Anchor update in sidelink positioning

Abstract

Embodiments of the present disclosure relate to apparatuses, methods, and computer readable storage media for anchor update in SL positioning. In the methods, a first apparatus transmits a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus. Then, the first apparatus monitors availability of a further anchor for positioning the second apparatus. In this way, the second apparatus can seamlessly switch between positioning anchors, without necessarily initiating a new discovery procedure, thus avoiding undesired latency and additional signaling.

Description

ANCHOR UPDATE IN SIDELINK POSITIONINGCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority from, and the benefit of, US Provisional Application No. 63 / 517354, filed August 3, 2023, the contents of which are hereby included by reference in their entirety.FIELDS

[0002] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for anchor update in sidelink (SL) positioning.BACKGROUND

[0003] Location-awareness is a fundamental aspect of wireless communication networks and will enable a myriad of location-enabled services in different applications. The integration and utilization of location information in day-to-day applications will grow significantly as the technology's accuracy evolves.

[0004] Many positioning technologies have been proposed and / or studied. SL positioning is based on the transmissions of SL positioning reference signal (SL-PRS) between an anchor and a target user equipment (UE) to enable localization of the target UE within precise latency and accuracy requirements of the corresponding SL positioning session. In a SL positioning scenario, a target UE may perform a SL positioning process, for example, by exchanging SL-PRS with one or more anchor UEs to determine its location. In terms of accuracy of the SL positioning, the anchor plays a very important role. Robustness and stability of the service of the anchor is one of relevant aspects to be enhanced.SUMMARY

[0005] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: transmit a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and monitor availability of a furtheranchor for positioning the second apparatus.

[0006] In a second aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: receive, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and determine availability of a further anchor for positioning the second apparatus at least based on the first indication.

[0007] In a third aspect of the present disclosure, there is provided a third apparatus. The third apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third apparatus at least to: receive, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and determine, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

[0008] In a fourth aspect of the present disclosure, there is provided a method. The method comprises: transmitting a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and monitoring availability of a further anchor for positioning the second apparatus.

[0009] In a fifth aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and determining availability of a further anchor for positioning the second apparatus at least based on the first indication.

[0010] In a sixth aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and determining, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

[0011] In a seventh aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for transmitting a first indication indicating anunavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for monitoring availability of a further anchor for positioning the second apparatus.

[0012] In an eighth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and means for determining availability of a further anchor for positioning the second apparatus at least based on the first indication.

[0013] In a ninth aspect of the present disclosure, there is provided a third apparatus. The third apparatus comprises means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for determining, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

[0014] In a tenth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the fourth aspect.

[0015] In an eleventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the fifth aspect.

[0016] In a twelfth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the sixth aspect.

[0017] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0019] FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

[0020] FIG. 2 illustrates a signaling chart for anchor update according to some example embodiments of the present disclosure;

[0021] FIG. 3 illustrates a signaling chart for anchor update according to some example embodiments of the present disclosure;

[0022] FIG. 4 illustrates a flowchart of a method implemented at a first device according to some example embodiments of the present disclosure;

[0023] FIG. 5 illustrates a flowchart of a method implemented at a second device according to some example embodiments of the present disclosure;

[0024] FIG. 6 illustrates a flowchart of a method implemented at a third device according to some example embodiments of the present disclosure;

[0025] FIG. 7 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0026] FIG. 8 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0027] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0028] Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

[0029] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0030] References in the present disclosure to “one embodiment,” “an embodiment,”“an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0031] It shall be understood that although the terms “first,” “second,”..., etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0032] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0033] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0035] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0036] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0037] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodimentsof the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0038] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0039] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devicesoperating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0040] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0041] FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the communication environment 100, there are a plurality of communication devices, for example, a first apparatus 110 and a second apparatus 120, and a third apparatus 130. Both the first apparatus 110 and the third apparatus 130 can communicate with the second apparatus 120.

[0042] In a SL positioning scenario, the second apparatus 120 may be a target UE that is performing a SL positioning process, for example, exchanging SL-PRS with two anchors (also referred to as anchor UEs) to determine its location. In such situation, the first apparatus 110 may be one of the anchors and the third apparatus 130 may be the other one of the anchors.

[0043] SL positioning (including ranging) have been supported in NR systems. For instance, it has been specified signalling and associated UE behavior for support of unicast, groupcast (not including many to one) and broadcast of SL PRS transmissions. Meanwhile, reporting signalling and procedures have been studied to facilitate support of SLpositioning in all coverage scenarios and for PC5-only and joint PC5-Uu scenarios. Furthermore, procedures for SL positioning between UEs (Protocol for Sidelink positioning procedures (SLPP)), as well as procedures for SL positioning between UEs and Location Management Function (LMF), are also under discussion.

[0044] As used herein, the term “Target UE” refers to a UE to be positioned (in this context, using SL, i.e., PC5 interface).

[0045] The term “anchor” or “anchor UE” refers to a UE supporting positioning of target UE, e.g., by transmitting and / or receiving reference signals for positioning, providing positioning-related information, etc., over the SL interface.

[0046] The term “server UE” refers to a SL Positioning Server UE, which is a UE offering method determination, assistant data distribution and / or location calculation functionalities for Sidelink Positioning and Ranging based service.

[0047] The term “sidelink positioning” refers to that a positioning UE uses reference signals transmitted over SL, i.e., PC5 interface, to obtain absolute position, relative position, or ranging information.

[0048] The term “ranging” refers to determination of the distance and / or the direction between a UE and another entity, e.g., anchor UE.

[0049] The term “sidelink positioning reference signal (SL PRS or SL-PRS)” refers to a reference signal transmitted over SL for positioning purposes.

[0050] The term “SL PRS (pre-)configuration” refers to (pre-)configured parameters of SL PRS such as time-frequency resources (other parameters are not precluded) including its bandwidth and periodicity.

[0051] SL positioning is based on the transmissions of positioning reference signal SL- PRS between the anchor and target UEs to enable localization of the target UE within precise latency and accuracy requirements of the corresponding SL positioning session. As shown in FIG. 1, it is illustrated a SL positioning scenario where a target UE is performing SL positioning session i.e., exchanging SL-PRS with two anchor UEs to determine its location.

[0052] Before and after the transmission and measurement of the SL PRSs, a series of steps may be taken place to enable SL positioning. Discovery procedure may be includedin the sidelink positioning procedure at least for out of coverage scenario. Discovery messages may be used to carry information for targeted discovery and candidate selection of SL positioning UEs, including at least the indication of anchor UE, target UE. and server UE roles.

[0053] In some cases, anchor UE selection may be performed in the sidelink positioning procedures at least for out of coverage scenario. Anchor UE selection may be supported by information about the candidate anchor UEs. At least the following list may be used in anchor UE selection: UE roles, supported positioning method, in coverage or not, RSRP, Line of sight (LOS) / Non line of sight (NLOS), Location, Public Land Mobile Network (PLMN), and / or the like. The UE role information may be indicated in the discovery Sidelink Positioning Protocol (SLPP) metafield.

[0054] In the following, for the purpose of illustration, some example embodiments are described with the first apparatus 110 operating as an anchor, the second apparatus 120 operating as a target UE that was served by the anchor, and the third apparatus 130 operating as a new anchor that replaces the previous anchor to serve the target UE. However, it is to be understood that the above examples are just discussed for purpose of illustrations rather than limitations.

[0055] Communications in the communication environment 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple -Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0056] On many occasions, at some points during an ongoing SL positioning process(sometimes also called as a SL positioning session), a UE that has been selected to serve as a positioning anchor (denoted as A-UE) may not be available or desirable any more to be involved in positioning a target UE (denoted as T-UE). This could be due to dynamic conditions, for example due to low power status at A-UE or due to degraded link quality between A-UE and T-UE.

[0057] Under such cases, typically a new anchor needs to be selected, e.g., so as to maintain required positioning quality of service (QoS). Conventional solutions do not address such required “anchor updates” in a proactive manner and an unavailable / unfavorable anchor may be identified only SL positioning measurements or upon timer expiry, resulting in unnecessary latency, signaling overhead, and / or poor positioning performance.

[0058] To at least solve the above issues and other potential issues, example embodiments of the present disclosure propose a proactive method to update anchor selection in a SL positioning session in case an anchor UE determines that it will be unavailable (e.g., due to reduced battery power) or unfavorable (e.g., going to have NLOS link to target UE) to serve positioning a target UE.

[0059] In this way, a target UE can seamlessly switch between positioning anchors if one of them becomes unavailable or undesirable, without necessarily initiating a new discovery procedure, thus saving from latency and additional signaling, while preserving its desired positioning QoS.

[0060] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0061] FIG. 2 illustrates a signaling chart 200 for anchor update according to some example embodiments of the present disclosure. For the purposes of discussion, the signaling chart 200 will be discussed with reference to FIG. 1, for example, by using the first apparatus 110, the second apparatus 120 and the third apparatus 130.

[0062] In embodiments shown with respect to FIG. 2, the first apparatus 110 may be a terminal device acting as an anchor or an anchor apparatus, for example, an anchor UE. The second apparatus 120 may be a terminal device acting as a target UE, and the third apparatus 130 may be a terminal device acting as a new anchor for positing the target UE.

[0063] In the signaling chart 200, the first apparatus 110 transmits (210) a firstindication indicating an unavailability of the first apparatus 110 to serve as an anchor for positioning a second apparatus. The unavailability indicating either the first apparatus 110 is undesired to be an anchor any more, or the first apparatus 110 is not suitable for example, due to lack of available resources, to be an anchor.

[0064] In some example embodiments, the first apparatus 110 may be first involved in a positioning session with the second apparatus 120. More specifically, the first apparatus 110 acted as an anchor for positing the second apparatus 120, that is, the target UE. Then, the first apparatus 110 may determine it is no longer suitable for acting as the anchor.

[0065] There may be various ways for the first apparatus 110 to determine whether it is suitable for acting as the anchor. In some example embodiments, the first apparatus 110 may determine whether itself will be unavailable or undesirable for the positioning based on a variety of factors, for example, but not limited in, power status of the first apparatus, mobility information of the first apparatus, synchronization information, sidelink traffic, a signal received from the second apparatus, a signal received from a nearby apparatus, a link quality between the first apparatus and the second apparatus, and / or a link quality between the first apparatus and the nearby apparatus.

[0066] If the first apparatus 110 determines, based on the above factors, either alone or in combination, that it will be unavailable for the positioning, it may transmit (210) the first indication indicating its unavailability. Alternatively, the first apparatus 110 may be not desired to serve the second apparatus 120 as an anchor any more for some reasons. Thus, the first apparatus 110 may transmit (210) the first indication indicating its unavailability.

[0067] The first indication may indicate various information, for example, but not limited in, the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range, capabilities to be supported by the further anchor, power to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, and / or network information indicating at least one network node for serving.

[0068] In some example embodiments, the first indication may be transmitted (210) via at least one additional field in a discovery solicitation message, for example, a Model Bdiscovery message. The transmission of the first indication may have different types. For example, in some example embodiments, the first indication may be broadcasted or groupcasted to nearby apparatuses. Alternatively, the first indication may be unicasted to a preselected candidate anchor, for instance, the third apparatus 130.

[0069] The second apparatus 120 receives (215) the first indication from the first apparatus 110. Then, the second apparatus 120 determines (230) availability of the further anchor for positioning the second apparatus at least based on the first indication.

[0070] The third apparatus 130 receives (220) the first indication from the first apparatus 110, and determines (225), based on the first indication, availability of the third apparatus 130 to be a further anchor for positioning the second apparatus 120. In other words, the third apparatus 130 will determine whether itself is suitable or available for acting as the new anchor (that is, the further anchor). In some example embodiments, the third apparatus 130 may transmit an indication (also referred to as “second indication” for purpose of discussion) indicating availability of the third apparatus 130 to serve as an anchor for positioning the second apparatus.

[0071] The second indication may be transmitted to the first apparatus 110, the second apparatus 120, and / or other nearby apparatus. In some example embodiments, if the second apparatus 120 receives the second indication, it may, for example, determines (230) availability of the further anchor for positioning the second apparatus based on both the first indication and the second indication.

[0072] Then, the first apparatus 110 monitors (235) availability of a further anchor for positioning the second apparatus 120. Thus, the first apparatus 110 may know whether there is a new anchor that is going to serve the second apparatus 120. In example embodiments, “availability” a further anchor may indicate that another device is available to be work as a new anchor, or that device is already selected as or determined as the new anchor.

[0073] The monitoring (235) may be implemented in a variety of ways. In some example embodiments, the first apparatus 110 may monitor (235) an indication (also referred to as the “second indication”) indicating availability of the third apparatus 130 to be the new anchor. If the first apparatus 110 receive this second indication from the third apparatus 130, it may determine whether there is a further anchor available for positioning the second apparatus 120 based thereon. Alternatively, the first apparatus 110 maymonitor (235) anchor information from the second apparatus 120 and make the above determination based on the anchor information received from the second apparatus 120. As a further alternative, the first apparatus 110 may set a timer at the start of monitoring the second indication or the anchor information and determine the availability of the new anchor based on the monitoring result of the second indication or the anchor information before expiration of the timer.

[0074] Specifically, in some example embodiments, the first apparatus 110 may receive, from the third apparatus 130, the second indication indicating availability of the third apparatus to serve as the further anchor (that is, the new anchor discussed above) for positioning the second apparatus 120.

[0075] In some example embodiments, the second indication may indicate information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus. Alternatively or in addition, the second indication may indicate the availability of the third apparatus for a time length, an area, a cell, a zone, or a range. As a further alternative or in addition, the second indication may indicate resource information of a reference signal to be transmitted from the third apparatus for positioning. The resource information of the reference signal, for instance, may comprise a periodicity of the reference signal, a bandwidth of the reference signal, a sequence identification of the reference signal, and / or the like.

[0076] It is to be understood that the above examples indicated by or comprised in the second indication are just discussed for illustration, rather than limitation. In some other example embodiments, other information may be indicated by the second indication as well.

[0077] The second indication may be transmitted via at least one additional field in a discovery response message, for example, a Model B discovery response message. In some example embodiments, the second indication may be broadcasted to nearby apparatuses. For example, the cast type of the Model B discovery message may be changed to groupcast to include the second apparatus 120 as a recipient. Alternatively, in some example embodiments, the second indication may be groupcasted to a group of apparatuses comprising the second apparatus 120.

[0078] As an alternative to determining the availability of the further anchor based onthe second indication, the first apparatus 110 may receive, from the second apparatus 120, the anchor information indicating whether the further anchor for positioning the second apparatus is available. In some example embodiments, the anchor information may comprise a third indication indicating that the third apparatus 130 is selected as the further anchor. Alternatively, the anchor information may comprise a fourth indication indicating that there is no anchor available for positioning the second apparatus 120.

[0079] As a further alternative to the above two ways, the first apparatus 110 may start a timer at the time that the first indication is transmitted. If that anchor information indicating whether the further anchor is available is not received until the timer expires, the first apparatus 110 may determine that there is no further anchor available for positioning the second apparatus. The timer may be preconfigured or predetermined in several ways. For example, this timer may be (pre-)configured by network e.g., LMF, gNB, or Server UE, can be pre-determined, e.g., by A-UE or server UE, or pre-specified as per the standard.

[0080] Alternatively, the first apparatus 110 may start another timer at the time that the first indication is transmitted. If a second indication indicating availability of the third apparatus 130 to serve as the further anchor is not received until the timer expires, the first apparatus 110 may determine that there is no further anchor available for positioning the second apparatus 120. Likewise, this timer may be preconfigured or predetermined in several ways. For example, this timer may be (pre-)configured by network e.g., LMF, gNB, or Server UE, can be pre-determined, e.g., by A-UE or server UE, or pre-specified as per the standard.

[0081] As such, anchor selection can be updated in a proactive way in a SL positioning session or process. In case an anchor UE determines that it will be unavailable (e.g., due to reduced battery power) or unfavorable (e.g., going to have NLOS link to target UE) to serve positioning a target UE, a new anchor may be selected efficiently and quickly. In this way, a target UE can seamlessly switch between positioning anchors if one of them becomes unavailable or undesirable, without necessarily initiating a new discovery procedure, thus saving from latency and additional signaling, while preserving its desired positioning QoS.

[0082] More details of embodiments of the present disclosure will be discussed with respect to FIG. 3, which illustrates a signaling chart 300 for anchor update according tosome example embodiments of the present disclosure. For the purposes of discussion, the signaling chart 300 will be discussed with reference to FIG. 1, for example, by using the first apparatus 110, the second apparatus 120 and the third apparatus 130.

[0083] In embodiments shown with respect to FIG. 3, the first apparatus 110 may be an original anchor (also referred to as “A-UE1” hereafter) that is serving the second apparatus 120. The second apparatus 120 may be a terminal device, e.g., a target UE (also referred to as “T-UE” hereafter). The third apparatus 130 may be a terminal device, which is a new anchor (also referred to as “A-UE2” hereafter) for positing the target UE.

[0084] In the embodiments discussed with respect to FIG. 3, the first apparatus 110, that is, A-UE1, may be involved in an ongoing positioning process with the second apparatus 120 (e.g., T-UE), by transmitting and / or receiving SL signals, e.g., SL PRS, to / from T-UE. For instance, A-UE1 determines that it will be unavailable and / or undesirable to serve T-UE as anchor, and sends a request to nearby UEs via SL (e.g., via additional field in ProSe Model B discovery solicitation message) to trigger a new anchor selection for T-UE.

[0085] As for a nearby UE, for example, the third apparatus 130 (e.g., A-UE2), upon receiving the SL message sent from A-UE1, it responds by indicating its availability to serve as an anchor for T-UE, (e.g., via additional field in ProSe Model B discovery response message), which can also indicate the source of trigger, i.e., A-UE1. This indication may be received by T-UE and / or A-UE1.

[0086] The second apparatus 120, that is, target UE (T-UE), receives indications sent by A-UE1 and / or A-UE2, and determines to select A-UE2 as a new anchor based on the indications. The second apparatus 120 may include A-UE2 into its positioning session (e.g., in addition to or in place of A-UE1).

[0087] Specifically, in the signaling chart 300, at first, the first apparatus 110 (e.g., A- UE1) is involved in an ongoing positioning process with the second apparatus 120 (e.g., T-UE). Then, the first apparatus 110 (e.g., A-UE1) determines or detects (305) its unavailability, that is, it will be unavailable and / or undesirable to serve positioning the second apparatus 120 (e.g., T-UE). In some example embodiments, the first apparatus 110 (e.g., A-UE1) may determine this by monitoring its power status, location information, sync, source, SL traffic, etc., as well as received signals from T-UE to monitor the link quality.

[0088] In Step 2, the first apparatus 110 (e.g., A-UE1) transmits (310) a first indication of the unavailability, for example, to the second apparatus 120 and / or the third apparatus 130. The first indication indicates that the first apparatus 110 will be unavailable and / or undesirable for positioning the second apparatus 120 (e.g., T-UE), and a need for a new anchor to serve the second apparatus 120 (e.g., T-UE).

[0089] In some example embodiments, the first apparatus 110 (e.g., A-UE1) may indicate its unavailability for a certain time frame and / or an area / range.

[0090] In some example embodiments, the first apparatus 110 (e.g., A-UE1) may transmit (310) the first indication via additional fields in Model B discovery solicitation message. In some example embodiments, the first indication may be broadcast / groupcast to nearby UEs, or unicast to the third apparatus 130 (e.g., A-UE2), which the first apparatus 110 (e.g., A-UE1) may has selected as a suitable candidate anchor to replace itself. In some example embodiments, the second apparatus 120 (e.g., T-UE) receives (315) the first indication from the first apparatus 110 (e.g., A-UE1) and determines (345) availability of the further anchor at least based on the first indication.

[0091] In some example embodiments, the first indication may impose conditions on becoming a new anchor, for example, supported UE capabilities, e.g., supported SL positioning method, SL PRS bandwidth, etc.. Alternatively or in addition, the first indication may indicate supported UE power / availability, and / or thresholds (min / max / range) on SL radio measurements, e.g., RSRP, ToA, etc. between A-UE1 and A-UE2 or between A-UE2 and T-UE1. Alternatively or in addition, the first indication may indicate whether LOS / NLOS / OLOS link exists between A-UE1 and A-UE2 or between A-UE2 and T-UE1. Alternatively or in addition, the first indication may indicate serving for certain time frame, area / zone / cell, etc., or being served by a certain PLMN, LMF, gNB, cell, etc..

[0092] The third apparatus 130 (e.g., A-UE2) receives (320) the first indication, and determines (325) its own availability to serve as a new anchor for the target UE, the second apparatus 120 (e.g., T-UE). For example, the determination (325) may be made by comparing its own status with the requested conditions. Then the third apparatus 130 (e.g., A-UE2) may transmit (330) a second indication with regards to its availability to the first apparatus 110 (e.g., A-UE1) and / or the second apparatus 120 (e.g., T-UE). Accordingly, the first apparatus 110 (e.g., A-UE1) may receive (340) the second indication, and / or thesecond apparatus 120 (e.g., T-UE) may receive (335) the second indication as well.

[0093] In some example embodiments, the second indication may be transmitted via additional fields in Model B discovery response message, and the cast type of Model B discovery message is changed to groupcast to include T-UE as a recipient.

[0094] In some example embodiments, the second indication may be broadcast or groupcast to nearby UEs, which may be received by A-UE2 and T-UE.

[0095] In some example embodiments, the second indication may be explicit with information relating to original requestor, i.e., A-UE1, for anchor update, session ID, or T-UE ID, and so on.

[0096] In some example embodiments, the second indication may be implicit by not sending a response message, meaning A-UE2 will not be available.

[0097] In some example embodiments, the third apparatus 130 (e.g., A-UE2) may indicate its availability for a certain time frame and / or an area / range.

[0098] In some example embodiments, the second indication may include the SL-PRS characteristics A-UE2 is able to transmit. As an example, A-UE2 may indicate the SL- PRS resources (SL-PRS periodicity and Bandwidth, etc.). The SL-PRS resource indication may be either in an absolute format or in a relative (delta) format with respect to A-UE1. For example, A-UE2 may indicate the delta resource information of its SL-PRS with respect to the SL-PRS of A-UE1.

[0099] The second apparatus 120 (e.g., T-UE) may receive (335) the second indication and may determine (345) availability of the further anchor based on the first indication and the second indication. For instance, the second apparatus 120 (e.g., T-UE) may determine (345) to select A-UE2 as its new positioning anchor.

[0100] Then, the second apparatus 120 (e.g., T-UE) may indicate its anchor selection to nearby UEs. For example, the second apparatus 120 (e.g., T-UE) may transmit (350) anchor information indicating whether the further anchor / new anchor for positioning the second apparatus is available. The anchor information may be broadcast / groupcast to nearby UEs, which may be received (355) by the first apparatus 110 (e.g., A-UE1) and received (360) by the third apparatus 130 (e.g., A-UE2).

[0101] In some example embodiments, the anchor information may be transmitted to apositioning server, such as LMF or a server UE, which determines the final selection of anchors and informs the UEs accordingly.

[0102] Finally, the second apparatus 120 (e.g., T-UE) continues SL positioning with the newly added anchor, the third apparatus 130 (e.g., A-UE2).

[0103] Additionally, in some example embodiments, not all potential anchors might be within communication range of the second apparatus 120 (e.g., T-UE), e.g., the second indication from the third apparatus 130 (e.g., A-UE2) may not be heard by the second apparatus 120 (e.g., T-UE). For such cases, a timer may be triggered at the transmitter, i.e., the first apparatus 110 (e.g., A-UE1) at the time of the transmission (310) of the first indication. If the first apparatus 110 (e.g., A-UE1) does not receive (355) the anchor information which includes an anchor selection indication from T-UE within the timer expiry, it implicitly deduces that the anchors it discovered are not heard, hence selected by the second apparatus 120 (e.g., T-UE). As an outcome, the first apparatus 110 (e.g., A- UE1) may continue to serve the second apparatus 120 (e.g., T-UE) as anchor until T-UE can find and select a new anchor.

[0104] In another example embodiment, another timer can be also started at the second apparatus 120 (e.g., T-UE) upon reception of the first indication. If the second apparatus 120 (e.g., T-UE) does not receive (335) any indication of availability of a new anchor until the timer expiry, it may provide feedback to the first apparatus 110 (e.g., A-UE1) about the situation that it couldn’t find or select a new anchor within the timer duration, and / or the second apparatus 120 (e.g., T-UE) itself starts a new anchor discovery and selection procedure, so as to avoid any delays in positioning.

[0105] In example embodiments, the timer(s) discussed above may be (pre-)configured by network e.g., LMF, gNB, or Server UE, can be pre-determined, e.g., by A-UE or server UE, or pre-specified as per the standard.

[0106] FIG. 4 shows a flowchart of an example method 400 implemented at a first device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0107] At block 410, the first apparatus 110 transmit a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a secondapparatus.

[0108] At block 420, the first apparatus 110 monitor availability of a further anchor for positioning the second apparatus.

[0109] In some example embodiments, the method 400 further comprises: determining whether the first apparatus will be unavailable or undesirable for the positioning based on at least one of the following: power status of the first apparatus, mobility information of the first apparatus, synchronization information, sidelink traffic, a signal received from the second apparatus, a signal received from a nearby apparatus, or a link quality between the first apparatus and the second apparatus, or a link quality between the first apparatus and the nearby apparatus; and in accordance with a determination that the first apparatus will be unavailable or undesirable for the positioning, transmitting the first indication.

[0110] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, powering to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

[0111] In some example embodiments, the first indication is transmitted via at least one additional field in a discovery solicitation message.

[0112] In some example embodiments, the first indication is broadcasted or groupcasted to nearby apparatuses, or wherein the first indication is unicasted to a preselected candidate anchor.

[0113] In some example embodiments, the method 400 further comprises: receiving, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus.

[0114] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, the availability of the third apparatus for a time length,an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0115] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0116] In some example embodiments, the second indication is transmitted via at least one additional field in a discovery response message.

[0117] In some example embodiments, the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

[0118] In some example embodiments, the method 400 further comprises: receiving, from the second apparatus, the anchor information indicating whether the further anchor for positioning the second apparatus is available.

[0119] In some example embodiments, the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0120] In some example embodiments, the method 400 further comprises: starting a first timer at the time that the first indication is transmitted; and in accordance with a determination that anchor information indicating whether the further anchor is available is not received until the first timer expires, determining that there is no further anchor available for positioning the second apparatus, or in accordance with a determination that a second indication indicating availability of the third apparatus to serve as the further anchor is not received until the first timer expires, determining that there is no further anchor available for positioning the second apparatus.

[0121] In some example embodiments, the first timer is preconfigured or predetermined.

[0122] In some example embodiments, the second apparatus is a target terminal device, and the first apparatus is anchor for positioning the target terminal device.

[0123] FIG. 5 shows a flowchart of an example method 500 implemented at a second device in accordance with some example embodiments of the present disclosure. For thepurpose of discussion, the method 500 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0124] At block 510, the second apparatus 120 receives, from a first apparatus 110, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus.

[0125] At block 520, the second apparatus 120 determines availability of a further anchor for positioning the second apparatus 120 at least based on the first indication.

[0126] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, powering to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

[0127] In some example embodiments, the first indication is received via at least one additional field in a discovery solicitation message.

[0128] In some example embodiments, the method 500 further comprises: receiving, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus; and determining the availability of a further anchor for positioning the second apparatus based on the first indication and the second indication.

[0129] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the third apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0130] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0131] In some example embodiments, the second indication is received via at least one additional field in a discovery response message.

[0132] In some example embodiments, the method 500 further comprises: transmitting anchor information indicating whether the further anchor for positioning the second apparatus is available.

[0133] In some example embodiments, the anchor information is transmitted in a broadcast or groupcast way.

[0134] In some example embodiments, the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0135] In some example embodiments, the method 500 further comprises: starting a second timer at the time that the first indication is received; and in accordance with a determination that the second indication is not received until the second timer expires, determining that there is no anchor available for positioning the second apparatus.

[0136] In some example embodiments, the second timer is preconfigured or predetermined.

[0137] FIG. 6 shows a flowchart of an example method 600 implemented at a third device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the third apparatus 130 in FIG. 1.

[0138] At block 610, the third apparatus 130 receives, from a first apparatus 110, a first indication indicating an unavailability of the first apparatus 110 to serve as an anchor for positioning a second apparatus 120.

[0139] At block 620, the third apparatus 130 determines, based on the first indication, availability of the third apparatus 130 to be a further anchor for positioning the second apparatus.

[0140] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, powering to be supportedby the further anchor, thresholds on sidelink radio measurements , a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

[0141] In some example embodiments, the first indication is received via at least one additional field in a discovery solicitation message.

[0142] In some example embodiments, the method 600 further comprises: transmitting a second indication indicating availability of the third apparatus to serve as an anchor for positioning the second apparatus.

[0143] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the second apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0144] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0145] In some example embodiments, the second indication is transmitted via at least one additional field in a discovery response message.

[0146] In some example embodiments, the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

[0147] In some example embodiments, the method 600 further comprises: receiving anchor information from the second apparatus, indicating whether the further anchor for positioning the second apparatus is available.

[0148] In some example embodiments, the anchor information comprises a third indication indicating that the third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0149] In some example embodiments, a first apparatus capable of performing any of the method 400 (for example, the first apparatus 110 in FIG. 1) may comprise means for performing the respective operations of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1.

[0150] In some example embodiments, the first apparatus comprises means for transmitting a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for monitoring availability of a further anchor for positioning the second apparatus.

[0151] In some example embodiments, the first apparatus further comprises: means for determining whether the first apparatus will be unavailable or undesirable for the positioning based on at least one of the following: power status of the first apparatus, mobility information of the first apparatus, synchronization information, sidelink traffic, a signal received from the second apparatus, a signal received from a nearby apparatus, or a link quality between the first apparatus and the second apparatus, or a link quality between the first apparatus and the nearby apparatus; and means for in accordance with a determination that the first apparatus will be unavailable or undesirable for the positioning, transmitting the first indication.

[0152] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, means for powering to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or means for network information indicating at least one network node for serving.

[0153] In some example embodiments, the first indication is transmitted via at least one additional field in a discovery solicitation message.

[0154] In some example embodiments, the first indication is broadcasted or groupcasted to nearby apparatuses, or wherein the first indication is unicasted to a preselected candidate anchor.

[0155] In some example embodiments, the first apparatus further comprises: means for receiving, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus.

[0156] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, the availability of the third apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0157] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0158] In some example embodiments, the second indication is transmitted via at least one additional field in a discovery response message.

[0159] In some example embodiments, the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

[0160] In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, the anchor information indicating whether the further anchor for positioning the second apparatus is available.

[0161] In some example embodiments, the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0162] In some example embodiments, the first apparatus further comprises: means for starting a first timer at the time that the first indication is transmitted; and means for in accordance with a determination that anchor information indicating whether the further anchor is available is not received until the first timer expires, determining that there is no further anchor available for positioning the second apparatus, or means for in accordance with a determination that a second indication indicating availability of the third apparatus to serve as the further anchor is not received until the first timer expires,determining that there is no further anchor available for positioning the second apparatus.

[0163] In some example embodiments, the first timer is preconfigured or predetermined.

[0164] In some example embodiments, the second apparatus is a target terminal device, and the first apparatus is anchor for positioning the target terminal device.

[0165] In some example embodiments, the first apparatus further comprises means for performing other operations in some example embodiments of the method 400 or the first apparatus 110. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the first apparatus.

[0166] In some example embodiments, a second apparatus capable of performing any of the method 500 (for example, the second apparatus 120 in FIG. 1) may comprise means for performing the respective operations of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1.

[0167] In some example embodiments, the second apparatus comprises means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and means for determining availability of a further anchor for positioning the second apparatus at least based on the first indication.

[0168] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, power to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

[0169] In some example embodiments, the first indication is received via at least one additional field in a discovery solicitation message.

[0170] In some example embodiments, the second apparatus further comprises: meansfor receiving, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus; and means for determining the availability of a further anchor for positioning the second apparatus based on the first indication and the second indication.

[0171] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the third apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0172] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0173] In some example embodiments, the second indication is received via at least one additional field in a discovery response message.

[0174] In some example embodiments, the second apparatus further comprises: means for transmitting anchor information indicating whether the further anchor for positioning the second apparatus is available.

[0175] In some example embodiments, the anchor information is transmitted in a broadcast or groupcast way.

[0176] In some example embodiments, the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0177] In some example embodiments, the second apparatus further comprises: means for starting a second timer at the time that the first indication is received; and means for in accordance with a determination that the second indication is not received until the second timer expires, determining that there is no anchor available for positioning the second apparatus.

[0178] In some example embodiments, the second timer is preconfigured or predetermined.

[0179] In some example embodiments, the second apparatus further comprises means for performing other operations in some example embodiments of the method 500 or the second apparatus 120. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the second apparatus.

[0180] In some example embodiments, a third apparatus capable of performing any of the method 600 (for example, the third apparatus 130 in FIG. 1) may comprise means for performing the respective operations of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The third apparatus may be implemented as or included in the third apparatus 130 in FIG. 1.

[0181] In some example embodiments, the third apparatus comprises means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for determining, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

[0182] In some example embodiments, the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, power to be supported by the further anchor, thresholds on sidelink radio measurements , a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

[0183] In some example embodiments, the first indication is received via at least one additional field in a discovery solicitation message.

[0184] In some example embodiments, the third apparatus further comprises: means for transmitting a second indication indicating availability of the third apparatus to serve as an anchor for positioning the second apparatus.

[0185] In some example embodiments, the second indication indicates at least one of the following: information for updating the anchor, the information comprising at leastone of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the second apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

[0186] In some example embodiments, the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

[0187] In some example embodiments, the second indication is transmitted via at least one additional field in a discovery response message.

[0188] In some example embodiments, the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

[0189] In some example embodiments, the third apparatus further comprises: means for receiving anchor information from the second apparatus, indicating whether the further anchor for positioning the second apparatus is available.

[0190] In some example embodiments, the anchor information comprises a third indication indicating that the third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

[0191] In some example embodiments, the third apparatus further comprises means for performing other operations in some example embodiments of the method 600 or the third apparatus 130. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the third apparatus.

[0192] FIG. 7 is a simplified block diagram of a device 700 that is suitable for implementing example embodiments of the present disclosure. The device 700 may be provided to implement a communication device, for example, the first apparatus 110 or the second apparatus 120 or the third apparatus 130 as shown in FIG. 1. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more communication modules 740 coupled to the processor 710.

[0193] The communication module 740 is for bidirectional communications. The communication module 740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 740 may include at least one antenna.

[0194] The processor 710 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0195] The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 724, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 722 and other volatile memories that will not last in the power-down duration.

[0196] A computer program 730 includes computer executable instructions that are executed by the associated processor 710. The instructions of the program 730 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 730 may be stored in the memory, e.g., the ROM 724. The processor 710 may perform any suitable actions and processing by loading the program 730 into the RAM 722.

[0197] The example embodiments of the present disclosure may be implemented by means of the program 730 so that the device 700 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 6. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0198] In some example embodiments, the program 730 may be tangibly contained in acomputer readable medium which may be included in the device 700 (such as in the memory 720) or other storage devices that are accessible by the device 700. The device 700 may load the program 730 from the computer readable medium to the RAM 722 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0199] FIG. 8 shows an example of the computer readable medium 800 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 800 has the program 730 stored thereon.

[0200] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0201] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0202] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0203] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0204] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0205] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separatelyor in any suitable sub-combination.

[0206] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A first apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: transmit a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and monitor availability of a further anchor for positioning the second apparatus.

2. The first apparatus of claim 1, wherein the first apparatus is caused to: determine whether the first apparatus will be unavailable or undesirable for the positioning based on at least one of the following: power status of the first apparatus, mobility information of the first apparatus, synchronization information, sidelink traffic, a signal received from the second apparatus, a signal received from a nearby apparatus, or a link quality between the first apparatus and the second apparatus, or a link quality between the first apparatus and the nearby apparatus; and in accordance with a determination that the first apparatus will be unavailable or undesirable for the positioning, transmit the first indication.

3. The first apparatus of claim 1 or 2, wherein the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor,power to be supported by the further anchor, thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

4. The first apparatus of any of claims 1 to 3, wherein the first indication is transmitted via at least one additional field in a discovery solicitation message.

5. The first apparatus of any of claims 1 to 4, wherein the first indication is broadcasted or groupcasted to nearby apparatuses, or wherein the first indication is unicasted to a preselected candidate anchor.

6. The first apparatus of any of claims 1 to 5, wherein the first apparatus is caused to: receive, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus.

7. The first apparatus of claim 6, wherein the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, the availability of the third apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

8. The first apparatus of claim 7, wherein the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

9. The first apparatus of any of claims 6 to 8, wherein the second indication is transmitted via at least one additional field in a discovery response message.

10. The first apparatus of any of claims 6 to 9, wherein the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

11. The first apparatus of any of claims 1 to 10, wherein the first apparatus is caused to: receive, from the second apparatus, the anchor information indicating whether the further anchor for positioning the second apparatus is available.

12. The first apparatus of claim 11, wherein the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

13. The first apparatus of any of claims 1 to 10, wherein the first apparatus is caused to: start a first timer at the time that the first indication is transmitted; and in accordance with a determination that anchor information indicating whether thefurther anchor is available is not received until the first timer expires, determine that there is no further anchor available for positioning the second apparatus, or in accordance with a determination that a second indication indicating availability of the third apparatus to serve as the further anchor is not received until the first timer expires, determine that there is no further anchor available for positioning the second apparatus.

14. The first apparatus of claim 13, wherein the first timer is preconfigured or predetermined.

15. The first apparatus of any of claims 1 to 14, wherein the second apparatus is a target terminal device, and the first apparatus is anchor for positioning the target terminal device.

16. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: receive, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and determine availability of a further anchor for positioning the second apparatus at least based on the first indication.

17. The second apparatus of claim 16, wherein the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, power to be supported by the further anchor,thresholds on sidelink radio measurements, a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

18. The second apparatus of claim 16 or 17, wherein the first indication is received via at least one additional field in a discovery solicitation message.

19. The second apparatus of any of claims 16 to 18, wherein the second apparatus is caused to: receive, from a third apparatus, a second indication indicating availability of the third apparatus to serve as the further anchor for positioning the second apparatus; and determine the availability of a further anchor for positioning the second apparatus based on the first indication and the second indication.

20. The second apparatus of claim 19, wherein the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the third apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

21. The second apparatus of claim 20, wherein the resource information of the reference signal comprises at least one of the following:a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

22. The second apparatus of any of claims 19 to 21, wherein the second indication is received via at least one additional field in a discovery response message.

23. The second apparatus of any of claims 16 to 22, wherein the second apparatus is caused to: transmit anchor information indicating whether the further anchor for positioning the second apparatus is available.

24. The second apparatus of claim 23, wherein the anchor information is transmitted in a broadcast or groupcast way.

25. The second apparatus of claim 23 or 24, wherein the anchor information comprises a third indication indicating that a third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

26. The second apparatus of any of claims 19 to 25, wherein the second apparatus is caused to: start a second timer at the time that the first indication is received; and in accordance with a determination that the second indication is not received until the second timer expires, determine that there is no anchor available for positioning the second apparatus.

27. The first apparatus of claim 26, wherein the second timer is preconfigured orpredetermined.

28. A third apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third apparatus at least to: receive, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and determine, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

29. The third apparatus of claim 28, wherein the first indication indicates at least one of the following: the unavailability of the first apparatus for a time length, an area, a cell, a zone, or a range; capabilities to be supported by the further anchor, power to be supported by the further anchor, thresholds on sidelink radio measurements , a type of a link between the first apparatus and a nearby apparatus or between the nearby apparatus and the second apparatus, serving information indicating a time length, an area, a cell, a zone, or a range of the further anchor, or network information indicating at least one network node for serving.

30. The third apparatus of claim 28 or 29, wherein the first indication is received via at least one additional field in a discovery solicitation message.

31. The third apparatus of any of claims 28 to 30, wherein the third apparatus is caused to:transmit a second indication indicating availability of the third apparatus to serve as an anchor for positioning the second apparatus.

32. The third apparatus of claim 31, wherein the second indication indicates at least one of the following: information for updating the anchor, the information comprising at least one of information relating to the first apparatus, a session identification, or information relating to the second apparatus, availability of the second apparatus for a time length, an area, a cell, a zone, or a range, or resource information of a reference signal to be transmitted from the third apparatus for positioning.

33. The third apparatus of claim 32, wherein the resource information of the reference signal comprises at least one of the following: a periodicity of the reference signal, a bandwidth of the reference signal, or a sequence identification of the reference signal.

34. The third apparatus of any of claims 31 to 33, wherein the second indication is transmitted via at least one additional field in a discovery response message.

35. The third apparatus of any of claims 31 to 34, wherein the second indication is broadcasted to nearby apparatuses, or wherein the second indication is groupcasted to a group of apparatuses comprising the second apparatus.

36. The third apparatus of any of claims 28 to 35, wherein the third apparatus is caused to:receive anchor information from the second apparatus, indicating whether the further anchor for positioning the second apparatus is available.

37. The third apparatus of claim 36, wherein the anchor information comprises a third indication indicating that the third apparatus is selected as the further anchor, or wherein the anchor information comprises a fourth indication indicating that there is no anchor available for positioning the second apparatus.

38. A method comprising: transmitting a first indication indicating an unavailability of a first apparatus to serve as an anchor for positioning a second apparatus; and monitoring availability of a further anchor for positioning the second apparatus.

39. A method comprising: receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and determining availability of a further anchor for positioning the second apparatus at least based on the first indication.

40. A method comprising: receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and determining, based on the first indication, availability of a third apparatus to be a further anchor for positioning the second apparatus.

41. A first apparatus comprising: means for transmitting a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for monitoring availability of a further anchor for positioning the secondapparatus.

42. A second apparatus comprising: means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning the second apparatus; and means for determining availability of a further anchor for positioning the second apparatus at least based on the first indication.

43. A third apparatus comprising: means for receiving, from a first apparatus, a first indication indicating an unavailability of the first apparatus to serve as an anchor for positioning a second apparatus; and means for determining, based on the first indication, availability of the third apparatus to be a further anchor for positioning the second apparatus.

44. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of any of claims 38-40.

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