WO2016023204A1

WO2016023204A1 - Time synchronization method, apparatus and system

Info

Publication number: WO2016023204A1
Application number: PCT/CN2014/084374
Authority: WO
Inventors: 张利
Original assignee: 华为技术有限公司
Priority date: 2014-08-14
Filing date: 2014-08-14
Publication date: 2016-02-18
Also published as: CN105531940B; CN105531940A

Abstract

Provided are a time synchronization method, apparatus and system. The method comprises: a CMTS device acquires a data flow from an SNI, extracts a time message from the data flow including the time message and a data message, then sends the time message to a CM via a signalling channel and sends the data message to the CM via a data channel, wherein the signalling channel and the data channel are different in working frequency points. Since the signalling channel transmitting the time message has a fixed processing time delay, there is no time delay variation, and precision of time information in the transmitted time message is guaranteed, so that precise time synchronization in a DOCSIS network can be realized.

Description

Time synchronization method, device and system

Technical field

Embodiments of the present invention relate to communication technologies, and in particular, to a time-simulating method, apparatus, and system. Background technique

The evolution of the mobile network from the macro base station to the micro base station will become the mainstream construction mode of the future 4G network, and the cable operator has wide coverage, high bandwidth capability Cable outside plant resources, and is in the field for broadband access. It has a wide range of mature engineering applications in equipment installation, and is therefore the best bearer backhaul network for indoor or outdoor deployment of micro base stations.

The current mainstream technology for cable TV access networks is Data Over Cable Service Interface Specifications (DOCSIS), among which Cable Modem Terminal Systems (CMTS) devices are used. The communication process with the cable modem terminal (Cable Modem, CM for short) is: The data frame received by the CMTS device from the external network is encapsulated in the Moving Pictures Experts Group (MPEG) time stamp (Timestamp, referred to as TS In the frame, the downlink data is modulated and mixed with the cable analog signal to output a radio frequency (Radio Frequency, abbreviated as: RF) signal to the Hybrid Fiber Coaxial (HFC) network, and the CMTS device simultaneously receives the uplink reception. The signal output by the machine, and the data signal is converted into an Ethernet frame to the data conversion module.

The most widely used and most mature technology in packet networks is the Institute of Electrical and Electronics Engineers (IEEE): 1588. V2 peer-to-peer technology. IEEE1588.V2 is a master-slave peer-to-peer system. During the peer-to-peer process of the system, the master clock periodically issues the precise clock protocol (Precision Time Protocol, PTP) and time information, and receives the master clock port from the clock port. The timestamp information sent by the system, based on which the system calculates the master-slave line time delay and the master-slave time difference. Since the IEEE 1588 Adaptive Clock Recovery (ACR) function can realize transparent transmission of clocks in the DOCSIS network, an adaptive method based on the Circuit Emulation Service (CES) is used to restore the source. Clocks, there are two implementations of the existing IEEE1588 ACR based frequency peers. The first is to deploy the 1588 ACR server (Server) as the clock source, and then start the 1588 ACR client (Client) function built in the base station to recover the clock signal directly from the data packet. The other way is to install the support on the base station side. The 1588 ACR's dedicated clock device is restored to the primary clock and then provided to the base station as an external clock source.

However, the IEEE 1588 ACR can only recover clock information, cannot recover time information, and the quality of the ACR recovery clock is very dependent on the performance of the DOCSIS bearer network. For example, the transmission delay, jitter, packet loss rate, and bandwidth can all recover the clock from the ACR. Accuracy has a serious impact. Summary of the invention

Embodiments of the present invention provide a method, apparatus, and system for time homology to achieve accurate time synchronism in a DOCSIS network.

In a first aspect, an embodiment of the present invention provides a method for time synchronization, including:

The cable modem terminal system CMTS device obtains a data stream from the service node interface SNI, and extracts a time message from the data stream; wherein the data stream includes a data message and the time message;

The CMTS device sends the time message to the cable modem terminal CM through the signaling channel, and sends the data packet to the CM through the data channel; wherein the signaling channel works with the data channel The frequency is different.

In a first possible implementation manner of the first aspect, the signaling channel is an out-of-band management channel OOB; wherein the OOB has a fixed baseband processing delay.

With reference to the first aspect, or the first possible implementation manner of the first aspect, in the second possible implementation manner, the extracting the time packet from the data stream includes:

The CMTS device extracts the time message from the data stream according to a message format. In a second aspect, an embodiment of the present invention provides a method for time synchronization, including:

The cable modem terminal CM receives the time message and the data message sent by the cable modem terminal system CMTS device; wherein the time message is sent by the CMTS device through a signaling channel, and the data message is the CMTS device Transmitted by the data channel, where the signaling channel is different from the working frequency of the data channel;

The CM merges the time message into the data packet through the user network interface UNI and sends the time message to the next-level mobile base station device. In a first possible implementation manner of the second aspect, the CM, by using the user network interface UNI, the time message is merged into the data packet and sent to the next-stage mobile base station device, including: the CM And sending, by the UNI, the time packet and the data packet to the next-level mobile base station device.

In a third aspect, an embodiment of the present invention provides a cable modem terminal system CMTS device, including:

An obtaining module, configured to obtain a data packet from the service node interface SNI, and extract a time packet from the data stream, where the data stream includes a data packet and the time packet;

a sending module, configured to send the time message to the cable modem terminal CM through a signaling channel, and send the data packet to the CM through a data channel; wherein the signaling channel and the data channel The frequency of work is different.

In a first possible implementation manner of the third aspect, the signaling channel is an outband management channel OOB; wherein the OOB has a fixed baseband processing delay.

With reference to the third aspect, or the first possible implementation manner of the third aspect, in a second possible implementation, the acquiring module is specifically configured to: extract the time from the data stream according to a packet format Message.

According to a fourth aspect, an embodiment of the present invention provides a cable modem terminal CM, including: a receiving module, configured to receive a time packet and a data packet sent by a cable modem terminal system CMTS device; wherein the time packet is The CMTS device is sent by using the signaling channel, where the data packet is sent by the CMTS device through a data channel, where the signaling channel is different from the working frequency of the data channel;

And a sending module, configured to merge the time message into the data message by using a user network interface UNI and send the time message to the next-stage mobile base station device.

In a first possible implementation manner of the fourth aspect, the sending module is configured to send, by using the UNI, the time packet and the data packet to the next-level mobile base station device.

The fifth aspect, the embodiment of the present invention provides a time-simulating system, such as the cable modem terminal system CMTS device according to any one of the third aspect to the second possible implementation manner of the third aspect, and the fourth aspect The cable modem terminal CM of any of the first possible implementations of the fourth aspect. The method, device and system for time-synchronization provided by the embodiment of the present invention acquires a data stream from the SNI through the CMTS device, and extracts a time packet from the data stream including the time packet and the data packet, and then the time packet The data packet is sent to the CM through the data channel through the signaling channel; wherein the signaling channel and the data channel have different operating frequencies; since the signaling channel of the transmission time packet has a fixed processing delay, there is no delay Jitter ensures the accuracy of the time information in the transmitted time message, so accurate time synchronization can be achieved in the DOCSIS network. DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description of the drawings used in the embodiments or the prior art description will be briefly described below. Obviously, the drawings in the following description It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

1 is a flow chart of a first embodiment of a method for time synchronization according to the present invention;

2 is a flowchart of Embodiment 2 of a method for time homology according to the present invention;

3 is a schematic structural diagram of an implementation manner of a method for time homogeneity according to the present invention;

4 is a schematic structural diagram of Embodiment 1 of a CMTS device according to the present invention;

FIG. 5 is a schematic structural diagram of Embodiment 1 of a CM according to the present invention. The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. The embodiments are a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

FIG. 1 is a flowchart of Embodiment 1 of a method for time synchronization of the present invention. The method provided in this embodiment may be performed by a CMTS device, as shown in FIG. 1. Specifically, the method provided in this embodiment may include:

S101. The CMTS device obtains a data stream from a service node interface (SNI), and extracts a time packet from the data stream. The data stream includes Data message and the time message.

It should be noted that the CMTS device completes the same as the primary clock when the device is initialized, and generates a local clock that is in phase with the primary clock. The time packet contains the local clock of the CMTS device.

In this step, since the data stream obtained from the SNI includes the data packet and the time packet, in order to extract the time packet from the data stream, the CMTS device extracts the time report from the data stream according to the packet format. For sending the time message to the CM through a separate signaling channel.

S102. The CMTS device sends the time packet to the CM through a signaling channel, and sends the data packet to the CM through a data channel. The signaling channel and the working frequency of the data channel The point is different.

Usually, the CMTS device modulates the time message by means of Quadrature Phase Shift Keying (QPSK) and then sends it to the CM through the signaling channel.

It should be noted that, since the signaling channel has a fixed processing delay, and the signaling channel can be implemented by using a separate uplink and downlink frequency point in the cable access system, the signaling channel can be frequency division multiplexed with the data channel. The way to achieve, and the signaling channel can use a relatively small spectrum width due to the small amount of data, such as 160KHz, 320KHz, and the consumption of system spectrum resources is also small.

Specifically, in this embodiment, the signaling channel may be an Out Of Band (OOB); wherein the OOB has a fixed baseband processing delay, that is, no delay jitter, so The accuracy of the time information transmitted through the OOB is guaranteed.

In the technical solution of the embodiment, the data stream is obtained from the SNI through the CMTS device, and the time packet is extracted from the data stream including the time packet and the data packet, and then the time packet is sent through the signaling channel and the data packet is sent. The data channel is sent to the CM. The signaling channel and the data channel have different operating frequencies. The signaling channel of the transmission time packet has a fixed processing delay, and there is no delay jitter, which ensures the transmission of the time packet. The accuracy of the time information allows accurate time synchronization in the DOCSIS network.

FIG. 2 is a flowchart of Embodiment 2 of a method for time homology according to the present invention. As shown in FIG. 2, the method provided in this embodiment may be specifically performed by a CM device. Specifically, the method for time synchronization provided in this embodiment may include:

The S20 CM receives the time packet and the data packet sent by the CMTS device, where the time packet is sent by the CMTS device through a signaling channel, and the data packet is sent by the CMTS device through a data channel, The signaling channel and the working frequency of the data channel Different

S202: The CM joins the time packet into the data packet through a user network interface (User Network Interface, UNI for short) and sends the time packet to the next-stage mobile base station device.

Specifically, the merging the time message into the data packet and sending it to the next-stage mobile base station device includes: sending, by the CM, the time packet and the data packet by using the UNI And sending, to the next-stage mobile base station device, the time packet and the data packet into a data stream, and transmitting the data packet to the next-level mobile base station device.

In the technical solution of the embodiment, the CM receives the time packet sent by the CMTS device through the signaling channel, and receives the data packet sent by the CMTS device through the data channel, where the signaling channel and the data channel have different working frequencies, and then pass The UNI combines the time packet into the data packet and sends it to the next-stage mobile base station device. Since the signaling channel has a fixed processing delay, the accuracy of the time information in the time packet received by the CM can be ensured, so that the UNI can be in the DOCSIS. Achieve accurate time peers in the network.

The method of the present invention will be further described below with reference to FIG.

In this embodiment, the time information, that is, the time packet, is separated from the broadband data channel in the joint interface of the SNI of the CMTS device, and is transmitted to the remote CM device by using a separate narrowband signaling channel, and then the UNI of the CM is integrated. After the time information received by the narrowband signaling channel, the time information of the next-stage mobile base station device along with the path data is used to complete the time synchronization.

As shown in FIG. 3, the technical solution of this embodiment mainly includes a TS & Phase Locked Loop (PLL) module, a Timing Media Access Control (MAC) module, and a Timing physical layer. (Physical Layer) module, where the TS&PLL module is responsible for generating a local clock that is in phase with the main clock, that is, time information; the Timing MAC module is responsible for encapsulating time information into a time message, and performing ranging and one-way delay estimation, and the like. Function; Timing PHY module is responsible for data modulation, in order to simplify the design, usually adopts QPSK mode; SNI/DTI PHY module is the time peer interface module of the physical layer of the uplink port, responsible for completing the time with the upper-level network device; UNI The /DTI PHY module is a time peer interface module of the physical layer of the user interface, and is responsible for providing precise time for the next-level mobile base station device; the MAC module and the PHY module are respectively the media access layer processing module and the physical layer processing module of the data channel.

The narrowband signaling channel is usually implemented by a separate uplink frequency point and a downlink frequency point in the cable access system, and the signal of the data channel is frequency division multiplexed, and the signaling channel is small due to the small amount of data. To use a relatively small spectrum width, such as 160KHz, 320KHZ, etc., the system spectrum resources are less expensive.

When a separate signaling channel is used to achieve time synchronization, the signaling channel can be implemented in the CMTS device with the DOCSIS on the CMTS device side, and the Field-Programmable Gate Array can be used in the CM device. Abbreviation: FPGA) implementation. Specifically, the CMTS device separates the time and phase information in the data channel of the uplink interface, and encapsulates the time information into a separate time packet, and works in a signaling channel at a different frequency point with the data channel to the CM in the HFC network. Pass time information to complete the same time.

In another feasible implementation, the OOB channel can be used as a signaling channel to transmit time information. It should be noted that the OOB channel is an independent bidirectional data channel established by the cable television access system outside the DOCSIS, and is used for transmitting an electronic program guide (Electronic Program Guide, EPG) program list and video on demand technology (Video On Demand : VOD) Information such as on-demand signaling and set-top box control signaling. The OOB channel physical layer adopts special uplink and downlink PHY and MAC technologies. The downlink channel frequency works at 70~130MHz, the spectrum bandwidth is l~2MHz; the uplink channel works at 5~42MHz, the spectrum bandwidth is 192KHz~2MHz, and the uplink and downlink PHYs are both Differential QPSK modulation is used. Because the OOB channel has the advantages of small data volume and simple technology, it is very suitable as a signaling channel for realizing time, so the time synchronization can be realized by protocol extension by means of the OOB channel, and no additional is generated for the cable television access system. Spectrum overhead.

Specifically, the OOB channel is mainly composed of an OOB demodulator (Demodulator), an OOB modulator (Modulator), a network controller (Network Controller), and a data transmission interface server (DTI Server) on the CMTS device side, among which, OOB The Demodulator is the upstream PHY of the OOB channel, and the OOB Modulator is the downstream PHY of the OOB channel. Since the OOB PHY baseband modulation processing provides a fixed baseband processing delay for the data link in units of fixed length frames, the Timing PHY module of this embodiment is used. The OOB PHY can be directly reused to provide a unified physical layer modulation module for OOB signaling data and Timing time and the same signaling data; the DTI Server provides a global clock function for all central office devices, and thus can be used as the TS&PLL module of this embodiment; The Controller can be an OOB MAC entity. It is usually implemented by a Central Processing Unit (CPU) and software. In this embodiment, a software module can be added to the Network Controller to extend the Timing MAC function.

At the CM terminal, the OOB PHY is usually implemented with an integrated chip, with the CMTS device. Similar to the terminal, it can also be used for the Timing PHY, and the Timing MAC can be realized by extending the CM CPU software.

As shown in FIG. 3, the process of implementing accurate time synchronization by the technical solution of this embodiment is specifically as follows:

On the CMTS device side, after the SNI/DTI PHY module completes the time synchronization of the upper-level network device, for the signaling channel, the TS&PLL module generates a local clock that is in phase with the main clock, that is, the time information, and then passes the time information to the Timing MAC. The module, the Timing MAC module encapsulates the time information into a time message, and passes the time message to the Timing PHY module, which modulates the time message and sends it to the remote CM device; meanwhile, at the SNI/DTI PHY After the module completes the time synchronization of the upper-level network device, for the data channel, the MAC module and the PHY module respectively process the data packet according to the prior art scheme, and then send the data packet to the remote CM device.

On the CM device side, for the data channel, the MAC module and the PHY module of the CM device also process the received data packet according to the prior art scheme, and then transmit the received data packet to the UNI/DTI PHY module. For the signaling channel, the CM device The Timing PHY module demodulates the received time message and passes it to the Timing MAC module. The Timing MAC module parses the time information from the time message and then passes the time information to the TS&PLL module. The TS&PLL module updates the local clock based on the time information. , generating new time information, and then transmitting the new time information to the UNI/DTI PHY module, and the UNI/DTI PHY module transmits the received data message together with the time information to the next-level mobile base station device, due to SNI/DTI The PHY module, TS&PLL module, Timing MAC module, Timing PHY module, and UNI/DTI PHY module all have fixed delays, so that the above technical solutions can achieve accurate time synchronization in the DOCSIS network.

The technical solution of this embodiment can implement time synchronization in the DOCSIS network.

FIG. 4 is a schematic structural diagram of Embodiment 1 of a CMTS device according to the present invention. As shown in FIG. 4, the CMTS device 10 provided in this embodiment may specifically include: an obtaining module 11 and a sending module 12.

The obtaining module 11 is configured to obtain a data stream from the SNI, and extract a time packet from the data stream, where the data stream includes a data packet and the time packet;

The sending module 12 is configured to send the time packet to the CM through a signaling channel, and send the data packet to the CM through a data channel, where the signaling channel and the working frequency of the data channel different. It should be noted that the CMTS device 10 completes the same as the primary clock when the device is initialized, and generates a local clock that is in phase with the primary clock. The time packet includes the local clock of the CMTS device 10.

Specifically, in order to extract the time packet from the data stream, the acquiring module 11 may specifically extract the time packet from the data stream according to the packet format, so as to pass the time packet through separate signaling. The channel is sent to the CM.

Generally, the sending module 12 uses the QPSK method to modulate the time message, and then sends the time message to the CM through the signaling channel.

In a feasible implementation manner, the signaling channel may be an OOB; wherein the OOB has a fixed baseband processing delay, that is, no delay jitter, so that the accuracy of time information transmitted through the OOB can be ensured.

The CMTS device provided in this embodiment may be used to implement the technical solution of the foregoing method embodiment, and the implementation principle and the technical effect are similar, and details are not described herein again.

FIG. 5 is a schematic structural diagram of Embodiment 1 of a CM according to the present invention. As shown in FIG. 5, the CM 20 provided in this embodiment may specifically include: a receiving module 21 and a sending module 22.

The receiving module 21 may be configured to receive a time packet and a data packet sent by the CMTS device, where the time packet is sent by the CMTS device by using a signaling channel, where the data packet is the CMTS device. Transmitted by the data channel, where the signaling channel is different from the working frequency of the data channel;

The sending module 22 can be configured to join the time message into the data message by using the UNI and send it to the next-level mobile base station device.

Specifically, the sending module 22 may send the time packet and the data packet to the next-level mobile base station device by using the UNI, gp, and the time packet and the data. The message is combined into one data stream and transmitted to the next-stage mobile base station device.

The CM provided in this embodiment may be used to implement the technical solution of the foregoing method embodiment, and the implementation principle and the technical effect are similar, and details are not described herein again. The embodiment provides a time-synchronized system. The system of the same time provided by the embodiment may include the CMTS device provided in the foregoing embodiment and the CM provided in the foregoing embodiment.

The CMTS device provided in this embodiment may include an obtaining module and a sending module. For details, refer to the obtaining module 11 and the sending module 12 in the CMTS device 10 of the foregoing embodiment, and details are not described herein again.

The CM provided in this embodiment may include a receiving module and a sending module. For details, refer to the receiving module 21 and the sending module 22 in the CM 20 of the foregoing embodiment, and details are not described herein again.

In the several embodiments provided by the present invention, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are merely illustrative. For example, the division of the unit is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored, or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.

The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, i.e., may be located in one place, or may be distributed over multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a hardware plus software functional unit.

The above-described integrated unit implemented in the form of a software functional unit can be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor to perform the method of various embodiments of the present invention. Partially. The foregoing storage medium includes: a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, which can store program code. .

Those skilled in the art will clearly understand that for the convenience and brevity of the description, only the above The division of each functional module is illustrated. In practical applications, the above function assignment can be completed by different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. For the specific working process of the device described above, reference may be made to the corresponding process in the foregoing method embodiments, and details are not described herein again.

It should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art The technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and the modifications or substitutions do not deviate from the technical solutions of the embodiments of the present invention. range.

Claims

Claim

A method of synchronizing time, characterized in that it comprises:

2. The method according to claim 1, wherein the signaling channel is an out-of-band management channel OOB; wherein the OOB has a fixed baseband processing delay.

The method according to claim 1 or 2, wherein the extracting the time message from the data stream comprises:

The CMTS device extracts the time message from the data stream according to a message format.

4. A method of synchronizing time, characterized in that it comprises:

The CM merges the time message into the data packet through the user network interface UNI and sends it to the next-stage mobile base station device.

The method according to claim 4, wherein the CM merges the time message into the data message through the user network interface UNI and sends the time message to the next-stage mobile base station device, including:

And sending, by the UNI, the time packet and the data packet to the next-level mobile base station device by using the UNI.

A cable modem terminal system CMTS device, comprising: an obtaining module, configured to acquire a data stream from a service node interface SNI, and extract a time packet from the data stream; wherein the data stream Containing a data message and the time message;

a sending module, configured to send the time message to the cable modem terminal CM through a signaling channel, and send the data packet to the CM through a data channel; wherein the signaling channel Different from the operating frequency of the data channel.

The CMTS device according to claim 6, wherein the signaling channel is an out-of-band management channel OOB; wherein the OOB has a fixed baseband processing delay.

The CMTS device according to claim 6 or 7, wherein the acquiring module is specifically configured to: extract the time packet from the data stream according to a packet format.

9. A cable modem terminal CM, comprising:

a receiving module, configured to receive a time packet and a data packet sent by the cable modem terminal system CMTS device, where the time packet is sent by the CMTS device through a signaling channel, and the data packet is the CMTS The device is sent by using a data channel, where the signaling channel is different from the working frequency of the data channel;

The CM according to claim 9, wherein the sending module is configured to send the time message and the data message together to the next-level mobile base station device by using the UNI.

A time-in-time system, comprising: a cable modem termination system CMTS device according to any of claims 6-8, and a cable modem terminal CM according to any of claims 9-10.