CN114125724B

CN114125724B - Time synchronization method and device

Info

Publication number: CN114125724B
Application number: CN202010889082.5A
Authority: CN
Inventors: 苏振华
Original assignee: Datang Mobile Communications Equipment Co Ltd
Current assignee: Datang Mobile Communications Equipment Co Ltd
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2022-07-29
Anticipated expiration: 2040-08-28
Also published as: CN114125724A

Abstract

The embodiment of the application provides a time synchronization method and a time synchronization device. The method comprises the following steps: receiving a Multicast Control Channel (MCCH) configuration message, and acquiring target configuration parameters carried in the MCCH configuration message; carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element; wherein the time synchronization response message includes: the control plane network element determines target wireless frame information of a target wireless frame according to the target configuration parameters; the target radio frame information at least comprises a target radio frame number; and updating the time synchronization parameter of the first wireless frame corresponding to the first moment according to the target wireless frame information. The embodiment of the application solves the problem that in the prior art, time is easily out of step in a message interaction mode between a user plane network element and a control plane network element.

Description

Time synchronization method and device

Technical Field

The present application relates to the field of mobile communications technologies, and in particular, to a time synchronization method and apparatus.

Background

In recent years, with the rapid development of mobile broadband applications, the traffic volume of mobile video services has increased dramatically; however, this presents greater challenges to mobile operators. On one hand, the fast growing video service brings huge network pressure, and the fast consumption of bandwidth causes operators to have to invest a large amount of cost to carry out network capacity expansion; on the other hand, mobile operators are faced with the trend of becoming pipelines, and lack effective business models for data services, especially video services. In order to solve the above problem, an Enhanced Multimedia Broadcast Multicast Service (eMBMS) based on the LTE technology has been developed.

eMBMS is a technology for carrying multimedia broadcast and multicast services in a wireless communication network, and provides a broadcast service to different User Equipments (UEs) through the same radio channel, thereby enabling simultaneous data transmission from a data service source to a plurality of users within a specific range. The eMBMS uses less network resources to simultaneously provide high-bandwidth services such as audio, video, push and the like for a large number of UEs with the same requirements, thereby greatly saving wireless air interfaces and network transmission resources, being more suitable for transmission and use of mobile video services on a wireless communication network at the present stage, and simultaneously providing more channels and clearer and smoother multimedia content, thereby obtaining better user experience and user viscosity.

eMBMS access networks are mainly classified into a Single Cell Point To multi Point (SC-PTM) mode and a multicast/multicast Single Frequency Network (MBMS) mode. The MBMS service of SC-PTM can only be transmitted within one cell, and both a Multicast Traffic Channel (MTCH) and a Multicast Control Channel (MCCH) are mapped to a Downlink Shared Channel (DL-SCH) for Multicast transmission. The MBSFN mode is that a plurality of cells (forming a concept of an MBSFN area) participating in eMBMS in a certain area transmit the same content on the same time and frequency resources, the MTCH and the MCCH are both mapped to a Multicast Channel (MCH) for Multicast transmission, and the UE combines signals from the plurality of cells as multipath signals, so that not only the coverage and transmission quality of a network are improved, but also the cell edge spectrum efficiency is improved. Therefore, the MBSFN mode can support single-cell transmission and is functionally compatible with SC-PTM, but SC-PTM cannot meet the functional requirements of MBSFN, and the eMBMS base station needs to implement the MBSFN mode.

The MBSFN area is composed of a group of cells in the MBSFN synchronization area, each cell corresponds to an MCH channel, the scheduling of a plurality of MCHs is realized by a Multi-cell/Multicast Coordination Entity (MCE) for synchronous transmission, and the MCCH and the MTCH are both mapped to the MCHs for point-to-multipoint transmission.

In order to ensure that the effective Time points of the control surface Information of the MCCH are the same among multiple cells, the MCE carries an updating Time sequence number cell (MCCH Update Time) in a signaling message (MBMS Scheduling Information) indicating that a base station adds/refreshes the MCCH content each Time, the value range of the cell is 0-255, and the MCCH modification period is taken as a step length; each time sequence number represents an explicit modification period number within the duration of one 256 modification period (256 times modification period); and determining the signaling effective time point according to the information such as the MCCH updating time sequence number, the modification period length (value range of 512 or 1024 radio frames), the repetition times (value range of 2 or 4), the radio frame offset, the subframe number and the like. However, the protocol does not specify the start time of the first 256 modification period, and the base station typically implements the following: starting with a configurable absolute start time (e.g., 1970/1/108:00:00, Beijing time), the absolute time is converted into a radio frame number and a subframe number, and the radio frame number and the subframe number are provided for each subsystem. For example, 256 modification periods are used as periods, and a plurality of 256 modification periods are formed on the time axis; in each 256 modification period, the starting time of each modification period can be represented by a time sequence number (0-255). The absolute start time of each modification period is equal to the absolute start time of the first 256 modification periods plus the offset value of the modification period from the first 256 modification periods.

For example, in a signaling message sent by the MCE to the base station, each cell is required to Update the MCCH content in an MCCH Update Time-5 modification periods. After receiving the signaling message, each base station may issue a modification Notification (Notification) in a modification period (MCCH Update Time ═ 4) before the modification period, and the UE receives the modification Notification in the previous modification period and receives the MCCH Update content in the next modification period. All cells are respectively controlled to update the MCCH content in the indicated specific modification period, the mechanism ensures that the multi-cells for updating the MCCH content are synchronous, and the problem that the MCCH is not synchronously transmitted due to different time points when MCE signaling is received by different cells is solved. In this way, all UEs in the multi-cell will receive the updated MCCH content at the same time point.

Part of user plane network elements in the eMBMS system, such as layer two (L2 layer), are responsible for scheduling MCCH and service data, L2 needs to know the radio frame number of data scheduling, but only maintain the radio frame number information inside L2, and not maintain the absolute time, so an Operation and Maintenance module (OM) of a control plane network element, such as a base station, needs to inform L2 of the correspondence between the absolute time and the radio frame number in advance, each time point corresponds to an absolute time stamp, and the time stamp is in the form of an integer with the absolute start time as a reference. In the query process of the corresponding relationship between the absolute time and the radio frame number between the OM and the L2, a message interaction mode is adopted, however, due to the time delay existing in the message interaction between the L2 and the OM, the time point when the L2 receives the response message is later than the sending time point when the response message is sent, and further, the air interface time point of the MCCH and the service data sent by the L2 is later than the time point specified by the core network, and finally, the time desynchronization is caused.

Disclosure of Invention

The embodiment of the application provides a time synchronization method and a time synchronization device, which are used for solving the problem that in the prior art, time is easily out of step in a message interaction mode between a user plane network element and a control plane network element.

In one aspect, an embodiment of the present application provides a time synchronization method, which is applied to a user plane network element, and the method includes:

receiving a Multicast Control Channel (MCCH) configuration message, and acquiring target configuration parameters carried in the MCCH configuration message;

carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element; wherein the time synchronization response message includes: the control plane network element determines target wireless frame information of a target wireless frame according to the target configuration parameters; the target radio frame information at least comprises a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message;

and updating the time synchronization parameter of the first wireless frame corresponding to the first moment according to the target wireless frame information.

On the other hand, an embodiment of the present application further provides a time synchronization method, which is applied to a control plane network element, and the method includes:

receiving a broadcast frame synchronization request message sent by a user plane network element, and acquiring a target configuration parameter carried in the broadcast frame synchronization request message;

determining target radio frame information of a target radio frame according to the target configuration parameters, wherein the target radio frame information at least comprises a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message;

and carrying the target wireless frame information in a time synchronization response message and sending the time synchronization response message to the user plane network element.

On the other hand, an embodiment of the present application further provides a time synchronization apparatus, which is applied to a user plane network element, and the apparatus includes:

the device comprises a parameter acquisition module, a parameter selection module and a parameter selection module, wherein the parameter acquisition module is used for receiving a Multicast Control Channel (MCCH) configuration message and acquiring target configuration parameters carried in the MCCH configuration message;

a response receiving module, configured to carry the target configuration parameter in a broadcast frame synchronization request message, send the broadcast frame synchronization request message to a control plane network element, and receive a time synchronization response message fed back by the control plane network element; wherein the time synchronization response message includes: the control plane network element determines target wireless frame information of a target wireless frame according to the target configuration parameters; the target radio frame information at least comprises a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message;

And the parameter updating module is used for updating the time synchronization parameter of the first wireless frame corresponding to the first moment according to the target wireless frame information.

On the other hand, an embodiment of the present application further provides a time synchronization apparatus, which is applied to a control plane network element, and the apparatus includes:

a request receiving module, configured to receive a broadcast frame synchronization request message sent by a user plane network element, and acquire a target configuration parameter carried in the broadcast frame synchronization request message;

an information determining module, configured to determine target radio frame information of a target radio frame according to the target configuration parameter, where the target radio frame information at least includes a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message;

and the message sending module is used for sending the target wireless frame information carried in the time synchronization response message to the user plane network element.

In yet another aspect, an embodiment of the present application further provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps in the time synchronization method as described above when executing the computer program.

In still another aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the steps in the time synchronization method as described above.

In the embodiment of the application, target configuration parameters carried in the MCCH configuration message are obtained; carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element; the time synchronization response message comprises a target radio frame number, the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from the first moment when the control plane network element receives the broadcast frame synchronization request message, and the time desynchronization caused by the time delay existing in the message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as the radio frames of the absolute time.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments of the present application will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.

Fig. 1 is a flowchart illustrating steps of a time synchronization method according to an embodiment of the present disclosure;

FIG. 2 is a diagram of a first example of an embodiment of the present application;

FIG. 3 is a flow chart of steps of a second example of an embodiment of the present application;

fig. 4 is a second flowchart illustrating steps of a time synchronization method according to an embodiment of the present application;

fig. 5 is a block diagram of a time synchronization apparatus according to an embodiment of the present disclosure;

fig. 6 is a second block diagram of a time synchronization apparatus according to an embodiment of the present application;

fig. 7 is a block diagram of an electronic device according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

In various embodiments of the present application, it should be understood that the sequence numbers of the following processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application. The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application are capable of operation in sequences other than those illustrated or described herein. In addition, "and/or" in the specification and claims means at least one of connected objects, a character "/" generally means that a preceding and succeeding related objects are in an "or" relationship.

In the embodiments provided herein, it should be understood that "B corresponding to a" means that B is associated with a from which B can be determined. It should also be understood that determining B from a does not mean determining B from a alone, but may be determined from a and/or other information.

Fig. 1 shows a flowchart of a time synchronization method according to an embodiment of the present application.

As shown in fig. 1, an embodiment of the present application provides a time synchronization method, which is applicable to a user plane network element, such as a layer two (L2 layer network element) network element; it can be understood that, in the embodiment of the present application, the user plane network element is exemplified as an L2 layer network element, and may also be applicable to other user plane network elements, and for avoiding repetition, details are not described herein again.

The method comprises the following steps:

step 101, receiving a Multicast Control Channel (MCCH) configuration message, and acquiring target configuration parameters carried in the MCCH configuration message.

The MCCH configuration message is sent by a higher layer (HL layer), such as an RRC layer, and includes target configuration parameters, such as an MCCH modification period, a synchronization period, and a message sequence number. The MCCH modification period is used to determine an effective time point of the control plane information among the multiple cells, for example, within the duration of one 256 × MCCH modification period, corresponding to a specific modification period number; and the base station determines the signaling effective time point according to the information such as the MCCH modification period sequence number, the modification period length (value range of 512 or 1024 radio frames), the repetition times (value range of 2 or 4), the radio frame offset, the subframe number and the like. The synchronization period is used to determine the offset of the start point of the synchronization period, and in each synchronization period, the L2 layer network element may request time synchronization once and send a broadcast frame synchronization request message to the OM network element. The message sequence number is used to indicate a sequence number for a message sent by a higher layer to the L2 layer, and the sequence number is typically in the range of 0 to 15. For convenience of description, hereinafter, the L2 layer network element is abbreviated as L2, and the OM network element is abbreviated as OM.

Step 102, carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element;

the L2 carries the target configuration parameter in a broadcast frame synchronization request message, sends the broadcast frame synchronization request message to the control plane network element, where the control plane network element is, for example, OM, and waits for the time synchronization response message fed back by OM. The time synchronization response message includes: the control plane network element determines target wireless frame information of a target wireless frame according to the target configuration parameters; the target radio frame information at least comprises a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message; the target wireless frame number is used for configuring absolute starting time, the first moment is the moment when OM receives the broadcast frame synchronization request message, after OM receives the broadcast frame synchronization request message, the OM delays a first preset number of wireless frames according to the current time to obtain the delayed wireless frame number, namely the target wireless frame number; thus, the time corresponding to the target wireless frame number is absolute time, and the base station configures an absolute starting time as a starting time; if the instant transmission is not delayed, the time point when the L2 receives the time synchronization response message is later than the transmission time point due to the time delay existing in the message interaction between the user plane network element and the control plane network element, and finally the time is out of step; in the embodiment of the present application, time loss due to time delay existing in message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as radio frames of absolute time.

And the value of the first preset number can be configured, for example, configured to be 1024 or the like, so that the time delay can be configured.

Step 103, updating the time synchronization parameter of the first radio frame corresponding to the first time according to the target radio frame information.

Time synchronization parameters such as synchronization cycle start offset, modification cycle number, and modification cycle position; and updating the time synchronization parameter according to the target wireless frame information, and taking an absolute timestamp corresponding to the target wireless frame as an absolute starting time reference to avoid the time synchronization process from being influenced by time delay existing in message interaction between the L2 and the OM.

In the embodiment of the application, target configuration parameters carried in MCCH configuration messages are obtained; carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element; the time synchronization response message comprises a target radio frame number, the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from the first moment when the control plane network element receives the broadcast frame synchronization request message, and the time desynchronization caused by the time delay existing in the message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as the radio frames of the absolute time. The embodiment of the application solves the problem that in the prior art, time is easily out of step in a message interaction mode between a user plane network element and a control plane network element.

In an optional embodiment, the step of receiving a multicast control channel, MCCH, configuration message comprises:

receiving a multicast control channel MCCH configuration message and starting a waiting response timer; optionally, the timing duration of the wait response timer may be set to 1024 Radio Frames (RF);

the step of receiving the time synchronization response message fed back by the control plane network element includes:

and receiving a time synchronization response message fed back by the control plane network element before the time-out of the waiting response timer.

Before the wait response timer expires, at the current time point (i.e. the first time), the L2 layer network element, for example, a Media Access Control (MAC) network element confirms that the time synchronization response message is received if the time synchronization response message with the same message sequence number as the broadcast frame synchronization request message is received; if the waiting response timer is overtime or the time synchronization response message with the same message sequence number is not received before the time is overtime, the MAC layer network element retransmits the broadcast frame synchronization request message to re-trigger the synchronization request. In addition, if the MAC layer network element receives a time synchronization response message with a different sequence number from the message before the wait response timer expires, the MAC layer network element may directly discard the time synchronization response message.

Specifically, in an optional embodiment, after the step of receiving the multicast control channel MCCH configuration message and starting the wait response timer, the method comprises:

and if the time synchronization response message with the same message sequence number as the broadcast frame synchronization request message is not received before the response waiting timer is overtime, retransmitting the broadcast frame synchronization request message to the control plane network element according to a preset retransmission cycle. For example, if the retransmission cycle is set to 5 minutes, the broadcast frame synchronization request message is retransmitted at a frequency of 5 minutes until synchronization is completed.

In an optional embodiment, the step of retransmitting the broadcast frame synchronization request message to the control plane network element according to a preset retransmission cycle includes:

and if the retransmission times exceed a preset retransmission threshold, executing alarm processing, for example, if the preset retransmission threshold is 5, if 5 continuous retransmissions still do not receive an effective time synchronization response message, executing alarm processing so as to check abnormal conditions in time.

In an optional embodiment, the target configuration parameters include: MCCH modification period (MCCH _ ModificationPeriod), synchronization period and message sequence number; in the embodiment of the application, the synchronization period is a cell configurable parameter, and the reliability of time synchronization can be ensured based on a periodic synchronization mechanism with the configurable period; the message sequence number is the sequence number of the broadcast frame synchronization request message.

The target radio frame information further includes: a target time offset value, a target sequence offset and a target modification period sequence number corresponding to the target radio frame number; as a first example, referring to fig. 2, numerals 0 to 255 on the time axis in fig. 2 denote modification period numbers; as shown in fig. 2, time t1 is the interactive signaling time point between L2 and OM, at which time L2 sends a broadcast frame synchronization request message to OM; the time t2 is a target time point; OM feeds back to L2 a time synchronization response message including the target radio frame number, the target time offset value (m in fig. 2), the target sequence offset (n in fig. 2), and the target modification period sequence number (i in fig. 2).

Referring to fig. 2, the target time offset value is the time offset of the modification period corresponding to the target time point, and the target sequence offset is the time offset of the synchronization sequence at the target time point (time t 2); the sequence number of the target modification period is the sequence number of the modification period in which the target time point is located; the target time point is a time point corresponding to the target wireless frame;

the time synchronization parameters include: the starting offset of the first synchronization cycle, the sequence number of the first modification cycle and the position of the first modification cycle, and the parameters in the time synchronization parameters are the parameters at the current moment.

In an optional embodiment, the method further comprises:

updating a wireless frame count according to the length of the synchronization period and the position of the target wireless frame in the synchronization period;

and the MAC layer network element updates the current wireless frame count according to the length of the synchronization period and the position of the target wireless frame in the synchronization period. The subsequent MAC restarts a new synchronization cycle when it counts to the maximum synchronization cycle. And the RRC sends the wireless frame count to the MAC in the cell configuration parameter, wherein the wireless frame count is greater than or equal to a preset count threshold value, and the next synchronization period is started.

In an alternative embodiment, step 103 includes the following first to fourth steps:

the method comprises the following steps that firstly, a time difference value between a first moment and a target time point is determined; and the target time point is a time point corresponding to the target wireless frame.

Wherein the time difference is determined according to the target radio frame number, the first preset number and a first radio frame number of the first radio frame; that is, the time difference includes: the sum of the target radio frame number and the first preset number, the difference obtained by subtracting the first radio frame number of the first radio frame, and the remainder obtained by complementing the difference with the first preset number are shown as the following first formula:

D_sfn＝(u16Sfn+X-u16CurrentSfn)mod 1024

Wherein D _ sfn represents the time difference; u16Sfn denotes a target radio frame number, X denotes a first preset number, for example 1024; u16CurrentSfn denotes the first radio frame number.

And secondly, determining the offset of the starting point of the first synchronization period according to the time difference, the offset of the target sequence and the synchronization period.

Wherein the first synchronization cycle start offset comprises: first synchronization data or zero;

the first synchronization data is the remainder obtained by adding the sum of the target sequence offset and the time difference value and dividing the sum by the synchronization period;

if the first synchronization data is greater than or equal to the synchronization period, the first synchronization period start offset comprises zero; otherwise, the first synchronization cycle start offset comprises the first synchronization data.

First synchronization data are determined, and according to the value of the synchronization period of the first synchronization data, the value is determined according to the following second formula:

Offset_syncPeriod

＝(u16SyncPeriodSfnOffset-D_sfn+Synchronisation_Period)Mod Synchronisation_Period

wherein Offset _ syncPeriod represents first synchronization data, u16syncPeriod sfnfoffset represents a target sequence Offset, and u16syncPeriod sfnfoffset is abbreviated as n; synchronization _ Period represents the synchronization Period; mod denotes a modulo operation.

And thirdly, determining a second time deviation value according to the first time deviation value, the time difference value and the MCCH modification period.

The second time offset value is the difference between the first time offset value and the time difference value, the sum of the first time offset value and the time difference value is added with a second preset number of MCCH modification periods, and the remainder is obtained by dividing the sum by the second preset number of MCCH modification periods;

alternatively, the second time offset value may be calculated using the following third formula:

M2＝(M1-D_sfn+Y*mcch_ModificationPeriod)Mod(256*mcch_ModificationPeriod)

wherein M2 represents the second time offset value; m1 denotes a first time offset value; y represents a second preset number, such as 256; MCCH _ ModificationPeriod represents an MCCH modification period.

The first time offset value is the product of the MCCH modification period and the target modification period sequence number, and is added with the target time offset value to obtain a sum value,

as shown in the fourth equation below:

M1＝mcch_ModificationPeriod*u8Counter+u8MCCHSfnOffset

where M1 denotes a first time offset value, as shown in fig. 2; u8Counter represents a target modification period number; u8mcchs fnoffset denotes a target time offset value, and u8mcchs fnoffset is abbreviated as m.

And fourthly, determining the sequence number of the first modification period and the position of the first modification period according to the second time offset value.

Wherein the first modified cycle position comprises: second synchronization data or zero;

firstly, second synchronous data are calculated, and then the value of the position of a first modification period is determined according to the second synchronous data and the size of the MCCH modification period;

specifically, the second synchronization data is a radio frame offset between the first time and the start of the MCCH modification period; as shown in the following fifth formula:

u8MCCHSfnOffset0＝M2 Mod mcch_ModificationPeriod

wherein u8MCCHSfnOffset0 represents second synchronization data,

if the second synchronization data is greater than or equal to the MCCH modification period, the first modification period position comprises zero; otherwise, the first modified cycle position includes the second synchronization data.

Optionally, in this embodiment of the present application, the first modification period sequence number includes third synchronization data or zero;

the third synchronization data is obtained by dividing the second time offset value by the MCCH modification period and rounding down;

as shown in the following sixth formula:

Counter0＝Floor(M2/mcch_ModificationPeriod)

where Counter0 indicates the third synchronization data, and Floor indicates the Floor operation.

If the third synchronization data is greater than or equal to the difference between the second preset number and one less, the second time offset value includes the third synchronization data, that is, when the Counter0 is greater than or equal to 255, the first modification period number (u8Counter0) is equal to Counter 0;

Otherwise, the first modification period number includes zero.

As a third example, referring to fig. 3, taking a user plane network element as a MAC layer network element and a control plane network element as an OM as an example, fig. 3 shows a specific example of the embodiment of the present application, which includes the following steps:

in step 301, the global variable g _ u8 sfntimesnreacready is 0 at system initialization.

Step 302, a time synchronization process is initiated.

After a cell configuration parameter MBMS service switch (u8MbmSSwitch) is turned on, a MAC layer network element receives MCCH configuration information (MSG _ RRCMAC _ MCCHCfgreq) of an HL layer, performs a time synchronization process, and extracts target configuration parameters in the MCCH configuration information, wherein the target configuration parameters comprise an MCCH modification Period (mcc _ modificationPeriod), a synchronization Period (synchronization _ Period) and a message Sequence Number (SN).

Step 303, start a wait response timer.

The MAC layer network element sends a broadcast frame synchronization request message to OM, and starts a one-TIME wait response TIMER (SFN _ TIME _ SYNC _ TIMER) with default duration of 1024 RF. The MCCH modification Period (mcc _ ModificationPeriod), synchronization-Period (synchronization-Period), and message Sequence Number (SN) are carried in the broadcast frame synchronization request message.

Step 304, a time synchronization response message is received.

Before the waiting response timer expires, at the current time point, that is, at the first time (u16CurrentSfn, u8CurrentSubSfn), if a time synchronization response message (MSG _ OMMAC _ sfntimesycrsp) with the same SN sequence number as the SN is received, the MAC layer network element sets the global variable g _ u8 sfntimesycready to 1.

Wherein the time synchronization response message includes: a message Sequence Number (SN), a target radio frame number (u16Sfn), a first modification period sequence number (MCCH modification period Counter value, u8Counter), a first synchronization period start Offset (Offset _ sync period), a first modification period position.

If the waiting response timer is overtime or the time synchronization response message with the same SN sequence number is not received before the time-out, the broadcast frame synchronization request message is retransmitted, and the process returns to step 303.

Step 305, calculating a time difference value;

calculating the difference between the current time point and the target time point according to the following formula:

d _ Sfn ═ u16Sfn +1024-u16CurrentSfn) mod 1024, and the first preset value is 1024.

At step 306, a first time offset value M1 is calculated.

The first time offset value is the offset of the target time point in the modification period sequence:

M1＝mcch_ModificationPeriod*u8Counter+u8MCCHSfnOffset。

step 307, first synchronization data is calculated.

Calculating first synchronization data, i.e. the offset of the current point in time from the start of the synchronization period, according to the following formula:

Offset_syncPeriod＝(u16SyncPeriodSfnOffset-D_sfn+Synchronisation_Period)Mod Synchronisation_Period

Wherein synchronization _ Period is a synchronization Period, and u16syncperiod sfnfoffset is a synchronization Period offset.

In step 308, a second time offset value is calculated.

The second time offset value is an offset of the current time point in the modification period sequence, as shown in the following formula:

M2＝(M1-D+256*mcch_ModificationPeriod)Mod(256*mcch_ModificationPeriod)

step 309, third synchronization data is calculated.

Calculating third synchronization data Counter0 according to the following formula, where the third synchronization data is a Counter value corresponding to the MCCH modification period at the current time point:

Counter0＝Floor(M2/mcch_ModificationPeriod

step 310, calculating second synchronization data.

Calculating second synchronization data u8MCCHs fnoffset0 according to the following formula, wherein the second synchronization data is a radio frame offset from the start of the MCCH modification period at the current time point:

u8MCCHSfnOffset0＝M2 Mod mcch_ModificationPeriod

step 311, in the modification period, the synchronization parameter is updated in 10ms interruption:

updating the first synchronization period starting Offset u8MCCHSfnOffset0, wherein when the updated Offset _ syncPerod is larger than or equal to the synchronization period configuration value, the Offset _ syncPerod is equal to 0; otherwise the first synchronization period starts with the updated value of Offset _ syncPeriod.

Update the first modification period position u8 mcchsnfoffoffset 0+ +; if the updated u8MCCHSfnOffset0 is not less than mcch _ ModifienPeriod value, u8MCCHSfnOffset0 is 0; and u8Counter0 counts.

Updating the first modification period sequence number, and when u8Counter0 is larger than or equal to 255, the first modification period sequence number is 0; and g _ u8SupperCounter counts.

At step 312, the synchronization request is retransmitted.

When g _ u8 SuperCounterN is greater than g _ u8 SuperCounterN, the MAC layer network element requests one synchronization from OM again.

If a response message with the same message sequence number is received before the timer is overtime, new time synchronization processing is carried out according to the steps 301 to 309; otherwise, sending a request every 5 minutes until synchronization is completed; the global variable g _ u8 SFNTimeSencReady for this process is 1.

And before the timer is overtime, if the MAC layer network element receives a response with a different sequence number from the request message, the MAC layer network element discards the response, and the MAC layer network element considers that no response message is received.

After the retransmission is started, the MAC layer network element needs to retransmit the request message N TIMEs after waiting for the response TIMER SFN _ TIME _ SYNC _ TIMER to expire, until the synchronization is completed. And reporting an alarm if no response is obtained after the request messages for N (5) times by default, and sending the request according to the frequency of 5 minutes until synchronization is completed.

Step 313, after the MBMS service switch u8MbmsSwitch is turned off, the global variable g _ u8 sfntimesnrayrcready is set to 0, and the synchronization related global variable is set to the initial value.

In the embodiment of the application, target configuration parameters carried in MCCH configuration messages are obtained; carrying the target configuration parameters in a broadcast frame synchronization request message, sending the broadcast frame synchronization request message to a control plane network element, and receiving a time synchronization response message fed back by the control plane network element; the time synchronization response message comprises a target radio frame number, the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from the first moment when the control plane network element receives the broadcast frame synchronization request message, and the time desynchronization caused by the time delay existing in the message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as the radio frames of the absolute time.

Referring to fig. 4, an embodiment of the present application further provides a time synchronization method, which is applied to a control plane network element, such as an OM network element, where the control plane network element is taken as the OM network element in the embodiment of the present application for illustration, and is also applicable to other control plane network elements, and in order to avoid repetition, details are not described here again;

the method comprises the following steps:

step 401, receiving a broadcast frame synchronization request message sent by a user plane network element, and acquiring a target configuration parameter carried in the broadcast frame synchronization request message.

The L2 carries the target configuration parameters in the broadcast frame synchronization request message and sends the broadcast frame synchronization request message to the OM, and the OM receives the broadcast frame synchronization request message and acquires the target configuration parameters carried in the broadcast frame synchronization request message; target configuration parameters such as MCCH modification period, synchronization period and message sequence number.

Specifically, the MCCH modification period is used to determine an effective time point of the control plane information between multiple cells, for example, within a duration of 256 × MCCH modification period, corresponding to an explicit modification period number; and the base station determines the signaling effective time point according to the information such as the MCCH modification period sequence number, the modification period length (value range of 512 or 1024 radio frames), the repetition times (value range of 2 or 4), the radio frame offset, the subframe number and the like. The synchronization period is used to determine the offset of the start of the synchronization period, and L2 may request time synchronization once in each synchronization period, and send a broadcast frame synchronization request message to OM. The message sequence number is used to indicate the sequence number of the message sent by the higher layer to L2, and the sequence number range is typically 0 to 15.

Step 402, determining target radio frame information of a target radio frame according to the target configuration parameters, wherein the target radio frame information at least comprises a target radio frame number; and the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from the first moment when the control plane network element receives the broadcast frame synchronization request message.

OM confirms the goal radio frame information of the goal radio frame according to the goal configuration parameter; the target radio frame information at least comprises a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message; the target wireless frame number is used for configuring absolute starting time, the first moment is the moment when OM receives the broadcast frame synchronization request message, after OM receives the broadcast frame synchronization request message, the OM delays a first preset number of wireless frames according to the current time to obtain the delayed wireless frame number, namely the target wireless frame number; thus, the time corresponding to the target wireless frame number is absolute time, and the base station configures an absolute starting time as a starting time; if the instant transmission is not delayed, the time point when the L2 receives the time synchronization response message is later than the transmission time point due to the time delay existing in the message interaction between the user plane network element and the control plane network element, and finally the time is out of step; in the embodiment of the present application, time loss due to time delay existing in message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as radio frames of absolute time.

And the value of the first preset number can be configured, for example, to be 1024 or the like, so that the delay can be configured.

Step 403, sending the target radio frame information carried in a time synchronization response message to the user plane network element.

And OM sends the target radio frame information carried in the time synchronization response message to the user plane network element, so that L2 updates the time synchronization parameter of the first radio frame corresponding to the first time according to the target radio frame information. Time synchronization parameters such as synchronization cycle start offset, modification cycle number, and modification cycle position; and updating the time synchronization parameter according to the target wireless frame information, and taking an absolute timestamp corresponding to the target wireless frame as an absolute starting time reference to avoid the time synchronization process from being influenced by time delay existing in message interaction between the L2 and the OM.

In the embodiment of the application, a broadcast frame synchronization request message sent by a user plane network element is received, and a target configuration parameter carried in the broadcast frame synchronization request message is acquired; determining target radio frame information of a target radio frame according to the target configuration parameters, wherein the target radio frame information at least comprises a target radio frame number; carrying the target wireless frame information in a time synchronization response message and sending the time synchronization response message to the user plane network element; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message, and time desynchronization caused by time delay existing in message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as radio frames of absolute time. The embodiment of the application solves the problem that in the prior art, time is easily out of step in a message interaction mode between a user plane network element and a control plane network element.

Referring to fig. 2, the target time offset value is the time offset of the modification period corresponding to the target time point, and the target sequence offset is the time offset of the synchronization sequence at the target time point (time t 2); the sequence number of the target modification period is the sequence number of the modification period in which the target time point is located; and the target time point is a time point corresponding to the target wireless frame.

In an optional embodiment, the step of determining target radio frame information of a target radio frame according to the target configuration parameter includes:

determining a target time offset value, a target sequence offset and a target modification cycle sequence number corresponding to the target radio frame number according to the target radio frame number;

wherein the target time offset value is a remainder obtained by dividing a third time offset value by the MCCH modification period; as shown in the following seventh formula:

m＝M3 Mod mcch_ModificationPeriod

where m represents a target time offset value, the same as u8mcchs fnoffset above; m3 denotes a third time offset value; the third time offset value is a remainder obtained by dividing the first absolute timestamp at the first time by a third preset number of MCCH modification periods, as shown in the following eighth formula:

M3＝P MOD Z*mcch-ModificationPeriod

z represents a third preset number, such as 256; p identifies a first absolute timestamp at a first time;

the target sequence offset is a remainder obtained by dividing the first absolute time stamp by the synchronization period; as shown in the following ninth formula:

n＝P MOD Synchronisation_Period

wherein n represents the target sequence offset, denoted as u16SyncPeriodSfnOffset above; synchronization _ Period represents the synchronization Period.

The target modification period number is a result of dividing the first time offset value by the MCCH modification period and rounding down, as shown in the following tenth formula:

i＝Floor(M1/mcch_ModificationPeriod)

wherein i represents a target modification period number, which is represented by u8Counter above; m1 denotes a first time offset value.

With the above description of the time synchronization method provided in the embodiment of the present application, a time synchronization apparatus provided in the embodiment of the present application will be described with reference to the accompanying drawings.

Referring to fig. 5, an embodiment of the present application further provides a time synchronization apparatus, which is applied to a user plane network element, and the apparatus includes:

a parameter obtaining module 501, configured to receive a multicast control channel MCCH configuration message, and obtain a target configuration parameter carried in the MCCH configuration message.

A response receiving module 502, configured to carry the target configuration parameter in a broadcast frame synchronization request message, send the broadcast frame synchronization request message to a control plane network element, and receive a time synchronization response message fed back by the control plane network element;

A parameter updating module 503, configured to update a time synchronization parameter of the first radio frame corresponding to the first time according to the target radio frame information.

In an optional embodiment, the parameter obtaining module 501 is configured to:

receiving a Multicast Control Channel (MCCH) configuration message and starting a waiting response timer;

the response receiving module 502 is configured to:

In an alternative embodiment, the apparatus comprises:

and a request retransmission module, configured to retransmit the broadcast frame synchronization request message to the control plane network element according to a preset retransmission cycle if the time synchronization response message with the same message sequence number as the broadcast frame synchronization request message is not received before the wait response timer times out.

In an optional embodiment, the request retransmission module comprises:

and the alarm submodule is used for executing alarm processing if the retransmission times exceed a preset retransmission threshold.

In an optional embodiment, the target configuration parameters include: an MCCH modification period, a synchronization period and a message sequence number;

the target radio frame information further includes: a target time offset value, a target sequence offset and a target modification period sequence number corresponding to the target radio frame number;

the time synchronization parameters include: a first synchronization cycle start offset, a first modification cycle sequence number, and a first modification cycle position.

In an optional embodiment, the parameter updating module 503 includes:

the difference value determining submodule is used for determining a time difference value between the first moment and the target time point; the target time point is a time point corresponding to the target wireless frame;

the first offset determining submodule is used for determining the offset of the starting point of the first synchronization period according to the time difference value, the offset of the target sequence and the synchronization period;

a second offset determining submodule, configured to determine a second time offset value according to the first time offset value, the time difference value, and the MCCH modification period; the second time offset value is the difference between the first time offset value and the time difference value, the sum of the first time offset value and the time difference value is added with a second preset number of MCCH modification periods, and the remainder is obtained by dividing the sum by the second preset number of MCCH modification periods; the first time offset value is a sum value obtained by adding the product of the MCCH modification period and the target modification period sequence number and the target time offset value;

And the modification period determining submodule is used for determining a first modification period sequence number and a first modification period position according to the second time deviation value.

In an optional embodiment, the time difference value is determined according to the target radio frame number, the first preset number and a first radio frame number of the first radio frame.

In an alternative embodiment, the first synchronization cycle start offset comprises: first synchronization data or zero;

the first synchronization data is the difference between the target sequence offset and the first preset number, the sum of the synchronization period is added, and the remainder of the synchronization period is divided by the sum of the target sequence offset and the first preset number;

In an alternative embodiment, the first modified cycle position comprises: second synchronization data or zero;

the second synchronization data is a radio frame offset between the first moment and the starting point of the MCCH modification period;

In an optional embodiment, the first modification period sequence number comprises third synchronization data or zero;

if the third synchronization data is greater than or equal to a difference value obtained by subtracting one from a second preset number, the second time offset value comprises the third synchronization data; otherwise, the first modification period number includes zero.

In an optional embodiment, the apparatus further comprises:

the counting module is used for updating the wireless frame counting according to the length of the synchronization period and the position of the target wireless frame in the synchronization period;

and if the wireless frame count is greater than or equal to a preset count threshold value, starting a next synchronization period.

The time synchronization apparatus provided in the embodiment of the present application can implement each process implemented by the base station side in the method embodiments of fig. 1 to fig. 3, and is not described here again to avoid repetition.

In the embodiment of the present application, the parameter obtaining module 501 obtains target configuration parameters carried in the MCCH configuration message; a response receiving module 502 sends the target configuration parameter carried in a broadcast frame synchronization request message to a control plane network element, and receives a time synchronization response message fed back by the control plane network element; the time synchronization response message comprises a target radio frame number, the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from the first moment when the control plane network element receives the broadcast frame synchronization request message, and the time desynchronization caused by the time delay existing in the message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as the radio frames of the absolute time.

Referring to fig. 6, an embodiment of the present application further provides a time synchronization apparatus, which is applied to a control plane network element, such as an OM network element, where the control plane network element is taken as the OM network element in the embodiment of the present application for illustration, and is also applicable to other control plane network elements, and in order to avoid repetition, details are not described here again; the device comprises:

a request receiving module 601, configured to receive a broadcast frame synchronization request message sent by a user plane network element, and acquire a target configuration parameter carried in the broadcast frame synchronization request message.

An information determining module 602, configured to determine target radio frame information of a target radio frame according to the target configuration parameter, where the target radio frame information at least includes a target radio frame number; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message;

A message sending module 603, configured to send the target radio frame information carried in the time synchronization response message to the user plane network element.

the target radio frame information further includes: and the target time offset value, the target sequence offset and the target modification period sequence number corresponding to the target radio frame number.

In an optional embodiment, the information determining module 602 is configured to:

wherein the target time offset value is a remainder obtained by dividing a third time offset value by the MCCH modification period; the third time offset value is a remainder obtained by dividing the first absolute timestamp at the first moment by a third preset number of MCCH modification periods;

the target sequence offset is a remainder obtained by dividing the first absolute time stamp by the synchronization period;

the target modification period number is a result of dividing the first time offset value by the MCCH modification period and rounding down.

The time synchronization apparatus provided in the embodiment of the present application can implement each process implemented by the base station side in the method embodiments of fig. 2 to fig. 4, and is not described here again to avoid repetition.

In the embodiment of the present application, a request receiving module 601 receives a broadcast frame synchronization request message sent by a user plane network element, and obtains a target configuration parameter carried in the broadcast frame synchronization request message; the information determining module 602 determines target radio frame information of a target radio frame according to the target configuration parameter, where the target radio frame information at least includes a target radio frame number; the message sending module 603 sends the target wireless frame information carried in a time synchronization response message to the user plane network element; the target radio frame number is a radio frame number corresponding to a first preset number of radio frames delayed from a first moment when the control plane network element receives the broadcast frame synchronization request message, and time desynchronization caused by time delay existing in message interaction between the user plane network element and the control plane network element is avoided by delaying the first preset number of radio frames as radio frames of absolute time.

On the other hand, the embodiment of the present application further provides an electronic device, which includes a memory, a processor, a bus, and a computer program stored on the memory and executable on the processor, and the processor implements the steps in the time synchronization method when executing the program.

For example, fig. 7 shows a schematic physical structure diagram of an electronic device.

As shown in fig. 7, the electronic device may include: a processor (processor)710, a communication Interface (Communications Interface)720, a memory (memory)730, and a communication bus 740, wherein the processor 710, the communication Interface 720, and the memory 730 communicate with each other via the communication bus 740. Processor 710 may call logic instructions in memory 730 to perform the following method:

Or

In addition, the logic instructions in the memory 730 can be implemented in the form of software functional units and stored in a computer readable storage medium when the software functional units are sold or used as independent products. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

In still another aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, where the computer program is implemented to perform the time synchronization method provided in the foregoing embodiments when executed by a processor, for example, the method includes:

Or

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims

1. A time synchronization method applied to a user plane network element is characterized in that the method comprises the following steps:

2. The time synchronization method of claim 1, wherein the target configuration parameters comprise: an MCCH modification period, a synchronization period and a message sequence number;

3. The method according to claim 2, wherein the step of updating the time synchronization parameter of the first radio frame corresponding to the first time according to the target radio frame information comprises:

determining a time difference between the first time and the target time point; the target time point is a time point corresponding to the target wireless frame;

determining the offset of the starting point of the first synchronization period according to the time difference, the offset of the target sequence and the synchronization period;

determining a second time offset value according to the first time offset value, the time difference value and the MCCH modification period;

And determining a first modification period sequence number and a first modification period position according to the second time deviation value.

4. The method according to claim 3, wherein the time difference is determined according to the target radio frame number, the first predetermined number, and a first radio frame number of the first radio frame.

5. The time synchronization method of claim 3, wherein the first synchronization period start offset comprises: first synchronization data or zero;

6. The time synchronization method of claim 3, wherein the first modification period position comprises: second synchronization data or zero;

7. The time synchronization method according to claim 6, wherein the first modification period sequence number includes third synchronization data or zero;

8. The method for time synchronization according to claim 2, further comprising:

9. A time synchronization method applied to a control plane network element is characterized in that the method comprises the following steps:

10. The time synchronization method of claim 9, wherein the target configuration parameters comprise: an MCCH modification period, a synchronization period and a message sequence number;

11. The method of claim 10, wherein the step of determining the target radio frame information of the target radio frame according to the target configuration parameter comprises:

the target modification period number is the result of dividing the first time offset value by the MCCH modification period and rounding down.

12. A time synchronization apparatus applied to a user plane network element, the apparatus comprising:

13. The apparatus for time synchronization according to claim 12, wherein the target configuration parameters comprise: an MCCH modification period, a synchronization period and a message sequence number;

14. The time synchronizer of claim 13, wherein the parameter update module comprises:

a second offset determining submodule, configured to determine a second time offset value according to the first time offset value, the time difference value, and the MCCH modification period;

15. The apparatus according to claim 14, wherein the time difference value is determined according to the target radio frame number, the first predetermined number, and a first radio frame number of the first radio frame.

16. The time synchronization apparatus of claim 14, wherein the first synchronization cycle start offset comprises: first synchronization data or zero;

17. The time synchronizer of claim 14, wherein the first modified cycle position comprises: second synchronization data or zero;

18. The time synchronizer of claim 17, wherein the first modification period number comprises a third synchronization data or zero;

19. The time synchronization apparatus of claim 13, wherein the apparatus further comprises:

20. A time synchronization apparatus applied to a control plane network element, the apparatus comprising:

21. The apparatus for time synchronization according to claim 20, wherein the target configuration parameters comprise: an MCCH modification period, a synchronization period and a message sequence number;

22. The time synchronization apparatus of claim 21, wherein the information determination module is configured to:

23. An electronic device comprising a processor, a memory and a computer program stored on the memory and executable on the processor, characterized in that the computer program, when executed by the processor, implements the steps of the time synchronization method according to any one of claims 1 to 11.

24. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the time synchronization method according to any one of claims 1 to 11.