Method of High Precision Time Synchronization with a Communication Network Grandmaster for User Plane Function

Described is a method of synchronizing a TSN NW-TT module inside a UPF with a Grandmaster (GM) in a Time Domain of the communication network. The method comprises receiving one or more PTP or gPTP messages on an N3 interface of the UPF. The method includes determining a first time offset value between the GM and the UPF N3 interface based on information received in the PTP or gPTP messages. A timing of the UPF N3 interface is adjusted using the determined first time offset value to synchronize the time between the UPF N3 interface and the GM. The method includes determining a second time offset value between the UPF N3 interface and the NW-TT module. A timing of the NW-TT module is adjusted using the determined second time offset value to synchronize the time between the NW-TT module and the GM.

FIELD OF THE INVENTION

The invention relates to a method of high precision time synchronization with a New Radio (NR) communication network Grandmaster (GM) especially for 5G User Plane Function (UPF). The invention is particularly useful for TSN technologies in wireless communication systems.

BACKGROUND OF THE INVENTION

Fifth-generation (5G) wireless communications and Time-Sensitive Networking (TSN) are key technologies for, for example, industrial communications such as 5G for wireless connectivity and TSN for wired connectivity. In addition to enhanced mobile bandwidth, 5G supports communications with unprecedented reliability and very low latency, as well as massive Internet of Things (IoT) connectivity.

TSN comprises a collection of Ethernet standards introduced by the Institution of Electrical and Electronic Engineers (IEEE) 802.1 group, defining mechanisms for deterministic communication over wired Ethernet links enabling guaranteed packet transport with bounded latency, low packet delay variation, and extremely low packet loss. Both technologies have been designed to provide converged communication for a wide range of services on a common network infrastructure. Significant benefits can be achieved by enabling TSN and 5G to work together.

For a seamless integration between a 5G system (5GS) and a TSN system, it was proposed by the 3rd Generation Partnership Project (3GPP) that the two systems interoperate in a transparent manner to minimize impact on other TSN entities. Therefore, the 5G system acts as one or more virtual TSN bridges of the TSN network. This virtual bridge model defines several gateways between the TSN and the 5G system including a network-side TSN translator (NW-TT) on the user plane function (UPF) side.

The Precision Time Protocol (PTP) or Generalized PTP (gPTP) is a computer networking protocol for synchronizing network elements' clocks. It is an important part of 5G mobile networks which require accurate time sources. The PTP or gPTP is a protocol used to synchronize clocks throughout the communication network, achieving clock accuracy in the sub-microsecond range, making it the perfect choice where strict time synchronization requirements must be met.

A PTP or gPTP system is formed by a clock source, a Grandmaster (GM), that transmits synchronization information toward multiple clock targets (slave devices).

IEEE 802.1AS comprises the IEEE standard for time synchronization of time-sensitive applications in local and metropolitan area networks using gPTP. GM/Slave refers to the timing source in the network being generated by a gPTP GM. The Slave clock utilizes an offset to adjust its time to agree with the Master clock. Other than offset adjustment, the clock frequency of the Slave should also be synchronized with the gPTP GM. Without frequency synchronization, the time of the Slave might still run faster or slower than the GM.

The 5G network supports time synchronization as defined by IEEE 802.1AS across 5G-based logical TSN bridges with Ethernet PDU (Packet Data Unit) session type in the TSN Time Domain. The 5G-based logical TSN bridge needs to calculate the residence time of the 5G network. The 5G network provides an internal system clock for 5G internal synchronization where the base station (gNB), the NW-TT at the UPF side and the device side TST translator (DS-TT) at the User Equipment (UE) side should all be synchronized in the 5G Time Domain with the 5G GM for residence time calculation.

TSN over 5G systems brings numerous benefits to communication networks, but these do not come without challenges.

What is desired is a method to assist time synchronization of an NW-TT module in the UPF with GM in the Time Domain, which is a key step for further supporting high precision time synchronization of TSN end stations over the communications network.

OBJECTS OF THE INVENTION

An object of the invention is to mitigate or obviate to some degree one or more problems associated with known methods of supporting high precision time synchronization of TSN end stations over the communications network.

The above object is met by the combination of features of the main claims; the sub-claims disclose further advantageous embodiments of the invention.

Another object of the invention is to provide a method and system to assist time synchronization of an NW-TT module in the UPF with GM in the Time Domain.

One skilled in the art will derive from the following description other objects of the invention. Therefore, the foregoing statements of object are not exhaustive and serve merely to illustrate some of the many objects of the present invention.

SUMMARY OF THE INVENTION

In a first main aspect, the invention provides a method of synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a communication network with a Grandmaster (GM) in a Time Domain of the communication network. The method comprises receiving one or more Precision Time Protocol (PTP) or Generalized Precision Time Protocol (gPTP) messages on an N3 interface of the UPF. The method includes determining a first time offset value (OffsetN3) between the GM and the UPF N3 interface based on information received in the one or more PTP or gPTP messages. A timing of the UPF N3 interface is adjusted using the determined first time offset value (OffsetN3) to synchronize the time between the UPF N3 interface and the GM. The method includes determining a second time offset value (OffsetNW-TT) between the UPF N3 interface and the NW-TT module. A timing of the NW-TT module is adjusted using the determined second time offset value (OffsetNW-TT) to synchronize the time between the NW-TT module and the GM.

Preferably, the method includes using the determined first time offset value (OffsetN3) to determine a UPF N3 interface clock frequency adjustment value, adjusting a clock frequency of the UPF N3 interface using the UPF N3 interface clock frequency adjustment value, using the second time offset value (OffsetNW-TT) to determine a NW-TT module clock frequency adjustment value, and adjusting a clock frequency of the NW-TT module using the NW-TT module clock frequency adjustment value.

In a second main aspect, the invention provides a UPF module for synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a communication network with a Grandmaster (GM) in a Time Domain of the communication network, the module comprising a memory storing machine-readable instructions and a processor for executing the machine-readable instructions such that, when the processor executes the machine-readable instructions, it configures the UPF module to perform the steps of the first main aspect of the invention.

In a third main aspect, the invention provides a Data Plane Clock Servo module in a UPF module for synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a communication network with a Grandmaster (GM) in a Time Domain of the communication network. The Data Plane Clock Servo module comprises: a first module for receiving a first time offset value (OffsetN3) between the GM and a UPF N3 interface or a second time offset value (OffsetNW-TT) between the UPF N3 interface and the NW-TT module, the first time offset value (OffsetN3) being determined from one or more Precision Time Protocol (PTP) or Generalized Precision Time Protocol (gPTP) messages received at the N3 interface, and the second time offset value (OffsetNW-TT) being determined from a hardware clock of the NW-TT module and a synchronized clock of the UPF N3 interface; a second module for determining if the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) is greater than a predetermined, calculated or selected time period; a Data Plane Clock Filter comprising a moving average filter which, upon receiving the first time offset value (OffsetN3) or the second time offset value (OffsetNW-TT), smooths the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) to attenuate impulse noise to generate a smoothed clock offset output for the 5G Data Plane Clock Offset Controller; a Data Plane Proportional-integral (PI) Controller for receiving the smoothed clock offset output for the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) to produce a fractional tick-rate adjustment u(t) value which coordinates the UPF N3 interface time with the GM tie or coordinates the NW-TT module time with the UPF N3 interface time; and a Data Plane Clock Frequency Adjuster for receiving the fractional tick-rate adjustment u(t) value for the UPF N3 interface or the NW-TT module to adjust the respective clock frequency accordingly; wherein the Data Plane Clock Offset Controller receives the smoothed clock offset output and adjusts the timing of the UPF N3 interface or the timing of the NW-TT module.

In a fourth main aspect, the invention provides a non-transitory computer-readable medium storing machine-readable instructions, wherein, when the machine-readable instructions are executed by a processor, they configure the processor to implement the method of the first main aspect of the invention.

The summary of the invention does not necessarily disclose all the features essential for defining the invention; the invention may reside in a sub-combination of the disclosed features.

The forgoing has outlined fairly broadly the features of the present invention in order that the detailed description of the invention which follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It will be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The following description is of preferred embodiments by way of example only and without limitation to the combination of features necessary for carrying the invention into effect.

It should be understood that the elements shown in the FIGS, may be implemented in various forms of hardware, software or combinations thereof. These elements may be implemented in a combination of hardware and software on one or more appropriately programmed general-purpose devices, which may include a processor, memory and input/output interfaces.

The present description illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope.

Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of systems and devices embodying the principles of the invention.

References to 5G radio equipment in the following description do not exclude the application of the methods described herein to radio equipment of compatible mobile communications systems.

The following description describes implementation of the present invention in a 5G communications network by way of example, but without limitation to implementation of the invention in suitable communications networks.

FIG.1provides a timing diagram for time synchronization of time-sensitive applications in local and metropolitan area networks in accordance with IEEE 802.1AS by way of example of a known timing offset adjustment method.

IEEE 802.1AS “IEEE Standard for Local and Metropolitan Area Networks—Timing and Synchronization for Time-Sensitive Applications” provides protocols, procedures, and managed objects for the transport of timing over local and metropolitan area networks.

Referring toFIG.1, the timing source in the network is generated by a gPTP GM (“TSN GM”)10. The Slave clock (“TSN Slave”)12utilizes an offset to adjust its time to agree with the Master clock of the gPTP GM10.

The steps for determining or calculating the offset includes first calculating a timing delay value related to the “Pdelay_Req” message and the “Pdelay_Response(T2)” message. The timing delay value is given by:

In a next step, a value for the timing offset for adjusting the timing of the Slave clock12to agree with the Master clock of the gPTP GM10makes use of the timing of the “Synch” message and is given by:

Other than the offset timing adjustment, the clock frequency of the Slave clock12should also be synchronized with the gPTP GM10, because, without clock frequency synchronization, the Slave clock12may still run faster or slower than the Master clock of the gPTP GM10despite the step of adjusting the timing of the Slave clock12to agree with the Master clock of the gPTP GM10using the determined timing offset value.

The “Follow_Up” message in the timing diagram ofFIG.1includes a correction field containing the message transit time and residence time as well as the “rateRatio” containing logical syntonization of a time aware system to the gPTP GM10frequency rate. The correction field C carries the time elapsed in the timeaware systems and on the links on the path between the gPTP GM10and the time-aware system preceding a last hop. The rate ratio allows for logical syntonization of a timeaware system to the gPTP GM10frequency rate.

IEEE 802.1AS-2011 defines the gPTP profile which, like all profiles of IEEE 1588, selects options from IEEE 1588, but also generalizes the network architecture to allow PTP to apply beyond wired Ethernet networks.

IEEE 1588 “IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems”. defines a protocol enabling precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing and distributed objects. The protocol is applicable to systems communicating by local area networks supporting multicast messaging including but not limited to Ethernet.

It will be understood therefore that nothing in the following description prevents the method in accordance with the invention being implemented as PTP packets in an IEEE 1588 compliant network as well as gPTP packets in an IEEE 802.1AS compliant network. The method of the invention enables both peer-to-peer mode of time synchronization using gPTP as well as end-to-end mode of time synchronization using PTP.

FIG.2provides a block schematic diagram illustrating the TSN Time Domain14and the 5G Time Domain16in a known IEEE 802.1AS compliant TSN Network.

The TSN Time Domain14for the 5G network supports time synchronization (as defined by IEEE 802.1AS) across 5G-based logical TSN bridge(s) with Ethernet Packet Data Unit (PDU) session type in the TSN Time Domain14. The 5G-based logical TSN bridge(s) needs to calculate the residence time of the 5G network.

The 5G Time Domain16for the 5G network provides an internal system clock for 5G internal synchronization where the gNB, the NW-TT at UPF side20and the DS-TT at UE side should all be synchronized in the 5G Time Domain with a 5G GM18for residence time calculation.

The present invention focuses on time synchronization in the 5G Time Domain16as will be described more fully hereinafter.

FIG.3provides a block schematic diagram illustrating in more detail the UPF20in the IEEE 802.1AS compliant TSN Network ofFIG.2.

Referring toFIG.3, the gNB22and the N3 interface24of the UPF20synchronize time through the gPTP protocol in accordance with the 3GPP specifications. However, the method by which the NW-TT module26at the N6 interface28on the UPF20synchronizes its time with the UPF N3 interface24is outside the scope of the 3GPP specifications. In the 3GPP specifications, the NW-TT module26is based on the N6 interface28of the UPF20. In most cases, the N3 interface24and the N6 interface-based NW-TT module26on the same UPF20use different network interfaces. However, different network interfaces commonly use different sources of oscillator and thus typically have different hardware clock sources which may vary in their respective timings. Without time synchronization of the NW-TT module26in the UPF20with the 5G GM18in the 5G Time Domain16, the residence time calculation of any 5G-based logical TSN bridge30(FIG.2) will be incorrect, which will cause incorrect time synchronization of TSN end stations32over the 5G communications network.

The present invention addresses the problem of how to enable the NW-TT module26in the UPF20to track the 5G GM18precisely with at least time synchronization and preferably also frequency synchronization. To this end, the present invention provides, as illustrated byFIG.4, a 5G Data Plane Clock Servo module40in the UPF20as illustrated inFIG.6.

FIG.4is a functional block schematic diagram of the 5G Data Plane Clock Servo module42in accordance with the invention. Shown also is a 5G Data Plane Application Layer50comprising a gPTP module52, a Packet Forwarding Control Protocol module54and a Bridge module56. The UPF N3 interface24and the NW-TT module26based at the N6 interface28are provided in a 5G Data Plane Interface Layer60.

The 5G Data Plane Clock Servo module42is provided in a 5G Data Plane Time Synchronization layer40and comprises a 5G Data Plane Clock Filter44, a 5G Data Plane Proportional-integral (PI) Controller45, a 5G Data Plane Clock Frequency Adjuster46, and a 5G Data Plane Clock Offset Controller47.

The 5G Data Plane Clock Filter44preferably comprises a moving average filter which, upon receiving a first time offset value or a second time offset value, as described more fully hereinafter, smooths the received first time offset value or second time offset value to attenuate impulse noise to generate a smoothed clock offset output for the 5G Data Plane Clock Offset Controller47.

The 5G Data Plane Proportional-integral (PI) Controller45for receives the smoothed clock offset output for the received first time offset value or second time offset value to produce a fractional tick-rate adjustment u(t) value which coordinates the UPF N3 interface24time with the 5G GM18time or coordinates the NW-TT module26time with the UPF N3 interface24time.

The 5G Data Plane Clock Frequency Adjuster46receives the fractional tick-rate adjustment u(t) value for the UPF N3 interface24or the NW-TT module26to adjust the respective clock frequency accordingly.

The 5G Data Plane Clock Offset Controller47receives the smoothed clock offset output and adjusts the timing of the UPF N3 interface24or the timing of the NW-TT module26.

FIG.5is a block schematic diagram of an improved radio equipment, device or network node comprising the 5G Data Plane Clock Servo module42in accordance with the invention. The improved radio equipment device70is connected to a gNB22operating in a 5G NR communications system environment, although the improved radio equipment device70of the invention is not limited to operating in a NR 5G communications system but could comprise a radio equipment device for any suitable communications network.

The radio equipment device70may comprise a plurality of functional blocks for performing various functions thereof. For example, the radio equipment device70includes receiver module72providing received signal processing and configured to provide received signals and/or information extracted therefrom to functional block module(s)74such as may comprise various data sink, control element(s), user interface(s), etc. Although receiver module72is described as providing received signal processing, it will be appreciated that this functional block may be implemented as a transceiver providing both transmitted and received signal processing. Irrespective of the particular configuration of receiver module72, embodiments include signal detection module76disposed in association with the receiver module72for facilitating accurate processing and/or decoding of received information and channel signals in accordance with the invention.

Although the signal detection module76is shown as being deployed as part of the receiver module72(e.g., comprising a portion of the radio equipment module control and logic circuits), there is no limitation to such a deployment configuration according to the concepts of the invention. For example, the signal detection module76may be deployed as a functional block of radio equipment device70that is distinct from, but connected to, receiver module72. The signal detection module76may, for example, be implemented using logic circuits and/or executable code/machine readable instructions stored in a memory78of the radio equipment device70for execution by a processor79to thereby perform functions as described herein. For example, the executable code/machine readable instructions may be stored in one or more memories78(e.g., random access memory (RAM), read only memory (ROM), flash memory, magnetic memory, optical memory or the like) suitable for storing one or more instruction sets (e.g., application software, firmware, operating system, applets, and/or the like), data (e.g., configuration parameters, operating parameters and/or thresholds, collected data, processed data, and/or the like), etc. The one or more memories78may comprise processor-readable memories for use with respect to one or more processors79operable to execute code segments of signal detection module76and/or utilize data provided thereby to perform functions of the signal detection module76as described herein. Additionally, or alternatively, the signal detection module76may comprise one or more special purpose processors (e.g., application specific integrated circuit (ASIC), field programmable gate array (FPGA), graphics processing unit (GPU), and/or the like configured to perform functions of the signal detection module76as described herein. The signal detection module76comprises the 5G Data Plane Clock Servo module42in accordance with the invention.

FIG.6is a block schematic diagram of the TSN Time Domain14and the 5G Time Domain16of the TSN Network outlining the steps of the method in accordance with the invention.

The UPF20transmits the gPTP messages between the TSN end stations for time synchronization in multiple TSN Time Domains as illustrated in the known manner. Meanwhile, The NW-TT module26in the UPF20also needs to synchronize its time with the 5G GM18in the 5G Time Domain16. The steps for time synchronization of the NW-TT module26with the 5G GM18in the 5G Time Domain16according to the invention involve a first part {circle around (1)} comprising the UPF20receiving or obtaining the 5G GM18clock via the underlying gPTP compatible transport network through the UPF N3 interface24by receiving one or more gPTP messages and then determining or calculating the first time offset value (OffsetN3) between the 5G GM18and the UPF N3 interface24based on information received in said one or more gPTP messages. In a second part {circle around (2)}, the UPF20adjusts a time of the UPF N3 interface24using the determined first time offset value (OffsetN3) to synchronize the time between the UPF N3 interface24and the 5G GM18. Preferably, the UPF20adjusts the time of the UPF N3 interface24using a smoothed value of the time offset value (OffsetN3) In a third part {circle around (3)}, the UPF20also determines a second time offset value (OffsetNW-TT) between the UPF N3 interface24and the NW-TT module26and adjusts a time of the NW-TT module26using the determined second time offset value (OffsetNW-TT) to synchronize the time between the NW-TT module26and the 5G GM18. Preferably, the UPF20adjusts the time of the NW-TT module26using a smoothed value of the second time offset value (OffsetNW-TT).

In the second part {circle around (2)}, the UFPF20preferably uses the determined first time offset value (OffsetN3) to determine a UPF N3 interface24clock frequency adjustment value and to adjust a clock frequency of the UPF N3 interface24using said UPF N3 interface clock frequency adjustment value. This may involve using the first time offset value (OffsetN3) as an input to the 5G Data Plane Clock Servo module42in the UPF20and based on said first time offset value (OffsetN3), performing the steps at the 5G Data Plane Clock Servo module of part {circle around (2)}.

In the third part {circle around (3)}, the UFPF20preferably uses the second time offset value (OffsetNW-TT) to determine a NW-TT module26clock frequency adjustment value and adjust a clock frequency of the NW-TT module26using the NW-TT module clock frequency adjustment value. This may involve using the using the second time offset value (OffsetNW-TT) as an input to the 5G Data Plane Clock Servo module42and, based on said second time offset value (OffsetNW-TT), performing the steps at the 5G Data Plane Clock Servo module42of: part {circle around (3)}.

FIG.7is a timing diagram showing transmission of time synchronization information for three adjacent time-aware systems in a TSN Network implementing the method in accordance with the invention.

The one or more PTP or gPTP messages received by the UPF N3 interface24of the UPF20contain synchronization information in peer-to-peer mode or end-to-end mode. The method comprises the steps of storing a first time T1relating to sending a PTP or gPTP “Pdelay_Req” message, extracting a second time T2from a PTP or gPTP “Pdelay_Resp” message, extracting a third time T3from a PTP or gPTP “Pdelay_Resp_Follow_Up” message, storing a fourth time T4relating to receiving a PTP or gPTP “Pdelay_Resp” message, and then determining a UPF N3 interface delay (DelayN3) from the formula:

The first time offset value (OffsetN3) between the 5G GM18and the UPF N3 interface24is derived from the UPF N3 interface delay (DelayN3). To obtain the first time offset value (OffsetN3) between the 5G GM18and the UPF N3 interface24, the method includes the steps of extracting a fifth time T5and a Correction Field (CF) elapsed time value from a PTP or gPTP “Follow_Up” message, storing a sixth time T6relating to receiving a PTP or gPTP “Sync message”, and then determining the first time offset value (OffsetN3) between the 5G GM and the UPF N3 interface from the formula:

The CF carries the time elapsed in the time-aware systems and on the links on the path between the 5G GM18and the time-aware system preceding the last hop. In this case it is the transmit time from a 5G GM master port to a gNB master port.

The second time offset value (OffsetNW-TT) between the UPF N3 interface and the NW-TT module is determined from a clock of the NW-TT module26and a synchronized clock of the UPF N3 interface24from the formula:

OffsetNW-TT=TNW-TT-TN⁢3,where TNW-TTis a time retrieved from the NW-TT module clock; andTN3is a time retrieved from the UPF N3 interface synchronized clock.

The second time offset value (OffsetNW-TT) between the UPF N3 interface and the NW-TT module is determined or calculated by the 5G Data plane Clock Offset Controller47.

FIG.8is a functional block schematic diagram of the 5G Data Plane Clock Servo module42implementing the steps of the method in accordance with the invention.

In the method, the first time offset value (OffsetN3) or the second time offset value (OffsetNW-TT) are used as inputs80to the 5G Data Plane Clock Servo module42in the UPF20.

The method may include determining at step82if the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) is greater than a predetermined, calculated or selected time period. The predetermined, calculated or selected time period may take different values dependent on different communication network scenarios and/or applications. In one embodiment, the predetermined, calculated or selected time period may equal 1 second. If yes, the method may involve at step81controlling the 5G Data Plane Clock Servo module42to send the first time offset value (OffsetN3) to the 5G Data Plane Clock Offset Controller47to adjust the time of the UPF N3 interface24with respect to the 5G GM18or to send or the second time offset value (OffsetNW-TT) to the 5G Data Plane Clock Offset Controller47to adjust the time of the NW-TT module26with respect to the 5G GM18.

If at step82, the determination is “no”, then using the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) as an input to the 5G Data Plane Clock Filter44. The 5G Data Plane Clock Filter44comprises a moving average filter and, upon receiving the first time offset value (OffsetN3) or the second time offset value (OffsetNW-TT), smooths the received first time offset value (OffsetN3) or second time offset value (OffsetNw-TT) to attenuate impulse noise to generate a smoothed clock offset output for the 5G Data Plane Clock Offset Controller47.

Referring toFIG.9which provides a functional block schematic diagram of the 5G Data Plane Clock Filter44, the moving average filter is based on a Low Pass Finite Impulse Response (FIR) filter as are commonly used for smoothing arrays and, in this instance, is used to smooth OffsetN3in part {circle around (2)} or OffsetNW-TTin part {circle around (3)}. The Impulse noise (occasionally large offset) could be due to periods of delayed execution caused by burst in processing or interrupted loads. The 5G Data Plane Clock Filter44attenuates the impulse noise to keep jitter out of the clock servo module42.

InFIG.9, the unit delay is preferably a z−1operator in Z-transform notation. The clock offset output y[n]from moving average filter is a two-sample average given by:

Referring again toFIG.8, the method includes using the 5G Data Plane Proportional-integral (PI) Controller45to receives the smoothed clock offset output for the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) and to produce a fractional tick-rate adjustment u(t) value which coordinates the UPF N3 interface time with the 5G GM time or coordinates the NW-TT module time with the UPF N3 interface time.

Referring toFIG.10which provides a functional block schematic diagram of a 5G Data Plane PI Controller45, the proportional (P) term tracks and corrects the direct input, which is the time difference between the two clocks, the integral (I) term tracks and corrects the steady-state error, which is the frequency difference between the two clocks, and the Kpand Kituning parameters may be either static or dynamically adjusted according to deployment scenarios such that:

u⁡(t)=Kp⁢e⁡(t)+Ki⁢∫0te⁡(τ)⁢dτ.where Kpis the proportional gain, a tuning parameter;Kiis the integral gain, a tuning parameter;e(t) is the Clock error(offset) between the 5G GM18and the UPF N3 interface24or the and NW-TT module26;t is the time or instantaneous time (current time t); andz is the variable of integration (takes on values from time 0 to the current time t).

The method also includes using 5G Data Plane Clock Frequency Adjuster46to receive the fractional tick-rate adjustment u(t) value for the UPF N3 interface or the NW-TT module and adjust the respective clock frequency accordingly.

The 5G Data Plane Clock Offset Controller47receives the smoothed clock offset output and adjusts the timing of the UPF N3 interface or the timing of the NW-TT module.

In brief, the method involves in part {circle around (2)} of having the UPF20use the first OffsetN3from part {circle around (1)} as one input of the 5G Data Plane Clock Servo module42in accordance with the invention to achieve the time synchronization between the UPF N3 interface24and the 5G GM18. The method also involves in part {circle around (3)} of having the UPF20use the second OffsetNW-TTcalculated by the 5G Data Plane Clock Offset Controller47as one input of the 5G Data Plane Clock Servo module42to achieve the time synchronization between the NW-TT module26and the UPF N3 interface24, in order to keep high precision time synchronization between the NW-TT module26on the UPF20with the 5G GM18.

Parts {circle around (2)} and {circle around (3)} share the same 5G Data Plane Clock Servo module42to adjust the clock frequencies and timing offsets. The 5G Data Plane Filter44and the 5G Data Plane PI Controller46in clock servo mediate the offsets to generate a fractional tick-rate adjustment that disciplines the clock frequency.

The invention also provides a 5G Data Plane Clock Servo module in a UPF module for synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a 5G communication network with a 5G Grandmaster (GM) in a 5G Time Domain of the 5G communication network, the 5G Data Plane Clock Servo module comprising: a module for receiving a first time offset value (OffsetN3) between the 5G GM and a UPF N3 interface or a second time offset value (OffsetNW-TT) between the UPF N3 interface and the NW-TT module, the first time offset value (OffsetN3) being determined from one or more Precision Time Protocol (PTP) or Generalized Precision Time Protocol (gPTP) messages received at the N3 interface, and the second time offset value (OffsetNW-TT) being determined from a hardware clock of the NW-TT module and a synchronized clock of the UPF N3 interface; a module for determining if the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) is greater than a predetermined, calculated or selected time period; a 5G Data Plane Clock Filter comprising a moving average filter which, upon receiving the first time offset value (OffsetN3) or the second time offset value (OffsetNW-TT), smooths the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) to attenuate impulse noise to generate a smoothed clock offset output for the 5G Data Plane Clock Offset Controller;a 5G Data Plane Proportional-integral (PI) Controller for receiving the smoothed clock offset output for the received first time offset value (OffsetN3) or second time offset value (OffsetNW-TT) to produce a fractional tick-rate adjustment u(t) value which coordinates the UPF N3 interface time with the 5G GM tie or coordinates the NW-TT module time with the UPF N3 interface time; and a 5G Data Plane Clock Frequency Adjuster for receiving the fractional tick-rate adjustment u(t) value for the UPF N3 interface or the NW-TT module to adjust the respective clock frequency accordingly; wherein the 5G Data Plane Clock Offset Controller receives the smoothed clock offset output and adjusts the timing of the UPF N3 interface or the timing of the NW-TT module.

The invention also provides a UPF module for synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a 5G communication network with a 5G Grandmaster (GM) in a 5G Time Domain of the 5G communication network, the module comprising a memory storing machine-readable instructions and a processor for executing the machine-readable instructions such that, when the processor executes the machine-readable instructions, it configures the UPF module to perform the steps of the method of any one of the appended method claims.

The invention also provides a non-transitory computer-readable medium storing machine-readable instructions, wherein, when the machine-readable instructions are executed by a processor, they configure the processor to implement the method of any one of the appended method claims.

The apparatus described above may be implemented at least in part in software. Those skilled in the art will appreciate that the apparatus described above may be implemented at least in part using general purpose computer equipment or using bespoke equipment.