WO2023232431A1

WO2023232431A1 - Positioning reference unit selection for sidelink positioning

Info

Publication number: WO2023232431A1
Application number: PCT/EP2023/062699
Authority: WO
Inventors: Oana-Elena Barbu; Prajwal KESHAVAMURTHY; Diomidis Michalopoulos
Original assignee: Nokia Technologies Oy
Priority date: 2022-06-02
Filing date: 2023-05-12
Publication date: 2023-12-07

Abstract

This document discloses a solution for facilitating positioning of a terminal device. According to an aspect, a method comprises: establishing (300) a sidelink positioning session with at least one anchor device (101, 102); causing (302) transmission of a positioning assistance request message during the sidelink positioning session, comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving (304), from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; and indicating (710) the selection to the selected at least one positioning reference unit.

Description

Positioning Reference Unit Selection for Sidelink Positioning

Field

Various embodiments described herein relate to the field of wireless communications and, particularly, to utilizing sidelink communications for positioning a terminal device of a cellular communication system.

Background

A modern cellular communication system provides capability for terminal devices to communicate directly with one another over sidelink connections without the need for routing traffic via a base station. Two resource allocation modes have been specified in 3GPP (Third Generation Partnership Project), and a terminal device may be configured with one of them to perform its sidelink transmissions to one or more other terminal devices. In a first mode, a sidelink transmission resource is assigned by a network such as a serving access node to the terminal device, while in a second mode the terminal device is able to autonomously select its sidelink transmission resources. The sidelink communications may be used for providing various communication services, and a positioning service is one of such services. In the positioning service, a terminal device having a need to determine its location may use one or more other terminal devices (anchor terminal devices) in close proximity for the positioning. Such an anchor device may be a mobile terminal device or a road-side unit at a fixed location.

A concept of positioning reference units (PRU) has been introduced, where a terminal device is positioned by using PRUs within a proximity of the terminal device. The locations of the PRUs may be known beforehand, e.g. be fixed, and they may help the terminal device in the positioning. The PRU may be distinguished from the anchor terminal device in the context of sidelink positioning so that the measurements may be conducted for a positioning reference signal communicated with the anchor terminal device. In other words, there may be no positioning reference signal transmission and measurement between the terminal device being positioning and the PRU. The PRU may measure the positioning reference signal communicated between the PRU and the anchor terminal device, or the PRU may provide other assistance data for the sidelink positioning carried out by the terminal device being positioned. A challenge with using the PRUs is that it would be efficient to select only PRU(s) that are truly required for positioning the terminal device. Brief description

Some aspects of the invention are defined by the independent claims.

Some embodiments of the invention are defined in the dependent claims.

The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention. Some aspects of the disclosure are defined by the independent claims.

According to an aspect, there is provided an apparatus comprising means for performing: establishing a sidelink positioning session with at least one anchor device; causing transmission of a positioning assistance request message during the sidelink positioning session, comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving, from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating the selection to the selected at least one positioning reference unit. In an embodiment, the apparatus further comprises means for communicating at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

In an embodiment, the means are configured to: receive the at least one positioning reference signal from the at least one anchor device and measure the positioning reference signal; receive said requested assistance data from the selected at least one positioning reference unit; and estimate the location of the apparatus on the basis of the measured positioning reference signal and the received assistance data.

In an embodiment, the means are configured to: receive, from the at least one anchor device during the establishment of the sidelink positioning session, information on whether or not assistance data has been needed in an earlier positioning session with the at least one anchor device; cause the transmission of the positioning assistance request upon determining on the basis of the information that said another terminal device has needed the assistance data in the positioning session with the at least one anchor device.

In an embodiment, the at least one anchor device comprises a plurality of anchor devices, and wherein the means are configured to receive said information from the plurality of anchor devices and to configure the selected at least one positioning reference unit to provide the assistance data only for such an anchor device that has informed the need for the assistance data.

In an embodiment, the means are configured to select for the sidelink positioning session multiple anchor devices that have informed the need for the assistance data, and to insert into the positioning assistance request message an identifier of each anchor device that has informed the need for the assistance data.

In an embodiment, the positioning assistance request comprises at least one information element indicating at least one of the at least one anchor device for which the assistance data is requested, and wherein the positioning assistance response indicates capability to measure at least one positioning reference signal and to generate the assistance data associated with the indicated at least one anchor device, and wherein the means are configured to select for the sidelink positioning session a positioning reference unit capable of measuring and generating the assistance data.

In an embodiment, the selected at least one positioning reference unit comprises a terminal device.

In an embodiment, the positioning assistance response indicates at least one condition under which the respective positioning reference unit is capable of providing the assistance data, and wherein the means are configured to perform the selection of the at least one positioning reference unit on the basis of the at least one condition.

In an embodiment, the positioning assistance request specifies multiple types of assistance data requested for the positioning session, and wherein the positioning assistance response indicates which type or types of the requested assistance data the respective positioning reference unit is capable of providing, and wherein the means are configured to perform the selection of the at least one positioning reference unit such that the selected at least one positioning reference unit is capable of providing all types of assistance data requested for the positioning session.

According to an aspect, there is provided an apparatus for a positioning reference unit, comprising means for performing: receiving a positioning assistance request message from a terminal device, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting to the terminal device a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving from the terminal device a message indicating that the apparatus has been selected as a positioning reference unit for the sidelink positioning session; receiving a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; and generating, on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the terminal device or to the at least one anchor device.

In an embodiment, the positioning assistance request message comprises at least one information element indicating the at least one anchor device, and wherein the positioning assistance request message or the message indicating the selection of the apparatus indicates a configuration of the positioning reference signal.

In an embodiment, the means are configured, upon receiving the positioning assistance request message, to determine at least one condition under which the apparatus is capable of providing the assistance data and indicate the at least one condition in the positioning assistance response message.

According to an aspect, there is provided an apparatus for an anchor device, comprising means for performing: storing information on that assistance data has been needed in at least one sidelink positioning session conducted with the apparatus; receiving, from a terminal device, a request for establishing a sidelink positioning session; transmitting a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the apparatus; and receiving, from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration.

In an embodiment, any one of the above-described means comprises at least one processor and at least one memory storing instructions that cause said performance of the apparatus.

According to an aspect, there is provided a method comprising: establishing, by a terminal device, a sidelink positioning session with at least one anchor device; causing, by the terminal device, transmission of a positioning assistance request message during the sidelink positioning session, the positioning assistance request message comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving, by the terminal device from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, by the terminal device, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating, by the terminal device, the selection to the selected at least one positioning reference unit; and communicating, by the terminal device, at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

In an embodiment, the method comprises receiving the at least one positioning reference signal from the at least one anchor device and measuring the positioning reference signal; receiving said requested assistance data from the selected at least one positioning reference unit; and estimating the location of the apparatus on the basis of the measured positioning reference signal and the received assistance data.

In an embodiment, the method comprises receiving, from the at least one anchor device during the establishment of the sidelink positioning session, information on whether or not assistance data has been needed in an earlier positioning session with the at least one anchor device; causing the transmission of the positioning assistance request upon determining on the basis of the information that said another terminal device has needed the assistance data in the positioning session with the at least one anchor device.

In an embodiment, the at least one anchor device comprises a plurality of anchor devices, and the method comprises receiving said information from the plurality of anchor devices and configuring the selected at least one positioning reference unit to provide the assistance data only for such an anchor device that has informed the need for the assistance data.

In an embodiment, the method comprises selecting for the sidelink positioning session multiple anchor devices that have informed the need for the assistance data, and inserting into the positioning assistance request message an identifier of each anchor device that has informed the need for the assistance data.

In an embodiment, the positioning assistance request comprises at least one information element indicating at least one of the at least one anchor device for which the assistance data is requested, and the positioning assistance response indicates capability to measure at least one positioning reference signal and to generate the assistance data associated with the indicated at least one anchor device, and method comprises selecting for the sidelink positioning session a positioning reference unit capable of measuring and generating the assistance data.

In an embodiment, the positioning assistance response indicates at least one condition under which the respective positioning reference unit is capable of providing the assistance data, and the method comprises performing the selection of the at least one positioning reference unit on the basis of the at least one condition.

In an embodiment, the positioning assistance request specifies multiple types of assistance data requested for the positioning session, and the positioning assistance response indicates which type or types of the requested assistance data the respective positioning reference unit is capable of providing, and the method comprises performing the selection of the at least one positioning reference unit such that the selected at least one positioning reference unit is capable of providing all types of assistance data requested for the positioning session.

According to an aspect, there is provided a method comprising: receiving, by a positioning reference unit, a positioning assistance request message from a terminal device, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting, by the positioning reference unit to the terminal device, a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving, by the positioning reference unit from the terminal device, a message indicating that the positioning reference unit has been selected as a positioning reference unit for the sidelink positioning session; receiving, by the positioning reference unit, a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; and generating, by the positioning reference unit on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the terminal device or to the at least one anchor device.

In an embodiment, the positioning assistance request message comprises at least one information element indicating the at least one anchor device, and the positioning assistance request message or the message indicating the selection of the apparatus indicates a configuration of the positioning reference signal.

In an embodiment, the method comprises: upon receiving the positioning assistance request message, determining at least one condition under which the positioning reference unit is capable of providing the assistance data and indicating the at least one condition in the positioning assistance response message.

According to an aspect, there is provided a method comprising: storing, by an anchor device, information on that assistance data has been needed in at least one sidelink positioning session conducted with the anchor device; receiving, by the anchor device from a terminal device, a request for establishing a sidelink positioning session; transmitting, by the anchor device, a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the anchor device; and receiving, by the anchor device from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration.

According to an aspect, there is provided a computer program product embodied on a computer-readable medium and comprising a computer program code readable by a computer for a terminal device, wherein the computer program code configures the computer to carry out a computer process comprising: establishing a sidelink positioning session with at least one anchor device; causing transmission of a positioning assistance request message during the sidelink positioning session, comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving, from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating the selection to the selected at least one positioning reference unit. In an embodiment, the computer process further comprises causing communication of at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

According to an aspect, there is provided a computer program product embodied on a computer-readable medium and comprising a computer program code readable by a computer for a positioning reference unit, wherein the computer program code configures the computer to carry out a computer process comprising: receiving a positioning assistance request message from a terminal device, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting to the terminal device a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving from the terminal device a message indicating that the apparatus has been selected as a positioning reference unit for the sidelink positioning session; receiving a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; and generating, on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the terminal device or to the at least one anchor device.

According to an aspect, there is provided a computer program product embodied on a computer-readable medium and comprising a computer program code readable by a computer for an anchor device, wherein the computer program code configures the computer to carry out a computer process comprising: storing, information on that assistance data has been needed in at least one sidelink positioning session conducted with the anchor device; receiving, from a terminal device, a request for establishing a sidelink positioning session; transmitting a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the anchor device; and receiving, from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration. List of drawings

Embodiments are described below, by way of example only, with reference to the accompanying drawings, in which

Figure 1 illustrates a wireless communication scenario to which some embodiments of the invention may be applied;

Figure 2 illustrates a sidelink-assisted positioning scenario;

Figures 3 and 4 illustrate processes for sidelink assisted positioning according to some embodiments;

Figure 5 illustrates a process for an anchor device to report a need for assistance data according to an embodiment;

Figure 6 illustrates a signaling diagram of an embodiment for establishing a positioning session;

Figures 7 and 8 illustrate procedures for arranging provision of assistance data for a positioning session; and

Figure 9 illustrates a block diagram of an apparatus according to an embodiment.

Description of embodiments

The following embodiments are examples. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words “comprising” and “including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the embodiments to such an architecture, however. A person skilled in the art will realize that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

Figure 1 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 1.

The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties.

The example of Figure 1 shows a part of an exemplifying radio access network.

Figure 1 shows terminal devices or user devices 100 and 102 configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) 104 providing the cell. (e/g)NodeB refers to an eNodeB or a gNodeB, as defined in 3GPP specifications. The physical link from a user device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage.

A communications system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used not only for signalling purposes but also for routing data from one (e/g)NodeB to another. The (e/g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point, an access node, or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e/g) NodeB includes or is coupled to transceivers. From the transceivers of the (e/g) NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), etc.

The user device (also called UE, user equipment, user terminal, terminal device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station. 5G specifications define two relay modes: out-of-band relay where same or different carriers may be defined for an access link and a backhaul link; and in-band-relay where the same carrier frequency or radio resources are used for both access and backhaul links. In-band relay may be seen as a baseline relay scenario. A relay node is called an integrated access and backhaul (1AB) node. It has also inbuilt support for multiple relay hops. 1AB operation assumes a so-called split architecture having CU and a number of DUs. An 1AB node contains two separate functionalities: DU (Distributed Unit) part of the 1AB node facilitates the gNB (access node) functionalities in a relay cell, i.e. it serves as the access link; and a mobile termination (MT) part of the 1AB node that facilitates the backhaul connection. A Donor node (DU part) communicates with the MT part of the 1AB node, and it has a wired connection to the CU which again has a connection to the core network. In the multihop scenario, MT part (a child 1AB node) communicates with a DU part of the parent 1AB node.

The user device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The user device may also utilize cloud. In some applications, a user device may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud. The user device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE) just to mention but a few names or apparatuses.

Various techniques described herein may also be applied to a cyberphysical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in Figure 1) may be implemented.

5G enables using multiple input - multiple output (M1M0) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being capable of being integrated with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-Rl operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave - sub-THz). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

The current architecture in LTE networks is fully distributed in the radio and typically fully centralized in the core network. The low-latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), critical communications (autonomous vehicles, traffic safety, realtime analytics, time-critical control, healthcare applications).

The communication system is also able to communicate with other networks 112, such as a public switched telephone network or the Internet, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Figure 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

Edge cloud may be brought into radio access network (RAN) by utilizing network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 105) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 108).

It should also be understood that the distribution of functions between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or node B (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway, maritime, and/or aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano) satellites are deployed). Each satellite 109 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node or by a gNB located on-ground or in a satellite.

It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e/g)NodeBs or may be a Home(e/g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (e/g)NodeBs of Figure 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e/g)NodeBs are required to provide such a network structure.

Figure 1 further illustrates direct device-to-device communication links between the terminal devices 100, 101, 102. These links may correspond to the sidelinks described in Background and defined in 3GPP specifications for 5G, for example. The sidelink is a communication paradigm in which the terminal devices communicate without relaying their data via the radio access network, e.g. the access node 104. That means that terminal devices may create an ad hoc network without using the radio access network as an intermediary. And as described in Background, the sidelinks may be employed for various purposes, e.g. the positioning of a terminal device.

Figure 2 illustrates a situation where a terminal device 100 may employ other terminal devices 101, 102, 130, 132 for positioning the terminal device 100 via sidelink communications with the other terminal devices. Sidelink positioning support the following use cases: In a sidelink absolute positioning solution, the locations of the other terminal devices 101, 102 (called anchor terminal devices in the following) are known, e.g. fixed. Accordingly, the absolute location may also be known (longitude and latitude), e.g. via triangular positioning. In a sidelink relative positioning, the location of the terminal device 100 is relative to a mobile anchor terminal device whose location is also unknown or at least with some reliability. Accordingly, the location of the terminal device 100 is only relative to the anchor terminal device(s) 101, 102. In a sidelink assisted positioning, the terminal device may receive location report(s) from the anchor terminal devices that know their location (with a certain accuracy), and the location of the terminal device may be computed on the basis of the location report(s) and additional measurements performed by the terminal device 100 or by an access node 104 serving the terminal device 100. In this case, the absolute location of the terminal device may be acquired with accuracy dependent on the positioning accuracy of the anchor node(s).

In the measurements (ranging) used in the positioning, one or more of the following measurements may be performed by measuring a reference signal, for example: downlink time difference of arrival (DL-TDOA) measured by the terminal device 100, uplink time difference of arrival (UL-TDOA) measured by the access node from a signal received from the terminal device 100, downlink angle of departure (DL-AoD) measured by the terminal device 100, uplink angle of arrival (UL-AoA) measured by the access node from a signal received from the terminal device 100, and multi-cell round trip time (Multi-RTT) where a round-trip time of the terminal device 100 is measured towards each of multiple cells or access nodes (a type of trilateration).

As illustrated in Figure 2 and described above, in the sidelink assisted positioning using the locations of the nearby anchor devices, the terminal device 100 may carry out the positioning by determining the location(s) of the anchor device(s) and measuring a positioning reference signal received from the anchor device(s). As described in Background, a concept of a positioning reference unit (PRU) has been introduced. The PRU may be described as an entity designated to compute positioning-related correction or other assistance data to be distributed to the terminal device 100 being positioned. The assistance data is used by the terminal device 100 to correct its own position measurements, and/or compute more accurate location estimates. In contrast to the anchor device, the PRU may neither measure positioning reference signals (PRSs) transmitted by the terminal device 100 nor transmits positioning reference signals with the intention to be measured by the terminal device 100. Instead, the PRU may be utilized as a reference unit that conducts similar measurements as the terminal device 100 that are then used to improve the positioning accuracy via additional measurements. For example, the assistance data may comprise information on whether or not a given link towards an anchor device (or a transmission-reception point, TRP, of a positioning reference signal) has a line-of-sight, and/or selecting the best PRS configuration (e.g. PRS beam) that the terminal device should measure, thus removing the need for an exhaustive beam sweep by the terminal device. The PRU selection for the positioning may be made by a location management function (LMF) in the core network 110 but, in the context of sidelink positioning, such a central entity may not be an efficient solution because of the mobility of the terminal devices and the fact that the anchor(s) and/or the PRU(s) also comprise terminal devices.

Figures 3 to 5 illustrate embodiments for the sidelink positioning of the terminal device 100. Figure 3 illustrates a method executed by an apparatus for the terminal device 100 that is being positioned, while Figure 4 illustrates a method executed by an apparatus for a PRU, e.g. a terminal device 130 or 132. Figure 5 illustrates a method executed by an apparatus for the anchor device, e.g. one of the terminal devices 101, 102. In an embodiment, method discussed with reference to Figure 3 is performed by the terminal device 100. In an embodiment, the method discussed with reference to Figure 4 is performed by an anchor device (e.g. terminal device 101, 102, 103).

Referring to Figure 3, the procedure for the terminal device 100 comprises: establishing (block 300) a sidelink positioning session with at least one anchor device 101, 102; causing transmission (block 302) of a positioning assistance request message during the sidelink positioning session, comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving (block 304), from at least one candidate positioning reference unit 130, 132, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting (block 306), for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating (block 306) the selection to the selected at least one positioning reference unit; and communicating (block 320) at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

As illustrated in Figure 3, block 320 may be realized via alternative positioning reference signal (PRS) transmission methods: one where the terminal device 100 receives the PRS(s) and one where the terminal device transmits the PRS(s). In the former embodiment, block 320 comprises receiving (block 308) a positioning reference signal from the at least one anchor device and measuring the positioning reference signal; receiving (block 310) said requested assistance data from the selected at least one positioning reference unit; and estimating (block 312) a location of the apparatus on the basis of the measured positioning reference signal and the assistance data. In the latter embodiment, block 320 comprises transmitting (block 314) a positioning reference signal, receiving positioning data (block 316) based on the positioning reference signal from the at least one anchor device, wherein the positioning data has been corrected on the basis of the assistance data or the assistance data is received in connection with the positioning data, and estimating the location of the apparatus on the basis of the received positioning data and the assistance data (block 312).

In some embodiments, an apparatus for the terminal device 100 does not carry out block 320. The terminal device may have different logical circuits or components with dedicated tasks. Therefore, a circuit carrying out the selection of the PRU(s) may be different from a circuit carrying out block 320.

Referring to Figure 4, the method for the PRU 130, 132 comprises: receiving (block 400) a positioning assistance request message from a terminal device 100, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting (block 402) to the terminal device a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving (block 404) from the terminal device a message indicating that the apparatus has been selected as a positioning reference unit for the sidelink positioning session; receiving (block 406) a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; generating (block 408), on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the at least one anchor device or to the terminal device, respectively.

The processes of Figures 3 and 4 provide a solution for the terminal device 100 carrying out the positioning to select the PRU(s) to provide the assistance data for the positioning session. Accordingly, the terminal device 100 may determine a suitable set of one or more PRUs for the positioning session. It also ensures that the PRU selection is carried out amongst the PRUs with capability of providing the required assistance data. Accordingly, the positioning accuracy of the terminal device may be increased efficiently.

Note that a peer terminal device 130, 132 may be suitable for the PRU role because it conducts similar measurements with similar hardware as the terminal device 100 being positioned. However, a terminal device suitable for operating as the PRU may not be suitable as the anchor device for various reasons. For example, the terminal device may not have enough battery power or its relative location to the terminal device 100 may not be suitable, e.g. it may reside between the anchor device and the terminal device 100 such that the measurements may not yield triangulation benefits. The location of the PRU (candidate) between the anchor device and the terminal device 100 may be detected by measuring an angle of arrival of a reference signal received from the anchor device at both the PRU (candidate) and the terminal device 100. If the angles -of-arrival are substantially identical or sufficiently close to one another, the PRU (candidate) and the terminal device may be determined to reside towards the same direction from the anchor device.

Referring to Figure 5, the process for the anchor device comprises: storing (block 500) information on that assistance data has been needed in at least one sidelink positioning session conducted with the anchor device; receiving (block 502), from a terminal device 100, a request for establishing a sidelink positioning session; transmitting (block 504) a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the apparatus; receiving (block 506), from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration.

In an embodiment where the anchor terminal device receives the positioning reference signal(s) from the terminal device, the anchor terminal device may in block 508 measure the positioning reference signal(s), receive the assistance data from the PRU(s), and to generate positioning data on the basis of the measurements and the assistance data. Then, the anchor device may transmit the positioning data to the terminal device 100.

The process of Figure 5 enables the terminal device 100 to determine the need for the assistance data from the PRU(s). Accordingly, the terminal device may proactively select the suitable PRUs and the positioning latency can be reduced in a case where the assistance data is needed. Additionally, the process of Figure 5 enables the terminal device 100 to make efficient selection of the anchor device(s) for the positioning session, e.g. to select such an anchor device that indicates no need for the assistance data.

As described above, in an embodiment the terminal device 100 receives, from the at least one anchor device during the establishment of the sidelink positioning session, information on whether or not assistance data has been needed in an earlier positioning session with the at least one anchor device. The terminal device 100 may then transmit the positioning assistance request upon determining, on the basis of the information, that said another terminal device has needed the assistance data in the positioning session with the at least one anchor device. Figure 6 illustrates a signaling diagram for this embodiment and the embodiment of Figure 5. With respect to the establishment of the positioning session (block 300), it includes in the context of this disclosure also the discovery of anchor devices and the need for the assistance data (steps 600 to 604 of Figure 6).

Referring to Figure 6, the terminal device 100 may detect a need for positioning the terminal device and, as a consequence, initiate the establishment of the positioning session in block 600. The need may be detected upon receiving a positioning request from a positioning application executed in the terminal device or upon receiving a state-of-the-art location request from the access node 104. Upon initiating the establishment of the positioning session, the terminal device 100 may start a procedure for selecting the anchor device(s) and the PRU(s) for the positioning session. In step 602, the terminal device transmits (e.g. broadcasts) a request for establishing a sidelink positioning session. Upon receiving the request, devices capable of operating as the anchor (terminal devices 101, 102 in this case) may determine whether or not to volunteer as an anchor for the sidelink positioning session. Upon determining to volunteer as the anchor, the respective device may generate a response to the request received in step 604. The response may indicate the capability for operating as the anchor for the sidelink positioning session, and the response may be transmitted by the respective devices (candidate anchor devices) 101, 102 instep 604. As described above in connection with Figure 5, the response may comprise the information on the need for the assistance data in the previous sidelink positioning session(s) conducted with the respective device 101, 102. Each candidate anchor device may, for example, inform the terminal device 100 that other terminal devices (presently or within a time window in the past) required the assistance data in relation to the respective candidate anchor device. The need for the assistance data may have emerged during the past sidelink positioning sessions in that the positioning terminal device had troubles in detecting the anchor device and/or in using measurements collected on the PRS transmitted by the anchor device. The anchor device may acquire such information from the positioning terminal device during the positioning session so that the anchor device may store the information in a database 66. In another embodiment, the information on the need for the assistance data with respect to a particular anchor device is broadcasted by one or more terminal devices that has/have conducted a positioning session with the anchor device.

The information on the past need for the assistance data may be conveyed in step 604 in an information element called “correction necessity info”. This information element may comprise, in addition to the indication of the past need for the assistance data, one of the following pieces of information: a timestamp indicating when the assistance data was requested for a sidelink PRS transmitted by the anchor device; type of needed assistance data such as line-of- sight (LOS) detection, transmission beam selection, sidelink angle-of-departure uncertainty for the sidelink PRS transmitted by the anchor device, and/or a time/frequency/angle offset of the sidelink PRS transmitted by the anchor device; and/or a degree of correction (accuracy improvement upon correction) achieved by the positioning terminal device(s) in the past positioning session(s). All necessary information may have been delivered to the anchor device from the respective positioning terminal device(s) during the past positioning session(s), e.g. at the end of the positioning session(s).

Upon receiving the response(s) in step 604, the terminal device 100 may carry out selection of at least one of the candidate anchor devices for the positioning session. The terminal device 100 may use in the selection the “correction necessity info” received in step 604 from the candidate anchor device(s). Additionally, or alternatively, the terminal device may use other information for determining whether or not assistance data is needed for each candidate anchor device. Such other information may represent a channel estimate of a radio channel between the terminal device and the respective candidate anchor device. In a case where the channel estimate is below a threshold, indicating channel conditions poorer than a threshold level, the terminal device 100 may determine that the assistance data is needed for the respective candidate anchor device. On the other hand, if the channel estimate is above the threshold, the terminal device may determine that no assistance data is required. The selection of the anchor device(s) for the positioning session may comprise prioritizing such candidate anchor devices that are deemed not to require the assistance data. In other words, in a case where the terminal device makes a decision between two candidate anchor devices from which only one requires the assistance data, the terminal device may select the one not requiring the assistance data. However, there exist situations where the terminal device selects one or more anchor devices requiring the assistance data, and let us focus on such situations. The terminal device selects the anchor device(s) amongst the candidate anchor devices in block 606. In step 608, the terminal device transmits a message addressed to the anchor device(s) selected for the positioning session. In an embodiment, the message transmitted in step 608 comprises a PRS configuration specifying parameters of the PRS signal(s) to be transmitted by the anchor device(s). The PRS configuration may define, for example, time-frequency resources of the PRS. Different PRS configuration may be provided to different anchor devices, if multiple anchor devices have been selected.

In an embodiment, the anchor device(s) is/are/comprise anchor terminal device(s) that may be mobile. In another embodiment, the anchor device(s) is/are/comprise road-side units (RSU) or other anchor devices disposed at fixed locations.

In an embodiment, the terminal device receives location(s) of the anchor device(s) in step 604 or in a message acknowledging the selection transferred in step 608. As described above, the location of the anchor device is known so that it may be used as a reference in block 312.

In an embodiment, an anchor device may indicate that no assistance data was needed but, during the location estimation or upon measuring the channel quality, the terminal device may detect the need for the assistance data. For example, if the terminal device is not capable of selecting a sufficient number of anchor devices for the positioning (e.g. for appropriate trilateration), the terminal device may detect the need for the assistance data via PRU selection.

Upon closing the positioning session, the terminal device 100 may report to the selected anchor device(s) whether or not the assistance data was needed or used or beneficial in the location estimation in block 312. In that manner, the anchor devices may maintain and update their databases 66 storing the information on whether or not the assistance data was needed.

Figure 7 illustrates a signaling diagram of an embodiment of the processes of Figures 3 and 4. Referring to Figure 7, the terminal device 100 establishes the positioning session in block 300, e.g. according to the procedure of Figure 6. In step 702, the terminal device 100 transmits (e.g. broadcasts) the positioning assistance request. The positioning assistance request may comprise one or more of the following information elements: a list of anchor devices (and their locations, if available), sidelink PRS configurations of the anchor device(s) for which the assistance data is requested, a maximum allowed PRU location uncertainty, type of correction data requested (e.g. time/angle/frequency offset correction, line-of-sight indication), duration within which the assistance data (requiring measurement of PRS by PRU) is required, a minimum PRU availability duration (duration of the positioning session), a minimum frequency of assistance data transmission support (number of assistance data transmissions per second).

Let us assume that the PRUs 130, 132 detect the positioning assistance request in step 702. In block 704, the PRUs 130, 132 determine their capability of detecting the indicated anchor device(s) and, optionally, capability of meeting the requirements indicated in the above-described information elements. Block 704 may also comprise determining at least one condition under which the respective PRU 130, 132 is capable of providing the assistance data. The conditions may be understood as a PRU budget, containing for example a subset of the sidelink PRSs the PRU is able to measure and for how long. In a case where the terminal device 100 indicates the specific requirements in the information elements of the positioning assistance request, the PRU 130, 132 may determine whether or not it is capable of meeting the requirements and determine to the capable of operating as the PRU for the positioning session, if it is capable of meeting the requirements. On the other hand, if the PRU is not capable of meeting at least one of the requirements, it may still propose the at least one condition under which it is capable of serving as the PRU for the positioning session. For example, if the PRU is not able to measure all indicated anchor devices, it may indicate to the terminal device that or those anchor devices it is capable of detecting and measuring. The proposal of amended requirements may be applied to the other requirements.

In steps 706 and 707, the PRUs 130, 132 respond to the positioning assistance request and volunteer as PRU candidates for the positioning session. The at least one condition per PRU candidate 130, 132 may also be comprised in the respective positioning assistance responses in steps 706, 707. For example, the terminal device may request the PRUs for time/frequency offset correction for the PRS(s) transmitted by the specified anchor device(s). This may be done by setting a ‘type of correction’ field of the positioning assistance request to ‘time-frequency offset’ and providing information on the list of anchor device(s) (and their location(s)) and optionally their PRS configurations. Similar approach applies to the other forms of assistance data.

Upon receiving the positioning assistance responses form the candidate PRUs in steps 706, 707 (and optionally from other PRU candidates), the terminal device may select one or more of the PRU candidates to serve as the PRU(s) in the positioning session (block 708). The selection may be based on the conditions reported in the positioning assistance responses, e.g. the indications which anchor device(s) each PRU candidate is capable of detecting. In step 710, the terminal device 100 indicates the PRU selection for the positioning session to the selected PRU(s) (PRU 132 in this example). In an embodiment, the PRU selection message comprises the PRS configuration(s) of the anchor device(s). Alternatively, the PRS configuration(s) may have been transmitted in the positioning assistance request in step 702.

In a situation where the terminal device 100 requests for multiple types of assistance data in the positioning assistance request, the candidate PRUs 130, 132 may indicate in the positioning assistance response which type or types of the requested assistance data the respective PRU 130, 132 is capable of providing. The terminal device 100 may then perform the selection of the PRU(s) for the positioning session such that the selected PRU(s) is/are capable of providing all types of assistance data requested by the terminal device 100 for the positioning session in step 702. For example, if a single PRU is capable of providing all the requested assistance data, such a PRU may be selected for the positioning session. The terminal device 100 may aim to minimize the number of PRUs selected for the positioning session, thus reducing signalling overhead. As a consequence, the terminal device 100 may select the PRUs with a criterion that the smallest number PRUs capable of together providing all the requested assistance data is selected. If a single PRU candidate is not capable of providing all the assistance data, the terminal device may still select the PRU candidate and at least one other PRU candidate that has indicated capability of providing the remaining assistance data. The terminal device may indicate the selection to the selected PRU(s) in step 710. Similarly, the terminal device may indicate to at least one PRU candidate about non-selection of the particular at least one PRU candidate for the positioning session. In this manner, all PRU candidates that provided the positioning assistance response will get the indication of the selection or non-selection.

Let us assume that the PRU 132 was selected because it can provide the assistance data for the selected anchor device 102. In step 712, the anchor device 102 transmits sidelink PRSs according to the PRS configuration, and the terminal device 100 and the selected PRU 132 measure the PRS transmissions in block 714, 716, respectively. The PRU 132 may compute the requested type of assistance data (requested in step 702) for the targeted anchor device indicated in step 702 in the indicated PRS resources. For example, the PRU 132 may compute ‘time-frequency offset’ corrections for the sidelink PRS(s) received from the anchor device 102 to increase location estimation accuracy. The time-frequency offset causes inaccuracy to the location estimation and, thus its correction improves the positioning accuracy. The correction parameters may be provided as the assistance data. Another embodiment of the assistance data is measurement of the distance and direction from the PRU 132 to the anchor device 102. In step 718, the PRU transmits the assistance data to the terminal device 100. In the embodiment where the assistance data comprises the time-frequency offset correction, the timefrequency offset correction parameters may be transmitted in step 718. As described above, the PRU may also be a terminal device with similar hardware as the terminal device 100. Therefore, the same time-frequency offset correction may apply to the terminal device 100. In an embodiment where the assistance data represents detection ofthe presence/absence of line-of-sight between the PRU and the anchor device, the assistance data may indicate whether or not the PRU has detected the line-of-sight (optionally with a metric indicating inaccuracy of the detection.

In block 720, the terminal device computes the location of the terminal device 100 on the basis of the measurements conducted in block 714 and the assistance data received in step 718. In the case where the assistance data comprises the line-of-sight indication, the terminal device may determine to use the line-of-sight (probability) in its location estimation algorithm, e.g. by weighting sidelink PRS measurements from different anchor devices based on the line-of- sight probability. Measurement of a PRS from an anchor device associated with the line-of-sight may be preferred over measurements of a PRS from an anchor devie with no line-of-sight. In the case where the assistance data comprises the timefrequency offset correction parameters, the terminal device 100 may apply a timefrequency offset indicated by the assistance data to the sidelink PRS measurements performed in block 714. to improve the positioning accuracy. In a case where the assistance data indicates the best beam of the anchor device for the measurements, the terminal device may select the respective beam for the measurements. In this case, block 718 may precede block 714.

In a case where the terminal device 100 selects for the sidelink positioning session multiple anchor devices that have informed the need for the assistance data, the terminal device 100 may insert into the positioning assistance request message transmitted in step 702 an identifier of each anchor device that has informed the need for the assistance data. In an embodiment, the positioning assistance request comprises at least one information element indicating at least one of the at least one anchor device for which the assistance data is requested, and the positioning assistance response indicates capability of the PRU to communicate at least one PRS with the at least one anchor device. In the embodiment of Figure 7, the capability of communicating the PRS(s) with the at least one anchor device may indicate capability of detecting and measuring at least one PRS received from the at least one anchor device. In another embodiment, the capability of communicating the PRS(s) with the at least one anchor device may indicate capability to transmit the PRS(s) with the terminal device 100 so that the anchor device(s) may measure the PRS(s). In this case, the anchor device(s) selected for the positioning session may measure the PRS(s) received from the terminal device and the selected PRU(s) and to terminal device may receive the assistance data from the selected anchor device(s). The terminal device 100 may then select for the sidelink positioning session a PRU capable of communicating the PRS(s) and thereby to assist in generating the assistance data together with the at least one anchor device.

In an embodiment, the PRU(s) monitor and store the assistance data (or various assistance data beforehand before the initiation of the positioning session and the associated transmission/reception of the positioning assistance request in step 702. When the terminal device 100 positioning assistance request is communicated in step 702 (or 302/400), the PRU 132 may compute or retrieve the requested assistance data and transmit the assistance data without additional measurements during the positioning session. In other words, block 716 may be omitted in this embodiment. In this embodiment, the terminal device may request in step 702 for all assistance data available for the indicated anchor device(s) which means that the positioning assistance request can be transmitted with small signaling overhead.

In an embodiment, the PRUs 130, 132 monitor for the sidelink PRS configuration transmitted by the terminal device in step 608 to the selected anchor device(s). Accordingly, the PRUs 130, 132 are capable of making a mapping between the terminal device 100 and the anchor devices selected by the terminal device 100 for the positioning session. In this embodiment, the positioning assistance request transmitted by the terminal device in step 702 may be left void of the list of anchor devices for which the assistance data is required. However, such information may still be sent in the positioning assistance request to inform the PRUs of those anchor devices for which the assistance data is not required. Therefore, the PRUs may determine only those anchor devices that shall be measured and send the assistance data only for those anchor devices.

Figure 8 illustrates an embodiment where the PRSs are transmitted by the terminal device 100 and measured by the anchor device(s) and the PRU(s). The steps with the same numbers as in Figure 7 represent the same or substantially similar functions. In other words, the selection of the anchor device(s) and the PRU(s) may follow the above-described principles. The PRS configuration transmitted to the selected PRU(s) and the selected anchor device(s) may indicate time-frequency resources where the terminal device shall transmit the PRS(s). In step 800, the terminal device 100 transmits the sidelink PRS(s) and the anchor device 102 and the PRU 132 measure the sidelink PRS(s) in blocks 801, 802. The measurement in block 802 may comprise the PRU 132 estimating its location on the basis of the measurements of the PRS(s) and comparing the estimated location of the PRU with a known location of the PRU. The difference between the estimated location of the PRU and the known location of the PRU may form the assistance data (applicable also to block 716). The assistance data may alternatively or additionally comprise any other piece of assistance data described above. The assistance data may be transmitted by the PRU 132 to the device that also measures the PRS(s), i.e. the anchor device in the case of Figure 8 (step 803). The anchor device 102 receiving the assistance data may then use the assistance data to correct its own measurements in block 804 (e.g. the time-frequency offset correction) and/or to collate the assistance data with the positioning data generated in block 801. In step 806, the anchor device 102 transmits the (corrected) positioning data and, optionally, the assistance data or some of the assistance data to the terminal device 100. The terminal device 100 may then carry out the estimation of the location of the terminal device 100 on the basis of the received positioning data that has either been corrected with the assistance data by the anchor device or on the basis of the positioning data that is corrected with the assistance data by the terminal device (block 808).

Figure 9 illustrates an apparatus comprising means for carrying out the process of Figure 3, 4, or 5, or any one of the embodiments described above. The apparatus may comprise a processing circuitry, such as at least one processor, and at least one memory 20 including computer program code or computer program instructions (software) 24, wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus to carry out the process of Figure 3, 4, or 5, or any one of its embodiments described above. The apparatus may be for the terminal device 100 (implementing the process of Figure 3), the PRU 130, 132 (implementing the process of Figure 4), or the anchor device 101, 102 (implementing the process of Figure 5). As described above, any one of these devices 100 to 102, 130, 132 may be a terminal device of the cellular communication system. The apparatus may be a circuitry or an electronic device realizing some embodiments of the invention in the terminal device. The apparatus carrying out the above-described functionalities may thus be comprised in such a device, e.g. the apparatus may comprise a circuitry such as a chip, a chipset, a processor, a micro controller, or a combination of such circuitries for the terminal device. The at least one processor or a processing circuitry may realize a communication controller 10 controlling communications in a radio interface of the cellular communication system in the above-described manner. The communication controller may be configured to establish and manage radio connections, transfer of data over radio resource control (RRC) connections with the access node 104.

The communication controller 10 may comprise a sidelink controller 12 configured to establish, manage, and terminate sidelink radio connections between the terminal device and the other terminal devices. The sidelink radio connections may occupy the same radio resources as a RRC connection and be at least partially controlled via the RRC connection.

The communication controller 10 may comprise a positioning circuitry 14 configured to carry out the positioning sessions in the apparatus by utilizing the sidelink-assisted positioning according to the procedure of Figure 3, 4, or 5, or any one of the embodiments thereof. For the purpose of operating in the terminal device 100 according to Figure 3, the positioning circuitry may comprise a location estimator 15 that may trigger the sidelink-assisted positioning, thus causing the apparatus to establish the sidelink positioning session with the anchor device(s) and to request for the assistance data from the PRU(s). The location estimator 15 may use the assistance data acquired in the above-described manner to correct the measurements performed by the apparatus itself to improve the positioning accuracy. The positioning circuitry may further comprise an anchor/PRU selection circuitry 17 configured to carry out block 606/708.

In the embodiment where the apparatus supports the operation as the anchor device, the apparatus comprises a circuitry 16 implementing the abovedescribed functions of the anchor device 101, 102. In other words, the apparatus may be configured to carry out the procedure of Figure 5 or 6, to store the database 66, and to transmit the PRSs during the positioning sessions.

In the embodiment where the apparatus supports the operation as the PRU 130, 132, the apparatus comprises a circuitry 18 implementing the abovedescribed functions of the PRU 130, 132. In other words, the apparatus may be configured to carry out the procedure of Figure 4 or the actions of the PRU in the process of Figure 7 or 8.

The apparatus may further comprise an application processor (not shown) executing one or more computer program applications that generate a need to transmit and/or receive data through the communication controller 10. The application processor may form an application layer of the apparatus. The application processor may execute computer programs forming the primary function of the apparatus. For example, if the apparatus is a sensor device, the application processor may execute one or more signal processing applications processing measurement data acquired from one or more sensor heads. If the apparatus is a computer system of a vehicle, the application processor may execute a media application and/or an autonomous driving and navigation application. Positioning of the apparatus may be beneficial for all these applications. The application processor may thus generate a command for executing the process of Figure 3.

The memory 20 may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The memory 20 may comprise the database 66 for storing the information on the need for the assistance data.

The apparatus may further comprise a communication interface 22 comprising hardware and/or software for providing the apparatus with radio communication capability, as described above. The communication interface 22 may include, for example, an antenna, one or more radio frequency filters, a power amplifier, and one or more frequency converters. The communication interface 22 may comprise hardware and software needed for realizing the radio communications over the radio interface, e.g. according to specifications of an LTE or 5G radio interface.

As used in this application, the term ‘circuitry’ refers to one or more of the following: (a) hardware-only circuit implementations such as implementations in only analog and/or digital circuitry; (b) combinations of circuits and software and/or firmware, such as (as applicable): (i) a combination of processor(s) or processor cores; or (ii) portions of processor(s)/software including digital signal processor(s), software, and at least one memory that work together to cause an apparatus to perform specific functions; and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of ‘circuitry’ applies to uses of this term in this application. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor, e.g. one core of a multi-core processor, and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular element, a baseband integrated circuit, an application-specific integrated circuit (ASIC), and/or a field- programmable grid array (FPGA) circuit for the apparatus according to an embodiment of the invention.

The processes or methods described in Figure 3 to 8, or any of the embodiments thereof may also be carried out in the form of one or more computer processes defined by one or more computer programs. The computer program(s) may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include transitory and/or non-transitory computer media, e.g. a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package. Depending on the processing power needed, the computer program may be executed in a single electronic digital processing unit or it may be distributed amongst a number of processing units. References to computer-readable program code, computer program, computer instructions, computer code etc. should be understood to express software for a programmable processor such as programmable content stored in a hardware device as instructions for a processor, or as configured or configurable settings for a fixed function device, gate array, or a programmable logic device.

Embodiments described herein are applicable to wireless networks defined above but also to other wireless networks. The protocols used, the specifications of the wireless networks and their network elements develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. An apparatus comprising means for performing: establishing a sidelink positioning session with at least one anchor device; causing transmission of a positioning assistance request message during the sidelink positioning session, comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving, from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating the selection to the selected at least one positioning reference unit; and communicating at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

2. The apparatus of claim 1, wherein the means are configured to: receive the at least one positioning reference signal from the at least one anchor device and measure the positioning reference signal; receive said requested assistance data from the selected at least one positioning reference unit; and estimate the location of the apparatus on the basis of the measured positioning reference signal and the received assistance data.

3. The apparatus of claim 1 or 2, wherein the means are configured to: receive, from the at least one anchor device during the establishment of the sidelink positioning session, information on whether or not assistance data has been needed in an earlier positioning session with the at least one anchor device; cause the transmission of the positioning assistance request upon determining on the basis of the information that said another terminal device has needed the assistance data in the positioning session with the at least one anchor device.

4. The apparatus of claim 3, wherein the at least one anchor device comprises a plurality of anchor devices, and wherein the means are configured to receive said information from the plurality of anchor devices and to configure the selected at least one positioning reference unit to provide the assistance data only for such an anchor device that has informed the need for the assistance data.

5. The apparatus of claim 3 or 4, wherein the means are configured to select for the sidelink positioning session multiple anchor devices that have informed the need for the assistance data, and to insert into the positioning assistance request message an identifier of each anchor device that has informed the need for the assistance data.

6. The apparatus of any preceding claim, wherein the positioning assistance request comprises at least one information element indicating at least one of the at least one anchor device for which the assistance data is requested, and wherein the positioning assistance response indicates capability to measure at least one positioning reference signal and to generate the assistance data associated with the indicated at least one anchor device, and wherein the means are configured to select for the sidelink positioning session a positioning reference unit capable of measuring and generating the assistance data.

7. The apparatus of any preceding claim, wherein the selected at least one positioning reference unit comprises a terminal device.

8. The apparatus of any preceding claim, wherein the positioning assistance response indicates at least one condition under which the respective positioning reference unit is capable of providing the assistance data, and wherein the means are configured to perform the selection of the at least one positioning reference unit on the basis of the at least one condition.

9. The apparatus of any preceding claim, wherein the positioning assistance request specifies multiple types of assistance data requested for the positioning session, and wherein the positioning assistance response indicates which type or types of the requested assistance data the respective positioning reference unit is capable of providing, and wherein the means are configured to perform the selection of the at least one positioning reference unit such that the selected at least one positioning reference unit is capable of providing all types of assistance data requested for the positioning session.

10. An apparatus for a positioning reference unit, comprising means for performing: receiving a positioning assistance request message from a terminal device, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting to the terminal device a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving from the terminal device a message indicating that the apparatus has been selected as a positioning reference unit for the sidelink positioning session; receiving a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; and generating, on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the terminal device or to the at least one anchor device.

11. The apparatus of claim 10, wherein the positioning assistance request message comprises at least one information element indicating the at least one anchor device, and wherein the positioning assistance request message or the message indicating the selection of the apparatus indicates a configuration of the positioning reference signal.

12. The apparatus of claim 10 or 11, wherein the means are configured, upon receiving the positioning assistance request message, to determine at least one condition under which the apparatus is capable of providing the assistance data and indicate the at least one condition in the positioning assistance response message.

13. An apparatus for an anchor device, comprising means for performing: storing information on that assistance data has been needed in at least one sidelink positioning session conducted with the apparatus; receiving, from a terminal device, a request for establishing a sidelink positioning session; transmitting a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the apparatus; and receiving, from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration.

14. The apparatus of any preceding claim 1 to 13, wherein the means comprises at least one processor and at least one memory storing instructions that cause said performance of the apparatus.

15. A method comprising: establishing, by a terminal device, a sidelink positioning session with at least one anchor device; causing, by the terminal device, transmission of a positioning assistance request message during the sidelink positioning session, the positioning assistance request message comprising at least one information element indicating that assistance data is requested for the sidelink positioning session; receiving, by the terminal device from at least one candidate positioning reference unit, at least one positioning assistance response message comprising at least one information element indicating capability to provide the requested assistance data; selecting, by the terminal device, for the sidelink positioning session amongst the at least one candidate positioning reference unit, at least one positioning reference unit that has indicated capability to provide the assistance data; indicating, by the terminal device, the selection to the selected at least one positioning reference unit; and communicating, by the terminal device, at least one positioning reference signal with at least the at least one anchor device and estimating a location of the terminal device on the basis of the positioning reference signal and assistance data provided by the selected at least one positioning reference unit.

16. A method comprising: receiving, by a positioning reference unit, a positioning assistance request message from a terminal device, comprising at least one information element indicating that assistance data is requested for a sidelink positioning session of the terminal device; transmitting, by the positioning reference unit to the terminal device, a positioning assistance response message comprising at least one information element indicating the capability to provide the requested assistance data; receiving, by the positioning reference unit from the terminal device, a message indicating that the positioning reference unit has been selected as a positioning reference unit for the sidelink positioning session; receiving, by the positioning reference unit, a positioning reference signal from at least one anchor device of the positioning session or from the terminal device and measuring the positioning reference signal; and generating, by the positioning reference unit on the basis of said measuring, assistance data for the sidelink positioning session and transmitting said assistance data to the terminal device or to the at least one anchor device.

17. A method comprising: storing, by an anchor device, information on that assistance data has been needed in at least one sidelink positioning session conducted with the anchor device; receiving, by the anchor device from a terminal device, a request for establishing a sidelink positioning session; transmitting, by the anchor device, a response to the request, the response indicating that the assistance data has been needed in at least one sidelink positioning session of the anchor device; and receiving, by the anchor device from the terminal device, a positioning reference signal configuration and transmitting or receiving a positioning reference signal according to the positioning reference signal configuration.

18. A computer program product embodied on a computer-readable medium and comprising a computer program code readable by a computer, wherein the computer program code configures the computer to carry out a computer process comprising the method of any one of claims 15 to 17.