GB2640207A - Sequence-based low power wakeup signal - Google Patents

Abstract

Example embodiments of the present disclosure are directed to sequence-based low power wakeup signal (LP-WUS). A method comprises receiving, at a second apparatus from a first apparatus, a LP-WUS message; and decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying (OOK) symbols included in at least one orthogonal frequency-division multiplexing (OFDM) symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.

Description

SEQUENCE-BASED LOW POWER WAKEUP SIGNAL

FIELD

[0001] Various example embodiments of the present disclosure generally relate to the 5 field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for sequence-based low power wakeup signal (LPWUS).

BACKGROUND

[0002] The study of LP-WUS and low power wake-up receiver (LP-WUR) in 5G new radio (NR) may enable more power efficient operation on user equipment (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

[0003] In a first 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: receive, from a first apparatus, a low-power-wake up signal, LP-WUS, message; and decode the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.

[0004] In a second aspect of the present disclosure, there is provided a method. The method comprises: receiving, at a second apparatus from a first apparatus, a low-powerwake up signal, LP-WUS, message; and decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.

[0005] In a third aspect of the present disclosure, there is provided a second apparatus.

The second apparatus comprises means for receiving, from a first apparatus, a low-powerwake up signal, LP-WUS, message; and means for decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.

[0006] In a fourth aspect of the present disclosure, there is provided a computer readable 10 medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the second aspect.

[0007] 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 15 become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Some example embodiments will now be described with reference to the accompanying drawings, where: [0009] FIG. I illustrates an example communication environment in which example embodiments of the present disclosure can be implemented; [0010] FIG. 2 illustrates a signaling chart for a communication in accordance with some example embodiments of the present disclosure; [0011] FIG. 3 illustrates a schematic diagram of different OOK ON durations overlaid 25 with different sequences in accordance with some example embodiments of the present disclosure (the OFDM cyclic prefix is omitted for simplicity); [0012] FIG. 4 illustrates a flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure; [0013] FIG. 5 illustrates a flowchart of a method implemented at a second apparatus in 30 accordance with some example embodiments of the present disclosure; [0014] FIG. 6 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and [0015] FIG. 7 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present di sclosure.

[0016] Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 30 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.

[0021] As used herein, "at least one of the following: <a list of two or more elements>" and "at least one of <a list of two or more elements>" and similar wording, where the list 5 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.

[0022] 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.

[0023] 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 [0024] 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 an 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.

[0025] 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.

[0026] 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-IoT) 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 (1G), 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.

[0027] 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 (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network 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 TAB node.

[0028] 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.

[0029] 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.

[0030] FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. As shown in FIG. 1, the communication network 100 may comprise a second apparatus 120 which may be, for example, a terminal device. In some example embodiments, the terminal device may also be discussed as a UE.

[0031] The communication network 100 may further comprise a first apparatus 110, 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.

[0032] A serving area provided by the first apparatus 110 is called a cell. The second apparatus 120 may communicate with the first apparatus 110 within the cell 102. The cell 15 currently serving the second apparatus 120 may be considered as a serving cell 102.

[0033] In the following, for the purpose of illustration, some example embodiments are described with the second apparatus 120 operating as a terminal device and the first apparatus 110 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.

[0034] In some example embodiments, if the second apparatus 120 is a terminal device and first apparatus 110 is a network device, a link from the first apparatus 110 to the second apparatus 120 is referred to as a downlink (DL), while a link from the second apparatus 120 to the first apparatus 110 is referred to as an uplink (UL). In DL, the first apparatus 110 is a transmitting (TX) apparatus (or a transmitter) and the second apparatus 120 is a receiving (RX) apparatus (or a receiver). In UL, the second apparatus 120 is a TX apparatus (or a transmitter) and the first apparatus 110 is a RX apparatus (or a receiver).

[0035] It is to be understood that the number of network devices and terminal devices 30 shown in FIG. 1 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.

[0036] 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 (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (60), 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 [0037] As described above, A study of LP-WUS and LP-WUR has been discussed for NR. This study considers the usage of a separate low-power wake-up receiver at the UE.

[0038] The LP-WUR may not be a separate receiver and can be implemented as a part of the Main Radio (MR). The intention is that the MR of the UE can be in a sleep mode (or even powered off) for power saving and be activated upon the reception of the WUS from the network. Basically, the network triggers the UE to wake-up exactly when needed in an event-driven manner, by transmitting a special WUS to the UE, which is monitored by the LP-WUR at the UE. When a UE receives the WUS, the LP-WUR can trigger the wake-up of the ordinary NR transceiver and communication can start. Thus, the ultra-low power receiver wakes up the MR and otherwise, the MR is OFF or kept in a deep sleep mode.

[0039] LP-WUS is currently considered for both IDLE/INACTIVE mode and Connected mode. Current discussions mainly focused on DL reception where LP-WUS can be used to wake up the MR to receive physical downlink control channel (PDCCH)/ 30 physical downlink shared channel (PDSCH) e.g., for paging or other data.

[0040] During the study item phase, it was considered that various alternative actions may be triggered by LP-WUS detection. In the IDLE/Inactive mode, upon receiving the wake-up signal from the gNB, the LR could wake up the MR to perform at least one of the following actions: monitoring the Paging Downlink Control Channel (PDCCH), monitoring the Early Paging Indicator (EPI), or initiating the Random Access Channel (RACH) procedure if the LP-WUS carries the UE ID (Temporary Mobile Subscriber Identity, TMSI).

[0041] Since the LR is designed to reduce the power consumption, the design of LPWUS primarily focuses on utilizing a waveform based on 00K. In 00K, the carrier signal is divided into ON durations and OFF durations, where the carrier signal is either turned on or off to represent binary values. When the carrier is on, it represents a logic 1, and when the carrier is off, it represents a logic 0. This modulation technique is commonly used for low-rate applications or in situations where power efficiency is important.

[0042] It is to be understood that that gNB may mimic'ing an OOK signal, by calculating the complex subcarrier values inside the WUS bandwidth such that the received signal at the LR after filtering looks like an OOK signal with ON periods and 15 OFF periods.

[0043] In some solutions, the design of LP-WUS incorporates the OOK modulation with or without a sequence embedded into the ON durations of the 00K signal. The goal is to integrate the 00K signal into the Orthogonal Frequency Division Multiplexing (OFDM) framework while minimizing impact on the legacy UEs.

[0044] LP-WUS and LP-WUR in 5G NR has been studied, which may refer to objectives listed as below:

Table 1

To specify an LP-WUS design commonly applicable to both IDLE/INACTIVE and CONNECTED modes (RANI, RAN4) Specify OOK (00K-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/INACTIVE 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, RANI, RAN3, RAN4) Specify LP-SS with periodicity with Yms for LP-WUR, for synchronization and/or RRM for serving cell. (RANI, RAN4) * LP-SS is based on 00K-I 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 WI.

* 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 WI. 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, RAN I) Check in RAN#1 05 for potential TU adjustment in RAN2 * Note: In CONNECTED mode, UE MR ultra-deep sleep is not considered, and UE RR_M/RLM/FIFD/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 prio tized 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 [0045] As described, LP-WUS with overlaid OFDM sequence(s) over OOK symbols, will be specified as part of the work item.

[0046] For each ON OOK symbol, there may be a set of several sequences which can be mapped symbol. The selected sequence may represent a bit pattern consisting of a single or multiple bits.

[0047] The benefit of transmitting sequences carrying more than 1 bit information, is that a UE which has the capability to do sequence-based reception, will be able to receive the WUS information in shorter time and will therefore be able to shut down the receiver sooner and therefore save power compared to the case where the sequence is just carrying a single bit of information.

[0048] LP-WUS with overlaid OFDM sequence(s) over OOK ON symbols allows to map each OOK ON symbol to bit patterns containing multiple bits and thereby such a sequence-based WUR will be able to receive the entire LP-WUS message in shorter time than the OOK receiver. However, since each possible bit pattern per ON symbol needs to be mapped to a sequence, then the Hamming distance will be reduced by 2k, where k is the number of bits per OOK ON symbol. 1.e. if there is just 1 bit per ON symbol, then a single sequence is enough, but if there are 2 bits per ON symbol, then 4 sequences are needed and likewise if there are 3 bits per ON symbol, then 8 sequences are needed. So, for a given sequence length, the Hamming distance will be reduced by 21 if k bits are carried by the sequence compared to the case where just 1 bit is carried by the sequence.

[0049] It is expected that the performance loss, due to the lower Hamming distance, of the LP-WUS sequence-based receiver can be improved without spending additional radio resources.

[0050] The present disclosure proposes a sequence-based LP-WUS transmission. In this solution, the first apparatus 110 determines a set of sequences associated with a low-power-wake up signal, LP-WUS, message to be transmitted and transmit, to a second apparatus, the LP-WUS message by overlaying the set of sequences at respective on-durations of a plurality of 00K symbols included in at least one OFD, symbol. Each sequence in the set of sequences is associated with a phase rotation.

[0051] Example embodiments of the present disclosure will be described in detail below 20 with reference to the accompanying drawings.

[0052] The reference now is made to FIG. 2, which illustrates a signaling flow 200 of communication in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 200 will be discussed with reference to FIG. 1, for example, by using the first apparatus 110 and the second apparatus 120 that manages a cell 102 currently serving the first apparatus 110.

[0053] In some scenarios, the first apparatus 110 used herein may be referred to as a LP-WUS transmitter, e.g., a network device like a gNB or an eNB. The second apparatus 120 used herein may be referred to as a LP-WUS receiver, e.g., a terminal device like a UE.

[0054] 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.

[0055] In the following, the solution of the present disclosure may be described with a LP-WUS message transmission and reception. It is to be understood that this solution may 5 also be used for a LP-SS transmission and reception, which may also belong to the scope of the present disclosure.

[0056] As shown in FIG. 2, the first apparatus 110 may determine (205) a set of sequences associated with LP-WUS message to be transmitted.

[0057] In some embodiments, the first apparatus 110 may determine information bits to 10 be carried by the LP-WUS message. For example, the information bits can be represented by { x"} := xo, xN_, , which are the N information bits carried by the LP-WUS message.

[0058] Then the first apparatus 110 may determine respective bits, from the information bits, to be transmitted at the respective on-durations of the plurality of OOK symbols and determine the set of sequences based on the respective bits and a relationship between a plurality of sets of reference bits and a set of reference sequences. For example, f s",1:= so, s1, ...stri may represent the L length sequence carried embedded in the 00K ON symbol.

[0059] A set of Nora potential embedded overlaid sequences of length Ns may be 20 represented as S, wherein Nasq represents the number of overlaid sequences. Each potential embedded overlaid sequence may carry log2(Arow) bits. That is, if s contains 8 sequences, then each sequence can carry 3 bits.

[0060] For example, the first apparatus 110 may obtain a pre-configured relationship between the plurality of sets of reference bits and the set of reference sequence. An 25 example of the relationship between the plurality of sets of reference bits and the set of reference sequence is listed as below: Table 2: Example of a mapping table between a set of symbols and the associated sequence and relative phase shift Bits mapped to transmit in Associated sequence sm Associated phase rotation 00K-ON symbol AOk of sequence relative to phase of last sequence 00 Soo 0 01 501 90 S10 180 11 511 270 [0061] As shown in Table 2, bits "00" mapped to transmit in 00K-ON symbol may correspond to sequence Soo, bits "01" mapped to transmit in 00K-ON symbol may correspond to sequence So), bits "10" mapped to transmit in 00K-ON symbol may correspond to sequence Sin, and bits "11" mapped to transmit in 00K-ON symbol may correspond to sequence [0062] Assuming that the LP-WUS message is to be transmitted is: { := 0110110011011100, each OOK on symbol has an overlaid sequence which carry 2 bits, meaning that 4 different sequences are needed. Based on the relationship as shown in Table 2, the set of sequences, corresponding to the information bits to be carried by the LP-WUS message, may be represented as: So), Sao, SL, Soo, Sil, So), Sii, Soo. Each sequence may be carried by an on-OOK symbol (i.e., on-duration of an OOK symbol). An example of different OOK ON durations overlaid with different sequences in accordance with some example embodiments of the present disclosure may be shown in FIG. 3.

[0063] As shown in FIG 3, OFDM symbol 311 includes OOK symbols 301-304 and the OFDM symbol 312 includes OOK symbols 305-308. Symbols 301, 304, 307 and 308 are OOK symbol 0, while symbols 302, 303, 305 and 306 are OOK symbol 1. The OOK symbols 301-308 are Manchester encoded 00K symbols, i.e., each consisting of an ON and OFF duration. Each on-duration of these OOK symbols are embedded with an overlaid sequence, namely Sol, Slo, Su, Soo, Sll, So], Sll, Soo.

[0064] In the determined set of sequences, each sequence in the set of sequences is associated with a phase rotation. More specifically, each sequence is associated with a phase rotation AOk of sequence relative to phase of last sequence. The respective phase rotation of the set of sequences may be pre-configured as shown in Table 2. That is, a phase rotation evenly distributed across 360° (0°, 90°, 180° and 270°), e.g., the sequence Soo is associated with the phase rotation 0°, the sequence So, is associated with the phase rotation 90°, the sequence Sio is associated with the phase rotation 180°, and the sequence SFr is associated with the phase rotation 270°.

[0065] Let { tk} := to, tr(-_, be the list of K phase rotated time domain sequences to be transmitted. The transmitted phase rotated time domain sequence in OOK symbol k, tk, can be expressed as: tk = sni,k * eiclk Where s",,k is the sequence carrying the bits mapped to OOK symbol k, the absolute phase of sequence tk is 0k = Ok_1+ AOk and AOk is the phase rotation associated with the sequence [0066] It is to be understood that the phase rotation of a sequence used hereinafter means that each complex value of the time domain sequence has been phase shifted, e.g. by multiplying the value with exp(j theta), where theta is phase shift.

[0067] It is to be understood that the sequence(s) mentioned hereinafter may be cyclic shifted constant amplitude zero auto-corelation (CAZAC) sequence(s), e.g., Zadoff-Chu 15 sequences.

[0068] There may be an alternative set of sequences for ON symbols mapped to OOK symbol 0 and OOK symbol 1, which will be a benefit when two ON symbols are next to each other (such as OOK symbols 305 and 306) to avoid a detecting a correlation peak from the neighboring symbol in case of large time dispersion.

[0069] A relationship between the different sequences used in neighboring 00K symbols are achieved by rotating the phase of the time domain samples, of the sequence on symbol N relative to the phase rotation of the sequence on previous symbol N-1.

[0070] It is to be understood that the mapping between a set of symbols and the associated sequence and relative phase shift (as shown in Table 2) may be pre-configured 25 for both first apparatus 110 and the second apparatus 120.

[0071] The phase rotation between the sequences used in successive ON symbols, N and N+1 is dictated by the symbol transmitted in symbol N. [0072] Then the first apparatus 110 may transmit (210), to the second apparatus 120, the LP-WUS message by overlaying the set of sequences (e.g., Soi, Sao, Sil, Soo, SII, Sol, 30 Sri,Soo) at respective on-durations of a plurality of OOK symbols (e.g., OOK symbols 301-308 shown in FIG. 3) included in at least one OFDM symbol (e. g., OFDM symbols 311 and 312 shown in FIG. 3) each sequence in the set of sequences is associated with a phase rotation.

[0073] That is, a list of information bits { x.,,} can then be mapped to sequences (2 bits 5 to one sequence in this example). A set of of sequences to transmit is shown along with the relative phase rotation to be applied to each of the sequences as below: Table 3: Example showing how a bit sequence is mapped to sequences and phase rotation OOK symbol # 0 1 2 3 4 5 6 7 Bit sequence to transmit 01 10 11 00 11 01 11 00 Sequence sm Soi Sio Sii Soo Sii Soi Sii Soo Phase rotation compared to N/A 180 270 0 270 90 270 0 previous sequence ABk Absolute phase 0 180 90 90 0 90 0 0 [0074] The absolute phase information in Table 3 is lost during transmission, but the relative phase rotation can be detected and compared with expected phase rotation for the 10 detected sequence [0075] Upon receiving the LP-WUS message, the second apparatus 120 may decode (215) the LP-WUS message.

[0076] At the second apparatus 120, i.e., the LP-WUS receiver, the phase rotation can be determined with good reliability by comparing the phase of the complex correlation peaks of the sequences in 00K symbols N-1 and N. Neighboring ON symbols are assumed to be received within the channel coherency time since they are received with less than an OFDM symbol distance and therefore changes in the radio channel is not having a significant impact on the phase rotation.

[0077] Potential mis-detected sequences can be identified by the receiver by 20 inconsistency between the detected sequence and the phase rotation relative to the last detected sequence. Notice that the sequences in successive ON symbols may be two different sequences, but still the relative phase rotation can be detected.

[0078] The alternative sequences can be tested in place of the mis-detected sequence to

IS

decide if any of those results in consistence between the sequence and the phase rotation.

[0079] If an alternative sequence is found to provide consistency, it can be verified if the updated decoded message is passing the CRC check (if the message has an appended CRC field).

[0080] Hereinafter the process of decoding and correction of the received LP-WUS message will be further described above in details. The example will follow the same used by the first apparatus 110 (i.e., the LP-W US transmitter) as described above. An example of detected sequence and phase rotation in the second apparatus is listed below.

Table 4: Example showing the detected sequence and phase rotat on n the receiver (d is the absolute phase in the receiver) OOK symbol # 0 1 2 3 4 5 6 7 Bit sequence to transmit 01 10 11 00 11 01 11 00 Sequence sin Soi S io Sii Soo Sul Sot Sii Soo Phase rotation compared to N/A 180 270 0 230 130 270 0 previous sequence A81 Absolute phase d 180 90+ 90+ 320 90+ 0+d 0+d +d d d +d d [0081] The second apparatus 120 may performs sequence detection by correlating with the set of possible sequences. The set may consist of cyclic shifted CAZAC sequenced (like e.g. Zadoff-Chu sequences) or it may consist of any other set of sequences e.g. with low cross correlation.

[0082] After finding the first sequence, each of the following detected sequences must be time offset with the duration of 1 or 2 OOK ON/OFF durations depending on the sequence of 00K symbols. For example, the detected/decoded sequence may be the Sequence s", as shown in Table 4, i.e., Soi, Stu, Sri, Soo, S;o, Sol, S;1, Soo.

[0083] The relative phase rotation between the complex correlation values of 20 neighboring sequences is compared with the set of valid phase rotations as associated with the detected sequence. Due to Manchester encoding, it is ensured that there are never more than 2 ON/OFF durations between consecutive ON symbols and therefore the propagation channel can be assumed to be within the channel coherency time. Consequently, the relative phase rotation of the sequences is not significantly impacted by changes in the radio channel.

[0084] The packet error detection may e.g. be done as a CRC check (outside the scope of this invention). Even if there is no CRC field, the second apparatus 120 may still use the phase rotation information to decide between sequences which have similar correlation peaks for a given OOK symbol.

[0085] Once it is concluded that the packet is erroneous, the second apparatus 120 can look for inconsistency in the sequence detections. This involves checking the magnitude of the correlation values, checking the relative time offset of the detected correlation peaks and checking the relative phase rotation of the correlation values against the expected phase rotations for the detected sequences.

[0086] For example, there is a first OOK symbol (00K symbol #4 in Table 4) and a second OOK symbol (00K symbol #5 in Table 4) that is subsequent in succession to the first OOK symbol, the second apparatus 120 may decode a first sequence (Sio) received at a first on-duration of the first OOK symbol and a second sequence (Soi) received at a second on-duration of the second OOK symbol and determine a relative phase rotation between the first sequence and the second sequence based on a pre-configured phase rotation offset associated with the second sequence. If the second apparatus 120 determines that the relative phase rotation is inconsistent with a detected phase rotation between the first sequence and the second sequence, determine a decoding error of the first sequence.

[0087] As described above, the sequence Stu is associated with the phase rotation 180° and the sequence Sol is associated with the phase rotation 90°. Compared to the Table 4, 25 it is obvious that the phase rotation corresponding to the decoded first sequence (Sio) on OOK symbol #4 and decoded second sequence (Soi) on OOK symbol #5 are incorrect.

[0088] The second apparatus 120 may obtain a set of possible sequences corresponding to the first OOK symbol. Then the second apparatus 120 may test each possible sequence in the set of possible sequences by replacing the decoded first sequence with the possible 30 sequence for testing. The possible testing/ hypothesis are listed below.

Table 5

00K symbol # Expected bit sequence Detected Sequence Delta Phase to previous sequence Absolute (accumulated) phase Hypothesis 1 4 5 00 01 Son S01 0 0 90+d 90+d Hypothesis 2 4 5 01 01 Sof Sol 270 180+d 90+d Hypothesis 3 4 5 11 01 S/I S01 270 90 180+d 90+d [0089] As shown in Table 5, the decoded sequence Sio on OOK symbol #4 may be replaced by sequence Soo, sequence Sol and sequence Sii in hypothesis 1, 2 and 3 respectively.

[0090] By checking the respective pre-configured phase rotation associated with the sequences (as shown in Table 2 and Table 3), it can be determined that hypothesis 1 and 2 fails since the detected sequence in 00K symbol #5 does not have the expected phase rotation compared to the phase detected in OOK symbol #4. Hypothesis 3 passes since it the detected sequence in 00K symbol #5 is consistent with the detected phase rotation compared to the sequence detected in 00K symbol #4.

[0091] That is, if a relative phase rotation between a selected possible sequence (e.g., sequence Si i) and the second sequence (sequence So) is consistent with a pre-configured phase rotation offset associated with the second sequence relative to a previous sequence of the second sequence, update the first sequence with the selected possible sequence.

[0092] Then the second apparatus 120 can now replace the corresponding bits in the LP-WUS message and, if the LP-WUS message has a CRC field, the second apparatus Is can recalculate the CRC checksum and compare with the CRC field to verify if the packet error has been resolved.

[0093] In some other example embodiments, if there are multiple detected sequences which have inconsistent phase rotation, then the second apparatus 120 may apply a 5 decoding scheme where the overall likelihood of the detected list of sequences and phase rotations are evaluated (like Trellis decoding). The second apparatus 120 may have a "cost" function for each transition from one detected sequence to the next, where the cost function is taking as input the correlation peak value, peak position and the phase deviation from the ideal phase rotation. The second apparatus 120 will then try to find the 10 set of bits (and corresponding sequences) which would result in the lowest overall cost. The second apparatus 120 may have to store correlation peaks for all possible sequences for each OOK symbol, such that the cost of selecting an alternative sequence can be evaluated.

[0094] In the present disclosure, as described above, it is proposed to add redundancy information in the form of phase rotation of the overlaid sequence in LP-WUS on-durations in the LP-WUS generation in transmitter. The relative phase rotation between the sequences 82\74 and SA, transmitted in OOK symbol N-1 and N is associated with the sequence transmitted in 00K symbol N. Adding this redundancy information does not require extra radio resources and has the benefit that it may be used to detect and correct mis-detected sequences in the receiver.

[0095] Specifically, the proposed delta phase coding of the applied sequences allows to correct some non-contiguous mis-detected sequences and this increased reliability of the WUS message comes without using extra radio resources. The increased reliability can be used to: mitigate the performance degradation by carrying more bits, N",q, per sequence, i.e., more bits per sequence means that more sequences are needed to indicate all combinations of bits, which means lower Hamming distance, which means lower performance), and to send more bits in shorter time means faster shut down of the receiver, which means power saving.

[0096] FIG. 4 shows a flowchart of an example method 400 implemented at a first 30 apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0097] At block 410, the first apparatus 110 determines a set of sequences associated with a LP-WUS message to be transmitted.

[0098] At block 420, the first apparatus 110 transmits, to a second apparatus, the LPWUS message by overlaying the set of sequences at respective on-durations of a plurality 5 of OOK symbols included in at least one OFDM symbol, wherein each sequence in the set of sequences is associated with a phase rotation.

[0099] In some example embodiments, the method 400 further comprises: determining information bits to be carried by the LP-WUS message; determining respective bits, from the information bits, to be transmitted at the respective on-durations of the plurality of OOK symbols; and determining the set of sequences based on the respective bits and a relationship between a plurality of sets of reference bits and a set of reference sequences.

[0100] In some example embodiments, the relationship between the plurality of sets of reference bits and the set of reference sequences are pre-configured.

[0101] In some example embodiments, each sequence in the set of sequences has a pre-15 configured phase rotation offset relative to a phase of a previous sequence in the set of sequences.

[0102] In some example embodiments, the plurality of OOK symbols at least comprises a first OOK symbol and a second OOK symbol that is subsequent in succession to the first OOK symbol, and wherein a relative phase rotation between a first sequence transmitted at the first OOK symbol of and a second sequence transmitted at the second 00K. symbol depends on the second sequence transmitted in the second OOK symbol.

[0103] In some example embodiments, the number of bits carried in a sequence is associated with the number of sequences in the set of the sequences.

[0104] In some example embodiments, the respective on-durations of the plurality OOK 25 symbols are determined based on a Manchester encoding on the plurality OOK symbols.

[0105] In some example embodiments, the set of sequences comprises one or more cyclic shifted sequence with zero auto-correlation and/or multiple sequences with zero/low cross correlation.

[0106] In some example embodiments, the first apparatus comprises a LP-WUS 30 transmitter, and the second apparatus comprises a LP-WUS receiver.

[0107] FIG. 5 shows a flowchart of an example method 500 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0108] At 510, the second apparatus 120 receives, from a first apparatus, a low-powerwake up signal, LP-WUS, message.

[0109] At block 520, the second apparatus 120 decodes the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.

[0110] In some example embodiments, the plurality of OOK symbols at least comprises a first OOK symbol and a second OOK symbol that is subsequent in succession to the first OOK symbol, and wherein the method 500 further comprises: decoding a first sequence received at a first on-duration of the first OOK symbol and a second sequence received at a second on-duration of the second OOK symbol; determining a relative phase rotation between the first sequence and the second sequence based on a pre-configured phase rotation offset associated with the second sequence; and in accordance with a determination that the relative phase rotation is inconsistent with a detected phase rotation between the first sequence and the second sequence, determining a decoding error of the first sequence.

[0111] In some example embodiments, the method 500 further comprises: obtaining a set of possible sequences corresponding to the first 00K symbol; replacing the first sequence with at least one possible sequence selected from the set of possible sequences other than the first sequence; and in accordance with a determination that a relative phase rotation between a selected possible sequence from the at least one possible sequence and the second sequence is consistent with a pre-configured phase rotation offset associated with the second sequence relative to a previous sequence of the second sequence, updating the first sequence with the selected possible sequence.

[0112] In some example embodiments, the method 500 further comprises: checking the selected possible sequence, in case of a replacement of second sequence by the selected possible sequence, by a cyclic redundancy check.

[0113] In some example embodiments, the method 500 further comprises: obtaining a relationship between the set of sequences and corresponding bits values; and determining information of the LP-WUS message based on the set of sequences and the relationship.

[01N] In some example embodiments, each sequence in the set of sequences has a pre-5 configured phase rotation offset relative to a phase of a previous sequence in the set of sequences.

[0115] In some example embodiments, the number of bits carried in a sequence is associated with the number of sequences in the set of the sequences.

[0116] In some example embodiments, the set of sequences comprises one or more 10 cyclic shifted sequence with zero auto-correlation and/or multiple sequences with zero/low cross correlation.

[0117] In some example embodiments, the second apparatus comprises a LP-WUS receiver, and the first apparatus comprises a LP-W US transmitter.

[0118] In some example embodiments, a first apparatus capable of performing any of the method 400 (for example, the first apparatus 110 in FIG. 1) may comprise means for performing the respective operations of the method 400. 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.

[0119] In some example embodiments, the first apparatus comprises means for determining a set of sequences associated with a LP-WUS message to be transmitted; and means for transmitting, to a second apparatus, the LP-W US message by overlaying the set of sequences at respective on-durations of a plurality of OOK symbols included in at least one OFDM symbol, wherein each sequence in the set of sequences is associated with a phase rotation.

[0120] In some example embodiments, the first apparatus comprises means for determining information bits to be carried by the LP-WUS message; means for determining respective bits, from the information bits, to be transmitted at the respective on-durations of the plurality of 00K symbols; and means for determining the set of sequences based on the respective bits and a relationship between a plurality of sets of reference bits and a set of reference sequences.

[0121] In some example embodiments, the relationship between the plurality of sets of reference bits and the set of reference sequences are pre-configured.

[0122] In some example embodiments, each sequence in the set of sequences has a pre-configured phase rotation offset relative to a phase of a previous sequence in the set of sequences.

[0123] In some example embodiments, the plurality of OOK symbols at least comprises a first OOK symbol and a second OOK symbol that is subsequent in succession to the first OOK symbol, and wherein a relative phase rotation between a first sequence transmitted at the first 00K symbol of and a second sequence transmitted at the second OOK symbol depends on the second sequence transmitted in the second OOK symbol.

[0124] In some example embodiments, the number of bits carried in a sequence is associated with the number of sequences in the set of the sequences.

[0125] In some example embodiments, the respective on-durations of the plurality OOK symbols are determined based on a Manchester encoding on the plurality OOK symbols.

[0126] In some example embodiments, the set of sequences comprises one or more cyclic shifted sequence with zero auto-correlation and/or multiple sequences with zero/low cross correlation.

[0127] In some example embodiments, the first apparatus comprises a LP-WUS transmitter, and the second apparatus comprises a LP-WUS receiver.

[0128] In some example embodiments, a second apparatus capable of performing any of the method 500 (for example, the second apparatus 120 in FIG. 1) may comprise means for performing the respective operations of the method 500. 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. I. [0129]In some example embodiments, the second apparatus comprises means for receiving, from a first apparatus, a low-power-wake up signal, LP-W US, message; and means for decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-W US message, wherein each sequence in the set of sequences is associated with a phase rotation.

[0130]In some example embodiments, the plurality of 00K symbols at least comprises a first OOK symbol and a second OOK symbol that is subsequent in succession to the first OOK symbol, and wherein the second apparatus comprises: means for decoding a first sequence received at a first on-duration of the first 00K symbol and a second sequence 5 received at a second on-duration of the second OOK symbol; means for determining a relative phase rotation between the first sequence and the second sequence based on a pre-configured phase rotation offset associated with the second sequence; and means for in accordance with a determination that the relative phase rotation is inconsistent with a detected phase rotation between the first sequence and the second sequence, determining 10 a decoding error of the first sequence.

[0131]In some example embodiments, the second apparatus comprises: means for obtaining a set of possible sequences corresponding to the first 00K symbol; means for replacing the first sequence with at least one possible sequence selected from the set of possible sequences other than the first sequence; and means for in accordance with a determination that a relative phase rotation between a selected possible sequence from the at least one possible sequence and the second sequence is consistent with a pre-configured phase rotation offset associated with the second sequence relative to a previous sequence of the second sequence, updating the second sequence with the selected possible sequence.

1013211n some example embodiments, the second apparatus comprises: means for checking 20 the selected possible sequence, in case of a replacement of second sequence by the selected possible sequence, by a cyclic redundancy check.

1013311n some example embodiments, the second apparatus comprises: means for obtaining a relationship between the set of sequences and corresponding bits values; and means for determining information of the LP-WUS message based on the set of sequences 25 and the relationship.

[0134]In some example embodiments, each sequence in the set of sequences has a pre-configured phase rotation offset relative to a phase of a previous sequence in the set of sequences.

1013511n some example embodiments, the number of bits carried in a sequence is 30 associated with the number of sequences in the set of the sequences.

[0136]In some example embodiments, the set of sequences comprises one or more cyclic shifted sequence with zero auto-correlation and/or multiple sequences with zero/low cross correlation.

[0137]ln some example embodiments, the second apparatus comprises a LP-WUS receiver, and the first apparatus comprises a LP-W US transmitter.

[0138] FIG. 6 is a simplified block diagram of a device 600 that is suitable for implementing example embodiments of the present disclosure. The device 600 may be provided to implement a communication device, for example, the first apparatus 110 or the network device 120 as shown in FIG. 1. As shown, the device 600 includes one or more processors 610, one or more memories 620 coupled to the processor 610, and one or more communication modules 640 coupled to the processor 610.

[0139] The communication module 640 is for bidirectional communications. The communication module 640 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 640 may include at least one antenna.

[0140] The processor 610 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 600 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.

[0141] The memory 620 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) 624, 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, a random-access memory (RAM) 622 and other volatile memories that will not last in the power-down duration.

[0142] A computer program 630 includes computer executable instructions that are executed by the associated processor 610. The instructions of the program 630 may include instructions for performing operations/acts of some example embodiments of the present disclosure. The program 630 may be stored in the memory, e.g., the ROM 624. The processor 610 may perform any suitable actions and processing by loading the program 630 into the RAM 622.

[0143] The example embodiments of the present disclosure may be implemented by means of the program 630 so that the device 600 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIGS. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0144] In some example embodiments, the program 630 may be tangibly contained in a computer readable medium which may be included in the device 600 (such as in the memory 620) or other storage devices that are accessible by the device 600. The device 600 may load the program 630 from the computer readable medium to the RAM 622 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).

[0145] FIG. 7 shows an example of the computer readable medium 700 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 700 has the program 630 stored thereon.

[0146] 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 [0147] 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 virtual processor, 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.

Machine-executable 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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 sub-combination.

[0152] 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 (13)

1. WHAT IS CLAIMED IS: 1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a further apparatus, a low-power-wake up signal, LP-WUS, message; and decode the LP-WUS message based on a set of sequences received at respective onto durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.
2. 2. The apparatus of claim 1, wherein the plurality of OOK symbols at least comprises 15 a first 00K symbol and a second OOK symbol that is subsequent in succession to the first OOK symbol, and wherein the apparatus is caused to: decode a first sequence received at a first on-duration of the first OOK symbol and a second sequence received at a second on-duration of the second 00K symbol; determine a relative phase rotation between the first sequence and the second 20 sequence based on a pre-configured phase rotation offset associated with the second sequence; and in accordance with a determination that the relative phase rotation is inconsistent with a detected phase rotation between the first sequence and the second sequence, determine a decoding error of the first sequence.
3. 3. The apparatus of claim 2, wherein the apparatus is caused to: obtain a set of possible sequences corresponding to the first OOK symbol; replace the first sequence with at least one possible sequence selected from the set of possible sequences other than the first sequence; and in accordance with a determination that a relative phase rotation between a selected possible sequence from the at least one possible sequence and the second sequence is consistent with a pre-configured phase rotation offset associated with the second sequence relative to a previous sequence of the second sequence, update the second sequence with the selected possible sequence.
4. 4. The apparatus of claim 3, wherein the apparatus is caused to: check the selected possible sequence, in case of a replacement of second sequence 5 by the selected possible sequence, by a cyclic redundancy check.
5. 5. The apparatus of any of claims 1-4, wherein the apparatus is caused to: obtain a relationship between the set of sequences and corresponding bits values; and determine information of the LP-WUS message based on the set of sequences and the relationship.
6. 6. The apparatus any of claims 1-5, wherein each sequence in the set of sequences has a pre-configured phase rotation offset relative to a phase of a previous sequence in the 15 set of sequences.
7. 7. The apparatus of any of claims 1-6, wherein the number of bits carried in a sequence is associated with the number of sequences in the set of the sequences.
8. 8. The apparatus of any of claims 1-7, wherein the set of sequences comprises one or more cyclic shifted sequence with zero auto-correlation and/or multiple sequences with zero/low cross correlation.
9. 9. The apparatus of any of claims 1-8, wherein the apparatus comprises a LP-WUS 25 receiver, and the further apparatus comprises a LP-WUS transmitter.
10. 10. The apparatus of any of claims 1-9, wherein each sequence in the set of sequences is associated with a bit combination.
11. 11. A method comprising: receiving, at an apparatus from a further apparatus, a low-power-wake up signal, LPWUS, message decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-W US message, wherein each sequence in the set of sequences is associated with a phase rotation.
12. 12. An apparatus comprising: means for receiving, from a further apparatus, a low-power-wake up signal, LP-W US, message; and means for decoding the LP-WUS message based on a set of sequences received at respective on-durations of a plurality of On-Off Keying, 00K, symbols included in at least one orthogonal frequency-division multiplexing, OFDM, symbol associated with the LP-WUS message, wherein each sequence in the set of sequences is associated with a phase rotation.
13. 13. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 11.