Control of time synchronization in wireless networks

Abstract

Controlling time synchronization in a wireless network. A method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station is disclosed. The method includes determining, at the UE, a requirement for time synchronization between the UE and the base station, generating a time synchronization control message for controlling a time synchronization process between the UE and the base station based on the determined requirement for time synchronization, and transmitting the time synchronization control message to the base station. A similar method can be performed at the base station with the base station transmitting the time synchronization control message to the UE.

Description

[Technical field]

[0001] The present invention relates generally to controlling time synchronization in wireless networks, and more particularly to controlling time synchronization between user equipment (UE) and base stations in a Radio Access Network (RAN) of a wireless network. [Background technology]

[0002] The uses of the Internet of Things (IoT) are expanding, and each use comes with certain constraints.

[0003] One of the applications of IoT is industry, e.g. production plants, power plants, etc., that use critical machines and multiple sensors and actuators. IoT or Industrial IoT (IIoT) allows for example to precisely track production lines by implementing the following functions (non-exhaustive list): predictive maintenance (avoiding production interruptions by identifying early signs of failure and proactively planning maintenance interventions), intelligent diagnostics (by recording operational data and repair history via sensors), optimization of production lines, optimization of production machines, etc.

[0004] With the development of 5G technology, a new generation of IoT is being developed that uses 5G as the access network. However, there is still a need to ensure that 5G networks are compatible with the time-sensitive applications implemented by IoT elements.

[0005] For that reason, accurate time synchronization is required in 5G networks. The challenging part for time synchronization in 5G systems is to ensure synchronization in the radio part (Radio Access Network (RAN)) of the 5G system with resource sharing and random time to access the medium. The time synchronization process in RAN is based on the transmission of a reference time by the base station (e.g., called gNB in ​​5G) to the user equipment (UE) in order to share a common time among all nodes in the same cell. Furthermore, to improve the accuracy of the time synchronization, a path delay compensation can be performed. This path delay compensation tries to compensate for the effect of signal propagation between the UE and the base station. Since the path delay is related to the UE-gNB distance, it will be different for each UE. The path delay compensation requires calculating the path delay between the UE and its associated gNB. The path delay calculation can be performed by various methods (e.g., Timing Advance, RTT-based) and is usually performed by the gNB. Thus, the obtained path delay value is applied to the reference time to compensate for the effect of the path delay. This additional feature is mandatory only for certain scenarios with strict delay requirements. For example, the 3GPP® consortium (RAN2 group) has agreed that for the synchronization budget of the air interface (Uu), the UE-UE synchronization budget can be ±145ns to ±275ns in a control-control scenario (machine-machine) and ±795ns to ±845ns in a power grid scenario. Furthermore, if the distance between the UE and the base station is short (e.g., less than 30 meters), the error introduced by the path delay can be considered negligible. It has been argued that path delay compensation is not mandatory in each situation (e.g., path or propagation delay compensation may be required in an indoor factory scenario, but not necessary for a power grid scenario). For example, 3GPP document R2-2006922 from Nokia suggests that the gNB (base station) should be able to enable and disable path delay compensation, but provides few details on how this can be achieved.

[0006] A time synchronization process based on the transmission of a reference time by the base station helps to ensure synchronization in the radio part of the 5G system, but it comes at a cost in terms of additional message exchanges, i.e. periodic transmission of the reference time from the base station to the UE and separate signals to estimate and convey the path delay, and in terms of additional processing for each node involved in the time synchronization process.

[0007] It is therefore desirable to provide improved time synchronization procedures and services between UEs and base stations (eg, in the RAN). Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station, comprising: determining a requirement for time synchronization between the UE and the base station; generating a time synchronization control message for controlling a time synchronization process between the UE and the base station based on the determined time synchronization requirement; transmitting the time synchronization control message to the base station; A method is provided that includes:

[0009] According to a second aspect of the present invention, there is provided a method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station, the method comprising the steps of: determining a requirement for time synchronization between the UE and the base station; generating a time synchronization control message for controlling a time synchronization process between the UE and the base station based on the determined time synchronization requirement; and transmitting the time synchronization control message to the UE.

[0010] According to a third aspect of the present invention, there is provided a method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station, comprising: receiving a time synchronization control message from the base station; Controlling a time synchronization process based on the received time synchronization control message; A method is provided that includes:

[0011] According to a fourth aspect of the present invention, there is provided a method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station, the method comprising the steps of: receiving a time synchronization control message from the UE; and controlling a time synchronization process based on the received time synchronization control message, wherein the controlling of the time synchronization process includes: Enabling the time synchronization process in the base station, or Disabling the time synchronization process in the base station, or Modifying the time synchronization process at the base station by enabling or disabling path delay compensation.

[0012] According to a fifth aspect of the present invention, there is provided a User Equipment (UE) for controlling time synchronization between the UE and a base station of a wireless network, as set forth in claim 30 of the accompanying claims.

[0013] According to a sixth aspect of the present invention, there is provided a base station for controlling time synchronization between a UE and a base station of a wireless network, as set forth in claim 31 of the accompanying claims.

[0014] According to a seventh aspect of the present invention, there is provided a time synchronization control message for controlling time synchronization between a UE and a base station of a wireless network, as set forth in claim 32 of the accompanying claims.

[0015] A node in a Radio Access Network receives a message that triggers the generation of a time synchronization control message, the time synchronization control message including a field that controls enabling / disabling of the time synchronization process, and the node transmits the message to control enabling / disabling of the time synchronization process.

[0016] Therefore, according to the present invention, signaling shall make it possible to enable and disable clock synchronization in the RAN (UE and gNB) only when necessary.

[0017] To optimize the use of resources in the RAN of a wireless network (such as a 5G network) (e.g., signaling between UEs and base stations and processing in the UEs and base stations), embodiments of the present invention are configured to enable time synchronization in the RAN only when necessary and disable time synchronization otherwise in order to reduce the amount of signaling and processing in the RAN. In some examples, path delay compensation (PDC) may also be enabled only when necessary and disabled otherwise. By using PDC only when necessary, this may provide an additional reduction in the amount of signaling and processing in the RAN and also avoid problems where the error introduced by PDC may be higher than the error without PDC.

[0018] The claims refer to, for example, time synchronization and PDC, enabling. The description refers to, in the description, enabling, and also refers to, starting or initiating. It will be understood that these terms are intended to be equivalent and interchangeable. Similarly, the claims refer to, and in the description, disabling, and also refers to, disabling and stopping. It will be understood that these terms are intended to be equivalent and interchangeable.

[0019] Further features of the invention are characterized by the other independent and dependent claims.

[0020] Any feature of one aspect of the invention may be applied to other aspects of the invention in any appropriate combination, in particular method aspects may be applied to apparatus / device / unit aspects and vice versa.

[0021] Furthermore, features implemented in hardware may be implemented in software and vice versa. Any references herein to software and hardware features should be interpreted accordingly. For example, according to another aspect of the present invention, there is provided a computer-readable storage medium storing at least one computer program including instructions that, when executed by a processing unit, cause the processing unit to perform a method according to any aspect or example above.

[0022] It should also be understood that specific combinations of the various features described and defined in any aspect of the present invention may be implemented and / or provided and / or used independently. [Brief description of the drawings]

[0023] Various aspects of the present invention will now be described, by way of example only, with reference to the following drawings, in which: [Figure 1] FIG. 1 is a block schematic diagram illustrating a 5G network interconnecting connected end devices. [Diagram 2] FIG. 2 is a block schematic diagram showing an example structure of a base station of the 5G network illustrated in FIG. [Diagram 3] FIG. 2 is a block schematic diagram showing an example structure of a user terminal of the 5G network illustrated in FIG. [Figure 4a] FIG. 4a is a flow diagram of a method for controlling time synchronization in a wireless network according to a first aspect of the present invention. [Figure 4b] FIG. 4b is a flow diagram of a method for controlling time synchronization in a wireless network according to a second aspect of the present invention. [Figure 5a]FIG. 5a is a flow diagram of an example method performed by a UE when triggered by the establishment of a PDU session according to one embodiment. [Figure 5b] FIG. 5b is a flow diagram of an example method performed by a UE when triggered by the release of a PDU session according to one embodiment. [Figure 5c] FIG. 5c is a flow diagram of an example method performed by a UE when triggered by a PDU session change, according to one embodiment. [Figure 5d] FIG. 5d is a flow diagram of an example method performed by a UE when triggered by a synchronization notification of an SMF according to one embodiment. [Figure 6a] FIG. 6a is a flow diagram of an exemplary method performed by a gNB when reference time information is transmitted in unicast mode according to one embodiment. [Figure 6b] FIG. 6b is a flow diagram of an exemplary method performed by a gNB when reference time information is transmitted in unicast mode and path delay is guaranteed by the gNB according to one embodiment. [Figure 6c] FIG. 6c is a flow diagram of an exemplary method performed by a gNB when reference time information is transmitted in broadcast mode according to one embodiment. [Figure 7a] FIG. 7a is a flow diagram of an exemplary method performed by a gNB when triggered by establishment of a PDU session, according to one embodiment. [Figure 7b] FIG. 7b is a flow diagram of an exemplary method performed by a gNB when triggered by the release of a PDU session, according to one embodiment. [Figure 7c] FIG. 7c is a flow diagram of an exemplary method performed by a gNB when triggered by a PDU session change, according to one embodiment. [Figure 7d] Figure 7d is a flow diagram of an exemplary method performed by a gNB when triggered by an SMF synchronization notification according to one embodiment. [Figure 8] FIG. 8 is a flow diagram of an exemplary method performed by a UE in response to a time synchronization control message received from a gNB, according to one embodiment. [Figure 9] FIG. 9 is a schematic diagram illustrating the system frame of a 5G network. [Figure 10] FIG. 10 is a schematic diagram illustrating the message flow between the UE and the base station for updating the time counter of the UE. [Figure 11] FIG. 11 is a schematic diagram illustrating an exemplary MAC CE signaling frame format used as a time synchronization control message according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Embodiments of the present invention are intended to be implemented in a wireless network, such as a fifth generation (5G) network, used to interconnect objects or terminals or end devices of a communication system 110 such as that shown in FIG.

[0025] The 5G network 100 includes a number of user equipments (UEs) 104a, 104b, also called mobile stations, that are wirelessly connected (as indicated by the dashed lines) to at least one base station 102 (gNB or gNodeB). The gNB 102 is connected to a wired core network 101, for example (e.g. using optical fiber) or wirelessly. The gNB 102 is part of the Radio Access Network of the 5G network 100 and uses radio frequencies to provide wireless connectivity to the UEs 104a, 104b.

[0026] In this 5G network 100, a common time reference is provided by a Grand Master clock (5G-GM) 103, which is defined in clause 5.27 of TS 23.501.

[0027] The 5G GM clock 103 may be connected to the core network 101 as shown in Figure 1, but may also be directly connected to a gNB or to one or more UEs 104a, 104b, such that devices connecting with the 5G GM clock 103 share a common time reference provided by the 5G GM clock 103 with other devices in the network.

[0028] According to some embodiments, the common time reference provided by the 5G GM clock 103 may be or may be based on a universal time reference, in which case the universal time reference may be obtained by the gNB 102 directly from a satellite system (not shown in FIG. 1).

[0029] As previously described, the 5g network 100 can be used to connect end devices 105a, 105b, and 105c, e.g., connected devices of an IoT network. The end devices can be, e.g., devices for industrial appliances, such as sensors and actuators. As can be seen in FIG. 1, the end devices 105a, 105b, and 105c are connected to the UEs 104a, 104b or to the core network 101 of the 5G network 100. The end devices 105b and 105c are connected to the UEs 104a, 104b through Device Side Time Sensitive Network (TSN) translators (DS-TT) 107b, 107c. The end device 105a is connected to the network core 101 of the 5G network 100 through a Network Side Time Sensitive Network (TSN) translator (NW-TT) 106. According to some embodiments, the end devices 105a, 105b, and 105c are wired connected to the DS-TT 107a, 107b or the NW-TT 106. According to some other embodiments, the end devices are directly connected to the UE and to the core network without using any translator device.

[0030] According to some embodiments, an end device and a UE may be integrated into one device.

[0031] In this way, the end devices 105a, 105b, and 105c share data using the 5G network. When implementing time-sensitive applications in IoT networks, accurate time synchronization between UEs is essential, especially in 5G networks. In other words, a Time Sensitive Network (TSN) that implements time-sensitive applications or services requires accurate time synchronization so that TSN nodes or elements have the same understanding of time and communication packets are delivered within a time budget.

[0032] The internal architecture of a base station, such as the gNB 102 of FIG. 1, is shown in FIG. 2 by way of a block schematic diagram.

[0033] The gNB 200 has a communication interface 205, such as a 5G New Radio (NR) interface 205, that enables it to communicate with the UEs 104a, 104b of the 5G network 100. The gNB may also have a number of different types of radio interfaces, such as LTE (4G) or other types of radio interfaces.

[0034] To communicate with the core network 101, the gNB also has a core network interface 204, as defined in clause 4.2 of TS 23.501.

[0035] Synchronization of the gNB with the 5G GM clock is handled by the 5G Time Synchronization Manager 203.

[0036] According to some embodiments, the 5G time synchronization manager 203 implements a time counter or timer (not shown) that is incremented by a local clock oscillator (not shown). The 5G time synchronization manager 203 continuously evaluates the clock difference between the time counter and the 5G GM clock. This evaluation can be done using the IEEE 1588 Precise Time Synchronization Protocol, implemented through the exchange of time synchronization packets with the 5G GM via the core network interface 204. The evaluated difference thus allows the 5G time synchronization manager 203 to determine a value to adjust its time counter.

[0037] According to some embodiments, the 5G time synchronization manager 203 continuously evaluates the clock difference between a time counter and a reference time received from a satellite system such as GPS.

[0038] In this way, the 5G time synchronization manager 203 provides the current time to the UE synchronization manager 201 based on its local time counter.

[0039] The UE synchronization manager 201 is configured to handle synchronization between the base stations of the 5G network 100 and the UEs 104a, 104b with the aim of synchronizing the time counters of all of these devices as accurately as possible.

[0040] To that end, the UE synchronization manager 201 may implement one or more mechanisms, such as one or more of the mechanisms described below in relation to Figure 10. The UE synchronization manager 201 is also configured to estimate and record a propagation delay between the gNB and each UE 104a, 104b for synchronization purposes.

[0041] The gNB further comprises a control manager 202 in which the gNB control protocols are implemented. The control protocols include at least the following protocols: RLC (Radio Link Control, TS38.322), PDCP (Packet Duplication Control Protocol, TS38.323), RRC (Radio Resources Control, TS38.331) and NAS (Network Access Stratum, TS24.501). Thus, the control manager 202 handles the generation of protocol packets that are exchanged with the core network 101 and the UEs via the core network interface 204 and the 5G NR interface 205, respectively.

[0042] The elements of gNB200 described above may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code via a computer-readable medium and executed by a hardware-based processing unit. The processing unit (not shown) may be a single processor or may include two or more processors that perform the processing necessary for the operation of gNB200. The number of processors and the allocation of processing functions to the processing units are a design matter for those skilled in the art.

[0043] The internal architecture of a UE, such as the UEs 104a, 104b of FIG. 1, is shown in FIG. 3 by way of a block schematic diagram.

[0044] The UE 300 has a communication interface 305, such as a 5G NR interface 305, through which the UE 300 can communicate with the gNBs 200, 102. The UE 300 may have several different types of radio interfaces, such as LTE (4G) or other types of radio interfaces.

[0045] Synchronization of the UE with the 5G GM clock is handled by the 5G Time Synchronization Manager 303.

[0046] According to some embodiments, the 5G time synchronization manager 303 implements a time counter or timer (not shown) that is incremented by a local clock oscillator (not shown). The 5G time synchronization manager 303 may correct or change the time counter when it receives a time counter calibration from the gNB synchronization manager 301 over the 5G NR interface 305.

[0047] Indeed, the gNB synchronization manager 301 stores the parameters necessary for synchronization provided by the gNB 102 and determined by the UE synchronization manager 201 of the gNB 102. Furthermore, the gNB synchronization manager 301 is also configured to evaluate and record the propagation delay between the UE 300 and the gNB 102.

[0048] A register in the UE 300 (which may be part of the gNB synchronization manager 301 or the 5G time synchronization manager 303) may have a RAN synchronization flag or field to indicate the current state of time synchronization in the UE 300 (i.e., RAN synchronization state). It may also have a RAN PDC flag or field to indicate the current state of PDC in the UE 300 (i.e., PDC state). When the RAN synchronization flag is set to "on", this corresponds to the RAN synchronization state in the UE 300 when the time synchronization process is in operation and the UE is performing operations according to the enabled time synchronization process (e.g., acquiring a reference time, etc.). When the RAN synchronization flag is set to "off", this corresponds to the RAN synchronization state in the UE 300 when the time synchronization process is inactive (i.e., disabled) and not used in the UE 300. When the RAN PDC flag is set to "on", this corresponds to the PDC state in the UE 300 when the PDC is in operation and the UE is performing operations for PDC (e.g., acquiring PDC information and calculating a path delay value, etc.). When the RAN PDC flag is set to "off", this corresponds to the PDC state in the UE 300 when the PDC is inactive (disabled) and not used in the UE 300. The 5G time synchronization manager 303 in the UE 300 may set the RAN synchronization flag and the RAN PDC flag in the registers. As described below, each time a time synchronization control message is sent to change the time synchronization and / or PDC state, the 5GS time synchronization manager 303 changes the state (RAN PDC state and / or RAN synchronization state) in the UE accordingly.

[0049] The UE 300 further comprises a control manager 302 in which the gNB control protocols are implemented. The control protocols include at least the following protocols: RLC (Radio Link Control, TS38.322), PDCP (Packet Duplication Control Protocol, TS38.323), RRC (Radio Resources Control, TS38.331), and NAS (Network Access Stratum, TS24.501). The control manager 302 handles the generation of protocol packets that are exchanged with the gNBs 200, 102 via the 5G NR interface 305.

[0050] The elements of the UE 300 described above may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code via a computer-readable medium and executed by a hardware-based processing unit. The processing unit (not shown) may be a single processor or may have two or more processors that perform the processing necessary for the operation of the UE 300. The number of processors and the allocation of processing functions to the processing units are a design matter for those skilled in the art.

[0051] Data exchanged between the gNBs and UEs of the gNB and network 100 via the 5G NR interfaces 205, 305 conforms to the frame format specified by the 3GPP NR PHY and MAC protocols, as defined in clauses 5 and 6 of TS38.300.

[0052] The exchanged frames, hereafter referred to as system frames, are organized in time and have a structure as shown in FIG.

[0053] The system frames follow one another in time, each system frame having a duration of 10 ms.

[0054] The system frames may be numbered using a system frame number (SFN), also called the system frame index. As can be seen in FIG. 9, the first system frame numbered #0 is followed by system frames #1, #2, and #3. As shown in FIG. 9, the numbering of the system frames may be done incrementally. In other words, every 10 ms, the system frame number is incremented, going from 0 to 1023, and when it reaches 1023, the numbering starts again at 0.

[0055] Thus, the gNB numbers the system frames using the SFN. The SFN is signaled to the UE using a System Frame Synchronization Signal. The System Frame Synchronization Signal is periodically transmitted from the gNB to the UE by signaling the 6 most significant bits of the so-called MIB (Master Information Block) field in the transmitted system frame and the 4 restart bits of the so-called PBCH field in the transmitted system frame.

[0056] Each system frame consists of 10 subframes ranging from 0 to 9.

[0057] Each subframe has a flexible number of slots, for example up to 64 slots. Each slot contains several Orthogonal Frequency Division Multiplexing (OFDM) slots, resulting in a maximum of 14 OFDM slots.

[0058] In this way, the system frame constitutes a common reference for the UE and the gNB. Thus, the system frame of a particular SFN is used for conventional adjustment of the time counter of a UE (such as UE 300).

[0059] A conventional adjustment of a time counter in a UE (such as UE 300) is shown in FIG.

[0060] Conventional time counter adjustment involves sending a reference time value (T R ) The reference time value corresponds to the transmission time of the system frame used as a reference.

[0061] After receiving a request from the UE for a reference time value for updating the time counter, or autonomously, the gNB selects a future reference system frame during which the gNB forces the UE to update its time counter with the reference time value provided by the gNB.

[0062] The reference time value may, for example, be the intended start or end time of transmission of a reference system frame by the gNB.

[0063] According to some embodiments, the reference time value is a planned or intended value of a time counter of the gNB that corresponds to the intended start or end transmission time of a reference system frame by the gNB.

[0064] As can be seen in FIG. 10, the reference time is - The current time of the gNB's time counter, which is continuously synchronized with the 5G GM clock thanks to the Synchronization Manager 203, - a period T representing the delay (in time counter units) that the gNB waits before transmitting a reference system frame to the UE; is equal to the sum of

[0065] According to some embodiments, the reference time may be, for example, - current time of the gNB's time counter synchronized to the 5G Grand Master clock thanks to the Synchronization Manager 203; - the remaining time before the start of the next system frame. Since a new system frame occurs every 10 ms, the remaining time can be obtained using an alarm counter set to 10 ms for each system frame start; and - 10ms x (referenceSFN-nextSFN), where referenceSFN is the SFN of a specified reference system frame and nextSFN is the SFN of the next system frame. Note that referenceSFN can be nextSFN. In this case, the reference time is calculated just before the transmission of the reference system frame and is included in the reference system frame, which is the case when SIB9 messages are used. Usually, referenceSFN refers to a future reference system frame, i.e. referenceSFN-nextSFN>0. may be determined by the gNB as the sum of

[0066] And the reference time T R and an indication of a reference system frame number, e.g., referenceSFN, is provided to the UE. Both of these elements may be transmitted together or separately.

[0067] According to some embodiments, the gNB may R An information element (referenceTimeInfo IE) including the referenceSFN and the referenceSFN is prepared. The referenceTimeInfo IE is then encapsulated in a System Information (SI) or Radio Resource Control (RRC) message, such as an SIB9 or DLInformationTransfer message.

[0068] The DLInformationTransfer message is transmitted prior to the reference system frame, as shown in FIG.

[0069] The SIB9 type reference system frame is a reference time T R Therefore, no other messages related to the reference system frame are transmitted first by the gNB.

[0070] Therefore, as shown in FIG. 10, when a message with reference time information is broadcast, the gNB transmits the message to the requesting UE or to multiple UEs.

[0071] When the DLInformationTransfer message is sent, later, a reference system frame is generated by the gNB when its time counter is equal to the reference time, and the reference system frame is sent to the UE (or to multiple UEs if the reference time information is broadcast).

[0072] When a reference system frame is detected by the UE based on the referenceSFN, the UE (its managers 301 and 302) that have previously received the reference time (or obtain the reference time from the SIB9 reference system frame) sets its time counter to the reference time.

[0073] In the particular case of SIB9, the reference time corresponds to the ending boundary of the system frame.

[0074] However, there is a delay between the moment the gNB transmits a reference system frame and the moment the UE receives it, as shown by the timing difference labeled "Error" in Figure 10. This delay, also called the propagation delay or path delay, represents the time of propagation of the wireless signal between the UE and the gNB.

[0075] Therefore, the above described synchronization mechanism is based on the assumption that the UE can ignore the propagation delay of the reference system frame used as a trigger for setting its local time counter to the reference time provided by the gNB.

[0076] It can be seen that when the UE sets the time counter with the reference time provided by the gNB, a persistent synchronization error occurs due to the propagation delay, which may not be compatible with some applications (e.g., time-sensitive applications), especially those that require accurate timestamps of the arrival or departure times of some packets. Indeed, the persistent synchronization error due to the propagation delay may result in errors in the timestamps of those packets, which may not be compatible with the requirements of time-sensitive applications.

[0077] To overcome this disadvantage, one of many different path or propagation delay compensation (PDC) processes or mechanisms or procedures may be used to correct or compensate for this error in the adjustment of the UE's conventional time counter. One example of a PDC process includes the Timing Advance mechanism defined in TS38.211, clause 4.3.1. Another example is the Round Trip Time (RTT) approach.

[0078] A Timing Advance (TA) mechanism may be used to allow the UE to calculate the propagation delay, as shown in FIG.

[0079] Essentially, the TA mechanism is used by the gNB to control the timing of the UE's uplink frames. To do so, the gNB provides the UE with a TA command, which includes several parameters. These parameters, including the TA parameter, define the time T before the next gNB downlink frame at which the UE should start transmitting its uplink frame. TA This makes it possible to determine

[0080] The TA command is provided by the gNB to the UE over the 5G NR interface. For its transmission, the TA command is encapsulated in various types of Protocol Data Units (PDUs), among the following types, all defined in TS38.321: - a Random Access Response MAC Protocol Data Unit (PDU), as defined in TS 38.321 subclause 6.1.5, 6.2.3, and 6.2.3a; and – Absolute Timing Advance Command MAC Control Element or Timing Advance Command MAC Control Element as defined in TS 38.321 subclause 6.1.3.4 and subclause 6.1.3.4a.

[0081] Depending on the type of TA command, the parameters provided are of different nature: In case of Random-Access Response and Absolute Timing Advance Command, the absolute value of the parameter TA is provided; In case of Timing Advance Command, only the modification of the previously provided TA is included in the TA command.

[0082] Thus, according to some embodiments, the TA command is then generated at the instant T TA The UE may include an absolute value of TA in the TA command field, which is used to determine: T TA =(N TA +N TA,offset )×T C , where: N TA =TA×16×64 / 2 μ , and μ is the subcarrier spacing setting Δf = 2μ × 15kHz defined in Table 4.2-1 of Section 4.2 of TS38.211, N TA,offset is a fixed offset used to calculate the timing advance, T C is the base time unit for New Radio defined in TS38.211, section 4.1.

[0083] According to another embodiment defined in TS 38.213, clause 4.2, the TA command is executed with the previously provided TA value (TA previous ), T.A. correction In this case, the previous T TA The adjustment to be applied to (TA correction -31)×16×64 / 2 μ is equal to.

[0084] Thus, to control the UE's uplink timing, the gNB sends a TA command in a control message to the UE in the network. The TA command is specific to a particular UE since it reflects the propagation delay of the given UE. The UE then determines the T TA Calculate.

[0085] Interestingly, the parameter N TA It can be seen that N is proportional to the round trip time between the gNB and the UE. TA can help determine the propagation delay, assuming that the propagation delay is symmetric. For example, the propagation delay between the UE and the gNB is (N TA ×T C ) / 2.

[0086] In this way, when the UE receives the TA command, it may be able to determine the propagation delay during transmission of the TA command, and the calculated propagation value may be used in adjusting the time counter as described above with the reference time and reference system frame transmitted by the gNB.

[0087] As can be seen in Fig. 10, a first TA command is received from the gNB and used by the UE to calculate the propagation delay. Then, when the reference system frame is detected, the time counter is adjusted to the reference time T R For example, the time counter is set using T R It is set to a value corresponding to the plus propagation delay.

[0088] As can be seen from the above discussion, in order to ensure accurate time synchronization for time-sensitive communications (TSC), a time synchronization process based on periodic transmission of a reference time from a gNB to a UE is used in a communication network implementing a time-sensitive application, including, for example, a wireless network as an access network (such as the 5G network 100 described above with reference to FIG. 1). To improve the accuracy of the time synchronization process, a path delay compensation (PDC) may be performed based on a dedicated signal exchange between the UE and the gNB to estimate and convey a path delay value. Thus, the time synchronization process and the PDC require radio and processing resources in the RAN of the 5G network.

[0089] As mentioned above, path delay compensation (PDC) requires the calculation of the path delay between a UE and its associated gNB. The path delay is related to the UE-gNB distance and is therefore different for each UE. The path delay calculation can be performed according to various methods (e.g. Timing Advance, RTT-based) and is usually performed by the gNB. The obtained path delay value is then applied to the reference time to compensate for the effect of the path delay. The path delay value may be applied by the gNB, i.e. the reference time is modified with the path delay value before the transmission of the reference time to the UE, in which case the modification of the reference time by the gNB is called pre-compensation. Otherwise, the path delay value is transmitted to each UE individually and applied by the UE. For the pre-compensation case, the reference time is potentially different for each UE and is therefore transmitted in a unicast message. If the UE applies the path delay, the reference time is the same for all UEs of the cell and can be transmitted in a broadcast or multicast message. For example, in some implementations of wireless networks where the UE and gNB are separated by a short distance (such as less than 30 meters), it may not be required, and indeed may be undesirable, to use PDC, e.g., the error caused by PDC may be higher than the error without PDC.

[0090] To optimize resource usage (e.g., signaling between UEs and base stations and processing therein) in a RAN of a wireless network (such as the 5G network 100 described above with reference to FIG. 1), embodiments of the present invention are configured to enable time synchronization in the RAN only when necessary and disable time synchronization in other cases to reduce the amount of signaling and processing in the RAN. In some examples, path delay compensation (PDC) may be enabled only when necessary and disabled in other cases. By using PDC only when necessary, this can provide an additional reduction in the amount of signaling and processing in the RAN and also avoids issues where errors due to PDC can be higher than errors without PDC.

[0091] 4a illustrates steps of a method 400 for controlling time synchronization in a wireless network (such as the 5G network 100 described above with reference to FIG. 1) including a UE and a base station. The method 400 may be performed in a UE (such as the UE 104a, 104b, 300 described above) or in a base station (such as the base station 102, 200 described above). For example, for a UE, a gNB synchronization manager 301 in the UE may perform the method 400. For a base station or a gNB, a UE synchronization manager 201 may perform the method 400.

[0092] Briefly, the method 400 includes, in step 402, determining a time synchronization request between the UE 104a, 104b, 300 and the base station 102, 200. In step 404, a time synchronization control message for controlling a time synchronization process or service between the UE and the base station (e.g., for controlling a time synchronization process in a RAN including the UE and the base station) is generated based on the determination in step 402. The time synchronization control message may include information for controlling an enablement of the time synchronization process, or for controlling a disablement of the time synchronization process, or for changing or modifying the time synchronization process when the time synchronization is in an operational state (e.g., for changing or modifying an option or additional function of the time synchronization process). The option or additional function may include a path delay compensation (PDC) of the time synchronization process, whereby a change in the time synchronization process may include enabling or activating the PDC, or disabling or deactivating the PDC. The option or additional function may also include various types or procedures of PDC (e.g., TA, RTT, pre-compensation, etc., some of which are described above). Thus, the time synchronization control message may include information for controlling activation of a time synchronization process with a specific type of PDC such that the time synchronization process is activated or activated with a specific type of PDC (e.g., TA, RTT, pre-compensation, etc.), or for changing the time synchronization process to use a different type of PDC. Also, the options or additional features may include one or more of different types of transport messages for transferring reference time information, different periodicities for the transmission of reference time information by the base station, and different periodicities for the transmission of PDC information by the base station. Thus, the time synchronization control message may include information for controlling activation of a time synchronization process with one or more features of the time synchronization process, and information for controlling activation of a PDC with one or more specific features for a PDC, if a PDC is required.If the time synchronization process is already in operation, the time synchronization control message may include information for modifying the time synchronization process to use a different function for the time synchronization process, and / or for enabling or disabling PDC with a specific PDC function, or for deactivating PDC, and / or for modifying PDC to use a different function for PDC when PDC is already in operation. In step 406, the time synchronization control message is sent to the base station (if the method 400 is performed in the UE) or to the UE (if the method is performed in the base station). Also, if the method is performed in the UE, the UE may enable, disable, or modify the time synchronization process in the UE in response to determining a request for time synchronization. Also, if the method is performed in the base station, the base station may enable, disable, or modify the time synchronization process in the base station in response to determining a request for time synchronization.

[0093] The time synchronization process is based on the base station transmitting a reference time to the UE (and potentially other UEs or other nodes in the RAN) to achieve time synchronization between the UE (and potentially other UEs or other nodes in the RAN) and the base station (e.g., gNB) when the base station and the UE share a common time or have the same understanding of time. Options or additional features of the time synchronization process, such as path delay compensation, may be enabled or operational for use in the time synchronization process, or may be disabled or inoperative based on a time synchronization request. When the time synchronization process is activated or operational or enabled in the base station, the base station transmits (e.g., periodically) reference time information to the UE (e.g., in an RRC or SIB9 message) to synchronize the time at the UE and the base station. In one example, the base station may also transmit path delay compensation (PDC) information if path delay compensation is also required to improve the accuracy of the time synchronization process. When the time synchronization process is disabled or ineffective in the base station, the base station does not transmit reference time information to the UE, thereby reducing the amount of signaling between the base station and the UE and the amount of processing in the UE and the base station. Similarly, when the PDC is disabled or ineffective in the base station, the base station does not transmit PDC information to the UE, thereby reducing the amount of signaling between the base station and the UE and the amount of processing in the UE and the base station. When the time synchronization process is activated or in operation or enabled in the UE, the UE operates to obtain the reference time information transmitted from the base station, process the received reference time information, and update the time counter of the UE. In one example, when path delay compensation is also required to improve the accuracy of the time synchronization process, the UE may operate to obtain path delay compensation (PDC) information transmitted from the base station, process the received PDC information, and update the time counter of the UE to compensate for the path or propagation delay. When the time synchronization process is disabled or turned off in the UE, the UE does not perform operations to obtain and process reference time information transmitted from the base station, thereby reducing the amount of signaling between the base station and the UE, and also the amount of processing in the UE and the base station.Similarly, when the PDC is disabled or inactive in the UE, the operation of obtaining and processing the PDC information from the base station is not performed, which reduces the amount of signaling between the base station and the UE, and also the amount of processing in the UE and the base station. Thus, by controlling the time synchronization process in the UE and the base station based on the determined time synchronization requirement, accurate time synchronization can be achieved when needed, while ensuring that radio resources and processing resources are used only when needed, rather than continuously. This can help reduce the amount of radio resources and processing resources required in the RAN to achieve accurate time synchronization.

[0094] As indicated by the dashed lines in Fig. 4a, the method 400 may further include receiving a message for triggering generation and / or transmission of a time synchronization control message in step 408. And, the determining in step 402 may include determining a request for time synchronization between the UE and the base station based on the received message. In one example, the message may be received from a core network entity of the wireless network.

[0095] The message may include a duration value corresponding to the duration for which the time synchronization process is operational. In response to receiving the message, the UE or gNB may send a time synchronization control message to enable the time synchronization process, and then, upon expiration of the duration, send a time synchronization control message to disable the time synchronization process. This means that the UE or gNB can automatically disable the time synchronization process without requiring a further message from the core network entity to disable the time synchronization process.

[0096] The message from the core network entity may include information to indicate a request for time synchronization in the RAN (i.e., between the UE and the base station).

[0097] For example, the message may be a synchronization notification sent from a Session Management Function (SMF) of a core network of a wireless network (such as the core network 101 of the 5G network 100 in FIG. 1). If the method 400 is performed in a UE, the synchronization notification may include information or a command (such as Port Management Information Container (PMIC) information) to enable or disable a Device Side TSN translator (DS-TT) function (such as DS-TT 107b, 107c in FIG. 1). If the command is to enable DS-TT, the UE determines that time synchronization is required. In this case, the time synchronization process may be activated or enabled. If the command is to disable DS-TT, the UE determines that time synchronization is not required. In this case, the time synchronization process may be deactivated or disabled. If the method 400 is performed in a base station, the message may be a synchronization notification including an information element (IE), such as an AN_Synchronization_Notification IE, described below with reference to FIG. 7d, to indicate a request for time synchronization between the UE and the base station. For example, a first information element indicates the identity of the UE (or all of the UEs in the base station's cell, if appropriate) to be configured, a second information element indicates whether time synchronization processing should be enabled or disabled, and a third information element indicates whether path delay compensation should be enabled or disabled.

[0098] In another example, the message sent from a core network entity such as an SMF may be a message associated with a Packet Data Unit (PDU) session between the UE and the base station and may include one or more of: QoS information for indicating a Quality of Service (QoS) required for the PDU session; or session identity information for indicating whether the PDU session is a PDU session for Time Sensitive Communication (TSC) for a Time Sensitive Network (TSN) application; or Single-Network Slice Selection Assistance Information (S-NSSAI) for indicating whether the PDU session is linked to a network slice for TSC. For example, as described in more detail below with reference to Figures 5a-5c and 7a-7c, the message may be a PDU SESSION ESTABLISHMENT ACCEPT message or a PDU SESSION MODIFICATION COMMAND message when received at the UE, and a PDU SESSION RESOURCE SETUP message or a PDU SESSION RELEASE REQUEST message or a PDU SESSION RESOURCE MODIFY REQUEST message when received at the gNB. The QoS information may include QoS flow description information, such as a 5QI value (described in more detail below), indicating a guaranteed bit rate (GBR) and a packet delay budget that defines the maximum time a packet shall spend in the network between the UE and the N6 termination point in the UPF (5.7.3.4 of TS 23.501). Furthermore, to derive the packet delay budget applied to the air interface (between the UE and the gNB), the fixed delay for the delay between the UPF terminating N6 and the 5G-AN (gNB) should be subtracted from the given packet delay budget (PDB). Some examples of fixed delays are given in the notes associated with Table 5.7.4-1 of TS 23.501.If the QoS information indicates that the PDU session requires a QoS that meets a predetermined time delay criterion or threshold, such as having a delay-critical guaranteed bit rate (GBR), the PDU session may be detected as a PDU session for a TSC that requires time synchronization. If the QoS information indicates that the PDU session requires a QoS that meets a second (stricter) time delay criterion or threshold, such as having a delay-critical guaranteed bit rate (GBR) with a very short or low packet delay budget, or a very short or low (e.g., very short or low may be less than 10 ms or less than 5 ms) packet delay budget applied to the radio interface between the UE and the gNB, the PDU session may be detected as a PDU session for a TSC that requires time synchronization and PDC. The session identity information may include a session identity or identifier that is associated with the PDU session once it is determined that the PDU session is for a TSC.

[0099] In another example (not shown in FIG. 4a), the method may further include detecting a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) for a Time Sensitive Network (TSN) application. And, the determining in step 402 may include determining the request for time synchronization based on the request for time synchronization of the detected PDU session for the TSC. In another example, the method may include detecting a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) and determining a change to the PDU session for the TSC. The determining in step 402 may include determining that the request for time synchronization includes determining a change to the request for time synchronization based on the change to the PDU session for the TSC. In both of these examples, detecting a PDU for the TSC may include determining a required Quality of Service (QoS) for the PDU session and detecting a PDU session for the TSC if the requested Quality of Service meets a predetermined time delay criterion (e.g., as described above), or determining session identity information associated with the PDU session and detecting a PDU session for the TSC if the session identity information indicates that the PDU session is for the TSC (e.g., as discussed above with respect to session identity or identifier).

[0100] In one example, the time synchronization control message includes at least one field for controlling the time synchronization process. For example, the time synchronization control message may include a first field for indicating whether the time synchronization process is active or inactive (or enabled or disabled), and may include a second field for indicating whether the path delay compensation is active or inactive (or enabled or disabled). In one example, the time synchronization control message is a MAC Control Element (MAC CE) having a time synchronization field or flag (e.g., bit 8) for indicating whether the time synchronization process is active or inactive, and a path delay compensation (PDC) field or flag (e.g., bit 7) for indicating whether the path delay compensation is active or inactive. In another example (where the UE transmits the time synchronization control message), the time synchronization control message is an RRC message, such as a UE Assistance Information message with an Information Element (IE) for providing information for controlling the time synchronization process, such as time synchronization and PDC configuration and activation information. The IE of the UE Assistance Information message may include a refTime-activation field indicating whether the time synchronization process is activated or deactivated, and a pdc-Activation field indicating whether the path delay compensation is activated or deactivated. In another example, the time synchronization control message may be an RRC reconfiguration message. The RRC reconfiguration message may include a RAN_synchronization field for indicating whether the time synchronization process is activated or deactivated, and a RAN_pdc field indicating whether the PDC is activated or deactivated.A time synchronization control message sent by the UE (whether it is a MAC CE message or an RRC message such as a UE AssistanceInformation message or an RRC reconfiguration message) may include one or more additional fields, each having one or more additional fields indicating the particular UE's preferences / configuration for time synchronization. For example: the additional field may indicate a type of transport message (unicast or broadcast) that is preferred for transferring the reference time information from the gNB to the UE; the additional field may indicate a required or preferred periodicity of the transmission of the reference time by the gNB (e.g., a value in ms or only once); the additional field may indicate a type of PDC supported by the UE (pre-compensation, RTT, TA, extended TA, etc.); the additional field may indicate a periodicity of the transmission of the PDC information by the gNB (e.g., a value in ms or on-demand); the additional field may indicate a scenario or environment in which the UE is operating, such as a control-control scenario or a power grid scenario or other operating scenario in which the UE is used; the additional field may indicate whether the UE should follow a timing error (Te-preference); the additional field may indicate a preferred TA granularity value (value of steps of correction of TA); etc. A time synchronization control message transmitted by the gNB (whether it is a MAC CE message or an RRC message) may include one or more additional fields, each of which has one or more additional fields indicating a specific configuration for time synchronization. For example: An additional field may indicate the type of PDC (pre-compensation, RTT, TA, extended TA, etc.) used by the gNB for time synchronization processing. Details of example time synchronization control messages are provided below.

[0101] 4b illustrates steps of a method 420 for controlling time synchronization in a wireless network (such as the 5G network 100 described above with reference to FIG. 1) including a UE and a base station. The method 420 may be performed by a UE (such as the UE 104a, 104b, 300 described above) or in a base station (such as the base station 102, 200 described above). For a UE, for example, a gNB synchronization manager 301 of the UE may perform the method 420. For a base station or a gNB, a UE synchronization manager 201 may perform the method 420.

[0102] Briefly, in step 422, a time synchronization control message is received. Then, in step 424, a time synchronization process is controlled according to the received time synchronization control message. When the method 420 is performed in a UE, the UE receives a time synchronization control message from a base station, and the UE controls a time synchronization process in the UE according to the received time synchronization control message. When the method 420 is performed in a base station, the base station receives a time synchronization control message from the UE, and the base station controls a time synchronization process in the base station according to the received time synchronization control message. Controlling the time synchronization process in the UE or base station may include starting or stopping (or enabling or disabling) the time synchronization process in the UE or base station, respectively, and may also include modifying the time synchronization process (e.g., changing options or additional features of the time synchronization process), such as starting or stopping a path delay compensation (PDC) in the UE and base station, respectively, when the time synchronization process is already in an operating state. In this way, the time synchronization in the RAN is started or enabled only when necessary, and is stopped or disabled in other cases, which helps to reduce the amount of signaling and processing in the RAN.

[0103] As mentioned above, according to an embodiment of the present invention, a time synchronization control message can be transmitted from a UE to a base station (e.g., a gNB) or from a base station (e.g., a gNB) to a UE. Further details of the present invention are provided below.

[0104] In the first embodiment, a UE (e.g., UE 104a, 104b in FIG. 1, UE 300 in FIG. 3 - for simplicity, hereinafter, reference number 300 is used for UE) determines a request for time synchronization between the UE and a base station (e.g., gNB 102 in FIG. 1 and gNB 200 in FIG. 2 - for simplicity, hereinafter, reference number 200 is used for base station or gNB), and generates a time synchronization control message accordingly. For example, the UE 300 determines whether time synchronization is required or whether a change (such as activation or deactivation of PDC) to an already operating time synchronization process is required. The UE 300 may receive a message that triggers the generation of a time synchronization control message. The time synchronization control message includes information for controlling the time synchronization process, such as activation or deactivation of the time synchronization process, or for changing the operating time synchronization process (e.g., changing an option or additional function of the time synchronization process), such as activation or deactivation of path delay compensation. For example, the time synchronization control message may include a field for controlling the activation / deactivation of a time synchronization process in the gNB 200. The time synchronization process is based on the transmission of a reference time by the gNB 200 to the UE 300 in order to share a common time among all nodes in the same cell. Furthermore, a path delay compensation may be performed to improve the accuracy of the time synchronization.

[0105] In one example, determining the request for time synchronization between UE300 and gNB200 may be based on detecting a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) for TSN applications and determining a request for time synchronization for the PDU session for TSC (e.g. during a PDU session establishment sequence), or based on detecting a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) for TSN applications and determining a change to the TSC PDU session, such as during a PDU session release procedure or a PDU session modification procedure.

[0106] Reference is now made to FIG. 5a, which illustrates a flow diagram of an exemplary method according to an embodiment of the present invention, executed in a UE 300, triggered by the establishment of a PDU session.

[0107] First, in step 501a, the UE 300 requests the establishment of a PDU session as described in section 6.4.1 of TS 24.501. The PDU SESSION ESTABLISHMENT REQUEST is sent from a core network entity, such as a Session Management Function (SMF), which is part of a core network (such as the 5G core network 101 in FIG. 1). This PDU SESSION ESTABLISHMENT REQUEST message contains all the information required to establish a PDU session. In step 502a, a determination is made as to whether this PDU session has some specific time synchronization requirements in terms of time synchronization (i.e., whether or not it requires or requires time synchronization, and possibly whether or not it uses PDC if it requires or requires time synchronization). For example, in step 502a, a determination is made as to whether a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) is detected. In the context of a Time Sensitive Network application, a 5G system is aggregated to a TSN system as a TSN bridge. Some specific entities, namely, DS-TT (Device Side TSN Translator 107b, 107c) and NW-TT (Network Side TSN Translator 106), are responsible for the translation between the TSN domain and the 5G domain. The DS-TT is associated with the UE specific to the TSN application (e.g., attached or embedded in the UE 300), and the NW-TT is attached to the User Plane Function (UPF) in the core network. The presence of the DS-TT in the UE 300 is related to the Time Sensitive Communication (TSC), and therefore it can be deduced that there is a need for time synchronization for the TSC. To configure the DS-TT, the 5G core network uses a Port Management Information message, which is a control message that contains information for configuring the DS-TT.Therefore, if a DS-TT is linked to the UE 300, the PDU SESSION ESTABLISHMENT REQUEST message includes DS-TT parameters: the TPMIC (Transfer of Port Management Information Containers, clause 9.11.4.12 of TS 24.501) bit is set in the 5GSM Capability Information Element and the Port Management Information Container (9.11.4.27) is placed. Therefore, if the PDU SESSION ESTABLISHMENT REQUEST includes DS-TT parameters, the RAN will also require time synchronization. In other words, in an exemplary implementation, if the UE 300 is linked or associated with a DS-TT, at the time of the request for the establishment of the PDU session, the UE 300 includes the DS-TT parameters in the PDU SESSION ESTABLISHMENT REQUEST message and detects that the requested PDU session is for a TSC and therefore time synchronization between the UE 300 and the gNB 200 of the RAN is required.

[0108] The PDU SESSION ESTABLISHMENT REQUEST also includes a PDU session identity or identifier used to identify the PDU session. This PDU session ID is present in all messages to control the PDU session. If the PDU session is classified with a need for time synchronization during step 502a, the UE 300 also associates the PDU session identity with the need for time synchronization. As a result, in the following PDU session procedures, the UE can know whether the session is classified with a need for time synchronization based only on the PDU session identity.

[0109] Otherwise, if time synchronization is not required (no branch in step 502a), the UE proceeds to end step 508a. In this case, since it was determined in step 502a that the PDU session does not require time synchronization, it is assumed that time synchronization is not operational and has not been previously activated since the messages sent as part of the PDU session establishment procedure are some of the first messages that data can be exchanged between the UE 300 and the gNB 200. In another example, if time synchronization is enabled by default in the RAN and is therefore operational when making the determination in step 502, the UE 300 may generate and send a time synchronization control message to the gNB 200 to inform the gNB that the UE does not require time synchronization and that time synchronization may be deactivated or disabled.

[0110] When the UE 300 determines its need for time synchronization, it shall inform the gNB 200 of the time synchronization request in order for the gNB 200 to configure and activate the time synchronization. Thus, when requesting the establishment of a PDU session, which is determined during step 502a to require or require time synchronization (yes branch in step 502a), the UE 300 creates or generates a time synchronization control message in step 503a. After creating or generating the time synchronization control message (step 503a), the UE 300 waits for a core network feedback on the establishment of the PDU session in order to determine whether the establishment of the PDU session is accepted (step 504a). In response to receiving a PDU SESSION ESTABLISHMENT ACCEPT message from the SMF of the core network (yes for step 504a), the UE 300 sends a time synchronization control message to its associated gNB 200 during step 506a and activates the time synchronization process during step 507a.

[0111] In other words, during step 507a, the UE 300 sets the RAN synchronization and RAN PDC states to "on" (e.g., the 5G Time Synchronization Manager 303 sets the RAN synchronization flag and the RAN PDC flag in the UE's register to "on" as described above) and tracks the reception of messages related to the reference time and possibly path delay compensation from the gNB. Otherwise, upon reception of a PDU SESSION ESTABLISHMENT REJECT (no branch in step 504a), the UE 300 deletes the time synchronization control message (step 505a) and ends the method (step 508a).

[0112] In another example implementation, the UE 300 may use the QoS parameters included in the PDU SESSION ESTABLISHMENT ACCEPT message to make a determination in step 502a as to whether the PDU session has some specific requirements in terms of time synchronization (i.e., whether it requests or requires time synchronization). For example, the determination may be made as to whether a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) has been detected. The UE analyzes the QoS flow description information element (9.11.4.12.1 of TS24.501) included in the PDU SESSION ESTABLISHMENT ACCEPT to check the 5QI parameter. For example, if the 5QI value corresponds to a delay-critical GBR (#82, #83, #84, #85) or other value indicating the need for time synchronization (new 5QI value), the UE 300 determines that there is a request or need for time synchronization (e.g., the PDU session is for TSC), determines the request for time synchronization, and sends the Radio Access A time synchronization control message is prepared to request the initiation of time synchronization processing in the RAN. The necessity of time synchronization can be determined if the PDU session is accepted with QoS parameters 5QI#82, #83, #84, or #85. The mapping of standardized 5QIs to QoS characteristics is described in Table 5.7.4-1 of 3GPP technical standard TS23.501. The smart grid scenario defined in the 3GPP consortium (RAN2 group) is similar to power distribution (5QI#85) and control-control is similar to individual automation (5QI#82 or #83) defined in the delay-critical GBR 5QI. One of the most important QoS characteristics of time sensitive communication is the packet delay budget (5.7.3.4 of TS23.501), which defines the maximum time a packet spends in the network between the UE and the N6 termination point in the UPF.Furthermore, a fixed delay for the delay between the UPF terminating N6 and the 5G-AN (gNB) should be subtracted from the given packet delay budget (PDB) to derive the packet delay budget applied to the air interface (between the UE and the gNB). An example of the fixed delay is given in the notes associated with table 5.7.4-1 of TS 23.501. For example, 5QI#85 may have a packet delay budget equal to 5 ms and may be considered as requiring time synchronization at the RAN level, and 5QI#3 may have a packet delay budget equal to 50 ms and may be considered as not requiring time synchronization at the RAN level. When the UE determines the need for time synchronization, it sends a signaling message (e.g., a time synchronization control message) to the gNB to initiate RAN time synchronization. For example, the need for time synchronization may be determined when a PDU session is accepted with a QoS parameter reflecting a packet delay budget value (or a packet delay budget applied to the radio interface between the UE and the gNB) that is below a threshold or time delay criterion (e.g., less than 10 ms or less than 5 ms).

[0113] The need for time synchronization may be determined for a Single Network Slice Selection Assistance Information (S-NSSAI) value having a Slice Service Type (SST) configured for Ultra Reliable Low Latency Communication (URLLC).

[0114] In another example implementation, the UE 300 may use the Single Network Slice Selection Assistance Information (S-NSSAI, section 9.11.2.8 of TS 24.501) included in the PDU SESSION ESTABLISHMENT ACCEPT message to make the determination in step 502a as to whether the PDU session has some specific requirements regarding time synchronization (requests or requires time synchronization). Network slices allow building several logical networks with different requirements on the same physical infrastructure. Identification of the network slice is performed using the S-NSSAI. The S-NSSAI (as defined in section 5.12.2.1 of TS 23.501) consists of two fields: Slice Service Type (SST), which is mandatory and refers to the expected behavior of the network slice in terms of features and services; and Slice Differentiator (SD), which is optional information complementing the slice / service type for differentiation between multiple network slices of the same slice / service type. Currently, five different values ​​of the service are standardized, as shown in Table 5.15.2.2-1 in TS 23.501. For example, to determine whether a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) is detected, the UE checks the S-NSSAI value. If the S-NSSAI value corresponds to a value indicating the need for time synchronization, the UE 300 determines that there is a request or need for time synchronization and prepares a time synchronization control message to request the activation of a time synchronization process in the Radio Access Network (RAN).The S-NSSAI indicating the need for time synchronization can be, for example, a new SST value for Time Sensitive Communication among the unused values ​​for the standardized SST values ​​(0 to 127); or it can be one SST value for a dedicated operator supported TSC service in the range (128 to 255) of operator specific values; or it can use a specific SD value to identify the current standardized service, for example SST value = 2 for Ultra Reliable Low Latency Communication with SD = 1 for the Time Sensitive addon. Knowledge of the specific value for Time Sensitive Communication can be standardized or shared during the preparation procedure (as described in clause 5.15 of TS 23.501), for example the registration of the UE to the core network.

[0115] In an alternative example to that shown in FIG. 5a, a time synchronization control message may be sent by UE300 to gNB200 immediately after it is generated or created in step 503a and before acceptance of the PDU session establishment (e.g., before acceptance of the PDU SESSION ESTABLISHMENT ACCEPT) to initiate a time synchronization process before the establishment.

[0116] In some cases, if a PDU session has a high priority, the probability of acceptance of the PDU session is high, and finally, if the PDU session is rejected (e.g., upon receipt of a PDU SESSION ESTABLISHMENT REJECT message), the UE 300 can send another time synchronization control message to stop or terminate the time synchronization process.

[0117] Reference is now made to FIG. 5b, which illustrates a flow diagram of an exemplary method performed by UE 300 when triggered by a PDU session release, according to an embodiment of the present invention.

[0118] First, in step 501b, UE 300 requests the release of a PDU session as described in section 6.4.3 of TS 24.501. The PDU SESSION RELEASE REQUEST is sent to the Session Management Function (SMF), which is a core network entity. The message mainly contains the reason for the release and the identity of the PDU session.

[0119] As explained above, a PDU session identity or identifier is used to identify a PDU session. Furthermore, during the establishment of a PDU session, the UE associates the need for time synchronization with the PDU session ID (step 502a in FIG. 5c). Thus, in step 502b, to check whether the PDU session requested for release is a PDU session with a need for time synchronization, the UE 300 uses the PDU session ID to verify whether the PDU session is flagged as having time synchronization required.

[0120] If the PDU session is identified as one that requires time synchronization (yes branch of step 502b), the UE 300 creates or generates a time synchronization control message to stop or terminate the time synchronization process in the RAN (503b).

[0121] Otherwise, if the session is not a session with time synchronization (no branch of step 502b), the UE proceeds to end step 508b. After creating or generating the time synchronization control message during step 504b, the UE 300 waits for feedback from the core network for PDU session release. If, upon receiving the PDU SESSION RELEASE REQUEST message and the PDU session ID, the SMF (core network entity) accepts the release of the PDU session, the SMF performs the PDU session release procedure requested by the network (as specified in clause 6.3.3 of TS 24.501), i.e., the SMF shall return a PDU SESSION RELEASE COMMAND to the UE 300, and the UE responds with a PDU SESSION RELEASE COMPLETE. As a result, upon receiving the PDU SESSION RELEASE COMMAND (yes branch in step 504b), the UE 300 considers the release accepted, and then the UE sends a time synchronization control message to the gNB associated with it (step 505b). Then, before disabling the time synchronization (step 506b), the UE checks whether other PDU sessions requiring time synchronization are always active. If there are no more active PDU sessions requiring time synchronization, the UE disables or terminates the time synchronization process in step 506b. In other words, the UE stops tracking the reception of messages related to the reference time and possibly path delay compensation from the gNB. Also, the state of RAN synchronization and RAN PDC is set to "off" (e.g., as described above, the 5G time synchronization manager 303 sets the RAN synchronization flag and the RAN PDC flag in the UE register to "off"). Otherwise, if at least one PDU session requiring time synchronization is always active, the time synchronization remains enabled or active.

[0122] Otherwise, upon receiving the PDU SESSION RELEASE REJECT (no branch in step 504b), the UE 300 deletes (507b) the time synchronization control message and ends the method (step 508b).

[0123] In an alternative example, the release request procedure is initiated by the network instead of the UE in step 501b by receiving a PDU SESSION RELEASE COMMAND message from the core network and checking whether the PDU session identity or identifier in the PDU SESSION RELEASE COMMAND message is associated with the need for time synchronization as described above. The UE then performs the same steps from 502b to 508b (except omitting steps 504b and 507b).

[0124] Reference is now made to FIG. 5c, which illustrates a flow diagram of an exemplary method performed by UE 300 when triggered by a PDU session modification, according to an embodiment of the present invention.

[0125] First, in step 501c, the UE 300 requests or receives a PDU session modification (described in TS 24.501 subclause 6.4.2 for the UE requested PDU session modification procedure and subclause 6.3.2 for the network requested PDU session modification procedure). The PDU SESSION MODIFICATION REQUEST is sent to a core network entity, the Session Management Function (SMF). As for the PDU session establishment procedure, the message includes a Requested QoS flow description field with a QoS flow description information element (subclause 9.11.4.12.1 in TS 24.501). The UE 300 can check the 5QI parameters included in the QoS flow description. If the 5QI value corresponds to a delay-critical guaranteed bit rate GBR (#82, #83, #84, #85) or any other value that indicates the need for time synchronization, the UE can determine that there is a need for time synchronization and in particular a need or request for time synchronization. The PDU SESSION MODIFICATION REQUEST may also contain the DS-TT parameters, i.e. the Port Management Information Container and the 5GSM Capabilities with TPMIC bits, as described above with respect to Fig. 5a for the PDU session establishment procedure. The UE 300 checks during step 502c whether the modification affects the time synchronization need, e.g. based on QoS parameters or DS-TT parameters (i.e. whether the modified PDU session requests or requires a modified time synchronization request). If the modification of the PDU session modifies the time synchronization need or requirement (yes branch of step 502c), there are two different cases:

[0126] Case 1: The PDU session is modified from a PDU session that requires time synchronization to a PDU session that does not require time synchronization (yes branch in step 502c, no branch in step 503c). For example, the 5QI may be modified from a value associated with a low packet delay budget (e.g., 5QI#85 with PDB=5ms) to a value associated with a high packet delay budget (e.g., 5QI#3 with PDB=50ms), i.e., time synchronization may no longer be required in the modified PDU session. In that case, the UE 300 creates or generates a time synchronization control message requesting the halting or termination of the time synchronization process in the RAN (step 504c). The UE then waits for feedback from the core network entity for the PDU session modification (505c).

[0127] If, upon receipt of the PDU SESSION MODIFICATION REQUEST message, the SMF accepts the request to modify the PDU session, the SMF (Core Network Entity) shall execute the PDU session modification procedure requested by the network (as specified in clause 6.3.2 of TS 24.501), i.e. the SMF returns a PDU SESSION MODIFICATION COMMAND to the UE 300, which responds with a PDU SESSION MODIFICATION COMPLETE or a PDU SESSION MODIFICATION COMMAND REJECT (which is unlikely to occur if the modification was requested by the UE). Thus, upon receiving the PDU SESSION MODIFICATION COMMAND, the UE 300 considers the modification accepted (yes branch of step 505c), after which the UE 300 sends a time synchronization control message to the associated gNB (step 506c). Then, before disabling the time synchronization, the UE 300 checks whether other PDU sessions that require time synchronization are still active. If there are no active PDU sessions that require time synchronization, the UE 300 disables or deactivates the time synchronization process in the UE (step 507c). In other words, the UE 300 stops tracking the reception of messages related to the reference time and possibly path delay compensation from the gNB. The UE also sets the state of RAN synchronization and RAN PDC to "off". Otherwise, if at least one PDU session that requires time synchronization is still active, the time synchronization remains enabled or active.

[0128] Upon receiving the PDU SESSION MODIFICATION REJECT (no branch in step 505c), the requested modification is rejected and the UE deletes the time synchronization control message (step 512c) and ends the method (step 513c).

[0129] Case 2: A PDU session is modified from a PDU session without the need for time synchronization to a PDU session with the need for time synchronization or a PDU session with adaptation with the need for time synchronization (yes branch in step 502c, yes branch in step 503c). For example, DS-TT parameters are added in the PDU SESSION MODIFICATION REQUEST message while they were not initially present during the establishment of the PDU session. In another example, 5QI may be modified from a value associated with a high packet delay budget (e.g. 5QI#3 with PDB=50ms) to a value associated with a low packet delay budget (e.g. 5QI#85 with PDB=5ms), i.e. the modified PDU session requires time synchronization. A PDU session may be modified with a packet delay budget that requires time synchronization, but may have stricter budget requirements. With stricter budget requirements, time synchronization may require, for example, path delay compensation in addition to the main time synchronization process. On the other hand, the modifications may lift the packet budget delay constraint, so that path delay compensation may become useless and unnecessary.

[0130] The UE 300 then creates or generates a time synchronization control message to reflect the requested modification (step 508c). For example, in the case of a modification requiring time synchronization with path delay compensation, the UE 300 generates a time synchronization control message to request initiation of a time synchronization process with path delay compensation in the RAN. The time synchronization control message generated by the UE 300 may be based on a MAC CE, as described below with reference to FIG. 11. With such a MAC CE time synchronization control message, a time synchronization field or flag (bit 8) of the time synchronization control message is enabled or set to "on", and a path delay compensation field or flag (bit 7) of the time synchronization control message is also enabled or set to "on". The UE 300 then waits for feedback from the core network entity on the modification of the PDU session.

[0131] Upon receiving the PDU SESSION MODIFICATION REQUEST message, if the SMF accepts the request to modify the PDU session, the SMF (core network entity) shall perform the network requested PDU session modification procedure (specified in clause 6.3.2 of TS 24.501), i.e. the SMF returns a PDU SESSION MODIFICATION COMMAND to the UE 300, which responds with a PDU SESSION MODIFICATION COMPLETE or (unlikely if the modification is requested by the UE) a PDU SESSION MODIFICATION COMMAND REJECT. As a result, upon receiving the PDU SESSION MODIFICATION COMMAND, the UE 300 considers the modification accepted (yes branch in step 509c), after which the UE 300 transmits (in step 510c) a time synchronization control message to its associated gNB. Then, in step 511c, depending on whether the PDU session is changed from a PDU session that does not require time synchronization to a PDU session that requires time synchronization or a PDU session with an adaptation that requires time synchronization, UE300 initiates time synchronization or adapts its time synchronization process based on the required correction (e.g., tracks the state of the reference time and path delay compensation messages, RAN synchronization and RAN PDC).

[0132] Upon receiving the PDU SESSION MODIFICATION REJECT (no branch in step 509c), the requested modification is rejected and the UE 300 deletes the time synchronization control message (step 512c) and ends the method (513c).

[0133] In another example, the UE 300 may determine the time synchronization request and any changes to the time synchronization request based on the S-NSSAI in a message received from a core network entity. For example, the message may be a CONFIGURATION UPDATE COMMAND received by the UE 300 from an Access and Mobility Function (AMF) in the core network. The S-NSSAI may be changed through this message as described in the Generic UE Configuration Update procedure (clause 5.4.4 in TS 24.501). In such a case, the UE 300 may determine from the message received from the AMF that the S-NSSAI value has been changed from a value associated with time-sensitive communication (e.g., SST value=5 for ultra-reliable low-latency communication or new SSST value=6 for time-sensitive communication) to an S-NSSAI with a value not requiring time synchronization (e.g., SST value=1 for 5G enhanced mobile broadband) or an existing SST value (e.g., SST=5 for ultra-reliable low-latency communication) and to no SD field in the SD value or message, i.e., the PDU session no longer requires time synchronization from the SD indicating the need for time synchronization. In this case, as in case 1 in step 504c above, the UE 300 creates or generates a time synchronization control message to request the stop or termination of the time synchronization process in the RAN.

[0134] Reference is now made to Figure 5d, which illustrates a flow diagram of an exemplary method performed by the UE 300 in accordance with an embodiment of the present invention when triggered by a synchronization notification received from a core network entity of a radio network (e.g., a core network entity of the core network 101 of the 5G network 100 of Figure 1). In other words, the UE may be instructed by an entity in the core network to initiate RAN time synchronization.

[0135] In a first step 501d, the UE 300 receives a synchronization notification from a core network entity, such as a Session Management Function (SMF), for example in the form of a Port Management Information Container (PMIC) message as defined in clause 9.11.4.27 of TS 24.501.

[0136] The PMIC carries information defined in TS 23.501, clause 5.28.3.1. The information carried in the PMIC is for configuring the Precision Time Protocol, which ensures synchronization of DS-TT and especially TSN applications. It includes port information elements such as "PTP instance ID", "defaultDS.clockIdentity" and "defaultDS.instanceEnable". The port information "PTP instance ID", "defaultDS.clockIdentity" and "defaultDS.instanceEnable" in the PMIC message can be used to inform the UE about the start or activation and the stop or deactivation of the time synchronization process or service, as described in TS 23.501, clause K.2.2. The "PTP instance ID", "defaultDS.clockIdentity" and "defaultDS.instanceEnable" port information can be exchanged between the core network and the UE to activate the RAN time synchronization. Another parameter of the configuration information provided by the PMIC message is the PTP profile (defined in IEEE Std1588-2019, clause 20.3.3). Each PTP profile defines a set of parameters to support applications that are more or less stringent in terms of synchronization accuracy. A PTP profile can be used to determine the need for PDC in addition to time synchronization.

[0137] In step 502d, the UE 300 checks the "defaultDS.instanceEnable" port information in the received Synchronization Notification PMIC message.

[0138] If "defaultDS.instanceEnable" is "True", in step 503d, UE300 checks the state of RAN synchronization. If RAN synchronization is set to "off" (no branch in step 503d), in step 507d, a time synchronization control message is created or generated to start or initiate a time synchronization process between UE300 and gNB200. In other words, the SMF may instruct the UE to start RAN clock synchronization (or RAN time synchronization) through writing Port Management Information. If RAN synchronization is "on" (yes branch in step 503d), in step 505d, UE300 checks the value of the port information received in the synchronization notification PMIC message (in step 501d) to determine whether the time synchronization requirements have changed such that the time synchronization process needs to be changed, for example by changing an option or additional feature such as PDC (path delay compensation). If the time synchronization requirement has changed (yes branch in step 505d), then in step 506d, UE 300 generates or creates a time synchronization control message to change the RAN synchronization option. If the time synchronization requirement has not changed (no branch in step 505d), then there is no need to send a time synchronization control message and UE 300 proceeds to end step 510d.

[0139] If "defaultDS.instanceEnable" is "False" in step 502d (no branch), then in step 504d, UE300 checks the state of RAN synchronization. If the state is "on" (yes branch in step 504d), then in step 508d, a time synchronization control message is created or generated between UE300 and gNB200 to stop, terminate or disable time synchronization processing in the RAN. If RAN synchronization is "off" (no branch in step 504d), there is no need to send a time synchronization control message and UE300 proceeds to end step 510d.

[0140] Step 505d includes checking both the RAN PDC state in the UE 300 and the port information "PTP Profile" (Precision Time Protocol Profile) of the received synchronization notification PMIC message. If the RAN PDC state is "ON" and "PTP Profile" points to a less demanding PTP profile, such as the "Default Delay Request-Response" profile, the PDC shall be stopped. On the other hand, if the PDC state is OFF and "PTP Profile" points to a more strict profile, such as the "802.1AS" profile, the PDC shall be started. PTP profiles are defined in IEEE Std1588-2019, section 20.3.3. Each PTP profile defines a set of parameters to support applications that are more strict or relatively less strict, for example in terms of synchronization precision. In other words, the necessity of the PDC (e.g., whether the PDC should be operational or inactive, and depending on the current state of the PDC, whether it should be started / activated (to make it operational), maintained in an active state, stopped / deactivated (to make it inactive), or maintained in an inactive state) can be determined based on the PTP profile parameters provided by the PMIC message.

[0141] In step 506d, a time synchronization control message is created or generated. The time synchronization control message generated by UE300 may be based on MAC CE, which will be described later with reference to FIG. 11. Using such MAC CE time synchronization control message, a time synchronization field or flag (bit 8) of the time synchronization control message is set for activation or set to "on" in step 506d. If the RAN PDC state is "not operational" or "off" due to a change in the synchronization requirement, as determined in step 505d, a path delay compensation (PDC) field or flag (bit 7) of the time synchronization control message is set for activation or set to "on". Thus, if the RAN PDC state is operational or "on", the PDC field of the time synchronization control message is set to "off". The RAN PDC state in UE300 changes to "on" and the time synchronization control message is transmitted in step 509d. In another example, the time synchronization control message generated by UE300 may be based on an RRC message, such as a UE Assistance Information message, which will be described later. For example, the IE of the UE Assistance Information message may include a refTime-activation field for indicating whether time synchronization processing is in an active or inactive state, and a pdc-Activation field for indicating whether path delay compensation is in an active or inactive state.

[0142] In step 507d, a time synchronization control message is created or generated. The time synchronization control message generated in UE300 may be based on the MAC CE, which will be described later with reference to FIG. 11. Using such a time synchronization control message of the MAC CE, in step 507d, a time synchronization field or flag (bit 8) of the time synchronization control message is set to be enabled or set to "on" and the RAN synchronization state in UE300 is set to operational or "on". If the port information "PTP Profile" indicates a less demanding PTP profile, such as the "Default Delay Request-Response" profile, then a path delay compensation (PDC) field or flag (bit 7) of the time synchronization control message is set to be disabled or set to "off" and the RAN PDC state in UE300 is set to inoperative or "off". On the other hand, if the "PTP Profile" indicates a more stringent profile, such as the 802.1AS profile, then both the PDC field of the time synchronization control message and the RAN PDC state of UE300 are set to "on". Then, in step 509d, a time synchronization control message is transmitted. In another example, the time synchronization control message generated by UE 300 may be based on an RRC message such as a UE Assistance Information message described later. For example, an IE of the UE Assistance Information message may include a refTime-activation field for indicating whether the time synchronization process is activated or deactivated, and a pdc-Activation field for indicating whether the path delay compensation is activated or deactivated.

[0143] In step 508d, a time synchronization control message is created or generated. The time synchronization control message generated by UE300 may be based on MAC CE, which will be described later with reference to FIG. 11. Using such a time synchronization control message of MAC CE, in step 508d, both a time synchronization field or flag (bit 8) and a path delay compensation (PDC) field or flag (bit 7) of the time synchronization control message are set to "off", along with both RAN synchronization and RAN PDC status in UE300. Then, in step 509d, a time synchronization control message is transmitted to stop, deactivate, or disable time synchronization processing in the RAN between UE300 and gNB200. In another example, the time synchronization control message generated by UE300 may be based on an RRC message, such as a UEAssistance Information message, which will be described later. For example, an IE in the UEAssistance Information message may include a refTime-activation field for indicating whether the time synchronization processing is activated or deactivated, and a pdc-Activation field for indicating whether the path delay compensation is activated or deactivated.

[0144] In another example, a duration value corresponding to the duration for which the time synchronization process should be active may be sent to UE 300 along with a synchronization notification from a core network entity. When the time synchronization process is activated or started based on the synchronization notification, deactivation of the time synchronization process may be performed autonomously or automatically by UE 300 after the duration expires without requiring a deactivation message to be sent from the SMF. For example, the duration may be used to set a timer in UE 300, and when the timer expires, the UE transmits a time synchronization control message to stop, deactivate or disable the time synchronization process in the RAN between UE 300 and gNB 200.

[0145] The gNB 200 receives a time synchronization control message from the UE 300. The time synchronization control message includes information for controlling a time synchronization process in the RAN between the UE and the base station. For example, the time synchronization control message may control the activation or termination of the time synchronization process in the RAN. In addition to the main process of time synchronization, i.e., the transmission of a reference time, the time synchronization control message may also control options or additional functions of the time synchronization process, such as whether path delay compensation should be activated.

[0146] Reference is now made to FIG. 6a, which illustrates a flow diagram of an exemplary method for controlling time synchronization in a wireless network, according to an embodiment of the present invention, performed by a gNB 200.

[0147] First, in step 601a, the gNB 200 receives a time synchronization control message from the UE 300. The time synchronization control message may be a MAC CE message as described below with reference to Fig. 11 or an RRC message (such as, but not limited to, other RRC messages such as an RRC reconfiguration complete, an RRC resume complete, or an RRC resume message that includes time synchronization parameters similar to those described for the UE Assistance Information message).

[0148] As described above, the time synchronization control message may include at least a first field or a time synchronization field for indicating whether the time synchronization process is in an active state or in an inactive state, and may include a second field or a PDC field for indicating whether the path delay compensation is in an active state or in an inactive state. For example, when the time synchronization control message generated by the UE 300 is based on a MAC CE described later with reference to FIG. 11, the time synchronization control message of such a MAC CE includes a time synchronization field or flag (bit 8) and a path delay compensation field or flag (bit 7). For example, when the time synchronization control message generated by the UE 300 is based on a UE Assistance Information message, the time synchronization control message includes a refTime-activation field for indicating whether the time synchronization process is in an active state or in an inactive state, and a pdc-Activation field for indicating whether the path delay compensation is in an active state or in an inactive state. Each field can be set to "on" or "off". The gNB200 then analyzes the time synchronization control message and checks whether a first field (e.g., a time synchronization field) is set to "on" (yes branch in step 602a). If the time synchronization field in the time synchronization control message is set to "on", then in step 603a, the gNB200 enables or initiates a time synchronization process, whereby the gNB200 schedules the transmission of a reference time to the UE300 that emits or transmits the time synchronization control message. The reference time information is carried by an RRC message (such as a DLInformationTransfer message) or a SIB9 message (e.g., in a unicast message).The time synchronization control message (whether it is a MAC CE message or a UE AssistanceInformation RRC message) may include an additional field indicating the UE preference / configuration (e.g., unicast or broadcast, a predefined periodicity for transmission of the reference time information (and PDC information, if necessary) by the gNB200. The gNB200 may transmit the reference time information to the UE300 based on the information in the additional field in the time synchronization control message.

[0149] Otherwise, if the time synchronization field is set to "off" (no branch in step 602a), in step 607a, gNB200 disables or terminates the time synchronization process, thereby causing gNB200 to disable or terminate the transmission of reference time information to UE300, and in step 608a, stops transmitting PDC messages for UE300 (if PDC is in an operational state).

[0150] After step 603a, gNB200 checks whether the PDC field or flag is set to ON (step 604a). If the PDC field or flag is set to “ON” in the time synchronization control message (yes branch in step 604a), gNB200 starts a process of calculating a path delay value between the UE and itself, and schedules the transmission of a path delay compensation message including the path delay value or including information representing the path delay value to UE300 (step 606a).

[0151] If the PDC field or flag is set to “off” (no branch in step 604a), the gNB200 stops sending path delay compensation messages to the UE if the PDC was previously set to “on” (step 605a).

[0152] Reference is now made to FIG. 6b, which illustrates a flow diagram of an exemplary method for controlling time synchronization in a wireless network, in accordance with an embodiment of the present invention, performed by a gNB 200.

[0153] In the case of pre-compensation, the PDC is applied directly to the reference time by the gNB 200 before transmitting the reference time to the UE 300. Pre-compensation is used when the reference time is to be transmitted to one UE (in a unicast message) to take into account propagation delays that may be different for different UEs.

[0154] First, in step 601b, gNB200 (e.g., UE synchronization manager 201 of the gNB) receives a time synchronization control message from UE300.

[0155] Then, gNB200 analyzes the time synchronization control message to check whether the time synchronization field or flag is set to "on" (yes branch in step 602b). If the time synchronization field or flag in the time synchronization control message is set to "on", gNB200 schedules the transmission of the reference time to UE300 emitting the time synchronization control message (step 603b). The reference time information is carried by an RRC message (such as a DLInformationTransfer message) or a SIB9 message. The time synchronization control message (whether it is a MAC CE message or a UE AssistanceInformation RRC message) may include an additional field indicating the UE preference / configuration for the transmission of the reference time information (and PDC information, if necessary) by gNB200 (e.g., unicast or broadcast, a predefined periodicity for the transmission of the reference time information, the type of PDC supported (pre-compensation, RTT, TA, etc.), or the like). gNB200 may transmit the reference time information to UE300 based on the information in the additional field in the time synchronization control message. If the UE supports only pre-compensation as a PDC type, the gNB must apply pre-compensation.

[0156] Otherwise, if time synchronization is set to "off" (no branch in step 602b), gNB200 disables the transmission of reference time information to UE300 (step 607b).

[0157] After step 603b, gNB200 checks whether the PDC field or flag is set to "on" (step 604b). If the PDC field or flag is set to "on" in the time synchronization control message, gNB200 starts (in step 606b) a process to calculate a path delay value between UE300 and itself and applies the path delay value to the reference time.

[0158] For example, the gNB can use the last calculated and transmitted TA and the formula (T TA -T C ×N TA,offset ) / 2, where T TA is the timing advance between the downlink and uplink frames, and T C is the basic time unit for New Radio as defined in TS38.211, section 4.1. TA is continuously determined by the gNB, which calculates the TA to be transmitted within the TA command thereafter. Thus, the determination of the guaranteed reference time is performed after the transmission of the TA command by the gNB. The gNB determines the compensated reference time by adjusting (adding) the reference time with the calculated path delay value.

[0159] If the PDC field or flag is set to “off” (no branch in step 604b), the gNB200 stops the process of calculating the path delay if PDC processing was previously set to “on” and stops applying the path delay to the reference time information (step 605b).

[0160] In another example, instead of completely disabling the transmission of the reference time information to the UE in step 607b, the gNB200 may not completely disable the transmission of the reference time, but may, for example, reduce the periodicity of the transmission of the reference time information to the UE300.

[0161] Reference is now made to FIG. 6c, which illustrates a flow diagram of an exemplary method for controlling time synchronization in a wireless network in accordance with an embodiment of the present invention, performed by gNB200.

[0162] In this example, the reference time is broadcast to all UEs in the cell, so that the gNB 200 checks whether there are no more UEs requesting time synchronization before disabling or terminating the time synchronization process and stopping the transmission of the reference time. As mentioned above, because the reference time is broadcast, pre-compensation of the path delay cannot be used.

[0163] First, in step 601c, the gNB 200 receives a time synchronization control message from the UE 300. The message can be a MAC CE as described with reference to Figure 11 or a RRC message (UE Assistance Information with information elements dedicated to time synchronization configuration and activation as described in further description).

[0164] The gNB200 then parses the time synchronization control message to see if a time synchronization field or flag is set to “on” (step 602c). If the field or flag in the time synchronization control message is set to “on”, the gNB200 performs another step (603c) to see if a time synchronization process has started.

[0165] If time synchronization has not yet started (no branch in step 603c), gNB200 schedules the transmission of the reference time (step 607c). The reference time information is broadcast in an RRC message or a SIB9 message. Step 608c is then performed as described below. The time synchronization control message (whether it is a MAC CE message or a UE AssistanceInformation RRC message) may include an additional field indicating a particular UE preference / configuration (e.g., unicast or broadcast, a predefined periodicity for the transmission of the reference time information, the type of PDC supported (pre-compensation, RTT, TA, etc.), or the like) for the transmission by gNB200 of the reference time information (and PDC information, if necessary). gNB200 may transmit the reference time information to UE300 based on the information in the additional field in the time synchronization control message.

[0166] Returning now to step 603c, if time synchronization has already started (yes branch in step 603c), the gNB200 proceeds directly to step 608c and checks whether the PDC field or flag is set to "on" in the time synchronization control message. If the PDC field or flag is set to "on" in the time synchronization control message, the gNB200 performs a process of calculating a path delay value between the UE300 and itself, and schedules the transmission of a path delay compensation including the path delay value or including information representing the path delay value (step 610c).

[0167] If the PDC field or flag is set to “off” (no branch in step 608c), the gNB300 stops calculating the path delay and stops sending a path delay message to the UE200 if the PDC was previously set to “on” (step 609c).

[0168] Returning to step 602c, if the time synchronization field or flag is set to "off" (no branch in step 602c), the gNB200 performs another step (step 604c) to check whether at least one UE300 in the cell requires time synchronization. If there is no UE in the cell that requires time synchronization (no branch in step 604c), the gNB200 terminates the operation of the time synchronization process, which disables the transmission of reference time information to UEs in the cell in step 605c and stops the transmission of PDC messages to the UEs (if PDC was previously enabled). Otherwise, if at least one UE requires time synchronization, the gNB200 stops (606c) the PDC process only for UEs that emit or transmit time synchronization control messages.

[0169] FIG. 11 illustrates an exemplary MAC CE signaling frame format used as a time synchronization control message according to an embodiment of the present invention.

[0170] This signaling frame is transmitted from UE300 to gNB200 or from gNB200 to UE300 as described herein.

[0171] The synchronization control message conforms to the MAC CE format described in TS 38.321, clause 6.1.3. As an example, the LCID field is shown here, and the MAC CE can also use the extended LCID field.

[0172] The MAC CE time synchronization control message includes at least a first field (e.g., a time synchronization field or flag (Time sync)) for indicating whether the time synchronization process is active or inactive. The Time sync field can be set to "on" or "off" to start / activate / enable or stop / terminate / disable the time synchronization process in the RAN.

[0173] The MAC CE time synchronization control message may further include a second field (e.g., a PDC field or flag) to activate or deactivate the PDC. The PDC field shall be set to "off" if the Time sync field is "off", otherwise it may be set to "on" or "off" depending on whether path delay compensation should be activated or not.

[0174] The MAC CE time synchronization control message may include additional information indicating a particular UE preference / configuration for the transmission of reference time information (and PDC information, if necessary) by gNB200 (e.g., unicast or broadcast, a predefined periodicity for the transmission of reference time information, the type of PDC supported (pre-compensation, RTT, TA, etc.), or the like).

[0175] In another example, the time synchronization control message may be an RRC message, such as a UE Assistance Information message with an Information Element (IE) for providing information for controlling the time synchronization process, such as time synchronization and PDC configuration and activation information. For example, the IE may include a first field (e.g., refTime-activation field) for indicating whether the time synchronization process is active or inactive, and a second field (e.g., pdc-Activation field) for indicating whether the PDC is active or inactive. The IE may include additional fields indicating a particular UE preference / configuration (e.g., unicast or broadcast, a predefined periodicity for the transmission of the reference time information (and PDC information, if necessary), the type of PDC supported (pre-compensation, RTT, TA, etc.), or the like) for the transmission of the reference time information (and PDC information, if necessary) by the gNB 200.

[0176] As described in section 6.2.2 of TS38.331, "the UEAssistanceInformation message is used to indicate UE assistance information to the network."

[0177] To configure time synchronization in the RAN (RAN synchronization), a UEAssistanceInformation-v17 information element (IE) is added, which includes a field related to the PDC and a field related to refTime (RAN synchronization).

[0178] For RAN synchronization, the UEAssistanceInformation-v17 IE contains the following fields: refTime-activation, which can be either "on" or "off" and instructs the gNB to start or stop synchronization to the radio network (e.g. to start / enable or deactivate / disable the time synchronization process in the UE or the gNB); referenceTimeInfo-Periodicity to inform the gNB whether the UE needs the reference time every few ms or only once, and referenceTimeInfo-transfer, which can be either broadcast or unicast to inform the gNB of the UE’s preference for the type of message to transfer reference time information.

[0179] For PDC, the UEAssistanceInformation-v17 IE contains the following fields: "pdc-Activation", which can be either "on" or "off" and instructs the gNB to start or stop path delay compensation for radio network synchronization (e.g. to start / enable or deactivate / disable PDC in the UE or gNB); "pdc-Type", which is an array giving the types of PDC supported by the UE, where each pdc-type is set to true if the UE supports this PDC type. For example: "pdc-Type", which can be "Pre-compensation" if path delay is applied by the gNB, "Legacy TA" if the path delay compensation scheme to be applied follows the Release-16 TA standard, or "Extended TA" if the path delay compensation scheme to be applied follows the Release-17 Timing Advance based standard, or "RTT" if the path delay compensation scheme to be applied follows the Release-17 Round Trip Time based standard, control - "pdc-scenario", which informs the gNB in ​​which scenario the UE is to be used in, e.g. to determine if PDC is required (this information can be obtained from the application layer), such as control scenario / environment, power grid environment scenario / environment, etc. "pdc-periodicity" to inform the gNB whether the UE requires PDC every few ms or only on demand.

[0180] Several other fields related to synchronization can be either "on" or "off" and can also be filled in such as "Te-preference" to instruct the gNB whether the UE should follow the timing error Te defined in either Release 16 or Release 17 (low timing error) "Te-preference" and "TA-granularity" to inform the gNB of the preferred TA granularity value (value of TA correction steps). Te is the UE transmit timing error as defined in TS38.133 clause 7.1.2. The TA granularity is the correction step applied to the TA command (discussed in more detail above and described in TS38.211 clause 4.3.1) to obtain the path delay value. The configurable TA granularity allows adaptation of the TA precision selected according to the type of use (scenario) or type of message (e.g. coarse granularity selected for absolute timing advance command MAC CE (TS38.321 clause 6.1.3.4a) and finest granularity selected for Update TA command MAC CE (TS38.321 clause 6.1.3.4)). For more details on TA granularity, see also 3GPP document R2-2100941 submitted by Canon Research Centre France.

[0181] All or some of the above mentioned fields may be placed in other RRC messages such as RRC reconfiguration complete, RRC resume complete, or RRC resume request message.

[0182] The UEAssistanceInformation message looks like this (additional information elements are in bold, mainly at the end): TIFF0007689581000001.tif245161TIFF0007689581000002.tif239161TIFF0007689581 000003.tif245161TIFF0007689581000004.tif245161TIFF0007689581000005.tif97161

[0183] In another example, the time synchronization control message may be an RRC reconfiguration message with information elements (IEs) for providing information for controlling the time synchronization process, such as time synchronization and PDC configuration and startup information.

[0184] As stated in section 6.2.2 of TS38.311, "The RRCReconfiguration message is a command to modify the RRC connection. It may carry information for measurement configuration, mobility control, radio resource configuration (including RB, MAC primary configuration, and physical channel configuration), and AS security configuration."

[0185] To configure RAN synchronization, an RRCReconfiguration-v17 information element is added. The IE may include a first field (e.g., RAN_synchronization field) for indicating whether the time synchronization process is active or inactive, and a second field (e.g., RAN_pdc field) for indicating whether the PDC is active or inactive. The RAN_synchronization field may be either "on" or "off", instructing the UE to start or stop synchronization to the radio network. The RAN_pdc field may also be either "on" or "off", instructing the UE to start or stop path delay compensation for synchronization to the radio network. Finally, the IE may include a third field (e.g., RAN_pdc_type) for indicating the type of path delay compensation scheme to be applied. For example, this RAN_pdc_type field can be R16 if the path delay compensation scheme to be applied is to comply with the Release-16 standard, can be R17_TA if the path delay compensation scheme to be applied is to comply with the Timing Advance based standard of Release-17, or can be R17_RTT if the path delay compensation scheme to be applied is to comply with the Round Trip Time based standard of Release-17.

[0186] The RRCReconfiguration message looks like this (additional information elements at the end): TIFF0007689581000006.tif245161TIFF0007689581000007.tif245161TIFF0007689581000008.tif244161TIFF0007689581000009.tif86161

[0187] In the second embodiment, a base station (such as gNB 102 in FIG. 1 or gNB 200 in FIG. 2, for simplicity, only reference number 200 is used for the base station or gNB) determines a request for time synchronization between a UE (such as UE 104a, 104b in FIG. 1, UE 300 in FIG. 3, for simplicity, only reference number 300 is used for the UE) and the base station, and generates a time synchronization control message accordingly. For example, the gNB 200 determines whether time synchronization is required or whether a change is required for an already active time synchronization process (such as activating or deactivating PDC). The gNB 200 may receive a message that triggers the creation of a time synchronization control message. The time synchronization control message includes information for controlling the time synchronization process, such as for activating or deactivating the time synchronization process, or for changing the active time synchronization process (e.g., changing an option or additional function of the time synchronization process), such as by activating or deactivating path delay compensation. In one example, the time synchronization control message includes a field for controlling the start / end of a time synchronization process in the UE.

[0188] Reference is now made to FIG. 7a, which illustrates a flow diagram of an exemplary method according to an embodiment of the present invention, performed by gNB 200 when triggered by the setup of a PDU session resource.

[0189] First, in step 1301, gNB200 receives a PDU SESSION RESOURCE SETUP REQUEST message (described in TS38.413, subclause 9.2.1.1). The purpose of the PDU Session Resource Setup procedure is to allocate resources in Uu and Ng-U for one or more PDU sessions and corresponding QoS flows, and to configure the corresponding DRB for a given UE. The PDU SESSION RESOURCE SETUP REQUEST is received from a core network entity, such as the Access and Mobility Management Function (AMF). This message contains all of the information required to set up a PDU session related to NG-RAN. To determine the requirement for time synchronization between UE300 and gNB200, a check is made in step 1302 as to whether this PDU session has certain requirements in terms of time synchronization (i.e. whether it requests or requires time synchronization, and possibly whether it requests or requires time synchronization with or without PDC). For example, the PDU SESSION RESOURCE SETUP REQUEST message contains the PDU SESSION RESOURCE SETUP REQUEST Transfer (clause 9.3.4.1 of TS38.413) Information Element (IE) implemented by the SMF. This IE contains at least the QoS Flow Level QoS Parameters (clause 9.3.1.12 of TS38.413) that indicate the need for time synchronization for the RAN. The QoS parameters include the Dynamic 5QI Descriptor (also known as non-standardized or non-preconfigured 5QI) (clause 9.3.1.18 of TS38.413) and Non Dynamic 5QI Descriptor (also known as standardized 5QI) (clause 9.3.1.28 of TS38.413) descriptions.These descriptors allow to define QoS parameters such as 5QI for Non-dynamic 5QI where there is a correspondence between 5QI values ​​and packet delay budget as defined in Table 5.7.4-1 of TS 23.501. For dynamic 5QI, packet delay budget and delay criticality parameters are directly accessible and can be specified independently of the 5QI value. For example, in step 1302, the gNB 200 determines the need or requirement for time synchronization if the new 5QI value corresponds to a delay-critical GBR (#82, #83, #84, #85) or other value, e.g., in Non-Dynamic 5QI, or for a low packet delay budget (<10 ms) or delay-critical QoS flow, e.g., in dynamic 5QI. The need for time delay can be determined when a PDU session is set up with QoS parameters of GBR #82, #83, #84, #85.

[0190] Also for step 1302, an optional parameter, Time Sensitive Communication (TSC) QoS Flow Information Element (IE), may be present in the PDU SESSION RESOURCE SETUP REQUEST Transfer. This IE provides traffic characteristics of the TSC QoS flow through TSC Assistance Information, including information such as traffic periodicity and burst arrival time. The TSC Assistance information may include information indicating the status of the NW-TT and DS-TT, or more generally the status of the time synchronization process or service, for notification to the gNB 200. Furthermore, the TSC Assistance information may include a duration value corresponding to the duration for which the time synchronization process is in an operational state. Based on the presence of the TSC QoS Flow, the gNB 200 may consider that time synchronization is required. For example, in step 502a, based on the presence of the TSC QoS Flow, the gNB 200 may detect a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC).

[0191] In another example, the gNB 200 may use the Single Network Slice Selection Assistance Information (S-NSSAI, clause 9.3.1.24 of TS38.413) included in the PDU SESSION RESOURCE SETUP REQUEST message to make a determination as to whether the PDU session has certain requirements in terms of time synchronization (i.e., requests or requires time synchronization) in step 1302. Network slices allow the creation of several logical networks with different requirements on the same physical infrastructure. Identification of the network slice is performed using the S-NSSAI. The S-NSSAI as defined in TS 23.501 subclause 5.12.2.1 consists of two fields: SST, which stands for Slice Service Type, which is mandatory and refers to the expected network slice behavior in terms of functions and services; and SD, which is Slice Differentiator, which is optional information that complements the Slice / Service type to differentiate between multiple network slices of the same Slice / Service type. Currently, five different service values ​​are standardized, as shown in table 5.15.2.2-1 of TS 23.501. For example, to determine whether a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) is detected, the gNB 200 checks the S-NSSAI value. If the S-NSSAI value corresponds to a value indicating that time synchronization is required, the gNB 200 determines that there is a request or need for time synchronization and then prepares a time synchronization control message to request the initiation of a time synchronization process in the Radio Access Network (RAN).The S-NSSAI indicating the need for time synchronization can be, for example, the SST value corresponding to Ultra Reliable Low Latency Communication (SST value = 2) or a new SST value (from 0 to 127) for Time Sensitive Communication among the values ​​not used as standardized SST values; or the use of one SST value within the range of operator-specific values ​​(from 128 to 255) for TSC services supported by a dedicated operator; or the use of a specific SD value to detail a currently standardized service, for example, SST value = 2 for Ultra Reliable Low Latency Communication with SD = 1 for the Time Sensitive addon. Knowledge of the specific value for Time Sensitive Communication may be standardized or shared during the preparation procedure (as described in TS 23.501, clause 5.15).

[0192] The PDU SESSION RESOURCE SETUP REQUEST also includes a PDU session identity or identifier used to identify the PDU session. This PDU session ID is present in all messages to control the PDU session. Also, if the PDU session is classified with a need for time synchronization (in step 1302), the gNB 200 associates the PDU session identity with the need for time synchronization. Thus, in the following PDU session procedures, the gNB 200 can know whether the session is classified with a need or requirement for time synchronization based only on the PDU session identity.

[0193] Based on the previous characteristics, the gNB 200 determines in step 1302 that time synchronization is required, and if the PDU session resource setup is successful (yes branch in step 1303), the gNB 200 creates a time synchronization control message to start the time synchronization process in the RAN (step 1304). In response to determining that time synchronization is required, the gNB transmits a signaling message (e.g., a time synchronization control message) to the UE to start the RAN time synchronization. In one example, the time synchronization control message includes a time synchronization field set to enabled or "on" and, optionally, a PDC field set to enabled or "on" if strict synchronization is required. The time synchronization control message can be a MAC Control Element (MAC CE) message, as described with reference to FIG. 11 for MAC CE. In another example, the time synchronization control message can be an RRC reconfiguration message, as described above. Then, in step 1305, gNB200 transmits a time synchronization control message to the associated UE, for example to the UE identified in the RAN UE NGAP ID parameter (defined in the PDU SESSION RESOURCE SETUP REQUEST). Then, in step 1306, gNB200 activates or starts the time synchronization process, i.e. starts transmitting the reference time and, if the time synchronization control message includes a PDC field, starts calculating the path delay according to the PDC state set in the PDC field of the time synchronization control message. Some UE preferences, such as type of transmission (unicast or broadcast), periodicity of transmission of the reference time, periodicity of transmission of PDC information, may have been previously received in gNB200 from UE300, for example via a UE AssistanceInformation RRC message. These preferences allow gNB200 to adapt or modify the time synchronization process performed in gNB200 according to the UE preferences.

[0194] Otherwise, if time synchronization is not required (no branch at step 1302) or if PDU session resource setup fails (no branch at step 1303), gNB200 proceeds to end step 1307.

[0195] Reference is now made to FIG. 7b, which illustrates a flow diagram of an exemplary method according to an embodiment of the present invention, performed by gNB 200 when triggered by the release of a PDU session resource.

[0196] First, in step 1401, the gNB 200 receives a PDU session release as described in clause 8.2.2 of TS 38.413. A PDU SESSION RESOURCE RELEASE REQUEST is received from a core network entity, the Access and Mobility Management Function (AMF). The message primarily contains the cause of the release and the identity or identifier of the PDU session.

[0197] As explained above, a PDU session identity or identifier (ID) is used to identify a PUD session. Furthermore, during the setup of PDU session resources, gNB200 associates (at step 1302) the need for time synchronization with the PDU session ID. Thus, gNB200 verifies whether the PDU session is flagged as requesting time synchronization using the PDU session ID to determine whether the PDU session for which release is being requested is a PDU session that needs or requests time synchronization (step 1402).

[0198] If the PDU session is identified as a session that requests or requires time synchronization, and if the resources of the PDU session are successfully released (yes branch at step 1403), gNB200 creates a time synchronization control message to stop or disable time synchronization processing in the RAN (step 1404).

[0199] Then, the gNB200 transmits a time synchronization control message to the UE300 associated with itself (at step 1405). Before disabling or terminating time synchronization, the gNB200 checks in step 1406 whether other PDU sessions requiring time synchronization are in a continuous operating state. If there are no more active PDU sessions requiring time synchronization, the gNB200 disables or terminates the time synchronization process in step 1406. In other words, the gNB200 stops broadcasting the reference time and possibly stops processing related to path delay compensation. In other cases, time synchronization remains enabled or in an active state because at least one PDU session requiring time synchronization is in a continuous operating state.

[0200] Otherwise, if the session is not a session that requires time synchronization (no branch at step 1402) or if the release of resources for the PDU session fails (no branch at step 1403), the gNB proceeds to end step 1407.

[0201] Reference is now made to FIG. 7c, which illustrates a flow diagram of an exemplary method according to an embodiment of the present invention, performed by gNB 200 when triggered by modification of PDU session resources.

[0202] First, in step 1501, the gNB 200 receives a modification of a PDU session resource (as described in TS 38.413 subclause 8.2.3). A PDU SESSION RESOURCE MODIFY REQUEST is received from a core network entity, the Access and Mobility Management Function (AMF). Like the PDU SESSION RESOURCE SETUP REQUEST procedure, the message includes QoS flow level QoS parameters with dynamic 5QI and Non-Dynamic 5QI descriptors, together with TSC Traffic Characteristics (PDU Session Resource Modify Request Transfer, as included in TS 38.413 subclause 9.3.4.3). The message may include an S-NSSAI to indicate whether the PDU session is linked to a network slice for the TSC. Based on these parameters, gNB200 may check in step 1502 whether the modification affects the requirement for time synchronization (i.e. whether the modified PDU session requests or needs time synchronization, and possibly whether the modified PDU session requires PDUs if the PDU session requires time synchronization). There are two different cases: if the modification of the PDU session results in a modification of the requirement or need for time synchronization (yes branch in step 1502) and if the modification of the resources of the PDU session is accepted (yes branch in step 1503).

[0203] Case 1: A PDU session is modified from one that requires time synchronization to one that does not require time synchronization (yes branch in step 1502, yes branch in step 1504). For example, the 5QI may be modified from a value associated with a low packet delay budget (e.g., 5QI#85 with PDB=5ms) to a value associated with a high packet delay budget (5QI#3 with PDB=50ms), i.e., the modified PDU session no longer requires time synchronization. In another example, the S-NSSAI value may be modified from a value associated with time-sensitive communication (e.g., SST value=5 for ultra-reliable low-latency communication or new SST value=6 for Time Sensitive Communication) to a value that does not require time synchronization (e.g., SST value=1 for 5G enhanced mobile broadband), or from an S-NSSAI value with an existing SST value (e.g., SST=5 for ultra-reliable low-latency communication) and an SD indicating that time synchronization is required to an SD value or to no SD field in the message, i.e., the PDU session no longer requires time synchronization. In that case, the gNB200 creates a time synchronization control message to request the RAN to stop or terminate the operation of the time synchronization process (step 1505). Then, the gNB200 transmits the time synchronization control message to the UE associated with itself (step 1506). Then, before disabling the time synchronization process in step 1507, the gNB200 checks whether other PDU sessions that require time synchronization are in a constant operating state. If there are no more PDU sessions requiring time synchronization, the gNB 200 disables or terminates the time synchronization process (step 1507). Otherwise, if at least one PDU session requiring time synchronization is in an active state at all times, the time synchronization remains enabled or in an active state.

[0204] Case 2: A PDU session is modified from a PDU session that does not require time synchronization to a PDU session that requires time synchronization or some adaptation of the need or requirement for time synchronization (yes branch in step 1502, no branch in step 1504). For example, a Time Sensitive Communication (TSC) parameter is added to the PDU SESSION RESOURCE MODIFY REQUEST message whereas it was not present at the time of resource setup of the initial PDU session. In such a case, the gNB 200 detects that the PDU session to be modified is a PDU session for TSC and therefore requires time synchronization. In another example, the packet delay budget value drops from 50 ms to 2 ms, i.e. the modified PDU session requires time synchronization. In the last example, a PDU session is modified with a packet delay budget that requires time synchronization but with a stricter budget requirement. With a stricter requirement, time synchronization may require, for example, path delay compensation in addition to the main time synchronization process. On the other hand, a modification may be that the packet delay budget constraint (eg, PDB from 2 ms to 15 ms) is lifted, such that path delay compensation becomes useless and is not required.

[0205] If so, in step 1508, gNB200 creates a time synchronization control message to reflect the required corrections. For example, gNB200 requests the initiation of a time synchronization process in the RAN with path delay compensation. Then, in step 1509, gNB200 transmits the time synchronization control message to UE300 associated with it, and in step 1510 adapts its synchronization process (e.g., starts broadcasting a reference time and performs path delay compensation for some UEs, if necessary).

[0206] Otherwise, if there are no corrections related to time synchronization (no branch at step 1502) or if correction of PDU session resources fails (no branch at step 1503), gNB200 proceeds to end step 1511.

[0207] In an alternative example, QoS monitoring (QoS Monitoring Request field in QoS Flow Level Parameters, clause 9.3.1.12 of TS38.413) may be requested by the network during PDU session resource setup or modification of PDU session resources. During monitoring, gNB200 may detect that the time synchronization requirement is no longer achieved for some UEs and accordingly activate or initiate path delay compensation (if it is not already activated or operational) by sending a time synchronization control message to those UEs. Thus, gNB200 may report this modification of QoS parameters using the PDU session resource notification.

[0208] Reference is now made to FIG. 7d, which illustrates a flow diagram of an exemplary method, in accordance with an embodiment of the present invention, performed by gNB200 when triggered by a synchronization notification sent by a core network entity.

[0209] For each UE 300, a core network entity (Session Management Function (SMF)) sends a start synchronization notification to the gNB 200. This synchronization notification is sent transparently to the gNB 200 via the Application Management Function (AMF). The format of this notification is as follows: TIFF0007689581000010.tif38161

[0210] The RAN_UE_NGAP_ID uniquely identifies the UEs that the gNB 200 should configure. Such identifiers are described in clause 9.3.3.1 of TS38.413. If the identifier is equal to 0xFFFFFFFF, all UEs known to the gNB should be configured.

[0211] RAN_synchronization can be either "on" or "off" and instructs the gNB to start or stop (e.g., start / enable or deactivate / disable) synchronization of the UE to the radio network.

[0212] RAN_pdc can be either "on" or "off" and indicates the starting or stopping (eg, activation / enabling or deactivation / disabling) of path delay compensation for UE synchronization to the wireless network.

[0213] RAN_pdc_type may be R16 if the applied path delay compensation scheme should follow the Release 16 standard, which means that the gNB200 should primarily instruct the UE to initiate or activate / enable PDC.

[0214] RAN_pdc_type may be R17_TA if the applied path delay compensation scheme shall follow the Timing Advance based standard of Release 17, which means that the gNB200 shall instruct the UE to follow the same PDC scheme and the gNB shall initiate or activate / enable related signaling including pre-compensation as necessary.

[0215] RAN_pdc_type can be R17_RTT if the applied path delay compensation scheme should follow the Round Trip Time based standard of Release 17. The operation of the gNB is similar to that described above.

[0216] In the first step 1601, gNB200 receives a synchronization notification from the SMF.

[0217] Then, in step 1602, the gNB 200 checks the RAN_synchronization in the synchronization notification. If this field is set to "on" (yes branch in step 1602), in step 1603, the gNB 200 creates or generates a time control synchronization message (such as a MAC CE time control synchronization message as described with reference to FIG. 11) directed to the UE referenced by the field RAN_UE_NGAP_ID with the Time sync field set to "on" and the PDC field set to the same value as the RAN_pdc field. In another example, the time control synchronization message can be sent as an RRC reconfiguration message as described above.

[0218] Then, in step 1604, a time synchronization control message is transmitted to the referenced UE.

[0219] In step 1605, the gNB 200 starts the time synchronization process by scheduling the transmission of a reference time. The reference time information is transmitted in an RRC message or an SIB9 message. The gNB 200 may also start a path delay compensation process as reflected by the RAN_pdc and RAN_pdc_type fields.

[0220] Returning to step 1602, if the RAN_synchronization field is set to "off" (no branch in step 1602), in step 1606, gNB200 creates or generates a time control synchronization message (MAC CE time control synchronization message as described with reference to FIG. 8) directed to the UE referenced by the field RAN_UE_NGAP_ID with the Time sync field set to "off" and the PDC field set to "off".

[0221] In step 1607, a time synchronization control message is sent to the referenced UE.

[0222] In step 1608, the gNB 200 disables the transmission of the reference time to stop or disable the time synchronization process. The reference time information is transmitted in an RRC message or an SIB9 message. The gNB 200 also stops, disables, or stops the path delay compensation process.

[0223] In another example, a duration value corresponding to a duration for which the time synchronization process should be active may be sent from a core network entity (SMF) along with the synchronization notification. Once the time synchronization process is activated or started based on the time notification, the time synchronization process may be deactivated autonomously or automatically by the gNB200 after the duration has elapsed without requiring a deactivation message to be sent from the SMF. For example, the duration may be used to set a timer in the gNB200, and when the timer expires, the gNB sends a time synchronization control message to the UE to stop or deactivate or disable the time synchronization process in the RAN between the UE300 and the gNB200.

[0224] FIG. 8 illustrates a flow diagram of an exemplary method performed by a UE 300 for controlling time synchronization in a wireless network in accordance with an embodiment of the present invention.

[0225] First, in step 1701, the UE 300 receives a time synchronization control message from the associated gNB 200. The time synchronization control message may be a MAC CE message as described above with reference to Figure 11 or an RRC reconfiguration message as described above.

[0226] As described above, the time synchronization control message may include at least a first field for indicating whether the time synchronization process is active or inactive, and may include a second field for indicating whether the path delay compensation is active or inactive. The time synchronization control message generated by the gNB 200 may be based on the MAC CE described with reference to FIG. 11. Such a time synchronization control message of the MAC CE includes a time synchronization field or flag (bit 8) and a path delay compensation field or flag (bit 7). Each field may be set to "on" or "off". Then, the UE 300 analyzes the time synchronization control message and checks whether the first field (e.g., the time synchronization field) is set to "on". If the time synchronization field in the time synchronization control message is set to "on" (yes branch in step 1702), in step 1703, the UE 300 starts or enables the time synchronization process in the UE 300. Then, in step 1704, UE300 checks whether a second field (e.g., a path delay compensation field) in the time synchronization control message is set to "on". If the PDC field in the time synchronization control message is set to "on" (yes branch in step 1704), in step 1706, UE300 starts or enables path delay compensation in UE300. If the PDC field in the time synchronization control message is set to "off" (no branch in step 1704), in step 1706, UE300 stops or disables path delay compensation in UE300.

[0227] Otherwise, if the time synchronization field is set to "off" (no branch at step 1702), at step 1707 UE300 disables or stops the time synchronization process at UE300.

[0228] Solutions have been proposed for controlling the activation of the PDC on the UE side, and more generally for controlling the activation of synchronization in the RAN. The above proposals show that this is achievable without requiring additional information from the core network, such as a time synchronization error budget.

[0229] To ensure accurate time synchronization for time-sensitive communications (TSC), the time synchronization process is based on periodic transmission of a reference time from the gNB to the UE. To improve the accuracy of the time synchronization process, a path delay compensation (PDC) based on the exchange of dedicated signals between the UE and the gNB to estimate and convey path delay values ​​can also be performed. Thus, the time synchronization process and PDC require radio and processing resources in the RAN of the 5G network.

[0230] According to one aspect of the invention, signaling allows enabling and disabling clock synchronization in the RAN (UE and gNB) only when necessary.

[0231] The NR IIoT Study Item (SI) concludes that certain enhancements in RAN capabilities at various layers should be specified for Rel-16 to support new use cases such as factory automation, transportation, power distribution, etc. This brings new QoS parameters for latency-critical applications in 5QI (TS23.501-Table 5.7.4-1). As explained above, smart grid scenarios are similar to power distribution and control-control are similar to the discrete automation defined in GBR 5QI where latency is critical.

[0232] The UE or gNB may use the QoS parameters included in the PDU SESSION message to make a determination as to whether the PDU session has any specific requirements regarding time synchronization (i.e., whether time synchronization is necessary or required). The UE or gNB may analyze the QoS flow description information element included in the PDU SESSION message to check the 5QI parameter. If the 5QI value corresponds to a delay-critical GBR (#82, #83, #84, #85), the UE or gNB may determine that there is a request or need for time synchronization (precise reference time with or without PDC).

[0233] According to an embodiment of the present invention, the need for time synchronization can be determined when a PDU session is accepted with QoS parameters of GBR#82, or #83, or #84, or #85.

[0234] In the context of Time Sensitive Network applications, 5G systems are aggregated into TSN systems as TSN bridges. Some specific entities, namely DS-TT (Device Side TSN Translator) and NW-TT (Network Side TSN Translator), are responsible for the translation between the TSN domain and the 5G domain. To configure DS-TT, the 5G Core uses the Port Management Information message, which is a control message that contains information to configure the Precision Time Protocol, which ensures the synchronization of DS-TT and especially TSN applications. One parameter of the configuration is the PTP profile (defined in IEEE Std1588-2019, section 20.3.3). Each PTP profile defines a set of parameters to support applications that are more or less strict in terms of synchronization accuracy.

[0235] According to an aspect of the present invention, the need for a PDC may be determined based on PTP profile parameters provided by a PMIC message.

[0236] When the UE determines the need for time synchronization, it notifies the gNB of the time synchronization request so that the gNB configures and activates the time synchronization, i.e., sends reference time information and optionally performs PDC calculations.

[0237] According to an aspect of the present invention, in response to determining the need for time synchronization, the UE sends a signaling message (e.g., a time synchronization control message) to the gNB to initiate RAN time synchronization.

[0238] Although the present invention has been described above with reference to embodiments and examples, it should be understood that the present invention is not limited to the above embodiments and examples. It will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention as defined in the appended claims. All features disclosed herein (including the appended claims, abstract and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. Each feature disclosed herein (including the appended claims, abstract and drawings) may be replaced by an alternative feature serving the same, equivalent or similar purpose, unless otherwise specified. Thus, unless otherwise specified, each feature disclosed is merely one example of a generic series of equivalent or similar features.

[0239] It should also be understood that the result of any of the above-mentioned comparisons, decisions, evaluations, selections, executions, actions, or considerations, e.g., selections made during the encoding or filtering process, may be indicated in or determinable / inferable from data in the bitstream, e.g., flags or data indicating the result, such that the indicated or determined / inferred result can be used in processing, e.g., during a decoding process, in lieu of actually performing the comparisons, decisions, evaluations, selections, executions, actions, or considerations.

[0240] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

[0241] In the above-mentioned embodiments and examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit.

[0242] Computer-readable media may include computer-readable storage media, which correspond to tangible media, such as data storage media, or communication media, including any medium that facilitates transfer of a computer program from one place to another, for example according to a communications protocol. In this manner, computer-readable media may generally correspond to (1) non-transitory tangible computer-readable storage media, or (2) a communication medium, such as a signal or carrier wave. Data storage media may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, code, and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

Claims

1. A method for controlling time synchronization in a wireless network including a user equipment (UE) and a base station, comprising: determining a request for time synchronization between the UE and the base station; and transmitting a time synchronization control message to the UE for controlling a time synchronization process between the UE and the base station based on the determined time synchronization request; The time synchronization control message includes type information indicating a specific type of propagation delay compensation (PDC) selected by the base station from a plurality of types of PDC for the time synchronization process. A method comprising:

2. Determining a requirement for time synchronization between the UE and the base station includes: determining that time synchronization between the UE and the base station is required; or determining that time synchronization between the UE and the base station is not required; or determining that time synchronization between the UE and the base station is required with a PDC; or determining that time synchronization between the UE and the base station is required without a PDC; 2. The method of claim 1, comprising:

3. Transmitting the time synchronization control message determining when the time synchronization process should be disabled based on the determined time synchronization request and sending the time synchronization control message to disable the time synchronization process accordingly; or determining when the time synchronization process should be enabled based on the determined time synchronization requirement and sending the time synchronization control message to enable the time synchronization process accordingly; or determining when the time synchronization process should be enabled and a PDC should be enabled based on the determined time synchronization requirement, and sending the time synchronization control message to enable the time synchronization process and a PDC accordingly; or determining when the time synchronization process should be enabled without a PDC based on the determined time synchronization request, and sending the time synchronization control message accordingly to enable the time synchronization process without the PDC; or determining when the time synchronization process is valid and should be changed based on the determined time synchronization requirement, and sending the time synchronization control message to change the time synchronization process accordingly; 2. The method of claim 1, comprising:

4. Transmitting the time synchronization control message determining when the time synchronization process is valid and should be changed based on the determined time synchronization requirement, and sending the time synchronization control message to change the time synchronization process accordingly, the time synchronization control message including information for enabling or disabling a PDC, or for changing a type of PDC if the PDC is valid. The method of claim 1.

5. receiving a message from a core network entity of the wireless network; transmitting the time synchronization control message includes transmitting the time synchronization control message in response to receiving the message. The method of claim 1.

6. receiving a message from a core network entity of the wireless network, the message including a duration time value corresponding to a duration time during which a time synchronization process is to be activated; transmitting the time synchronization control message includes transmitting a first time synchronization control message for enabling the time synchronization process, and transmitting a second time synchronization control message for disabling the time synchronization process when the duration time expires. The method of claim 1.

7. receiving a message from a core network entity of the wireless network, the message including information to indicate a request for the time synchronization between the UE and the base station; determining a request for time synchronization includes determining a request for time synchronization based on the received message; The method of claim 1.

8. 8. The method of claim 7, wherein the message is a synchronization notification including information elements for indicating a request for the time synchronization between the UE and the base station, a first information element indicating an identity of the UE to be configured, a second information element indicating whether the time synchronization process should be enabled or disabled, and a third information element indicating whether PDC should be enabled or disabled.

9. The method of claim 5 , wherein the message is a message associated with a Packet Data Unit (PDU) session between the UE and the base station.

10. The method of claim 6, wherein the message is associated with a Packet Data Unit (PDU) session between the UE and the base station and includes at least one of Quality of Service (QoS) information for indicating a Quality of Service (QoS) required for the PDU session, and session identity information for indicating whether the PDU session is for Time Sensitive Communication (TSC) for a Time Sensitive Network (TSN) application.

11. 2. The method of claim 1, further comprising: detecting a Packet Data Unit (PDU) session for Time Sensitive Communication (TSC) for a Time Sensitive Network (TSN) application; and determining a requirement for time synchronization between the UE and the base station based on the time synchronization requirement of the detected PDU session for TSC.

12. 2. The method of claim 1, further comprising: detecting a Packet Data Unit (PDU) session for a Time Sensitive Communication (TSC) for a Time Sensitive Network (TSN) application; and determining a change to the PDU session for the TSC, wherein determining the request for time synchronization comprises determining a change to the request for time synchronization based on the change to the PDU session for the TSC.

13. Detecting a PDU session for the TSC, Determining a Quality of Service (QoS) required for a PDU session, and detecting a PDU session for a TSC if the requested Quality of Service meets a predetermined time delay criterion; or determining session identity information associated with the PDU session, and detecting a PDU session for a TSC if the session identity information indicates that the PDU session is for a TSC; 12. The method of claim 11 , comprising:

14. receiving a message from a core network entity of the radio network, the message being associated with a Packet Data Unit (PDU) session between the UE and the base station, the message including a Single Network Slice Selection Assistance Information (S-NSSAI) for indicating the request for the time synchronization for the PDU session between the UE and the base station; determining a request for time synchronization includes determining a request for time synchronization based on the S-NSSAI in the received message; The method of claim 1.

15. 2. The method of claim 1, wherein the time synchronization control message includes information for controlling enabling of the time synchronization process with a particular type of PDC, the particular type being one of a plurality of types of PDCs that include Timing Advance (TA) Round Trip Time (RTT) pre-compensation.

16. The method of claim 1 , wherein the time synchronization control message includes information for enabling or disabling a PDC.

17. 2. The method of claim 1, wherein the time synchronization control message includes a first field for controlling the time synchronization process and a second field for indicating whether a PDC is in an operational state or in an inoperative state.

18. 2. The method of claim 1, wherein the time synchronization control message includes a first field for indicating whether the time synchronization process is in an operational state or in an inoperative state, and a second field for indicating whether a PDC is in an operational state or in an inoperative state.

19. The method of claim 1 , wherein the time synchronization control message is a MAC Control Element (MACCE) message or an RRC message.

20. 1. A base station for controlling time synchronization between a user equipment (UE) and a base station of a wireless network, comprising: A communication interface; A processing unit configured to carry out the method according to any one of claims 1 to 19; A base station having

21. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1 to 19.

22. 22. A computer readable storage medium having recorded thereon the computer program of claim 21.

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