WO2025233166A1

WO2025233166A1 - Method and device for enhancing the usage of random-access uplink resources by ambient iot devices by switching between random-access procedure types

Info

Publication number: WO2025233166A1
Application number: PCT/EP2025/061626
Authority: WO
Inventors: Rikin SHAH; David GONZALEZ GONZALEZ; Reuben GEORGE STEPHEN; Rajat PUSHKARNA
Original assignee: Aumovio Germany GmbH
Current assignee: Aumovio Germany GmbH
Priority date: 2024-05-07
Filing date: 2025-04-29
Publication date: 2025-11-13
Anticipated expiration: 2026-11-07
Also published as: DE102024204278A1

Abstract

The present disclosure relates to methods and devices for reducing collision probability on random access, RA, uplink resources by enabling a wireless device (25) of a user equipment, UE (20), to automatically switch from a first RA procedure type, contention-based, to a second RA procedure type different from the first RA procedure type.

Description

Method and device for enhancing the usage of random-access uplink resources by ambient loT devices by switching between random-access procedure types

Technical field

[0001] The present disclosure relates to wireless communication systems and relates more specifically to methods and devices for enhancing the usage of random-access 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 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 random-access uplink resources, i.e., uplink resources which are shared by a plurality of wireless devices, on which each of these wireless devices can decide on its own when to transmit uplink data, which uplink data may therefore collide with uplink data from other wireless devices with which these uplink resources are shared.

[0006] Examples of random-access, RA, uplink resources include random-access channel, RACH, uplink resources. Currently, the 3GPP specifications for 5G NR define different types of RA procedures for accessing RACH uplink resources, mainly two contention-based procedures and one contention free procedure. Contention-based procedures are true RA procedures used to access RACH uplink resources whereby a user equipment, UE, randomly selects RACH uplink resources such as a RA preamble. The current 5G NR specifications define two different types of contention-based RA procedures for RACH uplink resources, which differ by the number of steps used, namely a 4-step contentionbased RA procedure (based on the exchange of four messages Msg1 , Msg2, Msg3 and Msg4) and a 2-step contention-based RA procedure (based on the exchange of two messages MsgA and MsgB). The contention free RA procedure avoids collisions between UEs by allocating dedicated RACH uplink resources (e.g., RA preambles) to the UEs.

[0007] However, the risk of collisions and of congestion of the RA(CH) uplink resources increases as the number of A-loT devices deployed increases. Also, with many collisions due to A-loT devices willing to access RA uplink resources, the RAN might need to trigger retransmissions by the colliding A-loT devices, which would increase the signaling overhead for the RAN and the power consumption for the A-loT devices. Hence there is a need for improved RA procedures for A-loT devices and for facilitating the usage of different RA procedures by A-loT devices.

Summary

[0008] 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 signaling overhead for configuring RA procedures, in particular when different RA procedure types are available for wireless devices, such as A-loT devices.

[0009] For that purpose, it is proposed that the wireless device uses a first RA procedure type, contention-based, as long as a first RA procedure type failure criterion, evaluated by the wireless device, is not verified. When the first RA procedure type failure criterion is verified, the wireless device switches to using a second RA procedure type, different from the first RA procedure type. Hence, the wireless device evaluates on its own whether the RA procedure using the first RA procedure type succeeds. If the wireless device determines that the first RA procedure type has failed, it switches automatically to a different RA procedure type, e.g., a RA procedure type which may be contention-based but requiring a different number of steps to succeed or which may be contention free to ensure the success of the RA procedure once it is determined that the first RA procedure type has failed.

[0010] 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: performing a random-access, RA, procedure on RA uplink resources by using a first RA procedure type, wherein the first RA procedure type is contention-based, evaluating a first RA procedure type failure criterion based on a result of the RA procedure using the first RA procedure type, in response to the first RA procedure type failure criterion being verified: continuing the RA procedure on RA uplink resources by using a second RA procedure type different from the first RA procedure type.

[0011] 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.

[0012] In some embodiments of the method according to the first aspect, the second RA procedure type is contention-free or contention-based with fewer steps than the first RA procedure type.

[0013] In some embodiments of the method according to the first aspect, the first RA procedure type is a 4-step contention-based RA procedure.

[0014] In some embodiments of the method according to the first aspect, the second RA procedure type is a 2-step contention-based RA procedure.

[0015] In some embodiments of the method according to the first aspect, the first RA procedure type failure criterion is verified in response to the RA procedure using the first RA procedure type failing N times, wherein N is a preconfigured maximum number of failed attempts.

[0016] In some embodiments, the method according to the first aspect comprises receiving N from the RAN. [0017] In some embodiments of the method according to the first aspect, N is received in an uplink transmission triggering signal used to trigger an uplink transmission by the wireless device.

[0018] In some embodiments of the method according to the first aspect, the uplink transmission triggering signal is a paging message and/or a wake-up signal transmitted by the RAN that transitions the wireless device from a sleep mode to an active mode.

[0019] 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.

[0020] According to a second aspect, the present disclosure relates to a wireless device comprising at least one memory and at least one processor configured to carry out a method according to any one of the embodiments of the first aspect.

[0021] According to a third aspect, the present disclosure relates to a user equipment, UE, comprising a wireless device according to any one of the embodiments of the present disclosure.

[0022] According to a fourth aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, the method being implemented by a base station, BS, of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device, wherein the method comprises transmitting information to the wireless device for configuring a first randomaccess, RA, procedure type failure criterion to be evaluated by the wireless device for switching from using the first RA procedure type to using a second RA procedure type when performing a RA procedure on RA uplink resources, wherein the first RA procedure type is contention- based.

[0023] In some embodiments, the method according to the fourth aspect can further comprise one or more of the following optional features, considered either alone or in any technically possible combination.

[0024] In some embodiments of the method according to the fourth aspect, the second RA procedure type is contention-free or contention-based with fewer steps than the first RA procedure type.

[0025] In some embodiments of the method according to the fourth aspect, the first RA procedure type is a 4-step contention-based RA procedure.

[0026] In some embodiments of the method according to the fourth aspect, the second RA procedure type is a 2-step contention-based RA procedure.

[0027] In some embodiments of the method according to the fourth aspect, the information for configuring the first RA procedure type failure criterion includes a maximum number of failed attempts when using the first RA procedure type.

[0028] In some embodiments of the method according to the fourth aspect, the information for configuring the first RA procedure type failure criterion is determined based on a load level of the BS.

[0029] In some embodiments of the method according to the fourth aspect, the information for configuring the first RA procedure type failure criterion is transmitted in an uplink transmission triggering signal used to trigger an uplink transmission by the wireless device. [0030] In some embodiments of the method according to the fourth aspect, the uplink transmission triggering signal is a paging message and/or a wake-up signal that transitions the wireless device from a sleep mode to an active mode.

[0031] In some embodiments of the method according to the fourth 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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

[0036] 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.

[0037] 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

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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. [0045] 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.

[0046] 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.

[0047] 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). [0048] 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. [0049] 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.

[0050] 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.

[0051] 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.

[0052] 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. [0053] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] As discussed above, the present disclosure aims at proposing a solution for reducing signaling overhead for configuring RA procedures, in particular when different RA procedure types are available for wireless devices, such as A-loT devices.

[0059] For that purpose, it is proposed that the wireless device 25 uses a first RA procedure type, which is contention-based, as long as a first RA procedure type failure criterion, evaluated by the wireless device 25, is not verified. When the first RA procedure type failure criterion is verified, the wireless device 25 switches to using a second RA procedure type, different from the first RA procedure type. Hence, the wireless device 25 evaluates on its own whether the RA procedure using the first RA procedure type succeeds. If the wireless device 25 determines that the first RA procedure type has failed, it switches automatically to a different RA procedure type, e.g., a RA procedure type which may be also contentionbased or which may be contention free.

[0060] 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.

[0061] As illustrated by figure 4, the method 40 for exchanging data comprises a step S40 of performing a random-access, RA, procedure on RA uplink resources by using a first RA procedure type, wherein the first RA procedure type is contention-based.

[0062] In some examples, the step S40 of performing a RA procedure may be started by the wireless device 25 upon receiving from the RAN an uplink transmission triggering signal, transmitted by the RAN to trigger an uplink transmission by said wireless device 25 or by a group of wireless devices to which said wireless device 25 belongs (possibly all wireless devices in the coverage of the BS 30 of the RAN).

[0063] The first RA procedure type may be for example an RA procedure type that is predefined (e.g., specified by a standard) and used by default by the wireless device 25. In other examples, the first RA procedure type may be configured by the RAN. For example, the first RA procedure type may be indicated in the uplink transmission triggering signal (if any). However, other types of signaling messages may be used for configuring the first RA procedure type at the wireless device(s) 25 and the choice of a specific signaling message type corresponds to a specific but non-limitative embodiment of the present disclosure.

[0064] As illustrated by figure 4, the method 40 for exchanging data comprises a step S41 of evaluating a first RA procedure type failure criterion based on a result of the RA procedure using the first RA procedure type. Hence, the wireless device 25 evaluates whether the RA procedure can be considered to have failed when using the first RA procedure type.

[0065] If the first RA procedure type failure criterion is not verified (i.e., the RA procedure using the first RA procedure type cannot be considered to have failed yet, reference S41a in figure 4), the wireless device 25 continues the RA procedure with the same first RA procedure type (step S40), as illustrated by figure 4.

[0066] If the first RA procedure type failure criterion is verified (i.e., the RA procedure using the first RA procedure type is considered to have failed, reference S41 b in figure 4), the wireless device 25 switches to using a second RA procedure type, different from the first RA procedure type, and the method 40 for exchanging data comprises a step S42 whereby the wireless device 25 continues the RA procedure with the second RA procedure type.

[0067] The second RA procedure type may be for example an RA procedure type that is predefined (e.g., specified by a standard). In other examples, the second RA procedure type may be configured by the RAN. For example, the second RA procedure type may be indicated in the uplink transmission triggering signal (if any). However, other types of signaling messages may be used for configuring the second RA procedure type at the wireless device(s) 25 and the choice of a specific signaling message type corresponds to a specific but non-limitative embodiment of the present disclosure.

[0068] For example, the second RA procedure type is also contention-based, as the first RA procedure type.

[0069] In preferred embodiments, if the first RA procedure type and the second RA procedure type are both contention-based, then the second RA procedure type may be different from the first RA procedure type in that it requires fewer steps (i.e., fewer exchanges of messages) than the first RA procedure type. Such provisions enable the wireless device 25 to automatically switch to an RA procedure type requiring fewer steps when the first RA procedure type is considered to have failed, thereby reducing signaling overhead for the RAN. For example, if we consider existing RA procedures for RACH uplink resources, the first RA procedure type may correspond to the 4-step contention-based RA procedure and the second RA procedure type may correspond to the 2-step contentionbased RA procedure. Of course, other (e.g., contention-based) RA procedure types may be defined for e.g. A-loT devices and the present disclosure is not limited to existing (e.g., contention based) RA procedure types.

[0070] In other examples, the second RA procedure type may be contention free. In such examples, once the first RA procedure type is considered to have failed, the wireless device 25 therefore switches to contention free RA procedure which prevents collisions, to ensure that the RA procedure initiated by the wireless device 25 succeeds. For example, the wireless device may switch from a 4-step or 2-step contention-based RA procedure to a contention free RA procedure when the first RA procedure type failure criterion is verified. [0071] In general, the present disclosure may use any suitable type of first RA procedure type failure criterion and the choice of a specific first RA procedure type failure criterion corresponds to a specific but non-limitative embodiment of the present disclosure.

[0072] In some examples, the first RA procedure type failure criterion is verified in response to the RA procedure using the first RA procedure type failing successively N times, wherein N is a preconfigured maximum number of failed attempts. N is an integer. In some examples, N may be equal to 1 (N = 1). In preferred examples, N is greater than or equal to 2 (N > 2). In some examples, N is greater than or equal to 4 (N > 2), for example N = 10.

[0073] Hence, the wireless device 25, for example when it receives an uplink transmission triggering signal (if any), may set an internal counter nc to zero (nc = 0) and start performing the RA procedure using the first RA procedure type. Each time the RA procedure using the first RA procedure type fails, nc is incremented. If nc is different from N (nc N), then the wireless device 25 continues the RA procedure with the first RA procedure type (reference S41a in figure 4). If the RA procedure using the first RA procedure type succeeds, nc may be reset to zero. If, at some point, nc becomes equal to N (nc = N), then the wireless device 25 switches to the second RA procedure type and continues the RA procedure with the second RA procedure type (reference S41b in figure 4).

[0074] For example, the value of N may be predefined (e.g., specified by a standard). In other examples, the value of N may be configured by the RAN. For example, the value of N may be indicated in the uplink transmission triggering signal (if any). However, other types of signaling messages may be used for configuring the value of N, to be used by the wireless device 25 during the evaluation of the first RA procedure type failure criterion.

[0075] For example, the uplink transmission triggering signal may be a paging message.

[0076] Alternatively, or in combination thereof, the uplink transmission triggering signal may be a wake-up signal transmitted by the RAN that transitions the wireless device 25 from a sleep mode to an active mode, or a signaling message transmitted after such a wake-up signal. 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 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 the RAN 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.

[0077] 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.

[0078] In the example of figure 5, it is assumed in a non-limitative manner that the first RA procedure type failure criterion is configured at least in part by the BS 30. Accordingly, the method 50 for exchanging data comprises a step S50 of transmitting information to the wireless device 25 for configuring a first RA procedure type failure criterion to be evaluated by the wireless device 25 for switching from using the first RA procedure type to using a second RA procedure type when performing a RA procedure on RA uplink resources.

[0079] As discussed above, the first RA procedure type, at least, is contention-based and the second RA procedure type is different from the first RA procedure type. More generally, all that has been said previously regarding the first RA procedure type and the second RA procedure type applies similarly.

[0080] In some examples, the information for configuring the first RA procedure type failure criterion, transmitted during step S50, includes a maximum number N of successive failed attempts that are authorized when using the first RA procedure type (see above).

[0081] Any suitable type of signaling message may be used for transmitting the information for configuring the first RA procedure type failure criterion (e.g., the value of N) and the choice of a specific signaling message type corresponds to a specific but non-limitative embodiment of the present disclosure.

[0082] As discussed above, in some examples, the information for configuring the first RA procedure type failure criterion may be transmitted in an uplink transmission triggering signal used by the BS 30 to trigger an uplink transmission by one or a plurality of wireless devices 25. Such an uplink transmission triggering signal may therefore be a broadcast or multicast signaling message in some examples.

[0083] In some examples, the uplink transmission triggering signal may be a paging message. Alternatively, or in combination thereof, the uplink transmission triggering signal may be a wake-up signal transmitted that transitions the wireless device 25 from a sleep mode to an active mode, or a signaling message transmitted after such a wake-up signal.

[0084] In some examples, the BS 30 may adapt the information (e.g., value of N) transmitted for configuring the first RA procedure type failure criterion to the context. For example, the BS 30 may adjust this information 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 value of N 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 BS 30 may use a lower value for N when the estimated load level is high than when the estimated load level is low.

[0085] In some examples, the BS 30 may adapt the information (e.g., value of N) to a given group of wireless devices 25, i.e., the information transmitted may vary from a group of wireless devices 25 to another. For example, the BS 30 may set different values for N for UEs 20 having a UE identity known to the RAN and for UEs not having a UE identity known to the RAN. For example, the BS 30 may set a lower value for N for UEs 20 having a UE identity known to the RAN than for UEs not having a UE identity known to the RAN.

[0086] For example, the UE identity known to the RAN may be an identity assigned to the UE 20 by the RAN and/or an identity previously transmitted to the RAN by the UE 20.

[0087] For example, the identity assigned to the UE 20 by the RAN may correspond to a temporary mobile subscriber identity, TMSI, a 5G-S-TMSI, a 5G globally unique temporary identity, 5G-GUTI, a random identity generated by the RAN, etc., or any new type of identity that may be assigned by the RAN to identify A-loT devices. For example, the identity transmitted to the RAN by the UE 20 may correspond to an international mobile subscriber identity, I MSI , an international mobile equipment identity, I M El , a random identity generated by the UE 20, etc., or any new type of identity that may be associated to the UE 20 as an A-loT device that said UE 20 may share with the RAN.

[0088] In some examples, the UE identity known to the RAN may correspond to a UE contention resolution identity received during a previous successful access on contentionbased uplink resources. In the current RACH procedures of the existing version of the 5G NR standard, the UE contention resolution identity is typically received in the message Msg4 (in case of a 4-step RACH procedure) or in the message MsgB (in case of a 2-step RACH procedure). However, other RACH procedures may be defined for A-loT devices.

[0089] 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.

[0090] 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. [0091] 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 do not apply the present disclosure. For example, the present disclosure may apply e.g. only to A-loT devices whereas non-A-loT devices may perform legacy RA procedures.

Claims

1. 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) performing a random-access, RA, procedure on RA uplink resources by using a first RA procedure type, wherein the first RA procedure type is contentionbased,

(541) evaluating a first RA procedure type failure criterion based on a result of the RA procedure using the first RA procedure type, in response to the first RA procedure type failure criterion being verified: (S42) continuing the RA procedure on RA uplink resources by using a second RA procedure type different from the first RA procedure type.

2. The method (40) according to claim 1 , wherein the second RA procedure type is contention-free or contention-based with fewer steps than the first RA procedure type.

3. The method (40) according to any one of the preceding claims, wherein the first RA procedure type is a 4-step contention-based RA procedure.

4. The method (40) according to claim 3, wherein the second RA procedure type is a 2-step contention-based RA procedure.

5. The method (40) according to any one of the preceding claims, wherein the first RA procedure type failure criterion is verified in response to the RA procedure using the first RA procedure type failing N times, wherein N is a preconfigured maximum number of failed attempts.

6. The method (40) according to claim 5, comprising receiving N from the RAN.

7. The method (40) according to claim 6, wherein N is received in an uplink transmission triggering signal used to trigger an uplink transmission by the wireless device.

8. The method (40) according to claim 7, wherein the uplink transmission triggering signal is a paging message and/or a wake-up signal transmitted by the RAN that transitions the wireless device from a sleep mode to an active mode.

9. 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 of the wireless device.

10. A wireless device (25) comprising at least one memory and at least one processor configured to carry out a method (40) according to any one of the preceding claims. 11. A user equipment, UE (20), comprising a wireless device according to claim 10.

12. A method (50) for exchanging data in a wireless communication system, the method being implemented by a base station, BS (30), of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device (25), wherein the method comprises (S50) transmitting information to the wireless device for configuring a first random-access, RA, procedure type failure criterion to be evaluated by the wireless device for switching from using the first RA procedure type to using a second RA procedure type when performing a RA procedure on RA uplink resources, wherein the first RA procedure type is contention-based.

13. The method (50) according to claim 12, wherein the second RA procedure type is contention-free or contention-based with fewer steps than the first RA procedure type.

14. The method (50) according to any one of claims 12 to 13, wherein the first RA procedure type is a 4-step contention-based RA procedure.

15. The method (50) according to claim 14, wherein the second RA procedure type is a 2-step contention-based RA procedure.

16. The method (50) according to any one of claims 12 to 15, wherein the information for configuring the first RA procedure type failure criterion includes a maximum number of failed attempts when using the first RA procedure type.

17. The method (50) according to any one of claims 12 to 16, wherein the information for configuring the first RA procedure type failure criterion is determined based on a load level of the BS.

18. The method (50) according to any one of claims 12 to 17, wherein the information for configuring the first RA procedure type failure criterion is transmitted in an uplink transmission triggering signal used to trigger an uplink transmission by the wireless device.

19. The method (50) according to claim 18, wherein the uplink transmission triggering signal is a paging message and/or a wake-up signal that transitions the wireless device from a sleep mode to an active mode.

20. The method (50) according to any one of claims 12 to 19, 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.

21. A base station, BS (30), comprising at least one memory and at least one processor configured to carry out a method (50) according to any one of claims 12 to 20.

22. A wireless communication system comprising at least one base station (30) according to claim 21 and at least one user equipment (20) according to claim 11 .