CN1505882A - Zipper DMT(discrete multi-tone) system and method for determining timing advance in the same system - Google Patents

Abstract

Disclosed is a method for determining a timing advance in a zipper DMT system. A remote transmitting/receiving unit receives a training start signal from an optical network unit's transmitting/receiving unit, and transmits a response signal by a first timing advance before the time when a sample interval of the received signal is finished. When receiving the response signal, the optical network unit's transmitting/receiving unit calculates a number of delayed samples between a transmitting signal interval and a receiving signal interval at the optical network unit's transmitting/receiving unit, determines a second timing advance considering the number of delayed samples and the first timing advance, and transmits the second timing advance to the remote transmitting/receiving unit. The remote transmitting/receiving unit transmits a response signal by a second timing advance before the time when the sample interval of the received signal is finished.

Description

Zipper DMT system and the method for utilizing this systematic survey timing advance

Technical field

The present invention relates to a kind of regularly (timing) leading method of in zipper DMT (discrete multitone) system, determining.

Background technology

Along with being provided by network, the demand of multimedia service increases sharply day by day, developed use traditional copper wire cable and provide xDSL (digital subscriber line) method of message transmission rate, so that satisfy these demands from hundreds of kbps to tens Mbps without amplifier or repeater.

The xDSL method has developed into HDSL (high data rate DSL), SDSL (single line HDSL), ADSL (Asymmetrical Digital Subscriber Line), UADSL (general ADSL) and has developed the VDSL (DSL of super high bit rate) that sends data in from 300 to 1500 meters short distance with high data rate.

The modulation and demodulation method that xDSL uses comprises CAP (carrierfree AM/PM) method and QAM (quadrature amplitude modulation) method that is SCM (single-carrier modulated) method, and is DMT (discrete multitone) method of MCM (multi-carrier modulation) method.

The DMT method is divided into a plurality of narrowband subchannels with whole transport tapes, and transmits them, and the transmission cycle with each subchannel has increased according to number of sub-channels thus, and comes compensate for channel distortions by simple single tap equalizers.Equally, by the DMT code element is increased as protection Cyclic Prefix at interval, this method has kept the orthogonality between the subchannel, and has eliminated inner symbol interference, therefore, provides simple equaliser structure at receiving unit.In addition, this method can use IFFT (oppositely rapid fourier change) and FFT (rapid fourier change) to realize High Speed Modulation and demodulation process.

The factor that causes the DMT system to reduce performance comprises near-end cross (crosstalk) signal and echo (echo) signal the biglyyest.When two different transmitters send data simultaneously, that is to say, when they send the data of same frequency band simultaneously in identical linker group (binder group), just produced near end crosstalk signals.When the transmitter at same section sent data, echo-signal was to influence the noise that signal receives.

Developed zipper DMT method and prevented near end crosstalk signals and echo-signal, except Cyclic Prefix, also increased cyclic suffix, used cyclic suffix then at the terminal tail of signal.For the interference that makes near end crosstalk signals and echo-signal reduces to minimum, must keep the orthogonality between each frequency.Therefore, in order to guarantee the orthogonality between each frequency, zipper DMT method increases cyclic suffix to source signal, like this, has only a code element of near end crosstalk signals and echo-signal can be included in the symbol interval of received signal of each network terminal.

In addition, the U2 interface of remote site Tx/Rx (transmitter and receiver) unit is with reference to the U2 interface in the zipper DMT method, utilize the degree of timing advance to send signal before the starting point of the symbol interval of received signal, ONU (optical network unit) Tx/Rx unit and remote site Tx/Rx unit can send signal simultaneously like this.Usually, the number of samples with cyclic suffix is provided with greatlyyer than the number of samples of the timing advance of eliminating the interference of near end crosstalk signals and echo-signal.

In the prior art, timing advance is to determine from the impulse response or the transfer function of channel.Therefore, need handle the impulse response of channel or the estimation of transfer function, so that similarity method is as described above determined timing advance.

Summary of the invention

An advantage of the invention is interface, utilize ONU Tx/Rx unit and remote site Tx/Rx unit to send simultaneously and received signal with reference to U2.

Another advantage of the present invention is to utilize the Cyclic Prefix with minimum length to eliminate near end crosstalk signals and echo-signal.

Another advantage of the present invention is to measure one group of channel latency and determine timing advance.

The present invention postpones by the measurement group and definite timing advance is realized above-mentioned advantage.

In one aspect of the invention, zipper DMT system comprises: ONU Tx/Rx unit, and it comprises: a Tx buffer is used for the sampling that temporary transient storage will send; The one Tx sample counter is used to show a Tx samples counter value, the position of the output sampling of a Tx buffer in this value indication code element; The first rx buffering device is used for the sampling that temporary transient storage receives; An and Rx sample counter, be used to show a Rx samples counter value, the position of the input sample of the first rx buffering device in this value indication code element, described ONU Tx/Rx unit, be used for extracting sampling from a Tx buffer according to a Tx samples counter value, send this sampling, and from the first rx buffering device, extract sampling and receive this sampling according to a Rx samples counter value; And remote site Tx/Rx unit, it comprises: the 2nd Tx buffer is used for the sampling that temporary transient storage will send; The 2nd Tx sample counter is used to show the 2nd Tx samples counter value, the position of the output sampling of the 2nd Tx buffer in this value indication code element; The second rx buffering device is used for the sampling that temporary transient storage receives; And the 2nd Rx sample counter, be used to show the 2nd Rx samples counter value, the position of the second rx buffering device input sample in this value indication code element, described remote site Tx/Rx unit, from the 2nd Tx buffer, extract sampling according to the 2nd Tx samples counter value, from the second rx buffering device, extract sampling according to the 2nd Rx samples counter value, with this sampling of reception, wherein remote site Tx/Rx revises the unit the 2nd Tx samples counter value, and working as the signals sampling that received finishes when the U2 interface of remote site Tx/Rx unit by first timing advance at interval, send signal in advance, and when receiving second timing advance from ONU Tx/Rx unit, when sampling interval of received signal finishes U2 interface in remote site Tx/Rx unit according to second timing advance, remote site Tx/Rx unit sends signal in advance, wherein ONU Tx/Rx unit calculates in the Tx sigtnal interval of the U2 interface of ONU Tx/Rx unit and the quantity of the delay sampling of Rx in the sigtnal interval, and considers that first timing advance and delay sampling determine second timing advance.

ONU Tx/Rx unit and remote site Tx/Rx unit upgrade Cyclic Prefix with (Cyclic Prefix+first timing advance-second timing advance), and upgrade cyclic suffix with (cyclic suffix-first timing advance+second timing advance).

In another aspect of the present invention, utilizing ONU Tx/Rx unit and remote site Tx/Rx unit to carry out in the zipper DMT system of exchanges data, determine the method for timing advance, comprise: (a) remote site Tx/Rx unit, receive the training commencing signal from ONU Tx/Rx unit, and the sampling interval of working as the sampling that is received finishes to send response signal in advance when the U2 interface of remote site Tx/Rx unit according to first timing advance; (b) ONU Tx/Rx unit receives described response signal, and calculates in the Tx sigtnal interval of ONUTx/Rx unit and the quantity of the delay sampling of Rx in the sigtnal interval; (c) consider the quantity and first timing advance of delay sampling, ONU Tx/Rx determines second timing advance in the unit; (d) second timing advance is sent to remote site Tx/Rx unit; And (e) when sampling interval of received signal finishes U2 interface in remote site Tx/Rx unit according to second timing advance, remote site Tx/Rx unit sends response signal in advance.

Described (e) comprises that usefulness (Cyclic Prefix+first timing advance-second timing advance) upgrades Cyclic Prefix, and upgrades cyclic suffix with (cyclic suffix-first timing advance+second timing advance).

Described (b) comprises by deducting from Tx sample count value that group from the transmitter end of ONU Tx/Rx unit to the U2 interface of ONU Tx/Rx unit postpones and group from ONU Tx/Rx unit receiver end to the U2 interface of ONUTx/Rx unit postpones, wherein send the position of sampling in the Tx sample count value representation code element, determine the quantity of delay sampling.

Described (c) comprise by $\mathrm{TA}=\frac{(\mathrm{<figure-callout\; id="0"\; label="T\; A"\; filenames="A0280925900141.png,A0280925900151.png"\; state="\{\{state\}\}">T</figure-callout>}{A}_{}{}_0+\mathrm{\&Delta;})\mathrm{mod}{N}_T}{2}$ Determine second timing advance, wherein TA is second timing advance, TA ₀Be first timing advance, Δ is the quantity of delay sampling, N _TBe that sampling length and mod are modular arithmetics.

Description of drawings

The part of specification is quoted and constituted to these accompanying drawings in specification, represented one embodiment of the present of invention, and in conjunction with these explanations, be used to explain principle of the present invention:

Fig. 1 shows the block diagram of zipper DMT Tx/Rx (send and the receive) system according to the preferred embodiments of the present invention;

Fig. 2 explicit declaration is according to the schematic diagram of the number of samples of the employed code element of zipper DMT Tx/Rx system of the preferred embodiments of the present invention; And

Fig. 3 (a) shows according to the preferred embodiments of the present invention to 3 (c), the timing schematic diagram of the method for measurement timing advance.

Embodiment

In the following detailed description, just from considering to finish the explanation of best way of the present invention, only represent and the preferred embodiments of the present invention have been described.As to recognize, do not deviating under the prerequisite of the present invention, can revise each conspicuous aspect of the present invention.Therefore, accompanying drawing and explanation will be thought schematic naturally, rather than restrictive.

Below with reference to accompanying drawing zipper DMT system that determines timing advance and the method for determining timing advance in this system are described.

The detailed description of O-SIGNATURE, R-MSG1, R-ACK, O-UPDATE and R-IDLE message be provided at T1E1.4 VDSL (be the VDSL metal interface, third part: in the proposed standard technical specification of multi-carrier modulation transceiver).

With reference to figure 1 and Fig. 2, will the zippe r DMT Tx/Rx system of foundation the preferred embodiments of the present invention be described.

Fig. 1 shows the block diagram of zipper DMT Tx/Rx (send and the receive) system according to the preferred embodiments of the present invention, and Fig. 2 shows the number of samples according to the employed code element of zipper DMT Tx/Rx system of the preferred embodiments of the present invention.

As shown in Figure 1, described zipper DMT Tx/Rx system comprises ONU Tx/Rx unit 100 and remote site Tx/Rx unit 200.Tx/ Rx unit 100 and 200, is connected with 500 with interface 400 respectively as UTP (unshielded twisted pair) cable by channel 300.

Tx/ Rx unit 100 and 200 converts digital signal the physical layer signal of U2 interface 400 and 500 to, perhaps converts physical layer signal to digital signal.Described Tx/ Rx unit 100 and 200 comprises transmitter 110 and 210, transmission buffer 120 and 220, transmission sample counter 130 and 230, receiver 140 and 240, reception buffer 150 and 250 respectively, receives sample counter 160 and 260, and AFE (AFE (analog front end)) 170 and 270.

Transmitter 110 and 210 comprises Tx front controller 111 and 211.Described Tx front controller 111 and 211 temporarily is stored in transmitter 110 and 210 data of carrying out IFFT in transmission buffer 120 and 220, and the counting of foundation transmission sample counter 130 and 230 extracts data from transmission buffer 120 and 220, and the data of being extracted are sent to AFE 170 and 270, and control sends the count value of sample counter 130 and 230.

Receiver 140 and 240 comprises Rx front controller 141 and 241.Described Rx front controller 141 and 241 will temporarily be stored in by the data that AFE 170 and 270 provides in reception buffer 150 and 250, and the counting of foundation reception sample counter 160 and 260 extracts data from reception buffer 150 and 250, and the data of being extracted are sent to the FFT unit (not shown) of receiver 140 and 240, and control receives the count value of sample counter 160 and 2 60.

AFE 170 and 270 will be converted to physical layer signal (being analog signal) by the digital signal that transmitter 110 and 210 provides, and respectively they are sent to remote site Tx/Rx unit 200 and ONU Tx/Rx unit 100 by U2 interface 400 and 500, and will convert digital signal to by U2 interface 400 and 500 physical layer signals that received from remote site Tx/Rx unit 200 and ONU Tx/Rx unit 100, so that they are sent to receiver 140 and 240.

As shown in Figure 2, the quantity when the code element sound is set to N _SCThe time, the code element of zipper DMT has L _CPCyclic prefix samples, 2 N _SCSampling and L _CSThe cyclic suffix sampling.Be the number of samples N of single code element _TProvide by equation 1.

Equation 1

N _T＝L _CP+2N _SC+L _CS

As the Tx sample count value OTxSampleCnt that sends sample counter 130 and 230 count values and RTxSampleCnt representative in code element inside, the position of transmission buffer 120 and 220 output sampling, scope from 0 to N _T-1.Position from the Tx sample count value OTxSampleCntAtU2 of U2 interface and RTxSampleCntAtU2 indication U2 interface 400 and 500 transmission sampling in this code element.Consider that the group that outputs to U2 interface 400 and 500 from transmission buffer 120 and 220 postpones Δ in sending sample count value OTxSampleCnt and RTxSampleCnt _OTXAnd Δ _RTX, they are illustrated in the equation 2.

Equation 2

OTxSampleCntAtU2＝OTxSampleCnt-Δ _OTX

RTxSampleCntAtU2＝RTxSampleCnt-Δ _RTX

By identical mode, represented the position of the input sample of reception buffer 150 in the code element and 250 as the Rx sample count value ORxSampleCnt of the count value that receives sample counter 160 and 260 and RRxSampleCnt, scope from 0 to N _T-1.The position of U2 interface 400 and 500 reception sampling in U2 interface 400 and 500 Rx sample count value ORxSampleCntAtU2 and code element of RRxSampleCntAtU2 indication.Consider that the group that is input to U2 interface 400 and 500 from reception buffer 120 and 220 postpones Δ in Rx sample count value ORxSampleCnt and RRxSampleCnt _ORXAnd Δ _RRX, they are illustrated in the equation 3.

Equation 3

ORxSampleCntAtU2＝ORxSampleCnt-Δ _ORX

RRxSampleCntAtU2＝RRxSampleCnt-Δ _RRX

In a word, need to carry out initialization step, so that in the above-mentioned zipper DMT system that mentions, transmit data.Initialization step comprises startup (shaking hands) step, training step and Multiple Channel Analysis and exchange step.Starting (or shaking hands) step is to be used to check whether transmitter and receiver are ready to send the step of signal.Training step is the step that is used to make symbol synchronization and training equalizer (equalizer).Multiple Channel Analysis and exchange step are the SNR (signal to noise ratio) that is used to measure each subchannel, produce the appropriate bit table with bit Load Signal, and allow to carry out between transmitter and receiver the step of various parameter exchanges.In training step, determined timing advance.

, will describe according to the method for the timing advance of the preferred embodiments of the present invention to 3 (c) with reference to figure 3 (a) determining.

Fig. 3 (a) shows according to the preferred embodiments of the present invention to 3 (c), the timing schematic diagram of the method for measurement timing advance.

After carrying out initialized training step, in step S301, ONU Tx/Rx unit 100 repeatedly sends O-SIGNATURE message to remote site Tx/Rx unit 200, till receiving R-MSG1 from remote site Tx/Rx unit 200.O-SIGNATURE message with the territory that comprises bandwidth, RFI bandwidth and PSD is used to be provided with the required default value of transfer of data.Among the step S302, symbol synchronization is finished in remote site Tx/Rx unit 200, and the beginning equalizer convergence.

In step S303, when having finished equalizer convergence, remote site Tx/Rx unit 200 receives O-SIGNATURE message, and when beginning to receive O-SIGNATURE, the Tx sample count RTxSampleCnt of Tx front controller 211 remote site Tx/Rx unit 200 is set to N _T-TA ₀+ Δ _RTX+ Δ _RRXIn this example, consider channel latency, the sample count RTxSampleCntAtU2 in the U2-R interface becomes N _T-TA ₀+ Δ RRX.

Then, in step S304, remote site Tx/Rx unit 200 repeatedly sends R-MSG1 to ONU Tx/Rx unit 100, wherein R-MSG1 is the affirmation message after remote site Tx/Rx has received O-SIGNATURE message, and when Tx sample count RTxSampleCnt became 0, it began to send identical message.When Tx sample count RTxSampl eCnt near Δ _RTXThe time, the sample count in the U2-R interface becomes 0, and promptly the U2-R interface begins to send R-MSG1.As a result, the U2-R interface is to have precedence over Rx message according to TA ₀Send Tx message in advance.

In step S305, when symbol synchronization had been finished in ONU Tx/Rx unit 100, equalizer began convergence, and the difference DELTA of number of samples is set to the OTxSampleCnt-Δ between Tx signal and the Rx signal in the U2-O interface _ORX-Δ _OTXWhen having finished equalizer convergence in step S 306, ONUTx/Rx unit 100 receives the R-MSG1 message, and in step S307, before finishing in the sampling interval of R-MSG1, sends O-UPDATE message.In this example, when ONU Tx/Rx unit 100 receives R-MSG1, and Tx sample count OTxSampleCnt becomes at 0 o'clock, and its sends O-UPDATE message.O-UPDATE message comprises the territory that is used for the leading correction value of recording timing, and ONU Tx/Rx unit 100 writes down the timing advance of having revised in this territory, and sends this territory.The described timing advance of having revised is provided by equation 4.

Equation 4

$\mathrm{TA}=\frac{({\mathrm{TA}}_0+\mathrm{\&Delta;})\mathrm{mod}{N}_T}{2}$

Wherein TA is the timing advance of having revised, TA ₀Be previous timing advance, N _TBe sampling length, and mod is modular arithmetic.

In step S308, remote site Tx/Rx unit 200 receives O-UPDATE message, and storage package is contained in the TA in the O-UPDATE message, and in step S309, when Tx sample count value RTxSampleCnt becomes 0, remote site Tx/Rx unit 200 sends R-ACK message to ONU Tx/Rx unit 100, wherein R-ACK message is the affirmation message after remote site Tx/Rx unit 200 has received O-UPDATE message, and repeat to send R-IDLE message in step S310, wherein R-IDLE message is the insignificant message after sending R-ACK message.

In step S311, after receiving R-IDLE message, Tx sample count OTxSampleCnt is N _TDuring-(TA-Δ), the controller Tx sample count OTxSampleCnt of ONU Tx/Rx unit 100 is set to 0, and new Cyclic Prefix and cyclic suffix are set to L _CP+ TA ₀-TA and L _CP-(TA ₀-TA), to send new message.In this example, when Tx sample count RTxSampleCnt was 0, Cyclic Prefix and cyclic suffix that the controller of remote site Tx/Rx unit 200 is new were set to L _CS+ TA ₀-TA and L _CS-(TA ₀-TA), to send new message.

ONU Tx/Rx unit 100 comes the quantity of computing relay sampling and new timing advance according to the mode similar to above-mentioned processing, and when new timing advance and previous timing advance not simultaneously, the repetition above-mentioned steps.

Therefore, the group by measured channel postpones just can determine timing advance, and utilizes difference between existing timing advance and the new timing advance just can reduce the length of cyclic suffix.Also have, by according to the above-mentioned method of mentioning timing advance being set, ONU Tx/Rx unit and remote site Tx/Rx unit can send and received signal simultaneously with reference to the U2 interface.

Though in conjunction with thinking that at present most realistic and preferred embodiment describes the present invention, but should be appreciated that the present invention is not limited to the disclosed embodiments, on the contrary, the present invention wishes to cover various modifications and the equivalent in the spirit and scope that are contained in the accessory claim book.

The application requires following priority: the korean patent application sequence number 2002-5704 in Korea S Department of Intellectual Property, the applying date: on January 31st, 2002, quote its disclosure as a reference.

Claims (7)

1. a zipper DMT (discrete multitone) system comprises:

ONU (optical network unit) Tx/Rx (send and receive) unit, comprising: a Tx buffer is used for the sampling that temporary transient storage will send; The one Tx sample counter is used to show a Tx samples counter value, the position of the output sampling of a Tx buffer in this value indication code element; The first rx buffering device is used for the sampling that temporary transient storage receives; With a Rx sample counter, be used to show a Rx samples counter value, the position of the input sample of the first rx buffering device in this value indication code element, described ONU Tx/Rx unit, be used for extracting sampling from a Tx buffer according to a Tx samples counter value, send this sampling, from the first rx buffering device, extract sampling and receive this sampling according to a Rx samples counter value; With

Remote site Tx/Rx unit comprises: the 2nd Tx buffer is used for the sampling that temporary transient storage will send; The 2nd Tx sample counter is used to show the 2nd Tx samples counter value, the position of the output sampling of the 2nd Tx buffer in this value indication code element; The second rx buffering device is used for the sampling that temporary transient storage is received; And the 2nd Rx sample counter, be used to show the 2nd Rx samples counter value, the position of the input sample of the second rx buffering device in this value indication code element, described remote site Tx/Rx unit, be used for extracting sampling from the 2nd Tx buffer according to the 2nd Tx samples counter value, from the second rx buffering device, extract sampling according to the 2nd Rx samples counter value, and receive this sampling

Wherein said remote site Tx/Rx revises the 2nd Tx samples counter value in the unit, and working as the signals sampling that received finishes when the U2 interface of described remote site Tx/Rx unit by first timing advance at interval, send signal in advance, and when receiving second timing advance from ONU Tx/Rx unit, when sampling interval of received signal finishes U2 interface in remote site Tx/Rx unit by second timing advance, remote site Tx/Rx unit sends signal in advance

Wherein said ONU Tx/Rx unit calculates in the Tx sigtnal interval of the U2 interface of ONU Tx/Rx unit and the quantity of the delay sampling of Rx in the sigtnal interval, and considers that first timing advance and delay sampling determine second timing advance.

2. according to the zipper DMT system of claim 1, wherein ONU Tx/Rx unit and remote site Tx/Rx unit upgrade Cyclic Prefix with (Cyclic Prefix+first timing advance-second timing advance), and upgrade cyclic suffix with (cyclic suffix-first timing advance+second timing advance).

3. according to the zipper DMT system of one of claim 1 and 2, wherein, remote site Tx/Rx unit is defined as second timing advance $\mathrm{TA}=\frac{({\mathrm{TA}}_0+\mathrm{\&Delta;})\mathrm{mod}{N}_T}{2},$ Wherein TA is second timing advance, TA ₀Be first timing advance, Δ is the quantity of delay sampling, N _TBe that sampling length and mod are modular arithmetics, and described ONU Tx/Rx unit is defined as the OTxSampleCnt-Δ with the quantity of delay sampling _ORX-Δ _OTX, wherein OTxSampleCnt is a Tx sample count value, Δ _OTXBe that group from the transmitter end of ONU Tx/Rx unit to the U2 interface of ONU Tx/Rx unit postpones, and Δ _ORXBe that group from the receiver end of ONU Tx/Rx unit to the U2 interface of ONU Tx/Rx unit postpones.

4. one kind is being undertaken determining the method for timing advance in zipper DMT (discrete multitone) system of exchanges data by ONU (optical network unit) Tx/Rx (send and receive) unit and remote site Tx/Rx unit, comprising:

(a) remote site Tx/Rx unit receives the training commencing signal from ONU Tx/Rx unit, and receives the sampling interval of sampling when pressing the U2 interface of first timing advance end in remote site Tx/Rx unit when institute, sends response signal in advance;

(b) described ONU Tx/Rx unit receives described response signal, and calculates in the Tx sigtnal interval of described ONU Tx/Rx unit and the quantity of the delay sampling of Rx in the sigtnal interval;

(c) described ONU Tx/Rx unit considers that the quantity of delay sampling and first timing advance determine second timing advance;

(d) second timing advance is sent to remote site Tx/Rx unit; And

(e) when sampling interval of received signal finished U2 interface in remote site Tx/Rx unit by second timing advance, remote site Tx/Rx unit sent response signal in advance.

5. according to the method for claim 4, wherein (e) comprises that usefulness (Cyclic Prefix+first timing advance-second timing advance) upgrades Cyclic Prefix, and upgrades cyclic suffix with (cyclic suffix-first timing advance+second timing advance).

6. according to the method for one of claim 4 and 5, wherein said (b) comprises by deducting from Tx sample count value that group from the transmitter end of ONU Tx/Rx unit to the U2 interface of ONU Tx/Rx unit postpones and group from ONU Tx/Rx unit receiver end to the U2 interface of ONU Tx/Rx unit postpones, wherein Tx sample count value is used for representing that code element sends the position of sampling, determines the quantity of delay sampling.

7. according to the method for one of claim 4 and 5, wherein (c) comprise by $\mathrm{TA}=\frac{({\mathrm{TA}}_0+\mathrm{\&Delta;})\mathrm{mod}{N}_T}{2}$ Determine second timing advance, wherein TA is second timing advance, TA ₀Be first timing advance, Δ is the quantity of delay sampling, N _TBe that sampling length and mod are modular arithmetics.

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