A method for initiating a wireless energy transmission, a related energy harvesting device and a related radio network node

Abstract

A method performed by an energy harvesting device comprising an antenna array is disclosed, for initiating a wireless energy transmission to the energy harvesting device. The method comprises, upon detecting a need for energy transfer, configuring the antenna array in a retro-reflective configuration. The method comprises reconfiguring the antenna array in an energy harvesting configuration.

Description

[0001] A METHOD FOR INITIATING A WIRELESS ENERGY TRANSMISSION, A RELATED ENERGY HARVESTING DEVICE AND A RELATED RADIO NETWORK NODE

[0002] The present disclosure pertains to the field of wireless communications. The present disclosure relates to a method for initiating a wireless energy transmission to the energy harvesting device, a related energy harvesting device and a related radio network node.

[0003] BACKGROUND

[0004] Energy harvesting is currently being discussed as a promising technology for future Internet of Things (loT) systems, where wireless devices, such as sensors, being remotely located may lack connection to an electric grid and therefore have to rely on other types of energy transfer. One way for wireless device to harvest energy can be by wireless energy transfer from a radio network node. Since radio network nodes, such as gNBs, may have a plurality of antennas, the radio network node can spatially focus its energy transfer to a specific device. For this to work, a wireless device with very limited battery has to indicate to the radio network node that it needs an energy transfer, and the radio network node has to configure its beamforming so that it focuses its beams on the wireless device needing the energy transfer.

[0005] This may be solved by letting the wireless device transmit a pilot signal (such as a reference signal) to the radio network node. From this pilot signal, the radio network node may compute its beamforming. However, in case the wireless device does not have sufficient energy to transmit the pilot signal, such as if the wireless device is out of battery, which is the reason why it needs energy harvesting in the first place, it cannot notify the radio network node about the needed energy transfer. This may cause a catch-22 problem, where the wireless device must transmit a signal to receive the energy transfer but must first receive the energy to be able to transmit the signal.

[0006] SUMMARY

[0007] Accordingly, there is a need for devices and methods for initiating a wireless energy transmission to the energy harvesting device, which may mitigate, alleviate or address the shortcomings existing and may provide an energy efficient way of notifying the network that the energy harvesting device requires assistance, such as a wireless energy transfer, from the radio network node.

[0008] A method is disclosed, performed by an energy harvesting device comprising an antenna array, for initiating a wireless energy transmission to the energy harvesting device. The method comprises, upon detecting a need for energy transfer, configuring the antenna array in a retro- reflective configuration. The method may comprise reconfiguring the antenna array in an energy harvesting configuration.

[0009] Further, an energy harvesting device is provided, the energy harvesting device comprising memory circuitry, processor circuitry, and a wireless interface. The energy harvesting device is configured to perform any of the methods disclosed herein relating to the energy harvesting device.

[0010] It is an advantage of the present disclosure that the energy harvesting device can notify the radio network node that it requires assistance without having to transmit a signal. By configuring the antenna array in a retro-reflective configuration the energy harvesting device can reflect a signal from a radio network node back to the radio network node. This allows the energy harvesting device to initiate an energy transfer without having to use its transmitter to transmit a signal. Thereby, the energy harvesting device can initiate an energy transfer also when the energy level of the energy harvesting device is too low to transmit a signal.

[0011] A method is disclosed, performed by a radio network node. The method comprises detecting a reflection of a signal transmitted by the radio network node. The method may comprise activating, based on the retro-reflection, a wireless energy transfer in a direction of the reflection.

[0012] Further, a radio network node is provided, the radio network node comprising memory circuitry, processor circuitry, and a wireless interface. The radio network node is configured to perform any of the methods disclosed herein relating to the radio network node.

[0013] It is an advantage of the present disclosure that the radio network node can be notified by the energy harvesting device that it requires assistance, such as a wireless power transfer, without the energy harvesting device having to transmit a signal to the radio network node. By receiving a reflection of a signal transmitted by the radio network node, the radio network node may start the wireless energy transfer to the energy harvesting device. Thereby, the radio network node can activate the wireless energy transfer to the energy harvesting device also when the energy level of the energy harvesting device is too low to transmit a signal to the radio network node.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features and advantages of the present disclosure will become readily apparent to those skilled in the art by the following detailed description of examples thereof with reference to the attached drawings, in which: Fig. 1 is a diagram illustrating an example wireless communication system comprising an example radio network node and an example energy harvesting device according to this disclosure,

[0016] Fig. 2A-2B are diagrams illustrating example antenna arrays for which the solution according to this disclosure can be applied,

[0017] Fig. 3A-3B are diagrams illustrating example circuitry of an energy harvesting device according to this disclosure,

[0018] Fig. 4 is a flow-chart illustrating an example method, performed in an energy harvesting device, for initiating a wireless energy transmission to the energy harvesting device according to this disclosure,

[0019] Fig. 5 is a flow-chart illustrating an example method, performed in a radio network node of a wireless communication system, for transmitting wireless energy to the energy harvesting device according to this disclosure,

[0020] Fig. 6 is a block diagram illustrating an example energy harvesting device according to this disclosure, and

[0021] Fig. 7 is a block diagram illustrating an example radio network node according to this disclosure.

[0022] DETAILED DESCRIPTION

[0023] Various examples and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated example needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

[0024] The figures are schematic and simplified for clarity, and they merely show details which aid understanding the disclosure, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts. Fig. 1 is a diagram illustrating an example wireless communication system 1 comprising an example radio network node 400 and an example wireless device, such as an energy harvesting device 300, according to this disclosure.

[0025] As discussed in detail herein, the present disclosure relates to a wireless communication system 1 comprising a cellular system, for example, a 3GPP wireless communication system. The wireless communication system 1 comprises a wireless device 300 and / or a radio network node 400.

[0026] A radio network node disclosed herein refers to a radio access network (RAN) node operating in the radio access network, such as a base station, an evolved Node B, eNB, gNB in NR. In one or more examples, the RAN node is a functional unit which may be distributed in several physical units. In one or more examples, the radio network node is a functional unit which may be distributed in several physical units.

[0027] The wireless communication system 1 may in one or more examples, comprise a core network (CN) node. The CN node disclosed herein refers to a network node operating in the core network, such as in the Evolved Packet Core Network, EPC, and / or a 5G Core Network, 5GC.

[0028] The wireless communication system 1 described herein may comprise one or more energy harvesting devices 300, 300A, and / or one or more network nodes 400, such as one or more of a base station, an eNB, a gNB and / or an access point. An energy harvesting device may refer to a mobile device, a user equipment (UE), an Internet of Things (loT) device, such as a sensor, being configured to harvest energy for example from an energy transfer signal received from the radio network node. The energy harvesting device 300, 300A may be configured to communicate with and / or receive an energy transfer from the network node 400 via a wireless link (or radio access link) 10, 10A. In one or more examples, the energy harvesting device 300, 300A may receive a signal, such as a pilot signal, from the radio network node 400, and may reflect the signal back to the radio network node via the wireless link 10, 10A. The pilot signal may be a reference signal, such as a Channel State Information Reference Signal (CSI-RS) or a Demodulation Reference Signal (DM-RS).

[0029] The wireless communication system 1 described herein may comprise one or more energy harvesting devices 300, 300A, and / or one or more network nodes 400, such as one or more of a base station, an eNB, a gNB and / or an access point.

[0030] Figs. 2A and 2B illustrate retro-reflective configurations of two example antenna arrays 3031 according to the current disclosure. The retro-reflective configuration of the antenna arrays 3031 can herein also be referred to as Van Atta arrays. A retro-reflective configuration herein means that a received signal is reflected towards the same direction as it arrived from. Fig. 2A illustrates an example retro-reflective configuration for one-dimensional (1 D), such as linear, antenna arrays. Fig. 2B illustrates an example retro-reflective configuration for two-dimensional (2D) antenna arrays. To configure the antenna arrays 3031 in a retro reflective configuration pairs of antennas 3032, such as antenna elements, of the antenna array are connected according to the provided layout, using a wiring length for connecting the respective antenna pair corresponding to a factor, such as a multiple, of the wavelength ( ) of the signal. The wavelength may be a predetermined wavelength of a signal transmitted by the radio network node, such as a wavelength of a pilot signal transmitted, such as broadcasted, by the radio network node. The pilot signal may, in one or more example methods, be periodically broadcasted by the radio network node. In one or more examples, the 1 D antenna array of Fig. 2A may be configured such that a rightmost antenna element 3032 is connected to a leftmost antenna element 3032 of the antenna array 3031 , the second rightmost antenna element 3032 is connected to the second leftmost antenna element 3032, and so forth. A signal entering the leftmost antenna element in Fig. 2A would then leave the antenna array 3031 from the rightmost antenna element 3032, a signal entering the second leftmost antenna element 3032 would leave the antenna array 3031 from the second rightmost antenna element 3032, and so forth. Due to the wiring length between the connected antenna elements 3032 being a multiple of the wavelength, the phase of the signal leaving the rightmost antenna element 3032 is the same as the phase of the signal entering the leftmost antenna element 3032.

[0031] The same principle applies to the 2D antenna array 3031 of Fig. 2B, where each antenna element 3032 is paired with its diagonal counterpart, for example according to the pattern disclosed in Fig. 2B. In Fig. 2B antenna elements having the same number are paired. In other words, antenna elements 1-1 , 2-2, 3-3, 4-4, 5-5, 6-6, 7-7, 8-8 are paired.

[0032] Figs. 3A-3C illustrate an example circuitry 3034, such as power harvesting circuitry and / or a transceiver circuitry, of an energy harvesting device. The example circuitry 3034 comprises an example antenna array 3031 , such as a 1 D antenna array, comprising a plurality of antenna elements 3032. The antenna elements 3032 may be connected to an energy storage of the energy harvesting device via a set of switches 3033, wherein each antenna element is connected to the energy storage via a respective switch 3033 out of the set of switches. The set of switches is configured to switch the antenna array 3031 between a first mode, such as a retro-reflective mode, as shown in Fig. 3B, and a second mode, such as an energy harvesting mode, as shown in Fig. 3C. In the energy harvesting mode, the antenna array will not reflect the signal, the second mode thus effectively functions as the retro-reflective mode being switched off. In other words, the switches are configured to configure the antenna array in either the retro- reflective configuration of Figs. 2A, 2B, and / or 3B, or the energy harvesting configuration of Fig. 3C. The set of switches 3033 may be configured to be operated using less power than would be required for transmitting a signal to the radio network node, which may also require the energy harvesting device to perform a synchronization procedure with the radio network node. The energy harvesting device may thus be able to configure and / or reconfigure the circuitry, such as the antenna array, even though it does not have sufficient power to transmit any signal, allowing the energy harvesting device to reflect a signal transmitted by the radio network node.

[0033] In one or more example methods, the circuitry 3034 may be configured to sequentially switch between the first mode, such as the retro-reflective mode, and the second mode, such as the energy harvesting mode, to encode a binary pattern into the signal reflected back to the radio network node. The binary pattern may be decoded by the radio network node to determine which type of assistance the energy harvesting device requires. In one or more example methods, a request for energy transfer may be associated with a first specific binary pattern, while for example a request for service may be associated with a second specific binary pattern.

[0034] Fig. 4 shows a flow diagram of an example method 100, performed by an energy harvesting device according to the disclosure, for initiating a wireless energy transmission to the energy harvesting device. The energy harvesting device is the energy harvesting device disclosed herein, such as wireless device 300 of Fig. 1 , and Fig. 6.

[0035] In one or more example methods, the method comprises monitoring S101 a need for assistance from the network, such as a need for energy transfer or a need for service. In one or more example methods, the need for energy transfer may for example be monitored by monitoring an energy level of an energy storage of the energy harvesting device. In one or more example methods, the need for assistance and / or service may for example be monitored by monitoring one or more characteristics of the energy harvesting device, such as a temperature, and / or a battery life.

[0036] Detecting a need for an energy transfer may for example comprise the energy harvesting device detecting that the remaining energy level of the energy storage of the energy harvesting device is below a given energy threshold, such as the battery life remaining being below a given value. In other words, the energy harvesting device can for example be seen as being in need of energy transfer when the remaining energy level of the energy storage of the energy harvesting device is below the given energy threshold. The method 100 comprises, upon detecting a need for assistance, such as a need for energy transfer and / or a need for service, configuring S102 the antenna array in a retro-reflective configuration. The retro-reflective configuration is a configuration where a signal is transmitted back in the same direction as it reaches the energy harvesting device. In one or more example methods, the retro-reflective configuration is configured to operate at a preconfigured frequency.

[0037] In one or more example methods, the method comprises encoding S103 a binary pattern into a retro-reflected signal by switching between the retro-reflective configuration and the energy harvesting configuration in a predetermined sequence. The binary pattern may for example be seen as binary information provided by the energy harvesting device by switching between the retro-reflective configuration and the energy harvesting configuration. As stated in S208, the radio network node may, based upon this binary pattern (such as binary information), determine that a power transfer is required in a direction of the reflection of the signal, such as in a direction of the binary information. The retro-reflected signal may in one or more examples be a pilot signal transmitted, such as broadcasted, by the radio network node. The binary pattern may be used as a type of morse code to notify the radio network node about the assistance the energy harvesting device requires. In one or more example methods, different types of assistance requests or different types of messages may be associated with respective binary patterns. Thereby, the energy harvesting device may encode the reflected signal with a binary pattern for energy transfer request when the energy harvesting device requires an energy transfer from the radio network node, or with a binary pattern for a service request when the energy harvesting device requires a service. In one or more example methods, encoding S103 comprises encoding information indicative of a switching pattern used by the energy harvesting device for switching between the retro-reflective configuration and the energy harvesting configuration for receiving the energy transfer from the radio network node. In one or more example methods, the energy harvesting device may be configured to switch between the retro- reflective configuration and the energy harvesting configuration for receiving the energy transfer from the radio network node according to a predetermined pattern, so that the radio network node knows when the energy harvesting device is in the energy harvesting mode. For example, the switching pattern of the energy harvesting device may, in one or more examples be, retro- reflective configuration for 1s and energy harvesting configuration for 10s.

[0038] The method 100 comprises reconfiguring S104 the antenna array in an energy harvesting configuration. In one or more example methods, the energy harvesting configuration is a non- reflective configuration of the antenna array. The non-reflective configuration of the antenna array allows energy from a signal to be received by the energy harvesting device and stored in an energy storage of the energy harvesting device. In one or more example methods, the reconfiguring S104 is performed based on a trigger condition. In one or more example methods, the trigger condition is an experienced power level of a received signal meeting a power level criterion. The power level criterion may, in one or more examples, be a power level threshold. Upon the experienced power level of the received signal meeting or exceeding the power level threshold, the energy harvesting device may reconfigure the antenna array in the energy harvesting configuration. In one or more example methods, the trigger condition is an expiry of a predetermined time period. The time period may, in one or more example methods, be a time period from configuring the antenna array in the retro-reflective configuration. Upon the predetermined time period expiring, the energy harvesting device may reconfigure the antenna array into the energy harvesting configuration to harvest the energy from an upcoming energy transfer signal.

[0039] Fig. 5 shows a flow diagram of an example method 200, performed by a radio network node according to the disclosure, for wireless energy transfer. The radio network node is the radio network node disclosed herein, such as radio network node 400 of Fig. 1 , and Fig. 6.

[0040] In one or more example methods, the method comprises transmitting S202, such as broadcasting, a signal, such as a pilot signal. In one or more example methods, transmitting S202 the signal comprises periodically broadcasting S202A pilot signals.

[0041] The method 200 comprises detecting S204 a reflection of the signal transmitted by the radio network node. In one or more example methods, detecting S204 comprises detecting S204A a reflection of the transmitted pilot signal.

[0042] In one or more example methods, the method comprises detecting S206 a binary pattern in the reflection of the signal. The binary pattern may be used as a type of morse code to notify the radio network node about the assistance the energy harvesting device requires. In one or more example methods, different types of assistance requests or different types of messages may be associated with respective binary patterns. Thereby, the energy harvesting device may encode the reflected signal with a binary pattern for energy transfer request when the energy harvesting device requires an energy transfer from the radio network node, or with a binary pattern for a service request when the energy harvesting device requires a service.

[0043] In one or more example methods, the method comprises determining S208, based on the binary pattern, that assistance, such as a power transfer, is required in a direction of the reflection of the signal.

[0044] The method 200 comprises activating S210, based on the reflection of the signal, an assistance function, such as a wireless energy transfer in the direction of the reflection. In one or more example methods activating the assistance function may comprise sending service personnel in the direction of the reflection, such as to an energy harvesting device located in the direction of the reflection.

[0045] In one or more example methods, activating S210 comprises forming S210A a beam for the wireless energy transfer based on, such as derived from, the reflection of the signal. The signal may be reflected by the energy harvesting device in the same direction as it was received. Hence, the radio network node may determine a direction and / or location of the energy harvesting device based on the reflection of the signal, and may form a beam, such as a beam for energy transfer, in the direction of the energy harvesting device.

[0046] Fig. 6 shows a block diagram of an example energy harvesting device 300 according to the disclosure. The energy harvesting device 300 comprises memory circuitry 301 , processor circuitry 302, and a wireless interface 303, such as the antenna array. The energy harvesting device 300 may be configured to perform any of the methods disclosed in Fig. 4. In other words, the energy harvesting device 300 may be configured initiating a wireless energy transmission to the energy harvesting device.

[0047] The energy harvesting device 300 is configured to communicate with a network node, such as the radio network node disclosed herein, using a wireless communication system.

[0048] The energy harvesting device 300 is configured to, upon detecting a need for energy transfer, configure (such as using the wireless interface 303 and / or the processor circuitry 302) the antenna array in a retro-reflective configuration.

[0049] The energy harvesting device 300 is configured to, upon detecting a need for energy transfer, reconfigure (such as using the wireless interface 303 and / or the processor circuitry 302) the antenna array in an energy harvesting configuration.

[0050] The wireless interface 303 is configured for wireless communications via a wireless communication system, such as a 3GPP system, such as a 3GPP system supporting one or more of: New Radio, NR, Long Term Evolution, LTE, Narrow-band loT, NB-loT, and Long Term Evolution - enhanced Machine Type Communication, LTE-M, and 3GPP system operated in licensed bands or unlicensed bands.

[0051] The energy harvesting device 300 is optionally configured to perform any of the operations disclosed in Fig. 4 (such as any one or more of S102, S103, S104). The operations of the energy harvesting device 300 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 301 ) and are executed by processor circuitry 302).

[0052] Furthermore, the operations of the wireless device 300 may be considered a method that the energy harvesting device 300 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and / or software.

[0053] Memory circuitry 301 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 301 may include a nonvolatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 302. Memory circuitry 301 may exchange data with processor circuitry 302 over a data bus. Control lines and an address bus between memory circuitry 301 and processor circuitry 302 also may be present (not shown in Fig. 6). Memory circuitry 301 is considered a non-transitory computer readable medium.

[0054] Memory circuitry 301 may be configured to store information, such as information relating to the binary pattern, in a part of the memory.

[0055] Fig. 7 shows a block diagram of an example radio network node 400 according to the disclosure. The radio network node 400 comprises memory circuitry 401 , processor circuitry 402, and a wireless interface 403. The radio network node 400 may be configured to perform any of the methods disclosed in Fig. 2. In other words, the radio network node 400 may be configured for wireless energy transfer.

[0056] The radio network node 400 is configured to communicate with a wireless device, such as the energy harvesting device disclosed herein, using a wireless communication system.

[0057] The wireless interface 403 is configured for wireless communications via a wireless communication system, such as a 3GPP system, such as a 3GPP system supporting one or more of: New Radio, NR, Long Term Evolution, LTE, Narrow-band loT, NB-loT, and Long Term Evolution - enhanced Machine Type Communication, LTE-M, and 3GPP system operated in licensed bands or unlicensed bands.

[0058] The radio network node 400 is configured to detect (for example via the wireless interface 403 and / or the processor circuitry 402) a reflection of a signal transmitted by the radio network node.

[0059] The radio network node 400 is configured to activate, based on the reflection, a wireless energy transfer in a direction of the reflection. Processor circuitry 402 is optionally configured to perform any of the operations disclosed in Fig. 5 (such as any one or more of S202, S202A, S204, S204A, S206, S208, S210). The operations of the network node 400 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 401) and are executed by processor circuitry 402).

[0060] Furthermore, the operations of the radio network node 400 may be considered a method that the radio network node 400 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and / or software.

[0061] Memory circuitry 401 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 401 may include a nonvolatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 402. Memory circuitry 401 may exchange data with processor circuitry 402 over a data bus. Control lines and an address bus between memory circuitry 401 and processor circuitry 402 also may be present (not shown in Fig. 7). Memory circuitry 401 is considered a non-transitory computer readable medium.

[0062] Memory circuitry 401 may be configured to store information, such as information relating to the binary pattern, in a part of the memory.

[0063] Examples of methods and products (energy harvesting device and radio network node) according to the disclosure are set out in the following items:

[0064] Item 1 . A method performed by an energy harvesting device comprising an antenna array, for initiating a wireless energy transmission to the energy harvesting device, the method comprising: upon detecting a need for energy transfer, configuring (S102) the antenna array in a retro-reflective configuration, and reconfiguring (S104) the antenna array in an energy harvesting configuration.

[0065] Item 2. The method according to Item 1 , wherein the reconfiguring (S104) is performed based on a trigger condition. Item 3. The method according to Item 2, wherein the trigger condition is an experienced power level of a received signal meeting a power level criterion.

[0066] Item 4. The method according to Item 2, wherein the trigger condition is an expiry of a predetermined time period.

[0067] Item 5. The method according to any one of the previous Items, wherein the retro- reflective configuration is configured to operate at a preconfigured frequency.

[0068] Item 6. The method according to any of the previous Items, wherein the energy harvesting configuration is a non-reflective configuration of the antenna array.

[0069] Item 7. The method according to any one of the previous Items, wherein the method comprises encoding (S103) a binary pattern into a retro-reflected signal by switching between the retro-reflective configuration and the energy harvesting configuration in a predetermined sequence.

[0070] Item 8. A method performed by a radio network node, for wireless energy transfer, the method comprising: detecting (S204) a reflection of a signal transmitted by the radio network node, and activating (S210), based on the reflection, a wireless energy transfer in a direction of the reflection.

[0071] Item 9. The method according to Item 8, wherein activating (S210) comprises forming (S210A) a beam for the wireless energy transfer based on the reflection of the signal.

[0072] Item 10. The method according to any one of Items 8 and 9, wherein the method comprises: transmitting (S202) a pilot signal, wherein detecting (S204) comprises detecting (S204A) a reflection of the transmitted pilot signal.

[0073] Item 11. The method according to Item 10, wherein transmitting (S202) the pilot signal comprises periodically broadcasting (S202A) pilot signals.

[0074] Item 12. The method according to any one of Items 8 to 11 , wherein the method comprises: detecting (S206) a binary pattern in the reflection of the signal, and determining (S208), based on the binary pattern, that a power transfer is required in a direction of the reflection of the signal.

[0075] Item 13. An energy harvesting device comprising memory circuitry, processor circuitry, and a wireless interface, wherein the energy harvesting device is configured to perform any of the methods according to any of Items 1-7.

[0076] Item 14. A radio network node comprising memory circuitry, processor circuitry, and a wireless interface, wherein the radio network node is configured to perform any of the methods according to any of Items 8-12.

[0077] The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0078] It may be appreciated that Figures 1-7 comprise some circuitries or operations which are illustrated with a solid line and some circuitries, components, features, or operations which are illustrated with a dashed line. Circuitries or operations which are comprised in a solid line are circuitries, components, features or operations which are comprised in the broadest example. Circuitries, components, features, or operations which are comprised in a dashed line are examples which may be comprised in, or a part of, or are further circuitries, components, features, or operations which may be taken in addition to circuitries, components, features, or operations of the solid line examples. It should be appreciated that these operations need not be performed in order presented. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any order and in any combination. It should be appreciated that these operations need not be performed in order presented. Circuitries, components, features, or operations which are comprised in a dashed line may be considered optional.

[0079] Other operations that are not described herein can be incorporated in the example operations. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Certain features discussed above as separate implementations can also be implemented in combination as a single implementation. Conversely, features described as a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as any sub-combination or variation of any sub-combination.

[0080] It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed.

[0081] It is to be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements.

[0082] It is to be noted that the term "indicative of" may be seen as “associated with”, “related to”, “descriptive of’, “characterizing”, and / or “defining”. The terms “indicative of”, “associated with”, “related to”, “descriptive of’, “characterizing”, and “defining” can be used interchangeably. The term “indicative of” can be seen as indicating a relation. For example, weight data indicative of weight may comprise one or more weight parameters.

[0083] It is to be noted that the word "based on" may be seen as “as a function of” and / or “derived from”. The terms “based on” and “as a function of’ can be used interchangeably. For example, a parameter determined “based on” a data set can be seen as a parameter determined “as a function of” the data set. In other words, the parameter may be an output of one or more functions with the data set as an input.

[0084] A function may be characterizing a relation between an input and an output, such as mathematical relation, a database relation, a hardware relation, logical relation, and / or other suitable relations.

[0085] It should further be noted that any reference signs do not limit the scope of the claims, that the examples may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

[0086] The various example methods, devices, nodes and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer-readable medium, including computerexecutable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc. that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

[0087] Although features have been shown and described, it will be understood that they are not intended to limit the claimed disclosure, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the claimed disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed disclosure is intended to cover all alternatives, modifications, and equivalents.

Claims

CLAIMS1 . A method performed by an energy harvesting device comprising an antenna array, for initiating a wireless energy transmission to the energy harvesting device, the method comprising: upon detecting a need for energy transfer, configuring (S102) the antenna array in a retro-reflective configuration, and reconfiguring (S104) the antenna array in an energy harvesting configuration.

2. The method according to claim 1 , wherein the reconfiguring (S104) is performed based on a trigger condition.

3. The method according to claim 2, wherein the trigger condition is an experienced power level of a received signal meeting a power level criterion.

4. The method according to any of claims 2-3, wherein the trigger condition is one or more of an experienced power level of a received signal meeting a power level criterion, and an expiry of a predetermined time period.

5. The method according to any one of the previous claims, wherein the retro-reflective configuration is configured to operate at a preconfigured frequency.

6. The method according to any of the previous claims, wherein the energy harvesting configuration is a non-reflective configuration of the antenna array.

7. The method according to any one of the previous claims, wherein the method comprises encoding (S103) a binary pattern into a retro-refl ected signal by switching between the retro-reflective configuration and the energy harvesting configuration in a predetermined sequence.

8. A method performed by a radio network node, for wireless energy transfer, the method comprising: detecting (S204) a reflection of a signal transmitted by the radio network node, and activating (S210), based on the reflection, a wireless energy transfer in a direction of the reflection.

9. The method according to claim 8, wherein activating (S210) comprises forming (S210A) a beam for the wireless energy transfer based on the reflection of the signal.

10. The method according to any one of claims 8 and 9, wherein the method comprises: transmitting (S202) a pilot signal, wherein detecting (S204) comprises detecting (S204A) a reflection of the transmitted pilot signal.

11. The method according to claim 10, wherein transmitting (S202) the pilot signal comprises periodically broadcasting (S202A) pilot signals.

12. The method according to any one of claims 8 to 11 , wherein the method comprises: detecting (S206) a binary pattern in the reflection of the signal, and determining (S208), based on the binary pattern, that a power transfer is required in a direction of the reflection of the signal.

13. An energy harvesting device comprising memory circuitry, processor circuitry, and a wireless interface, wherein the energy harvesting device is configured to perform any of the methods according to any of claims 1-7.

14. A radio network node comprising memory circuitry, processor circuitry, and a wireless interface, wherein the radio network node is configured to perform any of the methods according to any of claims 8-12.

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