift information that frequency response causes.If selected for frequency range, wherein a frequency response It is linear for being close to, and such as, the signal in this frequency range has the most identical group delay, then letter Number group can be used to reduce the influence of noise caused because of Radio frequency interference (RFI) etc..May determine that signal The FEQ coefficient of group, and mathematical method can be used to calculate best straight line, such as, use minimum Quadratic method calculates, in order to close or coupling FEQ coefficient group.The slope of straight line can represent symbol Number alignment error.If symbols at error is substantially zero or can ignore, then slope is permissible Approximate zero.

Figure 11 shows an embodiment of symbols at error estimation 1100, described symbols at Error can be implemented by client node or CPE.Symbols at error estimation 1100 can use tone Group corrects the time stamp error caused by symbols at error.Function (tone) is FEQ The phase place of coefficient.Group's tone between tone 1 and tone 2 is substantially to have linear phase to change response Frequency range, described response can be equal to identical time delay.Frequency range can be arranged on greatly Away from the distance of channel median filter halt on body.Sub-curve chart (a) in Figure 11 shows The FEQ phase response of selected frequency range, sub-curve chart (b) shows in sub-curve chart (a) The linear fit curve of FEQ phase response, and sub-curve chart c shows in sub-curve chart (b) Linear fit slope of a curve.Sub-curve chart (d) shows the symbol obtained from sub-curve chart (c) Number alignment error, as shown in corresponding arrow line.Symbols at error estimation 1100 can be with use value Δ T (obtaining in sub-curve chart (c)), with stamp parameter Ts1 correction time, or another time stamp Parameter Tm2, as described further below.Delay1 represent at CPE 1230 receive symbol with from CPE 1230 transmits the process time delay between symbol, as shown in figure 12.Delay2 represents Receive symbol at CO 1210 and transmit the process time delay between symbol, such as Figure 12 from CO 1210 Shown in.

Figure 12 and Figure 13 shows that twisted-pair feeder propagation delay estimates an embodiment of 1200, institute State propagation delay to estimate to implement at CO and/or CPE.Figure 12 show CO 1210 with The delay composition of the DSL link between CPE 1230.Parameter, Δ t1 and Δ t1 ' represents CO number respectively Word processing or propagation time delay and CPE digital processing or receive time delay.These parameters be with Device-dependent preset parameter in CO 1210 and CPE 1230.Value can be obtained by test, Save as fixing systematic parameter subsequently.Parameter, Δ t2 and Δ t2 ' represents that CO transmits the analog circuit time Postpone and CPE receives analog circuit time delay.Parameter, Δ t2 and Δ t2 ' can be relatively fixed, and Can be obtained by simulation.These parameters can also be tested, such as, in the system in combination stage Period or tested before system deployment.Parameter, Δ t3 represents the downstream signal by copper cash Postpone.Owing to the length of copper cash can change, therefore, by standard in hundreds of rice to several kms Or current measuring technology possibly cannot highly precisely estimate signal time and postpone Δ t3.

Parameter, Δ t4 and Δ t4 ' represents CO digital processing respectively or receives time delay and CPE numeral Process or propagation time delay.These parameters are relevant to the equipment in CO 1210 and CPE 1230 Preset parameter.Value can be obtained by test, saves as fixing systematic parameter subsequently.Parameter Δ t5 and Δ t5 ' represents that CO receives analog circuit time delay and CPE transmits the analog circuit time respectively Postpone.Parameter, Δ t5 and Δ t5 ' can be relatively fixed, and can be obtained by simulation.These parameters Can also test, such as, survey during the system in combination stage or before system deployment Examination.Parameter, Δ t6 represents the time delay of the upward signal by copper cash.Owing to the length of copper cash is permissible Change in hundreds of rice to several kms, therefore, cannot by standard or current measuring technology possibly Highly precisely estimate signal time and postpone Δ t6.

As shown in figure 13, at based on time stamp Tm1 and CPE 1230 at CO 1210 Time stamp Ts1, can obtain the skew on down direction between CO 1210 and CPE 1230. Specifically, CO 1210 side, when transmitting first sample of symbol of time domain data, can touch Send out CO real-time clock 1326, to read actual time, it is simple to transmit described symbol.Described symbol can To be transmitted by following item: digital processing element 1326, digital-to-analogue (D/A) transducer 1314, CO analogue transmission circuit 1316, and it is couple to the CO hybrid circuit 1318 of copper stranded conductor.Therefore, Corresponding time stamp Tm1 ' can store in memory.Value Tm1 ' can be corrected into Tm1, Method is for prolonging plus CO digital processing or propagation time delay Δ t1 and CO transmission analog circuit time Δ t2 late, so that Tm1=Tm1 '+Δ t1+ Δ t2.

In CPE1230 side, when receive symbol the first sample time, can trigger CPE real-time time Clock 1338, to read the actual time receiving described symbol.Described symbol can be carried out by following item Receive: be couple to the CPE hybrid circuit 1346 of copper stranded conductor, CPE simulation receives circuit 1332, mould Number (A/D) transducer 1334, and digital processing element 1336.Therefore, corresponding time stamp Ts1 " can store in memory.The position of the first sample of the symbol received can be by symbol pair Quasi-function determines, and symbols at error can proceeded as above correct.Therefore, Ts1 is " permissible Being corrected into Ts1 ', and Ts1 ' can be corrected into Ts1, method receives simulation electricity for deducting CPE Road time delay Δ t2 ' and CPE digital processing or reception time delay Δ t1 ', so that Ts1=Ts1 ' -Δt1′Δt2′.Therefore, it can obtain the total drift on down direction, as follows:

Skew=Ts1-Tm1-Delay1.(3)

Based on another timestamp at the second time stamp Tm2 and CPE 1230 at CO1210 Note Ts2, can obtain the skew on up direction between CPE 1230 and CO 1210.Concrete and Speech, CPE 1230 side, when the first sample of the symbol of time domain data returns, can trigger CPE Real-time clock 1338, to read the actual time transmitting described symbol.Described symbol can be by following Item is transmitted: digital processing element 1340, D/A converter 1342, CPE analogue transmission circuit 1344, and CPE hybrid circuit 1346.Therefore, corresponding time stamp Ts2 ' can be stored in In memorizer.Value Ts2 ' can be corrected into Ts2, when method is plus CPE digital processing or transmission Between postpone Δ t4 ' and CPE and transmit analog circuit time delay Δ t5 ', so that Ts2=Ts2 '+Δ t4 ' +Δt5′。

CO 1210 side, when receiving the first sample of symbol, CO real-time clock can be triggered 1326, to read actual time, it is simple to receive described symbol.Described symbol can be entered by following item Row receives: CO hybrid circuit 1318, CO simulation receives circuit 1320, A/D converter 1322, And digital processing element 1324.Therefore, corresponding time stamp Tm2 " can be stored in memorizer In.The position of the first sample of the symbol received can be determined by symbols at function, and symbol Alignment error can proceeded as above correct.Therefore, Tm2 " Tm2 ' can be corrected into, and Tm2 ' can be corrected into Tm2, method for deduct CO receive analog circuit time delay Δ t5 and CO digital processing or reception time delay Δ t4, so that Tm2=Tm2 '-Δ t4-Δ t5.Therefore, The total drift on up direction can be obtained, as follows:

Skew=Ts2-Tm2-Delay2.(4)

In the case of Δ t3=Delay1=Delay2=Δ t6, CPE real-time clock can be obtained Skew between time and CO real-time clock time and time delay are as follows:

Skew=((Ts2+Ts1)-(Tm2+Tm1))/2, and

Delay=((Ts1-Ts2)-(Tm1-Tm2))/2.

Above-mentioned deviant can be used to CPE real-time clock is corrected into CO real-time clock.The above-mentioned time Postpone to comprise Δ t1, Δ t1 ', Δ t4 and Δ t4 ', normal digital logic circuit delays, example can be counted As, memorizer write latency or buffer read and postpone.For being transferred to CPE 1230 from CO 1210 Sample for reference point be likely to be of cost time or link delay, as follows:

L-Delay=Δ t1+ Δ t2+ delay+Δ t1 '+Δ t2 '.

Above-mentioned length of delay, and therefore L-Delay value can illustrate CPE real-time clock 1338 and CO The reason of timing slip is produced between real-time clock 1326.

Figure 14 shows that analog circuit postpones an embodiment of 1400, and described analog circuit postpones Can be used to estimate the above-mentioned Δ t2 at CO or CO emitter and the value of Δ t5.CO or CO launches Device can include D/A converter 1402, analogue filter circuit 1404, hybrid circuit and transformator 1406, Second analogue filter circuit 1408, and A/D converter 1410, they can enter as shown in figure 14 Row is arranged.Δ t2 represents the point " a " of the output of D/A converter 1402 and is couple to CO's Delay between the point " b " of the beginning of copper stranded conductor or wire.Δ t5 represents the beginning of copper stranded conductor Delay between the point " d " of the input end of point " c " and the second analogue filter circuit 1408.Meter Calculating will be in view of the circuit between 2 a and b and between 2 c and d when postponing.Can use Δ t2 and Δ t5 is estimated in the software simulations such as PS PICE simulation or MATLAB simulation.PSPICE or Circuit model in MATLAB can be designed according to the circuit in CO emitter, different chips The circuit of group supplier may be different.

In PSPICE simulates, such as, at the upstream frequency model of the signal transmitted by copper stranded conductor In enclosing, different frequency signals can have different length of delays.It is thereby possible to select postpone about The particular range of identical frequency signal.According to Information Mobile Service time synchronized requirement, can permit selected There is between different frequency in frequency range the difference of about 0.5 microsecond.Received by copper stranded conductor In the range of the downstream frequency of signal, delay variance can be selected to be less than about the widest of 0.5 microsecond Frequency range.In PSPICE or MATLAB simulates, GROUP DELAY can be used Algorithm obtains the delay of analog circuit.

Figure 15 shows an embodiment of digital delay circuit 1500, described digital delay circuit The data transmission time of occurrence at CO or access node may be caused to postpone.Digital delay circuit 1500 Can correspond to above-mentioned value Δ t1, and buffer delay 1502, high bandpass filter can be included (HDF) postpone 1504, and interpolater postpones 1506.Timing may be it is also contemplated that when calculating Δ t1 Logic and combinational logic circuit postpone (not shown).Such as, in digital processing element 1312, from The data of CO transmission may stand digital delay circuit 1500 (or length of delay of Δ t1).Subsequently, Such as, in D/A converter 1314, described data may postpone 1508 by experience D/A.Hardware sets Meter person can provide Δ t1 and/or the value of digital delay circuit 1500 or estimated value.

Above-mentioned HPF delay 1504 and interpolater postpone 1506 and can ring by finite impulse based on CO Answer the design architecture of (FIR) wave filter.Figure 16 shows the estimation 1600 of FIR digital delay circuit, Described estimation can use Finite Impulse Response filter delay algorithm to implement at access node or CO, with Estimate transmission delay Δ t1 and illustrate that HPF delay 1504 and interpolater postpone the reason of 1506. This Delay computing algorithm can be adapted certainly or based on ' group delay ' algorithm, such as, uses PSPICE Or MATLAB has simulated.The estimation 1600 of FIR digital delay circuit potentially includes with above-mentioned The similar step of symbols at error estimation 1100.

The estimation 1600 of FIR digital delay circuit can use tone group to correct by CO and CPE Between the time stamp error that causes of transmission delay.Function (tone) is HPF and/or interpolation The phase function of device coefficient, shown in sub-curve chart (a).Due to system exists noise and/or Other nonlinear source, therefore, phase function or curve may not be linear.Sub-curve chart (b) Show the linear fit curve of phase curve in sub-curve chart (a).Sub-curve chart c shows Linear fit slope of a curve in sub-curve chart (b).Sub-curve chart (d) shows according to son bent The HPF/ interpolator time that slope in line chart (c) obtains postpones, as shown in corresponding arrow line. Transmission delay estimates that 1600 can be used to obtain HPF digital filter and interpolater (being positioned at CO) Digital signal processing circuit postpone Δ t.The estimation 1600 of FIR digital delay circuit can also illustrate Any timing logic and combinational logic circuit postpone the reason of (being positioned at CO).

Figure 17 shows an embodiment of correct time distribution method 1700, and described method can Implemented by CO and CPE.Correct time distribution method 1700 can based on IEEE1588 method, And microsecond or submicrosecond level accuracy and precision can be provided.Described method can based on CO with Between CPE, such as, the exchange between clock at the master clock 1702 and CPE at CO is many Individual time stamp.Described time stamp can be used for calculating CO and CPE by CO and/or CPE subsequently Between clock timing offset error, and the transmission between CO and CPE or link delay.

Originally, can be by the very first time at the time Tm1, CO shown by master clock 1702 Stamp Tm1 is sent to CPE, and described very first time stamp can arrive CPE at time Ts1. Very first time stamp value Tm1 can be sent to CPE in synchronization message by CO.Very first time stamp Can arrive after first or the forward delay Delay1 that clock 1704 time Ts0 is counted CPE, the described phase Tm1 in the same time corresponding to master clock 1702 from clock time.Due to from clock Do not mate or misalignment between 1704 with master clock 1702, therefore, for the most in the same time, from Clock 1704 time Ts0 and may be not equal to or mates master clock 1702 time Tm1.Ts0 and Tm1 Between difference be properly termed as (between two clock timings) skew, and between Ts1 and Ts0 Difference may approximate Delay1.Therefore, described skew can be estimated as Ts1-Tm1- Delay1.Tm1 can be resend to CPE in follow-up (Follow-Up) message by CO.

It follows that by the time Ts2, CPE shown from clock 1704 can by second time Between stamp Ts2 be sent to CO, described second time stamp can arrive CO at time Tm2. CPE can send the second timestamp values Ts2 in postponing request (Delay-Req) message.Second Second or the revertive delay that time stamp can be counted master clock 1702 time (not shown) Arriving CO after Delay2, described master clock time is corresponding to from the phase Ts2 in the same time of clock 1404. Difference between master clock 1702 time and value Ts2 sending the second time stamp can be (two Between individual clock) same offset, and Tm2 and the master clock for sending the second time stamp Difference between 1702 times may approximate Delay2.Therefore, described skew can also be estimated Become Ts2-Tm2-Delay2.In the case of Delay1 and Delay2 is substantially equal, such as, Based on forward between CO and CPE and reversely the asymmetrical delay on (or uplink and downlink) direction it is assumed that Above-mentioned two equatioies for estimating skew can be simplified.In such a case, it is possible to obtain Skew, i.e. approximate the half of (Ts2+TS1)-(Tm2+Tm1).The list of symmetry can also be obtained To delay, i.e. approximate the half of (Ts1-TS2)-(Tm1-Tm2).

Figure 18 shows an embodiment of correct time distribution method 1800, and described method can To implement at client node or CPE.Correct time distribution method 1800 can be at block 1802 Place starts, and wherein can receive TOD and SNUM information.TOD and SNUM information can be from The access node or the CO that are couple to CPE send, and such as, are transmitted by EOC channel.TOD The PPS value at CO or signal is can correspond to SNUM information.TOD may indicate that for touching Send out the moment of the SNUM value relevant to the PPS value at CO or pulse.Such as, occur at CO When representing the PPS signal pulse of whole second event (integer second event), CO can record letter Number sample index value, such as, the SNUM value at time TOD.

At block 1804, TOD ' value can be obtained.Use at CPE the TOD that received and SNUM information and by considering (by EOC channel) transmission or link delay, Ke Yiji Calculate TOD ' value.Link delay can be considered during permission calculates and there is enough error margins. At block 1806, it is possible to use TOD, SNUM and TOD ' value and other errors or delay parameter Calculate SNUM ' value, as mentioned above.It is, for example possible to use equation (1) estimates SNUM ' Value.At block 1808, after obtaining SNUM ' value, PPS ' signal pulse can be produced.PPS signal arteries and veins Punching can produce at time TOD ' place.The above-mentioned steps of correct time distribution method 1800 can weigh Multiple execution, in order to after being worth the multiple follow-up SNUM ' values of acquisition by the TOD ' of multiple correspondences, produce Multiple follow-up PPS signal pulses.Such as, after each predetermined time interval, such as, the most each Second, can produce and transmit PPS signal pulse and corresponding temporal information (TOD ' at CPE continuously With SNUM ' information).

Figure 19 show an embodiment of emitter/receiver unit 1900, and described emitter/ Acceptor unit can be any device transmitting bag in a network.Such as, emitter/receiver unit 1900 may be located at CO or CPE.Emitter/receiver unit 1900 may include that one or many Individual inbound port or unit 1910, for receiving bag, object or TLV from other network componentses；Logic electricity Road 1920, is used for determining to send a packet to which network components；And one or more go out port or list Unit 1930, is used for transferring a frame to other network componentses.

Above-mentioned network components can be implemented in any general-purpose network component, such as computer or specific Network components, it has enough disposal ability, storage resource and network throughput capability to process on it Necessary workload.Figure 20 shows typical general-purpose network component 2000, and it is applicable to implement this The one or more embodiment of the parts disclosed in text.Network components 2000 comprises processor 2002 (being properly termed as central processor unit or CPU), described processor and the storage device comprising following item Communication: additional storage 2004, read only memory (ROM) 2006, random access memory (RAM) 2008, input/output (I/O) device 2010, and network connection device 2012.Processor 2002 Can implement as one or more cpu chips, or can be one or more special integrated electricity The part on road (ASIC).

Additional storage 2004 generally includes one or more disc driver or tape drive, And for data are carried out non-volatile memories, and if the off-capacity of RAM 2008 is with storage All working data, described additional storage is then used as overflow data storage device.Additional storage 2004 may be used for storage program, and when selecting to perform these programs, described program will be loaded into RAM In 2008.The instruction that ROM 2006 reads during being stored in execution program, thereby increases and it is possible to storage institute The data read.ROM 2006 is Nonvolatile memory devices, and its memory capacity is deposited relative to auxiliary For the relatively large storage capacity of reservoir 2004 generally the least.RAM2008 is used for storing volatibility number According to, it is also possible to it is used for storing instruction.Access ROM 2006 and RAM 2008 generally ratio and access auxiliary Memorizer 2004 wants fast.

At least one embodiment disclosed herein, and those of ordinary skill in the field are to described enforcement Change that the feature of example and/or described embodiment is made, combine and/or revise within the scope of the invention. The alternate embodiment obtained because combining, merge and/or omit the feature of described embodiment is also at this In bright scope.In the case of clearly stating numerical range or limiting, this type of expresses scope or restriction Should be understood to comprise to fall the iteration ranges in the scope clearly stated or restriction with formed objects Or limit and (such as, comprise 2,3,4 etc. from about 1 to about 10；Comprise 0.11 more than 0.10, 0.12,0.13 etc.).Such as, as long as disclosing and there is lower limit R_lWith upper limit R_uNumerical range, then special Any numeral in the range of described in Jie Shi not falling into.Specifically, disclose especially described in the range of with Lower numeral: R=R_l+k*(R_u-R_l), wherein k is to be incremented by with 1% in the range of 1% to 100% Variable, i.e. k is 1%, 2%, 3%, 4%, 7% ..., 70%, 71%, 72% ..., 97%, 96%, 97%, 98%, 99% or 100%.Additionally, disclose by as determined above the most especially Any numerical range that two R numerals of justice define.Art is used relative to any element of claim Language " optionally " is intended to described element, or is not required to described element, and both substitutes Scheme is all in the range of described claim.Should will use " including ", " comprising " and " having " The term bigger etc. scope be interpreted as support " by ... composition ", " substantially by ... composition " and The narrower terms of scope such as " generally by ... composition ".Therefore, protection domain is not by mentioned above Description limit, but be defined by the following claims, described scope comprises appended claims All equivalents of subject matter.Each and every claim is incorporated to explanation as further disclosure In book, and claims are embodiments of the invention.In the present invention to the discussion of reference it is not an admission that It is that prior art, especially publication date are after the earlier application priority date of subject application Any reference.The disclosure of all patents, patent application case and publication cited in the present invention In being expressly incorporated herein this in the way of introducing, its provide supplement the exemplary, procedural of the present invention or other Details.

Although the present invention has been provided that some embodiments, it should be appreciated that in the essence without departing from the present invention In the case of god or scope, disclosed system and method can come real by other concrete forms many Execute.The example of the present invention should be considered illustrative and not restrictive, and the present invention is not limited to herein Details given by Ben.Such as, various elements or parts can combine in another system or merge, Or some feature can be omitted or do not implement.

Additionally, without departing from the scope of the invention, described in various embodiments and explanation Can be with other system, module, technology for discrete or single technology, system, subsystem and method Or method is combined or merges.Show or be discussed as being coupled to each other or directly couple or communicate other Can also use electrically, mechanical system or other modes be by some interfaces, device or centre Parts indirectly couple or communicate.Other change, substituting and change example can be by the skill of art Art personnel determine, and can make in the case of without departing from the spirit and scope disclosed in Ben Wenben Go out.

Claims (13)

1. a system for clock rate synchronization, comprising:

Clock in access node, is used for providing Time of Day (TOD) value, described TOD value to show It is transferred to the moment of the reference point of the signal described access node of arrival of client node；And

Emitter, is used for obtaining relative TOD value, and described relative TOD value is passed by channel It is passed to described client node, in order to make the clock in described client node and the institute in described access node State clock rate synchronization；

Wherein said access node is positioned at Digital Subscriber Line (DSL) central office (CO), wherein said Client node is the customer rs premise equipment (CPE) being couple to described CO by copper stranded conductor,

Described clock in wherein said access node is come and net by NTR signal or Time of Day signal Network clock synchronizes,

Wherein said signal is the first time domain samples of the first data symbol in super frame period,

Wherein said reference point is U-O reference point or the output of IDFT of described access node,

Wherein said relative TOD value is that the described signal being transferred to described client node arrives access joint The value that during the described reference point of some side described, die sinking fixed value obtains, and

Wherein said channel is embedded operation channel (EOC) or expense (OH) frame；It enters one Step includes:

Clock in described client node, for arriving institute at the identical signal using described TOD value Time of Day (TOD') value is provided when stating the reference point of client node；And

Receptor, is used for obtaining relative TOD' value, and by described relative TOD' value with from described The described relative TOD value of transmitter receipt adjusts the described clock in described client node, in order to With the described clock rate synchronization in described access node,

Wherein said reference point is U-R reference point or the input of DFT of described client node,

Wherein said relative TOD' value is that the identical signal using described TOD value arrives client node side The value that obtains of the time die sinking fixed value of described reference point,

Wherein by described relative TOD' value and the described relative TOD value received from described access node The step adjusting the described clock in described client node includes estimating described relative TOD value and institute The skew stated between TOD' value was sent out during the current super frame cycle to preceding superframe cycle Raw change, and the described clock in described client node is adjusted by the change of described skew.

System the most according to claim 1, wherein said receptor uses described access further Described clock in node receives TOD value, and described TOD value is for be transferred to described client node Described signal arrives the described moment of the reference point of described access node side；Use in described client node Described clock obtain TOD' value, described TOD' value for use described TOD value described identical Signal arrives the described moment of the reference point of described client node side；Use described TOD value and link Propagation delay L-Delay estimate moment TIME；By the described clock at described client node from Described TOD' value is adjusted to described TIME, in order to same with the described clock time at described access node Step,

The described reference point of wherein said access node side is the described U-O reference of described access node Point or the described output of described IDFT, the described reference point of wherein said client node side is described visitor The described U-R reference point of family node or the described input of described DFT.

3. a method for access network signal processing, comprising:

Client node obtains relative TOD' value；And

Described visitor is adjusted with the relative TOD value received from access node by described relative TOD' value Clock in the node of family, in order to the described clock rate synchronization at described access node, wherein said Time of Day (TOD) value relatively is after described access node uses the clock in described access node to obtain It is sent to described client node by channel；

Wherein said relative TOD' value is to use the identical signal of described relative TOD value to arrive client's joint The value that the moment of the reference point of some side obtains with fixed value for mould, and

Wherein by described relative TOD' value and the described relative TOD value received from described access node The step adjusting the described clock in described client node includes estimating described relative TOD value and institute The skew stated between TOD' value was sent out during the current super frame cycle to preceding superframe cycle Raw change, and the described clock in described client node is adjusted by the change of described skew.

Method the most according to claim 3, wherein said access node is positioned at Digital Subscriber Line (DSL) central office (CO), wherein said client node is that the customer rs premise being couple to described CO sets Standby (CPE).

Method the most according to claim 3, wherein said relative TOD value is for being transferred to described visitor The value that the time die sinking fixed value of the reference point that the signal of family node arrives access node side obtains,

Wherein said signal is the first time domain samples of the first data symbol in super frame period,

Wherein said reference point is U-O reference point or the output of IDFT of described access node, and

Wherein said fixed value is 125 microseconds, or the multiple of 125 microseconds.

Method the most according to claim 3, the described clock in wherein said access node passes through NTR signal or Time of Day signal come Tong Bu with network clocking, and

Wherein said channel is embedded operation channel (EOC) or expense (OH) frame.

Method the most according to claim 3, the described reference point of wherein said client node side is The U-R reference point of described client node or the input of DFT, and

Wherein said fixed value is 125 microseconds, or the multiple of 125 microseconds.

Method the most according to claim 3, it farther includes:

Using the described clock in described access node to receive TOD value, described TOD value is transmission When arriving described reference point described of described access node side to the described signal of described client node Carve；

Using the described clock in described client node to obtain TOD' value, described TOD' value is for using The described identical signal of described TOD value arrives the described moment of the reference point of described client node side；

Use propagation delay L-Delay of described TOD value and link to estimate moment TIME；And

Described clock at described client node is adjusted to described TIME from described TOD' value, in order to With the described synchronizing clock time at described access node,

The U-O reference point that described reference point is described access node of wherein said access node side or The output of IDFT, and

The U-R reference point that described reference point is described client node of wherein said client node side or The input of DFT.

9. a method for access network signal processing, comprising:

Receive Time of Day (TOD) value and corresponding sample index (SNUM) value；

The 2nd TOD is obtained based on described TOD value, described SNUM value and propagation delay (TOD') value；

The second sample rope is obtained based on described TOD value, described TOD' value and multiple transmission parameter Draw (SNUM') value；And

Use adjusted clock, produce pulse per second (PPS) based on described TOD' value and described SNUM' value (PPS') signal pulse；The multiple PPS' pulses wherein forming PPS signal are to adjust based on described Clock, use from multiple TOD and the SNUM values received subsequently acquisition multiple SNUM' With TOD' value produce, and wherein said PPS signal be used for make time synchronized by network node, Or distribute the time exactly.

Method the most according to claim 9, wherein said SNUM' value is estimated as follows:

SNUM+ (TOD'-TOD-L-Delay-Δ sym-align)/Ts,

Wherein L-Delay is because of the delay in analogy and digital circuit, clock timing skew and copper cash Postponing and cause the link delay in network node, Δ sym-align is because of sample rate finite sum symbol pair Quasi-Algorithm Error and the symbols at error that causes, and Ts is between continuous P PS signal pulse Time interval.

11. methods according to claim 10, wherein use TOD, SNUM, TOD', L-Delay, Δ sym-align and Ts estimate described SNUM', decrease because channel or propagation are prolonged Late, sample clock frequency deviation and symbols at error and cause time distribution degradation.

12. methods according to claim 10, wherein Ts1, Ts2, Tm1 and/or Tm2 are Using the tone group with linear phase transformation response to be corrected by deviant, mode is for for institute High bandpass filter (the HPF)/interpolater coefficient stating tone group obtains the Linear Quasi of phase response curve Close, calculate the slope of described linear fit, and calculate correction value delta T based on described slope so that Correction Δ sym-align.

13. 1 kinds for distributing to the system of receiver node in a network by the time；Described system bag Include:

Receiver node；And

Access node, it is couple to described receiver node, and for during by channel by relative day Between (TOD) value be sent to described receiver node,

Wherein said relative TOD value for make clock in client node with in described access node Clock rate synchronization；Described receiver node is client node；Wherein said client node obtains relatively TOD' value, and by described relative TOD' value and the described relative TOD received from described access node Value adjusts the described clock in described client node, in order to the described clock at described access node Frequency Synchronization,

Wherein said relative TOD' value is to use the identical signal of described relative TOD value to arrive client's joint The value that the time die sinking fixed value of the reference point of some side obtains, and

Wherein by described relative TOD' value and the described relative TOD value received from described access node The step adjusting the described clock in described client node includes estimating described relative TOD value and institute The skew stated between TOD' value was sent out during the current super frame cycle to preceding superframe cycle Raw change, and the described clock in described client node is adjusted by the change of described skew.