Methods and devices for supporting positioning based on backscattering

Abstract

Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission by one or more radio nodes of the wireless system; transmitting (521), according to the configuration, wherein the reference signal is configured to indicate the first radio node as transmitter; obtaining (541, 551, 560) information indicative of time of reception of a backscattered signal (540) from the wireless device, said backscattered signal comprising a modulated version of the transmitted reference signal and being indicative of the first radio node as the transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

Description

[0001] METHODS AND DEVICES FOR SUPPORTING POSITIONING BASED ON

[0002] BACKSCATTERING

[0003] Technical field

[0004] This disclosure relates to solutions for use in a wireless system for facilitating positioning based on time travel measurement, such as round-trip time measurement or similar, between a wireless device to be positioned and one or more radio nodes of the wireless system. Specifically, solutions are related to positioning of low power devices operating by backscattering.

[0005] Background

[0006] Various protocols and technical requirements for wireless communication have been standardized under supervision of inter alia the 3rd Generation Partnership Project (3GPP). Improvement and further development are continuously carried out, and new or amended functions and features are thus implemented in successive releases of the technical specifications providing the framework for wireless communication.

[0007] Wireless communication may in various scenarios be carried out between a wireless network and a wireless device. Together, the wireless network and the wireless devices form a wireless system. The wireless network typically comprises a core network and an access network. The access network includes a plurality of access nodes, which historically have been referred to as base stations. In a 5G radio access network such a base station may be referred to as a gNB. Each gNB may have one or more Transmission and Reception Point(s) (TRP(s)). Each access node may be configured to serve one or more cells of a cellular wireless network. A variety of different types of wireless devices may be configured to communicate with the access network, and such wireless devices are generally referred to as User Equipment (UE). Communication which involves transmission from the UE and reception in the wireless network is generally referred to as Uplink (UL) communication, whereas communication which involves transmission from the wireless network and reception in the UE is generally referred to as Downlink (DL) communication. Every UE needs to be powered in some way to be able to communicate within the wireless system. Regardless of the capability of the UE, energy conservation is a relevant factor to consider. One development that can be identified in the evolving character of the specifications which provide regulations and guidelines for wireless communication, is the implementation of a larger variety of types of UEs, including UEs of lower complexity, as well as related regulations which may be simplified or relaxed with regard to communication configuration, associated with such lower complexity UEs. This can be seen as part of an evolution towards an Internet of Things (loT) context, where a vast amount of connectable UEs and UE types are conceivable, some of which may be configured only for simple communications tasks, such as to occasionally report a measured value of a certain parameter, such as radio signal measurement, positioning, and sensor output (e.g., temperature sensor, barometer sensor, humidity sensors, etc.). One of the considered UE types is ambient loT device. According to 3GPP TR 22.840 version 19.0.0 (2023-12), an Ambient Internet of Things (Ambient loT, AIoT) device is an ambient power-enabled Internet of Things device powered by energy harvesting, being either battery-less or with limited energy storage capability (e.g., using a capacitor). Target power consumption for ambient loT is expected to be very limited compared to existing low-power cellular devices. On the other hand, the existing positioning procedures and signaling are power consuming and therefore very demanding for the ambient loT devices. Backscattering is a technique used for transmission by loT device, enabling its low power operation. However, signaling and configuration according to legacy procedures may in many cases be challenging or even impossible for such types of UEs. In this context, legacy procedures for RAT-based positioning (RAT - Radio Access Technology) based on signal round trip-time (RTT) measurement are not suitable for low-power low-complexity ambient loT devices.

[0008] Summary

[0009] In view of the foregoing, it is an objective to present a solution for handling and facilitating positioning of wireless devices operating by backscattering. An aspect of this objective is to provide a solution for operating a radio node involved in such a process. Another aspect of this objective is to provide a solution for operating a location function, or location node, of a wireless network, which is involved in such a process.

[0010] The proposed solution is set out in the independent claims, whereas various examples thereof are set out in the dependent claims and in the following detailed description.

[0011] Brief description the drawings

[0012] Fig. 1A schematically illustrates an implementation of a wireless system, in which a UE communicates with a wireless network by radio communication with a radio node.

[0013] Fig. 2 schematically illustrates a general radio node, configured to operate in accordance with the proposed solution as laid out herein. The radio node may in various examples be an access node or base station of the wireless network, or a UE configured to communicate with the access node of the wireless network.

[0014] Fig. 3A illustrates an example of an AIoT wireless device which may transmit by backscattering of a received radio signal.

[0015] Fig. 3B illustrates details of an example configuration of the AIoT device of Fig. 3A.

[0016] Fig. 4 shows an example of a location node, configured to implement various aspects of the proposed solution.

[0017] Fig. 5A schematically illustrates an example context of positioning by trilateration, based on receiving backscattered reference signals, according to some examples of the proposed solution.

[0018] Fig. 5B shows a signaling diagram, illustrating various steps and aspects of different examples of the proposed solution.

[0019] Detailed description

[0020] In the following description, for the purposes of explanation and not limitation, details are set forth herein related to various examples. However, it will be apparent to those skilled in the art that the present invention may be practiced in other examples that depart from these specific details. In some instances, detailed descriptions of well- known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail. The functions of the various elements including functional blocks, including but not limited to those labeled or described as “computer”, “processor” or “controller”, may be provided through the use of hardware such as circuit hardware and / or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and / or computer-implemented and are thus machine-implemented. In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC), and (where appropriate) state machines capable of performing such functions. In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer and processor and controller may be employed interchangeably herein. When provided by a computer or processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, use of the term “processor” or “controller” shall also be construed to refer to other hardware capable of performing such functions and / or executing software, such as the example hardware recited above.

[0021] The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof. The terms “receive” or “receiving” data or information shall be understood as “detecting, from a received signal”. Fig. 1 illustrates a high-level perspective of operation of a wireless system, wherein a wireless communication network 100, denoted wireless network 100 for short herein, is configured to operate with various wireless devices. The wireless network 100 may be a radio communication network 100, configured to operate under the provisions specified by 3GPP, according to various examples. The wireless network 100 may comprise a core network (CN) 110, connectable to an external network 130 such as the Internet. The core network may comprise a plurality of core network nodes, which realize logical functions. For the example of a 5G system, this may inter alia include (though not shown in the drawing) the Access and Mobility Management Function (AMF), a Session Management Function (SMF), a User Plane Function (UPF), a Network Exposure Function (NEF), and an Application Function (AF), all of which are legacy functions of the 5G system. In some examples, a location node 140, or positioning node, may be configured in the wireless network. The location node 140 residing in the CN 110 may implement a Location Management Function (LMF) according to 3GPP provisions. In other examples, the location node 140 may be implemented as a separate entity outside the wireless network 100, connectable by a communication interface over a communication network 130.

[0022] The core network 110 is connected to at least one access network 120, e.g. Radio Access Network (RAN), comprising one or more base stations or access nodes, of which nodes 121, 122 and 123 are illustrated. For the sake of simplicity, reference will be made to access node 121 upon discussing related features and functions, but it shall be noted that a plurality of the access nodes of the RAN 120 may have similar or corresponding configuration. The access node 121 is a radio node configured for wireless communication on a physical channel with various wireless devices, including AIoT device 10. The drawing further indicates an intermediate node (IN)20, which may be configured to receive and transmit radio signals in communication with the RAN 120, and additionally communicate signals to and from the AIoT device 10. In some examples, the IN 20 is a UE, such as a wireless device. It should be noted, though, that where the role and functionality described herein for the IN 20 as being a UE may alternatively be carried out by another type of radio node, and that it need not be a mobile device. The physical channels may be used for setting up one or more logical channels. In some examples, the IN 20 may operate as an additional radio node involved in operation together with other radio nodes of the wireless network 100, for positioning of the AIoT device 10 according to the proposed solution.

[0023] In the drawing, arrows indicating communication paths are shown between the different access nodes 121-123 and the AIoT device 10, to illustrate backscattering by the AIoT device based on signals received from the respective access node. Moreover, a communication path is illustrated between the IN 20 and the AIoT device 10, indicating that the IN 20 in various examples can transmit radio signals and receive backscattering from the AIoT device 10. In this context, it may be noted that in some examples backscattering may be carried out omnidirectionally, wherein backscatter of a radio signal originating from a first radio node 121-123, 20 may be received in another one of those radio nodes. A communication path is further shown between the IN 20 and the access node 121, by means of which the IN 20 may communicate with the wireless network.

[0024] Before discussing further details and aspects of the proposed method, functional elements of the entities involved in carrying out the proposed solution will be briefly discussed with reference to the drawings.

[0025] Fig. 2 schematically illustrates a radio node 200, configured to carry out the various method steps outlined herein.

[0026] In various examples, the radio node is an access node of the wireless network 100, such as any of access nodes 121-123, i.e., a radio base station for operation in the radio network 100. In other examples, the radio node is an IN 20 configured for wireless communication with access nodes of the RAN 120, as indicated in Fig. 1. Such an IN 20 may be mobile or stationary, and the IN 20 may be a UE. The IN 20 may be configured, e.g., by an access node 121, to cooperate in a positioning service / procedure, so as to transmit radio signals and / or receive radio signals according to a radio configuration adapted for positioning of an AIoT device 10.

[0027] The radio node 200 may comprise a wireless transceiver 213, such as a radio transceiver for communicating with other entities of the wireless network 100. The transceiver 213 may thus include a radio receiver and transmitter for communicating through at least an air interface. The wireless transceiver 213, both in an access node 121-123 and an intermediate node IN 20, such as a UE, may be configured to transmit an RF signal, usable for AIoT devices to harvest energy and to transmit a backscattered signal. The radio node 200 may further comprise, or be connected to, an antenna 214 which may comprise a plurality of antennas (antenna elements) in an array configuration. The antenna array 214 is connected to the transceiver 213.

[0028] The radio node 200 further comprises logic circuitry 210 configured to control the radio node 200 to communicate with the other entities via the radio transceiver 213 on a physical channel. Where the radio node 200 is an access node, the logic circuitry 210 may be configured for resource allocation and may realize a scheduler for scheduling radio signal transmission.

[0029] The logic circuitry 210 may include a processing device 211, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. Processing device 211 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 211 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs.

[0030] The logic circuitry 210 may further include memory storage 212, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, memory storage 212 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. Memory storage 212 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 212 is configured for holding computer program code, which may be executed by the processing device 211, wherein the logic 210 is configured to control the radio node 200 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic 210.

[0031] Where the radio node 200 is an access node, an interface 215 is further included, configured for communication with the core network 110, such as the LMF 140. Further elements may be comprised in the radio node 200 but are left out of the drawing as they are not essential for the proposed solution, such as power supply, casing, etc.

[0032] Figs 3A and 3B schematically illustrates a wireless device 10 configured to operate in a wireless system comprising the wireless network 100. The wireless device is configured to operate by backscattering, i.e., to reflect incoming radio waves and add information to the backscattered signal, e.g., by modulation. For the sake of convenience, this type of wireless device is hereinafter referred to as an AIoT device by way of example, but it shall be noted that the proposed solution is not limited to any functions or features which may be deemed intimately linked to this term. It should further be noted that in some examples, the wireless device 10 may be capable of receiving and transmitting radio signals and data separately, as a standard legacy UE, but may at least be able to communicate by backscattering.

[0033] Fig. 3A shows some relevant elements or functions of the AIoT device 10. The UE 10 may however include other features and elements than those shown in the drawing or described herein, such as a casing, a user interface, sensors, etc., but these are left out for the sake of simplicity.

[0034] The AIoT 10 comprises a radio transceiver 313, for communicating in one or more frequency bands with other entities of the radio communication network 100, such as with the access node 121 or with another radio node over an air interface. The transceiver 313 may thus include a receiver chain (Rx) and a transmitter chain (Tx), for communicating over the air. The transceiver 313 may be or comprise a modem configured to encode, transmit, receive and decode data, conveyed using radio waves. In some examples, the transceiver may be configured to operate on a very low- complexity modulation, such as On-Off Keying (OOK) modulation, binary frequency shift keying (BFSK), and binary phase shift keying (BPSK), and is configured to use backscattering communication, as described with reference to Fig. 3B.

[0035] The AIoT 10 may further comprise an antenna system 314, which may include one or more antennas, antenna ports or antenna arrays. The antenna system 314 is connected to the transceiver 313.

[0036] The AIoT 10 further comprises logic circuitry 310 configured to control data and signal communication via the radio transceiver on a physical channel to a serving access node of the wireless network 100, and possibly data encoding and decoding. The logic circuitry is further configured to control the AIoT to carry out any of the steps associated with the proposed solution as outlined herein.

[0037] The logic circuitry 310 may include a processing device 311, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. The processing device 311 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 311 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs.

[0038] The logic circuitry 310 may further include memory storage 312, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, the memory storage 312 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. The memory storage 312 may further comprise a persistent memory, which is configured to maintain its state and hold its data even when not powered. The persistent memory may further be writable. The memory storage 312 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 312 is configured for holding computer program code, which may be executed by the processing device 311, wherein the logic circuitry 310 is configured to control the AIoT 10 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic circuitry 310.

[0039] The AIoT 10 further comprises an energy unit 315 that provides energy to the other components of the AIoT 10. In some examples, the energy unit 315 may comprise an energy storage, such as a capacitor or a battery. In some examples, the energy unit 315 is configured to harvest incoming radio frequency (RF) energy or other energy resources for instance light, kinetic energy, etc., which is used to power the other components of the AIoT 10, so as to enable certain processing and transmission or reception. Fig. 3B provides a schematic overview of such an example, usable in the AIoT 10, wherein the AIoT 10 may be configured as an ultra-low power loT device, that includes passive or semi-passive circuitry, and that harvests energy from a received RF signal to perform one or more tasks, such as transmission, reception, obtaining measurement etc. For transmission, the AIoT 10 thereby does not generate its own RF and is configured to employ so-called backscatter communication, similar to radio frequency identification (RFID) tags. In some examples, backscattering is when the transceiver 313 in the AIoT 10 uses a carrier wave, noted as RF in the drawing, for both energy harvesting and using it for transmission by reflecting the carrier back after modulating the carrier with data or information. Same reference numerals as used in Fig. 3A are used in Fig. 3B, although the functional elements are differently realized. In this context, and using the logical representation provided in Fig. 3B, the energy unit 315 may comprise a power harvesting circuit 316, connected to the antenna 314, a power management module and an energy storage. The transceiver 313 may comprise a communication control module, which is powered by the power management module. The communication control module may be connected to a demodulator for demodulating an incoming RF signal, and to a modulator for subsequently modulating an outgoing, “reflected”, RF signal. In some examples, the modulator is connected directly from the antenna 314. The AIoT device may thus be configured to transmit (backscatter) a backscattered signal which is the same as the incident signal, with some property being changed by modulation. The logic circuitry 310, comprising the processor 311 and memory 312, is likewise energized by the power management module and connected to control operation of the at least the transceiver 313.

[0040] For communication of radio signals with AIoT devices, it has been suggested to use the terms R2D (reader-to-device) and D2R (device-to reader). The device (D) refers to the ambient loT device and the reader (R) is either the intermediate node or the basestation. D2R is about backscattering / transmission from the device, this can be done in the DL spectrum or UL spectrum, depending on whether provided RF signal in either of the two spectrums and whether a frequency shifter is used or not to further transfer the signal to different frequency spectrum. The R2D is about reception at the device which could be a data / control / trigger signal or a carrier wave (RF signal). The data / control is transmitted in DL spectrum but the RF signal can be in either UL or DL spectrum. Additionally, the RF signal transmitter and backscatter signal receiver (Reader) are not always the same device. Backscatter is referred to as mono-static when reader and RF emitter / transmitter are the same device and bi-static backscattering when they are not.

[0041] Fig. 4 schematically illustrates an example of a location node 140 for use in a wireless system as presented herein, and for carrying out various method steps as outlined. The location node 140, which may alternatively be labelled positioning node, may be configured to control, order location, and / or estimate the location (based on the received measurement results) of wireless devices, such as the AIoT device 10, using at least RAT-based positioning. It may also be configured to control, receiving / transmitting the configuration of the radio node participating in positioning procedure of the wireless device, such as the AIoT device 10. The location node 140 may provide functionality of an LMF.

[0042] The location node 140 comprises logic circuitry 410 configured to determine configuration information (configuration for short) for reference signal transmission, for use by radio nodes 200, including various access nodes of the RAN, of the wireless system in a positioning / location operation to determine a location of wireless devices, e.g., the AIoT device 10. The configuration may comprise information related to the reference signal, such as radio resource information, and may comprise one or more parameter values defining, e.g., frequency bands or parts of bands, transmission repetition rates, timing information etc. The timing information may refer to a position in time of the radio resources, such as by reference to slots or sub-frame parts and may include frame / subframe number arrangement of reference signal transmission and periodicity of transmission.

[0043] The configuration may in some examples comprise information related to one or more AIoT devices, here exemplified as AIoT device 10, subjected to the positioning operation. In some examples, this information enables the radio node(s) 200 and / or the location node 140 to identify that a signal received in a radio node 200 is a backscattered signal. In some examples, this information enables the radio node(s) 200 and / or the location node 140 to identify that a signal received in a radio node 200 is backscattered from a particular AIoT device. This may include enabling the radio node 200 and / or the location node 140 to, based on a signal received in a radio node 200, uniquely identify the AIoT device 10, and / or determine that the received signal is backscattered from a certain type of AIoT device, and / or determine that the received signal is backscattered from a certain group of AIoT devices. In some examples, this information may comprise an ID of the AIoT device 10, and / or a modulation sequence which the AIoT device is configured to apply upon backscattering.

[0044] In some examples, the configuration is specifically adapted for positioning of AIoT devices, such as AIoT devices operating by backscattering. In this context, determining configuration may include receiving the configuration from one or more radio access nodes that may be involved in a positioning operation. The configuration may further include the location of radio nodes, such as access nodes 121-123 of the RAN 120, which may be used later for the positioning estimation of a wireless device based on obtained measurement of reference signal travel time. In this context, the location node may receive various parts of data of the configuration related to the resources, and further be configured to determine which radio resources to use and also the relation among them. The location node 140 may thereby be configured to determine scheduling of radio resources for one or more radio nodes, e.g., for use in association with a positioning request. The logic circuitry 410 may further be configured for making calculations and position estimations, based on measurement reports received associated with travel time between signal transmission and reception. The access nodes 121-123 report, to the LMF 140, the resource configuration comprising information on which resources they use for (AIoT) reference signal transmission. There may be one or more different sets of resources that can be used. Upon starting a positioning operation, the LMF 140 determines which access nodes to use (as Tx and / or Rx), the selected resources (e.g., set of resources) to be used, schedules the resources for reference signal transmission (e.g., the time to transmit the reference signal), and informs the access nodes accordingly.

[0045] The logic circuitry 410 may include a processing device 411, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. The processing device 411 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 411 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs.

[0046] The logic circuitry 410 may further include memory storage 412, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, the memory storage 412 may include a random-access memory (RAM), a dynamic random- access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. The memory storage 412 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid-state disk, etc.). The memory storage 412 is configured for holding computer program code, which may be executed by the processing device 411, wherein the logic circuitry 410 is configured to control the location node 140 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic circuitry 410.

[0047] The location node 140 may be realized in the cloud, or in one or more partitions of the core network 110, and may share parts of the logic circuitry with other entities of the wireless network 100.

[0048] The location node comprises one or more interfaces 413 for communicating with the RAN 120 and with wireless device, and with other entities of the wireless network 100.

[0049] Returning to what has been mentioned in the background section, new approaches and technologies, including positioning strategies, are needed supporting devices with no or very limited energy storage capability where the devices with energy storage do not need to be replaced or recharged manually. Conventional radio communication requires devices to generate radio signals using power-hungry analog components such as digital-to-analog converters (DACs), mixers, oscillators and power amplifiers in the transmitter and low noise amplifiers, mixers, oscillators, and analog-to-digital converters (ADCs) in the receiver.

[0050] With reference to the general description of the AIoT device 10 with reference to Figs 3A and 3B, it may be noted that for transmission, backscattering (BSC) is a potential candidate that can help avoid the use of power-hungry components. With backscatter communication, ultra-low power devices can transmit their information through modulating and reflecting RF signals instead of generating actual radio waves using power-hungry transmitters. For this, a BSC transmitter device uses an ultra-low power load modulator. For reception, simple and low-complexity modulations such as on-off-keying (OOK), binary frequency shift keying (BFSK) and pulse position modulation (PPM), allow for low-power low-complexity receiver design in the AIoT device 10.

[0051] Existing positioning procedures and signaling in the context of location / position measurements based on reference signal transmission, are power-consuming and therefore very demanding for ambient loT devices. In these existing techniques, scheduling and resource configuration of both DL and UL positioning reference signals, referred to as positioning reference signal (PRS) and sounding reference signal (SRS), respectively, need to be communicated in advance between the UE and the access node.

[0052] Both the UE and the access node need to be fully synchronized.

[0053] Additionally, reception of the PRS and transmission of SRS need a power- hungry OFDM (Orthogonal Frequency Division Multiplex) based receiver and transmitter at the UE.

[0054] To allow low-power operation of ambient loT, new positioning strategies are needed. These challenges are targeted by the proposed solution, as described herein, wherein the proposed solution relies on and involves a positioning methodology based on travel time of a reference signal and backscattering technique. The proposed solution thus comprises a method to carry out positioning for a backscattering device with network assistance for measurement.

[0055] According to one aspect, a method is suggested to be carried out in a first radio node 200 for supporting positioning of the backscattering wireless device 10 based on reference signal transmission in a wireless system. The radio node may be an access node 121 of the wireless network 200, or e.g. a UE 20 configured to cooperate in the positioning (e.g., by the access node 121).

[0056] It may be noted that, in order to support positioning, the objective for the radio node 200 is to obtain time measurements related to signal travel time, wherein the location node 140 subsequently may use the time measurement, preferably a combination of several time measurements obtained from different radio nodes at different locations, to determine a location estimation of the wireless device 10. This may be obtained based on multi-lateration, a well-known technology which will not be described in any deeper detail. Nevertheless, it may be noted that three or more time measurements obtained based on signals conveyed between the wireless device 10 and different radio nodes may be combined to establish the location estimate of the wireless device 10, based on known (or measured) positions of the radio nodes. Nevertheless, positioning may alternatively be carried out based on a time measurement using fewer radio nodes 200, such as one or two radio nodes 200.

[0057] Fig. 5A shows a setup for positioning of the AIoT device 10 according to one example of the proposed solution. Further aspects, examples and variants will be described with reference to the signaling diagram of Fig. 5B.

[0058] In Fig. 5A, three radio nodes 121, 122, 123 are shown, which participate in positioning of the AIoT device 10 in cooperation with the location node 140. In this drawing, the radio nodes are all base stations of the RAN 120, marked gNBs. For the purpose of positioning the AIoT device 10, where the location of each participating radio node is subsequently required, each radio node may be referred to as a Transmission and Reception Point (TRP), which comprises at least the antenna 214 of the radio node. In alternative embodiments, one or more of the radio nodes may be a UE 20 configured as an assisting / assistance radio node for signal transmission, reception, or both.

[0059] The radio nodes 121, 122, 123 transmit reference signals at known time occasions, i.e., at known times of transmission, wherein the reference signal is configured to be indicative of the radio node from which it is transmitted. This configuring of the reference signal may be carried out by the transmitting radio node in different ways, e.g., according to any of the following examples, alone or in combination.

[0060] In one example, this is obtained by the reference signal being configured with an ID associated with the transmitting radio node.

[0061] In one example, this is obtained by a radio node ID of the transmitting radio node being embedded in the signal.

[0062] In one example, this is obtained by configuring the reference signal with a certain signal characteristic which identifies the radio node from which it is transmitted.

[0063] In one example, the signal characteristic is obtained by radio resource configuration and / or resource allocation for the transmission of the reference signal.

[0064] In one example, the signal characteristic is obtained by configuring the reference signal with a certain sequence or modulation, indicative of the transmitting radio node. Said sequence or modulation may have a certain ID. In one example, the signal characteristic is obtained by scheduling of transmission time of the reference signal being distributed in time for the radio nodes involved in a positioning operation, such that a measured time of reception of the backscattered signal is sufficient to determine from which of the radio nodes the reference signal (that was backscattered) was transmitted. Such distribution in time may comprise configuring reference signal transmission from the radio nodes to be separated by more than a certain time, which may correlate with a distance exceeding a certain value. This may be based on an estimated area in which the AIoT device is located, and / or on known positions of the radio nodes.

[0065] The time of transmission may be defined by the configuration for the reference signal transmission. The configuration may comprise radio resource configuration and scheduling, as described. In some examples, the reference signal defined by the configuration may be a PRS signal. In some examples, the reference signals are dedicatedly designed for the purpose of AIoT positioning. In some examples, the configuration defines orthogonal reference signals, or reference signals with good auto- and cross- correlation properties, to be transmitted by the radio nodes involved in a positioning operation. In some examples, the reference signal is modulated by low complexity modulation. As opposed to legacy PRS, which uses OFDM, the modulation may use single carrier, and may in some examples be one of OOK, FSK, BFSK or BPSK. In some examples, the configuration may define a small bandwidth for the reference signal, such as 1MHz or 5MHz, and may be contiguous within a set of resource blocks (RB). The reference signals are indicated as si, S2, S3 in the drawing, where the numbering refers to the ID of the associated transmitting radio node 121 gNBi, 122 gNBi, and 123 gNBi, respectively. By way of example, the reference signals carrying information indicative of the gNB ID may comprise gold sequences of length 31, like the PRS of the NR (New Radio) system.

[0066] In broad terms, the AIoT device 10 retransmits a modulated version, r, of its received signal, s, by backscattering (see signal transmission 540 in Fig. 5B). At any given time, the AIoT device 10 receives the sum of any received signals and backscatters the signal, embedding its own AIoT ID or otherwise modulating the received signal s. The AIoT device may, as such, be configured according to one or more of the following examples: In some examples, the AIoT device 10 is configured to monitor and turn on its backscatter function only after detection of specifically configured radio signals, such as a wake-up signal indicating positioning operation, or a part of the reference signals configured for transmission in a positioning operation, such as an initial part. Such specifically configured radio signals are in some examples also referred to herein as trigger signals.

[0067] In some examples, the AIoT device 10 is configured to listen for specific sequences (e.g., sequence IDs) used in the reference signals (e.g., by correlating signals s against sequences generated using those specific sequences or sequence IDs). Different AIoT devices may be configured to listen for different sequences.

[0068] In some examples, the AIoT device 10 is configured to enable backscatter functionality only when those specific sequences or sequence IDs are detected.

[0069] In some examples, for received signals with detected sequences or sequence IDs other than said specific sequences or sequence IDs, and / or for other received RF signals, the AIoT device 10 may be configured to backscatter the incoming signals unmodulated or be configured to only harvest the energy from the received signal.

[0070] In some examples, the AIoT device 10 may be configured to modulate some information (such as information indicative of it being an AIoT type device and / or an ID associated with the AIoT device 10, as exemplified herein) on top of any detectable incoming reference signal s.

[0071] In some examples, the AIoT device 10 is configured to backscatter (e.g., activate backscatter functionality), in accordance with any of the mentioned examples, only at a certain time frame (duration), used for positioning. In some examples, such time frames may be preconfigured in the AIoT device 10, and may reoccur periodically or semi- persistently, according to a schedule known to the LMF 140 and / or the radio nodes. In some examples, such a time frame is activated as an On period of the AIoT device 10, responsive to receiving said specifically configured radio signals (trigger signals).

[0072] The outlined examples provide the benefit of different ways of enabling positioning of one (or many) intended AIoT device(s) 10 at a positioning operation without the radio nodes necessarily receiving backscattering from other backscattering devices.

[0073] The radio nodes receive the backscattered signal and correlates or maps it with the corresponding transmitted reference signal. This way, travel time (comprising e.g. timing measurement, round-trip-time (RTT) or transit time) of the signal can be determined based on the time of transmission of the reference signal and the time of reception of the backscattered signal configured to be indicative of the transmitting radio node. The RTT from the N number of transmitting radio nodes may be used to estimate the location of the AIoT device, e.g. by processing in the LMF 140 based on measurement reports indicative of the travel time. In some examples, the measurement report comprises the time of reception (e.g., a time stamp), wherein the travel time (e.g. RTT) may be calculated in the LMF 140 based on the known configuration. The measurement report may in such examples further comprise information indicative of the ID associated with the AIoT device 10, such as a device ID of the AIoT device 10 or a sequence ID used by the AIoT device 10 upon backscattering, as detected by the receiving radio node. The measurement report may further comprise or be indicative of an ID of the receiving radio node. In some examples, the measurement report may further comprise received signals strength, such as a Received Signal Strength Indicator (RSSI), of the backscattered signal. In other examples, the travel time is calculated in the receiving radio node and provided to the LMF 140 in the measurement report. In some examples, the receiving radio nodes also correlate the received backscatter signal r based on a known modulation technique applied by the AIoT device, to obtain the known AIoT device ID, necessary to distinguish the AIoT device 10 from other backscattering or transmitting devices.

[0074] The example of Fig. 5A shows N = 3 radio nodes and K = 1 AIoT devices and how their signals (s) are transmitted and backscattered (r). The example in this drawing indicates reception, in each radio node, of a modulated version of its own transmitted reference signal, such that each backscattered signal r is indicative of an ID associated with the AIoT device 10, such as comprising an embedded AIoT ID or being configured with a certain sequence ID as exemplified. It should be noted, though, as will be further described below, that in various examples one or more of the radio nodes may receive backscattered signals which are modulated versions of the reference signal transmitted by other radio nodes (than the receiving radio node). In such examples, correlation to obtain the radio node ID (of the transmitting radio node) from the backscattered signal, to link the time of transmission of the reference signal with the time of reception of the backscattered signal, may be carried out by one of the radio nodes or by the LMF 140. The reference signal is preferably a reference signal with good autocorrelation properties. In different examples, the reference signal comprises a gold sequence, m- sequence or Zadoff-Chu sequence, of a defined length. As noted, configuration of the reference signal may be handled in cooperation with a core network entity such as the LMF 140. For example, signal allocation, such as configuration of radio resources, is performed by radio node which will transmit the reference signal. Then, the radio node informs LMF 140 of the resource configuration. Allocation properties of the radio resources are configured in such a way that it is possible for the AIoT device 10 to backscatter the reference signal. In other words, the signal, s, is configured within a frequency layer possible for the AIoT device 10 to backscatter. This can be achieved by knowing (i.e., obtaining) the actual capability of the AIoT device 10. In this context, the capability of the AIoT device 10 may have been previously obtained as UE radio capability information, according to legacy procedures. In alternative examples, the configuration may configure the radio node(s) to transmit gradually over different selected frequency ranges where AIoT devices are allowed to operate or to transmit over a full set of configured frequency bands.

[0075] It may be the case that the AIoT device 10 might not always be awake for backscattering and therefore not respond. In such scenarios, the LMF 140 and the radio nodes cannot always expect a backscattered signal. However, the proposed solution is based on the notion that the AIoT device 10 at some points or periods can backscatter the transmitted reference signal intended for the positioning. In some examples, the configuration defines timing of the reference signal transmission based on a predetermined active period of the AIoT device 10. The active period may be configured by the wireless network 100, or be pre-configured in the AIoT device 10, and is thereby known to the LMF 140 and / or the radio nodes. In an alternative solution, the transmitting radio node is configured to first transmit a trigger signal, such as wakeup signal, to trigger or switch on the AIoT device 10 based on harvested energy from the trigger signal. This may in some examples trigger the AIoT device 10 to activate backscatter functionality, as previously described.

[0076] The AIoT device 10 is backscattering the sum of the signals transmitted from the radio nodes together with any disturbances, white or colored, at a given time. For example, if the radio nodes transmit their reference signals at the same time (i.e., at least overlapping) their signals will interfere at the AIoT device 10. For this reason, scheduling according to the configuration may for some examples comprise a comb structure of radio resources, corresponding to the PRS comb structure of 5G legacy systems where the nearby gNBs have different resource elements. In other examples, scheduling according to the configuration is separated in time for different radio nodes included in a positioning operation, such as corresponding to Time Division Multiple Access (TDMA). Each radio node configured by the LMF 140 to participate in a positioning operation, are thus configured with scheduling which defines transmission time divided by time gaps. The time gap is in such examples configured to ensure that reference signals from two or more radio nodes are not received concurrently in the AIoT device 10. The time gap may be defined using a time dimension, or as a number of symbols, slots or subframes. In some examples, the time gap is predefined. In another example, the LMF 140 is configured to selectively configure said time gaps, e.g. by selection of one of a plurality of usable time gaps. In some examples, the LMF 140 configures the time gap of the scheduling based on the location of the radio nodes involved in a positioning operation.

[0077] To mitigate interference at the receiving radio node, caused by multiple AIoT devices backscattering simultaneously, it is possible to apply different methods of interference mitigation. In one example, the modulation applied by the respective AIoT device is encoded with orthogonal words, or with good auto- cross- correlation properties, only, enabling the receiving radio nodes to resolve the modulated information. Additionally, in some examples the modulation involves shifting the center frequency of the backscattering.

[0078] The modulation performed in the AIoT device 10 according to the proposed solution involves adding information indicative of an ID of or associated with the AIoT device 10, such as the AIoT ID or an ID of a modulation sequence applied by the AIoT device 10. The AIoT ID may be unique or be shared by a group of AIoT devices. The objective is that the radio nodes may identify the AIoT device 10 performing the backscatter. The modulation applied at the AIoT device 10 may be of different kinds. In one example, as shown in Fig. 5A, a simple modulation scheme, e.g., On-Off keying (OOK), BFSK, BPSK ,is used. The possible implementation of a simple modulation is a switching off / ON different load impedances in a timely manner performing this modulation either in amplitude or frequency domain. Here the AIoT ID is fully represented in the added modulation of the received reference signal. The AIoT ID is in one example plain text, and in other examples embedded in a protocol, i.e., there is a mapping between actual AIoT ID and a label / ID of that AIoT device as conveyed in the backscattered signal, potentially also with other data (such as sensor data) concurrently transmitted by the AIoT device 10 in the backscattered signal. In some examples, the new AIoT label / ID can have shortened length compared to the actual AIoT ID and it may have restrictions, such as certain time or certain areas where the new AIoT label / ID can be used in. These examples allow for concurrent positioning and data exchange with additional data embedded in the protocol (i.e., in addition to the AIoT ID).

[0079] At each radio node, receiver branches of the transceiver 213 may cross-correlate the known transmitted signals { si, S2, ... SN} according to the configuration, with the received (modulated) backscattered signals {n, r2, ... I'K } . Where the scheduling is such that each r comprises a modulated sum of the reference signal transmissions from a plurality of radio nodes (e.g., in the case of a comb structure configuration of the reference signals), the receiving radio nodes need to exchange the radio node IDs or have them communicated by the LMF 140. Thus, each radio node is in one example configured to report, to the LMF 140, an indication of travel time, e.g., time-of- arrival / reception time, related to its own transmitted reference signal as well as the reference signals transmitted by other radio nodes involved in the positioning operation. In this context, the travel time obtained, based on time of reference signal transmission and time of reception of the backscattered signal, may comprise “transit-time” measurements in addition to (or in replacement of) round-trip-time measurements.

[0080] As noted, an alternative to using comb structure configuration of the reference signals is to include time gaps between transmissions of the reference signal from different radio nodes. In this case, the reference signals from multiple radio nodes are arranged in time division multiplexing manner. In some examples, each radio node involved in the positioning operation is configured to only monitor its own radio node ID in received backscattered signals, and / or to only monitor a time range configured for that radio node (separated from time ranges of the other radio nodes based on the time gap) when correlating with the backscattered signal. In some examples, the AIoT device 10 is configured to transmit a backscattered signal on a different carrier than the received reference signal, operating as excitation signal. In other words, the AIoT device 10 is configured to change the carrier frequency. A benefit of such a solution is that it reduces problems with interference. In some examples, the AIoT device 10 may backscatter with a certain time delay. The time delay can be caused by the hardware / software processing time in the AIoT device 10, such as filter group delay, switching time, signal processing through some units, etc. The time delay may also be affected by the device temperature. In such examples, AIoT delay / processing time can be signaled by the AIoT device 10 or preconfigured on network system level at e.g. provisioning / authentication / capability setting of the AIoT device 10. Information about any delay is important to not degrade travel time measurement accuracy. Also, if the time delays are inserted by the AIoT device, these delays are selected from a set of possible delays known to the radio node. Alternatively, the average value of possible time delays is used. The radio node may know this information can be up to the implementation of the radio node.

[0081] As noted, the example shown in Fig. 5A represents a case when multiple radio nodes transmit reference signals and calculate the timing measurement (time of reception and / or travel time, i.e. RTT) based on a backscattered signal which is a modulated version of its own reference signal. The obtained measurement result is sent to the LMF 140 in a report indicative of travel time. As indicated, this report may include the actual travel time, or only the time of reception, and further elements of information, as explained above. The LMF 140 is configured to calculate the positioning estimation, in order to estimate a position of the AIoT device 10, such as a geographical position or an area. In order for the LMF 140 to calculate the positioning estimation, multiple measurement results from different radio nodes are required so that LMF 140 can perform multi-lateration. For an accurate positioning estimation, those measurement results should be processed within a certain time window, to accommodate for mobility of the AIoT device 10 and / or alterations in propagation paths and fading. In one embodiment, the configuration defines transmission of reference signals from multiple radio nodes is arranged so that within a configured time window, reference signal transmission is scheduled to be executed from a group of radio nodes involved in the positioning operation. Each positioning estimate is thus configured to be based on the reference signals (from multiple radio nodes) within the time window. In some examples, the report indicative of travel time comprises a time stamp. The LMF 140 may thereby be configured to calculate the positioning estimation based on the obtained reports indicative of travel time, for which the time stamps are within the same configured time window. While the example of Fig. 5A illustrates reception in the respective radio nodes of backscattered signals r, which are modulated versions of each their own transmitted reference signals s, it has already been mentioned that the radio nodes may both receive and correlate with backscattered signals comprising modulated versions of reference signals from other radio nodes, or even of a sum of reference signals from different radio nodes.

[0082] In one example, only one radio node is configured to transmit reference signals, whereas that one radio node and the other radio nodes receive the backscattered signal and determines time of reception, for use in determining the travel time. In this context, said one radio node determines time of reception associated with RTT whereas the other radio nodes determine time of reception associated with transit time. Each radio node may be configured to send a respective report indicative of the travel time to the LMF 140. In a variant of this example, the radio nodes involved in the positioning operation, which are only configured to receive the backscattered signal, may report the time of reception to said one radio node configured to transmit the reference signal. This arrangement may be determined by the configuration for the positioning operation and may be prescribed by the LMF 140.

[0083] In another, related, example, one or more radio nodes may be configured to transmit positioning reference signals, and one or more assisting UEs 20 may be configured to monitor reception of the backscattered signal r. Configuring an assisting UE 20 may comprise transmitting UE configuration to the at UE 20, appointing it to cooperate in the positioning operation. Transmitting the UE configuration may be carried out in one or more messages, by one of the radio nodes or by the LMF 140, or with different parts of the UE configuration transmitted from the radio node and from the LMF 140. Configuring the assisting UE 20 may thus involve providing, by one of the radio nodes or by the LMF 140, UE configuration indicative of the configuration of the reference signals to identify at least time of transmission. The UE configuration provided to the assisting UE 20 may further comprise the AIoT ID (or any other parameters from which the superimposed OOK modulating signal of the AIoT device 10 can be derived), thus enabling the UE 20 to ascertain a backscattered signal from the associated AIoT device 10 based on the modulation applied by the AIoT device 10 to indicate said AIoT ID. The UE configuration may further comprise radio node ID of at least one of the radio nodes, and / or other parameters from which the reference signals can be derived. Such various details of the configuration of the reference signals have been outlined in the foregoing.

[0084] A benefit of transmitting the reference signal from one radio node and monitoring reception in another radio node (such as an assisting UE 20) is that the transmitting radio node need not operate in full-duplex mode.

[0085] Fig. 5B shows a signaling diagram, which comprises various steps and features included in methods according to the proposed solution, including those described in the foregoing. The diagram shows actions taken in and signals conveyed between various entities which may be involved in different examples of a positioning operation to related to obtaining an estimate of a position or location of the AIoT device 10. The drawing thus indicates the LMF 140 and one or more radio nodes 121, 122, 123 which are exemplified as access nodes of the RAN 120, as well as an intermediate node 10 which may be involved, such as an assisting UE 20. For the sake of clarity, it is pointed out that the different specific examples and details described in the foregoing, such as information related to signaling and configurations, are equally applicable in the various associated steps described with reference to Fig. 5B.

[0086] At 500, configuration for the reference signal transmission is determined. As described, this may involve several steps, e.g. including one or more of definition of configuration of radio resources (which may be configured by the respective access node 121-123) and scheduling of those resources for the radio nodes 121-123 that shall be involved in the positioning operation (which may be configured by the EMF 140), including timing information of transmission by the respective access node 121-123. The configuration may further be indicative of the time window in which to monitor reception of backscattered signals. As noted, determining the configuration may involve transmission of one or more messages between the EMF 140 and the access nodes 121- 123.

[0087] Determining the configuration may further comprise sending a positioning request 501, identifying the AIoT 10 to be positioned, from the EMF 140 to the radio nodes which are appointed to participate in the positioning operation. Appointing radio nodes may be based on a last known position or an assumed location area of the AIoT device 10, which as such may be obtained based on a last access node 121 which has communicated with the AIoT device 10 and possibly on predicted movement of the AIoT device 10. The positioning request may further comprise the AIoT ID of the AIoT device 10, and / or information indicative of a modulation applied by the AIoT device 10 to indicate its AIoT ID. In some examples, the positioning request is further indicative, for each respective radio node 121-123, of an instruction to transmit reference signals, to monitor reception of backscattered signals, or both.

[0088] At 510, one radio node 121 may further provide configuration to an intermediate node IN 20, to configure the IN 20 to participate in the positioning operation. In this context, the IN 20 may be a UE 20, configured to operate as an assisting radio node. This involves configuring the IN 20 as an assisting node to monitor reception of the backscattered signal based on the configuration. The configuration may comprise the configuration of the transmitted reference signals from AN 121-123, and the configuration may comprise information enabling the IN 20 to determine information (from a backscattered signal) indicative of the radio node which transmitted the reference signal. The configuration may further indicate required measurement report format / content (described with reference to 550 below).

[0089] At 515 a trigger signal is transmitted by at least one of the radio nodes 121-123. In an alternative, as described in the foregoing, the reference signal itself (e.g., a characteristic such as a sequence of the reference signal or of a part of a received reference signal) may act as the trigger signal. Various examples of how the AIoT device 10 may act based on receiving the trigger signal 515 have been described. As described, the trigger signal may be configured to act as a wake-up signal for the AIoT device 10, to prepare it for reference signal reception and backscattering, such as to activate backscatter functionality. In this context, RF energy from the trigger signal may be harvested by the AIoT device, to execute the wake up and / or to configure the AIoT device 10 to backscatter, and / or to introduce a modulation indicative of the ID of the AIoT device 10 upon backscattering. While the drawing indicates transmission of the trigger signal 515 by only one radio node 121, it may in some examples be transmitted by each access node 121-123 involved in the positioning operation.

[0090] 521, 522, 523, indicates the reference signals transmitted by the (appointed) radio node(s) 121, 122, 123 in accordance with the configuration, such as according to a scheduling obtained from the LMF 140. The reference signal is a positioning reference signal which may be configured for AIoT positioning, which is labelled PRS in the drawing. In some examples, the reference signals further serve as signals for harvesting and reusing energy in the AIoT device 10. Each reference signal transmission is configured to be indicative of the transmitting radio node, such as by comprising a radio node ID or sequence ID (ID_121, ID_122, ID_123) of the radio node that transmitted the reference signal. Further alternative examples are provided above. As noted, the transmission may be carried out based on scheduling of the reference signal transmission which is distributed in time among said one or more radio nodes 121, 122, 123. In this context, said transmission may be separated by a configured time gap, to ensure or increase the chances of receiving peaks of the backscattered signal only comprising a modulated version of one of the radio nodes 121, 122, 123 at a time.

[0091] At 530, a common indication is provided to indicate that one or more of the transmitted reference signals are received, modulated and backscattered by the AIoT device 10. This is obtained by modulating the reference signals to include an indication of the AIoT ID of the AIoT device 10 in the backscattered signal. In this context, it may be noted that in some examples the AIoT device 10 operates passively (i.e., backscattering operation without energy storage or very limited energy storage) and does not operate differently dependent on whether one or more reference signals are received concurrently; it merely modulates and backscatters. In some examples, the AIoT device is configured to backscatter and / or configured to include an indication of the AIoT ID, responsive to previously receiving the trigger signal 515.

[0092] 540 indicates the backscattered signal, as transmitted from the AIoT device 10. The backscattered signal 540 is a modulated version of the reference signal(s) received in the AIoT device and is indicative of the radio node(s) that transmitted those reference signal(s). A modulation is applied by the AIoT device 10, to obtain said modulated version. Information indicative of the AIoT ID may further be embedded in the backscattered signal by said modulation, according to one of the examples provided herein. In this context, it may be noted that while the drawing indicates AIoT ID in the backscattered signal 540, this ID need not be explicitly comprised. In some examples, the backscattered signal 540 is rather configured with a modulation having an ID, such as a sequence ID, which is implicitly linked to or associated with the ID of the AIoT device 10.

[0093] At 541-544, reception of the backscattered signal 540 in one or more of the radio nodes is indicated. The backscattered signal 540 is indicative of a modulation applied by the wireless device and of the radio node(s) that transmitted the reference signal(s). Information indicative of the AIoT ID of the AIoT device 10 is further embedded in the backscattered signal by said modulation based on, e.g., OOK, FSK, or PSK modulation. Reception in the UE 20, configured to operate as an assisting radio node, is specifically indicated at 544. In such an example, the UE 20 is configured, by the UE configuration, to determine the time of reception of the backscattered signal 540 in the UE 20. This may involve determining that the received backscattered signal 540 comprises or is indicative of the AIoT ID, e.g. based on knowledge of the modulation applied by the AIoT device 10.

[0094] The UE 20 may be configured, by means of the UE configuration, to transmit a reception report 550 for reception in the radio node 121 which appointed / configured the UE 20 to assist in the positioning operation. At step 55, the radio node 121 thus obtains information 550 indicative of the time of reception of a backscattered signal in the UE 20. The reception report may further be indicative of the radio node which transmitted the reference signal based on which the backscattered signal 540 was received. In one example, an ID of the transmitting radio node is determined by the UE 20, based on the received backscattered signal 540, and embeds information indicative of said ID in the reception report 550. In another example, the UE 20 embeds other information obtained based on receiving the backscattered signal 540, such as information of a characteristic of the backscattered signal 540, and includes such information in the reception report 550, wherein said information may be indicative of the transmitting radio node in accordance with any of the examples provided herein This information may subsequently be conveyed (step 580 below), by the radio node 121 which receives the reception message 550, in a measurement report to the LMF 140. Alternatively, the radio node 121, which receives the reception message 550, determines which radio node transmitted the reference signal, based on the received information, and includes information indicative of the transmitting radio node in the measurement report to the LMF 140. In an alternative example (not shown), the UE 20 may be configured, by means of the UE configuration, to transmit the reception report 550 directly to the LMF 140 by non-access stratum (NAS) signaling. In some examples, the UE 20 is configured to determine / calculate travel time from the transmitting radio node and the UE 20, based on the configuration which determines time of transmission of the reference signal, and determined time of reception of the backscattered signal 540. In such examples, the reception report 550 may comprise the determined travel time, also referred to herein as transit time. The reception message 550 may thereby be referred to as a measurement report.

[0095] At 560, the radio node(s) which receive the backscattered signal 540 process the received signal(s) to obtain the embedded indication of the AIoT ID by means of some detection strategy, e.g., correlation. The processing may involve one or more of matchfiltering with the one or more radio node IDs and measuring a power delay profile (PDP). The processing may comprise demodulating the signal, based on the known modulation applied by the AIoT device 10 (possibly based on one or more orthogonal words or with good auto- cross- correlation properties), correlation to determine radio node ID of the radio node which transmitted the signal which is backscattered, and determining a time of reception of the backscattered signal. At 570, the radio node(s) may optionally determine an estimate of travel time, associated with an occasion representing time of transmission of the reference signal and the time of reception of the backscattered signal which is a modulated version of the reference signal transmitted at that occasion. Where this relates to a reference signal transmitted by the receiving radio node, the travel time amounts to an RTT measure. In some examples, each radio node 121, 122, 123, 20 which obtains information indicative of time of reception of a backscattered signal 540 is further configured to calculate an associated estimate of travel time, based on the configuration (such as based on the scheduling). In other examples, obtained information of time of reception (e.g., reception in radio node 122) is relayed to the radio station which transmitted the reference signal (e.g., radio node 121), where calculation of an estimate of travel time based (RTT) is carried out. The receiving radio node 122 may be configured to determine the transmitting radio node 121 based on the received backscattered signal 540, as described. Where the backscattered signal was received in a a receiving radio node (such as 121 or the UE 20) which is different from the transmitting radio node (e.g., 121), the travel time may in some examples comprise only to a measure of transit time, between transmission from the transmitting radio node, via the AIoT device 10 which modulates and backscatters, to the receiving radio node.

[0096] At 580, the / each radio node transmits a measurement report for reception in the LMF 140. As described, this report may be transmitted separately by each receiving radio node, among the radio nodes 121-123 participating in the positioning operation. Alternatively, one of the radio nodes 121-123 participating in the positioning operation may obtain information indicative of travel time from the other radio nodes and transmit the report at 580 to the LMF 140. Where the travel time has already been determined at step 570, the travel time may be comprised in the measurement report 580.

[0097] Alternatively, the report 580 comprises an indication of the time of reception of the backscattered signal, wherein the travel time is subsequently calculated (590) in the LMF 140, based on the configuration which identifies the associated time of transmission.

[0098] The measurement report may comprise one or more of:

[0099] Information of an ID that can be associated with a particular AIoT device, such as sequence ID or an AIoT device ID, obtained based on the backscattered signal. The sequence ID may be linked to the modulation applied by the wireless device on the backscattered signal.

[0100] Information indicative of travel time, associated with that AIoT ID, such as time of reception, RTT or transit time.

[0101] Information indicative of quality of measurement, representing the quality of the obtained time measurement. For example, if the correlation process results in a high peak then it can be considered the obtained result is with a good quality.

[0102] Information indicating the radio node which transmitted the reference signal(s) which was backscattered, such as radio node ID(s) or other information as exemplified, obtained based on the backscattered signal.

[0103] Time stamp information associated with time of reception of the backscattered signal.

[0104] As noted previously, the measurement report may further comprise additional information. This may include RSSI of the received backscattered signal. This may be used by the LMF 140 to weigh the reports. The LMF 140 may in this context assign a smaller weight to measurement reports based on worse RSSI when estimating the location of the AIoT device 10. The RSSI also carries location information about the total distance traveled by the backscattered signal before reaching the receiving radio node. In some examples, where the AIoT device 10 introduces a time delay before backscattering as exemplified above, an indication of this time delay may also be included in the measurement report, unless already known by the LMF 140. At 590, the LMF 140 may estimate the position of the AIoT device 10, based on the report(s) received from the radio nodes 12-123. This may involve trilateration, and possibly additional separate positioning of the UE 20, if it is involved and its location is unknown. These steps may be carried out according to legacy procedures.

[0105] In broad context, from the viewpoint of a first radio node 121, a method is proposed for supporting positioning of a backscattering wireless device, also referred to as an AIoT device 10, based on reference signal transmission in a wireless system.

[0106] The method comprises determining 500 configuration for the reference signal transmission by one or more radio nodes of the wireless system. This may involve receiving scheduling of the reference signal. In this context, the configuration may identify time of transmission of the reference signal by the first radio node and optionally / alternatively by another of the one or more radio nodes. The time of transmission may be defined by radio resource configuration and by the scheduling.

[0107] The method further comprises obtaining 541, 551, information indicative of time of reception of a backscattered signal comprising a modulated version of a reference signal transmitted in accordance with said configuration, wherein the backscattered signal is indicative of an ID of the radio node that transmitted the reference signal. The obtaining is made in response to transmission of the reference signal.

[0108] The backscattered signal may thus be a modulated version of a reference signal transmitted by the first radio node itself, or a reference signal transmitted by another one of the one or more radio nodes. This may be determined based on the radio node ID indicated by the received backscattered signal.

[0109] The method further comprises transmitting 580, for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

[0110] In one specific example, the first radio node 121 both transmits the reference signal si and receives the backscattered signal n. In this context, the proposed solution involves a method carried out in the first radio node for supporting positioning of a backscattering wireless device 10 based on reference signal transmission in a wireless system, said method comprising: determining 500 configuration for the reference signal transmission; transmitting 521, according to the configuration, the reference signal configured to indicate an ID ID_121 of the first radio node; receiving 541, in response to the transmitting, a backscattered signal 540 comprising a modulated version of the transmitted reference signal, wherein the backscattered signal is indicative of said ID of the first radio node; transmitting 580, for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

[0111] From the viewpoint of location node 140 of the wireless system, a method is provided for positioning of a backscattering wireless device, i.e., the AIoT device 10. Said method comprises:

[0112] Determining 500 configuration for reference signal transmission by one or more radio nodes of a wireless system. This may involve obtaining radio resource configuration, by receiving from or negotiating with the radio nodes, and possibly determining. Determining the configuration may further comprise transmitting scheduling information for a positioning operation, to the radio nodes.

[0113] Receiving 580, from at least one of said radio nodes, a report indicative of travel time based on the configuration and time of reception in one of said radio nodes of a radio signal comprising a modulation, wherein said modulation is indicative of backscattering by the wireless device.

[0114] Determining 590, based on the received report, a location of the wireless device based on the travel time associated with reception in a number of said radio nodes.

[0115] Various details and aspects related to the proposed solution have been outlined in the foregoing. The proposed solution may further be embodied in accordance with any combination of the items set out below, and in accordance with the appended claims.

[0116] Item 1. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission by one or more radio nodes of the wireless system; obtaining (541, 551) information indicative of time of reception of a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of a reference signal transmitted in accordance with said configuration and being indicative of at least one of said radio nodes as transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

[0117] Item 2. The method of item 1, wherein an ID (ID_AIoT) associated with the wireless device is embedded in the backscattered signal by modulation.

[0118] Item 3. The method of item 2, wherein the ID associated with the wireless device, comprises a device ID or a sequence ID of a modulation applied by the wireless device on the backscattered signal.

[0119] Item 4. The method of any preceding item, wherein determining the travel time is carried out upon said wireless device being indicated in a positioning request (501).

[0120] Item 5. The method of any preceding item, wherein obtaining the information comprises receiving (541) the backscattered signal and determining the time of reception of the backscattered signal in the first radio node.

[0121] Item 6. The method of any of items 1-4, comprising: wherein obtaining the information comprises receiving (551) the information from the second radio node (20), wherein the information is indicative of the time of reception in the second radio node.

[0122] Item 7. The method of item 6, comprising: configuring (510) the second radio node (20) as an assisting node to monitor reception of the backscattered signal based on the configuration.

[0123] Item 8. The method of any preceding item, wherein the report comprises a time stamp indicative of said time of reception.

[0124] Item 9. The method of any preceding item, comprising: transmitting (521) the reference signal according to the configuration.

[0125] Item 10. The method of any preceding item, wherein the report comprises one or more of: an ID associated with the wireless device obtained based on the backscattered signal; information indicative the radio node that transmitted the reference signal, which is backscattered, obtained based on the backscattered signal; information indicative the radio node in which the backscattered signal was received. Item 11. The method of any preceding item, wherein the configuration defines timing of the reference signal transmission based on a predetermined active period of the wireless device.

[0126] Item 12. The method of any preceding item, wherein determining configuration comprises obtaining scheduling of the reference signal transmission.

[0127] Item 13. The method of item 12, wherein the scheduling is distributed in time among said one or more radio nodes.

[0128] Item 14. Method carried out in a location node of a wireless system for positioning of a backscattering wireless device, said method comprising: determining (500) configuration for reference signal transmission by one or more radio nodes of a wireless system; receiving (580), from at least one of said radio nodes, a report indicative of travel time based on the configuration and time of reception in one of said radio nodes of a backscattered signal from the wireless device (10), said backscattered signal comprising a modulation of the reference signal and being indicative of at least one of said radio nodes as transmitter of the reference signal; determining (590) a location of the wireless device based on the travel time associated with reception in a number of said radio nodes.

[0129] Item 15. The method of item 14, wherein the report comprises a time stamp indicative of said time of reception.

[0130] Item 16. The method of item 14 or 15, wherein the report comprises one or more of: an ID associated with the wireless device, obtained based on the backscattered signal; information indicative the radio node that transmitted the reference signal, which is backscattered, obtained based on the backscattered signal; information indicative the radio node in which the backscattered signal was received.

[0131] Item 17. The method of item 16, wherein the ID associated with the wireless device, comprises a device ID or a sequence ID of a modulation applied by the wireless device on the backscattered signal. Item 18. The method of any of items 14-17, wherein the configuration defines timing of the reference signal transmission based on a predetermined active period of the wireless device.

[0132] Item 19. The method of any of items 14-18, wherein the configuration comprises scheduling of the reference signal transmission which is distributed in time among said plurality of radio nodes.

[0133] Item 20. The method of any of items 14-18, wherein determining the configuration comprises receiving radio configuration from at least one of said one or more radio nodes.

[0134] Item 21. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission by one or more radio nodes of the wireless system; transmitting (521), according to the configuration, wherein the reference signal is configured to indicate the first radio node as transmitter; obtaining (541, 551) information indicative of time of reception of a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of the transmitted reference signal and being indicative of the first radio node as the transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

[0135] Item 22. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission; transmitting (521), according to the configuration, wherein the reference signal is configured to indicate the first radio node as transmitter; receiving (541) a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of the transmitted reference signal and being indicative of the first radio node as the transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

[0136] Item 23. The method of item 21 or 22, further characterized as set out in any of items 2-13.

[0137] Item 24. The method of any of items 1-13 or 21-23, further comprising: transmitting (515) a trigger signal for reception in the wireless device, to configure the wireless device to backscatter the reference signals.

[0138] Item 25. The method of item 24, wherein the trigger signal is configured to wake up the wireless device to monitor for the reference signals.

[0139] Item 26. The method of item 24 or 25, wherein the trigger signal is configured to activate backscatter functionality in the wireless device.

[0140] Item 27. The method of any of items 24-26, wherein the trigger signal configures the wireless device to introduce a modulation indicative of its ID upon backscattering.

[0141] Item 28. The method of any of items 24-27, wherein the trigger signal is transmitted prior to the reference signal.

[0142] Item 29. The method of any of items 24-28, wherein the trigger signal is transmitted prior to the reference signal.

[0143] Item 30. The method of any of items 24-28, wherein the trigger signal is transmitted as a part of the reference signal.

[0144] Item 31. The method of any of items 24-30, wherein the trigger signal comprises a predetermined sequence or sequence ID which the wireless device is configured to monitor.

[0145] Item 32. The method of any of items 24-31, wherein the trigger signal configures the wireless device to backscatter the reference signals for a certain duration.

[0146] Item 33. A wireless device (10), comprising: a radio transceiver (313); and an energy storage unit (315), configured to harvest radio frequency energy obtained by radio signal reception in the radio transceiver, wherein the radio transceiver is configured to transmit a backscattered signal based on a received reference signal, said backscattered signal comprising a modulated version of the reference signal. Item 34. The wireless device of item 33, wherein the transceiver is configured to modulate the backscattered signal to be indicative of an ID of the wireless device.

[0147] Item 35. The wireless device of item 33 or 34, wherein the transceiver is configured to backscatter reference signals responsive to receiving a trigger signal.

[0148] Item 36. The wireless device of item 35, wherein the wireless device is configured to wake to monitor for the reference signals, responsive to receiving the trigger signal.

[0149] Item 37. The wireless device of item 35 or 36, wherein the wireless device is configured to activate backscatter functionality, responsive to receiving the trigger signal.

[0150] Item 38. The wireless device of any of items 35-37, wherein the wireless device is configured to introduce a modulation indicative of its ID upon backscattering, responsive to receiving the trigger signal.

[0151] Item 39. The wireless device of any of items 35-38, wherein the wireless device is configured by receiving the trigger signal prior to the reference signal.

[0152] Item 40. The wireless device of any of items 35-38, wherein the wireless device is configured by receiving the trigger signal within the reference signal.

[0153] Item 41. The wireless device of any of items 35-38, wherein the wireless device is configured to backscatter the reference signals for a certain duration.

Claims

CLAIMS1. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission by one or more radio nodes of the wireless system; obtaining (541, 551) information indicative of time of reception of a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of a reference signal transmitted in accordance with said configuration and being indicative of at least one of said radio nodes as transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

2. The method of claim 1, wherein an ID (ID_AIoT) associated with the wireless device is embedded in the backscattered signal by modulation.

3. The method of claim 2, wherein the ID associated with the wireless device, comprises a device ID or a sequence ID of a modulation applied by the wireless device on the backscattered signal.

4. The method of any preceding claim, wherein determining the travel time is carried out upon said wireless device being indicated in a positioning request (501).

5. The method of any preceding claim, wherein obtaining the information comprises receiving (541) the backscattered signal and determining the time of reception of the backscattered signal in the first radio node.

6. The method of any of claims 1-4, comprising:wherein obtaining the information comprises receiving (551) the information from the second radio node (20), wherein the information is indicative of the time of reception in the second radio node.

7. The method of claim 6, comprising: configuring (510) the second radio node (20) as an assisting node to monitor reception of the backscattered signal based on the configuration.

8. The method of any preceding claim, wherein the report comprises a time stamp indicative of said time of reception.

9. The method of any preceding claim, comprising: transmitting (521) the reference signal according to the configuration.

10. The method of any preceding claim, wherein the report comprises one or more of: an ID associated with the wireless device obtained based on the backscattered signal; information indicative the radio node that transmitted the reference signal, which is backscattered, obtained based on the backscattered signal; information indicative the radio node in which the backscattered signal was received.

11. The method of any preceding claim, wherein the configuration defines timing of the reference signal transmission based on a predetermined active period of the wireless device.

12. The method of any preceding claim, wherein determining configuration comprises obtaining scheduling of the reference signal transmission.

13. The method of claim 12, wherein the scheduling is distributed in time among said one or more radio nodes.

14. Method carried out in a location node of a wireless system for positioning of a backscattering wireless device, said method comprising: determining (500) configuration for reference signal transmission by one or more radio nodes of a wireless system; receiving (580), from at least one of said radio nodes, a report indicative of travel time based on the configuration and time of reception in one of said radio nodes of a backscattered signal from the wireless device (10), said backscattered signal comprising a modulation of the reference signal and being indicative of at least one of said radio nodes as transmitter of the reference signal; determining (590) a location of the wireless device based on the travel time associated with reception in a number of said radio nodes.

15. The method of claim 14, wherein the report comprises a time stamp indicative of said time of reception.

16. The method of claim 14 or 15, wherein the report comprises one or more of: an ID associated with the wireless device, obtained based on the backscattered signal; information indicative the radio node that transmitted the reference signal, which is backscattered, obtained based on the backscattered signal; information indicative the radio node in which the backscattered signal was received.

17. The method of claim 16, wherein the ID associated with the wireless device, comprises a device ID or a sequence ID of a modulation applied by the wireless device on the backscattered signal.

18. The method of any of claims 14-17, wherein the configuration defines timing of the reference signal transmission based on a predetermined active period of the wireless device.

19. The method of any of claims 14-18, wherein the configuration comprises scheduling of the reference signal transmission which is distributed in time among said plurality of radio nodes.

20. The method of any of claims 14-18, wherein determining the configuration comprises receiving radio configuration from at least one of said one or more radio nodes.

21. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission by one or more radio nodes of the wireless system; transmitting (521), according to the configuration, wherein the reference signal is configured to indicate the first radio node as transmitter; obtaining (541, 551) information indicative of time of reception of a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of the transmitted reference signal and being indicative of the first radio node as the transmitter of the reference signal; transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

22. Method carried out in a first radio node (121) for supporting positioning of a backscattering wireless device (10) based on reference signal transmission in a wireless system, said method comprising: determining (500) configuration for the reference signal transmission; transmitting (521), according to the configuration, wherein the reference signal is configured to indicate the first radio node as transmitter; receiving (541) a backscattered signal (540) from the wireless device (10), said backscattered signal comprising a modulated version of the transmitted reference signal and being indicative of the first radio node as the transmitter of the reference signal;transmitting (580), for reception in a location node, a report indicative of travel time associated with time of transmission of the reference signal and the time of reception.

23. The method of claim 21 or 22, further characterized as set out in any of claims 2-13.

24. The method of any of claims 1-13 or 21-23, further comprising: transmitting (515) a trigger signal for reception in the wireless device, to configure the wireless device to backscatter the reference signals.

25. The method of claim 24, wherein the trigger signal is configured to wake up the wireless device to monitor for the reference signals.

26. The method of claim 24 or 25, wherein the trigger signal is configured to activate backscatter functionality in the wireless device.

27. The method of any of claims 24-26, wherein the trigger signal configures the wireless device to introduce a modulation indicative of its ID upon backscattering.

28. The method of any of claims 24-27, wherein the trigger signal is transmitted prior to the reference signal.

29. The method of any of claims 24-28, wherein the trigger signal is transmitted prior to the reference signal.

30. The method of any of claims 24-28, wherein the trigger signal is transmitted as a part of the reference signal.

31. The method of any of claims 24-30, wherein the trigger signal comprises a predetermined sequence or sequence ID which the wireless device is configured to monitor.

32. The method of any of claims 24-31, wherein the trigger signal configures the wireless device to backscatter the reference signals for a certain duration.

33. A wireless device (10), comprising: a radio transceiver (313); and an energy storage unit (315), configured to harvest radio frequency energy obtained by radio signal reception in the radio transceiver, wherein the radio transceiver is configured to transmit a backscattered signal based on a received reference signal, said backscattered signal comprising a modulated version of the reference signal.

34. The wireless device of claim 33, wherein the transceiver is configured to modulate the backscattered signal to be indicative of an ID of the wireless device.

35. The wireless device of claim 33 or 34, wherein the transceiver is configured to backscatter reference signals responsive to receiving a trigger signal.

36. The wireless device of claim 35, wherein the wireless device is configured to wake to monitor for the reference signals, responsive to receiving the trigger signal.

37. The wireless device of claim 35 or 36, wherein the wireless device is configured to activate backscatter functionality, responsive to receiving the trigger signal.

38. The wireless device of any of claims 35-37, wherein the wireless device is configured to introduce a modulation indicative of its ID upon backscattering, responsive to receiving the trigger signal.

39. The wireless device of any of claims 35-38, wherein the wireless device is configured by receiving the trigger signal prior to the reference signal.

40. The wireless device of any of claims 35-38, wherein the wireless device is configured by receiving the trigger signal within the reference signal.

41. The wireless device of any of claims 35-38, wherein the wireless device is configured to backscatter the reference signals for a certain duration.

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