WO2019096394A1

WO2019096394A1 - Processing device and method for beam failure recovery

Info

Publication number: WO2019096394A1
Application number: PCT/EP2017/079487
Authority: WO
Inventors: Chaitanya TUMULA; Bengt Lindoff; Rama Kumar Mopidevi; Neng Wang; Johan Hokfelt
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-11-16
Filing date: 2017-11-16
Publication date: 2019-05-23

Abstract

The invention relates to a processing device (100) for a client device (300), the processing device (100) comprising a physical, PHY, layer (102), and a Medium Access Control, MAC, layer (104). The PHY layer (102) monitors a quality of a serving BPL (502) associated with a downlink control channel and determines a beam failure event for the serving BPL (502) based on the monitored quality. The PHY layer (102) further provides an indication of the beam failure event to the MAC layer (104). The MAC layer (104) stops, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based Random Access, RA, procedure except a contention-based RA procedure associated with a Beam Failure Recovery Request, BFRQ, transmission. The MAC layer (104) further receives a BFRQ transmission initiation from the PHY layer (102) or an indication of a Radio Link Failure, RLF, event at a Radio Resource Control, RRC, layer (106). Furthermore, the invention also relates to a client device (300) comprising the processing device (100), corresponding methods, and a computer program.

Description

PROCESSING DEVICE AND METHOD FOR BEAM FAILURE RECOVERY

Technical Field

The invention relates to a processing device and a client device comprising such a processing device. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

The 5G cellular system, also called new radio (NR), is currently being standardized. NR is targeting radio spectrum from below 1 GHz up to and above 60 GHz. To allow for such diverse radio environments, not only different system bandwidths will be supported, but also different numerologies, such as different sub-carrier-spacings (SOS). Furthermore, for carrier frequencies over 10 GHz, multiple antennas and beamforming will be needed to combat the higher path loss at such high radio frequencies.

When beamforming is used, a next generation nodeB (gNB) transmits 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 need to perform beam monitoring. Hence, the gNB transmits known pilot signals in adjacent beams, which the UE receives and uses to detect possible transmit beams to switch to in case of changes in the radio environment. The principles behind beam monitoring can be compared to the cell search in legacy long term evolution (LTE), wideband code division multiple access (WCDMA) and high speed packet access (HSPA) systems. In such systems, the UE on a regular basis need to scan neighbouring cells for possible handover candidates.

Each possible connection between the UE and the gNB is called a beam pair link (BPL), where a BPL consists of the best match between a transmit beam and a receive beam. 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, e.g. during an initial access procedure. This set of BPLs 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 using control channel resources. The set of serving BPLs associated with the downlink control channels 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 all the serving BPLs associated with all the control channels fall below a threshold, UE declares a beam failure event and starts the beam recovery procedure by identifying a new candidate beam and initiating a transmission of a beam failure recovery request (BFRQ). If the beam failure event occurs, but the UE is unable to identify a new candidate beam, it cannot transmit a BFRQ and a radio link failure (RLF) may happen.

Summary

The inventors have found that, especially in case of transmit/receive beam correspondence at the UE, once the beam failure is detected at the UE, there are at least two possible scenarios: i) a new candidate beam is identified and a BFRQ is initiated, or ii) no new candidate beam is identified and RLF may occur, e.g. due to T310 timer expiry. Flence, from the time beam failure is detected at the UE to either new candidate beam is identified and BFRQ is initiated or no new candidate beam is identified and RLF occurs; if the UE has to transmit a signal in the uplink (UL) the UE will still use parameters and resources associated with the failed beams for transmission in the uplink. The transmission in the uplink may e.g. be related to the case that a scheduling request (SR) is triggered. Similarly, if the UE has to perform a new contention- based RACH procedure, for instance due to an SR failure event (such as reaching a limit on the maximum number of allowed SR transmissions) or a TA (time alignment) timer expiry event, the UE will use the parameters associated with the failed BPL(s). This leads to a waste of UL resources and increase of the UE power consumption.

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the present 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 processing device for a client device, the processing device is configured to be in a connected mode with a network access node using a serving beam pair link, BPL, associated with a downlink control channel; the processing device comprising a physical, PHY, layer, and a Medium Access Control, MAC, layer;

wherein the PHY layer is configured to

monitor a quality of the serving BPL associated with the downlink control channel, determine a beam failure event for the serving BPL based on the monitored quality, provide an indication of the beam failure event to the MAC layer;

wherein the MAC layer is configured to stop, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based Random Access, RA, procedure except a contention-based RA procedure associated with a Beam Failure Recovery Request, BFRQ, transmission,

receive a BFRQ transmission initiation from the PHY layer or an indication of a Radio Link Failure, RLF, event at a Radio Resource Control, RRC, layer.

The processing device may be configured to be in a connected mode with a network access node using one or more serving BPLs associated with multiple downlink control channel resources.

That the MAC layer stops a timer, a counter or a contention-based RA procedure can in this disclosure mean that the MAC layer stops the timer, the counter or the contention-based RA procedure such that it may later be restarted or reset.

A timer typically counts time, e.g. in form of Transmission Time Intervals (TTIs) or sub-frames. A counter typically counts events, e.g. SR transmissions. Both, timers and counters, are compared against their respective thresholds.

The contention-based RA procedure can in this disclosure be a new or a pending contention- based RA procedure.

The MAC layer can receive the BFRQ transmission initiation from the PHY layer after the MAC layer has stopped at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based RA procedure.

A beam failure can in this disclosure be understood to mean that the quality of all serving BPLs associated with all control channels has fallen below a threshold value. A beam failure event can occur when a network access node is not able to reach a client device with a control channel due to incorrect adjustment of beams. A beam failure event is usually detected at the PHY layer.

A RLF event may be triggered at the RRC layer for at least one of the following reasons: i) an indication from radio link control (RLC) layer that the maximum number of re-transmissions has been reached; ii) an indication from the MAC layer that random access problem occurs while neither T300, T301 , T304 nor T31 1 timers are running; iii) failure of receiving a handover command during T312 when T310 is running; iv) PHY layer problem detection based on radio link monitoring (RLM), e.g., upon T310 timer expiry. Hence, the RLF could be triggered due to several reasons. However, in case of beam failure detection and no new candidate beam identification at PHY layer, the T310 timer associated with RLM may expire leading to a RLF trigger. The timers T300, T301 , T304, T310, T31 1 , T312 are for example specified in the 3GPP 36.331 RRC protocol specification.

A processing device according to the first aspect provides a number of advantages over conventional solutions. An advantage of the processing device is that the MAC layer is informed by the PHY layer about a beam failure event and can hence stop or suspend new or pending scheduling requests and/or contention-based RA procedures. Thereby, system resources can be saved and power consumption in the processing device can be reduced compared to conventional solutions. The processing device may be implemented as a baseband processor for use in a client device.

In an implementation form of a processing device according to the first aspect, the MAC layer is configured to

send a BFRQ transmit instruction to the PHY layer in response to the reception of the BFRQ transmission initiation,

monitor a downlink control channel for a BFRQ response associated with the transmitted BFRQ.

The downlink control channel used for the BFRQ response can be pre-configured in the processing device, e.g. defined by a standard. In addition this downlink control channel used for the BFRQ response can be the same as the one associated with the serving BPL but can also be a different one.

An advantage with this implementation form is that the MAC layer and the PHY layer can recover quickly from a beam failure event. Further, by monitoring a downlink control channel for a BFRQ response associated with the transmitted BFRQ, the MAC layer can decide on the next step of action to execute in response to the stopped timer, counter associated with a SR configuration and the contention-based RA procedure.

In an implementation form of a processing device according to the first aspect, the MAC layer is configured to reset, upon successful reception of the BRFQ response, at least one of: the stopped timer associated with the scheduling request configuration and the stopped counter associated with the scheduling request configuration.

An advantage with this implementation form is that the MAC layer can reset the counters and timers associated with the SR configuration and resend the stopped SRs after a successful beam recovery procedure. By resetting the counters and timers, the MAC layer does not need to remember the previous values of SR counters and timers prior to receiving beam failure indication from the PHY layer.

restart, upon successful reception of the BRFQ response, at least one of: the stopped timer associated with the scheduling request configuration and the stopped counter associated with the scheduling request configuration.

An advantage with this implementation form is that the MAC layer can restart the counters and timers associated with the SR configuration and resend the stopped SRs after a successful beam recovery procedure. By restarting the counters and timers, the MAC layer can minimize the delay associated with transmitting the stopped SRs. This can also lead to saving uplink resources as the MAC layer can deduct the number of SRs transmitted prior to receiving the beam failure indication from the PHY layer and only transmit the remaining SRs after a successful beam recovery procedure.

restart, upon successful reception of the BRFQ response, the stopped contention-based RA procedure.

An advantage with this implementation form is that the MAC layer can restart the stopped contention-based RA procedure after successful beam recovery without waiting for further triggers. This will lead to minimizing delay associated with performing the RA procedure.

In an implementation form of a processing device according to the first aspect, the timer associated with the scheduling request configuration is a sr-ProhibitTimer timer, and/or the counter associated with the scheduling request configuration is a SR_COUNTER counter. An advantage with this implementation form is that by controlling sr-ProhibitTimer and SR_COUNTER, the MAC layer can control the transmission of SRs.

In an implementation form of a processing device according to the first aspect, the time alignment timer is associated with the serving BPL. In other words, the time alignment timer is dedicated to the serving BPL. Different serving BPLs therefore may have different time alignment timers.

An advantage with this implementation form is that by controlling the time alignment timer associated with the serving BPL, the transmissions in the uplink can be controlled after receiving the beam failure indication from the PHY layer.

In an implementation form of a processing device according to the first aspect the contention- based RA procedure is triggered by an event associated with uplink data arrival when the processing device is in connected mode.

An advantage with this implementation form is that, after receiving beam failure indication, by stopping the contention-based RA procedures associated with the uplink data arrival, the processing device will not transmit signals in the uplink, and thereby saving uplink resources and reducing power consumption in the processing device.

In an implementation form of a processing device according to the first aspect, the event associated with uplink data arrival corresponds to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a processing device for a client device, the processing device is configured to be in a connected mode with a network access node using a serving BPL associated with a downlink control channel; the processing device comprising a PHY layer and a MAC layer; wherein the PHY layer is configured to

receive an uplink transmission event trigger from the MAC layer, wherein the uplink transmission event trigger is associated with an uplink transmission to the network access node,

monitor a quality of the serving BPL associated with the downlink control channel, determine a beam failure state for the serving BPL associated with the downlink control channel based on the monitored quality, stop the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free RA procedure and transmission of a BFRQ.

The second aspect of the invention is an alternative to the first aspect of the invention but based on the same inventive idea. That is, both aspects of the invention avoid uplink transmissions instructed by higher layers directly upon detection of a beam failure event even before higher layers are informed about the beam failure event.

A processing device according to the second aspect provides a number of advantages over conventional solutions. An advantage of the processing device is that the PHY layer can detect a beam failure and stop (i.e. not perform) uplink transmissions when a beam failure has been detected. The PHY layer does not need to send an indication to the MAC layer, and the controlling mechanism for uplink signal transmissions can be implemented in the PHY layer. Thereby, system resources can be saved and power consumption in the processing device can be decreased compared to conventional solutions.

In an implementation form of a processing device according to the second aspect, the uplink transmission event is associated with at least one of: a scheduling request, a contention-free RA procedure, a contention-based RA procedure, and a BFRQ.

An advantage with this implementation form is that by considering the uplink transmission events associated with a scheduling request, a contention-free RA procedure, a contention- based RA procedure, and a BFRQ, the processing device can consider mentioned uplink transmission events and then can make a decision on whether to transmit the uplink signals depending on the beam failure state.

In an implementation form of a processing device according to the second aspect, the uplink transmission event associated with the contention-based RA procedure corresponds to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a client device for a wireless communication system, the client device comprising a processing device according to any of the implementation forms of a processing device according to the first aspect or the second aspect. A client device according to the third aspect provides a number of advantages over conventional solutions. An advantage of the client device is that the client device can detect a beam failure event and stop uplink transmissions when a beam failure event has occurred. Thereby, system resources can be saved and power consumption in the client device can be reduced compared to conventional solutions.

According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a processing device comprising a physical, PHY, layer, and a Medium Access Control, MAC, layer, the method comprises

monitoring, by the PHY layer, a quality of the serving BPL associated with the downlink control channel,

determining, by the PHY layer, a beam failure event for the serving BPL associated with a downlink control channel based on the monitored quality,

providing, by the PHY layer, an indication of the beam failure event to the MAC layer; stopping, by the MAC layer, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention- based Random Access, RA, procedure except a contention-based RA procedure associated with a Beam Failure Recovery Request, BFRQ, transmission,

receiving, by the MAC layer, a BFRQ transmission initiation from the PHY layer or an indication of a Radio Link Failure, RLF, event at a Radio Resource Control, RRC, layer.

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

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

According to a fifth aspect of the invention, the above mentioned and other objectives are achieved with a method for a processing device comprising a physical, PHY, layer, and a Medium Access Control, MAC, layer, the method comprises

receiving, by the PHY layer, an uplink transmission event trigger from the MAC layer, wherein the uplink transmission event trigger is associated with an uplink transmission to the network access node, monitoring, by the PHY layer, a quality of the serving BPL associated with the downlink control channel,

determining, by the PHY layer, a beam failure state for the serving BPL associated with the downlink control channel based on the monitored quality,

stopping, by the PHY layer, the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free RA procedure and transmission of a BFRQ.

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

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

The invention also relates to a computer program, characterized in code means, which when run by processing means causes said processing means to execute any method according to the present 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 present 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 present invention, in which:

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

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

- Fig. 3 shows a method according to an embodiment of the invention;

- Fig. 4 shows a client device according to an embodiment of the invention;

- Fig. 5 shows a wireless communication system according to an embodiment of the invention; - Fig. 6 shows a flow chart for a beam failure method according to an embodiment of the invention;

- Fig. 7 shows a flow chart for a beam failure method according to an embodiment of the invention;

- Fig. 8 shows a scenario where an indication of a beam failure event is received before a trigger for a scheduling request;

- Fig. 9 shows a scenario where an indication of a beam failure event is received after a scheduling request failure;

- Fig. 10 shows a scenario where an indication of a beam failure event is received after two scheduling request attempts.

Detailed Description

Fig. 1 shows a processing device 100 according to an embodiment of the invention. The processing device 100 comprises a physical, PHY, layer 102 and a Medium Access Control, MAC, layer 104 coupled to each other. The processing device 100 also comprises a Radio Resource Control (RRC) layer 106 in this example. The number of layers are not limited to mentioned three layers and often such a processing device 100 comprise further layers, such as conventional layers of layer 1 (L1 ), layer 2 (L2) and layer 3 (L3.) The PHY layer 102, the MAC layer 104 and the RRC layer 106 may be implemented in one or more processors (not shown in the Figs.) of the processing device 100 such that the processor is configured to execute the actions or corresponding steps and functions performed by the PHY layer 102, the MAC layer 104 and the RRC layer 106. The PHY layer 102, the MAC layer 104 and the RRC layer 106 could for example represent different sections of a program code running on the processor. In embodiments of the invention, the PHY layer 102, the MAC layer 104 and the RRC layer 106 may be implemented in a processor system (not shown in the Figs.) comprising one or more processors coupled to an input and an output, where the functions of PHY layer 102, the MAC layer 104 and the RRC layer 106 can be implemented in the same processor or in different processors.

The processing device 100 shown in Fig. 1 may be in a connected mode with a network access node 800 using at least one serving BPL 502 associated with a downlink control channel, as will be described with reference to Fig 5. Hence, the processing device 100 is in a connected mode in which it can communicate with the network access node 800 using the serving BPL 502. The connected mode may e.g. be a radio resource control (RRC) connected mode.

According to embodiments of the invention the PHY layer 102 of the processing device 100 is configured to monitor a quality of the serving BPL 502 associated with the downlink control channel and determine a beam failure event for the serving BPL 502 based on the monitored quality. The PHY layer 102 of the processing device 100 is further configured to provide an indication of the beam failure event to the MAC layer 104. The MAC layer 104 of the processing device 100 is configured to stop, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention- based RA procedure except a contention-based RA procedure associated with a BFRQ transmission. The MAC layer 104 of the processing device 100 is further configured to receive a BFRQ transmission initiation from the PHY layer 102 or an indication of a RLF event at a RRC layer 106.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a processing device 100, such as the one shown in Fig. 1 . The method 200 comprises monitoring 202, by the PHY layer 102, a quality of the serving BPL 502 associated with the downlink control channel and determining 204 a beam failure event for the serving BPL 502 based on the monitored quality. The method 200 further comprises providing 206, by the PHY layer 102, an indication of the beam failure event to the MAC layer 104. Furthermore, the method 200 comprises stopping 208, by the MAC layer 104, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based RA procedure except a contention-based RA procedure associated with a BFRQ transmission. The method 200 further comprises receiving 210, by the MAC layer 104, a BFRQ transmission initiation from the PHY layer 102 or an indication of a RLF event at a RRC layer 106.

According to embodiments of the invention the PHY layer 102 of the processing device 100 is configured to receive an uplink transmission event trigger from the MAC layer 104. The uplink transmission event trigger is associated with an uplink transmission to the network access node 800. The PHY layer 102 of the processing device 100 is further configured to monitor a quality of the serving BPL 502 associated with the downlink control channel and determine a beam failure state for the serving BPL 502 associated with the downlink control channel based on the monitored quality. Furthermore, the PHY layer 102 of the processing device 100 is configured to stop the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free RA procedure and transmission of a BFRQ. Fig. 3 shows a flow chart of a corresponding method 400 which may be executed in a processing device 100, such as the one shown in Fig. 1 . The method 400 comprises receiving 402, by the PFIY layer 102, an uplink transmission event trigger associated with an uplink transmission to the network access node 800 from the MAC layer 104. The method 400 further comprises monitoring 404, by the PFIY layer 102, a quality of the serving BPL 502 associated with the downlink control channel and determining 406 a beam failure state for the serving BPL 502 associated with the downlink control channel based on the monitored quality. Furthermore, the method 400 comprises stopping 408, by the PFIY layer 102, the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free RA procedure and transmission of a BFRQ.

The processing device 100 may be comprised in a client device, such as the client device 300 shown in Fig. 4. The processing device 100 may for example be a baseband processor with a memory having stored program code for performing the actions as described herein for use in the client device 300. In the embodiment shown in Fig. 4, the client device 300 comprises the processing device 100 and a transceiver 302. The processing device 100 is coupled to the transceiver 302 by communication means 304 known in the art. The client device 300 further comprises an antenna array 306 coupled to the transceiver 302, which means that the client device 300 is configured for wireless communications in a wireless communication system. The client device 300 shown in Fig. 3 may be in a connected mode with a network access node 800 using a serving beam pair link, BPL, 502 associated with a downlink control channel, as will be described with reference to Fig 5. Flence, the client device 300 may be in a connected mode in which it can communicate with the network access node 800 using the serving BPL 502. The connected mode may e.g. be a RRC connected mode.

Fig. 5 shows a wireless communication system 500 according to an embodiment of the invention. The wireless communication system 500 comprises a client device 300 and a network access node 800, both configured to operate in the wireless communication system 500. The client device 300 comprises a processing device 100. For simplicity, the wireless communication system 500 shown in Fig. 5 only comprises one client device 300 and one network access node 800. Flowever, the wireless communication system 500 may comprise any number of client devices 300 and any number of network access nodes 800 without deviating from the scope of the invention.

In the wireless communication system 500, beamforming is used such that data is transmitted in several directions in different BPLs between the client device 300 and the network access node 800. In Fig. 5, two BPLs 502, 504 are shown. Flowever, any number of BPLs may exist between the client device 300 and the network access node 800 without deviation from the scope of the invention. In Fig. 5, the client device 300 is in a connected mode with the network access node 800 using the BPL 502 as a serving BPL. The serving BPL 502 is associated with a downlink control channel (not shown in Fig. 5). The processing device 100 comprised in the client device 300 may detect if the serving BPL 502 associated with the downlink control channel fails, e.g. if the quality of the serving BPL 502 falls below a threshold value and accordingly declare a beam failure. Upon a detected beam failure, the processing device 100 performs procedures according to embodiments of the invention, which results in that system resources are saved and power consumption in the client device 300 is reduced. The procedures performed by the processing device 100 will now be further described below with reference to Fig. 6 and 7.

Fig. 6 shows a flow chart of a procedure 600 according to an embodiment of the invention. In the embodiment shown in Fig. 6, the procedure 600 is performed by the PHY layer 102 and the MAC layer 104 of a processing device 100. The processing device 100 is in a connected mode with a network access node 800 using a serving BPL 502 associated with a downlink control channel. In step 602, the PHY layer 102 determines a beam failure event for a serving BPL 502. As previously described the PHY layer 102 may determine the beam failure event based on the monitored quality of the serving BPL 502. The PHY layer 102 may e.g. determine the beam failure event for the serving BPL 502 by comparing a pre-defined first metric for the monitored quality with a pre-defined first threshold. The first pre-defined metric may e.g. be hypothetical physical downlink control channel (PDCCH) block error rate (BLER) associated with a control channel or layer 1 -reference signal received power (L1 -RSRP) measurements on reference signal resources associated with the serving BPL.

When a beam failure event is determined in step 602, the PHY layer 102 provides an indication of the beam failure event to the MAC layer 104 in step 604. In response to reception of the indication of the beam failure event, the MAC layer 104 stops, in step 606, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based RA procedure except a contention-based RA procedure associated with a BFRQ transmission. The timer associated with the scheduling request configuration may e.g. be a sr-ProhibitTimer timer. The counter associated with the scheduling request configuration may e.g. be a SR_COUNTER counter as defined in 3GPP 36.321 MAC protocol specification. Furthermore, the time alignment timer may be associated with the serving BPL 502. When the MAC layer 104 stops a contention-based RA procedure, the contention-based RA procedure may either be pending or a new one. Furthermore, the contention-based RA procedure may have been triggered by an event associated with uplink data arrival when the processing device 100 is in connected mode. The event associated with uplink data arrival may correspond to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset. A scheduling request failure event may be associated with a client device 300 not having physical uplink control channel (PUCCH) resources to transmit a scheduling request associated with the arrived uplink data.

In addition to providing an indication of the determined beam failure event to the MAC layer 104 in step 604, the PHY layer 102 starts a beam recovery procedure in step 608 when the beam failure event is determined. The beam recovery procedure is performed to identify a new candidate beam and may be performed using known procedures. For example, the new candidate beam may be identified based on a second predefined metric exceeding a predefined second threshold. The second predefined metric may e.g. correspond to hypothetical PDCCH BLER associated with a control channel or L1 -RSRP measurements on reference signals associated with one or more BPLs associated with a control channel.

If no new candidate beam is found by the PHY layer 102, the processing device 100 may wait for a RLF according to known procedures in the art (not shown in Fig. 6). The RLF may e.g. be triggered due to T310 timer expiry. On the other hand, if a new candidate beam is found by the PHY layer 102, the PHY layer 102 indicates to the MAC layer 104, in step 610, to initiate a BFRQ transmission. In response to the reception of the BFRQ transmission initiation from the PHY layer 102, the MAC layer 104 sends a BFRQ transmit instruction to the PHY layer 102 in step 612. The BFRQ transmit instruction comprises parameters selected by the MAC layer 104 and associated with the BFRQ transmission. In case the BFRQ transmission should be transmitted using a RA procedure, the parameters associated with the BFRQ transmission may comprise RA preamble, RA resources, RA preamble transmission power, etc. In case the BFRQ transmission should be transmitted using PUCCH, the parameters associated with the BFRQ transmission may comprise PUCCH resources.

In step 614 the PHY layer 102 performs the BFRQ transmission based on the BFRQ transmit instruction from the MAC layer 104. The BFRQ transmission may be performed N number of times, where N is a positive integer which may be configured by the network access node 800 and received by the processing device 100 in a suitable control channel.

Moreover, the MAC layer 104 starts, in step 616, to monitor a downlink control channel for a BFRQ response associated with the BFRQ transmission. This (e.g. pre-configured) downlink control channel can be the same as the one associated with the serving BPL. However, it can also be a further downlink control channel which is not associated with the serving BPL. If the MAC layer 104 receives the BFRQ response in a predefined random access response (RAR) time window, the beam recovery procedure is declared successful. In the event of successful beam recovery, the MAC layer 104 may reset or restart, in step 618, the timers, counters, or contention-based RACH procedures stopped in step 606. Hence, the MAC layer 104 may in step 618 either reset or restart, upon successful reception of the BRFQ response, at least one of: the stopped timer associated with the scheduling request configuration and the stopped counter associated with the scheduling request configuration. Furthermore, the MAC layer 104 may in step 618 restart, upon successful reception of the BRFQ response, the stopped contention-based RA procedure.

If the beam recovery is unsuccessful, the processing device 100 may wait for a RLF, e.g. due to T310 timer expiry, or the processing device 100 may indicate to the network access node 800 that the beam recovery procedure was unsuccessful. The processing device 100 performs said actions according to known procedures and these steps are therefore not shown in Fig. 6. The beam recovery procedure may e.g. be unsuccessful if the network access node 800 is unable to receive the BFRQ transmissions or the processing device 100 is unable to receive the BRFQ response transmitted by network access node 800.

Fig. 7 shows a flow chart of a procedure 700 according to an embodiment of the invention. In the embodiment shown in Fig. 7, the procedure 700 is performed by the PHY layer 102 of a processing device 100. The processing device 100 is in a connected mode with a network access node 800 using at least one serving BPL 502 associated with a downlink control channel. In step 702, the PHY layer 102 receives an uplink transmission event trigger from the MAC layer 104, where the uplink transmission event trigger is associated with an uplink transmission to the network access node 800. The uplink transmission event may be associated with at least one of: a scheduling request, a contention-free RA procedure, a contention-based RA procedure, and a BFRQ transmission. When the uplink transmission event is associated with a contention-based RA procedure, the contention-based RA procedure may correspond to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset.

Prior to transmitting the uplink transmission to the network access node 800, the PHY layer 102 determines a beam failure state for the serving BPL 502 in step 704. Step 704 may comprise the PHY layer 102 monitoring the quality of the serving BPL 502 associated with the downlink control channel and determining a beam failure state for the serving BPL 502 associated with the downlink control channel based on the monitored quality. As previously described with reference to Fig. 6 the PFIY layer 102 may e.g. determine the beam failure state for the serving BPL 502 by comparing a predefined first metric for the monitored quality with a predefined first threshold.

If the beam failure state determined in step 704 is not a failure state, i.e. the outcome of the check in step 704 is NO, the PFIY layer 102 transmits the uplink transmission to the network access node 800 in step 706. On the other hand, if the beam failure state determined in step 704 is a failure state, i.e. the outcome of the check in step 704 is YES, the PFIY layer 102 checks whether the uplink transmission event trigger is associated with a contention-free RA procedure or a BFRQ transmission in step 708.

If the uplink transmission event trigger is associated with a contention-free RA procedure or a BFRQ transmission, i.e. the outcome of the check in step 708 is YES, the PHY layer 102 transmits the uplink transmission to the network access node 800 in step 710. On the other hand, if the uplink transmission event trigger is not associated with a contention-free RA procedure or a BFRQ transmission, i.e. the outcome of the check in step 708 is NO, the PHY layer 102 stops the uplink transmission to the network access node 800 in step 712.

Further details related to the functions of the PHY layer 102 and the MAC layer 104 and the information being exchanged between the PHY layer 102 and the MAC layer 104 when the procedure 600 is performed in a processing device 100 will now be described with reference to Figs. 8-10, which show three different scenarios where a beam failure event indication is received by the MAC layer 104 at different stages of a scheduling request procedure.

Fig. 8 shows a scenario where the MAC layer 104 receives a trigger for scheduling request transmission after receiving an indication of a beam failure event from the PHY layer 102. In Fig. 8, the indication of a beam failure event IBFE from the PHY layer 102 is received by the MAC layer 104 in step I. At this point the MAC layer 104 stops timers and counters associated with one or more scheduling request transmissions. The MAC layer 104 thereafter receives a trigger for a scheduling request, e.g. receives uplink data, which would typically initiate a transmission of a scheduling request through the PHY layer 102. However, as the MAC layer 104 is aware of the beam failure event, the MAC layer 104 will not initiate the transmission of the scheduling request SR, as indicated by the crossed over arrow in step II in Fig. 8. Further, the MAC layer 104 receives a BFRQ transmission initiation IBFRQ from the PHY layer 102 in step III in Fig. 8 and a BFRQ is transmitted to the network access node 800 (not illustrated in Fig. 8). Fig. 9 shows a scenario where the MAC layer 104 stops a RA procedure associated with a scheduling request failure after receiving an indication of a beam failure event from the PFIY layer 102. In Fig. 9, assuming that the value of dsr_T ransMax (the maximum number of allowed transmissions of scheduling requests) is set to three, three scheduling requests SRs are transmitted by the MAC layer 104 in step l-lll. The time between the scheduling requests SRs is in this embodiment determined by a sr-ProhibitTimer timer. The number of SR attempts is tracked by a SR_COUNTER counter. After transmitting the three SRs, the SR_COUNTER reaches its limit (determined by dsr_T ransMax) and it is assumed that the processing device 100 has failed to receive any scheduling grants associated with the transmitted SRs. Hence, the MAC layer 104 should initiate a RA procedure associated with the scheduling request failure. However, before the RA procedure associated with the scheduling request failure is initiated, the MAC layer 104 receives an indication of a beam failure event IBFE from the PHY layer 102, in step IV. Hence, the MAC layer 104 stops the RA procedure associated with the scheduling request failure, as indicated by the crossed over arrow in step V in Fig. 9. The MAC layer 104 receives a BFRQ transmission initiation IBFRQ from the PHY layer 102 in step VI in Fig. 9 and a BFRQ is transmitted to the network access node 800 (not illustrated in Fig. 9).

Fig. 10 shows a scenario where the MAC layer 104 receives an indication of a beam failure event from the PHY layer 102 after two scheduling request transmissions, assuming that the value of dsr_T ransMax is set to three. After the two SR transmissions, the SR_COUNTER values is set to 1 (assuming it starts from 0). In Fig. 10, two scheduling requests SRs are transmitted by the MAC layer 104 in step l-ll. Before the third scheduling request SR is to be transmitted by the MAC layer 104, the MAC layer 104 receives an indication of a beam failure event IBFE from the PHY layer 102, in step III. Hence, the MAC layer 104 stops further transmissions of scheduling requests SRs, i.e. stops SR COUNTER and sr ProhibitTimer, i.e., the SR_COUNTER is stopped at 1. The third scheduling request SR is therefore not transmitted as indicated by the crossed over arrow in step IV in Fig. 10. Instead, the MAC layer 104 will receive a BFRQ transmission initiation IBFRQ from the PHY layer 102 in step V in Fig. 10 and a BFRQ is transmitted (not illustrated in Fig. 10). If the beam recovery procedure is successful, the MAC layer 104 will restart the SR_COUNTER, i.e., start the SR_COUNTER with value 1 and increment it by 1 , and transmit the third scheduling request SR, as shown in step VI in Fig. 10. Alternatively, the MAC layer 104 will reset the SR_COUNTER after a successful beam recovery procedure, i.e., start the SR_COUNTER with value 0. In this case, the scheduling request SR transmitted in step VI in Fig. 10 would be the first scheduling request SR in a new set of three scheduling request SR attempts. The client device 300 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 the present 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 800 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,“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 300 and the network access node 800 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present 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 together for performing the present solution.

Especially, the processor(s) of the client device 300 and the network access node 800 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 processing device (100) for a client device (300), wherein the processing device (100) is configured to be in a connected mode with a network access node (800) using a serving beam pair link, BPL, (502) associated with a downlink control channel; the processing device (100) comprising a physical, PHY, layer (102), and a Medium Access Control, MAC, layer (104); wherein the PHY layer (102) is configured to

monitor a quality of the serving BPL (502) associated with the downlink control channel, determine a beam failure event for the serving BPL (502) based on the monitored quality, provide an indication of the beam failure event to the MAC layer (104);

wherein the MAC layer (104) is configured to

stop, in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based Random Access, RA, procedure except a contention-based RA procedure associated with a Beam Failure Recovery Request, BFRQ, transmission,

receive a BFRQ transmission initiation from the PHY layer (102) or an indication of a Radio Link Failure, RLF, event at a Radio Resource Control, RRC, layer (106).

2. The processing device (100) according to claim 1 , wherein the MAC layer (104) is configured to

send a BFRQ transmit instruction to the PHY layer (102) in response to the reception of the BFRQ transmission initiation,

3. The processing device (100) according to claim 2, wherein the MAC layer (104) is configured to

reset, upon successful reception of the BRFQ response, at least one of: the stopped timer associated with the scheduling request configuration and the stopped counter associated with the scheduling request configuration.

4. The processing device (100) according to claim 2 or 3, wherein the MAC layer (104) is configured to

5. The processing device (100) according to any of claims 2 to 4, wherein the MAC layer (104) is configured to

6. The processing device (100) according to any of the preceding claims, wherein at least one of: the timer associated with the scheduling request configuration is a sr-ProhibitTimer timer, and the counter associated with the scheduling request configuration is a SR_COUNTER counter.

7. The processing device (100) according to any of the preceding claims, wherein the contention-based RA procedure is triggered by an event associated with uplink data arrival when the processing device (100) is in connected mode.

8. The processing device (100) according to claim 7, wherein the event associated with uplink data arrival corresponds to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset.

9. A processing device (100) for a client device (300), wherein the processing device (100) is configured to be in a connected mode with a network access node (800) using a serving beam pair link, BPL, (502) associated with a downlink control channel; the processing device (100) comprising a physical, PHY, layer (102) and a Medium Access Control, MAC, layer (104); wherein the PHY layer (102) is configured to

receive an uplink transmission event trigger from the MAC layer (104), wherein the uplink transmission event trigger is associated with an uplink transmission to the network access node (800),

monitor a quality of the serving BPL (502) associated with the downlink control channel, determine a beam failure state for the serving BPL (502) associated with the downlink control channel based on the monitored quality,

stop the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free Random Access, RA, procedure and transmission of a Beam Failure Recovery Request, BFRQ.

10. The processing device (100) according to claim 9, wherein the uplink transmission event is associated with at least one of: a scheduling request, a contention-free RA procedure, a contention-based RA procedure, and a BFRQ.

1 1. The processing device (100) according to claim 10, wherein the uplink transmission event associated with the contention-based RA procedure corresponds to at least one of: a scheduling request failure, a time alignment timer expiry, and a MAC reset.

12. A client device (400) for a wireless communication system (500), the client device (300) comprising a processing device (100) according to any of the proceeding claims.

13. A method (200) for a processing device (100) comprising a physical, PHY, layer (102), and a Medium Access Control, MAC, layer (104), the method (200) comprising

monitoring (202), by the PHY layer (102), a quality of a serving beam pair link, BPL, (502) associated with a downlink control channel,

determining (204), by the PHY layer (102), a beam failure event for the serving BPL (502) based on the monitored quality,

providing (206), by the PHY layer (102), an indication of the beam failure event to the MAC layer (104);

stopping (208), by the MAC layer (104), in response to reception of the indication of the beam failure event, at least one of: a timer associated with a scheduling request configuration, a counter associated with the scheduling request configuration, a time alignment timer, and a contention-based Random Access, RA, procedure except a contention-based RA procedure associated with a Beam Failure Recovery Request, BFRQ, transmission,

receiving (210), by the MAC layer (104), a BFRQ transmission initiation from the PHY layer (102) or an indication of a Radio Link Failure, RLF, event at a Radio Resource Control, RRC, layer (106).

14. A method (400) for a processing device (100) comprising a physical, PHY, layer (102), and a Medium Access Control, MAC, layer (104), the method (400) comprising

receiving (402), by the PHY layer (102), an uplink transmission event trigger from the MAC layer (104), wherein the uplink transmission event trigger is associated with an uplink transmission to the network access node (800),

monitoring (404), by the PHY layer (102), a quality of a serving beam pair link, BPL, (502) associated with a downlink control channel,

determining (406), by the PHY layer (102), a beam failure state for the serving BPL (502) associated with the downlink control channel based on the monitored quality,

stopping (408), by the PHY layer (102), the uplink transmission if the beam failure state is a failure state and the uplink transmission event trigger is not associated with at least one of: a contention-free Random Access, RA, procedure and transmission of a Beam Failure Recovery Request, BFRQ.

15. Computer program with a program code for performing a method according to claim 13 or 14 when the computer program runs on a computer.