Method, device and system for time synchronization

Abstract

The present disclosure generally relates to a method, device and system for synchronization in a wireless network. A method performed by a wireless device is disclosed. The method may include receiving a first message including clock configuration information from a first network element in the 5GS, the clock configuration information including at least one of: a GM clock list including a first GM clock and a second GM clock; a clock indicator for each GM clock in the GM clock list; a time difference between the first GM clock and the second GM clock; receiving first clock information of the first GM clock from a second network element in the 5GS; using the first GM clock as an active GM clock in response to the first clock information; and synchronizing with the 5GS based on the first clock information, and regarding the first GM clock as an active GM clock.

Description

Technical Field

[0001] The present disclosure relates generally to wireless communications, and more particularly to methods, devices, and systems for time synchronization and data transmission in wireless networks. Background Art

[0002] The ecosystem in wireless communication networks includes an increasing number of applications that require high availability, high throughput, real-time transmission, low latency and low jitter. Time-sensitive networking (TSN) is designed to manage latency between industrial devices in Ethernet networks. The combination of TSN and 5G systems can bring significant benefits to industrial use cases. Accurate and robust timing synchronization within 5GS and TSN is critical to meet performance requirements. Summary of the invention

[0003] The present disclosure relates to a method, device and system for time synchronization and data transmission in a wireless network.

[0004] In some embodiments, a method performed by a wireless device is disclosed. The method may include: receiving a first message including clock configuration information from a first network element in a 5GS, the clock configuration information including at least one of the following: a global master (GM) clock list, the GM clock list including at least a first GM clock and a second GM clock; a clock indicator of each GM clock in the GM clock list, the clock indicator including at least one of the following: a name of each GM clock in the GM clock list; an identifier of each GM clock in the GM clock list; or an index of each GM clock in the GM clock list; a time difference between the first GM clock and the second GM clock; receiving first clock information of the first GM clock from a second network element in the 5GS; using the first GM clock as an active GM clock in response to the first clock information; and synchronizing with the 5GS based on the first clock information and treating the first GM clock as an active GM clock.

[0005] In some embodiments, a method performed by a first network element is disclosed. The method may include: sending a first message including clock configuration information to a wireless device in a 5GS, the clock configuration information including at least one of the following: a global master (GM) clock list, the GM clock list including at least a first GM clock and a second GM clock; a clock indicator of each GM clock in the GM clock list, the clock indicator including at least one of the following: a name of each GM clock in the GM clock list; an identifier of each GM clock in the GM clock list; or an index of each GM clock in the GM clock list; a time difference between the first GM clock and the second GM clock; sending first clock information of the first GM clock to the wireless device, wherein the first clock information indicates that the first GM clock is an active GM clock; and treating the first GM clock as an active GM clock.

[0006] In some embodiments, there is a network element or device comprising a processor and a memory, wherein the processor is configured to read code from the memory and implement any method described in any embodiment.

[0007] In some embodiments, a computer program product includes a computer readable program medium code stored thereon, which, when executed by a processor, causes the processor to implement any method described in any embodiment.

[0008] Other aspects and alternatives of the above-described embodiments and their implementations are described in more detail in the following figures, description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example wireless communication network is shown.

[0010] Figure 2 An example wireless network node is shown.

[0011] Figure 3 An example user device is shown.

[0012] Figure 4 An example system architecture of a 5GS acting as a TSN bridge is shown.

[0013] Figure 5 An example 5GS time synchronization is shown where the 5GS detects a grand master clock switch.

[0014] Figure 6 Another example 5GS time synchronization is shown, where the 5GS detects a global master clock switch.

[0015] Figure 7 An example 5GS time synchronization is shown where the UE detects a global master clock switch.

[0016] Figure 8 An example 5GS time synchronization is shown where a clock indicator is added to the timestamp. DETAILED DESCRIPTION

[0017] Wireless communication network

[0018] Figure 1 An exemplary wireless communication network 100 is shown including a core network 110 and a radio access network (RAN) 120. The core network 110 also includes at least one mobility management entity (MME) 112 and / or at least one access and mobility management function (AMF). Other functions that may be included in the core network 110 are described in detail in the following. Figure 1120. The RAN 120 also includes a plurality of base stations, such as base stations 122 and 124. The base station may include at least one evolved NodeB (eNB) for 4G LTE, an enhanced LTE eNB (ng-eNB) or a next generation NodeB (gNB) for 5G New Radio (NR), or any other type of signal transmission / reception device, such as a UMTS NodeB. The eNB 122 communicates with the MME 112 via an S1 interface. Both the eNB 122 and the gNB 124 may be connected to the AMF 114 via an Ng interface. Each base station manages and supports at least one cell. For example, the base station gNB 124 may be configured to manage and support cell 1, cell 2, and cell 3.

[0019] The gNB 124 may include a central unit (CU) and at least one distributed unit (DU). The CU and the DU may be co-located in the same location, or may be located in different locations, respectively. The CU and the DU may be connected via an F1 interface. Alternatively, for an eNB capable of connecting to a 5G network, it may also be similarly divided into a CU and at least one DU, referred to as ng-eNB-CU and ng-eNB-DU, respectively. The ng-eNB-CU and the ng-eNB-DU may be connected via a W1 interface.

[0020] The wireless communication network 100 may include one or more tracking areas. A tracking area may include a group of cells managed by at least one base station. For example, tracking area 1, labeled 140, includes cell 1, cell 2, and cell 3, and may also include tracking areas that may be managed by other base stations and in Figure 1 The wireless communication network 100 may also include at least one UE 160. The UE may select a cell among a plurality of cells supported by a base station to communicate with the base station over an over-the-air (OTA) radio communication interface and resources, and may reselect a cell for communication as the UE 160 travels in the wireless communication network 100. For example, the UE 160 may initially select cell 1 to communicate with the base station 124, and may then reselect cell 2 at some later point in time. The cell selection or reselection by the UE 160 may be based on wireless signal strength / quality and other factors in the various cells.

[0021] The wireless communication network 100 may be implemented as, for example, a 2G, 3G, 4G / LTE or 5G cellular communication network. Accordingly, base stations 122 and 124 may be implemented as 2G base stations, 3G NodeBs, LTE eNBs or 5G NR gNBs. UE 160 may be implemented as a mobile or fixed communication device capable of accessing the wireless communication network 100. UE 160 may include, but is not limited to, mobile phones, laptops, tablets, personal digital assistants, wearable devices, Internet of Things (IoT) devices, MTC / eMTC devices, distributed remote sensor devices, roadside assistance devices, XR devices and desktop computers. UE 160 may also be generally referred to as a wireless communication device or a wireless terminal. UE 160 may support sidelink communication to another UE via a PC5 interface.

[0022] Although the following description focuses on Figure 1 The cellular wireless communication system shown, but the basic principles are applicable to other types of wireless communication systems for paging wireless devices. These other wireless systems may include, but are not limited to, Wi-Fi, Bluetooth, ZigBee, and WiMax networks.

[0023] Figure 2 An example of an electronic device 200 for implementing a network base station (e.g., a radio access network node), a core network (CN), and / or operations and maintenance (OAM) is shown. Optionally, in one implementation, the example electronic device 200 may include a radio transmit / receive (Tx / Rx) circuit system 208 for sending / receiving communications with a UE and / or other base stations. Optionally, in one implementation, the electronic device 200 may also include a network interface circuit system 209 for enabling the base station to communicate with other base stations and / or the core network, such as optical or wired interconnection, Ethernet, and / or other data transmission media / protocols. The electronic device 200 may optionally include an input / output (I / O) interface 206 for communicating with an operator or the like.

[0024] The electronic device 200 may also include a system circuit system 204. The system circuit system 204 may include (multiple) processors 221 and / or memory 222. The memory 222 may include an operating system 224, instructions 226, and parameters 228. The instructions 226 may be configured for one or more processors 221 to perform the functions of a network node. The parameters 228 may include parameters for supporting the execution of the instructions 226. For example, the parameters may include network protocol settings, bandwidth parameters, radio frequency mapping allocations, and / or other parameters.

[0025] Figure 3An example of an electronic device (e.g., user equipment (UE)) for implementing a terminal device 300 is shown. UE 300 may be a mobile device, such as a smart phone or a mobile communication module provided in a vehicle. UE 300 may include some or all of the following: a communication interface 302, a system circuit system 304, an input / output interface (I / O) 306, a display circuit system 308, and a storage device 309. The display circuit system may include a user interface 310. The system circuit system 304 may include any combination of hardware, software, firmware, or other logic / circuitry systems. The system circuit system 304 may be implemented, for example, with one or more systems on a chip (SoC), application specific integrated circuits (ASICs), discrete analog and digital circuits, and other circuit systems. The system circuit system 304 may be part of the implementation of any desired function in UE 300. In this regard, the system circuit system 304 may include logic for facilitating, for example, the following: decoding and playing music and video, such as MP3, MP4, MPEG, AVI, FLAC, AC3 or WAV decoding and playing; running applications; accepting user input; saving and retrieving application data; establishing, maintaining and terminating cellular phone calls or data connections, such as Internet connections; establishing, maintaining and terminating wireless network connections, Bluetooth connections or other connections; and displaying relevant information on the user interface 310. The user interface 310 and the input / output (I / O) interface 306 may include a graphical user interface, a touch-sensitive display, tactile feedback or other tactile output, voice or facial recognition input, buttons, switches, speakers, and other user interface elements. Other examples of the I / O interface 306 may include microphones, video and still image cameras, temperature sensors, vibration sensors, rotation and orientation sensors, headphone and microphone input / output jacks, universal serial bus (USB) connectors, memory card slots, radiation sensors (e.g., IR sensors), and other types of inputs.

[0026] refer to Figure 3, the communication interface 302 may include a radio frequency (RF) transmission (Tx) and reception (Rx) circuit system 316 for processing the transmission and reception of signals through one or more antennas 314. The communication interface 302 may include one or more transceivers. The transceiver may be a wireless transceiver that includes a modulation / demodulation circuit system, a digital-to-analog converter (DAC), a shaping table, an analog-to-digital converter (ADC), a filter, a waveform shaper, a filter, a preamplifier, a power amplifier, and / or other logic for transmitting and receiving through one or more antennas or (for some devices) through a physical (e.g., wired) medium. The signals sent and received may follow any of a variety of formats, protocols, modulations (e.g., QPSK, 16-QAM, 64-QAM, or 256-QAM), frequency channels, bit rates, and encodings. As a specific example, the communication interface 302 may include a transceiver that supports transmission and reception under 2G, 3G, BT, WiFi, Universal Mobile Telecommunications System (UMTS), High Speed ​​Packet Access (HSPA) +, 4G / Long Term Evolution (LTE), and 5G standards. However, the techniques described below are applicable to other wireless communication technologies, whether from the 3rd Generation Partnership Project (3GPP), the GSM Association, 3GPP2, IEEE, or other partners or standards bodies.

[0027] refer to Figure 3 , the system circuit system 304 may include one or more processors 321 and a memory 322. The memory 322 stores, for example, an operating system 324, instructions 326, and parameters 328. The processor 321 is configured to execute the instructions 326 to implement the desired functions of the UE 300. The parameters 328 may provide and specify configuration and operating options for the instructions 326. The memory 322 may also store any BT, WiFi, 3G, 4G, 5G, or other data that the UE 300 will send or has received through the communication interface 302. In various implementations, the system power of the UE 300 may be provided by a power storage device such as a battery or a transformer.

[0028] 5G Systems and Time-Sensitive Networks

[0029] Wireless communication systems and time-sensitive networks (TSN) are key technologies for industrial communications. For example, 5G can be used for wireless connections, while TSN can be used for wired connections.

[0030] To achieve seamless integration between the 5G system (5GS) and the TSN system, the 5GS can act as a virtual TSN bridge for the TSN network. Figure 4 An example system architecture of a 5GS acting as a TSN bridge is shown. The architecture defines several gateways between TSN and 5GS:

[0031] TSN Application Function (AF) 402, used to connect to the TSN Centralized User Configuration (CUC)

[0032] / Centralized Network Controller (CNC) entity and 5G control plane.

[0033] • Device-side TSN translator (DS-TT) 404 on the user equipment (UE) side.

[0034] Network-side TSN converter (NW-TT) 406 on the user plane function (UPF) side

[0035] like Figure 4 As shown, the 5GS may include a UE 408, a RAN 410, and a UPF 412. The 5GS is capable of performing time synchronization with an accuracy of 1 μs (microseconds), for example, by using the following mechanism: the RAN synchronizes its time with the UPF based on one of the following: a local site global navigation satellite system (GNSS) receiver (e.g., both the gNB and the UPF receive time from the GNSS); a local site clock (e.g., the gNB, UPF, and the Grand Master (GM) clock are collocated); or a transport network connection with cascaded Precision Time Protocol (PTP) capability (e.g., the gNB and UPF synchronize time with the GM clock via the generalized Precision Time Protocol (gPTP) or IEEE Standard 1588 (IEEE Precision Clock Synchronization Protocol Standard). The RAN may deliver its time to the UE via 5G Access Stratum (AS) signaling (e.g., System Information Block (SIB) or dedicated Radio Resource Control (RRC) signaling).

[0036] As a TSN bridge, 5GS can support time synchronization based on the generalized precision time protocol (gPTP) between TSN end stations and TSN working clocks, which depends on 5GS time synchronization. For example, during gPTP-based time synchronization between TSN end stations and TSN working clocks, it is assumed that the same clock as 5GS is used. For data packet delivery through 5GS, based on the ingress timestamp (when the data packet enters 5GS) and the egress timestamp (when the data packet leaves 5GS) of the data packet, the 5GS transmission delay can be derived.

[0037] As a TSN bridge, 5GS can also support deterministic transmission latency, which is achieved through the hold and forward function implemented in DS-TT and / or NW-TT (whose purpose is 5GS de-jitter). For example, for DL ​​transmission, the burst arrival time and period can be sent from AMF to UE via NAS message, based on which DS-TT can determine each burst arrival time. If the data burst arrives at DS-TT before the predefined burst arrival time, DS-TT will hold it and forward it to the next node at the predefined burst arrival time. For UL transmission, UPF can obtain the burst arrival time and period from AMF, based on which NW-TT can determine each burst arrival time. If the data burst arrives at NW-TT before the predefined burst arrival time, NW-TT will hold it and forward it to the next node at the predefined burst arrival time.

[0038] For synchronization purposes, multiple GM clocks can be supplied to 5GS and / or TSN in a 1:m (active:standby) configuration. One of the GM clocks can act as the active GM clock, while the other GM clocks can act as the standby GM clock. When the active GM clock fails or degrades, the standby GM clock will take over. When the GM clock switch occurs, there is a short transition period during which the data packets in the 5GS can be timestamped based on the old active GM clock or the new active GM clock. In order to correctly process the data packets, correct timing is required. Therefore, DS / TT and / or NW-TT may need to be able to identify the correct clock basis (for timestamps in data packets). That is, it is critical to be able to identify the correct GM clock from the old active GM clock and the new active GM clock.

[0039] In the present disclosure, various embodiments are disclosed so that the UE / DS-TT and / or UPF / NW-TT can identify the correct GM clock during GM clock switching.

[0040] The details of these embodiments are described below.

[0041] Example 1: 5GS time synchronization - 5GS detection of global master clock switching

[0042] When 5GS acts as a TSN bridge, there are at least two global master (GM) clocks in the system. Figure 5As shown, there are two GM clocks supplied, namely GM clock 1 and GM clock 2. In some example implementations, at a given moment, one GM clock may serve as the active clock, while the other(s) GM clocks may serve as the backup(s) clocks. When the active clock fails or degrades (e.g., accuracy falls below a threshold), a switchover may occur so that the backup GM clock may take over and become the active GM clock. Figure 5 In some example implementations not shown in FIG. 1 , more than one backup GM clock may be supplied.

[0043] Figure 5 Exemplary message flows and interactions between various network elements in a 5G system (5GS) for time synchronization based on (multiple) GM clocks are shown. The 5GS may include a core network and at least one base station (e.g., gNB), and may also include multiple UEs. In the core network, there are, among other network elements, a UPF and a network-side TSN converter (NW-TT). On the UE side, the UE may include a device-side TSN converter (DS-TT). The DS-TT may be implemented, for example, as a hardware module or a software module in the UE.

[0044] Step 1:

[0045] From the 5GS side, the UPF may provide GM clock information to the UE. The GM clock information may include at least one of the following: a list of available GM clocks; a clock indicator of each GM clock in the list of available GM clocks; or a time difference between each pair of GM clocks in the list of available GM clocks. The clock indicator may include one of the following: a name, an identifier, or an index of each GM clock.

[0046] Alternatively, the gNB can provide GM clock information to the UE.

[0047] If the GM clock information is updated, the UPF and / or gNB may send the updated GM clock information to the UE, so that the UE will have the latest GM clock information.

[0048] The list of available GM clocks may include the active GM clock currently used by the 5GS, and at least one backup GM clock to which the 5GS can switch.

[0049] The time difference between the two GM clocks may include: a time offset between the two GM clocks; or an absolute time of each of the two GM clocks (i.e., the time difference is implicit and can be derived based on the absolute time). Based on the time difference, when a handover occurs, the UE can derive the time of the new GM clock (which becomes active) based on the old GM clock (i.e., the failed or degraded GM clock that was previously active). The UE may also be able to derive the time of the previously active GM clock based on the new active GM clock and the time difference between the new GM clock and the old GM clock.

[0050] For example, refer to Figure 5 , the UPF provides the UE with a list of available GM clocks, which includes GM clock 1 and GM clock 2. In this example, GM clock 2 is 1 μs (microseconds) slower than GM clock 1. If a switch occurs (as shown in a later step), the UE can derive the time of GM clock 2 by subtracting 1 μs from the time of GM clock 1.

[0051] The GM clock information may be provided from the UPF to the UE via a non-access stratum (NAS) message. The GM clock information may also be provided from the gNB to the UE via an access stratum (AS) message (e.g., a system information block (SIB) or dedicated signaling). The gNB may obtain the GM clock information via various means. For example, the gNB may 1) obtain the GM clock information from the UPF via non-UE associated signaling; or 2) obtain the GM clock information from the Operation Administration and Maintenance (OAM) platform.

[0052] Step 2:

[0053] In this step, the 5GS is synchronizing its time with GM clock 1 (i.e., GM clock 1 is in active state). Specifically, the UPF and / or gNB may obtain time from GM clock 1 based on one of the following: a local on-site global navigation satellite system (GNSS) receiver, a local on-site clock, or a transport network connection with cascaded precision time protocol (PTP) capability. The gNB may then deliver the time information (which is based on GM clock 1) to the UE via AS signaling (e.g., SIB or dedicated radio resource control (RRC) signaling). The time information may include at least one of the following: the absolute time of GM clock 1; or a clock indicator of GM clock 1.

[0054] Step 3:

[0055] The time information sent to the UE in step 2 may indicate to the UE that the GM clock 1 is active. The UE continues to synchronize with the GM clock 1.

[0056] Step 4:

[0057] When processing data packets (e.g., user plane data packets, such as data packets for generalized precision time protocol (gPTP) messages), the NW-TT / UE-TT adds a timestamp in the data packet based on GM clock 1. When the data packet enters the 5GS, the timestamp may be marked, and the timestamp may be referred to as a 5GS ingress timestamp. For example, when the data packet enters the UPF or NW-TT, the downlink data packet may be marked, and when the data packet enters the UE-TT, the uplink data packet may be marked. The timestamp basis indicates which GM clock is used when adding the timestamp. In this step, the timestamp basis is GM clock 1.

[0058] Step 5:

[0059] GM clock 1 fails or degrades. Accordingly, 5GS switches to GM clock 2. Specifically, UPF and gNB obtain time from GM clock 2 based on one of the following: local site GNSS receiver, local site clock, or transport network connection with cascade PTP capability. The gNB can then deliver the time information (which is based on GM clock 2) to the UE via AS signaling (e.g., SIB or dedicated RRC signaling). The time information may include at least one of the following: the absolute time of GM clock 2; a GM clock switching indication; or a clock indicator of GM clock 2.

[0060] Step 6:

[0061] After receiving the time information sent by the gNB in ​​step 5, the UE may determine that there is a GM clock switch based on the GM clock switch indication or the clock indicator that implicitly indicates the GM clock change. The UE may then continue to synchronize with GM clock 2. For example, if the clock indicated by the clock indicator is different from the current clock, it indicates that there is a GM clock switch. The clock indicator may include an identifier of the clock, which may be a predefined clock indicator for each clock and may be used to uniquely identify the clock within the scope of the UE, gNB, and UPF. The clock indicator may include a GM clock index, a GM clock name, a GM clock identifier, etc.

[0062] In one implementation, the DS-TT may implement logic for detecting GM clock switching.

[0063] The UE continues to synchronize its timing with GM clock 2 which becomes the active GM clock. Step 7:

[0064] The NW-TT / UE-TT adds a timestamp in a data packet (eg, a user plane data packet, such as a gPTP message) based on the GM clock 2. In this step, the timestamp basis is the GM clock 2.

[0065] Step 8:

[0066] Based on the responsible entity (UE / DS-TT or UPF / NW-TT) and the direction of the user plane data, step 8 is split into step 8a and step 8b. Step 8a covers UE / DS-TT when processing downlink user plane data, and step 8b covers UPF / NW-T when processing uplink user plane data.

[0067] Step 8a:

[0068] When a GM clock switch occurs, there is a GM clock transition period in which the GM clock switch is performed. In the GM clock transition period, there may be a race condition, for example, for data packets that are served / processed during the transition period. For downlink UE data packets, such as data packets of gPTP messages, the NW-TT can add a timestamp when the data packet enters the 5GS. As mentioned above, this timestamp can be called a 5GS entry timestamp. Depending on the timing of the GM clock switch, the timestamp can be based on GM clock 1 (for example, before the switch is submitted) or GM clock 2 (for example, after the switch is submitted). When the data packet arrives at the UE, for synchronization purposes, the UE may need to use the same clock used to add the entry timestamp to process the data packet. Under race conditions, the UE may already know the GM clock switch and GM clock 2 is taking over. However, data packets arriving after the switch can still use the entry timestamp based on GM clock 1. This may be due to transmission and processing delays of data packets, which may be introduced in the 5GS and air interface. For example, the ingress timestamp may be added before the switch, but due to processing and transmission delays, when the data packet arrives at the UE, the GM clock switch has already been committed. Therefore, during the transition period, the UE / DS-TT may need to maintain dual GM clocks: the new active GM clock 2 (for simplicity, the new GM clock) and the previous active GM clock 1 (for simplicity, the old GM clock), instead of discarding the previous active clock (e.g., as Figure 5 GM clock 1 shown).

[0069] For downlink user plane data, when the UE / DS-TT detects the GM clock switch, the UE / DS-TT can determine the timestamp basis (i.e., whether the 5GS entry timestamp in the downlink user plane data (e.g., in the gPTP message) uses the new GM clock or the old GM clock) based on the 5GS time delay information. The 5GS time delay can be the duration between the moment the 5GS entry timestamp is added and the moment the UE / NW-TT receives the downlink user plane data.

[0070] In one implementation, if the 5GS time delay is invalid when derived based on the old GM clock, but valid when derived based on the new GM clock, the UE / DS-TT can determine that the 5GS ingress timestamp of the downlink user plane data is based on the new GM clock. Otherwise, if the 5GS time delay is invalid based on the new GM clock, but valid based on the old GM clock, the UE / DS-TT can determine that the 5GS ingress timestamp is based on the old GE clock.

[0071] In one implementation, if the delay is negative, too small (below the first threshold) or too large (above the second threshold), the delay is invalid. In other words, the delay may need to be within a delay range (as defined by the first threshold and the second threshold) to be valid. The delay range may be associated with the processing delay and transmission delay of the downlink user plane data. In one implementation, the delay range (or the first threshold and the second threshold) may be determined by the 5GS and signaled to the UE / DS-TT. In one implementation, the UE / D-STT may derive the delay range (or the first threshold and the second threshold), for example, based on historical statistics.

[0072] In one implementation, the timestamp basis can be determined based on the reception time sequence of the user plane data and the indication of the GM clock switch. For example, if the user plane data is received before the indication of the GM clock switch is received, the timestamp basis of the 5GS ingress timestamp of the user plane data is the old GM clock. Otherwise, the timestamp basis is the new GM clock.

[0073] In one implementation, when retransmission is performed for user plane data and / or an indication of a GM clock switch (e.g., via a hybrid automatic repeat request (HARQ)), the reception time of the user plane data and the reception time of the indication of the GM clock switch are measured using the first downlink grant time (rather than the grant time for the retransmission).

[0074] In one implementation, if latency is more trustworthy when measured based on the new GM clock, the timestamp basis for the 5GS ingress timestamps of user plane data is the new GM clock, and vice versa.

[0075] In one implementation, during the transition period, for example, the time of the old GM clock may be derived from the new GM clock based on the time difference.

[0076] In one implementation, after the transition period, the UE / DS-TT may stop using or discard the old GM clock. The duration of the transition period may be predefined, such as 1 millisecond, or signaled by the 5GS. Alternatively, the duration of the transition period may be derived by the UE, for example based on historical statistics.

[0077] In one implementation, the UE / DS-TT may stop using or discard the old GM clock after no more services are based on the old GM clock.

[0078] Step 8b:

[0079] When a GM clock switch occurs, there may be a race condition in the GM clock transition period, for example, for data packets served / processed during the transition period. For uplink UE data packets, such as data packets of gPTP messages, DS-TT can add a timestamp when the data packet enters DS-TT (or UE). The timestamp may be called a 5GS entry timestamp (for data packets entering 5GS from the UE side). Depending on the timing of the GM clock switch, the timestamp may be based on GM clock 1 (e.g., before the switch is submitted) or GM clock 2 (e.g., after the switch is submitted). When the data packet arrives at the core network (e.g., UPF or NW-TT), for synchronization purposes, the UPF may need to use the same clock used to add the entry timestamp to process the data packet. Under race conditions, the core network may already know the GM clock switch, and GM clock 2 is taking over. However, uplink data packets arriving after the switch can still use the entry timestamp based on GM clock 1. This may be due to transmission and processing delays of data packets, which may be introduced in the 5GS and air interfaces. For example, the ingress timestamp may be added to the uplink data before the switch, but due to processing and transmission delays, when the uplink data packet arrives at the core network, the GM clock switch has already been committed. Therefore, during the transition period, the UPF / NW-TT may need to maintain dual GM clocks: the new GM clock 2 and the old GM clock 1, instead of discarding the previously active clock (e.g., Figure 5 GM clock 1 shown).

[0080] For uplink user plane data, when UPF / NW-TT detects GM clock switching, UPF / NW-TT can determine the timestamp basis (i.e., whether the 5GS ingress timestamp in the uplink user plane data (e.g., in the gPTP message) uses the new GM clock or the old GM clock) based on the 5GS time delay information, similar to step 8a. UPF / NW-TT can then select the GM clock based on the determined timestamp basis and process the uplink data using the selected GM clock.

[0081] In one implementation, after a transition period, the UPF / NW-TT may stop using or discard the old GM clock. The duration of the transition period may be predefined, such as 1 millisecond. Alternatively, the duration of the transition period may be derived by the UPF / NW-TT, for example, based on historical statistics.

[0082] In one implementation, the UPF / NW-TT may stop using or discard the old GM clock after no services are based on it anymore.

[0083] Note that the transition periods in step 8b and step 8a may be the same or different. The selection or determination of the transition period may be based on actual deployment requirements.

[0084] Example 2: Time synchronization - 5GS detects global master clock switching

[0085] In this embodiment, the core network may initiate a GM clock switch and notify the UE / DS-TT. The notification may be based on a clock value tag or an explicit GM clock switch indication. More details will be described in detail in the following steps.

[0086] When 5GS acts as a TSN bridge, there are at least two global master (GM) clocks in the system. Figure 6 As shown, there are two GM clocks supplied, namely GM clock 1 and GM clock 2. In some example implementations, at a given moment, one GM clock can serve as the active clock, while the other GM clock can serve as the backup clock. When the active clock fails or degrades (e.g., accuracy falls below a threshold), a switchover can occur so that the backup GM clock can take over and become the active GM clock. Figure 6 In some example implementations not shown in FIG. 1 , more than one backup GM clock may be supplied.

[0087] Figure 6 An exemplary message flow and interaction between various network elements in a 5GS for time synchronization based on (multiple) GM clocks is shown. The 5GS may include a core network and at least one base station (e.g., gNB), and may also include multiple UEs. In the core network, among the various network elements, there are UPF and NW-TT. On the UE side, the UE may include a DS-TT.

[0088] Step 1:

[0089] In this step, the 5GS is synchronizing its time with GM clock 1 (i.e., GM clock 1 is in active state). Specifically, the UPF and / or gNB may obtain time from GM clock 1 based on one of the following: a local on-site global navigation satellite system (GNSS) receiver, a local on-site clock, or a transport network connection with cascaded precision time protocol (PTP) capability. The gNB may then deliver the clock information (which is based on GM clock 1) to the UE via AS signaling (e.g., SIB or dedicated RRC signaling). The clock information may include at least one of the following: an absolute time of GM clock 1; a GM clock value tag; or a clock switch indication for indicating that a GM clock switch has occurred. The clock value tag may be a number that is incremented when a GM clock switch occurs. If the clock value tag is the same as the clock value tag received from the previous message, no GM clock switch occurs. Otherwise, if the clock value tag has changed (e.g., incremented) from the previous clock value tag, a GM clock switch occurs.

[0090] In one implementation, even without GM clock switching, the clock information of the GM clock may be periodically sent to the UE. The UE may periodically use the clock information to calibrate its timing to synchronize with the active GM clock.

[0091] Step 2:

[0092] After receiving the message sent to the UE in step 1, the UE decides that there is no GM clock switch. The UE can choose to synchronize or resynchronize with GM clock 1.

[0093] Step 3:

[0094] When processing data packets (e.g., user plane data packets, such as gPTP messages), NW-TT / UE-TT adds a timestamp (i.e., 5GS ingress timestamp) in the data packets based on GM clock 1. In this step, the timestamp basis is GM clock 1.

[0095] Step 4:

[0096] GM clock 1 fails or degrades. Accordingly, the 5GS switches to GM clock 2. Specifically, the UPF and gNB obtain time from GM clock 2 based on one of the following: a local field GNSS receiver, a local field clock, or a transport network connection with cascaded PTP capability. The gNB can then deliver the clock information to the UE via AS signaling. The clock information may include at least one of the following: the absolute time of GM clock 2; a GM clock value tag; or a clock switch indication for indicating that a GM clock switch has occurred. Note that the clock value tag has changed (e.g., incremented) from the clock value tag in step 1.

[0097] Step 5:

[0098] After receiving the clock information sent by the gNB in ​​step 4, the UE may determine that there is a GM clock switch based on the clock switch indication or the GM clock value tag. The UE may then continue to synchronize with GM clock 2.

[0099] A change in the GM clock value tag from its previously received value indicates the presence of a GM clock switch. For example, the GM clock value tag may be incremented each time a GM clock switch occurs.

[0100] Step 6:

[0101] The NW-TT / UE-TT adds timestamps in data packets (eg, user plane data packets such as gPTP messages) based on the GM clock 2 .

[0102] Step 7:

[0103] Steps 7, 7a and 7b are similar to steps 8, 8a and 8b in Example 1, respectively, and the details are omitted herein.

[0104] Example 3: 5GS time synchronization - UE detects global master clock switching

[0105] When 5GS acts as a TSN bridge, there are at least two global master (GM) clocks in the system. Figure 7 As shown, there are two GM clocks supplied, namely GM clock 1 and GM clock 2. In some example implementations, at a given moment, one GM clock can serve as the active clock, while the other GM clock can serve as the backup clock. When the active clock fails or degrades (e.g., accuracy falls below a threshold), a switchover can occur so that the backup GM clock can take over and become the active GM clock. Figure 7 In some example implementations not shown in FIG. 1 , more than one backup GM clock may be supplied.

[0106] Figure 7 An exemplary message flow and interaction between various network elements in a 5GS for time synchronization based on (multiple) GM clocks is shown. The 5GS may include a core network and at least one base station (e.g., gNB), and may also include multiple UEs. In the core network, there are UPFs and NW-TTs. On the UE side, the UE may include a DS-TT.

[0107] Step 1:

[0108] Step 1 is similar to Step 1 in Example 1, and the details are omitted herein.

[0109] Step 2:

[0110] In this step, the 5GS is synchronizing its time with GM clock 1 (i.e., GM clock 1 is in active state). Specifically, the UPF and / or gNB may obtain time from GM clock 1 based on one of the following: a local site GNSS receiver, a local site clock, or a transport network connection with cascaded precision time protocol (PTP) capability. The gNB may then deliver the clock information (which is based on GM clock 1) to the UE via AS signaling (e.g., SIB or RRC signaling). The clock information may include at least one of the following: the absolute time of GM clock 1; the GM clock value tag; or the clock indicator of GM clock 1.

[0111] Step 3:

[0112] The clock information sent to the UE in step 2 may indicate to the UE that the GM clock 1 is active. The UE continues to synchronize with the GM clock 1.

[0113] Step 4:

[0114] When processing data packets (e.g., user plane data packets, such as gPTP messages), NW-TT / UE-TT adds timestamps (i.e., 5GS ingress timestamps) in the data packets based on GM clock 1. The timestamp basis is GM clock 1.

[0115] Step 5:

[0116] The UE detects that the GM clock 1 fails or degrades. Accordingly, the UE autonomously switches to the GM clock 2. Specifically, the UE may receive its time from the GM clock 2, for example, by directly receiving the GNSS clock.

[0117] Step 6:

[0118] The UE may provide a clock switching indication to the gNB via an AS message such as a MAC CE message or a dedicated RRC message.

[0119] The clock switching indication may include an indicator of GM clock 2. The indicator may be predefined and may uniquely identify the clocks in the UE and gNB. The indicator may include one of the following: a clock index, a clock name, or a clock identity.

[0120] Step 7:

[0121] The gNB may forward the clock switching indication to the UPF via non-UE associated signaling or UE associated signaling.

[0122] Alternatively, Figure 7 Not shown in the figure, the UE can send a clock switching indication directly to the UPF via a NAS message.

[0123] Step 8:

[0124] Then, the UE may continue to synchronize with the GM clock 2. Note that step 8 may be performed immediately after step 5 and before step 6. Alternatively, step 8 may be performed in parallel with step 6 and / or step 7.

[0125] Step 9:

[0126] The NW-TT / UE-TT adds timestamps in data packets (eg, user plane data packets such as gPTP messages) based on the GM clock 2 .

[0127] Step 10:

[0128] Steps 10, 10a and 10b are similar to steps 8, 8a and 8b in Embodiment 1, respectively, and the details are omitted herein.

[0129] Example 4: 5GS time synchronization with clock indicator in timestamp

[0130] In this embodiment, when a timestamp is added in a 5GS ingress data packet, a clock indicator indicating an active GM clock is added to the timestamp to explicitly indicate the timestamp basis.

[0131] Figure 8 An exemplary message flow and interaction between various network elements in a 5GS for time synchronization based on (multiple) GM clocks is shown. The 5GS may include a core network and at least one base station (e.g., gNB), and may also include multiple UEs. In the core network, there are UPFs and NW-TTs. On the UE side, the UE may include a DS-TT.

[0132] Step 1:

[0133] Step 1 is similar to Step 1 in Example 1, and the details are omitted herein.

[0134] Step 2:

[0135] In this step, the 5GS is synchronizing its time with GM clock 1 (i.e., GM clock 1 is in active state). Specifically, the UPF and / or gNB may obtain time from GM clock 1 based on one of the following: a local site GNSS receiver, a local site clock, or a transport network connection with cascaded precision time protocol (PTP) capability. The gNB may then deliver the clock information (which is based on GM clock 1) to the UE via AS signaling (e.g., SIB or RRC signaling). The clock information may include at least one of the following: the absolute time of GM clock 1; or a clock indicator of GM clock 1.

[0136] Step 3:

[0137] The clock information sent to the UE in step 2 may indicate to the UE that the GM clock 1 is active. The UE continues to synchronize with the GM clock 1.

[0138] Step 4:

[0139] When processing a data packet (e.g., a user plane data packet such as a gPTP message), the NW-TT / UE-TT adds a timestamp (i.e., a 5GS ingress timestamp) in the data packet based on GM clock 1. To explicitly indicate the timestamp basis (i.e., GM clock 1), the NW-TT / UE-TT may add a clock indicator of GM clock 1 in the timestamp or in another field coexisting with the timestamp.

[0140] Step 5:

[0141] GM clock 1 fails or degrades. Accordingly, 5GS switches to GM clock 2. Specifically, UPF and gNB obtain time from GM clock 2 based on one of the following: local field GNSS receiver, local field clock, or transport network connection with cascade PTP capability. The gNB can then deliver the clock information (based on GM clock 2) to the UE via AS signaling (e.g., SIB or dedicated RRC signaling). The clock information may include at least one of the following: the absolute time of GM clock 2; or the clock indicator of GM clock 2.

[0142] Step 6:

[0143] The UE may continue to synchronize with GM clock 2, as shown in step 5.

[0144] Step 7:

[0145] When processing data packets (e.g., user plane data packets such as gPTP messages), the NW-TT / UE-TT adds a timestamp (i.e., 5GS ingress timestamp) in the data packets based on GM clock 1. To explicitly indicate the timestamp basis (i.e., GM clock 2), the NW-TT / UE-TT may add a clock indicator of GM clock 2 in the timestamp or in another field coexisting with the timestamp.

[0146] Step 8:

[0147] Based on the responsible entity (UE / DS-TT or UPF / NW-TT) and the direction of the user plane data, step 8 is split into step 8a and step 8b. Step 8a covers UE / DS-TT when processing downlink user plane data, and step 8b covers UPF / NW-T when processing uplink user plane data.

[0148] Step 8a:

[0149] For downlink user plane data, the UE / DS-TT can determine the timestamp basis (i.e., whether the 5GS ingress timestamp in the downlink user plane data (e.g., in a gPTP message) uses the new GM clock or the old GM clock) based on a clock indicator added in the timestamp itself or in another field coexisting with the timestamp.

[0150] Step 8b:

[0151] For uplink user plane data, the UPF / NW-TT can determine the timestamp basis (i.e., whether the 5GS ingress timestamp in the downlink user plane data (e.g., in a gPTP message) uses the new GM clock or the old GM clock) based on a clock indicator added in the timestamp itself or in another field coexisting with the timestamp.

[0152] In the present disclosure, at least to save energy consumption at the base station, a DTX mode is introduced. The DTX mode can be applied to various levels for different granularities. For example, DTX can be applied to the cell level, the cell group level, the DU level, the DU group level, the base station level, etc. In the present disclosure, for exemplary purposes, it can be described at the cell level. The same basic principles apply to other levels.

[0153] The above description and accompanying drawings provide specific example embodiments and implementations. However, the described subject matter may be embodied in a variety of different forms, and therefore, the subject matter covered or claimed is intended to be interpreted as not being limited to any example embodiment described herein. It is intended to provide a reasonably broad scope for the subject matter claimed or covered. In addition, for example, the subject matter may be embodied as a method, device, component, system, or non-transitory computer-readable medium for storing computer code. Therefore, for example, the embodiment may take the form of hardware, software, firmware, storage medium, or any combination thereof. For example, the above method embodiment may be implemented by a component, device, or system including a memory and a processor by executing a computer code stored in the memory.

[0154] Throughout the specification and claims, terms may have subtle meanings that are suggested or implied from the context, beyond the explicitly stated meanings. Likewise, the phrase "in one embodiment / implementation" used herein does not necessarily refer to the same embodiment, and the phrase "in another embodiment / implementation" used herein does not necessarily refer to a different embodiment. For example, the claimed subject matter includes combinations of all or part of the example embodiments.

[0155] In general, terms can be understood at least in part from usage in context. For example, terms used herein (such as "and", "or", or "and / or") can include various meanings that can depend at least in part on the context in which such terms are used. In general, "or" if used to associate a list (such as A, B, or C) means A, B, and C, which is used in an inclusive sense here; and A, B, or C, which is used in an exclusive sense here. In addition, the term "one or more" used in this article can be used in a singular sense to describe any feature, structure, or characteristic, and can also be used in a plural sense to describe a combination of features, structures, and characteristics, which depends at least in part on the context. Similarly, terms such as "a", "an", or "the" can be understood to convey singular or plural usage, which depends at least in part on the context. In addition, the term "based on" can be understood to not necessarily be intended to convey a set of exclusive factors, but can allow for the presence of other factors that are not necessarily explicitly described, which depends at least in part on the context.

[0156] References to features, advantages, or similar language throughout the specification do not imply that all features and advantages that may be achieved with the present solution should be or are included in any single implementation thereof. Rather, language referring to features and advantages is understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussion of features and advantages and similar language throughout the specification may, but do not necessarily, refer to the same embodiment.

[0157] In addition, the above-mentioned features, advantages and characteristics of the present solution can be combined in any suitable manner in one or more embodiments. Based on the description herein, a person of ordinary skill in the relevant art will recognize that the present solution can be practiced without one or more specific features or advantages of a particular embodiment. In other cases, additional features and advantages that may not be present in all embodiments of the present solution can be recognized in certain embodiments.

Claims

1. A method for clock synchronization, performed by a wireless device in a 5G system (5GS), the method comprising: A first message including clock configuration information is received from a first network element in the 5GS, where the clock configuration information includes at least one of the following: A list of global master (GM) clocks, including at least a first GM clock and a second GM clock; A clock indicator of each GM clock in the GM clock list, wherein the clock indicator includes at least one of the following: The name of each GM clock in the GM clock list; an identifier of each GM clock in the list of GM clocks; or an index of each GM clock in the GM clock list; a time difference between the first GM clock and the second GM clock; receiving first clock information for the first GM clock from a second network element in the 5GS; In response to the first clock information, using the first GM clock as an active GM clock; as well as Synchronize with the 5GS based on the first clock information, and regard the first GM clock as the active GM clock.

2. The method according to claim 1, wherein the time difference between the first GM clock and the second GM clock comprises at least one of the following: A time offset between the first GM clock and the second GM clock; or The absolute time of each of the first GM clock and the second GM clock. 3 . The method according to claim 1 , wherein the first clock information comprises at least one of: an absolute time of the first GM clock; or a clock indicator of the first GM clock.

4. The method according to claim 1, further comprising: determining that the active GM clock switches from the first GM clock to the second GM clock; as well as When a user plane data packet enters the 5GS, a timestamp basis for an ingress timestamp of the user plane data packet is determined, wherein: The timestamp basis includes a first timestamp basis based on the first GM clock and a second timestamp basis based on the second GM clock; and The ingress timestamp of the user plane data packet is marked by the network-side time-sensitive network converter (NW-TT) in the 5GS when the NW-TT receives the user plane data packet. The method according to claim 4 , wherein the user plane data packets are downlink user plane data packets.

6. The method of claim 4, wherein the user plane data packets comprise packets for generalized PTP (gPTP) messages.

7. The method according to claim 4, further comprising: Based on the timestamp, the user plane data packet is processed.

8. The method of claim 4, wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a first delay for the user plane data packet in the 5GS based on the first GM clock, wherein the first delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the first GM clock; determining whether the first delay is valid; as well as In response to the first delay being valid, determining the timestamp basis for the ingress timestamp of the user plane data packet to be the first timestamp basis.

9. The method of claim 8, wherein determining whether the first delay is valid comprises: In response to the first delay, one of the following conditions is met: The first delay is negative; The first delay is below a first threshold; or the first delay is above a second threshold, determining that the first delay is invalid; and In response to the first delay being above the first threshold and below the second threshold, the first delay is determined to be valid.

10. The method of claim 9, wherein the first threshold and the second threshold are predetermined or signaled from the 5GS to the wireless device.

11. The method of claim 4, wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a second delay for the user plane data packet in the 5GS based on the second GM clock, wherein the second delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the second GM clock; determining whether the second delay is effective; as well as In response to the second delay being valid, determining the timestamp basis for the ingress timestamp of the user plane data packet to be the second timestamp basis.

12. The method according to claim 4, wherein: Before determining that the active GM clock is switched from the first GM clock to the second GM clock, the method further includes: receiving second clock information for the second GM clock from the 5GS, wherein the second clock information includes at least one of: an absolute time of the second GM clock; or an identifier of the second GM clock, the identifier of the second GM clock indicating a GM clock switch to the second GM clock; and Determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: In response to the wireless device receiving the user plane data packet at a time earlier than reception of the second clock information, determining that the timestamp basis for the ingress timestamp of the user plane data packet is the first timestamp basis; and In response to the reception time of the user plane data packet by the wireless device being earlier than the reception of the second clock information, determining the timestamp basis for the ingress timestamp of the user plane data packet to be the second timestamp basis.

13. The method of claim 4, wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: The timestamp basis for the ingress timestamp of the user plane data packet is determined based on a clock indicator in the ingress timestamp.

14. The method of claim 4, wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a first delay for the user plane data packet in the 5GS based on the first GM clock, wherein the first delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the first GM clock; determining a second delay for the user plane data packet in the 5GS based on the second GM clock, wherein the second delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the second GM clock; as well as In response to both the first delay and the second delay being valid, a more trusted delay is selected from the first delay and the second delay, and the timestamp basis for the ingress timestamp is determined based on the more trusted delay.

15. The method of claim 4, wherein: The first clock information also includes a clock indicator of the first GM clock; Determining that the active GM clock switches from the first GM clock to the second GM clock includes: receiving second clock information for the second GM clock from the 5GS, the second clock information comprising at least one of: an absolute time of the second GM clock; or a clock indicator of the second GM clock; and Based on the second clock information, it is determined that the active GM clock is switched from the first GM clock to the second GM clock.

16. The method of claim 15, wherein determining that the active GM clock switches from the first GM clock to the second GM clock based on the second clock information comprises: In response to the clock indicator in the second clock information being different from the clock indicator in the first clock information, it is determined that the active GM clock is switched from the first GM clock to the second GM clock.

17. The method of claim 4, wherein: The first clock information further includes at least one of the following: a clock value tag that is incremented if a GM clock switch occurs; or a clock switch indication used to indicate that the GM clock switch occurs; and Determining that the active GM clock switches from the first GM clock to the second GM clock includes: receiving second clock information for the second GM clock from the 5GS, the second clock information comprising at least one of the clock value tag or the clock switching indication; The active GM clock is determined to switch from the first GM clock to the second GM clock in response to one of the following: The clock value tag is incremented from its previous value; or The clock switch indication indicates that the GM clock switch occurs.

18. The method of claim 4, wherein determining that the active GM clock switches from the first GM clock to the second GM clock comprises: In response to detecting that the first GM clock fails or degrades, determining that the active GM clock switches from the first GM clock to the second GM clock.

19. The method according to claim 18, further comprising: A second message including a GM clock switching indication is sent to the 5GS, wherein the GM clock switching indication includes a clock indicator of the second GM clock.

20. The method of claim 19, wherein sending the second message comprises at least one of: Sending the second message to the base station in the 5GS via an access stratum (AS) message, wherein the AS message includes at least one of a media access control element (MAC CE) message or a radio resource control (RRC) message; wherein reception of the second message by the base station triggers the base station to forward the second message to a user plane function (UPF) in the 5GS via UE-associated signaling; or The second message is sent to a user plane function (UPF) in the 5GS via a non-access stratum (NAS) message.

21. The method according to claim 4, further comprising: When it is determined that no service is based on the first GM clock or no user data packet is based on the first GM clock, the first GM clock is stopped from being used or is discarded.

22. The method of claim 1, wherein the first network element comprises at least one of: UPF; or NW-TT.

23. The method of claim 1, wherein the second network element comprises a base station, the base station comprising at least one of: gNodeB(gNB); eNodeB (eNB); ng-eNodeB (ng-eNB); or NodeB.

24. A method for clock synchronization, performed by a first network element in a 5GS, the method comprising: Sending a first message including clock configuration information to a wireless device in the 5GS, wherein the clock configuration information includes at least one of the following: A list of global master (GM) clocks, including at least a first GM clock and a second GM clock; A clock indicator of each GM clock in the GM clock list, wherein the clock indicator includes at least one of the following: The name of each GM clock in the GM clock list; an identifier of each GM clock in the list of GM clocks; or an index of each GM clock in the GM clock list; a time difference between the first GM clock and the second GM clock; sending first clock information for the first GM clock to the wireless device, wherein the first clock information indicates that the first GM clock is an active GM clock; as well as The first GM clock is regarded as the active GM clock.

25. The method of claim 24, wherein the time difference between the first GM clock and the second GM clock comprises at least one of the following: A time offset between the first GM clock and the second GM clock; or The absolute time of each of the first GM clock and the second GM clock. 26 . The method according to claim 24 , wherein the first clock information comprises at least one of: an absolute time of the first GM clock; or a clock indicator of the first GM clock.

27. The method of claim 24, further comprising: detecting that the first GM clock fails or degrades; determining that the active GM clock switches from the first GM clock to the second GM clock; as well as A second message is sent to the wireless device, the second message instructing the active GM clock to switch from the first GM clock to the second GM clock.

28. The method of claim 27, wherein the second message includes a clock indicator of the second GM clock.

29. The method according to claim 28, further comprising: When a downlink user plane data packet for the wireless device enters the first network element, the clock indicator is added to a timestamp of the downlink user plane data packet, wherein the wireless device determines a clock basis for the downlink user plane data packet as the second GM clock based on the clock indicator.

30. The method of claim 27, wherein the second message includes at least one of: a clock value tag that is incremented if a GM clock switch occurs; or a clock switch indication used to indicate that the GM clock switch occurs.

31. The method of claim 27, further comprising: When a user plane data packet enters the 5GS, a timestamp basis for an ingress timestamp of the user plane data packet is determined, wherein: The timestamp basis includes a first timestamp basis based on the first GM clock and a second timestamp basis based on the second GM clock; and The ingress timestamp of the user plane data packet is marked by a device-side time-sensitive network converter (DS-TT) in the 5GS when the DS-TT receives the user plane data packet.

32. The method of claim 31 , wherein the user plane data packets are uplink user plane data packets.

33. The method of claim 31 , further comprising: Based on the timestamp, the user plane data packet is processed.

34. The method of claim 31 , wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a first delay of the user plane data packet in the 5GS based on the first GM clock, wherein the first delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the first network element using the first GM clock; determining whether the first delay is valid; as well as In response to the first delay being valid, determining the timestamp basis for the ingress timestamp of the user plane data packet to be the first timestamp basis.

35. The method of claim 34, wherein determining whether the first delay is valid comprises: In response to the first delay, one of the following conditions is met: The first delay is negative; The first delay is below a first threshold; or the first delay is above a second threshold, determining that the first delay is invalid; and In response to the first delay being above the first threshold and below the second threshold, the first delay is determined to be valid.

36. The method of claim 35, wherein the first threshold and the second threshold are predetermined or derived by the 5GS.

37. The method of claim 31 , wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a second delay for the user plane data packet in the 5GS based on the second GM clock, wherein the second delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the second GM clock; determining whether the second delay is effective; as well as In response to the second delay being valid, determining the timestamp basis for the ingress timestamp of the user plane data packet to be the second timestamp basis.

38. The method of claim 31 , wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: The timestamp basis is determined based on a clock indicator in the ingress timestamp.

39. The method of claim 31 , wherein determining the timestamp basis for the ingress timestamp of the user plane data packet comprises: determining a first delay for the user plane data packet in the 5GS based on the first GM clock, wherein the first delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the first GM clock; determining a second delay for the user plane data packet in the 5GS based on the second GM clock, wherein the second delay is associated with: the ingress timestamp of the user plane data packet; and a reception time of the user plane data packet measured by the wireless device using the second GM clock; as well as In response to both the first delay and the second delay being valid, a more trusted delay is selected from the first delay and the second delay, and the timestamp basis for the ingress timestamp is determined based on the more trusted delay.

40. The method of claim 24, further comprising: receiving, from the wireless device, a second message including a GM clock switching indication, the GM clock switching indication including a clock indicator of the second GM clock; In response to the GM clock switching indication, determining that the active GM clock is switched from the first GM clock to the second GM clock; as well as Based on the second GM clock, user plane data packets are processed.

41. The method of claim 24, wherein the first network element comprises at least one of: UPF; or NW-TT.

42. A device for wireless communication, comprising a memory for storing computer instructions and a processor in communication with the memory, wherein when the processor executes the computer instructions, the processor is configured to implement the method according to any one of claims 1 to 41.

43. A computer program product comprising a non-transitory computer readable program medium having computer code stored thereon, the computer code, when executed by one or more processors, causing the one or more processors to implement the method according to any one of claims 1 to 41.

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