Radio link monitoring using different power modes

Abstract

There is provided techniques for radio link monitoring operation. A method is performed by a user equipment configured to selectively operate with either a first power mode or a second power mode. The method comprises performing, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation. The method comprises performing, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

Description

[0001] RADIO LINK MONITORING USING DIFFERENT POWER MODES

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a user equipment, a computer program, and a computer program product for radio link monitoring operation.

[0004] BACKGROUND

[0005] In general terms, there are many procedures a user equipment (UE) can, or eve needs, to perform when being operatively connected to a network node.

[0006] One such procedure is radio link monitoring (RLM). In further detail, the UE performs RLM on active bandwidth part of the primary cell (PCell). Radio link monitoring can be performed based on different signal resources, as configured by the network node via radio resource control (RRC) signaling. In case of discontinuous reception (DRX), the UE assesses the radio link quality once per indication period. The quality is evaluated against thresholds (denoted Qout and Qin) provided by the network node in the parameter “rlmlnSyncOutOfSyncThreshold”. Qout represents the signal quality threshold below which the radio link is considered out of sync (indicating poor link quality). Qin represents the signal quality threshold above which the radio link is considered back in sync (indicating the link quality has recovered). The indication period is the maximum between the shortest periodicity for radio link monitoring resources and the DRX period. In non-DRX mode operation, the UE also assesses the radio link quality once per indication period. The radio link quality is evaluated over the previous time period against the same thresholds (Qout and Qin) as for DRX mode operation, but the UE determines the indication period as the maximum between the shortest periodicity for radio link monitoring resources and 10 ms.

[0007] In a fifth generation (5G) telecommunication system, the UE monitors the downlink radio link quality based on the reference signal (RS) configured as RLM-RS resources to detect the downlink radio link quality of the primary cell (PCell) and the primary secondary cell (PSCell). When no RLM-RS resources are configured, the UE will monitor the current synchronization signal block (SSB) for the downlink radio link quality. When a UE monitors the reference signals RLM-RS as configured by the network, a criteria or threshold definition is required to determine when the signal is above the worse threshold and when it is below the worse threshold. Two thresholds for entry and exit criteria with respect to when a UE can declare radio link failure and when it can exit the radio link failure (RLF) state have been defined. The same thresholds have been defined for fourth generation (4G) telecommunication systems, but the reference signals measured for RLM are different in 4G and 5G telecommunication systems.

[0008] Another such procedure is beam failure detection (BFD). In general terms, the BFD procedure is used to identify link degradation on individual beams and new beam establishment, without necessarily implying overall RLF. While RLF indications are provided via RRC signaling, e.g., at connection re-establishment, beam failure indications may be signaled from physical layer signaling via medium access control (MAC) control elements (CEs). Beam failure detection and recovery is specified in Section 5. 17 of the technical specification 3GPP TS 38.321 “NR; Medium Access Control (MAC) protocol specification”, version 18.2.0.

[0009] Another such procedure is cell reselection. In both RRC idle and RRC inactive modes, the UE is associated with a camping cell whose signal quality it monitors to ensure that it maintains a sufficient link quality to contact the network using a random access procedure or be contacted via paging. For the quality monitoring, the UE performs regular measurements of received signals, e.g., SSB, from the current camped cell. The UE may also perform measurements on neighboring cells based on measurement rules and may reselect which cell to camp on based on cell reselection criteria. The UE performs cell selection and reselection using the selection- or reselection-related parameters from system information (SIB). Typically, the UE selects the cell with the highest available link quality for camping.

[0010] Another such procedure is measurement reporting on protocol layer 3 (L3). In RRC connected mode, UE mobility is controlled by the network node (except partly for conditional handover). To enable the network node to take handover decisions, the UE is typically configured to measure and report e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), and / or signal to interference plus noise ratio (SINR) based on configured events. In 5G telecommunication systems these measurements can be performed based on e.g., SSBs or channels state information reference signals (CSI- RSs). One example of a commonly used event is event A2, which is triggered when the serving cell becomes worse than a configured threshold. Another commonly used event is event A3, which is triggered when a neighbor cell becomes a configurable offset better than the serving cell (PCell / PSCell).

[0011] In all RRC states, the measured values are typically filtered. The filtering serves two purposes; reducing noise and reducing effects of fast fading. With regards to the first aspect, if the noise is independent between samples, a more accurate measurement can generally be achieved by performing the measuring more frequently. However, this may not help against fading and filtering of the measured values is therefore performed.

[0012] Both in RRC idle, RRC inactive, and RRC connected mode, there are requirements on how much time the UE has until it needs to either report a measurement value after an event is fulfilled (as for RRC connected mode) or perform cell reselection after the reselection criteria is fulfilled (as for RRC idle and RRC inactive modes). For all RRC modes, these requirements are typically formulated as N times a time interval, where N is some positive integer. The time interval is typically the maximum of the DRX cycle length and the period of the reference signal to be measured, except for some special cases e.g., RRC connected mode without DRX and an SSB period of 20 ms where the interval is 40 ms. The value of N varies between RRC modes and typically with the DRX cycle length. One common case is N=5, which applies e.g., for intra-frequency measurements in RRC connected mode without gaps and for RRC idle and RRC inactive mode when the common DRX cycle length 1.28 s is used. In addition to the timing requirement, there are also accuracy requirements. In RRC connected mode there are explicit requirements that the reported value need to fulfill. In RRC idle and RRC inactive modes there are implicit accuracy requirements derived from cell reselection requirements, e.g., that the UE should only reselect to a cell if it is ranked to be 3 dB better than the serving cell.

[0013] Reference is here made to Fig. 1 which shows how the measured quantity of some link measurements varies over time. The dashed line represents the ideal value of the measured quantity and the solid line represents the measured quantity after filtering. The empty circles represents when there is a reference signal available for measurement (i.e., when there is a reference signal transmitted from the network), and the filled black circles represent when an available reference signal is used by the UE for a measurement. The filtering is performed such that specified requirements on both accuracy and delay are fulfilled. In Fig. 1 is shown an example of when the aforementioned event A2 is fulfilled (i.e., when the serving cell becomes worse than a configured threshold) and reported by the UE to the network. In this example, the A2 event is fulfilled after five measurements. One measurement is taken every fourth time a reference signal is available. This can for example represent an RRC connected mode DRX cycle of 80ms and an SSB period of 20ms.

[0014] The above procedures imply that the UE must perform many measurements in order to comply with all specified requirements when being operatively connected to a network node. The receiver in the UE thus needs to be activated for all these measurements. Hence, the above procedures come with a power consumption in the receiver, which contributes to reducing the battery time of the UE.

[0015] Hence, there is a need for improved radio link monitoring in the UE, at least with respect to the power consumption in the UE.

[0016] SUMMARY

[0017] An object of embodiments herein is to provide radio link monitoring in the UE with reduced power consumption in the UE.

[0018] A particular object is to enable the power consumption in the UE to be reduced whilst still enabling the UE to fulfil all configured reporting criteria.

[0019] According to a first aspect there is presented a method for radio link monitoring operation, performed by a user equipment configured to selectively operate with either a first power mode or a second power mode. The method comprises performing, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation. The method comprises performing, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition. According to a second aspect there is presented a user equipment for radio link monitoring operation. The user equipment is configured to selectively operate with either a first power mode or a second power mode and comprises processing circuitry. The processing circuitry is configured to cause the user equipment to perform, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation. The processing circuitry is configured to cause the user equipment to perform, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

[0020] According to a third aspect there is presented a computer program for radio link monitoring operation. The computer program comprises computer code which, when run on processing circuitry of a user equipment configured to selectively operate with either a first power mode or a second power mode, causes the user equipment to perform actions. One action comprises the user equipment to perform, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation. One action comprises the user equipment to perform, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

[0021] According to a fourth aspect there is presented a computer program product comprising a computer program according to the third aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0022] Advantageously, these aspects enable the UE to perform radio link monitoring with a low power consumption.

[0023] Advantageously, these aspects enable the UE to fulfil all configured reporting criteria even when the power consumption is lowered.

[0024] Advantageously, this enables the UE to operate using a low-power mode for as long time as possible and only active a high-power mode just before it needs to be used.

[0025] Advantageously, these aspects enable the main radio mode of the UE to remain asleep in routine scenarios without compromising the handling of RLF, beam failure, mobility criteria, or other types of radio events that may occur in rapidly changing radio environment situations.

[0026] Advantageously, these aspects enable the energy consumption in the UE to be reduced whilst maintaining robust performance of the UE. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0027] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0030] Fig. 1 schematically illustrates time variations of a measured quantity of link measurements according to an example;

[0031] Fig. 2 is a schematic diagram illustrating a communication network according to embodiments;

[0032] Fig. 3 is a block diagram of user equipment according to embodiments;

[0033] Fig. 4 is a flowchart of methods according to embodiments;

[0034] Figs. 5, 6, 7, and 8 schematically illustrates time variations of a measured quantity of link measurements according to embodiments;

[0035] Fig. 9 is a schematic diagram showing structural units of a user equipment according to an embodiment; and

[0036] Fig. 10 shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

[0037] DETAILED DESCRIPTION

[0038] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional. Fig. 2 is a schematic diagram illustrating a communication network 200 where embodiments presented herein can be applied. The communication network 200 comprises network nodes 210a, 210b provides network access to a UE 220 in cells 230a, 230b. Assuming that the UE 220 is located in cell 230a, then cell 230a becomes the serving cell, and network node 210a becomes the serving network node. Likewise, cell 230b becomes a neighbour cell and network node 210b becomes a neighbour network node. However, depending on the location of the UE 220 in the cell 230a, the UE 220 might still be capable of receiving and decoding signals as transmitted by the network node 210b in the cell 230b. There could be different examples of network nodes, such as (radio) access network node, radio base station, base transceiver station, node B (NB), evolved node B (eNB), gNB, access point, access node, integrated access and backhaul (IAB) node, transmission and reception point (TRP), etc. Likewise, there could be different examples of UEs, such as portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, smartphone, laptop computer, tablet computer, wireless sensor device, Internet of Things device, network equipped vehicle, network equipped gaming control, etc. It goes without saying that the communication network 100 generally comprises a plurality of network nodes, each serving their own cell.

[0039] As noted above, there is a need for improved radio link monitoring in the UE, at least with respect to the power consumption in the UE 220.

[0040] A particular object is therefore to enable the power consumption in the UE to be reduced whilst still enabling the UE to fulfil all configured reporting criteria.

[0041] According to the present disclosure, one way to achieve this is to use the main receiver (or some main power mode, hereinafter referred to as a second power mode) in the UE as little as possible, and instead use some other receiver (or some low-power power mode, hereinafter referred to as a first power mode) for some radio link monitoring operations to keep a low energy consumption in the UE. Examples of such radio link monitoring operations will be provided below.

[0042] In Fig. 3 is shown block diagrams of user equipment 300a, 300b, 300c, 300d with different examples of implementations of a low power mode unit 310, 310a, 310b with respect to a baseband unit (referred to as “modem baseband”) a radio modem (referred to as “Modem RF”, where RF is short for radio frequency). Here, the low power mode unit implements the first power mode whereas the main receiver implements the second power mode. In the user equipment 300a the low power mode unit 310 is separated from the radio modem 330 and the baseband unit 320. This user equipment 300a thus has a (separate) low power mode unit 310 with both radio reception capabilities and signal detection / demodulation capabilities. In the user equipment 300b, the user equipment 300b comprises a low power mode baseband unit 310a and a low power mode radio unit 310b that are separated from the radio modem 330 and the baseband unit 320. This user equipment 300b thus one (separate) low power mode unit 310b with radio reception capabilities and another (separate) low power mode unit 310a with signal detection / demodulation capabilities. In the user equipment 300c the low power mode unit 310a is separated from the baseband unit 320 but utilizes the radio interface of the radio modem 330. The radio modem 330 is thus common for the baseband unit 320 and the low power mode unit 310a. In the user equipment 300d the functionality of the low power mode unit is completely integrated with the radio modem 320 and the baseband unit 330 (and therefore not illustrated). The low power mode unit implementations in the user equipment 300a, 300b, 300c are thus using at least partly dedicated hardware for low power operation. Such dedicated hardware might be implemented to operate with very low energy consumption. Depending on the design constraints for its low power operation, the dedicated hardware might not be capable to detect or correctly receive (such as decode, demodulate, etc.) signals when the user equipment is located at the cell edge. In that case, the user equipment 300a: 300c might utilize its main receiver hardware for link monitoring in poor channel conditions. In some examples, the low power mode unit might, as in user equipment 300c, or use at least partly common hardware components. In some examples, the low power mode unit might, as in user equipment 300d, operate as a functionality fully within the common hardware, i.e., the transceiver used for regular user equipment operation. When using such a common hardware, the low power mode unit might still operate in different configurations or modes, where some hardware or software parameters are adapted depending on the usage of the low power mode unit. As example, the modem in the user equipment might have one or more specific operation modes for energy efficient link monitoring operation, where such efficient modes might imply that only strong signals can be detected in case sensitivity, linearity, and / or other requirements can be relaxed.

[0043] However, in case the first power mode is used for radio link monitoring operations, in an effort to keep energy consumption low in the UE, there is a risk that the UE will use the first power mode longer than assumed according to specifications. In turn, this may cause the second power mode to be activated too late for the necessary action to be performed, or completed (e.g., using the second power mode for performing a legacy measurement procedure). It can thus be risky from a specification compliance perspective to implement the usage of different power modes in a UE in the context of radio link monitoring. There is therefore a need for technologies that can ensure robustness of radio link monitoring without requiring continuous usage of the main receiver in the UE.

[0044] The embodiments disclosed herein therefore relate to techniques for radio link monitoring operation. In order to obtain such techniques, there is provided a UE 220, 300a:300d, a method performed by the UE 220, 300a:300d, a computer program product comprising code, for example in the form of a computer program, that when run on a UE 220, 300a:300d, causes the UE 220, 300a:300d to perform the method.

[0045] At least some of the herein disclosed embodiments are based on the UE performing measurements to monitor channel conditions for radio link monitoring measurements using a first power mode. The measurements performed may differ depending on the capabilities associated with the first power mode, but may for example include measurements on synchronization signal block (SSB) signals, tracking reference signals (TRSs), channel state information reference signals (CSI-RSs), etc. assuming that the UE can use the first power mode to detect such modulated signals. In further examples, the first power mode is used by the UE for receiving other signals as well, such as low power synchronization signals (LP-SSs), which the UE may use for channel quality measurements.

[0046] At least some of the herein disclosed embodiments are based on the reception of some link quality measurement obtained by the UE receiving signals using the first power mode triggering the UE to use a second power mode for a subsequent transceiver operation. As a non-limiting and illustrative example, the UE may use the second power mode for receiving further signals from the network or for performing an event reporting as the examples A2 and A3 event reports. Further examples of transceiver operations where the second power mode is used will be disclosed below.

[0047] Fig. 4 is a flowchart illustrating embodiments of methods for radio link monitoring operation. The methods are performed by the UE 220, 300a:300d. The UE 220, 300a:300d is configured to selectively operate with either a first power mode or a second power mode. The methods are advantageously provided as computer programs 1020.

[0048] S102: The UE 220, 300a:300d performs, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation.

[0049] S104: The UE 220, 300a:300d performs, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation. The transceiver operation is performed responsive to the first link quality measurements fulfilling a trigger condition.

[0050] Hence, when a channel monitoring-related or mobility event, for example an out-of-service (OOS) radio link failure occurrence, measurement report or cell reselection, is imminent, the second power mode is activated ahead of the time instance when the event will occur.

[0051] In this way the UE can thus use the first power mode when performing routine link monitoring and other housekeeping monitoring operations that can be performed during stable radio conditions. During such operations the second power mode can stay inactivated, and hence be in a deep sleep state or some other minimum power level. The second power mode is activated as soon as the link quality measurements fulfil the trigger condition. As will be explained further below, once the second power mode has been activated, the second power mode can be used for additional or more accurate measurements, or for performing network signaling procedures.

[0052] Embodiments relating to further details of radio link monitoring operation as performed by the UE 220, 300a:300d will now be disclosed with continued reference to Fig. 4.

[0053] Further aspects of the different power modes will be disclosed next. There could be different ways to define the first power mode and the second power mode. In some embodiments, the second power mode requires higher power consumption than the first power mode. In some examples, the second power mode requires at least 5 times higher power consumption than the first power mode. In some examples, the second power mode requires at least 10 times higher power consumption than the first power mode.

[0054] There could be different examples of first power modes. In some embodiments, using the first power mode comprises using a low power (LP) radio mode, a Wake-Up Radio mode, or a non-default radio mode, in the UE 220, 300a:300d. Likewise, there can be different examples of second power modes. In some embodiments, using the second power reception mode comprises using a non-LP radio mode, a non-Wake Up Radio mode, or a default radio mode, in the UE 220, 300a:300d.

[0055] Reference is here made to Fig. 5 which shows how the measured quantity of some link measurements varies over time. The dashed line represents the ideal value of the measured quantity and the solid line represents the measured quantity after filtering. The empty circles represents when there is a reference signal available for measurement (i.e., when there is a reference signal transmitted from the network), and the filled black circles represent when an available reference signal is used by the UE for a measurement. It is in the figure also indicated whether the first power mode or the second power mode is used. In Fig. 5 is shown an example of when the aforementioned event A2 is fulfilled (i.e., when the serving cell becomes worse than a configured threshold) and reported by the UE to the network. Filtering is performed such that RAN4 requirements on both accuracy and delay are fulfilled. In this example, the A2 event is fulfilled after 5 measurements (counting from when the true value has gone below the threshold). One measurement is taken every fourth time a reference signal is available. The second power mode is only activated after the trigger condition is fulfilled.

[0056] Further aspects of the radio link monitoring operation associated with the first link quality measurements, and further aspects of the first link quality measurements will be disclosed next.

[0057] In general terms, the radio link monitoring operation could relate to routine link monitoring and other housekeeping monitoring operations that can be performed during stable radio conditions. For example, the radio link monitoring operation is used by the UE to monitor the quality of its radio link with the network, or of individual beams supporting the radio link, as part of ensuring reliable communication for the UE. One purpose of the radio link monitoring operation is to detect when the quality of the radio link between the UE and the network node degrades to a point where the connection may be at risk of failure. The radio link monitoring thus allows the UE to assess whether the radio link is healthy or if it is in danger of becoming unusable. Further aspects of radio link monitoring are provided in 3GPP TS 38.300, “NR; NR and NG-RAN Overall description; Stage-2”, version 18.3.0.

[0058] In some non-limiting examples, the first link quality measurements pertain to any of: radio link monitoring, beam management, beam failure detection, reference signal received power (RSRP) io measurements or reference signal received quality (RSRQ) measurements of a serving cell 230a and at least one neighbor cell 230b. The RSRP and the RSRQ can thus be based on measurements made on signals transmitted by the network node of the serving cell 230a as well as signals transmitted by the network node of at least one neighbor cell 230b. The UE might continuously measures the quality of downlink reference signals, such as SSB, CSI-RS, TRS, etc., to assess the radio link quality. The quality of these signals helps the UE decide whether the radio link is in-sync or out-of-sync. Here, the radio link monitoring can be derived from link quality measurements in terms of RSRP, RSRQ, SNR, etc. on downlink reference signals such as SSB, CSI-RS, TRS, etc. Beam management and beam failure detection can be based on CSI-RS link quality measurements in terms of RSRP, RSRQ, SNR, etc. on downlink reference signals such as CSI-RS.

[0059] In some aspects, the first power mode is used for performing measurements at a higher rate (i.e., more often) than what is mandated by some specification. Hence, in some embodiments, the UE 220, 300a:300d is configured by a network node 210a to perform the first link quality measurements according to a measurement rate, but the first link quality measurements are performed with a rate faster than the measurement rate. This allows the condition to be fulfilled later in time and thus also allows the second power to be activated later, which improves power consumption (since the first power mode can be used as long as possible without impacting the performance).

[0060] Reference is here made to Fig. 6 which shows how the measured quantity of some link measurements varies over time. The dashed line represents the ideal value of the measured quantity and the solid line represents the measured quantity after filtering. The empty circles represents when there is a reference signal available for measurement (i.e., when there is a reference signal transmitted from the network), and the filled black circles represent when an available reference signal is used by the UE for a measurement. It is in the figure also indicated whether the first power mode or the second power mode is used. As can be seen, the UE uses the first power mode to obtain link measurements for all available measurement occasions.

[0061] In some aspects, filtering is adapted when the first link quality measurements are performed with a rate faster than the measurement rate. In one example, the adaptation can be performed in such a way that filter time constants are independent of the input rate. In another example, the time constants depend on the input rate of the filter. The former is suitable in scenarios where filtering is mainly performed for average out fast fading effects and the latter is suitable when filtering is mainly performed to average out noise.

[0062] If the first link quality measurements are to be performed with a rate faster than the measurement rate or not could, for example, depend on the relationship between the power consumption of the first power mode and the second power mode. If the power consumption of the first power mode is much lower than the second power mode (for example, the first power mode being 10% or less compared to the second power mode), the higher rate that is used for performing the first link quality measurements will result in lower energy consumption as the second power mode can be activated later. On the other hand, if the power consumption of the first power mode is only a bit lower than the second power mode, a normal measurement rate (e.g., according to specifications) and a bit earlier activation of the second power mode will lead to lower energy consumption. Hence, in some embodiments, the rate at which the first link quality measurements are performed depends on a power consumption relation between the first power mode and the second power mode.

[0063] As an alternative to using a higher measurement rate for performing the first link quality measurements, any thresholds used as conditions for activating the second power mode can be set such that the second power mode is activated earlier. This would allow some of the link quality measurements to be taken using the second power mode, which might improve the accuracy. This can be especially useful in low SINR / RSRP conditions.

[0064] As disclosed above, the transceiver operation in step SI 04 is performed responsive to the first link quality measurements fulfilling a trigger condition. That is, the second power mode is activated when the UE determines that a condition is met with respect to the first link quality measurements. Generally, the condition may be triggered based on a determined need to use the second power mode, e.g., due to a sensitivity requirement, determined mobility level, quickly reduced quality of measured signal, or some other performance related requirement. The trigger condition can be selected so as to activate the second power mode proactively so that the second power mode can be used when the UE needs to perform some required action as soon as some formally configured criterion for this action is fulfilled. Further aspects of different trigger conditions that can be used for this purpose will be disclosed next.

[0065] In some aspects, the trigger condition pertains to a limited capability of the first power mode, that is when the use of the first power mode is insufficient for the UE to complete a transceiver operation (as indicated by the first link quality measurements). Hence, in some embodiments, the trigger condition is fulfilled when the first power mode is not supported for, or compatible with, completing the transceiver operation associated with the first link quality measurements.

[0066] In some aspects, the trigger condition pertains to there being large variations in RSRP, RSRQ, SINR, etc. In particular, in some embodiments, the trigger condition is fulfilled when any of: an RSRP value, an RSRQ value, an SINR value of the first link quality measurements crosses a threshold value.

[0067] In some aspects, the trigger condition pertains to a cell reselection criterion being fulfilled. In particular, in some embodiments, the trigger condition is fulfilled when the first link quality measurements indicate fulfilment of a cell reselection criterion for the UE 220, 300a:300d.

[0068] In some aspects, the trigger condition pertains to the mobility of the UE being so hight that the UE is not able to use the first power mode for performing some transceiver operation. That is, in some embodiments, the trigger condition is fulfilled when the first link quality measurements indicate that a velocity of the UE 220, 300a:300d is higher than a velocity threshold value. Here, the velocity can be estimated via Doppler measurements based on the first link quality measurements. It is also understood that also other techniques can be used for estimating the velocity of the UE 220, 300a:300d.

[0069] In some aspects, the trigger condition depends on an event threshold configured by the network node 210a, such as aforementioned event A2 or event A3, or some out-of-service (OOS) criterion. Hence, in some embodiments, the trigger condition depends on event threshold values received by the UE 220, 300a:300d as configuration from a network node 210a serving the UE 220, 300a:300d. For example, if the transceiver operation in step SI 04 is a result of the serving cell quality becoming below some threshold (such as for an A2 event), the trigger condition can be set to be XI dB above the configured threshold for that event (e.g., XI dB above the configured threshold for the A2 event). For cases where an event is triggered because of a neighbor cell being better than the serving cell (such as for an A3 event), the trigger condition can be set to be X2 dB lower than the configured threshold for that event (e.g., X2 dB lower than the configured threshold for the A3 event).

[0070] In case the trigger condition ceases to be fulfilled, either while the second power mode is being activated or the second power mode has been activated, the second power mode can be deactivated, and measurements can again be performed using the first power mode, and thus step SI 02 can be entered again.

[0071] As disclosed above, the UE 220, 300a:300d in step SI 04 performs, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation. As an introductory example, the UE may either revert to channel monitoring or perform a mobility operation depending on whether the event has occurred or not. The mobility operation can e.g., be that one of the configured measurement reporting events are fulfilled and then the UE sends a measurement report according to standardized procedures. Alternatively, the mobility event can be that the cell reselection criteria are fulfilled for a neighbor cell and then the UE performs cell reselection according to standardized procedures. Further aspects of this transceiver operation will be disclosed next.

[0072] In some aspects, the transceiver operation pertains to receiving downlink control channel from its serving and / or neighbor cells. In particular, in some embodiments, the UE 220, 300a:300d is configured to perform (optional) step SI 04-4 as part of completing the transceiver operation in step SI 04.

[0073] S 104-2: The UE 220, 300a:300d receives a downlink control channel on which the downlink reference signals are sent.

[0074] In some aspects, the downlink control channel comprises downlink reference signals which the UE then measures on (whilst using the second power mode). That is, in some embodiments, receiving the downlink control channel comprises the UE using the second power mode for performing second link quality measurements on downlink reference signals. The second power mode can be used for performing a burst of multiple measurements, for the UE to quickly determine the quality of detected signals required to analyze one or more potential signal quality events. Hence, in some embodiments, the second link quality measurements comprise a measurement burst. The number of occasions in the burst might depend on the quality conditions (as assessed using the first link quality measurement). Hence, in some embodiments, the number of measurement occasions in the measurement burst depends on the first link quality measurements.

[0075] In other words, the a quality level can be used so that once the UE determines that a measurement quality of the first link quality measurements is below this first quality level, the second power mode can be activated for performing multiple measurements in a burst of measurements using the shortest available measurement interval based on the configured signaling setup to quickly determine whether the event is occurring and if so perform the event reporting according to network expectations. As will be explained next, this is in contrast to legacy behavior. According to a first example, the UE could according to legacy behavior be assumed to use the second power mode for all these measurements (since the first power mode would according to legacy behavior be assumed to be used only for wake-up signaling detection). According to a second example, the UE could according to legacy behavior try to use the first power mode for these measurements, but it would take too long before the second power mode is activated.

[0076] Reference is here made to Fig. 7 which shows how the measured quantity of some link measurements varies over time. The dashed line represents the ideal value of the measured quantity and the solid line represents the measured quantity after filtering. The empty circles represents when there is a reference signal available for measurement (i.e., when there is a reference signal transmitted from the network), and the filled black circles represent when an available reference signal is used by the UE for a measurement. It is in the figure also indicated whether the first power mode or the second power mode is used. As can be seen, once the second power mode has been activated, it is used for four consecutive measurements in a burst, to quickly perform the measurements enough to ensure that the expected level of measurement performance is achieved using the main receiver. Once a second trigger condition is fulfilled as defined by some specification, e.g., event A2, the UE uses the second power mode and performs action according to standardized procedures.

[0077] In some aspects, the transceiver operation pertains to a network signaling procedure. For example, the UE can use the second power mode for performing signaling and indications related to an ongoing monitoring or recovery procedure. In particular, in some embodiments, the UE 220, 300a:300d is configured to perform (optional) step SI 04-4 as part of completing the transceiver operation in step SI 04.

[0078] S 104-4: The UE 220, 300a:300d performs network signaling with a network node 210a serving the UE 220, 300a:300d.

[0079] In some embodiments, the network signaling pertains to transmission of an indication relating to the first link quality measurements. In some embodiments, the indication pertains to control signaling indicative of at least one of: connection re-establishment with reason radio link failure, cell reselection, a beam failure event, an indication of network configured, a measurement report. Examples of reporting criterion are provided in the context of event triggered measurement reports as described in 3GPP TS 38.331 version 18.2.0, or events within the UE for initiating L1 / L2 Triggered Mobility as e.g. described in 3GPP TS 38.300 version 18.2.0.

[0080] Hence, the transceiver operation can e.g., be that one of the configured measurement reporting events are fulfilled and then the UE can send a measurement report according to standardized procedures. Alternatively, the mobility event can be that the cell reselection criteria are fulfilled for a neighbor cell and then the UE can perform cell reselection according to standardized procedures.

[0081] Reference is here made to Fig. 8 which shows how the measured quantity of some link measurements varies over time. The dashed line represents the ideal value of the measured quantity and the solid line represents the measured quantity after filtering. The empty circles represents when there is a reference signal available for measurement (i.e., when there is a reference signal transmitted from the network), and the filled black circles represent when an available reference signal is used by the UE for a measurement. It is in the figure also indicated whether the first power mode or the second power mode is used. As can be seen, the herein disclosed embodiments allow for very short periods of activation and deactivation of the second power mode.

[0082] Next will be described an example where the herein disclosed embodiments are applied for RLM. It is assumed that the UE is configured according to appendix A.6.3.2. 1.1 in 3GPP TS 38.133 V18.5.0 (p. 2381), with the additions and changes as follows. The radio link monitoring RLM-RS is CSI-RS. The RRM for serving and neighbor cell monitoring RS is SSB, the connected mode DRX is configured with the period 1.28 seconds, and the connected mode WUS is configured for PDCCH / PDSCH scheduling indication. Consider a scenario where the UE is not being scheduled for data transmission, so the second power mode is not routinely activated. Instead, the first power mode is used for RRM and RLM activities, operating at a lower power / energy level than the second power mode. In a scenario with stable radio conditions, the RLM-RS is received at high signal levels, i.e. a signal level at which measurements using the first power mode are reliable. When the cell quality degrades, e.g. due to UE movement or increase in interference, the CSI-RS RSRQ or SINR measurements resulting from using the first power mode yields a lower result and once the result goes below a threshold, the second power mode is activated, entering a higher power / energy consumption mode. The second power mode is used for performing internal protocol layer 1 to protocol layer 3 (L1-L3) and optionally for performing additional LI measurements. After identifying a predetermined number of LI measurements below the OOS threshold, the UE performs an L3 RRC procedure to re-establish the RRC connection, where the reason for re-establishment is stated as RLF. The trigger for activating the second power mode is the RLM measurements performed using the first power mode. During the RLM RS quality degradation phase, the UE energy consumption can be at ultra-low level. By performing timely measurements using the first power mode and providing a timely wake-up trigger for activation of the second power mode, the UE can perform the reconnect action using the second power mode and with the correct timing.

[0083] In some situations, the radio conditions might be too challenging for using the first power mode to perform measurements with the required accuracy. For example, if the UE speed is very high or the SINR is very low. In such cases, measurements can be performed using the second power mode at a cost of a higher energy consumption. Similarly, for cases with traffic with strict latency and or reliability requirements, measurements can be done using the second power mode at a cost of a higher energy consumption.

[0084] Fig. 9 schematically illustrates, in terms of a number of structural units, the components of a user equipment 900 according to an embodiment. Processing circuitry 910 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1010 (as in Fig. 10), e.g. in the form of a storage medium 930. The processing circuitry 910 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0085] Particularly, the processing circuitry 910 is configured to cause the user equipment 900 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 930 may store the set of operations, and the processing circuitry 910 may be configured to retrieve the set of operations from the storage medium 930 to cause the user equipment 900 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0086] Thus the processing circuitry 910 is thereby arranged to execute methods as herein disclosed. The storage medium 930 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The user equipment 900 may further comprise a communications (comm.) interface 920 at least configured for communications with other entities, functions, nodes, and devices, as in Fig. 2. As such the communications interface 920 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 910 controls the general operation of the user equipment 900 e.g. by sending data and control signals to the communications interface 920 and the storage medium 930, by receiving data and reports from the communications interface 920, and by retrieving data and instructions from the storage medium 930. Other components, as well as the related functionality, of the user equipment 900 are omitted in order not to obscure the concepts presented herein.

[0087] Fig. 10 shows one example of a computer program product 1010 comprising computer readable storage medium 1030. On this computer readable storage medium 1030, a computer program 1020 can be stored, which computer program 1020 can cause the processing circuitry 910 and thereto operatively coupled entities and devices, such as the communications interface 920 and the storage medium 930, to execute methods according to embodiments described herein. The computer program 1020 and / or computer program product 1010 may thus provide means for performing any steps as herein disclosed.

[0088] In the example of Fig. 10, the computer program product 1010 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1010 could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1020 is here schematically shown as a track on the depicted optical disk, the computer program 1020 can be stored in any way which is suitable for the computer program product 1010.

[0089] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A method for radio link monitoring operation, performed by a user equipment (220, 300a:300d, 900) configured to selectively operate with either a first power mode or a second power mode, the method comprising: performing (SI 02), whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation; and performing (SI 04), whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

2. The method according to claim 1, wherein the second power mode requires higher power consumption than the first power mode, such as at least 5 times higher power consumption, preferably at least 10 times higher power consumption.

3. The method according to any preceding claim, wherein using the first power mode comprises using a low power, LP, radio mode, a Wake-Up Radio mode, or a non-default radio mode, in the user equipment (220, 300a:300d, 900).

4. The method according to any preceding claim, wherein using the second power reception mode comprises using a non-low power radio mode, a non-Wake Up Radio mode, or a default radio mode, in the user equipment (220, 300a:300d, 900).

5. The method according to any preceding claim, wherein the first link quality measurements pertain to any of: radio link monitoring, beam management, beam failure detection, reference signal received power measurements or reference signal received quality measurements of a serving cell (230a) and at least one neighbor cell (230b).

6. The method according to any preceding claim, wherein the user equipment (220, 300a:300d, 900) is configured by a network node (210a) to perform the first link quality measurements according to a measurement rate, and wherein the first link quality measurements are performed with a rate faster than the measurement rate.

7. The method according to claim 6, wherein the rate at which the first link quality measurements are performed depends on a power consumption relation between the first power mode and the second power mode.

8. The method according to any preceding claim, wherein the trigger condition is fulfilled when the first power mode is not supported for, or compatible with, completing the transceiver operation associated with the first link quality measurements.

9. The method according to any preceding claim, wherein the trigger condition is fulfilled when any of: a reference signal received power value, a reference signal received quality value, a signal to interference plus noise ratio value of the first link quality measurements crosses a threshold value.

10. The method according to any preceding claim, wherein the trigger condition is fulfilled when the first link quality measurements indicate fulfilment of a cell reselection criterion for the user equipment (220, 300a:300d, 900).

11. The method according to any preceding claim, wherein the trigger condition is fulfilled when the first link quality measurements indicate that a velocity of the user equipment (220, 300a:300d, 900) is higher than a velocity threshold value.

12. The method according to any preceding claim, wherein the trigger condition depends on event threshold values received by the user equipment (220, 300a:300d, 900) as configuration from a network node (210a) serving the user equipment (220, 300a:300d, 900).

13. The method according to any preceding claim, wherein completing the transceiver operation comprises: receiving (SI 04-2) a downlink control channel on which the downlink reference signals are sent.

14. The method according to claim 13, wherein receiving the downlink control channel comprises performing second link quality measurements on downlink reference signals.

15. The method according to claim 14, wherein the second link quality measurements comprise a measurement burst.

16. The method according to claim 15, wherein a number of measurement occasions in the measurement burst depends on the first link quality measurements.

17. The method according to any of claims 1 to 12, wherein completing the transceiver operation comprises: performing (SI 04-4) network signaling with a network node (210a) serving the user equipment (220, 300a:300d, 900).

18. The method according to claim 17, wherein the network signaling pertains to transmission of an indication relating to the first link quality measurements.

19. The method according to claim 18, wherein the indication pertains to control signaling indicative of at least one of: connection re-establishment with reason radio link failure, cell reselection, a beam failure event, an indication of network configured, a measurement report.1920. A user equipment (220, 300a:300d, 900) for radio link monitoring operation, the user equipment (220, 300a:300d, 900) being configured to selectively operate with either a first power mode or a second power mode and comprising processing circuitry (910), the processing circuitry being configured to cause the user equipment (220, 300a:300d, 900) to: perform, whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation; and perform, whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

21. The user equipment (220, 300a:300d, 900) according to claim 20, further being configured to perform the method according to any of claims 2 to 19.

22. A computer program (1020) for radio link monitoring operation, the computer program comprising computer code which, when run on processing circuitry (910) of a user equipment (220, 300a:300d, 900) configured to selectively operate with either a first power mode or a second power mode, causes the user equipment (220, 300a:300d, 900) to: perform (SI 02), whilst in connected discontinuous reception mode and using the first power mode, first link quality measurements associated with a radio link monitoring operation; and perform (SI 04), whilst in connected discontinuous reception mode and using the second power mode, a transceiver operation associated with the radio link monitoring operation, responsive to the first link quality measurements fulfilling a trigger condition.

23. A computer program product (1010) comprising a computer program (1020) according to claim 22, and a computer readable storage medium (1030) on which the computer program is stored.

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