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Title:
POWER SAVING FOR WIRELESS DEVICE
Document Type and Number:
WIPO Patent Application WO/2019/125425
Kind Code:
A1
Abstract:
According to an example aspect of the present invention, there is a method performed by a first device, comprising: receiving a first frame, from a second device, the first frame indicating that the second device is capable to provide clock service, transmitting, to the second device, a second frame indicating that the first device requests the clock service, switching from an awake state in which a main radio of the first device is enabled, to a doze state in which the main radio is disabled and a wake-up radio of the first device is enabled, and receiving a wake-up frame via the wake-up radio. In response to detecting that the received wake-up frame is related to the clock service, the first device performs a local action and remains in the doze state.

Inventors:
ALANEN OLLI PETTERI (FI)
RANTALA ENRICO HENRIK (US)
KASSLIN MIKA ILKKA TAPANI (FI)
MARIN JANNE (FI)
Application Number:
PCT/US2017/067525
Publication Date:
June 27, 2019
Filing Date:
December 20, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
NOKIA TECHNOLOGIES OY (FI)
NOKIA USA INC (US)
International Classes:
H04M7/00; H04J3/06
Foreign References:
US20160057605A12016-02-25
US20100246460A12010-09-30
US20160219510A12016-07-28
US20140269462A12014-09-18
US20170265130A12017-09-14
Download PDF:
Claims:
CLAIMS:

1. An apparatus comprising at least one processor, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to:

- receive a first frame, by a first wireless device from a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service,

- transmit, by the first wireless device to the second wireless device, a second frame indicating that the first wireless device requests the clock service,

- switch, by the first wireless device, from an awake state in which a main radio of the first wireless device is enabled, to a doze state in which the main radio is disabled and a wake- up radio of the first wireless device is enabled,

- receive, by the first wireless device, a wake-up frame via the wake-up radio,

- in response to receiving the wake-up frame and detecting that the wake-up frame is associated with the clock service, perform by the first wireless device a local action and remain in the doze state, and

- in response to receiving the wake-up frame and detecting that the wake-up frame is not associated with the clock service, switch by the first wireless device from the doze state to the awake state.

2. The apparatus of claim 1, wherein the at least one memory and the computer program code is configured to, with the at least one processor, further cause the apparatus to: receive, by the first wireless device from the second wireless device, a third frame acknowledging the second frame, and switch from the awake state to the doze state in response to the acknowledgement.

3. The apparatus of claim 1 or 2, wherein performing the local action comprises performing a local measurement and storing measurement results of the local measurement.

4. The apparatus of claim 3, wherein the at least one memory and the computer program code is configured to, with the at least one processor, further cause the apparatus to: transmit the measurement results to the second wireless device or a third device after receiving another wake-up frame, different from the wake-up frame associated with the clock service.

5. An apparatus comprising at least one processor, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to: - transmit a first frame, to a first wireless device by a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service,

- receive, from the first wireless device by the second wireless device, a second frame indicating that the first wireless device requests the clock service, and

- transmit, by the second wireless device, on the basis of the second frame, a wake-up frame associated with the clock service for causing the first wireless device to perform a local action without activating a main radio of the first wireless device.

6. The apparatus of claim 5, wherein the at least one memory and the computer program code is configured to, with the at least one processor, further cause the apparatus to: transmit, to the first wireless device a third frame acknowledging the second frame and the clock service.

7. The apparatus of any preceding claim, wherein the second frame further indicates at least one requested timing parameter for scheduling transmission of wake-up frames associated with the clock service.

8. The apparatus of any preceding claim, wherein the first frame is a publish message according to Wi-Fi neighbor awareness networking. 9. The apparatus of any preceding claim 1 to 7, wherein the first frame is one of a beacon, a probe response, or an association response in a wireless local area network.

10. The apparatus of any preceding claim, wherein the wake-up frame is unicast or multicast frame to a wake-up frame identifier indicated in the second frame.

11. The apparatus of any preceding claim, wherein the wake-up frame associated with the clock service comprises an indication of the clock service for preventing activation of the main radio.

12. The apparatus of claim 11, wherein the indication is provided by a wake-up frame type or a wake-up identifier specific for the clock service.

13. The apparatus of claim 8, wherein the second frame is a subscribe message according to Wi-Fi neighbor awareness networking. 14. The apparatus of any preceding claim, wherein the second wireless device is a wireless local area network terminal or access point and the first wireless device is a wireless local area network terminal.

15. A wireless communications device, comprising the apparatus of any preceding claim.

16. A method comprising:

- receiving a first frame, by a first wireless device from a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service,

- transmitting, by the first wireless device to the second wireless device, a second frame indicating that the first wireless device requests the clock service,

- switching, by the first wireless device, from an awake state in which a main radio of the first wireless device is enabled, to a doze state in which the main radio is disabled and a wake-up radio of the first wireless device is enabled,

- receiving, by the first wireless device, a wake-up frame via the wake-up radio,

- in response to receiving the wake-up frame and detecting that the wake-up frame is related to the clock service, performing by the first wireless device a local action and remaining in the doze state, and

- in response to receiving the wake-up frame and detecting that the wake-up frame is not related to the clock service, switching by the first wireless device from the doze state to the awake state. 17. The method of claim 16, further comprising:

- receiving, by the first wireless device from the second wireless device, a third frame acknowledging the second frame, and

- switching from the awake state to the doze state in response to the acknowledgement. 18. The method of claim 16 or 17, wherein performing the local action comprises performing a local measurement and storing measurement results of the local measurement.

19. The method of claim 18, wherein the measurement results are transmitted to the second wireless device or a third device after receiving another wake-up frame, different from the wake-up frame associated with the clock service.

20. A method comprising:

- transmitting a first frame, to a first wireless device by a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service, - receiving, from the first wireless device by the second wireless device, a second frame indicating that the first wireless device requests the clock service, and - transmitting, by the second wireless device, on the basis of the second frame, a wake-up frame associated with the clock service for causing the first wireless device to perform a local action without activating a main radio of the first wireless device. 21. The method of claim 20, further comprising:

- transmitting, to the first wireless device a third frame acknowledging the second frame and the clock service.

22. The method of any preceding claim 16 to 21, wherein the second frame further indicates at least one requested timing parameter for scheduling transmission of wake-up frames associated with the clock service.

23. The method of any preceding claim 16 to 22, wherein the first frame is a publish message according to Wi-Fi neighbor awareness networking.

24. The method of any preceding claim 16 to 22, wherein the first frame is one of a beacon, a probe response, or an association response in a wireless local area network.

25. The method of any preceding claim 16 to 24, wherein the wake-up frame is unicast or multicast frame to a wake-up frame identifier indicated in the second frame.

26. The method of any preceding claim 16 to 25, wherein the wake-up frame associated with the clock service comprises an indication of the clock service for preventing activation of the main radio.

27. The method of claim 26, wherein the indication is provided by a wake-up frame type or a wake- up identifier specific for the clock service.

28. The method of claim 23, wherein the second frame is a subscribe message according to Wi-Fi neighbor awareness networking.

29. The method of any preceding claim 16 to 28, wherein the second wireless device is a wireless local area network terminal or access point and the first wireless device is a wireless local area network terminal.

30. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least: - receive a first frame, by a first wireless device from a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service,

- transmit, by the first wireless device to the second wireless device, a second frame indicating that the first wireless device requests the clock service,

- switch, by the first wireless device, from an awake state in which a main radio of the first wireless device is enabled, to a doze state in which the main radio is disabled and a wake- up radio of the first wireless device is enabled,

- receive, by the first wireless device, a wake-up frame via the wake-up radio,

- in response to receiving the wake-up frame and detecting that the wake-up frame is associated with the clock service, perform by the first wireless device a local action and remain in the doze state, and

- in response to receiving the wake-up frame and detecting that the wake-up frame is not associated with the clock service, switch by the first wireless device from the doze state to the awake state.

31. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:

- transmit a first frame, to a first wireless device by a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service,

- receive, from the first wireless device by the second wireless device, a second frame indicating that the first wireless device requests the clock service, and

- transmit, by the second wireless device, on the basis of the second frame, a wake-up frame associated with the clock service for causing the first wireless device to perform a local action without activating a main radio of the first wireless device.

32. A computer program comprising code for, when executed in a data processing apparatus, to cause a method in accordance with at least one of claims 16 to 29 to be performed.

Description:
POWER SAVING FOR WIRELESS DEVICE FIELD

[0001] The present invention relates to wireless communications, and in particular to facilitating improved power saving for wireless devices.

BACKGROUND

[0002] Various power-saving mechanisms have been developed for wireless devices to allow a battery-operated device to“sleep” or enter an inactive mode between frame transmissions or when there is no data to transfer.

[0003] Wireless devices may have a power-save mode where a wireless device temporarily shuts down its main radio interface to reduce power consumption. In the sleeping state, the main radio may be temporarily shut down. The sleeping may have to be cancelled, e.g. for receiving information from the wireless network. The information may be provided in a beacon signal or another periodic broadcast signal, for example. There may be other reasons that cancel the sleeping and cause the device to activate its main radio interface for a frame transmission/reception.

[0004] With the fast increase of new devices being wirelessly connected and substantial traffic growth, requirements for wireless networks and connections are also changing. For example, various Internet of Things (IoT) devices may send occasionally or periodically uplink data while having high requirements on power-saving.

SUMMARY

[0005] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0006] According to a first aspect of the present invention, there is provided a method, comprising: receiving a first frame, by a first wireless device from a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service, transmitting, by the first wireless device to the second wireless device, a second frame indicating that the first wireless device requests the clock service, switching, by the first wireless device, from an awake state in which a main radio of the first wireless device is enabled, to a doze state in which the main radio is disabled and a wake-up radio of the first wireless device is enabled, receiving, by the first wireless device, a wake-up frame via the wake-up radio, in response to receiving the wake- up frame and detecting that the wake-up frame is related to the clock service, performing by the first wireless device a local action and remaining in the doze state, and in response to receiving the wake-up frame and detecting that the wake-up frame is not related to the clock service, switching by the first wireless device from the doze state to the awake state.

[0007] According to a second aspect of the present invention, there is provided a method, comprising: transmitting a first frame, to a first wireless device by a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service, receiving, from the first wireless device by the second wireless device, a second frame indicating that the first wireless device requests the clock service, and transmitting, by the second wireless device, on the basis of the second frame, a wake-up frame associated with the clock service for causing the first wireless device to perform a local action without activating a main radio of the first wireless device.

[0008] There are also provided apparatuses, computer programs, and computer-readable mediums configured to carry out features in accordance with the first and/or second aspect. According to an aspect, there is provided an apparatus comprising means for causing the apparatus to carry out the method of any one of the method claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGURE 1 illustrates a wireless communication system in which at least some embodiments of the present invention may be applied; [0010] FIGURE 2 illustrates wireless communications states in accordance with at least some embodiments of the present invention;

[0011] FIGURES 3 and 4 illustrate methods in accordance with at least some embodiments of the present invention;

[0012] FIGURES 5 and 6 illustrate signalling examples in accordance with at least some embodiments of the present invention; and

[0013] FIGURE 7 illustrates an example apparatus capable of supporting at least some embodiments of the present invention.

EMBODIMENTS [0014] FIGURE 1 illustrates an example wireless communication system. The wireless communication devices of Figure 1 comprise an access point (AP) 110 and a wireless terminal device (STA) 100. In case of IEEE 802.11-based wireless local area networks (WLANs), the AP 110 may be associated with a basic service set (BSS) which is a basic building block of IEEE 802.11-based WLANs. The most common BSS type is an infrastructure BSS that includes a single

AP together with all STAs associated with the AP. The AP may be a fixed AP or a mobile AP. The AP 110 may also provide access to other networks, such as the Internet. In an embodiment, the plurality of BSSs may interconnect to form an extended service set (ESS).

[0015] A terminal device 100 may establish and manage a peer-to-peer wireless network to which one or more other terminal devices 130 may associate. In such a case, the peer-to-peer wireless network may be established between two or more terminal devices. The terminal device managing the network may operate as an access point or node providing the other terminal device(s) with a connection to other networks, such as the Internet. In other embodiments, such routing functionality is not employed and the connection terminates in the terminal devices. One example technology of P2P connectivity is Wi-Fi neighbor Awareness Networking, also referred to as Wi-Fi Aware, facilitating discovery of devices and services within Wi-Fi range.

[0016] The AP 110 may be connected to further network elements, in an embodiment a network management system (NMS) 120. The NMS may maintain channel usage information of wireless networks of one or more APs and to configure the channel usage of the wireless networks. For example, it may control wireless networks located close to each other to operate on different channels and hence avoid interference between the networks. In an embodiment, the network management system 120 is comprised in one of the APs, e.g. in the AP 110. In another embodiment, the network management system is realized by an apparatus different from the APs, e.g. by a server computer to which the APs may connect via a wired or wireless connection. [0017] The terminal device 100 may discover the AP 110 through a network discovery process. A scanning device may actively transmit a scanning request message, such as a probe request message or a generic advertisement service (GAS) request, in order to obtain information of locally available access points or networks. Responding devices may transmit scanning response messages, such as probe response messages, comprising information on the responding device and its network. A terminal device 100 may establish a connection with any one of APs 110 it has detected to provide a wireless connection within the neighbourhood of the terminal device. The connection establishment may include authentication in which an identity of the terminal device is established in the AP. The authentication may comprise exchanging an encryption key used in the BSS. After the authentication, the AP and the terminal device 100 may carry out association in which the terminal device is fully registered in the BSS, e.g. by providing the terminal device with an association identifier (AID).

[0018] Power consumption continues to be an issue with wireless networks and mobile communication. IEEE 802.11 working group has developed power-save mechanisms like a power save (PS) mode to save power when the STA 100 is associated to an AP 110. By default, an associated STA is in active mode which enforces it to stay in an awake state when the STA is fully powered and able to transmit and receive frames with the AP. An associated STA may transition to the PS mode with explicit signalling and, while operating in the PS mode, it may save power by operating occasionally in a power-saving state, which may also be referred to as sleep or idle state. In the power-saving state, the STA is not able to transmit or receive frames but, on the other hand, power consumption of the STA is on a considerably lower level than in the awake state. The STA may wake up from the power-saving state to receive periodic beacon frames from the AP. While the STA is in the power-saving state, the AP buffers frames addressed to the STA. When the STA is awake, the AP indicates with beacon frames (in a traffic indication map, TIM, field) whether it has frames buffered to the STA.

[0019] Recent developments in 802.11 work groups have involved introduction of a new low-power radio interface called a wake-up radio. One purpose of the new radio interface is to enable further power-savings by allowing a main radio, which may also be referred to as a primary connectivity radio, used for data communication according to 802.11 specifications to be off for longer periods. The low-power radio may be referred to as a wake-up radio (WUR) or a low-power WUR (LP-WUR), and it is considered to be a companion radio to the main radio. A wireless device such as the STA 100 may comprise both a WUR receiver and the main 802.11 radio. An AP 110 may comprise a WUR transmitter and the main 802.11 radio. It has been proposed that the purpose of the wake-up radio is mainly to wake-up the main radio when the AP has data to transmit to a sleeping STA.

[0020] The wake-up radio interface may be designed such that it consumes less power than the main radio. The wake-up radio may employ a simpler modulation scheme than the main radio, e.g. the wake-up radio interface may use only on-off keying while the main radio uses variable modulations schemes such as phase-shift keying and (quadrature) amplitude modulation. The wake-up radio interface may operate on a smaller bandwidth than the smallest operational bandwidth of the main radio.

[0021] The term wake-up radio refers herein generally to a radio used to wake up a main radio primarily used for wireless data transfer. The wake-up radio may be used only for waking up the main radio of a wireless device. In some embodiments, the wake-up radio of the wireless device may comprise only a receiver. In other embodiments, the wireless device may have both a WUR receiver and a WUR transmitter. The wake-up radio may thus be powered on when the main radio is powered off. The term main radio refers generally to a radio primarily used for communication, and may be also referred to as primary connectivity radio (PCR). It is to be noted that in some embodiments a non-WLAN radio may serve as the main radio. For example a cellular radio or a short-range radio such as a Bluetooth radio, may serve as the main radio.

[0022] A wake-up radio of the STA 100 may be configured to receive and extract wake-up frames (WUF) transmitted by a wake-up radio of the AP 110. The wake-up radio of the STA may be capable of decoding the wake-up frames on its own without any assistance from the main radio. The wake-up radio may thus comprise, in addition to a radio frequency front-end receiver components, digital baseband receiver components and a frame extraction processor capable of decoding contents of a wake-up frame. The wake-up frame may comprise a destination address field indicating a STA that should wake up the main radio. The frame extraction processor may perform decoding of the destination address from a received wake-up frame and determine whether or not the destination address is an address of the STA of the frame extraction processor. If yes, it may output a wake-up signal causing the main radio to wake up for radio communication with an AP.

[0023] Figure 2 illustrates example modes or states for a wireless device, such as the STA

100 with the main radio and the WUR. The main radio is on during the awake state 200. The above-described use of the wake-up radio to wake up the main radio may be performed when the STA 100 is associated to the AP 110. When the STA disables the main 802.11 radio, it may enter a new power-saving mode or state, separate from the existing 802.11 power-saving modes or states, that is herewith referred to as a doze state 210, but may also be referred to as a WUR (sleep) mode or state, a dormant or idle mode or state, for example. The main radio is off and the wake-up radio is on during the doze state 210. [0024] When transitioning from the awake state 200 to the doze state 210, the WUR may be activated upon disabling the main radio. However, in other embodiments the WUR may be active also when the main radio is active. The doze state may be entered by doze state related signalling between the STA and the AP: The STA may send a doze state request to the AP during the awake state 200 via the main radio. The doze state 210 may be entered after a doze state response by the AP. In the doze state there may be a keep alive process: If the STA does not receive any WUR frame for a maximum idle period, the STA may return to the awake state 200 to listen to frames or send a frame for keep alive checking. The STA may thus return to the doze state 210 upon detecting a frame from its associated AP. It is to be noted that in some embodiments the doze state 210 may also comprise short periods when the main radio is on. In these embodiments, state 210 may be considered as the dormant state. Detailed implementation of the use of the wake-up receiver and state synchronization between the AP and the STA is still under development.

[0025] There may be a further power save mode or state 220, such as the IEEE 802.11 PS mode mentioned above. During the power save state 220 the main radio is on/off according to the applied power-saving mechanism, and the wake-up radio is off. It is to be appreciated that in some embodiments specific power-save state is not applied or there is no transition between the power saving mode 220 and the WUR mode 210. Further, in an embodiment, the wake-up radio is always on.

[0026] Minimization of power consumption is particularly important for ultra-low-power IoT devices, such as sensor devices configured to wirelessly send measurements. There is now provided a method and apparatus facilitating omitting maintenance of clock in a low-power device while in a power-saving mode. The clock maintenance may be outsourced to a clock service provider device from one or more other devices. The clock service providing device may send scheduled wake-up frame(s) to the other device(s) via wake-up radio(s), when the other device(s) are in a doze state. The wake-up frame may trigger a local action in the other device(s), such as a periodical environmental measurement or other type of observation. Thus, it is not necessary for the other devices to maintain a clock for local operations, but it is enough to have the wake-up radio on to receive the scheduled wake-up frame. This enables further power saving; the maintenance of accurate enough clock may be a bottleneck in the power consumption point-of- view, for example if there are multiple low power IoT devices in the same network which should do something at exactly the same time periodically.

[0027] Figures 3 and 4 illustrate methods for facilitating power-saving by a clock service.

The methods may be implemented in an apparatus comprising, connected to and/or controlling two radio interfaces according to some embodiments. Figure 3 illustrates a process for a first wireless device for utilizing an external clock service or outsourced clock to trigger a local observation while in a doze state, such as the STA 100, while Figure 4 illustrates a process for a wireless device such as the AP 110 or the terminal device 130, providing the clock service for the first wireless device.

[0028] Referring first to Figure 3, a method is provided for a first wireless device. The method may be applied in an apparatus, which may be comprised by the first wireless device and configured to cause the first wireless device to carry out at least the features disclosed in Figure 3. The first wireless device may be any type of wireless device comprising a main radio and a wake- up radio, such as an IoT device or a user device comprising an IEEE 802.11 main radio and a WUR. [0029] The process comprises, as performed by a first wireless device: A first frame is received 300 from a second wireless device, the first frame indicating that the second wireless device is capable to provide clock service. The clock service refers generally to a scheduled wake- up service. A second frame indicating that the first wireless device requests the clock service is transmitted 310 to the second wireless device. The first and second frame transmissions may be performed via the main radio.

[0030] The first wireless device switches 320 from an awake state, in which a main radio of the first wireless device is enabled, to a doze state in which the main radio is disabled and a wake- up radio of the first wireless device is enabled. The doze state refers generally to a state of the first wireless device where the main radio is disabled and the wake-up radio is enabled, and the awake state to a state of the first wireless device where the main radio is enabled, without limiting to the above-mentioned IEEE 802.11 states.

[0031] A wake-up frame is received 330 via the wake-up radio. The method may check 340 if the received wake-up frame is associated with the (requested) clock service. In response to receiving the wake-up frame and detecting that the wake-up frame is associated with the clock service, the first wireless device performs 350 a local action and remains in the doze state. In this embodiment, the first wireless device does not activate the main radio after receiving the wake-up frame.

[0032] In response to detecting that the received wake-up frame is not associated with the clock service, the first wireless device switches 360 from the doze state to the awake state. It is to be noted that in some embodiments the first wireless device may activate the main radio, for example to send a measurement report via the main radio, after receiving the wake-up frame not associated with the clock service, and then return in the doze state.

[0033] In an embodiment, a wake-up frame, associated with the (requested) clock service, may comprise a parameter value indicating that the first wireless device needs to activate the main radio, for example to send a measurement report via the main radio. In an embodiment, the parameter value may be included in every Nth wake-up frame associated with the clock service. In this way, it is possible to obtain measurement results related to local actions without necessarily sending a wake-up frame that is not associated with the clock service. [0034] With reference to Figure 4, a method is provided for a second wireless device. The method may be applied in an apparatus, which may be comprised by the second wireless device and configured to cause the second wireless device to carry out at least the features disclosed in Figure 4. The second wireless device may be configured to provide the scheduled wake-up service for the first wireless device, i.e. operate as a scheduled wake-up service provider for the first wireless device, which may operate as illustrated in Figure 3.

[0035] The process comprises, as performed by the second wireless device: A first frame is transmitted 420 to a first wireless device. The first frame indicates that the second wireless device is capable to provide clock service. A second frame, indicating that the first wireless device requests the clock service, is received 410 from the first wireless device. A scheduled wake-up frame associated with the clock service is transmitted 420 on the basis of the second frame for causing the first wireless device to perform a local action without activating a main radio of the first wireless device. For conciseness, the (scheduled) wake-up frame associated with the clock service is hereinafter referred to as the scheduled wake-up frame. The scheduled wake-up frame may thus be transmitted to the first wireless device operating in accordance with Figure 3.

[0036] The scheduled wake-up frame may comprise a parameter or other type of indication information indicating that it is a scheduled wake-up frame differentiating from other wake-up frames and which does not request wake-up of the main radio, for preventing activation of the main radio. The indication is included in the wake-up frame transmitted in block 420 and checked for in block 340. The indication may be provided by a new wake-up frame type or a wake-up identifier specific for the clock service. Further, also the second frame in block 310, 410 may comprise a similar indication on request for scheduled wake-up frame(s) differentiating from other wake-up frames and which does not request wake-up of the main radio. [0037] The methods illustrated in Figure 3 and 4 allow publication or advertisement of a scheduled wake-up service for other devices with wake-up radio, such as Wi-Fi Aware capable devices. The other devices can subscribe to the service and negotiate wake-up schedule for themselves and/or for other devices. The clock service provider will wake-up the dozing devices as agreed, thus enabling further power-saving in the dozing devices. [0038] It will be appreciated that various additions and modifications may be made to the methods illustrated in Figures 3 and 4, some example embodiments being illustrated below. It will be appreciated that the clock service may be continued after blocks 350 and 420 by the second wireless device returning to block 420 and transmitting subsequent scheduled wake-up frame(s) to the first wireless device returning to block 330. Such clock service may be continued until the first wireless device returns to the awake mode 200, duration for the clock service expires, or a specific frame is sent to end the clock service, for example.

[0039] In some embodiments, a third frame acknowledging the second frame and/or the clock service is transmitted between blocks 310 and 320 and 410 and 420 to the first wireless device from the second wireless device. The switch from the awake state 200 to the doze state 210 may be performed 320 in response to the acknowledgement. The second and the third frame may be used for negotiating clock service parameters, such as the wake-up schedule. There may be also further such negotiation messages after the second frame.

[0040] The third frame or other clock service negotiation frame from the second wireless device may indicate the allocated clock service parameter(s). If acceptable, the second wireless device may send the same clock service parameter information back to the as requested in the second frame. The information may be altered if the second wireless device is not capable of providing a requested parameter, for example. Alternatively, the AP may send only information that it has received or accepts the clock service parameters. This may be implicit by sending a response without any additional information but only by sending positive response frame accept parameters, or this can be explicit by having a new element included with accept or reject information included.

[0041] The first frame 300, 400 may comprise information indicating clock accuracy of the clock service provided by the second wireless device. The first wireless device may be configured to use the clock accuracy information to select an appropriate clock service provider between blocks 300 and 320 if there are multiple devices providing the service and hence multiple first frames received. It is to be appreciated that the first frame may comprise other clock service related and/or second wireless device related information affecting the selection of the clock service provider and/or the second frame, such as limitations on available cycles of transmitting the scheduled wake-up frames of the clock service. For example, the second wireless device may provide wake-up schedules with certain resolutions, such as once per hour, twice per hour, four times per hour, etc. Another example is that maximum and/or minimum periods are defined for transmitting the scheduled wake-up frames of the clock service.

[0042] The second frame 310, 410 may further indicate at least one requested timing parameter for scheduling transmission of wake-up frames, and the second wireless device may be configured to transmit 420 the scheduled wake-up frame according to the received timing parameter. The timing parameter may be implemented in various ways, depending on the local action, for example. The timing parameter may indicate at least some of: a time period between consecutive scheduled wake-up frames, e.g. in seconds, start time of or offset to the scheduled wake-up frame, and a time window of the scheduled wake-up frame, for example.

[0043] The second frame 310, 410 may indicate at least one destination or target of the clock service. Thus, the first wireless device may request clock service for one or more other devices. The second frame may specify one or more unicast or multicast wake-up identifiers (WIDs) of the intended receiving devices of the scheduled wake-up frame, and the second wireless device may be configured to send the scheduled wake-up frame to these devices. The second frame may indicate whether or not acknowledgements to the scheduled wake-up frames are provided.

[0044] In some embodiments, the second wireless device is an access point or other wireless access network element, such as the AP 110, and the first wireless device is a terminal device, such as the STA 100. However, it is to be appreciated that in alternative embodiments a terminal device, such as the STA 130, may operate as the second wireless device, hereafter also referred to as the second device, and a terminal, or even an access point may operate as the first wireless device, hereafter also referred to as the first device.

[0045] In some embodiments, the first, second, and third frames are transmitted 300, 310 and received 400, 410 via the main radio of the devices. The first, second and third frames may be new messages for the clock service, or the clock service related information and signalling may be included in a new information element of an existing signalling message, such as an appropriate IEEE 802.11 WLAN frame.

[0046] In some embodiments, the first frame 300, 400 is one of a publish message according to Wi-Fi neighbor awareness networking, a beacon, a probe response, or an association response in wireless local area network. The second frame 310, 410 may be one of Wi-Fi neighbor awareness message, a follow-up service (discovery) frame, a wake-up radio mode request (or some other message for indicating or requesting activation of the doze state), an association request with a clock service information element, or a reassociation request with a clock service information element, or another frame for subscribing to or requesting the clock service. The third frame may be an acknowledgment of the same frame type as the second frame. The second frame may comprise information on the requested clock service, but may also comprise other configuration information, such as WUR configuration information.

[0047] In a further example, upon detecting an available AP with clock service capability e.g. with probe request/response signaling, authentication and association signalling may be carried out between the STA 100 and the AP 110. The STA may thus agree with the AP on the clock service parameters that determine rules for the scheduled wake-up frame transmission to the device over the wake-up radio.

[0048] The scheduled wake-up frame may be a unicast frame or a multicast frame. The scheduled wake-up frame may be an unmodified wake-up frame, or a specific scheduled wake-up frame format or information element is used for the clock service. In an embodiment, the scheduled wake-up frame comprises a clock service or other type of reason code. The first device may be configured to prevent activation of the main radio on the basis of such indication or reason code. [0049] However, it is to be appreciated that the above messages represent only some examples of messages by which the information of blocks 300, 310, 320, 400, 410 may be delivered, and the clock service related information/signalling may be included in other suitable signaling messages. [0050] The local action 350 may comprise performing a local measurement and storing measurement results of the local measurement. The first device may operate as or be included in an IoT sensor device, for example. The measurement results may be transmitted to the second wireless device or a third device. The transmission may be arranged in response to receiving another wake- up frame not associated with the clock service, different from the scheduled wake-up frame, i.e. in connection with block 360. Some other examples of the local action include an output action at the first device, such as alerting the user by audible and/or visual output, activating or powering up the first device or an application/function thereof, providing an input to an application or function of the first device, or triggering another action by an application of the first device.

[0051] In some embodiments, at least some of the presently disclosed features are applied in devices supporting Wi-Fi Neighbor Awareness Networking or Wi-Fi Aware. For example, the first frame (block 300 and 400) may be a Wi-Fi publish frame adapted to comprise the indication of the clock service.

[0052] Figure 5 illustrates signalling between the first device and the second device according to an example embodiment applying Wi-Fi Aware networking. The devices may be any Wi-Fi Aware devices, wherein the second device is configured to provide the scheduled wake-up service for the first device, which may be a low-power IoT device, for example.

[0053] First, the clock service may be published by a Wi-Fi Aware Publish 500. Such publication may be an advertisement for locally detected device(s). A new service type and/or service identifier, for example with a service name:“org. wi-fi. aware. scheduledwakeup”, may be defined to be used for the clock service. The service provider may use the service name to publish the service. A service discovery frame used for publishing the service, may also comprise a clock accuracy field in a service info part of the frame.

[0054] The second device may request and subscribe to the clock service by sending a Wi

Fi Aware Subscribe 502. The subscribe frame 502 indicates at least the interest on the clock service. Subsequent follow-up frames 504 may be applied for negotiating parameters of the clock service. For example, the follow-up service discovery frame(s) 504 may indicate at least some of: desired schedule of the scheduled wake-up frame(s), destination(s) of the scheduled wake-up frame(s), and if acknowledgement of the scheduled wake-up frame(s) should be expected. [0055] After the clock service has been set, the first device may enter the doze state 506.

Figure 5 illustrates unicast clock service provision for a single device, so a unicast WUF 508 serves as the scheduled wake-up frame. After receiving the scheduled WUF 508, the first device performs the local action 510 and remains in the doze state 506. The first device may receive a subsequent WUF, which may be a scheduled WUF 512 of the clock service causing the first device to perform a subsequent local action (not shown). If the subsequent WUF 512 is not associated with the clock service, it causes the first device to switch from the doze state 506 to the awake state (and activate the main radio).

[0056] As mentioned above, in some embodiments the second device may be the AP 110 and the clock service may be provided for a plurality of STAs 100, 130. Hence, it will be appreciated that the first device may send the scheduled WUFs 508, 512 to a plurality of STAs in an infrastructure network, after setting up the clock service upon request from at least one of the STAs similarly as illustrated in Figure 5.

[0057] Figure 6 illustrates another signaling example in which the clock service is acquired for multiple other devices by the first device, in this example requested from a scheduled wake-up service provider 602 by a smart phone 604 for low power IoT devices 606, 608, and 610. The clock service may be published 500, subscribed 502 and negotiated 504 similarly as in connection with Figure 5, except now the smart phone requests the clock service for the IoT devices 606, 608, and 610 by indicating a multicast address. The IoT devices do not need to be Wi-Fi Aware capable, it is enough that they support the wake-up radio. The IoT devices may already be or set after 504 in the doze state 506. The service provider 602 sends a multicast WUF 612 for the IoT devices, which receive the WUF via their wake-up radios and perform the local action 614. Subsequent WUF(s) 616 (associated or not associated with the clock service) may be transmitted to the IoT devices (triggering further local action or state change, respectively). Hence, it will be appreciated that in some embodiments blocks 300-310 and 320-340 may be carried out by separate devices, and the second device may be send the scheduled wake-up frame to other device(s) than the first device.

[0058] In an alternative embodiment, the wake-up service provider 602 may use unicast

WUF messages to wake-up a group of devices. In such case, additional signaling would be needed to tell waked-up devices how much should they wait after WUF frame. [0059] While some embodiments have been described in the context of IEEE 802.11 based system, it should be appreciated that these or other embodiments of the invention may be applicable in connection with other technologies, such as with main radios operating according to other versions of the IEEE 802.11, WiMAX (Worldwide Interoperability for Microwave Access), UMTS LTE (Long-term Evolution for Universal Mobile Telecommunication System), LTE- Advanced, or a fifth generation cellular communication system (5G). Some embodiments may be applicable to networks having features defined by the IEEE 802.19.1 working group.

[0060] An electronic device comprising electronic circuitries may be an apparatus for realizing at least some embodiments of the present invention. The apparatus may be or may be comprised in a computer, a laptop, a tablet computer, a cellular phone, a machine to machine (M2M) device (e.g. an IoT sensor device), a wearable device, a base station, access point device or any other apparatus provided with radio communication capability. In another embodiment, the apparatus carrying out the above-described functionalities is comprised in such a device, e.g. the apparatus may comprise a circuitry, such as a chip, a chipset, a microcontroller, or a combination of such circuitries in any one of the above-described devices.

[0061] Figure 7 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is a device 700, which may comprise a communication device, such as the terminal device STA 100 or the access point AP 110. The device may include wake-up radio functionality in accordance with at least some of the embodiments illustrated above. For example, the device 700 may be configured to perform the method illustrated in Figure 3 and/or 4, and at least some of the further embodiments thereof.

[0062] Comprised in the device 700 is a processor 702, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. The processor 702 may comprise more than one processor. The processor may comprise at least one application-specific integrated circuit, ASIC. The processor may comprise at least one field-programmable gate array, FPGA. The processor may be means for performing method steps in the device. The processor may be configured, at least in part by computer instructions, to perform actions.

[0063] The device 700 may comprise memory 704. The memory may comprise random- access memory and/or permanent memory. The memory may comprise at least one RAM chip. The memory may comprise solid-state, magnetic, optical and/or holographic memory, for example. The memory may be at least in part accessible to the processor 702. The memory may be at least in part comprised in the processor 702. The memory 704 may be means for storing information. The memory may comprise computer instructions that the processor is configured to execute. When computer instructions configured to cause the processor to perform certain actions are stored in the memory, and the device in overall is configured to run under the direction of the processor using computer instructions from the memory, the processor and/or its at least one processing core may be considered to be configured to perform said certain actions. The memory may be at least in part comprised in the processor. The memory may be at least in part external to the device 700 but accessible to the device. According to an aspect, when the processor 702 executes computer program code stored in the memory 704, the computer program code causes the apparatus to carry out the functionalities according to any one of the embodiments of Figures 3 to 6.

[0064] The device 700 may comprise a main radio 706 and a wake-up radio 708. The main radio 706 and the WUR 708 may comprise standard well-known radio interface components, such as an amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas. The main radio 706 and the WUR 708 may be configured to operate in accordance with at least one cellular or non-cellular standard. The main radio comprises at least one transmitter and at least one receiver. The WUR 708 comprises a receiver and/or transmitter. The radios 706, 708 may comprise analogue radio communication components and digital baseband processing components for processing transmission and reception signals. The main radio 706 may support multiple modulation formats, whereas the WUR 708 may support a single modulation scheme only, e.g. the on-off keying. The main radio 706 may be configured to operate in accordance with long term evolution, LTE, WLAN, and/or worldwide interoperability for microwave access, WiMAX, standards, for example. The WUR 708 may be configured to operate according to IEEE 802.11 WUR, for example.

[0065] The device may comprise at least one controller controlling the main radio 706 and/or the WUR 708 wake-up radio functions according to presently disclosed embodiments. In particular, the controller may be arranged to cause at least some of the operations illustrated in connection with Figures 2 to 7, but may also be controlling other radio operations. The controller may be implemented by the processor 702, for example.

[0066] The device 700 may comprise one or more further radios 710, such as a transceiver for cellular communication and/or a near-field communication, NFC, transceiver. A further cellular radio may operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, IS-95, LTE, or 5G, for example. The NFC transceiver may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0067] The device 700 may comprise user interface, UI, 712. The UI may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing the device to vibrate, a speaker and a microphone. A user may be able to operate the device via the UI, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in the memory 704 or on a cloud accessible via the main radio 706, or via the further radio 710, and/or to play games.

[0068] The device 700 may comprise or be arranged to accept a user identity module or other IC module 714. The user identity module may comprise, for example, a subscriber identity module, SIM, card installable in the device 700. The user identity module 714 may comprise information identifying a subscription of a user of device 700. The user identity module 714 may comprise cryptographic information usable to verify the identity of a user of device 700 and/or to facilitate encryption of communicated information and billing of the user of the device 700 for communication effected via the device 700. [0069] The processor 702 may be furnished with a transmitter arranged to output information from the processor, via electrical leads internal to the device 700, to other devices comprised in the device. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 704 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise the processor may comprise a receiver arranged to receive information in the processor, via electrical leads internal to the device 700, from other devices comprised in the device 700. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from the radio 706, 708 for processing in the processor. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver. [0070] The device 700 may comprise further devices not illustrated in Figure 7. For example, the device may comprise at least one digital camera. Some devices 700 may comprise a back-facing camera and a front-facing camera. The device may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of the device. In some embodiments, the device lacks at least one device described above. For example, some devices may lack the further radio 710 and/or the user identity module 714.

[0071] The processor 702, the memory 704, the main radio 706, the WUR 708, the further radio 710, the UI 712 and/or the user identity module 714 may be interconnected by electrical leads internal to the device 700 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to the device, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0072] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. [0073] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0074] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0075] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0076] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0077] The verbs “to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

At least some embodiments of the present invention find industrial application in wireless communications.

ACRONYMS LIST

AID Association identifier AP Access point ASIC Application-specific integrated circuit BSS Basic service set ESS Extended service set FPGA Field-programmable gate array GAS Generic advertisement service GSM Global system for mobile communication LP-WUR Low -power WUR LTE Long term evolution M2M Machine to machine NFC Near-field communication NMS Network management system PCR Primary connectivity radio QoS Quality of service STA Station TIM Traffic indication map UI User interface WCDMA Wideband code division multiple access WID Wake-up identifier

WiMAX Worldwide interoperability for microwave access WLAN Wireless local area network

WUR Wake-up radio

WUF Wake-up frame