A clock signal transmission method, device and system

Abstract

The embodiments of the present application provide a method, device and system for transmitting a clock signal, which solves the problem of disorder in the clock synchronization mechanism caused by the clock signal sent by the master clock being transmitted back to the master clock when the master clock is on the terminal side. It includes: filtering out the port corresponding to the master clock according to the state of the port of the device-side repeater in the first clock domain, adding the terminal corresponding to the filtered port to the group corresponding to the multicast session, and transmitting the clock signal of the first clock domain through the multicast session. Or notifying the device-side repeater of the state of the port of the device-side repeater in the first clock domain, and after the device-side repeater receives the clock signal, filtering the received clock signal according to the state of the port. Or when the master clock in the first clock domain is on the terminal side, the identifier of the tunnel for transmitting the clock signal is carried in the data packet transmitted on the multicast session corresponding to the first clock domain, and the access network device does not transmit the clock signal to the terminal corresponding to the master clock after receiving the data packet.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a clock signal transmission method, device, and system. Background Art

[0002] The fifth generation (5G) network introduces time-sensitive communication (TSC) of time-sensitive network (TSN) to enable 5G networks to support industrial automation manufacturing applications with precise time control.

[0003] The TSC is to realize the transmission of clock synchronization messages (which may be referred to as clock signals in this application) between the terminal and the user plane function (UPF). During the transmission of the clock signal, if the master clock of a clock domain is located on the terminal side, the master clock can send the clock signal to the UPF through the terminal. After the UPF receives the clock signal from the terminal side, it sends the clock signal to the network side repeater. After the network side repeater receives the clock signal, it forwards the received clock signal to the external clock node. In addition, if there are other clocks other than the master clock on the terminal side, the network side repeater also needs to send the clock signal to other clocks other than the master clock on the terminal side through the UPF. For example, the network side repeater sends the clock signal to the UPF. After receiving the clock signal, the UPF will send the clock signal to each clock (including the master clock) in the clock domain on the terminal side.

[0004] As can be seen above, if the master clock is located on the terminal side, it may receive its own clock signal. In other words, the clock signal sent by the master clock is transmitted back to the master clock. For the master clock, there are clock signals received by the master clock and clock signals generated by the master clock itself. Both clock signals need to be sent to non-master clocks in the clock domain. This makes the reference time non-unique, disrupts the clock synchronization mechanism, and makes clock synchronization impossible. Summary of the Invention

[0005] The embodiments of the present application provide a clock signal transmission method, device and system to solve the problem that when the master clock is on the terminal side, the clock synchronization mechanism is disordered and clock synchronization cannot be achieved due to the clock signal sent by the master clock being transmitted back to the master clock.

[0006] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, the present application provides a method for transmitting a clock signal, the method comprising: a first session management network element receives first information indicating the identifier and status of a port of one or more device-side repeaters in a first clock domain, determines a terminal to join a group corresponding to a multicast session based on the first information and the correspondence between the port and the terminal, and sends a message including the identifier of the multicast session to an access network device corresponding to the terminal via a message associated with the terminal (e.g., the first terminal in the group corresponding to the multicast session). The port status comprises a first state or a second state, a port in the first state comprises a port of a device-side repeater connected to a master clock of the first clock domain, and a port in the second state comprises a port of a device-side repeater connected to a clock other than the master clock in the first clock domain, and the multicast session is used to transmit the clock signal of the first clock domain via multicast.

[0008] Based on the method described in the first aspect, the first session management network element can obtain the port of the device-side repeater in the first clock domain and the status of the port in the first clock domain, and determine the terminal to join the group corresponding to the multicast session in the first clock domain based on the port of the device-side repeater in the first clock domain and the status of the port, so as to send the clock signal through the multicast session, thereby improving resource utilization and transmission efficiency. At the same time, the terminal to join the group corresponding to the multicast session in the first clock domain is determined with reference to the status of the port, the port corresponding to the master clock is filtered out, and the terminal corresponding to the filtered port is added to the group corresponding to the multicast session, avoiding adding the terminal corresponding to the port corresponding to the master clock to the group, avoiding the clock signal sent by the master clock to be transmitted back to the master clock when the master clock is on the terminal side, and avoiding the problem that the clock synchronization mechanism is disordered and clock synchronization cannot be achieved.

[0009] In one possible design, the first session management network element determines the terminals to join the group corresponding to the multicast session based on the first information and the correspondence between ports and terminals. This includes: if the status of one or more ports corresponding to the first terminal are all in the second state, then determining to join the first terminal to the group corresponding to the multicast session; or if the ports of the device-side repeater corresponding to the second terminal are in the first state, then determining not to join the second terminal to the group corresponding to the multicast session. Based on this possible design, the ports corresponding to the master clock can be effectively and flexibly filtered out, preventing the clock signal emitted by the master clock from being transmitted back to the master clock.

[0010] In one possible design, the terminal corresponding to the port of the device-side repeater in the first clock domain is determined using any of the following methods: Method 1: The first session management network element searches for a corresponding relationship based on the port of the device-side repeater in the first clock domain, using the port as an index, and determines the terminal corresponding to the port in the corresponding relationship as the terminal corresponding to the port of the device-side repeater in the first clock domain. Method 2: The terminal managed / served by the first session management network element is obtained, and the corresponding relationship is searched using the terminal as an index to find the port in the first clock domain corresponding to the terminal in the corresponding relationship. Based on this possible design, the terminal corresponding to the port of the device-side repeater in the first clock domain can be found efficiently and flexibly.

[0011] In one possible design, the method further includes: the first session management network element determines to configure or establish a multicast session. The method for configuring or creating a multicast session may include: (1) when the number of terminals corresponding to the port of the device-side repeater in the first clock domain is greater than a preset threshold, determining to configure or create a multicast session; or, when the first session management network element receives an event notification from the first user-side network element, the notification event notification is used to notify the clock signal of the first clock domain to be transmitted, determining to configure or create a multicast session. That is, configuring or creating a multicast session according to the number of terminals or the user-side notification. (2) The first session management network element receives a first request from the first application function network element for requesting to configure or establish a multicast session, the first request carries at least one of the identifier of the first clock domain or the identifier of the multicast session, and the first session management network element determines to configure or establish a multicast session according to the first request. That is, the first session management network element configures or creates a multicast session according to the request of the first application function network element. Based on this possible design, multiple ways of triggering the first session management network element to configure or create a multicast session are provided, the application scenarios are flexible, and the scope of application is expanded.

[0012] In one possible design, the first session management network element obtains the first information, including: the first session management network element receives the first information from the first application function network element; the first application function network element is a time-sensitive network application function network element, such as a time-sensitive network application function (TSN AF), or a time-sensitive communication and clock synchronization function network element, such as a time-sensitive communication and time synchronization function (TSCTSF), that is, the first session management network element can obtain the port and port status of the device-side forwarder in the first clock domain from the TSN AF or TSCTSF.

[0013] In one possible design, the first information is carried in a first request for requesting configuration or establishment of a multicast session, and the first request carries at least one of an identifier of a first clock domain or an identifier of a multicast session. That is, when the first application function network element requests configuration or creation of a multicast session, the first information is sent to the mobility management network element, thereby simplifying the system design and saving signaling overhead.

[0014] In one possible design, the method further includes: the first session management network element sends an identifier of a terminal (such as a first terminal) to an access network device, so that the access network device sends a clock signal of a first clock domain to the terminal according to the identifier of the terminal.

[0015] In a second aspect, the present application provides another clock signal transmission method, the method comprising: a first application function network element receiving first information from a network-side forwarder indicating an identifier and port status of one or more device-side forwarders in a first clock domain, wherein the port status includes a first state or a second state, wherein ports in the first state include ports of device-side forwarders connected to a master clock of the first clock domain, and ports in the second state include ports of device-side forwarders connected to clocks other than the master clock in the first clock domain. The first application function network element sends first information to a first session management network element, so that the first session management network element determines, based on the first information, terminals to join a group corresponding to a multicast session, transmits clock signals of the first clock domain via the multicast session, thereby improving resource utilization and transmission efficiency, and triggering the first session management network element to filter out ports corresponding to the master clock based on the port status, and add terminals corresponding to the filtered ports to the group corresponding to the multicast session, thereby preventing ports corresponding to the master clock from being added to the group and avoiding problems such as clock synchronization mechanism disruption and failure to achieve clock synchronization caused by clock signals transmitted back to the master clock.

[0016] In one possible design, the first application function network element receives the first information from the network side forwarder, including: the first application function network element receives a management information container from the network side forwarder; wherein the management information container carries the first information, and the management information container can be a user plane node management information container (user plane node management information container, UMIC) or a bridge management information container (bridge management information container, BMIC), that is, the first information is effectively and flexibly carried in a container that only the first application function network element can recognize, thereby preventing the first information from being parsed and tampered with by other network elements during transmission, thereby ensuring the accuracy of the first information.

[0017] In one possible design, the method further includes: the first application function network element determining, based on the first information, to configure or establish a multicast session, and sending a first request to the first session management network element; wherein the first request is used to request configuration or establishment of a multicast session for the first clock domain, and the first request also carries at least one of an identifier of the first clock domain or an identifier of the multicast session. Based on this possible design, a multicast session can be configured or established at the request of the first application function network element, simplifying system design.

[0018] In one possible design, the first application function network element sends first information to the first session management network element, including: the first application function network element determines to configure or establish a multicast session based on the first information, and sends a first request carrying the first information to the first session management network element, that is, when the first application function network element requests the first session management network element to configure or establish a multicast session, the first information is sent to the first session management network element to reduce signaling overhead.

[0019] In the third aspect, the present application also provides a method for transmitting a clock signal, the method comprising: a first device side repeater receives first information from a first application function network element for indicating the status of a port of the first device side repeater in a first clock domain, and filters the received clock signal of the first clock domain according to the first information.

[0020] Based on the method described in the third aspect, when the device-side repeater connected to the terminal receives the clock signal of the first clock domain, the device-side repeater filters the clock signal according to the status of the port and determines whether to send the clock signal to the clock node through the port, thereby avoiding the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by the clock signal sent by the master clock being transmitted back to the master clock.

[0021] In one possible design, the first device side repeater filters the received clock signal based on the first information, including: if the port status is the second state, the first device side repeater sends the clock signal to the clock node through the port; or, if the port status is the first state, the first device side repeater discards the clock signal, that is, if the port status is the first state, it means that the port corresponds to the master clock, the clock signal is not sent through the port, the received clock signal is discarded, and the clock signal is prevented from being transmitted back to the master clock.

[0022] In one possible design, the first information is carried in a port container, such as a container that can only be recognized by the forwarder on the first device side, to prevent the first information from being parsed and tampered with by other network elements during transmission, thereby ensuring the reliability of the transmission of the first information.

[0023] In a fourth aspect, the present application also provides a method for transmitting a clock signal, the method comprising: a first application function network element receives second information from a network side repeater for indicating the identifier and status of a port of one or more device side repeaters in a first clock domain, the status of the port including a first state or a second state, the port in the first state including the port of the device side repeater connected to the master clock of the first clock domain, and the port in the second state including the port of the device side repeater connected to other clocks in the first clock domain that are not the master clock; the first application function network element sends first information to the first device side repeater based on the second information for indicating the status of the port of the first device side repeater in the first clock domain, so that the first device side repeater filters the received clock signal according to the status of the port, and avoids transmitting the clock signal back to the master clock through the port corresponding to the master clock.

[0024] In one possible design, the method also includes: the first application function network element determines to configure or establish a multicast session for the first clock domain based on the second information, and sends a first request carrying at least one of the identifier of the first clock domain or the identifier of the multicast session to the first session management network element, requesting the first session management network element to configure or create a multicast session so as to transmit the clock signal of the first clock domain through the multicast session, thereby improving resource utilization and transmission efficiency.

[0025] In one possible design, the first request also carries third information for indicating the identifier of the port of one or more device-side forwarders in the first clock domain, so that the first session management network element configures or creates a multicast session according to the number of terminals corresponding to the port, thereby simplifying the system design.

[0026] In a fifth aspect, the present application also provides a method for transmitting a clock signal, the method comprising: a first access network device receives a data packet carrying a clock signal and an identifier of an uplink tunnel corresponding to a first terminal, the uplink tunnel being a tunnel from the access network device corresponding to the first terminal (the access network device here and the first access network device receiving the data packet may be the same device or different devices) to the first user-plane network element, the first access network device sends a clock signal to other terminals except the first terminal according to the identifier of the uplink tunnel, that is, carries the identifier of the uplink tunnel of the terminal corresponding to the master clock in the data packet transmitted on the multicast session, so that the first access network device no longer transmits the clock signal to the master clock connected to the terminal corresponding to the uplink tunnel according to the identifier of the uplink tunnel, thereby avoiding transmission of the clock signal back to the master clock.

[0027] In one possible design, the first access network device sends a clock signal to terminals other than the first terminal based on an identifier of an uplink tunnel, including: if the first terminal is included in a terminal group that has joined a multicast session, then the first access network device sends the clock signal to terminals other than the first terminal in the terminals group that has joined the multicast session, for example, the first access network device sends the clock signal to terminals other than the first terminal in the terminals group using unicast. This prevents the clock signal from being transmitted back to the master clock.

[0028] In one possible design, the method further includes: the first access network device receiving first indication information from the first session management network element, instructing the first access network device to transmit a clock signal based on an identifier of an uplink tunnel carried in a data packet; the first access network device responding to the first indication information and transmitting the clock signal based on the identifier of the uplink tunnel. Specifically, under the instruction of the first session management network element, the first access network device detects the identifier of the uplink tunnel carried in the data packet, avoids returning the clock signal to the master clock based on the identifier of the uplink tunnel, and controls the transmission of the user plane clock signal by the control plane network element, thereby simplifying system design.

[0029] In the sixth aspect, the present application also provides a method for transmitting a clock signal, the method comprising: a first user-plane network element receives a clock signal through an uplink tunnel corresponding to a first terminal, the uplink tunnel can be understood as a tunnel / unicast transmission tunnel from an access network device corresponding to the first terminal to the first user-plane network element, the first user-plane network element sends a data packet carrying a clock signal and an identifier of the uplink tunnel to the first access network device, so that the first access network device filters out the first terminal corresponding to the master clock according to the identifier of the uplink tunnel, and does not send a clock signal to the first terminal, thereby avoiding transmission of the clock signal back to the master clock.

[0030] In one possible design, the method also includes: the first user plane network element receives second indication information from the first session management network element for indicating that the identifier of the uplink tunnel is carried in the data packet; in response to the second indication information, the first user plane network element sends a data packet to the access network device, that is, under the instruction of the first session management network element, the identifier of the uplink tunnel corresponding to the master clock is carried in the data packet, thereby avoiding the clock signal emitted by the master clock from being transmitted back to the master clock; at the same time, the control plane network element controls the transmission of the user plane clock signal, thereby simplifying the system design.

[0031] In a seventh aspect, the present application also provides a clock signal transmission method, the method comprising: a first session management network element sending first indication information to a first user plane network element, the first indication information being used to instruct the first user plane network element to carry an identifier of the uplink tunnel in a data packet transmitted over a multicast session after receiving a clock signal from an uplink tunnel. The first session management network element sending second indication information to a first access network device, the second indication information being used to instruct the access network device to send a clock signal to a terminal based on the identifier of the uplink tunnel. Specifically, the first session management network element instructs the first user plane network element to carry the identifier of the uplink tunnel of the first terminal corresponding to the master clock in a data packet and transmit it to the first access network device. Furthermore, the first session management network element instructs the first access network device to transmit the clock signal to terminals other than the first terminal based on the identifier of the uplink tunnel carried in the data packet. Specifically, the control plane network element controls the transmission of the clock signal and does not transmit the clock signal to the master clock to which the first terminal corresponding to the uplink tunnel is connected, thereby preventing the clock signal sent by the master clock from being transmitted back to the master clock and simplifying system design. It is understood that the first session management network element may send only one of the first indication information and the second indication information.

[0032] In one possible design, the method further includes: the first session management network element determines to configure or establish a multicast session, for example, if the first session management network element receives an event notification from the first user plane network element, the event notification being used to notify the clock signal of the first clock domain to be transmitted, then determining to configure or create a multicast session; or, if the number of terminals corresponding to the port of the device-side repeater in the first clock domain is greater than a preset threshold, then determining to configure or create a multicast session for the first clock domain; or, if it is determined that there is a terminal that requires the clock signal of the first clock domain among the terminals managed by the first session management network element, then determining to configure or create a multicast session; or, the first session management network element receives a first request from the first application function network element for requesting to configure or establish a multicast session, the first request carrying at least one of an identifier of the first clock domain or an identifier of the multicast session, and the first session management network element determines to configure or establish the multicast session based on the first request, that is, providing multiple ways to flexibly and effectively determine the configuration or creation of the multicast session, thereby simplifying system design.

[0033] In the eighth aspect, a communication device is provided for implementing the various methods mentioned above. The communication device may be the first session management network element in the first or seventh aspect, or a device that specifically performs the functions of the first session management network element; or the communication device may be the first application function network element in the second or fourth aspect, or a device that specifically performs the functions of the first application function network element; or the communication device may be the device-side forwarder in the third aspect, or a device that has the functions performed by the device-side forwarder; or the communication device may be the access network device in the fifth aspect, or a device that has the functions performed by the access network device; or the communication device may be the first user-plane network element in the sixth aspect, or a device that has the functions performed by the first user-plane network element. The communication device includes modules, units, or means corresponding to the above methods, and the modules, units, or means may be implemented by hardware, software, or by hardware executing the corresponding software implementation. The hardware or software includes one or more modules or units corresponding to the above functions. For example, in one possible design, the communication device may include a processing unit and a transceiver unit;

[0034] In a ninth aspect, a communication device is provided, comprising: a processor and a memory; the memory is configured to store computer instructions, and when the processor executes the instructions, the communication device performs the method described in any of the above aspects. The communication device may be the first session management network element described in the first aspect, or a device including the first session management network element.

[0035] In a tenth aspect, a communication device is provided, comprising: a processor; the processor is configured to be coupled to a memory, and after reading instructions from the memory, execute the method as described in any of the above aspects according to the instructions. The communication device can be the first session management network element in the first or seventh aspect, or a device that specifically performs the functions of the first session management network element; or the communication device can be the first application function network element in the second or fourth aspect, or a device that specifically performs the functions of the first application function network element; or the communication device can be the device-side forwarder in the third aspect, or a device that has the functions performed by the device-side forwarder; or the communication device can be the access network device in the fifth aspect, or a device that has the functions performed by the access network device; or the communication device can be the first user-plane network element in the sixth aspect, or a device that has the functions performed by the first user-plane network element.

[0036] In an eleventh aspect, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium. When the computer-readable storage medium is run on a computer, the computer can execute the method described in any one of the above aspects.

[0037] In a twelfth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the method described in any one of the above aspects.

[0038] In a thirteenth aspect, a communication device (e.g., a chip or a system on a chip) is provided, wherein the communication device includes a processor for implementing the functions described in any of the above aspects. In one possible design, the communication device also includes a memory for storing necessary program instructions and data. When the communication device is a system on a chip, it can be composed of a chip or include a chip and other discrete components.

[0039] Among them, the technical effects brought about by any design method in the eighth to thirteenth aspects can refer to the technical effects brought about by different design methods in the above aspects, and will not be repeated here.

[0040] In a fourteenth aspect, a communication system is provided, which includes a first session management network element; the first session management network element is used to obtain first information indicating the port identifier and port status of one or more device-side repeaters in the first clock domain, determine the terminal to join the group corresponding to the multicast session based on the first information and the correspondence between the port and the terminal, and send the identifier of the multicast session to the access network device corresponding to the terminal; the status of the port includes a first state or a second state, the port in the first state includes the port of the device-side repeater connected to the master clock of the first clock domain, and the port in the second state includes the port of the device-side repeater connected to the other clocks in the first clock domain that are not the master clock, and the multicast session is used to transmit the clock signal of the first clock domain via multicast.

[0041] Among them, the technical effects brought about by the fourteenth aspect can be referred to the technical effects brought about by the first aspect or the second aspect or any possible design of the first aspect or any possible design of the second aspect, and will not be repeated here.

[0042] In a fifteenth aspect, a communication system is provided, which includes a first application function network element and a first device-side repeater. The first application function network element is configured to receive second information from the network-side repeater indicating the identifier and status of a port of one or more device-side repeaters in a first clock domain, and send, based on the second information, first information to the first device-side repeater indicating the status of the port of the first device-side repeater in the first clock domain; the status of the port includes a first state or a second state, and the port in the first state includes the port of the device-side repeater connected to the master clock of the first clock domain, and the port in the second state includes the port of the device-side repeater connected to other clocks in the first clock domain that are not the master clock; the first device-side repeater is configured to receive the first information from the first application function network element, and filter the received clock signal of the first clock domain based on the first information.

[0043] Among them, the technical effects brought about by the fifteenth aspect can be referred to the technical effects brought about by the third aspect or the fourth aspect or any possible design of the third aspect or any possible design of the fourth aspect, and will not be repeated here.

[0044] In the sixteenth aspect, a communication system is provided, which includes a first user plane network element and a first access network device, wherein the first user plane network element is used to receive a clock signal of a first clock domain through an uplink tunnel corresponding to a first terminal, and send data carrying the clock signal and an identifier of the uplink tunnel to the first access network device; the first access network device is used to receive a data packet, and send the clock signal of the first clock domain to other terminals other than the first terminal according to the identifier of the uplink tunnel carried by the data packet.

[0045] Among them, the technical effects brought about by the sixteenth aspect can refer to the technical effects brought about by the fifth aspect or the sixth aspect or the seventh aspect or any possible design of the fifth aspect or any possible design of the sixth aspect or any possible design of the seventh aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of clock signal transmission between clock nodes;

[0047] Figure 2 This is a schematic diagram of the clock synchronization principle;

[0048] Figure 3 Schematic diagram of a 5G communication system serving as a boundary clock;

[0049] Figure 4 Schematic diagram of unicast and multicast transmission;

[0050] Figure 5 Schematic diagram of clock signal transmission within a 5G communication system Figure 1 ;

[0051] Figure 6 Schematic diagram of clock signal transmission within a 5G communication system Figure 2 ;

[0052] Figure 7 This is a diagram of the network architecture where the master clock is located on the terminal side.

[0053] Figure 8a Schematic diagram of clock signal transmission when the master clock is on the terminal side Figure 1 ;

[0054] Figure 8b Schematic diagram of clock signal transmission when the master clock is on the terminal side Figure 2 ;

[0055] Figure 9 A schematic diagram of the structure of a communication system provided in an embodiment of the present application;

[0056] Figure 10 A possible embodiment of the present application provides Figure 2 A schematic diagram of the network architecture corresponding to the communication system shown;

[0057] Figure 11 A schematic diagram of the structure of a communication device provided in an embodiment of the present application;

[0058] Figure 12 Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 1 ;

[0059] Figure 13a Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 2 ;

[0060] Figure 13b Schematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 1 ;

[0061] Figure 13c Schematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 2 ;

[0062] Figure 14 Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 3 ;

[0063] Figure 15a Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 4 ;

[0064] Figure 15bSchematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 3 ;

[0065] Figure 15c Schematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 4 ;

[0066] Figure 16 Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 5 ;

[0067] Figure 17a Interaction diagram of the clock signal transmission method provided in the embodiment of the present application Figure 6 ;

[0068] Figure 17b Schematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 5 ;

[0069] Figure 17c Schematic diagram of clock signal transmission when the master clock provided in the embodiment of the present application is on the terminal side Figure 6 ;

[0070] Figure 18 A schematic structural diagram of a communication device 180 provided in an embodiment of the present application;

[0071] Figure 19 A schematic structural diagram of a communication device 190 provided in an embodiment of the present application;

[0072] Figure 20 A schematic structural diagram of a communication device 200 provided in an embodiment of the present application;

[0073] Figure 21 A schematic structural diagram of a communication device 210 provided in an embodiment of the present application;

[0074] Figure 22 A schematic structural diagram of a communication device 220 provided in an embodiment of the present application;

[0075] Figure 23 A schematic diagram of the structure of a communication system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0076] Current time-sensitive networks (TSNs) use the generalized precision time protocol (gPTP) from the Institute for Electrical and Electronics Engineers (IEEE) 802.1AS standard. gPTP can be used to ensure clock synchronization between nodes that send and receive data (referred to as clock nodes or clocks), achieving, for example, nanosecond-level synchronization accuracy. For example, the tasks of playing audio and video may be performed on different nodes. These two nodes can use gPTP to maintain the same clock reference, otherwise the picture and sound may not align.

[0077] The current TSN standard defines clock domains (or domains) and three types of clock nodes as shown in Table 1: ordinary clocks (OCs), boundary clocks (BCs), and transparent clocks.

[0078] Table 1

[0079]

[0080] A clock domain includes OC and BC, and may also include TC. There is a master clock and one or more slave clocks in the OC. The master clock is a node with clock capabilities that provides a clock signal (such as a reference time) and is the source of the clock signal (or grandmaster). The slave clock can be a node with clock capabilities that receives the clock signal provided by the master clock and adjusts the local clock according to the clock signal to achieve clock synchronization. The slave clock is the destination of the clock signal (or end station). The slave clock can also be understood as a non-master clock. The master clock can send clock signals to the slave clock through the BC and / or TC in its clock domain. BC and TC can be understood as relay clocks on the transmission path between the master clock and the slave clock. BC and TC have the function of forwarding clock signals.

[0081] In the embodiment of the present application, each clock node has / corresponds to a port, which is deployed on a repeater / forwarding module. The repeater can be integrated into the clock node, deployed independently, or integrated into other devices connected to the clock node, such as a terminal connected to the clock node or a network-side device (such as a UPF). The port can be used to forward the clock signal sent by the clock node or to forward the clock signal to the clock node. In the TSN system, the clock signal of the clock domain is transmitted according to the state of the port corresponding to the clock node in the clock domain.

[0082] In the embodiment of the present application, the state of a port in the clock domain can be as described in Table 2, including master state, slave state, or passive state. A port in the master state can be called a master port (or simply port M), a port in the slave state can be called a slave port (or simply port S), and a port in the passive state can be called a passive port (or simply port P). Table 2 below shows a brief introduction to each type of port. It should be understood that Table 2 is only for illustrative purposes. The master state can also be named primary or replica, and the slave state can be called leader or follower.

[0083] Table 2

[0084]

[0085] In an embodiment of the present application, clock nodes in a clock domain can determine the status of their own ports in the clock domain in the following manner: the clock nodes send notification messages carrying their own parameters and configuration information to each other through their ports in the clock domain, and each clock node detects the notification messages sent by other clock nodes received on its port and the notification messages sent by itself on the port, and determines the status of the port of the clock node in the clock domain based on all notification messages received and sent on the port and the best master clock algorithm (BMCA) algorithm.

[0086] If the OC port is in the master state within the clock domain, it is determined to be the master clock within that clock domain. If the OC port is in the slave state within the clock domain, it is determined to be a slave clock within that clock domain. If the BC port is in the slave state within the clock domain, it is determined to be connected to the master clock and receiving clock signals. If the BC port is in the master state within the clock domain, it is determined to be connected to the slave clock and forwarding clock signals to the slave clock. In other words, the clock signal from the OC, acting as the master clock, can only be sent from the master port of the master clock to the slave port of the next node in the transmission path (such as the slave port of the BC or the slave port of the OC). Within the BC, clock signals can only be received by slave ports, sent to the master port, and then forwarded to the next node in the transmission path through the master port. The TC can be considered a transparent transmission path, without port state information.

[0087] For example, take the case where a port is deployed on a repeater and the repeater is deployed on a clock node. Figure 1 As shown, clock domain 1 contains four OCs: OC-1, OC-2, OC-3, and OC-4; two BCs: BC-1 and BC-2; and multiple TCs. BC-1 has four ports 1 through 4 in clock domain 1, and BC-2 has three ports 1 through 3 in clock domain 1. The BMCA algorithm determines that the port state of OC-1 is M, the port states of OC-2, OC-3, and OC-4 are S, and the states of the four ports of BC-1 are S, M, M, and P, respectively. The states of the three ports of BC-2 are S, M, and M, respectively. OC-1's M port sends a synchronization (sync) message to BC-1's port S. BC-1's port S forwards the received sync message to its two own ports M and port P. One BC-1 port M sends a sync message to OC-2's port S. Another BC-1 port M sends a sync message to BC-2's port S through the TC. BC-1's port P does not process the received sync message. After receiving the synchronization message, port S on BC-2 internally forwards it to its two ports M. Port M on BC-2 then forwards the received synchronization message to port S on OC-3 and port S on OC-4, respectively. Through the transmission of synchronization messages, the master and slave clocks achieve clock synchronization.

[0088] For example, in the embodiment of the present application, the working principle of synchronization between the master clock and the slave clock in gPTP is as follows: Figure 2 As shown, this may include:

[0089] 1) The master clock sends a synchronous (sync) message carrying a clock signal (such as the master clock's parameters and related configuration information) to the slave clock at time t1. The sync message may carry the time t1 of the sync message being sent, or the sync message may not carry t1, but a follow-up (follow_up) message is subsequently sent, carrying t1. Accordingly, the slave clock receives the sync message and records the time t2 of receiving the sync message based on its local clock. Optionally, the slave clock can obtain t1 by parsing the content of the sync message or the follow-up message, where the time difference between t2 and t1 is the sum of the signal transmission path delay (path_delay) and the difference between the master and slave clocks (clock_offset), that is:

[0090] t2–t1=path_delay+clock_offset formula (1).

[0091] 2) The slave clock sends a delay request (Delay_Req) ​​message to the master clock. The delay request message contains a clock signal (such as the parameters and related configuration information of the slave clock). The slave clock records the sending time t3 of the delay request message. After receiving the delay request message, the master clock records the receiving time t4 of the delay request message and carries t4 in a delay response (Delay_Resp) message to the slave clock. The slave clock records the time t4 when the master clock receives the delay request message obtained from the delay response message, where the time difference between t4 and t3 is the difference between the signal transmission path delay (path_delay) and the difference between the master and slave clocks (clock_offset), that is,

[0092] t4–t3=path_delay-clock_offset formula (2).

[0093] The slave clock is calculated according to the above formula (1) and formula (2):

[0094] path_delay=(t4–t3+t2–t1) / 2,

[0095] clock_offset=(t3–t4+t2–t1) / 2.

[0096] Furthermore, the slave clock can be synchronized according to the value of clock_offset to ensure that the master clock and the slave clock nodes have the same clock reference and keep pace with each other.

[0097] In an embodiment of the present application, a clock signal can be used to achieve clock synchronization between different clock nodes, so that the same clock reference can be maintained between different clock nodes. The clock signal can be understood as a clock synchronization signal or a reference time, and the message carrying the clock signal can be called a precision time protocol (PTP) message or a gPTP message. For example, the synchronous (sync) message, follow (follow_up) message, delay request (Delay_Req) ​​message, and delay response (Delay_Resp) message described in this application can be collectively referred to as a PTP message or a gPTP message.

[0098] In an embodiment of the present application, a notification (announce) message or a PTP message or a gPTP message can be carried in a PTP message and sent out. The message body of a PTP message may include a message header and other fields. The fields included in the PTP message are shown in Table 3 below. It should be understood that the bytes (Octets) occupied by each field in Table 3 and the offset (offset) of the field can be the values ​​described in Table 3 or other values ​​without limitation. The following is an introduction to the various fields shown in Table 3:

[0099] Message header: Refer to Table 4 below.

[0100] Current UtcOffset: This field defines the time difference between the Coordinated Universal Time (UTC) and the International Atomic Time (TAI) time scales.

[0101] Grandmaster Priority: This field indicates the user-defined priority of the grandmaster. Specifically, the grandmaster priority can include user-defined grandmaster priority 1 (grandmasterPriority1) and user-defined grandmaster priority 2. If the grandmaster priority 1 values ​​of the grandmasters in different clock domains are the same, the priorities of the grandmasters in different clock domains can be compared based on grandmaster priority 2.

[0102] GrandmasterClockQuality: This field defines the time quality level of the grandmaster clock.

[0103] Grandmaster Identity: This field defines the grandmaster's clock device ID.

[0104] Steps Removed: This field defines the number of clock hops between the grandmaster and slave devices. The number of clock hops can be understood as the number of intermediate nodes the clock signal passes through to reach the clock node. The Steps Removed field increments by 1 for each intermediate node passed along the clock signal's transmission path. In scenarios where a clock node may receive notification messages from the same grandmaster (or clock source) via multiple different paths, the Steps Removed field can be used to compare which path is closer or shorter.

[0105] Time Source: This field defines the time source type. For example, "Global Positioning System (GPS)" indicates the GPS satellite-transmitted clock, "PTP" indicates the PTP clock, "Network Time Freading (NTF)" indicates the NTF clock, and "Hand_set" indicates the manually adjusted clock. It should be understood that in this application, the clock source within a clock domain can be referred to as the master clock; the two are equivalent and can be used interchangeably.

[0106] Path trace TLV: Used to record the IDs of clock nodes along the entire transmission path (such as the ID of the master clock and the IDs of the BCs). As shown in Table 3, the Path trace TLV field exceeds 8 bits and occupies 4+8N bytes, where N is an integer greater than or equal to 0.

[0107] Table 3

[0108]

[0109] The header of the PTP message may include the fields shown in Table 4 below. It should be understood that the bytes and offsets occupied by each field in the header of the PTP message can be the values ​​shown in Table 4, or other values, without limitation. The following is an introduction to the various fields shown in Table 4:

[0110] Message Type: This field is used to indicate the type of PTP message. PTP message types include event messages and general messages.

[0111] Message Type Characteristics: This field is used to further subdivide the type of PTP message indicated by the message type. For example, an event message may include a message carrying any of the following messages: a synchronization message, a delay request (Delay_Req) ​​message, or a delay response (Delay_Resp) message. A general message may include a message carrying any of the following messages: a follow-up message, a follow-up response message, or a notification message.

[0112] PTP message minor version (minorVersionPTP) and PTP message version: together indicate the PTP protocol version.

[0113] Message Length: This field defines the total length of the PTP message sent, that is, the total length of the message body of the PTP message.

[0114] Clock Domain Number: This field defines the clock domain to which the PTP message belongs. For example, this field can be used together with the SdoId field to identify a clock domain. For example, if the clock domain number is 0, this field and the SdoId field together identify a clock domain. The SdoId field can include at least one of the majorSdoId and minorSdoId fields shown in Table 4.

[0115] Flags: This field is primarily used to indicate the type of message carried by the PTP message and / or the type of the next message to be carried by the PTP message. For example, bit 0 in the Flags field may indicate whether the message carried by the PTP message is sent by a port in the master state. Bit 1 in the Identifier field may indicate whether the message carried by the PTP message has a subsequent follow-up message.

[0116] Time Correction Field: This field defines the nanosecond (ns) level correction value for the dwell time of the clock signal carried in the PTP message when it passes through the TC.

[0117] Source port identifier (ID): This field defines the source port address information for sending PTP messages, including the clock node ID and port ID.

[0118] Sequence Number: This field defines the sequence number of different PTP messages.

[0119] Control field: This field defines the IEEE 1588v1 version that describes the message type.

[0120] Log message interval: This field defines and displays the negotiated message sending interval.

[0121] Table 4

[0122]

[0123] Currently, a communication system can be considered as a BC, and the OC can be connected to the communication system and transmit the clock signal through the communication system. The communication system can be a 3rd Generation Partnership Project (3GPP) communication system, such as a 4th Generation (4G) communication system, a Long Term Evolution (LTE) system, a 5th Generation (5G) communication system or a New Radio (NR) system, a next-generation communication system, or a non-3GPP communication system.

[0124] Take the 5G communication system as a BC, for example, Figure 3 This is a schematic diagram of using the 5G communication system as a boundary clock, as shown in Figure 3 As shown, the user plane function (UPF) side and the terminal side are externally or integrated with a translator (TS). The translator can be understood as an adapter. The translator can be used to forward clock signals. The translator has a port for forwarding clock signals. The state of the port can be any of the states described in Table 2 above, which can be a master state, a slave state, or a passive state. For example, Figure 3 The port of the repeater connected to the UPF can be set to S, and the port of the repeater connected to the terminal can be set to M. After the UPF receives the clock signal from the external clock through the port S of the repeater connected to it, the UPF sends the clock signal to the terminal (or user equipment (UE)) through the user plane transmission channel of the 5G communication system, and the terminal sends the clock signal to the clock node to be received through the port M of the repeater connected to the terminal.

[0125] In the embodiment of the present application, the external or integrated forwarder of the UPF can be called a network-side forwarder or a network-side time-sensitive network forwarder (network-side time-sensitive network translator, NW-TT) or other names, and the external or integrated forwarder on the terminal side can be called a device-side forwarder or a device-side time-sensitive network translator (device-side time-sensitive network translator, DS-TT) or other names, without limitation.

[0126] In one embodiment of the present application, the UPF can send a clock signal to the UE in a unicast manner. The unicast manner can be understood as establishing a user plane transmission channel (which can be called a unicast transmission channel) corresponding to the UE for transmitting the clock signal with the UE as the granularity. The user plane transmission channel can include the air interface connection between the UE and the RAN, and the N3 tunnel between the user plane network element and the access network device. The UPF can send a clock signal to the DS-TT connected to the UE through the user plane transmission channel corresponding to the UE. Figure 4 For example, N3 tunnels can be established for UE1, UE2, UE3 and UE4 respectively. UPF can send the received clock signal to UE1 through the user plane transmission channel corresponding to UE1, send the received clock signal to UE2 through the user plane transmission channel corresponding to UE2, send the received clock signal to UE3 through the user plane transmission channel corresponding to UE3, and send the received clock signal to UE4 through the user plane transmission channel corresponding to UE4.

[0127] In another embodiment of the present application, the UPF can send clock signals to the UE via multicast. Multicast can be understood as establishing an N3 tunnel (also known as a shared N3 tunnel) for multiple UEs in a clock domain, using the clock domain as the granularity. The UPF can send clock signals to the RAN via the N3 tunnel, and the RAN can then send the clock signals to multiple UEs. Clock signals are sent between the UPF and the RAN via a shared N3 tunnel, improving transmission resource utilization.

[0128] by Figure 4 For example, assuming that UE1, UE2, UE3, and UE4 correspond to the same clock domain, a shared N3 tunnel is established for UE1 and UE2. The UPF sends clock signals to RAN1 through this shared N3 tunnel, and RAN1 sends the received clock signals to UE1 and UE2. Similarly, a shared N3 tunnel is established for UE3 and UE4. The UPF sends clock signals to RAN2 through this shared N3 tunnel, and RAN2 sends the received clock signals to UE3 and UE4.

[0129] It should be understood that in the embodiment of the present application, N3 tunnel is an exemplary name for the tunnel, and N3 tunnel can also be named as a tunnel with other names. The N3 tunnel established with UE as the granularity can refer to the tunnel between the access network device corresponding to the UE and the UPF. The N3 tunnel established with UE as the granularity can be called an uplink tunnel or a downlink tunnel according to the transmission direction of the signal transmitted thereon (such as the clock signal described in this application). The uplink tunnel can be used to transmit signals sent from the access network device corresponding to the UE to the UPF, and the downlink tunnel can be used to transmit signals sent from the UPF to the access network device corresponding to the UE. Because the downlink tunnel is used to send signals for one UE to the access network device, that is, the downlink tunnel is used to send signals to the access network device in a unicast manner, the downlink tunnel in this application can be referred to as the unicast N3 tunnel corresponding to the UE or a unicast tunnel. The user plane transmission channel established at the UE granularity can be called a protocol data unit (PDU) session. The user plane network element corresponding to the PDU session can be called a first user plane network element or a unicast user plane network element. The session management network element corresponding to the PDU session can be called a first session management network element or a unicast session management network element. A UE can correspond to one or more PDU sessions. For example, a PDU session can be established for each of the two DS-TTs of UE1.

[0130] In the embodiment of the present application, the N3 tunnel established with the clock domain as the granularity can be called a shared N3 tunnel, a multicast N3 tunnel, or a multicast tunnel. The user plane transmission channel established with the clock domain as the granularity can be called a multicast session or a clock domain multicast session. The user plane network element corresponding to the multicast session can be the anchor point of the multicast session. The user plane network element corresponding to the multicast session can be called a multicast user plane network element, a second user plane network element, or a multicast and broadcast user plane function (MB-UPF). The session management network element that manages the multicast session can be called a multicast session management network element or a second session management network element.

[0131] The first user plane network element and the second user plane network element can be co-located or separately located. The second session management network element and the first session management network element can be co-located or separately located without limitation.

[0132] In an embodiment of the present application, the format of the PTP message carrying the clock signal is shown in Table 3. The message header of the PTP message includes a field for indicating the clock domain (such as the clock domain number field and the SdoId field) and an identifier of the source port, but does not include an identifier of the destination port. For the repeater that forwards the PTP message, it only knows which master clock sends the clock signal and which clock domain the clock signal belongs to, but does not know which clock node the PTP message is ultimately sent to. In addition, the network element that forwards the PTP message within the 5G communication system does not distinguish the states of different ports in different clock domains, and will send the PTP messages of all clock domains to the terminal, and forward them to the clock node through the port of the repeater connected to the terminal (the clock node can be called the end station in this application), and the clock node will filter the clock signal of the required clock domain.

[0133] Take the UPF sending the clock signal to the terminal in unicast mode as an example, for example, Figure 5 The figure shows the transmission diagram of clock signal 1 in clock domain 1. Figure 5 In this example, UE1 and UE2 correspond to RAN1. UE1 is connected to DS-TT1. Port 1 of DS-TT1 is connected to OC1 in clock domain 1. UE2 is connected to DS-TT2. Port 2 of DS-TT2 is connected to OC2 in clock domain 1 and OC3 in clock domain 2. Based on the concept of unicast clock signal transmission, PDU sessions are established for UE1's DS-TT1 and UE2's DS-TT2, respectively. These two PDU sessions share the UPF. After the UPF receives clock signal 1 through the NW-TT port, it cannot determine which UE the clock signal is intended for. Therefore, the UPF sends clock signal 1 to the RANs corresponding to all UEs it manages. For example, the UPF sends clock signal 1 to RAN1 through the N3 tunnel corresponding to UE1, and RAN1 sends clock signal 1 to UE1. The UPF sends clock signal 1 to RAN1 through the N3 tunnel corresponding to UE2, and RAN1 sends clock signal 1 to UE2. Each UE receives clock signal 1 and sends it to the clock node (such as end station) through the port of the DS-TT connected to it. The clock node then filters out the clock signal of the required clock domain. For example, Figure 5 In the example, UE1 sends clock signal 1 to OC1 through port 1 of DS-TT1. Since port 1 is in clock domain 1, OC1 receives clock signal 1 through port 1 and filters out the clock signal 1 it needs. UE2 sends clock signal 1 to OC2 and OC3 through port 2 of DS-TT2. Since OC2 is in clock domain 1, OC2 receives clock signal 1 through port 2 and filters out the clock signal 1 it needs. However, since OC3 is in clock domain 2, OC3 does not need clock signal 1.

[0134] Take the example of UPF sending clock signals to terminals via multicast, for example, Figure 6 Schematic diagram of transmitting clock signal 1 of clock domain 1 in multicast mode. Figure 6 In the figure, UE1 and UE2 correspond to RAN1, UE1 is connected to DS-TT1, port 1 of DS-TT1 is connected to OC1 in clock domain 1, UE2 is connected to DS-TT2, port 2 of DS-TT2 is connected to OC2 in clock domain 1 and OC3 in clock domain 2. Multicast session 1 is established with clock domain 1 as the granularity, and the group corresponding to multicast session 1 includes UE1 and UE2. After UPF receives clock signal 1 through the port of NW-TT, since multicast session 1 is established for clock domain 1, UPF sends clock signal 1 to RAN1 through the shared N3 tunnel corresponding to multicast session 1. After RAN1 receives clock signal 1, it sends clock signal 1 to UE1 and UE2 in the group corresponding to multicast session 1. Each UE sends the received clock signal to the terminal through the port of DS-TT connected to it, and the terminal filters the clock signal of the clock domain it needs. For example, in Figure 6 In the example, UE1 sends clock signal 1 to OC1 through port 1 of DS-TT1. Since port 1 is in clock domain 1, OC1 receives clock signal 1 through port 1 and filters out the required clock signal 1. UE2 sends clock signal 1 to OC2 through port 2 of DS-TT2. Since OC2 is in clock domain 1, OC2 receives clock signal 1 through port 2 and filters out the required clock signal 1. However, OC3 is in clock domain 2 and does not need clock signal 1.

[0135] In the embodiment of the present application, not only can NW-TT connect to the master clock and send the clock signal from the master clock to DS-TT, but DS-TT can also connect to the master clock and send the clock signal from the master clock to NW-TT and other DS-TT. Figure 7 The network architecture diagram for connecting DS-TT to the master clock is as follows: Figure 7As shown, the DS-TT connected to UE1 can connect to the master clocks of clock domain 1 and clock domain 2. After receiving clock signal 1 from clock domain 1 and clock signal 2 from clock domain 2, the DS-TT port sends clock signal 1 to the UPF via the N3 tunnel corresponding to UE1. The UPF forwards clock signal 1 to the port of the NW-TT connected to it, which then forwards it to terminal a in clock domain 1 via the NW-TT port. Furthermore, the UPF forwards clock signal 1 to the DS-TT connected to UE2, which then forwards it to terminal c in clock domain 1 via the DS-TT port. Similarly, UE1 sends clock signal 2 to the UPF via the N3 tunnel corresponding to UE1. The UPF forwards clock signal 2 to the port of the NW-TT connected to it, which then forwards it to terminal b in clock domain 2 via the NW-TT port.

[0136] In the embodiment of the present application, one or more ports can be deployed on a DS-TT, a port can be in one or more clock domains, the states of the same port in different clock domains can be the same or different, one or more DS-TTs can correspond to the same terminal, and one or more ports can correspond to the same terminal. For example, Figure 8a As shown, port 1 of DS-TT1, port 2 of DS-TT2, and port 3 of DS-TT3 correspond to UE1, UE2, and UE3 respectively, that is, one port of a DS-TT corresponds to one UE. Figure 8b As shown in the figure, port 1 is deployed on DS-TT1, and port 2 is deployed on DS-TT2. DS-TT1 and DS-TT2 are both connected to UE1. Port 1 of DS-TT1 and port 2 of DS-TT2 correspond to UE1, and multiple ports correspond to the same UE1. Port 3 is deployed on DS-TT3, which is in clock domains 1 and 2. DS-TT3 is connected to UE2, and port 3 of DS-TT3 corresponds to UE2. Port 4 of DS-TT4 and port 5 of DS-TT5 correspond to UE4 and UE5, respectively.

[0137] When DS-TT is connected to the master clock, that is, when the master clock is on the UE side, the clock signal sent by the master clock may be transmitted back to the master clock, causing the clock synchronization mechanism to be disordered and clock synchronization to be impossible.

[0138] For example, Figure 8a The clock signal transmission diagram when the master clock is on the terminal side is as follows: Figure 8aAs shown in the figure, port 1 of DS-TT1, port 2 of DS-TT2, and port 3 of DS-TT3 correspond to UE1, UE2, and UE3, respectively. OC1 connected to port 1, OC2 to port 2, and OC3 to port 3 are all in clock domain 1. OC3 connected to port 3 is the master clock of clock domain 1, meaning that the master clock of clock domain 1 is on the UE side. OC3 sends clock signal 1 from clock domain 1 uplink to the UPF via UE3. After receiving clock signal 1 from clock domain 1, the UPF sends it to the NW-TT, which then transmits clock signal 1 to other OCs. Because the NW-TT knows the port status of each clock node in clock domain 1 and knows that a DS-TT with a port in a non-slave state (such as master and / or passive state) is located on the UE side, the NW-TT sends clock signal 1 to the UPF. After receiving clock signal 1 from the NW-TT, the UPF sends clock signal 1 to RAN1 via unicast or multicast. RAN1 then sends clock signal 1 to UE1, UE2, and UE3. After receiving clock signal 1, each UE sends clock signal 1 to the DS-TT connected to it. For example, UE3 sends clock signal 1 to DS-TT3, which in turn sends clock signal 1 to OC3. Since OC3 is the master clock, the clock signal 1 sent by OC3 is transmitted back to itself, causing OC3 to resend clock signal 1 to other OCs, causing a clock signal 1 loop. This disrupts the clock synchronization mechanism and makes clock synchronization impossible.

[0139] For example, Figure 8b The clock signal transmission diagram when the master clock is on the terminal side is as follows: Figure 8bAs shown, port 3 of DS-TT3, to which UE2 is connected, is connected to two OCs, one in clock domain 1 and one in clock domain 2. The NW-TT is also connected to two OCs, one in clock domain 1 and one in clock domain 2. The OC connected to port 1 is in clock domain 1; ports 2, 4, and 5 are in clock domain 2. The OC in clock domain 1 connected to port 3 is the master clock for clock domain 1, meaning that UE2 corresponds to the master clock in clock domain 1, while the OC on the NW-TT is the master clock for clock domain 2. According to the multicast transmission method, multicast session 1 is established for clock domain 1, and multicast session 2 is established for clock domain 2. The group corresponding to multicast session 1 includes UE1 and UE2. UE1 and UE2 in the group correspond to RAN1, and RAN1 stores the correspondence between UE1 and UE2 in the group and multicast session 1. The group corresponding to the multicast session in clock domain 2 includes UE1, UE2, UE3, and UE4. UE1 and UE2 in the group correspond to RAN1, and RAN1 stores the correspondence between UE1 and UE2 and multicast session 2. UE3 and UE4 correspond to RAN2, and RAN2 stores the correspondence between UE3 and UE4 and multicast session 2. UE2 sends clock signal 1 from clock domain 1 uplink to the UPF. After receiving clock signal 1 from clock domain 1, the UPF sends clock signal 1 from clock domain 1 to the NW-TT, which then sends clock signal 1 to other OCs. Since the NW-TT knows the status of the ports of each clock node in the clock domain 1, it knows that the DS-TT of the port in the non-slave state (such as the master state and / or the passive state) is located on the UE side. At this time, the NW-TT sends the clock signal 1 to the UPF. After receiving the clock signal 1 of the clock domain 1, the UPF maps the clock signal 1 of the clock domain 1 to the multicast service quality flow (QoS flow, QF) corresponding to the multicast session 1 (for example, the clock signal 1 and the multicast QF identifier (multicast service quality flow identifier (QoS flow) The UPF receives clock signal 2 from clock domain 2 and maps it to the multicast QF corresponding to multicast session 2, which is then sent to RAN1 via multicast session 2. Based on the correspondence between the multicast QF and the multicast session, and the stored correspondence between UE1 and UE2 in the group and multicast session 1, RAN1 sends clock signal 1 to UE1 and UE2. Based on the correspondence between the multicast QF and the multicast session, and the stored correspondence between UE1 and UE2 in the group and multicast session 2, RAN1 sends clock signal 2 to UE1 and UE2. Each UE receives clock signal 2 via the DS-TT connected to it.For example, for UE2, UE2 will send clock signal 1 of clock domain 1 to DS-TT, and DS-TT will send clock signal 1 of clock domain 1 to the master clock connected to it, causing the clock signal sent by the master clock to be transmitted back to the master clock, resulting in a clock signal loop, disrupting the clock synchronization mechanism, and failing to achieve clock synchronization.

[0140] In order to solve the problem of clock signal transmission back to the master clock in the scenario where the master clock is located on the UE side, in one possible design, an embodiment of the present application provides a method for transmitting a clock signal, which may include: filtering out the port corresponding to the master clock according to the state of the port of the device side repeater in the first clock domain, adding the terminal corresponding to the filtered port to the group corresponding to the multicast session, and avoiding the clock signal transmitted on the multicast session from being transmitted back to the terminal corresponding to the master clock. For example, the method can refer to the following Figure 12 or Figure 13a The process shown.

[0141] In another possible design, the state of the port of the device-side repeater in the first clock domain is indicated to the device-side repeater. When the device-side repeater receives the clock signal, it determines the port corresponding to the master clock based on the state of the port and does not forward the clock signal through the port corresponding to the master clock. For example, this method refers to Figure 14 or Figure 15a As described in.

[0142] In another possible design, when the master clock of the first clock domain is located on the terminal side, after the terminal corresponding to the master clock sends the clock signal uplink, the first user plane network element carries the identifier of the uplink tunnel used by the terminal to send the clock signal uplink and the clock signal in the data packet and sends it to the access network device. After receiving the data packet, the access network device does not transmit the clock signal to the terminal corresponding to the uplink tunnel, thereby avoiding the clock signal from being transmitted back to the master clock. For example, this method can refer to the following Figure 16 or Figure 17a The process shown.

[0143] It should be noted that the multicast described in this application may refer to a communication method that sends the same clock signal to multiple nodes. The multicast described in this application can also be understood as groupcast, broadcast, or multicast / broadcast. That is, multicast, groupcast, broadcast, and multicast / broadcast are equivalent and can be used interchangeably. The multicast session described in this application can be understood as a multicast session or a multicast broadcast service session (MBS session), without limitation.

[0144] The clock signal transmission method provided by the embodiment of the present application is described below in conjunction with the accompanying drawings. It should be understood that the network architecture and service scenarios described in the embodiment of the present application are intended to more clearly illustrate the technical solutions of the embodiment of the present application and do not constitute a limitation on the technical solutions provided by the embodiment of the present application. It is known to those skilled in the art that with the evolution of network architecture and the emergence of new service scenarios, the technical solutions provided by the embodiment of the present application are also applicable to similar technical problems.

[0145] Below is Figure 9 Taking the communication system shown as an example, the clock signal transmission method provided in the embodiment of the present application is described.

[0146] like Figure 9 As shown, a communication system is provided in an embodiment of the present application. The communication system may include a device-side forwarder, a terminal, an access network device, a first session management network element, a first user plane network element, a first application function network element, and a network-side forwarder. Further, Figure 9 The communication system shown may further include a mobility management network element, a second session management network element, a second user plane network element, a policy control network element, and a network storage network element.

[0147] Among them, multiple terminals can form a group, and multiple terminals can receive the same data, such as clock signals in the same clock domain. The first user plane network element can be used to transmit the clock signal of the clock domain in a unicast manner. The first user plane network element can be called a unicast user plane network element. The second user plane network element can be used to transmit the clock signal of the clock domain in a multicast manner. The second user plane network element can be called a multicast user plane network element. The first session management network element can be a session management network element that manages PDU sessions. The first session management network element can be called a unicast session management network element. The second session management network element can be a session management network element that manages multicast sessions. The second session management network element can be called a multicast session management network element. In the present application, the first session management network element and the second session management network element can be co-located or deployed independently. The first user plane network element and the second user plane network element can be co-located or deployed independently.

[0148] Below Figure 9 This section introduces the network elements or devices involved in the shown architecture.

[0149] The device-side repeater can be connected to the terminal or integrated in the terminal. The device-side repeater can be used to forward the clock signal received by the terminal from the master clock to the terminal, or forward the clock signal sent by the master clock of the terminal to the terminal, so that the terminal forwards it to other slave clocks. The device-side repeater can be called DS-TT. The device-side repeater can have one or more ports for forwarding clock signals, and the state of the port can be any state described in Table 2 above, such as master state, slave state or passive state. After receiving the clock signal, the device-side repeater can forward the received clock signal to the terminal through the port in the master state. Specifically, the device-side repeater can be a high-precision synchronized cable, and the port of the device-side repeater can be a port of the cable.

[0150] A terminal may be a device for implementing wireless communication functions, such as a terminal or a chip that can be used in a terminal, which may be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; may also be deployed on water (such as a ship); and may also be deployed in the air (such as an airplane, a balloon, and a satellite). The terminal may be a user equipment (UE), an access terminal, a terminal unit, a terminal station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a wireless communication device, a terminal agent, or a terminal device in a 5G network or a future evolved public land mobile network (PLMN). The access terminal may be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication functions, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device or a wearable device, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, or an unmanned driving (self-driving). The wireless terminals can be used in various applications, such as wireless terminals in smart driving, wireless terminals in remote medical care, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, and wireless terminals in smart homes. The terminals can be mobile or fixed.

[0151] Access network equipment is mainly used to implement physical layer functions, resource scheduling and management, terminal access control, and mobility management. Access network equipment can be devices that support wired access or wireless access. Access network equipment may include, but is not limited to: next-generation base stations (gnodeB, gNB) in 5G, evolved node B (eNB), radio network controller (RNC), node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved node B, or home node B, HNB), baseband unit (BBU), transmitting and receiving point (TRP), transmitting point (TP), and mobile switching center.

[0152] The mobility management network element is mainly responsible for terminal access authentication, mobility management, and signaling interaction between various functional network elements. For example, it manages user registration status, user connection status, user registration and network access, tracking area updates, cell switching user authentication and key security.

[0153] The session management network element is mainly used to implement session management functions such as the establishment, release, and modification of user plane transmission channels. The user plane transmission channel described in this application can be referred to as a session, and the session described in this application can include a PDU session and a multicast session. As described above, a PDU session can be referred to as a unicast session, and a PDU session can be a user plane transmission channel for transmitting a clock signal established with the UE as the granularity. The PDU session can include an air interface connection between the UE and the RAN, and an N3 tunnel (or a unicast N3 tunnel) between the RAN and the UPF. A multicast session can be a user plane transmission channel for transmitting a clock signal established with the clock domain as the granularity, and a multicast session can include an air interface connection between multiple UEs and the RAN, and a shared N3 tunnel (or a multicast N3 tunnel) between the RAN and the UPF.

[0154] The user plane network element can serve as an anchor point on the user plane transmission channel to complete functions such as routing and forwarding of user plane data. For example, it establishes a channel (i.e., user plane transmission channel) with the terminal, forwards data packets (such as PTP messages) between the terminal and the data network (DN) on the channel, and is responsible for terminal data packet filtering, data forwarding, rate control, and generating billing information.

[0155] The network side repeater can be connected to the first user plane network element or integrated in the first user plane network element. The network side repeater can be used to forward the clock signal from the master clock received from the first user plane network element to the terminal station, or forward the clock signal sent by the master clock to the first user plane network element, so that the first user plane network element forwards it to other slave clocks. The network side repeater can be called NW-TT. The network side repeater can have one or more ports for forwarding clock signals, and the state of the port can be any of the states described in Table 2 above, such as master state, slave state or passive state. After receiving the clock signal from outside the communication system through the port in the slave state, the network side repeater can forward the received clock signal to the terminal station. Specifically, the network side repeater can be a high-precision synchronized cable, and the port of the network side repeater can be a port of the cable.

[0156] The first application function network element can provide clock signal transmission services to users. The first application function network element can be a time sensitive network application function (TSN AF) or a time sensitive communication and time synchronization function (TSCTSF).

[0157] The policy control network element can be used to provide policies to the mobility management network element and the session management network element, such as quality of service policy, slice selection policy, etc.

[0158] A network storage element can be used to store user data, such as user contract information, authentication or authorization data, etc. The network storage element can be a unified data management element (UDM), a network repository function (NRF), or a unified data repository (UDR).

[0159] It should be noted that Figure 9 This is just an example architecture diagram. Figure 9 In addition to the functional units shown in , the system may also include other functional network elements, such as: operation and management (O&M) network elements, etc., which are not limited in the embodiments of the present application. Figure 9 The names of the devices in the Figure 9In addition to the names shown, each device can also be named other names, such as replacing them with network element names with the same or similar functions, without restriction.

[0160] in, Figure 9 The system shown can be a 3GPP communication system, such as a 4G communication system, an LTE system, a 5G communication system or an NR system, a next-generation communication system, etc., or a non-3GPP communication system without limitation.

[0161] by Figure 9 The communication system shown is Figure 10 As an example, the 5G communication system shown in FIG. Figure 10 As shown, the entity corresponding to the first session management network element above may be a session management function (SMF) in a 5G communication system, the entity corresponding to the second session management network element above may be a multicast broadcast session management function (MB-SMF) in a 5G communication system, the entity corresponding to the first user plane network element above may be a UPF in a 5G communication system, and the entity corresponding to the second user plane network element may be a multicast broadcast user plane function (MB-UPF) in a 5G communication system. The entity corresponding to the access network device may be a radio access network (RAN) in a 5G communication system, the entity corresponding to the mobility management network element may be an access and mobility management function (AMF) in a 5G communication system, the policy control function may be a policy control function (PCF) in a 5G communication system, and the network storage network element corresponds to a UDM in a 5G communication system.

[0162] Figure 10 The interfaces between the network elements in the network are point-to-point interfaces. Figure 10 As shown, Figure 10The N1 interface is the reference point between the terminal and AMF; the N2 interface is the reference point between the RAN device and the AMF, which is used to send non-access stratum (NAS) messages and next generation application protocol (NGAP) messages; the N3 interface is the reference point between the RAN device and the UPF, which is used to transmit user plane data; the N4 interface is the reference point between the SMF and the UPF, which is used to transmit information such as tunnel identification information of the N3 connection, data cache indication information, and downlink data; the N9 interface is the reference point between the UPF and the UPF, etc., which will not be explained one by one here.

[0163] Optionally, the first session management network element, the device side forwarder, the access network device, the first application function network element or the first user plane network element in the embodiment of the present application can be referred to as a communication device, which can be a general device or a dedicated device, and the embodiment of the present application does not specifically limit this.

[0164] Optionally, the relevant functions of the first session management network element, the device-side forwarder, the access network device, the first application function network element, or the first user plane network element in the embodiment of the present application can be implemented by a single device, or can be implemented by multiple devices together, or can be implemented by one or more functional modules within a single device, and the embodiment of the present application does not specifically limit this. It is understandable that the above functions can be network elements in hardware devices, software functions running on dedicated hardware, or a combination of hardware and software, or virtualized functions instantiated on a platform (e.g., a cloud platform).

[0165] For example, the relevant functions of the first session management network element, the device side forwarder, the access network device, the first application function network element or the first user plane network element in the embodiment of the present application can be Figure 11 It is implemented by the communication device 1100 in. Figure 11 FIG. 1 is a schematic diagram of the structure of a communication device 1100 provided in an embodiment of the present application. The communication device 1100 includes one or more processors 1101, a communication line 1102, and at least one communication interface ( Figure 11 The example in which the communication interface 1104 and a processor 1101 are included is merely exemplary), and a memory 1103 may also be included optionally.

[0166] The processor 1101 may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of the program of the present application.

[0167] The communication line 1102 may include a path for connecting different components.

[0168] Communication interface 1104 can be used to communicate with other devices or communication networks, such as Ethernet, RAN, and wireless local area networks (WLAN). For example, communication interface 1104 can be a device such as a transceiver. Alternatively, communication interface 1104 can be a transceiver circuit located within processor 1101 to implement signal input and output to the processor.

[0169] The memory 1103 may be a device having a storage function. For example, it may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory may exist independently and be connected to the processor via a communication line 1102. The memory may also be integrated with the processor.

[0170] Among them, the memory 1103 is used to store computer-executable instructions for executing the solution of the present application, and the execution is controlled by the processor 1101. The processor 1101 is used to execute the computer-executable instructions stored in the memory 1103, thereby implementing the clock signal transmission method provided in the embodiment of the present application. Alternatively, optionally, in the embodiment of the present application, the processor 1101 may also perform processing-related functions in the clock signal transmission method provided in the following embodiment of the present application, and the communication interface 1104 is responsible for communicating with other devices or communication networks, which is not specifically limited in the embodiment of the present application.

[0171] Optionally, the computer-executable instructions in the embodiments of the present application may also be referred to as application code, which is not specifically limited in the embodiments of the present application.

[0172] In a specific implementation, as an embodiment, the processor 1101 may include one or more CPUs, such as Figure 11 In a specific implementation, as an embodiment, the communication device 1100 may include multiple processors, such as Figure 11 Processor 1101 and processor 1108 in FIG. Each of these processors can be a single-core processor or a multi-core processor. The processor here can include, but is not limited to, at least one of the following: a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a microcontroller unit (MCU), or an artificial intelligence processor, etc., and various types of computing devices that run software. Each computing device may include one or more cores for executing software instructions to perform calculations or processing.

[0173] In a specific implementation, as an embodiment, the communication device 1100 may further include an output device 1105 and an input device 1106. The output device 1105 communicates with the processor 1101 and can display information in various ways. For example, the output device 1105 can be a liquid crystal display (LCD), a light emitting diode (LED) display device, a cathode ray tube (CRT) display device, or a projector. The input device 1106 communicates with the processor 1101 and can receive user input in various ways. For example, the input device 1106 can be a mouse, a keyboard, a touch screen device, or a sensor device.

[0174] The communication device 1100 may also be referred to as a communication device, which may be a general-purpose device or a dedicated device. For example, the communication device 1100 may be a desktop computer, a portable computer, a network server, a personal digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal, an embedded device, the above-mentioned terminal, the above-mentioned network device, or a Figure 11 The embodiment of the present application does not limit the type of the communication device 1100. In addition, Figure 11 The structure shown in the figure does not constitute a limitation on the communication device, except Figure 11 In addition to the components shown, the communication device may include more or fewer components than shown, or combine certain components, or arrange the components differently.

[0175] In the embodiment of the present application, the chip system can be composed of chips, or can include chips and other discrete devices.

[0176] The following combination Figure 9-10 The communication system shown in the figure describes the clock signal transmission method provided by the embodiment of the present application. In the following embodiments, each device may have Figure 11 The components shown, and the actions, terms, etc. involved in each embodiment can refer to each other. The message name or parameter name in the message exchanged between devices in each embodiment is only an example. Other names can also be used in the specific implementation. For example, the multicast described in the embodiment of the present application can be replaced by terms such as broadcast, groupcast, multicast communication, multicast / broadcast or multicast / broadcast. The determination in the embodiment of the present application can also be understood as creation (create) or generation (generate), and the "include" in the embodiment of the present application can also be understood as "carry" or "include", which are explained uniformly here. In addition, the terms "first" and "second" in the embodiment of the present application are used to distinguish different objects, rather than to describe the specific order of objects. The embodiment of the present application does not limit the attributes of the different objects represented by "first" and "second".

[0177] like Figure 12 As shown, a clock signal transmission method provided by an embodiment of the present application can be applied to scenarios where clock signals are transmitted in a multicast manner. The method includes the following steps:

[0178] S1200. A first session management network element obtains first information.

[0179] The first session management network element may be a session management network element for managing the PDU session of the terminal, for example, the first session management network element may be Figure 10In the case where the first session management network element and the second session management network element are deployed independently, the first session management network element can be connected to the second session management network element (such as Figure 10 The multicast session described in this application may be a transmission tunnel for transmitting the clock signal of the first clock domain in a multicast manner.

[0180] The first information may be used to indicate the port identifier and the status of each port of the device-side repeater in the first clock domain. The first clock domain may be any clock domain. The device-side repeater may be a DS-TT, and the device-side repeater may be connected to a terminal or integrated into a terminal. The port of the device-side repeater may be connected to a terminal station of the first clock domain (such as an OC serving as a slave clock) or to a master clock of the first clock domain, without limitation.

[0181] The port identifier described in this application can be understood as the port identifier of the device-side forwarder (such as the ID+port ID of DS-TT or the port ID of DS-TT). The port identifier is used to identify a port on the device-side forwarder, that is, it can be understood that the port described in this application can be represented by the port identifier. The port identifier may include but is not limited to the port number (or port number), or the port index, or the media access control (MAC) address of the port. In an embodiment of the present application, the port identifier can be allocated by the first session management network element (such as SMF) / the first user plane network element (such as UPF) during the PDU session establishment process of the terminal corresponding to the port.

[0182] In an embodiment of the present application, a port state includes a first state or a second state. In an embodiment of the present application, a port in the first state includes a port of a device-side repeater connected to the master clock of the first clock domain (i.e., a port in a slave state), and a port in the second state includes a port of a device-side repeater connected to a clock other than the master clock in the first clock domain (i.e., a port in a master state). For example, the first state may include a slave state, and the second state may include a master state, or a master state and a passive state. For another example, the first state may include a slave state, or a slave state and a passive state, and the second state may include a master state. The description of the master state, slave state, and passive state is as described in Table 2 above and is not repeated here. In other words, if a port is connected to a terminal station in the first clock domain, the state of the port is a master state, i.e., the second state. If a port is connected to the master clock of the first clock domain, the state of the port is a slave state, i.e., the first state. If a port does not have the function of forwarding clock signals (or the port is not working), the state of the port may be a passive state. Whether the passive state belongs to the first state or the second state can be determined based on the actual configuration.

[0183] For example, Figure 8a As shown, port 1 of DS-TT1, port 2 of DS-TT2, and port 3 of DS-TT3 are in clock domain 1. The master clock OC3 of clock domain 1 is connected to port 3 of DS-TT3. Port 3 of DS-TT3 is in a slave state in clock domain 1. Port 1 of DS-TT1 and port 2 of DS-TT2 are connected to slave clocks OC1 and OC2 of clock domain 1. Port 1 of DS-TT1 and port 2 of DS-TT2 are in a master state in clock domain 1. That is, the first information may include {port 1 of DS-TT1, master state (second state); port 2 of DS-TT2, master state (second state); port 3 of DS-TT3, slave state (first state)}.

[0184] Exemplarily, the first information may further include an identifier of the first clock domain. The identifier of the first clock domain may be used to identify the first clock domain, for example, the identifier of the first clock domain may be a number or index of the first clock domain.

[0185] For example, Figure 8a As shown, as described above, if the first clock domain is clock domain 1, the first information may include clock domain 1 {port 1 of DS-TT1, master state (second state); port 2 of DS-TT2, master state (second state); port 3 of DS-TT3, slave state (first state)}.

[0186] For example, Figure 8b As shown, port 1 of DS-TT1 and port 3 of DS-TT3 are in clock domain 1, the master clock of clock domain 1 is on port 3 of DS-TT3, port 3 of DS-TT3 is connected to the master clock of clock domain 1, and the state of port 3 of DS-TT3 when belonging to the first clock domain is a slave state. Port 1 of DS-TT1 is connected to the slave clock of clock domain 1, so the state of port 1 of DS-TT1 when belonging to the first clock domain is a master state. If the first clock domain is clock domain 1, the first information may include clock domain 1 {port 1 of DS-TT1, master state (second state); port 3 of DS-TT3, slave state (first state)}.

[0187] like Figure 8bAs shown, port 2 of DS-TT2, port 3 of DS-TT3, port 4 of DS-TT4, and port 5 of DS-TT5 are in clock domain 2. The master clock of clock domain 2 is on the NW-TT side. Port 2 of DS-TT2, port 3 of DS-TT3, port 4 of DS-TT4, and port 5 of DS-TT5 are all connected to the slave clock of clock domain 2. The state of port 2 of DS-TT2, port 3 of DS-TT3, port 4 of DS-TT4, and port 5 of DS-TT5 is the master state when in clock domain 2. If the first clock domain is clock domain 2, the first information may include clock domain 2 {port 2 of DS-TT2, master state (second state); port 3 of DS-TT3, master state (second state); port 4 of DS-TT4, master state (second state); port 5 of DS-TT5, master state (second state)}.

[0188] Exemplarily, the first session management network element obtaining the first information may include: the first session management network element receiving the first information from the first application function network element. For example, after obtaining the first information, the first application function network element determines the first session management network element and sends the first information to the first session management network element. Optionally, the first information may be included in a first request, and the first request may be used to request the first session management network element to configure or establish a multicast session for the first clock domain.

[0189] In the embodiment of the present application, the first application function network element may be a time sensitive network application function network element (such as TSNAF) or a time sensitive communication and clock synchronization function network element (such as TSCTSF). The first application function network element may obtain the first information from the NW-TT and send the first information to the first session management network element. Specifically, the process is as follows Figure 13a As described in.

[0190] In an embodiment of the present application, the first session management network element is a session management network element that manages (such as configuring, creating, updating, and releasing) the PDU session of the terminal, and the terminal is connected to a device-side repeater in the first clock domain. There is a correspondence between the identifier of the first session management network element and the identifier of the terminal managed by the first session management network element, and there is a correspondence between the identifier of the port of the device-side repeater and the identifier of the terminal. These correspondences can be pre-stored in a network storage network element, such as a UDM. Before the first application function network element sends the first information to the first session management network element, the first application function network element can learn from the first information which ports of the device-side repeater are in the first clock domain, send the identifier of the port to the UDM, query the UDM to obtain the identifier of the first session management network element corresponding to the terminal corresponding to the port, and send the first information to the first session management network element according to the identifier of the first session management network element.

[0191] In the embodiment of the present application, the identifier of the first session management network element can be used to identify the first session management network element. The identifier of the first session management network element can be an Internet Protocol (IP) address, a Media Access Control (MAC) address, or a fully qualified domain name (FQDN) of the first session management network element.

[0192] S1201. A first session management network element determines a terminal to join a group corresponding to a multicast session based on first information and a correspondence between ports and terminals.

[0193] In the embodiment of the present application, the correspondence between the port and the terminal can be understood as the correspondence between the device-side repeater where the port is located and the terminal. In other words, the correspondence between the port and the terminal can include the correspondence between the identifier of the port of the device-side repeater and the identifier of the terminal. The correspondence between the port and the terminal is as described above. The example of the correspondence between the port and the terminal can be referred to above. Figure 8a 、 Figure 8b For example description.

[0194] The correspondence between the identifier of the port of the device-side forwarder and the identifier of the terminal can be stored on the first session management network element. For example, the context of the PDU session of the terminal stored on the first session management network element. After receiving the first information, the first session management network element can use the identifier of the port of the device-side forwarder as an index to search for the context of the PDU session stored by the first session management network element. The first session management network element determines the terminal corresponding to the port based on the context of the PDU session including the identifier of the port of the device-side forwarder.

[0195] Among them, the relevant description of the PDU session of the terminal is as described above, and the PDU session of the terminal may include the air interface connection between the terminal and the access network device, and the N3 tunnel between the access network device and the first user plane network element. The PDU session of the terminal may correspond to the device-side forwarder connected to the terminal, and one PDU session of the terminal may correspond to one or more device-side forwarders connected to the terminal. For example, the first session management network element may receive a session establishment request from the terminal that carries the identifier of the first clock domain and the identifier of the port of the device-side forwarder, and establish a PDU session for the terminal according to the session establishment request. One device-side forwarder may establish a corresponding PDU session, and the context of the PDU session of the terminal may not only carry the correspondence between the identifier of the port of the device-side forwarder and the identifier of the terminal, but optionally, the context of the PDU session of the terminal may also carry the identifier of the PDU session and other information about the PDU session.

[0196] For example, Figure 8a As shown in the figure, DS-TT1 connects to UE1, DS-TT2 connects to UE2, and DS-TT3 connects to UE3. Assuming that UE1, UE2, and UE3 correspond to SMF1 and are all managed by SMF, SMF1 establishes PDU Session 1 for UE1, PDU Session 2 for UE2, and PDU Session 3 for UE3. After the PDU sessions are established, SMF1 stores Context 1 of PDU Session 1 {UE1, Port 1 of DS-TT1}, Context 2 of PDU Session 2 {UE2, Port 2 of DS-TT2}, and Context 3 of PDU Session 3 {UE3, Port 3 of DS-TT3}. If the first information obtained by SMF1 includes clock domain 1 {Port 1 of DS-TT1, master state; Port 2 of DS-TT1, master state; Port 3 of DS-TT3, slave state}, SMF1 searches the locally stored PDU session context using Port 1 of DS-TT1 as an index, and determines that Port 1 of DS-TT1 corresponds to UE1. SMF1 searches the locally stored PDU session context using Port 2 of DS-TT2 as an index, and determines that Port 2 of DS-TT2 corresponds to UE2. SMF1 searches the locally stored PDU session context using Port 3 of DS-TT3 as an index, and determines that Port 3 of DS-TT3 corresponds to UE3.

[0197] Exemplarily, the first session management network element determines the terminal to join the group corresponding to the multicast session based on the first information and the correspondence between the port and the terminal, which may include: the first session management network element determines the terminal corresponding to the port of the device-side repeater in the first clock domain based on the first information and the correspondence between the port and the terminal, and according to the state of the port of the device-side repeater in the first clock domain, selects a port connected to a non-master clock (such as a slave clock) from the port of the device-side repeater, and adds the terminal corresponding to the selected port to the group corresponding to the multicast session.

[0198] In the embodiment of the present application, the first session management network element determining, based on the first information and the correspondence between the port and the terminal, the terminal corresponding to the port of the device-side repeater in the first clock domain may include: the first session management network element searching for the correspondence between the port and the terminal based on the port of the device-side repeater in the first clock domain, using the port as an index, and determining the terminal corresponding to the port in the correspondence as the terminal corresponding to the port of the device-side repeater in the first clock domain. Alternatively, the first session management network element may obtain a terminal managed / served by the first session management network element, search for the correspondence between the port and the terminal using the terminal as an index, and find the port in the first clock domain corresponding to the terminal in the correspondence.

[0199] In an embodiment of the present application, the first session management network element selects a port connected to a non-master clock (e.g., a slave clock) from the ports of the device-side forwarder based on the state of the port of the device-side forwarder in the first clock domain, and adds the terminal corresponding to the selected port to the group corresponding to the multicast session. The following two possible design methods may be used:

[0200] In one possible design, for each terminal corresponding to the port of the device-side repeater in the first clock domain, if the states of one or more ports on the device-side repeater corresponding to the terminal in the first clock domain are all in the second state (such as the master state), it means that the ports on the device-side repeater corresponding to the terminal are all connected to the slave clock of the first clock domain, rather than the master clock of the first clock domain, and the terminal is determined to be added to the group corresponding to the multicast session.

[0201] It should be understood that in an embodiment of the present application, if the number of terminals corresponding to ports of the device-side repeater in the first clock domain that are all in the second state is less than a preset threshold, for example, less than 2, then it can be determined to add the terminal to the group corresponding to the multicast session, or it can be determined not to add the terminal to the group corresponding to the multicast session, but to send a clock signal to the terminal in a unicast manner.

[0202] In another possible design, for each terminal corresponding to the port of the device-side repeater in the first clock domain, if there is a port in the first state (such as the slave state) among the ports on the device-side repeater corresponding to the terminal, it means that the port is connected to the master clock of the first clock domain, and the device-side repeater can receive the clock signal from the upstream through the port in the slave state. In order to prevent the terminal from forwarding the received clock signal of the first clock domain to the master clock of the first clock domain through the port, it is determined not to add the terminal to the group corresponding to the multicast session. After traversing each terminal, the terminals that do not join the group among the terminals corresponding to the ports of the device-side repeater are eliminated, and the remaining terminals after elimination are added to the group corresponding to the multicast session.

[0203] For example, if there are a first terminal and a second terminal, and the states of one or more ports on the device-side repeater corresponding to the first terminal are all in the second state (such as the master state) in the first clock domain, it means that the ports on the device-side repeater corresponding to the first terminal are all connected to the slave clock of the first clock domain, and the first terminal is determined to be added to the group corresponding to the multicast session. If there is a first port among the one or more ports on the device-side repeater corresponding to the second terminal, and the state of the first port in the first clock domain is the first state (such as the slave state), it means that the device-side repeater corresponding to the second terminal is connected to the master clock of the first clock domain, and the second terminal is determined not to be added to the group corresponding to the multicast session, that is, it is finally determined to add the first terminal to the group corresponding to the multicast session, but not to add the second terminal to the group corresponding to the multicast session.

[0204] The above possible design can also be understood as follows: the terminal corresponding to the device-side repeater is added to the group corresponding to the multicast session in the first clock domain only when all ports in the first clock domain are in the second state (such as the master state). If the terminal corresponding to the device-side repeater has a port in the first clock domain that is in the first state (such as the slave state), the terminal will not be added to the group corresponding to the multicast session in the first clock domain. Even if the device-side repeater has a port in the first clock domain that is in the second state (such as the master state), the terminal corresponding to the device-side repeater will not be added to the group corresponding to the multicast session.

[0205] Optionally, when there is a port in the first clock domain of the device-side repeater that is in the first state (such as the slave state), if the port in the first clock domain of the device-side repeater also has a port in the second state, the clock signal can be forwarded to other non-master clocks inside the device-side repeater. For example, after the slave state port of the device-side repeater receives the clock signal, the clock signal is sent to other non-master clocks through the second state port of other device-side repeaters of the terminal. Assuming that Figure 8b In the scenario shown, UE2 is also connected to a DS-TT6 of clock domain 1 (not shown in the figure), so DS-TT3 forwards the clock signal to the inside of DS-TT6 through UE2.

[0206] For example, in Figure 8a In the illustrated scenario, as described above, UE1 corresponds only to port 1 of DS-TT1 in the second state, and UE2 corresponds only to port 2 of DS-TT2 in the second state. Therefore, UE1 and UE2 are added to the group corresponding to the multicast session of clock 1. Since UE3 corresponds to port 3 of DS-TT3 in the first state, UE3 is not added to the group corresponding to the multicast session.

[0207] For example, in Figure 8bIn the illustrated scenario, since port 3 of DS-TT3 is in a slave state, i.e., the first state, UE2 corresponding to port 3 of DS-TT3 is not added to the group corresponding to the multicast session in clock domain 1 of RAN1. If port 1 of DS-TT1 is in a master state, i.e., the second state, UE1 corresponding to port 1 and other UEs (if any, not shown) located on RAN1 and corresponding to ports all in the second state are added to the group corresponding to the multicast session in clock domain 1 of RAN1. Alternatively, if UE1 is the only UE corresponding to ports all in the second state of RAN1, since the number of UEs eligible to join the group is less than a preset threshold 2, UE1 is not added to the group corresponding to the multicast session. Instead, the clock signal of clock domain 1 is transmitted to UE1 using the aforementioned unicast method. Similarly, port 2 of DS-TT2, port 3 of DS-TT3, port 4 of DS-TT4, and port 5 of DS-TT5 are in clock domain 2. The states of these ports in clock domain 2 are the main state, that is, the second state. UE1 and UE2 are added to the group corresponding to the multicast session in clock domain 2 under RAN1, and UE3 and UE4 are added to the group corresponding to the multicast session in clock domain 2 under RAN2.

[0208] In the embodiment of the present application, before S1201, the method may further include: the first session management network element determines to configure or create a multicast session, that is, after determining to configure or create a multicast session in the first clock domain, executing S1201.

[0209] In the embodiment of the present application, configuring a multicast session in the first clock domain can be understood as multicast broadcast service configuration (MBSsession configuration). During the process of configuring the multicast session in the first clock domain, terminals that join the multicast session in the first clock domain can be determined. In addition, configuring the multicast session in the first clock domain can also include configuring one or more of the following parameters: quality of service (QoS) information of the multicast session, multicast QFI, tunnel information of the second user plane network element (i.e., MB-UPF), service data flow (SDF) of the multicast session, packet detection rule (PDR) of the multicast session, and at least one of the forwarding action rule (FAR) associated with the PDR. Among these parameters, the QoS information of the multicast session can be configured by the first session management network element and sent to the second session management network element. Other parameters can be configured by the second session management network element. These parameters can be used to create, update, or modify the multicast session in the first clock domain.

[0210] In the embodiment of the present application, establishing a multicast session in the first clock domain can be understood as establishing an air interface connection between the access network device and the terminal, an N3 tunnel (which can be called a shared N3 tunnel) between the access network device and the second user plane network element (such as MB-UPF), and an N9 tunnel between the second user plane network element and the first user plane network element (such as UPF). The second user plane network element, the first user plane network element, and the access network device can create a multicast session in the first clock domain under the instruction / management of the first session management network element and the second session management network element.

[0211] In an embodiment of the present application, the first session management network element may send first configuration information to the first user plane network element; wherein the first configuration information is used to establish a transmission tunnel (i.e., an N9 tunnel) between the first user plane network element and the second user plane network element for transmitting clock signals in the first clock domain; the second user plane network element is the anchor point for the multicast session in the first clock domain. The first session management network element may send second configuration information to the second user plane network element through the second session management network element; wherein the second configuration information is used to establish a transmission tunnel (i.e., a shared N3 tunnel) between the second user plane network element and the access network device for transmitting clock signals in the first clock domain; wherein the second session management network element is the session management network element that manages the multicast session. Thus, a transmission channel is established between NW-TT->first user plane network element->second user plane network element->access network device.

[0212] It should be understood that if the first user plane network element and the second user plane network element are jointly arranged, for example, the second user plane network element is integrated into the first user plane network element, and the first user plane network element has the functions performed by the second user plane network element, then the second user plane network element described in this application can be understood as the first user plane network element.

[0213] Exemplarily, the first session management network element may determine to configure or create a multicast session in the following ways:

[0214] Method 1: The first session management network element determines, based on the first information, that the number of terminals corresponding to the port of the device-side repeater in the first clock domain is greater than a preset threshold, and then determines to configure or create a multicast session in the first clock domain.

[0215] The preset threshold value can be set as needed, for example, to 1, 2, or 3. Assuming that the preset threshold value is 1, Figure 8b As shown, port 1 of DS-TT1 and port 3 of DS-TT3 are in clock domain 1, port 3 corresponds to UE2 and port 1 corresponds to UE1, and the number of terminals corresponding to the ports in clock domain 1 is 2, so it is determined to configure or create a multicast session in clock domain 1.

[0216] Method 2: The first session management network element receives an event notification from the first user plane network element. The event notification can be used to notify the first session management network element of a first event. The first event is that the first user plane network element receives a clock signal from the first clock domain and is about to transmit the clock signal of the first clock domain to the terminal side. The first session management network element determines the configuration or creation of a multicast session in the first clock domain based on the event notification of the first user plane network element, that is, the configuration or creation of the multicast session in the first clock domain is learned from the user plane.

[0217] In an embodiment of the present application, the first user plane network element can be the anchor point of the PDU session of the terminal. The first user plane network element can also be called a unicast user plane network element. The first user plane network element can establish an N4 connection with the first session management network element, and under the configuration of the first session management network element, the received clock signal of the first clock domain is sent to the terminal through the PDU session of the terminal.

[0218] For example, when the first session management network element receives a session establishment request from a terminal that carries an identifier of the first clock domain and an identifier of a port of a device-side forwarder, and establishes a PDU session for the terminal between the network-side forwarder and the device-side forwarder for transmitting a clock signal of the first clock domain, it may send a subscription request carrying the identifier of the first clock domain to the first user-plane network element. The subscription request may be used to request the first user-plane network element to notify / report the first event to the first session management network element when the first event occurs, the first event being as described above. The first user-plane network element receives the subscription request, and in response to the subscription request, after receiving the clock signal of the first clock domain, the first user-plane network element sends an event notification to the first session management network element.

[0219] Optionally, after receiving the clock signal from the first clock domain, the first user plane network element, in addition to sending an event notification to the first session management network element, also locally caches the received clock signal from the first clock domain. For example, the first session management network element may further notify the first user plane network element to store the received clock signal from the first clock domain locally, and after the multicast session for the first clock domain is configured or created, notify the first user plane network element to send the locally cached clock signal from the first clock domain. For example, the above-mentioned event notification is also used to notify the first user plane network element to cache the received clock signal from the first clock domain. After receiving the clock signal from the first clock domain, the first user plane network element, in addition to sending an event notification to the first session management network element, also locally caches the received clock signal from the first clock domain. After the first session management network element completes configuring or creating the multicast session for the first clock domain, the first session management network element sends a release notification to the first user plane network element, notifying the first user plane network element to send the locally cached clock signal from the first clock domain.

[0220] Mode three: when it is determined that there is a terminal requiring a clock signal of the first clock domain among the terminals managed by the first session management network element, it is determined to configure or create a multicast session of the first clock domain.

[0221] For example, when the clock node connected to the terminal requires the clock signal of the first clock domain for time synchronization, the clock node can send demand information to the first session management network element through the port trigger terminal. The demand information is used to indicate that the clock signal of the first clock domain is required. The first session management network element determines, based on the demand information, that there are terminals among the terminals it manages that require the clock signal of the first clock domain, and determines to configure or create a multicast session for the first clock domain, that is, determines to configure or create a multicast session for the first clock domain based on the signaling message of the control plane.

[0222] Optionally, the above requirement information may be sent to the first session management network element during the process of establishing the PDU session of the terminal, thereby saving signaling overhead.

[0223] Mode 4: The first session management network element receives a first request from the first application function network element. The first request may be used to request configuration or creation of a multicast session. The first session management network element determines to configure or create the multicast session according to the first request.

[0224] The first request may carry at least one of an identifier of the first clock domain and an identifier of the multicast session. Furthermore, the first request may also carry the first information described in S1200. This means that the first request can be used to request the first session management network element to configure or create a multicast session and to send the first information to the first session management network element, thereby reducing signaling overhead.

[0225] It should be understood that the above-mentioned methods 2 to 4 can also be used to determine the configuration or create other sessions for transmitting clock signals, such as for determining or creating a PDU session for transmitting clock signals.

[0226] S1202. The first session management network element sends a multicast session identifier to the access network device corresponding to the terminal joining the group. Accordingly, the access network device receives the multicast session identifier from the first session management network element, so that the access network device learns that the terminal has joined the group corresponding to the multicast session based on the received multicast session identifier. For example, if the terminals joining the group corresponding to the multicast session include the first terminal, the first session management network element sends the multicast session identifier to the access network device corresponding to the first terminal. Accordingly, the access network device corresponding to the first terminal receives the multicast session identifier.

[0227] In an embodiment of the present application, the identifier of a multicast session can be used to identify a multicast session. The identifier of a multicast session can be understood as an identifier of a group corresponding to the multicast session (such as a temporary multicast group identifier (TMGI)), or a service identifier (service ID) of a multicast session, or packet filter information of a multicast session, or a service data flow (SDF) identification rule of a multicast session, or a multicast / broadcast service identifier (MBS ID), or a multicast / broadcast service session identifier (MBS session ID), or a multicast / broadcast service identifier, or one or more of a source specific IP address. These terms can be used interchangeably and are all used to identify a multicast session and are not limited here.

[0228] It should be noted that S1202 can be understood as the first session management network element sending a multicast session identifier to the access network device corresponding to each terminal joining the group. In this application, multiple different terminals joining the group can correspond to the same access network device or to different access network devices without limitation.

[0229] Taking the first terminal as an example, sending a multicast session identifier to the access network device corresponding to the first terminal is described below.

[0230] In one possible implementation, the first session management network element sends a multicast session identifier to the access network device corresponding to the first terminal via a message associated with the first terminal. Accordingly, the access network device corresponding to the first terminal receives the multicast session identifier via the message associated with the first terminal. Specifically, the multicast session identifier is sent to the access network device corresponding to the terminal via a terminal-associated message at the terminal granularity, so that the access network device is informed that the terminal has joined the group corresponding to the multicast session.

[0231] In an embodiment of the present application, the message associated with the first terminal may include a control plane signaling message associated with the first terminal between the first session management network element and the mobility management network element corresponding to the first terminal, and an N2 message between the access network device and the first terminal. One control plane signaling message corresponds to a PDU session of one terminal, and the control plane signaling message may be an N1N2 message, such as a service interface (Namf)_communication_N1N2 message transmission (Namf_Communication_N1N2Message Transfer) between the SMF and the AMF. One N2 message corresponds to one terminal, that is, the N2 message is based on the terminal granularity and corresponds to a certain terminal. The N2 message can be transmitted on the N2 link corresponding to the terminal.

[0232] Exemplarily, the specific process of the first session management network element sending the multicast session identifier to the access network device corresponding to the first terminal is as follows: the first session management network element carries the multicast session identifier in an N2 SM message (N2 SMInformation), and the first session management network element sends the N2 SM message to the mobility management network element corresponding to the first terminal through a control plane signaling message between the mobility management network element and the first session management network element. The control plane signaling message corresponds to the PDU session of the first terminal, and the control plane signaling message is Namf_Communication_N1N2MessageTransfer, that is, the first session management network element sends a Namf_Communication_N1N2MessageTransfer message carrying the N2 SM message to the mobility management network element. The mobility management network element receives a control plane signaling message from the first session management network element. Since the control plane signaling message corresponds to the PDU session of the first terminal, when the mobility management network element receives the control plane signaling message from the first session management network element, it can be learned that the control plane signaling message is a message corresponding to the PDU session of the first terminal. Then, based on the UE context of the first terminal stored in the mobility management network element, the access network device corresponding to the first terminal is learned, and an N2 SM message is sent to the access network device corresponding to the first terminal. For example, the mobility management network element carries the N2 SM message in an N2 message and sends it to the access network device. The access network device receives the N2 message and obtains the identifier of the multicast session from the N2 message.

[0233] Furthermore, after receiving the N2 message, the access network device can know that it is sent to the first terminal, obtain the multicast session identifier from the N2 SM message carried by the N2 message, and store the obtained multicast session identifier in correspondence with the first terminal to indicate that the first terminal joins the group corresponding to the multicast session. For example, the access network device stores the multicast session identifier in the PDU session context of the first terminal in the access network device or in the UE context of the first terminal in the access network device.

[0234] For example, Figure 8a As shown, the SMF determines to add UE1 and UE2 to the group. UE1 and UE2 are managed by RAN1 and AMF1. The SMF then sends the multicast session identifier to AMF1 via control signaling message 1 between the two parties. Control signaling message 1 corresponds to UE1's PDU session. After receiving the multicast session identifier, AMF1 learns that it is addressed to RAN1, which corresponds to UE1. It then sends an N2 message carrying the multicast session identifier to RAN1, which corresponds to UE1. RAN1 receives the N2 message carrying the multicast session identifier, learns that it is UE1's N2 message, obtains the multicast session identifier from it, and stores it in association with UE1. Similarly, the SMF can use this method to send the multicast session identifier to RAN2 via control plane signaling messages and N2 messages between the SMF and AMF1, which correspond to UE2, so that RAN2 can store the multicast session identifier in association with UE2.

[0235] The mobility management network element (MNE) may be the MNE corresponding to the terminal's PDU session and is the network element that provides non-access stratum (NAS) signaling services for the terminal. The MNE serves as the termination point for the terminal's NAS signaling and is used to manage / process the terminal's NAS signaling. For example, the MNE may be responsible for encrypting and integrity protecting the terminal's NAS signaling messages.

[0236] In an embodiment of the present application, the UE context of the terminal stored on the access network device (for example, the new generation application protocol (NGAP) UE context (NGAP UEcontext) of the terminal in the access network device) is related to the data transmission of the terminal. For example, the UE context of the terminal stored on the access network device may include information about the PDU session of the terminal, and the information about the PDU session includes unicast QoS parameters (for example, the QoS profile of unicast QF, the identifier of the N3 tunnel, etc.). It should be understood that the identifier of the N3 tunnel corresponding to the PDU session may include the identifier of the uplink tunnel (for example, the tunnel identifier of the first user plane network element) and the identifier of the downlink tunnel (the tunnel identifier of the access network device). Optionally, if the terminal joins the group corresponding to the multicast session through the access network device, the UE context of the terminal may also include information related to the multicast session, for example, the UE context of the terminal may include the identifier of the multicast session and the QoS information of the multicast session.

[0237] In an embodiment of the present application, the UE context of the terminal stored in the mobility management network element may include the terminal identification, the terminal location information, the terminal registration area, the terminal's current connection management (CM) connection status, etc. The mobility management network element can know which access network device can be used to locate or find the terminal based on the terminal's UE context.

[0238] In another possible implementation, the first session management network element sends the multicast session identifier and the terminal identifier to the access network device corresponding to the first terminal through a signaling message (the signaling message is not associated with a specific terminal and can be a newly added message). The terminal identifier here can include the identifier of the first terminal and can also include the identifiers of other terminals that join the group and are managed by the access network device. For example, the first session management network element carries the identifier of the terminal that joins the group (such as the first terminal) and the multicast session identifier in an N11 message, and sends the N11 message to the mobility management network element corresponding to the terminal. The mobility management network element sends the terminal identifier and the multicast session identifier to the access network device corresponding to the terminal based on the terminal identifier.

[0239] Accordingly, the access network device corresponding to the first terminal receives the identifier of the multicast session and the identifier of the terminal. Furthermore, the access network device can save the received identifier of the terminal, for example, saving the identifier of the terminal in the context of the multicast session on the access network device based on the identifier of the multicast session. That is, with the group corresponding to the multicast session as the granularity, the identifier of the multicast session and the identifiers of the terminals managed by it that have joined the group corresponding to the multicast session are sent to the access network device, so that the access network device knows which terminals managed by it have joined the group corresponding to the multicast session.

[0240] It should be understood that in the embodiment of the present application, the terminal identifier sent by the first session management network element to the access network device includes: the identifier of the terminal that joins the group corresponding to the multicast session and is managed by the access network device. In this case, it can be understood that the first session management network element sends a UE list to the access network device, and the UE list includes the identifiers of the terminals that join the group and are managed by the access network device. For example, Figure 8a As shown, SMF determines to add UE1 and UE2 to the group. Since UE1 and UE2 are managed by RAN1, SMF sends the UE list {UE1, UE2} and the QoS information of the multicast session to RAN1 through AMF.

[0241] The terminal identifier can be used to identify the terminal. Specifically, the terminal identifier can be the terminal's IP address, the terminal's media access control (MAC) address, the terminal's international mobile subscriber identity (IMSI), the terminal's subscriber permanent identifier (SUPI), or the terminal's temporary identifier (5G global user temporary identifier, 5G-GUTI).

[0242] Furthermore, the first session management network element can also send QoS information (which can be called multicast QoS information) and other information of the multicast session to the access network device (such as the access network device corresponding to the first terminal) so that the access network device can configure the air interface wireless bearer resources for transmitting clock signals for the terminal corresponding to the multicast session (such as the first terminal).

[0243] For example, taking the first terminal as an example, in one possible design, the first session management network element can send the multicast QoS information to the access network device corresponding to the first terminal through a message associated with the first terminal at the same time. Or in another possible design, when the first session management network element sends the terminal identifier and the multicast session identifier to the access network device, it sends the multicast QoS information to the access network device. For example, the first session management network element carries the terminal identifier, the multicast session identifier, and the QoS information of the multicast session in an N11 message and sends the N11 message to the mobility management network element corresponding to the terminal. The mobility management network element sends the terminal identifier, the multicast session identifier, and the QoS information of the multicast session to the access network device corresponding to the terminal based on the terminal identifier.

[0244] Furthermore, after the access network device receives the QoS information of the multicast session, the access network device can save the QoS information of the multicast session, such as saving the QoS information of the multicast session (such as the multicast QFI and the multicast session identifier, etc.) in the context of the multicast session on the access network device.

[0245] In an embodiment of the present application, the QoS information of a multicast session can be understood as a multicast QoS configuration (QoS Profile) of a multicast session. The QoS information of a multicast session can be used to establish or indicate the transmission resources for transmitting the clock signal of the first clock domain in a multicast manner in a multicast session. Specifically, the multicast QoS information can be used by the access network device to configure the air interface radio bearer resources (such as data radio bearer (DRB) or multicast radio bearer (MRB) or radio bearer (RB)) corresponding to the multicast session. The multicast QoS information may include one or more of the following: identification information of the multicast service quality flow (QoS flow, QF) (such as multicast QFI), QoS parameters corresponding to the multicast QF (for example, quality of service policy (QoS profile), including but not limited to the fifth generation service quality flow identifier (5 th The tunnel information corresponding to the multicast QF may be used to establish a shared N3 tunnel between the access network device and the second user plane network element (such as the MB-UPF).

[0246] Furthermore, after the access network device receives the QoS information of the multicast session, it can allocate the air interface radio bearer resources (such as DRB or MRB or RB) corresponding to the multicast session according to the QoS information of the multicast session. Furthermore, in the scenario where the access network device uses multicast to send a clock signal to the terminal, the access network device can also allocate a group-radio network temporary identity (G-RNTI) to the group corresponding to the multicast session, and the access network device configures the G-RNTI to the terminal in the group. Subsequently, the access network device can use the G-RNTI to scramble the downlink control information (DCI) to obtain the scrambled DCI, which can be used to schedule the physical downlink shared channel (PDSCH) carrying the clock signal. The access network device sends the scrambled DCI and the PDSCH carrying the clock signal. After the terminal successfully descrambles the scrambled DCI using the G-RNTI, it receives the clock signal on the PDSCH indicated by the DCI. Furthermore, the access network device can store the multicast session identifier, the multicast session QoS information, the identifier of the air interface wireless bearer resource corresponding to the multicast session (such as DRB ID or MRB ID, etc.), G-RNTI and other information, for example, in the local multicast session context.

[0247] Furthermore, the first session management network element may also send N4 configuration information to the second user plane network element via the second session management network element. The N4 configuration information is used by the second user plane network element to map the clock signal of the first clock domain to the multicast QF corresponding to the multicast session and send it to the access network device via the shared N3 tunnel. Specifically, the N4 configuration information may include one or more of the following: packet filtering information for the multicast session, SDF identification rules for the multicast session, multicast QFI, a multicast session identifier, and an identifier for the first clock domain.

[0248] Furthermore, if a shared N3 tunnel for transmitting the clock signal of the first clock domain is not established between the access network device and the second user plane network element (such as MB-UPF), the method also includes: establishing a shared N3 tunnel between the access network device and the second user plane network element (such as MB-UPF), and an N9 tunnel between the second user plane network element and the first user plane network element.

[0249] For example, the access network device allocates tunnel information (AN tunnel info) of the access network device (i.e., an identifier of a shared N3 tunnel) for the multicast session. The access network device sends the tunnel information of the access network device to the second user plane network element through the first session management network element and the second session management network element. The second user plane network element establishes a transmission tunnel (or a shared N3 tunnel) between the second user plane network element and the access network device based on the tunnel information of the access network device for transmitting the clock signal of the first clock domain in a multicast manner. The second user plane network element sends the tunnel information of the second user plane network element to the first user plane network element through the second session management network element and the first session management network element. If it is the first time that the N9 tunnel between the first user plane network element and the second user plane network element is established, the first session management network element also sends the identifier of the first clock domain to the first user plane network element, so that the first user plane network element stores the correspondence between the tunnel information of the second user plane network element and the first clock domain, such as storing the correspondence between the tunnel information of the second user plane network element and the identifier of the first clock domain, thereby establishing an N9 tunnel between the second user plane network element and the first user plane network element for transmitting the clock signal of the first clock domain.

[0250] Specifically, the process of establishing a shared N3 tunnel between the access network device and the second user plane network element (such as MB-UPF) and the N9 tunnel between the second user plane network element and the first user plane network element can refer to the following Figure 13a As described in S1309-S1311.

[0251] In the embodiment of the present application, the N3 tunnel corresponding to the multicast session may be referred to as a multicast N3 tunnel, or a shared N3 tunnel, or a multicast transmission tunnel, or a shared transmission tunnel, without limitation.

[0252] At this point, the tunnel between the first user plane network element and the second user plane network element (such as the N9 tunnel), the tunnel between the second user plane network element and the access network device (such as the shared N3 tunnel), and the air interface radio bearer between the access network device and the terminal are established. Subsequently, after the first user plane network element receives the clock signal from the first clock domain, it can send the clock signal to the second user plane network element through the tunnel between the first user plane network element and the second user plane network element based on the correspondence between the identifier of the first clock domain and the tunnel information of the second user plane network element. After receiving the clock signal, the second user plane network element can determine which multicast session / which shared N3 tunnel / which multicast QF the first clock domain corresponds to based on the N4 configuration information configured for it by the session management network element side, and send the clock signal to the access network device through the shared N3 tunnel. Since the shared N3 tunnel corresponds to the multicast session (or it can be understood that the multicast QF corresponds to the multicast session), after the access network device receives the clock signal from the shared N3 tunnel, it can know that it is the clock signal on a certain multicast session based on the context of the locally stored multicast session, and then determine the terminal to join the group corresponding to the multicast session, and send the clock signal to the terminal joining the group.

[0253] In an embodiment of the present application, the access network device may determine the terminals that join the group by any of the following methods: In one method, the access network device stores the correspondence between the multicast session and the terminal, for example, by storing the identifier of the multicast session in the UE context. The access network device may query the locally stored UE context of the terminal. If the identifier of the multicast session is stored in the UE context, the terminal is determined to join the group corresponding to the multicast session. In another method, the terminals that join the group are stored in the context of the multicast session in the form of a UE list. The access network device queries the locally stored context of the multicast session and, based on the UE list stored in the context of the multicast session, learns which terminals have joined the group corresponding to the multicast session.

[0254] In an embodiment of the present application, the access network device sending a clock signal to a terminal that has joined a group may include: for each terminal, the access network device sending the clock signal to the terminal through an air interface radio bearer resource corresponding to the terminal (which may be referred to as a unicast air interface radio bearer resource), which may be understood as a unicast transmission method of the access network device to the terminal. Alternatively, the access network device sends the clock signal to the terminals in the group through an air interface radio bearer resource corresponding to the multicast session (which may be referred to as a multicast air interface radio bearer resource), which may be understood as a multicast transmission method of the access network device to the terminals.

[0255] based on Figure 12According to the method shown, the first session management network element can obtain the status of the port in the clock domain, filter out the port corresponding to the master clock according to the status of the port, and add the terminal corresponding to the filtered port to the group corresponding to the multicast session, thereby avoiding adding the terminal corresponding to the master clock to the group, thereby avoiding the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by the clock signal emitted by the master clock being transmitted back to the master clock.

[0256] The following combination Figure 10 In the 5G communication system shown in the figure, it is assumed that the terminals include UE1-UEn, the device-side forwarders include DS-TT1-UEn, each DS-TT is connected to a clock node, and the DS-TT is connected to the UE correspondingly (for example, DS-TT1 is connected to UE1, DS-TT2 is connected to UE2, ... DS-TTn is connected to UEn correspondingly), the network-side forwarder is NW-TT, NW-TT is connected to a clock node, NW-TT is connected to UPF, the access network device is RAN, the mobility management network element is AMF, the session management network element that manages the multicast session of the first clock domain is MB-SMF, the session management network element that manages the PDU session of the UE is SMF, the anchor point of the PDU session is UPF, and the anchor point of the multicast session is MB-UPF. Figure 12 The following method is introduced:

[0257] Figure 13a A communication method for a multicast service provided in an embodiment of the present application is as follows: Figure 13a As shown, this may include:

[0258] S1301: SMF establishes a PDU session for each UE.

[0259] The UE may refer to a UE connected to a DS-TT. It should be understood that S1301 may refer to establishing a PDU session for each DS-TT in the first clock domain for each UE connected to the DS-TT. The PDU session may be used to transmit clock signals between the DS-TT and the NW-TT. The relevant description of the PDU session is as described above. The process of the SMF establishing the PDU session may include:

[0260] The SMF determines to configure or create the PDU session of the UE, configures the unicast QoS information and PDU session identifier corresponding to the PDU session, and sends the unicast QoS information and PDU session identifier corresponding to the PDU session to the RAN currently accessed by the UE, triggering the RAN to allocate air interface radio bearer resources between the UE and the RAN for transmitting the clock signal between the DS-TT and the NW-TT according to the unicast QoS information corresponding to the PDU session.

[0261] In one possible implementation, the SMF determines to configure or create a PDU session for the UE, which may include: when a clock node connected to a port of the DS-TT has a clock synchronization requirement, the clock node may send a request to the UE connected to the DS-TT through the port of the DS-TT, triggering the UE to send a session establishment request to the SMF through the AMF. The session establishment request may be used to request the establishment of the UE's PDU session. The session establishment request may carry the identifier of the DS-TT port, and may also carry the identifier of the clock domain and the identifier of the UE. After receiving the session establishment request, the SMF determines to configure or create the UE's PDU session according to the session establishment request.

[0262] In another possible implementation, SMF can refer to any one of the methods 2 to 4 in S1201 to determine the configuration or create a PDU session, which will not be described in detail.

[0263] Furthermore, if the N3 tunnel (referred to as a unicast N3 tunnel in this application) between the RAN and the UPF is not established, the RAN can also allocate a unicast tunnel identifier and send the unicast tunnel identifier to the SMF. The SMF sends the N4 configuration information to the UPF of the NW-TT connection to establish the N3 tunnel corresponding to the PDU session between the UPF of the NW-TT connection and the RAN. At this point, the PDU session is established, and the SMF returns a session establishment response to the UE through the AMF. The session establishment response may carry information such as the PDU session identifier.

[0264] Furthermore, after the UE's PDU session is established, the RAN may store the PDU session context. The PDU session context stored in the RAN may include the PDU session identifier and the configuration of the air interface radio bearer resources corresponding to the PDU session. The SMF may store the PDU session context. The PDU session context stored in the SMF may include the PDU session identifier, the unicast QFI corresponding to the PDU session, the UE identifier, and the DS-TT port identifier.

[0265] S1302: NW-TT receives the notification message.

[0266] It should be understood that in S1302 , the NW-TT may receive a notification message sent from each clock node in the first clock domain.

[0267] In the embodiments of the present application, the notification message can be understood as a clock notification message, which can carry relevant information about the clock node (such as the parameters of the clock node and the local clock configuration of the clock node). The notification message can be carried in a PTP message and sent to the NW-TT. The message header of the PTP message can include the fields shown in Table 4 above. The PTP message can also include the fields shown in Table 3 above, which are not detailed here.

[0268] For example, a clock node located on the network side can directly send a notification message to the NW-TT via a port of the connected NW-TT. A clock node located on the UE side can send a notification message to the NW-TT via a port of the connected DS-TT. For example, a clock node connected to a DS-TT sends a notification message to the UE via a port of the DS-TT. After receiving the notification message, the UE sends the notification message to the RAN. The RAN sends the notification message to the UPF via the UE's uplink tunnel. The UPF, upon receiving the notification message, forwards it to the NW-TT. The uplink tunnel described herein can be understood as the N3 tunnel from the RAN to the UPF. The uplink tunnel is established at the UE granularity.

[0269] For example, Figure 8a As shown, the clock nodes in clock domain 1 are: OC1, OC2, OC3, OC4 ( Figure 8a ), OC1, OC2, and OC3 are located on the UE side, OC1 is connected to port 1 of DS-TT1, OC2 is connected to port 2 of DS-TT2, OC3 is connected to port 3 of DS-TT3, and OC4 is connected to port 4 of NW-TT ( Figure 8a (not shown). Then OC1 sends a notification message to NW-TT through port 1 of DS-TT1, OC2 sends a notification message to NW-TT through port 2 of DS-TT2, OC3 sends a notification message to NW-TT through port 3 of DS-TT3, and OC4 sends a notification message to NW-TT through port 4 of NW-TT.

[0270] S1303 : The NW-TT determines the port in the first clock domain and the status of each port according to the received notification message.

[0271] It should be understood that in S1302 above, the NW-TT receives at least two notification messages. In S1303, the NW-TT determines the ports in the first clock domain and their status based on all received notification messages. The ports in the first clock domain may include ports of the DS-TT in the first clock domain and ports of the NW-TT in the first clock domain. For example, the NW-TT may receive notification messages from ports of the DS-TT and notification messages from its own ports.

[0272] For example, the NW-TT can determine the port in the first clock domain and the status of each port according to the BMCA algorithm and all received notification messages. Specifically, the process can refer to the existing technology and will not be described in detail.

[0273] S1304. The NW-TT sends first information to the first application function network element. Correspondingly, the first application function network element receives the first information.

[0274] The first application function network element may be the TSN AF or TSCTSF mentioned above. The description of the first information may refer to that in S1200 and will not be repeated here.

[0275] Exemplarily, the NW-TT sending the first information to the first application function network element may include: the NW-TT sending a management information container carrying the first information to the first application function network element. The management information container may be a user plane node management information container (UMIC) or a bridge management information container (BMIC). The management information container can be recognized and parsed only by the first application function network element. In this way, by carrying the first information in a container that only the first application function network element can recognize, the first information is prevented from being parsed and tampered with by other network elements during transmission, thereby ensuring the reliability of the transmission of the first information.

[0276] S1305: When the first application function network element is a TSN AF, the first application function network element determines to configure or create a multicast session in the first clock domain according to the first information, and the first application function network element sends a message 13a to the SMF. Correspondingly, the SMF receives the message 13a.

[0277] Exemplarily, the first application function network element determines the method for configuring or creating a multicast session in the first clock domain based on the first information, referring to method 1 in S1201. For example, the first application function network element determines the method for configuring or creating a multicast session in the first clock domain based on the first information, and the number of UEs corresponding to the port of the device-side forwarder in the first clock domain is greater than a preset threshold.

[0278] The message 13a may be used to request configuration or creation of a multicast session. The message 13a may carry at least one of an identifier of the first clock domain and an identifier of the multicast session. In this case, the message 13a may also carry the first information.

[0279] It should be understood that if the message 13a does not carry the first information, then Figure 13a The method may further include: the first application function network element sends the first information to the SMF, and correspondingly, the SMF receives the first information.

[0280] It should be understood that the message names or parameter names in the embodiments of the present application are only examples, and other names may be used in specific implementations. For example, message 13a may be described as a first request or a first request message.

[0281] S1306. The SMF determines to configure or create a multicast session in the first clock domain according to the message 13a, and then determines the UE to join the group corresponding to the multicast session according to the first information and the correspondence between the port and the UE.

[0282] The execution process of S1306 may refer to that in S1201 and will not be described in detail.

[0283] It should be noted that, in the embodiment of the present application, the first application function network element may also directly send the first information to the first session management network element, and the first session management network element determines to configure or create a multicast session for the first clock domain. For example, when the first application function network element is TSCTSF, the first application function network element does not perform the action of determining to configure or create a multicast session for the first clock domain based on the first information. S1305 can be replaced by the first application function network element sending the first information to the SMF, and S1306 can be replaced by the SMF determining to configure or create a multicast session for the first clock domain based on the first information, and then determining the UE to join the group corresponding to the multicast session based on the first information and the correspondence between the port and the UE.

[0284] S1307. The SMF sends the multicast session identifier to the RAN corresponding to the UE that joins the group corresponding to the multicast session through the MB-SMF. Correspondingly, the RAN receives the multicast session identifier.

[0285] The SMF may also send the UE identifier and the QoS information of the multicast session to the RAN.

[0286] S1308. The RAN allocates air interface radio bearer resources (such as DRB) corresponding to the multicast session.

[0287] Optionally, the RAN may allocate air interface radio bearer resources corresponding to the multicast session according to the QoS information.

[0288] Furthermore, if an N3 tunnel for transmitting the clock signal of the first clock domain in a multicast manner is not established between the RAN and the MB-UPF, the following steps S1309-S1311 are performed to establish a shared N3 tunnel between the RAN and the MB-UPF:

[0289] S1309: RAN allocates a shared N3 tunnel identifier, such as AN Tunnel Info, and sends the shared N3 tunnel identifier to SMF. Correspondingly, SMF receives the shared N3 tunnel identifier.

[0290] If SMF and MB-SMF are separate, that is, they are different session management network elements, and UPF and MB-UPF are separate, that is, they are different user plane network elements, execute the following S1310-S1311.

[0291] S1310: SMF sends the identifier of the shared N3 tunnel to MB-SMF, which then sends it to MB-UPF.

[0292] For example, the MB-SMF can include the shared N3 tunnel identifier in the N4 session configuration and send it to the MB-UPF. Accordingly, the MB-UPF receives the shared N3 tunnel identifier and, based on the shared N3 tunnel identifier, establishes a shared N3 tunnel between the MB-UPF and the RAN for multicast transmission of the clock signal of the first clock domain.

[0293] S1311: MB-UPF configures the identifier of the N9 tunnel of MB-UPF and sends the identifier of the N9 tunnel of MB-UPF to MB-SMF. MB-SMF sends the identifier of the N9 tunnel of MB-UPF to SMF, which then sends it to UPF to establish an N9 tunnel between MB-UPF and UPF for transmitting the clock signal of the first clock domain.

[0294] It should be noted that if the N9 tunnel between the MB-UPF and the UPF is established for the first time, the SMF may also send the identifier of the first clock domain to the UPF, instructing the UPF to send the clock signal of the first clock domain to the MB-UPF through the N9 tunnel between the UPF and the MB-UPF. The MB-UPF then sends the clock signal of the first clock domain to the RAN through the shared N3 tunnel between it and the RAN. The RAN then sends the clock signal of the first clock domain to the UEs in the group corresponding to the multicast session via unicast or multicast.

[0295] At this point, the N9 tunnel from UPF to MB-UPF for transmitting the clock signal of the first clock domain, the shared N3 tunnel from MB-UPF to RAN for transmitting the clock signal of the first clock domain, and the air interface connection between RAN and UE are established.

[0296] Furthermore, the UPF can receive clock signals from the first clock domain. For example, the UPF can receive clock signals from the first clock domain through a port on the NW-TT. When the master clock is located on the UE side, the clock signal from the first clock domain can be uploaded to the UPF through the uplink tunnel corresponding to the UE connected to the master clock. The UPF then forwards the clock signal to the NW-TT, which then sends it to the UPF through its port. When the master clock is located on the network side, the master clock can directly send the clock signal from the first clock domain to the UPF through a port on the NW-TT.

[0297] For example, in Figure 13a In the example, the master clock is located on the DS-TT1 side. The master clock can send a clock signal to UE1 through the port of DS-TT1. After receiving the clock signal, UE1 sends the clock signal to RAN. After receiving the clock signal, RAN can send the clock signal to UPF through the uplink tunnel corresponding to UE1. After receiving the clock signal, UPF sends the clock signal to NW-TT. NW-TT sends the clock signal to the forwarder (DS-TT and / or NW-TT) where the port is located in a non-slave state (for example, the master state). Figure 13a If the port of DS-TT2 is in the master state, NW-TT sends a clock signal to UPF, so that UPF sends a clock signal to DS-TT2.

[0298] Furthermore, the UPF sends the clock signal of the first clock domain to the MB-UPF through the N9 tunnel between the UPF and the MB-UPF. The MB-UPF sends the clock signal of the first clock domain to the RAN, and the RAN sends the clock signal to the UEs in the group corresponding to the multicast session. The specific process is as follows:

[0299] S1312: The UPF receives the clock signal of the first clock domain. If the UPF and the MB-UPF are different UPFs, the UPF forwards the clock signal of the first clock domain to the MB-UPF through the N9 tunnel. The MB-UPF then sends the clock signal of the first clock domain to the RAN through the shared N3 tunnel.

[0300] S1313: The RAN receives the clock signal of the first clock domain from the shared N3 tunnel, and sends the clock signal of the first clock domain to the UEs in the group corresponding to the multicast session via unicast or multicast.

[0301] If the master clock of the first clock domain is located on the UE side, since the group corresponding to the multicast session described in the embodiment of the present application does not include the UE corresponding to the master clock, the UPF can receive the clock signal of the first clock domain from the UE through the PDU session of the UE corresponding to the master clock, and send the clock signal of the first clock domain to other UEs except the UE through MB-UPF and RAN. That is, when the master clock is located on the UE side, the transmission path of the clock signal of the first clock domain is master clock->DS-TT (for example Figure 13a DS-TT1 in)->UE corresponding to the master clock (for example Figure 13a UE1 in the group) ->RAN->UPF->NW-TT->UPF->MB-UPF->RAN->UE in the group (e.g. Figure 13a It should be understood that in the present application, the RAN to which the UE corresponding to the master clock is connected and the RAN to which the UEs in the group are connected may be the same RAN or different RANs, without limitation.

[0302] If the master clock of the first clock domain is located on the network side, the UPF can receive the clock signal of the first clock domain through the NW-TT, and send the clock signal of the first clock domain to the UE through the MB-UPF and RAN. That is, when the master clock is connected to the NW-TT, the transmission path of the clock signal of the first clock domain is master clock->NW-TT->UPF->MB-UPF->RAN->UE in the group.

[0303] It should be understood that if the MB-UPF and UPF are co-located and the UPF has the functions of the MB-UPF, the paths between the UPF and MB-UPF and between the MB-UPF and the RAN can be replaced by the paths between the UPF and the RAN. For example, the master clock of the first clock domain is located at the UE side. The transmission path of the clock signal can be: master clock->DS-TT (for example Figure 13a DS-TT1 in)->UE corresponding to the master clock (e.g. Figure 13a UE1 in the group)->RAN->UPF->NW-TT->UPF->RAN->UE in the group (e.g. Figure 13a The master clock of the first clock domain is located on the network side. In the scenario where the clock signal is transmitted along the path of master clock -> NW-TT -> UPF -> RAN -> UE in the group.

[0304] Among them, in S1313, after receiving the clock signal from the first clock domain of the shared N3 tunnel, the RAN can determine which UEs join the group corresponding to the multicast session, and then send the clock signal of the first clock domain to the UEs in the group through unicast or multicast. Figure 12 The above is described in the embodiment shown and will not be described in detail.

[0305] S1314: The UE forwards the received clock signal of the first clock domain to the DS-TT connected thereto, so that the DS-TT forwards the clock signal to the clock node through the port of the DS-TT.

[0306] based on Figure 13a According to the method shown, TSN AF sends the status of the port of the clock domain that needs to be multicast to SMF, and SMF configures or creates a multicast session according to the status of the port of DS-TT in the clock domain, and sends the clock signal of the clock domain to the UE in the group corresponding to the multicast session. In this way, the clock signal can be sent in a multicast manner, thereby improving resource utilization and transmission efficiency. At the same time, according to the status of the port of DS-TT, the UE connected to the port corresponding to the master clock is filtered out, and the UE corresponding to the filtered DS-TT port is added to the group corresponding to the multicast session, thereby avoiding adding the UE corresponding to the master clock to the group, and avoiding the problem that the clock synchronization mechanism is disordered and clock synchronization cannot be achieved due to the clock signal sent by the master clock being transmitted back to the master clock.

[0307] For example, suppose MB-UPF and UPF are combined, such as Figure 13b As shown, OC1, OC2, and OC3 in clock domain 1 correspond to three UEs: UE1, UE2, and UE3, respectively. OC3 is the master clock, and port 3 of DS-TT3, to which OC3 is connected, is in slave state. UE3, corresponding to OC3, is not in the group corresponding to multicast session 1 in clock domain 1. UE1 and UE2 are in group corresponding to multicast session 1. OC3 sends clock signal 1 for clock domain 1 to the UPF via UE3's PDU session. The UPF then sends the clock signal to the NW-TT. The NW-TT determines the clock signal to send to the terminal based on the status of ports 2 and 1. The NW-TT sends clock signal 1 to the UPF. After receiving it, the UPF sends it to RAN1 via the shared N3 tunnel corresponding to multicast session 1. Because UE3 is not in the group corresponding to multicast session 1, the RAN does not send clock signal 1 to UE3. Instead, it sends clock signal 1 to UE1 and UE2, preventing the clock signal 1 from being transmitted back to OC3 via UE3.

[0308] For another example, assuming that MB-UPF and UPF are separately located, the clock signal of clock domain 1 is clock signal 1, and the clock signal of clock domain 2 is clock signal 2. Figure 13cAs shown, port 3 of the DS-TT to which UE2 is connected is connected to two OCs at the same time, one in each clock domain, and NW-TT is also connected to two OCs, one in each clock domain. The OC connected to port 1 is in clock domain 1; port 2, port 4, and port 5 are in clock domain 2. After BMCA, the OC of clock domain 1 of port 3 is the master clock of clock domain 1, that is, UE2 corresponds to the master clock of clock domain 1, and the OC on the NW-TT side is the master clock of clock domain 2. According to the method shown in Figure 13a, since port 3 is connected to the master clock, port 3 is in a slave state, and UE2 corresponding to port 3 will not join the multicast session of clock domain 1, and UE1 corresponding to port 1 will join the multicast session of clock domain 1. Similarly, according to Figure 13a The method shown establishes a multicast session in clock domain 1. The group corresponding to the multicast session in clock domain 1 includes UE1 and other UEs (not shown in the figure). UE1 and other UEs (not shown in the figure) in the group correspond to RAN1. RAN1 stores a correspondence between UE1 and other UEs (not shown) that have joined the group and the multicast session in clock domain 1. A multicast session in clock domain 2 is established. The group corresponding to the multicast session in clock domain 2 includes UE1, UE2, UE3, and UE4. UE1 and UE2 in the group correspond to RAN1. RAN1 stores a correspondence between UE1 and UE2 and the multicast session in clock domain 2. UE3 and UE4 correspond to RAN2. RAN2 stores a correspondence between UE3 and UE4 and the multicast session in clock domain 2. UE2 sends clock signal 1 uplink to UPF. After receiving clock signal 1, UPF sends clock signal 1 to MB-UPF, which sends it to RAN1 through the multicast session of clock domain 1. RAN1 sends clock signal 1 to UE1 and other UEs (not shown in the figure) in the group based on the stored correspondence between UE1 and other UEs (not shown in the figure) that join the group and the multicast session of clock domain 1, instead of sending clock signal 1 to UE2, to avoid clock signal 1 being transmitted back to the master clock. Similarly, after receiving clock signal 2 from NW-TT, UPF sends clock signal 2 to MB-UPF. MB-UPF sends clock signal 2 to RAN1 and RAN2 through the multicast session of clock domain 2. RAN1 sends clock signal 2 to UE1 and UE2 based on the correspondence between UE1 and UE2 and the multicast session of clock domain 2. RAN2 sends clock signal 2 to UE3 and UE4 based on the correspondence between UE3 and UE4 and the multicast session of clock domain 2. Figure 8b In comparison, since UE2 is excluded from the group corresponding to the multicast session of clock domain 1, RAN1 will not send clock signal 1 to UE2, avoiding the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by clock signal 1 being transmitted back to the master clock.

[0309] According to the above Figure 12-13c , SMF obtains the status of the port, eliminates the UE corresponding to the port connected to the master clock according to the status of the port, adds the UE corresponding to other ports to the group of the multicast session, and sends clock signals to the UEs in the group through the multicast session. This not only improves the resource rate, but also avoids the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by the transmission of clock signals back to the master clock because there is no terminal corresponding to the port connected to the master clock in the group.

[0310] Alternatively, the present application also provides another embodiment, in which the state of the port of the device-side repeater in the first clock domain is indicated to the device-side repeater. When the device-side repeater connected to the terminal receives the clock signal, the device-side repeater filters the received clock signal according to the port state. Specifically, the process can be referred to Figure 14 As described in.

[0311] like Figure 14 As shown, a clock signal transmission method provided by an embodiment of the present application can be applied in scenarios where clock signals are transmitted in a unicast manner, or in scenarios where clock signals are transmitted in a multicast manner. In scenarios where clock signals are transmitted in a multicast manner, unlike the above embodiment, all terminals corresponding to the ports of the device-side repeater in the first clock domain can be added to the group corresponding to the multicast session. The method includes the following steps:

[0312] S1400. The network-side forwarder obtains information a and sends information a to the first application function network element; correspondingly, the first application function network element receives information a.

[0313] Information a may indicate the status of a port of the device-side forwarder in the first clock domain and each port of the device-side forwarder in the first clock domain, where the status may include the second state or the first state. Specifically, for a description of information a, refer to the description of the first information in S1201. The process for the network-side forwarder to obtain information a may refer to the process for the NW-TT to obtain the status of the port in the first clock domain and each port in S1302-S1303, and is not further described here.

[0314] In the embodiment of the present application, the first application function network element may be a TSN AF or a TSCTSF.

[0315] It should be understood that the message names or parameter names in the messages in the embodiments of the present application are only examples, and other names may be used in specific implementations without limitation. For example, information a may also be described as the first information or other names.

[0316] S1401. The first application function network element sends information b to the first device-side forwarder. Correspondingly, the first device-side forwarder receives information b.

[0317] It should be understood that the first device-side repeater in S1401 may include all device-side repeaters in the first clock domain, that is, the first application function network element indicates to each device-side repeater in the first clock domain the status of the port on the device-side repeater in the first clock domain, and the port on the device-side repeater may include all ports in the first clock domain.

[0318] Furthermore, the information a may include the port identifiers and status of one or more device-side repeaters in the first clock domain, while the information b is the port status of the specific device-side repeater determined for that specific device-side repeater. In other words, the information b may be a subset of the information a.

[0319] Among them, information b can be used to indicate the status of the port of the first device side repeater in the first clock domain.

[0320] Specifically, information b may include the state of the port in the first clock domain. Optionally, information b may also include the identifier of the port, that is, in this case, information b may include the identifier of the port and the state of the port, so as to distinguish which port's state is indicated by information b when there are multiple ports. Optionally, information b may also include the identifier of the clock domain in which the port is located, that is, in this case, information b may include the identifier of the clock domain in which the port is located and the state of the port in the clock domain; or information b may include the identifier of the port, the identifier of the clock domain in which the port is located, and the state of the port in the clock domain, so as to distinguish the states of the same port in multiple different clock domains.

[0321] For example, Figure 8a As shown, NW-TT determines that port 1 of DS-TT1 is in master state when in clock domain 1, port 2 of DS-TT2 is in master state when in clock domain 1, and port 3 of DS-TT3 is in slave state when in clock domain 1. Then NW-TT sends information a {port 1 of DS-TT1, master state; port 2 of DS-TT2, master state; port 3 of DS-TT3, slave state} to TSN AF. After receiving information a, TSNAF sends {master state} to DS-TT1, indicating that port 1 of DS-TT1 is in master state, sends {master state} to DS-TT2, indicating that port 1 of DS-TT2 is in master state, and sends {slave state} to DS-TT3, indicating that port 3 of DS-TT3 is in slave state.

[0322] Optionally, information b may also include an identifier of the port of the first device-side forwarder. For example, TSN AF sends {DS-TT1 port 1, master status} to DS-TT1, {DS-TT2 port 2, master status} to DS-TT2, and {DS-TT3 port 3, slave status} to DS-TT3.

[0323] Optionally, the information b may also include an identifier of the clock domain. Figure 15c As shown, port 1 of DS-TT1 connected to UE1 is in clock domain 1 and in master state. Port 2 of DS-TT2 connected to UE1 is in clock domain 2 and in master state. Port 3 of DS-TT3 connected to UE2 is in slave state in clock domain 1 and in master state in clock domain 2. Port 4 of DS-TT4 connected to UE3 is in clock domain 2 and in master state. Port 5 of DS-TT5 connected to UE4 is in clock domain 2 and in master state. Then, TSN AF sends {DS-TT1 port 1, clock domain 1, master state} to DS-TT1, {DS-TT2 port 2, clock domain 2, master state} to DS-TT2, {DS-TT3 port 3, clock domain 1, slave state} and {DS-TT3 port 3, clock domain 2, master state} to DS-TT3, {DS-TT4 port 4, clock domain 2, master state} to DS-TT4, and {DS-TT4 port 5, clock domain 2, master state} to DS-TT5. Alternatively, TSN AF sends {clock domain 1, master state} to DS-TT1, {clock domain 2, master state} to DS-TT2, {clock domain 1, slave state} and {clock domain 2, master state} to DS-TT3, {clock domain 2, master state} to DS-TT4, and {clock domain 2, master state} to DS-TT5.

[0324] S1402. The first device-side repeater receives a clock signal in the first clock domain, and filters the received clock signal according to the state of the port of the first device-side repeater in the first clock domain.

[0325] In the embodiment of the present application, the filtering of the received clock signal by the first device side repeater can be understood as: screening the received clock signal, or determining whether to forward the clock signal, or determining whether to allow the clock signal to pass through the port, etc.

[0326] Specifically, the execution process of S1402 may include: if the port status is the second state, it means that the port is connected to a non-master clock, such as a slave clock, and the first device side repeater sends a clock signal to the clock node through the port; or, if the port status is the first state, it means that the port is connected to the master clock, and the first device side repeater discards the clock signal and does not send a clock signal to the clock node (master clock) connected to the port through the port.

[0327] It should be understood that Figure 14 Taking the device-side repeater filtering the clock signal according to the port status as an example, in addition to the device-side repeater, other devices can also filter the clock signal received by the port according to the port status. For example, when the device-side repeater is integrated in the terminal, the terminal can filter the received clock signal according to the port status.

[0328] In S1402, the device-side forwarder may receive a clock signal from a first clock domain on the network side (e.g., NW-TT) through a terminal connected thereto. For example, the NW-TT may receive a clock signal from a master clock in the first clock domain (the master clock may be located on the terminal side or the network side). The NW-TT sends the clock signal from the first clock domain to a first user-plane network element. The first user-plane network element sends the clock signal to the RAN via unicast or multicast, and the RAN sends the clock signal to the terminal.

[0329] The unicast mode is as described above, and may refer to the first user plane network element sending the clock signal through the PDU session of the terminal.

[0330] The multicast mode is as described above, which may refer to the first user plane network element sending a clock signal to the second user plane network element, and the second user plane network element sending the clock signal to the terminals in the group that joins the multicast session through the multicast session.

[0331] It should be noted that Figure 14 In the embodiment shown, the terminals that join the group corresponding to the multicast session are determined based on the ports of the device-side repeater in the first clock domain, and the determination method is the same as that of FIG. Figure 12 The determination method is different in Figure 14 The terminal corresponding to the master clock can also be added to the group corresponding to the multicast session, without filtering out the terminal corresponding to the master clock. Figure 14 In the method shown, the terminals corresponding to all ports on the terminal side and in the first clock domain can be added to the group corresponding to the multicast session. Of course, in another implementation, Figure 12 The embodiment can also be Figure 14 The present application is not limited thereto.

[0332] Figure 14In the illustrated embodiment, determining terminals to join the group corresponding to the multicast session may include: the first application function network element sending information c to the first session management network element. Information c may be used to indicate all ports located on the terminal side and in the first clock domain, and does not indicate the status of the ports. After receiving information c from the first application function network element, the first session management network element determines the terminals corresponding to all ports indicated by information c based on information b and the correspondence between ports and terminals, and adds the terminals corresponding to all ports to the group corresponding to the multicast session in the first clock domain. That is, unlike S1201, when determining terminals to join the group corresponding to the multicast session, S1402 does not distinguish between port statuses, does not filter terminals corresponding to ports connected to the master clock, and instead adds terminals corresponding to all ports in the first clock domain to the group corresponding to the multicast session. Terminals to join the group corresponding to the multicast session are determined.

[0333] For example, Figure 8a As shown in the figure, OC1, OC2 and OC3 in clock domain 1 correspond to three UEs: UE1, UE2 and UE3 respectively. Although OC3 is the master clock, port 3 of DS-TT3 connected to OC3 is in the slave state. Figure 14 In the method shown, the three UEs corresponding to OC1, OC2 and OC3: UE1, UE2 and UE3 can all be added to the group corresponding to the multicast session of clock domain 1.

[0334] based on Figure 14 According to the method shown, the first session management network element can obtain the port in the clock domain and send the port status to the device-side repeater. When the device-side repeater connected to the terminal receives the clock signal, the device-side repeater filters the received clock signal according to the master clock status to avoid the clock signal sent by the master clock being transmitted back to the master clock, which causes the clock synchronization mechanism to be disordered and the clock synchronization cannot be achieved.

[0335] The following combination Figure 10 In the 5G communication system shown in the figure, it is assumed that the terminals include UE1-UEn, the device-side forwarders include DS-TT1-UEn, each DS-TT is connected to a clock node, and the DS-TT is connected to the UE correspondingly (for example, DS-TT1 is connected to UE1, DS-TT2 is connected to UE2, ... DS-TTn is connected to UEn correspondingly), the network-side forwarder is NW-TT, NW-TT is connected to a clock node, NW-TT is connected to UPF, the access network device is RAN, the mobility management network element is AMF, the session management network element that manages the multicast session of the first clock domain is MB-SMF, the session management network element that manages the PDU session of the UE is SMF, the anchor point of the PDU session is UPF, and the anchor point of the multicast session is MB-UPF. Figure 14 The following method is introduced:

[0336] Figure 15a A communication method for a multicast service provided in an embodiment of the present application is as follows: Figure 15a As shown, this method can be applied to the scenario where the clock signal is transmitted in unicast mode, or it can also be applied to the scenario where the clock signal is transmitted in multicast mode. Figure 15a In the illustrated embodiment, all terminals corresponding to the ports of the device-side repeater in the first clock domain may be added to the group corresponding to the multicast session. The method may include:

[0337] S1501: SMF establishes a PDU session for each UE.

[0338] Among them, S1501 can refer to S1301 and will not be described in detail.

[0339] S1502: NW-TT receives the notification message.

[0340] Among them, S1502 can refer to S1302 and will not be described in detail.

[0341] S1503 : The NW-TT determines the port in the first clock domain and the status of each port according to the received notification message.

[0342] Among them, S1503 can refer to S1303 and will not be described in detail.

[0343] S1504. The NW-TT sends information a to the first application function network element. Correspondingly, the first application function network element receives information a.

[0344] Among them, S1504 can refer to S1304 and will not be described in detail.

[0345] S1505: The first application function network element sends information b to each DS-TT in the first clock domain. The information b indicates the status of the port of the DS-TT in the first clock domain. Correspondingly, the DS-TT receives the information b.

[0346] The description and sending method of information b may refer to that in S1401 and will not be described in detail here. Information b may be used by DS-TT to filter the received clock signal according to the status of the port.

[0347] It should be understood that Figure 15aThe master clock of the first clock domain can be located on the UE side or on the network side. When the master clock is located on the UE side, the clock signal of the first clock domain can be uploaded to the UPF through the uplink tunnel corresponding to the UE connected to the master clock, forwarded by the UPF to the NW-TT, and then sent by the NW-TT to the UPF through its port. When the master clock is located on the network side, the master clock can directly send the clock signal of the first clock domain to the UPF through the port of the NW-TT. After receiving the clock signal of the first clock domain, the UPF sends the clock signal of the first clock domain to the UE. After receiving the clock signal, the UE executes S1515-S1516.

[0348] For example, in Figure 15a In the example, the master clock is located on the DS-TT1 side. The master clock can send a clock signal to UE1 through the port of DS-TT1. After receiving the clock signal, UE1 sends the clock signal to RAN. After receiving the clock signal, RAN can send the clock signal to UPF through the uplink tunnel corresponding to UE1. After receiving the clock signal, UPF sends the clock signal to NW-TT. NW-TT sends the clock signal to the forwarder (DS-TT and / or NW-TT) where the port is located in a non-slave state (for example, the master state). Figure 15a If the port of DS-TT2 in the master state is in the master state, the NW-TT sends a clock signal to the UPF, so that the UPF sends clock signals to UE1 corresponding to DS-TT1 and UE2 corresponding to DS-TT2. After each UE receives the clock signal, it sends the clock signal to the DS-TT connected to it, and the DS-TT filters the received clock signal according to the port status.

[0349] In one possible implementation, after the UPF receives the clock signal of the first clock domain, the UPF sends the clock signal of the first clock domain to the UE via a unicast manner (such as the UE's PDU session).

[0350] In another possible implementation, after the UPF receives the clock signal of the first clock domain, the UPF sends the clock signal of the first clock domain to the RAN via multicast (for example, via a shared N3 tunnel), and the RAN sends the clock signal of the first clock domain to the UE. Specifically, the process is shown in S1506-S1514 below:

[0351] S1506: The first application function network element sends information c to the SMF. Correspondingly, the SMF receives information c.

[0352] Information c may be used to indicate a port of a device-side repeater in the first clock domain. For example, information c may include an identifier of the port of the device-side repeater in the first clock domain. Optionally, information c may also include an identifier of the first clock domain. In other words, information c may include the identifier of the port, or the identifier of the first clock domain and the identifier of the port.

[0353] Optionally, when the first application function network element is a TSN AF, the first application function network element may further determine to configure or create a multicast session for the first clock domain. After determining to configure or create the multicast session for the first clock domain, the first application function network element sends a message 15a to the SMF. Message 15a may be used to request the configuration or creation of the multicast session. Message 15a may carry at least one of an identifier of the first clock domain and an identifier of the multicast session. Optionally, message 15a also carries information c to save signaling overhead.

[0354] Exemplarily, the manner in which the first application function network element determines to configure or create a multicast session in the first clock domain may refer to the manner described in S1201. For example, when the first application function network element determines that the number of UEs corresponding to the port of the device-side forwarder in the first clock domain is greater than a preset threshold, the first application function network element determines to configure or create a multicast session in the first clock domain.

[0355] Optionally, when the first application function network element is not a TSN AF but a TSCTSF, the first application function network element does not perform the actions of determining the configuration or creating a multicast session in the first clock domain and sending the message 15a to the SMF.

[0356] S1507. The SMF determines to configure or create a multicast session in the first clock domain, and determines the UE to join the group corresponding to the multicast session based on the information c and the correspondence between the port and the UE.

[0357] Among them, the process of SMF determining the configuration or creation of a multicast session in the first clock domain refers to methods one to three in S1201, and can also be executed in accordance with method four in S1201 when the first application function network element sends message 15a, which will not be repeated here.

[0358] Among them, the SMF determines the UE to join the group corresponding to the multicast session based on the information c and the correspondence between the port and the UE, which may include: determining the UE corresponding to the port of the DS-TT in the first clock domain based on the information c and the correspondence between the port and the UE, and adding all determined UEs to the group corresponding to the multicast session.

[0359] For the description of the specific correspondence between the port and the UE, and the process of determining the UE corresponding to the port of the DS-TT in the first clock domain, refer to S1202 and are not described in detail.

[0360] S1508. The SMF sends the multicast session identifier to the RAN corresponding to the UE that joins the group corresponding to the multicast session through the MB-SMF. Correspondingly, the RAN receives the multicast session identifier.

[0361] The SMF may also send the UE identifier and the QoS information of the multicast session to the RAN corresponding to the UE that joins the group corresponding to the multicast session.

[0362] S1509. RAN allocates air interface radio bearer resources corresponding to the multicast session.

[0363] Furthermore, if a shared N3 tunnel for transmitting the clock signal of the first clock domain in a multicast manner is not established between the RAN and the MB-UPF, the following steps S1510 to S1512 are performed to establish a shared N3 tunnel between the RAN and the MB-UPF:

[0364] S1510: RAN allocates a shared N3 tunnel identifier, such as AN Tunnel Info, and sends the shared N3 tunnel identifier to SMF. Correspondingly, SMF receives the shared N3 tunnel identifier.

[0365] If SMF and MB-SMF are separate, that is, they are different session management network elements, and UPF and MB-UPF are separate, that is, they are different user plane network elements, execute the following S1511-S1512.

[0366] S1511: SMF sends the identifier of the shared N3 tunnel to MB-SMF, which then sends it to MB-UPF.

[0367] For example, the MB-SMF can include the shared N3 tunnel identifier in the N4 session configuration and send it to the MB-UPF. Accordingly, the MB-UPF receives the shared N3 tunnel identifier and, based on the shared N3 tunnel identifier, establishes a shared N3 tunnel between the MB-UPF and the RAN for multicast transmission of the clock signal of the first clock domain.

[0368] S1512: MB-UPF configures the identifier of the N9 tunnel of MB-UPF and sends the identifier of the N9 tunnel of MB-UPF to MB-SMF. MB-SMF sends the identifier of the N9 tunnel of MB-UPF to SMF, which then sends it to UPF to establish an N9 tunnel between MB-UPF and UPF for transmitting the clock signal of the first clock domain.

[0369] It should be noted that if the N9 tunnel between the MB-UPF and the UPF is established for the first time, the SMF may also send the identifier of the first clock domain to the UPF, instructing the UPF to send the clock signal of the first clock domain to the MB-UPF through the N9 tunnel between the UPF and the MB-UPF. The MB-UPF then sends the clock signal of the first clock domain to the RAN through the shared N3 tunnel between it and the RAN. The RAN then sends the clock signal of the first clock domain to the UEs in the group corresponding to the multicast session via unicast or multicast.

[0370] At this point, the N9 tunnel from UPF to MB-UPF for transmitting the clock signal of the first clock domain, the shared N3 tunnel from MB-UPF to RAN for transmitting the clock signal of the first clock domain, and the air interface connection between RAN and UE are established.

[0371] Furthermore, the UPF may receive the clock signal of the first clock domain and send the received clock signal of the first clock domain to the UE in the group corresponding to the multicast session through the MB-UPF and the RAN. The specific process is as follows:

[0372] S1513: The UPF receives the clock signal of the first clock domain. If the UPF and the MB-UPF are different UPFs, the UPF forwards the clock signal of the first clock domain to the MB-UPF through the N9 tunnel. The MB-UPF then sends the clock signal of the first clock domain to the RAN through the shared N3 tunnel.

[0373] It should be understood that the master clock of the first clock domain in S1513 can be located on the UE side or on the network side. When the master clock is located on the UE side, the clock signal of the first clock domain can be uploaded to the UPF through the uplink tunnel corresponding to the UE connected to the master clock, forwarded by the UPF to the NW-TT, and then sent by the NW-TT to the UPF through its port. When the master clock is located on the network side, the master clock can directly send the clock signal of the first clock domain to the UPF through the port of the NW-TT.

[0374] S1514: The RAN receives the clock signal of the first clock domain from the shared N3 tunnel, and sends the clock signal of the first clock domain to the UEs in the group corresponding to the multicast session via unicast or multicast.

[0375] If the master clock of the first clock domain is located on the UE side, the UPF can receive the clock signal of the first clock domain from the UE through the PDU session of the UE corresponding to the master clock, and send the clock signal of the first clock domain to each UE in the group corresponding to the multicast session through MB-UPF and RAN. That is, when the master clock is located on the UE side, the transmission path of the clock signal of the first clock domain is master clock->DS-TT (for example Figure 15aDS-TT1 in)->UE corresponding to the master clock (for example Figure 15a UE1 in the group) ->RAN->UPF->NW-TT->UPF->MB-UPF->RAN->UE in the group (e.g. Figure 15a It should be understood that in the present application, the RAN to which the UE corresponding to the master clock is connected and the RAN to which the UEs in the group are connected may be the same RAN or different RANs, without limitation.

[0376] If the master clock of the first clock domain is located on the network side, the UPF can receive the clock signal of the first clock domain through the NW-TT, and send the clock signal of the first clock domain to each UE in the group corresponding to the multicast session through the MB-UPF and RAN. That is, when the master clock is connected to the NW-TT, the transmission path of the clock signal of the first clock domain is master clock->NW-TT->UPF->MB-UPF->RAN->UE in the group (for example Figure 15a UE1 and UE2 in the UE).

[0377] It should be understood that if the MB-UPF and UPF are co-located and the UPF has the functions of the MB-UPF, the paths between the UPF and MB-UPF and between the MB-UPF and the RAN can be replaced by the paths between the UPF and the RAN. For example, the master clock of the first clock domain is located on the UE side. The transmission path of the clock signal can be: DS-TT->UE corresponding to the master clock (for example Figure 15a UE1 in the group) ->RAN->UPF->NW-TT->UPF->RAN->UE in the group (e.g. Figure 15a The master clock of the first clock domain is located on the network side. In the scenario where the clock signal is transmitted through the master clock->NW-TT->UPF->RAN->UE in the group (e.g. Figure 15a UE1 and UE2 in the UE).

[0378] S1515: The UE forwards the received clock signal of the first clock domain to the DS-TT connected thereto.

[0379] S1516. DS-TT filters the received clock signal according to the port status.

[0380] For example, if the state of the DS-TT port is the second state (such as the master state), the DS-TT sends the clock signal to the clock node through the DS-TT port; if the state of the DS-TT port is the first state (such as the slave state), the DS-TT discards the clock signal. Figure 15aIn the example, since DS-TT1 is connected to the master clock, the state of DS-TT1's port is the first state (e.g., slave state). DS-TT1 may not transmit the clock signal to the master clock connected to it through this port, but may discard the received clock signal. However, the state of DS-TT2's port is the second state (e.g., master state). DS-TT2 may transmit the clock signal to the clock node connected to it through this port.

[0381] based on Figure 15a In the method shown, the first application function network element sends the status of the DS-TT port in the clock domain to the DS-TT, and the DS-TT filters out the clock signal emitted by the master clock according to the status of the DS-TT port, thereby avoiding the problem of disordered clock synchronization mechanism and inability to achieve clock synchronization caused by the clock signal emitted by the master clock being transmitted back to the master clock.

[0382] For example, suppose MB-UPF and UPF are combined, such as Figure 15b As shown in the figure, OC1, OC2, and OC3 in clock domain 1 correspond to three UEs: UE1, UE2, and UE3, respectively. OC1 and OC2 are slave clocks, with ports 1 and 2 in master state. OC3 is the master clock, and port 3 of DS-TT3, to which OC3 is connected, is in slave state. OC3 sends clock signal 1 from clock domain 1 to the UPF via UE3's PDU session. The UPF then sends the clock signal to the NW-TT. The NW-TT determines whether to send the clock signal to the UE based on the status of ports 2 and 1. The NW-TT sends clock signal 1 to the UPF. After receiving it, the UPF sends it to RAN1 via unicast or multicast. Because RAN1 does not know the status of each port, it sends clock signal 1 to each of the three UEs corresponding to the ports. The UEs then send the clock signal to the ports of the DS-TT. After receiving clock signal 1, ports 1 and 2, in master state, send clock signal 1 to OC1 and OC2. Port 3, in slave state, discards clock signal 1 and does not send it to OC3, preventing clock signal 1 from being transmitted back to OC3.

[0383] For another example, suppose the clock signal of clock domain 1 is clock signal 1, and the clock signal of clock domain 2 is clock signal 2. As shown in Figure 15c, port 3 of the DS-TT to which UE2 is connected is connected to two OCs at the same time, one in each clock domain, and the NW-TT is also connected to two OCs, one in each clock domain. The OC connected to port 1 is in clock domain 1; port 2, port 4, and port 5 are in clock domain 2. After BMCA, the OC of clock domain 1 of port 3 is the master clock of clock domain 1, that is, UE2 corresponds to the master clock of clock domain 1, and the OC on the NW-TT side is the master clock of clock domain 2. According to Figure 15aIn the method shown, the TSN AF notifies each port of its port status. For example, if port 3 is connected to the master clock in clock domain 1, port 3 is in slave state in clock domain 1, while the other ports in clock domain 1 are in master state. Based on the concept of multicast clock signal transmission, a multicast session for clock domain 1 is established. The group corresponding to this multicast session in clock domain 1 includes UE1 and UE2. UE1 and UE2 in the group correspond to RAN1, and RAN1 stores the correspondence between UE1 and UE2 in the group and the multicast session in clock domain 1. A multicast session is established for clock domain 2. The group corresponding to this multicast session in clock domain 2 includes UE1, UE2, UE3, and UE4. UE1 and UE2 in the group correspond to RAN1, and RAN1 stores the correspondence between UE1 and UE2 and the multicast session in clock domain 2. UE3 and UE4 correspond to RAN2, and RAN2 stores the correspondence between UE3 and UE4 and the multicast session in clock domain 2. UE2 sends clock signal 1 uplink to the UPF. After receiving clock signal 1, the UPF sends it to the MB-UPF, which then forwards it to RAN1 via the multicast session in clock domain 1. RAN1 then forwards the clock signal to UE1 and UE2 in the group based on its stored correspondence between UE1 and UE2, which have joined the group, and their multicast session in clock domain 1. Similarly, after receiving clock signal 2 from the NW-TT, the UPF sends it to the MB-UPF, which then forwards it to RAN1 and RAN2 via the multicast session in clock domain 2. RAN1 forwards clock signal 2 to UE1 and UE2 based on their correspondence with the multicast session in clock domain 2. RAN2 forwards clock signal 2 to UE3 and UE4 based on their correspondence with the multicast session in clock domain 2. Each UE sends its received clock signal to the DS-TT, which determines whether to forward the clock signal to the clock node based on the status of its port. For example, UE2 forwards the clock signal of clock domain 1 to DS-TT3. DS-TT3 knows that the state of port 3 in clock domain 1 is a slave state and connected to the master clock, so it discards the clock signal 1 of clock domain 1 and only transmits the clock signal of clock domain 2 to the clock node connected to it, avoiding transmitting the clock signal of clock domain 1 back to the master clock. Figure 8b In comparison, DS-TT filters the clock signal according to the port status, avoiding the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by clock signal 1 transmitted back to the master clock.

[0384] above Figure 12-13cUse SMF to obtain the status of the port, remove the UE corresponding to the port connected to the master clock according to the status of the port, add the UE corresponding to other ports to the multicast session group, and send clock signals to the UEs in the group through the multicast session. Since there is no port connected to the master clock in the group, the problem of disordered clock synchronization mechanism and inability to achieve clock synchronization caused by the transmission of clock signals back to the master clock is avoided. Figure 14-15c When the device-side repeater connected to the terminal receives the clock signal, the device-side repeater filters the received clock signal according to the master clock status to avoid the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by the clock signal transmitted back to the master clock.

[0385] Alternatively, the present application also provides another embodiment, in which, when the master clock is on the UE side, the UPF carries the identifier of the uplink tunnel used to transmit the clock signal together with the clock signal in the data packet, and sends the data packet to the access network device. After receiving the data packet, the access network device does not send the clock signal to the terminal corresponding to the uplink tunnel based on the identifier of the uplink tunnel, so as to avoid the clock signal being transmitted back to the master clock through the terminal corresponding to the master clock. It should be understood that in this solution, the uplink tunnel used to transmit the clock signal can refer to the tunnel from the access network device to the first user plane network element (such as UPF), and the uplink tunnel is UE-granular. In other words, the identifier of the uplink tunnel can indirectly indicate which UE the clock signal comes from. Specifically, the method can refer to the following Figure 16 The process shown.

[0386] like Figure 16 As shown, a clock signal transmission method provided by an embodiment of the present application can be applied in scenarios where clock signals are transmitted in a unicast manner, or in scenarios where clock signals are transmitted in a multicast manner. In scenarios where clock signals are transmitted in a multicast manner, unlike the above embodiment, all terminals corresponding to the ports of the device-side repeater in the first clock domain can be added to the group corresponding to the multicast session. The method includes the following steps:

[0387] S1600: A first session management network element sends first indication information to a first access network device. Correspondingly, the first access network device receives the first indication information.

[0388] The first session management network element may be a session management network element for managing the PDU session of the terminal, for example, the first session management network element may be Figure 10 In the case where the first session management network element and the second session management network element are deployed independently, the first session management network element can be connected to the second session management network element (such as Figure 10The multicast session described in this application may be a transmission tunnel for transmitting the clock signal of the first clock domain in a multicast manner.

[0389] Among them, the first indication information can be used to instruct the first access network device to send the clock signal of the first clock domain to a specific terminal (such as other terminals except the terminal corresponding to the uplink tunnel) according to the identifier of the uplink tunnel carried in the data packet after receiving the data packet from the network side. The data packet may include the identifier of the uplink tunnel and the clock signal of the first clock domain. Specifically, the first indication information can be used to instruct the first access network device not to send the clock signal of the first clock domain to the terminal corresponding to the identifier of the uplink tunnel included in the data packet, and only to send the clock signal of the first clock domain to other terminals. Exemplarily, the first session management network element can send the first indication information to the first access network device during the process of establishing the PDU session of the terminal to save signaling overhead.

[0390] In an embodiment of the present application, the data packet may be referred to as a General Packet Radio Service (GPRS) Tunnel Transport Protocol-User (GTP-U) data packet. The uplink tunnel identifier may be carried in the header of the GTP-U data packet, and the clock signal of the first clock domain may be carried in the payload of the GTP-U data packet. The data packet may be sent by a network-side device (such as a second user-plane network element or MB-UPF) to the first access network device via a shared N3 tunnel, or by a network-side device (such as a first user-plane network element or UPF) to the first access network device via the N3 tunnel corresponding to the terminal's PDU session, without limitation.

[0391] In an embodiment of the present application, the identifier of the uplink tunnel can be allocated by the first user plane network element, and the identifier of the uplink tunnel can also be called the tunnel identifier of the first user plane network element. Specifically, the identifier of the uplink tunnel can be the IP address of the first user plane network element or the GTP-U endpoint identifier of the first user plane network element. When establishing a PDU session of a terminal, the identifier of the uplink tunnel corresponding to the PDU session is allocated by the first user plane network element, and is sent by the first session management network element to the first access network device, so that the first access network device stores the identifier of the uplink tunnel in the information of the PDU session of the terminal, so that the first access network device can know which first user plane network element the PDU session of the terminal corresponds to based on the identifier of the uplink tunnel.

[0392] It should be understood that the first access network device in S1600 may include an access network device corresponding to / connected to a terminal corresponding to a port in the first clock domain, among terminals managed / served by the first session management network element. Figure 17c In the example shown, it is assumed that the first clock domain is clock domain 2. The ports in clock domain 2 include port 2 of DS-TT2, port 3 of DS-TT3, port 4 of DS-TT4, and port 5 of DS-TT5. Port 2 of DS-TT2 corresponds to UE1, port 3 of DS-TT3 corresponds to UE2, port 4 of DS-TT4 corresponds to UE3, and port 5 of DS-TT5 corresponds to UE4. UE1 and UE2 correspond to RAN1, and UE3 and UE4 correspond to RAN2. Then, the SMF will send first indication information to RAN1 and RAN2, respectively, instructing them to send the clock signal of clock domain 2 to specific terminals (e.g., terminals other than the terminal corresponding to the uplink tunnel) based on the identifier of the uplink tunnel.

[0393] S1601: A first session management network element sends second indication information to a first user plane network element. Correspondingly, the first user plane network element receives the second indication information from the first session management network element.

[0394] The second indication information may be used to instruct the first user plane network element, upon receiving a clock signal from the first clock domain from the uplink tunnel, to carry the identifier of the uplink tunnel and the clock signal from the first clock domain in a data packet and send it to the access network device. Exemplarily, the first session management network element may send the second indication information to the first user plane network element during the N4 session configuration process to save signaling overhead.

[0395] It should be understood that the first user plane network element described in S1601 may include user plane network elements corresponding to all terminals corresponding to ports in the first clock domain. For example, the ports in the first clock domain include port 1 and port 2, port 1 corresponds to UE1, port 2 corresponds to UE2, UE1 corresponds to UPF1, and UE2 corresponds to UPF2. Then, the SMF sends second indication information to UPF1 and UPF2 respectively, instructing that after receiving the clock signal from the first clock domain of the uplink tunnel, the identifier and clock signal of the uplink tunnel are carried in the data packet and sent to the terminal side.

[0396] It should be understood that S1600 and S1601 are optional steps that can be executed or not. If not executed, the default or pre-configured access network device sends the clock signal of the first clock domain to the terminal according to the identifier of the uplink tunnel carried in the data packet, and the default or pre-configured first user plane network element receives the clock signal of the first clock domain from the uplink tunnel, and carries the identifier of the uplink tunnel and the clock signal in the data packet and sends it to the access network device. In addition, when S1600 and S1601 are executed, this application does not limit the execution order of S1600 and S1601, and can be executed according to Figure 16 The steps are executed in the order shown. Alternatively, S1601 may be executed first and then S1600, or S1600 and S1601 may be executed simultaneously without limitation.

[0397] S1602: The first terminal sends a clock signal in the first clock domain to a first user plane network element. Correspondingly, the first user plane network element receives the clock signal in the first clock domain.

[0398] The first terminal may be a terminal corresponding to a port of a device-side repeater connected to the master clock.

[0399] Exemplarily, the master clock can send a clock signal of the first clock domain to the first terminal through the port of the device-side repeater connected to it. After the first terminal receives the clock signal of the first clock domain, it sends the clock signal of the first clock domain to the access network device corresponding to the first terminal. After the access network device corresponding to the first terminal receives the clock signal, it sends the clock signal of the first clock domain to the first user-plane network element through the uplink tunnel between the access network device corresponding to the first terminal and the first user-plane network element (the uplink tunnel corresponds to the first terminal).

[0400] Furthermore, the first user-plane network element sends a clock signal of the first clock domain to a network-side forwarder (e.g., NW-TT) connected thereto. The network-side forwarder sends the clock signal of the first clock domain to the external clock node, and upon learning that a port in the first clock domain of the device-side forwarder is in the second state (e.g., the master state), sends the clock signal of the first clock domain to the first user-plane network element.

[0401] Furthermore, the first user-plane network element carries / encapsulates the clock signal from the network-side forwarder and the identifier of the uplink tunnel for transmitting the clock signal in S1602 in the same data packet. For example, after receiving the clock signal of the first clock domain from the network-side forwarder, the first user-plane network element carries the clock signal of the first clock domain and the identifier of the uplink tunnel in the data packet according to the second indication information.

[0402] S1603. The first user-plane network element sends a data packet to the first access network device. Correspondingly, the first access network device receives the data packet.

[0403] It should be understood that the first access network device in S1603 may include an access network device corresponding to an uplink tunnel for transmitting a clock signal or other access network devices, without limitation. Figure 8b As shown, the uplink tunnel of the clock signal of the transmission clock domain 1 corresponds to RAN1, and the RANs that receive data packets include RAN1 and RAN2.

[0404] In one possible implementation, the first user plane network element sends a data packet to the first access network device via multicast. For example, the first user plane network element sends the data packet to the second user plane network element via the N9 tunnel, and the second user plane network element sends the data packet to the first access network device via the shared N3 tunnel between the second user plane network element and the first access network device.

[0405] Among them, the N9 tunnel between the first user plane network element and the second user plane network element and the shared N3 tunnel between the second user plane network element and the first access network device can be established before S1603, or after the first user plane network element generates a data packet and before sending the data packet to the first access network device, without limitation. Figure 13a S1309-S1311 will not be elaborated on here.

[0406] It should be understood that if the first user plane network element and the second user plane network element are separately provided, that is, they are different user plane network elements, then the first user plane network element sends the data packet to the first access network device through the second user plane network element. If the first user plane network element and the second user plane network element are jointly provided, for example, the second user plane network element is integrated with the first user plane network element, and the first user plane network element has the functions performed by the second user plane network element, then the first user plane network element can directly send the data packet to the first access network device through the shared N3 tunnel between the first user plane network element and the first access network device.

[0407] In another possible implementation, the first user plane network element sends the data packet to the first access network device in a unicast manner. For example, the first user plane network element sends the data packet to the first access network device through the N3 tunnel corresponding to the PDU session of the terminal.

[0408] Among them, the relevant description of the terminal's PDU session is as described above, and the establishment process of the terminal's PDU session is as described in S1301, which will not be repeated here.

[0409] S1604. The first access network device sends a clock signal to other terminals except the first terminal according to the identifier of the uplink tunnel carried in the data packet.

[0410] The terminals described in S1604 may include terminals managed / served by the first access network device and corresponding to ports in the first clock domain, but do not include terminals corresponding to the identifier of the uplink tunnel. In a scenario where clock signals are transmitted in a multicast manner, the terminals described in S1604 may be understood as terminals that have joined a group corresponding to the multicast session, but do not include terminals corresponding to the identifier of the uplink tunnel.

[0411] Optionally, the first access network device obtains the identifier of the uplink tunnel from the data packet in response to the first indication information received in S1601, and uses the identifier of the uplink tunnel as an index to search for the information of the PDU session in the UE context of the local storage terminal. If there is a first terminal, and the identifier of the uplink tunnel in the information of the PDU session of the first terminal is the same as the identifier of the uplink tunnel carried by the data packet, it is determined that the uplink tunnel corresponds to the first terminal, and a clock signal is not sent to the first terminal, but is sent to other terminals other than the first terminal.

[0412] In one possible implementation, in a scenario where a first access network device receives a clock signal sent by a second user-side network element in a multicast manner, the first access network device sends a clock signal of a first clock domain to other terminals other than the first terminal based on the identifier of the uplink tunnel carried in the data packet, which may include: the first access network device determines the terminal to join the group, checks the PDU session information of each terminal in the group, and if the identifier of the uplink tunnel is carried in the PDU session information of the first terminal, it means that the uplink tunnel corresponds to the first terminal, the first terminal is connected to / corresponds to the master clock, and sends a clock signal to the terminals other than the first terminal in the group corresponding to the multicast session.

[0413] For example, the first access network device sends a clock signal to other terminals in the group corresponding to the multicast session except the first terminal through unicast (i.e., through the air interface wireless bearer resources / air interface connection corresponding to the terminal), avoiding sending the clock signal to all terminals joining the group, which causes the clock signal to be transmitted back to the master clock.

[0414] In the scenario where the clock signal is transmitted in multicast mode, the method for determining the terminals to be added to the group corresponding to the multicast session and establishing the multicast session can be referred to Figure 12 However, it should be noted that Figure 16 In the embodiment shown, the terminals that join the group corresponding to the multicast session are determined based on the ports of the device-side repeater in the first clock domain, and the determination method is the same as that of FIG. Figure 12 The determination method is different in Figure 16 The terminal corresponding to the master clock can also be added to the group corresponding to the multicast session, without filtering out the terminal corresponding to the master clock. Figure 16 In the method shown, terminals corresponding to all ports located at the terminal side and in the first clock domain are added to the group corresponding to the multicast session.

[0415] In one possible implementation, in a scenario where a first access network device receives a clock signal sent by a first user-plane network element in unicast mode, for each data packet received by the first access network device through the N3 tunnel corresponding to the PDU session of the terminal, the first access network device checks whether the locally stored information of the PDU session of the terminal includes the identifier of the uplink tunnel carried in the data packet. If included, it means that the uplink tunnel corresponds to the terminal, which means that the terminal is connected to the master clock and no clock signal is sent to the terminal. If the identifier of the uplink tunnel is not carried in the information of the PDU session of the terminal, the uplink tunnel that transmits the clock signal is not the uplink tunnel of the terminal, which means that the terminal is not connected to the master clock and no clock signal is sent to the terminal.

[0416] based on Figure 16 In the method shown, when the master clock is on the UE side, the first user-side network element carries the identifier of the uplink tunnel corresponding to the terminal connected to the master clock and the clock signal in a data packet, and sends the data packet to the access network device. After the access network device receives the data packet, it sends a clock signal to the terminal according to the identifier of the uplink tunnel carried, and does not send a clock signal to the terminal corresponding to the uplink tunnel, thereby avoiding the clock signal emitted by the master clock from being transmitted back to the master clock.

[0417] The following combination Figure 10 In the 5G communication system shown in the figure, it is assumed that the terminals include UE1-UEn, the device-side forwarders include DS-TT1-UEn, each DS-TT is connected to a clock node, and the DS-TT is connected to the UE correspondingly (for example, DS-TT1 is connected to UE1, DS-TT2 is connected to UE2, ... DS-TTn is connected to UEn correspondingly), the network-side forwarder is NW-TT, NW-TT is connected to a clock node, NW-TT is connected to UPF, the access network device is RAN, the mobility management network element is AMF, the session management network element that manages the multicast session of the first clock domain is MB-SMF, the session management network element that manages the PDU session of the UE is SMF, the anchor point of the PDU session is UPF, and the anchor point of the multicast session is MB-UPF. Figure 16 The following method is introduced:

[0418] Figure 17a A communication method for a multicast service provided in an embodiment of the present application is as follows: Figure 17a As shown, this method can be applied to the scenario where the clock signal is transmitted in unicast mode, or it can also be applied to the scenario where the clock signal is transmitted in multicast mode. Figure 17a In the illustrated embodiment, all terminals corresponding to the ports of the device-side repeater in the first clock domain may be added to the group corresponding to the multicast session. The method may include:

[0419] S1701: SMF establishes PDU sessions for each UE.

[0420] Among them, S1701 can refer to S1301 and will not be described in detail.

[0421] S1702: Optionally, the SMF sends first indication information to the RAN. Correspondingly, the RAN receives the first indication information.

[0422] The RAN may include a RAN that provides network services to a UE corresponding to a port in the first clock domain.

[0423] Among them, the relevant description of the first indication information can refer to S1600 and will not be repeated here.

[0424] S1703: Optionally, the SMF sends second indication information to the UPF. Correspondingly, the UPF receives the second indication information.

[0425] The UPF may include a UPF that provides user plane transmission services to the UE corresponding to the port in the first clock domain.

[0426] Among them, the relevant description of the second indication information can refer to S1600 and will not be repeated here.

[0427] S1704: NW-TT receives the notification message.

[0428] Among them, S1704 can refer to S1302 and will not be described in detail.

[0429] S1705 . The NW-TT determines the port in the first clock domain and the status of each port according to the received notification message.

[0430] Among them, S1705 can refer to S1303 and will not be described in detail.

[0431] S1706: When the master clock of the first clock domain is located at the UE1 side, the DS-TT1 connected to the master clock sends the clock signal of the first clock domain to the NW-TT. Correspondingly, the NW-TT receives the clock signal of the first clock domain.

[0432] For example, the master clock sends the clock signal of the first clock domain to the DS-TT1 to which it is connected. DS-TT1 sends the clock signal to UE1. After UE1 receives the clock signal, it sends the clock signal to RAN. After RAN receives the clock signal, it sends the clock signal to UPF through the uplink tunnel corresponding to UE1. UPF forwards the clock signal to NW-TT.

[0433] S1707. The NW-TT sends the clock signal of the first clock domain to the UPF, and the UPF receives the clock signal of the first clock domain.

[0434] For example, after receiving the clock signal from the first clock domain, the NW-TT can determine, based on the status of each port, whether to send the clock signal to the DS-TT corresponding to the port in the second state. For example, if the state of a port of DS-TT2 in the first clock domain is the master state, the NW-TT determines to send the clock signal of the first clock domain to DS-TT2 through the UPF.

[0435] S1708. The UPF generates a data packet carrying a clock signal and an identifier of the uplink tunnel corresponding to UE1.

[0436] Optionally, the UPF may generate a data packet carrying a clock signal and an identifier of the uplink tunnel corresponding to UE1 according to the second indication information received in S1703.

[0437] Furthermore, the UPF sends a data packet to the RAN. Figure 17a In the method shown, the UPF may send data packets to the RAN in a multicast manner or in a unicast manner.

[0438] The process of the UPF sending a data packet to the RAN in a multicast manner includes the process of establishing a multicast session as shown in S1709-S1716 and the process of sending a data packet to the RAN through the shared N3 tunnel corresponding to the multicast session as shown in S1717:

[0439] S1709 . The NW-TT sends information c to the first application function network element. Correspondingly, the first application function network element receives information c.

[0440] The first application function network element may be the TSN AF or TSCTSF mentioned above.

[0441] The information c may be used to indicate a port of a device-side repeater in the first clock domain. The information c may include an identifier of the port, or include an identifier of the first clock domain and an identifier of the port.

[0442] Exemplarily, the NW-TT sending information c to the first application function network element may include: the NW-TT sending a management information container carrying information c to the first application function network element. The management information container may be recognized and parsed only by the first application function network element. The management information container may be a UMIC or a BMIC. In this way, information c may be carried in a container that is only recognizable by the first application function network element, thereby preventing information c from being parsed and tampered with by other network elements during transmission, thereby ensuring the reliability of information c transmission.

[0443] S1710: The first application function network element sends information c to the SMF. Correspondingly, the SMF receives information c.

[0444] Optionally, when the first application function network element is a TSN AF, the first application function network element may further determine to configure or create a multicast session for the first clock domain. After determining to configure or create the multicast session for the first clock domain, the first application function network element sends message 17a to the SMF. Message 17a may be used to request the configuration or creation of the multicast session. Message 17a may carry at least one of an identifier of the first clock domain and an identifier of the multicast session. Optionally, message 17a also carries information c to save signaling overhead.

[0445] Exemplarily, the manner in which the first application function network element determines to configure or create a multicast session in the first clock domain may refer to the manner described in S1201. For example, when the first application function network element determines that the number of UEs corresponding to the port of the device-side forwarder in the first clock domain is greater than a preset threshold, the first application function network element determines to configure or create a multicast session in the first clock domain.

[0446] Optionally, when the first application function network element is not a TSN AF but a TSCTSF, the first application function network element does not perform the actions of determining the configuration or creating a multicast session in the first clock domain and sending message 17a to the SMF.

[0447] S1711. The SMF determines to configure or create a multicast session in the first clock domain, and determines the UE to join the group corresponding to the multicast session based on the information c and the correspondence between the port and the UE.

[0448] Among them, the process of SMF determining the configuration or creation of a multicast session in the first clock domain refers to methods one to three in S1201, and can also be executed in accordance with method four in S1201 when the first application function network element sends message 17a, which will not be repeated here.

[0449] Among them, the SMF determines the UE to join the group corresponding to the multicast session according to the information c and the correspondence between the port and the UE, which may include: determining the UE corresponding to the port of the DS-TT in the first clock domain according to the information c and the correspondence between the port and the UE, and adding all the determined UEs to the group corresponding to the multicast session. That is, the UE to join the group corresponding to the multicast session is determined according to the port of the device-side repeater in the first clock domain, and the determination method is the same as Figure 12 The determination method is different, and there is no need to filter out the UE corresponding to the master clock.

[0450] For the description of the specific correspondence between the port and the UE, and the process of determining the UE corresponding to the port of the DS-TT in the first clock domain, refer to S1202 and are not described in detail.

[0451] S1712. The SMF sends the multicast session identifier to the RAN corresponding to the UE that joins the group corresponding to the multicast session through the MB-SMF. Correspondingly, the RAN receives the multicast session identifier.

[0452] The SMF may also send the UE identifier and the QoS information of the multicast session to the RAN corresponding to the UE that joins the group corresponding to the multicast session.

[0453] S1713. The RAN allocates air interface radio bearer resources corresponding to the multicast session.

[0454] Furthermore, if a shared N3 tunnel for transmitting the clock signal of the first clock domain in a multicast manner is not established between the RAN and the MB-UPF, the following S1714-S1716 are executed:

[0455] S1714: RAN allocates a shared N3 tunnel identifier, such as AN Tunnel Info, and sends the shared N3 tunnel identifier to SMF. Correspondingly, SMF receives the shared N3 tunnel identifier.

[0456] If SMF and MB-SMF are separate, that is, they are different session management network elements, and UPF and MB-UPF are separate, that is, they are different user plane network elements, execute the following S1715-S1716.

[0457] S1715: SMF sends the identifier of the shared N3 tunnel to MB-SMF, which then sends it to MB-UPF.

[0458] For example, the MB-SMF can include the shared N3 tunnel identifier in the N4 session configuration and send it to the MB-UPF. Accordingly, the MB-UPF receives the shared N3 tunnel identifier and, based on the shared N3 tunnel identifier, establishes a shared N3 tunnel between the MB-UPF and the RAN for multicast transmission of the clock signal of the first clock domain.

[0459] S1716: MB-UPF configures the identifier of the N9 tunnel of MB-UPF and sends the identifier of the N9 tunnel of MB-UPF to MB-SMF. MB-SMF sends the identifier of the N9 tunnel of MB-UPF to SMF, which then sends it to UPF to establish an N9 tunnel between MB-UPF and UPF for transmitting the clock signal of the first clock domain.

[0460] It should be noted that if the N9 tunnel between the MB-UPF and the UPF is established for the first time, the SMF may also send the identifier of the first clock domain to the UPF, instructing the UPF to send the clock signal of the first clock domain to the MB-UPF through the N9 tunnel between the UPF and the MB-UPF. The MB-UPF then sends the clock signal of the first clock domain to the RAN through the shared N3 tunnel between it and the RAN. The RAN then sends the clock signal of the first clock domain to the UEs in the group corresponding to the multicast session via unicast or multicast.

[0461] At this point, the N9 tunnel from UPF to MB-UPF for transmitting the clock signal of the first clock domain, the shared N3 tunnel from MB-UPF to RAN for transmitting the clock signal of the first clock domain, and the air interface connection between RAN and UE are established.

[0462] S1717: The UPF sends the data packet generated in S1708 to the MB-UPF through the N9 tunnel. The MB-UPF receives the data packet and sends it to the RAN through the shared N3 tunnel. In response, the RAN receives the data packet.

[0463] The UPF sending the data packet to the RAN in unicast mode may include S1718:

[0464] S1718: The UPF sends a data packet to the RAN via the unicast N3 tunnel between it and the RAN. The RAN receives the data packet. The unicast N3 tunnel here can be understood as the N3 tunnel or downlink tunnel corresponding to the UE's PDU session.

[0465] S1719: The RAN sends a clock signal to other UEs except UE1 according to the identifier of the uplink tunnel corresponding to UE1 carried in the data packet.

[0466] Optionally, the RAN obtains the identifier of the uplink tunnel from the data packet in response to the first indication information received in S1702, and searches the PDU session information in the UE context of the local storage terminal using the identifier of the uplink tunnel as an index. If it is found that the identifier of the uplink tunnel in the information of the PDU session of UE1 is the same as the identifier of the uplink tunnel carried by the data packet, it is determined that the uplink tunnel corresponds to UE1, and the clock signal is not sent to UE1, but to other terminals other than the first terminal (such as Figure 17a UE2 in sends a clock signal.

[0467] Specifically, the execution process of S1719 can refer to that described in S1604 and will not be described in detail.

[0468] S1720: The UE forwards the received clock signal to the DS-TT connected to it. The DS-TT receives the clock signal and forwards the clock signal to the clock node connected to it.

[0469] based on Figure 17a In the method shown, when the master clock is on the UE side, the UPF carries the identifier of the uplink tunnel for transmitting the clock signal and the clock signal in the data packet and sends the uplink tunnel to the RAN. After the RAN receives the data packet, it does not send the clock signal to the UE corresponding to the uplink tunnel based on the identifier of the uplink tunnel carried in the data, thereby avoiding transmission anomalies caused by the clock signal being transmitted back to the master clock.

[0470] For example, suppose MB-UPF and UPF are combined, such as Figure 17b As shown, OC1, OC2, and OC3 in clock domain 1 correspond to three UEs: UE1, UE2, and UE3, respectively. OC1 and OC2 are slave clocks, and OC3 is the master clock. OC3 sends clock signal 1 from clock domain 1 to the UPF via uplink tunnel 3 corresponding to UE3. The UPF then sends the clock signal to the NW-TT. The NW-TT determines whether to send the clock signal to the terminal based on the status of port 2 and port 1. The NW-TT sends clock signal 1 to the UPF. After receiving clock signal 1, the UPF sends a data packet carrying clock signal 1 and the ID of uplink tunnel 3 to RAN1 via unicast or multicast. Based on the ID of uplink tunnel 3 carried in the data packet, RAN1 determines that clock signal 1 is from the master clock corresponding to UE3. RAN1 no longer sends clock signal 1 to UE3, but instead sends it to UE1 and UE2, preventing the clock signal from being transmitted back to OC3 via UE3.

[0471] For another example, suppose the clock signal of clock domain 1 is clock signal 1, and the clock signal of clock domain 2 is clock signal 2. Figure 17cAs shown, port 3 of the DS-TT to which UE2 is connected is connected to two OCs, one in each clock domain. The NW-TT is also connected to two OCs, one in each clock domain. The OC connected to port 1 is in clock domain 1; ports 2, 4, and 5 are in clock domain 2. After BMCA, the OC in clock domain 1 connected to port 3 becomes the master clock for clock domain 1. That is, UE2 corresponds to the master clock of clock domain 1, and the OC on the NW-TT side becomes the master clock for clock domain 2. Based on the concept of multicast clock signal transmission, a multicast session for clock domain 1 is established. The group corresponding to the multicast session for clock domain 1 includes UE1 and UE2. UE1 and UE2 in the group correspond to RAN1. RAN1 stores the correspondence between the UE1 and UE2 that have joined the group and the multicast session for clock domain 1. A multicast session for clock domain 2 is established. The group corresponding to the multicast session for clock domain 2 includes UE1, UE2, UE3, and UE4. UE1 and UE2 in the group correspond to RAN1. RAN1 stores the correspondence between UE1 and UE2 and the multicast session for clock domain 2. UE3 and UE4 correspond to RAN2. RAN2 stores the correspondence between UE3 and UE4 and the multicast session for clock domain 2. UE2 sends the clock signal of clock domain 1 to UPF through the uplink tunnel corresponding to UE2. After receiving clock signal 1, UPF carries the clock signal 1 and the identifier of the uplink tunnel corresponding to UE2 in the data packet and sends it to MB-UPF. MB-UPF sends it to RAN1 through the multicast session of clock domain 1. After receiving the data packet, RAN1 determines that UE1 and UE2 are in the group based on the stored correspondence between UE1 joining the group and the multicast session between UE2 and clock domain 1. At the same time, based on the identifier of the uplink tunnel carried in the data packet, it determines that the uplink tunnel corresponds to UE2. Instead of sending clock signal 1 of clock domain 1 to UE2, it sends clock signal 1 of clock domain 1 to UE1 in the group, avoiding transmitting the clock signal of clock domain 1 back to the master clock. Figure 8b In comparison, since the identifier of the uplink tunnel of the terminal corresponding to the master clock is carried in the data packet transmitted on the multicast session, it is easier for the RAN to identify which UE the master clock of the clock signal corresponds to, and not send the clock signal to the UE, avoiding the problem of clock synchronization mechanism disorder and inability to achieve clock synchronization caused by the clock signal transmitted back to the master clock.

[0472] It can be understood that the methods and / or steps implemented by the first session management network element, the device-side forwarder, the access network device, the first application function network element, and the first user plane network element in the above embodiments can also be implemented by components (such as chips or circuits) used for the first session management network element, the device-side forwarder, the access network device, the first application function network element, and the first user plane network element.

[0473] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between various network elements. Accordingly, the embodiment of the present application also provides a communication device, which can be the mobility management network element in the above embodiment, or a device including the mobility management network element, or a component that can be used for the mobility management network element. It can be understood that, in order to implement the above functions, the communication device includes a hardware structure and / or software module corresponding to each function. It should be easily appreciated by those skilled in the art that, in combination with the units and algorithm steps of the various examples described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in hardware or in a manner where computer software drives hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present application.

[0474] In the embodiment of the present application, the first session management network element, the device-side forwarder, the access network device, the first application function network element, and the first user plane network element can be divided into functional modules according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above-mentioned integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. There may be other division methods in actual implementation.

[0475] Figure 18 The structure diagram of a communication device 180 is shown. The communication device 180 can be a first session management network element, or a chip in the first session management network element, or a system on a chip. The communication device 180 can be used to perform the functions of the first session management network element involved in the above embodiment. As an implementation method, Figure 18 The communication device 180 shown includes: a transceiver unit 1801, a processing unit 1802;

[0476] In one possible design, transceiver unit 1801 is configured to receive first information indicating an identifier of a port of one or more device-side repeaters in a first clock domain and a status of the port. For a description of the status of the port, refer to the above. For example, transceiver unit 1801 supports communication device 180 in executing S1200.

[0477] Processing unit 1802 is configured to determine a terminal to join the group corresponding to the multicast session based on the first information and the correspondence between the port and the terminal, and to transmit, via transceiver unit 1801, a multicast session identifier including the multicast session identifier to the access network device corresponding to the terminal. The port may refer to a port of a device-side repeater, and the state of the port may include a first state or a second state. The multicast session is configured to transmit a clock signal in the first clock domain via multicast. For example, processing unit 1802 supports communication device 180 in executing S1201 and S1202.

[0478] Specifically, the above Figure 12-13a All relevant contents of each step involved in the method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 12-13a The method shown in the figure manages the function of the first session management network element in the method for transmitting the clock signal, and thus can achieve the same effect as the above-mentioned method for transmitting the clock signal.

[0479] In another possible design, the transceiver unit 1801 is used to send first indication information to the first user plane network element, instructing the first user plane network element to carry the tunnel identifier in the data packet transmitted on the multicast session after receiving the clock signal from the tunnel, and to send second indication information to the access network device, instructing the access network device to send a clock signal to the terminal joining the group corresponding to the multicast session according to the tunnel identifier.

[0480] Specifically, the above Figure 16-17a All relevant contents of each step involved in the method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 16-17a The method shown in the figure can achieve the same effect as the clock signal transmission method described above by using the function of the first session management network element in the clock signal transmission method. For example, the transceiver unit 1801 supports the communication device 180 to execute S1600 and S1601.

[0481] As another possible implementation method, Figure 18 The communication device 180 shown includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 180. For example, the processing module can support the communication device 180 to perform control functions, such as executing S1201. The communication module can integrate the functions of the transceiver unit 1801 and can be used to support the communication device 180 to execute S1200, S1600 and communicate with other network entities, such as Figure 10 The communication device 180 may further include a storage module for storing program codes and data of the communication device 180 .

[0482] Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 180 involved in the embodiment of the present application can be Figure 11 Communication device 1100 is shown.

[0483] Figure 19 The structure diagram of a communication device 190 is shown. The communication device 190 can be a first application function network element, or a chip in the first application function network element, or a system on a chip. The communication device 190 can be used to perform the functions of the first application function network element involved in the above embodiment. As an implementation method, Figure 19 The communication device 190 shown includes: a transceiver unit 1901.

[0484] In one possible design, the transceiver unit 1901 is used to receive first information from a network side repeater, indicating the port identifier and port status of one or more side repeaters of a device in a first clock domain, where the port status includes a first state or a second state, and send the first information to a first session management network element so that the first session management network element determines the terminal to join the group corresponding to the multicast session based on the first information, and sends the clock signal of the first clock domain through the multicast session.

[0485] In another possible design, the transceiver unit 1901 is used to receive second information from the network side repeater for indicating the identification of the port of the device side repeater in the first clock domain and the status of the port, where the status of the port includes the first status or the second status; and send first information to the first device side repeater for indicating the status of the port on the first device side repeater in the first clock domain, so as to facilitate the first device side repeater to filter the received clock signal according to the status of the port.

[0486] Specifically, the above Figure 12-17a All relevant contents of each step involved in the method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 12-17a The method shown in the figure implements the function of the first application function network element in the clock signal transmission method shown in the figure, thereby achieving the same effect as the above-mentioned clock signal transmission method.

[0487] As another possible implementation method, Figure 19The communication device 190 shown includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 190. For example, the processing module can support the communication device 190 to perform management functions. The communication module can integrate the functions of the transceiver unit 1901 and can be used to support the communication device 190 with other network entities, such as Figure 10 The communication device 190 may further include a storage module for storing program codes and data of the communication device 190 .

[0488] Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 190 involved in the embodiment of the present application can be Figure 11 Communication device 1100 is shown.

[0489] Figure 20 The structure diagram of a communication device 200 is shown. The communication device 200 can be a first device side repeater, or a chip in the first device side repeater, or a system on a chip. The communication device 200 can be used to perform the functions of the first device side repeater involved in the above embodiments. As an implementation method, Figure 20 The communication device 200 shown includes a transceiver unit 2001 and a processing unit 2002 .

[0490] The transceiver unit 2001 is configured to receive first information from a first device-side repeater indicating a state of a port on the first device-side repeater in a first clock domain. For example, the transceiver unit 2001 supports the communication apparatus 200 in executing S1401.

[0491] The processing unit 2002 is configured to filter the received clock signal of the first clock domain according to the first information. For example, the processing unit supports the communication device 200 to execute S1402.

[0492] Specifically, the above Figure 14-15a All relevant contents of each step involved in the embodiment of the method shown can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 14-15a The method shown in the figure implements the function of the device-side repeater in the clock signal transmission method shown in the figure, thereby achieving the same effect as the above-mentioned clock signal transmission method.

[0493] As another possible implementation method, Figure 20 The communication device 200 shown includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 200. For example, the processing module can support the communication device 200 to perform management functions. The communication module can integrate the functions of the transceiver unit 2001 and can be used to support the communication device 200 with other network entities, such as Figure 10 The communication device 200 may further include a storage module for storing program codes and data of the communication device 200 .

[0494] Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 200 involved in the embodiment of the present application can be Figure 11 Communication device 1100 is shown.

[0495] Figure 21 The structure diagram of a communication device 210 is shown. The communication device 210 can be an access network device, or a chip in the access network device, or a system on a chip. The communication device 210 can be used to perform the functions of the access network device involved in the above embodiment. As an implementation method, Figure 21 The communication device 210 shown includes a transceiver unit 2101 and a processing unit 2102 .

[0496] The transceiver unit 2101 is configured to receive a data packet carrying a clock signal and an identifier of an uplink tunnel corresponding to the first terminal. For example, the transceiver unit 2101 supports the communication device 210 in executing S1603.

[0497] The processing unit 2102 is configured to send a clock signal to other terminals except the first terminal according to the identifier of the uplink tunnel corresponding to the first terminal. For example, the processing unit 2102 supports the communication device 210 to execute S1604.

[0498] Specifically, the above Figure 16-17a All relevant contents of each step involved in the method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 16-17a The method shown in the figure accesses the function of the network device in the method for transmitting the clock signal, thereby achieving the same effect as the above-mentioned method for transmitting the clock signal.

[0499] As another possible implementation method, Figure 21 The communication device 210 shown includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 210. For example, the processing module can support the communication device 210 to perform management functions. The communication module can integrate the functions of the transceiver unit 2101 and can be used to support the communication device 210 with other network entities, such as Figure 10 The communication device 210 may further include a storage module for storing program codes and data of the communication device 210 .

[0500] Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 210 involved in the embodiment of the present application can be Figure 11 Communication device 1100 is shown.

[0501] Figure 22 The structure diagram of a communication device 220 is shown. The communication device 220 can be a first user plane network element, or a chip in the first user plane network element, or a system on chip. The communication device 220 can be used to perform the functions of the first user plane network element involved in the above embodiment. As an implementation method, Figure 22 The communication device 220 shown includes a transceiver unit 2201 .

[0502] The transceiver unit 2201 is configured to receive a clock signal through an uplink tunnel corresponding to the first terminal, and send a data packet carrying the clock signal and an identifier of the uplink tunnel corresponding to the first terminal to the first access network device.

[0503] Specifically, the above Figure 16-17a All relevant contents of each step involved in the method embodiment can be referred to the functional description of the corresponding functional module, and will not be repeated here. Figure 16-17a The function of the first user plane network element in the clock signal transmission method shown in the method achieves the same effect as the above-mentioned clock signal transmission method.

[0504] As another possible implementation method, Figure 22The communication device 220 shown includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 220. For example, the processing module can support the communication device 220 to perform management functions. The communication module can integrate the functions of the transceiver unit 2201 and can be used to support the communication device 220 with other network entities, such as Figure 10 The communication device 220 may further include a storage module for storing program codes and data of the communication device 220.

[0505] Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, and so on. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 220 involved in the embodiment of the present application can be Figure 11 Communication device 1100 is shown.

[0506] Figure 23 A structural diagram of a communication system provided in an embodiment of the present application is shown in FIG. Figure 23 As shown, the communication system may include: a terminal, a device-side forwarder 230, an access network device 231, a first session management network element 232, a first user plane network element 233, a first application function network element 234 and a network-side forwarder 235.

[0507] Among them, the device-side forwarder 230 has the same function as the above-mentioned communication device 200, the access network device 231 has the same function as the above-mentioned communication device 210, the first session management network element 232 has the same function as the above-mentioned communication device 180, the first user-plane network element 233 has the same function as the above-mentioned communication device 220, and the first application function network element 234 has the same function as the above-mentioned communication device 190, which will not be repeated.

[0508] The embodiment of the present application also provides a computer-readable storage medium. All or part of the processes in the above-mentioned method embodiments can be completed by a computer program to instruct the relevant hardware, and the program can be stored in the above-mentioned computer-readable storage medium. When the program is executed, it may include the processes of the above-mentioned method embodiments. The computer-readable storage medium can be a terminal in any of the above-mentioned embodiments, such as: an internal storage unit including a data sending end and / or a data receiving end, such as a hard disk or memory of the terminal. The above-mentioned computer-readable storage medium can also be an external storage device of the above-mentioned terminal, such as a plug-in hard disk equipped on the above-mentioned terminal, a smart memory card (smart media card, SMC), a secure digital (secure digital, SD) card, a flash card (flash card), etc. Further, the above-mentioned computer-readable storage medium can also include both the internal storage unit of the above-mentioned terminal and an external storage device. The above-mentioned computer-readable storage medium is used to store the above-mentioned computer program and other programs and data required by the above-mentioned terminal. The above-mentioned computer-readable storage medium can also be used to temporarily store data that has been output or is to be output.

[0509] It should be noted that the terms "first" and "second" in the specification, claims, and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products, or devices.

[0510] It should be understood that in this application, "at least one (item)" refers to one or more, "more than one" refers to two or more, "at least two (items)" refers to two or three and more than three, and "and / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0511] It should be understood that in the embodiments of the present application, "B corresponding to A" means that B is associated with A. For example, B can be determined based on A. It should also be understood that determining B based on A does not mean determining B based solely on A; B can also be determined based on A and / or other information. In addition, the "connection" in the embodiments of the present application refers to various connection methods, such as direct connection and indirect connection, to achieve communication between devices, and the embodiments of the present application do not impose any limitations on this.

[0512] Unless otherwise specified, the "transmission" (transmit / transmission) appearing in the embodiments of the present application refers to bidirectional transmission, including the actions of sending and / or receiving. Specifically, the "transmission" in the embodiments of the present application includes the sending of data, the receiving of data, or the sending of data and the receiving of data. In other words, the data transmission here includes uplink and / or downlink data transmission. Data may include channels and / or signals, uplink data transmission is uplink channel and / or uplink signal transmission, and downlink data transmission is downlink channel and / or downlink signal transmission. The "network" and "system" appearing in the embodiments of the present application express the same concept, and the communication system is the communication network.

[0513] Through the description of the above implementation methods, technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0514] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0515] The units described as separate components may or may not be physically separate, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple places. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0516] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0517] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

[0518] The above is only a specific embodiment of the present application, but the scope of protection of this application is not limited to this. Any changes or substitutions within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for transmitting a clock signal, characterized in that: The method comprises: The first access network device receives a data packet; wherein the data packet carries a clock signal of the first clock domain and an identifier of an uplink tunnel, the uplink tunnel corresponds to the first terminal, and the uplink tunnel is a tunnel from the access network device corresponding to the first terminal to the first user plane network element; The first access network device sends the clock signal of the first clock domain to other terminals except the first terminal according to the identifier of the uplink tunnel.

2. The method according to claim 1, characterized in that The first access network device sending, according to the identifier of the uplink tunnel, the clock signal of the first clock domain to other terminals except the first terminal, including: If the first terminal is included in the terminals that join the group corresponding to the multicast session, the first access network device sends the clock signal to the other terminals except the first terminal in the terminals that join the group corresponding to the multicast session.

3. The method according to claim 1 or 2, characterized in that The method further comprises: The first access network device receives first indication information from a first session management network element; The first access network device sending, according to the identifier of the uplink tunnel, a clock signal of the first clock domain to other terminals except the first terminal, includes: In response to the first indication information, the first access network device sends the clock signal of the first clock domain to other terminals except the first terminal according to the identifier of the uplink tunnel.

4. A method for transmitting a clock signal, characterized in that: The method comprises: The first user plane network element receives a clock signal of the first clock domain through an uplink tunnel corresponding to the first terminal; wherein the uplink tunnel is a tunnel from the access network device corresponding to the first terminal to the first user plane network element; The first user-plane network element sends a data packet to the first access network device; wherein the data packet carries the clock signal and the identifier of the uplink tunnel, and the identifier of the uplink tunnel is used by the first access network device to send the clock signal to other terminals except the first terminal.

5. The method according to claim 4, characterized in that The method further comprises: The first user plane network element receives second indication information from the first session management network element; The first user plane network element sends the data packet to the first access network device, including: the first user plane network element sends the data packet to the first access network device according to the second indication information.

6. The method according to claim 4 or 5, characterized in that The first user plane network element sending a data packet to the first access network device includes: The first user plane network element sends the data packet to the first access network device through a second user plane network element, wherein the second user plane network element is an anchor point of the multicast session of the first clock domain.

7. A communication system, characterized in that: The communication system comprises: A first user plane network element, configured to receive a clock signal of a first clock domain through an uplink tunnel corresponding to a first terminal; wherein the uplink tunnel is a tunnel from an access network device corresponding to the first terminal to the first user plane network element; The first user plane network element is further configured to send a data packet to the first access network device; wherein the data packet carries the clock signal of the first clock domain and the identifier of the uplink tunnel; The first access network device is configured to receive the data packet and send the clock signal to other terminals except the first terminal according to the identifier of the uplink tunnel.

8. A communication device, characterized in that: The communication device includes a processor and a communication interface, and the processor and the communication interface are used to support the communication device to execute the method according to any one of claims 1 to 3, or the method according to any one of claims 4 to 6.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and when the computer instructions are executed on a computer, the computer executes the method according to any one of claims 1 to 3 or the method according to any one of claims 4 to 6.

10. A computer program product, characterized in that The computer program product includes computer instructions, and when the computer instructions are run on a computer, the computer is caused to perform the method according to any one of claims 1 to 3 or the method according to any one of claims 4 to 6.

11. A chip, characterized in that: The chip is coupled to the memory and is used to read and execute program instructions stored in the memory to implement the method according to any one of claims 1 to 3, or the method according to any one of claims 4 to 6.

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