Method and apparatus for improving the use of contention-based uplink resources by ambient IoT devices

Abstract

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

Description

Technical area

[0001] The present disclosure relates to wireless communication systems, and more particularly, to methods and apparatus for improving the utilization of contention-based uplink resources by wireless devices harvesting ambient power. background

[0002] The Internet of Things (IoT) enables various devices to connect to the internet to send data, receive instructions, or both. Tens of billions of IoT devices are already deployed, and the global number of IoT devices is expected to grow rapidly. Thus, massive connectivity is required. However, powering these billions of IoT devices presents a critical challenge, and deploying power cables or regularly replacing / recharging batteries is not a practical solution.

[0003] 3GPP (Third Generation Partnership Project) is currently investigating new IoT technologies to open up new markets within 3GPP systems. These technologies can provide orders of magnitude higher connection counts and / or device density than existing 3GPP IoT technologies, and can provide orders of magnitude lower complexity and power consumption than existing 3GPP technologies, such as narrow-band IoT (NB-IoT) and long-term evolution-machine-type communications (LTE-MTC). Specifically, 3GPP currently defines ambient (A-loT) technologies (see, for example, technical report TR 38.848 V18.0).0) aiming to enable very low-power IoT devices, which could be either battery-less devices without energy storage capability (performing backscatter transmission) or devices with an energy storage that does not need to be manually replaced or recharged (performing wireless ambient energy harvesting (EH) from one or more energy sources).

[0004] By "very low-power" or "A-IoT" devices, the authors mean devices with a peak power consumption of less than 1 mW, or even less than 100 µW, or less than 10 µW. For example, Ambient IoT currently aims to enable A-IoT devices that have the following characteristics: - about 1 µW peak power consumption with energy storage, with neither DL (downlink) nor UL (uplink) amplification in the device (the UL transmission of the device is backscattered on an externally provided carrier wave), - below a few hundred µW peak power consumption with energy storage, with DL and / or UL amplification in the device (the UL transmission of the device can be generated internally by the device or backscattered on an externally provided carrier wave).

[0005] In some cases, such A-IoT devices can only initiate an uplink transmission when triggered by the radio access network (RAN). This also applies to contention-based uplink resources. By "contention-based uplink resources," the authors mean uplink resources shared by multiple wireless devices, on which each of these wireless devices can transmit uplink data at its own discretion. Therefore, this uplink data may collide with uplink data from other wireless devices with which these uplink resources are shared. Examples of contention-based resources include random-access channel (RACH) uplink resources or configured-grant (CG) shared uplink resources.

[0006] However, with an increase in the number of deployed A-IoT devices, the risk of collisions and congestion of contention-based uplink resources increases. Likewise, in the case of numerous collisions due to A-IoT devices attempting to access contention-based uplink resources, the radio access network (RAN) would have to trigger retransmissions by the colliding A-IoT devices, which would increase the signaling overhead for the RAN. Brief description

[0007] The present disclosure aims to improve the situation. In particular, the present disclosure aims to address at least some of the limitations of the prior art discussed above. In particular, the present disclosure aims to propose a solution for reducing the risk of collisions between uplink data from wireless devices, such as A-IoT devices, that wish to access contention-based uplink resources.

[0008] To this end, it is proposed that the RAN transmit an uplink transmission trigger signal to a wireless device, indicating to the wireless device that it can only use a specific subset of contention-based uplink resources from the total set of contention-based uplink resources. This enables the RAN to reduce the collision probability by more precisely controlling the allocation of contention-based uplink resources.

[0009] According to a first aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, wherein the method is implemented by a wireless device of the wireless communication system, wherein the wireless device comprises an energy harvesting unit configured to convert ambient energy into electrical energy that is stored in an energy storage unit of the wireless device, wherein the wireless device further comprises a communication unit configured to exchange data with a radio access network (RAN) of the wireless communication system, the method comprising: - receiving a trigger signal for an uplink transmission from the RAN, wherein the trigger signal for an uplink transmission contains information describing a subset of contention-based uplink resources from a predetermined set of contention-based uplink resources assigned to the wireless device for performing an uplink transmission, - Transmitting uplink data to the RAN using contention-based uplink resources from the subset of contention-based resources.

[0010] In some embodiments, the method according to the first aspect may further comprise one or more of the following optional features, which are contemplated either alone or in a technically possible combination.

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

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

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

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

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

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

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

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

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

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

[0021] In some embodiments of the method according to the first aspect, the trigger signal for an uplink transmission is a signaling message specifically addressed to the wireless device or to a group of wireless devices including the wireless device.

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

[0023] In some embodiments of the method according to the first aspect, the energy harvesting unit is a radio unit configured to convert a received radio frequency signal into electrical energy.

[0024] According to a second aspect, the present disclosure relates to a wireless device comprising at least one memory and at least one processor configured to perform a method according to any one of the embodiments of the first aspect.

[0025] According to a third aspect, the present disclosure relates to a user equipment (UE) comprising a wireless device according to any one of the embodiments of the present disclosure.

[0026] According to a fourth aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, wherein the method is 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 comprising an energy harvesting unit configured to convert ambient energy into electrical energy that is stored in an energy storage unit of the wireless device, wherein the method comprises transmitting, to the wireless device, a trigger signal for an uplink transmission, wherein the trigger signal for an uplink transmission contains information that specifies a subset of contention-based uplink resources from a predetermined set of contention-based uplink resources,assigned to the wireless device for performing an uplink transmission.

[0027] In some embodiments, the method according to the fourth aspect may further comprise one or more of the following optional features, which are contemplated either alone or in a technically possible combination.

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

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

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

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

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

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

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

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

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

[0037] In some embodiments of the method according to the fourth aspect, the trigger signal for an uplink transmission is a signaling message specifically addressed to the wireless device or to a group of wireless devices including the wireless device.

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

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

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

[0041] According to a fifth aspect, the present disclosure relates to a base station (BS) comprising at least one memory and at least one processor configured to perform a method according to one of the embodiments of the fourth aspect.

[0042] According to a sixth aspect, the present disclosure relates to a wireless communication system comprising at least one base station according to one of the embodiments of the present disclosure and at least one user device according to one of the embodiments of the present disclosure.

[0043] According to a seventh aspect, the present disclosure relates to a computer program product comprising instructions that, when executed by at least one processor, configure the at least one processor to perform a method for exchanging data according to any of the embodiments of the present disclosure. The computer program product may use any programming language and may be in the form of source code, object code, or any form between source code and object code, such as in a partially compiled form, or in any other desired form.

[0044] According to an eighth aspect, the present disclosure relates to a (non-transitory) computer-readable storage medium comprising instructions that, when executed by at least one processor, configure the at least one processor to perform a method for transmitting control messages according to any one of the embodiments of the present disclosure. Short description of the drawings

[0045] The invention will be better understood upon reading the following description, given as a non-limiting example, with reference to the figures in which: - Fig. 1: schematic representations of various possible topologies of a wireless communication system, - Fig. 2: a schematic representation of an example of a wireless device, - Fig. 3: a schematic representation of an example of a BS, - Fig. 4 and Fig. 5: Flowcharts illustrating examples of methods for exchanging data implemented by a wireless device of a UE and a BS, respectively.

[0046] In these figures, reference numerals that are identical from one figure to another indicate identical or similar elements. For clarity, the elements shown are not to scale unless expressly stated otherwise. Detailed description

[0047] The following detailed description with reference to the figures is intended to be a description of various configurations and is not intended to represent the only configurations in which the presently described concepts 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 example, while this disclosure may use 3GPP terminology, e.g., from 5G NR, to explain embodiments herein, this should not be seen as limiting the scope of the present disclosure.

[0048] In general, all terms used herein should be interpreted according to their usual meaning in the relevant technical field, unless another meaning is clearly indicated and / or clear from the context in which it is used. All references to an element, facility, component, means, step, etc., should be interpreted as referring to at least one occurrence of the element, facility, component, means, step, etc., unless expressly stated otherwise.Likewise, the order of steps of any methods disclosed herein, particularly in the figures, is provided for illustrative purposes only and is not intended to limit the present disclosure, which may be applied with the same steps performed in a different order and / or with all or part of the steps performed in parallel or together, unless a step is expressly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Furthermore, steps depicted in a figure that are surrounded by a dashed line are to be considered optional for the embodiment depicted in that figure. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, as appropriate.Likewise, any advantage of one embodiment may apply to any other embodiment, and vice versa. Other objects, features, and advantages of the included embodiments will become apparent from the following description.

[0049] Fig. Figure 1 schematically illustrates an example of a wireless communication system, which may be, for example, a 5G NR wireless communication system. In particular, Fig. 1 depicts a RAN of the wireless communication system used to exchange data with UEs 20 via radio signals. The RAN can, for example, send data to the UEs 20 (DL - downlink), such as data received from a core network (CN - core network, not shown in the figures). The RAN can also receive data from the UEs 20 (UL - uplink), and this data can be forwarded to the CN.

[0050] In the Fig. In the example illustrated in Figure 1, the RAN includes a base station (BS) 30. Of course, the RAN may include more than one BS 30 to expand the coverage area of the wireless communication system. Each of these BSs may be referred to as an NB, eNodeB (or eNB), gNodeB (or gNB in the case of a 5G NR wireless communication system), an access point, or the like, depending on the wireless communication standard(s) implemented.

[0051] In the Fig. In the example illustrated in Figure 1, only one UE 20 is shown, 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 Fig. Figure 1 schematically illustrates an example in which the UE 20 exchanges data (payload 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 Fig. Figure 1 schematically illustrates an example in which the UE 20 exchanges data (payload 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 can be, for example, a relay, an IAB (integrated access and backhaul) node, another UE 20, a repeater, a reconfigurable intelligent surface (RIS), etc.

[0052] Fig. 2 schematically illustrates an example of a wireless device 25 suitable for implementing any method discussed in the present disclosure and performed on a UE 20. Essentially, the wireless device 25 corresponds to a device that provides wireless connectivity to the RAN of the wireless communication system and that can be used to exchange data with the RAN. The wireless device 25 is, for example, an A-IoT device, i.e., a wireless device that has a peak power consumption of less than 1 mW, or even less than 100 µW, or even less than 10 µW.

[0053] Such a wireless device 25 may be incorporated in a UE 20 as shown by Fig. 2. The UE 20 may be, for example, a mobile 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 (IoT) device, such as a wireless camera, a smart sensor, a smart meter, smart glasses, a (manned or unmanned) vehicle, a Global Positioning System device, etc., or any other device capable of executing applications that require exchanging data with remote receivers via the wireless device 25.

[0054] As through Fig. 2, the wireless device 25 includes one or more processors 250 and one or more memories 251. The one or more processors 250 may include, for example, 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 non-volatile memory (magnetic hard drive, solid state memory, 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-encoded 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 on the side of a UE according to any of the embodiments disclosed herein.

[0055] As through Fig. As illustrated in Figure 2, the wireless device 25 also includes 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 example, be a 3G, 4G, 5G, NR, WiFi, WiMax, etc., transceiver or the like. In preferred embodiments, the (wireless) communication unit 253 includes a 5G NR wireless communication unit.

[0056] As discussed above, in some examples, communication unit 253 may include neither DL (downlink) nor UL (uplink) amplification capability (the UL transmission is backscattered on an externally provided carrier wave). In other examples, communication unit 253 may include DL and / or UL amplification (the UL transmission may be generated internally by the wireless device or backscattered on an externally provided carrier wave).

[0057] As through Fig. 2, the wireless device 25 also includes an energy harvesting unit 254 and a wireless device energy storage unit 255.

[0058] The energy storage unit 255 may be any type of electrical energy accumulator and may include, for example, one or more capacitors, one or more batteries, etc. The energy storage unit 255 is used to provide electrical energy to the other features of the wireless device 25 that require electrical energy, such as the one or more processors 250, the one or more memories 251, and in some cases, the (wireless) communication unit 253.

[0059] The energy harvesting unit 254 is configured to convert ambient energy into electrical energy, which is stored in the energy storage unit 255. By "ambient energy," the authors mean energy from energy sources external to the wireless device 25 that is received at the wireless device 25 without any wires between the energy sources and the wireless device 25. Thus, the energy harvesting unit 254 is configured such that the wireless device 25 can operate autonomously without the need to manually replace or recharge the energy storage unit 255. The energy harvesting unit 254 can, for example, collect energy from various energy sources, including solar, heat, motion or vibration, radio frequency (RF), etc.

[0060] In preferred embodiments, the energy harvesting unit 254 comprises at least one radio unit configured to convert RF signals into electrical energy, which is stored in the energy storage unit 255. These RF signals may, for example, be external RF signals, i.e., RF signals that do not originate from within the wireless communication system itself, but from RF sources located outside 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, the RF signals may originate from within the wireless communication system, for example, from BSs 30 of the RAN that may transmit an energy harvesting (RF) signal to wireless (A-IoT) devices 25 within their coverage area, and / or from devices separate from the BSs 30 but deployed to enable energy harvesting on the wireless (A-IoT) devices 25 of the wireless communication system. In some examples, if RF signals are used to feed electrical energy to the energy storage unit 255, the energy harvesting unit 254 may be included in the (wireless) communication unit 253.

[0061] Fig. 3 schematically illustrates an example of a BS 30 suitable for implementing a method discussed in the present disclosure as well as performed by the RAN.

[0062] As through Fig. 3, the OS 30 includes one or more processors 300 and one or more memories 301. The one or more processors 300 may include, for example, 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 memory (magnetic hard disk, solid state memory, 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 program-encoded 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 on the RAN side according to any of the embodiments disclosed herein.

[0063] As through Fig. 3, the BS 30 also includes a wireless communication unit 303 configured to exchange data with UEs 20 using radio signals, and in particular with (wireless) communication units 253 of wireless devices 25 included in these UEs 20. The wireless communication unit 303 may, for example, 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 includes a 5G NR transceiver. In some examples, the wireless communication unit 303 may also transmit carrier waves to the wireless devices 25, performing uplink transmissions with backscatter.

[0064] As through Fig. As illustrated in Figure 3, in some examples, the BS 30 may also include 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 fiber optic) and / or wireless.

[0065] As through Fig. 3, in some examples, the BS 30 may also include an energy harvesting signal generator 305 that generates energy harvesting (RF) signals that enable wireless devices 25 in its coverage area to feed electrical energy into their energy storage units 255 via their energy harvesting units 254. The energy harvesting (RF) signals may take any suitable form that enables 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 is a specific and non-limiting embodiment of the present disclosure. As noted above, such energy harvesting (RF) signals may, where appropriate, alternatively or in combination, be generated by other devices separate from the RAN's BSs 30.

[0066] As discussed above, the present disclosure aims to enable the RAN to reduce the probability of collisions by more precisely controlling the allocation of contention-based uplink resources to the wireless devices 25 in its coverage area. To this end, it is proposed that the set of contention-based uplink resources be divided into different subsets that can be allocated by the RAN to different wireless devices 25, with the allocated subset being communicated when the RAN initiates an uplink transmission by a wireless device 25.

[0067] The authors now present examples of signaling and decision strategies that can be implemented to reduce the collision probability for contention-based uplink resources.

[0068] Fig. 4 illustrates a diagram showing steps of an exemplary embodiment of a method 40 for exchanging data implemented by a wireless device 25 of a UE 20. Fig. 5 illustrates a diagram showing respective steps of an exemplary embodiment of a method 50 for exchanging data implemented by a BS 30 of the RAN.

[0069] As through Fig. 4, the method 40 for exchanging data includes a step S40 of receiving a trigger signal for an uplink transmission from the RAN.

[0070] To reduce its electrical power consumption, the wireless device 25 may be placed in a sleep mode. In such a case, the wireless device 25 must transition to an active mode to be able to perform the uplink data transmission. Such a transition may be triggered by the RAN sending a wake-up signal to the wireless device 25. In such a case, the trigger signal for an uplink transmission may correspond to the wake-up signal that transitions the wireless device 25 from a sleep mode to an active mode, or it may be transmitted by the RAN after it transmits a wake-up signal to the wireless device 25. Using the same signal for the wake-up signal and the trigger signal for an uplink transmission reduces the signaling overhead for the RAN compared to using separate signals.

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

[0072] By "contention-based uplink resources," the authors mean uplink resources shared by a plurality of wireless devices 25, on which each of these wireless devices 25 may transmit messages at its own discretion, and therefore these messages may collide with messages from other wireless devices 25 with which these uplink resources are shared.

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

[0074] Other examples of contention-based uplink resources in, for example, a 5G NR wireless communication system include shared uplink resources with a configured grant (CG). Such shared CG uplink resources are assigned, for example, to wireless devices 25 in the RRC_CONNECTED state. By "shared," the authors mean that these CG uplink resources can be shared by a plurality of wireless devices. However, a 5G NR wireless communication system can also assign dedicated CG uplink resources to a specific wireless device 25 in the RRC_CONNECTED state, which are intended to be used only by that specific wireless device 25 and are therefore not contention-based uplink resources.

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

[0076] It is noted that any suitable format may be used for the uplink transmission trigger signal, and that the selection of a specific format for the uplink transmission trigger signal corresponds to a specific, but non-limiting, embodiment of the present disclosure. For example, the uplink transmission trigger signal may be a signaling message specifically addressed to wireless device 25 or to a group of wireless devices including wireless device 25, in which case the same subset of contention-based uplink resources is allocated to a group of wireless devices 25.

[0077] Therefore, the uplink transmission trigger signal informs wireless device 25 of the subset of contention-based uplink resources it is permitted to use from the total set of contention-based uplink resources. In other words, wireless device 25 is not permitted to use the other contention-based uplink resources of the set that are not included in the subset notified by the uplink transmission trigger signal.

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

[0079] For example, with shared CG uplink resources, the set of shared CG uplink resources may include a set of shared CG opportunities, and the subset of shared CG uplink resources may consist of some of the upcoming shared CG opportunities. Thus, the wireless device 25 is authorized to use only some of the upcoming shared CG opportunities. For example, the set of shared CG opportunities corresponds to repeated time and frequency resources allocated by the RAN as shared CG uplink resources. Thus, the subset of shared CG uplink resources may correspond to some of these repeated time and frequency uplink resources, such that the shared CG opportunities that the wireless device 25 is authorized to use are limited in time and / or frequency with respect to all uplink resources allocated as shared CG uplink resources.

[0080] For example, for RACH uplink resources, the set of RACH uplink resources may include a set of random access opportunities and / or a set of random access preambles. Thus, the subset of RACH uplink resources may consist of some of the upcoming shared random access opportunities and / or some of the random access preambles.

[0081] For example, the set of random access opportunities corresponds to repeated time and frequency resources allocated by the RAN as RACH uplink resources. Thus, the subset of RACH uplink resources may correspond to some of these repeated time and frequency uplink resources, so that the random access opportunities that wireless device 25 may use are limited in time and / or frequency relative to all uplink resources allocated as random access uplink resources.

[0082] For example, the set of random access preambles corresponds to a set of 64 random access preambles from which the wireless device 25 can select a single random access preamble to initiate a random access procedure with a BS 30 of the RAN. Thus, the subset of RACH uplink resources may correspond to some of these 64 random access preambles, so that the random access preambles that the wireless device 25 may use are limited to fewer than 64 random access preambles. For example, the subset of RACH uplink resources may only include, for example, 8 or 16 of the 64 random access preambles.

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

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

[0085] Similarly, in the case of shared CG opportunities, the subset of contention-based uplink resources may include one or more shared CG opportunities. For example, wireless device 25 may use different shared CG opportunities to transmit uplink data related to different traffic classes. In other examples, wireless device 25 may use multiple shared CG opportunities to perform uplink data retransmission.

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

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

[0088] In preferred embodiments, the information describing the subset of contention-based uplink resources corresponds to a subset identifier that identifies a specific subset of contention-based uplink resources from a plurality of predetermined subsets of contention-based uplink resources. Thus, in such examples, it is sufficient to include the subset identifier in the trigger signal for an uplink transmission, thereby limiting the amount of data to be included in each trigger signal for an uplink transmission. The wireless device 25 must be previously preconfigured with an association between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers. In the non-limiting example of Fig. 4, the method 40 for exchanging data includes an optional prior step S43 of receiving this mapping from the RAN. For example, the mapping between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers may be received in system information broadcast by the RAN and / or in a signaling message specifically addressed to the wireless device 25 or to a group of wireless devices including the wireless device 25. It is noted that in some examples, it is possible to use different mappings (between subsets of contention-based uplink resources and subset identifiers) for different wireless devices 25 or different groups of wireless devices 25.

[0089] In some examples, the trigger signal for an uplink transmission may also include additional information regarding the use of the contention-based uplink resources.

[0090] For example, the trigger signal for an uplink transmission may include a backoff timer value to be used by the wireless device 25 to delay the uplink data transmission when using the subset of contention-based uplink resources. For example, in the case of RACH uplink resources, the RAN may provide a backoff timer used to delay the transmission of the selected random access preamble at the selected random access opportunity. For example, the RAN may provide different backoff timers to wireless devices 25 that are permitted to use the same subset of random access uplink resources to reduce the probability of collision between uplink transmissions from those wireless devices 25.

[0091] Alternatively, or in combination, the uplink transmission trigger signal may include a validity period for the allocation of the subset of contention-based uplink resources. Thus, upon receiving the uplink transmission trigger signal, the wireless device 25 may only use the specified subset during the validity period. For example, the wireless device 25 may start a timer set to the validity period, and once the timer expires, the wireless device 25 may no longer use the allocated subset of contention-based uplink resources. For example, once the timer expires, the wireless device 25 may need to receive another uplink transmission trigger signal before attempting another uplink data transmission.It is noted that such a validity period may also be preconfigured at the wireless device, e.g., predefined (e.g., specified by a standard) or previously received from the RAN (e.g., in system information broadcast by the RAN or in a signaling message specifically addressed to the wireless device 25 or to a group of wireless devices including the wireless device 25).

[0092] As discussed above, Fig. 5 is a diagram illustrating corresponding steps of an exemplary embodiment of a method 50 for exchanging data that may be implemented by a BS 30 when the wireless device 25 executes the method 40 for exchanging data that may be implemented by Fig. 4 is implemented.

[0093] As through Fig. 5, the method 50 for exchanging data includes a step S50 of transmitting, to the wireless device 25, a trigger signal for an uplink transmission (received by the wireless device 25 at step S40).

[0094] As discussed above, any suitable format may be used for the uplink transmission trigger signal, and the selection of a specific format for the uplink transmission trigger signal corresponds to a specific, but non-limiting, embodiment of the present disclosure. It is also noted that in some examples, the uplink transmission trigger signal may correspond to the wake-up signal transitioning wireless device 25 from a sleep mode to an active mode, or it may be transmitted by the RAN after it transmits a wake-up signal to wireless device 25. Also, the uplink transmission trigger signal may be a signaling message specifically addressed to a wireless device 25 or to a group of wireless devices 25.

[0095] As discussed above, the uplink transmission trigger signal includes information describing a subset of contention-based uplink resources from a predetermined set of contention-based uplink resources allocated to wireless device 25 for performing an uplink transmission. As discussed above, the set of contention-based uplink resources includes, for example, RACH uplink resources (random access preambles, random access opportunities, etc.) and / or shared CG uplink resources. Furthermore, in some examples, the uplink transmission trigger signal may also include additional information regarding the use of the contention-based uplink resources (e.g., backoff timers, validity periods, etc.).

[0096] In the Fig. 5, it is assumed in a non-limiting way that the information describing the subset of contention-based uplink resources is transmitted as a subset identifier, and the method 50 for exchanging data comprises an optional prior step S51 of transmitting, to the wireless device 25, prior to transmitting the trigger signal for an uplink transmission, an association between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers.

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

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

[0099] Alternatively, or in combination, the BS 30 may select the subset of contention-based uplink resources based on a load level of the BS. Thus, the method 50 for exchanging data may include a step (not shown in the figures) of estimating a (current or future) load level of the BS 30, and the subset of contention-based uplink resources may be selected based on the estimated load level. The load level represents the amount of traffic that the BS 30 must handle, e.g., in its entire coverage area (radio cell) or in a given beam, etc. For example, the load level may correspond to: a total number of UEs 20 having data to exchange with the BS 30, a total amount of uplink data to be received by the BS 30 from multiple UEs 20, etc.For example, the BS 30 may reduce the amount of contention-based uplink resources of a subset to be used for low priority uplink data when the load level is high (e.g., close to congestion) compared to when the load level is low.

[0100] For example, in examples where the BS 30 includes an energy harvesting signal generator 305, the BS 30 may begin transmitting an energy harvesting (RF) signal to the wireless device 25 before transmitting the trigger signal for an uplink transmission to the wireless device 25 (in Fig. 5 not shown).

[0101] It is emphasized that the present disclosure is not limited to the above exemplary embodiments. Variants of the above exemplary embodiments also fall within the scope of the present disclosure.

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, the wireless device comprising an energy harvesting unit (254) configured to convert ambient energy into electrical energy that is stored in an energy storage unit (255) of the wireless device, the wireless device further comprising a communication unit (253) configured to exchange data with a radio access network (RAN) of the wireless communication system, the method comprising: - (S40) receiving a trigger signal for an uplink transmission from the RAN, wherein the trigger signal for an uplink transmission contains information describing a subset of contention-based uplink resources from a predetermined set of contention-based uplink resources assigned to the wireless device for performing an uplink transmission, - (S42) Transmitting uplink data to the RAN using contention-based uplink resources from the subset of contention-based resources. [2] The method (40) of claim 1, wherein the set of contention-based uplink resources includes random access channel (RACH) uplink resources to be used by the wireless device entity to establish communication with the RAN. [3] The method (40) of claim 2, wherein the set of RACH uplink resources includes a set of random access preambles and the subset of RACH uplink resources includes a subset of the set of random access preambles. [4] The method (40) of any one of claims 2 to 3, wherein the set of RACH uplink resources includes a set of random access opportunities and the subset of RACH uplink resources includes a subset of the set of random access opportunities. [5] The method (40) of claim 4, wherein the subset of random access opportunities includes a plurality of random access opportunities. [6] The method (40) of claim 5, wherein the wireless device performs uplink data repetition when the subset of random access opportunities includes a plurality of random access opportunities. [7] The method (40) of any one of claims 2 to 6, wherein the uplink transmission trigger signal includes a backoff timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources. [8] The method (40) of claim 1, wherein the set of contention-based uplink resources includes configured grant (CG) shared uplink resources to be used by the wireless device to transmit uplink data to the RAN. [9] The method (40) of any preceding claim, wherein the trigger signal for an uplink transmission includes a validity period for the allocation of the subset of contention-based uplink resources. [10] The method (40) of any preceding claim, wherein the information describing the subset of contention-based uplink resources corresponds to a subset identifier that identifies a specific subset of contention-based uplink resources from a plurality of predetermined subsets of contention-based uplink resources. [11] The method (40) of claim 10, comprising receiving (S43), from the RAN, an association between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers. [12] The method (40) of any preceding claim, wherein the trigger signal for an uplink transmission is a signaling message specifically addressed to the wireless device or to a group of wireless devices including the wireless device. [13] The method (40) of any preceding claim, wherein the trigger signal for an uplink transmission is a wake-up signal transitioning the wireless device from a sleep mode to an active mode or a signaling message received after receiving a wake-up signal. [14] A wireless device (25) comprising at least one memory and at least one processor configured to perform a method (40) according to any one of the preceding claims. [15] A user equipment (UE) (20) comprising a wireless device according to claim 14. [16] A method (50) for exchanging data in a wireless communication system, the method being implemented by a base station (BS) (30) of a radio access network (RAN) of the wireless communication system, the BS being configured to exchange data with a wireless device (25) comprising an energy harvesting unit (254) configured to convert ambient energy into electrical energy that is stored in an energy storage unit (255) of the wireless device, the method comprising transmitting (S50) to the wireless device (25) a trigger signal for an uplink transmission, the trigger signal for an uplink transmission containing information that specifies a subset of contention-based uplink resources from a predetermined set of contention-based uplink resources,assigned to the wireless device for performing an uplink transmission. [17] The method (50) of claim 16, wherein the set of contention-based uplink resources includes random access channel (RACH) uplink resources to be used by the wireless device entity to establish communication with the RAN. [18] The method (50) of claim 17, wherein the set of RACH uplink resources includes a set of random access preambles and the subset of RACH uplink resources includes a subset of the set of random access preambles. [19] The method (50) of any one of claims 17 to 18, wherein the set of RACH uplink resources includes a set of random access opportunities and the subset of RACH uplink resources includes a subset of the set of random access opportunities. [20] The method (50) of claim 19, wherein the subset of random access opportunities includes a plurality of random access opportunities. [21] The method (50) of any one of claims 17 to 20, wherein the uplink transmission trigger signal includes a backoff timer value to be used by the wireless device to delay the uplink transmission when using the subset of RACH uplink resources. [22] The method (50) of claim 16, wherein the set of contention-based uplink resources includes configured grant (CG) shared uplink resources to be used by the wireless device to transmit uplink data to the RAN. [23] The method (50) of any one of claims 16 to 22, wherein the trigger signal for an uplink transmission includes a validity period for the allocation of the subset of contention-based uplink resources. [24] The method (50) of any one of claims 16 to 23, wherein the information describing the subset of contention-based uplink resources corresponds to a subset identifier that identifies a specific subset of contention-based uplink resources from a plurality of predetermined subsets of contention-based uplink resources. [25] The method (50) of claim 24, comprising transmitting (S51), to the wireless device, an association between a plurality of different subsets of contention-based uplink resources and a plurality of respective subset identifiers. [26] The method (50) of any one of claims 16 to 25, wherein the trigger signal for an uplink transmission is a signaling message specifically addressed to the wireless device or to a group of wireless devices including the wireless device. [27] The method (50) of any one of claims 16 to 26, wherein the trigger signal for an uplink transmission is a wake-up signal that transitions the wireless device from a sleep mode to an active mode, or is a signaling message transmitted after transmitting a wake-up signal. [28] The method (50) of any one of claims 16 to 27, comprising selecting (S52) the subset of contention-based uplink resources allocated to the wireless device from the set of contention-based uplink resources based on at least one property of uplink data to be transmitted by the wireless device and / or based on a load level of the BS. [29] Base station (BS - base station) (30) comprising at least one memory and at least one processor configured to carry out a method (50) according to any one of claims 16 to 28. [30] A wireless communication system comprising at least one base station (30) according to claim 29 and at least one user device (20) according to claim 15. [31] A computer program product (252, 302) comprising instructions that, when executed by at least one processor, configure the at least one processor to perform a method (40) according to any one of claims 1 to 13 or a method (50) according to any one of claims 16 to 28. [32] A computer-readable storage medium comprising instructions that, when executed by at least one processor, configure the at least one processor to perform a method (40) according to any one of claims 1 to 13 or a method (50) according to any one of claims 16 to 28.

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