Method and device for enhancing the usage of contention-based uplink resources by ambient IoT devices

Abstract

The present disclosure relates to methods and devices for enhancing the usage of contention-based uplink resources by a user equipment, UE (20), having a wireless device (25) comprising an energy harvesting unit (254) for collecting ambient energy.

Description

Method and device for enhancing the usage of contention-based uplink resources by ambient loT devicesTechnical field

[0001] The present disclosure relates to wireless communication systems and relates more specifically to methods and devices for enhancing the usage of contention-based uplink resources by wireless devices harvesting ambient 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] In some cases, such A-loT devices may only initiate an uplink transmission when triggered so by the radio access network, RAN. This holds also for contention-based uplink resources. By “contention-based uplink resources”, we mean uplink resources which are shared by a plurality of wireless devices, on which each of these wireless devices can decide on its own to transmit uplink data, which uplink data may therefore collide with uplink data from other wireless devices with which these uplink resources are shared. Examples of contention-based resources include random-access channel, RACH, uplink resources or common configured grant, CG, uplink resources.

[0006] However, the risk of collisions and of congestion of the contention-based uplink resources increases as the number of A-loT devices deployed increases. Also, with many collisions due to A-loT devices willing to access contention-based uplink resources, the radio access network, RAN, might need to trigger retransmissions by the colliding A-loT devices, which would increase the signaling overhead for the RAN.Summary

[0007] 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 reducing the risk of collisions between uplink data from wireless devices, such as A-loT devices, willing to access contention-based uplink resources.

[0008] For that purpose, it is proposed that the RAN transmits an uplink transmission triggering signal to a wireless device, which indicates to the wireless device that it can use only a specific subset of contention-based uplink resources, among the whole set of contention-based uplink resources. This enables the RAN to reduce collision probability by controlling more precisely the allocation of contention-based uplink resources.

[0009] 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: receiving an uplink transmission triggering signal from the RAN, wherein the uplink transmission triggering signal includes an information describing a subset of contention-based uplink resources, among a predetermined set of contention-based uplink resources, allocated to the wireless device for performing an uplinktransmission, transmitting uplink data to the RAN by using contention-based uplink resources among the subset of contention-based resources.

[0010] 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.

[0011] In some embodiments of the method according to the first aspect, the set of contention-based uplink resources includes random-access channel, RACH, uplink resources to be used by the wireless device unit to establish a communication with the RAN.

[0012] In some embodiments of the method according to the first aspect, the set of RACH uplink resources includes a set of random-access preambles, and the subset of RACH uplink resources includes a subset of the set of random-access preambles.

[0013] In some embodiments of the method according to the first aspect, the set of RACH uplink resources includes a set of random-access occasions, and the subset of RACH uplink resources includes a subset of the set of random-access occasions.

[0014] In some embodiments of the method according to the first aspect, the subset of random-access occasions includes a plurality of random-access occasions.

[0015] In some embodiments of the method according to the first aspect, the wireless device performs uplink data repetition when the subset of random-access occasions includes a plurality of random-access occasions.

[0016] In some embodiments of the method according to the first aspect, the uplink transmission triggering signal includes a back-off timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources.

[0017] In some embodiments of the method according to the first aspect, the set of contention-based uplink resources includes common configured grant, CG, uplink resources to be used by the wireless device to transmit uplink data to the RAN.

[0018] In some embodiments of the method according to the first aspect, the uplink transmission triggering signal includes a validity duration for the allocation of the subset of contention-based uplink resources.

[0019] In some embodiments of the method according to the first aspect, the information describing the subset of contention-based uplink resources corresponds to a subset identifier which identifies a specific subset of contention-based uplink resources among a plurality of predetermined subsets of contention-based uplink resources.

[0020] In some embodiments, the method according to the first aspect comprises receiving from the RAN a mapping between a plurality of different subsets of contention-based uplinkresources and a plurality of respective subset identifiers.

[0021] In some embodiments of the method according to the first aspect, the uplink transmission triggering signal is a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

[0022] In some embodiments of the method according to the first aspect, the uplink transmission triggering signal is a wake-up signal that transitions the wireless device from a sleep mode to an active mode or is a signaling message received after receiving a wakeup signal.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 an uplink transmission triggering signal, wherein the uplink transmission triggering signal includes an information describing a subset of contention-based uplink resources, among a predetermined set of contention-based uplink resources, allocated to the wireless device for performing an uplink transmission.

[0027] 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.

[0028] In some embodiments of the method according to the fourth aspect, the set of contention-based uplink resources includes random-access channel, RACH, uplink resources to be used by the wireless device unit to establish a communication with the RAN.

[0029] In some embodiments of the method according to the fourth aspect, the set of RACH uplink resources includes a set of random-access preambles, and the subset of RACHuplink resources includes a subset of the set of random-access preambles.

[0030] In some embodiments of the method according to the fourth aspect, the set of RACH uplink resources includes a set of random-access occasions, and the subset of RACH uplink resources includes a subset of the set of random-access occasions.

[0031] In some embodiments of the method according to the fourth aspect, the subset of random-access occasions includes a plurality of random-access occasions.

[0032] In some embodiments of the method according to the fourth aspect, the uplink transmission triggering signal includes a back-off timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources.

[0033] In some embodiments of the method according to the fourth aspect, the set of contention-based uplink resources includes common configured grant, CG, uplink resources to be used by the wireless device to transmit uplink data to the RAN.

[0034] In some embodiments of the method according to the fourth aspect, the uplink transmission triggering signal includes a validity duration for the allocation of the subset of contention-based uplink resources.

[0035] In some embodiments of the method according to the fourth aspect, the information describing the subset of contention-based uplink resources corresponds to a subset identifier which identifies a specific subset of contention-based uplink resources among a plurality of predetermined subsets of contention-based uplink resources.

[0036] In some embodiments, the method according to the fourth aspect comprises transmitting to the wireless device a mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers.

[0037] In some embodiments of the method according to the fourth aspect, the uplink transmission triggering signal is a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

[0038] In some embodiments of the method according to the fourth aspect, the uplink transmission triggering signal is a wake-up signal that transitions the wireless device from a sleep mode to an active mode or is a signaling message transmitted after transmitting a wake-up signal.

[0039] In some embodiments, the method according to the fourth aspect comprises selecting the subset of contention-based uplink resources allocated to the wireless device, among the set of contention-based uplink resources, based on at least one characteristic of uplink data to be transmitted by the wireless device and / or based on a load level of the BS.

[0040] In some embodiments, the method according to the fourth aspect comprises startingto transmit an energy harvesting signal to the wireless device before transmitting the signaling message to said wireless device.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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

[0045] 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.

[0046] 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

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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).

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] As discussed above, the present disclosure aims at enabling the RAN to reduce collision probability by controlling more precisely the allocation of contention-based uplink resources to the wireless devices 25 in its coverage. For that purpose, it is proposed that the set of contention-based uplink resources RAN is split into different subsets which may be allocated by the RAN to different wireless devices 25, the allocated subset being notified when the RAN triggers an uplink transmission by a wireless device 25.

[0067] We now present examples of signaling and decision strategies that may be implemented to reduce collision probability in contention-based uplink resources.

[0068] 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.

[0069] As illustrated by figure 4, the method 40 for exchanging data comprises a step S40 of receiving an uplink transmission triggering signal from the RAN.

[0070] 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. Using a same signal for the wake-up signal and the uplink transmission triggering signal reduces the signaling overhead for the RAN, compared to using separate signals.

[0071] The purpose of the uplink transmission triggering signal is to indicate to the wireless device 25 that it can initiate an uplink transmission on contention-based uplink resources.

[0072] By “contention-based uplink resources”, we mean uplink resources which are shared by a plurality of wireless devices 25, on which each of these wireless devices 25 can decide on its own to transmit messages, which messages may therefore collide with messages from other wireless devices 25 with which these uplink resources are shared.

[0073] Examples of contention-based uplink resources in e.g., a 5G NR wireless communication system include random access channel, RACH, uplink resources, which areused by the wireless devices 25 to establish a communication with a BS 30 of the RAN. Such RACH uplink resources are allocated to the wireless devices 25 regardless their radio resource control, RRC, state (e.g., RRC connected (RRC_CON NESTED), RRC idle (RRCJDLE), or RRC inactive (RRCJNACTIVE) state).

[0074] Other examples of contention-based uplink resources in e.g., a 5G NR wireless communication system include common configured grant, CG, uplink resources. Such common CG uplink resources are for example allocated to wireless devices 25 in RRC_CONNECTED state. By “common”, we mean that these CG uplink resources can be shared by a plurality of wireless devices. In turn, a 5G NR wireless communication system may also allocate dedicated CG uplink resources to a specific wireless device 25 in RRC_CONNECTED state, which are to be used only by this specific wireless device 25 and are therefore not contention-based uplink resources.

[0075] The uplink transmission triggering signal, transmitted during step S40, includes an information describing a subset of contention-based uplink resources, among a predetermined set of contention-based uplink resources, allocated to the wireless device 25 for performing an uplink transmission. The set contention-based uplink resources is for example preconfigured at the wireless device 25. For example, the set of RACH uplink resources is typically advertised by the RAN in system information broadcasted by a BS 30 to the wireless devices 25 in its coverage.

[0076] 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. For example, the uplink transmission triggering signal may be a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25, in which case the same subset of contention-based uplink resources is allocated to a group of wireless devices 25.

[0077] Therefore, the uplink transmission triggering signal notifies the wireless device 25 with the subset of contention-based uplink resources it is allowed to use among the whole set of contention-based uplink resources. In other words, the wireless device 25 is not allowed to use the other contention-based uplink resources of the set which are not included in the subset notified by the uplink transmission triggering signal.

[0078] As illustrated by figure 4, the method 40 for exchanging data comprises a step S41 of selecting contention-based uplink resources in the subset of contention-based uplink resources, and a step S42 during which the wireless device 25 transmits uplink data to the RAN by using the contention-based uplink resources selected in the subset of contention-based resources notified by the RAN.

[0079] For example, for common CG uplink resources, the set of common CG uplink resources may comprise a set of common CG occasions, and the subset of common CG uplink resources may consist in some of the upcoming common CG occasions. Hence, the wireless device 25 is authorized to use only some of the upcoming common CG occasions. For example, the set of common CG occasions corresponds to recurrent time and frequency resources that are allocated by the RAN as common CG uplink resources. Hence, the subset of common CG uplink resources may correspond to some of these recurrent time and frequency uplink resources, such that the common CG occasions that the wireless device 25 is allowed to use are restricted in time and / or frequency with respect to all uplink resources that are allocated as common CG uplink resources.

[0080] For example, for RACH uplink resources, the set of RACH uplink resources may comprise a set of random-access occasions and / or a set of random-access preambles. Hence, the subset of RACH uplink resources may consist in some of the upcoming common random-access occasions and / or in some of the random-access preambles.

[0081] For example, the set of random-access occasions corresponds to recurrent time and frequency resources that are allocated by the RAN as RACH uplink resources. Hence, the subset of RACH uplink resources may correspond to some of these recurrent time and frequency uplink resources, such that the random-access occasions that the wireless device 25 is allowed to use are restricted in time and / or frequency with respect to all uplink resources that are allocated as random-access uplink resources.

[0082] For example, the set of random-access preambles corresponds to e.g., a set of 64 random-access preambles from which the wireless device 25 may select a single randomaccess preamble to initiate a random-access procedure with a BS 30 of the RAN. Hence, the subset of RACH uplink resources may correspond to some of these 64 random-access preambles, such that the random-access preambles that the wireless device 25 is allowed to use are restricted to fewer than 64 random-access preambles. For example, the subset of RACH uplink resources includes only e.g., 8 or 16 of the 64 random-access preambles.

[0083] Hence, the probability of collision may be controlled by the RAN by allocating to a specific wireless device 25, when triggering an uplink transmission, fewer contention-based uplink resources than all contention-based uplink resources available. By allocating separate subsets of contention-based uplink resources to different wireless devices 25, collisions between these wireless devices 25 are avoided.

[0084] In the case of random-access occasions, the subset of contention-based uplink resources that may be used by the wireless device 25 may comprise one or more random-access occasions. For example, the wireless device 25 may use different random-access occasions for transmitting uplink data related to different traffic classes. For example, a traffic class may correspond to a priority level of the uplink data to be transmitted, to a latency requirement (quality of service, QoS) of the uplink data to be transmitted, etc. In other examples, the wireless device 25 may use several random-access occasions to perform uplink data repetition, to increase the probability that this uplink data is received successfully by the RAN.

[0085] Similarly, in the case of common CG occasions, the subset of contention-based uplink resources may comprise one or more common CG occasions. For example, the wireless device 25 may use different common CG occasions for transmitting uplink data related to different traffic classes. In other examples, the wireless device 25 may use several common CG occasions to perform uplink data repetition.

[0086] It should be noted that the information, included in the uplink transmission triggering signal, describing the subset of contention-based uplink resources that the wireless device 25 can use, can be provided in any suitable format, and the choice of a specific format corresponds to a specific but non-limitative embodiment of the present disclosure.

[0087] For example, the information provided in the uplink transmission triggering signal may include a complete description of all the contention-based uplink resources included in the subset. However, including such a complete description may increase the amount of data included in each uplink transmission triggering signal.

[0088] In preferred embodiments, the information describing the subset of contentionbased uplink resources corresponds to a subset identifier which identifies a specific subset of contention-based uplink resources among a plurality of predetermined subsets of contention-based uplink resources. Hence, it is sufficient in such examples to include the subset identifier in the uplink transmission triggering signal, thereby limiting the amount of data to be included in each uplink transmission triggering signal. The wireless device 25 needs to be preconfigured beforehand with a mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers. In the non-limitative example of figure 4, the method 40 for exchanging data comprises an optional prior step S43 of receiving this mapping from the RAN. For example, the mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers 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. It should be noted that, in some examples, it is possible to use different mappings (between subsets of contention-based uplink resources and subset identifiers) for different wireless devices 25 or different groups of wireless devices 25.

[0089] In some examples, the uplink transmission triggering signal may also include additional information regarding the usage of the contention-based uplink resources.

[0090] For example, the uplink transmission triggering signal may include a back-off timer value to be used by the wireless device 25 to delay the uplink data transmission when using the subset of contention-based uplink resources. For example, in the case of RACH uplink resources, the RAN may provide a back-off timer used to delay the transmission of the selected random-access preamble on the selected random-access occasion. For example, the RAN may provide different back-off timers to wireless devices 25 allowed to use the same subset of random-access uplink resources, in order to reduce the collision probability between the uplink transmissions from these wireless devices 25.

[0091] Alternatively, or in combination thereof, the uplink transmission triggering signal may include a validity duration for the allocation of the subset of contention-based uplink resources. Hence the wireless device 25, when it receives the uplink transmission triggering signal, is allowed to use the indicated subset only during the validity duration. For example, the wireless device 25 may start a timer set to the validity duration and, once the timer expires, the wireless device 25 may no longer use the allocated subset of contention-based uplink resources. For example, once the timer has expired, the wireless device 25 may need to receive a further uplink transmission triggering signal before attempting to perform a further uplink data transmission. It should be noted that such a validity duration, when used, may also be preconfigured at the wireless device, e.g., predefined (e.g., specified by a standard) or received beforehand from the RAN (e.g., in system information broadcasted by the RAN 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).

[0092] 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.

[0093] As illustrated by figure 5, the method 50 for exchanging data comprises a step S50 of transmitting to the wireless device 25 an uplink transmission triggering signal (received by the wireless device 25 during step S40).

[0094] As discussed above, 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 presentdisclosure. Also, it should be noted that, in some examples, 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. Also, the uplink transmission triggering signal may be a signaling message addressed specifically to a wireless device 25 or to a group of wireless devices 25.

[0095] As discussed above, the uplink transmission triggering signal includes an information describing a subset of contention-based uplink resources, among a predetermined set of contention-based uplink resources, allocated to the wireless device 25 for performing an uplink transmission. As discussed above, the set of contention-based uplink resources includes for example RACH uplink resources (random-access preambles, random-access occasions, etc.) and / or common CG uplink resources. Also, in some examples, the uplink transmission triggering signal may also include additional information regarding the usage of the contention-based uplink resources (e.g., back-off timer, validity duration, etc.).

[0096] In the example illustrated by figure 5, it is assumed in a non-limitative manner that the information describing the subset of contention-based uplink resources is transmitted as a subset identifier, and the method 50 for exchanging data comprises an optional prior step S51 of transmitting to the wireless device 25, before transmitting the uplink transmission triggering signal, a mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers.

[0097] In some examples, and as illustrated in a non-limitative manner in figure 5, the method 50 for exchanging data comprises a step S52 of selecting the subset of contentionbased uplink resources, to be used by a wireless device 25 or group of wireless devices 25, among the set of contention-based uplink resources. For example, the subset of contentionbased uplink resources to be used may be selected among a plurality of predetermined subsets, for example by changing the subset selected at each iteration of step S52.

[0098] In some examples, the BS 30 may select the subset of contention-based uplink resources based on at least one characteristic of uplink data to be transmitted by the wireless device 25 (or group of wireless devices 25). For example, the BS 30 may associate different subsets of contention-based uplink resources to different traffic classes (e.g., priority level, latency requirements, etc.), and the BS 30 may select the subset of contentionbased uplink resources to be used by a given wireless device 25 based on the traffic class of the uplink data that this wireless device 25 will attempt to transmit. Also, in some cases, the subset identifier transmitted to the wireless device 25 may be used by said wirelessdevice 25 to identify not only the subset of contention-based uplink resources it may use, but also the class of traffic it may transmit using these contention-based uplink resources.

[0099] Alternatively, or in combination thereof, the BS 30 may select the subset of contention-based uplink resources based on a load level of the BS. Hence, the method 50 for exchanging data may comprise a step (not represented in the figures) of estimating a (current or future) load level of the BS 30, and the subset of contention-based uplink resources may be selected based on the estimated load level. The load level is representative of the amount of traffic that the BS 30 needs to handle, e.g., it its entire coverage (cell) or in a given beam, etc. 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 BS 30 may decrease the amount of contention-based uplink resources of a subset to be used for low priority uplink data when the load level is high (e.g., close to congestion) compared to when the load level is low.

[0100] 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).

[0101] 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:(S40) receiving an uplink transmission triggering signal from the RAN, wherein the uplink transmission triggering signal includes an information describing a subset of contention-based uplink resources, among a predetermined set of contentionbased uplink resources, allocated to the wireless device for performing an uplink transmission,(S42) transmitting uplink data to the RAN by using contention-based uplink resources among the subset of contention-based resources.

2. The method (40) according to claim 1 , wherein the set of contention-based uplink resources includes random-access channel, RACH, uplink resources to be used by the wireless device unit to establish a communication with the RAN.

3. The method (40) according to claim 2, wherein the set of RACH uplink resources includes a set of random-access preambles, and the subset of RACH uplink resources includes a subset of the set of random-access preambles.

4. The method (40) according to any one of claims 2 to 3, wherein the set of RACH uplink resources includes a set of random-access occasions, and the subset of RACH uplink resources includes a subset of the set of random-access occasions.

5. The method (40) according to claim 4, wherein the subset of random-access occasions includes a plurality of random-access occasions.

6. The method (40) according to claim 5, wherein the wireless device performs uplink data repetition when the subset of random-access occasions includes a plurality of randomaccess occasions.

7. The method (40) according to any one of claims 2 to 6, wherein the uplink transmission triggering signal includes a back-off timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources.

8. The method (40) according to claim 1 , wherein the set of contention-based uplink resources includes common configured grant, CG, uplink resources to be used by the wireless device to transmit uplink data to the RAN.

9. The method (40) according to any one of the preceding claims, wherein the uplink transmission triggering signal includes a validity duration for the allocation of the subset of contention-based uplink resources.

10. The method (40) according to any one of the preceding claims, wherein the information describing the subset of contention-based uplink resources corresponds to a subset identifier which identifies a specific subset of contention-based uplink resources among a plurality of predetermined subsets of contention-based uplink resources.

11. The method (40) according to claim 10, comprising (S43) receiving from the RAN a mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers.

12. The method (40) according to any one of the preceding claims, wherein the uplink transmission triggering signal is a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

13. The method (40) according to any one of the preceding claims, wherein the uplink transmission triggering signal is a wake-up signal that transitions the wireless device from a sleep mode to an active mode or is a signaling message received after receiving a wakeup signal.

14. 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.

15. A user equipment, UE (20), comprising a wireless device according to claim 14.

16. 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 (S50) transmitting to the wireless device (25) an uplink transmission triggering signal, wherein the uplink transmission triggering signal includes an information describing a subset of contention-based uplink resources, among a predetermined set of contention-based uplink resources, allocated to the wireless device for performing an uplink transmission.

17. The method (50) according to claim 16, wherein the set of contention-based uplink resources includes random-access channel, RACH, uplink resources to be used by the wireless device unit to establish a communication with the RAN.

18. The method (50) according to claim 17, wherein the set of RACH uplink resources includes a set of random-access preambles, and the subset of RACH uplink resourcesincludes a subset of the set of random-access preambles.

19. The method (50) according to any one of claims 17 to 18, wherein the set of RACH uplink resources includes a set of random-access occasions, and the subset of RACH uplink resources includes a subset of the set of random-access occasions.

20. The method (50) according to claim 19, wherein the subset of random-access occasions includes a plurality of random-access occasions.

21. The method (50) according to any one of claims 17 to 20, wherein the uplink transmission triggering signal includes a back-off timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources.

22. The method (50) according to claim 16, wherein the set of contention-based uplink resources includes common configured grant, CG, uplink resources to be used by the wireless device to transmit uplink data to the RAN.

23. The method (50) according to any one of claims 16 to 22, wherein the uplink transmission triggering signal includes a validity duration for the allocation of the subset of contention-based uplink resources.

24. The method (50) according to any one of claims 16 to 23, wherein the information describing the subset of contention-based uplink resources corresponds to a subset identifier which identifies a specific subset of contention-based uplink resources among a plurality of predetermined subsets of contention-based uplink resources.

25. The method (50) according to claim 24, comprising (S51) transmitting to the wireless device a mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers.

26. The method (50) according to any one of claims 16 to 25, wherein the uplink transmission triggering signal is a signaling message addressed specifically to the wireless device or to a group of wireless devices which includes said wireless device.

27. The method (50) according to any one of claims 16 to 26, wherein the uplink transmission triggering signal is a wake-up signal that transitions the wireless device from a sleep mode to an active mode or is a signaling message transmitted after transmitting a wake-up signal.

28. The method (50) according to any one of claims 16 to 27, comprising (S52) selecting the subset of contention-based uplink resources allocated to the wireless device, among the set of contention-based uplink resources, based on at least one characteristic of uplink data to be transmitted by the wireless device and / or based on a load level of the BS.

29. A base station, BS (30), comprising at least one memory and at least oneprocessor configured to carry out a method (50) according to any one of claims 16 to 28.

30. A wireless communication system comprising at least one base station (30) according to claim 29 and at least one user equipment (20) according to claim 15.

31. 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 13 or a method (50) according to any one of claims 16 to 28.

32. 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 13 or a method (50) according to any one of claims 16 to 28.

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