METHOD, DEVICE AND SYSTEM FOR DYNAMIC TIME SETTING

Description

TECHNICAL FIELD

[0001] This application relates to the field of network communications, and in particular, to a dynamic time assignment method, apparatus, and system.BACKGROUND

[0002] Fiber to the distribution point (FTTdp) is a network communication solution using hybrid optical fibers / copper wires. In an FTTdp access scenario, an operator network is connected to a distribution point (dp) by using an optical fiber. At the distribution point, one FTTdp central office (CO) equipment changes the optical fiber to a twisted pair, and then the FTTdp CO equipment is connected to FTTdp customer premise equipment (CPE) by using the twisted pair as a transmission medium.

[0003] A digital subscriber line (DSL) technology is used as a manner of data transmission between conventional FTTdp CO equipment and conventional FTTdp CPE. However, with development of copper broadband access technologies, the manner of data transmission between the FTTdp CO equipment and the FTTdp CPE has been updated to a next-generation broadband access technology Gfast. In the Gfast technology, a time division duplex (TDD) mode is used. To be specific, some symbols in a TDD frame are used as downstream symbols for downstream data transmission, and the other symbols are used as upstream symbols for upstream data transmission.

[0004] For the TDD mode, a dynamic time assignment (DTA) mechanism can allocate proper length of an upstream transmission duration or a downstream transmission duration (symbols used for upstream or downstream data transmission) based on an upstream traffic change or a downstream traffic change.

[0005] In a process of implementing this application, the inventor finds that the prior art has at least the following problem:

[0006] The FTTdp CO equipment simultaneously accesses a plurality of signals. For the plurality of signals accessed by the FTTdp CO equipment, during dynamic time assignment, lengths of an upstream transmission duration or a downstream transmission duration in a same FTTdp CO frame need to be configured for each signal, otherwise upstream and downstream time of different signals are asynchronous. Consequently, near-end crosstalk and unstable statuses such as a bit error and disconnection are caused, affecting normal signal transmission.

[0007] XP044263039, titled "Fast Access to Subscriber Terminals (Gfast) - Physical layer spectification; G9701 (2014) Amendment 3 (04 / 17)" discloses a method for dynamic time assignment (DTA), which is to dynamically set and update the sharing of the TDD frame between upstream and downstream, by changing the number of downstream symbol periods (Mds) of the TDD frame during showtime upon request by the DRA.SUMMARY

[0008] To overcome near-end crosstalk caused by asynchronous upstream and downstream time in a multi-port scenario of FTTdp CO equipment, this application provides a dynamic time assignment method, apparatus, and system. The technical solutions are as follows.

[0009] The present invention is defined by the independent claims. Additional features of the invention are defined by the dependent claims.BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG 1 is a diagram of an application scenario according to an embodiment of the present invention; FIG 1B is a schematic diagram of forming near-end crosstalk according to an embodiment of the present invention; FIG 1C is a schematic diagram of forming far-end crosstalk according to an embodiment of the present invention; FIG 2 is a schematic diagram of a frame format according to an embodiment of the present invention; FIG 3 is a schematic diagram of a DTA mechanism according to an embodiment of the present invention FIG 4 is a schematic structural diagram of a dynamic time assignment apparatus according to an embodiment of the present invention; FIG 5 is a schematic structural diagram of another dynamic time assignment apparatus according to an embodiment of the present invention; FIG 6 is a flowchart of a dynamic time assignment method according to an embodiment of the present invention; FIG 6A to FIG 6H are schematic diagrams of dynamic time assignment according to an embodiment of the present invention; FIG 7 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention; FIG 8 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention; FIG 9 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention; FIG 10 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention; FIG 11 is a schematic structural diagram of a dynamic time assignment apparatus according to an embodiment of the present invention; FIG 12 is a schematic structural diagram of another dynamic time assignment apparatus according to an embodiment of the present invention; and FIG 13 is a schematic structural diagram of a dynamic time assignment system according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

[0011] To make the objectives, technical solutions, and advantages of this application clearer, the following further describes the implementations of this application in detail with reference to the accompanying drawings.

[0012] A "module" mentioned in this specification is a program or an instruction that is stored in a memory and that can implement some functions. A "unit" mentioned in this specification is a functional structure obtained through logical division. The "unit" may be implemented by hardware only or by a combination of software and hardware.

[0013] For ease of subsequent description, the following first describes an application scenario of the embodiments of the present invention with reference to FIG 1A.

[0014] As shown in FIG 1A, in an FTTdp access scenario, an optical line terminal (OLT) 101 is connected to FTTdp CO equipment 102 at a distribution point by using a passive optical network (PON), the FTTdp CO equipment 102 changes an optical fiber to a twisted pair, and then the FTTdp CO equipment 102 is connected to FTTdp CPE 103 by using the twisted pair.

[0015] The FTTdp CO equipment (that is, central office equipment) and the FTTdp CPE (that is, customer premise equipment) use a technology such as Gfast or a second generation very high speed digital subscriber line (VDSL2) for signal transmission. The following uses the Gfast as an example for description. When the Gfast technology is used, a plurality of signals are simultaneously accessed on the FTTdp CO equipment. Each signal is corresponding to one Gfast transceiver unit-CO side (FTU-O) and one Gfast transceiver unit-remote side (FTU-R). FTU-Os corresponding to the plurality of signals herein usually belong to one FTTdp CO equipment, and are in a one-to-one correspondence with a plurality of ports on the FTTdp CO equipment. FTU-Rs corresponding to all the signals belong to one FTTdp CPE.

[0016] The Gfast technology uses a TDD mode. One of an FTU-O and an FTU-R (the FTU-O and the FTU-R that are connected by using a same twisted pair) that are corresponding to a same signal in a same timeslot is used for transmission, and the other one of the FTU-O and the FTU-R is used for reception. A frame format used by the Gfast is shown in FIG 2. A superframe (SF) includes one TDD synchronization frame (TDDSF) and a plurality of TDD frames (TDDF). The TDD synchronization frame includes a downstream synchronization symbol (DSSS) and an upstream synchronization symbol (USSS). The TDD frame includes a downstream symbol (DS) and an upstream symbol (US). The downstream symbol is used to transmit downstream data (to be specific, the data is transmitted from a CO side to a remote side), and the upstream symbol is used to transmit upstream data (to be specific, the data is transmitted from a remote side to a CO side).

[0017] Crosstalk may occur between the plurality of signals accessed by the FTTdp CO equipment, and the crosstalk includes near-end crosstalk and far-end crosstalk. The near-end crosstalk means that, for transceiver units located at a same end, if one transceiver unit works in a sending state, and the other transceiver unit works in a receiving state, the transceiver unit in the sending state causes interference to the transceiver unit that is in the receiving state. FIG 1B is a schematic diagram of forming near-end crosstalk. An FTU-O 1 and an FTU-O 2 are used as an example. When the FTU-O 1 is in a sending state and the FTU-O 2 is in a receiving state, the FTU-O 1 causes interference to the FTU-O 2, forming near-end crosstalk. Dashed lines in FIG 1B show four near-end crosstalk forming manners. Due to the foregoing reason for causing near-end crosstalk, the near-end crosstalk does not occur provided that upstream and downstream time synchronization of a plurality of signals is ensured (that is, the plurality of signals are simultaneously in a sending or receiving state).

[0018] The far-end crosstalk means that interference is caused by a transceiver unit at one end that works in a sending state to a transceiver unit at another end that works in a receiving state (where the two transceiver units are corresponding to different signals). FIG 1C is a schematic diagram of forming far-end crosstalk. An FTU-O 1 and an FTU-R 2 are used as an example. When the FTU-O 1 is in a sending state and the FTU-R 2 is in a receiving state, the FTU-O 1 causes interference to the FTU-R 2, forming far-end crosstalk. Dashed lines in FIG 1C show four far-end crosstalk forming manners. The far-end crosstalk needs to be overcome by using a vectoring technology. Specifically, the vectoring technology is usually executed at the CO side (for example, the FTTdp CO equipment), and includes two aspects: downstream precoding and upstream joint reception.

[0019] The downstream precoding technology is as follows: A remote side (for example, the FTTdp CPE) feeds back far-end crosstalk information to a CO side, and the CO side obtains a "backward" crosstalk signal based on the far-end crosstalk information, and superimposes the "backward" crosstalk signal to a signal sent by the CO side, thereby implementing crosstalk cancellation. The downstream precoding technology mainly includes a linear precoding technology and a QR-Tomlinson-Harashima precoder (QRTHP) non-linear precoding technology. The upstream joint reception is as follows: A crosstalk canceller is disposed when a CO side receives a signal sent by a remote side, so that crosstalk in the signal is cancelled after the received signal passes through the crosstalk canceller.

[0020] In addition, for the TDD duplex manner, a DTA mechanism may further be used to allocate an appropriate upstream transmission ratio and / or an appropriate downstream transmission ratio based on a change of upstream and / or downstream traffic. The following briefly describes the DTA mechanism with reference to FIG 3: The CO side sends a DTA message by using downstream robustness management channel (RMC) message. The DTA message includes downstream transmission duration (Mds) and a DTA frame down count (DTAFDC). The DTA message is repeatedly sent by using RMC messages in all TDD frames, and Mds in the DTA message remains unchanged during repeated sending. However, the DTAFDC decreases gradually until the DTAFDC changes to 0, and then the CO side and the remote side make new Mds take effect. The Mds is duration (a quantity of symbols), used for downstream transmission, in a TDD frame after time assignment, and may also be referred to as a length of a downstream transmission duration. Making the new Mds take effect is adjusting a length of a downstream transmission duration in a TDD frame to the Mds, and adjusting a length of an upstream transmission duration to MF-Mds_New-A, where MF is a quantity of symbols included in the TDD frame, A is a quantity of symbols in the TDD frame that are used for upstream and downstream switching, and a value of A is usually 1. It should be noted that, referring to FIG 3, an upstream transmission duration and a downstream transmission duration include an RMC symbol each, and a part, before the RMC symbol (between expiration of a previous upstream and downstream switching time period and start of the RMC symbol), of each of the upstream transmission duration and the downstream transmission duration has fixed duration, that is, there is a fixed offset (FO). There is a time interval between an upstream transmission duration and a downstream transmission duration that are adjacent, and the time interval is used as an upstream and downstream switching time period. Each TDD frame includes two upstream and downstream switching time periods, and a sum of the two upstream and downstream switching time periods is the foregoing A symbols.

[0021] Only a single-port situation is mentioned in a current DTA mechanism. For a multi-port scenario of FTTdp CO equipment, during dynamic time assignment, upstream and downstream time need to be configured for all signals in a same TDD frame, otherwise upstream and downstream time may be asynchronous for different signals and consequently near-end crosstalk is caused.

[0022] However, in a multi-port scenario of the FTTdp CO equipment, an RMC channel in downstream of a port may be damaged by burst noise, an FTU-R is temporarily incapable of making new Mds take effect, or there may be another case. Consequently, near-end crosstalk is caused by asynchronous upstream and downstream time.

[0023] To overcome near-end crosstalk caused by asynchronous upstream and downstream time in a multi-port scenario of FTTdp CO equipment, the embodiments of the present invention provide a dynamic time assignment method, apparatus, and system. For details, refer to the following embodiments.

[0024] The following first describes, with reference to a specific hardware structure, a dynamic time assignment apparatus according to an embodiment of the present invention.

[0025] FIG 4 is a structural block diagram of a dynamic time assignment apparatus 140 according to an embodiment of the present invention. The dynamic time assignment apparatus 140 may be the foregoing central office equipment. Referring to FIG 4, the dynamic time assignment apparatus 140 may include components such as a processor 31 including one or more processing cores, a memory 32 including one or more computer readable storage media, and a communications interface 33. The processor 31 may be connected to the memory 32 and the communications interface 33 by using buses. A person skilled in the art may understand that the structure shown in FIG 4 does not constitute a limitation on the dynamic time assignment apparatus 140, and the dynamic time assignment apparatus 140 may include more or fewer components than those shown in the figure, a combination of some components, or components disposed differently.

[0026] The processor 31 is a control center of the dynamic time assignment apparatus 140, and is connected to all components of the entire dynamic time assignment apparatus 140 by using various interfaces and lines. By running or executing software programs and / or application program modules stored in the memory 32, and invoking data stored in the memory 32, the processor 31 performs various functions of the dynamic time assignment apparatus 140 and processes data, to perform overall monitoring on the dynamic time assignment apparatus 140. Optionally, the processor 31 may include one or more processing units, and the processing unit may be a central processing unit (CPU for short), a network processor (NP for short), or the like.

[0027] The communications interface 33 may be implemented as a communications chip. The communications chip may include a receiving module, a transmission module, a modulation and demodulation module, and the like, and is configured to: modulate and demodulate information, and receive or send the information by using a radio signal. The communications interface 33 is controlled by the processor 31.

[0028] The memory 32 may be configured to store various data, such as various configuration parameters, and a software program and / or an application program module. The software program and / or the application program module may be executed by the processor 31. The memory 32 may mainly include a program storage area and a data storage area. The program storage area may store an operating system 321 and an application program module 322 corresponding to at least one function, for example, an obtaining module and an adjustment module. The data storage area may store data created according to use of the dynamic time assignment apparatus 140, for example, a length of a new downstream transmission duration or a length of a current downstream transmission duration. In addition, the memory 32 may include a high-speed random access memory, and may further include a non-volatile memory such as at least one magnetic disk storage device, a flash memory device, or another non-volatile solid-state storage device. Correspondingly, the memory 32 may further include a memory controller, to provide the processor 31 with access to the memory 32.

[0029] The application program module 322 includes at least: an obtaining module 3220 configured to obtain the length of the new downstream transmission duration; and an adjustment module 3221 configured to adjust a length or lengths of an upstream transmission duration or a downstream transmission duration.

[0030] The obtaining module 3220 is configured to obtain the length of the new downstream transmission duration.

[0031] The adjustment module 3221 is configured to: when the length of the new downstream transmission duration is less than lengths of current downstream transmission durations of the at least two transceivers of the central office equipment, adjust lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration after shortening the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than lengths of current downstream transmission durations of the at least two transceivers, adjust the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration after shortening lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration. A sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

[0032] FIG 5 is a structural block diagram of a dynamic time assignment apparatus 240 according to an embodiment of the present invention. The dynamic time assignment apparatus 240 may be the foregoing customer premise equipment. Referring to FIG 5, the dynamic time assignment apparatus 240 may include components such as a processor 61 including one or more processing cores, a memory 62 including one or more computer readable storage media, and a communications interface 63. The processor 61 may be connected to the memory 62 and the communications interface 63 by using buses. A person skilled in the art may understand that the structure shown in FIG 5 does not constitute a limitation on the dynamic time assignment apparatus 240, and the dynamic time assignment apparatus 240 may include more or fewer components than those shown in the figure, a combination of some components, or components disposed differently.

[0033] The processor 61 is a control center of the dynamic time assignment apparatus 240, and is connected to all components of the entire dynamic time assignment apparatus 240 by using various interfaces and lines. By running or executing software programs and / or application program modules stored in the memory 62, and invoking data stored in the memory 62, the processor 61 performs various functions of the dynamic time assignment apparatus 240 and processes data, to perform overall monitoring on the dynamic time assignment apparatus 240. Optionally, the processor 61 may include one or more processing units. The processing unit may be a central processing unit (CPU for short), a network processor (NP for short), or the like.

[0034] The communications interface 63 may be implemented as a communications chip. The communications chip may include a receiving module, a transmission module, a modulation and demodulation module, and the like, and is configured to: modulate and demodulate information, and receive or send information by using a radio signal. The communications interface 63 is controlled by the processor 61.

[0035] The memory 62 may be configured to store various data, such as various configuration parameters, and a software program and / or an application program module. The software program and / or the application program module may be executed by the processor 61. The memory 62 may mainly include a program storage area and a data storage area. The program storage area may store an operating system 621 and an application program module 622 corresponding to at least one function, for example, an obtaining module and an adjustment module. The data storage area may store data created according to use of the dynamic time assignment apparatus 240, for example, a length of a new downstream transmission duration or a length of a current downstream transmission duration. In addition, the memory 62 may include a high-speed random access memory, and may further include a non-volatile memory such as at least one magnetic disk storage device, a flash memory device, or another non-volatile solid-state storage device. Correspondingly, the memory 62 may further include a memory controller, to provide the processor 61 with access to the memory 62.

[0036] The application program module 622 includes at least: an obtaining module 6220 configured to obtain the length of the new downstream transmission duration; and an adjustment module 6221 configured to adjust a length or lengths of an upstream transmission duration or a downstream transmission duration.

[0037] The obtaining module 6220 is configured to obtain the length of the new downstream transmission duration.

[0038] The adjustment module 6221 is configured to: when the length of the new downstream transmission duration is less than a length of a current downstream transmission duration of a transceiver of the customer premise equipment, adjust a length of a current upstream transmission duration of the transceiver of the customer premise equipment to a length of a new upstream transmission duration after shortening the length of the current downstream transmission duration of the transceiver of the customer premise equipment to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than a length of a current downstream transmission duration of a transceiver of the customer premise equipment, adjust the length of the current downstream transmission duration of the transceiver of the customer premise equipment to the length of the new downstream transmission duration after shortening a length of a current upstream transmission duration of the transceiver of the customer premise equipment to the length of the new upstream transmission duration. A sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

[0039] An embodiment of the present invention provides a dynamic time assignment method. Referring to FIG 6, the method is executed by central office equipment and customer premise equipment, and the central office equipment includes at least two transceivers. The dynamic time assignment method provided in the present invention may be applied to only some transceivers (at least two transceivers) of the central office equipment, or may be applied to all transceivers of the central office equipment. In this embodiment of the present invention, descriptions are provided by using an example in which all transceivers of the central office equipment need to adjust lengths of upstream and downstream transmission durations. Another embodiment may alternatively be specific for only some transceivers (for example, at least two transceivers) of the central office equipment. The dynamic time assignment method includes the following steps.

[0040] Step S10: The central office equipment obtains a length of a new downstream transmission duration.

[0041] Specifically, the central office equipment determines the length of the new downstream transmission duration based on at least one of conditions such as traffic and power consumption of at least two transceivers of the central office equipment. The action of determining a length of a new downstream transmission duration may be performed by a unit having a calculation function, such as a CPU or a digital signal processing (DSP) chip inside the central office equipment.

[0042] After obtaining the length of the new downstream transmission duration, the central office equipment may determine a length of a new upstream transmission duration based on the length of the new downstream transmission duration because the sum of the length of the upstream transmission duration and the length of the downstream transmission duration is equal to a total length of one transmission frame minus upstream and downstream switching duration. The transmission frame may be specifically a TDD frame. Certainly, in another embodiment, alternatively, the central office equipment may first obtain a length of a new upstream transmission duration, and then determine a length of a new downstream transmission duration based on the length of the new upstream transmission duration.

[0043] After obtaining the length of the new downstream transmission duration, the central office equipment may further compare the length of the new downstream transmission duration with a length of a current downstream transmission duration, to facilitate subsequent steps.

[0044] Step S11: The central office equipment sends a first instruction message to the customer premise equipment, where the first instruction message includes the length of the new downstream transmission duration.

[0045] In this step, the central office equipment may send the first instruction message by using a downstream RMC symbol. The first instruction message may be a DTA message. The new downstream transmission duration indicated by the first instruction message includes Mds_New symbols.

[0046] In this embodiment of the present invention, the downstream is from the central office equipment to the customer premise equipment, and the upstream is from the customer premise equipment to the central office equipment. The downstream transmission duration is duration including a symbol used for downstream transmission in one transmission frame, and the upstream transmission duration is duration including a symbol used for upstream transmission in one transmission frame.

[0047] In this embodiment of the present invention, the central office equipment sends one first instruction message by using each transceiver. First instruction messages sent by different transceivers are used to instruct to perform dynamic time assignment with transceivers of customer premise equipments that are corresponding to the transceivers of the central office equipment, and the first instruction messages sent by the different transceivers include the length of the same new downstream transmission duration.

[0048] Further, the first instruction message further includes effective time. First instruction messages sent by different transceivers may include same effective time, or first instruction messages sent by different transceivers may include different effective time. The effective time of the first instruction message is time at which the customer premise equipment is required or expected to shorten the length of the downstream transmission duration to the length of the new downstream transmission duration, or to shorten the length of the upstream transmission duration to the length of the new upstream transmission duration.

[0049] In this embodiment of the present invention, the first instruction message is used to instruct to change the length of the downstream transmission duration to min(Mds_old, Mds_new), and change the length of the upstream transmission duration to min(MF-Mds_old-A, MF-Mds_new-A). Mds_old is a quantity of symbols included in the current downstream transmission duration, and the current downstream transmission duration is a downstream transmission duration before a length of an upstream transmission duration or a downstream transmission duration (upstream transmission duration or downstream transmission duration) is adjusted based on the first instruction message. MF-Mds_New-A is the length of the new upstream transmission duration, and MF-Mds_Old-A is the length of the current upstream transmission duration.

[0050] Step S12: When the length of the new downstream transmission duration is less than a length of the current downstream transmission duration, the central office equipment and the customer premise equipment shorten a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0051] Specifically, the central office equipment shortens lengths of downstream transmission durations of all transceivers of the central office equipment to the length of the new downstream transmission duration. The customer premise equipment shortens a length of a downstream transmission duration of a transceiver of the customer premise equipment to the length of the new downstream transmission duration. The length of the upstream transmission duration of the transceiver is a length of a time period within which the transceiver transmits upstream data in one transmission frame, and the length of the downstream transmission duration of the transceiver is a length of a time period within which the transceiver transmits downstream data in one transmission frame. The length of the upstream transmission duration or the length of the downstream transmission duration may be a quantity of symbols included in the upstream transmission duration or the downstream transmission duration.

[0052] The shortening a length of a downstream transmission duration to the length of the new downstream transmission duration may include: determining a position of the last symbol of the downstream transmission duration without changing a position of the first symbol of the downstream transmission duration, and using the (Mds_New) th< (a quantity of symbols in the new downstream transmission duration) symbol as the last symbol of the downstream transmission duration.

[0053] Before the central office equipment has shortened the lengths of the downstream transmission durations of all the transceivers of the central office equipment to the length of the new downstream transmission duration, the method further includes the following step:

[0054] The central office equipment processes the (Mds_New+1) th< to the (Mds_Old) th< symbols in the downstream transmission durations by using a downstream precoding technology. For a signal for which a length of a downstream transmission duration has been shortened, an idle symbol (idle symbol) is transmitted in the (Mds_New+1) th< to the (Mds_Old) th< symbols in the downstream transmission duration. The idle symbol means that 0 is transmitted as an input signal in a symbol in which no data is sent. In a process of shortening the length of the downstream transmission duration, not all lengths of the downstream transmission durations corresponding to all the transceivers of the central office equipment can be shortened simultaneously. Therefore, when lengths of some downstream transmission durations are shortened, but lengths of the other downstream transmission durations are not shortened yet, processing still needs to be performed by using the downstream precoding technology in this period of time until lengths of all the downstream transmission durations are shortened, to overcome far-end crosstalk.

[0055] Processing the (Mds _New+1) th< to the (Mds_Old) th< symbols in the downstream transmission durations by using the downstream precoding technology means processing a signal by using the downstream precoding technology within a time period from the (Mds _New+1) th< to the (Mds_Old) th< symbols in the downstream transmission duration.

[0056] When performing processing by using the downstream precoding technology, the central office equipment needs to process each signal.

[0057] Certainly, for the 1 st< to the (Mds_New) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0058] It is easy to learn that, in this embodiment of the present invention, the central office equipment and the customer premise equipment may perform step S12 simultaneously, for example, the central office equipment and the customer premise equipment both perform step S12 after performing step S11; or may not perform step S12 simultaneously, for example, the central office equipment performs step S12 when or before performing step S11 (because the central office equipment may have determined the length of the new downstream transmission duration before step S11, step S12 may be performed first based on the length), but the customer premise equipment performs step S12 after performing step S11.

[0059] In this embodiment of the present invention, that the central office equipment shortens a length of a downstream transmission duration to the length of the new downstream transmission duration means that the central office equipment shortens a length of a sending duration by adjusting a configuration of a transmit end. That the customer premise equipment shortens a length of a downstream transmission duration to the length of the new downstream transmission duration means that the customer premise equipment shortens a length of a receiving interval by adjusting a configuration of a receive end.

[0060] Step S13: When the length of the new downstream transmission duration is greater than a length of the current downstream transmission duration, the central office equipment and the customer premise equipment shorten a length of an upstream transmission duration to the length of the new upstream transmission duration.

[0061] Specifically, the central office equipment shortens lengths of upstream transmission durations of all the transceivers of the central office equipment to the length of the new upstream transmission duration. The customer premise equipment shortens a length of an upstream transmission duration of the transceiver of the customer premise equipment to the length of the new upstream transmission duration.

[0062] The shortening a length of an upstream transmission duration to the length of the new upstream transmission duration may include: determining a position of the first symbol of the upstream transmission duration without changing a position of the last symbol of the upstream transmission duration, and using the (Mds_New-Mds_Old) th< symbol of the current upstream transmission duration as the first symbol of the new upstream transmission duration.

[0063] Correspondingly, a position of an RMC symbol in the upstream transmission duration is changed when or after the length of the upstream transmission duration is shortened. Specifically, the RMC symbol is moved backward by Mds_New-Mds_Old symbols.

[0064] Before all customer premise equipments have shortened lengths of upstream transmission durations of transceivers of customer premise equipments to the length of the new upstream transmission duration, the method further includes the following step: The central office equipment processes the 1 st< to the (Mds_New-Mds_Old) th< symbols in the upstream transmission durations by using an upstream joint reception technology. In a process of shortening the length of the upstream transmission duration, not all lengths of the upstream transmission durations corresponding to the transceivers of all the customer premise equipments can be shortened simultaneously. Therefore, when lengths of some upstream transmission durations are shortened, but lengths of the other upstream transmission durations are not shortened yet, processing still needs to be performed by using the upstream joint reception technology in this period of time until lengths of all the upstream transmission durations are shortened, to overcome far-end crosstalk.

[0065] The 1 st< to the (Mds_New-Mds_Old) th< symbols in the upstream transmission duration are processed by using the upstream joint reception technology, and a signal is processed by using the upstream joint reception technology within a time period from the 1 st< to the (Mds_New-Mds_Old) th< symbols in the upstream transmission duration.

[0066] When performing processing by using the upstream joint reception technology, the central office equipment needs to process each signal.

[0067] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0068] It is easy to learn that, in this embodiment of the present invention, the central office equipment and the customer premise equipment may perform step S13 simultaneously, for example, the central office equipment and the customer premise equipment both perform step S12 after performing step S11; or may not perform step S13 simultaneously, for example, the central office equipment performs step S13 when or before performing step S11, but the customer premise equipment performs step S13 after performing step S11. Step S13 and step S12 are optional, and only one step takes effect at a same time point.

[0069] In this embodiment of the present invention, that the central office equipment shortens a length of an upstream transmission duration to the length of the new upstream transmission duration means that the central office equipment shortens a length of a receiving interval by adjusting a configuration of a receive end. That the customer premise equipment shortens a length of an upstream transmission duration to the length of the new upstream transmission duration means that the customer premise equipment shortens a length of a sending duration by adjusting a configuration of a transmit end.

[0070] Step S14: After the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, or after the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration, the central office equipment sends second instruction message to the customer premise equipments.

[0071] The second instruction messages are used to instruct the customer premise equipments to adjust all of the lengths of the upstream transmission durations and / or the downstream transmission durations of the transceivers of all the customer premise equipments to the length of the upstream transmission duration and the length of the downstream transmission duration that are determined based on the length of the downstream transmission duration in the first instruction message.

[0072] Specifically, for details about how to determine that all of the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration, refer to the following descriptions.

[0073] In this embodiment of the present invention, the central office equipment sends one second instruction message by using each transceiver, and second instruction messages sent by different transceivers are used to instruct to perform dynamic time assignment with the transceivers of the customer premise equipments that are corresponding to the transceivers of the central office equipment. The second instruction messages sent by the different transceivers include the length of the same new downstream transmission duration, and the length of the new downstream transmission duration is the same as that in the first instruction message.

[0074] Further, the second instruction message further includes effective time. Second instruction messages sent by different transceivers may include same effective time, or second instruction messages sent by different transceivers may include different effective time. The effective time of the second instruction message is time at which the customer premise equipment adjusts (prolongs) the length of the upstream transmission duration to the length of the new upstream transmission duration, or to shorten the length of the downstream transmission duration to the length of the new downstream transmission duration.

[0075] In another embodiment, the second instruction message may alternatively have only an indication function, and does not include content such as a length and effective time of the new downstream transmission duration.

[0076] Further, the method further includes: determining, by the central office equipment, whether the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, or determining, by the central office equipment, whether the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration.

[0077] The downstream transmission durations of all the transceivers of the central office equipment are adjusted by the central office equipment. Therefore, the central office equipment can determine whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, only by recording adjustment time of a downstream transmission duration of each transceiver. The central office equipment uses two manners to determine whether the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration. One manner is that the central office equipment receives a third instruction message sent by the customer premise equipment, and performs determining based on the third instruction message, where the third instruction message is used to indicate a time point that is determined by the customer premise equipment and at which a transceiver of the customer premise equipment shortens a length of an upstream transmission duration to the length of the new upstream transmission duration. Another manner is that the central office equipment detects, frame by frame, a position of an upstream RMC symbol corresponding to the transceiver of the customer premise equipment and performs determining based on the position of the detected upstream RMC symbol. For details, refer to the following embodiments.

[0078] In this embodiment of the present invention, when the length of the new downstream transmission duration is less than the length of the current downstream transmission duration, the central office equipment and the customer premise equipment adjust a length of an upstream transmission duration after the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration and the lengths of the downstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new downstream transmission duration. Correspondingly, the central office equipment sends a second instruction message to the customer premise equipment after the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration and the lengths of the downstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new downstream transmission duration.

[0079] When the length of the new downstream transmission duration is greater than the length of the current downstream transmission duration, the central office equipment and the customer premise equipment may further adjust a length of a downstream transmission duration after the lengths of the upstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new upstream transmission duration and the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration. Correspondingly, the central office equipment sends a second instruction message to the customer premise equipment after the lengths of the upstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new upstream transmission duration and the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration.

[0080] Step S15: When the length of the new downstream transmission duration is less than the length of the current downstream transmission duration, the central office equipment and the customer premise equipment adjust a length of an upstream transmission duration to the length of the new upstream transmission duration.

[0081] Specifically, the central office equipment adjusts the lengths of the upstream transmission durations of all the transceivers of the central office equipment to the length of the new upstream transmission duration. The customer premise equipments adjust the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments to the length of the new upstream transmission duration.

[0082] The adjusting (prolonging) the length of the upstream transmission duration to the length of the new upstream transmission duration may include: determining a position of the first symbol of the upstream transmission duration without changing a position of the last symbol of the upstream transmission duration, and using the (Mds_Old-Mds_New) th< symbol of the current downstream transmission duration as the first symbol of the new upstream transmission duration.

[0083] Further, a position of an RMC symbol in the upstream transmission duration is changed. Specifically, the RMC symbol is moved forward by Mds_Old-Mds_New symbols.

[0084] After the central office equipment sends the second instruction message to the customer premise equipment, the method further includes: processing, by the central office equipment, the 1 st< to the (Mds_Old-Mds_New) th< symbols in the upstream transmission durations by using an upstream joint reception technology.

[0085] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0086] It is easy to learn that, in this embodiment of the present invention, the central office equipment and the customer premise equipment may perform step S15 simultaneously, for example, the central office equipment and the customer premise equipment both perform step S15 after performing step S14; or may not perform step S15 simultaneously, for example, the central office equipment performs step S15 when performing step S14, but the customer premise equipment performs step S15 after performing step S14.

[0087] Step S16: When the length of the new downstream transmission duration is greater than the current downstream transmission duration, the central office equipment and the customer premise equipment adjust a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0088] Specifically, the central office equipment adjusts the lengths of the downstream transmission durations of all the transceivers of the central office equipment to the length of the new downstream transmission duration. The customer premise equipments adjust the lengths of the downstream transmission durations of the transceivers of all the customer premise equipments to the length of the new downstream transmission duration.

[0089] The adjusting (prolonging) the length of the downstream transmission duration to the length of the new downstream transmission duration may include: determining a position of the last symbol of the downstream transmission duration without changing a position of the first symbol of the downstream transmission duration, and using the (Mds_New) th< symbol as the last symbol of the downstream transmission duration.

[0090] That is, in this embodiment of the present invention, a time length of a transmission duration corresponding to a sender (for example, a downstream transmission duration of the central office equipment or an upstream transmission duration of the customer premise equipment) is first shortened, and then a time length of a transmission duration corresponding to a receiver is prolonged.

[0091] After the central office equipment sends the second instruction message to the customer premise equipment, the method further includes the following step: The central office equipment processes the (Mds_Old+1) th< to the (Mds_New) th< symbols in the downstream transmission durations by using a downstream precoding technology. For a signal for which a length of the downstream transmission duration has been adjusted, an idle symbol is transmitted on the (Mds_Old+1) th< to the (Mds_New) th< symbols in the downstream transmission duration.

[0092] Certainly, for the 1 st< to the (Mds_Old) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0093] It is easy to learn that, in this embodiment of the present invention, the central office equipment and the customer premise equipment may perform step S16 simultaneously, for example, the central office equipment and the customer premise equipment both perform step S16 after performing step S14; or may not perform step S16 simultaneously, for example, the central office equipment performs step S16 after performing step S14, but the customer premise equipment performs step S16 after performing step S14. Step S16 and step S15 are optional, and only one step takes effect at a same time point.

[0094] The following further describes the method provided in this embodiment of the present invention by using FIG 6A to FIG 6D and FIG 6E to FIG 6H as examples. In the two examples, three signals corresponding to three transceivers of central office equipment (an FTU-O 1 to an FTU-O3) are used as an example for description. In practice, there may be more or fewer signals (at least two signals): In the examples shown in FIG 6A to FIG 6D, Mds_New<Mds_Old, that is, the length of the new downstream transmission duration (DS) is less than the length of the current downstream transmission duration. As shown in FIG 6A, before time assignment, a length of a downstream transmission duration is Mds_Old, and a length of an upstream transmission duration is MF-Mds_Old-A. As shown in FIG 6B, during time assignment, the length of the downstream transmission duration is first shortened to Mds_New until lengths of downstream transmission durations corresponding to all the transceivers of the central office equipment are all shortened to Mds_New, as shown in FIG 6C. Then, the length of the upstream transmission duration (US) is prolonged to MF-Mds_New-A, as shown in FIG 6D.

[0095] In the examples shown in FIG 6E to FIG 6H, Mds_New>Mds_Old, that is, the length of the new downstream transmission duration is greater than a length of a current downstream transmission duration. As shown in FIG 6E, before time assignment, a length of a downstream transmission duration is Mds_Old, and a length of an upstream transmission duration is MF-Mds_Old-A. As shown in FIG 6F, during time assignment, the length of the upstream transmission duration is first shortened to MF-Mds_New-A until lengths of upstream transmission durations corresponding to all the transceivers of the central office equipment are all shortened to MF-Mds_New-A, as shown in FIG 6G Then, the length of the downstream transmission duration is prolonged to Mds_New, as shown in FIG 6H.

[0096] FIG 7 is a flowchart of a dynamic time assignment method according to an embodiment of the present invention. In the method process provided in FIG 7, a length of a new downstream transmission duration is less than a length of a current downstream transmission duration, and in the method, customer premise equipment sends a second message (including effective time determined by the customer premise equipment) to central office equipment. Referring to FIG 7, the method includes the following steps. Step S20: The central office equipment obtains the length of the new downstream transmission duration;

[0097] For a specific procedure, refer to step S10.

[0098] Step S21: The central office equipment sends a first message to the customer premise equipment, where the first message includes Mds and effective time TDD 1, and the Mds includes the length of the new downstream transmission duration.

[0099] In this step, the first message may use a format of a DTA message, that is, the central office equipment sends the Mds to the customer premise equipment by sending a DTA message by using a downstream RMC symbol. The DTA message includes the Mds and DTAFDC (used to indicate a position of the TDD 1). The new downstream transmission duration indicated by the Mds includes Mds_New symbols. The DTAFDC is used to indicate effective time TDD 1, and the effective time is a time point that is determined by the central office equipment and at which the length of the downstream transmission duration is shortened to the length of the new downstream transmission duration.

[0100] The central office equipment may repeatedly send the DTA message in a TDD frame before the TDD 1 (including the TDD 1). A value of the Mds remains unchanged each time when the DTA message is sent, and a DTAFDC decreases gradually (1 is subtracted from each transmission frame) until the TDD 1; in this case, the DTAFDC changes to 0.

[0101] In this embodiment of the present invention, the central office equipment sends a first message to a transceiver of corresponding customer premise equipment by using each transceiver. A transceiver of the central office equipment and a transceiver of corresponding customer premise equipment are a transceiver of central office equipment and a transceiver of customer premise equipment that transmit a same signal.

[0102] The TDD 1 is determined by the central office equipment based on implementation capability of the central office equipment and implementation capability of the customer premise equipment, and the implementation capability of the customer premise equipment is reported to the central office equipment when the customer premise equipment is initialized. The implementation capability herein includes capability of each transceiver in the equipment, for example, a minimum initial DTAFDC value (min initial DTAFDC). For example, if the min initial DTAFDC value of the transceiver reported by the customer premise equipment during initialization is A0, the central office equipment is to send a first message in a TDD 0, and may shorten a downstream transmission duration or an upstream transmission duration in a TDD 0'. In this case, the TDD 1 may be equal to max(TDD 0', TDD 0+A0).

[0103] In this step, the TDD 1 is specifically a time point that is determined by the central office equipment and at which the length of the downstream transmission duration is shortened to the length of the new downstream transmission duration. It should be noted that, for transceivers of different customer premise equipments, specific positions of the TDD 1 indicated in the first message may also be different. The first message herein is the foregoing first instruction message.

[0104] Step S22: The customer premise equipment receives the first message, and determines whether the length of the downstream transmission duration can be shortened to the length of the new downstream transmission duration in the TDD 1.

[0105] In this step, after receiving the first message, the customer premise equipment obtains the Mds and the DTAFDC; determine the TDD 1 based on the DTAFDC; determines whether the length of the downstream transmission duration can be shortened to the length of the new downstream transmission duration in the TDD 1.

[0106] Specifically, the customer premise equipment determines, based on implementation capability of a transceiver, whether each transceiver can shorten a length of a downstream transmission duration to the length of the new downstream transmission duration in the TDD 1.

[0107] Step S23: The customer premise equipment sends a second message to the central office equipment, where the second message is used to indicate effective time determined by the customer premise equipment.

[0108] Specifically, the customer premise equipment needs to send a second message by using each transceiver. The second message is used to indicate effective time of each transceiver determined by customer premise equipment.

[0109] Specifically, if a transceiver of customer premise equipment can shorten a length of a downstream transmission duration to the length of the new downstream transmission duration in the TDD 1, the effective time of the transceiver of the customer premise equipment that is determined by the customer premise equipment and that is indicated by the second message is the TDD 1. If the transceiver of the customer premise equipment cannot shorten the length of the downstream transmission duration to the length of the new downstream transmission duration in the TDD 1, the effective time of the transceiver of the customer premise equipment that is determined by the customer premise equipment and that is indicated by the second message is a TDD 2. The TDD 2 is new effective time determined by the customer premise equipment, and the new effective time is a time point that is determined by the customer premise equipment and at which the length of the downstream transmission duration is shortened to the length of the new downstream transmission duration. It should be noted that, for transceivers of different customer premise equipments, specific positions of the TDD 2 indicated in the second message may also be different. The second message herein is the foregoing third instruction message.

[0110] Further, to simplify the second message, if the transceiver of the user equipment can shorten the length of the downstream transmission duration to the length of the new downstream transmission duration in the TDD 1, the second message may not include the TDD 1, but uses a simple acknowledgment (ACK) message to indicate that the transceiver of the customer premise equipment can shorten the length of the downstream transmission duration to the length of the new downstream transmission duration in the TDD 1.

[0111] In this step, the customer premise equipment sends the second message by using an upstream RMC symbol. The second message may use the DTAFDC to indicate the effective time TDD 2 determined by the customer premise equipment. The customer premise equipment may repeatedly send the second message in a TDD frame before the TDD 2 (including the TDD 2). A DTAFDC decreases gradually (1 is subtracted from each transmission frame) until the TDD 2; in this case, the DTAFDC changes to 0.

[0112] Step S24: The central office equipment and the customer premise equipment shorten a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0113] In this step, the central office equipment selects, based on a status of the central office equipment, an appropriate frame to shorten a length of a downstream transmission duration of each transceiver. The central office equipment determines, based on a time point at which the length of the downstream transmission duration of each transceiver is shortened to the length of the new downstream transmission duration, a time point at which lengths of downstream transmission durations of all transceivers of the central office equipment are shortened to the length of the new downstream transmission duration. The time point at which the lengths of the downstream transmission durations of all the transceivers of the central office equipment are shortened to the time of the length of the new downstream transmission duration is a time point at which the last transceiver in all the transceivers of the central office equipment shortens a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0114] For the customer premise equipment, if the customer premise equipment determines that a transceiver can shorten a length of a downstream transmission duration to the length of the new downstream transmission duration in the effective time TDD 1, the length of the downstream transmission duration of the transceiver is shortened in the TDD 1. If the customer premise equipment determines that a transceiver cannot shorten a length of a downstream transmission duration to the length of the new downstream transmission duration in TDD 1, the length of the downstream transmission duration of the transceiver is shortened in TDD 2.

[0115] In this step, the TDD 2 is specifically a time point that is determined by the customer premise equipment and at which a length of a downstream transmission duration of a transceiver is shortened to the length of the new downstream transmission duration.

[0116] Before the central office equipment has shortened the lengths of the downstream transmission durations of all the transceivers of the central office equipment to the length of the new downstream transmission duration, the method further includes the following step: The (Mds_New+1) th< to the (Mds_Old) th< symbols in the downstream transmission duration are processed by using a downstream precoding technology. For a signal for which a length of a downstream transmission duration has been shortened, an idle symbol (idle symbol) is transmitted in the (Mds_New+1) th< to the (Mds_Old) th< symbols in the downstream transmission duration. Mds_New is a quantity of symbols in the new downstream transmission duration; and Mds_Old is a quantity of symbols in the current downstream transmission duration.

[0117] Certainly, for the 1 st< to the (Mds_New) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0118] Step S25: When the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, the central office equipment sends third messages to the customer premise equipments, where the third message includes effective time TDD 3.

[0119] The TDD 3 is determined by the central office equipment based on implementation capability of the central office equipment and implementation capability of the customer premise equipment. For example, the central office equipment determines a time point at which the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, determines, based on the second message sent by the customer premise equipment, a time point at which lengths of downstream transmission durations of transceivers of all the customer premise equipments have been shortened to the length of the new downstream transmission duration, and selects the time point TDD 3 after the two determined time points, that is, the TDD 3 is located after the TDD 2.

[0120] In this step, the TDD 3 is specifically a time point that is determined by the central office equipment and at which a length of an upstream transmission duration is adjusted to a length of a new upstream transmission duration. For different transceivers of the customer premise equipments, values of the TDD 3 may be different. In this embodiment of the present invention, the central office equipment respectively sends third messages to transceivers of corresponding customer premise equipments by using all the transceivers. The third message herein is the foregoing second instruction message.

[0121] In this step, the central office equipment sends the third messages by using downstream RMC symbol. The third message may use a DTAFDC to indicate the effective time TDD 3 determined by the central office equipment. The central office equipment may repeatedly send the DTA message in a TDD frame before the TDD 3 (including the TDD 3), and a DTAFDC decreases gradually (1 is subtracted from each transmission frame) until the TDD 3, and the DTAFDC changes to 0.

[0122] Further, before the central office equipment sends the third messages to the customer premise equipments, the central office equipment further needs to determine whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the new downstream transmission duration.

[0123] The downstream transmission durations of all the transceivers of the central office equipment are adjusted by the central office equipment. Therefore, the central office equipment may record adjustment time of a downstream transmission duration of each transceiver. Whether the downstream transmission duration of each transceiver of the central office equipment has been shortened to the new downstream transmission duration is determined based on the recorded adjustment time of the downstream transmission duration of each transceiver.

[0124] Certainly, because all the transceivers of the central office equipment are controlled by the central office equipment, in an ideal state, it may be considered by default that all the transceivers shorten the lengths of the downstream transmission durations synchronously. In this way, the foregoing step of determining whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the new downstream transmission duration is omitted.

[0125] Step S26: The central office equipment and the customer premise equipment adjust a length of an upstream transmission duration to the length of the new upstream transmission duration.

[0126] Specifically, the central office equipment and the customer premise equipment start to adjust a length of an upstream transmission duration of a transceiver to the length of the new upstream transmission duration from the TDD 3, and do not require that adjustment of lengths of upstream transmission durations of all transceivers be completed in the TDD 3.

[0127] After the central office equipment sends the third messages to the customer premise equipment, the method further includes: processing the 1 st< to the (Mds_Old-Mds_New) th< symbols in the upstream transmission durations by using an upstream joint reception technology.

[0128] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0129] FIG 8 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention. A difference between the method shown in FIG 8 and the method shown in FIG 7 lies in that a length of a new downstream transmission duration is greater than a length of a current downstream transmission duration, and in the method, customer premise equipment sends a second message to central office equipment. Referring to FIG 8, the method includes the following steps.

[0130] Step S30: The central office equipment obtains the length of the new downstream transmission duration.

[0131] For a specific procedure, refer to step S10.

[0132] Step S31: The central office equipment sends a first message to the customer premise equipment, where the first message includes Mds and effective time TDD 1, and the Mds includes the length of the new downstream transmission duration.

[0133] In this step, the TDD 1 is a time point that is determined by the central office equipment and at which a length of an upstream transmission duration is shortened to the length of the new upstream transmission duration.

[0134] Step S32: The customer premise equipment receives the first message, and determines whether a length of an upstream transmission duration can be shortened to the length of the new upstream transmission duration in the TDD 1.

[0135] Step S33: The customer premise equipment sends a second message to the central office equipment, where the second message is used to indicate effective time determined by the customer premise equipment.

[0136] Specifically, if a transceiver of the customer premise equipment can shorten the length of the upstream transmission duration to the length of the new upstream transmission duration in the TDD 1, the effective time of the transceiver of the customer premise equipment that is determined by the customer premise equipment and that is indicated by the second message is the TDD 1. If the transceiver of the customer premise equipment cannot shorten the length of the upstream transmission duration to the length of the new upstream transmission duration in the TDD 1, the effective time of the transceiver of the customer premise equipment that is determined by the customer premise equipment and that is indicated by the second message is a TDD 2. The TDD 2 is new effective time determined by the customer premise equipment. It should be noted that, for transceivers of different customer premise equipments, specific positions of the TDD 2 indicated in the second message may also be different. In this step, the TDD 2 is a time point that is determined by the customer premise equipment and at which a length of an upstream transmission duration of a transceiver is shortened to the length of the new upstream transmission duration.

[0137] Further, to simplify the second message, if the transceiver of the user equipment can shorten the length of the upstream transmission duration to the length of the new upstream transmission duration in the TDD 1, the second message may not include the TDD 1, but uses a simple acknowledgment (ACK) message to indicate that the transceiver of the customer premise equipment can shorten the length of the upstream transmission duration to the length of the new upstream transmission duration in the TDD 1.

[0138] Further, the method further includes: determining, by the central office equipment, whether lengths of upstream transmission durations of transceivers of all customer premise equipments have been shortened to the length of the new upstream transmission duration. A specific process may include: receiving, by the central office equipment, second messages sent by the transceivers of all the customer premise equipments, where the second message is used to indicate a time point that is determined by customer premise equipment and at which a transceiver of the customer premise equipment shortens a length of an upstream transmission duration to the length of the new upstream transmission duration; determining, by the central office equipment based on the second messages, time points at which the transceivers of all the customer premise equipments shorten lengths of upstream transmission durations to the length of the new upstream transmission duration; and determining, by the central office equipment, based on the time points at which the transceivers of all the customer premise equipments shorten the lengths of the upstream transmission durations to the length of the new upstream transmission duration, whether the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration.

[0139] Specifically, the central office equipment compares a current time period (a transmission frame) with a latest time point in the time points at which the transceivers of all the customer premise equipments shorten the lengths of the upstream transmission durations to the latest time of the length of the new upstream transmission duration. If the latest time point is earlier than the current time point, it is determined that the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration. If the latest time point is not before the current time point, it is determined that a length of an upstream transmission duration of a transceiver of the customer premise equipment is not shortened to the length of the new upstream transmission duration.

[0140] Step S34: The central office equipment and the customer premise equipment shorten a length of an upstream transmission duration to the length of the new upstream transmission duration, where the sum of the length of the upstream transmission duration and the length of the downstream transmission duration is equal to a total length of one transmission frame minus upstream and downstream switching duration.

[0141] Before the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration, the method further includes the following step: processing the 1 st< to the (Mds_New-Mds_Old) th< symbols in the upstream transmission durations by using an upstream joint reception technology, where Mds_New is a quantity of symbols in the new downstream transmission duration, and Mds_Old is a quantity of symbols in the current downstream transmission duration.

[0142] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0143] Step S35: After the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration, the central office equipment sends third messages to the customer premise equipments, where the third message includes effective time TDD 3.

[0144] The central office equipment determines, based on the second instruction message, that the transceivers of all the customer premise equipments shorten a length of an upstream transmission duration to the length of the new upstream transmission duration in the TDD 2. Because transceivers of a plurality of customer premise equipments are included herein, the TDD 2 is the latest TDD 2 in the second messages sent by the transceivers of the plurality of customer premise equipments. Therefore, the central office equipment may instruct, by using the third messages, the customer premise equipments to adjust the lengths of the downstream transmission durations in the TDD 3 that is after the TDD 2. In this step, the TDD 3 is a time point that is determined by the central office equipment and at which a length of a downstream transmission duration is adjusted to the length of the new downstream transmission duration.

[0145] Step S36: The central office equipment and the customer premise equipment adjust a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0146] After the central office equipment sends the third message to the customer premise equipment, the method further includes: processing the (Mds _Old+1) th< to the (Mds_New) th< symbols in the downstream transmission durations by using a downstream precoding technology, where for a signal for which a length of a downstream transmission duration has been adjusted, an idle symbol is transmitted on the (Mds _Old+1) th< to the (Mds _New) th< symbols in the downstream transmission duration.

[0147] Certainly, for the 1 st< to the (Mds_Old) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0148] FIG 9 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention. In a method process provided in FIG 9, a length of a new downstream transmission duration is less than a length of a current downstream transmission duration, and in the method, customer premise equipment does not send a second message to central office equipment. Referring to FIG 9, the method includes the following steps.

[0149] Step S40: The central office equipment obtains the length of the new downstream transmission duration.

[0150] For a specific procedure, refer to step S10.

[0151] Step S41: The central office equipment sends a first message to the customer premise equipment, where the first message includes Mds and effective time TDD 1, and the Mds includes the length of the new downstream transmission duration.

[0152] In this step, the TDD 1 is specifically a time point that is determined by the central office equipment and at which the length of the downstream transmission duration is shortened to the length of the new downstream transmission duration.

[0153] Step S42: The customer premise equipment receives the first message.

[0154] Step S43: The central office equipment and the customer premise equipment shorten a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0155] Before the central office equipment shortens lengths of downstream transmission durations of all transceivers of the central office equipment to the length of the new downstream transmission duration, the method further includes: processing the (Mds _New+1) th< to the (Mds _Old) th< symbols in the downstream transmission durations by using a downstream precoding technology, where for a signal for which a length of a downstream transmission duration has been shortened, an idle symbol is transmitted in the (Mds_New+1) th< to the (Mds _Old) th< symbols in the downstream transmission duration, Mds_New is a quantity of symbols in the new downstream transmission duration, and Mds_Old is a quantity of symbols in the current downstream transmission duration.

[0156] Certainly, for the 1 st< to the (Mds_New) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0157] In this embodiment of the present invention, for a process in which the central office equipment and the customer premise equipment shorten a length of a downstream transmission duration to the length of the new downstream transmission duration, refer to step S24.

[0158] Step S44: When the lengths of the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, the central office equipment sends third messages to the customer premise equipments, where the third message includes effective time TDD 3.

[0159] In this step, the TDD 3 is specifically a time point that is determined by the central office equipment and at which a length of an upstream transmission duration is adjusted to the length of the new upstream transmission duration.

[0160] Further, the method further includes: The central office equipment further needs to determine whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the new downstream transmission duration.

[0161] The downstream transmission durations of all the transceivers of the central office equipment are adjusted by the central office equipment. Therefore, the central office equipment may record adjustment time of a downstream transmission duration of each transceiver; and determine, based on the recorded adjustment time of the downstream transmission duration of each transceiver, whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the new downstream transmission duration.

[0162] Certainly, because all the transceivers of the central office equipment are controlled by the central office equipment, in an ideal state, it may be considered by default that all the transceivers shorten the lengths of the downstream transmission durations synchronously. In this way, the foregoing step of determining whether the downstream transmission durations of all the transceivers of the central office equipment have been shortened to the new downstream transmission duration is omitted.

[0163] Step S45: The central office equipment and the customer premise equipment adjust a length of an upstream transmission duration to the length of the new upstream transmission duration.

[0164] After the central office equipment sends the third messages to the customer premise equipments, the method further includes: processing the 1 st< to the (Mds_Old-Mds_New) th< symbols in the upstream transmission durations by using an upstream joint reception technology.

[0165] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0166] In this embodiment of the present invention, for a process in which the central office equipment and the customer premise equipment adjust a length of an upstream transmission duration to the length of the new upstream transmission duration, refer to step S26.

[0167] FIG 10 is a flowchart of another dynamic time assignment method according to an embodiment of the present invention. A difference between the method shown in FIG 10 and the method shown in FIG 9 lies in that a length of a new downstream transmission duration is greater than a length of a current downstream transmission duration, and in the method, customer premise equipment does not send a second message to central office equipment. Referring to FIG 10, the method includes the following steps. Step S50: The central office equipment obtains a length of a new downstream transmission duration;

[0168] For a specific procedure, refer to step S10.

[0169] Step S51: The central office equipment sends a first message to the customer premise equipment, where the first message includes Mds and effective time TDD 1, and the Mds includes the length of the new downstream transmission duration.

[0170] In this step, the TDD 1 is specifically a time point that is determined by the central office equipment and at which a length of an upstream transmission duration is shortened to the length of the new upstream transmission duration.

[0171] Step S52: The customer premise equipment receives the first message.

[0172] Step S53: The central office equipment and the customer premise equipment shorten a length of an upstream transmission duration to the length of the new upstream transmission duration, where the sum of the length of the upstream transmission duration and the length of the downstream transmission duration is equal to a total length of one transmission frame minus upstream and downstream switching duration.

[0173] Before a length of an upstream transmission duration of a transceiver of the customer premise equipment is shortened to the length of the new upstream transmission duration, the method further includes: processing the 1 st< to the (Mds_New-Mds_Old) th< symbols in the upstream transmission durations by using an upstream joint reception technology, where Mds_New is a quantity of symbols in the new downstream transmission duration, and Mds_Old is a quantity of symbols in the current downstream transmission duration.

[0174] Certainly, for a subsequent symbol in the upstream transmission duration, processing needs to be performed by using the upstream joint reception technology at any time.

[0175] Step S54: After the customer premise equipments have shortened all of the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments to the length of the new upstream transmission duration, the central office equipment sends third messages to the customer premise equipments, where the third message includes effective time TDD 3.

[0176] In this step, the TDD 3 is specifically a time point that is determined by the central office equipment and at which the length of the downstream transmission duration is adjusted to the length of the new downstream transmission duration.

[0177] Further, the method further includes: determining, by the central office equipment, whether the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration. A specific process may include: detecting, by the central office equipment frame by frame, a position of an upstream RMC symbol corresponding to a transceiver of customer premise equipment, where when it is detected that the position of the upstream RMC symbol corresponding to the transceiver of the customer premise equipment is delayed, relative to the first position, by a quantity of symbols to be increased by the new downstream transmission duration, it indicates that the length of the upstream transmission duration corresponding to the transceiver of the customer premise equipment has been shortened to the length of the new upstream transmission duration, the first position is the position of the upstream RMC symbol before a point time at which the length of the upstream transmission duration is shortened to the length of the new upstream transmission duration; and determining, by the central office equipment based on positions of upstream RMC symbols corresponding to transceivers of all customer premise equipments, whether the lengths of the upstream transmission durations of the transceivers of all the customer premise equipments have been shortened to the length of the new upstream transmission duration.

[0178] That the central office equipment detects, frame by frame, a position of an upstream RMC symbol corresponding to a transceiver of each customer premise equipment means that positions of upstream RMC symbols corresponding to all transceivers are detected simultaneously in each transmission frame.

[0179] Step S55: The central office equipment and the customer premise equipment adjust a length of a downstream transmission duration to the length of the new downstream transmission duration.

[0180] After the central office equipment sends the third message to the customer premise equipment, the method further includes: processing the (Mds _Old+1) th< to the (Mds _New) th< symbols in the downstream transmission durations by using a downstream precoding technology, where for a signal for which a length of a downstream transmission duration has been adjusted, an idle symbol is transmitted in the (Mds_Old+1) th< to the (Mds _New) th< symbols in the downstream transmission duration.

[0181] Certainly, for the 1 st< to the (Mds _Old) th< symbols in the downstream transmission duration, processing needs to be performed by using the downstream precoding technology at any time.

[0182] An embodiment of the present invention provides a dynamic time assignment apparatus. The dynamic time assignment apparatus may be the foregoing central office equipment. FIG 11 presents a schematic structure of a dynamic time assignment apparatus.

[0183] The data transmission apparatus may be implemented as an entire access network device or a part of an access network device by using a dedicated hardware circuit or a combination of software and hardware. The dynamic time assignment apparatus includes an obtaining unit 400 and an adjustment unit 401. The obtaining unit 400 is configured to obtain a length of a new downstream transmission duration. The adjustment unit 401 is configured to: when the length of the new downstream transmission duration is less than lengths of current downstream transmission durations of the at least two transceivers of the central office equipment, adjust lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration after shortening the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than lengths of current downstream transmission durations of the at least two transceivers, adjust the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration after shortening lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration. A sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

[0184] Optionally, the dynamic time assignment apparatus further includes a sending unit 402 that sends a first instruction message and a second instruction message.

[0185] Optionally, the dynamic time assignment apparatus further includes a determining unit 403 configured to: determine whether lengths of downstream transmission durations of all transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, or determine whether lengths of upstream transmission durations of transceivers of all customer premise equipments have been shortened to the length of the new upstream transmission duration.

[0186] Optionally, the dynamic time assignment apparatus further includes a vectoring unit 404 configured to perform vectoring.

[0187] For related details, refer to the method embodiments corresponding to FIG 6 to FIG 10.

[0188] It should be noted that the adjustment unit 401, the determining unit 403, and the vectoring unit 404 may be implemented by a processor, or implemented by a processor by executing a program instruction in a memory. The obtaining unit 400 and the sending unit 402 may be implemented by a communications interface, or implemented by a communications interface in combination with a processor.

[0189] An embodiment of the present invention provides a dynamic time assignment apparatus. The dynamic time assignment apparatus may be the foregoing customer premise equipment. FIG 12 presents a schematic structural diagram of a dynamic time assignment apparatus.

[0190] The dynamic time assignment apparatus may be implemented as an entire access network device or a part of an access network device by using a dedicated hardware circuit or a combination of software and hardware. The dynamic time assignment apparatus includes an obtaining unit 800 and an adjustment unit 801. The obtaining unit 800 is configured to obtain a length of a new downstream transmission duration. The adjustment unit 801 is configured to: when the length of the new downstream transmission duration is less than a length of a current downstream transmission duration of a transceiver of the customer premise equipment, adjust a length of a current upstream transmission duration of the transceiver of the customer premise equipment to a length of a new upstream transmission duration after shortening the length of the current downstream transmission duration of the transceiver of the customer premise equipment to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than a length of a current downstream transmission duration of a transceiver of the customer premise equipment, adjust the length of the current downstream transmission duration of the transceiver of the customer premise equipment to the length of the new downstream transmission duration after shortening a length of a current upstream transmission duration of the transceiver of the customer premise equipment to the length of the new upstream transmission duration. A sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

[0191] Optionally, the dynamic time assignment apparatus further includes a sending unit 802 configured to send a third instruction message to the central office equipment.

[0192] For related details, refer to the method embodiments corresponding to FIG 6 to FIG 10.

[0193] It should be noted that, the adjustment unit 801 may be implemented by a processor, or implemented by a processor by executing a program instruction in a memory. The obtaining unit 800 and the sending unit 802 may be implemented by a communications interface, or implemented by a communications interface in combination with a processor.

[0194] An embodiment of the present invention provides a dynamic time assignment system. Referring to FIG 13, the dynamic time assignment system may include the foregoing central office equipment 1000 and the foregoing customer premise equipment 1010. The central office equipment 1000 includes the dynamic time assignment apparatus shown in FIG 11, and the customer premise equipment 1010 includes the dynamic time assignment apparatus shown in FIG 12.

[0195] All of examples in the foregoing plurality of embodiments are used to adjust a length or lengths of an upstream transmission duration or a downstream transmission duration based on an Mds parameter. In an optional embodiment, a length of a transmission duration in one direction (to be specific, one, whose length needs to be shortened, of a downstream transmission duration and an upstream transmission duration) may first be shortened by adjusting a transmission opportunity (Transmission Opportunity, TXOP) parameter (or an RMC symbol position and a TXOP parameter), and after lengths of transmission durations of all ports in the direction are all shortened (that is, after lengths of all downstream transmission durations or lengths of all upstream transmission durations are shortened), a length of a transmission duration in another direction is prolonged (one, whose length needs to be prolonged is prolonged, of a downstream transmission duration and an upstream transmission duration).

[0196] The TXOP parameter includes a regular operating duration length TTR, an interval symbol quantity TA, and a transmit budget Tbudget, and is a parameter that has been specified in the current G9701 standard. When a position of the RMC symbol and the Mds have been specified (if the two parameters are specified, positions of all symbols of a TDD frame are specified), the TXOP parameter may be adjusted through an RMC channel, and the change of the TXOP parameter may be used to adjust a position of a symbol that can be used to transmit data in the TDD frame. A total of TBudget symbols, to be specific, the 1 st< to the (TTR) th< symbols and the (TTR+TA+1) th< to the (TBudget+TA) th< symbols, in one TDD frame may be used to transmit data.

[0197] For example, when Mds_new<Mds_old, the TXOP parameter is adjusted in the downstream direction to ensure that a downstream transmission timeslot is in Mds_new symbols starting from a downstream transmission timeslot of the TDD frame. For example, the foregoing objectives are achieved by making the following hold true: TTR<Mds_new-DS RMC offset and TA+TTR>Mds_old-DS RMC offset.

[0198] It should be noted that the dynamic time assignment apparatuses provided in the foregoing embodiments use only division of the foregoing function modules as an example for description during dynamic time assignment. In actual application, the foregoing functions can be allocated to different function modules for implementation as required. To be specific, an inner structure of the device is divided into different function modules to implement all or some of the foregoing functions. In addition, the dynamic time assignment apparatuses provided in the foregoing embodiments are based on a same conception as the foregoing dynamic time assignment method embodiments, and for a specific implementation process, refer to the method embodiments, and details are not described again.

[0199] A person of ordinary skill in the art may understand that all or some of the steps of the foregoing embodiments may be implemented by hardware or a program instructing related hardware. The program may be stored in a computer readable storage medium. The storage medium may be a read-only memory, a magnetic disk, an optical disc, or the like.

[0200] The foregoing descriptions are merely optional embodiments of this application, but are not intended to limit this application. Any modification, equivalent replacement, or improvement made without departing from the principle of this application shall fall within the protection scope of this application.

Claims

1. A dynamic time assignment method, wherein the method is executed by central office equipment, the central office equipment comprises at least two transceivers, and the dynamic time assignment method comprises: Obtaining (S10), by the central office equipment, a length of a new downstream transmission duration; and when the length of the new downstream transmission duration is less than lengths of current downstream transmission durations of the at least two transceivers of the central office equipment, adjusting, by the central office equipment, lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration after shortening the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than lengths of current downstream transmission durations of the at least two transceivers, adjusting, by the central office equipment, the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration after shortening lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration; wherein a sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

2. The dynamic time assignment method according to claim 1, wherein the dynamic time assignment method further comprises: after the central office equipment obtains the length of the new downstream transmission duration, sending (S11), by the central office equipment, a first instruction message to customer premise equipment, wherein the first instruction message comprises the length of the new downstream transmission duration; and after the lengths of the downstream transmission durations of the at least two transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, or after lengths of upstream transmission durations of transceivers of at least two customer premise equipments have been shortened to the length of the new upstream transmission duration, sending, by the central office equipment, a second instruction message to the customer premise equipment, wherein the second instruction message is used to instruct the customer premise equipment to respectively adjust a length parameter of an upstream transmission duration and / or a length parameter of a downstream transmission duration of a transceiver of the customer premise equipment to a length of an upstream transmission duration and a length of a downstream transmission duration that are determined based on the length of the downstream transmission duration in the first instruction message, and the transceivers of the at least two customer premise equipments and the at least two transceivers of the central office equipment are disposed correspondingly.

3. The dynamic time assignment method according to claim 2, wherein the sending, by the central office equipment, a first instruction message to customer premise equipment comprises: sending, by the central office equipment, the first instruction message by using a downstream robustness management channel, RMC, symbol; and the sending (S14), by the central office equipment, a second instruction message to the customer premise equipment comprises: sending, by the central office equipment, the second instruction message by using an RMC symbol.

4. The dynamic time assignment method according to claim 1, wherein the method further comprises: determining, by the central office equipment, whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration.

5. The dynamic time assignment method according to claim 4, wherein the determining, by the central office equipment, whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration comprises: receiving, by the central office equipment, third instruction messages sent by transceivers of at least two customer premise equipments, wherein the third instruction messages are used to indicate time points that are determined by the customer premise equipments and at which the transceivers of the customer premise equipments shorten the lengths of the upstream transmission durations to the length of the new upstream transmission duration; determining, by the central office equipment based on the third instruction message, a time point at which the transceivers of the at least two customer premise equipments shorten the lengths of the upstream transmission durations to the length of the new upstream transmission duration; and determining, by the central office equipment based on the time point at which the transceivers of the at least two customer premise equipments shorten the lengths of the upstream transmission durations to the length of the new upstream transmission duration, whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration.

6. The dynamic time assignment method according to claim 4, wherein the determining, by the central office equipment, whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration comprises: detecting, by the central office equipment frame by frame, positions of upstream RMC symbols corresponding to the transceivers of the at least two customer premise equipments, wherein when it is detected that a position of an upstream RMC symbol corresponding to a transceiver of first customer premise equipment is delayed, relative to a first position, by a quantity of symbols by which the new downstream transmission duration is to be increased, a length of an upstream transmission duration corresponding to the transceiver of the first customer premise equipment has been shortened to the length of the new upstream transmission duration; the first position is the position of the upstream RMC symbol before a time point at which the length of the upstream transmission duration is shortened to the length of the new upstream transmission duration; and the at least two customer premise equipments comprise the first user equipment; and determining, by the central office equipment based on detected positions of upstream RMC symbols corresponding to the transceivers of the at least two customer premise equipments, whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration.

7. The dynamic time assignment method according to any one of claims 1 to 6, wherein when the length of the new downstream transmission duration is less than the lengths of the current downstream transmission durations of the at least two transceivers of the central office equipment, the dynamic time assignment method further comprises: before the lengths of the downstream transmission durations of the at least two transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, processing, by the central office equipment, the (Mds_New+1)th to the (Mds_Old)th symbols in the downstream transmission durations by using a downstream precoding technology, wherein the (Mds_New+1)th to the (Mds _Old)th symbols in the downstream transmission durations are idle symbols, Mds_New is a quantity of symbols in the new downstream transmission duration, and Mds_Old is a quantity of symbols in the current downstream transmission duration.

8. The dynamic time assignment method according to any one of claims 1 to 6, wherein when the length of the new downstream transmission duration is greater than the lengths of the current downstream transmission durations of the at least two transceivers of the central office equipment, the dynamic time assignment method further comprises: before the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration, processing, by the central office equipment, the 1st to the (Mds_New-Mds_Old)th symbols in the upstream transmission durations by using an upstream joint reception technology, wherein Mds_New is a quantity of symbols in the new downstream transmission duration, and Mds_Old is a quantity of symbols in the current downstream transmission duration.

9. A dynamic time assignment apparatus, wherein the dynamic time assignment apparatus comprises: an obtaining unit (400), configured to obtain a length of a new downstream transmission duration; and an adjustment unit (401), configured to: when the length of the new downstream transmission duration is less than lengths of current downstream transmission durations of at least two transceivers of the central office equipment, adjust lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration after shortening the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration; or when the length of the new downstream transmission duration is greater than lengths of current downstream transmission durations of the at least two transceivers, adjust the lengths of the current downstream transmission durations of the at least two transceivers to the length of the new downstream transmission duration after shortening lengths of current upstream transmission durations of the at least two transceivers to a length of a new upstream transmission duration; and a sum of the length of the new upstream transmission duration and the length of the new downstream transmission duration is equal to a length obtained by subtracting upstream and downstream switching duration from one transmission frame.

10. The dynamic time assignment apparatus according to claim 9, wherein the apparatus further comprises: a sending unit (402), configured to: after the central office equipment obtains the length of the new downstream transmission duration, send a first instruction message to customer premise equipment, wherein the first instruction message comprises the length of the new downstream transmission duration; and after the lengths of the downstream transmission durations of the at least two transceivers of the central office equipment have been shortened to the length of the new downstream transmission duration, or after lengths of upstream transmission durations of transceivers of at least two customer premise equipments have been shortened to the length of the new upstream transmission duration, send a second instruction message to the customer premise equipment, wherein the second instruction message is used to instruct the customer premise equipment to respectively adjust a length parameter of an upstream transmission duration and / or a length parameter of a downstream transmission duration of a transceiver of the customer premise equipment to a length of an upstream transmission duration and a length of a downstream transmission duration that are determined based on the length of the downstream transmission duration in the first instruction message, and the transceivers of the at least two customer premise equipments and the at least two transceivers of the central office equipment are disposed correspondingly.

11. The dynamic time assignment apparatus according to claim 10, wherein the sending unit (402) is configured to: send the first instruction message by using a downstream RMC symbol; and send the second instruction message by using an RMC symbol.

12. The dynamic time assignment apparatus according to claim 10 or 11, wherein the dynamic time assignment apparatus further comprises: a determining unit (403), configured to determine whether the lengths of the upstream transmission durations of the transceivers of the at least two customer premise equipments have been shortened to the length of the new upstream transmission duration.

13. A dynamic time assignment system, wherein the dynamic time assignment system comprises central office equipment and customer premise equipment, and the central office equipment comprises the dynamic time assignment apparatus according to any one of claims 9 to 12.