NETWORKS

Field

[0001] The subject matter described herein generally relates to cellular systems and more particularly, to cellular systems including 5G wireless communication networks. Yet more particularly, the subject matter described herein relates to time synchronization monitoring.

Background

[0002] In wireless communication systems, it is desirable to deploy accurate time sources to avoid unwelcomed surprises during a time master failure. Security mechanisms of the system may depend on timing synchronization. For example, a Precision Time Protocol (PTP) protocol could be attacked due to delay attacks, master spoof Denial of Service (DoS) attacks, announce packet DoS attacks or master clock takeover attacks, compromising the PTP -based system time accuracy. Also Global Navigation Satellite Systems (GNSS) systems may suffer a GNSS spoofing attack.

[0003] According to, 3GPP TS 23.502 version 16.5.0 Release 16, a User Plane function (UPF) monitors the drift between Time Sensitive Networking (TSN) time and 5G time. The UPF updates the offset to a Session Management Function (SMF) when the difference between the current measurement and the previously reported measurement is larger than a threshold using the N4 Report Procedure (3GPP TS 23.502 version 16.5.0 Release 16). The SMF may then use this information to trigger a Protocol Data Unit (PDU) Session Modification in order to update the TSC Assistance Information (TSCAI) parameter to the NG-RAN without requiring AN or N1 specific signaling exchange with the User Equipment (UE).

Summary

[0004] By default, according to 3GPP TS 23.502 version 16.5.0, when a gPTP Time Domain (TD) is configured in the 5G communication system, the UEs may have two time references (i.e. 5G clock and gPTP TD clock). The UE can get gPTP TD clock if the UE is a user of the Device-side TSN Translator (DS-TT) or if the UE is a grandmaster (GM). For critical time synchronization use cases, it may not be enough to transfer time accurately from a GM to a slave and the system needs to prove that the slaves are synchronized as required.

[0005] The present disclosure addresses this problem and others by the following aspects and embodiments.

[0006] According to an aspect, a method for monitoring a time synchronization between a user equipment and a mobile communication network is provided, the method comprising, at the user equipment: tracking a first time signal, receiving a second time signal from the mobile communication network, determining a time difference between the first time signal and the second time signal and in response to determining that the time difference exceeds a given threshold, sending a message indicating the time difference to the mobile communication network.

[0007] In some method embodiments, if the time difference is below the given threshold, the user equipment performs a self calibration of a system time of the user equipment.

[0008] In some method embodiments, the first time signal is received from the mobile communication network via a control plane.

[0009] In some method embodiments, the first time signal is received from a base station.

[0010] In some method embodiments, the first time signal is received by one of more system information messages broadcast by the base station.

[0011] In some method embodiments, the first time signal comprises timing information for Coordinated Universal Time (UTC) and/or a satellite system time.

[0012] In some method embodiments, the satellite system time comprises a GPS time.

[0013] In some method embodiments, the second time signal is received via a user plane.

[0014] In some method embodiments, the second time signal is received from a core network of the mobile communication network.

[0015] In some method embodiments, the second time signal is received by (g)PTP- packets.

[0016] In some method embodiments, the second time signal originates from a grandmaster clock.

[0017] In some embodiments, the method further comprises that the user equipment comprises an internal clock generating internal time signals and that the determination of a time difference between the first time signal and the second time signal comprises: determining a first time difference between the first time signal and the internal time signal, determining a second time difference between the second time signal and the internal time signal and determining a relation between the first time difference and the second time difference. A message is sent to the communication network in response to determining that the first time difference or the second time difference or the relation between the first time difference and the second time difference exceeds a given threshold, wherein the message comprises an indication on the relation between the first time difference and the second time difference.

[0018] In some method embodiments, the mobile communication network is a 5G network.

[0019] According to an aspect, a user equipment operable in a mobile communication network is provided. The user equipment comprises at least on processor and at least one memory including computer program code causing the user equipment, when executed with the at least one processor, to: track a first time signal, receive a second time signal from the mobile communication network, determine a time difference between the first time signal and the second time signal, and in response to the determination that the time difference exceeds a given threshold, send a message indicating the time difference to the mobile communication network.

[0020] In some embodiments, if the time difference is below the given threshold, the user equipment performs a self calibration of a system time of the user equipment.

[0021] In some embodiments, the first time signal is received from the mobile communication network via a control plane.

[0022] In some embodiments, the first time signal is received from a base station.

[0023] In some embodiments, the first time signal is received by one of more system information messages broadcast by the base station.

[0024] In some embodiments, the first time signal comprises timing information for Coordinated Universal Time (UTC) and/or a satellite system time.

[0025] In some embodiments, the satellite system time comprises a GPS time.

[0026] In some embodiments, the second time signal is received via a user plane.

[0027] In some embodiments, the second time signal is received from a core network of the mobile communication network.

[0028] In some embodiments, the second time signal is received by (g)PTP- packets.

[0029] In some embodiments, the second time signal originates from a grandmaster clock. [0030] In some embodiments, the user equipment comprises an internal clock generating internal time signals. The determination of a time difference between the first time signal and the second time signal comprises: the determination of a first time difference between the first time signal and the internal time signal, the determination of a second time difference between the second time signal and the internal time signal and the determination of a relation between the first time difference and the second time difference. A message is sent to the communication network in response to determining that the first time difference or the second time difference or the relation between the first time difference and the second time difference exceeds a given threshold, wherein the message comprises an indication on the relation between the first time difference and the second time difference.

[0031] In some embodiments, the mobile communication network is a 5G network and the user equipment operates according to 5G specifications.

[0032] According to an aspect, a computer program product is provided comprising program instructions stored on a computer readable medium to execute the method steps according to any one of the method embodiments outlined above when said program is executed on a user equipment.

[0033] According to an aspect, a method for time synchronization between a user equipment tracking a first time signal from a first time source and a mobile communication network is provided. The mobile communication network comprises a network element and a second time source. The method comprises, at the network element: sending, to the user equipment, a second time signal provided by the second time source, receiving a message from the user element, the message comprising an indication on a time difference between the first time signal and the second time signal. The method comprises further, at the network element, in response to receiving the message and according to given criteria, commanding the user equipment to execute at least one of the following actions: switch to the first time source, switch to the second time source, initialize a search for a new second time source, send a notification to a further network element of the mobile communication network.

[0034] In some method embodiments, the mobile communication network comprises the first time source and the first time signal is sent to the user equipment via a control plane.

[0035] In some method embodiments, the first time signal comprises timing information for Coordinated Universal Time (UTC) and/or a satellite system time.

[0036] In some method embodiments, the satellite system time comprises a GPS time. [0037] In some method embodiments, the first time signal is sent via a base station.

[0038] In some method embodiments, the second time signal is sent via a user plane.

[0039] In some method embodiments, the second time signal is sent by (g)PTP- packets.

[0040] In some method embodiments, the second time signal originates from a grandmaster clock.

[0041] In some method embodiments, the first time source comprises a satellite network or a base station.

[0042] In some method embodiments, the first time source comprises a 5G clock.

[0043] In some method embodiments, the second time source comprises a grandmaster.

[0044] In some method embodiments, the mobile network element comprises a base station.

[0045] In some method embodiments, the base station comprises a gNB station.

[0046] In some method embodiments, the search for the new second time source comprises the execution of a Best Master Clock Algorithm (BCMA).

[0047] According to an aspect, a network element for time synchronization between a user equipment tracking a first time signal from a first time source and a mobile communication network is provided. The network element is operable in a mobile communication network. The mobile communication network comprises a second time source. The network element comprises at least one processor, and at least one memory including computer program causing the network element, when executed with the at least one processor, to: send, to a user equipment, a second time signal provided by the second time source and receive a message from the user element, the message comprising an indication on a time difference between the first time signal and the second time signal. The computer program further causes the network element to, in response to receiving the message and according to given criteria, command the user equipment to execute at least one of the following actions: switch to the first time source, switch to the second time source, initialize a search for a new second time source, send a notification to a further network element of the mobile communication network.

[0048] In some embodiments, the mobile communication network comprises the first time source and the first time signal is sent to the user equipment via a control plane.

[0049] In some embodiments, the first time signal comprises timing information for Coordinated Universal Time (UTC) and/or a satellite system time. [0050] In some embodiments, the satellite system time comprises a GPS time.

[0051] In some embodiments, the first time signal is sent via a base station.

[0052] In some embodiments, the second time signal is sent via a user plane.

[0053] In some embodiments, the second time signal is sent by (g)PTP- packets.

[0054] In some embodiments, the second time signal originates from a grandmaster clock.

[0055] In some embodiments, the first time source comprises a satellite network or a base station.

[0056] In some embodiments, the first time source comprises a 5G clock.

[0057] In some embodiments, the second time source comprises a grandmaster.

[0058] In some embodiments, the mobile network element comprises a base station.

[0059] In some embodiments, the base station comprises a gNB station.

[0060] In some embodiments, the search for the new second time source comprises the execution of a Best Master Clock Algorithm (BCMA).

[0061] According to a further aspect, a computer program product is provided comprising program instructions stored on a computer readable medium to execute the method steps according to any one of the method embodiments outlined above when said program is executed on a network element.

[0062] Further optional refinements are set forth in the detailed description given below.

Brief Description of the Drawings

[0063] A better understanding of the subject matter described herein can be obtained when the following detailed description of various embodiments is considered in conjunction with the following drawings, in which:

[0064] FIG. 1 illustrates a simplified wireless communication system, according to some embodiments.

[0065] FIG. 2 illustrates a base station (BS) in communication with a user equipment (UE) according to some embodiments.

[0066] FIG. 3 illustrates a simplified block diagram of a UE according to some embodiments.

[0067] FIG. 4 visualizes functional components of a UE according to some embodiments.

[0068] FIG. 5 shows a sequence chart for monitoring a time synchronization in a network according to an embodiment.

[0069] FIG. 6 shows a sequence chart for monitoring a time synchronization in a network according to a further embodiment.

[0070] FIG. 7 illustrates a way to track on a timing drift with reference to one or more time sources.

[0071] FIG. 8 is a process diagram for tracking on a timing drift with reference to one or more time sources.

[0072] FIG. 9 illustrates the time-dependent variation of a time difference against upper and lower boundaries.

[0073] FIG. 10 shows a sequence chart for a time synchronization between a user equipment and a network.

[0074] FIG. 11 illustrates a workflow to configure the time synchronization performance monitoring in a 5G network. Detailed Description

[0075] FIG. 1 illustrates a simplified wireless communication system 100, according to some embodiments. It is noted that the system of FIG. 1 is merely one example of a possible system, and that features of the subject matter described herein may be implemented in any of various systems, as desired.

[0076] As shown, the wireless communication system 100 includes a base station 110-1 which communicates over a transmission medium with one or more user devices 120. In FIG. 1, only three user devices 120-1, 120-2, and 120-3 are shown, without limitation. Each of the user devices 120-1, 120-2, and 120-3 may be referred to herein as a "user equipment" (UE). Thus, the user devices 120 are referred to as UEs or UE devices.

[0077] As used herein, the term "user equipment" may refer to any of various types of computer systems devices which are mobile or portable and which perform wireless communications. Examples of UEs include mobile telephones or smart phones, portable gaming devices, laptops, wearable devices (e.g., smart watch, smart glasses), Personal Digital Assistants (PDAs), portable Internet devices, music players, data storage devices, or other handheld devices, etc. In general, the term "UE" or "UE device" can be broadly defined to encompass any electronic, computing, and/or telecommunications device (or combination of devices) which is easily transported by a user and capable of wireless communication.

[0078] The base station (BS) 110-1 may be a base transceiver station (BTS) or cell site (a "cellular base station"), and may include hardware that enables wireless communication with the UEs 120.

[0079] As used herein, the term "base station" has the full breadth of its ordinary meaning, and at least includes a wireless communication station installed at a fixed location and used to communicate as part of a wireless telephone system or radio system.

[0080] The communication area (or coverage area) of the base station 110 may be referred to as a "cell." The base station 110 and the UEs 120 may be configured to communicate over the transmission medium using any of various radio access technologies (RATs), also referred to as wireless communication technologies, or telecommunication standards, such as GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE- Advanced (LTE-A), 5G new radio (5GNR), HSPA, 3GPP2 CDMA2000 (e.g, IxRTT, IxEV- DO, HRPD, eHRPD), etc. If the base station 110-1 is implemented in the context of LTE, it may alternately be referred to as an "eNodeB" or "eNB". If the base station 110-1 is implemented in the context of 5GNR, it may alternately be referred to as "gNodeB" or "gNB". [0081] As shown, the base station 110-1 may also be equipped to communicate with a network 130 (e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities). Thus, the base station 110-1 may facilitate communication between the user devices 120 and/or between the user devices 120 and the network 130. In particular, the cellular base station 110-1 may provide UEs 120 with various telecommunication capabilities, such as voice, SMS and/or data services.

[0082] The base station 110-1 and other similar base stations (such as base stations 110-2 and 110-3) operating according to the same or a different cellular communication standard may thus be provided as a network of cells, which may provide continuous or nearly continuous overlapping service to UEs 120 and similar devices over a geographic area via one or more cellular communication standards.

[0083] Thus, while base station 110-1 may act as a "serving cell" for UEs 120 as illustrated in FIG. 1, each UE 120 may also be capable of receiving signals from (and possibly within communication range of) one or more other cells (which might be provided by base stations 110 and/or any other base stations), which may be referred to as "neighboring cells". Such cells may also be capable of facilitating communication between user devices 120 and/or between user devices 120 and the network 130. Such cells may include "macro" cells, "micro" cells, "pico" cells, and/or cells which provide any of various other granularities of service area size. For example, base stations 110-1 and 110-2 illustrated in FIG. 1 might be macro cells, while base station 110-3 might be a micro cell. Other configurations are also possible.

[0084] In some embodiments, base station 110-1 may be a next generation base station, e.g., a 5G New Radio (5G NR) base station, or "gNB". In some embodiments, a gNB may be connected to a legacy evolved packet core (EPC) network and/or to a NR core (NRC) network. In addition, a gNB cell may include one or more transition and reception points (TRPs). In addition, a UE capable of operating according to 5GNR may be connected to one or more TRPs within one or more gNBs.

[0085] The UE 120 may be capable of communicating using multiple wireless communication standards. For example, the UE 120 may be configured to communicate using a wireless networking (e.g., Wi-Fi) and/or peer-to-peer wireless communication protocol (e.g., Bluetooth, Wi-Fi peer-to-peer, etc.) in addition to at least one cellular communication protocol (e.g., GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE-A, 5G NR, HSPA, 3GPP2 CDMA2000 (e g., IxRTT, IxEV-DO, HRPD, eHRPD), etc.). The UE 120 may also or alternatively be configured to communicate using one or more global navigational satellite systems (GNSS, e.g., GPS or GLONASS), one or more mobile television broadcasting standards (e.g., ATSC-M/H or DVB-H), and/or any other wireless communication protocol, if desired. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0086] FIG. 2 illustrates user equipment 120 (e.g., one of the devices 120-1, 120-2 and 120-3) in communication with a base station 110, according to some embodiments. The UE 120 may be a device with cellular communication capability such as a mobile phone, a handheld device, a computer or a tablet, or virtually any type of wireless device.

[0087] The UE 120 may include a processor that is configured to execute program instructions stored in memory. The UE 120 may perform any of the method embodiments described herein by executing such stored instructions. Alternatively, or in addition, the UE 120 may include a programmable hardware element such as a field-programmable gate array (FPGA) that is configured to perform any of the method embodiments described herein, or any portion of any of the method embodiments described herein.

[0088] The UE 120 may include one or more antennas for communicating using one or more wireless communication protocols or technologies. In some embodiments, the UE 120 may be configured to communicate using, for example, CDMA2000 (IxRTT/lxEV- DO/HRPD/eHRPD) or LTE using a single shared radio and/or GSM or LTE using the single shared radio. The shared radio may couple to a single antenna, or may couple to multiple antennas (e.g., for MIMO) for performing wireless communications. In general, a radio may include any combination of a baseband processor, analog RF signal processing circuitry (e.g., including filters, mixers, oscillators, amplifiers, etc.), or digital processing circuitry (e.g., for digital modulation as well as other digital processing). Similarly, the radio may implement one or more receive and transmit chains using the aforementioned hardware. For example, the UE 120 may share one or more parts of a receive and/or transmit chain between multiple wireless communication technologies, such as those discussed above.

[0089] In some embodiments, the UE 120 may include separate transmit and/or receive chains (e.g., including separate antennas and other radio components) for each wireless communication protocol with which it is configured to communicate. As a further possibility, the UE 120 may include one or more radios which are shared between multiple wireless communication protocols, and one or more radios which are used exclusively by a single wireless communication protocol. For example, the UE 120 might include a shared radio for communicating using either of LTE or 5G NR (or LTE or IxRTT or LTE or GSM), and separate radios for communicating using each of Wi-Fi and Bluetooth™. Other configurations are also possible.

[0090] FIG. 3 illustrates a simplified block diagram of a UE 120, according to some embodiments. It is noted that the block diagram of the UE 120 of FIG. 3 is only one example of a possible user device. According to embodiments, UE 120 may be a user device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and/or a combination of devices, among other devices.

[0091] As shown, the UE 120 may include a set of components configured to perform core functions. For example, this set of components may be implemented as a system on chip (SOC), which may include portions for various purposes. Alternatively, this set of components may be implemented as separate components or groups of components for the various purposes. The set of components may be coupled (e.g., communicatively; directly or indirectly) to various other circuits of the UE 120.

[0092] The UE 120 may include at least one antenna 312 in communication with a transmitter 314 and a receiver 316. Alternatively, transmit and receive antennas may be separate. The UE 120 may also include a processor 320 configured to provide signals to and receive signals from the transmitter 314 and receiver 316, respectively, and to control the functioning of the UE 120. Processor 320 may be configured to control the functioning of the transmitter 314 and receiver 316 by effecting control signaling via electrical leads to the transmitter 314 and receiver 316. Likewise, the processor 320 may be configured to control other elements of the UE 120 by effecting control signaling via electrical leads connecting processor 320 to the other elements, such as a display or a memory. The processor 320 may, for example, be embodied in a variety of ways including circuitry, at least one processing core, one or more microprocessors with accompanying digital signal processor(s), one or more processor(s) without an accompanying digital signal processor, one or more coprocessors, one or more multi-core processors, one or more controllers, processing circuitry, one or more computers, various other processing elements including integrated circuits (for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and/or the like), or some combination thereof. Accordingly, although illustrated in FIG. 3 as a single processor, in some example embodiments the processor 320 may comprise a plurality of processors or processing cores. [0093] The UE 120 may be capable of operating with one or more air interface standards, communication protocols, modulation types, access types, and/or the like. Signals sent and received by the processor 320 may include signaling information in accordance with an air interface standard of an applicable cellular system, and/or any number of different wireline or wireless networking techniques, comprising but not limited to Wi-Fi, wireless local access network (WLAN) techniques, such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, 802.16, 802.3, ADSL, DOCSIS, and/or the like. In addition, these signals may include speech data, user generated data, user requested data, and/or the like.

[0094] For example, the UE 120 and/or a cellular modem therein may be capable of operating in accordance with various first generation (1G) communication protocols, second generation (2G or 2.5G) communication protocols, third-generation (3G) communication protocols, fourth-generation (4G) communication protocols, fifth-generation (5G) communication protocols, Internet Protocol Multimedia Subsystem (IMS) communication protocols (for example, session initiation protocol (SIP) and/or the like. For example, the UE 120 may be capable of operating in accordance with 2G wireless communication protocols IS- 136, Time Division Multiple Access TDMA, Global System for Mobile communications, GSM, IS-95, Code Division Multiple Access, CDMA, and/or the like. In addition, for example, the UE 120 may be capable of operating in accordance with 2.5G wireless communication protocols General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), and/or the like. Further, for example, the UE 120 may be capable of operating in accordance with 3G wireless communication protocols, such as Universal Mobile Telecommunications System (UMTS), Code Division Multiple Access 2000 (CDMA2000), Wideband Code Division Multiple Access (WCDMA), Time Division-Synchronous Code Division Multiple Access (TD-SCDMA), and/or the like. The UE 120 may be additionally capable of operating in accordance with 3.9G wireless communication protocols, such as Long Term Evolution (LTE), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and/or the like. Additionally, for example, the UE 120 may be capable of operating in accordance with 4G wireless communication protocols, such as LTE Advanced, 5G, and/or the like as well as similar wireless communication protocols that may be subsequently developed.

[0095] It is understood that the processor 320 may include circuitry for implementing audio/video and logic functions of the UE 120. For example, the processor 320 may comprise a digital signal processor device, a microprocessor device, an analog-to-digital converter, a digital-to-analog converter, and/or the like. Control and signal processing functions of the UE 120 may be allocated between these devices according to their respective capabilities. The processor 320 may additionally comprise an internal voice coder (VC) 320a, an internal data modem (DM) 320b, and/or the like. Further, the processor 320 may include functionality to operate one or more software programs, which may be stored in memory. In general, the processor 320 and stored software instructions may be configured to cause the UE 120 to perform actions. For example, the processor 320 may be capable of operating a connectivity program, such as a web browser. The connectivity program may allow the UE 120 to transmit and receive web content, such as location-based content, according to a protocol, such as wireless application protocol (WAP), hypertext transfer protocol (HTTP), and/or the like.

[0096] The UE 120 may also comprise a user interface including, for example, an earphone or speaker 324, a ringer 322, a microphone 326, a display 328, a user input interface, and/or the like, which may be operationally coupled to the processor 320. The display 328 may, as noted above, include a touch sensitive display, where a user may touch and/or gesture to make selections, enter values, and/or the like. The processor 320 may also include user interface circuitry configured to control at least some functions of one or more elements of the user interface, such as the speaker 324, the ringer 322, the microphone 326, the display 328, and/or the like. The processor 320 and/or user interface circuitry comprising the processor 320 may be configured to control one or more functions of one or more elements of the user interface through computer program instructions, for example, software and/or firmware, stored on a memory accessible to the processor 320, for example, volatile memory 340, non-volatile memory 342, and/or the like. The UE 120 may include a battery for powering various circuits related to the mobile terminal, for example, a circuit to provide mechanical vibration as a detectable output. The user input interface may comprise devices allowing the UE 120 to receive data, such as a keypad 330 (which can be a virtual keyboard presented on display 328 or an externally coupled keyboard) and/or other input devices.

[0097] As shown in FIG. 3, the UE 120 may also include one or more mechanisms for sharing and/or obtaining data. For example, UE 120 may include a short-range radio frequency (RF) transceiver and/or interrogator 364, so data may be shared with and/or obtained from electronic devices in accordance with RF techniques. The UE 120 may include other short- range transceivers, such as an infrared (IR) transceiver 366, a Bluetooth™ (BT) transceiver 368 operating using Bluetooth™ wireless technology, a wireless universal serial bus (USB) transceiver 370, a Bluetooth™ Low Energy transceiver, a ZigBee transceiver, an ANT transceiver, a cellular device-to-device transceiver, a wireless local area link transceiver, and/or any other short-range radio technology. The UE 120 and, in particular, the short-range transceiver may be capable of transmitting data to and/or receiving data from electronic devices within the proximity of the apparatus, such as within 10 meters, for example. The UE 120 including the Wi-Fi or wireless local area networking modem may also be capable of transmitting and/or receiving data from electronic devices according to various wireless networking techniques, including 6LoWpan, Wi-Fi, Wi-Fi low power, WLAN techniques such as IEEE 802.11 techniques, IEEE 802.15 techniques, IEEE 802.16 techniques, and/or the like.

[0098] The UE 120 may comprise memory, such as a subscriber identity module (SIM) 338, a removable user identity module (R-UIM), an eUICC, an UICC, and/or the like, which may store information elements related to a mobile subscriber. In addition to the SIM, the UE 120 may include other removable and/or fixed memory. The UE 120 may include volatile memory 340 and/or non-volatile memory 342. For example, the volatile memory 340 may include Random Access Memory (RAM) including dynamic and/or static RAM, on-chip or off- chip cache memory, and/or the like. The non-volatile memory 342, which may be embedded and/or removable, may include, for example, read-only memory, flash memory, magnetic storage devices, for example, hard disks, floppy disk drives, magnetic tape, optical disc drives and/or media, non-volatile random access memory (NVRAM), and/or the like. Like volatile memory 340, the non-volatile memory 342 may include a cache area for temporary storage of data. At least part of the volatile and/or non-volatile memory may be embedded in the processor 320. The memories may store one or more software programs, instructions, pieces of information, data, and/or the like which may be used by the apparatus for performing operations disclosed herein.

[0099] The memories may comprise an identifier, such as an International Mobile Equipment Identification (IMEI) code, capable of uniquely identifying the UE 120. The memories may comprise an identifier, such as an international mobile equipment identification (IMEI) code, capable of uniquely identifying the UE 120. In the example embodiment, the processor 320 may be configured using computer code stored at memory 340 and/or 342 to cause the processor 320 to perform operations disclosed herein.

[0100] Some of the embodiments disclosed herein may be implemented in software, hardware, application logic, or a combination of software, hardware, and application logic. The software, application logic, and/or hardware may reside on the memory 340, the processor 320, or electronic components, for example. In some example embodiment, the application logic, software or 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 non-transitory media 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 or data processor circuitry, with examples depicted at FIG. 3, computer-readable medium may comprise a non-transitory computer-readable storage medium that may be any media that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0101] FIG. 4 shows the internal UE architecture according to 3GPP TS 24.002 V16.0.0. The term "Mobile Station" (MS) is synonymous with the term "User Equipment" (UE) in 3G terminology. The UE is connected to the network (UTRAN, E-UTRAN, or 5G Access Network/Core Network) via the Uu or NWu interface. The UE comprises the ME (Mobile Equipment) and the USIM, both being coupled via the Cc interface. The USIM is an application which resides on the UICC (Universal Integrated Circuit Card), an IC card specified in 3 GPP TS 31.101. The ME, in turn, comprises the TE (Terminal Equipment) and the MT (Mobile Termination), both being coupled via the R interface. The MT performs core mobile communications functions such as radio transmission termination, radio transmission channel management, speech en-/decoding, error protection, flow control, rate adaption of user data, and mobility management, as well as presenting a man-machine interface to a user. The MT includes the TA (Terminal Adaptor).

[0102] FIG. 5 relates to monitoring a time synchronization in a network. The UE 120 tracks, in activity 500, a first time signal. The first time signal may be obtained by the UE from any suitable time source to which the UE120 has access to, including, but not necessarily, the mobile communication network 140. At the UE 120, a second signal is received in activity 510 from the network 140 and, in activity 520, a time difference between the first time signal and the second time signal is determined. In activity 530, in response to determining that the time difference exceeds a given threshold, a message indicating the time difference to the network 140 is sent to the mobile communication network 140.

[0103] In some embodiments, the first time signal is received at the UE 120 from the network 140, as exemplarily visualized by FIG. 5, or from a different entity.

[0104] The methodologies for monitoring time synchronization as described herein facilitates the UE 120 to perform a time synchronization using an additional time source, which may be regarded as a trusted time source and which may provide the first time signal. The accuracy of the (second) time source under test may then be assessed. As a result, the second time source may subsequently be regarded as an untrusted or currently incorrect time source and may be dropped by the UE 120 and replaced by an alternative trusted second time source. [0105] A mobile communication network 140 may comprise of a network as described by the IEEE 1588 standards. According these standards, a network 140 comprises a hierarchical master-slave architecture for clock time distribution. The network 140 may comprise of one or more network segments and one or more clocks. A clock may either comprise the source of (master) or destination for (slave) a time synchronization reference. A clock may comprise multiple network connections (boundary clock) and may synchronize one network segment to another. A network segment may comprise a synchronization master (grandmaster) selected for each of the network segments in the network 140. The grandmaster may transmit synchronization information to the clocks residing on its network segment. The boundary clocks with a presence on that segment then may relay accurate time to the other segments to which they are also connected. The user equipment (UE) 120 is connected to the network 140, e. g. via the Device-side TSN Translator (DS-TT), and receives the time signals from the network 140.

[0106] As an example, the message may be sent in activity 530 to the Access and Mobility Management Function (AMF) unit, the Session Management Function (SMF) unit, the Network Exposure Function (NEF) unit or the Application Function (AF) of the network 140. In some embodiments, the network element that receives the message sent from the UE 120 is a gNB (if RRC signaling is applied). Then the gNB sends the message to the AMF, if a Mobility Management Transport message is used, or to the SMF, if a Session Management Transport message is used. Later, the AMF/SMF may forward the notification to the PCF/NEF and then NEF to AF.

[0107] According to embodiments, as shown in FIG. 6, if the time difference is below the given threshold, the UE 120 performs, in activity 540, a self calibration of a system time of the UE 120. Depending on the service configuration, the UE 120 performs the self-calibration with the time sources it has, such as e. g. a satellite system time or the Coordinated Universal Time (UTC). The self-calibration can be periodic, or requested by the network 140, or triggered due to other events. The self calibration may comprise the correction of the time of an internal clock or the time domain under test of the UE 120. According to embodiments, the first time signal is received via a control plane. According to embodiments, the first time signal is received from a base station 110, such as e. g. an eNB base station or an gNB base station by using, as an example, a 4G/5G eNB/gNB protocol stack that may also be applied in cellular base-stations used in various network forms such as small cells, heterogenous networks (HetNets) and Cloud Radio Access Networks. The first time signal may also received from any other base station. According to embodiments, the first time signal is received by one or more system information broadcast messages by the base station 110, such as System Information Block 9 (SIB9) broadcasting messages or as unicast via Radio Resource Control (RRC) messages.

[0108] According to some embodiments, the first time signal comprises timing information for Coordinated Universal Time (UTC) and/or a satellite system time. According to some further embodiments, the satellite system may comprise a GPS system. The satellite system may also comprise systems such as the Russian navigation satellite system GLONASS (“Globalnaya navigatsionnaya sputnikovaya sistema” or "Global Navigation Satellite System), the Chinese navigation satellite system BeiDou, the European navigation satellite system Galileo, the Indian regional navigation satellite system IRNSS or the Japanese navigation satellite system QZSS.

[0109] According to embodiments, the second time signal is received via a user plane, that may comprise user plane functions providing the packet processing foundation for Service Based Architectures (SBAs). The user plane functions may be implemented as a pure cloud native network function using modern microservices methodologies and deployable within a serverless framework.

[0110] According to embodiments, the second time signal is received from a core network 130 of the network 140. The core network 130 may be configured to establish reliable and secure connectivity of the UE 120 to the network 140 and access to its services, to determine the quality of service and enforce it through policy allowing services differentiation and handles wide area mobility of e. g. the UE 120 throughout the network 140. The core network 130 may be configured that each Network Function (NF) may be able to provide one or more services to other NFs via Application Programming Interfaces (API). Each Network Function (NF) may be formed by a combination of small pieces of software code called as microservices. Some microservices may be reused for different NFs, thereby allowing upgrades and new functionalities to be deployed with minimum impact on running services.

[0111] According to embodiments, the second time signal is received by (g)PTP-packets. The second time signal may also be received by PTP-packets. The PTP- or (g)PTP-packets may be received by the UE 120 by a user plane.

[0112] PTP may use the same epoch as Unix time (start of 1 January 1970). The Unix time is based on Coordinated Universal Time (UTC) and is subject to leap seconds. PTP may be based on International Atomic Time (TAI). A PTP grandmaster may communicate the current offset between UTC and TAI, so that UTC can be computed from the received PTP time. [0113] PTP messages may use the User Datagram Protocol over Internet Protocol (UDP/IP) for transport. PTP messages may also use the IPv4 or the IPv6 protocol for transport. The PTP messages may be relayed by any existing Layer 2 protocol (Layer 2 described according to the Open Systems Interconnection model - OSI), such as 3GPP Layer 2, Ethernet or Wi-Fi. PTP messages may be sent using multicast or unicast messaging.

[0114] PTP messages may comprise the following message types:

Sync, Follow Up, Delay Req and Delay Resp messages which may be comprised by ordinary and boundary clocks and may communicate time-related information to synchronize clocks across the network 140.

- Pdelay Req, Pdelay Resp and Pdelay Resp Follow Up messages which may be comprised by transparent clocks and may measure delays across the communications medium so that delays may be compensated by the network 140.

- Announce messages may be comprised by a best master clock algorithm (BCMA) to e. g. build a clock hierarchy and select the grandmaster, as described e. g. in IEEE 1588- 2008.

- Management messages may be comprised by network management to e. g. monitor, configure and maintain a PTP system.

Signaling messages may be comprised for e. g. non-time-critical communications between clocks, as described e. g. in IEEE 1588-2008.

[0115] According to embodiments, the second time signal originates from a grandmaster clock. The grandmaster clock may receive UTC-based time information from an external time reference, most commonly a global navigation satellite system (GNSS), via a GNSS-receiver. The time information may then distributed downstream to other clocks, by using, as an example, a (g)PTP service over Ethernet ports.

[0116] A way to keep the timing, such as a Time Stamp Counter (TSC) timing, in a device is to have a free running reference clock in the device and keep track on the timing drift with reference to one or more time sources, as schematically shown in FIG. 7. Referring to FIG. 7, UE 120 comprises of an internal clock 600, and timing information of the first time signal and the second time signal is given as input to the free running clock and the first and second time differences are derived.

[0117] Therefore, according to embodiments, the user equipment (UE 120) comprises an internal clock 600 generating internal time signals. As shown in FIG. 8, the determination of a time difference between the first time signal and the second time signal comprises, in activity 800, the determination of a first time difference between the first time signal and the internal time signal, the determination, in an activity 810, of a second time difference between the second time signal and the internal time signal and the determination, in an activity 820, of a relation between the first time difference and the second time difference. The relation between the first time difference and the second time difference may be a difference between the first time signal and the second signal. Furthermore, in response to determining that the first time difference or the second time difference or the relation between the first time difference and the second time difference exceeds a given threshold, a message is sent to the mobile communication network 140 (activity 830). The message comprises an indication on the relation between the first time difference and the second time difference.

[0118] According to FIG. 8, if the given threshold is not exceeded, the UE performs a selfcalibration (activity 840), which may comprise the adaptation of its internal clock to the first or the second time source.

[0119] The threshold may be a time threshold to be compared with e. g. the time difference between the first time signal and the second time signal. The threshold may be set by the Session Management Functions (SMF) of the network 140.

[0120] The threshold may be defined as upper and lower boundaries or limits and may be stored as one or more constant values in the UE 120. As shown in FIG. 9. The time difference is checked (or tracked) against the upper and lower boundaries to ensure the time difference and thereby the performance of the internal clock 600 in the systems are within the specifications as set by e. g. the Access and Mobility Management Function (AMF) or Policy Control Function (PCF). The threshold may be defined in the range of microseconds or nanoseconds. This may reflect the variations in the accuracy of the internal clock and the first and the second time source, which may contribute, in consequence, to the uncertainties in the determination of the first time difference and the second time difference and the relation between the first and the second time difference. The variations in the accuracy may take the forms of time and frequency offsets.

[0121] According to embodiments, the network 140 is a 5G network according to 5C 3GPP specifications.

[0122] FIG. 10 relates to time synchronization between a user equipment 120 tracking a first time signal from a first time source and a network 140 which may be employed subsequently to the sequence of FIG. 5. The network 140 comprises a network element 110, such as a base station and a second time source. The network 140 sends, in an activity 900, to the user equipment 120a second time signal provided by the second time source and receives, in an activity 910, a message from the user element, the message comprising an indication on a time difference between the first time signal and the second time signal. In response to receiving the message, according to given criteria, the network 140 commands the user equipment to execute at least one of the following actions (activities 920 and 930): switch to the first time source; switch to the second time source;

- initialize a search for a new second time source; send a notification to a further network element of the mobile communication network 140.

[0123] In some embodiments, the network element 110 may comprise of several subelements. In some embodiments, the first time signal and the second time signal may originate from different sub-elements of network element 110.

[0124] As an example, the further network element may comprise the Access and Mobility Management Function (AMF) unit, the Session Management Function (SMF) unit, the Network Exposure Function (NEF) unit or the Application Function (AF) of the network 140.

[0125] According to embodiments, the mobile communication network 140 comprises the first time source and the first time signal is sent to the UE 120 via a control plane.

[0126] According to embodiments, the first time signal is sent from a local base station such as an eNB or a gNB station by using, as an example a 4G/5G eNB/gNB protocol stack that may also be applied in cellular base-stations used in various network forms such as small cells, heterogenous networks (HetNets) and Cloud Radio Access Networks. The first time signal may also be sent from any other base station.

[0127] According to embodiments the second time signal is sent via a user plane, that may comprise user plane functions providing the packet processing foundation for Service Based Architectures (SBAs). The user plane functions may be implemented as a pure cloud native network function using modern microservices methodologies and deployable within a serverless framework. [0128] According to embodiments, the second time signal is sent by gPTP- packets. The second time signal may also be sent by PTP -packets. The PTP- or gPTP-packets may be sent by the network element 110 by a user plane.

[0129] According to embodiments, the first time source comprises a satellite network or a base station, such as a global navigation satellite system (GNSS) or an eNB or gNB base station or any other base station. According to some further embodiments, the satellite system may comprise a GPS system. The satellite system may also comprise systems such as the Russian navigation satellite system GLONASS (“Globalnaya navigatsionnaya sputnikovaya sistema” or "Global Navigation Satellite System), the Chinese navigation satellite system BeiDou, the European navigation satellite system Galileo, the Indian regional navigation satellite system IRNSS or the Japanese navigation satellite system QZSS.

[0130] According to embodiments, the first time source comprises a 5G clock. The 5G clock may be comprised in a base station, such as an eNB or a gNB base station or any other base station.

[0131] According to embodiments, the second time source comprises a grandmaster. The grandmaster may provide standard time information to other clocks across the network 140. A grandmaster clock may be comprised by any network element such as a base station or a user equipment, such as UE 120.

[0132] According to embodiments, the mobile network element comprises a local base station, such as an eNB or a gNB base station or any other base station. The base station may also serve small cell networks such as microcell- picocell and femtocell as well as attocellnetworks.

[0133] In some embodiments, the search for the new second time source comprises the execution of a Best Master Clock Algorithm (BCMA). This may be a modified Best Master Clock Algorithm (BMC A) to force the UE 201 to drop a bad grandmaster and select a new grandmaster form a number of candidate clocks. A best master clock algorithm (BCMA) may perform a distributed selection of the best candidate clock based on:

A clock identifier, which may comprise a universally unique numeric identifier for the clock.

Clock quality, which may be quantified by e. g. the versions of IEEE 1588. According to these versions, clock quality may be quantified based on expected timing deviation. Clock precedence, which comprises an administratively assigned precedence hint used by the BMCA to help select a grandmaster for e. g a PTP domain.

Clock variance, which may comprise an estimate of the stability of a clock based on observation of its performance against the PTP reference.

[0134] FIG. 11 relates to a workflow to configure the time synchronization performance monitoring in a 5G network.

[0135] Referring to FIG. 11, an Application Function (AF) 130-4 requests (activities 1000 and 1010), by using the Network Exposure Function (NEF) 130-3, the time synchronization performance monitoring targeting a specific UE, such as UE 120. The Policy Charging Function (PCF) 130-6 authorizes (activity 1020) the request and decides the policies to apply for the monitoring based on the AF 130-4 request (e.g. command the UE 120 when a problem is detected, expose slave performance, or trigger other events in the 5GS). The PCF 130-6 forwards (activities 1030, 1040, 1050) the synchronization performance policy to the core entities of the network 140 that require to be configured such as the Access and Mobility Management Function (AMF) 130-1 or the Session Management Function (SMF), the NEF 130-3 and the AF 130-4. Once the AMF 130-1 receives the synchronization performance monitoring configuration, it configures the RAN to report UE calibration results and forwards the information to the RAN (activity 1060). Then, the RAN reconfigures measurement reporting of the UE to include the report of the self-calibration result (activity 1070).

[0136] The UE 120 receives, a 5G clock signal via control plane messages (e.g. Radio Resource Control - RRC/ System Information Block 9 - SIB9) and another time reference source, such as a grandmaster time signal 130-5 via user plane (g)PTP messages (activity 510, see also FIG. 5).

[0137] Depending on the service configuration, the UE 120 performs (activity 1080) the self-calibration with at least one of the two time sources (e.g. the self calibration can be periodic, or requested by the network, or triggered due to other events). The result of the self-calibration is then reported (activity 1090) from the UE 120 to the network 140 via RRC signaling if needed (e.g. self-calibration failure is reported). By checking the configured slave monitoring policy (activity 1100), the network 140 can use this report to expose the slave performance to the AF (activities 1110 and 1120) or to command the UE to take action.

[0138] The workflow as illustrated by FIG. 11 exposes framework extensions to request the monitoring of synchronization performance at the UE side. With respect to current telecommunication standards, such as 3 GPP specifications, additional Information Elements (IES) between core network entities, gNB, and UE are configured to distribute the synchronization performance monitoring configuration/policy. Extensions may be required for:

AM policy control services between PCF and AMF;

- Notification procedures between the AMF and gNB. The AMF will need to be subscribed to monitoring events for specific UEs to be notified when there is a selfcalibration failure;

- RRC signaling to configure new measurements for the UE to report to the gNB.

[0139] Further, as shown by the workflow as illustrated by FIG. 11, any synchronization performance monitoring policies are determined at the PCF based on AF’s request. The synchronization performance monitoring policies may include UE triggers to perform the self- calibration (e.g. periodic, on demand, or event-triggered) and report the result and actions to take after a self-calibration failure.

[0140] As described in IEEE 1588, one of the ways to keep the Time Stamp Counter (TSC) timing in a device is to have a free running reference clock 600 and keep track on the timing drift.

[0141] By using the free running clock 600 in the UE 120 while relying on a separate adjustment like a separate Phase Locked Loop (PLL) feed, it is possible to track the time difference (delta) between a 5G system clock providing the first time signals and the free running clock 600 and between the Time Sensitive Networking (TSN) system providing the second time signals and the free running clock as two separate independent clock regulation systems.

[0142] In a UE serving interface between 5G system 100 and the Time Sensitive Networking (TSN) network based on the proposal from IEEE 1588, three different clock/ timing references in the wireless communication system 100 are comprised:

The timing and frequency reference from 5G system. The timing and frequency reference may be based e. g. on the GPS reference clock.

The time reference calibration from the TSN system. The reference accuracy may be set by the accuracy of a grandmaster 130-5.

The free running clock 600 itself. The accuracy is depending on the design. As more accurate a reference clock operates as more reliable it will be to determine the time difference (delta) from the other two systems. [0143] Limits for the tracking algorithm can be derived from the hardware specification of the free running clock 600 and the possible achievable accuracy of the time stamp (according to IEEE 1588).

[0144] As any hardware ages, the corresponding parameters of the free running clock, such as drift over temperature, calibration tolerances and the accuracy of the timestamp from the network (either 5G or TSN) may change as an effect of the aging.

[0145] The tracking of the time difference (delta) from zero timing offset may be handled in a software (SW) algorithm. The time difference (delta) is checked for upper and lower boundary to ensure the time difference (delta) and thereby the clock performance in the systems are within the specification (as shown in FIG. 9). The current time difference (delta) correction is compared to the expected time correction and the tolerances in the system. If the limits are exceeded a message with the information of the failing system can be send (activity 530 of FIG. 5) e. g. to the AMF 130-1, the NEF 130-3 or the AF 130-4.

[0146] The software (SW) algorithm may run in several separate algorithms which are combined at the end. After the Time of Day (ToD) as received e. g. from a 5G system clock and a corresponding Pulse per Second (PPS) are passed to a first SW algorithm, as shown in activity 801 of FIG. 8, a first time difference (first delta) between the PPS and the current timing in the free running clock is computed (activity 800 of FIG. 8). The first delta value may be used for device compensation such as the correction of the free running clock toward the 5G system.

[0147] After a time signal is received from e. g. a grandmaster e. g. in response to a time calibration signal (activity 510 of FIGs. 5 and 8), a corresponding second time difference (second delta) is computed by a second SW algorithm (activity 810 of FIG. 8), and the second delta may be used for device compensation such as the correction the free running clock toward the TSN system. For the deriving of a correction value, a comparison between the two deltas can be used for correcting the free running clock resulting e. g. of the usage of the 5G clock to correct the free running device.

[0148] By a combination algorithm employed e. g. in activity 820 of FIG. 8, the computed delta values (or compensation values) are compared and checked against the limits, such as the upper and lower boundaries of FIG. 9. This loop may be repeated as long the limits are not exceeded. If the limits are exceeded a message are send to the failing system, e. g. the grandmaster.

[0149] For (g)PTP networks, the subject-matter as described herein may be used as a complement to the user plane functions (UPF) performing the monitoring of the two clocks for uplink synchronization use cases when the UPF forwards packets transparently (i.e. a UE 120 being a grandmaster and providing time to other UEs, such as UEs 120-1, 120-2, 120-3).

[0150] The subj ect-matter as described enables UEs and core network parts of the network

140 to configure and expose a slave performance monitoring service and furthermore enables a UE to perform the self-calibration using two different time sources.

[0151] The subject matter described herein may be embodied in systems, apparatus, methods, and/or articles depending on the desired configuration. For example, the user equipment (or one or more components therein) and/or the processes described herein can be implemented using one or more of the following: a processor executing program code, an application-specific integrated circuit (ASIC), a digital signal processor (DSP), an embedded processor, a field programmable gate array (FPGA), and/or combinations thereof. These various implementations may include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. These computer programs (also known as programs, software, software applications, applications, components, program code, or code) include machine instructions for a programmable processor, and may be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the term "computer-readable medium" refers to any computer program product, machine-readable medium, computer-readable storage medium, apparatus and/or device (for example, magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions. Similarly, systems are also described herein that may include a processor and a memory coupled to the processor. The memory may include one or more programs that cause the processor to perform one or more of the operations described herein.

[0152] Although a few variations have been described in detail above, other modifications or additions are possible. In particular, further features and/or variations may be provided in addition to those set forth herein. Moreover, the implementations described above may be directed to various combinations and sub-combinations of the disclosed features and/or combinations and sub-combinations of several further features disclosed above. Other embodiments may be within the scope of the following claims. [0153] If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the abovedescribed functions may be optional or may be combined. Although various aspects of some of the embodiments are set out in the independent claims, other aspects of some of the embodiments 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. It is also noted herein that while the above describes example embodiments, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications that may be made without departing from the scope of some of the embodiments as defined in the appended claims. Other embodiments may be within the scope of the following claims. The term "based on" includes "based on at least". The use of the phase "such as" means "such as for example" unless otherwise indicated.