Low-power-wake up signal message with circular shifted sequence

Abstract

Example embodiments of the present disclosure are directed to low-power-wake up signal (LP-WUS) message with circular shifted sequence. A method comprises in accordance with a determination that a LP-WUS from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and determining, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception (c-DRX) to be monitored; and monitoring a downlink transmission from the second apparatus within the subset of the on-duration window.

Description

Low-power-wake up signal message with circular shifted sequenceCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from, and the benefit of, US Provisional Application No. 63 / 702780, filed October 3, 2024, which is hereby incorporated by reference in its entirety.FIELD

[0002] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for low-power-wake up signal message with circular shifted sequence.BACKGROUND

[0003] The study of low power wake-up signal (WUS) and low power wake-up receiver (LP-WUR) in 5G new radio (NR) may enable more power efficient operation on UE and more optimal resource allocation for network. The main radio of UE can be in a sleep mode (or even powered off) for power saving and the low power radio is not power off and can be in sleep between the reception of the LP- WUS from the network.SUMMARY

[0004] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and determine, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and monitor a downlink transmission from the second apparatus within the subset of the on-duration window.

[0005] In a second aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: generate a low- power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and transmit the LP-WUS at least to the first apparatus.

[0006] In a third aspect of the present disclosure, there is provided a method. The methodcomprises: in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and determining, based on the circular shift, a subset of the on- duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and monitoring a downlink transmission from the second apparatus within the subset of the on-duration window.

[0007] In a fourth aspect of the present disclosure, there is provided a method. The method comprises: generating a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and transmitting the LP-WUS at least to the first apparatus.

[0008] In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and means for determining, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and means for monitoring a downlink transmission from the second apparatus within the subset of the on-duration window.

[0009] In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for generating a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and means for transmitting the LP-WUS at least to the first apparatus.

[0010] In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the third aspect.

[0011] In an eighth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the fourth aspect.

[0012] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensiblethrough the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0014] FIG. 1A illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

[0015] FIG. 1 B illustrates example state transition of a receiver of a device according to some example embodiments of the present disclosure;

[0016] FIGS. 2A-2E illustrates examples of different LP-WUS operations used in conjunction with C-DRX;

[0017] FIG. 3 illustrates a LP-WUS in accordance with some example embodiments of the present disclosure;

[0018] FIG. 4 illustrates time domain circular shift of sequences in accordance with some example embodiments of the present disclosure;

[0019] FIG. 5 illustrates different subgroups in accordance with some example embodiments of the present disclosure;

[0020] FIG. 6 illustrates an example of the probability of data arrival for an XR use case in accordance with some example embodiments of the present disclosure;

[0021] FIG. 7 illustrates a flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0022] FIG. 8 illustrates a flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0023] FIG. 9 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0024] FIG. 10 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0025] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0026] Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

[0027] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0028] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0029] It shall be understood that although the terms “first,” “second,”..., etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0030] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0031] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0033] As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause a first apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0034] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0035] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE- A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-loT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1 G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), 5.5G, the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0036] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (I AB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-groundnetwork device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0037] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0038] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0039] FIG. 1A illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. As shown in FIG. 1A, the communication network 100 may comprise a first apparatus 110 which may be, for example, a terminal device. Insome example embodiments, the terminal device may also be discussed as a UE.

[0040] The communication network 100 may further comprise a second apparatus 120, which may be, for example, a network device. In some example embodiments, the network device may be discussed as a BS, a gNB, or an eNB.

[0041] A serving area provided by the second apparatus 120 is called a cell. The first apparatus 110 may communicate with the second apparatus 120 within the cell 102. The cell currently serving the first apparatus 110 may be considered as a serving cell 102.

[0042] In the following, for the purpose of illustration, some example embodiments are described with the first apparatus 110 operating as a terminal device and the second apparatus 120 operating as a network device. However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

[0043] In some example embodiments, if the first apparatus 110 is a terminal device and second apparatus 120 is a network device, a link from the second apparatus 120 to first apparatus 110 is referred to as a downlink (DL), while a link from the first apparatus 110 to second apparatus 120 is referred to as an uplink (UL). In DL, the second apparatus 120 is a transmitting (TX) apparatus (or a transmitter) and the first apparatus 110 is a receiving (RX) apparatus (or a receiver). In UL, the first apparatus 110 is a TX apparatus (or a transmitter) and the second apparatus 120 is a RX apparatus (or a receiver).

[0044] It is to be understood that the number of network devices and terminal devices shown in FIG. 1A is given for the purpose of illustration without suggesting any limitations. The communication environment 100 may include any suitable number of network devices and terminal devices.

[0045] Communications in the communication environment 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1 G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0046] A study of LP-WUS and LP-WUR has been discussed for NR. The study evaluated the usage of an additional LP-WUR at the UE to reduce the overall UE power consumption. The defining principle behind this scheme is that the main radio / receiver (MR) of the UE can be put into a sleep mode (or even powered off) for power saving when not being needed for any processing (e.g., traffic / measurements) and then be easily woken up as and when required by the network upon the reception by the LP-WUR of a newly defined WUS.

[0047] Basically, the network may trigger the UE to wake-up in a WUS monitoring occasion, by transmitting a special WUS to the UE, which is monitored by the dedicated LP-WUR at the UE. When a UE receives the WUS, the WUR receiver can trigger the wake-up of the ordinary NR MR transceiver and communication can start.

[0048] Thus, the ultra-low power receiver wakes up the MR, otherwise, the MR can be OFF or kept in a deep sleep mode, as shown in FIG. 1 B, which shows an example of UE operation with LP-WUR. The assumption can also be that the low-power wake-up receiver can be operated in an always ‘on’ manner with very low power consumption. In fact, it is expected that the LP-WUR will consume significantly less power compared to the MR transceiver, by designing a simple (WUS) signal and the use of dedicated hardware for its monitoring, which is only able to receive the WUS. It is also possible that MR and LR may be simultaneously switched on, which may impact the power consumption.

[0049] 5G systems are designed and developed targeting for both mobile telephony and vertical use cases. Besides latency, reliability, and availability, UE energy efficiency is also critical to 5G. Currently, 5G devices may have to be recharged per week or day, depending on individual's usage time. In general, 5G devices consume tens of milliwatts in RRC idle / inactive state and hundreds of milliwatts in RRC connected state. Designs to prolong battery life is a necessity for improving energy efficiency as well as for better user experience.

[0050] Energy efficiency is even more critical for UEs without a continuous energy source, e.g., UEs using small rechargeable and single coin cell batteries. Among vertical use cases, sensors and actuators are deployed extensively for monitoring, measuring, charging, etc. Generally, their batteries are not rechargeable and expected to last at least few years. Wearables include smart watches, rings, eHealth related devices, and medical monitoring devices. With typical battery capacity, it is challenging to sustain up to 1-2 weeks as required.

[0051] The power consumption depends on the configured length of wake-up periods, e.g., paging cycle. To meet the battery life requirements above, long extended discontinuous reception (eDRX) cycle may be used, resulting in high latency, which is not suitable for such services with requirements of both long battery life and low latency. For example, in fire detection and extinguishment use case, fire shutters shall be closed and fire sprinklers shall be turned on by the actuators within 1 to 2 seconds from the time the fire is detected by sensors, long eDRX cycle cannot meet the delay requirements.eDRX is apparently not suitable for latency-critical use cases.

[0052] The Rel-18 study item for "Study on low-power wake up signal and receiver for NR" includes investigations to the followings:- The low-power wake-up signal and receiver, including power saving benefit, coverage, system overhead impact, network energy impact and other related aspects.- The receiver architecture for low-power wake-up receiver and provide analysis for power consumption, noise figure and etc.- L1 design and procedure changes needed to support the low-power wake-up signal and evaluations for the link performances.- Higher layer protocol changes needed to support the low-power wake-up signals.- Related RAN4 impacts.

[0053] In RRC I DLE / INACTIVE modes, it's observed that significant UE power saving gain (up to more than 90%) is obtained by using LP-WUS / WUR to trigger UE MR paging monitoring compared with existing l-DRX operation (with and without PEI), if sufficient relaxation to MR RRM measurement is applied. Further, compared with existing eDRX operation, significant paging latency reduction and moderate UE power saving gain is observed, if LP-WUS monitoring and the corresponding paging monitoring after MR wake-up is performed not restricted within existing PTW of eDRX.

[0054] In RRC CONNECTED mode, it's observed that moderate UE power saving gain (up to more than 10%) is obtained with marginal impact to capacity by using LP-WUS / WUR to trigger UE MR PDCCH monitoring compared with existing UE power saving techniques, across different types of XR traffic and system load scenarios. It's also observed that significant UE power saving gain (up to more than 60%) and moderate UPT improvement (up to more than 10%) is obtained for FTP and IM traffic, when the UE MR enters deep sleep state during LR LP-WUS monitoring. Furthermore, Rel-18 study verified the feasibility on serving cell RRM measurement offloading from UE MR to LP-WUR by reasonable evaluation methodology. RAN4 also identified some issues which could be further discussed in Wl phase.

[0055] Based on the SI outcome, it is proposed to specify LP-WUS / WUR in Rel-19.

[0056] The objectives of SI or Core part Wl or Testing part Wl are the following:• To specify an LP-WUS design commonly applicable to both I DLE / I NACTIVE and CONNECTED modes (RAN1 , RAN4).• Specify OOK (OOK-1 and / or OOK-4) based LP-WUS with overlaid OFDM sequence(s) over OOK symbol.• The LP-WUS design shall ensure that for IDLE / I NACTIVE operation, the same information is delivered irrespective of LP-WUR type. The OFDM sequence can carry information.• At least duty-cycled monitoring of LP-WUS is supported.. For IDLE / INACTIVE modes.• Specify procedure and configuration of LP-WUS indicating paging monitoring triggered by LP-WUS, including at least configuration, sub-grouping and entry / exit condition for LP-WUS monitoring (RAN2, RAN1 , RAN3, RAN4).• Specify LP-SS with periodicity with Yms for LP-WUR, for synchronization and / or RRM for serving cell. (RAN1 , RAN4).• LP-SS is based on OOK-1 and / or OOK-4 waveform with or without overlaid OFDM sequences.Further down selection between with and without overlaid OFDM sequences is to be done within Wl.• Note: For LP-WUR that can receive existing PSS / SSS, existing PSS / SSS can be used for synchronization and RRM instead of LP-SS.• Y will be decided within Wl. 320ms is the start point.• Specify further RRM relaxation of UE MR for both serving and neighbor cell measurements, and UE serving cell RRM measurement offloaded from MR to LP-WUR, including the necessary conditions (RAN4, RAN2).• For CONNECTED mode, specify procedures to allow UE MR PDCCH monitoring triggered by LP-WUS including activation and deactivation procedure of LP-WUS monitoring (RAN2, RAN1).• Check in RAN#105 for potential TU adjustment in RAN2.• Note: In CONNECTED mode, UE MR ultra-deep sleep is not considered, and UERRM / RLM / BFD / CSI measurements are performed by MR.• Note: The target coverage of LP-WUS and LP-SS shall be the coverage of PUSCH for message3.• Note: The optimization of LP-WUS signal design for idle / inactive mode is prioritized over the optimization for connected mode.• Specify the necessary RAN4 core requirement(s) to support the feature (RAN4).• This objective is to be further refined in RAN#103.

[0057] Low-power Receiver (LR) types mainly include envelope detector and sequence detector. Envelope detector is only capable of detecting ON / OFF keying, and it has no IQ branch to perform coherent / sequence detection. Envelope receiver can only receive LP-WUS and LP-SS. Sequence detector can use IQ branches to perform coherent detection with sequence detection (SD). It consumes more power due to the better accuracy of crystal oscillators (XO) used to drive the PLLs. Sequence detector can receive also SSB in addition to LP-WUS.

[0058] As part of the SI, LP-WUS may be used in a variety of ways in CONNECTED mode. In this case, LP-WUS is used to inform the UE when to monitor the PDCCH, i.e. as long as the LP-WUS is absent, the UE may skip PDCCH monitoring. Multiple options are being discussed as can be seen from table 1 :Table 10059] It should be understood that the above directions / solutions are NOT Mutually Exclusive absolutely, e.g. some overlap may exist between direction 3 and direction 2, or between option 2 andoption 4, based on the detailed design for each direction / option. The detailed design would be further determined in Wl, if included.

[0060] In direction 1 above, LP-WUS is used in conjunction with C-DRX. LP-WUS could be configured outside the DRX active time with either of the following two options:- Same function as Rel-16 DCP to indicate whether to start the next drx-on-durationTimer (i.e. option1 above).- To indicate UE to enters into active time for PDCCH monitoring (i.e. option 2 above).

[0061] Some examples for different options in direction 1 are shown as illustrated in FIGS. 2A-2E. For option 1 , as an example 200A shown in FIG. 2A, LP-WUS is used similar as Rel-16 DCP. It should be noted that a longer time offset may likely have to be applied to cover the MR transition time compared to DCP.

[0062] For option 2, as shown in FIG. 2B and FIG. 2C, LP-WUS could be used at any time outside C-DRX active time to indicate UE to enter into active time. FIG. 2B shows an example 200B for option 2 with 'duty-cycled' LP-WUS. FIG. 2C shows an example 200C for option 2 with 'continuous' LP-WUS.

[0063] In direction 2 above, LP-WUS is used in conjunction with C-DRX as the direction 1 or without C-DRX. In the latter case, the LP-WUS is used to indicate UE to activate / resume PDCCH monitoring. Some other solutions used to indicate UE to stop the PDCCH monitoring should be used in conjunction with LP-WUS, e.g. Rel-17 PDCCH monitoring adaptation.

[0064] For option 4, as shown in FIG. 2D and FIG. 2E, LP-WUS could be used at any time regardless of whether C-DRX is configured or not. FIG. 2D shows an example 200D for option 4 with 'duty-cycled' LP-WUS. FIG. 2E shows an example 200E for option 4 with 'continuous' LP-WUS.

[0065] In direction 3, the detailed design should be determined based on physical layer design / restriction.

[0066] The corresponding pros / cons for the above options on LP-WUS using in RRC_CONNECTED are summarized in table 2.Table 2informing the UE to wake up for the next C-DRX On-duration which spans over multiple PDCCH periods.

[0068] Continue with reference to FIG. 2A, an LP-WUS wakeup message is scheduled before the C-DRX On-duration configured for a given UE. When the LR of the UE detects the wakeup message, it will wake up the MR to receive PDCCH’s during the next coming On-duration. However, the On- duration spans multiple PDCCH’s and the MR may spend power on receiving and decoding PDCCH’s which does not carry control information for it.

[0069] In accordance with some example embodiments of the present disclosure, there is provided a solution for low-power-wake up signal message with circular shifted sequence. In this solution, the first apparatus, in a case where a low-power-wake up signal (LP-WUS) from a second apparatus is detected, determines, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs. Then the first apparatus determines, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception (c-DRX) to be monitored and monitor a downlink transmission from the second apparatus within the subset of the on-duration window.

[0070] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0071] FIG. 3 illustrates a LP-WUS 300 in accordance with some example embodiments of the present disclosure. The first apparatus 110 may receive LP-WUS from the second apparatus 120. In some example embodiments, the first apparatus 110 includes a LP-WUS receiver, and the second apparatus 120 includes a LP-WUS transmitter

[0072] In some example embodiments, as shown in FIG. 3, the LP-WUS 300 includes multiple ON symbols / OFF symbols associated with the Manchester encoded symbol. Each ON symbol may be associated with a subgroup of terminal devices. A terminal device, which belongs to a subgroup, itmay decode the ON symbol, e.g., an overlaid sequence on the ON symbol, to which this subgroup is associated. Multiple ON symbols and OFF symbols make up an OFDM symbol. In some example embodiments, the ON symbol is comprised in a Manchester encoded symbol. An association between the ON symbols and subgroups of terminal devices may be known by both network and terminal device.

[0073] That is to say, respective subgroup of terminal devices is mapped to the plurality of ON symbols associated with the WUS signal 300. Respective overlaid sequences corresponding to the plurality of ON symbols have a same or different circular shifts.

[0074] If the LP-WUS from the second apparatus 120 is detected, the first apparatus 110 may determine an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs on a plurality of ON symbols.

[0075] As an example of the LP-WUS 300 shown in FIG. 3 by assuming OOK4 with M=4, SOS = 30 kHz and a sampling frequency of 7,68MHz. The overlaid sequence may be a circular shifted or noncircular shifted constant amplitude zero auto-correlation (CAZAC) sequence and is overlaid in time domain. The correlation needs to be performed in time domain as well. In an example, the sampling frequency at the first apparatus 110 is 7.68MHz and the ON duration of OOK symbol is 33us equal to 256 samples. It is to be understood that the gNB is not transmitting a traditional OOK signal, but instead mimics an OOK signal by sending a sequence in the ON symbols, which is observed as power by the ED based receiver.

[0076] In some example embodiments, the circular shift of k may be determined by the following formula: s’[i] = s[(i-k) mod / V]Where, the circular shift of k means that the samples of the sequence are shifted k samples, but using modulo sequence length, N, i.e. new sample index = (old sample index - k) modulo N. s’ denotes the circular shifted sequence and s denotes the original sequence of N samples.

[0077] FIG. 4 illustrates time domain circular shift of sequences in accordance with some example embodiments of the present disclosure. As mentioned above, the circular shift of sequences can be calculated by the above formula. This can be done independently for each subgroup of the wakeup message. In FIG. 4, 1 OFDMA symbol may have two ON symbols, each of them may be associated with a subgroup of terminal devices, e.g., subgroup A and subgroup B. The determined circular shift of sequence on first ON symbol associated with subgroup A is 25% and the determined circular shift of sequence on second ON symbol associated with subgroup B is 75%. If the first apparatus 110 belongs to the subgroup A, the first apparatus 110 may determine an overlaid sequence with a circular shift 25% associated with this ON symbol.

[0078] Multiple subgroups scheduled in different segments can therefore be woken up by the sameWUS wakeup message. In some example embodiments, the circular shift could indicate a segment of the on-duration to monitor.

[0079] Further, the first apparatus 110 may determine, based on the circular shift, the subset of the on-duration window for a connected mode discontinuous reception (c-DRX) to be monitored. In some example embodiments, each circular shift value in the set of circular shift values may be associated to one subset of the on-duration window in the plurality of subsets.

[0080] In some example embodiments, in the process of monitoring, the first apparatus 110 may obtain association between a set of circular shift values and a plurality of subsets of the on-duration window, and determine the subset of the on-duration window to be monitored based on the association and the circular shift of the determined overlaid sequence.

[0081] As an example, time domain location of the plurality of subsets of the on-duration window may be indicated by the circular shift as a start of the on-duration window. As an example:- 0% circular shift means the terminal device may monitor full on-duration window.- 20% circular shift means the terminal device may monitor the segment between 0% to 25% of the on-duration window.- 40% circular shift means the terminal device may monitor the segment between 25% to 50% of the on-duration window.- 60% circular shift means the terminal device may monitor the segment between 50% to 75% of the on-duration window.- 80% circular shift means the terminal device may monitor the segment between 75% to 100% of the on-duration window.

[0082] In some other example embodiments, the time domain location of the plurality of subsets of the on-duration window may be indicated by the circular shift as a center of the on-duration window. As an example:- 0% circular shift means the terminal device may monitor full on-duration window.- 20% circular shift means the terminal device may monitor only the center 20% of the on-duration window.- 40% circular shift means the terminal device may monitor only the center 40% of the on-duration window.- 60% circular shift means the terminal device may monitor only the center 60% of the on-duration window.- 80% circular shift means the terminal device may monitor only the center 80% of the on-duration window.

[0083] It should be understood that the time domain location of the plurality of subsets of the on-duration window may also indicated by the circular shift as an end of the on-duration window.

[0084] FIG. 5 illustrates different subgroups in accordance with some example embodiments of the present disclosure. As shown in FIG. 5, the different subgroups may point to independent segments of the on-duration window. For example, if a terminal device belonging to the subgroup 1 determines that a corresponding sequence with circular shift and the circular shift is associated with a first segment of on duration window of c-DRX, the terminal device may monitor PDCCH on the first segment, if a terminal device belonging to the subgroup 2 determines that a corresponding sequence with circular shift and the circular shift is associated with a second segment of on duration window of c-DRX, the terminal device may monitor PDCCH on the second segment.

[0085] Embodiments of the present disclosure may also allow the second apparatus 120 to dynamically scale how big a fraction of the on-duration window that is monitored by the first apparatus 110 and thereby account for the current traffic load and the amount of data to send to the first apparatus 110. In high traffic load use-cases it is beneficial to use a wide window to ease the scheduling but with additional power consumption of the first apparatus 110. On the other hand, in low traffic load use-cases it may be possible to perform scheduling in a narrower window and this can benefit the power consumption of the first apparatus 110.

[0086] In some example embodiments, the first apparatus 110 may determine, based on the circular shift, a fraction of a downlink monitoring occasion to be monitored versus one or more downlink monitoring occasions to be skipped; and monitor the downlink transmission based on the fraction. In this case the circular shift is telling the fraction of monitored versus skipped PDCCH’s. E.g. 20% would mean receive every 5th PDCCH and skip 4. Like explained above this can be used to dynamically adjust the number of monitored PDCCH’s which may be dynamically updated depending on the network load.

[0087] In poor signal conditions, the correlation peak of the expected sequence and the received signal may only result in a weak correlation value, or the propagation channel may result in multiple correlation peaks with similar magnitude. In such cases, the first apparatus 110 shall fall back to default behavior and monitor the complete on-duration window. The second apparatus 120 may provide a LP-RSRP and / or LP-RSRQ threshold at which the first apparatus 110 shall fall back to default behavior.

[0088] To ensure that the LR of the first apparatus 110 can distinguish the discrete circular shifts, the shift needs to be large enough to accommodate any frequency offset as well as delay spread of the channel.

[0089] The advantage of using a circular shifted sequence is that it requires less computations compared to correlating with multiple different sequences. However, it is understood that the above proposed embedded information could also be carried by a set of different sequences eachrepresenting a mapping similar to the ones listed above using the circular shift approach.

[0090] The embodiments of the present disclosure allow first apparatus 110 to save power by selectively monitoring the part of the on-duration window which may contain data for the first apparatus 110.

[0091] A single LP-WUS wakeup message can be used to wake up the first apparatus 110’s even if they shall receive different parts of the on-duration window.

[0092] On the other hand, the network can scale the fraction of the on-duration window that the first apparatus 110 monitors, thereby allowing the second apparatus 120 to dynamically scale the window according to traffic load and required data to deliver to the first apparatus 110.

[0093] FIG. 6 illustrates an example 600 of the probability of data arrival for an XR use case in accordance with some example embodiments of the present disclosure. In the following, it is illustrated how the network load may be used to scale the part of the on-duration, which the first apparatus 110 supporting WUS mode needs to monitor.

[0094] In FIG. 6, an XR use case is assumed, where new frames may be received every 16,67ms corresponding to 60FPS update rate. During high network load, the monitored part of the on-duration is high because the network needs to schedule many the first apparatus 110’s and therefore may need to additional scheduling flexibility. On the other hand, during low network load, fewer the first apparatus 110’s needs to be scheduled and the network can schedule the data more accurately for each frame and therefore the first apparatus 110 only needs to monitor a smaller part of the on- duration.

[0095] Dynamic changes in network load may cause different jitter on the second apparatus 120 scheduling. In low load conditions the jitter may be low and the first apparatus 110 may monitor a smaller fraction of the on-duration compared to the high load case.

[0096] FIG. 7 shows a flowchart of an example method 700 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0097] At block 710, in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, at block 720, the first apparatus determines, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs, and

[0098] At block 730, the first apparatus determines, based on the circular shift, a subset of the on- duration window for a connected mode discontinuous reception, c-DRX, to be monitored.

[0099] At block 740, the first apparatus monitors a downlink transmission from the second apparatus within the subset of the on-duration window.

[0100] In some example embodiments, the method 700 further comprises: obtaining associationbetween a set of circular shift values and a plurality of subsets of the on-duration window; and determining the subset of the on-duration window to be monitored based on the association and the circular shift of the determined overlaid sequence.

[0101] In some example embodiments, the plurality of subsets of the on-duration window are evenly distributed on the on-duration window.

[0102] In some example embodiments, time domain location of the plurality of subsets of the on- duration window is indicated by the circular shift as at least one of a center of the on-duration window or a start of the on-duration window or an end of the on-duration window.

[0103] In some example embodiments, each circular shift value in the set of circular shift values is associated to one subset of the on-duration window in the plurality of subsets.

[0104] In some example embodiments, the method 700 further comprises: determining, based on the circular shift, a fraction of a downlink monitoring occasion to be monitored versus one or more downlink monitoring occasions to be skipped; and monitoring the downlink transmission based on the fraction.

[0105] In some example embodiments, respective subgroup of terminal devices is mapped to the plurality of ON symbols associated with the WUS signal, and wherein respective overlaid sequences corresponding to the plurality of ON symbols have a same or different circular shifts.

[0106] In some example embodiments, the overlaid sequence comprises a circular shifted or noncircular shifted constant amplitude zero auto-correlation, CAZAC, sequences.

[0107] In some example embodiments, the ON symbol is comprised in a Manchester encoded symbol.

[0108] In some example embodiments, the overlaid sequence, in addition to the circular shift, indicates same information as indicated by all ON symbols or all Manchester encoded symbols comprised in an OFDM symbol, wherein the OFDM symbol comprises the ON symbol.

[0109] In some example embodiments, the on-duration window is at least one of the following: determined based on an on-duration timer, or determined when the on-duration is running.

[0110] FIG. 8 shows a flowchart of an example method 800 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0111] At block 810, the second apparatus generates a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices.

[0112] At block 820, the second apparatus transmits the LP-WUS at least to the first apparatus.

[0113] In some example embodiments, a first apparatus capable of performing any of the method700 (for example, the first apparatus 110 in FIG. 1 ) may comprise means for performing the respective operations of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1 .

[0114] In some example embodiments, the first apparatus comprises means for in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and means for determining, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and means for monitoring a downlink transmission from the second apparatus within the subset of the on-duration window.

[0115] In some example embodiments, the first apparatus further comprises: means for obtaining association between a set of circular shift values and a plurality of subsets of the on-duration window; and means for determining the subset of the on-duration window to be monitored based on the association and the circular shift of the determined overlaid sequence.

[0116] In some example embodiments, the plurality of subsets of the on-duration window are evenly distributed on the on-duration window.

[0117] In some example embodiments, time domain location of the plurality of subsets of the on- duration window is indicated by the circular shift as at least one of a center of the on-duration window or a start of the on-duration window or an end of the on-duration window.

[0118] In some example embodiments, each circular shift value in the set of circular shift values is associated to one subset of the on-duration window in the plurality of subsets.

[0119] In some example embodiments, the first apparatus further comprises: means for determining, based on the circular shift, a fraction of a downlink monitoring occasion to be monitored versus one or more downlink monitoring occasions to be skipped; and means for monitoring the downlink transmission based on the fraction.

[0120] In some example embodiments, respective subgroup of terminal devices is mapped to the plurality of ON symbols associated with the WUS signal, and wherein respective overlaid sequences corresponding to the plurality of ON symbols have a same or different circular shifts.

[0121] In some example embodiments, the overlaid sequence comprises a circular shifted or noncircular shifted constant amplitude zero auto-correlation, CAZAC, sequences.

[0122] In some example embodiments, the ON symbol is comprised in a Manchester encoded symbol.

[0123] In some example embodiments, the overlaid sequence, in addition to the circular shift, indicates same information as indicated by all ON symbols or all Manchester encoded symbolscomprised in an OFDM symbol, wherein the OFDM symbol comprises the ON symbol.

[0124] In some example embodiments, the on-duration window is at least one of the following: determined based on an on-duration timer, or determined when the on-duration is running.

[0125] In some example embodiments, a second apparatus capable of performing any of the method 800 (for example, the second apparatus 120 in FIG. 1 ) may comprise means for performing the respective operations of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1.

[0126] In some example embodiments, the second apparatus comprises means for generating a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and means for transmitting the LP-WUS at least to the first apparatus.

[0127] FIG. 9 is a simplified block diagram of a device 900 that is suitable for implementing example embodiments of the present disclosure. The device 900 may be provided to implement a communication device, for example, the first apparatus 110 or the second apparatus 120 as shown in FIG. 1. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processor 910, and one or more communication modules 940 coupled to the processor 910.

[0128] The communication module 940 is for bidirectional communications. The communication module 940 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 940 may include at least one antenna.

[0129] The processor 910 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0130] The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 924, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, arandom-access memory (RAM) 922 and other volatile memories that will not last in the power-down duration.

[0131] A computer program 930 includes computer executable instructions that are executed by the associated processor 910. The instructions of the program 930 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 930 may be stored in the memory, e.g., the ROM 924. The processor 910 may perform any suitable actions and processing by loading the program 930 into the RAM 922.

[0132] The example embodiments of the present disclosure may be implemented by means of the program 930 so that the device 900 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 8. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0133] In some example embodiments, the program 930 may be tangibly contained in a computer readable medium which may be included in the device 900 (such as in the memory 920) or other storage devices that are accessible by the device 900. The device 900 may load the program 930 from the computer readable medium to the RAM 922 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e. , tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0134] FIG. 10 shows an example of the computer readable medium 1000 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 1000 has the program 930 stored thereon.

[0135] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0136] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non-transitory computer readable medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target physical or virtualprocessor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machineexecutable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0137] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general-purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0138] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0139] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0140] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment.Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable subcombination.

[0141] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:1 . A first apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and determine, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and monitor a downlink transmission from the second apparatus within the subset of the on- duration window.

2. The first apparatus of claim 1 , wherein the first apparatus is caused to: obtain association between a set of circular shift values and a plurality of subsets of the on- duration window; and determine the subset of the on-duration window to be monitored based on the association and the circular shift of the determined overlaid sequence.

3. The first apparatus of claim 2, wherein the plurality of subsets of the on-duration window are evenly distributed on the on-duration window.

4. The first apparatus of claim 2, wherein time domain location of the plurality of subsets of the on-duration window is indicated by the circular shift as at least one of a center of the on-duration window or a start of the on-duration window or an end of the on-duration window.

5. The first apparatus of any of claims 2-4, wherein each circular shift value in the set of circular shift values is associated to one subset of the on-duration window in the plurality of subsets.

6. The first apparatus of claim 1 , wherein the first apparatus is caused to: determine, based on the circular shift, a fraction of a downlink monitoring occasion to be monitored versus one or more downlink monitoring occasions to be skipped; andmonitor the downlink transmission based on the fraction.

7. The first apparatus of any of claims 1-6, wherein respective subgroup of terminal devices is mapped to the plurality of ON symbols associated with the WUS signal, and wherein respective overlaid sequences corresponding to the plurality of ON symbols have a same or different circular shifts.

8. The first apparatus of any of claims 1 -7, wherein the overlaid sequence comprises a circular shifted or non-circular shifted constant amplitude zero auto-correlation, CAZAC, sequences.

9. The first apparatus of any of claims 1 -8, wherein the ON symbol is comprised in a Manchester encoded symbol.

10. The first apparatus of any of claims 1 -8, wherein the overlaid sequence, in addition to the circular shift, indicates same information as indicated by all ON symbols or all Manchester encoded symbols comprised in an OFDM symbol, wherein the OFDM symbol comprises the ON symbol.11 . The first apparatus of any of claims 1-10, wherein the on-duration window is at least one of the following: determined based on an on-duration timer, or determined when the on-duration is running.

12. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: generate a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and transmit the LP-WUS at least to the first apparatus.

13. A method comprising: in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, anoverlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; determining, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and monitoring a downlink transmission from the second apparatus within the subset of the on- duration window.

14. A method comprising: generating a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and transmitting the LP-WUS at least to the first apparatus.

15. A first apparatus comprising: means for in accordance with a determination that a low-power-wake up signal, LP-WUS, from a second apparatus is detected, determine, on a plurality of ON symbols associated with the WUS signal, an overlaid sequence with a circular shift associated with an ON symbol mapped to a subgroup to which the first apparatus belongs; and means for determining, based on the circular shift, a subset of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored; and means for monitoring a downlink transmission from the second apparatus within the subset of the on-duration window.

16. A second apparatus comprising: means for generating a low-power-wake up signal, LP-WUS, indicating a plurality of overlaid sequences with respective circular shifts corresponding to different subsets of the on-duration window for a connected mode discontinuous reception, c-DRX, to be monitored by respective subgroup of terminal devices; and means for transmitting the LP-WUS at least to the first apparatus.

17. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 13 or the method of claim 14.

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