Method and device for performing an uplink transmission at an ambient-iot device by adapting uplink data packet sizes to a level of stored electrical energy

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 adapt uplink data packet sizes to a level of stored electrical energy.

Description

Method and device for performing an uplink transmission at an ambient-loT device by adapting uplink data packet sizes to a level of stored electrical energyTechnical field

[0001] The present disclosure relates to wireless communication systems and relates more specifically to methods and devices for enabling a wireless device relying on ambient energy harvesting to adapt uplink data packet sizes to a level of stored electrical energy.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 provided externally).

[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 adjust the sizes of the uplink data packets transmitted to the radio access network, RAN.

[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, 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, transmitting the uplink data to the RAN in one or more uplink data packets having sizes determined based on the level of stored electrical energy.

[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, the method according to the first aspect comprises determining a maximum uplink data packet size for transmitting uplink data to the RAN based on the level of stored electrical energy, wherein the sizes of the one or more uplink data packets transmitted are determined based the determined maximum uplink data packet size.

[0011] In some embodiments, the method according to the first aspect comprises splitting the uplink data to be transmitted into a plurality of uplink data packets having sizes complying with the determined maximum uplink data packet size in response to determiningthat the amount of uplink data to be transmitted is greater than said determined maximum uplink data packet size.

[0012] In some embodiments of the method according to the first aspect, the determination of uplink data packet sizes based on the level of stored electrical energy uses information received from the RAN.

[0013] In some embodiments of the method according to the first aspect, the information comprises a mapping between at least one energy level threshold and at least one associated maximum uplink data packet size.

[0014] In some embodiments of the method according to the first aspect, the information is 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.

[0015] In some embodiments of the method according to the first aspect, when the uplink data is transmitted in a plurality of uplink data packets, each uplink data packet of the plurality of uplink data packets is transmitted with an indication regarding remaining uplink data packets pending transmission.

[0016] In some embodiments of the method according to the first aspect, the indication regarding remaining uplink data packets pending transmission corresponds to an indication of the number of remaining uplink data packets pending transmission or to an indication of whether there remain uplink data packets pending transmission.

[0017] In some embodiments of the method according to the first aspect, the indication regarding remaining uplink data packets pending transmission is transmitted via L1 and / or L2 signaling.

[0018] In some embodiments of the method according to the first aspect, the wireless device determines that uplink data is to be transmitted by receiving a signaling message from the RAN.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 a base 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 the determination of uplink data packet sizes based on a level of electrical energy stored in the energy storage unit.

[0023] 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.

[0024] In some embodiments of the method according to the fourth aspect, the information related to the determination of uplink data packet sizes based on the level of stored electrical energy comprises a mapping between at least one energy level threshold and at least one associated maximum uplink data packet size.

[0025] In some embodiments of the method according to the fourth aspect, the information related to the determination of uplink data packet sizes based on the level of stored electrical energy 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.

[0026] In some embodiments, the method according to the fourth aspect comprises controlling the information to be transmitted to the wireless device based on one or more environment parameters.

[0027] In some embodiments of the method according to the fourth aspect, the information to be transmitted to the wireless device is controlled based on a load level of the BS.

[0028] In some embodiments, the method according to the fourth aspect comprises transmitting a signaling message to the wireless device as an indication that uplink data is to be transmitted to the RAN by the wireless device.

[0029] 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 signaling message to said wireless device.

[0030] In some embodiments, the method according to the fourth aspect comprises receiving an uplink data packet from the wireless device and an associated indication regarding remaining uplink data packets pending transmission, and generating an energyharvesting signal for the wireless device in response to the indication indicating that there is at least one remaining uplink data packets pending transmission.

[0031] 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.

[0032] 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.

[0033] 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 any programming 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.

[0034] 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

[0035] 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.

[0036] 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

[0037] The detailed description set forth below, with reference to the figures, is intended asa 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.

[0038] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. 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.

[0039] 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.

[0040] 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.

[0041] 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 (I AB) node, another UE 20, a repeater, a reconfigurable intelligent surface (RIS), etc.

[0042] 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 pW, or even lower than 10 pW.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 generated internally by the wireless device or be backscattered on a carrier wave provided externally).

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0052] 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 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 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.

[0053] 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.

[0054] 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.

[0055] 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 specificenergy 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.

[0056] As discussed above, the present disclosure aims at enabling a wireless device 25 to adjust uplink data packet sizes based on the level of electrical energy stored in its energy storage unit 255. Considering the level of stored electrical energy to adapt the sizes of the uplink data packets enables reducing the probability that the transmission of an uplink data packet fails. Indeed, this enables to ensure that the level of stored electrical energy is sufficient for transmitting a given uplink data packet and, in some cases, it may ensure that it can be transmitted with sufficient transmission power to enable the RAN to decode it.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 datais 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.

[0063] 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 triggered by 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.

[0064] It should be noted that is also possible, in some examples, to consider also other parameters to determine whether uplink data is to be transmitted. For example, the wireless device 25 may also consider the channel quality of the propagation channel between the RAN and the wireless device 25 before initiating an uplink data transmission. For example, the wireless device 25 may determine that uplink data can be transmitted if the channel quality level is above a predetermined minimum channel quality level. In turn, if the channel quality level is below the predetermined minimum channel quality level, then the wireless device 25 may decide to delay or cancel the transmission of uplink data to the RAN.

[0065] 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 the present disclosure. 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. The channel quality level may also be estimated on another reference signal transmitted by the RAN.

[0066] 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 andthe 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.

[0067] As illustrated by figure 4, the method 40 for exchanging data comprises a step S43 of transmitting the uplink data to the RAN in one or more uplink data packets having sizes determined based on the measured level of stored electrical energy.

[0068] For example, and as illustrated in figure 4, the sizes of the one or more uplink data packets may be determined based on a maximum uplink packet data size, which is determined, based on the level of stored electrical energy, during a step S42. The sizes of the one or more uplink data packets to be transmitted may then be determined during step S43 based the determined maximum uplink data packet size determined during step S42, by ensuring that each uplink data packet to be transmitted has a size which complies the determined maximum packet size. For example, if the amount of uplink data to be transmitted is greater than said determined maximum uplink data packet size, the wireless device 25 may split the uplink data to be transmitted into a plurality of uplink data packets in such a way that each uplink data packet resulting from the splitting has a size lower than said determined maximum uplink data packet size. Preferably, when the uplink data is split into a plurality of uplink data packets based on the level of stored electrical energy, these uplink data packets are transmitted separately, e.g., during separate uplink transmission occasions, to enable the energy harvesting unit 254 to collect electrical energy between the transmission of two successive uplink data packets.

[0069] For example, the determination, by the wireless device 25, of uplink data packet sizes based on the level of stored electrical energy uses predefined information (e.g., specified by a standard or by calibration of the wireless device 25) or information received from the RAN.

[0070] For example, the information used to determine the uplink data packet sizes may correspond to a preconfigured function which outputs a maximum uplink data packet size in response to an input level of electrical energy stored in the energy storage unit 255.

[0071] In other examples, the information used to determine the uplink data packet sizes may correspond to a mapping between at least one energy level threshold and at least one associated maximum uplink data packet size. In some cases, the information correspondsto a mapping between a plurality of different energy level thresholds and respective different maximum uplink data packet sizes. Hence, the wireless device 25 may select the maximum uplink data packet size by comparing the measured level of stored electrical energy to the plurality of energy level thresholds of the mapping.

[0072] Table 1 represents an example of mapping between a plurality of energy level thresholds and a plurality of respective maximum uplink data packet sizes.Table 1

[0073] 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 packet sizes are defined by different values DPS1 , DPS2 and DPS3 which are such that 0 < DPS1 < DPS2 < DPS3. For example, if we denote by EL the measured level of electrical energy stored in the energy storage unit 255: if EL < EL1 , then it is possible to delay or cancel the transmission of uplink data, if EL1 < EL < EL2, then the maximum uplink data packet size is DPS1 , if EL2 < EL < EL3, then the maximum uplink data packet size is DPS2, if EL > EL3, then the maximum uplink data packet size is DPS3.

[0074] Hence, the maximum uplink data packet size used may be the one 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 packet sizes, and other decision strategies may also be considered when using such a mapping.

[0075] In the non-limitative example illustrated by figure 4, it is assumed that the information used to determine the uplink data packet sizes (e.g., mapping between a plurality of energy level thresholds and a plurality of maximum uplink data packet sizes) is received from the RAN, during a step S44 of the method 40 for exchanging data.

[0076] For example, the received information may comprise a single mapping between a plurality of energy level thresholds and a plurality of maximum uplink data packet sizes. In other examples, the received information may include 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 received, based on the uplink data transmission context (traffic class, channel quality level, etc.).

[0077] For example, the information used to determine the uplink data packet sizes 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.

[0078] In some examples, when the uplink data to be transmitted is split into a plurality of uplink data packets based on the level of stored electrical energy, then the wireless device 25 may optionally transmit each uplink data packet with an indication regarding remaining uplink data packets pending transmission. In other words, the wireless device 25, when transmitting an uplink data packet which is the result of a splitting of the whole uplink data to be transmitted, indicates whether this uplink data packet will be followed by at least one other uplink data packet resulting from the same splitting. Such an indication, when present, may for instance be used by the RAN to trigger the generation of an energy harvesting signal towards the wireless device 25, to enable it to collect electrical energy for the transmission of the subsequent uplink data packet.

[0079] For example, the indication regarding remaining uplink data packets pending transmission is transmitted via L1 and / or L2 signaling. However, any suitable format may be used for the transmission of this indication, and the choice of a specific format corresponds to a specific but non-limitative embodiment of the present disclosure.

[0080] For example, the indication regarding remaining uplink data packets pending transmission corresponds to an indication of the number of remaining uplink data packets pending transmission. In such a case, the RAN knows how many uplink data packets it may expect to receive after the current one. For example, 3 bits may be used to provide such an indication, to indicate up to 7 remaining uplink data packets to be received.

[0081] In other examples, the indication regarding remaining uplink data packets pending transmission consists in an indication of whether there remain uplink data packets pending transmission. In such a case, the RAN knows only if the current uplink data packet will be followed by another one. Hence, a single bit may be used to provide such an indication, with e.g., a value ‘1’ indicating that there are more uplink data packets to be received and a value ‘0’ indicating that the current uplink data packet is the last one.

[0082] 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.

[0083] As illustrated by figure 5, the method 50 for exchanging data comprises a step S51 of transmitting to the wireless device 25 information related to the determination of uplink data packet sizes based on a level of electrical energy stored in the energy storage unit 255 (e.g., mapping between a plurality of energy level thresholds and a plurality of maximum uplink data packet sizes). As discussed above, this information may be 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.

[0084] In some examples, and as illustrated by figure 5, the method 50 for exchanging data may comprise an optional step S50 of controlling the information related to the determination of uplink data packet sizes, to be transmitted to the wireless device 25, based on one or more environment parameters (channel quality level, load level, etc.).

[0085] For example, the step S50 may comprise estimating a (current or future) load level of the BS 30, and adjusting, based on the estimated load level, the information related to the determination of uplink data packet sizes 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 packet sizes may be lower when the load level is high (e.g., close to network 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 packet sizes, among a plurality of predetermined mappings associated to respective different load levels.

[0086] As indicated above, other environment parameters may also be considered, alternatively or in combination with the load level. For example, the maximum uplink data packet sizes may be lower when the channel quality is poor than when the channel quality is good (e.g., to enable the wireless device 25 to increase the transmission power when the channel quality is poor).

[0087] 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 S52 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, itshould be noted that, in some examples, the information related to the determination of the uplink packet data sizes may be included in the uplink transmission triggering signal, i.e. , the steps S51 and S52 may correspond to a single and same step.

[0088] 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 (not represented in figure 5).

[0089] As discussed above, in some embodiments, the wireless device 25 may receive, with an uplink data packet, an indication regarding remaining uplink data packets pending transmission. It is assumed in the non-limitative example of figure 5 that such an indication is transmitted by the wireless device 25, and the method 50 of exchanging data comprises a step S53 of receiving an uplink data packet from the wireless device 25, during which the BS 30 evaluates whether there are remaining uplink data packets pending transmission.

[0090] In response to determining that there is at least one remaining uplink data packet pending transmission at the wireless de vice 25 (reference S53a in figure 5), the step S53 is repeated. In the non-limitative example of figure 5, the BS 30 further starts generating an energy harvesting signal for the wireless device 25, during a step S54. In turn, if there are no further uplink data packets pending transmission at the wireless device 25 (reference S53b in figure 5), the steps S53 and S54 are not repeated.

[0091] 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 (40) 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, in response to determining that uplink data is to be sent to the RAN:(S41) measuring a level of the electrical energy stored in the energy storage unit, (S43) transmitting the uplink data to the RAN in one or more uplink data packets having sizes determined based on the level of stored electrical energy.

2. The method (40) according to claim 1 , comprising (S42) determining a maximum uplink data packet size for transmitting uplink data to the RAN based on the level of stored electrical energy, wherein the sizes of the one or more uplink data packets transmitted are determined based the determined maximum uplink data packet size.

3. The method (40) according to claim 2, comprising splitting the uplink data to be transmitted into a plurality of uplink data packets having sizes complying with the determined maximum uplink data packet size in response to determining that the amount of uplink data to be transmitted is greater than said determined maximum uplink data packet size.

4. The method (40) according to any one of the preceding claims, wherein the determination of uplink data packet sizes based on the level of stored electrical energy uses information received from the RAN.

5. The method (40) according to claim 4, wherein the information comprises a mapping between at least one energy level threshold and at least one associated maximum uplink data packet size.

6. The method (40) according to any one of claims 4 to 5, wherein the information is 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.

7. The method (40) according to any of the preceding claims, wherein, when the uplink data is transmitted in a plurality of uplink data packets, each uplink data packet of the plurality of uplink data packets is transmitted with an indication regarding remaining uplink data packets pending transmission.

8. The method (40) according to claim 7, wherein the indication regarding remaining uplink data packets pending transmission corresponds to an indication of the number of remaining uplink data packets pending transmission or to an indication of whether there remain uplink data packets pending transmission.

9. The method (40) according to any of claims 7 to 8, wherein the indication regarding remaining uplink data packets pending transmission is transmitted via L1 and / or L2 signaling.

10. A wireless device (25) comprising at least one memory and at least one processor configured to carry out a method (40) according to any one of the preceding claims.

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

12. A method (50) 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 (S51) transmitting to the wireless device (25) information related to the determination of uplink data packet sizes based on a level of electrical energy stored in the energy storage unit.

13. The method (50) according to claim 12, wherein the information related to the determination of uplink data packet sizes based on the level of stored electrical energy comprises a mapping between at least one energy level threshold and at least one associated maximum uplink data packet size.

14. The method (50) according to any one of claims 12 to 13, wherein the information related to the determination of uplink data packet sizes based on the level of stored electrical energy 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.

15. The method (50) according to any one of the preceding claims 12 to 14, comprising (S50) controlling the information to be transmitted to the wireless device based on one or more environment parameters.

16. The method (50) according to claim 15, wherein the information to be transmitted to the wireless device is controlled based on a load level of the BS.

17. The method (50) according to any one of claims 12 to 16, comprising (S53) receiving an uplink data packet from the wireless device and an associated indication regarding remaining uplink data packets pending transmission, and (S54) generating anenergy harvesting signal for the wireless device in response to the indication indicating that there is at least one remaining uplink data packets pending transmission.

18. A base station, BS (30), comprising at least one memory and at least one processor configured to carry out a method (50) according to any one of claims 12 to 17.

19. A wireless communication system comprising at least one base station (30) according to claim 18 and at least one user equipment (20) according to claim 11 .

20. 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 (40) according to any one of claims 1 to 9 or a method (50) according to any one of claims 12 to 17.

21. 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 (40) according to any one of claims 1 to 9 or a method (50) according to any one of claims 12 to 17.

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