WO2019242853A1

WO2019242853A1 - Client device and methods for efficient beam management

Info

Publication number: WO2019242853A1
Application number: PCT/EP2018/066431
Authority: WO
Inventors: Bengt Lindoff; Wenquan HU; Rama Kumar Mopidevi
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2019-12-26
Anticipated expiration: 2020-12-20

Abstract

The invention relates to efficient beam management in a client device. According to embodiments of the invention the client device (100) manipulates at least one of a timer, a counter associated with a beam failure indication and a scheduled measurement gap if the timer would be running during the scheduled measurement gap. By manipulating at least one of the timer, the counter and the scheduled measurement gap according to embodiments of the invention a well defined client device behaviour is provided. Thereby, increased reliability and robustness of the wireless communication system is possible. Furthermore, the invention also relates to a corresponding method and a computer program.

Description

CLIENT DEVICE AND METHODS FOR EFFICIENT BEAM MANAGEMENT

Technical Field

The invention relates to a client device for efficient beam management. Furthermore, the invention also relates to a corresponding method and a computer program.

Background

The 5G cellular system, New Radio (NR), is currently being standardized and is targeting radio spectrum from below 1 GHz up to and above 60 GHz. To allow for such diverse radio environments, NR will support both different system bandwidths and different numerologies, i.e. different sub-carrier-spacings, from 15 kHz up to 120 or even 240 kHz. Furthermore, for 10+ GHz carriers, multiple antennas and beamforming are assumed to be used to combat the higher path loss at such high radio frequencies.

When beamforming is used, a next generation nodeB (gNB) comprising multiple antennas may transmit data in several directions in different transmit beams. The user equipment (UE) therefore has to tune its own receive antennas in different receive beam directions to communicate with the gNB. In order for the UE to be able to detect and track the transmit beams of the gNB, the UE performs beam monitoring. Hence, the gNB transmits known pilot signals in serving and adjacent beams, which the UE receives and uses to detect possible transmit beams, so called candidate beams, to switch to in case of changes in the radio environment.

Each possible connection between the UE and the gNB is sometimes called a beam pair link (BPL), where a BPL consists of a transmit beam associated to the transmitter and a receive beam associated to the receiver. Hence, a BPL can be seen as a spatial direction of a radio transmission, where the transmit beam corresponds to a certain spatial transmission direction and the receive beam corresponds to a certain spatial receiver direction. Furthermore, the spatial directions are further generated in the transmitter and receiver by different spatial transmission and reception parameters tuning the respective antenna transmit and receive panel in the respective spatial direction. The gNB will configure a set of BPLs for the UE to monitor. The configured set of monitored BPLs may be based on which BPL the UE has detected. This set can for example comprise all the BPLs associated with control channels and data channels between the gNB and the UE. The gNB will also configure a set of serving BPLs which will be used to transmit associated control information to the UE. The set of serving BPLs is a subset or equal to the set of monitored BPLs. The UE monitors the quality of the set of monitored BPLs and reports the quality in beam measurement report to the gNB. When the quality of the received signal in a BPL is below a threshold indicating unreliable detection, the BPL is in failure. If all serving BPLs for a UE are in failure, a beam failure is declared and the UE performs a beam recovery procedure. The aim of the beam recovery procedure is to find a suitable candidate beam quickly and recover the radio link before the higher layer radio link monitoring procedure indicates a radio link failure. To re-establish the failed radio link as quickly as possible becomes especially important in case of low-latency services, such as e.g. ultra-reliable low-latency communications (URLLC) services.

Since NR is based on a lean design without any common reference signals as in LTE, the network access node may configure reference signals, such as channel state information reference signal (CSI-RS) individually per serving beam depending on for instance the service used for respective beam. The periodicity of reference signals, such as CSI-RS, in NR could be configured to be 5, 10, 20, 40, 80, 160, 320, 640 slots, however all periodicities will not be used for all sub-carrier spacings. Since the time-duration of slot depends on the sub-carrier spacing (SCS=15 kHz, slot=1 ms, SCS=120 kHz, slot =0,125 ms), different slot configurations may be common for different SCSs. Typical values of CSI-RS periodicities will be in the range of 10-40 ms. A serving beam, may be a high throughput narrow beam where large antenna gain is needed for achieving good signal-to noise and interference ratio (SINR) and by that high throughput. Since the beam form the network access node is narrow, there is a need for a short RS periodicity in order for the UE to track possible movement and perform beam switching to candidate beams. For example, the serving beam may be configured with CSI-RS with periodicity of 10 ms that is Quasi-Co-Located (QCL) with a dedicated physical control channel and physical data channel transmitted in the same serving beam. If two signals are spatial QCLed, it means that the UE can assume that the two signals are transmitted in the same direction from the network access node. Another serving downlink beam, may however be a“fallback” beam the UE have for control signalling. This beam may be a wide beam, in order to reduce the risk for dropping the connection, and physical control and physical data channels may for instance be QCLed with the network access node synchronization signal block (SSB), and hence the reference signal (RS) used for beam monitoring may be the SSB signals, and these signals are typically configured to have a periodicity of 20 ms. Since this serving beam is a wide beam, the need for beam switching is lower and hence a lower RS periodicity is needed.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions. Another objective of embodiments of the invention is to provide a solution which provides improved beam management compared to conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a client device for a wireless communication system, the client device being configured to

start a timer upon detection of a beam failure indication associated to at least one serving beam for the client device;

determine that a measurement gap is scheduled for the client device; and

manipulate at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap.

To manipulate any of the timer, the counter and the scheduled measurement gap can herein mean that the client device performs some processing on any of the mentioned timer, counter and scheduled measurement gap. Examples of manipulation are given in different implementation forms of the client device according to the first aspect.

The client device usually monitors reference signals and a downlink control channel from a serving cell, such as the physical downlink control channel. The downlink control channel can be sent in different spatial directions by beamforming, and the client device monitors reference signals that are quasi-co-located with the downlink control channel from the serving cell, and hence transmitted in the same direction as the downlink control channel. Therefore, the spatial direction, or the corresponding beam, the client device has to monitor of the downlink control channel can be labelled as a serving downlink beam.

The client device herein is configured with at least one measurement gap. The measurement gap can e.g. be configured according to previous control signalling from a serving cell or its associated network access node; according to predefined rules in the client device itself, or a combination thereof, i.e. a semi static configuration. The concept of measurement gap is e.g. defined in the NR standard. During a measurement gap the client device is not able to perform beam monitoring on the one or more serving beams.

An advantage of the client device according to the first aspect is that a clear and predictable behaviour for the client device is provided. Thereby, the behaviour of the client device in case the measurement gap collides with a beam monitoring instance can follow well defined rules stipulated herein as manipulations. This means increased reliability and robustness of the wireless communication system, especially when all client devices of the system follow the same behaviour patterns.

In an implementation form of a client device according to the first aspect, manipulate the counter comprises at least one of

reset a value of the counter; and

increment or decrement a value of the counter.

An advantage with this implementation form is that by manipulating the counter in a consistent way where all client devices follows the same manipulation of the counter the reliability and robustness of the wireless communication system can be increased.

In an implementation form of a client device according to the first aspect, the client device is further configured to at least one of

reset the value of the counter if the timer will expire during the scheduled measurement gap; and

increment or decrement the value of the counter if the timer will expire during the scheduled measurement gap.

By resetting the value of the counter if the timer expires during the scheduled measurement gap, the client device will have a predictable behaviour and by that the reliability and robustness of the wireless communication system is increased.

By incrementing or decrementing the value of the counter if the timer expires during the scheduled measurement gap the beam failure detection process is speeded up; even in the case the scheduled measurement gap collides with beam monitoring of reference signals. Beam recovery procedure is hence not affected by the scheduled measurement gap, and beam recovery is triggered fast thereby improving the user experience due to faster recovery from beam failure, e.g. due to bad link or temporary broken link.

In an implementation form of a client device according to the first aspect, the client device is further configured to at least on of

reset the value of the counter based on the scheduled measurement gap; and increment or decrement the value of the counter based on the scheduled measurement gap.

An advantage with this implementation form is that the manipulation may be dependent on duration of the measurement gap and/or periodicity and offset of the measurement gap and by that improved beam failure procedures can be achieved for different durations and/or periodicities and offsets of the measurement gap.

reset the value of the counter based on the duration of the scheduled measurement gap; and

increment or decrement the value of the counter based on the duration of the scheduled measurement gap.

An advantage with this implementation form is that the manipulation is dependent on the duration of the scheduled measurement gap and by that improved beam failure procedure can be achieved for different time durations of the scheduled measurement gap.

In an implementation form of a client device according to the first aspect, the client device is further configured to

initiate a beam recovery procedure if the value of the counter exceeds a threshold value.

Thereby, a possible beam failure can be handled by using a beam recovery procedure.

In an implementation form of a client device according to the first aspect, manipulate the timer comprises at least one of

restart the timer;

suspend and thereafter resume the timer; and

increase a value of the timer.

An advantage with this implementation form is that the scheduled measurement gap can be made transparent in the sense that the timer in the beam failure procedure does not take the measurement gap into account.

In an implementation form of a client device according to the first aspect, the client device is further configured to restart the timer without changing a value of the counter if the timer will expire during the scheduled measurement gap.

By restarting the timer without resetting the counter, if the timer expires during the scheduled measurement gap, a simple way to handle the problem of a measurement gap colliding with beam monitoring reference signals is provided. This enables low cost and low complexity implementation in the client device since restarting a timer does not require any additionally advanced hardware and/or software solution.

suspend the timer at the start of the scheduled measurement gap and thereafter resume the timer at the end of the scheduled measurement gap.

By suspending the timer during the scheduled measurement gap and thereafter resume the timer once the scheduled measurement gap has ended, has the advantage of removing the time for the scheduled measurement gap in the beam failure detection procedure. Thereby, the timer associated to the beam failure is made transparent for the scheduled measurement gap. This implies low cost and low complexity implementation in the client device.

increase the value of the timer based on the duration of the scheduled measurement gap.

By increasing the value of the timer based on the duration of the scheduled measurement gap the timer associated to the beam failure is made transparent for the scheduled measurement gap. This implies low cost and low complexity implementation in the client device.

manipulate the timer if the timer will expire before the end of the scheduled measurement gap.

An advantage of manipulating the timer, if the duration of the scheduled measurement gap is longer than the remaining time of the timer, is that adaptation of a beam failure procedure can be made if the beam failure procedure is affected by the scheduled measurement gap. Improved performance in the wireless communication system is thereby achieved.

In an implementation form of a client device according to the first aspect, manipulate the scheduled measurement gap comprises at least one of

suspend the scheduled measurement gap; and

shorten the duration of the scheduled measurement gap.

A controlled way of suspending or shorten a scheduled measurement gap is defined by this implementation form which means that the behaviour of the client device is predictable and consistent. This implies increased capacity in the wireless communication system.

In an implementation form of a client device according to the first aspect, the timer is a beam failure detection timer.

In an implementation form of a client device according to the first aspect, the counter is a beam failure indication counter.

start the timer, determine that a measurement gap is scheduled, and manipulate at least one of the timer, the counter and the scheduled measurement gap in a medium access control layer of the client device.

detect the beam failure indication associated to the serving beam in a physical layer of the client device; and

send the detection of the beam failure indication associated to the serving beam to the medium access control layer.

detect the beam failure indication associated to the serving beam if a quality of the serving beam is lower than a quality threshold value. According to a second aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device, the method comprises

starting a timer upon detection of a beam failure indication associated to at least one serving beam for the client device;

determining that a measurement gap is scheduled for the client device; and

manipulating at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap.

The method according to the second aspect can be extended into implementation forms corresponding to the implementation forms of the client device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.

The advantages of the methods according to the second aspect are the same as those for the corresponding implementation forms of the client device according to the first aspect.

The invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to embodiments of the invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

- Fig. 1 shows a client device according to an embodiment of the invention;

- Fig. 2 shows a method for a client device according to an embodiment of the invention;

- Fig. 3 illustrates interaction between the MAC layer and physical layer of a client device according to an embodiment of the invention; - Fig. 4 shows a wireless communication system according to an embodiment of the invention; and

- Fig. 5 shows a flow chart of an embodiment of the invention.

Detailed Description

In NR, the UE can be configured with so called measurement gaps in order to perform measurements on other beams or cells (e.g. candidate beams or candidate cells) that requires other radio settings and/or configurations than the serving beam(s) of a serving cell. Since the UE is not able to perform simultaneous monitoring of serving beams as well as measurements on candidate beams, if the candidate beams require other radio configurations, measurement gaps during which the UE does not need to monitor the control channels for the serving beams and cells, have been introduced.

However, it has been recognised by the inventors that if a measurement gap is scheduled during a time period in which reference signals for beam monitoring for the serving cell is to be received, the UE cannot perform beam monitoring. Hence, the scenario when a beam failure detection timer, associated to beam monitoring procedure, expires during a measurement gap has been overlooked and it is currently unclear how to handle such a case. To remedy such a drawback and uncertainty the inventors therefore herein present a solution including a client device as shown in Fig. 1 and a corresponding method as shown in Fig. 2.

Fig. 1 shows a client device 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the client device 100 comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100 further comprises an antenna or antenna array 1 10 coupled to the transceiver 104, which means that the client device 100 is configured for wireless communications in a wireless communication system. That the client device 100 is configured to perform certain actions should in this disclosure be understood to mean that the client device 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.

According to embodiments of the invention the client device 100 is configured to start a timer upon detection of a beam failure indication associated to at least one serving beam for the client device. The client device 100 is further configured to determine that a measurement gap is scheduled for the client device 100 and thereafter manipulates at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap. That means that the timer runs after the start of the scheduled measurement gap and before the end of the scheduled measurement gap.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a client device 100, such as the one shown in Fig. 1. The method 200 comprises starting 202 a timer upon detection of a beam failure indication associated to at least one serving beam for the client device. The method 200 further comprises determining 204 that a measurement gap is scheduled for the client device 100 and manipulating 206 at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap.

Fig. 3 illustrates a MAC layer (also sometimes denoted MAC entity) 120 and a physical (PHY) layer 130 of a protocol stack of the client device 100. According to this embodiment the PHY layer 130 is configured to detect a beam failure indication associated to a serving beam. Upon detection of the beam failure indication, the PHY layer 130 sends the beam failure indication 140 to the MAC layer 120 as illustrated in Fig. 3. The PHY layer 130 can detect the beam failure indication associated to the serving beam if a quality of the serving beam(s) is lower than a quality threshold value. Mentioned quality threshold value is usually given by a standard, such as the LTE or NR standard. The quality of a beam can be determined using different methods. For example, in NR the client device 100 measures/estimates the signal-to-noise and interference (SINR) ratio on channel state information reference signal (CSI-RS) or synchronization signal block (SSB) and maps the measured/estimated SINR to a hypothetical block error rate (BLER). If the mapped BLER is higher than the threshold value the serving beam is considered unreliable (or the corresponding PDCCH monitoring) and a beam failure indication is determined/declared.

The MAC layer 120 in Fig. 3 receives the beam failure indication from the PHY layer 130 and performs any of the manipulation of the timer, the counter and the scheduled measurement gap according to embodiments of the invention. The MAC layer 120 is also responsible for starting the timer and determining that a measurement gap is scheduled for the client device 100. According to embodiments of the invention the timer can be a beam failure detection timer and the counter can be a beam failure indication counter. For these selections of timer and counter direct additions to the NR standard are presented later in the present disclosure.

Fig. 4 shows a wireless communication system 500 according to an implementation of the invention. The wireless communication system 500 comprises a client device 100 and a network access node 300 configured to operate in the wireless communication system 500. For simplicity, the wireless communication system 500 shown in Fig. 4 only comprises one client device 100 and one network access node 300. However, the wireless communication system 500 may comprise any number of client devices 100 and any number of network access nodes 300 without deviating from the scope of the invention. The client device 100 and the network access node 300 are configured to interwork in the wireless communication system 500. The network access node 300 or its associated serving cell 310 can be configured to provide one or more serving beams 502 to the client device 100 when the client device 100 is in connected mode with the network access node 300. In Fig. 5 three serving beams 502 are illustrated.

Fig. 5 shows a flowchart of a detailed method according to an embodiment of the invention. The method shown in Fig. 5 can be implemented, mutatis mutandis, in a client device 100, such as the one shown in Fig. 1.

At step 602 in Fig. 5, the MAC layer 120 of the client device 100 starts a timer. The timer is started when a beam failure indication has been received from the PHY layer 130. In NR such a timer would correspond to a beamFailureDetectionTimer. Further, the MAC layer 120 also determines that a measurement gap is scheduled for the client device 100. One way to determine the scheduled measurement gap is by deriving control information in a control message from the network access node 300. In NR the measurement gap is indicated in radio resource control (RRC) signalling from the gNB to the UE. The RRC signalling in NR indicates the measurement gap configuration including such parameters as measurement gap periodicity and duration of the measurement gap. During a measurement gap, the radio receiver of the client device 100 will be allocated to other purposes than reception of data and beam monitoring of serving beams during the measurement gap. The measurement gaps defined in NR can have a duration between 1.5-6.0 ms and with a periodicity of 20-160 ms. During beam management, in case the client device 100 uses analogue beamforming, the client device 100 for monitoring a receive beam different from the serving receive beam needs a measurement gap in order to monitor the receive beam by performing measurements.

At step 604 in Fig. 5, the PHY layer 130 of the client device 100 monitors reference signals for each serving beam and declares a beam failure indication if the quality of all the serving beams are below a threshold value. The beam failure indication is thereafter sent from the PHY layer 130 to the MAC layer 120. In NR the PHY layer 130 performs beam monitoring on a configured set qO of reference signals, which may be periodic CSI-RS or SSB transmitted in downlink serving beams. Each serving beam is monitored according to the respective reference signal periodicity. In case the channel quality of all the serving beams, measured on its respective reference signals, is below a preconfigured threshold, a beam failure indication (sometime also denoted as beam failure instance) is determined or declared by the PHY layer 130 and reported to the MAC layer 120. An acceptable channel quality can be defined as a hypothetical physical downlink control channel (PDCCH) block error rate (BLER) is above a certain threshold, e.g. 10%.

Steps 602 and 604 in Fig. 5 do not have to be performed in the sequential order as given in Fig. 5 and can e.g. be performed in the reverse order, or in parallel.

At step 606 in Fig. 5, the MAC layer 120 receives the beam failure indication from the PHY layer 130 and increments the value of the counter accordingly. In NR the counter would correspond to a beam failure indication counter. The beam failure indication can be reported with a period of the maximum of the smallest reference signal periodicity, and a pre-configured lowest periodicity, e.g. 2 ms. At the reception of the beam failure indication from the PHY layer 130 the MAC layer 120 increases the value of the counter, and if the counter exceeds a preconfigured value M, a beam (failure) recovery procedure is triggered. The beam recovery procedure is usually pre-defined by a standard which implies that the client device 100 will act according to such a procedure. The intention of the beam recovery procedure is that the client device 100 should find new candidate beam(s) quickly and recover prior to the higher layer radio link monitoring procedure indicates a radio link failure (RLF). As previously described, the beam recovery procedure is initiated if the value of the counter exceeds a pre-configured threshold. This threshold is in NR a beamFailurelnstanceMaxCount. However, in at least some embodiments of the invention the threshold for triggering the beam recovery procedure can be chosen to be smaller than the beamFailurelnstanceMaxCount threshold, and in this latter case an earlier beam failure recovery procedure is therefore triggered. For example, in order to avoid further collisions between the expiry of the timer and the scheduled measurement gap the beam failure procedure can be triggered earlier by having a lower value of the threshold for triggering the beam recovery procedure. Furthermore, at the reception of the beam failure indication the MAC layer 120 also starts the timer. If the timer expires, the value of the counter is reset, meaning that no further beam failure indication was received within in the relevant time window.

At step 608 in Fig. 5, the MAC layer 120 checks if the condition that the timer would be running during the scheduled measurement gap is fulfilled. If the mentioned condition is fulfilled the MAC layer 120 performs any manipulation according to embodiments of the invention in steps 610 to 614 which is described more in detail below. It is to be noted that the manipulation can be performed on only one of the mentioned timer, counter and scheduled measurement gap. However, in other cases the manipulation can be performed on two or all of the mentioned timer, counter and scheduled measurement gap. Hence, all combinations of manipulation are within the scope of the invention.

Step 610 in Fig. 5 relates to how the MAC layer 120 manipulates the counter according to embodiments of the invention. In an embodiment the MAC layer 120 performs at least one of resetting the value of the counter, and incrementing or decrementing the value of the counter. The value of the counter may be incremented or decremented with a static value, e.g. with value 1. In case the value of the counter is incremented this can be interpreted as that a so called“virtual beam failure indication” has been received by the MAC layer 120 during the measurement gap. Since the client device 100 cannot measure the quality of serving beams in a measurement gap, the client device 100 may therefore assume that the serving beam(s) is still unreliable (given that the beam failure indication counter has started, i.e. the counter > threshold > 0) and hence a virtual beam failure indication can be assumed to be determined by the PHY layer 130.

In embodiments of the invention, whether to reset or increment or decrement the value of the counter can be dependent on the value of the counter itself. For example, if the value of the counter is closer to the preconfigured threshold M than zero, the MAC layer 120 can increment the value of the counter since it is likely that the beam quality really is bad. Otherwise if the value of the counter is closer to zero than M the MAC layer 120 may reset the value of the counter since it is likely that the earlier beam failure indication is unreliable. All measurements are made with uncertainty and the existence of noise and/or interference can result in unreliable beam failure indications.

These manipulations on the counter are in further embodiments dependent on the scheduled measurement gap. Especially, the duration of the scheduled measurement gap is considered when resetting and/or incrementing or decrementing the value of the counter. For example, the value of the increment or decrement can depend on the duration of the scheduled measurement gap. In one case the counter is increased with a larger value if the duration of the scheduled measurement gap is longer compared to the case when the duration is shorter.

Further, the resetting and/or incrementing or decrementing of the value of the counter is in an embodiment only performed conditioned that the timer will expire during the scheduled measurement gap. This is due to the fact that the value of the counter should not be changed when the timer is running. Step 612 in Fig. 5 relates to how the MAC layer 120 manipulates the timer according to embodiments of the invention. In this respect mentioned manipulation comprises at least one of restarting the timer, suspending and thereafter resuming the timer, and increasing a value of the timer. Manipulation of the timer is in some embodiments only performed if the timer will expire before the end of the scheduled measurement gap.

In one case the timer is restarted without changing the value of the counter if the timer will expire during the scheduled measurement gap. This is a simple way of manipulation. In another case the timer is suspended at the start of the scheduled measurement gap and thereafter resumed at the end of the scheduled measurement gap. This case can be interpreted as an approach when the scheduled measurement gap is ignored in respect of the timer. In one case the value of the timer is increased based on the duration of the scheduled measurement gap. All these manipulations relate to the aspect of excluding the scheduled measurement gap in the beam failure indication timing.

Step 614 in Fig. 5 relates to how the MAC layer 120 manipulates the scheduled measurement gap according to embodiments of the invention. The reason why the scheduled measurement gap is manipulated is that in some scenarios the beam failure indication can and should have higher priority than the measurement gap and hence a beam failure indication procedure should be prioritized before the measurement gap. This is one reason why the measurement gap is manipulated.

Two main manipulations are herein proposed, i.e. to suspend the scheduled measurement gap, or to shorten the duration of the scheduled measurement gap. The scheduled measurement gap can be suspended as long as the value of the counter is larger than 0. This approach may be suitable in scenarios where the network access node 300 also transmits CSI-RS or SSB from serving beams in measurement gaps to the client device 100 (other client devices may use that CSI-RS or SSB for beam monitoring as well) and hence the client device 100 therefore prioritizes to perform measurement of serving beam(s) over measurement gaps if the value of the counter is larger than 0. On the other hand the duration of the scheduled measurement gap can be shortened. By shortening the scheduled measurement gap there can be time dedicated to both beam monitoring in respect of the serving beam and measurements on other beams, such as candidate beams. For example, the measurement gap can have a duration of several OFDM symbols, e.g. 10 OFDM symbols, which means that some of the 10 OFDM symbols could be allocated for beam monitoring and the remaining OFDM symbols for measurements of candidate beams. In the following disclosure non-limiting examples on how various embodiments of the invention could be added and implemented in the NR standard are described. The additions, depending on embodiments are made to the MAC-layer TS38.321 specification, section 5.14 titled “Handling of measurement gaps” and section 5.17 titled“Beam failure recovery procedure”, respectively. The UE mentioned in these sections corresponds to the present client device 100. The additions to the specification TS38.321 are given in italics.

Section 5.14“Handling of measurement gaps”

Section 5.14 of TS38.321 specification can be reformulated as one of the following examples below.

Example 1

During a measurement gap, the MAC entity shall:

1 > not perform the transmission of HARQ feedback, SR, and CSI;

if beamFailureDetectionTimer is running and the measurement gap is larger than remaining time of a running beamFailureDetectionTimer,

suspend beamFailureDetectionTimer, and

resume the beamFailureDetectionTimer after the measurement gap;

1 > not report SRS;

1 > not transmit on UL-SCH except for Msg3 as specified in subclause 5.4.2.2;

1 > if the ra-ResponseWindow or the ra-ContentionResolutionTimer is running:

2> monitor the PDCCH as specified in subclauses 5.1.4 and 5.1 .5.

1 > else:

2> not monitor the PDCCH.

Example 2

During a measurement gap, the MAC entity shall:

1 > not perform the transmission of HARQ feedback, SR, and CSI;

if beamFailureDetection Timer is running,

suspend beamFailureDetectionTimer, and

resume the beamFailureDetectionTimer after the measurement gap;

1 > not report SRS;

1 > not transmit on UL-SCH except for Msg3 as specified in subclause 5.4.2.2;

1 > if the ra-ResponseWindow or the ra-ContentionResolutionTimer is running:

2> monitor the PDCCH as specified in subclauses 5.1.4 and 5.1 .5.

1 > else:

2> not monitor the PDCCH. Example 3

During a measurement gap, the MAC entity shall:

1 > not perform the transmission of HARQ feedback, SR, and CSI;

if beamFailureDetection Timer expires

do not reset BFI_counter, and

restart beamFailureDetection Timer;

1 > not report SRS;

1 > not transmit on UL-SCH except for Msg3 as specified in subclause 5.4.2.2;

1 > if the ra-ResponseWindow or the ra-ContentionResolutionTimer is running:

2> monitor the PDCCH as specified in subclauses 5.1.4 and 5.1.5.

1 > else:

2> not monitor the PDCCH.

Example 4

During a measurement gap, the MAC entity shall:

1 > not perform the transmission of HARQ feedback, SR, and CSI;

1 > not report SRS;

1 > not transmit on UL-SCH except for Msg3 as specified in subclause 5.4.2.2;

1 > if the ra-ResponseWindow or the ra-ContentionResolutionTimer is running:

2> monitor the PDCCH as specified in subclauses 5.1.4 and 5.1.5.

If beamFailureDetectionTimer running and measurement gap is larger than remaining time of beamFailureDetection Timer

suspend measurement gap and monitor PDCCH (on serving cell/beam)

1 > else:

2> not monitor the PDCCH.

Example 5

During a measurement gap, the MAC entity shall:

1 > not perform the transmission of HARQ feedback, SR, and CSI;

1 > not report SRS;

1 > not transmit on UL-SCH except for Msg3 as specified in subclause 5.4.2.2;

1 > if the ra-ResponseWindow or the ra-ContentionResolutionTimer is running:

2> monitor the PDCCH as specified in subclauses 5.1.4 and 5.1.5.

if beamFailureDetectionTimer running and measurement gap is larger than beamFailureDetectionTimer and if BFI_COUNTER > configured threshold [note: configured threshold can be beamFailurelnstanceMaxCount] initiate beam failure recovery procedure

else stop beamFailureDetectionTimer;

1 > else:

2> not monitor the PDCCH.

Section 5.17“Beam Failure Detection and Recovery procedure”

Section 5.17 of TS38.321 specification can be reformulated as the following example.

Example 1

The following UE variables are used for the beam failure detection procedure:

BFi_COUNTER\ counter for beam failure instance indication which is initially set to 0. The MAC entity shall:

1 > if beam failure instance indication has been received from lower layers:

2> start or restart the beamFailureDetectionTimer,

2> increment BFI_COUNTER by 1 ;

2> if BFI_COUNTER = beamFailurelnstanceMaxCount + 1 :

3> initiate a Random Access procedure (see subclause 5.1 ) on the SpCell by applying the parameters configured in BeamFailureRecoveryConfig.

1 > if the beamFailureDetectionTimer expires:

2> if no measurement gap

3>. set BFI_COUNTER to 0.

else if beamFailureDetectionTimer expires during a measurement gap and if the beamFailureDetection Timer expires:

increment BFI_COUNTER by 1;

1 > if the Random Access procedure is successfully completed (see subclause 5.1 ):

2> consider the Beam Failure Recovery procedure successfully completed.

Example 2

The following UE variables are used for the beam failure detection procedure:

1 > if beam failure instance indication has been received from lower layers:

2> start or restart the beamFailureDetectionTimer,

2> increment BFI_COUNTER by 1 ;

2> if BFI_COUNTER = beamFailurelnstanceMaxCount + 1 :

3> initiate a Random Access procedure (see subclause 5.1 ) on the SpCell by applying the parameters configured in BeamFailureRecoveryConfig. if the beamFailureDetectionTimer expires:

if no measurement gap

set BFI_COUNTER to 0.

restart beamFailureDetection Timer;

2> consider the Beam Failure Recovery procedure successfully completed.

Example 3

The following UE variables are used for the beam failure detection procedure:

1 > if beam failure instance indication has been received from lower layers:

2> start or restart the beamFailureDetectionTimer,

2> increment BFI_COUNTER by 1 ;

2> if BFI_COUNTER = beamFailurelnstanceMaxCount + 1 :

3> initiate a Random Access procedure (see subclause 5.1 ) on the SpCell by applying the parameters configured in BeamFailureRecoveryConfig. set BFI_COUNTER to 0.

[Note: this also holds if beamFailureDetection timer expires during a measurement gap] 1 > if the Random Access procedure is successfully completed (see subclause 5.1 ):

2> consider the Beam Failure Recovery procedure successfully completed.

The client device 100 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer- comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as New Radio. The network access node 300 herein may also be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter,“gNB”,“gNodeB”,“eNB”, “eNodeB”,“NodeB” or“B node”, depending on the technology and terminology used. The radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio network access node may also be a base station corresponding to the fifth generation (5G) wireless systems.

Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that embodiments of the client device 100 and the network access node 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged togetherfor performing the solution.

Especially, the processor(s) of the client device 100 and the network access node 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. A client device (100) for a wireless communication system (500), the client device (100) being configured to

start a timer upon detection of a beam failure indication associated to at least one serving beam (502) for the client device (100);

determine that a measurement gap is scheduled for the client device (100); and manipulate at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap.

2. The client device (100) according to claim 1 , wherein manipulate the counter comprises at least one of

reset a value of the counter; and

increment or decrement a value of the counter.

3. The client device (100) according to claim 2, configured to at least one of

4. The client device (100) according to claim 2 or 3, configured to at least one of

5. The client device (100) according to claim 4, configured to at least one of

6. The client device (100) according to any of claims 2 to 5, configured to

7. The client device (100) according to any of the preceding claims, wherein manipulate the timer comprises at least one of

restart the timer;

suspend and thereafter resume the timer; and

increase a value of the timer.

8. The client device (100) according to claim 7, configured to

restart the timer without changing a value of the counter if the timer will expire during the scheduled measurement gap.

9. The client device (100) according to claim 7 or 8, configured to

10. The client device (100) according to any of claims 7 to 9, configured to

1 1. The client device (100) according to any of claims 7 to 10, configured to

12. The client device (100) according to any of the preceding claims, wherein manipulate the scheduled measurement gap comprises at least one of

suspend the scheduled measurement gap; and

shorten the duration of the scheduled measurement gap.

13. The client device (100) according to any of the preceding claims, wherein the timer is a beam failure detection timer.

14. The client device (100) according to any of the preceding claims, wherein the counter is a beam failure indication counter.

15. The client device (100) according to any of the preceding claims, configured to

start the timer, determine that a measurement gap is scheduled, and manipulate at least one of the timer, the counter and the scheduled measurement gap in a medium access control layer of the client device (100).

16. The client device (100) according to claim 15, configured to

detect the beam failure indication associated to the serving beam (502) in a physical layer of the client device (100); and

send the detection of the beam failure indication associated to the serving beam (502) to the medium access control layer.

17. A method for a client device (100), the method (200) comprising

starting (202) a timer upon detection of a beam failure indication associated to at least one serving beam (502) for the client device (100);

determining (204) that a measurement gap is scheduled for the client device (100); and manipulating (206) at least one of the timer, a counter associated with the beam failure indication and the scheduled measurement gap if the timer would be running during the scheduled measurement gap.

18. Computer program with a program code for performing a method according to claim 17 when the computer program runs on a computer.