Method and device for performing energy saving in a UE initiating an uplink transmission when performing discontinuous reception

Abstract

The present disclosure relates to methods and devices for enabling a user equipment, UE (20), to reduce its energy consumption during a discontinuous reception, DRX, cycle when the UE needs to initiate an uplink, UL, transmission.

Description

Method and device for performing energy saving in a UE initiating an uplink transmission when performing discontinuous receptionTechnical field

[0001] The present disclosure relates to wireless communication systems and relates more specifically to methods and devices for saving energy on a user equipment, UE, side of the wireless communication system.Background

[0002] To reduce energy consumption, discontinuous reception, DRX, has been introduced in 3GPP (Third Generation Partnership Project) wireless communication systems. Basically, in DRX, the UE periodically goes to sleep for an asleep duration during which a physical downlink control channel, PDCCH, is not monitored before waking up for an awake duration to monitor the PDCCH for possible downlink control data. The amount of energy that can be saved depends on how long and how often the UE remains asleep. Of course, the longer the UE remains asleep, the greater the amount of energy saved.

[0003] To enhance energy savings without sacrificing latency in 5G or New Radio (NR) wireless communication systems, 3GPP is willing to define a new architecture for UEs (see e.g., the technical report TR 38.869).

[0004] Basically, current UEs need to periodically wake up once per DRX cycle, which dominates the energy consumption in periods with no signaling or data traffic. If UEs were able to wake up only when they are triggered, e.g., paging, energy consumption could be dramatically reduced. As investigated by 3GPP, this is achieved by providing the UE with both a main radio, MR, unit, and a low power wake-up receiver, LP-WUR.

[0005] Basically, the MR unit corresponds to the 5G NR wireless communication unit, and the LP-WUR corresponds to a wireless communication unit that is used to monitor a wakeup signal with low power consumption. Once the wake-up signal is detected, the LP-WUR can trigger the MR unit which can transition from a low power state to an active state.

[0006] The active state corresponds to a state in which the MR unit can exchange data with a radio access network, RAN, of the wireless communication system. The low power state corresponds to any state in which the MR unit cannot exchange data with the RAN.

[0007] By “low power” state, we mean that the mean power consumption of the MR unit in the low power state is lower than (and preferably significantly lower than, e.g., ten times or even a hundred times lower than) the mean power consumption of the MR unit in the active state.

[0008] By “low power” wake-up receiver, we mean that the LP-WUR is used for receiving a wake-up signal while the MR unit is in a low power state. Of course, the monitoring of thewake-up signal should be done with a low power consumption, and the mean power consumption of the LP-WUR should therefore be lower than (and preferably significantly lower than, e.g., ten times or even a hundred times lower than) the mean power consumption of the MR unit when it is in the active state.

[0009] Hence, the energy consumption is reduced by placing the MR unit in a low power state (e.g., turned off). The MR unit is not required to wake-up periodically and may wakeup only when triggered by the LP-WLIR. Since the LP-WLIR may monitor the wake-up signal continuously, or at least frequently, the MR unit can be possibly awakened by the LP-WLIR at any time, thereby further enabling low latency.

[0010] For example, the LP-WLIR may be used when the UE performs DRX. As discussed above, DRX is based on a DRX cycle which comprises a DRX active period, during which the UE needs to wake up for the awake duration, and a DRX inactive period, during which the UE goes to sleep for the asleep duration. Based on the DRX cycle, it is possible to use the LP-WUR to wake up the UE for the next DRX active period only when a wake-up signal is detected during the current DRX inactive period. If no wake-up signal is received during the DRX inactive period, then the UE may skip the next DRX active period, and the MR unit may remain in a low power state during the next DRX active period (without monitoring the PDCCH).

[0011] Hence, the LP-WUR may be used to wake-up the UE for a DRX active period only when the RAN intends to transmit control data to the UE, via the PDCCH, during this DRX active period.

[0012] However, the MR unit needs also to be placed in the active state to perform PDCCH monitoring after the UE has initiated an uplink, UL, transmission. For example, the UE may initiate an UL transmission by transmitting to the RAN a random preamble on a randomaccess channel, RACH, or by transmitting a scheduling request, SR, message to the RAN. After such an UL transmission (RACH or SR) is initiated by the UE, the UE needs to monitor the PDCCH with its MR unit in the active state (for receiving a random-access response, RAR, or an UL grant). However, such an UL transmission may be initiated by the UE even during a DRX inactive period, requiring the MR unit to be transitioned to the active state during this DRX inactive period.

[0013] Hence, there is a need for further reducing energy consumption.Summary

[0014] The present disclosure aims at improving the situation. In particular, the present disclosure aims at addressing at least some of the limitations of the prior art discussed above. In particular, the present disclosure aims at proposing a solution for reducing the energy consumption during DRX inactive periods of a DRX cycle.

[0015] In particular, the present disclosure aims at proposing a solution applicable even to UEs which are not equipped with an LP-WUR, in some embodiments at least.

[0016] 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 comprising a main radio, MR, unit configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the wireless device is configured with a discontinuous reception, DRX, cycle, wherein the DRX cycle comprises a DRX active period during which the MR unit may monitor a downlink, DL, for detecting a downlink, DL, transmission initiated by the RAN and a DRX inactive period during which the MR unit does not perform DL monitoring for detecting a DL transmission initiated by the RAN, wherein the method comprises, in response to the wireless device determining, during a current DRX inactive period, that an uplink, UL, transmission, is to be initiated by the wireless device: evaluating whether the UL transmission can be delayed to a following DRX active period, in response to determining that the UL transmission can be delayed to a following DRX active period: delaying the UL transmission to a following DRX active period, in response to determining that the UL transmission cannot be delayed to a following DRX active period: initiating the UL transmission during the current DRX inactive period.

[0017] 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.

[0018] In some embodiments of the method according to the first aspect, the MR unit is in a low power mode at the beginning of the DRX inactive period and, when the wireless device determines, during the current DRX inactive period, that an UL transmission is to be initiated by the wireless device: the MR unit is maintained in the low power mode in response to determining that the UL transmission can be delayed to a following DRX active period, the MR unit is transitioned to an active state during the current DRX inactive period in response to determining that the UL transmission cannot be delayed to a following DRX active period.

[0019] In some embodiments of the method according to the first aspect, the evaluating whether the UL transmission can be delayed to a following DRX active period comprises evaluating whether at least one following DRX active period is set to start within a predetermined time interval.

[0020] In some embodiments of the method according to the first aspect, different time intervals are associated respectively to different priority levels, and the evaluating whether the UL transmission can be delayed to a following DRX active period comprises: determining a priority level associated to the UL transmission to be initiated, selecting the time interval associated to the determined priority level.

[0021] In some embodiments of the method according to the first aspect, the priority level of the UL transmission to be initiated is determined based on a logical channel, LCH, for which the UL transmission is to be initiated.

[0022] In some embodiments of the method according to the first aspect, a high priority level is associated to a time interval having a greater duration than a time interval associated to a low priority level.

[0023] In some embodiments, the method according to the first aspect comprises receiving beforehand, from the RAN, a time interval configuration for each time interval.

[0024] In some embodiments of the method according to the first aspect, each time interval configuration is received in system information broadcasted by the RAN and / or in a radio resource control, RRC, message transmitted by the RAN.

[0025] In some embodiments of the method according to the first aspect: the wireless device comprises a low-power wake-up receiver, LP-WUR, configured to monitor a wake-up signal transmitted by the RAN and to trigger a transition of the MR unit to an active state in response to detecting a wake-up signal, the method comprises, in response to determining that a plurality of following DRX active periods is set to start within the time interval, the UL transmission is initiated in a following DRX active period selected among the plurality of following DRX active periods based on wake-up signal detection during the time interval.

[0026] In some embodiments of the method according to the first aspect, the following DRX active period selected among the plurality of following DRX active periods corresponds to: the DRX active period which immediately follows a DRX inactive period, within the time interval, during which a wake-up signal is detected by the LP-WUR, or, in response to not detecting a wake-up signal in a DRX inactive period within the time interval: the last following DRX active period among the plurality of following DRX active periods.

[0027] 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.

[0028] 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 presentdisclosure.

[0029] 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 main radio, MR, unit of a wireless device, wherein the BS is configured with a discontinuous reception, DRX, cycle, wherein the DRX cycle comprises a DRX active period during which the BS may initiate a downlink, DL, transmission to the MR unit of the wireless device and a DRX inactive period during which the BS cannot initiate a DL transmission to the MR unit of the wireless device, wherein the method comprises transmitting a time interval configuration to the wireless device for configuring in said wireless device a time interval, wherein the time interval is to be used by the wireless device to determine whether an uplink, UL, transmission to be initiated in a DRX inactive period can be delayed to a following DRX active period.

[0030] 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.

[0031] In some embodiments of the method according to the fourth aspect, the BS transmits to the wireless device different time interval configurations associated respectively to different priority levels.

[0032] In some embodiments of the method according to the fourth aspect, each time interval configuration is transmitted in system information broadcasted by the BS and / or in a radio resource control, RRC, message.

[0033] In some embodiments of the method according to the fourth aspect: the wireless device comprises a low-power wake-up receiver, LP-WLIR, configured to monitor a wake-up signal transmitted by the BS and to trigger a transition of the MR unit to an active state in response to detecting a wake-up signal, the method comprises, in response to determining that a DL transmission is to be initiated by the BS in a DRX active period which follows a current DRX inactive period: transmitting a wake-up signal to the wireless device in the current DRX inactive period.

[0034] 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.

[0035] 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 anyone of the embodiments of the present disclosure.

[0036] 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.

[0037] According to an eighth aspect, the present disclosure relates to a (non-transitory) computer-readable storage medium comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method for transmitting control messages according to any one of the embodiments of the present disclosure.Brief description of figures

[0038] 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 : a schematic representation of an example of wireless communication system comprising a BS and UEs,Figure 2: a schematic representation of an example of a wireless device, Figure 3: a schematic representation of an example of a BS,Figure 4: a flow chart illustrating an example of a method for exchanging data implemented by a wireless device of a UE,Figure 5: schematic representations of different scenarios for an example involving a time interval for evaluating whether an UL transmission can be delayed,Figure 6: schematic representations of an example involving different time intervals for evaluating whether an UL transmission can be delayed,Figure 7: schematic representations of different scenarios for an example involving wake-up signal detection for selecting a following DRX active period for initiating a delayed UL transmission,Figure 8: a flow chart illustrating an example of a method for exchanging data implemented by a BS.

[0039] 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

[0040] The detailed description set forth below, with reference to the figures, is intended asa description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For instance, although 3GPP terminology, from e.g., 5G NR, may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the present disclosure.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In the example illustrated by figure 1 , two UEs 20 are represented. The UEs 20 arelocated in a coverage 31 of the BS 30. The coverage 31 of the BS 30 corresponds for example to the area in which UEs can decode a PDCCH transmitted by the BS 30.

[0045] 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.

[0046] 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. 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.

[0047] 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.

[0048] As illustrated by figure 2, the wireless device 25 comprises also a main radio, MR, unit 253. As discussed above, the MR unit 253 corresponds to a main wireless communication unit of the wireless device 25, used for exchanging data with BSs 30 of the RAN using radio signals. The MR 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 MR unit 253 corresponds to a 5G NR wireless communication unit.

[0049] As illustrated in the non-limitative example of figure 2, the wireless device 25 may optionally comprise a low power wake-up signal receiver, LP-WUR, 254.

[0050] It is emphasized that, unless stated otherwise, the embodiments of the present disclosure can be applied with a wireless device 25 having only a MR unit 253 and no LP- WUR 254. Of course, increased energy savings can be achieved with a LP-WUR 254, asdiscussed above. When present, the LP-WUR 254 corresponds to a secondary wireless communication unit of the wireless device 25, that is used to monitor a wake-up signal, transmitted by BSs 30 of the RAN, with low power consumption. The wake-up signal may take any form enabling it to be detected with low power consumption. Non-limitative examples for the wake-up signal and the LP-WLIR 254 are provided in the technical report TR 38.869. It should be noted that, in some examples, the wake-up signal can even be a specific 5G NR signal, for instance using a low-level modulation and coding scheme, MCS, in which case the LP-WLIR 254 can consist in the components of a 5G NR wireless communication unit strictly required to be able to detect such a specific 5G NR signal.

[0051] As discussed above, the purpose of the LP-WLIR 254 is mainly to monitor and detect a (DL) wake-up signal transmitted by the RAN of the wireless communication system. As such, the LP-WLIR 254 may be only unidirectional, i.e. , with only receiving capabilities (DL) and no transmitting capabilities (UL). However, in some examples, the LP-WLIR 254 may also have transmitting capabilities, such that it can also transmit (UL) data to the RAN.

[0052] As discussed above, the MR unit 253 may be placed in an active state or in a low power state.

[0053] The active state corresponds to any state in which the MR unit 253 can exchange data with the RAN.

[0054] The low power state corresponds to a state in which the MR unit 253 cannot exchange data with the RAN. For example, the low power state corresponds to the MR unit 253 being asleep. If the wireless device 25 comprises a LP-WUR 254, the MR unit 253 does not have to wake-up periodically in the low power state, and the MR unit 253 may be ultra- deeply asleep and may even be turned off since the LP-WUR 254 can be used to turn the MR unit 253 on. It should be noted that it is possible to consider different low power states for the MR unit 253, having different respective mean power consumptions. For example, it is possible to consider a very low power state, having the lowest mean power consumption, and one or more intermediate low power states having a mean power consumption greater than the mean power consumption of the very low power state. For example, the very low power state may correspond to the MR unit 253 being turned off, and an intermediate low power state may correspond to the MR unit 253 being asleep without being turned off.

[0055] It should be noted that, in some examples, the LP-WUR 254 (when present) may also be configured to trigger the MR unit 253 when other conditions are verified. For example, the LP-WUR 254 may be configured to trigger the MR unit 253 if a predetermined timer has expired without detecting a wake-up signal. Such a timer may be used to ensure that the wireless device 25 can return to the active state when e.g., the wireless device 25 has moved out of the coverage of the wake-up signal. Of course, the duration of this timershould be sufficiently high to ensure that the MR unit 253 can remain in a low power state over long periods.

[0056] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0057] 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 CPU, a DSP, an FPGA, an 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 program-code 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.

[0058] 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 MR 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 corresponds to a 5G NR transceiver.

[0059] As illustrated in the non-limitative example of figure 3, the BS 30 may optionally comprise a wake-up signal transmitter, WUT, 304, configured to transmit wake-up signals to UEs having a wireless device 25 which includes a LP-WUR 254. In the example illustrated by figure 3, the WUT 304 is represented as separate from the wireless communication unit 303. However, the WUT 304 may also be included in the wireless communication unit 303, e.g., if the wireless communication unit 303 is a 5G NR transceiver and if the wake-up signal is a specific 5G NR signal.

[0060] As discussed above for the LP-WUR 254, the purpose of the WUT 304, if present and separate from the wireless communication unit 30, is mainly to transmit a (DL) wakeup signal. As such, the WUT 304 may be only unidirectional, i.e., with only transmitting capabilities (DL) and no receiving capabilities (UL). However, in some examples, the WUT 304 may also have receiving capabilities, such that it can also receive (UL) data from a LP- WUR 254 of a UE 20.

[0061] As illustrated in the non-limitative example of figure 3, the BS 30 may optionally comprise a network communication unit 305, 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.

[0062] As discussed above, the present disclosure aims at further reducing energy consumption when performing discontinuous reception, DRX. It should be noted that DRX encompasses also extended DRX, eDRX, as defined by 3GPP. In DRX, the wireless device 25 operates according to a DRX cycle which comprises: a DRX active period during which the MR unit 253 of the wireless device 25 may monitor a DL for detecting a DL transmission initiated by the RAN (e.g., control data transmitted to the wireless device 25 via the PDCCH), and a DRX inactive period during which the MR unit 253 does not perform DL monitoring for detecting a DL transmission initiated by the RAN.

[0063] By DL transmission “initiated by the RAN” we mean that the DL transmission from the RAN is not triggered by a previous UL transmission from the wireless device 25.

[0064] When performing DL (e.g., PDCCH) monitoring during a DRX active period, the MR unit 253 is typically in the active state. In turn, when DL monitoring is not required (e.g., during a DRX inactive period), the MR unit 253 may be in a low power state.

[0065] In this DRX cycle context, the present disclosure relates to how uplink, UL, transmissions initiated by the wireless devices 25 can be managed to reduce energy consumption during DRX inactive periods.

[0066] By UL transmission “initiated by the wireless device” we mean that the UL transmission from the wireless device 25 is not triggered by a previous DL transmission from a BS 30 of the RAN. As discussed above, an UL transmission initiated by the wireless device 25 will typically trigger a DL transmission by the RAN, such that an UL transmission initiated by the wireless device 25 typically requires putting the MR unit 253 in the active state to perform DL (e.g., PDCCH) monitoring. The MR unit 253 may also be placed in the active state to perform the UL transmission initiated by the wireless device 25. However, in some examples, it is also possible to use the LP-WUR 254 to perform the UL transmission initiated by the wireless device 25 (provided an LP-WUR 254 is present and has transmitting capabilities).

[0067] Hence, in the prior art, if the wireless device 25 initiates an UL transmission during a DRX inactive period, the MR unit 253 may have to be placed in the active state during this DRX inactive period to perform at least DL (e.g., PDCCH) monitoring for a DL transmission triggered by the UL transmission initiated by the wireless device 25, which increases the energy consumption during the DRX inactive period.

[0068] To reduce the energy consumption during DRX inactive periods due to UL transmissions to be initiated by the wireless device 25, it is proposed to try and delay the UL transmission to a following DRX active period when possible. Indeed, since the MR unit253 may have to be placed in the active state for the purpose of performing DL monitoring for detecting DL transmissions initiated by the RAN during the DRX active periods, it is possible to benefit from this placement in the active state to further perform DL monitoring for DL transmissions triggered by the UL transmission initiated by the wireless device 25. If the UL transmission can be delayed, it is therefore possible to reduce the energy consumption during the DRX inactive period and to make a more efficient use of the DRX active period during which the MR unit 253 may be placed in the active to perform DL monitoring for both detecting DL transmissions initiated by the RAN and receiving DL transmissions responding to the UL transmission initiated by the wireless device 25.

[0069] 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 8 represents a diagram showing corresponding steps of an exemplary embodiment of a method 80 for exchanging data, which is implemented by a BS 30 of the RAN.

[0070] As illustrated by figure 4, the method 40 for exchanging data comprises a step S40 of determining, during a current DRX inactive period, that an UL transmission is to be initiated by the wireless device 25. For example, the UE 20 may have data, related to an application layer running in the UE 20, that needs to be transmitted to the RAN. In such a case, the UE 20 may notify the wireless device 25 that it needs to transmit data to the RAN, and such a notification from the application layer of the UE 20 may be used to determine that an UL transmission is to be initiated by the wireless device 25.

[0071] As illustrated by figure 4, the method 40 for exchanging data comprises a step S41 of evaluating whether the UL transmission can be delayed to a following DRX active period.

[0072] If it is determined that the UL transmission can be delayed to a following DRX active period (reference S41a in figure 4), then the method 40 for exchanging data comprises a step S42 of delaying the UL transmission to a following DRX active period and, once in said following DRX active period, a step S43 of initiating the UL transmission. As discussed above, in some examples, the step S43 of initiating the UL transmission may comprise transmitting a random preamble in the RACH or transmitting a SR message to the RAN. Indeed, the SR procedure enables a wireless device 25 to request UL resources for transmitting data to the RAN. For that purpose, the wireless device 25 may be allocated with SR (UL) resources which may be used to transmit an UL request (SR message, for requesting additional UL resources for an upcoming transmission). Such SR resources can for example be allocated by the RAN to a wireless device 25 in a radio resource control, RRC, connected state (RRC_CONNECTED) or in an RRC inactive state (RRCJNACTIVE).

[0073] In turn, if it is determined that the UL transmission cannot be delayed to a following DRX active period (reference S41 b in figure 4), then the method 40 of exchanging datacomprises a step S44 of initiating the UL transmission during the current DRX inactive period. As discussed above, in some examples, the step S44 of initiating the UL transmission may similarly comprise transmitting a random preamble in the RACH or transmitting a SR message to the RAN.

[0074] In general, the MR unit 253 of the wireless device 25 will be in a low power state during the current DRX inactive period when it is determined that an UL transmission is to be initiated. If it is determined that the UL transmission can be delayed (reference S41a in figure 4), then the MR unit 253 may be maintained in a low power state during the step S42 of delaying the UL transmission to a following DRX active period, and the MR unit 253 may be transitioned to the active state only during said following DRX active period. If it is determined that the UL transmission cannot be delayed (reference S41 b in figure 4), then the MR unit 253 may be transitioned to the active state during the step S44 of initiating the UL transmission during the current DRX inactive state e.g., to initiate the UL transmission and to perform DL monitoring for a DL transmission responding to the initiated UL transmission.

[0075] Different methods may be used to evaluate whether an UL transmission to be initiated may be delayed to a following DRX active period, and the choice of a specific method corresponds to a specific but non-limitative embodiment of the present disclosure.

[0076] For example, the evaluating of whether the UL transmission can be delayed to a following DRX active period may be based on a predetermined time interval having e.g., a predetermined duration. For example, the time interval may be started once it is determined that an UL transmission needs to be initiated by the wireless device 25. If at least one following DRX active period is set to start within this time interval (i.e. , the time interval is set to end after the beginning of at least one following DRX active period), then it may be considered that the UL transmission can be delayed to a following DRX active period (reference S41a in figure 4). In turn, if no following DRX active period is set to start within this time interval (i.e., the time interval is set to end before the beginning of any following DRX active period), then it may be considered that the UL transmission cannot be delayed to a following DRX active period (reference S41b in figure 4).

[0077] Figure 5 represents schematically different scenarios involving such a predetermined time interval. In figure 5, the time interval considered is assumed to have a duration AT and to be started at a time TO in the current DRX inactive period when it is determined that an UL transmission is to be initiated by the wireless device 25.

[0078] In the example illustrated by part a) of Figure 5, the time interval ends before the beginning of the DRX active period that immediately follows the current DRX inactive period. In such a case it is determined that the UL transmission cannot be delayed to a followingDRX active period (reference S41 b in figure 4).

[0079] In the example illustrated by part b) of Figure 5, the time interval ends during the DRX active period that immediately follows the current DRX inactive period. In such a case it is determined that the UL transmission can be delayed to the DRX active period that immediately follows the current DRX inactive period (reference S41a in figure 4).

[0080] In the example illustrated by part c) of Figure 5, a plurality of following DRX active periods are set to start within the time interval (i.e., before TO + AT). In such a case it is determined that the UL transmission can be delayed to a following DRX active period (reference S41a in figure 4). Since a plurality of following DRX active periods are set to start within the time interval, the UL transmission may be initiated in any following DRX active period selected among said plurality of following DRX active periods. The selection of a following DRX active period in such a case is further discussed hereinbelow.

[0081] In some cases, it is possible to consider different time intervals, e.g., having different predetermined durations, when evaluating whether the UL transmission can be delayed to a following DRX active period.

[0082] Figure 6 represents schematically an example involving different predetermined time intervals. More specifically, in figure 6, three different time intervals are considered: a first time interval having a duration AT 1 , a second time interval having a duration AT2 greater than AT 1 , a third time interval having a duration AT3 greater than AT2.

[0083] In the example illustrated by figure 6, each time interval is started at a time TO in the current DRX inactive period when it is determined that an UL transmission is to be initiated by the wireless device 25.

[0084] Part a) of figure 6 represents the case where the first time interval is considered. As illustrated by part a) of figure 6, the first time interval ends before the beginning of any following DRX active period. Accordingly, when considering the first time interval, it is determined that the UL transmission cannot be delayed (reference S41b in figure 4).

[0085] Part b) of figure 6 represents the case where the second time interval is considered. As illustrated by part b) of figure 6, the second time interval ends during the DRX active period that immediately follows the current DRX inactive period. Accordingly, when considering the second time interval, it is determined that the UL transmission can be delayed (reference S41b in figure 4), but only to the DRX active period that immediately follows the current DRX active period.

[0086] Part c) of figure 6 represents the case where the third time interval is considered. As illustrated by part c) of figure 6, the third time interval is such that it covers the beginning of three following DRX active periods. Accordingly, when considering the third time interval, itis determined that the UL transmission can be delayed (reference S41b in figure 4). In practice, the UL transmission can be delayed to any one of the three following DRX active periods (referred to by respectively #1 , #2 and #3 in figure 6) which are set to start within the third time interval (i.e. , before TO + AT).

[0087] For example, the different time intervals which may be considered during step S41 may be associated to respective different priority levels. For example, it is possible to consider a time interval having a short duration for an UL transmission having a high priority level (e.g., the first time interval having the duration AT1), and to use a time interval having a lower duration for an UL transmission having a lower priority level (e.g., the third time interval having the duration AT3). Hence, high priority UL transmissions may be less frequently delayed to a following DRX active period than low priority UL transmissions, thereby reducing latency for high priority UL transmissions.

[0088] In such a case, the wireless device 25 may for example determine the priority level of the UL transmission to be initiated, and then use the time interval associated to the determined priority level. For example, if it is determined that the UL transmission to be initiated has a high priority level, the wireless device 25 may select the first time interval. In turn, if it is determined that the UL transmission to be initiated has a low priority level, the wireless device 25 may select the second time interval or the third time interval.

[0089] In some cases, different logical channels, LCH, may be defined between the wireless device 25 and the RAN, associated to respective different priority levels. In such cases, the priority level of the UL transmission to be initiated may be determined based on the LCH for which the UL transmission is to be initiated. For example, it is possible to define three different LCHs, e.g., a first logical channel LCH1 having a high priority level, a second logical channel LCH2 having a medium priority level and a third logical channel LCH3 having a low priority level. In such a case: an UL transmission related to the first logical channel LCH1 may use the first time interval to determine whether it can be delayed to a following DRX active period, an UL transmission related to the second logical channel LCH2 may use the second time interval to determine whether it can be delayed to a following DRX active period, an UL transmission related to the third logical channel LCH3 may use the third time interval to determine whether it can be delayed to a following DRX active period.

[0090] For example, if more than one LCH has data available, to be transmitted to the RAN, the wireless device 25 may use e.g., the time interval associated to the LCH, among the LCHs having data available, having the greater priority level. For example, if the second logical channel LCH2 and the third logical channel LCH3 have data available, the wireless device 25 may use the second time interval. In other examples, it is also possible to handlethese logical channels separately, via separate UL transmissions.

[0091] In some examples, the time interval(s) may be predefined at the wireless device 25. In other examples, each time interval may be set by the wireless device 25, or by the RAN. In the latter case, and as illustrated in a non-limitative manner by figure 4, the method 40 for exchanging data comprises a prior step S45 of receiving, from the RAN, a time interval configuration (defining e.g., the duration of the time interval) for each time interval. For example, such a time interval configuration may be received by the wireless device 25 in system information broadcasted by a BS 30 of the RAN and / or it may be received in a radio resource control, RRC, message transmitted by a BS 30 of the RAN. Of course, other control messages can be used by the RAN to transmit a time interval configuration to the wireless device 25.

[0092] As discussed above, in some cases, there may be more than one following DRX active period during which the delayed UL transmission may initiated (see e.g., part c) of figure 5). In such a case, different selection strategies may be considered, and the choice of a specific strategy corresponds to a specific but non-limitative embodiment of the present disclosure. Different strategies are discussed below, as non-limitative examples.

[0093] According to an example, it is possible to always initiate the delayed UL transmission in the first following DRX active period, i.e. , the DRX active period that immediately follows the current DRX inactive period. Such a selection strategy enables to limit the latency introduced by delaying the UL transmission.

[0094] According to another example, it is possible to always initiate the delayed UL transmission in the last following DRX active period, i.e., the following DRX active period that is the last to start within the considered time interval.

[0095] According to another example, it is possible to select randomly a following DRX active period among the plurality of following DRX active periods which may be considered for delaying the UL transmission.

[0096] According to another example, it is possible to rely on wake-up signal detection for selecting a following DRX active period, if the wireless device 25 comprises a LP-WUR 254.

[0097] Indeed, as discussed above, the wireless device 25 may be configured to perform PDCCH monitoring during a DRX active period only if it detects a wake-up signal during the preceding DRX inactive period. Hence, the RAN may transmit a wake-up signal to the wireless device 25 during a current DRX inactive period to notify the wireless device 25 that said RAN will initiate a DL transmission during the next DRX active period. If no wake-up signal is detected by the LP-WUR 254 during the current DRX inactive period, then the wireless device 25 may skip PDCCH monitoring during the next DRX active period (and the MR unit 253 may remain in the low power state).

[0098] Hence, when the wireless device 25 needs to initiate an UL transmission during a following DRX active period, it may rely on wake-up signal detection to try and initiate the UL transmission during a following DRX active period during which the RAN also intends to initiate a DL transmission.

[0099] Figure 7 represents schematically different scenarios involving such a selection based on wake-up signal detection. In the examples illustrated by figure 7, it is assumed in a non-limitative manner that three possible following DRX active periods are set to start within the considered time interval of duration AT. Hence, there are three possible following DRX active periods (referred to by respectively #1 , #2 and #3 in figure 7) during which the delayed UL transmission can be initiated.

[0100] Part a) represents an example in which the RAN initiates a DL transmission during one of the three possible following DRX active periods. In this example, the DL transmission is initiated by the RAN during the second possible following DRX active period (#2). Accordingly, the RAN does not transmit a wake-up signal during the DRX inactive period preceding the first possible following DRX active period, and the MR unit 253 of the wireless device 25 may remain in a low power state (e.g., turned off) during the first possible following DRX active period since no UL transmission is to be initiated and no DL monitoring is to be performed for detecting a DL transmission initiated by the RAN. The RAN transmits a wakesignal to the wireless device 25 at a time T 1 during the DRX inactive period preceding the second possible following DRX active period. Accordingly, the MR unit 253 needs to be transitioned to the active state to perform PDCCH monitoring during the second possible DRX active period (#2), and the wireless device 25 takes advantage of this by also initiating the UL transmission during this second possible DRX active period (#2).

[0101] Part b) represents an example in which the RAN does not initiate a DL transmission during one of the three possible following DRX active periods. Accordingly, no wake-up signal is transmitted by the RAN during the DRX inactive periods within the considered time interval. In such a case, since no wake-up signal is detected, the wireless device 25 initiates the UL transmission during the third possible following DRX active period since it is the last possible following DRX active period during which the delayed UL transmission can be initiated by the wireless device 25. Hence, the MR unit 253 of the wireless device 25, while in a low power state during the first and second possible following DRX active periods, is transitioned to the active state during the third possible following DRX active period, to initiate the delayed UL transmission.

[0102] As discussed above, figure 8 represents a diagram showing corresponding steps of an exemplary embodiment of a method 80 for exchanging data, which may be implemented by a BS 30 when the wireless device 25 implements the method 40 for exchanging dataillustrated by figure 4 (including the optional step S45).

[0103] As illustrated by figure 8, the method 80 for exchanging data comprises a step S80 of transmitting a time interval configuration to the wireless device 25, for configuring in said wireless device 25 the time interval to be used by the wireless device 25 during step S41. As discussed above, the BS 30 may transmit a plurality of time interval configurations, for instance for configuring in the wireless device 25 different time intervals associated respectively to different priority levels. As discussed above, each time interval configuration may be transmitted in system information broadcasted by the BS and / or in a RRC message. Of course, other control messages can be used by the BS 30 to transmit a time interval configuration to the wireless device 25.

[0104] In some examples, the BS 30 may comprise a WUT 304 which may be used to transmit a wake-up signal to an LP-WLIR 254 of the wireless device 25. In such a case, the method 80 for exchanging data may optionally comprise, during a DRX inactive period, a step S81 of evaluating whether a DL transmission is to be initiated by the BS 30 in the next DRX active period. If a DL transmission is to be initiated in the next DRX active period (reference S81a in figure 8), the method 80 for exchanging data comprises a step S82 of transmitting a wake-up signal to the wireless device 25 in the current DRX inactive period and a step S83 of initiating the DL transmission during the next DRX active period. In turn (reference S81b in figure 8), no wake-up signal is transmitted during the current DRX inactive period, and no DL transmission is initiated by the BS 30 during the DRX active period which immediately follows the current DRX inactive period. As discussed above, such a wake-up signal may be used by the wireless device 25 to select a following DRX active period for initiating a delayed UL transmission, when a plurality of following DRX active periods can be used for initiating said delayed UL transmission.

[0105] It is emphasized that the present disclosure is not limited to the above exemplary embodiments. Variants of the above exemplary embodiments are also within the scope of the present disclosure.

Claims

Claims1. A method (40) for exchanging data in a wireless communication system, the method being implemented by a wireless device (25) comprising a main radio, MR, unit (253) configured to exchange data with a radio access network, RAN, of the wireless communication system, wherein the wireless device (25) is configured with a discontinuous reception, DRX, cycle, wherein the DRX cycle comprises a DRX active period during which the MR unit may monitor a downlink, DL, for detecting a downlink, DL, transmission initiated by the RAN and a DRX inactive period during which the MR unit does not perform DL monitoring for detecting a DL transmission initiated by the RAN, wherein the method comprises, in response to the wireless device (S40) determining, during a current DRX inactive period, that an uplink, UL, transmission, is to be initiated by the wireless device:(S41) evaluating whether the UL transmission can be delayed to a following DRX active period, in response to determining that the UL transmission can be delayed to a following DRX active period: (S42) delaying the UL transmission to a following DRX active period, in response to determining that the UL transmission cannot be delayed to a following DRX active period: (S44) initiating the UL transmission during the current DRX inactive period.

2. The method (40) according to claim 1 , wherein the MR unit is in a low power mode at the beginning of the DRX inactive period and, when the wireless device determines, during the current DRX inactive period, that an UL transmission is to be initiated by the wireless device: the MR unit is maintained in the low power mode in response to determining that the UL transmission can be delayed to a following DRX active period, the MR unit is transitioned to an active state during the current DRX inactive period in response to determining that the UL transmission cannot be delayed to a following DRX active period.

3. The method (40) according to any one of the preceding claims, wherein the evaluating whether the UL transmission can be delayed to a following DRX active period comprises evaluating whether at least one following DRX active period is set to start within a predetermined time interval.

4. The method (40) according to claim 3, wherein different time intervals are associated respectively to different priority levels, and the evaluating whether the UL transmission can be delayed to a following DRX active period comprises: determining a priority level associated to the UL transmission to be initiated,selecting the time interval associated to the determined priority level.

5. The method (40) according to claim 4, wherein the priority level of the UL transmission to be initiated is determined based on a logical channel, LCH, for which the UL transmission is to be initiated.

6. The method (40) according to any one of claims 4 to 5, wherein a high priority level is associated to a time interval having a greater duration than a time interval associated to a low priority level.

7. The method (40) according to any one of claims 3 to 6, comprising (S45) receiving beforehand, from the RAN, a time interval configuration for each time interval.

8. The method (40) according to claim 7, wherein each time interval configuration is received in system information broadcasted by the RAN and / or in a radio resource control, RRC, message transmitted by the RAN.

9. The method (40) according to any one of claims 3 to 8, wherein: the wireless device comprises a low-power wake-up receiver, LP-WUR (254), configured to monitor a wake-up signal transmitted by the RAN and to trigger a transition of the MR unit to an active state in response to detecting a wake-up signal, the method comprises, in response to determining that a plurality of following DRX active periods is set to start within the time interval, the UL transmission is initiated in a following DRX active period selected among the plurality of following DRX active periods based on wake-up signal detection during the time interval.

10. The method (40) according to claim 9, wherein the following DRX active period selected among the plurality of following DRX active periods corresponds to: the DRX active period which immediately follows a DRX inactive period, within the time interval, during which a wake-up signal is detected by the LP-WUR, or, in response to not detecting a wake-up signal in a DRX inactive period within the time interval: the last following DRX active period among the plurality of following DRX active periods.

11. 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.

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

13. A method (80) 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 main radio, MR, unit (253) of a wireless device (25), wherein the BS is configured with a discontinuous reception, DRX, cycle, wherein the DRX cycle comprises a DRX active period during which the BS may initiate a downlink, DL, transmission to the MR unit of the wirelessdevice and a DRX inactive period during which the BS cannot initiate a DL transmission to the MR unit of the wireless device, wherein the method comprises (S80) transmitting a time interval configuration to the wireless device for configuring in said wireless device a time interval, wherein the time interval is to be used by the wireless device to determine whether an uplink, UL, transmission to be initiated in a DRX inactive period can be delayed to a following DRX active period.

14. The method (80) according to claim 13, wherein the BS transmits to the wireless device different time interval configurations associated respectively to different priority levels.

15. The method (80) according to claim 14, wherein each time interval configuration is transmitted in system information broadcasted by the BS and / or in a radio resource control, RRC, message.

16. The method (80) according to any one of claims 13 to 15, wherein: the wireless device comprises a low-power wake-up receiver, LP-WLIR (254), configured to monitor a wake-up signal transmitted by the BS and to trigger a transition of the MR unit to an active state in response to detecting a wake-up signal, the method comprises, in response to determining that a DL transmission is to be initiated by the BS in a DRX active period which follows a current DRX inactive period: (S82) transmitting a wake-up signal to the wireless device in the current DRX inactive period.

17. A base station, BS (30), comprising at least one memory and at least one processor configured to carry out a method (80) according to any one of claims 13 to 16.

18. A wireless communication system comprising at least one base station (30) according to claim 17 and at least one user equipment (20) according to claim 12.

19. A computer program product (252, 302) comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method (40) according to any one of claims 1 to 10 or a method (80) according to any one of claims 13 to 16.

20. A computer-readable storage medium comprising instructions which, when executed by at least one processor, configure said at least one processor to carry out a method (40) according to any one of claims 1 to 10 or a method (80) according to any one of claims 13 to 16.

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