WO2025054822A1

WO2025054822A1 - Method and apparatus for selection of wireless power transfer serving device

Info

Publication number: WO2025054822A1
Application number: PCT/CN2023/118334
Authority: WO
Inventors: Lei SU; Vinh Van Phan
Original assignee: Nokia Shanghai Bell Co., Ltd; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2023-09-12
Filing date: 2023-09-12
Publication date: 2025-03-20

Abstract

Embodiments of the present disclosure provide a method and an apparatus for selection of wireless power transfer, WPT, serving device. A method (300) performed by a first terminal device may comprise: transmitting (S306), to the second terminal device, a request for a WPT; and receiving (S308), from the second terminal device, a response indicating a target serving device for the WPT. According to embodiments of the present disclosure, the exemplary embodiments of the present disclosure propose a mechanism that, a WPT consuming device may request to (re) select a WPT serving device. A better candidate for WPT service to the WPT consuming device may be provided. Therefore, a working state of the WPT consuming device may be better retained.

Description

METHOD AND APPARATUS FOR SELECTION OF WIRELESS POWER TRANSFER SERVING DEVICE

TECHNICAL FIELD

Various example embodiments of the present disclosure relate generally to the technology of communication, and in particular to a method and an apparatus for selection of wireless power transfer, WPT, serving device.

BACKGROUND

WPT technology may be applied to a lot of kinds of devices in communication system, such as internet of things (IoT) device.

For example, an ambient IoT device refers to a 3GPP IoT device which is much smaller and cheaper compared to previous generations of IoT, like the NB (narrow band) -IoT/LTE (long term evolution) -M (machine) /RedCap. Both Ambient IoT and Ambient computing rely upon energy harvesting as one of the key mechanisms for powering and enabling the technology. Energy harvesting, as it applies to Ambient IoT and Ambient Computing, is the harnessing of the power in ambient radio waves to power tiny computers. This is very similar to the way that solar panels harvest visible sunlight to power electric devices. This radio wave energy harvesting capability, enabled inside Ambient IoT tags, frees IoT from the monetary/replacement burden of batteries or direct power connectivity. Ambient IoT support is being added to the wireless standards that enable the world’s phones, smart speakers, and access points.

SUMMARY

This summary is provided to introduce some aspects in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Specific method and apparatus for selection of wireless power transfer, WPT, serving device may be provided.

A first aspect of the present disclosure provides a method performed by a first terminal device, comprising: transmitting, to a second terminal device, a request for a wireless power transfer, WPT; and receiving, from the second terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the method further comprises: determining a low power state. The request is a selection or reselection request.

In exemplary embodiments of the present disclosure, the response further indicates resource allocation for the WPT.

In exemplary embodiments of the present disclosure, the request comprises at least one of: a location information, and a requirement of the first terminal device. The requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.

In exemplary embodiments of the present disclosure, the target serving device for the WPT is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.

In exemplary embodiments of the present disclosure, the second terminal device is a current serving device of the first terminal device for the WPT; and the first terminal device determines that the WPT from the second terminal device does not fulfil the requirement of the first terminal device, based on at least one of: a received power from the WPT, a signal received power from the second terminal device, or a transmission power headroom of the second terminal device for the WPT.

In exemplary embodiments of the present disclosure, the first terminal device receives a report comprising the transmission power headroom of the second terminal device for the WPT from the second terminal device. The report is in a response from the second terminal device to the first terminal device, or is in a separate report from the second terminal device to the first terminal device.

In exemplary embodiments of the present disclosure, the first terminal device is communicating with the second terminal device via sidelink. The second terminal device is a relay between the first terminal device and a network device, or the first terminal device is communicating with the second terminal device without a network device.

In exemplary embodiments of the present disclosure, the WPT is via a plurality of sidelink, SL, transmissions.

A second aspect of the present disclosure provides a method performed by a second terminal device, comprising: receiving, from a first terminal device, a request for a wireless power transfer, WPT; and transmitting, to the first terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the request is a selection or reselection request.

In exemplary embodiments of the present disclosure, the method further comprises: transmitting, to a network device, a first message comprising at least a part of the request; and receiving, from the network device, the response.

In exemplary embodiments of the present disclosure, the first message further comprises a transmission power headroom of the second terminal device for the WPT.

In exemplary embodiments of the present disclosure, the method further comprises: determining that the second terminal device is not able to fulfil the requirement of the first terminal device; transmitting, to at least one terminal device, a second message comprising at least a part of the request; receiving, from the at least one terminal device, at least one acknowledgement; selecting the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.

In exemplary embodiments of the present disclosure, selecting (S416) the target serving device is further based on a distance between the target serving device and the first terminal device.

In exemplary embodiments of the present disclosure, the target serving device is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.

In exemplary embodiments of the present disclosure, the second terminal device is a current serving device of the first terminal device for the WPT.

A third aspect of the present disclosure provides a method performed by a third terminal device, comprising: receiving, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and transmitting, to the second terminal device or the network device, an acknowledgement.

In exemplary embodiments of the present disclosure, the requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.

A fourth aspect of the present disclosure provides a method performed by a network device, comprising: receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT; determining a target serving device for the WPT, based at least on the request; and transmitting, to the second terminal device, a response indicating the target serving device for the WPT.

In exemplary embodiments of the present disclosure, the method further comprises: determining that the second terminal device is not able to fulfil the requirement of the first terminal device; transmitting, to at least one terminal device, a second message comprising at least a part of the request; receiving, from the at least one terminal device, at least one acknowledgement; and selecting the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.

In exemplary embodiments of the present disclosure, selecting the target serving device for the WPT is further based on a distance between the target serving device and the first terminal device.

In exemplary embodiments of the present disclosure, the first terminal device is communicating with the second terminal device via sidelink. The second terminal device is a relay between the first terminal device and a network device.

A fifth aspect of the present disclosure provides a first terminal device comprising means configured for: transmitting, to the second terminal device, a request for WPT; and receiving, from the second terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any of embodiments of the first aspect.

In exemplary embodiments of the present disclosure, the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first terminal device to perform the method according to any of embodiments of the first aspect.

A sixth aspect of the present disclosure provides a second terminal device comprising means configured for: receiving, from a first terminal device, a request for wireless power transfer, WPT; and transmitting, to the first terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any of embodiments of the second aspect.

In exemplary embodiments of the present disclosure, the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second terminal device to perform the method according to any of embodiments of the second aspect.

A seventh aspect of the present disclosure provides a third terminal device comprising means configured for: receiving, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and transmitting, to the second terminal device or the network device, an acknowledgement.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any of embodiments of the third aspect.

In exemplary embodiments of the present disclosure, the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third terminal device to perform the method according to any of embodiments of the third aspect.

An eighth aspect of the present disclosure provides a network device comprising means configured for: receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT; determining a target serving device for the WPT, based at least on the request; and transmitting, to the second terminal device, a response indicating the target serving device for the WPT .

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any of embodiments of the fourth aspect.

In exemplary embodiments of the present disclosure, the means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network device to perform the method according to any of embodiments of the fourth aspect.

A ninth aspect of the present disclosure provides a computer-readable storage medium storing instructions, which when executed by at least one processor of a terminal device, cause the at least one processor of a terminal device to perform the method according to any of embodiments of the first, second, or third aspects, or when executed by at least one processor of a network device, cause the at least one processor of a network device to perform the method according to any of embodiments of the fourth aspect.

A tenth aspect of the present disclosure provides an apparatus. The apparatus comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform the method according to any of embodiments of the first, second, third, fourth aspects.

In exemplary embodiments of the present disclosure, the apparatus is or is comprised in a first, second, or third terminal device, or a network device.

Embodiments herein afford many advantages. According to embodiments of the present disclosure, an improved manner for selection of wireless power transfer, WPT, serving device may be provided.

According to embodiments of the present disclosure, the exemplary embodiments of the present disclosure propose a mechanism that, a WPT consuming device may request to (re) select a WPT serving device. A better candidate for WPT service to the WPT consuming device may be provided. Therefore, a working state of the WPT consuming device may be better retained.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:

FIG. 1 is a diagram showing general microwave rectifier conversion efficiency curve at different input power.

FIG. 2 is a diagram showing some exemplary observations.

FIG. 3A is a flow chart showing a method performed by a first terminal device, according to exemplary embodiments of the present disclosure.

FIG. 3B is a flow chart showing further steps of the method as shown in FIG. 3A, according to exemplary embodiments of the present disclosure.

FIG. 4A is a flow chart showing a method performed by a second terminal device, according to exemplary embodiments of the present disclosure.

FIG. 4B is a flow chart showing further steps of the method as shown in FIG. 4A, according to exemplary embodiments of the present disclosure.

FIG. 4C is a flow chart showing further steps of the method as shown in FIG. 4A, according to exemplary embodiments of the present disclosure.

FIG. 5A is a flow chart showing a method performed by a third terminal device, according to exemplary embodiments of the present disclosure.

FIG. 5B is a flow chart showing further steps of the method as shown in FIG. 5A, according to exemplary embodiments of the present disclosure.

FIG. 6A is a flow chart showing a method performed by a network device, according to exemplary embodiments of the present disclosure.

FIG. 6B is a flow chart showing further steps of the method as shown in FIG. 6A, according to exemplary embodiments of the present disclosure.

FIG. 7 is a diagram showing a relay UE in SL Mode A is WPT incapable or WPT power limited.

FIG. 8 is a diagram showing a SL UE in SL Mode B is WPT incapable or WPT power limited.

FIG. 9 is a diagram showing required messages to support WPT based triggers for WPT-serving UE (re) selection in SL Mode A.

FIG. 10 is a diagram showing required messages to support WPT based triggers for WPT-serving UE (re) selection in SL Mode B.

FIG. 11 is a block diagram showing an exemplary structure for a first terminal device, according to exemplary embodiments of the present disclosure.

FIG. 12 is a block diagram showing an exemplary structure for a second terminal device, according to exemplary embodiments of the present disclosure.

FIG. 13 is a block diagram showing an exemplary structure for a third terminal device, according to exemplary embodiments of the present disclosure.

FIG. 14 is a block diagram showing an exemplary structure for a network device, according to exemplary embodiments of the present disclosure.

FIG. 15 is a block diagram showing an apparatus/computer readable storage medium, according to embodiments of the present disclosure.

FIG. 16 is a block diagram showing exemplary apparatus units for a first terminal device, which is suitable for performing the method according to embodiments of the disclosure.

FIG. 17 is a block diagram showing exemplary apparatus units for a second terminal device, which is suitable for performing the method according to embodiments of the disclosure.

FIG. 18 is a block diagram showing exemplary apparatus units for a third terminal device, which is suitable for performing the method according to embodiments of the disclosure.

FIG. 19 is a block diagram showing exemplary apparatus units for a network device, which is suitable for performing the method according to embodiments of the disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for better understanding, rather than limitations on the scope of the present disclosure. The described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless clearly given and/or implied from the context. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate.

As used herein, the term “network” or “communication network” refers to a network following any suitable communication standards (such for an internet network, or any wireless network) . For example, wireless communication standards may comprise WLAN (Wireless Local Area Network) , new radio (NR) , long term evolution (LTE) , LTE-Advanced, 5G NR, etc. In the following description, the terms “network” and “system” can be used interchangeably.

The term “network node” refers to a network device or network entity or network function or any other devices (physical or virtual) in a communication network. For example, the network node in the network may include a base station (BS) , an access point (AP) , or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNodeB or gNB) , a remote radio unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.

The term “terminal device” refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device refers to a mobile terminal, user equipment (UE) , a non-APdevice (such as a non-AP Station (STA) ) , or other suitable devices. The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, a wearable device, a vehicle-mounted wireless terminal device, a vehicle, and the like.

As one example, a terminal device may represent a device configured for communication in accordance with one or more communication standards promulgated by any standard organization, such as 3^rd generation partnership project, 3GPP.

As yet another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another terminal device and/or network equipment. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, for example refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed terms.

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

Exemplary embodiments of the disclosure are relevant to a method and an apparatus for selection/reselection of wireless power transfer, WPT, serving device.

The 3GPP system architecture and radio network working groups discuss the requirements of more general new radio (NR) proximity services (ProSe) . For ProSe, there is an inherent need to provide reliable out-of-coverage services, support communications among emergency rescue personnel, and quickly connect out-of-coverage areas to infrastructure nodes. To meet the requirements of ProSe, 3GPP extend the capabilities of the Rel (Release) -16 NR PC5 interface by enabling UE-based relaying via sidelink. UE-based relaying can be useful in both partial (spotty) coverage and out-of-coverage situations, and further coverage extension by establishing multi-hop (Rel-18) communication paths, utilizing UE to UE (U2U) or UE to Network (U2N) relaying situations. These relaying features may require some new solutions in network control, resource allocation, end-to-end quality of service (QoS) management and UE/relay discovery and selection.

For example, ambient IoT tag may communicate with network directly via Uu, or over Sidelink relay link and serving relay UE’s Uu. The tag can also communicate with Sidelink UE directly over NR PC5 interface. Ambient IoT tag may harvest Sidelink signal power while receiving data.

During RF energy harvesting, the Radio Frequency to Direct Current (RF-DC) conversion efficiency is approximately equal to rectifier diode efficiency. FIG. 1 (from “Theoretical Analysis of RF-DC Conversion Efficiency for Class-F Rectifiers” ) shows a general microwave rectifier conversion efficiency curve at different input power, where the efficiency firstly increases monotonically to its maximum value at a specific input power level and then decreases as the input power becomes larger. The diode efficiency changes at the low input power region and the high input power region are caused by the following two different mechanisms, respectively:

· loss due to forward diode build-in potential in the low input power region; and

· loss due to diode breakdown voltage in the high input power region.

3GPP Service and System Aspect (SA) 1 Rel-19 Technical Report (TR) 22.840 (V0.3.0) (2022-11) is studying potential Ambient/Passive IoT device energy harvesting solutions.

1 Scope

The present document provides Stage 1 potential 5G service requirements for ambient power-enabled Internet of Things (i.e., Ambient IoT) . In the context of the present document, Ambient power-enabled Internet of Things device is an IoT device powered by energy harvesting, being either battery-less or with limited energy storage capability (e.g., using a capacitor) and the energy is provided through the harvesting of radio waves, light, motion, heat, or any other power source that could be seen suitable. An ambient IoT device has low complexity, small size and lower capabilities and lower power consumption than previously defined 3GPP IoT devices (e.g., NB-IoT/eMTC devices) . Ambient IoT devices can be maintenance free and can have long life span (e.g., more than 10 years) .

The aspects addressed in the present document include:

- Study use cases of ambient power-enabled Internet of Things and identify potential service requirements, including:

● Security aspects, e.g., authentication and authorization, etc.

● Network selection, access control, connection, mobility and identification management

● Charging (e.g., per data volume, per message)

● Aspects related to stakeholder models (e.g., involving interactions in PLMNs, NPNs or other parties)

● Positioning

● Aspects on device life cycle management related to 3GPP system.

To address TR 22.840 use cases and scenarios, RAN Rel-19 SI “FS_Ambient_IoT_RAN” (RP-223396) is proposing Uu and Sidelink based Ambient/Passive IoT device energy harvesting.

· Identify the suitable deployment scenarios and their characteristics, at least for the use cases/services agreed in SAT1’s “Study on Ambient power-enabled internet of Things” , comprising among at least the following aspects

· Indoor/outdoor environment

· Basestation characteristics, e.g. macro/micro/pico cells-based deployments

· Connectivity topologies. including which node (s) , e.g. basestation, UE, relay, repeater, etc. can communicate with target devices

· TDD/FDD, and frequency bands in licensed or unlicensed spectrum

· Coexistence with UEs and infrastructure in frequency bands for existing 3GPP technologies

· Device originated and or device terminated traffic assumption

The exemplary embodiments of the present disclosure are on selection/reselection of Wireless Power Transmission (WPT) -serving UE. For example, some embodiments may be targeted to reselect a U2N relay UE or a Sidelink (SL) UE which is the best candidate for WPT, while Ambient IoT tag requests a new WPT service or update of current WPT service via Sidelink.

FIG. 2 is a diagram showing some exemplary observations.

While Ambient IoT tag is communicating with gNB via a relay UE (SL Mode A) , or with a SL UE (SL Mode B) directly, the tag needs WPT and requests it from the (relay) communicating UE. Further, the tag is harvesting WPT signal power and expects to improve RF-DC conversion efficiency. The observed problems that should be solved at least include the followings.

For example, in mode A in the left side of the FIG. 2, in a step 1a, the remote tag-1 transmits a WPT request to the SL Relay-1, which is incapable for WPT. In a step 2a, the SL Relay-1 transmits Tag’s location and preferred WPT-RSRP to the gNB. In a step 3, the gNB pages the SL UE-3 with tag’s location and preferred WPT-RSRP. In a step 4, the SL UE-3 transmits an ACK to the gNB. In a step 5a, the gNB transmits, via the SL Relay-1, information about new Relay UE-3 to the remote tag-1.

Further, in a step 1b in mode A, the remote tag-2 transmits a WPT reselection request to the SL Relay-2, which is with limited power for WPT. In a step 2b, the SL Relay-2 transmits its Tx power headroom (actively or query based) , Tag’s location and preferred WPT-RSRP to the gNB. In a step 3, the gNB pages the SL UE-3 with tag’s location and preferred WPT-RSRP. In a step 4, the SL UE-3 transmits an ACK to the gNB. In a step 5b, the gNB transmits, via the SL Relay-2, information about new Relay UE-3 to the remote tag-2.

For example, in mode B in the right side of the FIG. 2, in a step 1a, the remote tag-1 transmits a WPT request to the SL UE-1, which is incapable for WPT. In a step 2a, the SL UE-1 transmits Tag’s location and preferred WPT-RSRP to the SL UE-3. In a step 3a, the SL UE-3 transmits an ACK to the SL UE-1. In a step 4a, the SL UE-1 transmits information about new SL UE-3 to the remote tag-1.

Further, in mode B, in a step 1b, the remote tag-2 transmits a WPT reselection request to the SL UE-2, which is with limited power for WPT. In a step 2b, the SL UE-2 transmits Tag’s location and preferred WPT-RSRP to the SL UE-3. In a step 3b, the SL UE-3 transmits an ACK to the SL UE- 2. In a step 4b, the SL UE-2 transmits information about new SL UE-3 to the remote tag-2.

Observation-1: in case the communicating (relay) SL UE is not able to provide WPT to Tag, or the Tag considers that the current communicating (relay) UE might not be the best candidate for WPT service, it is not clear how to discover and reselect a communicating (relay) SL UE that fulfils the Tag’s expectation.

Observation-2: during WPT service duration, the Tag or the communicating (relay) SL UE may move away from one another. It will cause WPT receiving power change and the power change directly impacts the RF-DC conversion efficiency. There may be a need for the Tag to know the remaining WPT transmission power from the communicating (relay) SL UE, for communicating (relay) UE reselection, which is targeted for best RF-DC conversion efficiency.

As shown in FIG. 3A, a first aspect of the present disclosure provides a method 300 performed by a first terminal device, comprising: a step S306, transmitting, to the second terminal device, a request for a wireless power transfer, WPT; and a step S308, receiving, from the second terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the method further comprises: a step S302, determining a low power state. The request is a selection or reselection request.

In exemplary embodiments of the present disclosure, the response further indicates resource allocation (e.g., radio frequency, RF, resources) for the WPT.

In exemplary embodiments of the present disclosure, the request comprises at least one of: a location information, or a requirement of the first terminal device. The requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.

In exemplary embodiments of the present disclosure, the second terminal device is a current serving device of the first terminal device for the WPT; and the first terminal device determines that the WPT from the second terminal device does not fulfil the requirement of the first terminal device based on at least one of: a received power from the WPT, a signal received power from the second terminal device, or a transmission power headroom of the second terminal device for the WPT.

According to embodiments of the present disclosure, not only a current received power, but also a power headroom may be considered. Therefore, whether the second terminal device is capable of providing further wireless power can be accurately estimated.

In exemplary embodiments of the present disclosure, a requirement of the first terminal device is indicated by a preferred signal received power.

In exemplary embodiments of the present disclosure, the first terminal device determines the low power state, based at least on that a battery power is below a preconfigured threshold.

In exemplary embodiments of the present disclosure, the WPT is via a plurality of sidelink, SL, transmissions .

As shown in FIG. 4A, a second aspect of the present disclosure provides a method 400 performed by a second terminal device, comprising: a step S402, receiving, from a first terminal device, a request for a wireless power transfer, WPT; and a step S404, transmitting, to the first terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the response further indicates resource allocation (such as radio frequency, RF, resources) for WPT.

In exemplary embodiments of the present disclosure, the method 400 further comprises: a step S406, transmitting, to a network device, a first message comprising at least a part of the request; and a step S408, receiving, from the network device, the response.

According to embodiments of the present disclosure, the (re) selection of a target serving device for WPT may be mainly controlled by a network device, such as a base station.

In exemplary embodiments of the present disclosure, the method further comprises: a step S410, determining that the second terminal device is not able to fulfil the requirement of the first terminal device; a step S412, transmitting, to at least one terminal device, a second message comprising at least a part of the request; a step S414, receiving, from the at least one terminal device, at least one acknowledgement; a step S416, selecting the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.

According to embodiments of the present disclosure, the (re) selection of a target serving device for WPT may be mainly controlled by the second terminal device.

In exemplary embodiments of the present disclosure, selecting (S416) the target serving device is further based on a distance between the target serving device and the first terminal device. For example, the at least one terminal device may indicate, to the second terminal device, its location information or its distance to the first terminal device.

According to embodiments of the present disclosure, the distance, which may cause loss of the signal power, may be considered while reselecting the target serving device.

In exemplary embodiments of the present disclosure, the target serving device for WPT is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.

As shown in FIG. 5A, a third aspect of the present disclosure provides a method 500 performed by a third terminal device, comprising: a step S502, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and a step S506, transmitting, to the second terminal device or the network device, an acknowledgement.

In exemplary embodiments of the present disclosure, the method 500 further comprises: a step S508, receiving, from the second terminal device or the network device, an indication to provide WPT to the first terminal device.

In exemplary embodiments of the present disclosure, the third terminal device determines whether the third terminal device is able to fulfil a requirement of the first terminal device, based at least on a distance between the third terminal device and the first terminal device, and the requirement of the first terminal device.

In exemplary embodiments of the present disclosure, the requirement of the first terminal device is indicated by a preferred signal received power.

In exemplary embodiments of the present disclosure, the first terminal device is communicating with the second terminal device via sidelink. The second terminal device is a relay for the first terminal device and the network device, or the first terminal device is communicating with the second terminal device without the network device.

In exemplary embodiments of the present disclosure, the first terminal device is a WPT consuming device. The second terminal device is a WPT serving device. The third terminal device is a WPT serving device.

As shown in FIG. 6A, a fourth aspect of the present disclosure provides a method 600 performed by a network device, comprising: a step S602, receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT; a step S604, determining a target serving device for the WPT, based at least on the request; and a step S606, transmitting, to the second terminal device, a response indicating the target serving device for the WPT.

In exemplary embodiments of the present disclosure, the request is a selection request or a reselection request.

In exemplary embodiments of the present disclosure, the response further indicates resource allocation (such as radio frequency, RF, resources) for the WPT.

In exemplary embodiments of the present disclosure, the method further 600 comprises: a step S608, determining that the second terminal device is not able to fulfil the requirement of the first terminal device; a step S610, transmitting, to at least one terminal device, a second message comprising: at least a part of the request; a step S612, receiving, from the at least one terminal device, at least one acknowledgement; and a step S614, selecting the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.

In exemplary embodiments of the present disclosure, selecting the target serving device for the WPT further based on a distance between the target serving device and the first terminal device.

Accordingly, in exemplary embodiments of the present disclosure, the serving gNB (in a SL Mode A) or the communicating SL UE (in a SL Mode B) is responsible to discover and reselect a new (relay) SL UE which fulfils the Tag’s WPT expectation, based on current communicating (relay) SL UE WPT capability, WPT power headroom and Tag’s location.

When an Ambient IoT Tag communicating with gNB via a relay UE (SL Mode A) , or with a SL UE (SL Mode B) , is in low battery power state (e.g., is below a preconfigured threshold and no longer fulfils the energy needed for regular SL transmission) , the Tag should request WPT from the communicating UE.

The Tag harvests signal power from transmissions of WPT message from the communicating or WPT-serving UE over SL on preconfigured or dynamically reserved resources. While performing WPT message transmission, the WPT-serving UE may also inform the Tag WPT of the signal power headroom via Sidelink Control Information (SCI) or Media Access Control (MAC) Control Element (CE) or the WPT message.

When the Tag is receiving the WPT message for WPT and the Tag detects that the current communicating UE may not be the best candidate for WPT service due to, e.g., “0” power headroom as indicated and the received WPT power still lower than Tag’s preferred WPT-RSRP (Reference Signal Received Power) condition, the Tag should trigger WPT-serving UE reselection.

The Tag may indicate its current location and preferred WPT-RSRP condition to the communicating UE, in a WPT service request message or a WPT reselection request message.

If the communicating UE is capable and able to fulfil the requested WPT:

● In SL Mode A (in which a SL communication is still controlled/scheduled by a base station) , upon receiving the Tag’s request, the communicating UE as a U2N relay UE may report its current WPT power headroom, the Tag’s location and preferred WPT-RSRP condition to the serving gNB. If the relay UE’s latest Transmission (Tx) power headroom indicates that it’s qualified to support SL-WPT for the Tag, the gNB signals SL-WPT resources to the relay UE and the Tag.

● In SL Mode B (in which a SL communication is performed without a base station) , if the communicating UE has enough Tx power to fulfil the Tag’s preferred WPT-RSRP condition, upon receiving the Tag’s request, the communicating UE may respond the Tag with reserved or dedicated SL-WPT resources and adjust its transmission power to fulfil the Tag’s expectation.

As shown in FIG. 7, if the communicating UE is incapable or not able to fulfil the requested WPT:

● In SL Mode A, if the relay UE (SL Relay-1) is WPT incapable:

■ Upon receiving the Tag’s request (from Remote Tag-1) , the UE informs the serving gNB of its WPT capability, the Tag’s location and preferred WPT-RSRP.

● In SL Mode A, if the relay UE (SL Relay-2) is WPT power limited:

■ Upon receiving the Tag’s request (from Remote Tag-2) , the UE informs the serving gNB of its current power headroom, the Tag’s location and preferred WPT-RSRP.

● In SL Mode A, if the relay UE is WPT incapable or its current Tx power headroom indicates that it’s not qualified to support SL-WPT for the Tag, the serving gNB may page all UEs within proximity of the Tag’s location and preferred WPT-RSRP condition. Upon receiving the Tag’s information in the paging message, individual UE being paged may determine if it can fulfil the Tag’s WPT expectation based on the UE’s location, the Tag’s location, the UE’s transmission power and the Tag’s preferred WPT-PSRP condition, and then send Acknowledgement (ACK) or Negative Acknoweledgement (NACK) back to the serving gNB. The serving gNB may decide the target relay UE or, that is, reselect the target relay UE (SL UE-3) among the UEs ACKed in their page responses and then signal the relay UE and the Tag about the target relay UE.

As shown in FIG. 8, in SL Mode B, if the communicating UE is SL-WPT incapable (such as SL UE-1) or hasn’ t enough Tx power (such as SL UE-2) to fulfil the Tag’s preferred WPT-RSRP condition, upon receiving the Tag’s request (from Remote Tag-1 or Remote Tag-2) , the communicating UE may announce the Tag’s location and preferred WPT-RSRP condition to the UEs in proximity via, e.g., ProSe Solicitation message. Upon receiving the Solicitation message, individual UE may determine if it can fulfil the Tag’s WPT expectation based on the UE’s location, the Tag’s location, the UE’s transmission power and the Tag’s preferred WPT-PSRP condition, and then send back ACK or NACK to the communicating UE via, e.g., ProSe Response message. The communicating UE may decide the target serving UE among the UEs ACKed in their ProSe Responses and then signal the Tag the target serving UE (such as SL UE-3) .

The precondition of the procedure may include:

1. The Ambient IoT Tag is communicating with gNB via a relay UE,

2. The WPT service has started, and the Tag receive “0” WPT power headroom, or

3. The WPT service may not start.

In FIG. 9, the Tag is an example for the first terminal device, Relay UE is an example for the second terminal device, the Target Relay UE is an example for the third terminal device, and the gNB is an example for the network device.

Step 1. When the Tag’s battery power is below a preconfigured threshold, if the WPT service isn’ t started, the Tag sends a WPT (re) selection Request to the U2N relay UE, otherwise, the Tag sends a WPT Reselection Request to the U2N relay UE. The request message includes Tag location and preferred WPT-RSRP.

Step 2a. Upon receiving Tag’s request, the relay UE reports UE SL WPT capability, current WPT Tx power headroom, Tag location and preferred WPT-RSRP to the serving gNB.

Otherwise, if the relay UE does not report its own WPT Tx power headroom in step 2b, the gNB may query it in step 2c, and then the relay UE responds to the gNB with the WPT Tx power headroom in step 2d.

Step 3. If the serving relay UE is WPT capable, the serving gNB verifies Tag SL-RSRP, UE WPT power headroom and Tag’s preferred WPT-RSRP and signal (Step 3a) SL-WPT resource to the serving relay UE and the Tag, in case the serving relay UE has enough transmission power to fulfil Tag’s preferred WPT-RSRP. If the serving relay UE is WPT incapable or hasn’ t enough transmission power for the preferred WPT-RSRP, the serving gNB pages (Step 3b) all RRC IDLE/Inactive UEs and send RRC Reconfiguration to RRC Connected UEs within proximity of the Tag’s location and the preferred WPT-RSRP.

Step 4. Upon receiving a paging message including Tag’s location and preferred WPT-RSRP, the individual UE in proximity calculates the distance to the Tag and the required transmission power, such as based on Free Space Path Loss. If the required transmission power is supported by the individual UE, the individual UE sends ACK in the paging response or RRC Reconfiguration Complete message.

Step 5. Upon receiving ACKed paging response or RRC Reconfiguration Complete message, the serving gNB selects the UE among the UEs which ACKed in their page responses, e.g., the UE which has a shortest distance to the Tag, and signals the serving relay UE and the Tag about the selected UE as target relay UE.

Upon receiving the instruction from the serving gNB, the Tag may reselect the target relay UE to create Sidelink connection for subsequent WPT service.

In FIG. 10, the Tag is an example for the first terminal device, the SL-WPT serving UE is an example for the second terminal device, the Target WPT-serving UE is an example for the third terminal device.

The precondition of the procedure may include:

1. The Ambient IoT Tag is communicating with a SL UE,

2. The WPT service has started, and the Tag receive “0” WPT power headroom.

In step 0a, the SL-WPT serving UE may provide its WPT Tx power headroom to the Tag.

Otherwise, the Tag may query WPT Tx power headroom in step 0b, and then the SL-WPT serving UE responds to the Tag with the WPT Tx power headroom in step 0c.

Step 1. When the Tag’s battery power is below a preconfigured threshold, the Tag sends a WPT Reselection Request to the SL -WPT serving UE. The request message includes Tag’s location and preferred WPT-RSRP. The Tag may send SL measurement report to the SL-WPT serving UE includes Tag location and preferred WPT-RSRP.

Step 2. The UE verifies Tag SL-RSRP, UE WPT power headroom and Tag preferred WPT-RSRP. If the SL-WPT serving UE hasn’ t enough transmission power for the preferred WPT-RSRP, the UE announces all UEs within proximity of the Tag’s location and the preferred WPT-RSRP.

Step 3. Upon receiving an announcement including a Tag’s location and preferred WPT-RSRP, the individual UE in proximity calculates the distance to the Tag and the required transmission power, such as based on Free Space Path Loss. If the required transmission power is supported by the individual UE, the individual UE ACKs in the announcement response.

Step 4. Upon receiving the ACKed announcement response, the SL-WPT serving UE may decide the target WPT-serving UE among the UEs which ACKed in their announcement responses, e.g., the UE which has a shortest distance to the Tag, and signal the Tag about the selected UE. Upon receiving the instruction from the serving SL UE, the Tag may reselect the signaled UE to create Sidelink connection for subsequent WPT service.

As shown in FIG. 11, the first terminal device 110 comprises means 1100 configured for: transmitting, to the second terminal device, a request for the WPT; and receiving, from the second terminal device, a response indicating a target serving device for WPT.

In exemplary embodiments of the present disclosure, the means 1100 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 3.

In exemplary embodiments of the present disclosure, the means 1100 comprise: at least one processor 1102; and at least one memory 1104 storing instructions that, when executed by the at least one processor 1102, cause the performance of the first terminal device 110.

As shown in FIG. 12, the second terminal device 120 comprises means 1200 configured for: receiving, from a first terminal device, a request for wireless power transfer, WPT; and transmitting, to the first terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the means 1200 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 4A, 4B, 4C.

In exemplary embodiments of the present disclosure, the means 1200 comprise: at least one processor 1202; and at least one memory 1204 storing instructions that, when executed by the at least one processor 1202, cause the performance of the second terminal device 120.

FIG. 13 is a block diagram showing an exemplary structure for a third network node, according to exemplary embodiments of the present disclosure.

As shown in FIG. 13, the third terminal device 130 comprises means 1300 configured for: receiving, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and transmitting, to the second terminal device or the network device, an acknowledgement.

In exemplary embodiments of the present disclosure, the means 1300 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 5A, 5B.

In exemplary embodiments of the present disclosure, the means 1300 comprise: at least one processor 1302; and at least one memory 1304 storing instructions that, when executed by the at least one processor 1302, cause the performance of the third terminal device 130.

As shown in FIG. 14, the network device 140 comprises means 1400 configured for: receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT; determining a target serving device for the WPT, based at least on the request; and transmitting, to the second terminal device, a response indicating the target serving device for the WPT.

In exemplary embodiments of the present disclosure, the means 1400 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 6A, 6B.

In exemplary embodiments of the present disclosure, the means 1400 comprise: at least one processor 1402; and at least one memory 1404 storing instructions that, when executed by the at least one processor 1402, cause the performance of the network device 140.

The processor 1102, 1202, 1302, 1402 may be any kind of processing component, such as one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs) , special-purpose digital logic, and the like. The memory 1104, 1204, 1304, 1404 may be any kind of storage component, such as read-only memory (ROM) , random-access memory, cache memory, flash memory devices, optical storage devices, etc.

As shown in FIG. 15, a computer-readable storage medium 150 storing instructions 151, which when executed by at least one processor of a terminal device (such as the first, second, third terminal device) , cause the at least one processor of the terminal device to perform the method according to any of the embodiments above mentioned, such as shown in FIG. 3, 4A, 4B, 4C, 5A, 5B; or when executed by at least one processor of a network device, cause the at least one processor of the network device to perform the method according to any of the embodiments above mentioned, such as shown in FIG. 6A, 6B.

In addition, the present disclosure may also provide a carrier containing the computer program/instructions as mentioned above. The carrier is one of an electronic signal, optical signal, radio signal, or the above computer readable storage medium. The computer readable storage medium can be, for example, an optical compact disk or an electronic memory device like a RAM (random access memory) , a ROM (read only memory) , Flash memory, magnetic tape, CD-ROM, DVD, Blue-ray disc and the like.

As shown in FIG. 16, the first terminal device 160 may include: a transmitting unit 1606 configured for, transmitting, to the second terminal device, a request for WPT; and a receiving unit 1608, receiving, from the second terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the first terminal device 160 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 3.

As shown in FIG. 17, the second terminal device 170 may include: a receiving unit 1702 configured for, receiving, from a first terminal device, a request for wireless power transfer, WPT; and a transmitting unit 1704 configured for, transmitting, to the first terminal device, a response indicating a target serving device for the WPT.

In exemplary embodiments of the present disclosure, the second terminal device 170 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 4A, 4B, 4C.

As shown in FIG. 18, the third terminal device 180 may include: a receiving unit 1802 configured for, receiving, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and a transmitting unit 1806, transmitting, to the second terminal device or the network device, an acknowledgement.

In exemplary embodiments of the present disclosure, the third terminal device 180 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 5A, 5B.

As shown in FIG. 19, the network device 190 may include: a receiving unit 1902 configured for, receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT; a determining unit 1904 configured for, determining a target serving device for the WPT, based at least on the request; and a transmitting unit 1906 configured for, transmitting, to the second terminal device, a response indicating the target serving device for the WPT.

In exemplary embodiments of the present disclosure, the network device 190 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 6A, 6B.

The term ‘unit’ may have conventional meaning in the field of electronics, electrical devices and/or electronic devices and may include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

As used in the present disclosure, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analogy and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analogy and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. ”

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

With these units, the apparatus may not need a fixed processor or memory, any kind of computing resource and storage resource may be arranged from at least one network node/device/entity/apparatus relating to the communication system. The virtualization technology and network computing technology (e.g., cloud computing) may be further introduced, so as to improve the usage efficiency of the network resources and the flexibility of the network.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment comprises not only prior art means, but also means for implementing the one or more functions of the corresponding apparatus described with the embodiment and it may comprise separate means for each separate function, or means that may be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more apparatuses) , firmware (one or more apparatuses) , software (one or more modules/units) , or combinations thereof. For a firmware or software, implementation may be made through modules (e.g., procedures, functions, and so on) that perform the functions described herein.

In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionalities may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

As described in above exemplary embodiments of this disclosure, embodiments herein afford many advantages. According to embodiments of the present disclosure, the exemplary embodiments of the present disclosure propose a mechanism that, a WPT consuming device may request to (re) select a WPT serving device. A better candidate for WPT service to the WPT consuming device may be provided. Therefore, a working state of the WPT consuming device may be better retained.

It should be understood that the above embodiments are only for illustration but not limitation. The present disclosure may be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the disclosure. All changes to these embodiments not departing from the meaning and equivalency of the appended claims are intended to be comprised herein.

REFERENCES

The followings are the references which are incorporated herein in their entirety:

Theoretical Analysis of RF-DC Conversion Efficiency for Class-F Rectifiers, Jiapin Guo, etc., IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 62, NO. 4, APRIL 2014

3GPP TR 22.840 V0.3.0 (2022-11) , 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Ambient power-enabled Internet of Things (Release 19)

RP-223396, 3GPP TSG RAN#98e, Electronic Meeting, December 12 –16, 2022, SID revised: Study on Ambient IoT

Claims

A method (300) performed by a first terminal device, comprising:

transmitting (S306) , to a second terminal device, a request for a wireless power transfer, WPT; and

receiving (S308) , from the second terminal device, a response indicating a target serving device for the WPT.
The method (300) according to claim 1, further comprising:

determining (S302) a low power state; and

wherein the request is a selection or reselection request.
The method (300) according to claim 1 or 2,

wherein the response further indicates resource allocation for the WPT.
The method (300) according to any of claims 1 to 3,

wherein the request comprises at least one of: a location information, or a requirement of the first terminal device; and

wherein the requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.
The method (300) according to claim 4,

wherein the target serving device for the WPT is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.
The method (300) according to any of claims 1 to 5,

wherein the second terminal device is a current serving device of the first terminal device for the WPT; and

wherein the first terminal device determines that the WPT from the second terminal device does not fulfil the requirement of the first terminal device based on at least one of: a received power from the WPT, a signal received power from the second terminal device, or a transmission power headroom of the second terminal device for the WPT.
The method (300) according to claim 6,

wherein the first terminal device receives a report comprising the transmission power headroom of the second terminal device for the WPT from the second terminal device; and

wherein the report is in a response from the second terminal device to the first terminal device, or is in a separate report from the second terminal device to the first terminal device.
The method (300) according to any of claims 1 to 7,

wherein the first terminal device is communicating with the second terminal device via sidelink; and

wherein the second terminal device is a relay between the first terminal device and a network device, or the first terminal device is communicating with the second terminal device without a network device.
The method (300) according to any of claims 1 to 8,

wherein the WPT is via a plurality of sidelink, SL, transmissions.
A method (400) performed by a second terminal device, comprising:

receiving (S402) , from a first terminal device, a request for a wireless power transfer, WPT; and

transmitting (S404) , to the first terminal device, a response indicating a target serving device for the WPT.
The method (400) according to claim 10,

wherein the request is a selection or reselection request.
The method (400) according to claim 10 or 11,

wherein the response further indicates resource allocation for the WPT.
The method (400) according to any of claims 10 to 12,

wherein the request comprises at least one of: a location information, or a requirement of the first terminal device; and

wherein the requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.
The method (400) according to any of claims 10 to 13, further comprising:

transmitting (S406) , to a network device, a first message comprising at least a part of the request; and

receiving (S408) , from the network device, the response.
The method (400) according to claim 14,

wherein the first message further comprises a transmission power headroom of the second terminal device for the WPT.
The method (400) according to any of claims 10 to 15, further comprising:

determining (S410) that the second terminal device is not able to fulfil the requirement of the first terminal device;

transmitting (S412) , to at least one terminal device, a second message comprising at least a part of the request;

receiving (S414) , from the at least one terminal device, at least one acknowledgement;

selecting (S416) the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.
The method (400) according to claim 16,

wherein selecting (S416) the target serving device is further based on a distance between the target serving device and the first terminal device.
The method (400) according to claim 16 or 17,

wherein the target serving device is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.
The method (400) according to any of claims 10 to 18,

wherein the second terminal device is a current serving device of the first terminal device for the WPT.
The method (400) according to any of claims 10 to 19,

wherein the first terminal device is communicating with the second terminal device via sidelink; and

wherein the second terminal device is a relay between the first terminal device and a network device, or the first terminal device is communicating with the second terminal device without a network device.
The method (400) according to any of claims 10 to 20,

wherein the WPT is via a plurality of sidelink, SL, transmissions.
A method (500) performed by a third terminal device, comprising:

receiving (S502) , from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and

transmitting (S506) , to the second terminal device or the network device, an acknowledgement.
The method (500) according to claim 22,

wherein the requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.
The method (500) according to any of claims 22 to 23,

wherein the WPT is via a plurality of sidelink, SL, transmissions.
A method (600) performed by a network device, comprising:

receiving (S602) , from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT;

determining (S604) a target serving device for the WPT, based at least on the request; and

transmitting (S606) , to the second terminal device, a response indicating the target serving device for the WPT.
The method (600) according to claim 25,

wherein the request is a selection or reselection request.
The method (600) according to claim 25 or 26,

wherein the requirement includes at least one of: a preferred received power, a preferred time duration, a preferred transmission frequency or periodicity, or preferred transmission resources for the WPT.
The method (600) according to any claims 25 to 27,

wherein the first message further comprises a transmission power headroom of the second terminal device for the WPT.
The method (600) according to any claims 25 to 28,

wherein the response further indicates resource allocation for the WPT.
The method (600) according to any of claims 25 to 29, further comprising:

determining (S608) that the second terminal device is not able to fulfil the requirement of the first terminal device;

transmitting (S610) , to at least one terminal device, a second message comprising at least a part of the request;

receiving (S612) , from the at least one terminal device, at least one acknowledgement; and

selecting (S614) the target serving device for the WPT from the at least one terminal device, based at least on the at least one acknowledgement.
The method (600) according to claim 30,

wherein selecting the target serving device for the WPT further based on a distance between the target serving device and the first terminal device.
The method (600) according to any of claims 25 to 31,

wherein the target serving device for the WPT is a third terminal device, when the second terminal device is not able to fulfil the requirement of the first terminal device.
The method (600) according to any of claims 25 to 32,

wherein the first terminal device is communicating with the second terminal device via sidelink; and

wherein the second terminal device is a relay between the first terminal device and a network device.
The method (600) according to any of claims 25 to 33,

wherein the WPT is via a plurality of sidelink, SL, transmissions.
A first terminal device (110) comprising means (1100) configured for:

transmitting, to a second terminal device, a request for a wireless power transfer, WPT; and

receiving, from the second terminal device, a response indicating a target serving device for the WPT.
The first terminal device (110) according to claim 35, wherein the means (1100) are further configured for performing the method according to any of claims 2 to 9.
The first terminal device (110) according to claim 35 or 36, wherein the means (1100) comprise:

at least one processor (1102) ; and

at least one memory (1104) storing instructions that, when executed by the at least one processor (1102) , cause the first terminal device (110) to perform the method according to any of claims 1 to 9.
A second terminal device (120) comprising means (1200) configured for:

receiving, from a first terminal device, a request for wireless power transfer, WPT; and

transmitting, to the first terminal device, a response indicating a target serving device for the WPT.
The second terminal device (120) according to claim 38, wherein the means (1200) are further configured for performing the method according to any of claims 11 to 21.
The second terminal device (120) according to claim 38 or 39, wherein the means (1200) comprise:

at least one processor (1202) ; and

at least one memory (1204) storing instructions that, when executed by the at least one processor (1202) , cause the second terminal device (120) to perform the method according to any of claims 10 to 21.
A third terminal device (130) comprising means (1300) configured for:

receiving, from a second terminal device or a network device, a message comprising a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of: a location information or a requirement of the first terminal device for the WPT; and

transmitting, to the second terminal device or the network device, an acknowledgement.
The third terminal device (130) according to claim 41, wherein the means (1300) are further configured for performing the method according to any of claims 23 to 24.
The third terminal device (130) according to claim 41 or 42, wherein the means (1300) comprise:

at least one processor (1302) ; and

at least one memory (1304) storing instructions that, when executed by the at least one processor (1302) , cause the third terminal device (130) to perform the method according to any of claims 22 to 24.
A network device (140) comprising means (1400) configured for:

receiving, from a second terminal device, a first message including a request for a wireless power transfer, WPT, for a first terminal device, the request comprising at least one of a location information or a requirement of the first terminal device for the WPT;

determining a target serving device for the WPT, based at least on the request; and

transmitting, to the second terminal device, a response indicating the target serving device for the WPT.
The network device (140) according to claim 44, wherein the means (1400) are further configured for performing the method according to any of the claims 26 to 34.
The network device (140) according to claim 44 or 45, wherein the means (1400) comprise:

at least one processor (1402) ; and

at least one memory (1404) storing instructions that, when executed by the at least one processor (1402) , cause the network device (140) to perform the method according to any of claims 25 to 34.
A computer-readable storage medium (150) storing instructions (151) , which when executed by at least one processor of a terminal device, cause the at least one processor of a terminal device to perform the method according to any of claims 1 to 24, or when executed by at least one processor of a network device, cause the at least one processor of a network device to perform the method according to any of claims 25 to 34.