Method and device for enhancing the usage of RACH uplink resources by ambient IoT devices by allocating mutually exclusive backoff delay ranges

Abstract

The present disclosure relates to methods and devices for reducing collision probability on random access channel, RACH, uplink resources by enabling user equipment, UEs (20), to use mutually exclusive backoff delay ranges or by enabling a radio access network, RAN, to control in a centralized manner the backoff delay values to be used by different UEs.

Description

Method and device for enhancing the usage of RACH uplink resources by ambient loT devices by allocating mutually exclusive backoff delay rangesTechnical 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, such as random-access channel (RACH) uplink resources, by wireless devices, for example 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 providedexternally).

[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.

[0006] However, the risk of collisions and of congestion of the RACH uplink resources increases as the number of A-loT devices deployed increases. Contention resolution usually relies on each A-loT device selecting randomly a backoff delay value in a backoff delay range indicated by the RAN, used for delaying a subsequent attempt to access the RACH uplink resources. However, even if the RAN may increase the backoff delay range to try and reduce the risk of collisions, the latter will remain high when the number of A-loT devices deployed is important. With many collisions due to A-loT devices willing to access RACH uplink resources, the number of retransmissions per A-loT device will increase (impacting the power consumption of the A-loT devices) together with signaling overhead.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 RACH uplink resources, and more specifically when using a backoff delay value to delay a (re)transmission on RACH uplink resources.

[0008] For that purpose, it is proposed that mutually exclusive backoff delay ranges, or different backoff delay values allocated by the RAN, may be used by the wireless devices. This enables to reduce collision probability by enabling wireless devices to select backoff delay values in respective mutually exclusive backoff delay ranges or by enabling the RAN to allocate dedicated backoff delay values to different wireless devices.

[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 a communication unit configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the method comprises: receiving from the RAN an identifier of a backoff delay range,determining a backoff delay range to be used, among a plurality of different backoff delay ranges, based on the received identifier, selecting a backoff delay value within the determined backoff delay range, using the selected backoff delay value for delaying an access on random-access channel, RACH, uplink resources, wherein the plurality of different backoff delay ranges are mutually exclusive.

[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 backoff delay range to be used is determined based on a mapping between the plurality of different backoff delay ranges and a plurality of respective backoff delay range identifiers.

[0012] In some embodiments of the method according to the first aspect, the backoff delay range identifier is received in a signaling message addressed specifically to the wireless device.

[0013] In some embodiments of the method according to the first aspect, the backoff delay range identifier is received in an uplink transmission triggering signal or in a response from the RAN to a user equipment, UE, capability message sent by the wireless device, or in a wake-up signal transmitted by the RAN that transitions the wireless device from a sleep mode to an active mode.

[0014] 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.

[0015] 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.

[0016] In some embodiments of the method according to the first aspect, 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.

[0017] In some embodiments of the method according to the first aspect, the plurality of different backoff delay ranges correspond to respective non-overlapping portions of a backoff delay interval [0, BDVmax], wherein BDVmax corresponds to a maximum backoff delay value.

[0018] According to a second aspect, the present disclosure relates to a wireless devicecomprising 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.

[0019] 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.

[0020] 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 plurality of wireless devices, wherein the method comprises: selecting, among a plurality of different backoff delay ranges, a backoff delay range to be used by a wireless device for selecting a backoff delay value for delaying an access on random-access channel, RACH, uplink resources, transmitting an identifier of the selected backoff delay range to the wireless device, wherein the plurality of different backoff delay ranges are mutually exclusive.

[0021] 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.

[0022] In some embodiments of the method according to the fourth aspect, the backoff delay range identifier is transmitted in a signaling message addressed specifically to the wireless device.

[0023] In some embodiments of the method according to the fourth aspect, the backoff delay range identifier is transmitted in an uplink transmission triggering signal or in a response from the BS to a user equipment, UE, capability message sent by the wireless device, or in a wake-up signal transmitted by the BS that transitions the wireless device from a sleep mode to an active mode.

[0024] 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.

[0025] 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.

[0026] In some embodiments of the method according to the fourth aspect, the wireless device comprises an energy harvesting unit configured to convert ambient energy intoelectrical energy that is stored in an energy storage unit of the wireless device.

[0027] In some embodiments of the method according to the fourth aspect, the plurality of different backoff delay ranges correspond to respective non-overlapping portions of a backoff delay interval [0, BDVmax], wherein BDVmax corresponds to a maximum backoff delay value.

[0028] In some embodiments of the method according to the fourth aspect, the backoff delay range to be used by the wireless device is selected by the BS, among the plurality of different backoff delay ranges, based on at least one characteristic of the wireless device.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 exchanging data according to any one of the embodiments of the present disclosure.Brief description of figures

[0033] 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,Figure 6: a flow chart illustrating another example of a methods for exchanging data implemented by a wireless device of a UE,Figures 7 and 8: flow charts illustrating other examples of methods for exchanging data implemented by a wireless device of a UE and a BS, respectively.

[0034] 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

[0035] The detailed description set forth below, with reference to the figures, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For instance, although 3GPP terminology, from e.g., 5G NR, may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the present disclosure.

[0036] 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.

[0037] 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 exchangedata 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.

[0038] 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.

[0039] In the example illustrated by figure 1 , only one UE 20 is represented, which includes a wireless device 25 that provides the UE 20 with wireless connectivity to the RAN of the wireless communication system. Part a) of figure 1 represents schematically an example in which the UE 20 exchanges data (useful data and control data) directly with a BS 30 of the RAN (referred to as Topology 1 in TR 38.848 V18.0.0). Part b) of figure 1 represents schematically an example in which the UE 20 exchanges data (useful data and control data) indirectly with a BS 30 of the RAN, via one or more intermediate nodes 31 (referred to as Topology 2 in TR 38.848 V18.0.0). Each intermediate node 31 may be e.g., a relay, an integrated access and backhaul (IAB) node, another UE 20, a repeater, a reconfigurable intelligent surface (RIS), etc.

[0040] 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.

[0041] 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.

[0042] 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 forinstance 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.

[0043] 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.

[0044] 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).

[0045] In the non-limitative example 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] In some examples, the electrical energy collected by the energy harvesting unit 254 may be provided directly to the other equipment of the wireless device 25, in which case the energy storage unit 255 is optional and needs not to be included in the wireless device.

[0050] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0051] 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.

[0052] 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 wirelesscommunication unit 303 may also transmit carrier waves to the wireless devices 25 which perform uplink backscattering transmissions.

[0053] 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.

[0054] As illustrated by figure 3, the BS 30 may comprise also, in some examples, an energy harvesting signal generator 305, which generates energy harvesting (RF) signals which enable wireless devices 25 in its coverage to collect electrical energy in their energy storage units 255, via their energy harvesting units 254. The energy harvesting (RF) signals may take any suitable form enabling the energy harvesting units 254 to store electrical energy in the energy storage units 255 of the wireless devices 25. The choice of a specific energy harvesting (RF) signal format consists in a specific and non-limitative embodiment of the present disclosure. As mentioned above, when present, such energy harvesting (RF) signals may alternatively, or in combination thereof, be generated by other equipment separate from BSs 30 of the RAN.

[0055] As discussed above, the present disclosure aims at proposing a solution for reducing the risk of collisions between uplink data from wireless devices 25, such as A-loT devices, willing to access RACH uplink resources, and more specifically when using a backoff delay value to delay a (re)transmission on RACH uplink resources. For that purpose, it is proposed that mutually exclusive backoff delay ranges, or different backoff delay values allocated by the RAN, may be used by the wireless devices 25. This enables to reduce collision probability by enabling wireless devices 25 to select backoff delay values in respective mutually exclusive backoff delay ranges or by enabling the RAN to allocate dedicated backoff delay values to different wireless devices.

[0056] We now present examples of signaling and decision strategies that may be implemented to reduce collision probability in contention-based uplink resources.

[0057] 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.

[0058] As illustrated by figure 4, the method 40 for exchanging data comprises a step S40 of receiving from the RAN an identifier of a backoff delay range.

[0059] In the existing version of the 5G NR standard, during the RACH procedure, the gNB provides (in a random-access response, RAR, message) the UEs with a backoff indicator(Bl) which identifies a backoff parameter value BPV which corresponds to the maximum backoff delay value that a UE may randomly select. Hence, the Bl indicates a backoff delay range which extends from 0 to the indicated BPV (i.e. , a UE randomly selects a backoff delay value in the interval [0, BPV]). The mapping between each Bl and the associated BPV can be found in Table 7.2-1 of the technical specification TS 38.321 V18.0.0. Even if the gNB may adjust the backoff delay range by selecting a different BPV, the possible backoff delay ranges are overlapping ones, since they all include at least the interval [0, BPVmin], wherein BPVmin corresponds to the smallest possible backoff parameter value (5 ms according to Table 7.2-1 in TS 38.321 V18.0.0). Hence, UEs receiving simultaneously a same Bl, or even different Bls, may (re)transmit their RACH preambles simultaneously because they consider a same backoff delay range or overlapping backoff delay ranges.

[0060] In the present disclosure, it is proposed to use instead a plurality of predetermined mutually exclusive backoff delay ranges.

[0061] By “mutually exclusive” backoff delay ranges, we mean that the backoff delay ranges do not overlap each other (except maybe for a boundary backoff delay value of a backoff delay range which may be in common with another backoff delay range). Hence, if two wireless devices 25 use different backoff delay ranges, the backoff delay values that they will select are necessarily different. Two such wireless devices 25 therefore cannot start transmitting their respective RACH preambles at the same time when attempting to use the same RACH uplink resources, since they cannot select the same backoff delay value.

[0062] It should be noted that any suitable format may be used for the identifier of the backoff delay range to be used, among the plurality of possible (mutually exclusive) backoff delay ranges, and that the choice of a specific format corresponds to a specific but non- limitative embodiment of the present disclosure.

[0063] Also, the identifier of the backoff delay range to be used may be included in any suitable signaling message type, and the choice of a specific signaling message type corresponds to a specific but non-limitative embodiment of the present disclosure. For example, the backoff delay range identifier may be received in a signaling message addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25. Generally speaking, the RAN may allocate the same backoff delay range to a plurality of wireless devices 25, and the corresponding backoff delay range identifier may be sent to these wireless devices 25 in separate dedicated signaling messages and / or in one or more multicast signaling messages (with each multicast signaling message having a plurality of recipient wireless devices 25).

[0064] For example, the backoff delay range identifier may be included in a response fromthe RAN to a UE capability message (radio resource control, RRC, message) transmitted by the wireless device 25.

[0065] According to another example, the backoff delay range identifier may be included in an uplink transmission triggering signal sent by the RAN to trigger an uplink transmission by the wireless device 25 or by a group of wireless devices which includes said wireless device 25.

[0066] According to another example, the backoff delay range identifier may be included in a wake-up signal transmitted by the RAN that transitions the wireless device 25 from a sleep mode to an active mode. Indeed, 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 exchange data with the RAN. 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, if any, may correspond to the wakeup 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.

[0067] Depending on the embodiments, the allocation of a specific backoff delay range to a given wireless device 25 may be static (e.g., configured once for via e.g., a response to a UE capability message) and / or dynamic (e.g., it can change from one uplink transmission to another via e.g., an uplink transmission triggering signal or a wake-up signal).

[0068] In this example, the allocation of the backoff delay ranges to the wireless devices 25 in controlled by the RAN, which can modify the allocation dynamically if required. For example, the RAN may trigger substantially simultaneously an uplink transmission by a plurality of wireless devices 25 and may allocate different backoff delay ranges to at least some of these wireless devices 25 to reduce the collision probability.

[0069] As illustrated by figure 4, the method 40 for exchanging data comprises a step S41 of determining the backoff delay range to be used, among the plurality of different backoff delay ranges, based on the received identifier.

[0070] For example, the wireless device 25 may determine the backoff delay range to be used based on a mapping between the plurality of different backoff delay ranges and a plurality of respective backoff delay range identifiers, which mapping may be preconfigured beforehand at the wireless device 25. For example, the mapping between the plurality of different backoff delay ranges and the plurality of respective backoff delay range identifiers may be 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. In the latter case, the signaling message 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.

[0071] Table 1 represents a non-limitative example of mapping between the plurality of different backoff delay ranges and the plurality of respective backoff delay range identifiers. In this example, 4 (four) different (and mutually exclusive) backoff delay ranges are considered in a non-limitative manner. Of course, it is possible to consider a different number of backoff delay ranges in other examples.Table 1

[0072] In the example of Table 1 , the different backoff delay range identifiers are defined by different values I D1 , ID2, ID3 and ID4 (for example I D1 = 1 , ID2 = 2, ID3 = 3, ID4 = 4). Each different backoff delay range is defined by a minimum backoff delay value BDVkmin and a maximum backoff delay value BDVkmax, with k e {1, 2, 3, 4} and (BDVkmin < BDVkmax). For example:BDV1min = 0,- BDV1 max — BDV2min,- BDV2 max — BDV3min,BDV3max — BDV4mi

[0073] Hence, in this example, the mutually exclusive backoff delay ranges may have boundary backoff delay values in common (for example if BDV1max = BDV2min).

[0074] Table 2 represents another non-limitative example of mapping between the plurality of different backoff delay ranges and the plurality of respective backoff delay range identifiers, in which the backoff delay ranges are defined by their maximum backoff delay value. In this example, 4 (four) different (and mutually exclusive) backoff delay ranges are considered in a non-limitative manner. Of course, it is possible to consider a different number of backoff delay ranges in other examples.Table 2

[0075] In the example of Table 2, the different backoff delay range identifiers are defined by different values I D1 , ID2, ID3 and ID4 (for example I D1 = 1 , ID2 = 2, ID3 = 3, ID4 = 4). Each different backoff delay range is defined by a maximum backoff delay value BDVk with k e {1 , 2, 3, 4} and BDV1 < BDV2 < BDV3 < BDV4. In this example: the backoff delay range associated to ID1 corresponds to [0, BDV1], the backoff delay range associated to ID2 corresponds to [BDV1 , BDV2] (or ]BDV1 , BDV2]), the backoff delay range associated to ID3 corresponds to [BDV2, BDV3] (or ]BDV2, BDV3]), the backoff delay range associated to ID4 corresponds to [BDV3, BDV4] (or ]BDV3, BDV4]).

[0076] As illustrated by figure 4, the method 40 for exchanging data comprises a step S42 of selecting, within the determined backoff delay range, a backoff delay value to be used for delaying a (re)transmission on RACH uplink resources. The method 40 for exchanging data further comprises a step S43 of using the selected backoff delay value for delaying an access on the RACH uplink resources. For example, the backoff delay value may be selected randomly in the backoff delay range indicated by the RAN.

[0077] It should be noted that the step S42 of selecting the backoff delay value and the step S43 of using the selected backoff delay value may be executed before any transmission on the RACH uplink resources, or only before some of the transmissions on the RACH uplink resources. For example, selecting and using the selected backoff delay may be applied only during a contention resolution procedure, before performing a retransmission of a RACH preamble if the previous transmission failed due to a collision with transmissions from other wireless devices attempting to access the RACH uplink resources.

[0078] 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.

[0079] As illustrated by figure 5, the method 50 for exchanging data comprises a step S50 of selecting, among a plurality of different backoff delay ranges, a backoff delay range to be used by a wireless device 25 during a RACH procedure. As discussed above, the plurality of different backoff delay ranges are mutually exclusive and all that has been said before in relation with figure 4 applies also to figure 5.

[0080] As discussed above, the BS 30 may select the backoff delay range such that not allwireless devices 25 in its coverage are allocated the same backoff delay range. However, the BS 30 can allocate the same backoff delay range to some of the wireless devices 25 in its coverage, for example to wireless devices 25 considered to belong to a same group.

[0081] In some examples, the BS 30 may select the backoff delay range to be used by the wireless device 25, among the plurality of different backoff delay ranges, based on at least one characteristic of the wireless device 25.

[0082] For example, the considered characteristic(s) of the wireless device 25 may include a traffic class of uplink data to be transmitted by said wireless device 25. For example, the BS 30 may associate different backoff delay ranges to different traffic classes (e.g., priority level, latency requirements, etc.) and the BS 30 may select the backoff delay range 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. If we consider the examples given by Table 1 and Table 2, then the BS 30 may use the backoff delay ranges associated to ID1 and ID2 for wireless devices 25 having a high priority level and, in turn, it may use the backoff delay ranges associated to ID3 and ID4 for wireless devices 25 having a low priority level.

[0083] Alternatively, or in combination thereof, the considered characteristic(s) of the wireless device 25 may include a type of said wireless device 25. For example, section 4.3 of the technical report TR 38.848 V18.0.0 defines different types of A-loT devices, based mainly on electrical energy storage capability and independent signal generation / amplification capability. Currently, the technical report TR 38.848 V18.0.0 defines in non-limitative manner types A (no electrical energy storage, no independent signal generation / amplification), B (with electrical energy storage, no independent signal generation) and C (with electrical energy storage, with independent signal generation). For example, the BS 30 may associate different backoff delay ranges to different A-loT device types and the BS 30 may select the backoff delay range to be used by a given wireless device 25 based on the A-loT device type of this wireless device 25.

[0084] Alternatively, or in combination thereof, the BS 30 may select the backoff delay range to be used based on a load level of the BS 30. 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 backoff delay range 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 be used to decide which backoff delay ranges can be allocated. For example, if we consider the examples given by Table 1 and Table 2, then the BS 30 may decide to use only the backoff delay ranges associated to ID1 and ID2 if the estimated load level islow. In turn, the BS 30 may decide to use all available backoff delay ranges if the estimated load level is high.

[0085] As illustrated by figure 5, the method 50 for exchanging data comprises a step S51 of transmitting an identifier of the selected backoff delay range to the wireless device 25. Of course, the identifier transmitted corresponds to the identifier associated to the selected backoff delay range. Hence, the BS 30 may either select directly a backoff delay range identifier during step S50, or it may select a backoff delay range in which case the associated identifier may be retrieved from, e.g., a preconfigured mapping between the plurality of different backoff delay ranges and the plurality of respective backoff delay range identifiers, as discussed above.

[0086] As discussed above, any suitable format may be used for transmitting the backoff delay range identifier to the wireless device 25 and the choice of a specific format corresponds to a specific but non-limitative embodiment of the present disclosure.

[0087] For example, the backoff delay range identifier may be 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. For example, the backoff delay range identifier may be transmitted by the BS 30: in a response to a UE capability message (radio resource control, RRC, message) transmitted by the wireless device 25, or in an uplink transmission triggering signal sent by the RAN to trigger an uplink transmission by the wireless device 25 or by a group of wireless devices which includes said wireless device 25, or in a wake-up signal transmitted by the RAN that transitions the wireless device 25 from a sleep mode to an active mode (which may be an uplink transmission triggering signal in some cases), etc.

[0088] Figure 6 represents a diagram showing steps of an exemplary embodiment of a method 60 for exchanging data, which is implemented by a wireless device 25 of a UE 20.

[0089] The embodiment illustrated by figure 6 is similar to the examples illustrated by figures 4 and 5 in that it relies on a plurality of mutually exclusive backoff delay ranges. Hence, all that has been said previously in relation to the different (mutually exclusive) backoff delay ranges applies also to the example of figure 6. However, in the non-limitative example of figure 6, the backoff delay range to be used by a given wireless device 25 is not indicated explicitly by the RAN, but it is determined by the wireless device 25.

[0090] As illustrated by figure 4, the method 60 for exchanging data comprises a step S60 of determining a backoff delay range to be used, among the plurality of (mutually exclusive)different backoff delay ranges.

[0091] For example, the wireless device 25 may select the backoff delay range based on at least one characteristic of said wireless device 25.

[0092] As discussed above, the considered characteristic(s) of the wireless device 25 may include a traffic class of uplink data to be transmitted by said wireless device 25 (e.g., priority level, latency requirements, etc.). Alternatively, or in combination thereof, the considered characteristic(s) of the wireless device 25 may include a type of said wireless device 25, for example an A-loT device type of the wireless device 25.

[0093] For example, a mapping between the plurality of different backoff delay ranges and a plurality of respective values of the considered characteristic of the wireless device 25 may be preconfigured at the wireless device 25.

[0094] For example, the mapping between the plurality of different backoff delay ranges and the plurality of respective values of the considered characteristic of the wireless device 25 may be 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. In the latter case, the signaling message 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.

[0095] Table 3 represents a non-limitative example of mapping between the plurality of different backoff delay ranges and the plurality of respective values of a characteristic of the wireless device 25 (e.g., traffic class, type of the wireless device, etc.). In this example, 4 (four) different (and mutually exclusive) backoff delay ranges are considered in a non- limitative manner. Of course, it is possible to consider a different number of backoff delay ranges in other examples.Table 3

[0096] In the example of Table 3, the different characteristic values are identified as CV1 , CV2, CV3 and CV4, which may correspond to either an actual characteristic value or to an identifier of an actual characteristic value (for example CV1 = 1 , CV2 = 2, CV3 = 3, CV4 = 4 which define different priority level values and / or different A-loT device types). Each different backoff delay range is defined by a minimum backoff delay value BDVkmin and a maximum backoff delay value BDVkmax, with k e {1 , 2, 3, 4} and (BDVkmin < BDVkmax). Forexample, and as discussed above:BDV1 min = 0,- BDV1 max — BDV2min,- BDV2 max — BDV3min,BDV3max — BDV4min-

[0097] Table 4 represents another non-limitative example of mapping between the plurality of different backoff delay ranges and the plurality of respective values of a characteristic of the wireless device 25 (e.g., traffic class, type of the wireless device, etc.), in which the backoff delay ranges are defined by their maximum backoff delay value. In this example, 4 (four) different (and mutually exclusive) backoff delay ranges are considered in a non- limitative manner. Of course, it is possible to consider a different number of backoff delay ranges in other examples.Table 4

[0098] In the example of Table 4, the different characteristic values are identified as CV1 , CV2, CV3 and CV4, which may correspond to either an actual characteristic value or to an identifier of an actual characteristic value (for example CV1 = 1 , CV2 = 2, CV3 = 3, CV4 = 4 which define different priority level values and / or different A-loT device types). Each different backoff delay range is defined by a maximum backoff delay value BDVk with k e {1 , 2, 3, 4} and BDV1 < BDV2 < BDV3 < BDV4. In this example: the backoff delay range associated to CV1 corresponds to [0, BDV1], the backoff delay range associated to CV2 corresponds to [BDV1 , BDV2] (or ]BDV1 , BDV2]), the backoff delay range associated to CV3 corresponds to [BDV2, BDV3] (or ]BDV2, BDV3]), the backoff delay range associated to CV4 corresponds to [BDV3, BDV4] (or ]BDV3, BDV4]).

[0099] As illustrated by figure 6, the method 60 for exchanging data comprises a step S61 of selecting, within the determined backoff delay range, a backoff delay value to be used for delaying a (re)transmission on RACH uplink resources. The method 60 for exchanging data further comprises a step S62 of using the selected backoff delay value for delaying an access on the RACH uplink resources. For example, the backoff delay value may be selected randomly in the backoff delay range determined by the wireless device 25.

[0100] It should be noted that the step S61 of selecting the backoff delay value and the step S62 of using the selected backoff delay value may be executed before any transmission on the RACH uplink resources, or only before some of the transmissions on the RACH uplink resources. For example, selecting and using the selected backoff delay value may be applied only during a contention resolution procedure, before performing a retransmission of a RACH preamble if the previous transmission failed due to a collision with transmissions from other wireless devices attempting to access the RACH uplink resources.

[0101] In some examples, the wireless device 25 determines the backoff delay range to be used in response to receiving an uplink transmission triggering signal from the RAN (not represented in the figures), which may be addressed specifically to the wireless device 25 or to a group of wireless devices which includes said wireless device 25. In some examples, the uplink transmission triggering signal may be a wake-up signal that transitions the wireless device from a sleep mode to an active mode or it may be a signaling message received after receiving a wake-up signal.

[0102] Figure 7 represents a diagram showing steps of an exemplary embodiment of a method 70 for exchanging data, which is implemented by a wireless device 25 of a UE 20. Figure 8 represents a diagram showing corresponding steps of an exemplary embodiment of a method 80 for exchanging data, which is implemented by a BS 30 of the RAN.

[0103] In the examples illustrated by figures 7 and 8, the RAN controls directly the backoff delay values to be used by the respective wireless devices 25 when attempting to access RACH uplink resources. Since the RAN controls the backoff delay values used by the different wireless devices 25, (re)transmissions from these wireless devices 25 on the RACH uplink resources can be scheduled by the RAN to avoid collisions, turning the RACH uplink resources into contention-free uplink resources for these wireless devices 25.

[0104] As illustrated by figure 7, the method 70 for exchanging data comprises a step S70 of receiving from the RAN an identifier of a backoff delay value.

[0105] In the existing version of the 5G NR standard, each UE selects randomly the backoff delay value it may use during the RACH procedure, within a backoff delay range indicated by the gNB. In the present case, it is the RAN that selects the backoff delay values to be used by the wireless devices 25 in a centralized manner, such that collisions can be avoided.

[0106] It should be noted that any suitable format may be used for the identifier of the backoff delay value to be used, among a plurality of predetermined different backoff delay values, and that the choice of a specific format corresponds to a specific but non-limitative embodiment of the present disclosure.

[0107] Also, the identifier of the backoff delay value to be used may be included in anysuitable signaling message type, and the choice of a specific signaling message type corresponds to a specific but non-limitative embodiment of the present disclosure.

[0108] For example, the backoff delay value identifier may be received in a signaling message addressed specifically to the wireless device 25.

[0109] For example, the backoff delay value identifier may be included in a response from the RAN to a UE capability message (radio resource control, RRC, message) transmitted by the wireless device 25.

[0110] According to another example, the backoff delay value identifier may be included in a physical layer, L1 , signaling message transmitted by the RAN to the wireless device 25.

[0111] According to another example, the backoff delay value identifier may be included in an uplink transmission triggering signal sent by the RAN to trigger an uplink transmission by the wireless device 25.

[0112] According to another example, the backoff delay value identifier may be included in a wake-up signal transmitted by the RAN that transitions the wireless device 25 from a sleep mode to an active mode. Indeed, 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 exchange data with the RAN. 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, if any, may correspond to the wakeup 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.

[0113] Depending on the embodiments, the allocation of a specific backoff delay value to a given wireless device 25 may be static (e.g., configured once for via e.g., a response to a UE capability message) and / or dynamic (e.g., it can change from one uplink transmission to another via e.g., an uplink transmission triggering signal or a wake-up signal).

[0114] In this example, the allocation of the backoff delay values to the wireless devices 25 in controlled by the RAN, which can modify the allocation dynamically if required.

[0115] As illustrated by figure 7, the method 70 for exchanging data comprises a step S71 of determining the backoff delay value to be used, among the plurality of different backoff delay values, based on the received identifier.

[0116] For example, the wireless device 25 may determine the backoff delay value to be used based on a mapping between the plurality of different backoff delay values and a plurality of respective backoff delay value identifiers, which mapping may be preconfiguredbeforehand at the wireless device 25. For example, the mapping between the plurality of different backoff delay values and the plurality of respective backoff delay value identifiers may be 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. In the latter case, the signaling message 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.

[0117] Table 5 represents a non-limitative example of mapping between the plurality of different backoff delay values and the plurality of respective backoff delay value identifiers. In this example, N different backoff delay values are considered in a non-limitative manner.Table 5

[0118] In the example of Table 5, the different backoff delay value identifiers are defined by different values ID1 , ID2, ID3, ID4, ... , IDN (for example ID1 = 1 , ID2 = 2, ID3 = 3, ID4 = 4, ... , IDN = N). The different backoff delay values are referred to as BDV1 , BDV2, BDV3, BDV4, ... , BDVN with for example 0 < BDV1 < BDV2 < BDV3 < BDV4 < ... < BDVN. For example, the backoff delay values BDV1 , BDV2, BDV3, BDV4, ... , BDVN may be regularly spaced in [0, BDVmax], wherein BDVmax may correspond to BDVN.

[0119] As illustrated by figure 7, the method 70 for exchanging data comprises a step S72 of using the determined backoff delay value for delaying an access on the RACH uplink resources. It should be noted that the step S72 of using the determined backoff delay value may be executed before any transmission on the RACH uplink resources, or only before some of the transmissions on the RACH uplink resources. For example, using the selected backoff delay may be applied only during a contention resolution procedure, before performing a retransmission of a RACH preamble if the previous transmission failed due to a collision with transmissions from other wireless devices attempting to access the RACH uplink resources.

[0120] As discussed above, figure 8 represents a diagram showing corresponding steps of an exemplary embodiment of a method 80 for exchanging data, which may be implemented by a BS 30 when the wireless device 25 implements the method 70 for exchanging dataillustrated by figure 7.

[0121] As illustrated by figure 8, the method 80 for exchanging data comprises a step S80 of selecting, among a plurality of different backoff delay values, a backoff delay value to be used by a wireless device 25 during a RACH procedure.

[0122] As discussed above, the BS 30 may select the backoff delay values such that the wireless devices 25 in its coverage are allocated different backoff delay values, at least those wireless devices 25 attempting to use a same RACH occasion.

[0123] In some examples, the BS 30 may select the backoff delay value to be used by the wireless device 25, among the plurality of different backoff delay values, based on at least one characteristic of the wireless device 25. For example, the considered characteristic(s) of the wireless device 25 may include a traffic class of uplink data to be transmitted by said wireless device 25 (e.g., priority level, latency requirements, etc.). Alternatively, or in combination thereof, the considered characteristic(s) of the wireless device 25 may include a type of said wireless device 25, for example an A-loT device type of the wireless device.

[0124] As illustrated by figure 8, the method 80 for exchanging data comprises a step S81 of transmitting an identifier of the selected backoff delay value to the wireless device 25. Of course, the identifier transmitted corresponds to the identifier associated to the selected backoff delay value. Hence, the BS 30 may either select directly a backoff delay value identifier during step S80, or it may select a backoff delay value in which case the associated identifier may be retrieved from, e.g., a preconfigured mapping between the plurality of different backoff delay values and the plurality of respective backoff delay value identifiers, as discussed above.

[0125] As discussed above, any suitable format may be used for transmitting the backoff delay value identifier to the wireless device 25 and the choice of a specific format corresponds to a specific but non-limitative embodiment of the present disclosure.

[0126] For example, the backoff delay value identifier may be transmitted in a signaling message addressed specifically to the wireless device 25. For example, the backoff delay value identifier may be transmitted by the BS 30: in a response to a UE capability message (radio resource control, RRC, message) transmitted by the wireless device 25, or in an L1 signaling message, or in an uplink transmission triggering signal sent by the RAN to trigger an uplink transmission by the wireless device 25, or in a wake-up signal transmitted by the RAN that transitions the wireless device 25 from a sleep mode to an active mode (which may be an uplink transmissiontriggering signal in some cases), etc.

[0127] 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.

[0128] For example, the present disclosure has been made by considering mainly the case of A-loT devices. However, the present disclosure can also be used for non-A-loT devices.

[0129] It should also be noted that there can be a coexistence in the wireless communication system between wireless devices 25 which apply the present disclosure and wireless devices which perform legacy contention resolution (i.e., using overlapping backoff delay ranges). For example, the present disclosure may apply e.g. only to A-loT devices whereas non-A-loT devices may perform legacy contention resolution.

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 a communication unit (253) configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the method comprises:(540) receiving from the RAN an identifier of a backoff delay range,(541) determining a backoff delay range to be used, among a plurality of different backoff delay ranges, based on the received identifier,(542) selecting a backoff delay value within the determined backoff delay range,(543) using the selected backoff delay value for delaying an access on randomaccess channel, RACH, uplink resources, wherein the plurality of different backoff delay ranges are mutually exclusive.

2. The method (40) according to claim 1 , wherein the backoff delay range to be used is determined based on a mapping between the plurality of different backoff delay ranges and a plurality of respective backoff delay range identifiers.

3. The method (40) according to any one of the preceding claims, wherein the backoff delay range identifier is received in a signaling message addressed specifically to the wireless device.

4. The method (40) according to any one of the preceding claims, wherein the backoff delay range identifier is received in an uplink transmission triggering signal or in a response from the RAN to a user equipment, UE, capability message sent by the wireless device, or in a wake-up signal transmitted by the RAN that transitions the wireless device from a sleep mode to an active mode.

5. The method (40) according to any one of the preceding claims, 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.

6. The method (40) according to any one of the preceding claims, wherein the plurality of different backoff delay ranges correspond to respective non-overlapping portions of a backoff delay interval [0, BDVmax], wherein BDVmax corresponds to a maximum backoff delay value.

7. 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.

8. A user equipment, UE (20), comprising a wireless device according to claim 7.

9. 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 plurality of wireless devices (25), wherein the method comprises:(550) selecting, among a plurality of different backoff delay ranges, a backoff delay range to be used by a wireless device (25) for selecting a backoff delay value for delaying an access on random-access channel, RACH, uplink resources,(551) transmitting an identifier of the selected backoff delay range to the wireless device, wherein the plurality of different backoff delay ranges are mutually exclusive.

10. The method (50) according to claim 9, wherein the backoff delay range identifier is transmitted in a signaling message addressed specifically to the wireless device.

11. The method (50) according to any one of claims 9 to 10, wherein the backoff delay range identifier is transmitted in an uplink transmission triggering signal or in a response from the BS to a user equipment, UE, capability message sent by the wireless device, or in a wake-up signal transmitted by the BS that transitions the wireless device from a sleep mode to an active mode.

12. The method (50) according to any one of claims 9 to 11 , 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.

13. The method (50) according to any one of claims 9 to 12, wherein the plurality of different backoff delay ranges correspond to respective non-overlapping portions of a backoff delay interval [0, BDVmax], wherein BDVmax corresponds to a maximum backoff delay value.

14. The method (50) according to any one of claims 9 to 13, wherein the backoff delay range to be used by the wireless device is selected by the BS, among the plurality of different backoff delay ranges, based on at least one characteristic of the wireless device.

15. 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 9 to 14.

16. A wireless communication system comprising at least one base station (30) according to claim 15 and at least one user equipment (20) according to claim 8.

17. 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 6 or a method (50) according to any one of claims 9 to 14.

18. 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 6 or a method (50) according to any one of claims 9 to 14.

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