Method and device for triggering an uplink transmission at an ambient-iot device based on a level of stored electrical energy and on a channel quality level

Abstract

The present disclosure relates to methods and devices for enabling a user equipment, UE (20), which includes a wireless device (25) having an energy harvesting unit (254) which stores electrical energy in an energy storage unit (255) of the wireless device, to determine whether an uplink data transmission is to be initiated based on a level of electrical energy stored in the energy storage unit (255) and based on a channel quality level.

Description

Method and device for triggering an uplink transmission at an ambient-loT device based on a level of stored electrical energy and on a channel quality levelTechnical field

[0001] The present disclosure relates to wireless communication systems and relates more specifically to methods and devices for enabling a wireless device with ultra-low power consumption to determine whether an uplink data transmission is to be initiated based at least on a level of electrical energy stored in an energy storage unit of the wireless device. Background

[0002] The internet of things (loT) allows various devices to connect to the internet to send data, receive instructions, or both. Tens of billions of loT devices are already deployed and the global number of loT devices is expected to increase rapidly. Thus, massive connectivity is needed. However, powering these billions of loT devices is a critical challenge, and deploying power cables or regularly replacing / recharging batteries is not a viable solution.

[0003] 3GPP (Third Generation Partnership Project) is investigating new loT technologies to open new markets within 3GPP systems, whose number of connections and / or device density can be orders of magnitude higher than existing 3GPP loT technologies, and which can provide complexity and power consumption orders-of-magnitude lower than existing 3GPP technologies such as narrow-band-loT (NB-loT) and long-term evolution-machine- type communications (LTE-MTC). More specifically, 3GPP is currently defining Ambient- loT (A-loT) technologies (see e.g., the technical report TR 38.848 V18.0.0) aiming at enabling ultra-low power consumption loT devices, which could be either batteryless devices with no energy storage capability (performing backscattering transmission) or devices with energy storage that do not need to be replaced or recharged manually (performing wire-free energy harvesting (EH) from one or more energy sources).

[0004] By “ultra-low power consumption” devices, or “A-loT” devices, we mean devices having a peak power consumption lower than 1 mW, or even lower than 100 pW or lower than 10 pW. For instance, Ambient-loT currently aims at enabling A-loT devices having the following characteristics:- around 1 pW peak power consumption with energy storage, with neither downlink (DL) nor uplink (UL) amplification in the device (the device’s UL transmission is backscattered on a carrier wave provided externally), below a few hundred pW peak power consumption with energy storage, with DL and / or UL amplification in the device (the device’s UL transmission may be generated internally by the device or be backscattered on a carrier wave providedexternally).

[0005] Typically, such A-loT devices will have only limited energy storage, and the usage of the electrical energy stored needs to be optimized to reduce the probability that an uplink data transmission would fail. Indeed, failed uplink data transmissions result in uplink resources wastage and increased electrical energy consumption and need to be avoided.Summary

[0006] The present disclosure aims at improving the situation. In particular, the present disclosure aims at addressing at least some of the limitations of the prior art discussed above. In particular, the present disclosure aims at proposing a solution for enabling reducing the probability of failed uplink data transmissions from wireless devices such as A-loT devices.

[0007] For that purpose, it is proposed to evaluate a level of electrical energy stored at a wireless device, and to use the level of stored electrical energy to determine if the wireless device can proceed with an uplink data transmission or if the uplink data transmission should be delayed instead.

[0008] According to a first aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, the method being implemented by a wireless device of the wireless communication system, wherein the wireless device comprises an energy harvesting unit configured to convert ambient energy into electrical energy that is stored in an energy storage unit of the wireless device, the wireless device further comprising a communication unit configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the method comprises determining an energy level threshold based on an estimated channel quality level of a propagation channel between the RAN and the wireless device and, in response to determining that uplink data is to be sent to the RAN:- measuring a level of the electrical energy stored in the energy storage unit,- evaluating an uplink transmission triggering criterion by comparing the level of the stored electrical energy to the determined energy level threshold, in response to the uplink transmission triggering criterion being verified: transmitting uplink data to the RAN, in response to the uplink transmission triggering criterion not being verified: delaying the transmission of the uplink data to the RAN.

[0009] In some embodiments, the method according to the first aspect can further comprise one or more of the following optional features, considered either alone or in any technically possible combination.

[0010] In some embodiments of the method according to the first aspect, the energy level threshold is selected among a plurality of different energy level thresholds, by using a preconfigured mapping between the plurality of different energy level thresholds and respective associated channel quality levels.

[0011] In some embodiments of the method according to the first aspect, the mapping between the plurality of different energy level thresholds and their respective associated channel quality levels is predefined or received in system information broadcasted by the RAN or received in a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

[0012] In some embodiments of the method according to the first aspect, the transmission of the uplink data to the RAN is delayed until the uplink transmission triggering criterion is verified.

[0013] In some embodiments of the method according to the first aspect, the uplink transmission triggering criterion is verified when the level of stored electrical energy is greater than the determined energy level threshold.

[0014] In some embodiments of the method according to the first aspect, the uplink transmission triggering criterion is verified, regardless of the level of stored electrical energy:- when the delay introduced for performing the transmission of the uplink data reaches a predetermined maximum delay, or- when the number of skipped uplink transmission occasions reaches a predetermined maximum number of skipped uplink transmission occasions.

[0015] In some embodiments of the method according to the first aspect, the wireless device determines that uplink data is to be transmitted by receiving an uplink transmission triggering signal from the RAN.

[0016] In some embodiments of the method according to the first aspect, the energy harvesting unit is a radio unit configured to convert a received radiofrequency signal into electrical energy.

[0017] According to a second aspect, the present disclosure relates to a wireless device comprising at least one memory and at least one processor configured to carry out a method according to any one of the embodiments of the first aspect.

[0018] According to a third aspect, the present disclosure relates to a user equipment, UE, comprising a wireless device according to any one of the embodiments of the present disclosure.

[0019] According to a fourth aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, the method being implemented by abase station, BS, of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device which comprises an energy harvesting unit configured to convert ambient energy into electrical energy that is stored in an energy storage unit of the wireless device, wherein the method comprises transmitting to the wireless device information related to at least one channel quality level and to at least one energy level threshold.

[0020] In some embodiments, the method according to the fourth aspect can further comprise one or more of the following optional features, considered either alone or in any technically possible combination.

[0021] In some embodiments of the method according to the fourth aspect, the information related to at least one channel quality level and to at least one energy level threshold comprises a mapping between a plurality of different energy level thresholds and respective associated channel quality levels.

[0022] In some embodiments, the method according to the fourth aspect comprises transmitting an uplink transmission triggering signal to the wireless device as an indication that uplink data is to be transmitted to the RAN by the wireless device.

[0023] In some embodiments, the method according to the fourth aspect comprises starting to transmit an energy harvesting signal to the wireless device before transmitting the uplink transmission triggering signal to said wireless device.

[0024] In some embodiments of the method according to the fourth aspect, the information related to at least one channel quality level and to at least one energy level threshold is broadcasted in system information and / or is transmitted in a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

[0025] According to a fifth aspect, the present disclosure relates to a base station, BS, comprising at least one memory and at least one processor configured to carry out a method according to any one of the embodiments of the fourth aspect.

[0026] According to a sixth aspect, the present disclosure relates to a wireless communication system comprising at least one base station according to any one of the embodiments of the present disclosure and at least one user equipment according to any one of the embodiments of the present disclosure.

[0027] According to a seventh aspect, the present disclosure relates to a computer program product comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method for exchanging data according to any one of the embodiments of the present disclosure. The computer program product can use anyprogramming language, and can be in the form of source code, object code, or in any intermediate form between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0028] According to an eighth aspect, the present disclosure relates to a (non-transitory) computer-readable storage medium comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method for transmitting control messages according to any one of the embodiments of the present disclosure.Brief description of figures

[0029] The invention will be better understood upon reading the following description, given as an example that is in no way limiting, and made in reference to the figures which show:Figure 1 : schematic representations of different possible topologies of a wireless communication system,Figure 2: a schematic representation of an example of a wireless device,Figure 3: a schematic representation of an example of a BS,Figures 4 and 5: flow charts illustrating examples of methods for exchanging data implemented by a wireless device of a UE and a BS, respectively,- Figures 6 and 7: flow charts illustrating other examples of methods for exchanging data implemented by a wireless device of a UE and a BS, respectively,- Figures 8 and 9: flow charts illustrating other examples of methods for exchanging data implemented by a wireless device of a UE and a BS, respectively.

[0030] In these figures, references identical from one figure to another designate identical or analogous elements. For reasons of clarity, the elements shown are not to scale, unless explicitly stated otherwise.Detailed description

[0031] The detailed description set forth below, with reference to the figures, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For instance, although 3GPP terminology, from e.g., 5G NR, may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the present disclosure.

[0032] 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 isimplied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. Also, the order of steps of any methods disclosed herein, in particular in the figures, is provided only for illustration purposes and is not meant to limit the present disclosure which may be applied with the same steps executed in a different order and / or with all or part of the steps executed in parallel or jointly, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Also, in a figure, steps represented surrounded by a dashed line are to be considered as optional for the embodiment represented in this figure. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0033] Figure 1 represents schematically an example of wireless communication system, which may be for example a 5G NR wireless communication system. More specifically, figure 1 represents a RAN of the wireless communication system, which is used exchange data with UEs 20 via radio signals. For example, the RAN may send data to the UEs 20 (downlink, DL), for instance data received from a core network (CN, not represented in the figures). The RAN may also receive data from the UEs 20 (uplink, UL), which data may be forwarded to the CN.

[0034] In the example illustrated by figure 1 , the RAN comprises one base station, BS, 30. Of course, the RAN may comprise more than one BS 30 to increase the coverage of the wireless communication system. Each of these BSs may be referred to as NB, eNodeB (or eNB), gNodeB (or gNB, in the case of a 5G NR wireless communication system), an access point or the like, depending on the wireless communication standard(s) implemented.

[0035] In the example illustrated by figure 1 , only one UE 20 is represented, which includes a wireless device 25 that provides the UE 20 with wireless connectivity to the RAN of the wireless communication system. Part a) of figure 1 represents schematically an example in which the UE 20 exchanges data (useful data and control data) directly with a BS 30 of the RAN (referred to as Topology 1 in TR 38.848 V18.0.0). Part b) of figure 1 represents schematically an example in which the UE 20 exchanges data (useful data and control data) indirectly with a BS 30 of the RAN, via one or more intermediate nodes 31 (referred to as Topology 2 in TR 38.848 V18.0.0). Each intermediate node 31 may be e.g., a relay, an integrated access and backhaul (IAB) node, another UE 20, a repeater, a reconfigurableintelligent surface (RIS), etc.

[0036] Figure 2 represents schematically an example of a wireless device 25 suitable for implementing any method, discussed in the present disclosure, performed at a UE 20. Basically, the wireless device 25 corresponds to an apparatus that provides wireless connectivity with the RAN of the wireless communication system, and that can be used to exchange data with said RAN. The wireless device 25 is for example an A-loT device, i.e., a wireless device having a peak power consumption lower than 1 mW, or even lower than 100 W, or even lower than 10 pW.

[0037] Such a wireless device 25 may be included in a UE 20, as illustrated by figure 2. The UE 20 may for instance be a cellular phone, a wireless modem, a wireless communication device, a handheld device, a laptop computer, or the like. In preferred examples, the UE 20 may also be an Internet of Things (loT) equipment, like a wireless camera, a smart sensor, a smart meter, smart glasses, a vehicle (manned or unmanned), a global positioning system device, etc., or any other equipment that may run applications that need to exchange data with remote recipients, via the wireless device 25.

[0038] As illustrated by figure 2, the wireless device 25 comprises one or more processors 250 and one or more memories 251 . The one or more processors 250 may include for instance a central processing unit (CPU), a digital signal processor (DSP), a field- programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc. The one or more memories 251 may include any type of computer readable volatile and nonvolatile memories (magnetic hard disk, solid-state disk, optical disk, electronic memory, etc.). The one or more memories 251 may store a computer program product 252, in the form of a set of program-code instructions to be executed by the one or more processors 250 to implement all or part of the steps of a method for exchanging data, performed at a UE’s side, according to any one of the embodiments disclosed herein.

[0039] As illustrated by figure 2, the wireless device 25 comprises also a (wireless) communication unit 253 configured to exchange data (directly or indirectly) with BSs 30 of the RAN using radio signals. The communication unit 253 may implement one or more wireless communication protocols, and may for instance be a 3G, 4G, 5G, NR, WiFi, WiMax, etc. transceiver or the like. In preferred embodiments, the (wireless) communication unit 253 comprises a 5G NR wireless communication unit.

[0040] As discussed above, the communication unit 253 may comprise in some examples neither downlink (DL) nor uplink (UL) amplification capabilities (the UL transmission is backscattered on a carrier wave provided externally). In other examples, the communication unit 253 may comprise DL and / or UL amplification (the UL transmission may be generatedinternally by the wireless device or be backscattered on a carrier wave provided externally).

[0041] As illustrated by figure 2, the wireless device 25 comprises also an energy harvesting unit 254 and an energy storage unit 255 of the wireless device.

[0042] The energy storage unit 255 may be any type of electrical energy accumulator, and may comprise e.g., one or more capacitors, one or more batteries, etc. The energy storage unit 255 is used to provide electrical energy to the other equipment of the wireless device 25 which require electrical energy, such as the one or more processors 250, the one or more memories 251 and, in some examples, the (wireless) communication unit 253.

[0043] The energy harvesting unit 254 is configured to convert ambient energy into electrical energy that is stored in the energy storage unit 255. By “ambient energy” we mean energy from energy sources that are external to the wireless device 25, which is received at the wireless device 25 without any wires between the energy sources and the wireless device 25. Hence, the energy harvesting unit 254 is such that the wireless device 25 may operate in an autonomous manner, without having to replace or recharge manually the energy storage unit 255. The energy harvesting unit 254 may for example collect energy from various energy sources including solar, thermal, motion or vibration, radiofrequency (RF), etc.

[0044] In preferred embodiments, the energy harvesting unit 254 comprises at least a radio unit configured to convert RF signals into electrical energy that is stored in the energy storage unit 255. These RF signals may for instance be external RF signals, i.e., RF signals which do not originate from within the wireless communication system itself but from RF sources which are external to the wireless communication system. For example, external RF signals may originate from external 3G, 4G, 5G, NR, WiFi, WiMax, Bluetooth, DAB, etc., devices located in the vicinity of the wireless device 25. Alternatively, or in combination thereof, the RF signals may originate from within the wireless communication system, for example from BSs 30 of the RAN which may transmit an energy harvesting (RF) signal to (A-loT) wireless devices 25 in their coverage, and / or from equipment separate from the BSs 30 but deployed to enable energy harvesting at the (A-loT) wireless devices 25 of the wireless communication system. In some examples, when RF signals are used to collect electrical energy into the energy storage unit 255, the energy harvesting unit 254 may be included in the (wireless) communication unit 253.

[0045] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0046] As illustrated by figure 3, the BS 30 comprises one or more processors 300 and one or more memories 301. The one or more processors 300 may include for instance a centralprocessing unit (CPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc. The one or more memories 301 may include any type of computer readable volatile and non-volatile memories (magnetic hard disk, solid-state disk, optical disk, electronic memory, etc.). The one or more memories 301 may store a computer program product 302, in the form of a set of programcode instructions to be executed by the one or more processors 300 to implement all or part of the steps of a method for exchanging data, performed at the RAN’s side, according to any one of the embodiments disclosed herein.

[0047] As illustrated by figure 3, the BS 30 comprises also a wireless communication unit 303, configured to exchange data with UEs 20 using radio signals, and more specifically with (wireless) communication units 253 of wireless devices 25 included in these UEs 20. The wireless communication unit 303 may for instance be a 3G, 4G, 5G, NR, WiFi, WiMax, etc. transceiver or the like. In preferred embodiments, the wireless communication unit 303 of the BS 30 comprises a 5G NR transceiver. In some examples, the wireless communication unit 303 may also transmit carrier waves to the wireless devices 25 which perform uplink backscattering transmissions.

[0048] As illustrated by figure 3, the BS 30 may comprise also, in some examples, a network communication unit 304, configured to exchange data with other base stations of the RAN and / or with the CN. The network communication unit 305 may support one or more suitable communication protocols, which may be wired (including optical) and / or wireless.

[0049] As illustrated by figure 3, the BS 30 may comprise also, in some examples, an energy harvesting signal generator 305, which generates energy harvesting (RF) signals which enable wireless devices 25 in its coverage to collect electrical energy in their energy storage units 255, via their energy harvesting units 254. The energy harvesting (RF) signals may take any suitable form enabling the energy harvesting units 254 to store electrical energy in the energy storage units 255 of the wireless devices 25. The choice of a specific energy harvesting (RF) signal format consists in a specific and non-limitative embodiment of the present disclosure. As mentioned above, when present, such energy harvesting (RF) signals may alternatively, or in combination thereof, be generated by other equipment separate from BSs 30 of the RAN.

[0050] As discussed above, the present disclosure aims at enabling a wireless device 25 to decide whether an uplink data transmission can be initiated by considering directly or indirectly a level of electrical energy stored in its energy storage unit 255. Considering the level of stored electrical energy can be used to e.g., avoid initiating the uplink data transmission when the stored electrical energy is low, which could lead to a failed uplinkdata transmission. Hence, taking into account the level of stored electrical energy can reduce the probability of failed uplink transmissions for A-loT devices.

[0051] We now present examples of signaling and decision strategies that may be implemented to achieve a higher probability of successful uplink data transmissions by the wireless device 25, thereby reducing uplink resources wastage and energy consumption.

[0052] Level of stored electrical energy

[0053] Figure 4 represents a diagram showing steps of an exemplary embodiment of a method 40 for exchanging data, which is implemented by a wireless device 25 of a UE 20. Figure 5 represents a diagram showing corresponding steps of an exemplary embodiment of a method 50 for exchanging data, which is implemented by a BS 30 of the RAN.

[0054] As illustrated by figure 4, the method 40 for exchanging data comprises a step S40 of determining that uplink data is to be sent by the wireless device 25.

[0055] In some examples, the step S40 may consist in detecting that uplink data is available at the UE 20 and should be transmitted by the wireless device 25 to the RAN.

[0056] Alternatively, or in combination thereof, the wireless device 25 may determine that uplink data is to be transmitted to the RAN when it detects an upcoming UL transmission occasion. For example, an UL transmission occasion corresponds to UL resources that the wireless device 25 can use. For example, such UL resources may be e.g., contention-based UL resources such as random-access channel (RACH) UL resources or configured grant (CG) UL resources, etc. In other examples, such UL resources may be allocated specifically to the wireless device 25, such as scheduling request, SR, resources.

[0057] Alternatively, or in combination thereof, an uplink data transmission may be triggered by the RAN. In such examples, the step S40 may comprise receiving an uplink transmission triggering signal from the RAN. Hence, if the wireless device 25 receives such an uplink transmission triggering signal from the RAN, the wireless device 25 may evaluate whether the uplink data transmission can be initiated, for example in an upcoming UL transmission occasion. Of course, such an uplink data transmission should be initiated only if uplink data is available at the UE 20 or can be collected by the UE in response to receiving the uplink transmission triggering signal from the RAN. In the present disclosure, we assume in a non- limitative manner that uplink data is available or can be collected by the UE 20, and we focus on other conditions that the wireless device 25 may consider in order to decide whether the uplink data transmission should be initiated.

[0058] To reduce its electrical energy consumption, the wireless device 25 may be placed in a sleep mode. In such a case, the wireless device 25 needs to transition to an active mode to be able to perform the uplink data transmission. Such a transition may be triggeredby the RAN, by sending a wake-up signal to the wireless device 25. In such a case, the uplink transmission triggering signal may correspond to the wake-up signal which transitions the wireless device 25 from a sleep mode to an active mode, or it may be transmitted by the RAN after it has transmitted a wake-up signal to the wireless device 25.

[0059] As illustrated by figure 4, the method 40 for exchanging data comprises, in response to determining during step S40 that uplink data is to be transmitted, a step S41 of measuring a level of the electrical energy stored in the energy storage unit 255. The level of stored electrical energy may be measured by using any method known to the skilled person and the choice of a specific method corresponds to a specific but non-limitative embodiment of the present disclosure. Also, the measured electrical energy level may take any suitable format enabling it to be compared to e.g., a threshold. For example, the level of stored electrical energy may correspond to an energy value, expressed e.g., in Joules or watt- hours, or to a percentage indicating the charge of the energy storage unit 255 (with e.g., 0% indicating that the energy storage unit 255 is empty and 100% indicating that the energy storage unit 255 is fully charged), etc.

[0060] As illustrated by figure 4, the method 40 for exchanging data comprises then a step S42 of evaluating an uplink transmission triggering criterion by comparing the level of the stored electrical energy to a predetermined energy level threshold. If the uplink transmission triggering criterion is verified (reference S42a in figure 4), the method 40 for exchanging data comprises a step S43 of transmitting uplink data (i.e., all or part of the uplink data available at the wireless device 25) to the RAN. In turn, if the uplink transmission triggering criterion is not verified (reference S42b in figure 4), the method 40 for exchanging data comprises a step S44 of delaying the transmission of the uplink data to the RAN.

[0061] Hence, the wireless device 25 takes into account the level of electrical energy stored in the energy storage unit 255 before initiating the uplink data transmission, to evaluate whether the level of stored electrical energy is sufficient for the uplink data transmission to likely succeed. For example, the uplink transmission triggering criterion is verified when the level of the stored electrical energy is greater than the predetermined energy level threshold. If the level of stored electrical energy is not considered sufficient, the uplink data transmission is delayed e.g., to a subsequent uplink transmission occasion, to enable the wireless device 25 to further harvest electrical energy into the energy storage unit 255.

[0062] It should be noted that is also possible, in some examples, to consider also other parameters to determine whether the wireless device 25 can initiate the uplink data transmission. For example, the evaluation of the uplink transmission triggering criterion may also consider the volume of uplink data to be transmitted, the channel quality of thepropagation channel between the RAN and the wireless device 25, etc. More generally, the uplink transmission triggering criterion may consider any parameter that is relevant for evaluating whether the uplink data transmission is likely to succeed, the level of stored electrical energy being an important parameter in the context of A-loT devices. Hence, in some examples, the uplink transmission triggering criterion may be considered verified when the level of the stored electrical energy is greater than the predetermined energy level threshold and when one or more other conditions are verified, for example when the channel quality level is greater than a predetermined channel quality level threshold, etc.

[0063] For example, the energy level threshold may be predefined at the wireless device 25 (e.g., specified by a standard or by calibration of the wireless device 25).

[0064] In other examples, and as illustrated by figure 4, the method 40 for exchanging data may include a prior step S45 of receiving from the RAN information related to at least one energy level threshold, and the energy level threshold may be determined by the wireless device 25 based the received information. For example, the received information may comprise the values of one or more energy level thresholds that can be used by the wireless device 25. For example, the received information may consist in a single energy level threshold, that the wireless device 25 may use directly in the evaluation of the uplink transmission triggering criterion. In other examples, the received information may include a plurality of different energy level thresholds which may be associated e.g., to respective traffic classes (e.g., priority of uplink data to be transmitted, etc.), to respective channel quality levels, to respective volumes of uplink data to be transmitted, etc. In such a case, the wireless device 25 may select an energy level threshold, among the plurality of energy level thresholds received, based on the uplink data transmission context (traffic class, channel quality level, volume of uplink data, etc.).

[0065] For example, the information related to at least one energy level threshold may be received in system information broadcasted by the RAN and / or in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25. In the latter case, the uplink transmission triggering signal, if any, may include an identifier of the wireless device 25 or of the group of wireless devices, to enable the wireless device 25 to detect that it is the recipient of this information.

[0066] As indicated above, the uplink data transmission is delayed (step S44) when the uplink transmission triggering criterion is not verified. For example, the uplink data transmission may be delayed by a predetermined delay, which starts when determining that the uplink data transmission is to be delayed. In such a case, the uplink data transmission may be initiated once the predetermined delay has expired without having to re-evaluatethe uplink transmission triggering criterion.

[0067] In other examples, and as illustrated by figure 4, the evaluation of the uplink transmission triggering criterion may be executed in a recurrent manner, for example at each subsequent uplink transmission occasion, until said uplink transmission triggering criterion becomes verified. For example, the uplink data transmission may be initiated as soon as the level of stored electrical energy becomes greater than the predetermined energy level threshold.

[0068] In some examples, the uplink transmission triggering criterion may become verified at some point regardless of the level of stored electrical energy, to ensure that the uplink data transmission is not delayed indefinitely. For example, the uplink transmission triggering criterion may become verified when the delay introduced for performing the transmission of the uplink data reaches a predetermined maximum delay. According to another example, the uplink transmission triggering criterion may become verified when the number of skipped uplink transmission occasions reaches a predetermined maximum number of skipped uplink transmission occasions. Hence, such provisions ensure that the uplink data transmission is not delayed by more than a predetermined maximum delay or by more than a predetermined maximum number of skipped uplink transmission occasions.

[0069] In alternate examples, the uplink data to be transmitted may be discarded if the uplink transmission triggering criterion remains not verified after a predetermined maximum delay or after a predetermined maximum number of skipped uplink transmission occasions.

[0070] As discussed above, figure 5 represents a diagram showing corresponding steps of an exemplary embodiment of a method 50 for exchanging data, which may be implemented by a BS 30 when the wireless device 25 implements the method 40 for exchanging data illustrated by figure 4.

[0071] As illustrated by figure 5, the method 50 for exchanging data comprises a step S50 of transmitting to the wireless device 25 information related to at least one energy level threshold (received by the wireless device 25 during step S45), to be used by the wireless device 25 to evaluate the uplink transmission triggering criterion. As discussed above, this information may be e.g., broadcasted in system information and / or transmitted in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25.

[0072] In some examples, the method 50 for exchanging data may comprise a step (not represented in the figures) of estimating a channel quality level of the propagation channel between the BS 30 and the wireless device 25, and a step (not represented in the figures) of determining the least one energy level threshold based on the estimated channel qualitylevel. Indeed, the energy level threshold may be adjusted based on the channel quality level. For example, the energy level threshold may be lower when the channel quality is good than when the channel quality is poor. For example, the BS 30 may select an energy level threshold among a plurality of predetermined energy level thresholds associated to respective different channel quality levels.

[0073] In the example of figure 5, it is assumed in a non-limitative manner that the wireless device 25 determines that uplink data is to be transmitted when it receives an uplink transmission triggering signal from the RAN. Accordingly, the method 50 for exchanging data comprises a step S51 of transmitting an uplink transmission triggering signal to the wireless device 25 as an indication that uplink data is to be transmitted to the RAN. It should be noted that any suitable format may be used for the uplink transmission triggering signal, and that the choice of a specific format for the uplink transmission triggering signal corresponds to a specific but non-limitative embodiment of the present disclosure. Also, it should be noted that, in some examples, the information related to at least one energy level threshold may be included in the uplink transmission triggering signal, i.e., the steps S50 and S51 may correspond to a single and same step.

[0074] In examples where the BS 30 comprises an energy harvesting signal generator 305, the BS 30 may for example start transmitting an energy harvesting (RF) signal to the wireless device 25 before transmitting the uplink transmission triggering signal to said wireless device 25.

[0075] Level of stored electrical energy and channel quality level

[0076] Figure 6 represents a diagram showing steps of an exemplary embodiment of a method 60 for exchanging data, which is implemented by a wireless device 25 of a UE 20. Figure 7 represents a diagram showing corresponding steps of an exemplary embodiment of a method 70 for exchanging data, which is implemented by a BS 30 of the RAN.

[0077] As illustrated by figure 6, the method 60 for exchanging data comprises a step S60 of determining an energy level threshold based on an estimated channel quality level of the propagation channel between the RAN and the wireless device 25.

[0078] The channel quality level may be estimated by the wireless device 25, or by the RAN and transmitted to the wireless device 25. For example, the channel quality level may correspond to one or more among a reference signal received power (RSRP), a received signal strength indicator (RSSI), a reference signal received quality (RSRQ), a channel quality indicator (CQI), a signal to noise ratio (SNR), etc. The present disclosure may use any method known to the skilled person for estimating the channel quality level, and the choice of a specific method corresponds to a specific but non-limitative embodiment of thepresent disclosure.

[0079] The wireless device 25 may for example determine an energy level threshold to be used by using a preconfigured function which outputs an energy level threshold in response to an input channel quality level.

[0080] For example, the wireless device 25 may be preconfigured with a mapping between a plurality of different energy level thresholds and respective associated different channel quality levels, and the wireless device 25 may select the energy level threshold which, according to the preconfigured mapping, is associated to the estimated channel quality level.

[0081] For example, the mapping between the plurality of different energy level thresholds and the respective associated channel quality levels may be predefined at the wireless device 25 (e.g., specified by a standard or by calibration of the wireless device 25).

[0082] In other examples, and as illustrated by figure 6, the method 60 for exchanging data may include a prior step S66 of receiving from the RAN the mapping between the plurality of different energy level thresholds and the respective associated channel quality levels. In some examples, the wireless device 25 may receive a plurality of such mappings which may be associated e.g., to respective traffic classes (e.g., priority of uplink data to be transmitted, etc.), to respective volumes of uplink data transmitted, etc. In such a case, the wireless device 25 may select a mapping, among the plurality of mappings, based on the uplink data transmission context (traffic class, volume of uplink data, etc.).

[0083] For example, the at least one mapping between the plurality of different energy level thresholds and the respective associated channel quality levels may be received in system information broadcasted by the RAN and / or in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25. In the latter case, the uplink transmission triggering signal, if any, may include an identifier of the wireless device 25 or of the group of wireless devices, to enable the wireless device 25 to detect that it is the recipient of this information.

[0084] As illustrated by figure 6, the method 60 for exchanging data comprises a step S61 of determining that uplink data is to be sent by the wireless device 25. All that has been said for the step S40 of the method 40 for exchanging data in figure 4 applies similarly for the step S61 of the method 60 of exchanging data in figure 6.

[0085] In figure 6, the step S60 of determining the energy level threshold is represented as if executed before the step S61 of determining that uplink data is to be transmitted. As indicated above, the order of the steps in the figures is provided for illustration purposes only and is in no way limiting. For example, the step S61 of determining the energy level threshold may be executed simultaneously with or after the step S61 of determining thatuplink data is to be transmitted. For example, if the wireless device 25 receives an uplink transmission triggering signal as an indication from the RAN that uplink data is to be transmitted, then it is possible to estimate the channel quality level by using the received uplink transmission triggering signal, or by using the received wake-up signal, if any.

[0086] As illustrated by figure 6, the method 60 for exchanging data comprises, in response to determining during step S61 that uplink data is to be transmitted, a step S62 of measuring a level of the electrical energy stored in the energy storage unit 255. All that has been said for the step S41 of the method 40 for exchanging data in figure 4 applies similarly for the step S62 of the method 60 of exchanging data in figure 6.

[0087] As illustrated by figure 6, the method 60 for exchanging data comprises then a step S63 of evaluating an uplink transmission triggering criterion by comparing the level of the stored electrical energy to the energy level threshold determined during step S62. If the uplink transmission triggering criterion is verified (reference S63a in figure 6), the method 60 for exchanging data comprises a step S64 of transmitting uplink data (i.e. , all or part of the uplink data available at the wireless device 25) to the RAN. In turn, if the uplink transmission triggering criterion is not verified (reference S63b in figure 6), the method 60 for exchanging data comprises a step S65 of delaying the transmission of the uplink data to the RAN. All that has been said for the step S42 of the method 40 for exchanging data in figure 4 applies similarly for the step S63 of the method 60 of exchanging data in figure 6.

[0088] As discussed above, figure 7 represents a diagram showing corresponding steps of an exemplary embodiment of a method 70 for exchanging data, which may be implemented by a BS 30 when the wireless device 25 implements the method 60 for exchanging data illustrated by figure 6.

[0089] As illustrated by figure 7, the method 70 for exchanging data comprises a step S70 of transmitting to the wireless device 25 information related to at least one channel quality level and to at least one associated energy level threshold (received by the wireless device 25 during step S66). As discussed above, the transmitted information corresponds for instance to a function which outputs an energy level threshold in response to an input channel quality level, or to a mapping between a plurality of different energy level thresholds and respective associated channel quality levels, etc. As discussed above, this information may be e.g., broadcasted in system information and / or transmitted in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25.

[0090] In the example of figure 7, it is assumed in a non-limitative manner that the wireless device 25 determines that uplink data is to be transmitted when it receives an uplinktransmission triggering signal from the RAN. Accordingly, the method 70 for exchanging data comprises a step S71 of transmitting an uplink transmission triggering signal to the wireless device 25 as an indication that uplink data is to be transmitted to the RAN. All that has been said for the step S51 of the method 50 for exchanging data in figure 5 applies similarly for the step S71 of the method 70 of exchanging data in figure 7.

[0091] In examples where the BS 30 comprises an energy harvesting signal generator 305, the BS 30 may for example start transmitting an energy harvesting (RF) signal to the wireless device 25 before transmitting the uplink transmission triggering signal to said wireless device 25.

[0092] Level of stored electrical energy and volume of uplink data

[0093] Figure 8 represents a diagram showing steps of an exemplary embodiment of a method 80 for exchanging data, which is implemented by a wireless device 25 of a UE 20. Figure 9 represents a diagram showing corresponding steps of an exemplary embodiment of a method 90 for exchanging data, which is implemented by a BS 30 of the RAN.

[0094] As illustrated by figure 8, the method 80 for exchanging data comprises a step S80 of determining that uplink data is to be sent by the wireless device 25. All that has been said for the step S40 of the method 40 for exchanging data in figure 4 applies similarly for the step S80 of the method 80 of exchanging data in figure 8.

[0095] As illustrated by figure 8, the method 80 for exchanging data comprises, in response to determining during step S80 that uplink data is to be transmitted:- a step S81 of measuring a level of the electrical energy stored in the energy storage unit 255, and- a step S82 of determining a volume of uplink data to be transmitted.

[0096] All that has been said for the step S41 of the method 40 for exchanging data in figure 4 applies similarly for the step S81 of the method 80 of exchanging data in figure 8.

[0097] The volume of uplink data to be transmitted may take any suitable format enabling it to be compared to e.g., a threshold. For example, the volume of uplink data may correspond to a number of bits, a number of bytes, etc., that the wireless device 25 needs to transmit to the RAN.

[0098] As illustrated by figure 8, the method 80 for exchanging data comprises then a step S83 of evaluating an uplink transmission triggering criterion by comparing the level of the stored electrical energy to a predetermined energy level threshold and by comparing the volume of uplink data to be transmitted to at least one predetermined maximum uplink data volume associated to the at least one energy level threshold. If the uplink transmission triggering criterion is verified (reference S83a in figure 8), the method 80 for exchangingdata comprises a step S84 of transmitting uplink data (i.e., all or part of the uplink data available at the wireless device 25) to the RAN. In turn, if the uplink transmission triggering criterion is not verified (reference S83b in figure 8), the method 80 for exchanging data comprises a step S85 of delaying the transmission of the uplink data to the RAN.

[0099] Hence, the wireless device 25 takes into account both the level of stored electrical energy and the volume of uplink data before initiating the uplink data transmission. For example, to be verified, the uplink transmission triggering criterion may require a higher level of stored electrical energy for transmitting a large volume of uplink data than for transmitting a small volume of uplink data. Hence, in some examples, the wireless device 25 may adjust the energy level threshold based on the volume of uplink data to be transmitted or, alternatively, it may adjust the maximum uplink data volume based on the level of electrical energy stored in the energy storage unit 255.

[0100] It should be noted that is also possible, in some examples, to consider also other parameters to determine whether the wireless device 25 can initiate the uplink data transmission. For example, the evaluation of the uplink transmission triggering criterion may also consider the channel quality of the propagation channel between the RAN and the wireless device 25. For example, the uplink transmission triggering criterion may be considered not verified as soon as the channel quality level is below a predetermined minimum channel quality level. In turn, if the channel quality level is above the predetermined minimum channel quality level, then the wireless device may further evaluate the level of stored electrical energy and the volume of uplink data to be transmitted, as discussed above, to decide whether the uplink data transmission can be initiated.

[0101] In some examples, the evaluation of the uplink transmission triggering criterion may use a preconfigured mapping between a plurality of different energy level thresholds and respective associated different maximum uplink data volumes.

[0102] For example, the mapping between the plurality of different energy level thresholds and the respective associated maximum uplink data volumes may be predefined at the wireless device 25 (e.g., specified by a standard or by calibration of the wireless device 25).

[0103] In other examples, and as illustrated by figure 8, the method 80 for exchanging data may include a prior step S86 of receiving from the RAN the mapping between the plurality of different energy level thresholds and the respective associated maximum uplink data volumes. In some examples, the wireless device 25 may receive a plurality of such mappings which may be associated e.g., to respective traffic classes (e.g., priority of uplink data to be transmitted, etc.), to respective channel quality levels, etc. In such a case, the wireless device 25 may select a mapping, among the plurality of mappings, based on theuplink data transmission context (traffic class, channel quality level, etc.).

[0104] For example, the at least one mapping between the plurality of different energy level thresholds and the respective associated maximum uplink data volumes may be received in system information broadcasted by the RAN and / or in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25. In the latter case, the uplink transmission triggering signal, if any, may include an identifier of the wireless device 25 or of the group of wireless devices, to enable the wireless device 25 to detect that it is the recipient of this information.

[0105] Table 1 represents an example of mapping, between the plurality of energy level thresholds and the plurality of respective maximum uplink data volumes.Table 1

[0106] In the example of Table 1 , the different energy level thresholds are defined by different values EL1 , EL2 and EL3 which are such that 0 < EL1 < EL2 < EL3. The different maximum uplink data volumes are defined by different values DV1 , DV2 and DV3 which are such that 0 < DV1 < DV2 < DV3. For example, if we denote by EL the measured level of electrical energy stored in the energy storage unit 255 and by DV the determined volume of uplink data to be transmitted by the wireless device 25:- if EL < EL1 , then the uplink transmission triggering criterion is not verified regardless of the volume of uplink data to be transmitted,- if EL1 < EL < EL2, then the maximum uplink data volume is DV1 and the uplink transmission triggering criterion if verified if DV < DV1 (and not verified if DV > DV1 ),- if EL2 < EL < EL3, then the maximum uplink data volume is DV2 and the uplink transmission triggering criterion if verified if DV < DV2 (and not verified if DV > DV2), if EL > EL3, then the maximum uplink data volume is DV3 and the uplink transmission triggering criterion if verified if DV < DV3 (and not verified if DV > DV3).

[0107] Hence, the uplink transmission triggering criterion is for example verified when the volume of uplink data to be transmitted is lower than the maximum uplink data volume associated to the greatest energy level threshold which is lower than the level of the stored electrical energy. Of course, other formats may be considered for the mapping between a plurality of energy level thresholds and a plurality of maximum uplink data volumes, and other decision strategies may also be considered when using such a mapping.

[0108] As indicated above, the uplink data transmission is delayed (step S85) when theuplink transmission triggering criterion is not verified. For example, the uplink data transmission may be delayed by a predetermined delay, which starts when determining that the uplink data transmission is to be delayed. In such a case, the uplink data transmission may be initiated once the predetermined delay has expired without having to re-evaluate the uplink transmission triggering criterion.

[0109] In other examples, and as illustrated by figure 8, the evaluation of the uplink transmission triggering criterion may be executed in a recurrent manner, for example at each subsequent uplink transmission occasion, until said uplink transmission triggering criterion becomes verified. For example, the uplink data transmission may be initiated as soon as the level of stored electrical energy becomes greater than the predetermined energy level threshold. In some examples, the uplink transmission triggering criterion may also become verified at some point regardless of the level of stored electrical energy, to ensure that the uplink data transmission is not delayed indefinitely. For example, the uplink transmission triggering criterion may become verified when the delay introduced for performing the transmission of the uplink data reaches a predetermined maximum delay. According to another example, the uplink transmission triggering criterion may become verified when the number of skipped uplink transmission occasions reaches a predetermined maximum number of skipped uplink transmission occasions.

[0110] In alternate examples, the uplink data to be transmitted may be discarded if the uplink transmission triggering criterion remains not verified after a predetermined maximum delay or after a predetermined maximum number of skipped uplink transmission occasions.

[0111] As discussed above, figure 9 represents a diagram showing corresponding steps of an exemplary embodiment of a method 90 for exchanging data, which may be implemented by a BS 30 when the wireless device 25 implements the method 80 for exchanging data illustrated by figure 8.

[0112] As illustrated by figure 9, the method 90 for exchanging data comprises a step S90 of transmitting to the wireless device 25 information related to at least one energy level threshold and to at least one maximum uplink data volume (received by the wireless device 25 during step S86), to be used during the evaluation of the uplink transmission triggering criterion. As discussed above, the transmitted information corresponds for instance to a mapping between a plurality of energy level thresholds and a plurality of maximum uplink data volumes. As discussed above, this information may be e.g., broadcasted in system information and / or transmitted in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25.

[0113] In some examples, the method 90 for exchanging data may comprise a step (notrepresented in the figures) of estimating a (current or future) load level of the BS 30, and a step (not represented in the figures) of adjusting, based on the estimated load level, the information related to at least one energy level threshold and to at least one maximum uplink data volume which is transmitted to the wireless device 25. The load level is representative of the amount of traffic that the BS 30 needs to handle. For example, the load level may correspond to a total number of UEs 20 having data to exchange with the BS 30, a total amount of uplink data that is to be received by the BS 30 from multiple UEs 20, etc. For example, the maximum uplink data volumes may be lower when the load level is high (e.g., close to network congestion) than when the load level is low. Alternatively, or in combination thereof, the energy level thresholds may be higher when the load level is high (e.g., close to congestion) than when the load level is low. For example, the BS 30 may select a mapping, between a plurality of energy level thresholds and a plurality of maximum uplink data volumes, among a plurality of predetermined mappings associated to respective different load levels.

[0114] In the example of figure 9, it is assumed in a non-limitative manner that the wireless device 25 determines that uplink data is to be transmitted when it receives an uplink transmission triggering signal from the RAN. Accordingly, the method 90 for exchanging data comprises a step S91 of transmitting an uplink transmission triggering signal to the wireless device 25 as an indication that uplink data is to be transmitted to the RAN.

[0115] In examples where the BS 30 comprises an energy harvesting signal generator 305, the BS 30 may for example start transmitting an energy harvesting (RF) signal to the wireless device 25 before transmitting the uplink transmission triggering signal to said wireless device 25. All that has been said for the step S51 of the method 50 for exchanging data in figure 5 applies similarly for the step S91 of the method 90 of exchanging data in figure 9.

[0116] It is emphasized that the present disclosure is not limited to the above exemplary embodiments. Variants of the above exemplary embodiments are also within the scope of the present disclosure.

Claims

Claims1. A method (60) for exchanging data in a wireless communication system, the method being implemented by a wireless device (25) of the wireless communication system, wherein the wireless device comprises an energy harvesting unit (254) configured to convert ambient energy into electrical energy that is stored in an energy storage unit (255) of the wireless device, the wireless device further comprising a communication unit (253) configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the method comprises (S60) determining an energy level threshold based on an estimated channel quality level of a propagation channel between the RAN and the wireless device (25) and, in response to determining that uplink data is to be sent to the RAN:(562) measuring a level of the electrical energy stored in the energy storage unit,(563) evaluating an uplink transmission triggering criterion by comparing the level of the stored electrical energy to the determined energy level threshold, in response to the uplink transmission triggering criterion being verified: (S64) transmitting uplink data to the RAN, in response to the uplink transmission triggering criterion not being verified: (S65) delaying the transmission of the uplink data to the RAN.

2. The method (60) according to claim 1 , wherein the energy level threshold is selected among a plurality of different energy level thresholds, by using a preconfigured mapping between the plurality of different energy level thresholds and respective associated channel quality levels.

3. The method (60) according to claim 2, wherein the mapping between the plurality of different energy level thresholds and their respective associated channel quality levels is predefined or received in system information broadcasted by the RAN or received in a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

4. The method (60) according to any one of the preceding claims, wherein the transmission of the uplink data to the RAN is delayed until the uplink transmission triggering criterion is verified.

5. The method (60) according to any one of the preceding claims, wherein the uplink transmission triggering criterion is verified when the level of stored electrical energy is greater than the determined energy level threshold.

6. The method (60) according to any one of the preceding claims, wherein the uplink transmission triggering criterion is verified, regardless of the level of stored electrical energy:- when the delay introduced for performing the transmission of the uplink data reaches a predetermined maximum delay, or- when the number of skipped uplink transmission occasions reaches a predetermined maximum number of skipped uplink transmission occasions.

7. The method (60) according to any one of the preceding claims, wherein the wireless device determines that uplink data is to be transmitted by receiving an uplink transmission triggering signal from the RAN.

8. The method (60) according to any one of the preceding claims, wherein the energy harvesting unit is a radio unit configured to convert a received radiofrequency signal into electrical energy.

9. A wireless device (25) comprising at least one memory and at least one processor configured to carry out a method (60) according to any one of the preceding claims.

10. A user equipment, UE (20), comprising a wireless device according to claim 9.

11. A method (70) for exchanging data in a wireless communication system, the method being implemented by a base station, BS (30), of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device (25) which comprises an energy harvesting unit (254) configured to convert ambient energy into electrical energy that is stored in an energy storage unit (255) of the wireless device, wherein the method comprises (S70) transmitting to the wireless device (25) information related to at least one channel quality level and to at least one energy level threshold.

12. The method (70) according to claim 11 , wherein the information related to at least one channel quality level and to at least one energy level threshold comprises a mapping between a plurality of different energy level thresholds and respective associated channel quality levels.

13. The method (70) according to any one of claims 11 to 12, comprising (S71) transmitting an uplink transmission triggering signal to the wireless device as an indication that uplink data is to be transmitted to the RAN by the wireless device (25).

14. The method (70) according to claim 13, comprising starting to transmit an energy harvesting signal to the wireless device (25) before transmitting the uplink transmission triggering signal to said wireless device.

15. The method (70) according to any one of claims 11 to 14, wherein the information related to at least one channel quality level and to at least one energy level threshold is broadcasted in system information and / or is transmitted in a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes saidwireless device.

16. A base station, BS (30), comprising at least one memory and at least one processor configured to carry out a method (70) according to any one of claims 11 to 15.

17. A wireless communication system comprising at least one base station (30) according to claim 16 and at least one user equipment (20) according to claim 10.

18. A computer program product (252, 302) comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method (60) according to any one of claims 1 to 8 or a method (70) according to any one of claims 11 to 15.

19. A computer-readable storage medium comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method (60) according to any one of claims 1 to 8 or a method (70) according to any one of claims 11 to 15.

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