Method and device for performing energy saving in a ue performing discontinuous reception

Abstract

The present disclosure relates to methods and devices for enabling a user equipment, UE (20), having a low power wake-up signal receiver, LP-WUR (254), to reduce its energy consumption during a discontinuous reception, DRX, active period of a DRX cycle.

Description

Method and device for performing energy saving in a UE 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 the wake-up signal should be done with a low power consumption, and the mean powerconsumption 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 the 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 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. However, the UE needs to remain awake for the whole awake duration of the DRX active period, because the UE does not know beforehand when the control data will be transmitted by the RAN during the DRX active period.

[0012] Hence, there is a need for further reducing energy consumption.Summary

[0013] 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 duration during which the MR unit needs to remain in the active state within a DRX active period of a DRX cycle.

[0014] According to a first aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, the method being implemented by a wireless device of the wireless communication system, wherein the wireless device comprises a main radio, MR, unit, configured to exchange data with a radio access network, RAN, of the wireless communication system, and 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, wherein the wireless deviceis configured with a discontinuous reception, DRX, cycle, wherein the DRX cycle comprises a DRX active period during which the wireless device may receive control data from the RAN via a physical downlink control channel, PDCCH, and a DRX inactive period during which the wireless device does not perform PDCCH monitoring, wherein the DRX active period comprises an inactive subperiod followed by an active subperiod and wherein, in response to the LP-WLIR detecting a wake-up signal during a DRX inactive period, the method comprises, during the following DRX active period: performing wake-up signal monitoring by the LP-WLIR during the inactive subperiod, with the MR unit in a low power state, in response to detecting a wake-up signal during the inactive subperiod: triggering a transition of the MR unit to the active state and performing PDCCH monitoring during the active subperiod.

[0015] 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.

[0016] In some embodiments of the method according to the first aspect, the MR unit is maintained in the low power state during the active subperiod, in response to not detecting a wake-up signal during the inactive subperiod.

[0017] In some embodiments of the method according to the first aspect, the LP-WLIR does not perform wake-up signal monitoring during the active period, in response to not detecting a wake-up signal during the inactive subperiod.

[0018] In some embodiments, the method according to the first aspect comprises receiving a DRX active period configuration defining the inactive subperiod and the active subperiod within the DRX active period.

[0019] In some embodiments of the method according to the first aspect, the DRX active period configuration is received in system information broadcasted by the RAN and / or the DRX active period configuration is received in a radio resource control, RRC, reconfiguration message transmitted by the RAN.

[0020] In some embodiments of the method according to the first aspect, if no wake-up signal is detected during a DRX inactive period, the wireless device does not perform PDCCH monitoring during the following DRX active period.

[0021] In some embodiments of the method according to the first aspect, the DRX active period comprises a plurality of active subperiods and / or the DRX active period comprises a plurality of inactive subperiods.

[0022] In some embodiments of the method according to the first aspect, the DRX active period starts with an active subperiod.

[0023] In some embodiments of the method according to the first aspect, during the DRX inactive period, the MR unit is maintained in a low power state different than the low power state used during the inactive subperiod of the DRX active period.

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

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

[0026] According to a fourth aspect, the present disclosure relates to a method for exchanging data in a wireless communication system, the method being implemented by a base station, BS, of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device, wherein the wireless device comprises a main radio, MR, unit and a low power wake-up receiver, LP-WLIR wherein the LP-WLIR is configured to detect 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 transmitted by the BS, 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 transmit control data to the wireless device via a physical downlink control channel, PDCCH, and a DRX inactive period during which the BS does not transmit control data to the wireless device via the PDCCH, wherein the DRX active period comprises at least on inactive subperiod and at least one active subperiod, and wherein the BS is configured to transmit control data to the wireless device, via the PDCCH, only in the at least one active subperiod.

[0027] In some embodiments, the method according to the fourth aspect can further comprise one or more of the following optional features, considered either alone or in any technically possible combination.

[0028] In some embodiments, the method according to the fourth aspect comprises, in response to determining that control data is to be transmitted in an active subperiod which follows an inactive subperiod of the DRX active period: transmitting a wake-up signal to the wireless device in said inactive subperiod.

[0029] In some embodiments, the method according to the fourth aspect comprises, in response to determining that control data is to be transmitted in a DRX active period: transmitting a wake-up signal to the wireless device in the DRX inactive period which is followed by said DRX active period.

[0030] In some embodiments, the method according to the fourth aspect comprisestransmitting a DRX active period configuration to the wireless device, wherein the DRX active period configuration defines the at least one inactive subperiod and the at least one active subperiod within the DRX active period.

[0031] In some embodiments of the method according to the fourth aspect, the DRX active period configuration is transmitted in system information broadcasted by the RAN and / or the DRX active period configuration is transmitted in a radio resource control, RRC, reconfiguration message transmitted to the wireless device.

[0032] In some embodiments of the method according to the fourth aspect, the DRX active period starts with an active subperiod.

[0033] 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.

[0034] According to a sixth aspect, the present disclosure relates to a wireless communication system comprising at least one base station according to any one of the embodiments of the present disclosure and at least one user equipment according to any one of the embodiments of the present disclosure.

[0035] 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.

[0036] 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

[0037] 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: schematic representations of examples of different DRX active periodconfigurations,Figure 5: schematic representations illustrating the operation of a wireless device during a DRX cycle,Figures 6 and 7: flow charts illustrating examples of methods for exchanging data implemented by a BS and a wireless device of a UE, respectively.

[0038] 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

[0039] The detailed description set forth below, with reference to the figures, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For instance, although 3GPP terminology, from e.g., 5G NR, may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the present disclosure.

[0040] 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.

[0041] Figure 1 represents schematically an example of wireless communication system, which may be for example a 5G NR wireless communication system. More specifically, figure 1 represents a RAN of the wireless communication system, which is used exchangedata with UEs 20 via radio signals. For example, the RAN may send data to the UEs 20 (downlink, DL), for instance data received from a core network (CN, not represented in the figures). The RAN may also receive data from the UEs 20 (uplink, UL), which data may be forwarded to the CN.

[0042] 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.

[0043] In the example illustrated by figure 1 , two UEs 20 are represented. The UEs 20 are located 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] As illustrated by figure 2, the wireless device 25 comprises also a main radio, MR, unit 253, and a low power wake-up signal receiver, LP-WUR, 254.

[0048] 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] The LP-WLIR 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.

[0050] 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.

[0051] The wireless device 25 is adapted to be operated in at least two operating modes which include a normal operating mode and a low power operating mode: in the normal operating mode, the MR unit 253 is in an active state, in the low power operating mode, the MR unit 253 is in a low power state and the LP-WUR 254 is configured to trigger a transition to the normal operating mode in response to detecting a wake-up signal transmitted by the RAN.

[0052] As discussed above, the active state corresponds to any state in which the MR unit 253 can exchange data with the RAN without being triggered by the LP-WUR.

[0053] The low power state corresponds to a state in which the MR unit 253 cannot exchange data with the RAN without being triggered by the LP-WUR 254. For example, the low power state corresponds to the MR unit 253 being always asleep. However, since the MR unit 253 does not have to wake-up periodically in the low power state, thanks to the LP- WUR 254, 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. Also, 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 lowpower 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.

[0054] It should be noted that, in some examples, the LP-WLIR 254 may also be configured to trigger the MR unit 253 when other conditions are verified. For example, the LP-WLIR 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 timer should be sufficiently high to ensure that the MR unit 253 can remain in a low power state over long periods.

[0055] Figure 3 represents schematically an example of a BS 30 suitable to implement any method, discussed in the present disclosure, performed by the RAN.

[0056] 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.

[0057] 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.

[0058] As illustrated by figure 3, the BS 30 comprises also 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.

[0059] As discussed above for the LP-WUR 254, the purpose of the WUT 304, if separate from the wireless communication unit 30, is mainly to transmit a (DL) wake-up 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.

[0060] As illustrated by figure 3, the BS 30 may comprise also 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.

[0061] 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 inactive period during which the wireless device 25 does not perform PDCCH monitoring, and a DRX active period during which the wireless device 25 may receive control data from the RAN via the PDCCH.

[0062] To reduce the need for maintaining the MR unit 253 in the active state during the DRX active period, it is proposed to split the DRX active period into a plurality of subperiods which include: one or more inactive subperiods during which the RAN cannot transmit control data to the wireless device 25 via the PDCCH, and one or more active subperiods during which the RAN may transmit control data to the wireless device 25 via the PDCCH.

[0063] Since no control data can be received via the PDCCH during an inactive subperiod of the DRX active period, the MR unit 253 of the wireless device 25 may be put in a low power state during each inactive subperiod of the DRX active period, such that the MR unit 253 no longer needs to be in the active state during the whole duration of the DRX active period. Also, and as will be discussed below, if the DRX active period includes an active subperiod which follows an inactive subperiod, the RAN may use said inactive subperiod to indicate whether said RAN intends to send control data via the PDCCH during the following active subperiod. For instance, such an indication may be sent as a wake-up signal to be detected by the LP-WUR 254 of the wireless device 25. Hence, if a wake-up signal is detected during an inactive subperiod of the DRX active period, the MR unit 253 may transition to the active state for the following active subperiod of the DRX active period. Inturn, if no wake-up signal is detected during an inactive subperiod, the MR unit 253 may remain in a low power state during the following active subperiod. Also, in some cases, if no wake-up signal is detected by the LP-WLIR 254 during an inactive subperiod of the DRX active period, then the LP-WLIR 254 may also transition to a low-power state (e.g., turned off) for the duration of the following active subperiod of the DRX active period, to further reduce energy consumption during the DRX active period. In some examples, the LP-WLIR 254 may also be placed in a low power state (e.g., turned off) during all active subperiods of the DRX active period.

[0064] As discussed above, the DRX active period may comprise one or more active subperiods and one or more inactive subperiods, arranged such that the DRX active period is composed of an alternation of active subperiod(s) and inactive subperiod(s). In other words, an active subperiod cannot be immediately followed or preceded by another active subperiod, and an inactive subperiod cannot be immediately followed or preceded by another inactive subperiod. Preferably, an inactive subperiod is always followed by an active subperiod, to be able to indicate to the wireless device 25 whether its MR unit 253 needs to be put in the active state for said following active subperiod.

[0065] Figure 4 represents schematically different examples of DRX active period configurations.

[0066] In the example illustrated by part a) of Figure 4, the DRX active period comprises a single inactive subperiod followed by a single active subperiod.

[0067] In the example illustrated by part b) of Figure 4, the DRX active period comprises three subperiods. More specifically, the DRX active period starts with a first active subperiod, followed by an inactive subperiod, followed by a second active subperiod. In such a case, when a wake-up signal is detected in the previous DRX inactive period, the MR unit 253 transitions to the active state for the duration of the first active subperiod to perform PDCCH monitoring. During the inactive subperiod, no PDCCH monitoring is performed, and the MR unit 253 may be put in a low power state. The LP-WLIR 254 performs wake-up signal monitoring during the inactive subperiod. If a wake-up signal is detected, the MR unit 253 transitions to the active for the duration of the second active subperiod to perform PDCCH monitoring. If no wake-up signal is detected, the MR unit 253 may remain in a low power state for the duration of the second active subperiod. The LP-WLIR 254 does not need to perform wake-up signal monitoring during the second active subperiod such that, in some examples, it can be put into a low power state.

[0068] In the example illustrated by part c) of Figure 4, the DRX active period comprises four subperiods. More specifically, the DRX active period starts with a first inactive subperiod, followed by a first active subperiod, followed by a second inactive subperiod,followed by a second active subperiod.

[0069] In the example illustrated by part d) of Figure 4, the DRX active period comprises five subperiods. More specifically, the DRX active period starts with a first active subperiod, followed by a first inactive subperiod, followed by a second active subperiod, followed by a second inactive subperiod, followed by a third active subperiod.

[0070] In some examples, it is possible to consider an identical duration for all inactive subperiods and for all active subperiods. However, it is also possible to consider a duration for the inactive subperiods that is different from the duration of the active subperiods. Also, the inactive subperiods may have all the same duration, or the duration may vary from one inactive subperiod to another. Similarly, the active subperiods may have all the same duration, or the duration may vary from one active subperiod to another.

[0071] Other DRX active period configurations can be considered, for example comprising additional active subperiods and / or additional inactive subperiods compared to the examples provided in figure 4. The choice of a specific DRX active period configuration corresponds to a specific but non-limitative embodiment of the present disclosure.

[0072] In some examples, the DRX active period configuration may be predefined. In other examples, the DRX active period configuration may be set by the wireless device 25, or by the RAN. In the latter case, the DRX active period configuration to be used by the wireless device 25 is for instance received by the wireless device 25 in system information broadcasted by a BS 30 of the RAN and / or received in a radio resource control, RRC, reconfiguration message transmitted by a BS 30 of the RAN. Of course, other control messages can be used by the RAN to transmit a DRX active period configuration to the wireless device 25. In some cases, the DRX active period configuration may be transmitted together with a DRX cycle configuration which defines the DRX active period and the DRX inactive period within the DRX cycle.

[0073] Figure 5 represents schematically non-limitative examples of how the wireless device 25 may reduce its energy consumption, by assuming in a non-limitative manner the DRX active period configuration represented in part d) of figure 4.

[0074] In the example illustrated by figure 5, the LP-WLIR 254 performs wake-up signal monitoring during the DRX inactive period of the DRX cycle, while the MR unit 253 is in a low power state, for example the very low power state discussed above.

[0075] In part a) of figure 5, no wake-up signal is detected by the LP-WLIR 254, such that no PDCCH monitoring is performed during the following DRX active period. The MR unit 253 may therefore remain in a low power state during the whole DRX active period, thereby reducing energy consumption compared to performing PDCCH monitoring at each DRX active period. Also, in some examples, and as illustrated in a non-limitative manner in parta) of figure 5, the LP-WLIR 254 may also be placed in a low power state (e.g., turned off) during the whole DRX active period.

[0076] In part b) of figure 5, a wake-up signal is detected by the LP-WLIR 254 at a time TO within the DRX inactive period. Accordingly, the wireless device 25 considers that it might receive control data via the PDCCH during the next DRX active period. Since the DRX active period starts with a first active subperiod, the LP-WLIR 254 transitions the MR unit 253 to the active state for the duration of the first active subperiod, during which the wireless device 25 may receive control data via the PDCCH. Since no control data is to be received via the PDCCH during the first inactive subperiod, the MR unit 253 may be put in a low power state for the duration of the first inactive subperiod. However, the LP-WLIR 254 performs wake-up signal monitoring during the first inactive subperiod. The LP-WLIR 254 detects a wake-up signal at a time T1 within the first inactive subperiod, which means that the RAN may transmit control data via the PDCCH during the following active subperiod, i.e., the second active subperiod. Accordingly, the LP-WLIR 254 transitions the MR unit 253 to the active state for the duration of the second active subperiod, during which the wireless device 25 may receive control data via the PDCCH. Since no control data is to be received via the PDCCH during the second inactive subperiod, the MR unit 253 may be put in a low power state for the duration of the second inactive subperiod. However, the LP-WLIR 254 performs wake-up signal monitoring during the second inactive subperiod. In the example illustrated by part b) of figure 5, no wake-up signal is detected during the second inactive subperiod, which means that the RAN does not intend to transmit control data via the PDCCH during the following subperiod, i.e., the third active subperiod. Accordingly, the MR unit 253 may be kept in a low power state during the third active subperiod. Also, the LP- WUR 254 does not need to perform wake-up signal monitoring during the third active subperiod. Accordingly, the LP-WLIR 254 may be placed in a low power state during the third active subperiod. For example, the LP-WLIR 254 may be turned off during the third active subperiod. In some examples, and as illustrated in a non-limitative manner in part b) of figure 5, the LP-WLIR 254 may also be placed in a low power state (e.g., turned off) during all active subperiods of the DRX active period.

[0077] It should be noted that the same low power state of the MR unit 253 may be used during both the DRX inactive period and the DRX active period. However, it is also possible, in some cases to use different low power states of the MR unit 253 during respectively the DRX inactive period and the DRX active period. For example, the low power state used during the DRX inactive period may correspond to the very low power state of the MR unit 253 discussed above, while the low power state used during the DRX active period may correspond to an intermediate low power state of the MR unit 253.

[0078] Figure 6 represents a diagram showing steps of an exemplary embodiment of a method 60 for exchanging data, which is implemented by a BS 30. Figure 7 represents a diagram showing corresponding steps of an exemplary embodiment of a method 70 for exchanging data, which is implemented by a wireless device 25 of a UE 20. It should be noted that figures 6 and 7 show only a single inactive subperiod and a single active subperiod, but the corresponding steps can also be repeated if the DRX active period comprises more than one inactive subperiod and / or more than one active subperiod.

[0079] As discussed above, the DRX active period comprises one or more inactive subperiods and one or more active subperiods, and the BS 30 is configured to transmit control data to the wireless device 25 of a UE 20, via the PDCCH, only in active subperiod(s). In other words, no control data can be transmitted to the wireless device 25 via the PDCCH during inactive subperiods of the DRX active period.

[0080] In the non-limitative example illustrated by figure 6, the method 60 for exchanging data comprises, during an inactive subperiod of the DRX active period, a step S60 of evaluating whether control data is to be transmitted to the wireless device 25 via the PDCCH in the following active subperiod. If control data is to be transmitted via the PDCCH in the following active subperiod (reference S60a in figure 6), the method 60 for exchanging data comprises a step S61 of transmitting a wake-up signal to the wireless device 25 in the current inactive subperiod and a step S62 of transmitting control data to the wireless device 25 via the PDCCH during the following active subperiod. In turn (reference S60b in figure 6), no wake-up signal is transmitted during the current inactive subperiod (and no control data is transmitted to the wireless device 25 via the PDCCH during the following active subperiod).

[0081] In some examples, and as illustrated by figure 6, the method 60 for exchanging data comprises, during a DRX inactive period, a step S63 of evaluating whether control data is to be transmitted to the wireless device 25 via the PDCCH in the following DRX active period. If control data is to be transmitted via the PDCCH in the following DRX active period (reference S63a in figure 6), the method 60 for exchanging data comprises a step S64 of transmitting a wake-up signal to the wireless device 25 in the current DRX inactive period. In turn (reference S63b in figure 6), no wake-up signal is transmitted during the current DRX inactive period (and no control data is transmitted to the wireless device 25 via the PDCCH during the following DRX active period).

[0082] In some examples, and as illustrated in the non-limitative example of figure 6, the method 60 for exchanging data comprises a step S65 of transmitting a DRX active period configuration to the wireless device 25. As discussed above, the DRX active period configuration may be transmitted e.g., in system information broadcasted by the BS 30and / or in a radio resource control, RRC, reconfiguration message transmitted to the wireless device 25 (if the wireless device 25 is in the RRC_CONNECTED state).

[0083] As discussed above, figure 7 represents a diagram showing corresponding steps of an exemplary embodiment of a method 70 for exchanging data, which may be implemented by a wireless device 25 when the BS 30 implements the method 60 for exchanging data illustrated by figure 6.

[0084] As illustrated by figure 7, the method 70 for exchanging data comprises, during a DRX active period, a step S70 of performing wake-signal monitoring during an inactive subperiod, by the LP-WLIR 254 (while the MR unit 253 is in a low power state). If no wakeup signal is detected during the current inactive subperiod (reference S70b in figure 7) no PDCCH monitoring is performed during the following active subperiod, and the MR unit 253 may be maintained in a low power state for the duration of the following active subperiod (and, in some examples, the LP-WLIR 254 does not perform wake-up signal monitoring during the following active subperiod and may be placed in a low power state). In turn (reference S70a in figure 7), the method 70 for exchanging data comprises a step S71 of triggering a transition of the MR unit 253 to the active state and a step S72 of performing PDCCH monitoring during the following active subperiod.

[0085] In some examples, and as illustrated by figure 7, the method 70 for exchanging data comprises, during a DRX inactive period, a step S73 of performing wake-signal monitoring, by the LP-WLIR 254 (while the MR unit 253 is in a low power state).

[0086] If no wake-up signal is detected during the current DRX inactive period (reference S73b in figure 7) no PDCCH monitoring is performed during the following DRX active period, and the MR unit 253 may be maintained in a low power state for the duration of the following DRX active period (and, in some examples, the LP-WLIR 254 does not perform wake-up signal monitoring during the following DRX active period and may be placed in a low power state). Hence, the steps S70, S71 and S72 discussed above are not executed.

[0087] In turn (reference S73a in figure 7), the method 70 for exchanging data executes the steps S70, S71 and S72 as discussed above.

[0088] In some examples, and as illustrated by the figure 7, the method 70 for exchanging data comprises a step S74 of receiving a DRX active period configuration from the RAN, to be used during the DRX active period(s). As discussed above, the DRX active period configuration is for example received in system information broadcasted by the RAN and / or in a radio resource control, RRC, reconfiguration message transmitted by the RAN.

[0089] It is emphasized that the present disclosure is not limited to the above exemplary embodiments. Variants of the above exemplary embodiments are also within the scope of the present disclosure.

Claims

Claims1. A method (70) for exchanging data in a wireless communication system, the method being implemented by a wireless device (25) of the wireless communication system, wherein the wireless device comprises a main radio, MR, unit (253), configured to exchange data with a radio access network, RAN, of the wireless communication system, and a low- power wake-up receiver, LP-WLIR (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, 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 wireless device (25) may receive control data from the RAN via a physical downlink control channel, PDCCH, and a DRX inactive period during which the wireless device (25) does not perform PDCCH monitoring, wherein the DRX active period comprises an inactive subperiod followed by an active subperiod and wherein, in response to the LP- WUR (254) detecting a wake-up signal during a DRX inactive period, the method comprises, during the following DRX active period:(S70) performing wake-up signal monitoring by the LP-WLIR (254) during the inactive subperiod, with the MR unit in a low power state, in response to detecting a wake-up signal during the inactive subperiod: (S71) triggering a transition of the MR unit to the active state and (S72) performing PDCCH monitoring during the active subperiod.

2. The method (70) according to claim 1 , wherein, in response to not detecting a wake-up signal during the inactive subperiod, the MR unit is maintained in the low power state during the active subperiod.

3. The method (70) according to claim 2, wherein, in response to not detecting a wake-up signal during the inactive subperiod, the LP-WLIR does not perform wake-up signal monitoring during the active period.

4. The method (70) according to any one of the preceding claims, comprising (S74) receiving a DRX active period configuration defining the inactive subperiod and the active subperiod within the DRX active period.

5. The method (70) according to claim 4, wherein the DRX active period configuration is received in system information broadcasted by the RAN and / or the DRX active period configuration is received in a radio resource control, RRC, reconfiguration message transmitted by the RAN.

6. The method (70) according to any one of the preceding claims, wherein, if no wakeup signal is detected during a DRX inactive period, the wireless device (25) does not perform PDCCH monitoring during the following DRX active period.

7. The method (70) according to any one of the preceding claims, wherein the DRX active period comprises a plurality of active subperiods and / or the DRX active period comprises a plurality of inactive subperiods.

8. The method (70) according to any one of the preceding claims, wherein the DRX active period starts with an active subperiod.

9. The method (70) according to any one of the preceding claims, wherein, during the DRX inactive period, the MR unit is maintained in a low power state different than the low power state used during the inactive subperiod of the DRX active period.

10. A wireless device (25) comprising at least one memory (251) and at least one processor (250) configured to carry out a method (70) according to any one of the preceding claims.

11. A user equipment, UE (20), comprising a wireless device according to claim 10.

12. A method (60) for exchanging data in a wireless communication system, the method being implemented by a base station, BS (30), of a radio access network, RAN, of the wireless communication system, wherein the BS is configured to exchange data with a wireless device (25), wherein the wireless device comprises a main radio, MR, unit (253) and a low power wake-up receiver, LP-WLIR (254), wherein the LP-WLIR is configured to detect 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 transmitted by the BS, 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 transmit control data to the wireless device via a physical downlink control channel, PDCCH, and a DRX inactive period during which the BS does not transmit control data to the wireless device via the PDCCH, wherein the DRX active period comprises at least on inactive subperiod and at least one active subperiod, and wherein the BS is configured to transmit control data to the wireless device, via the PDCCH, only in the at least one active subperiod.

13. The method (60) according to claim 12, comprising, in response to determining that control data is to be transmitted in an active subperiod which follows an inactive subperiod of the DRX active period: (S60) transmitting a wake-up signal to the wireless device in said inactive subperiod.

14. The method (60) according to any one of claims 12 to 13, comprising, in response to determining that control data is to be transmitted in a DRX active period: (S63) transmitting a wake-up signal to the wireless device in the DRX inactive period which is followed by said DRX active period.

15. The method (60) according to any one of claims 12 to 14, comprising (S65) transmitting a DRX active period configuration to the wireless device, wherein the DRXactive period configuration defines the at least one inactive subperiod and the at least one active subperiod within the DRX active period.

16. The method (60) according to claim 15, wherein the DRX active period configuration is transmitted in system information broadcasted by the RAN and / or the DRX active period configuration is transmitted in a radio resource control, RRC, reconfiguration message transmitted to the wireless device.

17. The method (60) according to any one of claims 12 to 16, wherein the DRX active period starts with an active subperiod.

18. A base station, BS (30), comprising at least one memory (301) and at least one processor (300) configured to carry out a method (60) according to any one of claims 12 to 17.

19. A wireless communication system comprising at least one base station (30) according to claim 18 and at least one user equipment (20) according to claim 11 .

20. 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 (70) according to any one of claims 1 to 9 or a method (60) according to any one of claims 12 to 17.

21. 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 (70) according to any one of claims 1 to 9 or a method (60) according to any one of claims 12 to 17.

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