WO2025190502A1

WO2025190502A1 - Radio access network clock quality information propagation by mobile devices

Info

Publication number: WO2025190502A1
Application number: PCT/EP2024/057054
Authority: WO
Inventors: Min Wang; Nianshan SHI
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2024-03-15
Filing date: 2024-03-15
Publication date: 2025-09-18
Anticipated expiration: 2026-09-15

Abstract

A wireless device (10) receives information from a further wireless device (10). The information indicates quality of a clock of a Radio Access Network, RAN, node (100) in proximity of the further wireless device (10). Based on the information, the wireless device (10) controls wireless communication of the wireless device.

Description

Radio Access Network clock quality information propagation by mobile devices

Technical Field

The present invention relates to methods for controlling wireless communication and to corresponding devices, systems, and computer programs.

Background

Current wireless communication networks, e.g., based on the 4G (4th Generation) LTE (Long Term Evolution) or 5G (5th Generation) NR technology as specified by 3GPP (3rd Generation Partnership Project), also support D2D communication modes to enable direct communication between UEs (user equipments), sometimes also referred to as sidelink communication. Such D2D communication modes may for example be used for vehicle communications, e.g., including communication between vehicles, between vehicles and roadside communication infrastructure and, possibly, between vehicles and cellular networks. Due to wide range of different types of devices that might be involved in the communication with the vehicles, vehicle-to-everything (V2X) communication is another term used to refer to this class of communication. Vehicle communications have the potential to increase traffic safety, reduce energy consumption and enable new services related to intelligent transportation systems.

Sidelink communication may for example be used to enable relaying, such as UE-to-Network (U2N) relay operation or UE-to-UE (U2U) relay operation. For example. 3GPP TR 23.752 V17.0.0, clause describes layer-2 (L2) based U2N relay operation and the underlying protocol architecture. Here, the L2 U2N Relay UE provides a forwarding functionality for relaying any type of traffic over the sidelink radio interface, also denoted as “PC5”. The L2 U2N Relay UE also provides functionality to support connectivity to the 5GS (5G System) for a Remote UEs. A UE is considered to be a Remote UE if it has successfully established a PC5 link to the L2 U2N Relay UE. A Remote UE can be located within NG-RAN (Next Generation) Radio Access Network) coverage or outside of NG-RAN coverage.

Fig. 1A illustrates the protocol stack for user plane transport in L2 U2N relay operation, related to a PDU (Packet Data Unit) Session. The PDU layer corresponds to the PDU carried between the Remote UE and the Data Network (DN) over the PDU session. It is noted that the two endpoints of the PDCP (Packet Data Convergence Protocol) link are the Remote UE and the gNB (which is the radio access node or base station in the NR technology). The relay function is performed below PDCP. This means that data security is ensured between the Remote UE and the gNB without exposing raw data at the U2N Relay UE. The adaptation relay layer within the UE-to-Network Relay UE can differentiate between signalling radio bearers (SRBs) and data radio bearers (DRBs) for a particular Remote UE. The adaption relay layer is also responsible for mapping PC5 traffic to one or more DRBs (Data Radio Bearers) of the Uu interface (which is the radio interface for downlink/uplink communication between gNB and UE.

Fig. 1 B illustrates the control plane protocol stack of the NAS (Non-Access Stratum) connection forthe Remote UE to the NAS-MM (NAS mobility management) and NAS-SM (NAS session management) components. NAS messages are transparently transferred between the Remote UE and 5G-AN (5G Access Network) overthe L2 U2N Relay UE. This is accomplished using:

- PDCP end-to-end connection where the role of the U2N Relay UE is to relay the PDUs over the signaling radio bearer without any modifications.

- N2 connection between the 5G-AN and AMF (Access and Mobility Management Function) over N2.

- N11 connection AMF and SMF (Session Management Function) over N11.

The task of the U2N Relay UE is to relay the PDUs from the signaling radio bearer without any modifications.

Further, clause 6.6 of 3GPP TR 23.752 V17.0.0 (2021-03) also describes Layer 3 (L3) U2N Relay operation. As illustrated in Fig. 2A, in this case a ProSe 5G U2N Relay entity provides a functionality to support connectivity to the network for Remote UEs. L3 U2N Relay operation can be used for both public safety services and commercial services, e.g., an interactive service. A UE is considered to be a Remote UE for a certain ProSe U2N Relay if it has successfully established a PC5 link to this ProSe 5G U2N Relay. A Remote UE can be located within NG-RAN coverage or outside of NG-RAN coverage. The ProSe 5G U2N Relay typically relays unicast traffic (uplink and downlink) between the Remote UE and the network. The ProSe U2N Relay typically provides generic functions for relay any IP (internet Protocol) traffic. One-to-one Direct Communication is used between Remote UEs and the ProSe 5G U2NN Relays for unicast traffic. Fig. 2B illustrates the protocol stack for L3 U2N Relay operation.

Some services operated on a UE rely on a clock within the RAN, in the following also denoted as RAN clock. The RAN clock may for example be used for purposes of controlling transmission timing or reception timing of messages, and in some cases there are requirements on quality of the RAN clock. Examples of such services are public safety services. 3GPP TR 23.700-25 V18.1.0 (2023-03) describes that RAN clock quality information may be provided to a UE while the UE is in RRC_Connected state. Specifically, if a UE is subscribed for Access Stratum Time Synchronization (ASTI) in the UDM (Unified Data Management), the "Access and Mobility Subscription data" may additionally contain the following clock quality reporting control information:

- Clock quality detail level: Indicates whether and which clock quality information to provide to the UE and can take one of the following values: clock quality metrics or acceptable/not acceptable indication;

- Clock quality acceptance criteria for the UE (if the clock quality level equals "acceptable/not acceptable indication": The clock quality acceptance criteria for the UE. Acceptance criteria can be defined based on the following attributes: time source, traceability to UTC (Coordinated Universal Time) or GNSS (Global Navigation Satellite System), synchronization state, clock accuracy, PTP (Precision Time Protocol) clock class, frequency stability.

- Acceptable clock accuracy, acceptable frequency stability, or the like.

Whether and which clock quality information to provide to the UE depends on the needs of the time service consumer, which is here also denoted as client network operator. Therefore, the clock quality detail level and clock quality acceptance criteria are based on the parameters and their values specified in the agreement between the 5G network operator and the client network operator. The clock quality acceptance criteria refer to the quality with which 5G access stratum time needs to be delivered to and received by the UE, which may also consider propagation delays. Additional inaccuracies in the UE, e.g., if the 5G access stratum time is delivered to devices attached to the UE, are not included in the clock quality acceptance criteria because they are assumed to be budgeted by the client network operator when agreeing the required clock accuracy with the 5G network operator.

If an AF (Application Function) requests Access Stratum Time Synchronization (ASTI) for a UE, then the AF may provide clock quality reporting control information and service acceptance criteria (defined based on the following attributes: time source, traceability to UTC or GNSS, synchronization state, clock accuracy, PTP clock class, frequency stability to an entity denoted as TSCTSF (Time-Sensitive Communication and Time Synchronization Function). The TSCTSF then provides the clock quality reporting control information to AMF.

When the AMF provides the 5G access stratum time distribution indication and the Uu time synchronization error budget to NG-RAN, AMF also includes the clock quality reporting control information. Based on the clock quality reporting control information received from AMF, the RAN reports its timing synchronization status to the UE using unicast RRC (Radio Resource Control ) signaling:

If clock quality detail level is set to "clock quality metrics", then the RAN provides clock quality metrics to the UE that reflect its current timing synchronization status. Here, clock quality metrics may include: clock accuracy, PTP clock class, traceability to UTC, frequency stability, time source, synchronization state.

If clock quality detail level is set to "acceptable/not acceptable indication", then the RAN provides an acceptable indication to the UE if the RAN's timing synchronization status matches the acceptance criteria received from AMF; otherwise RAN indicates "not acceptable" to the UE.

When determining the clock quality metrics for a UE and when determining whether clock quality is acceptable or not acceptable for a UE, RAN considers whether propagation delay compensation is performed.

In view of the above, the following is noted in relation to the network timing synchronization status and reporting functionalities described in 3GPP TR 23.700-25 V18.1.0::

The “clock quality reporting control information” sent by AMF to gNB manages the NG- RAN timing synchronization status notifications to the UE;

If "clock quality metrics” is set, gNB provides clock quality metric to the UE reflects gNB’s current timing synchronization status;

If “acceptable/not acceptable indication is set, the gNB provides the indication according to if it matches the acceptance criteria sent from AMF.

Attributes that can be used for clock quality acceptance criteria depend on RAN capabilities.

However, the known mechanism of providing RAN clock quality information is only applicable to a UE which is in RRC_Connected state. This may cause limitations on the services which utilize the information, e.g., public safety services. In principle, public safety services concern all UEs regardless of their RRC states or their coverage status, including out-of-coverage (OOC) UEs or Remote UEs in a U2N Relay scenario.

Accordingly, there is a need for techniques which allow for enhancing the availability of RAN clock quality information.

Summary According to an embodiment, a method of controlling wireless communication is provided. According to the method, a wireless device receives information from a further wireless device. The information indicates quality of a clock of a RAN node in proximity of the further wireless device. Based on the information, the wireless device controls wireless communication of the wireless device.

According to a further embodiment a method of controlling wireless communication is provided. According to the method, a wireless device receives information from a RAN node in proximity of the wireless device. The information indicates quality of a clock of the RAN node. Further, the wireless device provides the information to a further wireless device.

According to a further embodiment a method of controlling wireless communication is provided. According to the method, a RAN node determines whether a first wireless device is entitled to receive information indicating quality of a clock of the RAN node. In response to determining that the first wireless device is entitled to receive the information, the RAN node providing the information via a second wireless device to the first wireless device.

According to a further embodiment, a wireless device is provided. The wireless device is configured to receive information from a further wireless device. The information indicates quality of a clock of a RAN node in proximity of the further wireless device. Further, the wireless device is configured to, based on the information, control wireless communication of the wireless device.

According to a further embodiment, a wireless device is provided. The wireless device comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the wireless device is operative to receive information from a further wireless device. The information indicates quality of a clock of a RAN node in proximity of the further wireless device. Further, the memory contains instructions executable by said at least one processor, whereby the wireless device is operative to, based on the information, control wireless communication of the wireless device.

According to a further embodiment, a wireless device is provided. The wireless device is configured to receive information from a RAN node in proximity of the wireless device. The information indicates quality of a clock of the RAN node. Further, the wireless device is configured to provide the information to a further wireless device. According to a further embodiment, a wireless device is provided. The wireless device comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the wireless device is operative to receive information from a RAN node in proximity of the wireless device. The information indicates quality of a clock of the RAN node. Further, the memory contains instructions executable by said at least one processor, whereby the wireless device is operative to provide the information to a further wireless device.

According to a further embodiment, a RAN node is provided. The RAN node is configured to determine whether a first wireless device is entitled to receive information indicating quality of a clock of the RAN node. Further, the RAN node is configured to, in response to determining that the first wireless device is entitled to receive the information, provide the information via a second wireless device to the first wireless device.

According to a further embodiment, a RAN node is provided. The RAN node comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the RAN node is operative to determine whether a first wireless device is entitled to receive information indicating quality of a clock of the RAN node. Further, the memory contains instructions executable by said at least one processor, whereby the RAN node is operative to, in response to determining that the first wireless device is entitled to receive the information, provide the information via a second wireless device to the first wireless device.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a wireless device. Execution of the program code causes the wireless device to receive information from a further wireless device. The information indicates quality of a clock of a RAN node in proximity of the further wireless device. Further, execution of the program code causes the wireless device to, based on the information, control wireless communication of the wireless device.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a wireless device. Execution of the program code causes the wireless device to receive information from a RAN node in proximity of the wireless device. The information indicates quality of a clock of the RAN node. Further, execution of the program code causes the wireless device to provide the information to a further wireless device.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a RAN node. Execution of the program code causes the RAN node to determine whether a first wireless device is entitled to receive information indicating quality of a clock of the RAN node. Further, execution of the program code causes the RAN node to, in response to determining that the first wireless device is entitled to receive the information, provide the information via a second wireless device to the first wireless device.

Details of such embodiments and further embodiments will be apparent from the following detailed description of embodiments.

Brief Description of the Drawings

Figs. 1A and 1 B schematically illustrate a protocol stack of L2 U2N relay operation.

Figs. 2A and 2B schematically illustrate L3 U2N relay operation.

Fig. 3 schematically illustrates a wireless communication network in accordance with an embodiment.

Fig. 4 schematically illustrates an example of processes according to an embodiment.

Figs. 5A and 5B schematically illustrate a SL message format according to an embodiment.

Fig. 6 schematically illustrates a further SL message format according to an embodiment.

Figs. 7A and 7B schematically illustrate a further SL message format according to an embodiment.

Fig. 8 shows a flowchart for schematically illustrating a method according to an embodiment.

Fig. 9 shows a flowchart for schematically illustrating a further method according to an embodiment. Fig. 10 shows a flowchart for schematically illustrating a further method according to an embodiment.

Fig. 11 schematically illustrates structures of a wireless device according to an embodiment.

Fig. 12 schematically illustrates structures of a RAN node according to an embodiment.

Detailed Description of Embodiments

In the following, concepts in accordance with exemplary embodiments of the invention will be explained in more detail and with reference to the accompanying drawings. The illustrated embodiments relate to control of wireless communication of one or more wireless devices (WDs). The WDs may include various types of UEs. As used herein, the term WD refers to a device capable, configured, arranged, and/or operable to communicate wirelessly with network nodes and/or other WDs. Unless otherwise noted, the term WD may be used interchangeably herein with UE. Communicating wirelessly may involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. In some embodiments, a WD may be configured to transmit and/or receive information without direct human interaction. For instance, a WD may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the network. Examples of a WD include, but are not limited to, a smart phone, a mobile phone, a cell phone, a Voice over IP (VoIP) phone, a wireless local loop phone, a desktop computer, a Personal Digital Assistant (PDA), a wireless camera, a gaming console or device, a music storage device, a playback appliance, a wearable terminal device, a wireless endpoint, a mobile station, a tablet, a laptop, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), a smart device, a wireless Customer Premise Equipment (CPE), a vehicle mounted wireless terminal device, a connected vehicle, etc. In some examples, in an Internet of Things (loT) scenario, a WD may also represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another WD and/or a network node. The WD may in this case be a Machine- to-Machine (M2M) device, which may in a 3GPP context be referred to as a Machine-Type Communication (MTC) device. As one particular example, the WD may be a UE implementing the 3GPP Narrowband loT (NB-loT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, home or personal appliances (e.g., refrigerators, televisions, etc.), or personal wearables (e.g., watches, fitness trackers, etc.). In other scenarios, a WD may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. A WD as described above may represent the endpoint of a wireless connection, in which case the device may be referred to as a wireless terminal. Furthermore, a WD as described above may be mobile, in which case it may also be referred to as a mobile device or a mobile terminal. The illustrated concepts particularly concern WDs that support D2D communication, for example by implementing a 3GPP standard for sidelink communication, Vehicle-to-Vehicle (V2V), Vehicle-to-lnfrastructure (V2I), Vehicle-to- Everything (V2X). The WDs supporting D2D communication are herein also referred to as D2D communication devices. The D2D communication may for example be based on the LTE radio technology or the NR radio technology as specified by 3GPP, e.g., on the PC5 SL interface of the LTE or NR technology. However, it is noted that the illustrated concepts could also be applied to other radio technologies, e.g., a WLAN (Wireless Local Area Network) technology.

Some of the following explanations are made in the context of the NR technology, e.g., for two or more SL UEs that are deployed in or in proximity of a same or different NR cells. However, it is noted the illustrated concepts may be applied to LTE or any other technology that enables the direct connection of two (or more) nearby devices. The illustrated concepts may also be applicable to relay scenarios including U2N Relay or U2U Relay where the remote UE and the relay UE may be based on LTE sidelink or NR sidelink, the Uu connection between the relay UE and the base station may be LTE Uu or NR Uu.

As used herein, the terms “direct connection” or “direct path” may refer to a connection between a UE and a gNB (or other type of RAN node), while we use terms “indirect connection” or “indirect path” may refer to a connection between a remote UE and a gNB (or other type of RAN node) via a relay UE.

In the illustrated concepts, information on quality of a clock of a RAN node may be efficiently not only to WDs which are connected to the RAN node, e.g., to UEs in RRC Connected state, but also to other UEs. For this purpose, a first WD may receive the information on the quality of the clock of the RAN node from a second WD, which is in proximity to the RAN node. The second WD may receive the information on the quality of the clock from the RAN node and may then propagate this information via a direct connection, e.g., a sidelink (SL) connection, to the first WD.

Fig. 3 illustrates exemplary structures of the wireless communication network. In particular, Fig. 3 shows UEs 10 which are served by access nodes 100 of the wireless communication network. Here, it is noted that the wireless communication network may actually include a plurality of access nodes 100 that may serve a number of cells within the coverage area of the wireless communication network.

The access nodes 100 may be regarded as being part of an RAN of the wireless communication network. The access nodes 100 may thus also be denoted as RAN nodes. Further, Fig. 3 schematically illustrates a CN (Core Network) 210 of the wireless communication network. In Fig. 1 , the CN 210 is illustrated as including a GW (gateway) 220 and one or more control node(s) 240. The GW 220 may be responsible for handling user plane data traffic of the UEs 10, e.g., by forwarding user plane data traffic from a UE 10 to a network destination or by forwarding user plane data traffic from a network source to a UE 10. Here, the network destination may correspond to another UE 10, to an internal node of the wireless communication network, or to an external node which is connected to the wireless communication network. Similarly, the network source may correspond to another UE 10, to an internal node of the wireless communication network, or to an external node which is connected to the wireless communication network. The GW 220 may for example correspond to a UPF (User Plane Function) of the 5G Core (EGC) or to an SGW (Serving Gateway) or PGW (Packet Data Gateway) of the 4G EPC (Evolved Packet Core). The control node(s) 240 may for example be used for controlling the user data traffic, e.g., by providing control data to the access node 100, the GW 220, and/or to the UE 10. The control node(s) 240 may for example include an AMF and/or an SMF.

As illustrated by solid double-headed arrows, the access nodes 100 may send downlink (DL) wireless transmissions to at least some of the UEs 10, and some of the UEs 10 may send uplink (UL) wireless transmissions to the access node 100. Further, as illustrated by broken double-headed arrows, some of the UEs 10 may perform SL transmissions.

The DL transmissions, UL transmissions, and/or SL transmissions may be used to provide various kinds of services to the UEs 10, e.g., a voice service, a multimedia service, or some other data service. Such services may be hosted in the CN 210, e.g., by a corresponding network node. By way of example, Fig. 3 illustrates an application service platform 250 provided in the CN 210. Further, such services may be hosted externally, e.g., by an AF (application function) connected to the CN 210. By way of example, Fig. 3 illustrates one or more application servers 300 connected to the CN 210. The application server(s) 300 could for example connect through the Internet or some other wide area communication network to the CN 210. The application service platform 250 may be based on a server or a cloud computing system and be hosted by one or more host computers. Similarly, the application server(s) 300 may be based on a server or a cloud computing system and be hosted by one or more host computers. The application server(s) 300 may include or be associated with one or more AFs that enable interaction with the CN 210 to provide one or more services to the UEs 10, corresponding to one or more applications. These services or applications may generate the user data traffic conveyed by the DL transmissions, the UL transmissions, and/or the SL transmissions. Accordingly, the application server(s) 300 may include or correspond to the above-mentioned network destination and/or network source for the user data traffic. In the respective UE 10, such service may be based on an application (or shortly “app”) which is executed on the UE 10. Such application may be pre-installed or installed by the user. Such application may generate at least a part of the user plane data traffic between the UEs 10 and the access node 100.

In accordance with the illustrated concepts, any of the RAN nodes 100 may provide information on its clock quality, i.e., RAN clock quality information, to at least some of the UEs 10. For a UE 10 which is not directly connected to the RAN node 100, the RAN clock quality information may be provided indirectly via another UE 10, e.g., via a relay path that includes one or more other UEs 10 acting as relay. The relay path may based on L2 U2N relay operation or L3 U2N relay operation.

In the illustrated examples, the RAN clock quality information may include one or more of the following:

Clock quality detail level: indicates whether and which clock quality information to provide to the UE and can take one of the following values: clock quality metrics or acceptable/not acceptable indication;

Clock quality acceptance criteria for the UE (if the clock quality level equals "acceptable/not acceptable indication": the clock quality acceptance criteria for the UE. Acceptance criteria can be defined based on the following attributes: time source, traceability to UTC or GNSS, synchronization state, clock accuracy, PTP clock class, frequency stability, (e.g. acceptable clock accuracy, acceptable frequency stability, etc.).

The UE 10 may report requirements or needs concerning RAN clock quality to a CN entity (e.g., AMF or SMF) via NAS signaling. The RAN node 100 may then be configured by the CN to report the RAN clock quality information accordingly.

In some scenarios, any of the UEs 10 may consider the RAN clock quality information and/or requirements on RAN clock quality in selection or reselection of a relay UE. For example, the existing relay selection and reselection mechanisms may be supplemented by functionalities that enable a remote UE to select a relay UE considering the RAN clock quality information that the relay UE has available or requires. In some cases, the selection or selection may be done in such a way that the selected relay UE has the same or similar RAN clock quality information and/or related requirements. This selection may be assisted by distributing the RAN clock quality information in an area where multiple UEs 10 could make use of it, e.g., for public safety services.

In some scenarios, a UE 10, e.g., which is capable of SL relay, i.e., to operate as a remote UE or a relay UE, may send signaling which carries the information on RAN clock quality of a RAN node 100 in proximity of the UE 10. The UE 10 may receive this information from the RAN node 100, or this information could correspond to RAN clock quality expected based on requirements of the UE 10 and/or capabilities of the UE 10. In some scenarios, the signaling sent by the UE 10 may be broadcast signaling. Alternatively or in addition, groupcast signaling or unicast signaling could be utilized. Examples of messages of the signaling that may carry the RAN clock quality information include: one or more SL discovery messages, one or more PC5-S (PC5 Signaling protocol) messages, one or more messages of an application layer, one or more MAC CEs (Medium Access Control Control Elements), one or more control PDUs of a RAN protocol layer, e.g., SDAP (Service Data Adaptation Protocol), PDCP, RLC (Radio Link Control), or the like, layer 1 (L1) signaling (i.e., physical layer signaling) carried by SL physical channels e.g., PSSCH (Physical SL Shared Channel), PSCCH (Physical SL Control Channel), PSFCH (Physical SL Feedback Channel), PSBCH (Physical SL Broadcast Channel), or the like.

The RAN clock quality information may be signaled by the UE 10 to other UEs 10 in proximity in a broadcast fashion or groupcast fashion.

In some scenarios, upon triggering of relay selection or relay reselection procedure, a remote UE 10 may search candidate relay UEs 10 in its proximity. The remote UE 10 may then select a relay UE which fulfils one or more of the following criteria.

The relay UE 10 provides the strongest SL connection to the remote UE 10, e.g., radio channel quality of the sidelink connection between the remote UE and the relay UE is strongest among all relay UE candidates .

The relay UE 10 provides strongest Uu connection to the RAN node 100, e.g., radio channel quality of the Uu connection between the relay UE 10 and the RAN node 100 is strongest among all relay UE candidates. The RAN clock quality information and/or RAN clock quality requirements of the relay UE 10 is the same or similar as that of the remote UE 10.

For example, the result of such relay selection or rely reselection may be that the remote UE 10 and the relay UE 10 have the same or at least similar acceptable RAN clock accuracy requirements and/or that the remote UE 10 and the relay UE 10 have the same or at least similar acceptable RAN clock frequency stability requirements. Here, the requirements may be compared in terms of a metric representing clock accuracy and may be regarded as being similar if the deviation of the metric does not exceed a threshold.

In some scenarios, a remote UE 10 may be triggered to reselect another relay UE 10 when any of the following conditions is met: if the current relay UE 10 has changed its RAN clock quality information so that the current relay UE 10 cannot comply with the requirements of the remote UE 10 for its RAN clock quality requirement;

• if the remote UE 10 has changed its RAN clock quality requirements so that the current relay UE 10 cannot comply with these requirements;

• if the remote UE 10 has changed its interest for public safety services or some other service(s). The new service(s) may be associated with different requirements on RAN clock quality so that the current relay UE 10 cannot comply with these requirements.

Fig. 4 shows an example of processes in accordance with the above principles. The processes involve a remote UE 10, a relay UE 10, and a RAN node 100, e.g., corresponding to any of the RAN nodes 100 and UEs 10 in Fig. 3. As further detailed below, the processes involve that the relay UE 10 forwards RAN clock quality information of the RAN node 100 to the remote UE 10. In the example of Fig. 4, it is assumed that the processes also include selection of the relay UE 10, which may therefore initially be regarded as a candidate relay UE. It is however noted that similar processes could also be used in case that the remote UE 10 has already selected the relay UE 10 as its relay and established a U2N relay connection to the RAN node 100 via the relay UE 10.

At block 401 , a relay discovery procedure is triggered at the remote UE 10. As a result, the remote UE 10 and the (candidate) relay UE 10 engage in discovery signaling 402. The discovery signaling 402 may include one or more discovery messages sent by the remote UE 10 and one or more discovery responses sent by the relay UE 10. The remote UE 10 may supplement one or more of such discovery messages by information of the RAN clock requirements of the remote UE 10. Similarly, the (candidate) relay UE 10 may supplement one or more of the discovery responses with information on the RAN clock quality requirements of the (candidate) relay UE 10.

At block 403, the remote UE 10 performs relay selection or relay reselection, which may be based on the discovery signaling 402. Specifically, the remote UE 10 may select a relay UE which, according to the information received with the discovery signaling, has the same or at least similar RAN clock requirements as the remote UE 10. In the example of Fig. 4, it is assumed that the remote UE 10 selects the relay UE 10 and performs relay connections establishment via the relay UE 10, as indicated by 404.

Subsequently, the RAN node 100 may report RAN clock quality information via the relay UE 10 to the remote UE 10. In the example of Fig. 4, this is illustrated by messages 405, 407, which indicate the RAN clock quality information from the RAN node 100 to the relay UE 10, and messages 406, 408, which propagate the RAN clock quality information from the relay UE 10 to the remote UE 10. In the following, variants of how the relay UE 10 may propagate the RAN clock quality information will be explained in more detail. The RAN clock quality information can be reported in terms of a clock quality metric or in terms of a clock quality acceptance status report. In the latter case, the report could merely indicate whether the RAN clock quality is acceptable for the remote UE 10 or not. Criteria for determining acceptance can be provided by AMF and may depend on capabilities of the remote UE 10.

In some variants, the relay UE 10 may forward received system information carrying the status of the RAN clock quality information, e.g., at least a part of a System Information Block (SIB), such as SIB9. The forwarded information may indicate whether the RAN clock quality information has changed since the last reception by the remote UE. The information may be forwarded by PC5-RRC signaling, e.g., by a message denoted as “UuMessageT ransferSidelink”.

Upon reception of the signaling indicating that the RAN clock quality information has changed, the remote UE 10 may apply one of the following options to obtain the updated RAN clock quality information from the RAN node 100.

Option 1 : If the remote UE 10 is in RRC Connected state, the remote UE 10 may wait for reception of dedicated RRC signaling (e.g., message denoted as “DLlnformationTransfer”) from the RAN node 100, which carries the updated RAN clock quality information.

Option 2: If the remote UE 10 is in RRC Idle state, the remote UE 10 may first switch to RRC Connected state. After that, the remote UE 10 may wait for reception of dedicated RRC signaling (e.g., a DLlnformationTransfer message) from the RAN node 100, which carries the updated RAN clock quality information.

Option 3: If the remote UE 10 is in RRC Inactive state, the remote UE 10 may first switch to RRC Connected state. After that, the remote UE 10 may wait for reception of dedicated RRC signaling (e.g., a DLlnformationTransfer message) from the RAN node 100, which carries the updated RAN clock quality information. Alternatively, the remote UE 10 may remain in RRC Inactive state and applies an SDT procedure via the relay UE 10 to receive the updated RAN clock quality information from the RAN node 100. In this case, the relay UE 10 may also be in RRC Inactive state and first obtain the updated RAN clock quality information from the RAN node 100 via the SDT procedure. After that, the relay UE 10 may forward the received RAN clock quality information to the remote UE 10 via a PC5-RRC signaling. As one possible alternative, the remote UE 10 may determine whether to switch to RRC Connected state or remain in RRC Inactive state upon reception of the signaling indicating that the RAN clock quality information has changed. In this case, the remote UE 10 may need to inform the RAN node 100 of the remote UE’s 10 determination. As another alternative, the RAN node 100, i.e., serving gNB of the relay UE 10, may determine whether the remote UE 10 should switch to RRC Connected state or remain in RRC Inactive state upon reception of the signaling indicating that the RAN clock quality information has changed. The RAN node 100 may configure the remote UE 10 accordingly when the remote UE 10 establishes its RRC connection towards the RAN node 100 via the relay UE 10. It is noted that for any of the above options, the relay UE 10 may first need to switch to RRC Connected state before the remote UE 10 changes its RRC state towards the RAN node 100.

As mentioned above, in some scenarios a relay UE 10 may forward its received RAN clock quality information, e.g., as received from the RAN node via a DLlnformationTransfer message, to each connected remote UE 10 using a PC5-RRC signaling. In such cases, the RAN clock quality information may be forwarded in a unicast manner.

The PC5-RRC signaling may include a message denoted as “NotificationMessageSidelink”, see 3GPP TS 38.331 V17.6.0 (2023-09), which may be supplemented with the RAN clock quality information. Figs. 5A and 5B illustrate an example of a corresponding ASN1 format of the NotificationMessageSidelink message. Elements used for conveying the RAN clock quality information are highlighted in bold face. It however noted that other types of PC5-RRC messages could be used in addition or as an alternative to the NotificationMessageSidelink message. Examples of such messages are a message denoted as “UEAssistancelnformationSidelink” and a message denoted as “UuMessageTransferSidelink” (see 3GPP TS 38.331 V17.6.0). Further, it would be possible to define one or more now PC5- RRC messages for conveying the RAN clock quality information from the relay UE 10 to the remote UE 10.

In some scenarios, the relay UE 10 may forward the RAN clock quality information via a SL MIB (Master Information Block) to the remote UE 10. For example, the RAN clock quality information could be forwarded via SL-BCH (SL Broadcast Channel) on the SBCCH (SL Broadcast Control Channel) logical channel. In this way, the relay UE 10 may efficiently provide the RAN clock quality information to multiple neighbor UEs, which may have the same or similar RAN clock quality requirements. For obtaining the RAN clock quality information, the neighbor UEs don’t need to maintain or establish a PC5-RRC connection with the relay UE. Figs. 6, 7 A, and 7B illustrate possible message formats which may be used for implementing this way of conveying the RAN clock quality information. Fig. 6 shows a modified format of a message denoted as “SBCCH-SL-BCH-MESSAGE” (see 3GPP TS 38.331 V17.6.0). The SBCCH-SL-BCH-MESSAGE class is a set of PC5-RRC messages that may be sent from UE to the UE via SL-BCH on the SBCCH logical channel. As indicated by bold face elements, the refers to an extension, denoted as “masterlnformationBlockSidelinkExtension”. A possible message format of the extension is illustrated by Figs. 7A and 7B. As shown, the extension includes an indicator denoted as “eventID-TSS”. The eventide-TSS indicator may correspond to the status of the 5G access stratum time distribution parameter “Clock Quality Reporting Control Information” as defined in 3GPP TS 23.501 V18.4.0 (2023-12). Each neighbor UE may store the received eventID-TSS in the SL MIB. Whenever the received eventID-TSS is different from the stored eventID-TSS, this indicates to the remote UE 10 that the current serving RAN node 100, i.e., the serving gNB of the relay UE, has changed its RAN clock quality information.

In some scenarios, the relay UE 10 could perform a handover from one RAN node 100 to another RAN node 100, e.g., from a source gNB to a target gNB. In such cases, the relay UE 10 may signal the following information to its connected remote UE(s) when it has completed the handover: ID of the target gNB and RAN clock quality information of the target gNB. Alternatively, the relay UE 10 could signals the this information to all neighbor UEs in proximity of the relay UE 10, e.g., using broadcast SL signaling.

When the remote UE 10 receives the RAN clock quality information from the relay UE 10, the remote UE 10 may provide the received RAN clock quality information to higher protocol layers of the relevant service(s)- The service(s) can then for example adjust transmission and/or reception timing of messages according to the received RAN clock quality information. The service(s) may for example correspond to a public safety service. The relay UE 10 may inform the network about its own RAN clock quality requirements and whether it supports the transfer of the RAN clock quality information to a remote UE. This could be accomplished via NAS signaling or via a subscription. For example, if this information is available in the CN, the AMF could transfer the information to the RAN node 100, e.g., during a UE Initial Context Setup procedure or UE Context Modification procedure. Upon reception of the information, the RAN node 100 may decide to increase the frequency to send the RAN clock quality information to the given UE. Further, the AMF could transfer authorization information to the RAN node 100, indicating the UE 100 is allowed to perform RAN clock quality information transfer or broadcast. With respect to the remote UE 10, the CN may store authorization information indicating whether the remote UE 10 is entitled to receive the RAN clock quality information via a relay UE, and the AMF may transfer this information to the RAN node 100. For example, such authorization information could be provided in an element of the 5G ProSe Authorized Information Element (IE) defined in clause 9.3.1.233 of 3GPP TS 38.413 V17.7.0 (2023-12). The authorization information may be based on a subscription of the remote UE 10 to an access stratum service for distribution of RAN clock quality information. Depending on the authorization information, the RAN node 100 may decide whether to provide the RAN clock quality information via the relay UE 10 to the remote UE 10.

Fig. 8 shows a flowchart for illustrating a method, which may be utilized for implementing the illustrated concepts. The method of Fig. 8 may be used for implementing the illustrated concepts in a WD, e.g., corresponding to any of the above-mentioned UEs 10, specifically the remote UE 10. In some scenarios, the WD may be a vehicle or vehicle-mounted device, but other types of WD, e.g., as mentioned above, could be used as well.

If a processor-based implementation of the wireless device is used, at least some of the steps of the method of Fig. 8 may be performed and/or controlled by one or more processors of the WD. Such WD may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 8.

At step 810, the WD may receive information from other WDs, the information indicating requirements on RAN clock quality of the other WDs. For example, such information could be received in discovery signaling from the other WDs.

At step 820, the WD may select a relay WD. In some scenarios, selection of a relay WD may be based on one or more criteria according to which the quality of the clock of a RAN node is acceptable for the WD and one or more criteria according to which the quality of the clock of a RAN node is acceptable for the relay WD. For example, the WD could select the relay WD in such a way that the WD and the relay WD have the same or at least similar requirements concerning the quality of the clock of the RAN node. Such selection may for example be based on the information received at step 810.

At step 830, the WD receives information from a further wireless device, the information indicating quality of a clock of a RAN node in proximity of the further WD. In some scenarios, the WD may receive the information based on a subscription of the WD to an access stratum time distribution service. Alternatively or in addition, the WD could receive the information in response to a request. For example, the WD could send a request for the information via the further WD to the RAN node. In some scenarios, the WD may receive the information while the further WD operates as a relay for connecting the wireless device to the RAN node. In some cases, the WD could also receive the information without selecting the further WD as a relay, e.g., by broadcast signaling from the further WD.

The WD may receive the information by one or more of: one or more SL discovery messages; SL control signaling, e.g., based on PC5-S; a MAC CE; a control PDU of a RAN protocol; or physical layer signaling on a SL channel. In some scenarios, the WD may receive the information by one or more broadcast messages and/or by one or more groupcast messages.

The information may indicate the quality of the clock in terms of clock accuracy or clock frequency stability. For this purpose, the information may include a metric representing clock accuracy or a metric representing clock frequency stability. Alternatively or in addition, the information could include an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the WD. Such criteria may at least in part be configurable by a CN node, e.g., an AMF, and may depend on capabilities of the WD.

At step 840, the WD controls wireless communication of the WD based on the information received at step 830, e.g., by controlling timing of one or more services operated on the wireless device. The timing may for example include transmission timing and/or reception timing of messages of the service. This control may be accomplished on higher protocol layers, e.g., the service layer or application layer. The service can for example correspond to a public safety service. For example, the RAN node could determine whether the quality of the clock is acceptable for the WD, considering acceptance criteria received from AMF and/or propagation delay compensation for the WD, potential propagation delay between the WD and the RAN node. Fig. 9 shows a flowchart for illustrating a method, which may be utilized for implementing the illustrated concepts. The method of Fig. 9 may be used for implementing the illustrated concepts in a WD, e.g., corresponding to any of the above-mentioned UEs 10, specifically the relay UE 10. In some scenarios, the WD may be a vehicle or vehicle-mounted device, but other types of WD, e.g., as mentioned above, could be used as well.

If a processor-based implementation of the wireless device is used, at least some of the steps of the method of Fig. 8 may be performed and/or controlled by one or more processors of the WD. Such WD may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 9.

At step 910, the WD may send information to other WDs, the information indicating requirements on RAN clock quality of the WD. For example, such information could be sent in discovery signaling.

At step 920, the WD receives information from a RAN node in proximity of the WD, the information indicating quality of a clock of the RAN node.

At step 930, the WD provides the information to a further WD. In some scenarios, the WD may send the information based on a subscription of the further WD to an access stratum time distribution service. Alternatively or in addition, the WD could send the information in response to a request, e.g., from the further WD. In some scenarios, the WD may send the information while the WD operates as a relay for connecting the further WD to the RAN node. In some cases, the WD could also send the information without operating as a relay of the further WD, e.g., by broadcast signaling to neighboring WDs.

The WD may send the information by one or more of: one or more SL discovery messages; SL control signaling, e.g., based on PC5-S; a MAC CE; a control PDU of a RAN protocol; or physical layer signaling on a SL channel. In some scenarios, the WD may send the information by one or more broadcast messages and/or by one or more groupcast messages.

The information may indicate the quality of the clock in terms of clock accuracy or clock frequency stability. For this purpose, the information may include a metric representing clock accuracy or a metric representing clock frequency stability. Alternatively or in addition, the information could include an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the further WD. Such criteria may at least in part be configurable by a CN node, e.g., an AMF, and may depend on capabilities of the further WD.

Fig. 10 shows a flowchart for illustrating a method, which may be utilized for implementing the illustrated concepts. The method of Fig. 10 may be used for implementing the illustrated concepts in a RAN node, e.g., corresponding to any of the above-mentioned RAN nodes 100. In some scenarios, the RAN node may be a gNB.

If a processor-based implementation of the RAN node is used, at least some of the steps of the method of Fig. 10 may be performed and/or controlled by one or more processors of the RAN node. Such wireless device may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 10.

At step 1010, the RAN node may determine whether a first WD is entitled to receive information indicating quality of a clock of the RAN node. This determination may be based on a subscription of the first WD to an access stratum time distribution service.

At step 1020, the RAN node may provide the information indicating the quality via a second WD to the first WD. This is accomplished in response to determining that the first WD is entitled to receive the information.

The RAN node may provide the information while the second wireless device operates as a relay for connecting the first WD to the RAN node. In some scenarios, the RAN node may provide the information in response to a request from the first WD. The RAN node may provide the information by one or more of: a MAC CE; RRC signaling; or a control PDU of a RAN protocol.

The information may indicate the quality of the clock in terms of clock accuracy or clock frequency stability. For this purpose, the information may include a metric representing clock accuracy or a metric representing clock frequency stability. Alternatively or in addition, the information could include an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the first WD. Such criteria may at least in part be configurable by a CN node, e.g., an AMF, and may depend on capabilities of the first WD.

Fig. 11 illustrates a processor-based implementation of a wireless device 1100 which may be used for implementing the above-described concepts. For example, the structures as illustrated in Fig. 11 may be used for implementing the concepts in any of the above-mentioned UEs 10.

As illustrated, the wireless device 1100 includes one or more wireless interfaces 1110. The wireless interface(s) 1110 may for example be based on the NR technology or the LTE technology. However, other radio technologies, such as WLAN or Bluetooth, could be used as well. The wireless interface(s) 1110 may support SL communication, e.g., on the PC5 interface of the NR technology or the PC5 interface of the LTE technology.

Further, the wireless device 1100 may include one or more processors 1150 coupled to the wireless interface(s) 1110 and a memory 1160 coupled to the processor(s) 1150. By way of example, the wireless interface(s) 1110, the processor(s) 1150, and the memory 1160 could be coupled by one or more internal bus systems of the wireless device 1100. The memory 1160 may include a Read-Only-Memory (ROM), e.g., a flash ROM, a Random Access Memory (RAM), e.g., a Dynamic RAM (DRAM) or Static RAM (SRAM), a mass storage, e.g., a hard disk or solid state disk, or the like. As illustrated, the memory 1160 may include software 1170 and/or firmware 1180. The memory 1160 may include suitably configured program code to be executed by the processor(s) 1150 so as to implement the above-described functionalities for controlling wireless communication, such as explained in connection with Figs. 8 or 9.

It is to be understood that the structures as illustrated in Fig. 11 are merely schematic and that the wireless device 1100 may actually include further components which, for the sake of clarity, have not been illustrated, e.g., further interfaces or further processors. Also, it is to be understood that the memory 1160 may include further program code for implementing known functionalities of a UE. According to some embodiments, also a computer program may be provided for implementing functionalities of the wireless device 1100, e.g., in the form of a physical medium storing the program code and/or other data to be stored in the memory 1160 or by making the program code available for download or by streaming.

Fig. 12 schematically illustrates a processor-based implementation of a RAN node 1200, which may be used for implementing the above-described concepts. For example, the structures as illustrated in Fig. 12 may be used for implementing the concepts in one or more of the above- mentioned RAN nodes 100 or similar access nodes.

As illustrated, the RAN node 1200 may include a wireless interface 1210 and a network interface 1220. The wireless interface 1110 may be used for wireless communication with one or more wireless devices, such as the above-mentioned UEs 10. The network interface 1220 may be used for communication with one or more other nodes of a wireless communication network, e.g., other RAN nodes or CN nodes.

Further, the RAN node 1200 may include one or more processors 1250 coupled to the interfaces 1210, 1220 and a memory 1260 coupled to the processor(s) 1250. By way of example, the interfaces 1210, 1220, the processor(s) 1250, and the memory 1260 could be coupled by one or more internal bus systems of the RAN node 1200. The memory 1260 may include a ROM, e.g., a flash ROM, a RAM, e.g., a DRAM or SRAM, a mass storage, e.g., a hard disk or solid state disk, or the like. As illustrated, the memory 1260 may include software 1270 and/or firmware 1280. The memory 1260 may include suitably configured program code to be executed by the processor(s) 1250 so as to implement the above-described functionalities for controlling wireless communication, such as explained in connection with Fig. 10

It is to be understood that the structures as illustrated in Fig. 12 are merely schematic and that the RAN node 1200 may actually include further components which, for the sake of clarity, have not been illustrated, e.g., further interfaces or further processors. Also, it is to be understood that the memory 1260 may include further program code for implementing known functionalities of a gNB of the NR technology, an eNB of the LTE technology, or similar type of access node. According to some embodiments, also a computer program may be provided for implementing functionalities of the RAN node 1200, e.g., in the form of a physical medium storing the program code and/or other data to be stored in the memory 1260 or by making the program code available for download or by streaming.

As can be seen, the concepts as described above may be used for efficiently enhancing availability of RAN clock quality information to wireless devices, including remote UEs using U2N relaying, OOC UEs, UEs in RRC Idle state, or UEs in RRC Inactive state. In this way, useability of services requiring RAN clock quality information, such as public safety services, can be improved. In the context of the concepts, also relay selection/or reselection may be enhanced to consider RAN clock quality information or RAN clock quality requirements.

It is to be understood that the examples and embodiments as explained above are merely illustrative and susceptible to various modifications. For example, the illustrated concepts may be applied in connection with various kinds of radio technologies and direct communication, without limitation the SL mode of the LTE technology or NR technology, e.g., in connection with WLAN technologies or other wireless ad-hoc network technologies. Further, the concepts may be applied with respect to various types of UEs. Further, the concepts may be applied in connection with various services which may benefit from RAN clock quality information. Moreover, it is to be understood that the above concepts may be implemented by using correspondingly designed software to be executed by one or more processors of an existing device or apparatus, or by using dedicated device hardware. Further, it should be noted that the illustrated apparatuses or devices may each be implemented as a single device or as a system of multiple interacting devices or modules.

Claims

1. A method of controlling wireless communication, the method comprising: a wireless device (10; 1100) receiving information from a further wireless device (10; 1100), the information indicating quality of a clock of a radio access network, RAN, node (100; 1200) in proximity of the further wireless device (10; 1100); and based on the information, the wireless device (10; 1100) controlling wireless communication of the wireless device (10; 1100).

2. The method according to claim 1 , wherein said controlling wireless communication comprises controlling timing of one or more services operated on the wireless device (10; 1100).

3. The method according to claim 1 or 2, wherein said controlling wireless communication comprises selection of a relay wireless device (10; 1100).

4. The method according to claim 3, wherein selection of the relay wireless device (10; 1100) is based on one or more criteria according to which the quality of the clock of a RAN node (100; 1200) is acceptable for the wireless device (10; 1100) and one or more criteria according to which the quality of the clock of a RAN node (100; 1200) is acceptable for the relay wireless device (10; 1100).

5. The method according to any of the preceding claims, wherein the wireless device (10; 1100) receives the information based on a subscription of the wireless device (10; 1100) to an access stratum time distribution service.

6. The method according to any of the preceding claims, wherein the wireless device (10; 1100) receives the information in response to a request.

7. The method according to any of the preceding claims, wherein the wireless device (10; 1100) receives the information while the further wireless device (10; 1100) operates as a relay for connecting the wireless device (10; 1100) to the RAN node (100; 1200).

8. The method according to any of the preceding claims, wherein the wireless device (10; 1100) receives the information by one or more of: one or more sidelink discovery messages; sidelink control signaling; a control element of Medium Access Control signaling; a control Protocol Data Unit of a RAN protocol; physical layer signaling on a sidelink channel.

9. The method according to any of the preceding claims, wherein the wireless device (10; 1100) receives the information by one or more broadcast messages and/or by one or more groupcast messages.

10. The method according to any of the preceding claims, wherein the information indicates the quality of the clock in terms of clock accuracy or clock frequency stability.

11. The method according to any of the preceding claims, wherein the information comprises an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the wireless device (10; 1100).

12. The method according to claim 11 , wherein the criteria are at least in part configurable by a core network node (240).

13. A method of controlling wireless communication, the method comprising: a wireless device (10; 1100) receiving information from a radio access network, RAN, node (100; 1200) in proximity of the wireless device, the information indicating quality of a clock of the RAN node (100; 1200); and the wireless device (10; 1100) providing the information to a further wireless device (10; 1100).

14. The method according to claim 13, wherein the wireless device (10; 1100) provides the information based on a subscription of the further wireless device (10; 1100) to an access stratum time distribution service.

15. The method according to claim 13 or 14, wherein the wireless device (10; 1100) provides the information in response to a request from the further wireless device (10; 1100).

16. The method according to any of claims 13 to 15, wherein the wireless device (10; 1100) provides the information while the wireless device (10; 1100) operates as a relay for connecting the further wireless device (10; 1100) to the RAN node.

17. The method according to any of claims 13 to 16, wherein the wireless device (10; 1100) provides the information by one or more of: one or more sidelink discovery messages; sidelink control signaling; a control element of Medium Access Control signaling; a control Protocol Data Unit of a RAN protocol; physical layer signaling on a sidelink channel.

18. The method according to any of claims 13 to 17, wherein the wireless device (10; 1100) provides the information by one or more broadcast messages and/or by one or more groupcast messages.

19. The method according to any of claims 13 to 18, wherein the information indicates the quality of the clock in terms of clock accuracy or clock frequency stability.

20. The method according to any of claims 13 to 19, wherein the information comprises an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the further wireless device (10; 1100).

21. The method according to claim 20, wherein the one or more criteria are at least in part configurable by a core network node (100; 1200).

22. A method of controlling wireless communication, the method comprising: a radio access network, RAN, node (100; 1200) determining whether a first wireless device (10; 1100) is entitled to receive information indicating quality of a clock of the RAN node (100; 1200); and in response to determining that the first wireless device (10; 1100) is entitled to receive the information, the RAN node (100; 1200) providing the information via a second wireless device (10; 1100) to the first wireless device (10; 1100).

23. The method according to claim 22, wherein said determining whether the first wireless device (10; 1100) is entitled to receive the information is based on a subscription of the first wireless device (10; 1100) to an access stratum time distribution service.

24. The method according to claim 22 or 23, wherein the RAN node (100; 1200) provides the information in response to a request from the first wireless device (10; 1100).

25. The method according to any of claims 22 to 24, wherein the RAN node (100; 1200) provides the information while the second wireless device (10; 1100) operates as a relay for connecting the first wireless device (10; 1100) to the RAN node.

26. The method according to any of claims 22 to 25, wherein the RAN node (100; 1200) provides the information by one or more of: a control element of Medium Access Control signaling; a control Protocol Data Unit of a RAN protocol.

27. The method according to any of claims 22 to 26, wherein the information indicates the quality of the clock in terms of clock accuracy or clock frequency stability.

28. The method according to any of claims 22 to 27, wherein the information comprises an indication whether or not the quality of the clock is acceptable according to one or more criteria defined for the first wireless device (10; 1100).

29. The method according to claim 28, wherein the one or more criteria are at least in part configurable by core network node (240).

30. The method according to claim 28 or 29, wherein the one or more criteria are at least in part configurable by a core network node (240).

31. A wireless device (10; 1100) for a wireless communication system, the wireless device (10; 1100) being configured to:

- receive information from a further wireless device (10; 1100), the information indicating quality of a clock of a radio access network, RAN, node (100; 1200) in proximity of the further wireless device (10; 1100); and - based on the information, control wireless communication of the wireless device (10; 1100).

32. The wireless device (10; 1100) according to claim 31 , wherein the wireless device (10; 1100) is configured to perform a method according to any one of claims 2 to 12.

33. The wireless device (10; 1100) according to claim 31 or 32, comprising: at least one processor (1150), and a memory (1160) containing program code executable by the at least one processor (1150), whereby execution of the program code by the at least one processor (1150) causes the wireless device (10; 1100) to perform a method according to any one of claims 1 to 12.

34. A wireless device (10; 1100) for a wireless communication system, the wireless device (10; 1100) being configured to:

- receive information from a radio access network, RAN, node (100; 1200) in proximity of the wireless device (10; 1100), the information indicating quality of a clock of the RAN node (100; 1200); and

- provide the information to a further wireless device (10; 1100).

35. The wireless device (10; 1100) according to claim 34, wherein the wireless device (10; 1100) is configured to perform a method according to any one of claims 14 to 21.

36. The wireless device (10; 1100) according to claim 34 or 35, comprising: at least one processor (1150), and a memory (1160) containing program code executable by the at least one processor (1150), whereby execution of the program code by the at least one processor (1150) causes the wireless device (10; 1100) to perform a method according to any one of claims 13 to 21.

37. A radio access network, RAN, node (100; 1200) for a wireless communication system, the RAN node (100; 1200) being configured to:

- determine whether a first wireless device (10; 1100) is entitled to receive information indicating quality of a clock of the RAN node (100; 1200); and

- in response to determining that the first wireless device (10; 1100) is entitled to receive the information, provide the information via a second wireless device (10; 1100) to the first wireless device (10; 1100).

38. The RAN node (100; 1200) according to claim 37, wherein the RAN node (100; 1200) is configured to perform a method according to any one of claims 23 to 30.

39. The RAN node (100; 1200) according to claim 37 or 38, comprising: at least one processor (1250), and a memory (1260) containing program code executable by the at least one processor (1250), whereby execution of the program code by the at least one processor (1250) causes the RAN node (100; 1200) to perform a method according to any one of claims 22 to 30.

40. A computer program or computer program product comprising program code to be executed by at least one processor (1150) of a wireless device (10; 1100), whereby execution of the program code causes the wireless device (10; 1100) to perform a method according to any one of claims 1 to 21.

41. A computer program or computer program product comprising program code to be executed by at least one processor (1250) of a radio access network, RAN, node (100; 1200), whereby execution of the program code causes the RAN node (100; 1200) to perform a method according to any one of claims 22 to 30.