WO2023212836A1

WO2023212836A1 - Apparatus and method for discovering positioning reference user equipment on sidelink

Info

Publication number: WO2023212836A1
Application number: PCT/CN2022/090839
Authority: WO
Inventors: Joerg Schaepperle; Torsten WILDSCHEK; Mikko Saily; Yong Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2022-05-03
Filing date: 2022-05-03
Publication date: 2023-11-09

Abstract

Example embodiments relate to apparatus and method for discovering positioning reference user equipment on sidelink. A terminal device may be configured to transmit a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices, receive a positioning reference reply from the one or more reference devices, and select at least one reference device from the one or more reference devices for positioning of the terminal device based at least in part on the received positioning reference reply. The positioning reference reply may include positioning reference measurement capability of the one or more reference devices.

Description

APPARATUS AND METHOD FOR DISCOVERING POSITIONING REFERENCE USER EQUIPMENT ON SIDELINK

TECHNICAL FIELD

Exemplary embodiments described herein generally relate to communication technologies, and more particularly, to apparatuses and methods for discovering positioning reference user equipments (UEs) on sidelink.

BACKGROUND

Terrestrial network-based positioning technology includes a trilateration method where a user equipment (UE) measures positioning reference signals (PRSs) from multiple transmission and reception points (TRPs) , and the position of the UE can be calculated from the PRS measurements and the position coordinates of the multiple TRPs. Apparently, precise PRS measurement is essential for the positioning accuracy. Double differential measurement can be used to mitigate PRS time/phase uncertainties in the TRPs and the UEs, thereby improving the positioning accuracy.

SUMMARY

A brief summary of exemplary embodiments is provided below to provide basic understanding of some aspects of various embodiments. It should be noted that this summary is not intended to identify key features of essential elements or define scopes of the embodiments, and its sole purpose is to introduce some concepts in a simplified form as a preamble for a more detailed description provided below.

In a first aspect, an example embodiment of a terminal device is provided. The terminal device may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the terminal device at least to transmit a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices, receive a positioning reference reply from the one or more reference devices, and select at least one reference device from the one or more reference devices for positioning of the terminal device based at least in part on the received positioning reference reply. The positioning reference reply may include positioning reference measurement capability of the one or more reference devices.

In a second aspect, an example embodiment of a reference device is provided. The reference device may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the reference device at least to receive, from a terminal device, a positioning reference request on a sidelink between the terminal device and the reference device, and transmit a positioning reference reply to the terminal device in response to the positioning reference request, the positioning reference reply including positioning reference measurement capability of the reference device.

Example embodiments of methods, apparatus and computer program products are also provided. Such example embodiments generally correspond to the above example embodiments, and a repetitive description thereof is omitted here for convenience.

Other features and advantages of the example embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of example embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described, by way of non-limiting examples, with reference to the accompanying drawings.

Fig. 1 is a schematic diagram illustrating a communication network in which example embodiments of the present disclosure can be implemented.

Fig. 2 is a schematic diagram illustrating an example scenario where example embodiments of the present disclosure can be applied.

Fig. 3 is a schematic interaction diagram illustrating a procedure for selecting a positioning reference UE according to an example embodiment of the present disclosure.

Fig. 4A is a schematic interaction diagram illustrating UE assisted positioning according to an example embodiment of the present disclosure.

Fig. 4B is a schematic interaction diagram illustrating UE assisted positioning according to another example embodiment of the present disclosure.

Fig. 5 is a schematic interaction diagram illustrating UE based positioning according to an example embodiment of the present disclosure.

Fig. 6 illustrates a schematic block diagram of a device according to an example embodiment of the present disclosure.

Throughout the drawings, same or similar reference numbers indicate same or similar elements. A repetitive description on the same elements would be omitted.

DETAILED DESCRIPTION

Herein below, some example embodiments are described in detail with reference to the accompanying drawings. The following description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known circuits, techniques and components are shown in block diagram form to avoid obscuring the described concepts and features.

As used herein, the term "network device" refers to any suitable entities or devices that can provide cells or coverage, through which the terminal device can access the network or receive services. The network device can provide a positioning service to UEs camping in cells served by the network device or by a neighboring network device by transmitting downlink positioning reference signal (DL PRS) to the UEs and/or receiving and measuring uplink sounding reference signal (UL SRS) from the UEs. The network device may be commonly referred to as a base station. The term "base station" used herein can represent a node B (NodeB or NB) , an evolved node B (eNodeB or eNB) , a gNB, an access point, a transmission and reception point (TRP) , or the like. The base station may be embodied as a macro base station, a relay node, or a low power node such as a pico base station or a femto base station. The base station may consist of several distributed network units, such as a central unit (CU) , one or more distributed units (DUs) , one or more remote radio heads (RRHs) . The RRHs may also be referred to as or implemented as transmission points (TPs) , transmission and reception points (TRPs) , radio units (RUs) , remote radio units (RRUs) , active antenna units (AAUs) and the like. The number and functions of these distributed units depend on the selected split RAN architecture.

As used herein, the term "terminal device" or "user equipment" (UE) refers to any entities or devices that can wirelessly communicate with the network devices or with each other. The terminal device can perform a network positioning procedure by receiving and measuring DL PRS from serving and neighboring network devices and/or transmitting UL SRS to the serving and neighboring network devices. Examples of the terminal device can include a mobile phone, a mobile terminal (MT) , a mobile station (MS) , a subscriber station (SS) , a portable subscriber station (PSS) , an access terminal (AT) , a computer, a wearable device, an on-vehicle communication device, a machine type communication (MTC) device, a D2D communication device, a V2X communication device, a sensor and the like. The term "terminal device" can be used interchangeably with a UE, a user terminal, a mobile terminal, a mobile station, or a wireless device.

Fig. 1 illustrates an example communication network 100 in which exemplary embodiments of the present disclosure can be implemented. Referring to Fig. 1, the communication network 100 may include a plurality of UEs 110a-b (each also individually referred to as UE 110 or collectively as UEs 110) in wireless communication with a plurality of TRPs 120a-b (each also individually referred to as TRP 120 or collectively as TRPs 120) . It would be appreciated that the communication network 100 may include more UEs and more TRPs, although two UEs and two TRPs are shown in Fig. 1. As mentioned above, the TRPs 120 may be implemented as a base station such as a macro base station, a pico base station and a femto base station, or as a remote radio head (RRH) of a base station. The locations of the TRPs 120 are already known and usually fixed.

The TRPs 120 may broadcast positioning reference signals (PRSs) to surrounding UEs. The UE 110 can measure arrival time or phase of the PRSs from multiple TRPs 120 to estimate UE position relative to the TRPs 120. In UE assisted positioning, the UE 110 may transmit the PRS measurements to a location server 130 where the PRS measurements are processed to obtain the position of the UE 110. The location server 130 may be implemented as a location management function (LMF) in the core network or as a location management component (LMC) in the radio access network (RAN) e.g. in the serving base station of the UE 110. In UE based positioning, the UE 110 may include a location management component (LMC) implemented to calculate the position of the UE 110 based on the PRS measurements. Throughout the present disclosure, the term “positioning reference signal” may refer to any downlink reference signal that can be used to perform positioning measurements, of which examples may include for example synchronization signal block (SSB) , cell-specific reference signal, sounding reference signal (SRS) , phase tracking reference signal (PT-RS) , and the positioning reference signal defined in 3GPP specifications.

In a double differential measurement solution, two UEs, including a target UE 110a of which the position is unknow and a reference UE 110b of which the position is already known, can synchronously measure the PRSs from a pair of

TRPs

120a, 120b, and a double differential measurement can be obtained by subtracting the PRS measurements between the TRPs and between the UEs. For example, referring to Fig. 1, the target UE 110a measures arrival time or phase of the PRSs from the

TRPs

120a, 120b and obtains PRS measurements M1, M2, respectively. Similarly, the reference UE 110b measures arrival time or phase of the PRSs from the

TRPs

120a, 120b and obtains PRS measurements M3, M4, respectively. A double differential measurement Mdd can be calculated as Mdd=(M1-M2) - (M3-M4) . To determine the position of the target UE 110a, three independent double differential measurements are needed, which can be acquired by the target and reference UEs observing at least four TRPs. As the double differential measurement Mdd can cancel PRS time/phase uncertainties in the TRPs and the UEs, it can improve positioning accuracy.

To apply the double differential measurement solution for high accuracy positioning, a precondition is that the target UE has to discover at least one reference UE with known position. Fig. 2 illustrates an example scenario of discovering a reference UE for the target UE. Referring to Fig. 2, multiple TRPs 120 and multiple reference UEs 110b may be deployed e.g. in a factory hall. For each target UE 110a, one or more reference UEs 110b need to be selected from the set of all available reference UEs and assigned to the target UE 110a for the double differential measurement. However, as the position of the target UE 110a is not known, the target UE 110a does not know which reference UEs 110b are appropriate to it and how to select the reference UEs 110b. In addition, in case of UE based positioning, measurement results need to be reported from the reference UE 110b to the target UE 110a. If the reference UE 110b transmits the measurement reports via the RAN to the target UE 110a, the reporting delay is high, which is undesirable especially for carrier-phase based positioning because the carrier phase changes quickly.

Example embodiments described herein provide a reference UE discovery mechanism, which can find one or more reference UEs that have a similar radio channel to the target UE. The mechanism can select reference UEs in proximity of the target UE without knowing the position of the target UE. It can be performed via sidelink communications and would not cause additional network signaling overhead. With appropriate reference UEs selected, the mechanism can also improve positioning accuracy of the target UE. In some example embodiments, the reference UEs can transmit measurement reports directly to the target UE via sidelink communication, which can minimize the reporting delay and accelerate the positioning procedure. It would be desirable especially for carrier-phase based positioning because the carrier phase changes quickly.

Fig. 3 illustrates a procedure of selecting a positioning reference UE for a target UE according to an example embodiment of the present disclosure. The reference UE selection procedure may be implemented by a target UE and one or reference UEs. For example, the target UE 110a and the references UE 110b described above with respect to Figs. 1-2 may be configured to perform the reference UE selection procedure. The target UE 110a and the reference UEs 110b each may include a plurality of components, modules, means or elements to perform operations discussed below, and the components, modules, means and elements may be implemented in various manners including but not limited to for example software, hardware, firmware or any combination thereof.

Referring to Fig. 3, at an operation 210, the target UE 110b may optionally receive a positioning reference advertisement from the reference UEs 110b. The positioning reference advertisement may include an identifier or address of the reference UEs 110b. From the positioning reference advertisement, the target UE 110b can know which UEs are providing a positioning reference service. In an example, the positioning reference advertisement may further include position coordinates of the reference UEs 110b. The references UE 110b may transmit the positioning reference advertisement via broadcast or groupcast on sidelink. For example, the groupcast may be transmitted to e.g. a group “positioning reference service” , and UEs which need to receive the service for the purpose of e.g. high accuracy positioning may join the group. In some example embodiments, the operation 210 may be omitted.

The target UE 110b may also optionally receive a positioning reference trigger indication from a location server 130 serving the target UE 110b or from a base station to which the target UE 110b is connected, at an operation 211. The positioning reference trigger indication may be transmitted by a new message or by extending an existing message with a new information element. With the positioning reference trigger indication, the location server 130 or the serving base station may instruct the target UE 110b to initiate a process for discovering reference UEs on sidelink. The location server 130 may transmit the positioning reference trigger indication via LTE positioning protocol (LPP) to the target UE 110b, or via NR positioning protocol a (NRPPa) to the serving base station of the target UE 110b first and then the serving base station may send the positioning reference trigger indication to the target UE 110b.

At an operation 212, the target UE 110a may transmit a positioning reference request to the reference UEs 110b on sidelinks between the target UE 110a and the reference UEs 110b. In an example, the target UE 110a may transmit the positioning reference request in response to the positioning reference trigger indication received at the operation 211. The positioning reference request may be transmitted via broadcast communication to nearby UEs, or via groupcast communication to a group of reference UEs 110b. For example, a sidelink group “positioning reference UEs” can be defined/configured which contain all reference UEs, and information of the group may be informed to the target UE 110a via the positioning reference advertisement or on the sidelink broadcast channel.

The positioning reference request may contain information of the target UE 110a and positioning reference requirements of the target UE 110a. For example, the information of the target UE 110a may include identifier or address of the target UE 110a, and optionally the state of the target UE 110a. The state of the target UE 110a may indicate if the target UE 110a is in an RRC connected, inactive or idle state. The positioning reference requirements of the target UE 110a may include for example a first list of TRPs 120 measurable for the target UE 110a. That is, the target UE 110a can measure the PRSs transmitted from the first list of TRPs 120. For the purpose of double differential measurements, it would be desirable that the reference UE for the target UE 110a can measure as many TRPs in the first list as possible. The positioning reference requirements may also include signal level information of the first list of TRPs 120 measured at the target UE 110a. The signal level information may be represented by e.g. measured SSB power from the TRPs 120. Since the signal level is generally in inverse proportion to a distance from the target UE 110a to the TRP, the signal level can reflect which TRPs are close to the target UE 110a, and it would be desirable that the reference UE for the target UE 110a is also close to such TRPs. In an example, the first list of TRPs 120 may be ordered in a descending order of the signal level. In an example, the positioning reference requirements may also include beam direction information of the TRPs 120, which indicates the strongest beam for the target UE 110a. The beam direction information may be represented by a beam index e.g. an SSB index of the strongest beam. Also, it is desirable that the reference UE for the target UE 110a can measure the same beam of the TRPs 120.

Based on the positioning reference request, the reference UEs 110b may determine at an operation 214 whether they can provide a positioning reference service to the target UE 110a. For being able to provide the positioning reference service, it may be required that the reference UEs 110b know their own positions, can perform positioning measurements, and can report their positions and positioning measurements to the network or to neighboring UEs. Or the reference UEs 110b may simply know by configuration that it is capable of and intended for serving as a reference UE to provide the positioning reference service to other UEs. Usually the reference UEs 110b may have fixed and precisely calibrated position coordinates. In an example, the location server 130 may know the position coordinates of the reference UEs 110b and the reference UEs 110b do not need to report their positions to the location server 130. In the operation 214, the reference UEs 110b may evaluate if they can provide the positioning reference service to the target UE 110a by determining for example whether they can measure the PRSs from at least a threshold number of TRPs listed in the positioning reference request, whether the signal level measured at the reference UE from the TRPs is close to the signal level of the TRPs indicated in the positioning reference request, and whether the reference UE measures the same strongest beam from the TRPs as the target UE 110a does. In some example embodiments, the reference UEs 110b also determines whether they can provide the positioning reference service to the target UE 110b based on the state of the target UE 110b. For example, some reference UEs may provide the positioning reference service only to target UEs in the RRC connected state, while some other reference UEs may also provide the positioning reference service to target UEs in the RRC inactive and/or idle state. The reference UEs 110b can run an algorithm to determine how much it meets the positioning reference requirements indicated in the positioning reference request and determine whether the reference UEs 110b can function as a reference UE for the target UE 110a.

If one or more reference UEs 110b determines at the operation 214 that they can serve as the reference UE for the target 110a, they can send a positioning reference reply to the target UE 110a at an operation 216. By sending the positioning reference reply, the reference UEs 110b indicate to the target UE 110a that they are capable of providing a positioning reference service to the target UE 110a. The positioning reference reply may contain explicit or implicit information about positioning reference measurement capability of the reference UE, which implies that the reference UE is capable of serving as a reference UE and will provide positioning reference measurements. The positioning reference measurement capability may include for example a second list of TRPs, signal level information and beam direction information of the TRPs, and position coordinates of the reference UE. In an example, the second list of TRPs may include TRPs that can be measured at both the target UE 110a and the reference UE 110b, i.e. the second list of TRPs may be selected from the first list of TRPs indicated in the positioning reference request. In another example, the second list of TRPs may include TRPs that can be measured at the reference UE 110b, and the target UE 110a or the location server 130 can determine whether the target UE 110a and the reference UE 110b can receive the PRS from the same TRP based on the first list of TRPs and the second list of TRPs. The signal level information of the TRPs may be represented by measured SSB power from the TRPs. In an example, the second list of TRPs may be ordered in a descending order of the signal level. The beam direction information of the TRPs may indicate the strongest beam for the reference UE and it may be represented by a beam index e.g. an SSB index of the strongest beam. The positioning reference reply may further contain information about the reference UE such as identifier or address, state of the reference UE.

At an operation 218, optionally, the target UE 110a may perform channel measurements on the reference UEs 110b from which the positioning reference reply is received. For example, the target UE 110a may measure sidelink SSB power of the reference UEs 110b. The larger the measured SSB power, the closer the reference UE 110b is to the target UE 110a. In another example, the target UE 110a may measure round trip time between the target UE and the reference UEs 110b by exchanging messages, and the round trip time is in proportion to a distance between the target UE 110a and the reference UEs 110b. In some example embodiments, the operation 218 may be omitted because the positioning reference measurement capability indicated in the positioning reference reply can also reflect the location area of the reference UEs 110b at least to some extent.

Then the target UE 110a may select at least one reference UE 110b based on the positioning reference reply received at the operation 216 and optionally the channel measurements performed at the operation 218. The target UE 110a may select one or more best reference UEs 110b which receive the PRS on the same or similar beams of the same TRPs and measure the same or similar signal level from the TRPs as the target UE 110a does. Optionally, the channel measurements of the reference UEs 110b would also be considered because the reference UE having higher channel measurement would be closer to the target UE 110a and hence have similar radio channel as the target UE 110a. The target UE 110a may run an algorithm to compare the positioning reference requirements of the target UE 110a and the positioning reference measurement capability of the reference UEs and rank the reference UEs by similarity between the positioning reference requirements and the positioning reference measurement capability. Then the target UE 110a may select a predetermined number of best reference UEs with the similarity above a threshold. If all the reference UEs have a similarity below the threshold, no reference UE 110b can be used for the target UE 110a, and the target UE 110a may re-perform the procedure until it finds a reference UE having a similarity above the threshold.

With the procedure of Fig. 3, the target UE 110a can select one or more reference UEs close to the target UE without knowing the position of the target UE. The procedure can be performed when the target UE 110a is in the RRC connected, inactive or idle state, and it would not increase network signaling overhead because the procedure can be performed on sidelink communications.

Fig. 4A illustrates a UE assisted positioning procedure according to an example embodiment of the present disclosure. The procedure can be performed following the procedure of Fig. 3 when the target UE 110a has selected one or more reference UEs 110b.

Referring to Fig. 4A, the target UE 110a may transmit a positioning reference report indicating the selection of the one or more reference UEs 110b to the location server 130 at an operation 310. In an example, the positioning reference report may be transmitted via an LTE Positioning Protocol (LPP) message from the target UE 110a to the location server 130. In another example, the target UE 110a may send the positioning reference report to a base station to which the target UE 110a connects, and then the base station may send the report to the location server 130 via an NR Positioning Protocol a (NRPPa) message. The positioning reference report may include identifier or address of the selected reference UEs 110b for the target UE 110a. Optionally, the positioning reference report may further include position coordinates of the selected reference UEs 110b.

At an operation 311, the network may configure positioning reference signal (PRS) for the target UE 110a and the reference UEs 110b. For example, the location server 130 may provide PRS configuration over LPP to the target UE 110a and the reference UEs 110b. The PRS configuration may contain information of the PRSs transmitted at TRPs 120 in proximity of the target UE 110a or the reference UEs 110b.

Then the target UE 110a and the reference UEs 110b may receive and measure the PRSs transmitted from the TRPs 120 based on the PRS configuration received from the location server 130 at

operations

312 and 314, respectively. The target UE 110a may transmit a measurement report to the location server 130 at an operation 316, and the reference UEs 110b may transmit a measurement report to the location server 130 at an operation 318. The measurement report may include time/phase values or time/phase differences of the PRSs measured from a plurality of TRPs 120. It would be appreciated that the reported time/phase values or time/phase differences from the reference UEs may contain the same impairments (i.e., time and phase errors resulting from unknown delays in the transmit chain of the TRPs 120) as those from the target UE. The location server 130 may combine the measurement report of the target UE 110a with the measurement report of the reference UE 110b selected for the target UE 110a to calculate double differential measurements as discussed above with respect to Fig. 1.By calculating the double differences, the impairments included in the reported time/phase values or time/phase differences may be cancelled out. The location server 130 may calculate a position of the target UE 110a based on the double differential measurements, position coordinates of relevant TRPs 120, and position coordinates of relevant reference UEs 110b, and send the calculated position to the target UE 110a e.g. via LTE Positioning Protocol (LPP) signaling. Since the impairments included in the reported time/phase values or time/phase differences are cancelled out when calculating the double differences, accuracy of position estimation for the target UE 110a is improved.

Fig. 4B illustrates a UE assisted positioning procedure according to another example embodiment of the present disclosure. In the procedure of Fig. 4B, operations similar to those shown in Fig. 4A are denoted with similar reference numerals and a repetitive description thereof is omitted here.

Referring to Fig. 4B, the target UE 110a transmits the positioning reference report indicating the selected one or more reference UEs 110b to the location server 130 at the operation 310. At an operation 321, the network may configure uplink sounding reference signal (UL SRS) for the target UE 110a and the reference UEs 110b. For example, the serving base station of a UE (i.e., the target UE 110a or the reference UE 110B) may configure time and frequency resources for the UE to transmit UL SRS. The serving base station may also send the SRS configuration to the location server 130. The location server 130 may transmit the SRS configuration of the UE to neighboring base stations so that the serving and neighboring base stations can receive and measure the SRS transmitted from the UE.

Based on the SRS configuration, then the target UE 110a may transmit UL SRS to the TRPs 120 at an operation 322 and the reference UEs 110b may transmit UL SRSs to the TRPs 120 at an operation 324. The TRPs 120 may measure arrival time or phase of the UL SRSs transmitted from the target UE 110a and the reference UEs 110b based on the used positioning method.

Then at an operation 326, the TRPs 120 may transmit the measurement results to the location server 130 via e.g. NRPPa messages. The location server 130 may combine the measurement result relating to the target UE 110a with the measurement result relating to the reference UE 110b selected for the target UE 110a to calculate double differential measurements as discussed above with respect to Fig. 1. The location server 130 may calculate a position of the target UE 110a based on the double differential measurements, position coordinates of relevant TRPs 120, and position coordinates of relevant reference UEs 110b. Since the impairments included in the measured time/phase values or time/phase differences are cancelled out when calculating the double differences, accuracy of position estimation for the target UE 110a is improved. The location server 130 may send the calculated position coordinates to the target UE 110a e.g. via LTE Positioning Protocol (LPP) signaling.

Fig. 5 illustrates a UE based positioning procedure according to an example embodiment of the present disclosure. The procedure can be performed following the procedure of Fig. 3 when the target UE 110a has selected one or more reference UEs 110b.

Referring to Fig. 5, at an operation 410, the target UE 110a may establish a sidelink communication connection with the selected reference UEs 110b so that the selected reference UEs 110b can report measurements to the target UE 110a on the connection. In an example, the established communication connection may be a unicast connection on which the reference UE 110b can transmit measurements to the target UE 110a. In another example, the communication connection may be a groupcast connection by which the reference UE 110b can transmit measurements to a group of target UEs including the target UE 110a. When a reference UE can provide positioning reference for a plurality of target UEs, the groupcast connection would be preferred. A group can be defined/configured to include a plurality of target UEs serviced by a reference UE, and a target UE can be added into the group by transmitting a subscribe message to the reference UE or removed from the group by transmitting a unsubscribe message to the reference UE. In yet another example, the communication connection may be a broadcast connection and the reference UE can broadcast measurements to all nearby UEs including the target UE 110a.

The target UE 110a may transmit a measurement request to the selected reference UEs 110b at an operation 412. The measurement request may specify measurements needed at the target UE 110a. For example, the measurement request may contain a third list of TRPs 120 to be measured at the reference UEs 110b (also at the target UE 110a) , measurement type e.g. time or phase, measurement periodicity and the number of measurements needed at the target UE 110a. For double differential measurements, the measurement request may also specify pairing relation of the third list of TRPs.

In an example embodiment, if the reference UE 110b is providing the positioning reference service to other target UEs, the target UE 110a may transmit a registration request for the ongoing positioning reference service to the reference UE 110b. The registration request may contain the third list of TRPs of which the measurements need to be transmitted to the target UE 110a. In an example, the reference UE 110b may respond with a positioning reference service acknowledgement/confirmation message (not shown) to confirm successful registration of the target UE 110a. In an example embodiment, the reference UE 110b may take the measurement request as the registration request to the positioning reference service, and the operation 218 may be omitted.

Then the reference UE 110b may transmit measurement reports via the sidelink communication connection established at the operation 410 to the target UE 110a according to the measurement request, at operations 416a-n. The measurement report may include PRS arrival time/phase values measured with respect to the respective TRPs 120 or time/phase differences relating to pairs of TRPs 120. As mentioned above, the time/phase values or time/phase differences measured at the reference UEs 110b include the same impairments, i.e. time and phase errors resulting from unknown delays in the transmit chain of the TRPs 120, as those measured at the target UE 110a. The target UE 110a may combine measurements received from the reference UEs 110b with measurements generated at the target UE 110a to calculate double differences as discussed above with respect to Fig. 1. By calculating the double differences, the impairments included in the measured time/phase values or time/phase differences may be cancelled out. The target UE 110a may calculate its position coordinates based on the double differences, position coordinates of relevant TRPs 120, and position coordinates of relevant reference UEs 110b. Since the impairments included in the measured time/phase values or time/phase differences are cancelled out when calculating the double differences, accuracy of position estimation for the target UE 110a is improved. In an example, the target UE 110a may send the position estimation to the location server 130 via LPP signaling or to a base station to which the target UE 110a is connected.

In the procedure of Fig. 5, the measurement reports may be transmitted from the reference UEs 110b to the target UE 110a directly via the sidelink communication. It can minimize the reporting delay and accelerate the positioning procedure, which is beneficial especially for carrier-phase based positioning because the carrier phase changes quickly.

Fig. 6 illustrates a schematic block diagram of a device 500 according to an example embodiment of the present disclosure. The device 500 may be implemented as the target UE 110a and/or the reference UE 110b discussed above.

Referring to Fig. 6, the device 500 may comprise one or more processors 511, one or more memories 512 and one or more transceivers 513 interconnected through one or more buses 514. The one or more buses 514 may be address, data, or control buses, and may include any interconnection mechanism such as series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. Each of the one or more transceivers 513 may comprise a receiver and a transmitter, which are connected to one or more antennas 516. The device 500 may wirelessly communicate with a network device or a terminal device through the one or more antennas 516. The one or more memories 512 may include computer program code 515. The one or more memories 512 and the computer program code 515 may be configured to, when executed by the one or more processors 511, cause the device 500 to perform operations relating to the target UE 110a and/or operations relating to the reference UE 110b as described above.

The one or more processors 511 discussed above may be of any appropriate type that is suitable for the local technical network, and may include one or more of general purpose processors, special purpose processor, microprocessors, a digital signal processor (DSP) , one or more processors in a processor based multi-core processor architecture, as well as dedicated processors such as those developed based on Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuit (ASIC) . The one or more processors 511 may be configured to control other elements of the UE/network device and operate in cooperation with them to implement the procedures discussed above.

The one or more memories 512 may include at least one storage medium in various forms, such as a volatile memory and/or a non-volatile memory. The volatile memory may include but not limited to for example a random access memory (RAM) or a cache. The non-volatile memory may include but not limited to for example a read only memory (ROM) , a hard disk, a flash memory, and the like. Further, the one or more memories 512 may include but not limited to an electric, a magnetic, an optical, an electromagnetic, an infrared, or a semiconductor system, apparatus, or device or any combination of the above.

Some exemplary embodiments further provide computer program code or instructions which, when executed by one or more processors, may cause a device or apparatus to perform the procedures described above. The computer program code for carrying out procedures of the exemplary embodiments may be written in any combination of one or more programming languages. The computer program code may be provided to one or more processors or controllers of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

Some exemplary embodiments further provide a computer program product or a computer readable medium having the computer program code or instructions stored therein. The computer readable medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but is not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

It would be understood that blocks in the drawings may be implemented in various manners, including software, hardware, firmware, or any combination thereof. In some embodiments, one or more blocks may be implemented using software and/or firmware, for example, machine-executable instructions stored in the storage medium. In addition to or instead of machine-executable instructions, parts or all of the blocks in the drawings may be implemented, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-Programmable Gate Arrays (FPGAs) , Application-Specific Integrated Circuits (ASICs) , Application-Specific Standard Products (ASSPs) , System-on-Chip systems (SOCs) , Complex Programmable Logic Devices (CPLDs) , etc.

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

Although the subject matter has been described in a language that is specific to structural features and/or method actions, it is to be understood the subject matter defined in the appended claims is not limited to the specific features or actions described above. On the contrary, the above-described specific features and actions are disclosed as an example of implementing the claims

Certain abbreviations that may be found in the description and/or in the figures are herewith defined as follows:

LMC Location Management Component

LMF Location Management Function

LPP LTE Positioning Protocol

NRPPa NR Positioning Protocol a

PRS Positioning Reference Signal

SSB Synchronization Signal Block

SRS Sounding Reference Signal

TRP Transmission and Reception Point

UE User Equipment

Claims

A terminal device comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the terminal device at least to:

transmit a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices;

receive a positioning reference reply from the one or more reference devices, the positioning reference reply including positioning reference measurement capability of the one or more reference devices; and

select at least one reference device from the one or more reference devices for positioning of the terminal device, based at least in part on the received positioning reference reply.
The terminal device of Claim 1 wherein the positioning reference request is transmitted via broadcast or groupcast communication, and the groupcast communication is directed to a group of reference devices.
The terminal device of Claim 1 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device at least to:

receive a positioning reference advertisement before transmitting the positioning reference request, the positioning reference advertisement including information of the one or more reference devices.
The terminal device of Claim 1 wherein the positioning reference request includes one or more of:

a first list of network devices measurable for the terminal device;

signal level information of the first list of network devices measured at the terminal device; and

beam direction information of the first list of network devices with respect to the terminal device.
The terminal device of Claim 1 wherein the positioning reference measurement capability indicated in the positioning reference reply includes one or more of:

a second list of network devices measurable for the reference device;

signal level information of the second list of network devices measured at the reference device;

beam direction information of the second list of network devices with respect to the reference device; and

position coordinates of the reference device.
The terminal device of Claim 1 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device at least to:

perform channel measurements on the one or more reference devices from which the positioning reference reply is received, the at least one reference device being selected based at least in part on the channel measurements.
The terminal device of Claim 1 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device at least to:

report the selection of the at least one reference device to a network device to which the terminal device is connected and/or to a location server servicing the terminal device.
The terminal device of Claim 1 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device at least to:

establish a communication connection with the at least one reference device;

transmit a measurement request to the at least one reference device; and

receive a measurement report from the at least one reference device.
The terminal device of Claim 8 wherein the measurement request includes one or more of:

a third list of network devices to be measured;

network device pairing information; and

measurement type.
The terminal device of Claim 8 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device at least to:

transmit a registration request for a positioning reference service to the at least one reference device before receiving the measurement report.
The terminal device of Claim 1 wherein the positioning reference request is transmitted in response to a positioning reference trigger indication received from a location server or a network device to which the terminal device is connected.
A reference device comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the reference device at least to:

receive, from a terminal device, a positioning reference request on a sidelink between the terminal device and the reference device; and

transmit a positioning reference reply to the terminal device in response to the positioning reference request, the positioning reference reply including positioning reference measurement capability of the reference device.
The reference device of Claim 12 wherein the positioning reference request is received on broadcast or groupcast communication, and the groupcast is directed to a device group including a plurality of reference devices.
The reference device of Claim 12 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the reference device at least to:

transmit a positioning reference advertisement, the positioning reference advertisement including information of one or more reference devices.
The reference device of Claim 12 wherein the positioning reference request includes one or more of:

a first list of network devices measurable for the terminal device;

signal level information of the first list of network devices measured at the terminal device, and

beam direction information of the first list of network devices with respect to the terminal device.
The reference device of Claim 15 wherein the reference device transmits the positioning reference reply when it determines from the positioning reference request that it is capable of providing positioning reference to the terminal device.
The reference device of Claim 12 wherein the positioning reference measurement capability indicated in the positioning reference reply includes one or more of:

a second list of network devices measurable for the reference device;

signal level information of the second list of network devices measured at the reference device;

beam direction information of the second list of network devices with respect to the reference device; and

position coordinates of the reference device.
The reference device of Claim 12 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the reference device at least to:

establish a communication connection with the terminal device;

receive a measurement request from the terminal device; and

transmit a measurement report to the terminal device in response to the measurement request.
The reference device of Claim 18 wherein the measurement request includes one or more of:

a third list of network devices to be measured;

network device pairing information; and

measurement type.
The reference device of Claim 18 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the reference device at least to:

receive a registration request for a positioning reference service from the terminal device, the measurement report being transmitted in the positioning reference service.
A method implemented at a terminal device comprising:

transmitting a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices;

receiving a positioning reference reply from the one or more reference devices, the positioning reference reply including positioning reference measurement capability of the one or more reference devices; and

selecting at least one reference device from the one or more reference devices for positioning of the terminal device, based at least in part on the received positioning reference reply.
The method of Claim 21 wherein the positioning reference request is transmitted via broadcast or groupcast communication, and the groupcast communication is directed to a group of reference devices.
The method of Claim 21 further comprising:

receiving a positioning reference advertisement before transmitting the positioning reference request, the positioning reference advertisement including information of the one or more reference devices.
The method of Claim 21 wherein the positioning reference request includes one or more of:

a first list of network devices measurable for the terminal device;

signal level information of the first list of network devices measured at the terminal device; and

beam direction information of the first list of network devices with respect to the terminal device.
The method of Claim 21 wherein the positioning reference measurement capability indicated in the positioning reference reply includes one or more:

a second list of network devices measurable for the reference device;

signal level information of the second list of network devices measured at the reference device; and

beam direction information of the second list of network devices with respect to the reference device.
The method of Claim 21 further comprising:

perform channel measurements on the one or more reference devices from which the positioning reference reply is received, the at least one reference device being selected based at least in part on the channel measurements.
The method of Claim 21 further comprising:

report the selection of the at least one reference device to a network device to which the terminal device is connected and/or to a location server servicing the terminal device.
The method of Claim 21 further comprising:

establishing a communication connection with the at least one reference device;

transmitting a measurement request to the at least one reference device; and

receiving a measurement report from the at least one reference device.
The method of Claim 28 wherein the measurement request includes one or more of:

a third list of network devices to be measured;

network device pairing information; and

measurement type.
The method of Claim 28 further comprising:

transmitting a registration request for a positioning reference service to the at least one reference device before receiving the measurement report.
The method of Claim 21 wherein the positioning reference request is transmitted in response to a positioning reference trigger indication received from a location server or a network device to which the terminal device is connected.
A method implemented at a reference device comprising:

receiving, from a terminal device, a positioning reference request on a sidelink between the reference device and the terminal device; and

transmitting a positioning reference reply to the terminal device in response to the positioning reference request, the positioning reference reply including positioning reference measurement capability of the reference device.
The method of Claim 32 wherein the positioning reference request is received via broadcast or groupcast communication, and the groupcast communication is directed to a device group including a plurality of reference devices.
The method of Claim 32 further comprising:

transmitting a positioning reference advertisement, the positioning reference advertisement including information of the one or more reference devices.
The method of Claim 32 wherein the positioning reference request includes one or more of:

a first list of network devices measurable for the terminal device;

signal level information of the first list of network devices measured at the terminal device, and

beam direction information of the first list of network devices with respect to the terminal device.
The method of Claim 35 wherein the reference device transmits the positioning reference reply when it determines from the positioning reference request that it is capable of providing positioning reference to the terminal device.
The method of Claim 32 wherein the positioning reference measurement capability indicated in the positioning reference reply includes one or more of:

a second list of network devices measurable for the reference device;

signal level information of the second list of network devices measured at the reference device;

beam direction information of the second list of network devices with respect to the reference device; and

position coordinates of the reference device.
The method of Claim 32 further comprising:

establishing a communication connection with the terminal device;

receiving a measurement request from the terminal device; and

transmitting a measurement report to the terminal device in response to the measurement request.
The method of Claim 38 wherein the measurement request includes one or more of:

a third list of network devices to be measured;

network device pairing information; and

measurement type.
The method of Claim 38 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the reference device at least to:

receive a registration request for a positioning reference service from the terminal device, the measurement report being transmitted in the positioning reference service.
An apparatus comprising:

means for transmitting by a terminal device, a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices;

means for receiving a positioning reference reply from the one or more reference devices, the positioning reference reply including positioning reference measurement capability of the one or more reference devices; and

means for selecting at least one reference device from the one or more reference devices for positioning of the terminal device, based at least in part on the received positioning reference reply.
An apparatus comprising:

means for receiving, at a reference device and from a terminal device, a positioning reference request on a sidelink between the reference device and the terminal device; and

means for transmitting a positioning reference reply to the terminal device in response to the positioning reference request, the positioning reference reply including positioning reference measurement capability of the reference device.
A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of a terminal device, causing the terminal device at least to:

transmit a positioning reference request on one or more sidelinks between the terminal device and one or more reference devices;

receive a positioning reference reply from the one or more reference devices, the positioning reference reply including positioning reference measurement capability of the one or more reference devices; and

select at least one reference device from the one or more reference devices for positioning of the terminal device, based at least in part on the received positioning reference reply.
A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of a reference device, causing the reference device at least to:

receive from a terminal device, a positioning reference request on a sidelink between the reference device and the terminal device; and

transmit a positioning reference reply to the terminal device in response to the positioning reference request, the positioning reference reply including positioning reference measurement capability of the reference device.