Wake-up signal handling in a radio access network

Abstract

A technique for wake-up signal handling in a radio access network is described. As to one aspect of the technique, a method (300) performed by a radio device (100) for detecting a wake-up signal, WUS, from a radio access network, RAN (500), is provided. The method (300) comprises monitoring (304) a configured set of radio resources of the RAN (500) for detecting the WUS, optionally associated with a network node (200) of the RAN (500). In response to detecting (306) the WUS (900) in the monitored (304) radio resources, the method (300) comprises transitioning (308) the radio device (100) from an energy-saving state (602) to an active state (604). The detecting (306) of the WUS (900) comprises correlating the monitored (304) radio resources with a candidate sequence of orthogonal frequency-division multiplexing, OFDM, symbols.

Description

[0001] WAKE-UP SIGNAL HANDLING IN A RADIO ACCESS NETWORK

[0002] Technical Field

[0003] The present disclosure relates to a technique for wake-up signal handling in a radio access network. More specifically, and without limitation, a method performed by a radio device for detecting a wake-up signal, and a method performed by a network node for transmitting a wake-up signal, as well as corresponding devices, are provided.

[0004] Background

[0005] Wireless communication systems, including those standardized by the Third Generation Partnership Project (3GPP) and addressed by the O-RAN Alliance, continue to evolve toward enhanced energy efficiency and reliable connectivity. These systems incorporate ever-greater numbers of devices that frequently enter energy-saving states (i.e., low-power modes) to reduce power consumption when communication is not urgently needed or not ongoing. In this context, dedicated wake-up signals are studied to enable a radio device to transition on demand from an energy-saving state to an active state.

[0006] Such wake-up mechanisms may be simultaneously required to maintain low-power consumption while ensuring robust detection or transmission of signals in challenging radio environments. Efficient design and allocation of these signals are key to reducing overall network congestion and optimizing the battery lifetime of largely varying radio devices.

[0007] However, conventional approaches may fall short in effectively balancing energy consumption, detectability, and reliable signaling of wake-up events in diverse deployments. This shortcoming underscores a need for technical improvements in how wake-up signals are handled within a radio access network.

[0008] Summary

[0009] Accordingly, there is a need for a technique that handles wake-up signals in a radio access network so as to achieve reliable wake-up events with minimized power consumption for a variety of radio devices and network infrastructures.According to a first method aspect, a method performed by a radio device for detecting a wake-up signal from a radio access network is provided. The method comprises monitoring a configured set of radio resources of the radio access network for detecting the wake-up signal. The wake-up signal is optionally associated with a network node of the radio access network and / or the radio device. The method further comprises, in response to detecting the wake-up signal in the monitored radio resources, transitioning the radio device from an energy-saving state to an active state. The detecting of the wake-up signal comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequency-division multiplexing (OFDM) symbols.

[0010] By monitoring specific radio resources, embodiments of the radio device operate in a power-efficient manner until the detected wake-up signal triggers further activity. The transition from an energy-saving state to an active state only upon this trigger prevents unnecessary power usage. The correlation step with a candidate sequence of OFDM symbols robustly identifies the wake-up event, thereby ensuring accurate detection under variable channel conditions. In this way, the method addresses the technical problem of reducing power consumption while maintaining reliable signal detection.

[0011] In other words, as to a first method aspect, a method performed by a radio device for detecting a wake-up signal (WUS) from a radio access network (RAN) is provided. The method comprises monitoring a configured set of radio resources of the RAN for detecting the WUS, optionally associated with a network node of the RAN. In response to detecting the WUS in the monitored radio resources, the method comprises transitioning the radio device from an energy-saving state to an active state. Detecting the WUS comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequency-division multiplexing (OFDM) symbols.

[0012] The associated network node may transmit the WUS on the configured set of radio resources. Alternatively or in addition, the associated network node may be a serving network node serving the radio device and / or a serving cell serving the radio device. The detecting may be a step of the method, e.g. a sub-step of the monitoring or a substep of the transitioning. Alternatively or in addition, the correlating may be a step of the method, e.g. a sub-step of the monitoring, a substep of the detecting, or a substep of the transitioning.

[0013] The radio resource may be a (e.g., continuous) time resource.The correlating of the candidate sequence and the monitored radio resource may encompass computing a cross-correlation between the candidate sequence and the monitored radio resource and / or computing a convolution between the candidate sequence and the monitored radio resource. Alternatively or in addition, the correlating may be performed in the time domain and / or in the frequency domain.

[0014] The radio device may be a mobile terminal or user-end communication apparatus (e.g., a battery-powered device) equipped with necessary hardware and software to perform radio reception in the RAN.

[0015] In some embodiments, the detecting may further comprise applying an on-off keying (OOK) to the candidate sequence, optionally applying, in the time domain, an envelope of the OOK to the candidate sequence, and / or wherein the candidate sequence applied with the OOK may be correlated with the monitored radio resources.

[0016] Herein, applying the envelope of the OOK may be referred to as overlaying the OOK with the sequence of OFDM symbols. The candidate sequence applied with the envelope of the OOK may be the candidate sequence overlaid with (e.g., gated by) the envelope of the OOK.

[0017] In some embodiments, each OFDM symbol in the candidate sequence may comprise, or correspond to, at least one of the following: a waveform of a Zadoff-Chu sequence (ZCSeq), optionally an inverse Fourier Transform of a ZCSeq; a waveform of an M-sequence (MSeq), optionally an inverse Fourier Transform of a MSeq; and a waveform of a Gold sequence (GSeq), optionally an inverse Fourier Transform of a GSeq.

[0018] The Fourier Transform may be a Discrete Fourier Transform (DFT).

[0019] In some embodiments, the method may further comprise: receiving, from the or another network node of the RAN, configuration information indicative of at least one of: the configured set of radio resources; the candidate sequence of OFDM symbols; a set of the OFDM symbol sequences, wherein the detecting may comprise correlating each of the OFDM symbol sequences with the monitored radio resources or selecting the candidate sequence out of the set of OFDM symbol sequences; the OOK, optionally the timedomain envelope of the OOK, applied to the candidate sequence; and a set of OOKs, optionally a set of time-domain envelopes of the OOK, wherein the detecting may comprise applying each of the OOKs or each of the envelops or selecting the applied OOK or the applied envelop.Embodiments of the radio device can reliably detect a low-power wake-up signal (WUS) while limiting energy consumption due to the energy-saving state. By receiving a configuration that identifies candidate OFDM-based sequences (e.g., derived from a Zadoff-Chu sequence), and / or applying an on-off keying (OOK) envelope to those sequences in the time domain, the radio device achieves robust WUS detection with reduced complexity and lower false alarm rates.

[0020] The configuration information may encompass (e.g., radio resource control (RRC) or downlink control information ( DCI )) signaling from the network node, e.g. specifying how the WUS is formed, e.g. including which OFDM-based sequences are allowed or relevant.

[0021] The candidate sequence and / or each of the set of OFDM symbol sequences may be derived from a Zadoff-Chu sequence (ZCSeq).

[0022] Detecting the WUS by applying an on-off keying envelope may encompass the radio device performing time gating of the OFDM waveform, e.g. switching it on or off according to the OOK (i.e., an OOK pattern or the envelope of the OOK). Detecting the WUS may identify the WUS from among possible candidates by the combination of ZCSeq and OOK.

[0023] In an example RAN, the network node (e.g., a base station) transmits the WUS formed by overlaying a sequence of Zadoff-Chu-based OFDM symbols with an OOK envelope. The radio device, e.g., prior to entering in the energy saving-mode, may have received the configuration information indicative of which candidate sequence or set of OFDM symbol sequences to expect as the WUS. By correlating against the configured sequence(s), e.g. including applying the OOK, the radio device may determine whether it has been addressed by the WUS, e.g. thus waking up its higher-power receiver only when needed.

[0024] In some embodiments, the candidate sequence and / or each sequence in the set of OFDM symbol sequences may fulfill a predefined cross-correlation selection criterion; and / or the OFDM symbol sequences may be a subset of all sequences of a predefined length, K, that fulfill a predefined cross-correlation selection criterion; and / or the OFDM symbol sequences may be a subset of all permutations of the OFDM symbol sequences that fulfill a predefined cross-correlation selection criterion; and / or OFDM symbol sequences may be arranged in temporal order to fulfil a predefined cross-correlation selection criterion.In some embodiments, the predefined cross-correlation selection criterion, when applied to a given sequence of OFDM symbols, requires that the cross-correlation between each pair of OFDM symbols in the given sequence fulfills the predefined cross-correlation selection criterion, optionally is less than a predefined cross-correlation selection threshold value.

[0025] For example, the OFDM symbols in the respective sequence (e.g., the candidate sequence or each of the OFDM symbol sequences) must fulfill a criterion for the cross-correlation pairwise.

[0026] In some embodiments, the predefined cross-correlation criterion, when applied to a given sequence of OFDM symbols, requires that the cross-correlation between each pair of subsequent OFDM symbols that are subsequent in the temporal order of the given sequence, fulfills the predefined cross-correlation selection criterion, optionally that the cross-correlation may be less than a predefined cross-correlation selection threshold value.

[0027] For example, the OFDM symbols in the respective sequence (e.g., the candidate sequence or each of the OFDM symbol sequences) must fulfill a criterion for the cross-correlation between neighboring or consecutive OFDM symbols.

[0028] In some embodiments, the predefined selection cross-correlation criterion further depends on the applied OOK, wherein the cross-correlation may be computed after applying the OOK.

[0029] The OOK may be applied to one or each of the OFDM symbols that are cross-correlated.

[0030] In some embodiments, the candidate sequence or each of the OFDM symbol sequences may be a finite collection of waveforms, each uniquely determined by a root index and / or a cyclic shift (CS) of an underlying Zadoff-Chu sequence (ZCSeq).

[0031] In some embodiments, the candidate sequence or each of the OFDM symbol sequences correspond to an underlying Zadoff-Chu sequence (ZCSeq) determined by a root index and / or a cyclic shift (CS) wherein the ZCSeq may be mapped onto subcarriers to form an OFDM symbol.In some embodiments, the WUS may be detected if a result of the correlating with the monitored radio resources fulfills a predefined cross-correlation detection criterion, optionally if the result exceeds a predefined cross-correlation detection threshold value.

[0032] In some embodiments, the predefined cross-correlation detection criterion requires more cross-correlation than the predefined cross-correlation selection criterion, optionally wherein the predefined cross-correlation detection threshold value may be greater than the predefined cross-correlation selection threshold value.

[0033] In some embodiments, the method may further comprise at least one of, and / or wherein the radio device transitions from the energy-saving state to the active state for at least one of: receiving, in the active state, a subsequent transmission from a network node of the RAN; performing, in the active state, a sensory function and / or transmitting to the network node a result of the sensory function; receiving, in the active state, scheduling communication from the network node; monitoring, in the active state, a control channel of the network node, or a cell of the network node, in a subsequent time interval; and transmitting data to the network node and / or receiving data from the network node.

[0034] The control channel may be a subsequent channel carrying downlink control or paging messages.

[0035] In some embodiments, the network node may be associated with the detected WUS and / or a serving network node serving the radio device.

[0036] In some embodiments, a power consumption of the radio device or a transceiver of the radio device may be less in the energy-saving state compared to the active state; and / or wherein the active state may be a radio resource control (RRC) connected state; and / or wherein the energy-saving state may be an inactive state or an idle state of the radio device relative to network node or the RAN.

[0037] The energy-saving state may be a standby mode of the radio device or of a transceiver of the radio device.

[0038] In some embodiments, the configured and / or monitored set of radio resources may be or may comprise a contiguous sequence of orthogonal frequency division multiplexing (OFDM) symbols, optionally wherein the correlating may comprise cross-correlating the OFDM symbols of the candidate sequence or each of the OFDM symbol sequence withthe OFDM symbols of the monitored radio resources in pairs according to their temporal order.

[0039] In some embodiments, the radio resources may be monitored within a discontinuous reception (DRX) cycle, and / or in advance of an ON-duration of the DRX cycle.

[0040] In some embodiments, the method may further comprise determining, from the configuration information, a number of Y OFDM symbols, wherein each sequence in the set of OFDM symbol sequences and / or the candidate sequence may be a sequence of the OFDM symbols selected from the Y OFDM symbols, optionally according to the crosscorrelation selection criterion.

[0041] Each of the Y OFDM symbols may be derived from a unique combination of at least one root index and at least one cyclic shift of the Zadoff-Chu sequence (ZCSeq).

[0042] By determining Y distinct OFDM symbols (e.g., based on ZCSeq), the radio device can reduce memory requirements while still achieving robust detection. This limited set of sequences provides a controlled balance between detection accuracy and implementation cost.

[0043] Herein, the root index may encompass a parameter, q, used in generating of Zadoff-Chu sequences (ZCSeqs). ZCSeqs with different root indices may have mutually low crosscorrelation. Alternatively or in addition, the cyclic shift (CS) may encompass an integer offset in the sequence index domain of the ZCSeq (or a subcarrier domain) that shifts the Zadoff-Chu sequence. ZCSeqs with CSs may have mutually low cross-correlation.

[0044] The number (Y) of OFDM symbols may be a total count of unique ZCSeqs formed by each permissible pair of root index and cyclic shift.

[0045] In an example RAN, the network node selects Y = 4, 8, or 16 sequences for the WUS, e.g. as indicated in the configuration information.

[0046] In some embodiments, the detecting may comprise correlating each of the OFDM symbol sequences in the set of OFDM symbol sequences with the monitored radio resources or selecting the candidate sequence out of the set of OFDM symbol sequences.In some embodiments, the method may further comprise, optionally upon receiving the configuration information: generating the set of OFDM symbol sequences, and / or loading the set of OFDM symbol sequences into a local memory of the radio device.

[0047] In some embodiments, the set of OFDM symbol sequences may comprise only those OFDM symbols that: are indicated in the configuration information received from the network node, and / or correspond to a limitation in the number of OFDM symbols indicated in the configuration information received from the network node, and / or fulfill the cross-correlation selection criterion.

[0048] When monitoring the radio resources, the radio device may correlate the monitored radio resources (e.g., the received OFDM symbol on these resources) with the smaller loaded set, e.g. thus saving power and memory.

[0049] In some embodiments, a capability of the radio device and / or the configuration information received from the network node limits a number of root indices of the ZCSeq, underlying the candidate sequence or the set of OFDM symbol sequences, optionally wherein the capability may comprise a memory usage constraint, and / or wherein the radio device discards OFDM symbols that exceed said limit.

[0050] Restricting the number of possible root indices for the ZCSeqs bounds a memory requirement of the radio device and computational complexity. Fewer root indices can reduce the required correlation references, which lowers energy consumption. The limit may be an upper bound on the number of root indices, e.g. a device-specific or RAN-imposed constraint that ensures hardware feasibility (e.g., limiting needed correlation filters or stored references).

[0051] In an example RAN, a low-cost sensor node as the radio device may support at most X root indices. The network node may configure up to that limit so the radio device can still decode the WUS. If more roots are signaled, the radio device ignores them or interprets them as invalid, ensuring stable operation within resource constraints.

[0052] In some embodiments, the method may further comprise determining, optionally from the configuration information or another indication from the network node, a timedomain on-off keying rate, M denoting the number of on-off-keying chips per OFDM symbol, and applying the rate M to gate the candidate sequence in each OFDM symbol.By using an adjustable OOK rate M, the radio device can trade off transmission duration against detection performance. A larger M may allow finer granularity and potentially more codepoints, while a smaller M may simplify processing.

[0053] M may be a natural number, e.g. a power of two. The time-domain OOK rate, M, may indicate how many discrete on / off segments ("chips") occupy one OFDM symbol's duration. For example, if M=2, each OFDM symbol is split into two intervals. The radio device may determine whether each interval is ON or OFF, effectively shaping the WUS. The value M may be configured by the network node to balance coverage or throughput requirements.

[0054] In some embodiments, applying the OOK may comprise: partitioning each OFDM symbol into M sub-intervals and multiplying the received OFDM waveform by an on-off gating pattern such that the on-off pattern selectively zeroes at least a portion of the waveform in each sub-interval.

[0055] The selective zeroing in sub-intervals may enforce the OOK envelope, e.g. allowing the radio device to identify a characteristic time-domain pattern that boosts detection reliability and / or is backward compatible with radio devices only capable of OOK decoding without correlating ZCSeqs underlying the ON sub-intervals.

[0056] The on-off gating pattern (i.e., the envelope) may be a sequence of multipliers (1 or 0) applied to each sub-interval, preserving the OFDM sample during ON intervals and setting it to zero during OFF intervals. For example, if M=4 and each symbol is 1 millisecond, the method may split the symbol into four 0.25 ms segments. During OFF intervals, the radio device expects no signal content, which aids in correlation-based detection.

[0057] In some embodiments, the method may further comprise determining, optionally from the received configuration information, a number, K, of OFDM symbols over which the WUS may be spread in the time domain, optionally wherein the correlation may comprise cross-correlating each of the K OFDM symbols of the monitored radio resources with the candidate sequence or each of the OFDM symbol sequences.

[0058] Spreading the wake-up signal over K symbols can increase robustness of the WUS detection and allows encoding a greater number of distinct messaging patterns without overly increasing complexity per OFDM symbol.The number, K, of OFDM symbols may be a configured integer count of consecutive OFDM symbols forming the total WUS. The partial codepoint may be a piece or subsymbol code indication that, along with others in the K-symbol structure, composes the entire WUS code. For instance, for K=3, the WUS has a three-symbol structure.

[0059] Alternatively or in addition, the radio device may correlate each OFDM symbol for the presence of one among the Y candidate waveforms, and reconstructs the total codepoint from the detected arrangement of the OFDM symbols in sequence.

[0060] In some embodiments, the radio device determines a partial codepoint based on the cross-correlating of the K OFDM symbols, and / or wherein the radio device determines a codepoint from the monitored OFDM sequences across the K symbols by using a predefined mapping rule that associates each temporal arrangement of the OFDM symbols with a distinct codepoint among a set of multiple codepoints.

[0061] Mapping each sequence arrangement to a unique codepoint enables the radio device to identify which subgroup or group of sub-devices is addressed, thereby reducing false device wake-ups and saving battery life.

[0062] The predefined mapping rule may encompass a look-up table or algorithm that translates a pattern (e.g., S3 in symbol 1, S2 in symbol 2, SI in symbol 3) into a discrete codepoint.

[0063] As an example, the network node can define 32 possible codepoints for 32 subgroups. The mapping rule is signaled to the radio device, which then only wakes up fully if the detected pattern corresponds to its assigned subgroup's codepoint.

[0064] In some embodiments, the transitioning of the radio device may be in response to, and / or the detecting may be based upon, successfully identifying a codepoint from a or the mapping rule applied to the monitored radio resources, optionally only if that codepoint corresponds to a radio device subgroup to which the radio device may be assigned.

[0065] Selectively monitoring of further channels depending on the codepoint can decrease power consumption as the radio device avoids unnecessary reception when the WUS is not intended for it.

[0066] The assigned subgroup may comprise a grouping of radio device that share the same codepoint. Only these devices wake up to listen further.In an example, once the radio device determines it is not part of the indicated subgroup, it immediately returns to sleep, e.g., avoiding the battery drain of a full receiver operation.

[0067] In some embodiments, the radio device may store only a subset of the OFDM symbol sequences, optionally wherein each subset includes fewer than Y OFDM symbols and / or wherein the radio device discards OFDM symbol sequences whose potential codepoints are not associated with the radio device.

[0068] By locally storing only relevant sequences, the radio device optimizes in-device memory usage and speeds correlation, thereby reducing detection time and power.

[0069] The subset of the OFDM symbols may be a smaller selection of waveforms from the set of OFDM symbol sequences, e.g., selected based on which codepoints the radio device is likely to encounter and / or only codepoints that represent a subgroup of the radio device or a universal paging group. For instance, if the RAN supports Y=16 OFDM symbols, but the radio device only belongs to 2 subgroups, the node may configure these 2, optionally and a minimal set for system overhead. The radio device may use limited references to detect or dismiss the WUS quickly.

[0070] In some embodiments, detecting the WUS includes measuring a correlation metric of the correlation, optionally a cross-correlation, with each candidate sequence out of the OFDM symbol sequences over multiple correlation lags, optionally to accommodate a timing uncertainty, and identifying the WUS if the correlation metric exceeds a or the cross-correlation threshold value.

[0071] The lags may account for timing uncertainty and may prevent misalignment or Doppler shifts from causing false negatives. Thus, the radio device may maintain robust detection even under varying channel conditions.

[0072] The correlation metric may be a computed measure, e.g., a magnitude of the crosscorrelation, between received samples of each OFDM symbol in the monitored radio resource and the reference candidate sequence. The multiple correlation lags may encompass offsets in the time domain used to handle timing drift and / or multi-path delays. For example, the radio device may run partial correlations at various offsets. If any offset yields a sufficiently high match, the device concludes that sequence is present.In some embodiments, the or another configuration information from the network node may be indicative of a range of correlation lags for root indices and / or cyclic shifts that are expected in a cell of the network node, optionally wherein the radio device discards correlation results outside the configured range.

[0073] Limiting the lag search window may improve false-alarm performance by preventing the radio device from spuriously matching extraneous signals.

[0074] The range of correlation lags may be an interval of possible time offsets (e.g., ±4 samples), e.g. centered on the expected arrival time, optionally beyond which the correlation result is disregarded. In an example, the network node signals that the maximum timing error is ±1 microsecond. The radio device may only check that limited range, ignoring any out-of-bounds correlation peaks.

[0075] In some embodiments, the method may further comprise selecting a set of root indices and / or a set of cyclic shifts to form a combined set of Y OFDM symbols, optionally based on the cross-correlation selection criterion and / or such that pairs of the OFDM symbols exhibit low cross-correlation across one or more time offsets within a defined detection window.

[0076] The set of OFDM symbol sequences may be based (e.g., exclusively) on the selected Y OFDM symbols. Ensuring low cross-correlation across candidate sequences may reduce the likelihood of mistaking one sequence for another, thereby reducing false wake-ups and improving detection accuracy.

[0077] Herein, low cross-correlation may be a property whereby distinct OFDM symbols have cross-correlation values below the predefined selection threshold, e.g. when aligned or slightly misaligned. For instance, the network node may choose four root indices, each with four cyclic shifts, from pre-validated sets. The radio device may obtain these sets (e.g., in the configuration information), e.g. ensuring that correlation-based detection remains robust with minimal mutual interference.

[0078] In some embodiments, the radio device accesses a predefined table, optionally in local memory of the radio device, the table specifying permissible root indices and / or cyclic shifts, optionally for a predefined length or each of multiple length of the ZCSeq, and / or the radio device discarding any combination of root index and cyclic shift not present in the table.The radio device may thereby generate candidate OFDM symbols for the set of OFDM symbol sequences, ensuring consistency of low cross-correlation across different network deployments and simplifying device-side implementation.

[0079] The predefined table may comprise a reference list embedded in configurable memory or firmware of the radio device and / or configured by the network node. The table may enumerate valid root index cyclic shift pairs. By way of example, the network node (e.g., caused by a network operator) may publish or signal the table for each possible sequence length (e.g., 31, 61, 131). The radio device may access (e.g., reference) that table so all radio devices in the RAN can share the same candidate ZCSeqs for WUS detection.

[0080] In some embodiments, the method may further comprise mapping a subgroup of radio devices to one of a plurality of codepoints, each codepoint corresponding to a temporal arrangement of multiple, optionally K (OFDM) symbols in sequence.

[0081] The method may enable the radio device to identify a subgroup-specific WUS. Associating each subgroup with a different multi-symbol arrangement allows a single wake-up signal resource to address multiple device groups, improving resource usage and minimizing battery drain across all devices.

[0082] The subgroup may encompass a set of radio devices that share the same wake-up pattern. The arrangement of candidate OFDM symbols may be a specific sequence pattern (e.g., SI then S3 then S2) mapped to that subgroup.

[0083] In an loT scenario, thousands of sensors may be divided into 32 subgroups. The network node may transmit a single WUS with a pattern corresponding to two or three candidate sequences. Only devices in the signaled subgroup may proceed to decode subsequent data.

[0084] In some embodiments, wherein, if the radio device determines its assigned subgroup corresponds to a common codepoint and / or a codepoint not associated with a subgroup, the radio device decodes, in the active state, an associated paging region for cell-specific or system-wide control signaling.

[0085] The common codepoint may be a universal or "all-subgroup" codepoint, which may allow the network node to alert every device for critical system messages, ensuring reliable mass notification without enumerating individual subgroups, e.g., for an emergency or broadcast.In some embodiments, the detecting of the WUS may comprise correlating a partial or complete concatenation of multiple, optionally K (OFDM) symbols forming a compound waveform for extended codepoint determination.

[0086] Concatenating multiple sequences can increase a cross-correlation peak and / or a representable code space while maintaining low cross-correlation. This can improve selectivity of the WUS when more subgroups or more precise addressing is required. The longer compound waveform may each occupy one or more OFDM symbols. For instance, to encode 32 different codepoints from only Y=8 OFDM symbols, the network node may schedule 2 or 3 consecutive OFDM symbols, optionally each with an assigned ZCseq-based OFDM symbol. The radio device may detect the concatenation for advanced subgroup mapping.

[0087] In some embodiments, detecting the WUS may comprise calculating a cross-correlation among the candidate OFDM symbols to verify that a detected sequence arrangement yields minimal average cross-correlation relative to other permutations.

[0088] By verifying that the detected pattern provides the best and / or lowest cross-correlation mismatch, the radio device may further reduce incorrect detections and unnecessarily activating higher-power states. False-alarm performance may refer to a probability of incorrectly identifying a codepoint, leading to unnecessary power consumption.

[0089] In some embodiments, the method may further comprise adapting a predefined crosscorrelation detection threshold value based on measured cross-correlation distributions in a current radio environment, optionally wherein the radio device raises or lowers the cross-correlation detection threshold value to maintain a target wake-up reliability.

[0090] Adaptive thresholding can allow the radio device to cope with changing noise (e.g., SNR) or interference (e.g., SINR), ensuring consistent wake-up performance even as channel conditions fluctuate.

[0091] Herein, the cross-correlation detection threshold value may be a configurable numeric criterion above which a correlation result is considered a valid wake-up.

[0092] In dense deployments, interference might increase. The radio device may monitor correlation statistics over time, adjusting the threshold to optimize reliability. Thenetwork node may signal permissible ranges or instruct the device to remain within certain false-alarm constraints.

[0093] In some embodiments, the method may further comprise, upon detection of the WUS and / or when in the active state, activating a transceiver or receiver chain within the radio device solely for the duration of a control and / or data reception interval, and then returning to the energy-saving state.

[0094] Temporarily enabling only the receiver or transceiver when needed reduces overall power consumption by lengthening the energy-saving state. The (e.g., higher-power) receiver or transceiver chain may be a primary radio receiver capable of decoding data channels of the network node, e.g. as opposed to the specialized low-power portion dedicated to wake-up detection.

[0095] In an loT sensor as an example of the radio device, the radio device may remain in the energy-saving state until its WUS is detected. Then the radio device activates a main receiver (e.g., as RF and / or baseband chain) to handle scheduled data transmissions, and return to the energy-saving state when completed.

[0096] According to a second method aspect, a method performed by a network node for transmitting a wake-up signal in a radio access network (RAN) is provided. The method comprises configuring a group of radio devices to monitor a configured set of radio resources of the radio access network for detecting the wake-up signal, optionally associated with the network node and / or the group of radio devices. The method further comprises transmitting the wake-up signal, wherein the wake-up signal comprises a sequence of orthogonal frequency-division multiplexing (OFDM) symbols. The method also comprises, in response to the wake-up signal, transmitting data to or receiving data from at least one of the radio devices in the group.

[0097] By configuring the group of radio devices to monitor specific resources, embodiments of the network node ensure efficient allocation of signaling overhead. The wake-up signal, formed with a defined sequence of orthogonal frequency-division multiplexing symbols, enables the addressed radio devices to detect it reliably. Once the wake-up signal is transmitted, data exchange occurs as needed with only those devices intended to become active. This directly solves the technical need of selectively activating low-power devices on demand while avoiding extraneous signaling that would otherwise degrade network efficiency.In other words, as to a second method aspect, a method performed by a network node for transmitting a wake-up signal (WUS) in a radio access network (RAN) is provided. The method comprises configuring a group of radio devices to monitor a configured set of radio resources of the RAN for detecting the WUS, optionally associated with the network node and / or the group of radio devices. The method further comprises transmitting the WUS, wherein the WUS comprises a sequence of orthogonal frequency-division multiplexing (OFDM) symbols. In response to the WUS, the method comprises transmitting data to and / or receiving data from at least one of the radio devices in the group.

[0098] The second method aspect may further comprise any feature and / or any step disclosed in the context of the first method aspect, or a feature and / or step corresponding thereto, e.g., a receiver counterpart to a transmitter feature or step.

[0099] In some embodiments, the method may further comprise any one of the features and steps described herein in connection with detecting the WUS, or corresponding features and steps applied mutatis mutandis.

[0100] The technique may be applied in the context of 3GPP New Radio (NR), NR Advanced, and beyond fifth generation (5G) radio access technology.

[0101] The technique may be implemented in accordance with a 3GPP specification, e.g., for 3GPP release 19 or beyond. The technique may be implemented for 3GPP NR according to a modification or extension of the 3GPP document TR 38.869, version 0.4.0, "Study on low-power Wake-up Signal and Receiver for NR"; 3GPP RP-234056, New WID: Low-power wake-up signal and receiver for NR (LP WUS / WUR)"; 3GPP TS 38.211, "NR; Physical channels and modulation", version 17.0.0; 3GPP TS 38.213, "NR; Physical layer procedures for control", version 17.0.0; and 3GPP TS 38.331, "NR; Radio Resource Control (RRC); Protocol specification", version 16.7.0.

[0102] Any aspect may use OFDM sequences for wake-up signals.

[0103] Any embodiment of any aspect may implement or fulfill at least one of the following items:

[0104] • The Zadoff-Chu (ZC) sequence defines the frequency domain coding of the WUS, since the ZC sequence, ZC(n) with n being a frequency domain index, is iDFT'ed to become a time-domain signal, i.e. the ZC waveform.

[0105] • Y = 4, 8, 16 is the number of candidate OFDM sequences.Each candidate OFDM sequence corresponds to a Zadoff-Chu (ZC) sequence of a specific length and unique combination of cyclic shift (CS) and root index value used to generate the Zadoff-chu sequence.

[0106] Hence, Y = number of roots (Nroot) * number of CSs (Ncs).

[0107] Equivalently in the time domain after iDFT, the number of different ZC waveforms is Y.

[0108] • It is beneficial to limit Nroot<= X to fulfil UE memory limitations.

[0109] • On-Off-Keying (OOK) defines the time domain coding of the WUS.

[0110] • A rate of the OOK is M, i.e. the number of OOK chips per OFDM symbol. This is noted as "OOK-M". For example, M = 1, 2, 4, 8 or 16.

[0111] • K is the length of the WUS in terms of OFDM symbols. For example, K = 2 or K = 3 OFDM symbols. In other words, K is the number of OFDM symbols over which the WUS coding is spread.

[0112] • Hence, there are YKdifferent ZC codings (e.g., as a frequency domain contribution).

[0113] • Applying the OOK in the time domain to the K OFDM symbols is referred to as "overlaying". In other words, the WUS results from OOK overlaid with OFDM sequences.

[0114] In a first variant of any embodiment, overlaid (e.g. in the WUS resulting from "OOK-M waveform with overlaid OFDM sequence") may mean that the OFF times of the OOK leads to a portion of the OFDM sequence missing in the resulting WUS. For example, the K OFDM symbols forming the OFDM sequence is multiplied time-wise with the OOK symbol. In other words, The "OOK-M waveform with overlaid OFDM sequence" means that during each OFDM symbol, there are M "chips" of on-off-keying (OOK), and the time-domain OFDM signal is "gated" (e.g., transmitted at nonzero amplitude in the ON sub-intervals and set to zero in the OFF sub-intervals).

[0115] In a second variant of any embodiment, the OFDM sequence is "cut" and (e.g., losslessly) re-distributed (e.g., spread) in the time domain according to the ON time of the OOK. In other words, instead the OFF portion being physically omitted (by a zero amplitude), the OFDM waveform is cut and shifted to the ON subintervals (e.g., in a lossless manner).

[0116] • Hence, in a purely combinational sense, there are YK*

[0117]

[0118] different codepoints, with

[0119]

[0120] ways to choose the ON / OFF envelope (time-domain part) if each "chip" can be independently ON or OFF. In practice, only certain subsets may be used as WUS, so the above product form is the theoretical maximum. • "UE subgroups" "subgroups", "UE group" and "subgroup" are synonymous and refer to those UEs, among all UEs served in a cell, which share the same WUS. Inother words, a single WUS codepoint addresses that entire subgroup of UEs. There are N UE subgroups.

[0121] • The granularity of the "UE subgroups", i.e. the number N of different WUSs, is a trade-off between the complexity of the WUS coding and the risk of waking up too many UEs that are actually not addressed.

[0122] • The technical problem relates to selecting the Y ZC-sequence candidates to reduce memory and power requirements for the UE. This further leads to the problem when the number of Y candidates for (to be overlaid) ZC-sequences is less than the number of / V UE subgroups to be distinctively addressed by the WUS (e.g., N=32 different WUSs). Hence, in the context of the unified (harmonized) WUS design (e.g., the overlaying), the problem

[0123] o relates to arranging K ZC-waveforms out of the Y candidates for the ZC- waveform [which theoretically is YKdifferent codings] and o relates to the need for the time-domain part of the WUS coding [which theoretically is

[0124]

[0125] being greater than 1.

[0126] In any radio access technology (RAT), the technique may be implemented for SL relay selection. The SL may be implemented using proximity services (ProSe), e.g. according to a 3GPP specification.

[0127] Any radio device may be a user equipment (UE), e.g., according to a 3GPP specification. The radio device and the RAN (e.g., the network node or any further network node serving the radio device) may be wirelessly connected in an uplink (UL) and / or a downlink (DL) through a Uu interface. Alternatively or in addition, a sidelink (SL) may enable a direct radio communication between proximal radio devices, e.g., the remote radio device and the relay radio device, optionally using a PC5 interface. Services provided using the SL or the PC5 interface may be referred to as proximity services (ProSe). Any radio device (e.g., a remote radio device and / or a relay radio device) supporting a SL may be referred to as ProSe-enabled radio device. The relay radio device may also be referred to as ProSe UE-to-Network Relay.

[0128] The radio device and / or the RAN (e.g., the network node or further network nodes) may form, or may be part of, a radio network, e.g., according to the Third Generation Partnership Project (3GPP) or according to the standard family IEEE 802.11 (Wi-Fi). The first method aspect and the second method aspect may be performed by one or more embodiments of the radio device and the relay radio device or the network node (or any other node of the RAN, e.g., including base station functionality), respectively.The RAN may comprise one or more network nodes (e.g., base stations) performing the second method aspect. Alternatively or in addition, the radio network may be a vehicular, ad hoc and / or mesh network comprising two or more radio devices, e.g., acting as the radio device (first aspect) and the relay radio device (second aspect).

[0129] Any of the radio devices may be a 3GPP user equipment (UE) or a Wi-Fi station (STA). The radio device may be a mobile or portable station, a device for machine-type communication (MTC), a device for narrowband Internet of Things (NB-loT) or a combination thereof. Examples for the UE and the mobile station include a mobile phone, a tablet computer and a self-driving vehicle. Examples for the portable station include a laptop computer and a television set. Examples for the MTC device or the NB-loT device include robots, sensors and / or actuators, e.g., in manufacturing, automotive communication and home automation. The MTC device or the NB-loT device may be implemented in a manufacturing plant, household appliances and consumer electronics.

[0130] Whenever referring to the RAN, the RAN may be implemented by one or more base stations, which functionality may be split across multiple network node (e.g., a central unit and a distributed unit).

[0131] The radio device may be wirelessly connected or connectable (e.g., according to a radio resource control, RRC, state or active mode) with the network node of the RAN (or the relay radio device of the mesh network). The relay radio device may be wirelessly connected or connectable (e.g., according to a radio resource control, RRC, state or active mode) with at least one base station of the RAN.

[0132] The network node (e.g., a base station) may encompass any station that is configured to provide radio access to any of the radio devices. The network node may correspond to one or more cells (e.g., serving cells for the radio device), a transmission and reception point (TRP), a central unit (CU), a distributed unit (DU), a radio access node or an access point (AP). The network node (and / or the relay radio device) may provide a data link to a host computer providing user data to the (e.g., remote) radio device or gathering user data from the (e.g., remote) radio device. Examples for the base stations may include a 3G base station or Node B (NB), 4G base station or eNodeB (eNB), a 5G base station or gNodeB (gNB), a Wi-Fi AP and a network controller (e.g., according to Bluetooth, ZigBee or Z-Wave).The RAN may be implemented according to the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), 3GPP Long Term Evolution (LTE) and / or 3GPP New Radio (NR).

[0133] Any aspect of the technique may be implemented on a Physical Layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, a packet data convergence protocol (PDCP) layer, and / or a Radio Resource Control (RRC) layer of a protocol stack for the radio communication.

[0134] Herein, referring to a protocol of a layer may also refer to the corresponding layer in the protocol stack. Vice versa, referring to a layer of the protocol stack may also refer to the corresponding protocol of the layer. Any protocol may be implemented by a corresponding method.

[0135] As to another aspect, a computer program product is provided. The computer program product comprises program code portions for performing any one of the steps of the first or second method aspect disclosed herein when the computer program product is executed by one or more computing devices. The computer program product may be stored on a computer-readable recording medium. The computer program product may also be provided for download, e.g., via the radio network, the RAN, the Internet and / or the host computer. Alternatively, or in addition, the method may be encoded in a Field-Programmable Gate Array (FPGA) and / or an Application-Specific Integrated Circuit (ASIC), or the functionality may be provided for download by means of a hardware description language.

[0136] As to a first device aspect, a device for receiving a WUS is provided. The device may be configured to perform any one of the steps of the first method aspect. As to a further first device aspect, a device for receiving a WUS is provided. The device comprises processing circuitry (e.g., at least one processor and a memory). Said memory comprises instructions executable by said at least one processor whereby the device is operative to perform any one of the steps of the first method aspect.

[0137] In other words, as to a first device aspect, a radio device for detecting a wake-up signal (WUS) from a radio access network (RAN) is provided. The radio device comprises memory operable to store instructions and processing circuitry operable to execute the instructions, such that the radio device is operable to monitor a configured set of radio resources of the RAN for detecting the WUS, optionally associated with a network node of the RAN. In response to detecting the WUS in the monitored radio resources, the radiodevice transitions from an energy-saving state to an active state. Detecting the WUS comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequency-division multiplexing (OFDM) symbols.

[0138] In some embodiments, the radio device may further be operable to perform any one of the features described herein in connection with detecting the WUS.

[0139] As to another first device aspect, a radio device for detecting a wake-up signal (WUS) from a radio access network (RAN) is provided. The radio device is configured to monitor a configured set of radio resources of the RAN for detecting the WUS, optionally associated with a network node of the RAN. In response to detecting the WUS in the monitored radio resources, the radio device transitions from an energy-saving state to an active state. Detecting the WUS comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequency-division multiplexing (OFDM) symbols.

[0140] In some embodiments, the radio device may further be configured to perform any one of the features described herein in connection with detecting the WUS.

[0141] As to a second device aspect, a device for transmitting a WUS is provided. The device may be configured to perform any one of the steps of the second method aspect. As to a further second device aspect, a device for transmitting a WUS is provided. The device comprises processing circuitry (e.g., at least one processor and a memory). Said memory comprises instructions executable by said at least one processor whereby the device is operative to perform any one of the steps of the second method aspect.

[0142] In other words, as to a second device aspect, a network node for transmitting a wake-up signal (WUS) in a radio access network (RAN) is provided. The network node comprises memory operable to store instructions and processing circuitry operable to execute the instructions, such that the network node is operable to configure a group of radio devices to monitor a configured set of radio resources of the RAN for detecting the WUS, optionally associated with the network node and / or the group of radio devices. The network node is further operable to transmit the WUS, wherein the WUS comprises a sequence of orthogonal frequency-division multiplexing (OFDM) symbols. In response to the WUS, the network node is further operable to transmit data to and / or receive data from at least one of the radio devices in the group.

[0143] In some embodiments, the network node may further be operable to perform any one of the features described herein in connection with transmitting the WUS.As to another second device aspect, a network node for transmitting a wake-up signal (WUS) in a radio access network (RAN) is provided. The network node is configured to configure a group of radio devices to monitor a configured set of radio resources of the RAN for detecting the WUS, optionally associated with the network node and / or the group of radio devices. The network node is further configured to transmit the WUS, wherein the WUS comprises a sequence of orthogonal frequency-division multiplexing (OFDM) symbols. In response to the WUS, the network node is further configured to transmit data to and / or receive data from at least one of the radio devices in the group.

[0144] In some embodiments, the network node may further be configured to perform any one of the features described herein in connection with transmitting the WUS.

[0145] As to a still further aspect a communication system comprising at least one radio device and at least one network node according to the afore-mentioned aspects is provided. Alternatively or in addition, communication system comprises a host computer. The host computer comprises a processing circuitry configured to provide user data, e.g., included in a secondary cell synchronized using the subject technique. The host computer further comprises a communication interface configured to forward the user data to a cellular network (e.g., the RAN and / or the base station) for transmission to a UE. A processing circuitry of the cellular network is configured to execute any one of the steps of the second method aspects. The UE comprises a radio interface and processing circuitry, which is configured to execute any one of the steps of the first method aspects.

[0146] The communication system may further include the UE. Alternatively, or in addition, the cellular network may further include one or more base stations configured for radio communication with the UE and / or to provide a data link between the UE and the host computer using the first and / or second method aspects.

[0147] The processing circuitry of the host computer may be configured to execute a host application, thereby providing the user data and / or any host computer functionality described herein. Alternatively, or in addition, the processing circuitry of the UE may be configured to execute a client application associated with the host application.

[0148] Any one of the devices, the UE, the network node, the base station, the communication system or any node or station for embodying the technique may further include any feature disclosed in the context of the method aspect, and vice versa. Particularly, anyone of the units and modules disclosed herein may be configured to perform or initiate one or more of the steps of the method aspect.

[0149] Brief Description of the Drawings

[0150] Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:

[0151] Fig. 1 shows a schematic block diagram of an embodiment of a device for being woken up;

[0152] Fig. 2 shows a schematic block diagram of an embodiment of a device for triggering wake-up;

[0153] Fig. 3 shows a flowchart for a method of receiving a WUS, which method may be implementable by the device of Fig. 1;

[0154] Fig. 4 shows a flowchart for a method of transmitting a WUS, which method may be implementable by the device of Fig. 2;

[0155] Fig. 5 schematically illustrates a first example of a radio network comprising embodiments of the devices of Figs. 1 and 2 for performing the methods of Figs.

[0156] 3 and 4, respectively;

[0157] Fig. 6A schematically illustrates a sequence of WUSs and Paging Occasions;

[0158] Fig. 6B shows a schematic block diagram of an embodiment of the device of Fig. 1;

[0159] Fig. 6C schematically illustrates a second example of a radio network comprising embodiments of the devices of Figs. 1 and 2 for performing the methods of Figs.

[0160] 3 and 4, respectively;

[0161] Fig. 6D schematically illustrates a first example of a time domain structure of a WUS, which may be implemented in any embodiment;

[0162] Fig. 6E schematically illustrates a second example of a time domain structure of a WUS, which may be implemented in any embodiment;Fig. 6F schematically illustrates a third example of a radio network comprising embodiments of the devices of Figs. 1 and 2 for performing the methods of Figs.

[0163] 3 and 4, respectively;

[0164] Fig. 7 schematically illustrates OFDM symbols selected for forming an example of the WUS;

[0165] Fig. 8 shows a diagram for a cross-correlation used as a selection criterion;

[0166] Fig. 9 schematically illustrates a combined OFDM symbol sequence for forming a WUS;

[0167] Fig. 10 shows a schematic block diagram of a radio device embodying the device of Fig. 1;

[0168] Fig. 11 shows a schematic block diagram of a network node embodying the device of Fig. 2; and

[0169] Fig. 12 schematically illustrates an example telecommunication network connected via an intermediate network to a host computer.

[0170] Detailed Description

[0171] In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a specific network environment in order to provide a thorough understanding of the technique disclosed herein. It will be apparent to one skilled in the art that the technique may be practiced in other embodiments that depart from these specific details. Moreover, while the following embodiments are primarily described for a New Radio (NR) or 5G implementation, it is readily apparent that the technique described herein may also be implemented for any other radio communication technique, including a Wireless Local Area Network (WLAN) implementation according to the standard family IEEE 802.11, 3GPP LTE (e.g., LTE-Advanced or a related radio access technique such as MulteFire), for Bluetooth according to the Bluetooth Special Interest Group (SIG), particularly Bluetooth Low Energy, Bluetooth Mesh Networking and Bluetooth broadcasting, for Z-Wave according to the Z-Wave Alliance or for ZigBee based on IEEE 802.15.4.

[0172] Moreover, those skilled in the art will appreciate that the functions, steps, units and modules explained herein may be implemented using software functioning in conjunctionwith a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer, e.g., including an Advanced RISC Machine (ARM). It will also be appreciated that, while the following embodiments are primarily described in context with methods and devices, the invention may also be embodied in a computer program product as well as in a system comprising at least one computer processor and memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

[0173] Fig. 1 schematically illustrates a block diagram of an embodiment of a device for performing the method of embodiment 1. The device may comprise modules as indicated in Fig. 1, e.g. for performing the first method aspect.

[0174] Any of the modules of the device 100 may be implemented by units configured to provide the corresponding functionality. The device 100 may also be referred to as, or may be embodied by, a radio device (or briefly: the UE). The radio device 100 and the network node may be in direct radio communication, e.g., at least for monitoring the WUS at the radio device 100. The network node may be embodied by below-mentioned device 200.

[0175] Fig. 2 schematically illustrates a block diagram of an embodiment of a device for performing the method of embodiment 39. The device may comprise modules as indicated in Fig. 2, e.g. for performing the second method aspect.

[0176] Any modules of the device 200 may be implemented by units configured to provide the corresponding functionality.

[0177] The device 200 may also be referred to as, or may be embodied by, a network node 200 (further below also referred to by reference sign 1100 and 1212). The network node 200 and the radio device 100 may be in direct radio communication, for example at least for the transmission of the WUS at the network node 200. The radio device may be embodied by the above-mentioned device 100.

[0178] Fig. 3 illustrates an embodiment of a method 300 performed by a radio device 100, e.g. as indicated in Fig. 3 and / or the embodiment 1.

[0179] The method 300 may be performed by the device 100. For example, the modules 104 and 106 may perform the steps 304 and 306, respectively.Fig.4 depicts a flowchart for a method 400 performed by a network node 200. The method 400 may comprise the steps indicated in Fig. 4 and / or embodiment 39.

[0180] The method 400 may be performed by the device 200. For example, the modules 202 and 204 may perform the steps 402 and 404, respectively.

[0181] In any aspect, the technique may be applied to uplink (UL), downlink (DL) or direct communications between radio devices, e.g., device-to-device (D2D) communications or sidelink (SL) communications.

[0182] Each of the transmitting station 100 and receiving station 200 may be a radio device or a base station. Herein, any radio device may be a mobile or portable station and / or any radio device wirelessly connectable to a base station or RAN, or to another radio device. For example, the radio device may be a user equipment (UE), a device for machine-type communication (MTC) or a device for (e.g., narrowband) Internet of Things (loT). Two or more radio devices may be configured to wirelessly connect to each other, e.g., in an ad hoc radio network or via a 3GPP SL connection. Furthermore, any base station may be a station providing radio access, may be part of a radio access network (RAN) and / or may be a node connected to the RAN for controlling the radio access. For example, the base station may be an access point, for example a Wi-Fi access point.

[0183] For example, the network node 200 may adapt configuration and / or transmission of the WUS 900 (e.g., the configured set of radio resources and / or the candidate sequence of OFDM symbols) depending on noise or a signal-to-noise ratio (SNR), and / or interference or a signal-to-interference-and-noise ratio (SINR) on a channel or radio link (e.g., responsive to a measurement report).

[0184] Furthermore, "predefined" may encompass stored in memory (e.g., in a Subscriber Identity Module, SIM) of the transmitting wireless device, or hard-coded or hard-wired in the transmitting wireless device, or preconfigured or configured by a network node or radio access network (RAN) for the transmitting wireless device (e.g., preconfigured while in coverage prior to performing the method out of coverage, or configured while in coverage when performing the method).

[0185] The radio spectrum shared by multiple RATs and / or in FR2 may comprise an unlicensed spectrum.Herein, a list of the form A, B, and / or C (also written as A, B and / or C) may correspond to at least one or each of A, B, and C, i.e., A and / or B and / or C.

[0186] Fig. 5 illustrates a radio network 500 that encompasses a radio device 100 and a network node 200 embodying the devices 100 and 200.

[0187] Embodiments of the device may comprise a wake-up receiver 702, e.g. as indicated in Fig. 6B.

[0188] Any embodiment may use a wake-up signal (WUS) composed of one or more OFDM symbols (e.g. derived from a Zadoff-Chu sequence, ZCSeq) and an on-off-keying (OOK) in a unified design of the WUS, e.g. composed by overlaid sequences.

[0189] Any embodiment may be based on at least one of the following features.

[0190] A wake-up receiver (WUR), also referred to as 'wake-up radio', involves use of a low- power receiver in UEs, which detects a wake-up signal (WUS) that is specially designed to be highly energy efficient. The WUS is used to activate the main (baseband / RF / less power efficient) receiver to carry out more complex communication or sensory functions. Typical actions after activation may be reception of an incoming paging indication on the Packet Data Control Channel (PDCCH) during paging occasions (PO), further scheduling communication on the Packet Data Shared Channel (PDSCH). As 5G-Advanced transitions to 6G in the next decade, there is a stated intention to introduce sensory functions into cellular radios capable of functionality that may allow environmental awareness, mapping, and the detection of objects or motion. The WUR is mainly useful in lowering energy consumption and improving device battery life or trading off reduction of latency (through shorter discontinuous reception intervals) for fixed energy consumption by preventing more complex functions from operating unless needed.

[0191] Fig. 6A schematically illustrates locations of a WUS 900 and the paging occasion (used in the steps 308 and 408) to which it is associated. The WUS in black is associated to the radio device 100, which is thus entering the active state 604 from the energy-saving state 602.

[0192] The WUR 702 has the following characteristics:

[0193] - Extremely low power, simple and low-cost receiver architecture, relaxed requirements, noisier (i.e., less accurate) clock or oscillator;- Significant power saving gain by maximizing the time in which the main receiver can be in the sleep mode;

[0194] - Enablers for zero energy / battery-less devices, and energy harvesting operations;

[0195] - Compromised coverage due to lower receiver sensitivity.

[0196] As an example, Fig. 6B shows a dedicated wake up radio (WUR) is used for monitoring a wake-up signal (WUS). Once the WUR 702 detects the WUS 900 as one likely addressed to itself, it activates the main (baseband / RF / less power efficient) receiver to detect further incoming messages. Thus, the main receiver can go to sleep mode and save power until it is triggered by WUR. The WUS is itself transmitted using an OFDM-based transmitter from the network using equipment that is shared with the base station for cellular communication.

[0197] Fig. 6B illustrates a dedicated wake-up radio 702 for the radio device 100 accompanying the main receiver 704 of the radio device 100. The Fig. 6B is schematic and does not necessarily represent a typical implementation. For instance, the antenna and some components in the RF front-end may or may not be shared.

[0198] Any embodiment of the device 100 may comprise a NR WUR 702, e.g. according to the following 3GPP standardization. The Release 18 study item on "low-power wake-up signal and receiver for NR" is completed and the technical report is provided in: TR 38.869, V0.4.0, "Study on low-power Wake-up Signal and Receiver for NR" [2], In Release 19 Work Item various design aspects of WUS / WUR are specified. For Release 19, the objective is to specify the wake-up signal for both RRC Idle / lnactive and RRC Connected states: RP-234056, New WID: Low-power wake-up signal and receiver for NR (LP WUS / WUR) [3], Some of the objectives are listed below:

[0199] The objectives of the work item are the following:

[0200] • To specify an LP-WUS design commonly applicable to both IDLE / INACTIVE and CONNECTED modes (RANI, RAN4)

[0201] • Specify OOK (OOK-1 and / or OOK-4) based LP-WUS with overlaid OFDM sequence(s) over OOK symbol

[0202] • 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.

[0203] • 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)

[0204] • Specify LP-SS with periodicity with Yms for LP-WUR, for synchronization and / or RRM for serving cell. (RANI, RAN4)

[0205] • 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

[0206] PSS / SSS can be used for synchronization and RRM instead of LP-SS.

[0207] • 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)

[0208] Unified WUS design: OOK overlaid with OFDM sequences:

[0209] The WUR is expected to have limited capabilities in terms of supported modulation schemes, synchronization, and receiver architecture. For example, the WUR may only support a simple modulation scheme such as on-off keying (OOK) and employ time domain envelope detection. Nevertheless, in some other cases, a low power wake-up receiver can be more capable, e.g., capable of receiving an OFDM-based signal or both OOK-based and OFDM-based signals.

[0210] Specifically, any embodiment may have the following types of WUR 702:

[0211] OOK-based WUR: supports on-off keying (OOK) modulation and employs time domain envelope detection.

[0212] OFDM-based WUR: more capable receiver that can receive OFDM-based signals such as PSS / SSS, and capable of processing l / Q samples. For synchronization, existing PSS / SSS can be used.

[0213] In Release 19 LP-WUS / WUR work item, one objective is to specify a unified signal design that accommodates OOK and OFDM waveform, i.e., overlayed OFDM sequences over OOK symbols. Within the scope of Release 19, the same information is delivered irrespective of LP-WUR type and the OFDM sequence can carry information. We refer to the term unified WUS or harmonized WUS as a WUS which can be utilized by any WUR regardless of its architecture / capability (e.g., WUR capable of receiving OOK-based signal only, OFDM-based signal only, or both). WUS information payload typicallycarries some information. The information for example can be about UE group for which the WUS is intended. An illustrative figure for the unified LP-WUS design is shown in Fig. 6C.

[0214] Fig. 6C illustrates a unified LP-WUS design. Fig. 6D shows an example of the WUS 900 resulting from OOK 904 overlaid with OFDM sequences (i.e., OFDM symbol sequences) 902.

[0215] At least some embodiments may address at least one of the following problems. Based on 3GPP agreements, the overlaid OFDM sequences for Release 19 WUS will be based on Zadoff-Chu (ZC) sequences. However, the details of the sequences are lacking in prior art, i.e. specifically, the roots and cyclic shifts (CS) for the ZC sequences used to identify the OFDM sequences.

[0216] Also lacking in prior art are efficient solutions for identifying ordering of OFDM sequences for mapping one or more codepoints to multiple OFDM symbols when the WUS spans multiple OFDM symbols. For example, when the OFDM sequences are chosen from a small candidate set of OFDM sequences or when the number of subgroups is larger than the number of sequence candidates).

[0217] In Release 19, the maximum number of subgroups to be indicated by WUS is 32, which is larger than the number of overlaid sequences (e.g., YKas combined CZ-coding contribution). Solutions are needed to indicate 32 subgroups with OFDM WUS using number of overlaid sequences smaller than 32 (e.g., 4, 8, 16).

[0218] In RAN1#119, the following was agreed:

[0219] Agreement

[0220] CS(s) and / or root(s) used for overlaid OFDM sequence in the time

[0221] domain are derived from RRC signaling:

[0222] FFS: the set of values of CS and root for configuration

[0223] FFS: details of the RRC signaling

[0224] In addition, to limit the memory size of UE for storing sequences, the number of sequence roots should be limited to X. In RANl#120, the following was agreed:

[0225] Agreement

[0226] For idle mode, regarding the maximum number of candidates overlaid sequences to carry LP-WUS information per OOK ON chip for one cell:

[0227] support maximum 16 candidates overlaid sequences for M=1support maximum 8 candidates overlaid sequences for M=2 support maximum 4 candidates overlaid sequences for M=4

[0228] For candidate overlaid sequences across all OOK ON chips of LP- WUS, the number of roots (in specification) is up to [FFS: X], FFS whether the number of roots can be different for different M value.

[0229] More specifically at least some embodiments may address at least one of the following problems: The problem to determine sets of roots and / or cyclic shifts (CSs) of ZC sequences for different cases based on the above constraints (i.e., on the number of ZC sequences and roots), and / or the problem to determine a pattern and / or ordering of multiple (e.g., K) OFDM sequences to indicate a number of subgroups larger than the number of sequence candidates

[0230] Independent or in combination with the listed embodiments, any aspect may comprise at least one of the following steps: Determination of suitable sets of OFDM sequences to carry WUS information based on the sequence length, number of sequence candidates, and / or constraints on the sequences (e.g., limits on the number of different roots). For Zadoff-Chu sequences, suitable sets of roots and cyclic shifts are determined. Moreover, efficient methods of mapping OFDM sequences to symbols of a LP-WUS are described below, especially for cases where a large number (A / ) of codepoints are to be indicated by LP-WUS using OFDM sequences chosen from a small (Y<N) set of candidate OFDM sequences.

[0231] Furthermore, the tables presented in Part A of the embodiments can be included in technical specifications for generating and detecting the OFDM sequences. The UE 100 (herein referenced for brevity and not limitation as an example of the radio device) may be configured with one or multiple of the entries in the tables. For more detailed implementation, at least one feature of the Embodiments Part A and / or some examples in the section at the end of Part A, and / or the Embodiments Part B and / or some examples in the section at the end of Part B may be implemented.

[0232] Independent or in combination with the listed embodiments, any aspect may comprise at least one of the following steps: a UE determining a specific pattern / arrangement / ordering of OFDM sequences (e.g., as disclosed in at least one Tables A-l to A-6) on a set of symbols used for LP-WUS monitoring, wherein the OFDM sequences are chosen from a small (Y<N) candidate set of OFDM sequences.Alternatively or in addition, a UE determining a set of candidate OFDM sequences for LP-WUS, wherein the candidate OFDM sequences are obtained from Zadoff-Chu (ZC) sequences (ZCSeqs) with specific sets of root indices (e.g., as shown in at least one of the Tables B3 to B8) and / or specific combinations of cyclic shifts (shown in at least one of the Tables Bl to B2).

[0233] Monitoring of LP-WUS

[0234] UEs may support reception of low-power wake-up signal (WUS) to achieve power saving. UEs may receive LP-WUS using a LP-WUR (low-power wake up signal). LP-WUR is generally expected to operate with much lower active power compared to the UE main receiver and thus have limited capabilities in terms of supported modulation schemes, synchronization, and receiver architecture. LP-WUS is transmitted from the network to UE and can be used to trigger UE to monitor PDCCH, e.g., paging PDCCH in RRC-I DLE / I N ACTIVE. The LP-WUS can carry some information about UE subgroup, e.g., to indicate which UE to wake up upon detecting the LP-WUS. There can be different types of WUR such as OOK-based or OFDMbased. The WUS can have a unified structure which is an OOK overlaid with OFDM sequences.

[0235] In one OFDM symbol, there can be one or multiple OOK symbols / segments / chips. Specifically, OOK with parameter M (examples of M are {1,2,4,8,16}) means within one OFDM symbol there are M ON or OFF symbols of OOK (see Fig. 6E).The OFDM WUR detects WUS information by detecting the OFDM sequences (as illustrated in Fig. 6F).

[0236] The overlaid OFDM sequences for WUS can be created based on Zadoff-Chu (ZC) sequences. The length of the ZC sequence is the largest prime number less than or equal to 12*X / M where X is the number of resource blocks and M is modulation order of OOK (e.g., M=l,2,4). Considering X=ll PRBs (e.g. as agreed in Release 19), the ZC sequence lengths are:

[0237] • ZC length =131 for M=l;

[0238] • ZC length =61 for M=2;

[0239] • ZC length =31 for M=4.

[0240] Fig. 6E shows schematically a further example of OOK-M 904 overlaid with OFDM sequences 902, here for M=2 in this example. Fig. 6F shows schematically a still further example of the WUS 900 with overlaid OFDM sequences 902.

[0241] Monitoring of LP-WUS generally implies actions performed by a UE to detect or decode a LP-WUS. The UE can attempt to detect LP-WUS in a set of time / frequency resources. The time resources can be OFDM symbols and the frequency resources can be physical resource blocks (PRBs) or subcarriers within the PRBs. The time resources can also be referred in terms of LP-WUS monitoring occasions (MOs). The UE typically determines LP-WUS information upon successful detection / decoding of LP-WUS. Based on LP-WUS information, the UE can determine whether to monitor paging PDCCH in one or more subsequent paging occasions (POs) associated with the detected LP-WUS. The UE typically determines whether it is being paged or not based on information scheduled by a paging PDCCH.UEs monitoring a PO can be divided into multiple UE subgroups. For example, LP-WUS information can be wake-up indication for one or more subgroups that a UE belongs to. If the UE determines that LP-WUS information indicates 'wake up' for its subgroup(s), it monitors one or more POs associated with the LP-WUS and if LP-WUS information does not indicates 'wake up' for its subgroup(s), it skips monitoring the associated one or more POs. This enables energy efficient UE operation. Indication of 'wake-up' via LP-WUS information can for example be successful decoding of one or more code-points decoded from LP-WUS or successful decoding that one or more bit positions in a bitmap decoded from LP-WUS are set to a specific bit-value (e.g., '1'). The one or more code-points can be associated to the one or more subgroups that the UE belongs to ('code-point based' LP-WUS information).

[0242] Each subgroup can be indicated via a sequence (or codepoint). Multiple sequences are used to address different subgroups. A UE needs to detect its own sequence to find whether its subgroup is being addressed by the network. In the unified WUS, multiple overlaid OFDM sequences can carry the WUS information.

[0243] Below determination of suitable pattern / ordering of multiple OFDM sequences to indicate codepoints / subgroups is discussed. Also, determination of suitable sets of ZC sequence roots and cyclic shifts is discussed.

[0244] Embodiments, Part A

[0245] In an embodiment (E0), a UE determines a set of OFDM symbols in a LP-WUS monitoring occasion (e.g., pl,p2...pJ in Fig. 7 for Embodiments, Part A). From the set of OFDM symbols the UE can determine a set of symbols (e.g., OOK ON symbols) used for LP-WUS monitoring (e.g., ql,q2,... qK in Fig. 7 for Embodiments, Part A, in some cases these can be same as pl,p2...pJ). The UE determines LP-WUS information from one or more OFDM sequences (e.g., S1,S2,... SL in Fig. 7 for Embodiments, Part A) detected from the set of symbols. The UE can determine LP-WUS information based on OFDM sequences detected in one or more symbols of the set of symbols (different OFDM sequences can be detected by the UE on different symbols) and based on an ordering / pattern / arrangement in which the OFDM sequences are detected. The OFDM sequence detected on a symbol can be a sequence that belongs to a set of Y candidate OFDM sequences.

[0246] The set of Y candidate OFDM sequences can be predefined or can be determined by the UE based on gNB signaling. For example, there can be set of Y=4 candidate OFDM sequences (e.g., SI, S2,..S4) where each candidate OFDM sequence corresponds to a Zadoff-Chu (ZC) sequence of a specific length and unique combination of cyclic shift and root index value used to generate the Zadoff-chu sequence. The length of all candidate OFDM sequences can be same. The candidate OFDM sequences can be obtained by truncating or extending ZC sequences. Instead of ZC, in some examples, the candidate OFDM sequences can also be M-sequences or Gold sequences.

[0247] LP-WUS information can be determined by the UE by determining whether a code-point is indicated by LP-WUS or not. Upon detecting that the code-point is indicated, the UE can monitor a corresponding PDCCH. For example, the PDCCH can be a paging PDCCH in PO associated with the MO in which the LP-WUS is received. The indicated code-point can be a code-point that belongs to a candidate set of N code-points (e.g., Zl, Z2, ...ZN).The UE can determine the candidate set of N code-points based on a number of subgroups (N_sg) parameter. For example, if Nsg=8, there can be N=9 code-points in the candidate set (e.g., one code-point corresponding to each subgroup of 8 subgroups and one common code-point corresponding to all subgroups). For example, if Nsg=15, there can be N=16 code-points in the candidate set (e.g., one code-point corresponding to each subgroup of 15 subgroups and one common code-point corresponding to all subgroups)

[0248] The number of candidates in the candidate set of code-points can be typically larger than the number of candidates in the candidate set of OFDM sequences, i.e., N can be larger than Y. Having N>Y reduces UE complexity and improves UE power consumption. Small Y may imply fewer correlations in some UE implementations. Large N implies more subgroups which in turn reduces false wake-ups to receive paging.

[0249] The UE can determine whether a code-point is indicated by using one or more mapping rules between the set of N code-points and the order / pattern / arrangement of the OFDM sequences (e.g., S1,S2,...SL in the figure) detected in one or more symbols of the set of symbols.

[0250] In a simple case where Y=N, the mapping rule can be that each candidate OFDM sequence is mapped to a corresponding candidate code-point using one-to-one mapping. For example, code-point Zi is mapped to sequence Si, and if UE detects sequence Si in one or more symbols in set of symbols, it determines that code-point Zi is indicated by LP-WUS. If there is more than one symbol in the set of symbols, si may be repeated in multiple symbols to improve reliability.

[0251] In cases where Y<N, the mapping rule can be such that each code-point in the candidate set of code-points is associated with a corresponding unique order / pattern / arrangement in which the OFDM sequences are detected on one or more symbols in the set of symbols. In one example, to determine LP-WUS information from K=3 symbols with N=32 candidates in the candidate set of code-points and Y=4 candidate OFDM sequences (S1,S2,S3,S4), the combinations shown in below Table A-l can be used.Table A-l: Arrangement of sequences for 32 codepoints, 4 sequence candidates, 3 symbols

[0252]

[0253] Fig. 8 for Embodiments, Part A, shows the average cross-correlation for different sequence / codepoint indices (cross-correlation of each sequence with others) for case (based on above table) and a reference case considering 32 codepoints (Zi, i=l-32), 4 sequences (Sk, k=l-4), and 3 OOK ON symbols. This result shows that the average cross correlation is smaller with the pattern shown in the table above. For the reference case, a mapping of sequences similar to Table A-7 is assumed, where each OFDM sequence is mapped to two bits (e.g., SI: 00, S2: 01, S3:10, S4:ll) and each subgroup ID or corresponding codepoint is represented by bits created with 3 OFDM sequences. Forexample, subgroup ID 4 is associated with bits "00,10,0" which can be formed by SI, S3, Sl= "00,10,00" (by discarding the right-most bit) which is mapped to codepoint Z5 in Table A-l.

[0254] Fig. 8 for Embodiments, Part A, shows an average cross-correlation for different sequence / codepoint indices (cross-correlation of each sequence with others).

[0255] In another example, to determine LP-WUS information from K=2 symbols with N=16 candidates in the candidate set of code-points and Y=4 candidate OFDM sequences (S1,S2,S3,S4), the combinations shown in below Table A-2 can be used

[0256] Table A-2: Arrangement of sequences for 16 codepoints, 4 sequence candidates, 2

[0257] symbols

[0258]

[0259] In another example, to determine LP-WUS information from K=2 symbols with N=8 candidates in the candidate set of code-points and Y=4 candidate OFDM sequences (S1,S2,S3,S4), the combinations shown in below Table A-3 can be used

[0260] Table A-3: Arrangement of sequences for 8 codepoints, 4 sequence candidates, 2 symbols

[0261]

[0262]

[0263] In another example, to determine LP-WUS information from K=2 symbols with N=32 candidates in the candidate set of code-points and Y=8 candidate OFDM sequences (S1,S2,...,S8), the combinations shown in below Table A-4 can be used.

[0264] Table A-4: Arrangement of sequences for 32 codepoints, 8 sequence candidates, 2

[0265] symbols

[0266]

[0267] In another example, to determine LP-WUS information from K=2 symbols with N=16 candidates in the candidate set of code-points and Y=8 candidate OFDM sequences (S1,S2,...,S8), the combinations shown in below Table A-5 can be used

[0268] Table A-5: Arrangement of sequences for 32 codepoints, 8 sequence candidates, 2

[0269] symbols

[0270]

[0271] In another example, to determine LP-WUS information from K=2 symbols with N=32 candidates in the candidate set of code-points and Y=16 candidate OFDM sequences (S1,S2,...,S16), the combinations shown in below Table A-6 can be used

[0272] Table A-6: Arrangement of sequences for 32 codepoints, 16 sequence candidates, 2

[0273] symbols

[0274]

[0275]

[0276] In one example embodiment, a candidate set Y OFDM sequences (e.g., {sl,s2,...SY}) is determined bythe UEvia higher layersignalingorvia a predefined table. Multiple mapping rules (e.g., multiple Tables like Table Al-Table A6 above) for different combinations of N (number of code-points in the candidate set of code-points) and K (number of symbols in which a code-point is detected) can be predefined. The UE determines N based on higher layer signaling (e.g., from a RRC parameter indicating number of subgroups (N_sg)) and determines K based on higher layer signaling (e.g., based on one or more of a RRC parameter indicating number OFDM symbols in a MO, a RRC parameter indicating number OOK symbols in an OFDM symbol, a RRC parameter indicating repetitions of LP-WUS). To determine whether a LP-WUS code-point Zi is indicated, UE uses the mapping rule corresponding to the determined combination of N and K and, from the mapping rule, it determines the unique pattern / order / arrangement of the OFDM sequences on the K Symbols corresponding to code-point Zi, and if that unique pattern / order / arrangement of OFDM sequences is detected, it determines that code-point zi is indicated by LP-WUS. In another example embodiment, which can be a more specific example of Embodiments discussed above, a code-point Zi (in the candidate set of N code-points Z1,Z2,...ZN) can correspond to a bit-sequence or codeword (e.g., bitl,bit2,...bitW-l,bitW as shown in Fig. 7 for Embodiments, Part A). The length of the codeword (i.e., W) can be determined based on N (e.g., W=ceil(log2(N))). The UE can determine the corresponding ordering / pattern / arrangement in which the OFDM sequences are to be detected in the Symbols for the codepoint by using the order in which of multiple sub-blocks of bits in the codeword are arranged and by using mapping rules (e.g., Table A-7 orTable A-8 below) that map candidate OFDM sequences to different possible combinations of bits within eachsubblock. The subblock can have different lengths. The maximum length of any subblock can be Q = cei I ( log2(Y))

[0277] For example, considering Y=8 candidate OFDM sequences, to detect a code-point Zi from N=32 possible codepoints, the UE can consider the codeword corresponding to that codepoint (e.g., codeword with bit-sequence bitl, bit2,bit3, bit4, bit5) and consider multiple subblocks (e.g., ceil(W / log2(Y)) = 2 subblocks), each with length smaller than or equal to ceil(log2(Y))=3 bits (one subblock of length 3bits and another subblock of length 2bits) starting from the edge of the codeword. For example, starting from the least significant bits of the codeword. In a more detailed example, the first subblock can be bit3,bit4,bit5 and second subblock can be bitl, bit2. The UE can then use a corresponding mapping rule for the corresponding subblock length (i.e., three bits length or two bits length) to determine the OFDM sequence mapped for that subblock. If bit3,bit4,bit5 of the codeword of codepoint zi maps to OFDM sequence si and bitl,bit2 map to OFDM sequence sj , the UE determines that codepoint zi is indicated if OFDM sequence pattern si,sj is detected in the Symbols of LP-WUS.

[0278] In one example, the mapping between subblock bits and candidate OFDM sequences can be such that one candidate OFDM sequence is mapped to multiple subblock length (e.g., rows 1-4 in Table A-7). Such a mapping reduces UE complexity as Y is kept to a small value. In another example, the mapping between subblock bits and candidate OFDM sequences can be such that different subblock lengths are mapped to different sets of OFDM sequences (e.g., Table A-8). Such a mapping provides more flexibility but increases the number of candidate OFDM sequences. With such a mapping, the subblocks from the codeword are determined by first considering all subblocks with maximum possible subblock length, and then considering subblock with next smaller length. For example, if codeword length W is 7bits then considering a mapping in Table A-8, the two subblocks of 3 bits each and one subblock of lbit are considered for the codeword. If codeword length W is 5 bits, two subblocks one of 3bits and other of 2 bits are considered.

[0279] Table A-7

[0280]

[0281] Table A-8

[0282]

[0283] In some alternatives, it can be considered that N long sequences are constructed by concatenating G short sequences where there are Y possible short sequences (i.e., the short sequences are the candidate OFDM sequences discussed above). A long sequence can be denoted as Xr (r=l, 2,..., N) with each sequence corresponding to one codepoint in the candidate set of codepoints (Z1,Z2,...ZN). A short sequence can be denoted as Si (i=l,2,..,Y). In Figure A-3, for example, a long sequence Xr is created by concatenating three short sequences {Si, Sj, Sk}. Each sequence Si can be a ZC sequence with specific root, cyclic shift, and length.

[0284] Sequences Xr can be constructed based on Si sequences such that the cross-correlation among the Xr sequence pairs is minimized. In this case, suitable selection of Si sequences and their pattern / order is beneficial. Suitable patterns of Si for different values of N, G, and Y values for creating Zr sequences can for example based on the following criteria:

[0285] - the maximum cross correlation among Zr pairs is minimized; and / or

[0286] - the average cross correlation among all Zr pairs is minimized.

[0287] In general, minimizing the cross-correlation among sequences is beneficial to minimize false alarms due to wrong sequence detections.

[0288] Fig. 9 schematically illustrates a long sequence by concatenating multiple sequences. The OFDM sequence patterns in Tables A2-A6 can be alternately considered to provide suitable long sequences Xi for different values of N (number of subgroups / codepoints), Y (number of sequence candidates), and G (number of concatenated sequences, e.g., if one sequence per symbol then number of symbols in the Tables is same as number of concatenated sequences ). Tables A3-A6 can be in the specifications and used in the RRC configurations.The UE can be configured with one or multiple sequence indexes in the table or can determines its sequence in the table based on its subgroup ID. The UE can then attempt to detect a sequence (e.g., Xi) which is composed of multiple sequences (Sk) over multiple symbols. The number of sequences (Sk) can depend on the supported OOK modulation order [M]. For example, 16 sequences for M=l, 8 sequences for M=2, and 4 sequences for M=4. In some examples, the number of symbols K can be a number of OOK symbols which also depends on the M value. For example, 3 OOK symbols for M=4, and 2 OOK symbols for M=1 or 2.

[0289] Alternatively, the UE may be configured with set of sequences (Sk) and the order of the sequences to detect.

[0290] For example, the UE with subgroup ID 5, and 3 candidate sequences may detect sequence X5=[S3, S2,S1] which spans over three symbols (symbol 1: S3, symbol 2: S2, symbol 3: SI). The UE may determine the construction of X5 sequence using a pre-defined table (e.g., one of the tables A2-A6).

[0291] Example A-l: Method in a UE comprising

[0292] • Determining a set of K symbols for monitoring a low power wake up signal (LP-WUS) • Determining a code-point (Zi) for detection of the LP-WUS wherein the codepoint (Zi) is linked to the UE and the codepoint belongs to a set of N candidate codepoints • Determining a pattern[ / ordering / arrangement] of one or more OFDM sequences associated with the codepoint (Zi) based on one or more of the following characteristics

[0293] o the pattern[ / ordering / arrangement] is determined based on one or more combinations of OFDM sequences in one or more of Tables A2-A6 o each OFDM sequence of the one or more OFDM sequences is mapped to one or more symbols of the set of K symbols and

[0294] o each sequence of the one or more OFDM sequences belongs to a set of Y<N candidate OFDM sequences

[0295] • detecting that codepoint (Zi) is indicated by LP-WUS and performing PDCCH monitoring in response to the detection.

[0296] Embodiments, Part B

[0297] The set of Y candidate OFDM sequences discussed in previous section (2.7.1.2 -Embodiments 1) can be predefined or can be determined by the UE based on gNB signaling. The OFDM sequences can be based on ZC sequences with different roots and / or cyclic shifts (CS). In general, sequences need be properly chosen to have low cross-correlation and to minimize the false alarms. A set of suitable roots and CSs which result in the minimum cross-correlation among different sequences can be identified.

[0298] For example, Y can be the number of sequence candidates and L can be the sequence length of ZC sequences from which the sequence candidates are obtained. The length andnumber of overlaid OFDM sequences can depend on the value of number of OOK symbols M (e.g., M=l,2,4) per OFDM symbol. For example, ZC sequence length L (prime length) can be 131, 61, 31 for M=l, 2,4, respectively.

[0299] * N= 16, 1=131 (applicable to M=l)

[0300] * N= 8, L=61 (applicable to M=2)

[0301] * N= 4, L=31 (applicable to M=4)

[0302] The candidate Y OFDM sequences can be obtained by truncating or extending ZC sequences with length L.

[0303] For a given L and root index q, the ZC sequence is defined as:

[0304]

[0305] A sequence created by cyclic shift (c) of x(n) is given by xcs= x(n + c).

[0306] Selection of cyclic shifts for ZC sequences:

[0307] Two sequences can have same roots but different cyclic shifts. To ensure minimum cross correlation between sequences (especially under timing error / uncertainty), the cyclic shifts must be separated as much as possible.

[0308] In one embodiment, the candidate sequences are such that for ZC sequence length L, and N_cs cyclic shifts, the cyclic shifts are calculated by below formula.

[0309] c_i=floor (L*(i-1) / N_cs), wherein i=l, 2,..., N_cs.

[0310] In one embodiment, the candidate sequences are such that for ZC sequence length L, and N_cs cyclic shifts, the cyclic shifts are selected from one or more of the combinations in Table B-l below. For example, for a ZC sequence length 131, the combinations of 2, 4, and 8 cyclic shifts are {0, 65}, {0,32,65,98}, and {0,16,32,49,65,81,98,114}, respectively. For a ZC sequence length 61, the combinations of 2, 4, and 8 cyclic shifts are {0,30}, {0,15,30,45}, and {0,7,15,22,30,38,45,53}, respectively. For a ZC sequence length 31, the combinations of 2, 4, and 8 cyclic shifts are {0,15}, {0,7,15,23}, and {0,3,7,11,15,19,23,27}, respectively. In a more specific example, if the ZC sequence length is 131, 4 cyclic shifts are configured from {0,32,65,98} for each root indices.

[0311] Sets in Table B-l ensure that sequences have minimum cross correlation under timing uncertainty. Such table can be in predefined in the specifications or combinations provided in the Table can be configured to the UE via RRC signaling.Table B-l: Cyclic shift combinations for sequences for different ZC sequence length (L) and number of cyclic shifts (N_cs).

[0312]

[0313] In one embodiment, the cyclic shifts associated with the candidate sequences are chosen such that there is equal separation between consecutive cyclic shifts (except between first and last one).

[0314] In another example, the cyclic shifts are determined based on the following equation that ensures equal separation between consecutive cyclic shifts (except between first and last one):

[0315] c_i= (i-l)*floor (L / N_cs), where i=l, 2,..., N_cs.

[0316] In one embodiment, the candidate sequences are such that for ZC sequence length L, and N_cs cyclic shifts, the cyclic shifts are selected from one or more of the combinations in Table B-2 below. For example, for a ZC sequence length 131, the sets of 2, 4, and 8 cyclic shifts are {0, 65}, {0,32,64, 96}, and {0,16,32,48,64,80, 96, 112}, respectively. For a ZC sequence length 61, the sets of 2, 4, and 8 cyclic shifts are {0,30}, {0,15,30,45}, and {0, 7, 14, 21, 28, 35, 42, 49}, respectively. For a ZC sequence length 31, the sets of 2, 4, and 8 cyclic shifts are {0,15}, {0,7,14,21}, and {0,3,6,9,12,15,18,21}, respectively.

[0317] Sets in Table B-2 ensure that sequences have minimum cross correlation under timing uncertainty with more uniform distribution of cyclic shifts. Such table can be in predefined in the specifications or combinations provided in the Table can be configured to the UE via RRC signaling.

[0318] Table B-2 : Cyclic shift combinations for sequences for different ZC sequence length (L) and number of cyclic shifts (N_cs).

[0319]

[0320] The UE can be configured with at least one of the cyclic shift values (or index of the value in the set c_i) in the above tables based on for example OOK modulation order [M], ZC sequence length [L], number of different cyclic shifts [N_cs], The UE may detect the sequence with the configured cyclic shift and determine its subgroup ID. For example, if UE is configured with cyclic shift 64 for L=131 then UE detects a candidate sequence that is derived from a ZC sequence of length L-131 and cyclic shift 64.

[0321] Selection of roots for ZC sequences:

[0322] Candidate sequences can also be created using different ZC root indices. For ZC sequence length L, there are L-l possible ZC sequences with different roots. Sets of root indices can be identified such they result in minimum cross correlation among the candidate sequences. The cross correlation metric can be considered to minimize the false alarm probability due to UE that falsely detects an unintended sequence (i.e., detecting sequence B instead of sequence A). Cross correlation can be considered over different window sizes depending on the expected timing error and timing misalignment between different sequences. The suitable set of sequences (with minimum cross correlation) depends on the correlation window. Specifically, in suitable set, the maximum cross-correlation value among pairs is minimum compared to all possible sets. For a suitable sequence set of size 3 with sequences {ai,aj,ak}, the max [cross-corr (ai,aj), cross-corr (ai,ak), cross-corr (aj,a k)] is minimum among other combinations.

[0323] For example, cross correlation can be considered over entire sequence length (i.e., all lags) and also over + / -1 us window (+ / -4 samples lag in the correlation).

[0324] In one embodiment, the UE can be configured with at least one of the root values (or index of the value in the set of roots) in the below tables based on for example OOK modulation order [M], ZC sequence length [L], number of different roots. The UE may detect the sequence with the configured root and determine its subgroup ID. For example, if UE is configured with root 25 for L=31 then UE detects a candidate sequences determined from a ZC sequence with L=31 and root 25.

[0325] In one embodiment, the candidate sequences are such that for ZC sequence length L, and N_root root indices, the root indices are selected from one or more of the sets shown in one or more of Tables B-3 to B-8 below.

[0326] For example, as shown in Table B-3, for a ZC sequence length 31, the sets of 2, 3, and 4 root indices can be {14, 16}, {4, 6, 17}, and {5, 12, 23, 25}, respectively. For example, as shown in Table B-4, for a ZC sequence length 61, the sets of 2, 3, and 4 root indices can be {1, 60}, {21, 23, 30}, and {11, 35, 42, 44}, respectively. For example, as shown in Table B-5, for a ZC sequence length 131, the sets of 2, 3, and 4 root indices are {1, 130}, {41, 43, 45}, and {2, 65, 68, 88}, respectively.

[0327] Table B-3-Table B-5 show sets of root indices for different numbers of roots (2,3, or 4 roots) and different sequence lengths. Larger number of roots can increase the UE complexity and smaller is preferred as it requires smaller memory size for storing the sequences. Such tables can be in predefined in the specifications or sets provided in the Table can be configured to the UE via RRC signaling.* Sets of root indices selected to minimize correlation over entire sequence length, all lags):

[0328] Table B-3: Sets of root indices for sequence length 31

[0329]

[0330] Table B-4: Sets of root indices for sequence length 61

[0331]

[0332] Table B-5: Sets of root indices for sequence length 131

[0333]

[0334] * Sets of root indices selected to minimize correlation over window of + / -4 samples lag corresponding to around 1 us timing uncertainty or detection window) are provided in Table B-6. For example, for a ZC sequence length 31, the sets of 2, 3, and 4 root indices are {1, 4}, {1, 4, 13}, and {5, 8, 23, 26}, respectively. For a ZC sequence length 61, thesets of 2, 3, and 4 root indices are {1, 2}, {1, 3, 57}, and {10, 31, 34, 44}, respectively. For a ZC sequence length 131, the sets of 2, 3, and 4 root indices are {1, 2}, {1, 2, 15}, and {1, 2, 57, 126}, respectively. In a more specific example, if the ZC sequence length is 31, 4 root indices are configured from {5, 12, 23, 25} for each cyclic shifts.

[0335] Table B-6: Sets of root indices for sequence length 31

[0336]

[0337] Table B-7: Sets of root indices for sequence length 61

[0338]

[0339]

[0340] Table B-8: Sets of root indices for sequence length 131

[0341]

[0342] In above discussion, floor() is a rounding function that rounds a real number to a closest integer smaller than the real number. Alternate rounding functions such as ceiling() that rounds to closest integer larger than the real number can also be used.

[0343] The UE may be configured with one or more combinations of cyclic shifts and one or more sets of root indices based on which it can determine the candidate OFDM sequences. For example, let N_cs and N_root be the number of different cyclic shifts and root indices for the sequences, respectively. In this case, for each root index, there can be N_cs different cyclic shifts. The total number of sequences which can be created with the combination of roots and cyclic shifts is (N_csx N_root). For example, with 4 root indices [N_root] and 4 cyclic shifts [N_cs] for each root, 16 different sequences can be created. Depending on the number of required sequences, different combinations of roots and cyclic shifts can be considered. For example,

[0344] 16 sequences: {N_cs=8, N_root=2}, {N_cs=4, N_root=4}

[0345] 8 sequences: {N_cs=8, N_root=l}, {N_cs=4, N_root=2}, {N_cs=2, N_root=4}

[0346] 4 sequences: {N_cs=4, N_root=l}, {N_cs=2, N_root=2}, {N_cs=l, N_root=4}

[0347] In general, sequences with different roots are more robust against timing error / uncertainty compared to sequences with the same root but different cyclic shifts.

[0348] For example, to create 16 sequences of length 131 using Table B-l-Table B-8, the following combinations of root indices and cyclic shifts can be used:

[0349] * Root indices: {2, 65, 68, 88}, cyclic shifts for each root: {0,32,65,98}

[0350] * Root indices: {1, 130}, cyclic shifts for each root: {0,16,32,49,65,81,98,114} For example, to create 8 sequences of length 61 using Table B-l-Table B-8, the following combinations of root indices and cyclic shifts can be used:

[0351] * Root indices: {one root index from 1-61, for example root index 1}, cyclic shifts for each root: {0,7,15,22,30,38,45,53}

[0352] * Root indices: {1, 60}, cyclic shifts for each root: {0,15,30,45}

[0353] * Root indices: {11, 35, 42, 44}, cyclic shifts for each root: {0,30}

[0354] For example, to create 4 sequences of length 31 using Table B-l-Table B-8, the following combinations of root indices and cyclic shifts can be used:

[0355] * Root indices: {one root index from 1-31, for example root index 1}, cyclic shifts for each root: {0,7,15,23}

[0356] * Root indices: {14, 16}, cyclic shifts for each root: {0,15}* Root indices: {5, 12, 23, 25}, cyclic shifts for each root: {one cyclic shift from 0-30, for example cyclic shift 0}

[0357] Examples

[0358] Example B-l: Method in a UE comprising

[0359] * determining a code-point (Zi) for detection of a low power wake up signal (LP- WUS) wherein the codepoint (Zi) is linked to the UE and the codepoint belongs to a set of N candidate codepoints

[0360] * determining one or more OFDM sequences associated with the codepoint (Zi) where each OFDM sequence of the one or more OFDM sequences belongs to a set of Y candidate OFDM sequences and the candidate OFDM sequences are derived from Zadoff-Chu (ZC) sequences with one or more of the following characteristics o the cyclic shifts of the ZC sequences are based on one or more of combinations shown in one or more of Table B-l-Table B-2.

[0361] o the root indices of the ZC sequences are based on one or more sets shown in one or more of Table B-3-Table B-8.

[0362] * detecting that codepoint (Zi) is indicated by LP-WUS and performing PDCCH monitoring in response to the detection.

[0363] Example B-2: Method in Example B-l, wherein the combinations of cyclic shifts are determined based on RRC signaling.

[0364] Example B-3: Method in Example B-l or Example B-2, wherein the sets of root indices are determined based on RRC signaling.

[0365] Example B-4: Method in Example B-l, where the candidate OFDM sequences are derived from Zadoff-Chu (ZC) sequences such that for at least one set of root indices in one or more Table B-3-Table B-8, the corresponding combinations of cyclic shifts are determined from RRC signaling.

[0366] Example B-5: Method in any of Examples B-l to B-4, further comprising,

[0367] * determining a set of K symbols for monitoring the LP-WUS

[0368] * determining a pattern[ / ordering / arrangement] of one or more OFDM sequences associated with the codepoint (Zi) where

[0369] o each OFDM sequence of the one or more OFDM sequences is mapped to one or more symbols of the set of K symbols and

[0370] o each sequence of the one or more OFDM sequences belongs to a set of Y<N candidate OFDM sequencesExample B-6: Method in Example B-5, wherein the pattern or ordering or arrangement is determined based on one or more combinations of OFDM sequences in one or more of Table A-2- Table A-6.

[0371] Additional embodiments

[0372] Notations:

[0373] * CS: cyclic shift

[0374] * CP: codepoint (or sequence)

[0375] * M: number of OOK symbols per OFDM symbol (e.g., M=l,2,4)

[0376] * N_sg: number of subgroups

[0377] * Nseq: number of overlaid sequences

[0378] * sgid: subgroup ID

[0379] How to determine candidate seq per sym (roots and CSs of sequences):

[0380] Option 1 (read some predefined rows from a predefined table based on N_sg)

[0381] For M=4, technical specification has 4 roots and everyone has CS=0.

[0382] For M=2, technical specification has 4 roots (different from the ones chosen for other M) and for each root 2 CS (from Table B-l or B-2).

[0383] For M=l, technical specification has 4 roots (different from the ones chosen for other M) and for each root 4 CS (from Table B-l or B-2).

[0384] Option 4 (gNB configures {root,cs} list whose length is based on N_sg, the root and cs candidate sets are predefined but combinations are not)

[0385] For M=4, technical specification has 4 roots.

[0386] For M=2, technical specification has 4 roots (different from the ones chosen for other M) and 2CS per root and gNB configures N_seq combinations {root index, CS index} with candidate set of roots in Table B-3-Table B-8 and candidate CS in Table B-l-Table B-2, wherein N_seq = min (8, N_sg+1).

[0387] For M=l, technical specification has 4 roots (different from the ones chosen for other M) and 4CS per root and gNB configures N_seq combinations {root index, CS index} with candidate set of roots in Table B-3-Table B-8 and candidate CS in Table B-l-Table B-2, wherein N_seq = min (16, N_sg+1)Mapping one or more seq to one or more symbols to convey a codepoint:

[0388] Option 1

[0389] K symbols are determined based on K = ceil(log2((Nsg+l) / log2(Nseq))

[0390] - For M=4

[0391] For M=2, if K=2 determine {si,sj} pattern corresponding to codepoint from predefined table for 2 symbols. If K=l, sgidO = 1stposition in the list of Nseq, subgroup ID 1 (sgidl) = 2ndposition in the list of Nseq,... all SGs is the last one. For M=l, if K=2 determine {si,sj} pattern corresponding to codepoint from predefined table for 2 symbols. If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one.

[0392] Option 2

[0393] K symbols are determined based on K = ceil(log2((Nsg+l) / log2(Nseq))

[0394] - For M=4

[0395] For M=2, if K=2 gNB configures a list of length Nsg+1 combinations {si,sj} . If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one

[0396] For M=l, if K=2 gNB configures a list of length Nsg+1 combinations {si,sj} . If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one

[0397] Option 1-1

[0398] K symbols are determined based on K = ceil(log2((Nsg+l) / log2(Nseq))

[0399] - For M=4

[0400] For M=2, if K=2 determine {si,sj} pattern corresponding to codepoint from predefined table for 2 symbols. If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one

[0401] For M=l, if K=2 determine {si,sj} pattern corresponding to codepoint from predefined table for 2 symbols. If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one

[0402] Option 2-1

[0403] K symbols where K is configured by gNBFor M=4

[0404] For M=2, if K=2 gNB configures a list of length Nsg+1 combinations {si,sj} . If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one.

[0405] For M=l, if K=2 gNB configures a list of length Nsg+1 combinations {si,sj} . If K=l, sgidO = 1stposition in the list of Nseq, sgidl = 2ndposition in the list of Nseq,... all SGs is the last one.

[0406] Herein, when referring to Release 19 Network Energy Saving, an energy improvement may be calculated or estimated at the network level.

[0407] Fig. 10 shows a schematic block diagram for an embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 1004 for performing the method 300 and memory 1006 coupled to the processors 1004. For example, the memory 1006 may be encoded with instructions that implement at least one of the modules 104 and 106.

[0408] The one or more processors 1004 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 100, such as the memory 1006, radio device functionality. For example, the one or more processors 1004 may execute instructions stored in the memory 1006. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 100 being configured to perform the action.

[0409] As schematically illustrated in Fig. 10, the device 100 may be embodied by a radio device 1000, e.g., functioning as a UE. The radio device 1000 comprises a radio interface 1002 coupled to the device 100 for radio communication with one or more network nodes, e.g., functioning as base stations or relay UE.

[0410] Fig. 11 shows a schematic block diagram for an embodiment of the device 200. The device 200 comprises processing circuitry, e.g., one or more processors 1104 for performing the method 400 and memory 1106 coupled to the processors 1104. Forexample, the memory 1106 may be encoded with instructions that implement at least one of the modules 202 and 204.

[0411] The one or more processors 1104 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 200, such as the memory 1106, network node functionality. For example, the one or more processors 1104 may execute instructions stored in the memory 1106. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 200 being configured to perform the action.

[0412] As schematically illustrated in Fig. 11, the device 200 may be embodied by a network node 1100, e.g., functioning as a gNB base station. The network node 1100 comprises a radio interface 1102 coupled to the device 200 for radio communication with one or more radio devices, e.g., functioning as a UE.

[0413] With reference to Fig. 12, in accordance with an embodiment, a communication system 1200 includes a telecommunication network 1210, such as a 3GPP-type cellular network, which comprises an access network 1211, such as a radio access network, and a core network 1214. The access network 1211 comprises a plurality of base stations 1212a, 1212b, 1212c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 1213a, 1213b, 1213c. Each base station 1212a, 1212b, 1212c is connectable to the core network 1214 over a wired or wireless connection 1215. A first user equipment (UE) 1291 located in coverage area 1213c is configured to wirelessly connect to, or be paged by, the corresponding base station 1212c. A second UE 1292 in coverage area 1213a is wirelessly connectable to the corresponding base station 1212a. While a plurality of UEs 1291, 1292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1212.

[0414] Any of the base stations 1212 and the UEs 1291, 1292 may embody the device 200 and 100, respectively.The telecommunication network 1210 is itself connected to a host computer 1230, which may be embodied in the hardware and / or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 1230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 1221, 1222 between the telecommunication network 1210 and the host computer 1230 may extend directly from the core network 1214 to the host computer 1230 or may go via an optional intermediate network 1220. The intermediate network 1220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 1220, if any, may be a backbone network or the Internet; in particular, the intermediate network 1220 may comprise two or more sub-networks (not shown).

[0415] The communication system 1200 of Fig. 12 as a whole enables connectivity between one of the connected UEs 1291, 1292 and the host computer 1230. The connectivity may be described as an over-the-top (OTT) connection 1250. The host computer 1230 and the connected UEs 1291, 1292 are configured to communicate data and / or signaling via the OTT connection 1250, using the access network 1211, the core network 1214, any intermediate network 1220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 1250 may be transparent in the sense that the participating communication devices through which the OTT connection 1250 passes are unaware of routing of uplink and downlink communications. For example, a base station 1212 need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 1230 to be forwarded (e.g., handed over) to a connected UE 1291. Similarly, the base station 1212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1291 towards the host computer 1230.

[0416] By virtue of the methods 300 and / or 400 being performed by any one of the UEs 1291 or 1292 and / or any one of the base stations 1212, the performance or range of the OTT connection 1250 can be improved, e.g., in terms of increased energy efficiency and / or reduced latency. More specifically, the host computer 1230 may indicate, to the RAN 500 (e.g., on an application layer), a QoS of traffic to be delivered to a radio device 100. The QoS may in turn trigger transmission of the WUS 900 and / or data transmission and reception according to an embodiment of the methods 300 and 400.Abbreviation Explanation

[0417] ADC Analog to Digital Converter

[0418] DMRS Demodulation reference signal

[0419] DRX Discontinuous Reception

[0420] ID Identity

[0421] IFFT Inverse Fast Fourier Transform

[0422] LNA Low-noise Amplifier

[0423] MIB Master Information Block

[0424] OFDM Orthogonal Frequency Division Multiplexing

[0425] OOK On-Off Keying

[0426] PAPR Peak-to-average power ratio

[0427] PBCH Physical Broadcast Channel

[0428] PSS Primary Synchronization Signal

[0429] RSRP Reference Signal Received Power

[0430] RSRQ Reference Signal Received Quality

[0431] SSB Synchronization Signal Block

[0432] SSS Secondary Synchronization Signal

[0433] SINR Signal to noise plus interference

[0434] TRS Tracking reference signal

[0435] WUR Wake-up radio / receiver

[0436] WUS Wake-up signal

[0437] As has become apparent from above description, at least some embodiments of the technique use specific pattern of OFDM sequences, e.g. in Embodiments Part A, to reduce the cross-correlation between different patterns, which is beneficial to reduce false alarms due to wrong sequence detections.

[0438] The specific sets of root indices, combinations of cyclic shifts, e.g. according to Embodiments Part B, can result in reducing cross-correlation among different sequences which also is beneficial to reduce false alarms due to wrong sequence detections.

[0439] In more generality, these or further embodiments enable efficient and / or low-complexity schemes for UEs 100 to detect LP-WUS. The suitable sets of sequences ensure minimum cross-correlations among sequences and minimize the false alarms which are detrimental to UE power consumption and network overhead / energy consumption. For the network node 200, same or further embodiments are beneficial in terms of resource efficiency, low-complexity, and scheduling flexibility. The embodiments are also useful for enabling low power devices in 6G.Many advantages of the present invention will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the units and devices without departing from the scope of the invention and / or without sacrificing all of its advantages. Since the invention can be varied in many ways, it will be recognized that the invention should be limited only by the scope of the following claims.

Claims

Claims1. A method (300) performed by a radio device (100) for detecting a wake-up signal, WUS, from a radio access network, RAN (500), the method (300) comprising:monitoring (304) a configured set of radio resources of the RAN (500) for detecting the WUS, optionally associated with a network node (200) of the RAN (500);in response to detecting (306) the WUS (900) in the monitored (304) radio resources, transitioning (308) the radio device (100) from an energy-saving state (602) to an active state (604),wherein the detecting (306) of the WUS (900) comprises correlating the monitored (304) radio resources with a candidate sequence of orthogonal frequency-division multiplexing, OFDM, symbols.

2. The method (300) of claim 1, wherein the detecting (306) further comprises applying an on-off keying, OOK, to the candidate sequence,optionally applying, in the time domain, an envelope of the OOK to the candidate sequence, and / or wherein the candidate sequence applied with the OOK is correlated with the monitored (304) radio resources.

3. The method (300) of claim 1 or 2, wherein each of the OFDM symbols in the candidate sequence comprises, or corresponds to, at least one of:a waveform of a Zadoff-Chu sequence, ZCSeq, optionally an inverse Fourier Transform of a ZCSeq;a waveform of an M-sequence, MSeq, optionally an inverse Fourier Transform of a MSeq; anda waveform of a Gold sequence, GSeq, optionally an inverse Fourier Transform of a GSeq.

4. The method (300) of any one of claims 1 to 3, further comprising: receiving (302), from the or another network node (200) of the RAN (500), configuration information indicative of at least one of:the configured set of radio resources;the candidate sequence of OFDM symbols;a set of the OFDM symbol sequences, wherein the detecting (306) comprises correlating each of the OFDM symbol sequences with the monitored (304) radio resources or selecting the candidate sequence out of the set of OFDM symbol sequences;the OOK, optionally the time-domain envelope of the OOK, applied to the candidate sequence; anda set of OOKs, optionally a set of time-domain envelopes of the OOK, wherein the detecting (306) comprises applying each of the OOKs or each of the envelops or selecting the applied OOK or the applied envelop.

5. The method (300) of any one of claims 1 to 4, wherein the candidate sequence and / or each sequence in the set of OFDM symbol sequences fulfils a predefined cross-correlation selection criterion; and / orwherein the OFDM symbol sequences is a subset of all sequences of a predefined length, K, that fulfill a predefined cross-correlation selection criterion; and / orwherein the OFDM symbol sequences is a subset of all permutations of the OFDM symbol sequences that fulfills a predefined cross-correlation selection criterion; and / orwherein OFDM symbol sequences are arranged in temporal order to fulfil a predefined cross-correlation selection criterion.

6. The method (300) of claim 5, wherein the predefined cross-correlation selection criterion, when applied to a given sequence of OFDM symbols, requires that the cross-correlation between each pair of OFDM symbols in the given sequence fulfills the predefined cross-correlation selection criterion, optionally are less than a predefined cross-correlation selection threshold value.

7. The method (300) of claim 5 or 6, wherein the predefined cross-correlation criterion, when applied to a given sequence of OFDM symbols, requires that the cross-correlation between each pair of subsequent OFDM symbols that are subsequent in the temporal order of the given sequence, fulfills the predefined cross-correlation selection criterion, optionally that the cross-correlation is less than a predefined cross-correlation selection threshold value.

8. The method (300) of any one of claims 5 to 7, wherein the predefined selection cross-correlation criterion further depends on the applied OOK, wherein the cross-correlation is computed after applying the OOK.

9. The method (300) of any one of claims 1 to 8, wherein the candidate sequence or each of the OFDM symbol sequences is a finite collection of waveforms, each uniquely determined by a root index and / or a cyclic shift, CS, of an underlying Zadoff-Chu sequence, ZCSeq.

10. The method (300) of any one of claims 1 to 9, wherein the candidate sequence or each of the OFDM symbol sequences correspond to an underlying Zadoff-Chu sequence, ZCSeq, determined by a root index and / or a cyclic shift, CS, wherein the ZCSeq is mapped onto subcarriers to form an OFDM symbol.

11. The method (300) of any one of claims 1 to 10, wherein the WUS (900) is detected if a result of the correlating with the monitored (304) radio resources fulfills a predefined cross-correlation detection criterion,optionally if the result exceeds a predefined cross-correlation detection threshold value.

12. The method (300) of any one of claims 1 to 11, wherein the predefined cross-correlation detection criterion requires more cross-correlation than the predefined cross-correlation selection criterion,optionally wherein the predefined cross-correlation detection threshold value is greater than the predefined cross-correlation selection threshold value13. The method (300) of any one of claims 1 to 12, further comprising at least one of, and / or wherein the radio device (100) transitions (308) from the energysaving state (602) to the active state (604) for at least one of:receiving, in the active state (604), a subsequent transmission from a network node (200) of the RAN (500);performing, in the active state (604), a sensory function and / or transmitting to the network node (200) a result of the sensory function;receiving, in the active state (604), scheduling communication from the network node (200);monitoring, in the active state (604), a control channel of the network node (200), or a cell of the network node (200), in a subsequent time interval; and transmitting data to the network node (200) and / or receiving data from the network node (200).

14. The method (300) of any one of claims 1 to 13, wherein the network node (200) is associated with the detected WUS (900) and / or a serving network node (200) serving the radio device (100).

15. The method (300) of any one of claims 1 to 14, wherein a power consumption of the radio device or a transceiver of the radio device (100) is less in the energy-saving state (602) compared to the active state (604); and / or wherein the active state (604) is a radio resource control, RRC, connected state; and / orwherein the energy-saving state (602) is an inactive state or an idle state of the radio device relative to network node (200) or the RAN (500).

16. The method (300) of any one of claims 1 to 15, wherein the configured (302) and / or monitored (304) set of radio resources is or comprises a contiguous sequence of orthogonal frequency division multiplexing, OFDM, symbols, optionally wherein the correlating comprises cross-correlating the OFDM symbols of the candidate sequence or each of the OFDM symbol sequence with the OFDM symbols of the monitored (304) radio resources in pairs according to their temporal order.

17. The method (300) of any one of claims 1 to 16, wherein the radio resources are monitored (304) within a discontinuous reception, DRX, cycle, and / or in advance of an ON-duration of the DRX cycle.

18. The method (300) of any one of claims 1 to 17, further comprising determining, from the configuration information, a number of Y OFDM symbols, wherein each sequence in the set of OFDM symbol sequences and / or the candidate sequence is a sequence of the OFDM symbols selected from the Y OFDM symbols, optionally according to the cross-correlation selection criterion.

19. The method (300) of any one of claims 1 to 18, wherein the detecting (306) comprises correlating each of the OFDM symbol sequences in a or the set of OFDM symbol sequences with the monitored (304) radio resources or selecting the candidate sequence out of the set of OFDM symbol sequences.

20. The method (300) of any one of claims 1 to 19, further comprising, optionally upon receiving the configuration information:generating the set of OFDM symbol sequences, and / orloading the set of OFDM symbol sequences into a local memory of the radio device (100).

21. The method (300) of claim 20, wherein the set of OFDM symbol sequences comprises only those OFDM symbols that:are indicated in the configuration information received (302) from the network node (200), and / orcorrespond to a limitation in the number of OFDM symbols indicated in the configuration information received (302) from the network node (200), and / or fulfill the cross-correlation selection criterion.

22. The method (300) of any of claims 1 to 21, wherein a capability of the radio device (100) and / or the configuration information received (302) from the network node (200) limits a number of root indices of the ZCSeq, underlying the candidate sequence or the set of OFDM symbol sequences,optionally wherein the capability comprises a memory usage constraint, and / or wherein the radio device (100) discards OFDM symbols that exceed said limit.

23. The method (300) of any one of claims 1 to 22, further comprising determining, optionally from the configuration information or another indication from the network node (200), a time-domain on-off keying rate, M denoting the number of on-off-keying chips per OFDM symbol, and applying the rate M to gate the candidate sequence in each OFDM symbol.

24. The method (300) of any one of claims 1 to 23, wherein applying the OOK comprises:partitioning each OFDM symbol into M sub-intervals and multiplying the received OFDM waveform by an on-off gating pattern such that the on-off pattern selectively zeroes at least a portion of the waveform in each sub-interval.

25. The method (300) of any one of claims 1 to 24, further comprising determining, optionally from the received (302) configuration information, a number, K, of OFDM symbols over which the WUS (900) is spread in the time domain,optionally wherein the correlation comprises cross-correlating each of the K OFDM symbols of the monitored (304) radio resources with the candidate sequence or each of the OFDM symbol sequences.

26. The method (300) of claim 25, wherein the radio device (100) determines a partial codepoint based on the cross-correlating of the K OFDM symbols, and / or wherein the radio device (100) determines a codepoint from the monitored (304) OFDM sequences across the K symbols by using a predefined mapping rule that associates each temporal arrangement of the OFDM symbols with a distinct codepoint among a set of multiple codepoints.

27. The method (300) of any one of claims 1 to 26, wherein the transitioning (308) of the radio device (100) is in response to, and / or the detecting (306) is based upon, successfully identifying a codepoint from a or the mapping rule applied to the monitored (304) radio resources, optionally only if that codepoint corresponds to a radio device subgroup to which the radio device is assigned.

28. The method (300) of any one of claims 1 to 27, wherein the radio device stores only a subset of the OFDM symbol sequences,optionally wherein each subset having fewer than Y OFDM symbols and / or discarding OFDM symbol sequences which potential codepoints are not associated with the radio device (100).

29. The method (300) of any one of claims 1 to 28, wherein detecting (306) the WUS (900) includes measuring a correlation metric of the correlation, optionally a cross-correlation, with each candidate sequence out of the OFDM symbol sequences over multiple correlation lags, optionally to accommodate a timing uncertainty, and identifying the WUS (900) if the correlation metric exceeds a or the cross-correlation threshold value.

30. The method (300) of claim 29, wherein the or another configuration information from the network node (200) is indicative of a range of correlation lags for root indices and / or cyclic shifts that are expected in a cell of the network node (200),optionally wherein the radio device (100) discards correlation results outside the configured range.

31. The method (300) of any one of claims 1 to 30, further comprising selecting a set of root indices and / or a set of cyclic shifts to form a combined set of Y OFDM symbols,optionally based on the cross-correlation selection criterion and / or such that pairs of the OFDM symbols exhibit low cross-correlation across one or more time offsets within a defined detection window.

32. The method (300) of claim 31, wherein the radio device (100) accesses a predefined table, optionally in local memory of the radio device (100), the table specifying permissible root indices and / or cyclic shifts, optionally for a predefined length or each of multiple length of the ZCSeq, and / or the radio device (100) discarding any combination of root index and cyclic shift not present in the table.

33. The method (300) of any one of claims 1 to 32, wherein, for a given L and root index q, the ZCSeq is definedoptionally wherein a sequence created by cyclic shift, c, of x(n is given by Xcs—x n+c)-34. The method (300) of at least any one of claims 3, 10 or 23, wherein the length of the ZCSeq is the largest prime number less than or equal to 12-X / M, wherein X is the number of resource blocks and M is modulation order of OOK.

35. The method (300) of claim 34, wherein ZCSeq length L or prime length is 131 for M=1 and / or £=61 for M=2 and / or £=31 for M=4.

36. The method (300) of claim 31 or 32, wherein Y is number Nrootof roots times number Ncsof CSs.

37. The method (300) of any one of claims 1 to 36, wherein the cyclic shifts associated with the candidate sequences are chosen such that there is equal separation between consecutive cyclic shifts except between first and last one.

38. The method (300) of any one of claims 1 to 37, wherein the cyclic shifts are determined based on the following equation that ensures equal separation between consecutive cyclic shifts except between first and last one and / or according to:wherein i = 1, 2, ...,NCS.

39. The method (300) of any one of claims 1 to 38, wherein the candidate sequences are such that for ZCSeq length L, and Ncscyclic shifts, the cyclic shifts ctare selected from one or more of the combinations below Tableand / or wherein, for a ZCSeq length 131, the sets of 2, 4, and 8 cyclic shifts are {0, 65}, {0,32,64, 96}, and {0,16,32,48,64,80, 96, 112}, respectively, for a ZCSeq length 61, the sets of 2, 4, and 8 cyclic shifts are {0,30}, {0,15,30,45}, and {0, 7, 14, 21, 28, 35, 42, 49}, respectively, and for a ZCSeq length 31, the sets of 2, 4, and 8 cyclic shifts are {0,15}, {0,7,14,21}, and {0,3,6,9,12,15,18,21}, respectively.

40. The method (300) of any one of claims 1 to 39, wherein, for each root index, there are Ncsdifferent cyclic shifts; and / or a total number of sequences which can be created with the combination of roots and cyclic shifts is Ncs■ Nroot.

41. The method (300) of any one of claims 1 to 40, further comprising mapping a subgroup of radio devices to one of a plurality of codepoints, each codepoint corresponding to a temporal arrangement of multiple, optionally K, OFDM symbols in sequence.

42. The method (300) of claim 41, wherein, if the radio device (100) determines its assigned subgroup corresponds to a common codepoint and / or a codepoint not associated with a subgroup, the radio device (100) decodes, in the active state (604), an associated paging region for cell-specific or system-wide control signaling.

43. The method (300) of any one of claims 1 to 42, wherein the detecting (306) of the WUS (900) comprises correlating a partial or complete concatenation of multiple, optionally K, OFDM symbols forming a compound waveform for extended codepoint determination.

44. The method (300) of any one of claims 1 to 43, wherein detecting (306) the WUS (900) comprises calculating a cross-correlation among the candidate OFDM symbols to verify that a detected sequence arrangement yields minimal average cross-correlation relative to other permutations.

45. The method (300) of any one of claims 1 to 44, further comprising adapting a or the predefined cross-correlation detection threshold value based on measured cross-correlation distributions in a current radio environment, optionally wherein the radio device (100) raises or lowers the crosscorrelation detection threshold value to maintain a target wake-up reliability.

46. The method (300) of any one of claims 1 to 45, further comprising, upon detection (306) of the WUS (900) and / or when in the active state (604), activating a transceiver or receiver chain (704) within the radio device (100) solely for the duration of a control and / or data reception interval, and then returning to the energy-saving state (602).

47. A method (400) performed by a network node (200) for transmitting a wake-up signal, WUS (900), in a radio access network, RAN (500), the method (400) comprising:configuring (402) a group of radio devices (100) to monitor a configured set of radio resources of the RAN (500) for detecting the WUS (900), optionally associated with the network node (200) and / or the group of radio devices (100);transmitting (404) the WUS (900), wherein the WUS (900) comprises a sequence of orthogonal frequency-division multiplexing, OFDM, symbols; and in response to the WUS (900), transmitting (408) data to or receiving (408) data from at least one of the radio devices (100) in the group.

48. The method (400) of claim 47, further comprising the features and steps according to any one of claims 2 to 46, or corresponding features and steps applied mutatis mutandis according to any one of claims 2 to 46.

49. A computer program product comprising program code portions for performing the steps of any one of the claims 1 to 46 or 47 to 48 when the computer program product is executed on one or more computing devices (1004; 1104), optionally stored on a computer-readable recording medium (1006; 1106).

50. A radio device (100; 1000; 1291; 1292) for detecting a wake-up signal, WUS (900), from a radio access network, RAN (500), the radio device (100; 1000; 1291; 1292) comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the radio device (100; 1000; 1291; 1292) is operable to:monitor a configured set of radio resources of the RAN (500) for detecting the WUS (900), optionally associated with a network node (200) of the RAN (500);in response to detecting the WUS (900) in the monitored radio resources, transitioning the radio device (100) from an energy-saving state (602) to an active state (604),wherein the detecting of the WUS (900) comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequencydivision multiplexing, OFDM, symbols.

51. The radio device (100; 1000; 1291; 1292) of claim 50, further operable to perform the steps of any one of claims 2 to 46.

52. A radio device (100; 1000; 1291; 1292) for detecting a wake-up signal, WUS (900), from a radio access network, RAN (500), the radio device (100; 1000; 1291; 1292) being configured to:monitor a configured set of radio resources of the RAN (500) for detecting the WUS (900), optionally associated with a network node (200) of the RAN (500);in response to detecting the WUS (900) in the monitored radio resources, transitioning the radio device (100) from an energy-saving state (602) to an active state (604),wherein the detecting of the WUS (900) comprises correlating the monitored radio resources with a candidate sequence of orthogonal frequencydivision multiplexing, OFDM, symbols.

53. The radio device (100; 1000; 1291; 1292) of claim 52, further configured to perform the steps of any one of claims 2 to 46.

54. A network node (200; 1100; 1212) for transmitting a wake-up signal, WUS (900), in a radio access network, RAN (500), the network node (200; 1100; 1212) comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the network node (200; 1100; 1212) is operable to:configure a group of radio devices (100) to monitor a configured set of radio resources of the RAN (500) for detecting the WUS (900), optionally associated with the network node (200) and / or the group of radio devices (100);transmit the WUS (900), wherein the WUS (900) comprises a sequence of orthogonal frequency-division multiplexing, OFDM, symbols; andin response to the WUS (900), transmit data to or receive data from at least one of the radio devices (100) in the group.

55. The network node (200; 1100; 1212) of claim 54, further operable to perform any one of the steps of claim 48.

56. A network node (200; 1100; 1212) for transmitting a wake-up signal, WUS (900), in a radio access network, RAN (500), the network node (200; 1100; 1212) being configured to:configure a group of radio devices (100) to monitor a configured set of radio resources of the RAN (500) for detecting the WUS (900), optionally associated with the network node (200) and / or the group of radio devices (100);transmit the WUS (900), wherein the WUS (900) comprises a sequence of orthogonal frequency-division multiplexing, OFDM, symbols; andin response to the WUS (900), transmit data to or receive data from at least one of the radio devices (100) in the group.

57. The network node (200; 1100; 1212) of claim 56, further configured to perform the steps of claim 48.

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