WO2020081060A1 - Synchronization in wireless networks for supporting ieee tsn-based industrial automation - Google Patents

Abstract

In a wireless communication system, maximum propagation delay thresholds are received of first and second switches of a corresponding TSN system, the received maximum propagation delay thresholds related to exchanging PTP packets between the first and second switches. The first switch is connected to a UE and the second switch is connected to a UPF in the wireless communication system. A deterministic lifetime is determined for individual PTP packets of the switches to be transferred on a corresponding communication session between the UE and the UPF. The deterministic lifetime is configured to the UE and the UPF so these meet the deterministic lifetime for the communication session. A network element such as the UE or UPF receives indication of the deterministic lifetime and forwards a received packet to an associated switch in the TSN system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

Description

Synchronization in Wireless Networks for Supporting IEEE TSN-based Industrial

Automation

TECHNICAL FIELD

[0001] This invention relates generally to industrial automation (IA) and other time- sensitive networking (TSN) applications and, more specifically, relates to synchronizing between wireless and TSN-based networks.

BACKGROUND

[0002] This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described.

Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, at the beginning of the detailed description section.

[0003] Time sensitive networking (TSN) is being standardized by IEEE 802.1 to provide industrial networks with deterministic delay to handle time sensitive traffic. Currently, wired links are assumed for connecting the sensors and controllers. Moving from wired to wireless sensors and actuators provide advantages, such as mobility, scalability, low cost maintenance, and the like. To connect the wireless devices to a TSN network, wireless transmission technologies such as the ones defined in 3 GPP are necessary. While description herein centers on 3GPP networks, these networks could be generalized to any wireless communication system.

[0004] A key feature necessary to achieve deterministic end-to-end (E2E) latency in a TSN network is by synchronizing all the network elements to a master clock in the system. In the conventional TSN network with wired links, this is achieved to a precision of fraction of a nanosecond. However, for wireless links, the maximum precision possible is limited to the sampling time, e.g., for 20 MHz bandwidth this corresponds to 32 nanoseconds. In order to achieve deterministic E2E (end-to-end) latency for a system with both a wireless network and a TSN network, new mechanisms are needed. BRIEF SUMMARY

[0005] This section is intended to include examples and is not intended to be limiting.

[0006] In an exemplary embodiment, a method is disclosed that includes receiving, in a wireless communication system, maximum propagation delay thresholds of first and second switches of a corresponding time sensitive networking system. The received maximum propagation delay thresholds relate exchanging precision timing protocol packets between the first and second switches. The first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system. The method includes determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds. The method also includes configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session.

[0007] An additional exemplary embodiment includes a computer program, comprising code for performing the method of the previous paragraph, when the computer program is run on a processor. The computer program according to this paragraph, wherein the computer pro gram is a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer.

[0008] An exemplary apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform at least the following: receiving, in a wireless communication system, maximum propagation delay thresholds of first and second switches of a corresponding time sensitive networking system, the received maximum propagation delay thresholds related to exchanging precision timing protocol packets between the first and second switches, wherein the first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system;

determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds; and configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session.

[0009] An exemplary computer program product includes a computer-readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: code for receiving, in a wireless communication system, maximum propagation delay thresholds of first and second switches of a corresponding time sensitive networking system, the received maximum propagation delay thresholds related to exchanging precision timing protocol packets between the first and second switches, wherein the first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system; code for determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds; and code for configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session.

[0010] In another exemplary embodiment, an apparatus comprises: means for receiving, in a wireless communication system, maximum propagation delay thresholds of first and second switches of a corresponding time sensitive networking system, the received maximum propagation delay thresholds related to exchanging precision timing protocol packets between the first and second switches, wherein the first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system; means for determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds; and means for configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session.

[0011] Another example is a method that comprises receiving, at a wireless network element in a wireless communication system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system. The timing information includes a deterministic lifetime for individual packets. The method includes receiving, at the wireless network element, a packet sent on the communication session. The method further includes forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

[0012] An additional exemplary embodiment includes a computer program, comprising code for performing the method of the previous paragraph, when the computer program is run on a processor. The computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer.

[0013] An exemplary apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform at least the following: receiving, at a wireless network element in a wireless communication system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system, the timing information including a deterministic lifetime for individual packets; receiving, at the wireless network element, a packet sent on the communication session; and forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

[0014] An exemplary computer program product includes a computer-readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: code for receiving, at a wireless network element in a wireless communication system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system, the timing information including a deterministic lifetime for individual packets; code for receiving, at the wireless network element, a packet sent on the

communication session; and code for forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

[0015] In another exemplary embodiment, an apparatus comprises: means for receiving, at a wireless network element in a wireless communication system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system, the timing information including a deterministic lifetime for individual packets; means for receiving, at the wireless network element, a packet sent on the communication session; and means for forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the cket being determined to reach the deterministic lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the attached Drawing Figures:

[0017] FIG. 1 A is a schematic representation of a motion control system;

[0018] FIG. 1B is block diagram of how the motion control system of FIG. 1A might be integrated into a system with both a cellular wireless network and a TSN network;

[0019] FIG. 2 is a table illustrating typical characteristics of motion control systems for three major applications;

[0020] FIG. 3 illustrates communication paths for isochronous control cycles within factory units;

[0021] FIGS. 4A and 4B are block diagrams of one possible and non-limiting exemplary system in which the exemplary embodiments maybe practiced, where FIG. 4B illustrates possible internal details certain ones of the entities in FIG. 4A;

[0022] FIG. 5 is a block diagram of an 802.1 AS-Rev time-aware system architecture that is used in some exemplary embodiments;

[0023] FIG. 6 illustrates a PTP operation between a UE-side TSN switch and a UPF-side TSN switch of the corresponding TSN system over the“5G as TSN link” in accordance with an exemplary embodiment; [0024] FIG. 6A illustrates a PTP operation between a UE-side TSN switch and a UPF-side TSN switch of the corresponding TSN system over the“5G as TSN link”, where the “5G as TSN link” has implemented a virtual switch, in accordance with an exemplary embodiment;

[0025] FIG. 7 is a logic flow diagram for synchronization in wireless networks for supporting IEEE TSN-based industrial automation, performed by a TSN-support NF, according to some embodiments of the invention; and

[0026] FIG. 8A is a logic flow diagram for synchronization in wireless networks for supporting IEEE TSN-based industrial automation, performed by a TSN-serving UE, according to some embodiments;

[0027] FIG. 8B is a logic flow diagram for synchronization in wireless networks for supporting IEEE TSN-based industrial automation, performed by a UPF, according to some embodiments; and

[0028] FIG. 9 is a signaling diagram illustrating network signaling between some involved network entities, implementing some embodiments of the proposed mechanisms as examples.

DETAILED DESCRIPTION OF THE DRAWINGS

[0029] The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

[0030] 3 GPP third generation partnership project

[0031] 5G fifth generation

[0032] 5GC 5G core network

[0033] 5GN 5G network

[0034] AF application function

[0035] AMF access and mobility management function

[0036] a.k.a. also known as

[0037] AP Application

[0038] AS Access Stratum

[0039] BS base station

[0040] Cn core network

[0041] CNC centralized network configuration (or configurator) [0042] CU central unit

[0043] CUC centralized user configuration (or configurator)

[0044] DL Downlink

[0045] DRB data radio bearer

[0046] DU distributed unit

[0047] E2E end-to-end

[0048] eNB (or eNodeB) evolved Node B (e.g., an LTE base station)

[0049] gNB (or gNodeB) base station for 5G/NR, i.e , a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC

[0050] EN-DC E-UTRA-NR dual connectivity

[0051] en-gNB or En-gNB node providing NR user plane and control plane protocol terminations towards the UE, and acting as secondary node in EN-DC

[0052] E-UTRA evolved universal terrestrial radio access, i.e., the LTE radio access technology

[0053] gPTP generalized PTP

[0054] HFN hyper frame number

[0055] IA industrial automation or industrial automation and

control

[0056] I/F interface

[0057] LLDP Link Layer Discovery Protocol

[0058] LTE long term evolution

[0059] MAC medium access control (layer)

[0060] MBMS multimedia broadcast multicast service

[0061] MME mobility management entity

[0062] MCE network control element

[0063] MD media dependent

[0064] NETCONF Network Configuration Protocol

[0065] NAS Non-Access Stratum

[0066] NF network function

[0067] ng orNG new generation [0068] ng-eNB or NG-eNB new generation eNB

[0069] NR new radio

[0070] N/W or NW network

[0071] PCF policy control function

[0072] PDCP packet data convergence protocol

[0073] PDU Protocol Data Unit

[0074] PHY physical layer

[0075] PTP Precision Timing Protocol

[0076] QCI Quality of Service (QoS) Class Identifier

[0077] QoS quality of service

[0078] RAN radio access network

[0079] RB Radio Bearer

[0080] Rel release

[0081] RLC radio link control

[0082] RRH remote radio head

[0083] RRC radio resource control

[0084] RU radio unit

[0085] Rx receiver

[0086] S/A sensor/actuator

[0087] SDAP service data adaptation protocol

[0088] SDU Service Data Unit

[0089] SFN system frame number

[0090] SGW serving gateway

[0091] SMF session management function

[0092] SNMP Simple Network Management Protocol

[0093] TR technical re ort

[0094] TS technical specification

[0095] TSN time sensitive networking or time sensitive network

[0096] TTI transmission time interval

[0097] Tx transmitter

[0098] UE user equipment (e.g., a wireless, typically mobile device)

[0099] UL Uplink [00100] UPF user plane function

[00101] URLLC ultra-reliable low latency communication

[00102] WG working group

[00103] The word“exemplary” is used herein to mean“serving as an example, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims.

[00104] The rest of this document is divided, for ease of reference, into different sections.

[00105] 1. Introduction

[00106] The exemplary embodiments herein maybe targeted for, e.g., 5G support of time-sensitive operations including challenging industrial automation (IA) use cases such as motion control ones in which applications running in a number of devices belonging to the same IA system are strictly synchronized and controlled by a master or central server with high-precision timing in order to ensure correct operation of the belonging IA system. See, for instance, 3GPP TR22.804,“Study on Communication for Automation in Vertical Domains,” 1.0.0, December 2017. E2E communications required for IA systems are considered as being highly time sensitive and need high reliability. In some challenging IA applications that rely on cyclic communications for essential control loops, E2E URLLC with extremely low packet delay jitter is needed to meet short cycle time requirements. See, e.g., 3GPP TR 38.913,“Study on Scenarios and Requirements for Next Generation Access Technologies,” 14.3.0, June 2017. The semantics and technical characteristics of motion-control use cases for example are illustrated in 3GPP TR 22.804, as follows.

[00107] FIGS. 1 A and 1B are used to provide an overview of how IA systems might be structured. FIG. 1A is a modified version of a schematic representation of a motion control system, and corresponds to Figure 5.3.2.1-1 from 3GPP TR 22.804,“Study on Communication for Automation in Vertical Domains,” 1.0.0, December 2017. A motion control system (and corresponding cycle) 1 is illustrated. A motion controller 2 sets setpoints 4 and sends these through a motor drive 5 to actuators 6. The actuators 6 act 8 on those set points 4 in order to perform the processes 10. There is a sensing 12 by the sensors 14 to sense the actual values 15 and send these back to the motor drive 5, which sends get points 18 to the motion controller 2.

[00108] FIG. 1B is block diagram of how the motion control system 1 of FIG 1A might he integrated into a system with both a cellular wireless network 100 and a TSN network 101. This is a simple introduction, and these networks are described in more detail below. In the IA system 90, used in a location such as in a factory, of FIG 1B, the wireless network 100 comprises the RAN node 170, the UPF 38, and the UEs 110-1, 110-2, and 110-3, while the TSN network 101 comprises the TSN switch 39, UE-side switches 38, and the end stations 34. The IA system 90 also includes the controller 2, motor drives 5, and motors 19. There are three UEs, UE1 110-1, UE2 110-2, and UE 3 110-3, connected via corresponding wireless links 111-1, 111-2, and 111-3 to the RAN node 170. Each UE 110 has a corresponding UE side boundary TSN switch 38-1, 38-2, and 38-3, and end station 34-1, 34-2 or 34-3 and a corresponding motor drive 5-1, 5-1, or 5-3 connected to a corresponding motor 19-1, 19-2, or 19-3. This illustrates one example for integrated the motion control system 1 into the IA system 90.

[00109] FIG. 2 is a table illustrating typical characteristics of motion control systems for three major applications, and corresponds to Table 5.3.2.1-1 from 3GPP TR 22.804,“Study on Communication for Automation in Vertical Domains,” 1.0.0, December 2017. The table shows applications 20, number (#) of sensors/actuators 22, typical message size 24, cycle time T_cyc!e 26, and service area 28. Thus, the cycle time 26 for the cycle 1 can be quite short, as little as 0.5 milliseconds (ms).

[00110] 1.1 Introduction from 3 GPP TS 22.261

[00111] Further details of the motion control use cases are described in 3 GPP TS 22.261,“Service requirements for the 5G system; Stage 1,” 16.3.0, March 2018. These are described below and much of the text in this section comes from 3GPP TS 22 261.

[00112] In Annex D of 3GPP TS 22.261 , considered to be informative, some critical-communication use cases are illustrated. Section D.1 concerns discrete automation - motion control.

[00113] This section details that industrial factory automation requires communications for closed-loop control applications. Examples for such applications are motion control of robots, machine tools, as well as packaging and printing machines. All other discrete-automation applications are addressed in Annex D.2. [00114] The corresponding industrial communication solutions are referred to as fieldbusses. The pertinent standard suite is IEC 61158. Note that clock synchronization is an integral part of fieldbusses used for motion control.

[00115] In motion control applications, a controller interacts with a large number of sensors and actuators (e.g., up to 100), which are integrated in a manufacturing unit. The resulting sensor/actuator density is often very high (up to 1 m ³, i.e., one sensor per cubic meter). Many such manufacturing units may have to be supported within close proximity within a factory (e.g., up to 100 in automobile assembly line production).

[00116] In a closed-loop control application (see FIG. 1A), the controller periodically submits instructions to a set of sensor/actuator devices, which return a response within a cycle time. The messages, referred to as telegrams, are typically small (¾X 56 bytes). The cycle time can be as low as 2 ms (or lower according to FIG. 2), setting stringent end-to-end latency constraints on telegram forwarding (1 ms). Additional constraints on isochronous telegram delivery add tight constraints on jitter (1 ps), and the communication service has also to be highly available (99,9999%).

[00117] Multi-robot cooperation is a case in closed-loop control where a group of robots collaborate to conduct an action, for example, symmetrical welding of a car body to minimize deformation. This requires isochronous operation between all robots. For multi-robot cooperation, the jitter (l ps) is among the command messages of a control event to the group robots.

[00118] To meet the stringent requirements of closed-loop factory automation, the following considerations may have to be taken:

[00119] - Limitation to short-range communications.

[00120] Use of direct device connection between the controller and actuators.

[00121] Allocation of licensed spectrum for closed-loop control operations. Licensed spectrum may further be used as a complement to unlicensed spectrum, e.g., to enhance rehab ility.

[00122] - Reservation of dedicated air-interface resources for each link.

[00123] - Combination of multiple diversity techniques to approach the high reliability target within stringent end-to-end latency constraints such as frequency, antenna, and various forms of spatial diversity, e.g., via relaying. [00124] - Utilizing OTA time synchronization to satisfy jitter constraints for isochronous operation.

[00125] A typical industrial closed-loop motion control application is based on individual control events. Each closed-loop control event consists of a downlink transaction followed by a synchronous uplink transaction, both of which are executed within a cycle time. Control events within a manufacturing unit may have to occur isochronously. Factory automation considers application-layer transaction cycles between controller devices and sensor/actuator devices. Each transaction cycle consists of (1) a command sent by the controller to the sensor/actuator (downlink), (2) application-layer processing on the sensor/actuator device, and (3) a subsequent response by the sensor/actuator to the controller (uplink). Cycle time includes the entire transaction from the transmission of a command by the controller to the reception of a response by the controller. It includes all lower layer processes and latencies on the air interface as well the application-layer processing time on the sensor/actuator.

[00126] FIG. 3 illustrates communication paths for isochronous control cycles within factory units and corresponds to Figure D.l-l from 3GPP TS 22.261,“Service requirements for the 5G system; Stage 1,” 16.3.0, March 2018. Figure D.l-l depicts how communication may occur in factory automation. In this use case, communication is confined to local controller-to-sensor/actuator interaction within each manufacturing unit. Repeaters may provide spatial diversity to enhance reliability. In a first step, the controller requests sensor data (or an actuator to conduct actuation) from the sensor/actuator (S/A) using isochronous requests. In a second step, the sensor (S/A) sends measurement information (or acknowledges actuation) to the controller.

[00127] In section D.1.1 , service area and connection density, it is indicated that the maximum service volume in motion control is currently set by hoisting solutions, i.e. cranes, and by the manipulation of large machine components, e.g., propeller blades of wind-energy generators. Cranes can be rather wide and quite high above the shop floor, even within a factory hall. In addition, they typically travel along an entire factory hall. An approximate dimension of the service area is 100 x 100 x 30 m. Note that production cells are commonly much smaller (< 10 x 10 x 3 m). There are typically about 10 motion-control connections in a production cell, which results in a connection density of up to 10⁵ km ² (i.e., 100,000 per square kilometer). [00128] This ends the description from 3GPP TS 22.261,“Service requirements for the 5G system; Stage 1,” 16.3.0, March 2018.

[00129] 1.2 Introduction for TSN

[00130] In current techniques for providing needed networking and

communication support for IA systems, IEEE 802.1 TSN has emerged as a popular technology. See, e.g., Cisco,“Time-Sensitive Networking: A Technical Introduction,” White Paper (2017).

[00131] This white paper states the following:

[00132] “In its simplest form, TSN is the IEEE 802.1Q defined standard technology to provide deterministic messaging on standard Ethernet. TSN technology is centrally managed and delivers guarantees of delivery and minimized jitter using time scheduling for those real-time applications that require determinism.

[00133] TSN is a Layer 2 technology. The IEEE 802. IQ standards work at OSI Layer 2. TSN is an Ethernet standard, not an Internet Protocol standard. The forwarding decisions made by the TSN bridges use the Ethernet header contents, not the IP address. The payloads of the Ethernet frames can be anything and are not limited to Internet Protocol. This means that TSN can be used in any environment and can carry the payload of any industrial application.

[00134] TSN is a technology focused on time. TSN was developed to provide a way to make sure information can travel from point A to point B in a fixed and predictable amount of time.

[00135] • TSN flow: T erm used to describe the time-critical

communication between end devices. Each flow has strict time requirements that the networking devices honor. Each TSN flow is uniquely identified by the network devices.

[00136] · End devices: These are the source and destinations of the TSN flows. The end devices are running an application that requires deterministic communication. These are also referred to as talkers and listeners.”

[00137] This ends the quotation from the white paper.

[00138] Timing and synchronization in IEEE 802.1 TSN will be based on IEEE 802.1AS-Rev standard (see 5.IEEE P802.lAS-Rev/D7.3, Draft Standard to Local and Metropolitan Area Networks— Timing and Synchronization for Time-Sensitive Applications (August 2, 2018)) which will define a profile of IEEE 1588 PTP (see National Instruments, “Special Focus: Understanding the IEEE 1588 Precision Time Protocol,” (2005)) applicable in the context of IEEE Std 802.1Q.

[00139] The National Instruments article states the following:

[00140] “The IEEE 1588 precision time protocol (PTP) provides a standard method to synchronize devices on a network with sub-microsecond precision. The protocol synchronizes slave clocks to a master clock ensuring that events and timestamps in all devices use the same time base. IEEE 1588 is optimized for user-administered, distributed systems; minimal use of network bandwidth; and low processing overhead.”

[00141] All of this illustrates that the synchronization between devices is very important.

[00142] 2. Overview of exemplary systems

[00143] This section has an overview of exemplary systems suitable for implementing exemplary embodiments.

[00144] TSN provides deterministic messaging for those real-time applications that require determinism. TSN makes sure that a packet of a uniquely identified TSN flow is delivered from one point to another point of the TSN in a fixed and predictable amount of time. TSN therefore provides synchronized and guaranteed packet delivery with strictly constrained packet delay variation or, a.k.a., jitter, using time scheduling across TSN that can be centrally managed by a so-called Centralized Network Configuration (CNC) entity in practical centralized TSN systems. TSN is focused on time and the time synchronization across TSN is provided by using PTP. Note that the CNC is referred to as the Centralized Network

Configuration and the CUC is referred to as Centralized User Configuration in IEEE

P801.1 Qcc/D2.3 , Draft Standard for Local and Metropolitan Area Networks— Bridges and Bridged Networks (May 3 , 2018). However, we will also refer to these as configurators (e.g., a Centralized User Configurator).

[00145] A 5G cellular network, however capable, has so far not been designed to provide synchronized packet delivery with deterministic QoS, especially in terms of: (i) delivering a packet considering the corresponding absolute time window; and (ii) delivering the packet in a synchronized manner between multiple UE(s), UPFs, RAN nodes and applications (apart from MBMS and/or broadcast). One principle behind current cellular networks is to provide a radio access connection to a mobile UE for various local and remote access applications and services. The radio access connection is provided and handled separately from transport- and application- level connections, following the model of separating between RAN and CN, C-plane (control plane) and U-plane (user plane), AS and NAS on C-plane coupled with flexible bearer service and QoS resolution. There is no strict timing synchronization of packet transmissions on the C-plane and U-plane. The radio transmissions between UE and BS of a serving RAN are synchronized for Tx/Rx radio operations on PHY and up to lower MAC for LI transport blocks on the basis of predefined TTI for UL and DL separately. There is no strict timing for data transmissions on L2 and above, including upper MAC, RLC, PDCP and RRC on C-plane, except for timer operations guarding expected Tx/Rx events which are on the order of tens of milliseconds. NAS level signaling and timer operation between UE and CN for C-plane may adopt some system timing resolved using, e.g., SFN and HFN as in LTE for instance. In other words, the packet transmission and delivery in cellular networks so far are asynchronous.

[00146] Thus, using a cellular network to provide radio connectivity for TSN end-points must consider how to leverage non-strict or unspecified synchronicity or timing of current cellular packet access for the strictly synchronized and deterministic messaging of TSN.

[00147] Turning to FIGS. 4A and 4B, these are block diagrams of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced, where FIG. 4B illustrates possible internal details of the entities in FIG. 4A. In FIG. 4A, the cellular wireless network 100 (referred to also as a serving 5G networkbelow) interfaces witha TSN network 101 in the LA. system 90, which might be used for instance in a factory.

[00148] The TSN network 101 comprises a CUC 30, a CNC 32, a TSN switch 39, two end stations 34-1 and 34-2, aUE side boundary TSN switch 36 (also referred to as a UE side TSN switch herein), and a UPF side boundary TSN switch 37 (also referred to as a UPF sign TSN switch herein). The UE side boundary TSN switch 36 is connected to the TSN end station 34-1 (in the TSN system 101) via a link 40, which is typically a non-wireless link such as an Ethernet cable, although optical fiber or other links might be used. Similarly, the UPF side boundary TSN switch 37 is connected to the TSN switch 39 (in the TSN system 101) via a link 41, which is typically a non-wireless link such as an Ethernet cable, although optical fiber or other links might be used. The following interfaces are used: ES-C between the CUC 30 and the end stations 34-1 and 34-2; and TSN-C between the CNC 32 and the UE side boundary TSN switch 36, the UPF side boundary TSN switch 37, and the TSN switch 39. The UE side boundary TSN switch 36 is connected to the UE 110 through a link 42, and the UPF 38 is connected to the UPF side boundary TSN switch 37 via a link 44.

[00149] The cellular wireless network 100 in this example has an extended 5G boundary 105 in supporting TSN. The cellular wireless network 100 comprises a UE 110, a RAN node 170, a UPF 38, an AMF 40, an SMF 42, a PCF 44 and a TSN-support network function (NF) 150. At least the TSN support NF 150 is implemented by a network control element (NCE) 190. The UPF 38 is implemented in a network element (NE) 190’. The NCE 190 is shown as also implementing some or all of the AMF and/or the SMF and/or the PCF. The following interfaces are illustrated: N1 between the AMF 40 and the UE 110; N2 between the AMF 40 and the RAN node 170; N3 between the RAN node 170 and the UPF 38; N6 between the UPF 38 and the UPF side boundary TSN switch 37; N4 between the UPF 38 and the SMF 42; Nl 1 between the AMF 40 and the SMF 42; and N7 between the SMF 42 and the PCF 44. There is also an N5 interface between the TSN support NF 150 and the CNC 32.

[00150] FIG. 4B shows isolated elements from FIG. 4A. In FIG. 4B, the user equipment (UE) 110, radio access network (RAN) node 170, and network control element(s) 190 are illustrated. In FIG. 4B, a user equipment (UE) 110 is in wireless communication with and part of the cellular wireless network 100. A UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133. The one or more buses 127 maybe address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a TSN module 140, comprising one of or both parts 140-1 and/or 140-2, which may be implemented in a number of ways. The TSN module 140 maybe implemented in hardware as TSN module 140-1, such as being implemented as part of the one or more processors 120. The TSN module 140-1 maybe implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the TSN module 140 maybe implemented as TSN module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125 and the computer program code 123 maybe configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with RAN node 170 via a wireless link 111.

[00151] The RAN node 170 is a base station that provides access by wireless devices such as the UE 110 to the wireless network 100. The RAN node 170 maybe, for instance, a base station for 5G, also called New Radio (NR). In 5 G, the RAN node 170 may be a NG-RAN node, which is defined as either a gNB or an ng-eNB. A gNB is a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to a 5GC (e.g., the network control element(s) 190). The ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC. The NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DUs) (gNB-DUs), of which DU 195 is shown. Note that the DU may include or be coupled to and control a radio unit (RU). The gNB-CU is a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the Fl interface connected with the gNB-DU. The Fl interface is illustrated as reference 198, although reference 198 also illustrates a link between remote elements of the RAN node 170 and centralized elements of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU One gNB-CU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface 198 connected with the gNB-CU. Note that the DU 195 is considered to include the transceiver 160, e.g., as part of an RU, but some examples of this may have the transceiver 160 as part of a separate RU, e.g., under control of and connected to the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station, for LTE (long term evolution), or any other suitable base station.

[00152] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor(s) 152, memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memory/memories and processors), and/or other hardware, but these are not shown. The one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the RAN node 170 to perform one or more of the operations as described herein.

[00153] The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 communicate using, e.g., hnk 176. The link 176 may be wired or wireless or both and may implement, e.g., an Xn interface for 5G, an XI interface for LTE, or other suitable interface for other standards.

[00154] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like.

[00155] The wireless network 100 may include a network control element or elements NCE(s) 190 or network element(s) NE(s) 190’ that may include core network functionality, and which provides connectivity via a link or links 181 with a further network, such as a telephone network and/or a data communications network (e.g., the Internet). Such core network functionality for 5G may include access and mobility management functions) (AMF(S)) and/or user plane functions (UPF(s)) and/or session management function(s) (SMF(s)). Such core network functionality for LTE may include MME (Mobility Management Entity)/SGW (Serving Gateway) functionality. These are merely exemplary functions that may be supported by the network control element(s) 190, and note that both 5G and LTE functions might be supported. The RAN node 170 is coupled via a link 131 to the network control element (NCE) 190. The link 131 maybe implemented as, e.g., an NG interface for 5G, or an SI interface for LTE, or other suitable interface for other standards. The NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The NCE 190 includes a TSN support NF 150, comprising one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways. The TSN support NF 150 may be implemented in hardware as TSN support NF 150-1, such as being implemented as part of the one or more processors 175. The TSN support NF 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the TSN support NF 150 may be implemented as TSN support NF 150-2, which is implemented as computer program code 173 and is executed by the one or more processors 175. In a further example, the UPF 38 maybe implemented by anNE 190’ and implemented as UPF 38-1 as hardware (e.g., in the one or more processors 175 or other circuitry) or as UPF 38-2 as computer program code 171 that is executed bythe one or more processors 175. The one or more memories 171 and the computer program code 173 are therefore configured, with the one or more processors 175, to cause the NCE 190 to perform the operations described herein.

[00156] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.

[00157] The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and maybe implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, and 171 maybe means for performing storage functions. The processors 120, 152, and 175 maybe of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non- limiting examples. The processors 120, 152, and 175 maybe means for performing functions, such as controlling the UE 110, RAN node 170, and other functions as described herein

[00158] The structure in FIGS. 4A and 4B is based on an interworking model between TSN and 5G cellular networks, in which the serving 5G cellular network provides a smart radio access connection for a TSN transport link between a UE-side TSN switch 36 and a UPF-side TSN switch 37 as shown in FIG. 4A, rather than integrated functions of a TSN bridge towards a TSN end-station or end-point via a UE 110. This structure, therefore, is referred to as the“5G as TSN link” option.

[00159] In brief, in the“5G as TSN link”, the serving 5G cellular network provides a smart radio access connection for a TSN transport link between a UE-side TSN switch and a UPF-side TSN switch. The principles as well as motivations for the“5G as TSN link” include one or more of the following.

[00160] 1 ) This provides a clear functional split between different domains:

User-, TSN Ethernet- and 5G System domains.

[00161] 2) This provides a robust adaptation to all the architecture models of

TSN, as identified in a IEEE 802.lQcc specification.

[00162] 3) This provides full control in providing required synchronicity and determinism within the 5G domain, i.e., via an enhanced QoS framework of 5G, for serving individual TSN flows.

[00163] 4) This provides flexibility in providing redundancy and seamless mobility for serving TSN.

[00164] 5) This provides reducing requirements for determinism within the 5G domain as much as possible.

[00165] In the“5G as TSN link” option, the following functionality may be implemented.

[00166] 1) The UE-side boundary TSN switch 36 is responsible for the last-stage

TSN timing towards the TSN end-station 34-1 (e.g., an application within a host), instead of the serving 5G network, whereas the UPF-side boundary TSN switch 37 is taking care of the TSN timing towards TSN in the network/application side.

[00167] 2) The serving 5G network 100 has control over at least the UE-side boundary TSN switch 36 and optionally the UPF-side boundary TSN switch 37, along with setting the propagation delays for the connection between the two boundary switches 36, 37. In general, it is assumed that the serving 5G network 100 is connected to the UPF side boundary TSN switch(es) 37 of individual TSN(s) being served. The serving 5G network 100 may optionally have one or more additional TSN switches (not shown) in between the two boundary switches 36, 37 so as to decompose the connection between the two boundary switches into more than one more controllable links if needed. These additional TSN switches are in between the two boundary switches 36, 37 and within the extended 5G boundary 105 and under control of 5G network 100, whereas TSN switch 39 is native to TSN network 101, i.e., fully controlled by TSN network 101 and not 5G network 100. Hence, this kind of additional TSN switch is more like the UE-side TSN switch 36 from a 5G network control perspective. However, there may be differences between this kind of TSN switch and the UE-side TSN switch 36, from 5G network access and connectivity perspectives. In general, the serving 5G network 100 may use TSN switches as a means to communicate and get scheduled times from the TSN controller (CNC 30). It is noted that the switch is a universal element of communication networks. The serving 5G network domain with such TSN switch or switches is referred to as an extended 5G boundary 105. As described previously additional TSN switches maybe used between the two boundary switches 36, 37 and under control of 5G network 100, as clarified above. Note also that it is optional to have UPF side boundary TSN switch 37 under control of 5G network 100. Upon activation of a UE-side TSN switch 36 or a TSN switch in between the two boundary switches 36, 37 under control of the serving 5G network 100, the serving 5G network 100 may provide a smart radio access connection for interconnecting the TSN switch to the corresponding TSN system via a corresponding UPF-side boundary TSN switch 37.

[00168] 3) The serving 5G network 100 may provide smart radio access services for transporting TSN data traffic between a UE-side boundary TSN switch 36 and a UPF-side boundary TSN switch 37 with QoS control as per an individual TSN flow or as per a class of TSN flows which have, e.g., the same E2E latency and reliability requirements. That is, the “5G as TSN link” may be dynamically adapted based on QoS requirements of individual TSN flows to be served by the 5G network 100. The“5G as TSN link” assumes that UE-side devices including TSN end-station(s) 34, UE-side boundary TSN switch 36 and UE 110, irrespective of whether they are integrated or not, are on the same platform, i.e , associated to each other beforehand and moving together.

[00169] The“5G as TSN link” therefore introduces the UE-side TSN switch 36 per TSN-serving UE 110. Hence, the“5G as TSN link” assumes that the TSN domain is able to accommodate as many TSN switches as the number of needed TSN-serving UEs. The TSN control overhead, i.e., due to TSN-C signaling concerning network configuration and management of UE-side TSN switches (but not TSN flows), is therefore scaled up with the number of needed TSN-serving UEs. On the other hand, having the UE-side TSN switch does not cause scalability issue to the serving 5G network 100, as the serving 5G network 100 needs to provide connections and services to all the needed TSN-serving UEs 110 anyways. To leverage the scalability issue towards the TSN domain while taking control of at least UE-side TSN switches 36, the introduced TSN-support NF 150 may be acting as a CNC proxy to all the TSN switches 36 in the extended 5G boundary, and is referred to as the secondary CNC. The CNC 32 of TSN is referred to as the primary CNC. The secondary CNC may feed the primary CNC 32 with all the needed information related to all TSN switches within the extended 5G boundary.

[00170] As described above, TSN-support NF 150 is introduced in the structure of FIG.4A for facilitating C-plane network control of the serving 5G network for TSN support including the above features.

[00171] It is recognized that TSN is focused on time and the time

synchronization across IEEE 802.1 TSN is based on IEEE 802.lAS-Rev standard (see IEEE P802.lAS-Rev/D7.3, Draft Standard to Local and Metropolitan Area Networks— Timing and Synchronization for Time-Sensitive Applications (August 2, 2018)) that defines the use of IEEE 1588 PTP (see National Instruments,“Special Focus: Understanding the IEEE 1588 Precision Time Protocol” (2005)) where applicable in the context of TSN. Hence, 5G support of TSN, however, imposes a need for supporting 802.1 AS-Rev synchronization and PTP. This description therefore considers how the“5G as TSN link” may support 802.1 AS-Rev synchronization effectively, and further synchronization issues within the 5G domain which are important to 5G support of TSN.

[00172] An 802.1 AS-Rev compliant network for gPTP-based distribution of time synchronization consists of time-aware systems (i.e. time-aware relays and time-aware end-stations) connected by physical medium. The“5G as TSN link”, in the sense of

802.1 AS-Rev, is rather a logical segment of the medium connecting the two time-aware relays, the UE-side TSN switch 36 and UPF-side TSN switch 37. As such, the“5G as TSN link” structure is not required to implement time-aware system model shown in FIG. 5, which is a block diagram of an 802.1 AS-Rev time-aware system architecture 500 that is used in some exemplary embodiments. This structure is also referred to as an 802.1 AS time-aware relay 500. This figure has been copied from 802.1 AS-Rev/D7.3, see Figure 7-8, but the structure is used in an exemplary embodiment for TSN switched 36, 37 (see FIG. 6) and is therefore modified. The switches 36, 37 can use the media dependent time-aware system entities 510-1 and 510-2 to provide interfaces between wireless network 100 and TSN system 101. This is explained in more detail below. Also shown are a media independent entity 530 and a time-aware higher-layer application 540.

[00173] Furthermore, as the“5G as TSN link” allows for a clear separation or functional split between the 5G and TSN domains, it is not necessary for the serving 5G network 100 and a corresponding TSN system 101 being served to share or synchronize to the same clock or use the same synchronization mechanism. Exemplary embodiments herein focus on how to enable the“5G as TSN link” to forward PTP packets between the UE-side TSN switch 36 and corresponding UPF-side TSN switch 37 with a deterministic delay in order to allow the UE-side TSN switch 36 to synchronize to the corresponding TSN system 101 using PTP. This is needed even before serving any actual TSN flow.

[00174] A few remarks are made now for reasons in order to highlight technical effects and benefits of exemplary embodiments described herein. The need for supporting IEEE 802.1 AS-Rev and IEEE 1588 PTP has been established in the ongoing 3GPP SA2 SI: 5G System Rel-l6 FS_Vertical_LAN. See the following: S2-188342,“Solution of time

synchronization”, Huawei, 3GPP SA2 WG2 #128Bis, 20-24 August 2018; S2-188125,‘Time Synchronization Support of 3GPP Network”, Samsung, 3GPP SA2 WG2 #l28Bis, 20-24 August 2018; and S2-188103,“Synchronization”, Nokia, 3 GPP SA2 WG2 #l28Bis, 20-24 August 2018. Different assumptions/models for 5G-TSN integration/interworking and synchronization solutions are addressed in these references. In S2-188342, for instance, techniques are provided for synchronizing the clock between UE and UPF on transport layer based on using the same packet-based mechanism of IEEE 1588 PTP. In S2-188125 and S2-188103, the serving 5G network is modelled as a TSN bridge, that is,“UPF<->UE” of the serving 5G network is a“time-aware relay”, as opposed to the“5G as TSN link” model. That is,“UPF<->UE” of the serving 5G network is a segment of the medium connecting the two time-aware relays we consider herein. The issue of how the serving 5G network supports forwarding PTP packets in particular is not addressed in S2-188342, S2-188125, and

S2-188103.

[00175] IEEE 802.1 AS-Rev (see IEEE P802.1AS-Rev/D7.3, Draft Standard to Local and Metropolitan Area Networks— Timing and Synchronization for Time- Sensitive Applications (August 2, 2018)) allows native path delay measurements between ingress and egress nodes of a CSN (coordinated shared network) wherein the ingress and egress nodes behave as time-aware relays in accordance with IEEE 802.lAS-Rev. The“5G as TSN link” considered herein does not assume that UPF and UE are time-aware relays in accordance with IEEE 802.1 AS-Rev and therefore the CSN native path delay measurements as described in IEEE 802.1 AS-Rev 16.4.3.2 may not be applicable. Instead, an exemplary embodiment herein considers that native methods are used to measure the residence time of individual PTP packets between the UE-side TSN switch 36 and corresponding UPF-side TSN switch 37 spent within the serving 5G network 100 and to ensure that the residence time of the individual PTP packets is deterministic.

[00176] 3. Overview of certain exemplary embodiments

[00177] This section describes an overview of some exemplary embodiments. As described above, exemplary embodiments herein focus on how to enable the“5G as TSN link” to forward PTP packets between the UE-side TSN switch 36 and corresponding UPF-side TSN switch 37 with a deterministic delay in order to allow the UE-side TSN switch 36 to synchronize to the corresponding TSN system 101 using PTP. This is needed even before serving any actual TSN flow. FIG. 6 is used to explain one example of how the“5G as TSN link’ may provide a deterministic D_5G delay for messages exchanged between the switches 36 and 37 (e.g., in references 630 and 640, described below).

[00178] Referring to FIG. 6, this figure illustrates a PTP operation between the UE-side TSN switch and the UPF-side TSN switch of the corresponding TSN system over the “5G as TSN link”, in accordance with an exemplary embodiment. The“5G as TSN link” structure 600, which uses the serving 5G network 100, supports 802.1 AS-Rev for the purpose of time synchronization between UPF side switches 37 and UE side switches 36. The synchronization maybe based on, e.g., using IEEE 1588 PTP.

[00179] In FIG. 6, the“5G as TSN link” structure 600 is forwarding IEEE 1588

PTP messages for propagation delay measurements 630 (Pdelay_Req, Pdelay_Resp, Pdelay_Resp_Follow_Up) and for the transport of time (e.g., TSN clock) synchronization 640 (Sync and Follow_Up) between media dependent ports of the UE side and UPF side switches 36, 37, operating as 802.1 AS time-aware relays 500, without altering their timestamps. Any discrepancy between the measured delay D 610 and the delay experienced by the Sync message will translate into synchronization error. It is therefore important that the“5G as TSN link” structure 600 provides constant and preferably symmetric delay D_5G 620 (depending on capabilities of time-aware relays to compensate the asymmetry). [00180] The link 42 in this example maybe an Ethernet cable, as the media dep endent (MD) entity (e . g. , port) 510-2 for the UE side boundary TSN switch 36 comprises a full-duplex Ethernet port. Similarly, the link 44 in this example may be an Ethernet cable, as the MD entity (e.g., port) 510-1 for the UPF side boundary TSN switch 37 comprises a full-duplex Ethernet port. The UE side boundary TSN switch 36 has an MD entity (e.g., port) 510-1 that connects to link 40, and the UPF side boundary TSN switch 37 has an MD entity (e.g., port) 510-2 that connects to link 41.

[00181] Certain exemplary embodiments propose the following mechanisms for the serving 5G network 100 to provide smart transport services of PTP messages between the UE-side TSN switch 36 and UPF-side TSN switch 37 of the corresponding TSN system 101. The exemplary proposed mechanisms are described from a control entity of the serving 5G network, referred to as the TSN-support NF 150. This NF 150 is introduced for addressing network control functions of a serving 5G network for TSN support using the“5G as TSN link” structure 600 in general. The TSN-support NF 150 maybe introduced into the 3GPP 5G network 100 as a separate NF and/or as an extension of the existing NF(s) such as AMF 40/SMF 42 and/or PCF 44 or an access function (AF), for examples. The following exemplary mechanisms may be used.

[00182] 1) TSN-support NF 150 receives the maximum propagation delay thresholds (e.g., meanLinkDelayThresh) (max. prop delay ths. 605) of individual UE-side 36 and UPF-side 37 TSN switches per corresponding ports that should not be exceeded during the PTP -based propagation delay measurements in order for the ports to be marked as

PTP-capable. Note that meanLinkDelayThresh is adopted and specified in P802.1 AS-Rev. This is defined as a propagation time threshold, above which a port is not considered capable of participating in the IEEE 802.1 AS protocol. There is one instance of this variable for all the domains (per port). The variable is accessible by all the domains. Note that the variable name may be changed or different, as this variable name has changed over time, but the concept of having a propagation time threshold that is known and has to be met should remain the same. This information may be received either from TSN-serving UE 110 for associated UE-side TSN switch 36 or from CNC 32 of the corresponding TSN system 101 or via PCF 44 or AF (not shown) for UPF-side TSN switch 37 and UE-side TSN switch 36.

[00183] One possible determination of meanLinkDelayThresh is explained using the example of FIG. 6. The UPF side boundary TSN switch 37 initiates propagation delay measurements towards the UE side boundary TSN switch 36 by sending Pdelay_Req on MD port 510-1, whose type maybe, e.g., 1000BASE-X. If the results, meanLinkDelay, of those measurements (e.g., determined by receiving the Pdelay_Resp) indicate that meanLinkDelay> meanLinkDelayThresh, switch 37 will conclude that its link towards switch 36 is not capable of forwarding PTP messages and the MD port 510-1 will be blocked.

Therefore, it is important to ensure latency shorter than meanLinkDelayTresh over“5G as TSN link” structure 600.

[00184] 2) The TSN-support NF 150, based on the received maximum propagation delay thresholds 605 of a UE-side TSN switch and a corresponding interconnected UPF-side TSN switch, determines permitted 5G forwarding delay D_SG 620 <

meanLinkDelayThresh (e.g., 605). TSN-support NF 150 then triggers to configure the corresponding PDU session that is used for transferring PTP packets between the TSN-serving UE 110 and corresponding UPF 38 with 5QI (which is the QCI of 5G) that guarantees 5G bearer service for the corresponding PTP messaging with latency smaller than D_SG 620 as well as a deterministic lifetime for individual PTP packets transferred on the corresponding PDU session set equal to D_SQ 620. As is known, a UE receives services through a Protocol Data Unit (PDU) session, which is a logical connection between the UE and data network. Note that the PTP messaging should observe deterministic delay. Hence, it is helpful for the serving 5G network 100 to provide deterministic forwarding of PTP packets with a constant forwarding delay or packet lifetime of D_5G 620. That is, the“5G as TSN link” structure 600 emulates a physical wire whose delay is expected to be deterministic. After switches 37 and 36 perform link delay measurements (e.g., using Pdelay_Req/Resp/Resp_Follow_Up PTP messages) to determine this delay, they expect that Sync message will experience the same delay, so that UE side boundary TSN switch 3 can synchronize to UPF side boundary TSN switch 37 by adding the delay to the timestamp (as one example) in the Sync. If every PTP message would experience different delay, this would likely not be possible.

[00185] If meanLinkDelayThresh 605 cannot be met, the TSN-support NF 105 may initiate to create one or multiple virtual time-aware relays with the functionality of 802 1 AS-Rev time-aware relays in the path between the UE-side 36 and UPF-side 37 switches in a way that meanLinkDelayThresh 605 between the UE-side (UPF-side) TSN switch and the closest virtual time-aware relay can be met. In more detail, the delay threshold is between two neighboring time-aware relays and threshold is defined per port of an individual time-aware relay towards its neighbor. Hence, using an additional virtual time-aware relay in between the two switches 36 and 37 (and not between the UE 110 and the UE side TSN switch 36) is a way to decompose the neighbor relationship between the two switches 36 and 37. This is described below in reference to FIG. 6A. The link between the UE side switch 36 and the virtual time-aware relay may fit for the meanLinkDelayThresh of the UE side switch 36 and the link between the UPF side switch 37 and the virtual time-aware relay may fit for the

meanLinkDelayThresh of the UPF side switch 37. The virtual time-aware relay and how to make it fit is under control of 5G network.

[00186] 3) The TSN-support NF 150 may further configure the TSN-serving UE

110 (and UPF 38) to schedule the delivery of PTP packets to the UE-side switch 36 (e.g., and UPF-side switch 37) once their lifetime inside the serving 5G equals D_SG 620, or to drop them otherwise.

[00187] Referring now to FIG 6 A, this figure illustrates a PTP operation between a UE-side TSN switch 36 and a UPF-side TSN switch 37 of the corresponding TSN system over the“5G as TSN link” structure 600-1 , where the“5G as TSN link” structure 600-1 also has implemented a virtual time-aware relay 650 (e.g., a version 500-3 of a time-aware relay 500 described in FIG. 5), in accordance with an exemplary embodiment. There is a link 642 between the UE 110 and the virtual time-aware relay 650 and a link 644 between the virtual time-aware relay 650 and the UPF 644.

[00188] The propagation delay measurements 630-1 and 630-2 are performed, with measurement 630-1 occurring between the MD time-aware system entity 510-1 of the UPF side boundary TSN switch 37 and the MD time-aware system entity 510-2 of the virtual time-aware relay 650, and measurement 630-2 occurring between the MD time-aware system entity 510-1 of the virtual time-aware relay 650 and the MD time-aware system entity 510-2 of the UE side boundary TSN switch 36. The measured delays of 630-1 and 630-2 are, respectively, D’ 610-1 and D” 610-2. Since both D’ 610-1 and D” 610-2 should be smaller than meanLinkDelayThresh, TSN-support NF 150 should determine and configure the permitted 5G forwarding delays D’_SG 620-1 < meanLinkDelayThresh and D”_5Q 620-2 < meanLinkDelayThresh, where“<” means“less than”. The transport of time synchronization between 37 and 36 occurs in two steps: 640-1 and 640-2.

[00189] The TSN support fimction 150 in block 690 determines to implement time-aware relay 650 and causes the 5GN (5G network) 100 to implement the relay 650. The determination may be based on, e.g., if the supported deterministic lifetime on the

communication session between the first and second switches is larger than a maximum propagation delay threshold, the virtual switch 650 maybe implemented to make it possible that the supported lifetime between the first switch and the virtual switch and between the second switch and the virtual switch is smaller than the maximum propagation delay threshold.

[00190] FIGS. 7, 8A, and 8B illustrate some embodiments from perspectives of the TSN-supportNF 150 (FIG. 7), the TSN-serving UE (FIG. 8), and the UPF 38, which may be used to further understand the TSN-support NF - a network control entity, and the UE as these relate to exemplary embodiments.

[00191] Turning to FIG. 7, this figure is a logic flow diagram for

synchronization in wireless networks for supporting IEEE TSN-based industrial automation, performed by a TSN-support NF 150, according to some embodiments. This figure also illustrates the operation of an exemplary method or methods, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments. In an example, the TSN-support NF 150, as implemented by the NCE 190, performs the blocks in FIG. 7.

[00192] In block 710, the TSN support NF 150 performs the operation of receiving maximum propagation delay thresholds of a UE-side TSN switch 36 and a UPF-side TSN switch 37 of a corresponding TSN system 101. The received maximum propagation delay thresholds relate to exchanging PTP packets between the UE-side TSN switch and the UPF-side TSN switch 37. In block 720, the TSN support NF 150 performs the operation of determining a deterministic lifetime for individual PTP packets of the UE-side TSN switch 36 and the UPF-side TSN switch 37 to be transferred on a corresponding communication (e.g., PDU) session between the TSN-serving UE 110 and UPF 38, based on the received maximum propagation delay thresholds. The communication session may be a PDU session, but other types of communication sessions may also be performed. The TSN support NF 150 in block 730 performs the operation of configuring the deterministic lifetime for individual PTP packets on the corresponding communication (e.g., PDU) session to the TSN-serving UE and UPF. Note that configuration TSN-support NF 150 may also configure a common clock timing to the UE 110 and UPF 38. That is, at least both the UE 110 and UPF 38 use a common clock and the corresponding timing. The use and configuration of the common clock timing is considered as a working assumption herein. It should be noted that the common clock timing could be configured separately from the deterministic lifetime, e.g., in different signaling at a different time, in different messages or different information elements of the same signaling, and the like.

[00193] Referring to FIGS. 8A and 8B, a logic flow diagram is shown for synchronization in wireless networks for supporting IEEE TSN-based industrial automation, performed by a TSN-serving UE (FIG. 8A) or a UPF (FIG. 8B), according to some embodiments. This figure further illustrates the operation of an exemplary method or methods, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments. The blocks in FIG. 8A are assumed to be performed by the HE 110, under control (at least in part) of the TSN module 140. The blocks in FIG. 8B are assumed to be performed by a UPF 38, as implemented by a network element 190’.

[00194] The UE 110 in block 810 performs the operation of receiving timing information related to a communication (e.g., PDU) session set up to carry expected PTP packets for an associated UE-side TSN switch 36. A PDU session is one example of a communication session that may be set up. The timing information includes a deterministic lifetime for individual PTP packets (and may include common clock timing, as previously described). In block 820, the UE 110 performs the operation of receiving a PTP packet sent on the communication (e.g., PDU) session. The UE 110, in block 830, performs the operation of forwarding the PTP packet to the associated UE-side TSN switch 36 in response to a lifetime of the PTP packet being determined to reach the deterministic lifetime.

[00195] FIG 8B is similar to FIG. 8A, except performed by a UPF 38, as implemented by a network element (NE) 190’. In block 810’, the UPF 38 performs the operation of receiving timing information related to a communication (e.g., PDU) session set up to carry expected PTP packets for an associated UPF-side TSN switch, the timing information including a deterministic lifetime for individual PTP packets (e.g., and common clock timing). In block 820, the UPF 38 performs the operation of receiving a PTP packet sent on the communication (e.g., PDU) session. In block 830’, the UPF 38 (as implemented by the NE 190) performs the operation of forwarding the PTP packet to the associated UPF-side TSN switch 39 in response to a lifetime of the PTP packet being determined to reach the deterministic lifetime.

[00196] 4. Additional exemplary details

[00197] The previous section contained an overview of certain exemplary embodiments, and this section provides more detail regarding exemplary embodiments.

[00198] The delay D_JG 620 maybe applied to forwarding individual PTP packets in both directions, from and to the TSN-serving UE 110, corresponding to UL and DL directions of the cellular serving 5G network 100. This means the serving 5G network 100 provides symmetric delays needed for PTP. However, 802.lAS-Rev considers support for asymmetric delays and in this case the serving 5G network may also set different D_5G 620 for UL and DL, and these are referred to as DJGUL and D_5GDL, e.g. as UL and DL deterministic lifetimes, respectively. Thus, the setting of D_¾G 620 may need to take into account the maximum propagation delay thresholds from both the UE-side TSN switch 36 and the UPF-side TSN switch 37. In the case of having the symmetric delays D_5GUL⁼D5GDL⁼D5G, the D_5G 620 should be smaller than the smaller one of the two maximum propagation delay thresholds from the UE-side 36 and UPF-side 37 TSN switches.

[00199] An exemplary embodiment aims for the serving 5G network 100 to provide deterministic (and, e.g., symmetric) forwarding delay of PTP packets, set to D_5G, between the UE-side TSN switch 36 and corresponding UPF-side TSN switch 37, which is desirable if not necessary for the synchronization and operation of the corresponding TSN system 101. This implies that the bearer services over the corresponding PDU session of the serving 5G network for forwarding PTP packets are somewhat time-synchronized so that the TSN-serving UE 110 and UPF 38 terminating the corresponding PDU session is able to determine the time duration a received PTP packet is spending in the serving 5G network 100, i.e., lifetime of the received PTP packet, and ensure that the received PTP packet is forwarded to the UE-side or UPF-side TSN switch in response to the lifetime of the received PTP packet reaching the configured D_5G. This may be facilitated by, for example, having the network entities which are involved in providing the corresponding PDU session, including at least the TSN-serving UE 110 and UPF 38 (and, e.g., optionally the serving RAN node 170) synchronized to a common clock (that is, a clock used by both the UE 110 and the UPF 38). Furthermore, an individual PTP packet transferred over the corresponding PDU session maybe associated with a timestamp set to the time the PTP packet arrives at the serving 5G network 100, e.g., the boundary TSN switch 36 or 37, which may be considered to be the transmitter of the corresponding PDU session. In one option, the timestamp may be included in the header of, e.g., the SDU or PDU carrying the PTP packet between the involved network entities over specified interfaces between them. Thus, at least the TSN-serving UE 110 and UPF 38, which terminate the corresponding PDU session, could be synchronized and configured with timing information including common clock timing and D_SG in order to set or monitor the timestamp or lifetime of an SDU carrying the individual PTP packet, as well as to schedule the delivery of the PTP packet to the UE-side or UPF-side TSN switch. In another option, the ingress time of an individual PTP packet maybe signaled (e.g., as a timestamp) in a separate message separate from but along with another message containing the corresponding PTP packet between the corresponding TSN-serving UE 110 and UPF 38. This other option aims to avoid the need for hardware time stamping of PTP-carrying PDUs. That is, one possible reason for sending the timestamp in a separate message is due to possible hardware limitations, e.g , if a PTP packet cannot be time stamped“on-the-fly” when this packet passes certain a reference point in the protocol stack.

[00200] It is further noted that there maybe many options to implement clock synchronization or time alignment between the corresponding TSN-serving UE 110 and UPF 38 within the serving 5G network domain including GPS based or SIB16-based UTC options or some options provided in the following: S2-188342,“Solution of time synchronization”, Huawei, 3GPP SA2 WG2 #128Bis, 20-24 August 2018; S2-188125,“ Time Synchronization Support of3GPP Network”, Samsung, 3GPP SA2 WG2 #l28Bis, 20-24 August 2018; and S2-188103,“Synchronization”, Nokia, 3 GPP SA2 WG2 #128Bis, 20-24 August 2018.

However, this is not in the focus of this disclosure.

[00201] FIG. 9 illustrates network signaling between some involved network entities, implementing some embodiments of the proposed mechanisms as examples. That is, this figure illustrates providing smart transfer for PTP between a UE-side TSN switch 36 and a UPF-side TSN switch 37.

[00202] In this example, the UE side boundary TSN switch 36 is integrated with or connected to (see block 910) the TSN serving UE 110. The UPF side boundary TSN switch 37 is also interconnected to the UPF 38 (see block 915). The UE side boundary TSN switch 36 and the TSN serving UE 110 perform UE side activation in block 920. In general, this means the UE’s operation is activated. It maybe, e.g., the device is switched on, or device is plugged in, or the device starts to operate from idle mode, and the like, then the device starts to setup the connection to the TSN network 101. In block 930, C-plane connection setup and signaling related to TSN are performed between the UE 110, the serving RAN node 170, the TSN support NF 150, and the AMF/SMF/PCF/AF 905. The label of“AMF/SMF/PCF/AF” means there is some function in the serving 5G network that performs some or all of these functions.

[00203] The UE side boundary TSN switch 36 sends (see signaling 935) via PTP a meahLinkDelayThresh 906 to the TSN serving UE 110. The meanLinkDelayThresh 906 is for use by the serving 5G network and is maximum propagation delay threshold 605 described above. The TSN serving UE 110 forwards, via PTP, a MaxPropDelayThres 941 to the TSN support NF 150 via signaling 940. The MaxPropDelayThres 941 is a maximum propagation delay threshold to be used by the serving 5G network 100 and is similar to the

meanLinkDelayThresh 906 e.g., the content/value of these thresholds maybe the same.

Similar operations occur from the other side of the network: the UPF side boundary TSN switch 37 sends (see signaling 950) via PTP a meanLinkDelayThresh 907 to the

AMF/SMF/PCF/AF 905; and the AMF/SMF/PCF/AF 905 forwards, via PTP, a

MaxPropDelayThres 946 to the TSN support NF 150 via signaling 945. The thresholds 941, 946 maybe the same, although in some embodiments, the UL threshold (e.g., threshold 941) and the DL threshold (e.g., threshold 946) maybe different.

[00204] In block 955, the TSN support NF 150 performs the operation of determining a deterministic lifetime for PTP packets. In an example, the deterministic lifetime is D5_G 620, as in the examples described above. In block 960, the operation of initiating the connection setup for PTP with the deterministic lifetime for PTP packets is performed between the TSN support NF 150 and the AMF/SMF/PCF/AF 905. Note that the TSN support NF 150 and the AMF/SMF/PCF/AF 905 are involved in the PDU session management and configuration of QoS and therefore use the deterministic lifetime for this management and configuration. In block 965, the PDU session and associated DRB set up for PTP transfer with QoS and timing configuration including the deterministic lifetime for PTP packets, and this occursbetween the TSN serving UE 110, the serving RAN node 170, the TSN support NF 150, the AMF/SMF/PCF/AF 905, and the UPF 38. The signaling 970 indicates that the PTP communication occurs between the UE side boundary TSN switch 36 and the UPF side boundary TSN switch 37. Note that the propagation delay measurement 630 and the transport of time-synchronization 640 may be performed in the signaling 970. [00205] The proposed techniques maybe applied for different PDU sessions of the TSN-serving UE 110, carrying either PTP or TSN flows with different synchronization or QoS requirements in terms of, e.g. , required synchronization accuracies, packet delays and delay jitters. Thus, setting D5G for different PDU sessions may take into account different parameters.

[00206] 5. Additional description

[00207] As used in this application, the term“circuitry” may refer to one or more or all of the following:

[00208] (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

[00209] (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and/or digital hardware circuit(s) with

software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processors)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

[00210] (c) hardware circuit(s) and orprocessor(s), such as a microprocessor s) or a portion of a microprocessors), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.”

[00211] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[00212] Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, an instruction set) is maintained on any one of various conventional computer-readable media. In the context of this document, a“computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in FIG. 4B. A computer-readable medium may comprise a computer-readable storage medium (e.g., memories 125, 155, 171 or other device) that maybe any media or means that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable storage medium does not comprise propagating signals.

[00213] If desired, the different functions discussed herein maybe performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or maybe combined.

[00214] Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[00215] It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

Claims

CLAIMS What is claimed is:

1. A method, comprising:

receiving, in a wireless communication system, maximum propagation delay

thresholds of first and second switches of a corresponding time sensitive networking system, the received maximum propagation delay thresholds related to exchanging precision timing protocol packets between the first and second switches, wherein the first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system;

determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds; and configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session

2. The method of claim 1 , wherein:

determining a deterministic lifetime further comprises determining an uplink

deterministic lifetime and determining a downlink deterministic lifetime; and configuring the deterministic lifetime to the user equipment and the user plane function further comprises configuring the downlink deterministic lifetime to at least the user equipment and configuring the uplink deterministic lifetime to at least the user plane function.

3. The method of any of claims 1 or 2, further comprising configuring a clock timing to the user equipment and the user plane function for use by the user equipment and the user plane function to synchronize to a clock that is common to the user equipment and the user plane function.

4. The method of any of claims 1 to 3, further comprising deciding to have at least one time-aware relay between the first switch and the second switch and implementing the at least one time-aware relay between the first switch and the second switch, wherein the at least one time aware relay is implemented in the wireless communication system.

5. The method of any of claims 1 to 4, performed by a network control element in the wireless communication system.

6. The method of claim 5, performed by a time sensitive networking-support network function implemented by the network control element.

7. A method, comprising:

receiving, at a wireless network element in a wireless communication system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system, the timing information including a deterministic lifetime for individual packets; receiving, at the wireless network element, a packet sent on the communication session; and

forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

8. The method of claim 7, wherein the wireless network element is a first wireless network element and the packet is sent from a second wireless network element in the wireless communication system, and wherein both the first and second wireless network elements are synchronized to a common clock.

9. The method of claim 7 or 8, further comprising receiving clock timing for a clock common to both the first and second wireless network elements and synchronizing the first wireless network element with the clock based on the clock timing.

10. The method of claim 7 to 9, wherein the packet is associated with a timestamp set to a time the packet arrived at a boundary TSN switch of the wireless communication system, and the method further comprises the wireless network element receiving the packet comparing via a comparison the timestamp with a time determined by wireless network element receiving the packet and determining the lifetime using the comparison.

11. The method of claim 10, wherein the timestamp is included in a header of a data unit carrying the packet and received by the wireless network element receiving the packet.

12. The method of claim 11 , wherein the data unit comprises one of a service data unit or a protocol data unit.

13. The method of claim 10, wherein the packet is received in a message and wherein the timestamp is included in a separate message but is received along with the message containing the packet.

14. The method of any of claims 7 to 13 , wherein the wireless network element comprises a user equipment and the method is performed by the user equipment.

15. The method of any of claims 7 to 13, wherein the wireless network element comprises a user plane function and the method is performed by the user plane function.

16. An apparatus, comprising:

means for receiving, in a wireless communication system, maximum propagation delay thresholds of first and second switches of a corresponding time sensitive networking system, the received maximum propagation delay thresholds related to exchanging precision timing protocol packets between the first and second switches, wherein the first switch is connected to a user equipment in the wireless communication system and the second switch is connected to a user plane function in the wireless communication system;

means for determining a deterministic lifetime for individual precision timing protocol packets of the first and second switches to be transferred on a corresponding communication session between the user equipment and the user plane function, based on the received maximum propagation delay thresholds; and means for configuring the deterministic lifetime to the user equipment and the user plane function for use by the user equipment and the user plane function so the user equipment and the user plane function meet the deterministic lifetime for precision timing protocol packets for the communication session.

17. The apparatus of claim 16, wherein:

the means for determining a deterministic lifetime further comprises means for

determining an uplink deterministic lifetime and determining a downlink deterministic lifetime; and

the means for configuring the deterministic lifetime to the user equipment and the user plane function further comprises means for configuring the downlink deterministic lifetime to at least the user equipment and configuring the uplink deterministic lifetime to at least the user plane function.

18. The apparatus of any of claims 16 or 17, further comprising means for configuring a clock timing to the user equipment and the user plane function for use by the user equipment and the user plane function to synchronize to a clock that is common to the user equipment and the user plane function.

19. The apparatus of any of claims 16 to 18, further comprising means for deciding to have at least one time-aware relay between the first switch and the second switch and means for implementing the at least one time-aware relay between the first switch and the second switch, wherein the at least one time aware relay is implemented in the wireless communication system.

20. The apparatus of any of claims 16 to 19, performed by a network control element in the wireless communication system.

21. The apparatus of claim 20, performed by a time sensitive networking-support network function implemented by the network control element.

22. An apparatus, comprising:

means for receiving, at a wireless network element in a wireless communication

system, timing information related to a communication session set up to carry precision timing protocol packets for an associated switch in a time sensitive networking system, the timing information including a deterministic lifetime for individual packets;

means for receiving, at the wireless network element, a packet sent on the

communication session; and

means for forwarding, from the wireless network element, the packet to the associated switch in the time sensitive networking system in response to a lifetime of the packet being determined to reach the deterministic lifetime.

23. The apparatus of claim 22, wherein the wireless network element is a first wireless network element and the packet is sent from a second wireless network element in the wireless communication system, and wherein both the first and second wireless network elements are synchronized to a common clock.

24. The apparatus of claim 22 or 23, further comprising means for receiving clock timing for a clock common to both the first and second wireless network elements and means for synchronizing the first wireless network element with the clock based on the clock timing.

25. The apparatus of claim 22 to 24, wherein the packet is associated with a timestamp set to a time the packet arrived at a boundary TSN switch of the wireless communication system, and the apparatus further comprises means for the wireless network element receiving the packet comparing via a comparison the timestamp with a time determined by wireless network element receiving the packet and means for determining the lifetime using the comparison.

26. The apparatus of claim 25, wherein the timestamp is included in a header of a data unit carrying the packet and received by the wireless network element receiving the packet.

27. The apparatus of claim 26, wherein the data unit comprises one of a service data unit or a protocol data unit.

28. The apparatus of claim 25, wherein the packet is received in a message and wherein the timestamp is included in a separate message but is received along with the message containing the packet.

29. A user equipment comprising the apparatus of any of claims 22 to 28.

30. A user plane function comprising the apparatus of any of claims 22 to 28.

31. A communication system comprising an apparatus of any of claims 16 to 21 and an apparatus of any of claims 22 to 29.

32. The apparatus of claim 31 , further comprising the time sensitive network system.

33. A computer program comprising code for performing the method of any of claims 1 to 15, when the computer program is run on a processor

34. The computer program according to claim 33, wherein the computer program is a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer.