WO2023046261A1

WO2023046261A1 - Methods and apparatuses for network assisted positioning for out of coverage terminals

Info

Publication number: WO2023046261A1
Application number: PCT/EP2021/075930
Authority: WO
Inventors: Rajesh Babu NATARAJAN; Pallab Gupta; Malathi PONNIAH; Nagaraj RAJAGOPALAN; Bharath Ramesh KASHYAP
Original assignee: Nokia Technologies Oy
Priority date: 2021-09-21
Filing date: 2021-09-21
Publication date: 2023-03-30
Also published as: EP4406305A1

Abstract

There are provided measures for network assisted positioning for out of coverage terminals. Such measures comprise, at a of a location management function entity of a mobile network, receiving (S101) a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating (S102) a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

Description

Title

METHODS AND APPARATUSES FOR NETWORK ASSISTED POSITIONING FOR OUT OF COVERAGE TERMINALS

Field

Various example embodiments relate to network assisted positioning for out of coverage terminals. More specifically, various example embodiments exemplarily relate to measures (including methods, apparatuses and computer program products) for realizing network assisted positioning for out of coverage terminals.

Background

The present specification generally relates to positioning of a terminal, i.e., to determination of a location of the terminal, and in particular to the determination of the location of the terminal in a case that the terminal is out of network coverage.

Figure 16 shows a schematic diagram of signaling sequences, and in particular illustrates a signaling sequence of a procedure for multi-RTT (RTT: round trip time) positioning (e.g. TS 38.305).

More specifically, Figure 16 shows the messaging between a location management function (LMF), gNBs and a user equipment (UE) to perform an LMF-initiated location information transfer procedure for Multi-RTT.

Figure 17 shows a schematic diagram of signaling sequences, and in particular illustrates a signaling sequence of a procedure for uplink angle-of- arrival (UL-AoA) positioning (e.g. TS 38.305). More specifically, Figure 17 shows the messaging between the LMF, gNBs and the UE to perform the UL-AoA procedure.

Figure 18 shows a schematic diagram illustrating a coordinate system and quantities underlying measurements of an angle of arrival.

According to UL-AoA measurements in 5G NR. (e.g. TS 38.215 V16.1.0), the UL AoA is defined by two angles, namely the azimuth angle (illustrated as <P in Figure 18) and the vertical (zenith) angle (illustrated as 0 in Figure 18).

Further, the UL AoA is defined with respect to one of the spherical coordinate systems "global coordinate system (GCS)" and "rotated local coordinate system (LCS)".

In the global coordinate system (GCS), the azimuth angle is measured relative to geographical North and the vertical angle is measured relative to the zenith.

In the rotated local coordinate system (LCS), the LCS is rotated by bearing, with downtilt and slant angles relative to GCS (e.g. as defined in TS 38.901), and the azimuth angle is measured relative to the x-axis of the LCS and the vertical angle is measured relative to the z-axis of the LCS.

Figure 19 shows a schematic diagram of signaling sequences, an in particular illustrates a procedure for public safety direct discovery with proximityservices (ProSe) Direct Discovery Model B (e.g. TS 23.303).

Here, the discoverer is the ProSe remote UE, and the discoveree is the relay UE which is already connected to the network.

That is, currently known are location services and a positioning procedure for a UE within network radio coverage. However, no network assisted positioning procedure for a UE that is out of network radio coverage is known.

Figure 20 shows a schematic diagram of signaling sequences, and in particular illustrates communication in relation to direct communication via ProSe UE-to-network relay (e.g. TS 23.303).

A ProSe UE-to-network relay capable UE may attach to the network (if it is not already connected) and connect to a packet data network (PDN) connection enabling the necessary relay traffic, or it may need to connect to additional PDN connection(s) in order to provide relay traffic towards remote UE(s). PDN connection(s) supporting UE-to-network relay shall only be used for remote ProSe UE(s) relay traffic.

One-to-one ProSe direct communication may be realized by establishing a secure layer-2 link over PC5 between two UEs.

Figure 21 shows a schematic diagram of signaling sequences, and in particular illustrates a 5GC-MT-LR (5GC: 5G core (network), MT-LR: mobile terminated location request) procedure for a regulatory location service (e.g. TS 23.273).

More specifically, general network positioning for LCS clients external to the public land mobile network (PLMN) for the regulatory location service for nonroaming scenario is shown. In this scenario, it is assumed that the target UE is identified using a subscription permanent identifier (SUPI) or generic public subscription identifier (GPSI).

This procedure is applicable to a request from an LCS client for a current location of the target UE, and it is assumed that the LCS client is authorized to use the location service and no privacy verification is required. Figure 22 shows a schematic diagram of signaling sequences, and in particular illustrates a UE assisted and a UE based positioning procedure (e.g. TS 23.273).

More specifically, a positioning procedure used by an LMF to support UE based positioning, UE assisted positioning and delivery of assistance data is shown. The procedure is based on use of the Long Term Evolution (LTE) positioning protocol (LPP) as e.g. defined in TS 36.355 between the LMF and the UE.

That is, as mentioned above, currently known are location services and a positioning procedure for a UE within network radio coverage.

However, no MT-LR procedure for a UE that is out of radio coverage is known.

Hence, the problem arises that no network assisted positioning procedure for a UE that is out of network radio coverage is known. Further, the problem arises that no MT-LR procedure for a UE that is out of radio coverage is known.

Hence, there is a need to provide for network assisted positioning for out of coverage terminals.

Summary

Various example embodiments aim at addressing at least part of the above issues and/or problems and drawbacks.

Various aspects of example embodiments are set out in the appended claims.

According to an exemplary aspect, there is provided a method of a location management function entity of a mobile network, the method comprising receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided a method of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the method comprising receiving respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling respective times of receipt of said respective sidelink positioning reference signals, transmitting respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, sampling respective times of transmission of said respective sidelink sounding reference signals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and transmitting respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided a method of a terminal connected to at least one base station of base stations of a mobile network, the method comprising transmitting a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, sampling a time of transmission of said sidelink positioning reference signal, receiving a sidelink sounding reference signal from said first terminal, sampling a time of receipt of said sidelink sounding reference signal, transmitting said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and transmitting said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

According to an exemplary aspect, there is provided a method of a mobility management function entity of a mobile network, the method comprising receiving, from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

According to an exemplary aspect, there is provided a method of a subscription management function entity of a mobile network, the method comprising receiving an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, receiving, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

According to an exemplary aspect, there is provided a method of a location function entity of a mobile network, the method comprising transmitting, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, receiving, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and transmitting, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

According to an exemplary aspect, there is provided an apparatus of a location management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating circuitry configured to estimate a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the apparatus comprising receiving circuitry configured to receive respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling circuitry configured to sample respective times of receipt of said respective sidelink positioning reference signals, transmitting circuitry configured to transmit respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, wherein said sampling circuitry is configured to sample respective times of transmission of said respective sidelink sounding reference signals, wherein said transmitting circuitry is configured to transmit said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and to transmit respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a terminal connected to at least one base station of base stations of a mobile network, the apparatus comprising transmitting circuitry configured to transmit a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal, sampling circuitry configured to sample a time of transmission of said sidelink positioning reference signal, receiving circuitry configured to receive a sidelink sounding reference signal from said first terminal, wherein said sampling circuitry is configured to sample a time of receipt of said sidelink sounding reference signal, wherein said transmitting circuitry is configured to transmit said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and to transmit said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a mobility management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive, from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting circuitry configured to transmit, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

According to an exemplary aspect, there is provided an apparatus of a subscription management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, and to receive, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting circuitry configured to transmit, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

According to an exemplary aspect, there is provided an apparatus of a location function entity of a mobile network, the apparatus comprising transmitting circuitry configured to transmit, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, and receiving circuitry configured to receive, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and wherein said transmitting circuitry is configured to transmit, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

According to an exemplary aspect, there is provided an apparatus method of a location management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal, and estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform receiving respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling respective times of receipt of said respective sidelink positioning reference signals, transmitting respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, sampling respective times of transmission of said respective sidelink sounding reference signals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and transmitting respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a terminal connected to at least one base station of base stations of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform transmitting a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, sampling a time of transmission of said sidelink positioning reference signal, receiving a sidelink sounding reference signal from said first terminal, sampling a time of receipt of said sidelink sounding reference signal, transmitting said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and transmitting said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

According to an exemplary aspect, there is provided an apparatus of a mobility management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform receiving, from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal. According to an exemplary aspect, there is provided an apparatus of a subscription management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform receiving an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, receiving, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

According to an exemplary aspect, there is provided an apparatus of a location function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform transmitting, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, receiving, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and transmitting, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

According to an exemplary aspect, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present disclosure), is configured to cause the computer to carry out the method according to any one of the aforementioned method- related exemplary aspects of the present disclosure.

Such computer program product may comprise (or be embodied) a (tangible) computer-readable (storage) medium or the like on which the computerexecutable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof.

Any one of the above aspects enables an efficient (cooperative) positioning of a terminal, e.g. a UE, that is out of coverage of its respective serving network to thereby solve at least part of the problems and drawbacks identified in relation to the prior art.

By way of example embodiments, there is provided network assisted positioning for out of coverage terminals. More specifically, by way of example embodiments, there are provided measures and mechanisms for realizing network assisted positioning for out of coverage terminals. Thus, improvement is achieved by methods, apparatuses and computer program products enabling/realizing network assisted positioning for out of coverage terminals.

Brief description of the drawings

In the following, the present disclosure will be described in greater detail by way of non-limiting examples with reference to the accompanying drawings, in which

Figure 1 is a block diagram illustrating an apparatus according to example embodiments,

Figure 2 is a block diagram illustrating an apparatus according to example embodiments,

Figure 3 is a block diagram illustrating an apparatus according to example embodiments,

Figure 4 is a block diagram illustrating an apparatus according to example embodiments,

Figure 5 is a block diagram illustrating an apparatus according to example embodiments,

Figure 6 is a block diagram illustrating an apparatus according to example embodiments,

Figure 7 is a block diagram illustrating an apparatus according to example embodiments,

Figure 8 is a block diagram illustrating an apparatus according to example embodiments, Figure 9 is a block diagram illustrating an apparatus according to example embodiments,

Figure 10 is a schematic diagram of a procedure according to example embodiments,

Figure 11 is a schematic diagram of a procedure according to example embodiments,

Figure 12 is a schematic diagram of a procedure according to example embodiments,

Figure 13 is a schematic diagram of a procedure according to example embodiments,

Figure 14 is a schematic diagram of a procedure according to example embodiments,

Figure 15 is a schematic diagram of a procedure according to example embodiments,

Figure 16 shows a schematic diagram of signaling sequences,

Figure 17 shows a schematic diagram of signaling sequences,

Figure 18 shows a schematic diagram illustrating a coordinate system and quantities underlying measurements of an angle of arrival,

Figure 19 shows a schematic diagram of signaling sequences,

Figure 20 shows a schematic diagram of signaling sequences, Figure 21 shows a schematic diagram of signaling sequences,

Figure 22 shows a schematic diagram of signaling sequences,

Figure 23 shows a schematic diagram of an example of a system environment according to example embodiments,

Figure 24 shows a schematic diagram of an example of a system environment according to example embodiments,

Figure 25 shows a schematic diagram of an example of a system environment according to example embodiments,

Figure 26 shows a schematic diagram of an example of a system environment according to example embodiments,

Figure 27 shows a schematic diagram of signaling sequences according to example embodiments,

Figure 28 (Figures 28A and 28B) shows a schematic diagram of signaling sequences according to example embodiments,

Figure 29 shows a schematic diagram of signaling sequences according to example embodiments,

Figure 30 shows a schematic diagram of signaling sequences according to example embodiments,

Figure 31 shows a schematic diagram of an example of a system environment illustrating positioning principles according to example embodiments,

Figure 32 shows a schematic diagram of signaling sequences according to example embodiments, Figure 33 shows a schematic diagram of signaling sequences according to example embodiments, and

Figure 34 is a block diagram alternatively illustrating apparatuses according to example embodiments.

Detailed description

The present disclosure is described herein with reference to particular nonlimiting examples and to what are presently considered to be conceivable embodiments. A person skilled in the art will appreciate that the disclosure is by no means limited to these examples, and may be more broadly applied.

It is to be noted that the following description of the present disclosure and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments. Namely, the present disclosure and its embodiments are mainly described in relation to 3GPP specifications being used as non-limiting examples for certain exemplary network configurations and deployments. As such, the description of example embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the disclosure in any way. Rather, any other communication or communication related system deployment, etc. may also be utilized as long as compliant with the features described herein.

Hereinafter, various embodiments and implementations of the present disclosure and its aspects or embodiments are described using several variants and/or alternatives. It is generally noted that, according to certain needs and constraints, all of the described variants and/or alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various variants and/or alternatives).

According to example embodiments, in general terms, there are provided measures and mechanisms for (enabling/realizing) network assisted positioning for out of coverage terminals.

As discussed above, no network assisted positioning procedure for a UE that is out of network radio coverage and no MT-LR procedure for a UE that is out of radio coverage are known.

Thus, according to example embodiments, options are proposed below to enable a positioning procedure for an out of coverage UE by using the ProSe interface.

These options include

1.) positioning of a ProSe enabled remote UE (out of coverage UE) by applying a Multi-RTT positioning technique when multiple ProSe enabled UEs (Relay UEs) are in the proximity of the Remote UE, and

2.) positioning of a ProSe enabled remote UE (out of coverage UE) by applying a Multi-RTT positioning technique with UL-AoA positioning between the remote UE and the relay UE, when only one ProSe enabled UE-to-network relay UE is in the proximity of the remote UE.

Further, according to example embodiments, a method to enable an MT-LR location procedure for an out of coverage UE by using the ProSe interface is proposed. Heretofore, the ProSe procedure itself is enhanced (enhancement 1.)), and the location procedure is enhanced (enhancement 2.)).

In this specification, the following terms are used with the following meaning:

A remote UE is a ProSe enabled UE which is out of network coverage. Relay UEs are ProSe enabled UEs which are connected to the network and are in proximity of the Remote UE.

A UE-to-network relay UE is the relay UE through which the remote UE establishes a PDN connection with the network.

In brief, according to example embodiments, according to option 1.) above, a procedure of positioning of a ProSe enabled remote UE (out of coverage UE) when multiple ProSe enabled UE-to-network relay UEs (via PC5 interface) are available in the proximity of the remote UE is provided.

As a pre-condition thereof, the remote UE (out of coverage UE) and relay UE have discovered each other using ProSe/PC5 communication, and a PDN connection is established with at least one relay UE as per current 3GPP standards specified procedure.

This procedure of positioning of a ProSe enabled remote UE with multiple ProSe enabled UE-to-network relay UEs (option 1.)) may comprise one or more of the following steps:

1. A positioning reference signal (SL-PRS-DL) is introduced in sidelink (SL) between a relay UE and a remote UE.

2. A sounding reference signal (SL-SRS-P) is used for positioning in SL between the relay UE and the remote UE.

3. An LMF, upon receiving a request from an access and mobility management function (AMF) to find the position of the remote UE, requests the remote UE, which has already established a PDN connection with the relay UE, to get all the proximity UEs available via PC5 interface. This is described in more detail below with reference to Figure 28. a. Once the remote UE receives the request from the LMF via the relay UE using the PC5 interface, the remote UE may use the ProSe Direct Discovery Model B method: i. By broadcasting a solicitation message and an indication that the discoveree needs to be connected to the network and listing the positioning procedures supported, so that the LMF can use them in aiding the location of the remote UE. ii. The remote UE receiving a corresponding response message with an indication that a proximity UE supports the positioning procedure needed for aiding positioning of the remote UE. b. The remote UE then prepares the list of proximity UEs (that responded to the solicitation message, which are connected to the network and also support positioning procedures needed in aiding positioning of the remote UE) and provides the list to the UE-to-network relay UE via the PC5 interface, which then forwards the list to the LMF. c. The LMF validates the list of UEs belonging to the same PLMN and served by the same AMF and uses them (and their serving base stations) for the positioning procedure as mentioned below. d. The LMF may also obtain the current positions of the relay UEs (UEs selected in 3.c. above, i.e., those UEs from the list which belong to the same PLMN and are served by the same AMF) based on existing positioning procedures. This position is used as reference to calculate the remote UE's position more accurately. Positioning of the remote UE (out of coverage UE) is done with reference to the relay UE positions as follows: a. Using multi-RTT measurements from relay UE to remote UE: i. The relay UE sends the SL-PRS transmit time to the LMF. This is described in more detail below with reference to Figure 30. ii. The remote UE sends the SL-PRS receive time from each relay UE to the LMF, via the UE-to-network relay UE (for example, the remote UE may send the measurement in PC5 interface and later the UE-to-network relay UE could forward it to the LMF via LPP protocol). iii. The relay UE also sends the transmit time of the SL-SRS- P to the LMF. iv. Each relay UE sends the SL-SRS-P receive time from the remote UE to the LMF. v. The LMF, knowing the transmit time of SL-PRS of the relay UE and of SL-SRS-P of the remote UE, upon receiving the receive time of SL-PRS and SL-SRS-P from the remote UE (via the relay UE) and the relay UE, respectively, calculates the round trip time (RTT) between each relay UE and remote UE and thus estimates the position of thr remote UE based on multi-RTT measurements from different relay UEs. It is noted that the positioning of the remote UE is based on reference to all the relay UE's positioning. b. Similarly in 4.b., at least three propagation delay estimates (relay UEs and remote UE) are considered for the remote UE positioning. c. It is noted that the Remote UE uses the PC5 interface and communicates its location information, i.e., SL-PRS measurement information, to the relay UE, which forwards the same to the LMF. d. Similarly, the relay UE measures SL-SRS-P measurements and sends the same to the LMF. e. The LMF uses these measurements between multiple relay UE(s) and the remote UE and then calculates the RTT between relay UE and remote UE and estimates the remote UE positioning.

Further, according to example embodiments, according to option 2.) above, a procedure of positioning of a ProSe enabled remote UE (out of coverage UE) when only one UE-to-network relay UE (via which the remote UE has established a PDN connection) is available in the proximity of the remote UE is provided.

This procedure of positioning of a ProSe enabled remote UE with only one UE- to-network relay UE (option 2.)) may be similar to the procedure of positioning of a ProSe enabled remote UE with multiple ProSe enabled UE-to- network relay UEs (option 1.)) except for that:

- along with the multi-RTT method specified above to measure the RTT between the relay UE and the remote UE, a Sidelink - Angle of Arrival (SL-AoA) at the relay UE from the remote UE measurement is also foreseen to improve the accuracy, and

- since only one relay UE is available in the proximity of the remote UE, multiple measurements are foreseen to enhance the accuracy of the measurements.

Further, according to example embodiments, according to enhancement 1.) above, the ProSe procedure for direct communication via ProSe UE-to- network relay is enhanced in that

1. a relay service code for location service may be preconfigured, and the remote UE may discover a ProSe UE-to-network relay that indicates this service code in the announcement message, and

2. after the ProSe UE-to-network relay UE discovery by the remote UE (which is out of network coverage) and establishment of the PDN connection with the remote UE, the ProSe UE-to-network relay UE may update the AMF about the remote UE details (UE ID, IP address); the AMF may further provide an indication to the home subscriber server (HSS) / unified data management (UDM) that the remote UE is reachable using the ProSe interface via the UE-to- network relay UE from the AMF.

Further, according to example embodiments, according to enhancement 2.) above, the positioning procedure (5GC-MT-LR procedure) is enhanced in that: 1. based on a location request from an LCS client, the gateway mobile location centre (GMLC) may query the UDM to get the details of the serving AMF; in response, the GMLC receives an indication that the target UE is reachable via a ProSe UE-to- network relay UE for location procedure and the serving AMF identifier,

2. the GMLC may initiate a request towards the serving AMF to provide the current location of the remote UE; the Namf_Location_ProvidePositioningInfo is enhanced or a new service operation can be introduced, to indicate that the request is for positioning of a remote ProSe UE and includes information about the target remote UE,

3. the AMF may provide the details of the ProSe UE-to-network relay UE along with the information about the remote UE (based on the mapping between the remote UE and the ProSe UE-to-network relay UE it maintains) to the LMF for the positioning procedure; the AMF may also indicate to the LMF that the remote UE is reachable via ProSe UE-to-network relay UE,

4. the LMF may forward the positioning message via the AMF to the ProSe UE-to-network relay UE with an indication that the location procedure message is for the remote UE,

5. the ProSe UE-network-relay UE may send a new PC5 control message (e.g. DL positioning message) to the remote UE, and

6. the remote UE may do the positioning calculation and respond with a new PC5 control message (e.g. UL positioning message) to the ProSe UE-network-relay UE, which forwards the same to the AMF (where AMF forwards the same to LMF).

Example embodiments are specified below in more detail.

Figure 1 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a network entity 10 such as (or hosting) a location management function entity (e.g. a location management function (LMF)) (of a mobile network) comprising a receiving circuitry 11 and an estimating circuitry 12. The receiving circuitry 11 receives a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal. The estimating circuitry 12 estimates a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals. Here, the plurality of third terminals includes said second terminal. Further, each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network. Figure 10 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 1 may perform the method of Figure 10 but is not limited to this method. The method of Figure 10 may be performed by the apparatus of Figure 1 but is not limited to being performed by this apparatus.

As shown in Figure 10, a procedure according to example embodiments comprises an operation of receiving (S101) a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and an operation of estimating (S102) a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals. Here, the plurality of third terminals includes said second terminal. Further, each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

Figure 2 is a block diagram illustrating an apparatus according to example embodiments. In particular, Figure 2 illustrates a variation of the apparatus shown in Figure 1. The apparatus according to Figure 2 may thus further comprise a calculating circuitry 21, a transmitting circuitry 22, a verifying circuitry 23, a considering circuitry 24, and/or a triggering circuitry 25.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 1 (or 2) may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving respective times of transmission of respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, an operation of receiving respective times of receipt of said respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, an operation of receiving respective times of transmission of respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, an operation of receiving respective times of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, and an operation of calculating said respective round trip times between each of said at least one of said plurality of third terminals and said first terminal based on said respective times of transmission of said respective sidelink positioning reference signals, said respective times of receipt of said respective sidelink positioning reference signals, said respective times of transmission of said respective sidelink sounding reference signals, and said respective times of receipt of said respective sidelink sounding reference signals. According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving respective angles of arrival of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, wherein at said estimating (S102), said location of said first terminal is estimated further based on said respective angles of arrival of receipt of said respective sidelink sounding reference signals.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting, towards each of said at least one of said plurality of third terminals, respective sidelink positioning reference signal configuration information.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting, towards said second terminal, a request for positioning said first terminal.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said second terminal, sidelink sounding reference signal configuration information of said first terminal, and an operation of transmitting, towards each of said at least one of said plurality of third terminals, said sidelink sounding reference signal configuration information of said first terminal. According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting, towards said first terminal, via said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving said list of proximity terminal candidates. Here, the list of proximity terminal candidates includes said plurality of third terminals.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of verifying, for each proximity terminal candidate of said list of proximity terminal candidates, whether said respective proximity terminal candidate belongs to a predetermined public land mobile network and is served by a predetermined mobility management function entity, and an operation of considering each proximity terminal candidate of said list of proximity terminal candidates which belongs to said predetermined public land mobile network and is served by said predetermined mobility management function entity as one of said plurality of third terminals.

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of triggering identification of said respective locations of each of said at least one of said plurality of third terminals.

Figure 3 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a first terminal 30 such as a remote user equipment (UE) (out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal) comprising a receiving circuitry 31, a sampling circuitry 32, and a transmitting circuitry 33. The receiving circuitry 31 receives respective sidelink positioning reference signals from each of at least one of a plurality of third terminals. The sampling circuitry 32 samples respective times of receipt of said respective sidelink positioning reference signals. The transmitting circuitry 33 transmits respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals. The sampling circuitry 32 samples respective times of transmission of said respective sidelink sounding reference signals. The transmitting circuitry 33 transmits said respective times of receipt of said respective sidelink positioning reference signals to said second terminal. The transmitting circuitry 33 transmits respective times of transmission of said respective sidelink sounding reference signals to said second terminal. Here, said plurality of third terminals includes said second terminal. Further, each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network. Figure 11 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 3 may perform the method of Figure 11 but is not limited to this method. The method of Figure 11 may be performed by the apparatus of Figure 3 but is not limited to being performed by this apparatus.

As shown in Figure 11, a procedure according to example embodiments comprises an operation of receiving (Sill) respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, an operation of sampling (SI 12) respective times of receipt of said respective sidelink positioning reference signals, an operation of transmitting (SI 13) respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, an operation of sampling (S114) respective times of transmission of said respective sidelink sounding reference signals, an operation of transmitting (SI 15) said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and an operation of transmitting (SI 16) respective times of transmission of said respective sidelink sounding reference signals to said second terminal. Here, the plurality of third terminals includes said second terminal. Further, each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

Figure 4 is a block diagram illustrating an apparatus according to example embodiments. In particular, Figure 4 illustrates a variation of the apparatus shown in Figure 3. The apparatus according to Figure 4 may thus further comprise a considering circuitry 41 and/or a calculating circuitry 42.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 3 (or 4) may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes.

According to a variation of the procedure shown in Figure 11, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving a request for information on a location of said first terminal.

According to a variation of the procedure shown in Figure 11, exemplary additional operations and exemplary details of the transmitting operation (S113) (transmitting said respective sidelink sounding reference signals) are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving sidelink sounding reference signal configuration information of said first terminal. Further, such exemplary transmitting operation (S113) (transmitting said respective sidelink sounding reference signals) according to example embodiments may comprise an operation of considering said sidelink sounding reference signal configuration information of said first terminal.

According to a variation of the procedure shown in Figure 11, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

According to a variation of the procedure shown in Figure 11, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting, to each of proximity terminals in a proximity of said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, and an operation of receiving, from at least one of said proximity terminals, a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

According to a variation of the procedure shown in Figure 11, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting a list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received.

According to further example embodiments, said list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received corresponds to said plurality of third terminals.

According to a variation of the procedure shown in Figure 11, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of calculating said location of said first terminal, and an operation of transmitting said information on said location of said first terminal to said second terminal.

Figure 5 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a terminal 50 such as a relay user equipment (UE) (connected to at least one base station of base stations of a mobile network) comprising a transmitting circuitry 51, a sampling circuitry 52, and a receiving circuitry 53. The transmitting circuitry 51 transmits a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal. The sampling circuitry 52 samples a time of transmission of said sidelink positioning reference signal. The receiving circuitry 53 receives a sidelink sounding reference signal from said first terminal. The sampling circuitry 52 samples a time of receipt of said sidelink sounding reference signal. The transmitting circuitry 51 transmits said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network. The transmitting circuitry 51 transmits said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network. Figure 12 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 5 may perform the method of Figure 12 but is not limited to this method. The method of Figure 12 may be performed by the apparatus of Figure 5 but is not limited to being performed by this apparatus.

As shown in Figure 12, a procedure according to example embodiments comprises an operation of transmitting (S121) a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, an operation of sampling (S122) a time of transmission of said sidelink positioning reference signal, an operation of receiving (S123) a sidelink sounding reference signal from said first terminal, an operation of sampling (S124) a time of receipt of said sidelink sounding reference signal, an operation of transmitting (S125) said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and an operation of transmitting (S126) said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

Figure 6 is a block diagram illustrating an apparatus according to example embodiments. In particular, Figure 6 illustrates a variation of the apparatus shown in Figure 5. The apparatus according to Figure 6 may thus further comprise a considering circuitry 61, a determining circuitry 62, and/or a forwarding circuitry 63.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 5 (or 6) may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes. According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of sampling an angle of arrival of receipt of said sidelink sounding reference signal, and an operation of transmitting said angle of arrival of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

According to a variation of the procedure shown in Figure 12, exemplary additional operations and exemplary details of the transmitting operation (S121) (transmitting said sidelink positioning reference signal) are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said location management function entity of said mobile network, sidelink positioning reference signal configuration information. Further, such exemplary transmitting operation (S121) (transmitting said sidelink positioning reference signal) according to example embodiments may comprise an operation of considering said sidelink positioning reference signal configuration information.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said location management function entity of said mobile network, sidelink sounding reference signal configuration information of said first terminal.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, an operation of determining that said terminal is connected to said mobile network and provides said positioning assistance service, and an operation of transmitting, to said first terminal, a confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

According to further example embodiments, said terminal is said second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said location management function entity of said mobile network, a request for positioning said first terminal, an operation of determining sidelink sounding reference signal configuration information of said first terminal, an operation of transmitting said sidelink sounding reference signal configuration information of said first terminal to said first terminal, and an operation of transmitting said sidelink sounding reference signal configuration information of said first terminal to said location management function entity of said mobile network.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of transmitting a request for information on a location of said first terminal to said first terminal. According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said first terminal, respective times of receipt of respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, an operation of receiving, from said first terminal, respective times of transmission of respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, an operation of transmitting said respective times of receipt of said respective sidelink positioning reference signals to said location management function entity of said mobile network, and an operation of transmitting said respective times of transmission of said respective sidelink sounding reference signals to said location management function entity of said mobile network. Here, the plurality of third terminals includes said second terminal. Further, each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said location management function entity of said mobile network, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service, and an operation of transmitting said request for said list of proximity terminal candidates to said first terminal.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said first terminal, a list including each of proximity terminals from which a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received by said first terminal, and an operation of transmitting said list to said location management function entity of said mobile network.

According to further example embodiments, said list corresponds to said plurality of third terminals.

According to a variation of the procedure shown in Figure 12, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from said first terminal, said information on said location of said first terminal, and an operation of forwarding said information on said location of said first terminal towards a mobility management function entity of said mobile network.

Figure 7 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a network entity 70 such as (or hosting) a mobility management function entity (e.g. a mobility management entity (MME) or an access and mobility management function (AMF)) (of a mobile network) comprising a receiving circuitry 71 and a transmitting circuitry 72. The receiving circuitry 71 receives, from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal. The transmitting circuitry 72 transmits, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal. Figure 13 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 7 may perform the method of Figure 13 but is not limited to this method. The method of Figure 13 may be performed by the apparatus of Figure 7 but is not limited to being performed by this apparatus. As shown in Figure 13, a procedure according to example embodiments comprises an operation of receiving (S131), from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and an operation of transmitting (S132), towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 7 may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes.

According to a variation of the procedure shown in Figure 13, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to example embodiments may comprise an operation of receiving, from a location function entity of said mobile network, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal, and an operation of transmitting, to a location management function entity of said mobile network, a request for locating said first terminal.

Figure 8 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a network entity 80 such as (or hosting) a subscription management function entity (e.g. a home subscriber server (HSS) or a unified data management (UDM)) (of a mobile network) comprising a receiving circuitry 81 and a transmitting circuitry 82. The receiving circuitry 81 receives an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal. The receiving circuitry 81 receives, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal. The transmitting circuitry 82 transmits, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal. Figure 14 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 8 may perform the method of Figure 14 but is not limited to this method. The method of Figure 14 may be performed by the apparatus of Figure 8 but is not limited to being performed by this apparatus.

As shown in Figure 14, a procedure according to example embodiments comprises an operation of receiving (S141) an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, an operation of receiving (S142), from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and an operation of transmitting (S143), to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal. In an embodiment at least some of the functionalities of the apparatus shown in Figure 8 may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes.

Figure 9 is a block diagram illustrating an apparatus according to example embodiments. The apparatus may be a network entity 90 such as (or hosting) a location function entity (e.g. a gateway mobile location centre (GMLC)) (of a mobile network) comprising a transmitting circuitry 91 and a receiving circuitry 92. The transmitting circuitry 91 transmits, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal. The receiving circuitry 92 receives, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal. The transmitting circuitry 91 transmits, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal. Figure 15 is a schematic diagram of a procedure according to example embodiments. The apparatus according to Figure 9 may perform the method of Figure 15 but is not limited to this method. The method of Figure 15 may be performed by the apparatus of Figure 9 but is not limited to being performed by this apparatus.

As shown in Figure 15, a procedure according to example embodiments comprises an operation of transmitting (S151), to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, an operation of receiving (S152), from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and an operation of transmitting (S153), to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 9 may be shared between two physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes.

Example embodiments outlined and specified above are explained below in more specific terms.

Figures 23 and 24 show schematic diagrams of examples of a system environment according to example embodiments. In particular, while Figure 23 illustrates a scenario underlying the procedure according to option 1.) outlined above, Figure 24 illustrates a scenario underlying the procedure according to option 2.) outlined above.

Furthermore, Figure 24 as well illustrates a scenario underlying the procedures according to enhancements 1.) and 2.) outlined above. However, it is to be understood that the procedures according to enhancements 1.) and 2.) outlined above are applicable as well to the scenario illustrated in Figure 23.

In the reference architecture for 5GS LCS shown in Figures 23 and 24, ProSe enabled UEs are considered. A ProSe UE-to-network relay UE is connected to the 5GS network, while the ProSe remote UE is connected (established PDN connection) to the 5GS network via the ProSe UE-to-network relay UE.

Figure 27 shows a schematic diagram of signaling sequences according to example embodiments. Enhancements to the ProSe procedure according to enhancement 1.) outlined above are explained with reference to Figure 27.

In detail, according to example embodiments, a relay service code for the location service is preconfigured, and the remote UE discovers a ProSe UE- to-network relay UE that indicates this service code in its announcement message during the ProSe Discovery procedure.

After the ProSe UE-to-network relay UE discovery by the remote UE (which is out of network coverage) and establishment of the PDN connection with the remote UE, the ProSe UE-to-network relay UE updates the AMF about the remote UE details (UE ID, IP address). The AMF further provides an indication to the HSS/UDM that the remote UE is reachable using the ProSe interface via UE-to-network relay UE from the AMF.

Heretofore, as illustrated in Figure 27, step 7 is introduced into the ProSe procedure (e.g. as defined in TS 23.303, section 5.4.4 "Direct communication via ProSe UE-to-Network Relay").

In this step 7 of Figure 27, MME/AMF provides an indication to HSS/UDM that the (remote) UE is reachable via a UE-to-network relay UE. While it is understood to the skilled person that the MME is a 4G entity, similar functionality may be provided by the 5G entity AMF or entities of future standards. Hence, while ProSe is defined for LTE/4G network, an adaptation of ProSe in 5GS is ongoing e.g. in Rel. 17, equivalent nodes of network functions (NF) are represented for both LTE/4G and 5G (5GS, 5GC). The same holds true for example for HSS and UDM.

To enable the LCS services for out of coverage UE's, according to example embodiments, the ProSe interface PC5 is reused between the UE's, which is a precondition.

Figure 33 shows a schematic diagram of signaling sequences according to example embodiments. Enhancements to the location procedure according to enhancement 2.) outlined above are explained with reference to Figure 33.

As is derivable from Figure 33 showing an MT-LR procedure for an out of coverage UE connected via a ProSe UE-to-network relay UE, according to example embodiments (in addition to steps of an MT-LR procedure e.g. as defined in TS 23.273, section 6.1), based on a location request from an LCS client, the GMLC queries the UDM to get the details of the serving AMF. In response thereto, the GMLC receives an indication that the target UE is reachable via a ProSe UE-to-network relay UE for location procedure and the serving AMF identifier.

Further, according to example embodiments, the GMLC initiates a request towards the serving AMF to provide the current location of the remote UE. The Namf_Location_ProvidePositioningInfo is enhanced or a new service operation is introduced, to indicate that the request is for positioning of a remote ProSe UE and includes information about the target remote UE.

Further, according to example embodiments, the AMF provides the details of the ProSe UE-to-network relay UE along with the information about the remote UE (based on the mapping between the remote UE and the ProSe UE- to-network relay UE it maintains) to the LMF for the positioning procedure. The AMF also indicates to the LMF that the remote UE is reachable via ProSe UE-to- network relay UE.

Further, according to example embodiments, the LMF forwards the positioning message via the AMF to the ProSe UE-to-network relay UE with an indication that the location procedure message is for the remote UE.

Further, according to example embodiments, the ProSe UE-to-network relay UE sends a new PC5 control message (e.g. the DL positioning message) to the remote UE.

Finally, according to example embodiments, the remote UE does the positioning calculation and responds with a new PC5 control message (e.g. the UL positioning message) to the ProSe UE-to-network relay UE, which forwards the same to the AMF (and the AMF forwards the same to the LMF).

Utilizing the enhancements 1.) and 2.) outlined, specified, and explained above, options 1.) and 2.) may be implemented as follows.

In particular, according to example embodiments, option 1.) may be implemented utilizing the following main steps for remote UE positioning.

1. The HSS/UDM is updated whenever a remote UE and a relay UE discovered each other and a PDN connection is established. This is explained below with reference to Figures 26 and 27 (direct communication via ProSe UE-to-network relay).

2. The LMF, upon getting a request for locating a remote UE, triggers the other proximity UE's discovery by remote UE via a UE-to- network relay UE (with which the remote UE already established a PDN connection). This is explained below with reference to Figure 28 (LMF discovery of other ProSe enabled proximity UEs (relay UEs) of the remote UE). 3. The LMF introduces a new algorithm for remote UE positioning using the relay UEs position as below: a. The LMF triggers multi-RTT measurements between the relay UEs (the list of ProSe enabled proximity UEs discovered by the remote UE, which shares the list to LMF via the relay UE) and gNBs (based on the list of ProSe enabled proximity UEs received from the remote UE, LMF queries and receives the serving gNB's list of those ProSe enabled proximity UEs from the AMF) and estimates the relay UEs positioning (e.g. as per current 3GPP standards), and b. the LMF triggers the multi-RTT measurements between the remote UE with all the discovered relay UEs and estimates the remote UE positioning. This is explained below with reference to Figure 30 (Multi-RTT positioning for remote UE with reference to relay UE(s)).

Remote UE to relay UE discovery and updating it to the UDM according to option 1.) according to example embodiments are explained with reference to Figures 25 to 27.

Figure 25 and 26 show schematic diagrams of examples of a system environment according to example embodiments. Figure 27 shows a schematic diagram of signaling sequences according to example embodiments.

In particular, Figure 25 illustrates a gNB to relay UE(s) to remote UE connectivity diagram.

According thereto, as a scenario underlying example embodiments, the remote UE is connected with three relay UE(s). As a first step whenever the remote UE or UE-to- network relay UE discover each other for positioning service and after PDN connection establishment, the AMF indicates the same to the UDM/HSS that the remote UE shall be reachable via UE-to- network relay.

Figure 26 illustrates a non-roaming architecture of interconnection between 5G core (5GC) and evolved packet core (EPC) in which the call flow illustrated in Figure 27 may be implemented. Since ProSe is defined for LTE/4G network, and adaptation of ProSe in 5GS is ongoing in Rel. 17, equivalent nodes/NFs are represented for both LTE and 5GC.

As illustrated in Figure 27, and as already explained above with respect to enhancement 1.), according to example embodiments, a ProSe procedure is enhanced by introduction of step 7, where the MME/AMF provides an indication to the HSS/UDM that the remote UE is reachable via a UE-to- network relay UE.

To enable the LCS services for out of coverage UE's, according to example embodiments, the ProSe interface PC5 between the UE's is reused, which is a precondition.

LMF discovery of other proximity UEs (relay UEs) of the remote UE according to option 1.) according to example embodiments are explained with reference to Figure 28. Figure 28 (Figures 28A and 28B) shows a schematic diagram of signaling sequences according to example embodiments. In particular, Figure 28 illustrates the LMF discovery of other proximity UEs (relay UEs) of the remote UE according to example embodiments.

In brief, according to example embodiments, the LMF, upon getting a request for locating a remote UE, triggers discovery of the other proximity UEs by the remote UE via a relay UE with which the remote UE already established a PDN connection.

In detail, according to example embodiments, the GMLC, when it receives the location request from a LCS client for the UE (step 1 of Figure 28A), queries the UDM and discovers that the UE is a remote UE and served by a relay UE (steps 2 and 3 of Figure 28A).

Then, according to example embodiments, the GMLC indicates the same to it's serving AMF, and requests to share location details of the remote UE (step 4 of Figure 28A), which in turn sends the request to LMF with remote UE and serving relay UE details (step 5 of Figure 28A).

Further, according to example embodiments, the LMF, upon receiving the request to locate the remote UE, which is out of coverage, and based on LPP capabilities supported by both the relay UEs and the remote UE, decides to perform network based multi-RTT technique to locate the remote UE (before step 9 of Figure 28B).

Further, according to example embodiments, the LMF introduces a new procedure (step 9 of Figure 28B) to request the serving relay UE (to which PDN connection is established), to get the list of ProSe enabled proximity UEs of the remote UE.

Furthermore, according to example embodiments, the serving relay UE forwards this request to remote UE via a PC5 interface (step 10 of Figure 28B).

Still further, according to example embodiments, the remote UE further uses the Model B ProSe discovery method to get the ProSe enabled relay UEs in it's proximity, which are offering positioning service (steps 10, 11, 12, 13, 14, 15, 16 of Figure 28B), and sends the list to the LMF (first via relay UE using PC5 interface and later relay UE forwards the list to the LMF) (step 17 of Figure 28B).

According to example embodiments, the other relay UEs may be served by different gNBs but all are served by the same AMF. Remote UE (out of coverage UE) positioning using Relay UEs according to option 1.) according to example embodiments are explained with reference to Figures 29 and 30.

Figures 29 and 30 show schematic diagrams of signaling sequences according to example embodiments.

Namely, according to example embodiments, the LMF triggers multi-RTT measurements between the relay UEs, which are discovered as explained with reference to Figure 28, in addition to the serving relay UE, and gNBs, and estimates the relay UEs positioning (e.g. as per current 3GPP standards).

Similarly, according to example embodiments, the LMF triggers the multi-RTT measurements between the relay UEs and the remote UE.

Using minimum propagation delays estimated between at least three relay UEs and remote UE, the LMF estimates the remote UE position.

In order to perform multi-RTT between the remote UE and relay UEs, according to example embodiments, SL-PRS and SL-SRS-P signaling is introduced between the relay UE and the remote UE, as illustrated in Figure 29.

As is derivable from Figure 30, illustrating Multi-RTT positioning for remote UE with reference to relay UE(s) according to example embodiments, the LMF determines that the SL-PRS transmission points (TRP) configuration information is desired and requests the same from the Relay UE(s) (steps 1, 2, 3 of Figure 30).

Further, according to example embodiments, the LMF then requests the positioning requests from the serving Relay UE (to which PDN connection is established for positioning service as explained with reference to Figures 25 to 27) (step 4 of Figure 30), and the serving relay UE decides and in turn configures the SL-SRS-P resource set for the remote UE and provides the same SL-SRS-P configuration information to the remote UE and the LMF (step 5, 6 of Figure 30). The LMF then provides the UL information to the selected relay UEs/TRPs to perform UL measurements. The LMF also sends SL-PRS configuration details of these relay UEs to the remote UE and asks the remote UE to send it's location information (steps 7, 8, 10 of Figure 30).

Further, according to example embodiments, the remote UE then calculates SL-PRS measurements from all these selected relay UEs. Similarly, the relay UEs calculate the SL-SRS-P measurements.

Further, according to example embodiments, the LMF receives both SL-PRS and SL-SRS-P measurements from the remote UE and the relay UEs and calculates the RTT and estimates the remote UE position with reference to the relay UEs (steps 12, 13, 14 (15, 16) of Figure 30; after step 16 of Figure 30).

Finally, according to example embodiments, the LMF sends the estimated remote UE location details to the AMF, which in turn sends it to GMLC and finally to the LCS client (after step 16 of Figure 30).

Further, according to example embodiments, option 2.) may be implemented utilizing the following main steps for remote UE positioning.

1. The HSS/UDM is updated whenever a remote UE and a relay UE discovered each other and a PDN connection is established. This is explained above with reference to Figures 26 and 27 (direct communication via ProSe UE-to-network relay).

2. The LMF, upon getting a request for locating a remote UE, triggers a procedure according to option 1.) for Multi-RTT positioning between the relay UE (for which PDN connection is established) and the remote UE.

3. Along with that, a SL-AoA at the relay UE from the remote UE measurement is effected/considered to improve the accuracy. This is explained below with reference to Figure 32 (SL-SRS-P AoA positioning for remote UE with reference to relay UE(s))

Since only one relay UE is available in the proximity of the remote UE, according to example embodiments, multiple measurements are effected to enhance the accuracy of the measurements for both measurement procedures according to option 1.) and option 2.). Even if there is a single relay UE, there is a possibility to calculate the location of the remote UE with better/higher accuracy. For example, in the diagram illustrated in Figure 31, if it is considered that the remote UE does not have network coverage, in that case there is high possibility that the remote UE is in the area marked as R- UE (i.e. in an area which is covered by the ("central") relay UE but is not covered by any of the three based stations).

Figure 32 shows a schematic diagram of signaling sequences according to example embodiments, and in particular illustrates SL-SRS-P AoA positioning for a remote UE with reference to relay UE(s).

As is derivable from Figure 32, according to example embodiments, the LMF determines that the SL-SRS TRPs configuration information is desired and requests the same from the serving relay UE (to which PDN connection is established) (step 1 of Figure 32).

Further, according to example embodiments, the LMF requests the positioning request from the serving relay UE (step 2 of Figure 32), and the serving relay UE decides and in turn configures the SL-SRS-P resource set for the remote UE and provides the same SL-SRS-P configuration information to the remote UE and the LMF (steps 3 and 4 of Figure 32). The LMF then provides the UL information to the serving relay UEs/TRPs to perform UL measurements (step 5 of Figure 32). Further, according to example embodiments, the serving relay UE measures the SL-SRS-P, SL-SRS-P AoA and SL-SRS-P RSRP (optional) measurements (before step 6 of Figure 32).

Further, according to example embodiments, the LMF estimates the remote UEs position based on multiple measurements of RTT between the serving remote UE and the relay UE and multiple SL-SRS-P AoA measurements received from the relay UE (step 6 of Figure 32; after step 6 of Figure 32).

Further, according to example embodiments, the LMF sends the estimated remote UE location details to the AMF, which in turn sends it to the GMLC and finally to the LCS client (after step 6 of Figure 32).

Advantageously, according to example embodiments, the extension of the LCS services is extended to UEs which are out of network coverage by using the existing ProSe interface with/via sidelinking functionality, potentially along with the enhancements as explained above.

The above-described procedures and functions may be implemented by respective functional elements, processors, or the like, as described below.

In the foregoing exemplary description of the network entity, only the units that are relevant for understanding the principles of the disclosure have been described using functional blocks. The network entity may comprise further units that are necessary for its respective operation. However, a description of these units is omitted in this specification. The arrangement of the functional blocks of the devices is not construed to limit the disclosure, and the functions may be performed by one block or further split into sub-blocks.

When in the foregoing description it is stated that the apparatus, i.e. network entity (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that a (i.e. at least one) processor or corresponding circuitry, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured circuitry or means for performing the respective function (i.e. the expression "unit configured to" is construed to be equivalent to an expression such as "means for").

In Figure 34, an alternative illustration of apparatuses according to example embodiments is depicted. As indicated in Figure 34, according to example embodiments, the apparatus (network entity) 10' (corresponding to the location management function entity 10) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. Further, according to example embodiments, the apparatus (network entity) 30' (corresponding to the first (remote) terminal 30) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. Further, according to example embodiments, the apparatus (network entity) 50' (corresponding to the (relay) terminal 50) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. Further, according to example embodiments, the apparatus (network entity) 70' (corresponding to the mobility management function entity 70) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. Further, according to example embodiments, the apparatus (network entity) 80' (corresponding to the subscription management function entity 80) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. Further, according to example embodiments, the apparatus (network entity) 90' (corresponding to the location function entity 90) comprises a processor 341, a memory 342 and an interface 343, which are connected by a bus 344 or the like. The apparatuses 10', 30', 50', 70', 80', 90' may be connected with other apparatuses (e.g. respectively other of the apparatuses 10', 30', 50', 70', 80', 90') via link 345, respectively. The processor 341 and/or the interface 343 may also include a modem or the like to facilitate communication over a (hardwire or wireless) link, respectively. The interface 343 may include a suitable transceiver coupled to one or more antennas or communication means for (hardwire or wireless) communications with the linked or connected device(s), respectively. The interface 343 is generally configured to communicate with at least one other apparatus, i.e. the interface thereof.

The memory 342 may store respective programs assumed to include program instructions or computer program code that, when executed by the respective processor, enables the respective electronic device or apparatus to operate in accordance with the example embodiments.

In general terms, the respective devices/apparatuses (and/or parts thereof) may represent means for performing respective operations and/or exhibiting respective functionalities, and/or the respective devices (and/or parts thereof) may have functions for performing respective operations and/or exhibiting respective functionalities.

When in the subsequent description it is stated that the processor (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that at least one processor, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured means for performing the respective function (i.e. the expression "processor configured to [cause the apparatus to] perform xxx-ing" is construed to be equivalent to an expression such as "means for xxx-ing").

According to example embodiments, an apparatus representing the location management function entity 10 (of a mobile network) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal (thus the apparatus comprising corresponding means for receiving), and to perform estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals (thus the apparatus comprising corresponding means for estimating), wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to example embodiments, an apparatus representing the first (remote) terminal 30 (out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform receiving respective sidelink positioning reference signals from each of at least one of a plurality of third terminals (thus the apparatus comprising corresponding means for receiving), to perform sampling respective times of receipt of said respective sidelink positioning reference signals (thus the apparatus comprising corresponding means for sampling), to perform transmitting respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals (thus the apparatus comprising corresponding means for transmitting), to perform sampling respective times of transmission of said respective sidelink sounding reference signals, to perform transmitting said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and to perform transmitting respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

According to example embodiments, an apparatus representing the (relay) terminal 50 (connected to at least one base station of base stations of a mobile network) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform transmitting a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal (thus the apparatus comprising corresponding means for transmitting), to perform sampling a time of transmission of said sidelink positioning reference signal (thus the apparatus comprising corresponding means for sampling), to perform receiving a sidelink sounding reference signal from said first terminal (thus the apparatus comprising corresponding means for receiving), to perform sampling a time of receipt of said sidelink sounding reference signal, to perform transmitting said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and to perform transmitting said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

According to example embodiments, an apparatus representing the mobility management function entity 70 (of a mobile network) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform receiving, from a second terminal connected to at least one base station of base stations of said mobile network and providing through- connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal (thus the apparatus comprising corresponding means for receiving), and to perform transmitting, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal (thus the apparatus comprising corresponding means for transmitting).

According to example embodiments, an apparatus representing the subscription management function entity 80 (of a mobile network) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform receiving an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal (thus the apparatus comprising corresponding means for receiving), to perform receiving, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and to perform transmitting, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal (thus the apparatus comprising corresponding means for transmitting).

According to example embodiments, an apparatus representing the location function entity 90 (of a mobile network) comprises at least one processor 341, at least one memory 342 including computer program code, and at least one interface 343 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 341, with the at least one memory 342 and the computer program code) is configured to perform transmitting, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal (thus the apparatus comprising corresponding means for transmitting), to perform receiving, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal (thus the apparatus comprising corresponding means for receiving), and to perform transmitting, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal. For further details regarding the operability/functionality of the individual apparatuses, reference is made to the above description in connection with any one of Figures 1 to 33, respectively.

For the purpose of the present disclosure as described herein above, it should be noted that

- method steps likely to be implemented as software code portions and being run using a processor at a network server or network entity (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module(s) thereof, (e.g., devices carrying out the functions of the apparatuses according to the embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;

- devices, units or means (e.g. the above-defined network entity or network register, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved; - an apparatus like the user equipment and the network entity /network register may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present disclosure. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

The present disclosure also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are applicable.

In view of the above, there are provided measures for network assisted positioning for out of coverage terminals. Such measures exemplarily comprise, at a of a location management function entity of a mobile network, receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

Even though the disclosure is described above with reference to the examples according to the accompanying drawings, it is to be understood that the disclosure is not restricted thereto. Rather, it is apparent to those skilled in the art that the present disclosure can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

List of acronyms and abbreviations 3GPP Third Generation Partnership Project

5GC 5G core (network)

AMF access and mobility management function

EPC evolved packet core

GCS global coordinate system

GMLC gateway mobile location centre

GPSI generic public subscription identifier

HSS home subscriber server

LCS (rotated) local coordinate system

LCS location services

LMF location management function

LPP LTE positioning protocol

LTE Long Term Evolution

MME mobility management entity

MT-LR mobile terminated location request

NF network function

PDN packet data network

PLMN public land mobile network

ProSe proximity-services

PRS positioning reference signal

RTT round trip time

SL sidelink

SL-AoA Sidelink - Angle of Arrival

SRS sounding reference signal

SUPI subscription permanent identifier

TRP transmission point

UDM unified data management

UE user equipment

UL-AoA uplink angle-of-arrival

Claims

1. A method of a location management function entity of a mobile network, the method comprising receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

2. The method according to claim 1, further comprising receiving respective times of transmission of respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receiving respective times of receipt of said respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receiving respective times of transmission of respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, receiving respective times of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, and calculating said respective round trip times between each of said at least one of said plurality of third terminals and said first terminal based on said respective times of transmission of said respective sidelink positioning reference signals, said respective times of receipt of said respective sidelink positioning reference signals, said respective times of transmission of said respective sidelink sounding reference signals, and said respective times of receipt of said respective sidelink sounding reference signals.

3. The method according to claim 2, further comprising receiving respective angles of arrival of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, wherein at said estimating, said location of said first terminal is estimated further based on said respective angles of arrival of receipt of said respective sidelink sounding reference signals.

4. The method according to any of claims 1 to 3, further comprising transmitting, towards each of said at least one of said plurality of third terminals, respective sidelink positioning reference signal configuration information.

5. The method according to any of claims 1 to 4, further comprising transmitting, towards said second terminal, a request for positioning said first terminal.

6. The method according to any of claims 1 to 5, further comprising receiving, from said second terminal, sidelink sounding reference signal configuration information of said first terminal, and transmitting, towards each of said at least one of said plurality of third terminals, said sidelink sounding reference signal configuration information of said first terminal.

7. The method according to any of claims 1 to 6, further comprising transmitting, towards said first terminal, via said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

8. The method according to claim 7, further comprising receiving said list of proximity terminal candidates, wherein said list of proximity terminal candidates includes said plurality of third terminals.

9. The method according to claim 8, further comprising verifying, for each proximity terminal candidate of said list of proximity terminal candidates, whether said respective proximity terminal candidate belongs to a predetermined public land mobile network and is served by a predetermined mobility management function entity, and considering each proximity terminal candidate of said list of proximity terminal candidates which belongs to said predetermined public land mobile network and is served by said predetermined mobility management function entity as one of said plurality of third terminals.

10. The method according to any of claims 1 to 9, further comprising triggering identification of said respective locations of each of said at least one of said plurality of third terminals.

11. A method of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the method comprising receiving respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling respective times of receipt of said respective sidelink positioning reference signals, transmitting respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, sampling respective times of transmission of said respective sidelink sounding reference signals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and transmitting respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

12. The method according to claim 11, further comprising receiving a request for information on a location of said first terminal.

13. The method according to claim 11 or 12, further comprising receiving sidelink sounding reference signal configuration information of said first terminal, wherein in relation to said transmitting said respective sidelink sounding reference signals, the method further comprises considering said sidelink sounding reference signal configuration information of said first terminal.

14. The method according to any of claims 11 to 13, further comprising receiving, from said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

15. The method according to claim 14, further comprising transmitting, to each of proximity terminals in a proximity of said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, and receiving, from at least one of said proximity terminals, a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

16. The method according to claim 15, further comprising transmitting a list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received.

17. The method according to claim 16, wherein said list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received corresponds to said plurality of third terminals.

18. The method according to claim 12, further comprising calculating said location of said first terminal, and transmitting said information on said location of said first terminal to said second terminal.

19. A method of a terminal connected to at least one base station of base stations of a mobile network, the method comprising transmitting a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, sampling a time of transmission of said sidelink positioning reference signal, receiving a sidelink sounding reference signal from said first terminal, sampling a time of receipt of said sidelink sounding reference signal, transmitting said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and transmitting said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

20. The method according to claim 19, further comprising sampling an angle of arrival of receipt of said sidelink sounding reference signal, and transmitting said angle of arrival of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

21. The method according to claim 19 or 20, further comprising receiving, from said location management function entity of said mobile network, sidelink positioning reference signal configuration information, wherein in relation to said transmitting said sidelink positioning reference signal, the method further comprises considering said sidelink positioning reference signal configuration information.

22. The method according to any of claims 19 to 21, further comprising receiving, from said location management function entity of said mobile network, sidelink sounding reference signal configuration information of said first terminal.

23. The method according to any of claims 19 to 22, further comprising receiving, from said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, determining that said terminal is connected to said mobile network and provides said positioning assistance service, and transmitting, to said first terminal, a confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

24. The method according to any of claims 19 to 23, wherein said terminal is said second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal.

25. The method according to claim 24, further comprising receiving, from said location management function entity of said mobile network, a request for positioning said first terminal, determining sidelink sounding reference signal configuration information of said first terminal, transmitting said sidelink sounding reference signal configuration information of said first terminal to said first terminal, and transmitting said sidelink sounding reference signal configuration information of said first terminal to said location management function entity of said mobile network.

26. The method according to claim 24 or 25, further comprising transmitting a request for information on a location of said first terminal to said first terminal.

27. The method according to claim 26, further comprising receiving, from said first terminal, respective times of receipt of respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, receiving, from said first terminal, respective times of transmission of respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said location management function entity of said mobile network, and transmitting said respective times of transmission of said respective sidelink sounding reference signals to said location management function entity of said mobile network, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

28. The method according to any of claims 24 to 27, further comprising receiving, from said location management function entity of said mobile network, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service, and transmitting said request for said list of proximity terminal candidates to said first terminal.

29. The method according to any of claims 24 to 28, further comprising receiving, from said first terminal, a list including each of proximity terminals from which a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received by said first terminal, and transmitting said list to said location management function entity of said mobile network.

30. The method according to claim 29, wherein said list corresponds to said plurality of third terminals.

31. The method according to claim 26, further comprising receiving, from said first terminal, said information on said location of said first terminal, and forwarding said information on said location of said first terminal towards a mobility management function entity of said mobile network.

32. A method of a mobility management function entity of a mobile network, the method comprising receiving, from a second terminal connected to at least one base station of base stations of said mobile network and providing through- connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

33. The method according to claim 32, further comprising receiving, from a location function entity of said mobile network, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal, and transmitting, to a location management function entity of said mobile network, a request for locating said first terminal.

34. A method of a subscription management function entity of a mobile network, the method comprising receiving an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, receiving, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

35. A method of a location function entity of a mobile network, the method comprising transmitting, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, receiving, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and transmitting, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

36. An apparatus of a location management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating circuitry configured to estimate a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

37. The apparatus according to claim 36, further comprising receiving circuitry configured to receive respective times of transmission of respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receive respective times of receipt of said respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receive respective times of transmission of respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, and to receive respective times of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, and calculating circuitry configured to calculate said respective round trip times between each of said at least one of said plurality of third terminals and said first terminal based on said respective times of transmission of said respective sidelink positioning reference signals, said respective times of receipt of said respective sidelink positioning reference signals, said respective times of transmission of said respective sidelink sounding reference signals, and said respective times of receipt of said respective sidelink sounding reference signals.

38. The apparatus according to claim 37, further comprising receiving circuitry configured to receive respective angles of arrival of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, wherein said estimating circuitry is configured to estimate said location of said first terminal further based on said respective angles of arrival of receipt of said respective sidelink sounding reference signals.

39. The apparatus according to any of claims 36 to 38, further comprising transmitting circuitry configured to transmit, towards each of said at least one of said plurality of third terminals, respective sidelink positioning reference signal configuration information.

40. The apparatus according to any of claims 36 to 39, further comprising transmitting circuitry configured to transmit, towards said second terminal, a request for positioning said first terminal.

41. The apparatus according to any of claims 36 to 40, further comprising receiving circuitry configured to receive, from said second terminal, sidelink sounding reference signal configuration information of said first terminal, and transmitting circuitry configured to transmit, towards each of said at least one of said plurality of third terminals, said sidelink sounding reference signal configuration information of said first terminal.

42. The apparatus according to any of claims 36 to 41, further comprising transmitting circuitry configured to transmit, towards said first terminal, via said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

43. The apparatus according to claim 42, further comprising receiving circuitry configured to receive said list of proximity terminal candidates, wherein said list of proximity terminal candidates includes said plurality of third terminals.

44. The apparatus according to claim 43, further comprising verifying circuitry configured to verify, for each proximity terminal candidate of said list of proximity terminal candidates, whether said respective proximity terminal candidate belongs to a predetermined public land mobile network and is served by a predetermined mobility management function entity, and considering circuitry configured to consider each proximity terminal candidate of said list of proximity terminal candidates which belongs to said predetermined public land mobile network and is served by said predetermined mobility management function entity as one of said plurality of third terminals.

45. The apparatus according to any of claims 36 to 44, further comprising triggering circuitry configured to trigger identification of said respective locations of each of said at least one of said plurality of third terminals.

46. An apparatus of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the apparatus comprising receiving circuitry configured to receive respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling circuitry configured to sample respective times of receipt of said respective sidelink positioning reference signals, transmitting circuitry configured to transmit respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, wherein said sampling circuitry is configured to sample respective times of transmission of said respective sidelink sounding reference signals, wherein said transmitting circuitry is configured to transmit said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and to transmit respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

47. The apparatus according to claim 46, further comprising receiving circuitry configured to receive a request for information on a location of said first terminal.

48. The apparatus according to claim 46 or 47, further comprising receiving circuitry configured to receive sidelink sounding reference signal configuration information of said first terminal, and considering circuitry configured to consider said sidelink sounding reference signal configuration information of said first terminal.

49. The apparatus according to any of claims 46 to 48, further comprising receiving circuitry configured to receive, from said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

50. The apparatus according to claim 49, further comprising transmitting circuitry configured to transmit, to each of proximity terminals in a proximity of said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, and receiving circuitry configured to receive, from at least one of said proximity terminals, a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

51. The apparatus according to claim 50, further comprising transmitting circuitry configured to transmit a list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received.

52. The apparatus according to claim 51, wherein said list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received corresponds to said plurality of third terminals.

53. The apparatus according to claim 47, further comprising calculating circuitry configured to calculate said location of said first terminal, and transmitting circuitry configured to transmit said information on said location of said first terminal to said second terminal.

54. An apparatus of a terminal connected to at least one base station of base stations of a mobile network, the apparatus comprising transmitting circuitry configured to transmit a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, sampling circuitry configured to sample a time of transmission of said sidelink positioning reference signal, receiving circuitry configured to receive a sidelink sounding reference signal from said first terminal, wherein said sampling circuitry is configured to sample a time of receipt of said sidelink sounding reference signal, wherein said transmitting circuitry is configured to transmit said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and to transmit said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

55. The apparatus according to claim 54, further comprising sampling circuitry configured to sample an angle of arrival of receipt of said sidelink sounding reference signal, and transmitting circuitry configured to transmit said angle of arrival of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

56. The apparatus according to claim 54 or 55, further comprising receiving circuitry configured to receive, from said location management function entity of said mobile network, sidelink positioning reference signal configuration information, and considering circuitry configured to consider said sidelink positioning reference signal configuration information.

57. The apparatus according to any of claims 54 to 56, further comprising receiving circuitry configured to receive, from said location management function entity of said mobile network, sidelink sounding reference signal configuration information of said first terminal.

58. The apparatus according to any of claims 54 to 57, further comprising receiving circuitry configured to receive, from said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, determining circuitry configured to determine that said terminal is connected to said mobile network and provides said positioning assistance service, and transmitting circuitry configured to transmit, to said first terminal, a confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

59. The apparatus according to any of claims 54 to 58, wherein said terminal is said second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal.

60. The apparatus according to claim 59, further comprising receiving circuitry configured to receive, from said location management function entity of said mobile network, a request for positioning said first terminal, determining circuitry configured to determine sidelink sounding reference signal configuration information of said first terminal, transmitting circuitry configured to transmit said sidelink sounding reference signal configuration information of said first terminal to said first terminal, and to transmit said sidelink sounding reference signal configuration information of said first terminal to said location management function entity of said mobile network.

61. The apparatus according to claim 59 or 60, further comprising transmitting circuitry configured to transmit a request for information on a location of said first terminal to said first terminal.

62. The apparatus according to claim 61, further comprising receiving circuitry configured to receive, from said first terminal, respective times of receipt of respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, and to receive, from said first terminal, respective times of transmission of respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, and transmitting circuitry configured to transmit said respective times of receipt of said respective sidelink positioning reference signals to said location management function entity of said mobile network, and to transmit said respective times of transmission of said respective sidelink sounding reference signals to said location management function entity of said mobile network, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

63. The apparatus according to any of claims 59 to 62, further comprising receiving circuitry configured to receive, from said location management function entity of said mobile network, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service, and transmitting circuitry configured to transmit said request for said list of proximity terminal candidates to said first terminal.

64. The apparatus according to any of claims 59 to 63, further comprising receiving circuitry configured to receive, from said first terminal, a list including each of proximity terminals from which a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received by said first terminal, and transmitting circuitry configured to transmit said list to said location management function entity of said mobile network.

65. The apparatus according to claim 64, wherein said list corresponds to said plurality of third terminals.

66. The apparatus according to claim 61, further comprising receiving circuitry configured to receive, from said first terminal, said information on said location of said first terminal, and forwarding circuitry configured to forward said information on said location of said first terminal towards a mobility management function entity of said mobile network.

67. An apparatus of a mobility management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive, from a second terminal connected to at least one base station of base stations of said mobile network and providing through-connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting circuitry configured to transmit, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

68. The apparatus according to claim 67, further comprising receiving circuitry configured to receive, from a location function entity of said mobile network, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal, and transmitting circuitry configured to transmit, to a location management function entity of said mobile network, a request for locating said first terminal.

69. An apparatus of a subscription management function entity of a mobile network, the apparatus comprising receiving circuitry configured to receive an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, and to receive, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting circuitry configured to transmit, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

70. An apparatus of a location function entity of a mobile network, the apparatus comprising transmitting circuitry configured to transmit, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, and receiving circuitry configured to receive, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and wherein said transmitting circuitry is configured to transmit, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

71. An apparatus of a location management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving a request for locating a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, and estimating a location of said first terminal based on respective round trip times between each of at least one of a plurality of third terminals and said first terminal and on respective locations of each of said at least one of said plurality of third terminals, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

72. The apparatus according to claim 71, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving respective times of transmission of respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receiving respective times of receipt of said respective sidelink positioning reference signals from each of said at least one of said plurality of third terminals to said first terminal, receiving respective times of transmission of respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, receiving respective times of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, and calculating said respective round trip times between each of said at least one of said plurality of third terminals and said first terminal based on said respective times of transmission of said respective sidelink positioning reference signals, said respective times of receipt of said respective sidelink positioning reference signals, said respective times of transmission of said respective sidelink sounding reference signals, and said respective times of receipt of said respective sidelink sounding reference signals.

73. The apparatus according to claim 72, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving respective angles of arrival of receipt of said respective sidelink sounding reference signals from said first terminal to each of said at least one of said plurality of third terminals, wherein at said estimating, said location of said first terminal is estimated further based on said respective angles of arrival of receipt of said respective sidelink sounding reference signals.

74. The apparatus according to any of claims 71 to 73, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting, towards each of said at least one of said plurality of third terminals, respective sidelink positioning reference signal configuration information.

75. The apparatus according to any of claims 71 to 74, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting, towards said second terminal, a request for positioning said first terminal.

76. The apparatus according to any of claims 71 to 75, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said second terminal, sidelink sounding reference signal configuration information of said first terminal, and transmitting, towards each of said at least one of said plurality of third terminals, said sidelink sounding reference signal configuration information of said first terminal.

77. The apparatus according to any of claims 71 to 76, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting, towards said first terminal, via said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

78. The apparatus according to claim 77, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving said list of proximity terminal candidates, wherein said list of proximity terminal candidates includes said plurality of third terminals.

79. The apparatus according to claim 78, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : verifying, for each proximity terminal candidate of said list of proximity terminal candidates, whether said respective proximity terminal candidate belongs to a predetermined public land mobile network and is served by a predetermined mobility management function entity, and considering each proximity terminal candidate of said list of proximity terminal candidates which belongs to said predetermined public land mobile network and is served by said predetermined mobility management function entity as one of said plurality of third terminals.

80. The apparatus according to any of claims 71 to 79, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : triggering identification of said respective locations of each of said at least one of said plurality of third terminals.

81. An apparatus of a first terminal out of radio coverage of base stations of a mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, sampling respective times of receipt of said respective sidelink positioning reference signals, transmitting respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, sampling respective times of transmission of said respective sidelink sounding reference signals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said second terminal, and transmitting respective times of transmission of said respective sidelink sounding reference signals to said second terminal, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

82. The apparatus according to claim 81, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving a request for information on a location of said first terminal.

83. The apparatus according to claim 81 or 82, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving sidelink sounding reference signal configuration information of said first terminal, wherein in relation to said transmitting said respective sidelink sounding reference signals, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : considering said sidelink sounding reference signal configuration information of said first terminal.

84. The apparatus according to any of claims 81 to 83, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said second terminal, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service.

85. The apparatus according to claim 84, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting, to each of proximity terminals in a proximity of said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, and receiving, from at least one of said proximity terminals, a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

86. The apparatus according to claim 85, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting a list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received.

87. The apparatus according to claim 86, wherein said list including each of said proximity terminals from which said respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received corresponds to said plurality of third terminals.

88. The apparatus according to claim 82, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : calculating said location of said first terminal, and transmitting said information on said location of said first terminal to said second terminal.

89. An apparatus of a terminal connected to at least one base station of base stations of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting a sidelink positioning reference signal to a first terminal out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal connected to at least one base station of said base stations of said mobile network and providing through-connection to said mobile network for said first terminal, sampling a time of transmission of said sidelink positioning reference signal, receiving a sidelink sounding reference signal from said first terminal, sampling a time of receipt of said sidelink sounding reference signal, transmitting said time of transmission of said sidelink positioning reference signal to a location management function entity of said mobile network, and transmitting said time of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

90. The apparatus according to claim 89, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : sampling an angle of arrival of receipt of said sidelink sounding reference signal, and transmitting said angle of arrival of receipt of said sidelink sounding reference signal to said location management function entity of said mobile network.

91. The apparatus according to claim 89 or 90, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said location management function entity of said mobile network, sidelink positioning reference signal configuration information, wherein in relation to said transmitting said sidelink positioning reference signal, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : considering said sidelink positioning reference signal configuration information.

92. The apparatus according to any of claims 89 to 91, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said location management function entity of said mobile network, sidelink sounding reference signal configuration information of said first terminal.

93. The apparatus according to any of claims 89 to 92, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said first terminal, an enquiry for proximity terminal candidates required to be connected to said mobile network and to provide said positioning assistance service, determining that said terminal is connected to said mobile network and provides said positioning assistance service, and transmitting, to said first terminal, a confirmation indicating connectedness to said mobile network and provision said positioning assistance service.

94. The apparatus according to any of claims 89 to 93, wherein said terminal is said second terminal connected to at least one base station of said base stations of said mobile network and providing through- connection to said mobile network for said first terminal.

95. The apparatus according to claim 94, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said location management function entity of said mobile network, a request for positioning said first terminal, determining sidelink sounding reference signal configuration information of said first terminal, transmitting said sidelink sounding reference signal configuration information of said first terminal to said first terminal, and transmitting said sidelink sounding reference signal configuration information of said first terminal to said location management function entity of said mobile network.

96. The apparatus according to claim 94 or 95, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting a request for information on a location of said first terminal to said first terminal.

97. The apparatus according to claim 96, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said first terminal, respective times of receipt of respective sidelink positioning reference signals from each of at least one of a plurality of third terminals, receiving, from said first terminal, respective times of transmission of respective sidelink sounding reference signals to each of said at least one of said plurality of third terminals, transmitting said respective times of receipt of said respective sidelink positioning reference signals to said location management function entity of said mobile network, and transmitting said respective times of transmission of said respective sidelink sounding reference signals to said location management function entity of said mobile network, wherein said plurality of third terminals includes said second terminal, and wherein each of said plurality of third terminals is connected to at least one respective base station of said base stations of said mobile network.

98. The apparatus according to any of claims 94 to 97, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said location management function entity of said mobile network, a request for a list of proximity terminal candidates reachable by said first terminal which are connected to said mobile network and provide a positioning assistance service, and transmitting said request for said list of proximity terminal candidates to said first terminal.

99. The apparatus according to any of claims 94 to 98, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said first terminal, a list including each of proximity terminals from which a respective confirmation indicating connectedness to said mobile network and provision said positioning assistance service is received by said first terminal, and transmitting said list to said location management function entity of said mobile network.

100. The apparatus according to claim 99, wherein said list corresponds to said plurality of third terminals.

101. The apparatus according to claim 96, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from said first terminal, said information on said location of said first terminal, and forwarding said information on said location of said first terminal towards a mobility management function entity of said mobile network.

102. An apparatus of a mobility management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from a second terminal connected to at least one base station of base stations of said mobile network and providing through- connection to said mobile network for a first terminal out of radio coverage of said base stations of said mobile network, an indication that said first terminal is connected to said mobile network through said second terminal, and transmitting, towards a subscription management function entity of said mobile network, an indication that said first terminal is reachable via said second terminal.

103. The apparatus according to claim 102, wherein the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving, from a location function entity of said mobile network, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal, and transmitting, to a location management function entity of said mobile network, a request for locating said first terminal.

104. An apparatus of a subscription management function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving an indication that a first terminal is reachable via a second terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through said second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through- connection to said mobile network for said first terminal, receiving, from a location function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for said first terminal, and transmitting, to said location function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal.

105. An apparatus of a location function entity of a mobile network, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : transmitting, to a subscription management function entity of said mobile network, a request for a mobility management function entity of said mobile network responsible for a first terminal, wherein said first terminal is out of radio coverage of base stations of said mobile network and connected to said mobile network through a second terminal, and said second terminal is connected to at least one base station of base stations of said mobile network and provides through-connection to said mobile network for said first terminal, receiving, from said subscription management function entity of said mobile network, a message indicative of that said first terminal is reachable via said second terminal and a mobility management function entity of said mobile network responsible for said second terminal, and transmitting, to said mobility management function entity of said mobile network responsible for said second terminal, a request for position information on said first terminal indicative of that said first terminal is reachable via said second terminal.

106. A computer program product comprising computer-executable computer program code which, when the program is run on a computer, is configured to cause the computer to carry out the method according to any one of claims 1 to 10, 11 to 18, 19 to 31, 32 to 33, 34 or 35.

107. The computer program product according to claim 106, wherein the computer program product comprises a computer-readable medium on which the computer-executable computer program code is stored, and/or wherein the program is directly loadable into an internal memory of the computer or a processor thereof.